WorldWideScience

Sample records for arid vadose zone

  1. Sensitivity of Vadose Zone Water Fluxes to Climate Shifts in Arid Settings

    Energy Technology Data Exchange (ETDEWEB)

    Pfletschinger, H. [Federal Waterways Engineering and Research Inst. (BAW), Karlsruhe (Germany); Technical Univ. of Darmstadt (Germany). Inst. of Applied Geosciences; Prömmel, K. [Freie Univ., Berlin (Germany); Schüth, C. [Technical Univ. of Darmstadt (Germany). Inst. of Applied Geosciences; Herbst, M. [Agrosphere (IBG-3), Julich (Germany); Engelhardt, I. [Technical Univ. of Darmstadt (Germany). Inst. of Applied Geosciences; Agrosphere (IBG-3), Julich (Germany)

    2014-01-01

    Vadose zone water fluxes in arid settings are investigated regarding their sensitivity to hydraulic soil parameters and meteorological data. The study is based on the inverse modeling of highly defined soil column experiments and subsequent scenario modeling comparing different climate projections for a defined arid region. In arid regions, groundwater resources are prone to depletion due to excessive water use and little recharge potential. Especially in sand dune areas, groundwater recharge is highly dependent on vadose zone properties and corresponding water fluxes. Nevertheless, vadose zone water fluxes under arid conditions are hard to determine owing to, among other reasons, deep vadose zones with generally low fluxes and only sporadic high infiltration events. In this study, we present an inverse model of infiltration experiments accounting for variable saturated nonisothermal water fluxes to estimate effective hydraulic and thermal parameters of dune sands. A subsequent scenario modeling links the results of the inverse model with projections of a global climate model until 2100. The scenario modeling clearly showed the high dependency of groundwater recharge on precipitation amounts and intensities, whereas temperature increases are only of minor importance for deep infiltration. However, simulated precipitation rates are still affected by high uncertainties in the response to the hydrological input data of the climate model. Thus, higher certainty in the prediction of precipitation pattern is a major future goal for climate modeling to constrain future groundwater management strategies in arid regions.

  2. Underground Corrosion of Activated Metals in an Arid Vadose Zone Environment

    Energy Technology Data Exchange (ETDEWEB)

    Adler Flitton, Mariana Kay; Mizia, Ronald Eugene; Bishop, Carolyn Wagoner

    2002-04-01

    The subsurface radioactive disposal site located at the Idaho National Engineering and Environmental Laboratory contains neutron-activated metals from nonfuel nuclear-reactor- core components. A long-term corrosion test is being conducted to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements in an arid vadose zone environment. The tests use nonradioactive metal coupons representing the prominent neutron-activated material buried at the disposal location, namely, Type 304L stainless steel, Type 315L stainless steel, nickel-chromium alloy (UNS NO7718), beryllium, aluminum 6061-T6, and a zirconium alloy, (UNS R60804). In addition, carbon steel (the material presently used in the cask disposal liners and other disposal containers) and a duplex stainless steel (UNS S32550) (the proposed material for the high- integrity disposal containers) are also included in the test program. This paper briefly describes the test program and presents the early corrosion rate results after 1 year and 3 years of underground exposure.

  3. Underground Corrosion of Activated Metals in an Arid Vadose Zone Environment

    Energy Technology Data Exchange (ETDEWEB)

    Adler Flitton, M.K; Mizia, R.E.; Bishop, C.W.

    2001-10-24

    The subsurface radioactive disposal site located at the Idaho National Engineering and Environmental Laboratory contains neutron-activated metals from nonfuel nuclear-reactor- core components. A long-term corrosion test is being conducted to obtain site-specific corrosion rates to support efforts to more accurately estimate the transfer of activated elements in an arid vadose zone environment. The tests use nonradioactive metal coupons representing the prominent neutron-activated material buried at the disposal location, namely, Type 304L stainless steel, Type 315L stainless steel, nickel-chromium alloy (UNS NO7718), beryllium, aluminum 6061-T6, and a zirconium alloy, (UNS R60804). In addition, carbon steel (the material presently used in the cask disposal liners and other disposal containers) and a duplex stainless steel (UNS S32550) (the proposed material for the high- integrity disposal containers) are also included in the test program. This paper briefly describes the test program and presents the early corrosion rate results after 1 year and 3 years of underground exposure.

  4. Significance of water fluxes in a deep arid-region vadose zone to waste disposal strategies

    Energy Technology Data Exchange (ETDEWEB)

    Johnejack, K.R.; Blout, D.O.; Sully, M.J.; Emer, D.F.; Hammermeister, D.P. [Reynolds Electrical and Engineering Co., Inc., Las Vegas, NV (United States); Dever, L.G.; O`Neill, L.J. [DOE Nevada Operations Office, Las Vegas, NV (United States). Waste Management Div.; Tyler, S.W. [Desert Research Institute, Reno, NV (United States). Water Resources Center; Chapman, J. [Desert Research Institute, Las Vegas, NV (United States). Water Resources Center

    1994-03-01

    Recently collected subsurface site characterization data have led to the development of a conceptual model of water movement beneath the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site (NTS) that differs significantly from the conceptual model of water movement inherent in Resource Conservation and Recovery Act (RCRA) regulations. At the Area 5 RWMS, water fluxes in approximately the upper 75 m (250 ft) of the vadose zone point in the upward direction (rather than downward) which effectively isolates this region from the deep (approximately 250 m (820 ft)) uppermost aquifer. Standard RCRA approaches for detection and containment (groundwater monitoring and double liners/leachate collection/leak detection systems) are not able to fulfill their intended function in this rather unique hydrogeologic environment. In order to better fulfill the waste detection and containment intentions of RCRA for mixed waste disposal at the Area 5 RWMS, the Department of Energy, Nevada Operations Office (DOE/NV) is preparing a single petition for both a waiver from groundwater monitoring and an exemption from double liners with leachate collection/leak detection. DOE/NV proposes in this petition that the containment function of liners and leachate collection is better accomplished by the natural hydrogeologic processes operating in the upper vadose zone; and the detection function of groundwater monitoring and the leak detection system in liners is better fulfilled by an alternative vadose zone monitoring system. In addition, an alternative point of compliance is proposed that will aid in early detection, as well as limit the extent of potential contamination before detection. Finally, special cell design features and operation practices will be implemented to limit leachate formation, especially while the cell is open to the atmosphere during waste emplacement.

  5. LONG-TERM COLLOID MOBILIZATION AND COLLOID-FACILITATED TRANSPORT OF RADIONUCLIDES IN A SEMI-ARID VADOSE ZONE

    Energy Technology Data Exchange (ETDEWEB)

    Markus Flury; James B. Harsh; Fred Zhang; Glendon W. Gee; Earl D. Mattson; Peter C. L

    2012-08-01

    The main purpose of this project was to improve the fundamental mechanistic understanding and quantification of long-term colloid mobilization and colloid-facilitated transport of radionuclides in the vadose zone, with special emphasis on the semi-arid Hanford site. While we focused some of the experiments on hydrogeological and geochemical conditions of the Hanford site, many of our results apply to colloid and colloid-facilitated transport in general. Specific objectives were (1) to determine the mechanisms of colloid mobilization and colloid-facilitated radionuclide transport in undisturbed Hanford sediments under unsaturated flow, (2) to quantify in situ colloid mobilization and colloid-facilitated radionuclidetransport from Hanford sediments under field conditions, and (3) to develop a field-scale conceptual and numerical model for colloid mobilization and transport at the Hanford vadose zone, and use that model to predict long-term colloid and colloid- facilitated radionuclide transport. To achieve these goals and objectives, we have used a combination of experimental, theoretical, and numerical methods at different spatial scales, ranging from microscopic investigationsof single particle attachment and detachment to larger-scale field experiments using outdoor lysimeters at the Hanford site. Microscopic and single particle investigations provided fundamental insight into mechanisms of colloid interactions with the air-water interface. We could show that a moving air water interface (such as a moving water front during infiltration and drainage) is very effective in removing and mobilizing particles from a stationary surface. We further demonstrated that it is particularly the advancing air-water interface which is mainly responsible for colloid mobilization. Forces acting on the colloids calculated from theory corroborated our experimental results, and confirm that the detachment forces (surface tension forces) during the advancing air-water interface

  6. In situ vadose zone bioremediation.

    Science.gov (United States)

    Höhener, Patrick; Ponsin, Violaine

    2014-06-01

    Contamination of the vadose zone with various pollutants is a world-wide problem, and often technical or economic constraints impose remediation without excavation. In situ bioremediation in the vadose zone by bioventing has become a standard remediation technology for light spilled petroleum products. In this review, focus is given on new in situ bioremediation strategies in the vadose zone targeting a variety of other pollutants such as perchlorate, nitrate, uranium, chromium, halogenated solvents, explosives and pesticides. The techniques for biostimulation of either oxidative or reductive degradation pathways are presented, and biotransformations to immobile pollutants are discussed in cases of non-degradable pollutants. Furthermore, research on natural attenuation in the vadose zone is presented.

  7. Appraisal of nuclear waste isolation in the vadose zone in arid and semiarid regions (with emphasis on the Nevada Test Site)

    Energy Technology Data Exchange (ETDEWEB)

    Wollenberg, H.A.; Wang, J.S.Y.; Korbin, G.

    1983-05-01

    An appraisal was made of the concept of isolating high-level radioactive waste in the vadose zone of alluvial-filled valleys and tuffaceous rocks of the Basin and Range geomorphic province. Principal attributes of these terranes are: (1) low population density, (2) low moisture influx, (3) a deep water table, (4) the presence of sorptive rocks, and (5) relative ease of construction. Concerns about heat effects of waste on unsaturated rocks of relatively low thermal conductivity are considered. Calculations show that a standard 2000-acre repository with a thermal loading of 40 kW/acre in partially saturated alluvium or tuff would experience an average temperature rise of less than 100{sup 0}C above the initial temperature. The actual maximum temperature would depend strongly on the emplacement geometry. Concerns about seismicity, volcanism, and future climatic change are also mitigated. The conclusion reached in this appraisal is that unsaturated zones in alluvium and tuff of arid regions should be investigated as comprehensively as other geologic settings considered to be potential repository sites.

  8. Vadose Zone Hydrology and Eco-hydrology in China

    Science.gov (United States)

    Wang, Wenke

    2016-04-01

    Vadose zone hydrology has long been a concern regarding groundwater recharge, evaporation, pollution, and the ecological effects induced by groundwater and water & salt contents in the unsaturated zone. The greater difference between day and night temperatures in arid and semi-arid areas influences water movement and heat transport in the vadose zone, and further influences the water and heat fluxes between the water table and the atmosphere as well as ecological environment. Unfortunately, these studies are lack in a systematic viewpoint in China. One of the main reasons is that the movement of water, vapor and heat from the surface to the water table is very complex in the arid and semi-arid areas. Another reason is lack of long term field observations for water content, vapor, heat, and soil matrix potential in the vadose zone. Three field observation sites, designed by the author, were set up to measure the changes in climate, water content , temperature and soil matrix potential of the unsaturated zone and groundwater level under the different conditions of climate and soil types over the period of 1-5 years. They are located at the Zhunngger Basin of Xinjing Uygur Autonomous Region in northwestern China, the Guanzhong Basin of Shaanxi Province in central China, and the Ordos Basin of the Inner Monggol Autonomous Region in north China, respectively. These three field observation sites have different climate and soil types in the vadose zone and the water table depth are also varied. Based on the observation data of climate, groundwater level, water content, temperature and soil matrix potential in the vadose zone from the three sites in associated with the field survey and numerical simulation method, the water movement and heat transport in the vadose zone, and the evaporation of phreatic water for different groundwater depths and soil types have been well explored. The differences in water movement of unsaturated zone between the bare surface soil and

  9. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2005-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center [INTEC] at the Idaho National Laboratory [INL]). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate (primarily calcite) in groundwater and vadose zone systems. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by (a) increasing pH and alkalinity and (b) liberating cations from the aquifer matrix by cation exchange reactions. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which is produced in situ by native urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long term. We are currently conducting field based activities at both the INL Vadose Zone Research Park (VZRP), an uncontaminated surrogate site for the strontium-90 contaminated vadose zone at INTEC and at the strontium-90 contaminated aquifer of 100-N area of the Hanford site.

  10. The Mojave vadose zone: a subsurface biosphere analogue for Mars.

    Science.gov (United States)

    Abbey, William; Salas, Everett; Bhartia, Rohit; Beegle, Luther W

    2013-07-01

    If life ever evolved on the surface of Mars, it is unlikely that it would still survive there today, but as Mars evolved from a wet planet to an arid one, the subsurface environment may have presented a refuge from increasingly hostile surface conditions. Since the last glacial maximum, the Mojave Desert has experienced a similar shift from a wet to a dry environment, giving us the opportunity to study here on Earth how subsurface ecosystems in an arid environment adapt to increasingly barren surface conditions. In this paper, we advocate studying the vadose zone ecosystem of the Mojave Desert as an analogue for possible subsurface biospheres on Mars. We also describe several examples of Mars-like terrain found in the Mojave region and discuss ecological insights that might be gained by a thorough examination of the vadose zone in these specific terrains. Examples described include distributary fans (deltas, alluvial fans, etc.), paleosols overlain by basaltic lava flows, and evaporite deposits.

  11. Dynamics of Vadose Zone Transport: a Field and Modeling Study using the Vadose Zone Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Carrigan, C R

    2001-01-01

    A stated need of the DOE EM program is a better understanding of basic vadose zone fluid flow and contaminant transport processes for the purpose of making improved estimates of contaminant release rates and fluxes across the vadose zone to the water table at DOE sites such as the tank farms at Hanford. We investigate details of the modes of contaminant transport with the aid of infiltration experiments designed to elucidate how vadose zone characteristics such as preferential pathways, heterogeneities, and relative permeabilities influence the transport of contamination in liquid, gas and colloidal phases to the water table. Beyond enhancing our basic understanding of vadose zone transport processes, this EMSP project is designed result in a vadose-zone-transport-characterization methodology that can be generalized to other DOE sites.

  12. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of 90Strontium & Other Divalent Metals & Radionuclides at Arid West DOE Sites

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant; Cosgrove, Donna M.; Colwell, Rick S.

    2004-06-01

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center (INTEC) at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  13. Trace Metals in Groundwater & the Vadose Zone Calcite: In Situ Containment & Stabilization of Strontium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.

    2004-12-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  14. Microbial reduction of hexavalent Chromium under vadose zone conditions

    Energy Technology Data Exchange (ETDEWEB)

    Oliver, D S.(unknown); Brockman, Fred J.(BATTELLE (PACIFIC NW LAB)); Bowman, Robert (VISITORS); Kieft, Thomas L.(BATTELLE (PACIFIC NW LAB))

    2003-01-01

    Hexavalent chromium[Cr(VI)] is a common constituent of wastes associated with nuclear reactor operation and fuel processing. Improper disposal at facilities in arid and semi-arid regions has led to contamination of underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) contamination using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those found in the vadose zone, and to evaluate the potential for enhancing biological reduction of Cr(VI) through the addition of nutrients. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic carbon (molasses). Nutrient amendments resulted in up to 87% Cr(VI) reduction in unsaturated batch experiments. Molasses and nitrate additions to 15-cm length unsaturated flow columns receiving 65 mg L-1 Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-day experiment. All of the immobilized Cr was in the form of Cr (III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy; and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  15. Trace Metals in Groundwater & Vadose Zone Calcite: In Situ Containment & Stabilization of Stronthium-90 & Other Divalent Metals & Radionuclides at Arid West DOE

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W

    2003-06-01

    Radionuclide and metal contaminants such as strontium-90 are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., strontium-90) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for recapture in a more stable solid phase (co-precipitation rather than adsorption). Our specific research objectives include: * Elucidation of the mechanisms and rates for the release of sorbed trace metals and their subsequent sequestration by co-precipitation in calcite induced by urea hydrolysis. * Evaluation at the field scale of the influence of

  16. Vadose Zone Transport Field Study: Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Andy L.; Conrad, Mark E.; Daily, William D.; Fink, James B.; Freedman, Vicky L.; Gee, Glendon W.; Hoversten, Gary M.; Keller, Jason M.; Majer, Ernest L.; Murray, Christopher J.; White, Mark D.; Yabusaki, Steven B.; Zhang, Z. F.

    2006-07-31

    From FY 2000 through FY 2003, a series of vadose zone transport field experiments were conducted as part of the U.S. Department of Energy’s Groundwater/Vadose Zone Integration Project Science and Technology Project, now known as the Remediation and Closure Science Project, and managed by the Pacific Northwest National Laboratory (PNNL). The series of experiments included two major field campaigns, one at a 299-E24-11 injection test site near PUREX and a second at a clastic dike site off Army Loop Road. The goals of these experiments were to improve our understanding of vadose zone transport processes; to develop data sets to validate and calibrate vadose zone flow and transport models; and to identify advanced monitoring techniques useful for evaluating flow-and-transport mechanisms and delineating contaminant plumes in the vadose zone at the Hanford Site. This report summarizes the key findings from the field studies and demonstrates how data collected from these studies are being used to improve conceptual models and develop numerical models of flow and transport in Hanford’s vadose zone. Results of these tests have led to a better understanding of the vadose zone. Fine-scale geologic heterogeneities, including grain fabric and lamination, were observed to have a strong effect on the large-scale behavior of contaminant plumes, primarily through increased lateral spreading resulting from anisotropy. Conceptual models have been updated to include lateral spreading and numerical models of unsaturated flow and transport have revised accordingly. A new robust model based on the concept of a connectivity tensor was developed to describe saturation-dependent anisotropy in strongly heterogeneous soils and has been incorporated into PNNL’s Subsurface Transport Over Multiple Phases (STOMP) simulator. Application to field-scale transport problems have led to a better understanding plume behavior at a number of sites where lateral spreading may have dominated waste

  17. Preliminary study of radioactive waste disposal in the vadose zone

    Energy Technology Data Exchange (ETDEWEB)

    1978-09-01

    To investigate the characteristics of the vadose zone with respect to radioactive waste disposal, the mechanics of unsaturated flow in arid regions and the geohydrology of four areas with a deep water table were studied. The studies indicated that (1) arid sites with a water table deeper than 200 m can be found in at least three distinct geologic settings in the western United States, (2) the physics of unsaturated flow in soils and rock with interstitial porosity at low water contents, particularly under thermal gradients, is not yet completely understood, and (3) under certain conditions unsaturated flow can be so slow that analytic modeling of an unflawed repository is unnecessary to prove effective containment.

  18. Calibrating Vadose Zone Models with Time-Lapse Gravity Data

    DEFF Research Database (Denmark)

    Christiansen, Lars; Hansen, A. B.; Looms, M. C.

    2009-01-01

    hydrogeological parameters. These studies focused on the saturated zone with specific yield as the most prominent target parameter. Any change in storage in the vadose zone has been considered as noise. Our modeling results show a measureable change in gravity from the vadose zone during a forced infiltration...... experiment on 10m by 10m grass land. Simulation studies show a potential for vadose zone model calibration using gravity data in conjunction with other geophysical data, e.g. cross-borehole georadar. We present early field data and calibration results from a forced infiltration experiment conducted over 30...... days and discuss the potential for gravity measurements in vadose zone model parameter estimation....

  19. Optimization of remediation strategies using vadose zone monitoring systems

    Science.gov (United States)

    Dahan, Ofer

    2016-04-01

    In-situ bio-remediation of the vadose zone depends mainly on the ability to change the subsurface hydrological, physical and chemical conditions in order to enable development of specific, indigenous, pollutants degrading bacteria. As such the remediation efficiency is much dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. These conditions are usually determined in laboratory experiments where parameters such as the chemical composition of the soil water solution, redox potential and water content of the sediment are fully controlled. Usually, implementation of desired optimal degradation conditions in deep vadose zone at full scale field setups is achieved through infiltration of water enriched with chemical additives on the land surface. It is assumed that deep percolation into the vadose zone would create chemical conditions that promote biodegradation of specific compounds. However, application of water with specific chemical conditions near land surface dose not necessarily results in promoting of desired chemical and hydraulic conditions in deep sections of the vadose zone. A vadose-zone monitoring system (VMS) that was recently developed allows continuous monitoring of the hydrological and chemical properties of deep sections of the unsaturated zone. The VMS includes flexible time-domain reflectometry (FTDR) probes which allow continuous monitoring of the temporal variation of the vadose zone water content, and vadose-zone sampling ports (VSPs) which are designed to allow frequent sampling of the sediment pore-water and gas at multiple depths. Implementation of the vadose zone monitoring system in sites that undergoes active remediation provides real time information on the actual chemical and hydrological conditions in the vadose zone as the remediation process progresses. Up-to-date the system has been successfully implemented in several studies on water flow and contaminant transport in

  20. Deficiencies in Vadose Zone Understanding at the INEEL

    Energy Technology Data Exchange (ETDEWEB)

    Wood, Thomas Ronald; Bates, Dona Louise; Bishop, Carolyn Wagoner; Heard, Robert Eugene; Hubbell, Joel Michael; Hull, Laurence Charles; Lehman, Richard Michael; Magnuson, Swen O; Mattson, Earl Douglas; Mccarthy, James Michael; Porro, Indrek; Ritter, Paul David; Roddy, Michael Scott; Singler, Robert Edward; Smith, Richard Paul

    2000-08-01

    Subsurface contamination in the vadose zone, that portion of the subsurface pathway between land surface and an underlying aquifer, poses environmental problems at the Idaho National Engineering and Environmental Laboratory (INEEL) in eastern Idaho and across the U.S. Department of Energy complex. Assessing potential adverse impacts from these contaminated sites requires an understanding of the mechanisms controlling contaminant transport. Currently, vadose zone experts at the INEEL cannot with confidence predict the movement of water and contaminants in the complex, heterogeneous, fractured subsurface at the INEEL, especially within the vadose zone. In the draft version (Revision 1) of the Vadose Zone Deficiencies document, deficiencies in scientific understanding of flow and transport processes in the vadose zone at the INEEL were identified and grouped into 13 categories and recommendations were provided to address each of the deficiencies. The draft document provided the basis for an INEEL Vadose Zone Workshop that was conducted October 20 and 21, 1999, in Idaho Falls, Idaho. The workshop was conducted to group and rank the previously identified deficiencies and for the subsequent development of science plans to address the deficiencies that limit reliable predictions of water and contaminant movement in the subsurface. The workshop participants, comprising INEEL and scientists and project managers and non-INEEL scientists knowledgeable about the vadose zone, developed science- and technology-based recommendations derived through a series of technical sessions at the workshop. In this document, the final version of the Vadose Zone Deficiencies document, the draft document has been incorporated, largely intact, as well as the results from the workshop. The workshop participants grouped the deficiencies in vadose zone understanding at the INEEL into seven categories. These seven categories will be the focus areas of five science plans that are being developed to

  1. Characterizing Organic-Liquid Sources in the Vadose Zone

    Science.gov (United States)

    Brusseau, M. L.; Truex, M.; Mainhagu, J.; Morrison, C.; Oostrom, M.; Carroll, K. C.; Yeh, T.

    2010-12-01

    There are two primary concerns associated with sites that contain contaminant sources located in the vadose zone. First, discharge of contaminant vapor from the vadose-zone source may impact the underlying groundwater. This could contribute to overall risk posed by the site, and delay attainment of groundwater cleanup goals. Second, contaminant vapor from the vadose-zone source may migrate to the land surface and transfer into buildings, thereby causing vapor intrusion. The decision to require remediation of a vadose-zone source zone is typically based on assessing the potential impact of the vadose-zone source on groundwater or vapor intrusion. Concomitantly, setting appropriate vadose-zone remediation goals once the decision is made, as well as evaluating attainment of these remediation goals, requires evaluating these persistent sources in terms of their impact on groundwater remediation goals or vapor-intrusion concerns. These issues are of particular relevance for soil-vapor extraction (SVE), which is the presumptive remedy for vadose-zone systems contaminated by chlorinated solvents. Characterizing the impact of vadose-zone contaminant sources on groundwater or vapor intrusion requires determination of the contaminant mass discharge from the source. A vadose-zone characterization technology is presented that can provide direct measures of vapor-phase contaminant mass discharge, characterize mass-transfer conditions, and provide a higher resolution characterization of the source distribution. This technology is a combination of two recently developed methods (vapor-phase mass discharge method and vapor-phase tomography) and two existing methods (pneumatic tomography and tracer tomography). The technology is designed to be used in a tiered approach that is sensitive to associated cost-benefits, and is responsive to specific requirements of the site. Example applications are presented.

  2. ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.

  3. Optimization of Remediation Conditions using Vadose Zone Monitoring Technology

    Science.gov (United States)

    Dahan, O.; Mandelbaum, R.; Ronen, Z.

    2010-12-01

    Success of in-situ bio-remediation of the vadose zone depends mainly on the ability to change and control hydrological, physical and chemical conditions of subsurface. These manipulations enables the development of specific, indigenous, pollutants degrading bacteria or set the environmental conditions for seeded bacteria. As such, the remediation efficiency is dependent on the ability to implement optimal hydraulic and chemical conditions in deep sections of the vadose zone. Enhanced bioremediation of the vadose zone is achieved under field conditions through infiltration of water enriched with chemical additives. Yet, water percolation and solute transport in unsaturated conditions is a complex process and application of water with specific chemical conditions near land surface dose not necessarily result in promoting of desired chemical and hydraulic conditions in deeper sections of the vadose zone. A newly developed vadose-zone monitoring system (VMS) allows continuous monitoring of the hydrological and chemical properties of the percolating water along deep sections of the vadose zone. Implementation of the VMS at sites that undergoes active remediation provides real time information on the chemical and hydrological conditions in the vadose zone as the remediation process progresses. Manipulating subsurface conditions for optimal biodegradation of hydrocarbons is demonstrated through enhanced bio-remediation of the vadose zone at a site that has been contaminated with gasoline products in Tel Aviv. The vadose zone at the site is composed of 6 m clay layer overlying a sandy formation extending to the water table at depth of 20 m bls. The upper 5 m of contaminated soil were removed for ex-situ treatment, and the remaining 15 m vadose zone is treated in-situ through enhanced bioremedaition. Underground drip irrigation system was installed below the surface on the bottom of the excavation. Oxygen and nutrients releasing powder (EHCO, Adventus) was spread below the

  4. Vadose Zone Transport Field Study: FY 2002 Status Report

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Anderson L.; Gee, Glendon W.; Zhang, Z. F.; Keller, Jason M.

    2003-01-02

    This work reported here is part of the U. S. Department of Energy’s Science and Technology Initiative to develop improved conceptual models of flow and transport in the vadose zone, particularly for the Hanford Site, Washington. The National Academy of Sciences has identified significant knowledge gaps in conceptual model development as one reason for discovery of subsurface contamination in unexpected places. Inadequate conceptualizations limits, not only the understanding of long-term fate and transport, but also the selection and design of remediation technologies. Current conceptual models are limited partly because they do not account for the random heterogeneity that occurs under the extremes of very nonlinear flow behavior typical of the Hanford vadose zone. A major improvement in conceptual modeling of the Hanford vadose zone includes a better understanding and description of soil anisotropy, a property that appears to control much of the subsurface flow and transport in layered sediments at the Hanford Site.

  5. Continuous monitoring of water flow and solute transport using vadose zone monitoring technology

    Science.gov (United States)

    Dahan, O.

    2009-04-01

    contaminant transport in various hydrological and geological setups. These include floodwater infiltration in arid environments, land use impact on groundwater quality, and control of remediation process in a contaminated vadose zone. The data which is collected by the VMS allows direct measurements of flow velocities and fluxes in the vadose zone while continuously monitoring the chemical evolution of the percolating water. While real time information on the hydrological and chemical properties of the percolating water in the vadose is essential to prevent groundwater contamination it is also vital for any remediation actions. Remediation of polluted soils and aquifers essentially involves manipulation of surface and subsurface hydrological, physical and biochemical conditions to improve pollutant attenuation. Controlling the biochemical conditions to enhance biodegradation often includes introducing degrading microorganisms, applying electron donors or acceptors, or adding nutrients that can promote growth of the desired degrading organisms. Accordingly real time data on the hydrological and chemical properties of the vadose zone may be used to select remediation strategies and determine its efficiency on the basis of real time information.

  6. SEQUESTRATION AND TREATMENT OF VADOSE ZONE SOLVENTS USING EDIBLE OILS

    Energy Technology Data Exchange (ETDEWEB)

    Riha, B; Brian02 Looney, B; Richard Hall (NOEMAIL), R

    2008-03-28

    Edible oils have emerged as an effective treatment amendment for a variety of contaminants. When applied to chlorinated volatile organic compounds (cVOCs) in the saturated zone, edible oils have been shown to enhance anaerobic bioremediation and sequester the contaminants. However, edible oils have not been applied to the vadose zone for contaminant treatment. Soybean oil was injected into the vadose zone in M-Area at the Department of Energy's (DOE) Savannah River Site (SRS) as a research study to evaluate the effectiveness of edible oils for solvent sequestration and the ability to change a vadose system from aerobic to anaerobic to initiate reductive dechlorination. The proposed use of this technique would be an enhanced attenuation/transition step after active remediation. The goals of the research were to evaluate oil emplacement methods and monitoring techniques to measure oil placement, partitioning and degradation. Gas sampling was the cornerstone for this evaluation. Analyses for cVOCs and biotransformation products were performed. Overall, the cVOC concentration/flux reduction was 75-85% in this vadose zone setting. Destruction of the cVOCs by biotic or abiotic process has not yet been verified at this site. No reductive dechlorination products have been measured. The deployment has resulted in a substantial generation of light hydrocarbon gases and geochemical conditions that would support cometabolism.

  7. Effects of remediation amendments on vadose zone microorganisms

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Hannah M.; Tilton, Fred A.

    2012-08-10

    Surfactant-based foam delivery technology has been studied to remediate Hanford 200 area deep vadose zone sediment. However, the surfactants and remediation amendments have an unknown effect on indigenous subsurface microorganisms. Microbial populations are important factors to consider in remediation efforts due to their potential to alter soil geochemistry. This project focuses on measuring microbial metabolic responses to remediation amendments in batch and column studies using Deep Vadose Zone Sediments. Initial studies of the microbes from Hanford 200 area deep vadose zone sediment showed surfactants sodium dodecyl sulfate (SDS) and cocamidopropyl betaine (CAPB) and remediation amendment calcium polysulfide (CPS) had no affect on microbial growth using BiologTM Ecoplates. To move towards a more realistic field analog, soil columns were packed with Hanford 200 Area sediment. Once microbial growth in the column was verified by observing growth of the effluent solution on tryptic soy agar plates, remedial surfactants were injected into the columns, and the resulting metabolic diversity was measured. Results suggest surfactant sodium dodecyl sulfate (SDS) stimulates microbial growth. The soil columns were also visualized using X-ray microtomography to inspect soil packing and possibly probe for evidence of biofilms. Overall, BiologTM Ecoplates provide a rapid assay to predict effects of remediation amendments on Hanford 200 area deep vadose zone microorganisms.

  8. Transport and degradation of contaminants in the vadose zone

    NARCIS (Netherlands)

    Schotanus, D.

    2013-01-01

    Leaching of contaminants from the vadose zone to the groundwater depends on the soil properties and the infiltration rate. In this thesis, organic degradable contaminants were studied, such as de-icing chemicals (consisting of propylene glycol, PG) and pesticides. Heterogeneous soil properties lead

  9. Vadose zone-attenuated artificial recharge for input to a ground water model.

    Science.gov (United States)

    Nichols, William E; Wurstner, Signe K; Eslinger, Paul W

    2007-01-01

    Accurate representation of artificial recharge is requisite to calibration of a ground water model of an unconfined aquifer for a semiarid or arid site with a vadose zone that imparts significant attenuation of liquid transmission and substantial anthropogenic liquid discharges. Under such circumstances, artificial recharge occurs in response to liquid disposal to the vadose zone in areas that are small relative to the ground water model domain. Natural recharge, in contrast, is spatially variable and occurs over the entire upper boundary of a typical unconfined ground water model. An improved technique for partitioning artificial recharge from simulated total recharge for inclusion in a ground water model is presented. The improved technique is applied using data from the semiarid Hanford Site. From 1944 until the late 1980s, when Hanford's mission was the production of nuclear materials, the quantities of liquid discharged from production facilities to the ground vastly exceeded natural recharge. Nearly all hydraulic head data available for use in calibrating a ground water model at this site were collected during this period or later, when the aquifer was under the diminishing influence of the massive water disposals. The vadose zone is typically 80 to 90 m thick at the Central Plateau where most production facilities were located at this semiarid site, and its attenuation of liquid transmission to the aquifer can be significant. The new technique is shown to improve the representation of artificial recharge and thereby contribute to improvement in the calibration of a site-wide ground water model.

  10. Calibrating vadose zone models with time-lapse gravity data

    DEFF Research Database (Denmark)

    Christiansen, Lars; Binning, Philip John; Rosbjerg, Dan

    2011-01-01

    The vadose zone plays an important role in the hydrologic cycle. Various geophysical methods can determine soil water content variations in time and space in volumes ranging from a few cubic centimeters to several cubic meters. In contrast to the established methods, time-lapse gravity measurements...... of changes in soil water content do not rely on a petrophysical relationship between the measured quantity and the water content but give a direct measure of the mass change in the soil. Only recently has the vadose zone been systematically incorporated when ground-based gravity data are used to infer...... hydrologic information. In this study, changes in the soil water content gave rise to a measurable signal in a forced infiltration experiment on a 107-m2 grassland area. Time-lapse gravity data were able to constrain the van Genuchten soil hydraulic parameters in both a synthetic example and a field...

  11. Microbial reduction of hexavalent chromium under vadose zone conditions.

    Science.gov (United States)

    Oliver, Douglas S; Brockman, Fred J; Bowman, Robert S; Kieft, Thomas L

    2003-01-01

    Hexavalent chromium [Cr(VI)] is a common contaminant associated with nuclear reactors and fuel processing. Improper disposal at facilities in and and semiarid regions has contaminated underlying vadose zones and aquifers. The objectives of this study were to assess the potential for immobilizing Cr(VI) using a native microbial community to reduce soluble Cr(VI) to insoluble Cr(III) under conditions similar to those in the vadose zone, and to evaluate the potential for enhancing biological Cr(VI) reduction through nutrient addition. Batch microcosm and unsaturated flow column experiments were performed. Native microbial communities in subsurface sediments with no prior Cr(VI) exposure were shown to be capable of Cr(VI) reduction. In both the batch and column experiments, Cr(VI) reduction and loss from the aqueous phase were enhanced by adding high levels of both nitrate (NO3-) and organic C (molasses). Nutrient amendments resulted in up to 87% reduction of the initial 67 mg L(-1) Cr(VI) in an unsaturated batch experiment. Molasses and nitrate additions to 15 cm long unsaturated flow columns receiving 65 mg L(-1) Cr(VI) resulted in microbially mediated reduction and immobilization of 10% of the Cr during a 45-d experiment. All of the immobilized Cr was in the form of Cr(III), as shown by XANES analysis. This suggests that biostimulation of microbial Cr(VI) reduction in vadose zones by nutrient amendment is a promising strategy, and that immobilization of close to 100% of Cr contamination could be achieved in a thick vadose zone with longer flow paths and longer contact times than in this experiment.

  12. Trace Metals in Groundwater and Vadose Zone Calcite: In Situ Containment and Stabilization of Stronthium-90 and Other Divalent Metals and Radionuclides at Arid Western DOE Sites: Final Report for Award Number DE-FG07-02ER63486 to the University of Idaho (RW Smith) Environmental Management Science Program Project Number 87016

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko

    2007-11-07

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) energy research and weapons complex. In situ containment and stabilization of these contaminants represents a cost-effective treatment strategy that minimizes workers’ exposure to hazardous substances, does not require removal or transport of contaminants, and generally does not generate a secondary waste stream. We have investigated an in situ bioremediation approach that immobilizes radionuclides or contaminant metals (e.g., strontium-90) by their microbially facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Calcite, a common mineral in many aquifers and vadose zones in the arid west, can incorporate divalent metals such as strontium, cadmium, lead, and cobalt into its crystal structure by the formation of a solid solution. Collaborative research undertaken by the Idaho National Laboratory (INL), University of Idaho, and University of Toronto as part of this Environmental Management Science Program project has focused on in situ microbially-catalyzed urea hydrolysis, which results in an increase in pH, carbonate alkalinity, ammonium, calcite precipitation, and co-precipitation of divalent cations. In calcite-saturated aquifers, microbially facilitated co-precipitation with calcium carbonate represents a potential long-term contaminant sequestration mechanism. Key results of the project include: **Demonstrating the linkage between urea hydrolysis and calcite precipitation in field and laboratory experiments **Observing strontium incorporation into calcite precipitate by urea hydrolyzers with higher distribution coefficient than in abiotic **Developing and applying molecular methods for characterizing microbial urease activity in groundwater including a quantitative PCR method for enumerating ureolytic bacteria **Applying the suite of developed molecular methods to assess the feasibility of the

  13. Effect of vadose zone on the steady-state leakage rates from landfill barrier systems.

    Science.gov (United States)

    Celik, B; Rowe, R K; Unlü, K

    2009-01-01

    Leakage rates are evaluated for a landfill barrier system having a compacted clay liner (CCL) underlain by a vadose zone of variable thickness. A numerical unsaturated flow model SEEP/W is used to simulate the moisture flow regime and steady-state leakage rates for the cases of unsaturated zones with different soil types and thicknesses. The results of the simulations demonstrate that harmonic mean hydraulic conductivity of coarse textured vadose zones is 3-4 orders of magnitude less than saturated hydraulic conductivity; whereas, the difference is only one order of magnitude for fine textured vadose zones. For both coarse and fine textured vadose zones, the effective hydraulic conductivity of the barrier system and the leakage rate to an underlying aquifer increases with increasing thickness of the vadose zone and ultimately reaches an asymptotic value for a coarse textured vadose zone thickness of about 10m and a fine textured vadose zone thickness of about 5m. Therefore, the fine and coarse textured vadose zones thicker than about 5m and 10m, respectively, act as an effective part of the barrier systems examined. Although the thickness of vadose zone affects the effective hydraulic conductivity of the overall barrier system, the results demonstrated that the hydraulic conductivity of the CCL is the dominant factor controlling the steady-state leakage rates through barrier systems having single low permeability clay layers.

  14. A Catalog of Vadose Zone Hydraulic Properties for the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, Eugene J.; Khaleel, Raziuddin; Heller, Paula R.

    2001-09-24

    The purpose of this catalog is to integrate all available soil physics data and information from vadose zone characterization and performance assessments into one useable, scientifically defensible document.

  15. Tank waste remediation system vadose zone program plan

    Energy Technology Data Exchange (ETDEWEB)

    Fredenburg, E.A.

    1998-07-27

    The objective of the vadose zone characterization under this program is to develop a better conceptual geohydrologic model of identified tank farms which will be characterized so that threats to human health and the environment from past leaks and spills, intentional liquid discharges, potential future leaks during retrieval, and from residual contaminants that may remain in tank farms at closure can be explicitly addressed in decision processes. This model will include geologic, hydrologic, and hydrochemical parameters as defined by the requirements of each of the TWRS programs identified here. The intent of this TWRS Vadose Zone Program Plan is to provide justification and an implementation plan for the following activities: Develop a sufficient understanding of subsurface conditions and transport processes to support decisions on management, cleanup, and containment of past leaks, spills, and intentional liquid discharges; Develop a sufficient understanding of transport processes to support decisions on controlling potential retrieval leaks; Develop a sufficient understanding of transport processes to support decisions on tank farm closure, including allowable residual waste that may remain at closure; and Provide new information on geotechnical properties in the 200 Area to supplement data used for design and performance assessment for immobilized low-activity waste disposal facilities.

  16. From Field- to Landscape-Scale Vadose Zone Processes: Scale Issues, Modeling, and Monitoring

    NARCIS (Netherlands)

    Corwin, D.L.; Hopmans, J.; Rooij, de G.H.

    2006-01-01

    Modeling and monitoring vadose zone processes across multiple scales is a fundamental component of many environmental and natural resource issues including nonpoint source (NPS) pollution, watershed management, and nutrient management, to mention just a few. In this special section in Vadose Zone Jo

  17. Summary of Vadose -- Zone Conceptual Models for Flow and Contaminant Transport and 1999 - 2003 Progress on Resolving Deficiencies in Understanding the Vadose Zone at the INEEL

    Energy Technology Data Exchange (ETDEWEB)

    Robert C. Starr; Dana L. Dettmers; Brennon R. Orr; Thomas R. Wood

    2003-12-01

    The thick vadose zone that underlies the Idaho National Engineering and Environmental Laboratory has been recognized both as an avenue through which contaminants disposed at or near the ground surface can migrate to groundwater in the underlying Eastern Snake River Plain aquifer, and as a barrier to the movement of contaminants into the aquifer. Flow and contaminant transport in the vadose zone at the INEEL is complicated by the highly heterogeneous nature of the geologic framework and by the variations in the behavior of different contaminants in the subsurface. The state of knowledge concerning flow and contaminant transport in the vadose zone at and near the INEEL IN 1999 was summarized in Deficiencies in Vadose Zone Understanding at the Idaho National Engineering and Environmental Laboratory (Wood et al., 2000). These authors identified deficiencies in knowledge of flow and contaminant transport processes in the vadose zone, and provided recommendations for additional work that should be conducted to address these deficiencies. In the period since (Wood et al., 2000) was prepared, research has been published that, to some degree, address these deficiencies. This document provides a bibliography of reports, journal articles, and conference proceedings published 1999 through mid-2003 that are relevant to the vadose zone at or near the INEEL and provides a brief description of each work. Publications that address specific deficiencies or recommendations are identified, and pertinent information from selected publications is presented.

  18. Vadose Zone Weathering Rates Inferred from U-Series Disequilibrium

    Science.gov (United States)

    Maher, K.; Depaolo, D. J.; Steefel, C.; Christensen, J. N.

    2003-12-01

    The U-series isotope system can be used to quantify reaction rates in aquifers and thick vadose zone environments. The approach is based on the α -recoil of 234Th atoms across grain boundaries, which enriches the pore fluid in 234U. Dissolution of the solid phase releases mainly 238U to the pore fluid, so that the 234U/238U activity ratio of the pore fluid is a measure of the local ratio of the dissolution U flux to the α -recoil flux. The interpretation of U-series disequilibrium in weathering environments depends on the α -recoil flux, which is highly dependent on both the distribution of U and the grain size distribution of the soil. The recoil length of the 234Th atom in a silicate is approximately 700 Å, therefore the fine-grained material, with a greater surface area to volume ratio, contributes a significant amount of the 234U to the porewater. As a result, estimates of the recoil flux based on the mean grain size may under predict the supply of 234U by over an order of magnitude. In order to quantify the reaction rate, this recoil flux must be accurately measured by consideration of the recoil contribution of the fine-grained material, despite the fact that it may only comprise a small fraction of the total mass of the sediment. U concentrations and high precision isotope measurements (234U/238U) of pore fluids, mineral separates, and grain size intervals are used to constrain reaction rates for a 70 m vadose zone core from eastern Washington State. The pore water 234U/238U activity ratios range from 1.04 to 1.20 in the pore fluids, and from 0.94 to 1.0 in the various size fractions. Data from the solid phases is used to construct a predictive model for α -recoil flux in heterogeneous soil. The calculated recoil loss, which considers each grain size interval, is up to 7 times greater than for a geometric prediction based on the mean grain size. The measured 234U/238U ratios for the vadose zone, in conjunction with the estimates for the a-recoil flux

  19. EVALUATION OF VADOSE ZONE TREATMENT TECHNOLOGIES TO IMMOBILIZE TECHNETIUM-99

    Energy Technology Data Exchange (ETDEWEB)

    PETERSEN, S.W.

    2006-03-15

    The Hanford Site End State Vision document (DOE/RL-2003-59) states: ''There should be an aggressive plan to develop technology for remediation of the contamination that could get to the groundwater (particularly the technetium [{sup 99}Tc])''. In addition, there is strong support from the public and regulatory agencies for the above statement, with emphasis on investigation of treatment alternatives. In July 2004, PNNL completed a preliminary evaluation of remediation technologies with respect to their effectiveness and implementability for immobilization of {sup 99}Tc beneath the BC Cribs in the 200 West Area (Truex, 2004). As a result of this evaluation, PNNL recommended treatability testing of in situ soil desiccation, because it has the least uncertainty of those technologies evaluated in July 2004 (Treatability Test Outline, September 30, 2004). In 2005, DOE-RL and Fluor Hanford convened an independent technical panel to review alternative remediation technologies, including desiccation, at a three-day workshop in Richland, Washington. The panel was composed of experts in vadose-zone transport, infiltration control, hydrology, geochemistry, environmental engineering, and geology. Their backgrounds include employment in academia, government laboratories, industry, and consulting. Their review, presented in this document, is based upon written reports from Hanford, oral presentations from Hanford staff, and each panel members' years of experience in their particular field of expertise. The purpose of this report is to document the panel's evaluation of various treatment alternatives with potential for minimizing contaminant migration in the deep vadose zone at the Department of Energy Hanford Site. The panel was tasked with assessing the most viable and practical approach and making recommendations for testing. The evaluation of vadose-zone treatment alternatives was conducted to be broadly applicable at a variety of locations at

  20. An alternative tensiometer design for deep vadose zone monitoring

    Science.gov (United States)

    Moradi, A. B.; Kandelous, M. M.; Hopmans, J. W.

    2015-12-01

    The conventional tensiometer is among the most accurate devices for soil water matric potential measurements, as well as for estimations of soil water flux from soil water potential gradients. Uncertainties associated with conventional tensiometers such as caused by ambient temperature effects and the draining of the tensiometer tube, as well as their limitation for deep soil monitoring has prevented their widespread use for vadose zone monitoring, despite their superior accuracy, in general. We introduce an alternative tensiometer design that offers the accuracy of the conventional tensiometer, while minimizing afore-mentioned uncertainties and limitations. The proposed alternative tensiometer largely eliminates temperature-induced diurnal fluctuations and uncertainties associated with the draining of the tensiometer tube, and removes the limitation in installation depth. In addition, the manufacturing costs of this alternative tensiometer design is close to that of the conventional tensiometer, while it is especially suited for monitoring of soil water potential gradients as required for soil water flux measurements.

  1. Vadose Zone Modeling Workshop proceedings, March 29--30, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Khaleel, R.

    1993-08-01

    At the Hanford Site, the record of decision for remediation of CERCLA sites is largely based on results of the baseline risk and performance assessment of the remedial action alternatives. These assessments require the ability to predict the fate and transport of contaminants along appropriate exposure pathways which, in case of the Hanford Site, includes the migration of contaminants through the vadose zone to the water table. Listed below are some of the requirements, as prescribed by the regulators, relative to CERCLA risk and performance assessment at Hanford. A workshop was organized by the Environmental Risk and Performance Assessment Group, Westinghouse Hanford Company on March 29--30, 1993 at the Richland Best Western Tower Inn. During the workshop, an assessment was made of the need for and scope of various tasks being conducted or planned as part of the Hanford Site waste isolation performance assessment/risk assessment activities. Three external, nationally-recognized experts served as part of a review panel for the workshop: (a) Professor Lynn Gelhar of MIT; (b) Professor Peter Wierenga of University of Arizona; and (c) Dr. Rien van Genuchten of US Salinity Laboratory, Riverside, California. The technical experts provided their perspectives on the current state-of-the-art in vadose zone flow and transport modeling. In addition, the technical experts provided an outside independent assessment of the work being performed or planned in support of various activities identified in TPA Milestone M-29-02. This document includes the following: Recommendations from the three peer reviewers; areas of expertise of the three peer reviewers; workshop agenda; copies of viewgraphs (where available) from presenters at the workshop; workshop minutes; and list of workshop attendees.

  2. Characterization of Direct Push Vadose Zone Sediments from the T and TY Waste Management Areas

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Valenta, Michelle M.; Serne, R. Jeffrey; Bjornstad, Bruce N.; Lanigan, David C.; Iovin, Cristian; Clayton, Ray E.; Geiszler, Keith N.; Clayton, Eric T.; Kutnyakov, Igor V.; Baum, Steven R.; Lindberg, Michael J.; Orr, Robert D.

    2007-06-08

    This report contains all the geochemical and selected physical characterization data collected on vadose zone sediment recovered from 5 direct push characterization holes emplaced to investigate vadose zone contamination associated with leaks from tanks 241-TY-105 (UPR-200-W-152) and 241-TY-106 (UPR-200-W-153). Tank 241-TY-105 is estimated to have leaked 35,000 gal of tributyl phosphate (TBP) waste from the uranium recovery process to the vadose zone in 1960. Tank 241-TY-106 is estimated to have leaked 20,000 gal of TBP-uranium recovery waste to the vadose zone in 1959. Although several drywells in the vicinity of tank 241-TY-106 contain measurable quantities of cesium-137 and/or cobalt-60, their relatively low concentrations indicate that the contaminant inventory in the vadose zone around tank 241-TY-106 is quite small. Additionally, this report contains all the geochemical and selected physical characterization data collected on vadose zone sediment recovered from 7 direct push characterization holes emplaced to investigate vadose zone contamination associated with an overfill event and leak from tank 241-T-101.

  3. Organic Carbon Inventories and Vertical Fluxes Through the Vadose Zone into Groundwater at the Rifle, Colorado River Floodplain Site

    Science.gov (United States)

    Tokunaga, T. K.; Wan, J.; Dong, W.; Williams, K. H.; Robbins, M.; Kim, Y.; Faybishenko, B.; Conrad, M. E.; Christensen, J. N.; Gilbert, B.; Dayvault, R. D.; Long, P. E.; Hubbard, S. S.

    2013-12-01

    Understanding carbon inventories and fluxes within the vadose zone and groundwater of semi-arid regions is challenging because of their typically deep profiles, moderately low soil organic carbon (SOC) inventories, low dissolved organic carbon (DOC) fluxes, and slow changes in soil inorganic carbon (SIC) inventories. The remediated uranium/vanadium mill tailings site situated on a floodplain at Rifle, Colorado possesses a number of characteristics that facilitate investigation of subsurface carbon fluxes. These include locally derived fill soil having SOC and SIC concentrations representative of the region, established vegetation cover (perennial grasses and shrubs) on the fill, boundaries between the fill and underlying alluvium distinguishable through concentrations of SIC and other chemical components, predictable groundwater flow and interaction with the adjacent Colorado River, and a clearly delineated impermeable lower boundary (Wasatch Formation shale) at depths ranging from 6 to 7.5 m. Environmental characteristics of this site permit year-round sampling of both pore water and pore gas throughout most of the moderately deep (~ 3.5 m) vadose zone. Within this well-defined hydrological system, we recently installed a suite of tensiometers, pore water (vadose zone and groundwater) samplers, gas samplers, and neutron probe access tubes at three sites along a transect aligned with the groundwater flow direction in order to determine inventories and fluxes of water, carbon, and other components. The tensiometer and piezometer measurements are revealing impacts of infiltration and groundwater recharge events, evapotranspiration, and capillary fringe-groundwater interactions. The results of pore water analyses are showing relatively high concentrations of DOC (up to 4 mM) in the vadose zone, and particulate organic carbon (POC) mobile in the capillary fringe. Differences in DOC characteristics are being determined using a variety of analytical techniques. Hydraulic

  4. A vadose zone water fluxmeter with divergence control

    Science.gov (United States)

    Gee, G. W.; Ward, A. L.; Caldwell, T. G.; Ritter, J. C.

    2002-08-01

    Unsaturated water flux densities are needed to quantify water and contaminant transfer within the vadose zone. However, water flux densities are seldom measured directly and often are predicted with uncertainties of an order or magnitude or more. A water fluxmeter was designed, constructed, and tested to directly measure drainage fluxes in field soils. The fluxmeter was designed to minimize divergence. It concentrates flow into a narrow sensing region filled with a fiberglass wick. The wick applies suction, proportional to its length, and passively drains the meter. The meter can be installed in an augured borehole at almost any depth below the root zone. Water flux through the meter is measured with a self-calibrating tipping bucket, with a sensitivity of ~4 mL tip-1. For our meter this is equivalent to detection limit of ~0.1 mm. Passive-wick devices previously have not properly corrected for flow divergence. Laboratory measurements supported predictions of a two-dimensional (2-D) numerical model, which showed that control of the collector height H and knowledge of soil hydraulic properties are required for improving divergence control, particularly at fluxes below 1000 mm yr-1. The water fluxmeter is simple in concept, is inexpensive, and has the capability of providing continuous and reliable monitoring of unsaturated water fluxes ranging from less than 1 mm yr-1 to more than 1000 mm yr-1.

  5. Data Assimilation for Vadose Zone Flow Modeling Using the Ensemble Kalman Filter

    Science.gov (United States)

    Zhang, Y.; Schaap, M. G.; Zha, Y.; Xue, L.

    2015-12-01

    The natural system is open and complex and the hydraulic parameters needed for describing flow and transport in the vadose zone are often poorly known, making it prone to multiple interpretations, mathematical descriptions and uncertainty. Quite often a reasonable "handle" on a sites flow characteristics can be gained only through direct observation of the flow processes itself, determination of the spatial- and probability distributions of material properties combined with computationally expensive inversions of the Richards equation. In groundwater systems, the ensemble Kalman filter (EnKF) has proven to be an effective alternative to model inversions by assimilating observations directly into an ensemble of groundwater models from which time and/or space-variable variable probabilistic quantities of the flow process can be derived. Application of EnKF to Richards equation-type unsaturated flow problems, however, is more challenging than in groundwater systems because the relation of state and model parameters is strongly nonlinear. In addition, the type of functional dependence of moisture content and hydraulic conductivity on matric potential leads to high-dimensional (in the parameter space) problems even under conditions where closed-form expressions of these models such as van Genuchten-Mualem formulations are used. In this study, we updated soil water retention parameters and hydraulic conductivity together and used Restart EnKF, which rerun the nonlinear model from the initial time to obtain the updated state variables, in synthetic cases to explore the factors that may influence estimation results, including the initial estimate, the ensemble size, the observation error, and the assimilation interval. We embedded the EnKF into the Bayesian model averaging framework to enhance the model reliability and reduce predictive uncertainties. This approach is evaluated from a 15 m deep semi-arid highly heterogeneous and anisotropic vadose zone site at the

  6. Remedy Evaluation Framework for Inorganic, Non-Volatile Contaminants in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Carroll, Kenneth C.

    2013-05-01

    Contaminants in the vadose zone may act as a potential long-term source of groundwater contamination and need to be considered in remedy evaluations. In many cases, remediation decisions for the vadose zone will need to be made all or in part based on projected impacts to groundwater. Because there are significant natural attenuation processes inherent in vadose zone contaminant transport, remediation in the vadose zone to protect groundwater is functionally a combination of natural attenuation and use of other remediation techniques, as needed, to mitigate contaminant flux to groundwater. Attenuation processes include both hydrobiogeochemical processes that serve to retain contaminants within porous media and physical processes that mitigate the rate of water flux. In particular, the physical processes controlling fluid flow in the vadose zone are quite different and generally have a more significant attenuation impact on contaminant transport relative to those within the groundwater system. A remedy evaluation framework is presented herein that uses an adaptation of the established EPA Monitored Natural Attenuation (MNA) evaluation approach and a conceptual model based approach focused on identifying and quantifying features and processes that control contaminant flux through the vadose zone. A key concept for this framework is to recognize that MNA will comprise some portion of all remedies in the vadose zone. Thus, structuring evaluation of vadose zone waste sites to use an MNA-based approach provides information necessary to either select MNA as the remedy, if appropriate, or to quantify how much additional attenuation would need to be induced by a remedial action (e.g., technologies considered in a feasibility study) to augment the natural attenuation processes and meet groundwater protection goals.

  7. Colloid Facilitated Transport of Radioactive Cations in the Vadose Zone: Field Experiments Oak Ridge

    Energy Technology Data Exchange (ETDEWEB)

    James E. Saiers

    2012-09-20

    The overarching goal of this study was to improve understanding of colloid-facilitated transport of radioactive cations through unsaturated soils and sediments. We conducted a suite of laboratory experiments and field experiments on the vadose-zone transport of colloids, organic matter, and associated contaminants of interest to the U.S. Department of Energy (DOE). The laboratory and field experiments, together with transport modeling, were designed to accomplish the following detailed objectives: 1. Evaluation of the relative importance of inorganic colloids and organic matter to the facilitation of radioactive cation transport in the vadose zone; 2. Assessment of the role of adsorption and desorption kinetics in the facilitated transport of radioactive cations in the vadose zone; 3. Examination of the effects of rainfall and infiltration dynamics and in the facilitated transport of radioactive cations through the vadose zone; 4. Exploration of the role of soil heterogeneity and preferential flow paths (e.g., macropores) on the facilitated transport of radioactive cations in the vadose zone; 5. Development of a mathematical model of facilitated transport of contaminants in the vadose zone that accurately incorporates pore-scale and column-scale processes with the practicality of predicting transport with readily available parameters.

  8. Evaluation of Soil Flushing for Application to the Deep Vadose Zone in the Hanford Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Oostrom, Martinus; Zhang, Z. F.; Carroll, Kenneth C.; Schramke, Janet A.; Wietsma, Thomas W.; Tartakovsky, Guzel D.; Gordon, Kathryn A.; Last, George V.

    2010-11-01

    Soil flushing was included in the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau as a technology with the potential to remove contaminants from the vadose zone. Soil flushing operates through the addition of water, and if necessary an appropriate mobilizing agent, to mobilize contaminants and flush them from the vadose zone and into the groundwater where they are subsequently captured by a pump-and-treat system. There are uncertainties associated with applying soil flushing technology to contaminants in the deep vadose zone at the Hanford Central Plateau. The modeling and laboratory efforts reported herein are intended to provide a quantitative assessment of factors that impact water infiltration and contaminant flushing through the vadose zone and into the underlying groundwater. Once in the groundwater, capture of the contaminants would be necessary, but this aspect of implementing soil flushing was not evaluated in this effort. Soil flushing was evaluated primarily with respect to applications for technetium and uranium contaminants in the deep vadose zone of the Hanford Central Plateau.

  9. Technical Basis for Evaluating Surface Barriers to Protect Groundwater from Deep Vadose Zone Contamination

    Energy Technology Data Exchange (ETDEWEB)

    Fayer, Michael J.; Ward, Anderson L.; Freedman, Vicky L.

    2010-02-03

    This document presents a strategy for evaluating the effectiveness of surface barriers for site-specific deep vadose zone remediation. The strategy provides a technically defensible approach to determine the depth to which a surface barrier can effectively isolate contaminants in the vadose at a specific site as a function of subsurface properties, contaminant distribution, barrier design, and infiltration control performance. The strategy also provides an assessment of additional data and information needs with respect to surface barrier performance for deep vadose zone applications. The strategy addresses the linkage between surface barriers and deep vadose zone in situ remediation activities, monitoring issues, and emerging science, technology, and regulatory objectives. In short, the report documents the existing knowledge base, identifies knowledge needs (based on data gaps), and suggests tasks whose outcomes will address those knowledge needs. More important, the report serves as a starting point to engage the regulator and stakeholder community on the viability of deploying surface barriers for deep vadose zone contamination. As that engagement unfolds, a systematic methodology can be formalized and instituted. The strategy is focused on deep vadose zone contamination and the methods needed to determine the impact to groundwater from those deep vadose zone contaminants. Processes that affect surface barrier performance, recharge in the areas surrounding the surface barrier, and the near-surface vadose zone beneath the barrier are acknowledged but are not addressed by this strategy. In addition, the collection of site-specific data on contaminant distribution and geologic structure and properties are programmatic responsibilities and are not provided by this strategy.

  10. Adaptive Fusion of Stochastic Information for Imaging Fractured Vadose Zones

    Science.gov (United States)

    Daniels, J.; Yeh, J.; Illman, W.; Harri, S.; Kruger, A.; Parashar, M.

    2004-12-01

    A stochastic information fusion methodology is developed to assimilate electrical resistivity tomography, high-frequency ground penetrating radar, mid-range-frequency radar, pneumatic/gas tracer tomography, and hydraulic/tracer tomography to image fractures, characterize hydrogeophysical properties, and monitor natural processes in the vadose zone. The information technology research will develop: 1) mechanisms and algorithms for fusion of large data volumes ; 2) parallel adaptive computational engines supporting parallel adaptive algorithms and multi-physics/multi-model computations; 3) adaptive runtime mechanisms for proactive and reactive runtime adaptation and optimization of geophysical and hydrological models of the subsurface; and 4) technologies and infrastructure for remote (pervasive) and collaborative access to computational capabilities for monitoring subsurface processes through interactive visualization tools. The combination of the stochastic fusion approach and information technology can lead to a new level of capability for both hydrologists and geophysicists enabling them to "see" into the earth at greater depths and resolutions than is possible today. Furthermore, the new computing strategies will make high resolution and large-scale hydrological and geophysical modeling feasible for the private sector, scientists, and engineers who are unable to access supercomputers, i.e., an effective paradigm for technology transfer.

  11. Vadose Zone Hydrogeology Data Package for Hanford Assessments

    Energy Technology Data Exchange (ETDEWEB)

    Last, George V.; Freeman, Eugene J.; Cantrell, Kirk J.; Fayer, Michael J.; Gee, Glendon W.; Nichols, William E.; Bjornstad, Bruce N.; Horton, Duane G.

    2006-06-01

    This data package documents the technical basis for selecting physical and geochemical parameters and input values that will be used in vadose zone modeling for Hanford assessments. This work was originally conducted as part of the Characterization of Systems Task of the Groundwater Remediation Project managed by Fluor Hanford, Inc., Richland, Washington, and revised as part of the Characterization of Systems Project managed by the Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy, Richland Operations Office (DOE-RL). This data package describes the geologic framework, the physical, hydrologic, and contaminant transport properties of the geologic materials, and deep drainage (i.e., recharge) estimates, and builds on the general framework developed for the initial assessment conducted using the System Assessment Capability (SAC) (Bryce et al. 2002). The general approach for this work was to update and provide incremental improvements over the previous SAC data package completed in 2001. As with the previous SAC data package, much of the data and interpreted information were extracted from existing documents and databases. Every attempt was made to provide traceability to the original source(s) of the data or interpretations.

  12. Atrazine retention and degradation in the vadose zone at a till plain site in central Indiana

    Science.gov (United States)

    Bayless, E.R.

    2001-01-01

    The vadose zone was examined as an environmental compartment where significant quantities of atrazine and its degradation compounds may be stored and transformed. The vadose zone was targeted because regional studies in the White River Basin indicated a large discrepancy between the mass of atrazine applied to fields and the amount of the pesticide and its degradation compounds that are measured in ground and surface water. A study site was established in a rotationally cropped field in the till plain of central Indiana. Data were gathered during the 1994 growing season to characterize the site hydrogeology and the distribution of atrazine, desethylatrazine, deisopropylatrazine, didealkylatrazine and hydroxyatrazine in runoff, pore water, and ground water. The data indicated that atrazine and its degradation compounds were transported from land surface to a depth of 1.5 m within 60 days of application, but were undetected in the saturated zone at nearby monitoring wells. A numerical model was developed, based on the field data, to provide information about processes that could retain and degrade atrazine in the vadose zone. Simulations indicated that evapotranspiration is responsible for surface directed soil-moisture flow during much of the growing season. This process causes retention and degradation of atrazine in the vadose zone. Increased residence time in the vadose zone leads to nearly complete transformation of atrazine and its degradation products to unquantified degradation compounds. As a result of mascropore flow, small quantities of atrazine and its degradation compounds may reach the saturated zone.

  13. Short-term and long-term Vadose zone monitoring: Current technologies, development, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris

    1999-05-01

    At Hanford, Savannah River, Oak Ridge, Idaho National Engineering and Environmental Laboratory (INEEL), and other DOE sites, field vadose zone observations have shown complex water seepage and mass transport behavior in a highly heterogeneous, thick vadose zone on a variety of scales. Recent investigation showed that severe contamination of soils and groundwater by organic contaminant and nuclear waste occurred because of water seepage and contaminant transport along localized, preferential, fast flow within the heterogeneous vadose zone. However, most of the existing characterization and monitoring methods are not able to locate these localized and persistent preferential pathways associated with specific heterogeneous geologic features, such as clastic dikes, caliche layers, or fractures. In addition, changes in the chemical composition of moving and indigenous solutes, particularly sodium concentration, redox conditions, biological transformation of organic materials, and high temperature, may significantly alter water, chemicals, and bio-transformation exchange between the zones of fast flow and the rest of the media. In this paper, using the data from Hanford and INEEL sites, we will (1) present evidence that central problems of the vadose zone investigations are associated with preferential, fast flow phenomena and accelerated migration of organic and radioactive elements, (2) identify gaps in current characterization and monitoring technologies, and (3) recommend actions for the development of advanced vadose zone characterization and monitoring methods using a combination of hydrologic, geochemical, and geophysical techniques.

  14. A National Roadmap for Vadose Zone Science and Technology

    Energy Technology Data Exchange (ETDEWEB)

    Kowall, Stephen Jacob

    2001-08-01

    This roadmap is a means of achieving, to the best of our current knowledge, a reasonable scientific understanding of how contaminants of all forms move in the vadose geological environments. This understanding is needed to reduce the present uncertainties in predicting contaminant movement, which in turn will reduce the uncertainties in remediation decisions.

  15. Vadose Zone Sampling Methods for Detection of Preferential Pesticides Transport

    Science.gov (United States)

    Peranginangin, N.; Richards, B. K.; Steenhuis, T. S.

    2003-12-01

    Leaching of agricultural applied chemicals through the vadose zone is a major cause for the occurrence of agrichemicals in groundwater. Accurate soil water sampling methods are needed to ensure meaningful monitoring results, especially for soils that have significant preferential flow paths. The purpose of this study was to assess the capability and the effectiveness of various soil water sampling methods in detecting preferential transport of pesticides in a strongly-structured silty clay loam (Hudson series) soil. Soil water sampling devices tested were wick pan and gravity pan lysimeters, tile lines, porous ceramic cups, and pipe lysimeters; all installed at 45 to105 cm depth below the ground surface. A reasonable worse-case scenario was tested by applying a simulated rain storm soon after pesticides were sprayed at agronomic rates. Herbicides atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) and 2,4-D (2,4-dichloro-phenoxyacetic acid) were chosen as model compounds. Chloride (KCl) tracer was used to determine spatial and temporal distribution of non-reactive solute and water as well as a basis for determining the retardation in pesticides movement. Results show that observed pesticide mobility was much greater than would be predicted by uniform flow. Under relatively high soil moisture conditions, gravity and wick pan lysimeters had comparably good collection efficiencies, whereas the wick samplers had an advantage over gravity driven sampler when the soil moisture content was below field capacity. Pipe lysimeters had breakthrough patterns that were similar to pan samplers. At small plot scale, tile line samplers tended to underestimate solute concentration because of water dilution around the samplers. The use of porous cup samplers performed poorly because of their sensitivity to local profile characteristics: only by chance can they intercept and sample the preferential flow paths that are critical to transport. Wick sampler had the least

  16. Gas-Phase Treatment of Technetium in the Vadose Zone at the Hanford Site Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    Technetium-99 (Tc-99) is present in the vadose zone of the Hanford Central Plateau and is a concern with respect to the protection of groundwater. The persistence, limited natural attenuation mechanisms, and geochemical behavior of Tc-99 in oxic vadose zone environments must be considered in developing effective alternatives for remediation. This report describes a new in situ geochemical manipulation technique for decreasing Tc-99 mobility using a combination of geochemical Tc-99 reduction with hydrogen sulfide gas and induced sediment mineral dissolution with ammonia vapor, which create conditions for deposition of stable precipitates that decrease the mobility of Tc-99. Laboratory experiments were conducted to examine changes in Tc-99 mobility in vadose zone sediment samples to evaluate the effectiveness of the treatment under a variety of operational and sediment conditions.

  17. TECHNICAL BASIS FOR EVALUATING SURFACE BARRIERS TO PROTECT GROUNDWATER FROM DEEP VADOSE ZONE CONTAMINATION

    Energy Technology Data Exchange (ETDEWEB)

    FAYER JM; FREEDMAN VL; WARD AL; CHRONISTER GB

    2010-02-24

    The U.S. DOE and its predecessors released nearly 2 trillion liters (450 billion gallons) of contaminated liquid into the vadose zone at the Hanford Site. Some of the contaminants currently reside in the deeper parts of the vadose zone where they are much less accessible to characterization, monitoring, and typical remediation activities. The DOE Richland Operations Office (DOE-RL) prepared a treatability test plan in 2008 to examine remediation options for addressing contaminants in the deep vadose zone; one of the technologies identified was surface barriers (also known as engineered barriers, covers, and caps). In the typical configuration, the contaminants are located relatively close to the surface, generally within 15 m, and thus they are close to the base of the surface barrier. The proximity of the surface barrier under these conditions yielded few concerns about the effectiveness of the barrier at depth, particularly for cases in which the contaminants were in a lined facility. At Hanford, however, some unlined sites have contaminants located well below depths of 15 m. The issue raised about these sites is the degree of effectiveness of a surface barrier in isolating contaminants in the deep vadose zone. Previous studies by Hanford Site and PNNL researchers suggest that surface barriers have the potential to provide a significant degree of isolation of deep vadose zone contaminants. The studies show that the actual degree of isolation is site-specific and depends on many factors, including recharge rates, barrier size, depth of contaminants, geohydrologic properties ofthe sediments, and the geochemical interactions between the contaminants and the sediments. After the DOE-RL treatability test plan was published, Pacific Northwest National Laboratory was contracted to review the information available to support surface barrier evaluation for the deep vadose zone, identify gaps in the information and outcomes necessary to fill the data gaps, and outline

  18. TECHNICAL BASIS FOR EVALUATING SURFACE BARRIERS TO PROTECT GROUNDWATER FROM DEEP VADOSE ZONE CONTAMINATION

    Energy Technology Data Exchange (ETDEWEB)

    FAYER JM; FREEDMAN VL; WARD AL; CHRONISTER GB

    2010-02-24

    The U.S. DOE and its predecessors released nearly 2 trillion liters (450 billion gallons) of contaminated liquid into the vadose zone at the Hanford Site. Some of the contaminants currently reside in the deeper parts of the vadose zone where they are much less accessible to characterization, monitoring, and typical remediation activities. The DOE Richland Operations Office (DOE-RL) prepared a treatability test plan in 2008 to examine remediation options for addressing contaminants in the deep vadose zone; one of the technologies identified was surface barriers (also known as engineered barriers, covers, and caps). In the typical configuration, the contaminants are located relatively close to the surface, generally within 15 m, and thus they are close to the base of the surface barrier. The proximity of the surface barrier under these conditions yielded few concerns about the effectiveness of the barrier at depth, particularly for cases in which the contaminants were in a lined facility. At Hanford, however, some unlined sites have contaminants located well below depths of 15 m. The issue raised about these sites is the degree of effectiveness of a surface barrier in isolating contaminants in the deep vadose zone. Previous studies by Hanford Site and PNNL researchers suggest that surface barriers have the potential to provide a significant degree of isolation of deep vadose zone contaminants. The studies show that the actual degree of isolation is site-specific and depends on many factors, including recharge rates, barrier size, depth of contaminants, geohydrologic properties ofthe sediments, and the geochemical interactions between the contaminants and the sediments. After the DOE-RL treatability test plan was published, Pacific Northwest National Laboratory was contracted to review the information available to support surface barrier evaluation for the deep vadose zone, identify gaps in the information and outcomes necessary to fill the data gaps, and outline

  19. Migration and degradation of fuel vapours in the vadose zone. Field experiment at airbase Værløse

    DEFF Research Database (Denmark)

    Christophersen, Mette; Broholm, Mette Martina; Kjeldsen, Peter

    2002-01-01

    Fuel has been spilled in the vadose zone at many sites. An artificial jet fuel source has been installed in a vadose zone (3.5 m sand) at Airbase Værløse. The field experiment is conducted to investigate the natural attenuation potential in order to obtain better evaluations of the risk for ground...

  20. Evaluation of In Situ Grouting as a Potential Remediation Method for the Hanford Central Plateau Deep Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Pierce, Eric M.; Nimmons, Michael J.; Mattigod, Shas V.

    2011-01-11

    The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau report identifies in situ grouting as a potential remediation technology for the deep vadose zone and includes a planned effort to evaluate in situ grouting to provide information for future feasibility studies. This report represents the first step in this evaluation effort.

  1. Vadose zone transport field study: Detailed test plan for simulated leak tests

    Energy Technology Data Exchange (ETDEWEB)

    AL Ward; GW Gee

    2000-06-23

    The US Department of Energy (DOE) Groundwater/Vadose Zone Integration Project Science and Technology initiative was created in FY 1999 to reduce the uncertainty associated with vadose zone transport processes beneath waste sites at DOE's Hanford Site near Richland, Washington. This information is needed not only to evaluate the risks from transport, but also to support the adoption of measures for minimizing impacts to the groundwater and surrounding environment. The principal uncertainties in vadose zone transport are the current distribution of source contaminants and the natural heterogeneity of the soil in which the contaminants reside. Oversimplified conceptual models resulting from these uncertainties and limited use of hydrologic characterization and monitoring technologies have hampered the understanding contaminant migration through Hanford's vadose zone. Essential prerequisites for reducing vadose transport uncertainly include the development of accurate conceptual models and the development or adoption of monitoring techniques capable of delineating the current distributions of source contaminants and characterizing natural site heterogeneity. The Vadose Zone Transport Field Study (VZTFS) was conceived as part of the initiative to address the major uncertainties confronting vadose zone fate and transport predictions at the Hanford Site and to overcome the limitations of previous characterization attempts. Pacific Northwest National Laboratory (PNNL) is managing the VZTFS for DOE. The VZTFS will conduct field investigations that will improve the understanding of field-scale transport and lead to the development or identification of efficient and cost-effective characterization methods. Ideally, these methods will capture the extent of contaminant plumes using existing infrastructure (i.e., more than 1,300 steel-cased boreholes). The objectives of the VZTFS are to conduct controlled transport experiments at well-instrumented field sites at

  2. Estimating the Impact of Vadose Zone Sources on Groundwater to Support Performance Assessment of Soil Vapor Extraction

    Energy Technology Data Exchange (ETDEWEB)

    Oostrom, Martinus [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rice, Amy K. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Carroll, Kenneth C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Becker, Dave [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Simon, Michelle A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-03-13

    Soil vapor extraction (SVE) is a prevalent remediation approach for volatile contaminants in the vadose zone. To support selection of an appropriate endpoint for the SVE remedy, an evaluation is needed to determine whether vadose zone contamination has been diminished sufficiently to protect groundwater. When vapor-phase transport is an important component of the overall contaminant fate and transport from a vadose zone source, the contaminant concentration expected in groundwater is controlled by a limited set of parameters, including specific site dimensions, vadose zone properties, and source characteristics. An approach was developed for estimating the contaminant concentration in groundwater resulting from a contaminant source in the vadose zone based on pre-modeling contaminant transport for a matrix of parameter value combinations covering a range of potential site conditions. An interpolation and scaling process are then applied to estimate groundwater impact for site-specific conditions.

  3. Climate, soil, and vegetation controls on the temporal variability of vadose zone transport

    NARCIS (Netherlands)

    Harman, C.J.; Rao, P.S.C.; Basu, N.B.; McGrath, G.S.; Kumar, P.; Sivapalan, M.

    2011-01-01

    Temporal patterns of solute transport and transformation through the vadose zone are driven by the stochastic variability of water fluxes. This is determined by the hydrologic filtering of precipitation variability into infiltration, storage, drainage, and evapotranspiration. In this work we develop

  4. The effect of subsurface military detonations on vadose zone hydraulic conductivity, contaminant transport and aquifer recharge

    NARCIS (Netherlands)

    Lewis, J.; Burman, J.; Edlund, C.; Simonsson, L.; Berglind, R.; Leffler, P.; Qvarfort, U.; Thiboutot, S.; Ampleman, G.; Meuken, D.; Duvalois, W.; Martel, R.; Sjöström, J.

    2013-01-01

    Live fire military training involves the detonation of explosive warheads on training ranges. The purpose of this experiment is to evaluate the hydrogeological changes to the vadose zone caused by military training with high explosive ammunition. In particular, this study investigates artillery ammu

  5. Performance Evaluation of Automated Passive Capillary Sampler for Estimating Water Drainage in the Vadose Zone

    Science.gov (United States)

    Passive capillary samplers (PCAPs) are widely used to monitor, measure and sample drainage water under saturated and unsaturated soil conditions in the vadose zone. The objective of this study was to evaluate the performance and accuracy of automated passive capillary sampler for estimating drainage...

  6. Impact of CO2 Intrusion into USDWs, the Vadose Zone, and Indoor Air

    Science.gov (United States)

    The U.S. Environmental Protection Agency’s (EPA) Water Research Program in the Office of Research and Development is conducting research to better detect and quantify leakage into USDWs, the vadose zone, the atmosphere, and buildings. Research in this initiative is focused in thr...

  7. Transport and degradation of propylene glycol in the vadose zone: model development and sensitivity analysis

    NARCIS (Netherlands)

    Schotanus, D.; Meeussen, J.C.L.; Lissner, H.; Ploeg, van der M.J.; Wehrer, M.; Totsche, K.U.; Zee, van der S.E.A.T.M.

    2014-01-01

    Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well

  8. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jacques, D.; Jessen, S.;

    2014-01-01

    The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying mechan...

  9. Engineering report single-shell tank farms interim measures to limit infiltration through the vadose zone

    Energy Technology Data Exchange (ETDEWEB)

    HAASS, C.C.

    1999-10-14

    Identifies, evaluates and recommends interim measures for reducing or eliminating water sources and preferential pathways within the vadose zone of the single-shell tank farms. Features studied: surface water infiltration and leaking water lines that provide recharge moisture, and wells that could provide pathways for contaminant migration. An extensive data base, maps, recommended mitigations, and rough order of magnitude costs are included.

  10. Characterization of Direct Push Vadose Zone Sediments from the 241-U Single-Shell Tank Farm

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Valenta, Michelle M.; Serne, R. Jeffrey; Bjornstad, Bruce N.; Lanigan, David C.; Iovin, Cristian; Clayton, Ray E.; Geiszler, Keith N.; Clayton, Eric T.; Kutnyakov, Igor V.; Baum, Steven R.; Lindberg, Michael J.; Orr, Robert D.

    2007-12-20

    The overall goals of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., are 1) to define risks from past and future single-shell tank farm activities, 2) to identify and evaluate the efficacy of interim measures, and 3) to aid, via collection of geochemical information and data, the future decisions that must be made by the U.S. Department of Energy (DOE) regarding the near-term operations, future waste retrieval, and final closure activities for the single-shell tank Waste Management Areas (WMAs). For a more complete discussion of the goals of the Tank Farm Vadose Zone Project, see the overall work plan, Phase 1 RCRA Facility Investigation/Corrective Measures Study Work Plan for the Single-Shell Tank Waste Management Areas (DOE 1999). Specific details on the rationale for activities performed at WMA U are found in Crumpler (2003). To meet these goals, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory (PNNL) to perform detailed analyses of vadose zone sediment collected within the U Single-Shell Tank Farm. Specifically, this report contains all the geochemical and selected physical characterization data collected on vadose zone sediment recovered from ten direct push characterization holes emplaced to investigate vadose zone contamination associated with potential leaks within the 241-U Single-Shell Tank Farm. Specific tanks targeted during this characterization campaign included tanks 241-U-104/241-U-105, 241-U-110, and 241-U-112. Additionally, this report compiles data from direct push samples collected north of tank 241-U-201, as well as sediment collected from the background borehole (C3393). After evaluating all the characterization and analytical data, there is no question that the vadose zone in the vicinity of tanks 241-U-104 and 241-U-105 has been contaminated by tank-related waste. This observation is not new, as gamma logging of drywells in the area has identified uranium contamination at the

  11. Bioremediation of RDX in the vadose zone beneath the Pantex Plant

    Energy Technology Data Exchange (ETDEWEB)

    Shull, T.L.; Speitel, G.E. Jr.; McKinney, D.C. [Univ. of Texas, Austin, TX (United States). Dept. of Civil Engineering

    1999-01-01

    The presence of dissolved high explosives (HE), in particular RDX and HMX, is well documented in the perched aquifer beneath the Pantex Plant, but the distribution of HE in the vadose zone has not yet been well defined. Although current remediation activities focus on the contamination in the perched aquifer, eventually regulatory concern is likely to turn to the residual contamination in the vadose zone. Sources of HE include the infiltration of past wastewater discharges from several HE-processing facilities through the ditch drainage system and leachate from former Landfill 3. With limited existing data on the HE distribution in the vadose zone and without preventive action, it must be assumed that residual HE could be leached into infiltrating water, providing a continuing supply of contamination to the perched aquifer. The purpose of this project was to more closely examine the fate and transport of HE in the vadose zone through mathematical modeling and laboratory experimentation. In particular, this report focuses on biodegradation as one possible fate of HE. Biodegradation of RDX in the vadose zone was studied because it is both present in highest concentration and is likely to be of the greatest regulatory concern. This study had several objectives: determine if indigenous soil organisms are capable of RDX biodegradation; determine the impact of electron acceptor availability and nutrient addition on RDX biodegradation; determine the extent of RDX mineralization (i.e., conversion to inorganic carbon) during biodegradation; and estimate the kinetics of RDX biodegradation to provide information for mathematical modeling of fate and transport.

  12. Vadose Zone Monitoring as a Key to Groundwater Protection from Pollution Hazard

    Science.gov (United States)

    Dahan, Ofer

    2016-04-01

    Minimization subsurface pollution is much dependent on the capability to provide real-time information on the chemical and hydrological properties of the percolating water. Today, most monitoring programs are based on observation wells that enable data acquisitions from the saturated part of the subsurface. Unfortunately, identification of pollutants in well water is clear evidence that the contaminants already crossed the entire vadose-zone and accumulated in the aquifer water to detectable concentration. Therefore, effective monitoring programs that aim at protecting groundwater from pollution hazard should include vadose zone monitoring technologies that are capable to provide real-time information on the chemical composition of the percolating water. Obviously, identification of pollution process in the vadose zone may provide an early warning on potential risk to groundwater quality, long before contaminates reach the water-table and accumulate in the aquifers. Since productive agriculture must inherently include down leaching of excess lower quality water, understanding the mechanisms controlling transport and degradation of pollutants in the unsaturated is crucial for water resources management. A vadose-zone monitoring system (VMS), which was specially developed to enable continuous measurements of the hydrological and chemical properties of percolating water, was used to assess the impact of various agricultural setups on groundwater quality, including: (a) intensive organic and conventional greenhouses, (b) citrus orchard and open field crops , and (c) dairy farms. In these applications frequent sampling of vadose zone water for chemical and isotopic analysis along with continuous measurement of water content was used to assess the link between agricultural setups and groundwater pollution potential. Transient data on variation in water content along with solute breakthrough at multiple depths were used to calibrate flow and transport models. These models

  13. Evaluating Contaminant Flux from the Vadose Zone to the Groundwater in the Hanford Central Plateau. SX Tank Farms Case Study

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oostrom, Martinus [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Last, George V. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Strickland, Christopher E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tartakovsky, Guzel D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-09-01

    At the DOE Hanford Site, contaminants were discharged to the subsurface through engineered waste sites in the Hanford Central Plateau. Additional waste was released through waste storage tank leaks. Much of the contaminant inventory is still present within the unsaturated vadose zone sediments. The nature and extent of future groundwater contaminant plumes and the growth or decline of current groundwater plumes beneath the Hanford Central Plateau are a function of the contaminant flux from the vadose zone to the groundwater. In general, contaminant transport is slow through the vadose zone and it is difficult to directly measure contaminant flux in the vadose zone. Predictive analysis, supported by site characterization and monitoring data, was applied using a structured, systems-based approach to estimate the future contaminant flux to groundwater in support of remediation decisions for the vadose zone and groundwater (Truex and Carroll 2013). The SX Tank Farm was used as a case study because of the existing contaminant inventory in the vadose zone, observations of elevated moisture content in portions of the vadose zone, presence of a limited-extent groundwater plume, and the relatively large amount and wide variety of data available for the site. Although the SX Tank Farm case study is most representative of conditions at tank farm sites, the study has elements that are also relevant to other types of disposal sites in the Hanford Central Plateau.

  14. Analysis of vadose zone tritium transport from an underground storage tank release using numerical modeling and geostatistics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K.H.

    1997-09-01

    Numerical and geostatistical analyses show that the artificial smoothing effect of kriging removes high permeability flow paths from hydrogeologic data sets, reducing simulated contaminant transport rates in heterogeneous vadose zone systems. therefore, kriging alone is not recommended for estimating the spatial distribution of soil hydraulic properties for contaminant transport analysis at vadose zone sites. Vadose zone transport if modeled more effectively by combining kriging with stochastic simulation to better represent the high degree of spatial variability usually found in the hydraulic properties of field soils. However, kriging is a viable technique for estimating the initial mass distribution of contaminants in the subsurface.

  15. ANNUAL REPORT FOR ENVIRONMENTAL MANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACE METALS IN GROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 AND OTHER DIVALENT METALS AND RADIONUCLIDES AT ARID WESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko; Ferris, F. Grant; Cosgrove, Donna M.; Colwell, F. S.

    2003-06-15

    Radionuclide and metal contaminants such as 90Sr are present beneath U.S. Department of Energy (DOE) lands in both the groundwater (e.g., 100-N area at Hanford, WA) and vadose zone (e.g., Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory). In situ containment and stabilization of these contaminants is a cost-effective treatment strategy. However, implementing in situ containment and stabilization approaches requires definition of the mechanisms that control contaminant sequestration. We are investigating the in situ immobilization of radionuclides or contaminant metals (e.g., 90Sr) by their facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Our facilitated approach, shown schematically in Figure 1, relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity. Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation process tends to be irreversible and many western aquifers are saturated with respect to calcite, the coprecipitated metals and radionuclides will be effectively removed from the aqueous phase over the long-term. Another advantage of the ureolysis approach is that the ammonium ions produced by the reaction can exchange with radionuclides sorbed to subsurface minerals, thereby enhancing the availability of the radionuclides for re-capture in a more stable solid phase (co-precipitation rather than adsorption).

  16. Deep Vadose Zone-Applied Field Research Initiative Fiscal Year 2011 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Wellman, Dawn M.; Johnson, Timothy C.; Smith, Ronald M.; Truex, Michael J.; Matthews, Hope E.

    2011-10-01

    This annual report describes the background of the Deep Vadose Zone-Applied Field Research Initiative, and some of the programmatic approaches and transformational technologies in groundwater and deep vadose zone remediation developed during fiscal year 2011. The Department of Energy (DOE) Office of Technology Innovation and Development's (OTID) mission is to transform science into viable solutions for environmental cleanup. In 2010, OTID developed the Impact Plan, Science and Technology to Reduce the Life Cycle Cost of Closure to outline the benefits of research and development of the lifecycle cost of cleanup across the DOE complex. This plan outlines OTID's ability to reduce by $50 billion, the $200 billion life-cycle cost in waste processing, groundwater and soil, nuclear materials, and deactivation and decommissioning. The projected life-cycle costs and return on investment are based on actual savings realized from technology innovation, development, and insertion into remedial strategies and schedules at the Fernald, Mound, and Ashtabula sites. To achieve our goals, OTID developed Applied Field Research Initiatives to facilitate and accelerate collaborative development and implementation of new tools and approaches that reduce risk, cost and time for site closure. The primary mission of the Deep Vadose Zone-Applied Field Research Initiative (DVZ-AFRI) is to protect our nation's water resources, keeping them clean and safe for future generations. The DVZ-AFRI was established for the DOE to develop effective, science-based solutions for remediating, characterizing, monitoring, and predicting the behavior and fate of deep vadose zone contamination. Subsurface contaminants include radionuclides, metals, organics, and liquid waste that originated from various sources, including legacy waste from the nation's nuclear weapons complexes. The DVZ-AFRI project team is translating strategy into action by working to solve these complex challenges in a

  17. Research Plan: Foam Delivery of Remedial Amendments to Deep Vadose Zone for Metals and Radionuclides Remediation

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Lirong; Hart, Andrea T.; Szecsody, James E.; Zhang, Z. F.; Freedman, Vicky L.; Ankeny, Mark; Hull, Laurence; Oostrom, Martinus; Freshley, Mark D.; Wellman, Dawn M.

    2009-01-16

    Research proposals were submitted to the Scientific and Technical Basis for In Situ Treatment of Metals and Radionuclides Technical Working Group under the US Department of Energy (DOE) Environmental Management Office (specifically, EM-22). After a peer review and selection process, the proposal, “Foam Delivery of Remedial Amendments to Deep Vadose Zone for Metals and Radionuclides Remediation,” submitted by Pacific Northwest National Laboratory (PNNL) was selected for support by the program. A research plan was requested for this EM funded project. The overall objective of this project is to develop foam delivery technology for the distribution of remedial amendments to deep vadose zone sediments for in situ immobilization of metal and radionuclide contaminants. The focus of this research in FY 2009 is on the physical aspects of the foam delivery approach. Specific objectives are to 1) study the foam quality (i.e. the gas volume fraction in foam) influence on injection pressure, 2) study the sediment air permeability influence on injection pressure, 3) investigate liquid uptake in sediment and determine whether a water front will be formed during foam delivery, 4) test amendment distance (and mass) delivery by foam from the injection point, 5) study the enhanced sweeping over heterogeneous systems (i.e., low K zones) by foam delivery relative to water-based delivery under vadose zone conditions, and 6) numerically simulate foam delivery processes in the vadose zone. Laboratory scale experiments will be conducted at PNNL to study a range of basic physical aspects of the foam propagation in sediments, including foam quality and sediment permeability influence on injection pressure, liquid uptake, and foam sweeping across heterogeneous systems. This study will be augmented with separate studies to be conducted at MSE Technology Applications, Inc. (MSE) to evaluate foam transport and amendment delivery at the intermediate-scale. The results of intermediate

  18. Mechanisms affecting the infiltration and distribution of ethanol-blended gasoline in the vadose zone.

    Science.gov (United States)

    McDowell, Cory J; Powers, Susan E

    2003-05-01

    One- and two-dimensional experiments were conducted to examine differences in the behavior of gasoline and gasohol (10% ethanol by volume) as they infiltrate through the unsaturated zone and spread at the capillary fringe. Ethanol in the spilled gasohol quickly partitions into the residual water in the vadose zone and is retained there as the gasoline continues to infiltrate. Under the conditions tested, over 99% of the ethanol was initially retained in the vadose zone. Depending on the volume of gasoline spilled and the depth to the water table, this causes an increase in the aqueous-phase saturation and relative permeability, thus allowing the ethanol-laden water to drain into the gasoline pool. Under the conditions tested, the presence of ethanol does not have a significant impact on the overall size or shape of the resulting gasoline pool at the capillary fringe. Residual gasoline saturations in the vadose zone were significantly reduced however because of reduced surface and interfacial tensions associated with high ethanol concentrations. The flux of ethanol in the effluent of the column ranged from 1.4 x 10(-4) to 4.5 x 10(-7) g/(cm2 min) with the LNAPL and from 6 x 10(-3) to 3.0 x 10(-4) g/(cm2 min) after water was introduced to simulate rain infiltration. The experimental results presented here illustrate that the dynamic effects of ethanol partitioning into the aqueous phase in the vadose zone create an initial condition that is significantly different than previously understood.

  19. The Use of Radar Methods to Determine Moisture Content in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Rosemary Knight

    2003-12-28

    Water content is a critical parameter affecting both liquid-phase and vapor-phase contaminant transport in the vadose zone. This means that accurate estimate of in situ water content must be obtained in order to design for the appropriate handling or remediation of a contaminated region of the vadose zone. Traditional methods of sampling the subsurface by drilling and/or direct sampling are very time consuming, limited in terms of spatial coverage, and have the associated risk of contacting and increasing the size of the contaminated area. One solution is to use geophysical methods which can provide a high-resolution, non-invasive means of sampling or imagin the subsurface.

  20. Science Road Map for Phase 2 of the Tank-Farm Vadose Zone Program

    Energy Technology Data Exchange (ETDEWEB)

    Zachara, John M.; Freshley, Mark D.; Mann, Frederick M.

    2008-08-18

    Phase 1 of the Tank-Farm Vadose Zone Program (TFVZP) developed information on the nature and extent of vadose zone contamination in the tank farms through field studies, laboratory analyses and experiments, and historical data searches; assembled data and performed tank-farm risk analysis; and initiated interim corrective actions to lessen the impacts of tank leak contaminants. Pacific Northwest National Laboratory scientists and external collaborators at universities and U.S. Department of Energy user facilities sampled and analyzed contaminant plumes. These types of activities will continue during Phase 2 of the TFVZP to refine and expand scientific understanding of the subsurface beneath tank farms, especially of water movement, residual waste leaching, and contaminant transport.

  1. Macroscopic relationship for preferential flow in the vadose zone:Theory and validation

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Preferential flow commonly observed in unsaturated soils allows rapid movement of solute from the ground surface or vadose zone to the groundwater, bypassing a significant volume of unsaturated soil and increasing the risk of groundwater contamination. A variety of evidence indicates that complex preferential flow patterns observed from fields are fractals. This paper discusses a macroscopic relationship for modeling preferential flow in the vadose zone. Conceptually, the flow domain can be divided into active and inactive regions. Flow occurs preferentially in the active region (characterized by fractals), and inactive region is simply bypassed. The portion of the active region was found to be a power function of saturation. The validity of this macroscopic relationship is demonstrated by its consistency with field observations and the related numerical experiments.

  2. Experimental and Numerical Investigations of Soil Desiccation for Vadose Zone Remediation: Report for Fiscal Year 2007

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Andy L.; Oostrom, Mart; Bacon, Diana H.

    2008-02-04

    Apart from source excavation, the options available for the remediation of vadose zone metal and radionuclide contaminants beyond the practical excavation depth (0 to 15 m) are quite limited. Of the available technologies, very few are applicable to the deep vadose zone with the top-ranked candidate being soil desiccation. An expert panel review of the work on infiltration control and supplemental technologies identified a number of knowledge gaps that would need to be overcome before soil desiccation could be deployed. The report documents some of the research conducted in the last year to fill these knowledge gaps. This work included 1) performing intermediate-scale laboratory flow cell experiments to demonstrate the desiccation process, 2) implementing a scalable version of Subsurface Transport Over Multiple Phases–Water-Air-Energy (STOMP-WAE), and 3) performing numerical experiments to identify the factors controlling the performance of a desiccation system.

  3. A comprehensive analysis of contaminant transport in the vadose zone beneath tank SX-109

    Energy Technology Data Exchange (ETDEWEB)

    Ward, A.L.; Gee, G.W.; White, M.D.

    1997-02-01

    The Vadose Zone Characterization Project is currently investigating the subsurface distribution of gamma-emitting radionuclides in S and SX Waste Management Area (WMA-S-SX) located in the 200 West Area of the US Department of Energy`s Hanford Site in southeastern Washington State. Spectral-gamma logging of boreholes has detected elevated {sup 137}Cs concentrations as deep as 38 m, a depth considered excessive based on the assumed geochemistry of {sup 137}Cs in Hanford sediments. Routine groundwater sampling under the Resource Conservation and Recovery Act (RCRA) have also detected elevated levels of site-specific contaminants downgradient of WMA-S-SX. The objective of this report is to explore the processes controlling the migration of {sup 137}Cs, {sup 99}Tc, and NO{sub 3} through the vadose zone of WMA-S-SX, particularly beneath tank SX-109.

  4. Effects of Lime and Concrete Waste on Vadose Zone Carbon Cycling

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, Søren; Postma, D.;

    2014-01-01

    In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination of exper......In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination.......) grown on podzolic soil material, we have investigated inorganic carbon cycling through the gaseous and liquid phases and how it is affected by different soil amendments. The mesocosm amendments comprised the addition of 0, 9.6, or 21.2 kg m−2 of crushed concrete waste (CCW) or 1 kg lime m−2. The CCW...

  5. Effects of lime and concrete waste on Vadose Zone carbon cycling

    OpenAIRE

    Thaysen, Eike Marie; Jessen, Søren; Postma, D; Jakobsen, R.; Jacques, D; Ambus, Per; E. Laloy; Jakobsen, Iver

    2014-01-01

    In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination of experimental and modeling tools to determine ongoing biogeochemical processes. Our results demonstrate that lime and CCW amendments to acid soil contribute to the climate forcing by largely increasing the ...

  6. Remediation of Deep Vadose Zone Radionuclide and Metal Contamination: Status and Issues

    Energy Technology Data Exchange (ETDEWEB)

    Dresel, P. Evan; Truex, Michael J.; Cantrell, Keri

    2008-12-30

    This report documents the results of a PNNL literature review to report on the state of maturity of deep vadose zone remediation technologies for metal contaminants including some radionuclides. Its recommendations feed into decisionmakers need for scientific information and cost-effective in situ remediation technlogies needed under DOE's Environmental Management initiative Enhanced Remediation Methods: Scientific & Technical Basis for In Stu Treatment Systems for Metals and Radionuclides.

  7. Vadose Zone Transport Field Study: Detailed Test Plan for Simulated Leak Tests

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Anderson L.; Gee, Glendon W.

    2000-06-23

    This report describes controlled transport experiments at well-instrumented field tests to be conducted during FY 2000 in support of DOE?s Vadose Zone Transport Field Study (VZTFS). The VZTFS supports the Groundwater/Vadose Zone Integration Project Science and Technology Initiative. The field tests will improve understanding of field-scale transport and lead to the development or identification of efficient and cost-effective characterization methods. These methods will capture the extent of contaminant plumes using existing steel-cased boreholes. Specific objectives are to 1) identify mechanisms controlling transport processes in soils typical of the hydrogeologic conditions of Hanford?s waste disposal sites; 2) reduce uncertainty in conceptual models; 3) develop a detailed and accurate data base of hydraulic and transport parameters for validation of three-dimensional numerical models; and 4) identify and evaluate advanced, cost-effective characterization methods with the potential to assess changing conditions in the vadose zone, particularly as surrogates of currently undetectable high-risk contaminants. Pacific Northwest National Laboratory (PNNL) manages the VZTFS for DOE.

  8. Characterization of Vadose Zone Sediment: Uncontaminated RCRA Borehole Core Samples and Composite Samples

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Schaef, Herbert T.; Williams, Bruce A.; Lanigan, David C.; Horton, Duane G.; Clayton, Ray E.; Mitroshkov, Alexandre V.; Legore, Virginia L.; O' Hara, Matthew J.; Brown, Christopher F.; Parker, Kent E.; Kutnyakov, Igor V.; Serne, Jennifer N.; Last, George V.; Smith, Steven C.; Lindenmeier, Clark W.; Zachara, John M.; Burke, Deborah S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.14, 4.16, 5.20, 5.22, 5.43, and 5.45. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc. asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is one in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from Resource Conservation and Recovery Act (RCRA) borehole bore samples and composite samples.

  9. A vadose zone Transport Processes Investigation within the glacial till at the Fernald Environmental Management Project.

    Energy Technology Data Exchange (ETDEWEB)

    Schwing, J. (FERMCO Technology Development, Cincinnati, OH); Roepke, Craig Senninger; Brainard, James Robert; Glass, Robert John, Jr.; Mann, Michael J. A.; Holt, Robert M.; Kriel, Kelly

    2007-08-01

    This report describes a model Transport Processes Investigation (TPI) where field-scale vadose zone flow and transport processes are identified and verified through a systematic field investigation at a contaminated DOE site. The objective of the TPI is to help with formulating accurate conceptual models and aid in implementing rational and cost effective site specific characterization strategies at contaminated sites with diverse hydrogeologic settings. Central to the TPI are Transport Processes Characterization (TPC) tests that incorporate field surveys and large-scale infiltration experiments. Hypotheses are formulated based on observed pedogenic and hydrogeologic features as well as information provided by literature searches. The field and literature information is then used to optimize the design of one or more infiltration experiments to field test the hypothesis. Findings from the field surveys and infiltration experiments are then synthesized to formulate accurate flow and transport conceptual models. Here we document a TPI implemented in the glacial till vadose zone at the Fernald Environmental Management Project (FEMP) in Fernald, Ohio, a US Department of Energy (DOE) uranium processing site. As a result of this TPI, the flow and transport mechanisms were identified through visualization of dye stain within extensive macro pore and fracture networks which provided the means for the infiltrate to bypass potential aquatards. Such mechanisms are not addressed in current vadose zone modeling and are generally missed by classical characterization methods.

  10. Evaluating Transport and Attenuation of Inorganic Contaminants in the Vadose Zone for Aqueous Waste Disposal Sites

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oostrom, Martinus [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tartakovsky, Guzel D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-09-01

    An approach was developed for evaluating vadose zone transport and attenuation of aqueous wastes containing inorganic (non-volatile) contaminants that were disposed of at the land surface (i.e., directly to the ground in cribs, trenches, tile fields, etc.) and their effect on the underlying groundwater. The approach provides a structured method for estimating transport of contaminants through the vadose zone and the resulting temporal profile of groundwater contaminant concentrations. The intent of the approach is also to provide a means for presenting and explaining the results of the transport analysis in the context of the site-specific waste disposal conditions and site properties, including heterogeneities and other complexities. The document includes considerations related to identifying appropriate monitoring to verify the estimated contaminant transport and associated predictions of groundwater contaminant concentrations. While primarily intended for evaluating contaminant transport under natural attenuation conditions, the approach can also be applied to identify types of, and targets for, mitigation approaches in the vadose zone that would reduce the temporal profile of contaminant concentrations in groundwater, if needed.

  11. CO2 phase mutation by fluctuating water table in the vadose zone over a CCS site

    Science.gov (United States)

    Joun, W.; Ha, S. W.; Kim, H. H.; Kim, T. W.; Lee, S. S.; Lee, K. K.

    2015-12-01

    Geological sequestration of carbon dioxide (CO2) is one of the feasible plans to control greenhouse gas emissions. In order to be more perfect, the plan has to prove that the injected CO2 gas will not be leaking. Even if CO2 leaking happens, we should possess a technique which provides information on specific aquifer system before critical effect to ground and subsurface environments. Many parameters have been utilized for early detection before risk to environments by sensing CO2 gas concentration, electric conductivity, pH, and ion analysis. However, these are not enough to all CCS sites for leakage detection. For example, the importance of gas leaking path is emphasized because finding the dominant gas flow path can reduce risk and provide a quick estimation. Herein, we investigate dissolved solute degassing and vertical flow from saturated zone to unsaturated zone in shallow depth aquifer. Especially we focused on the water table fluctuation effect. Based on field data and basic parameters, we perform a pilot scale gas injection test and calculate gas flow saturation with STOMP simulator. The CO2 gas concentrations at different depth levels according to amount of injected CO2 infused water, CO2 gas saturation in vadose zone have different concentration values. If we estimate this phenomenon in vadose zone by using CO2 gas detection method, we could presume that the CO2 dissolved in shallow groundwater is degassing and flow upward into vadose zone. However, the concentration level and change patterns are not same and will be changed according to the pattern of water table fluctuation. This study could be usefully applied to strategic CCS environmental monitoring of CO2 leakage.Acknowledgement: Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003).

  12. Transport and degradation of propylene glycol in the vadose zone: model development and sensitivity analysis.

    Science.gov (United States)

    Schotanus, D; Meeussen, J C L; Lissner, H; van der Ploeg, M J; Wehrer, M; Totsche, K U; van der Zee, S E A T M

    2014-01-01

    Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well as anaerobic degradation occurs in the vadose zone. Therefore, the model included both types of degradation, which was made possible by assuming advection-controlled (mobile) and diffusion-controlled (immobile) zones. In the mobile zone, oxygen can be transported by diffusion in the gas phase. The immobile zone is always water-saturated, and oxygen only diffuses slowly in the water phase. Therefore, the model is designed in a way that the redox potential can decrease when PG is degraded, and thus, anaerobic degradation can occur. In our model, manganese oxide (MnO2, which is present in the soil) and NO3- (applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation. The application of NO3- does not result in a lower leaching of PG nor in a slower depletion of MnO2. The thickness of the snowcover influences the leached fraction of PG, as with a high infiltration rate, transport is fast, there is less time for degradation and thus more PG will leach. The model showed that, in this soil, the effect of the water flow dominates over the effect of the degradation parameters on the leaching at a 1-m depth.

  13. High resolution imaging of vadose zone transport using surface and crosswell ground penetrating radar methods

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Kenneth H.; Kowalsky, Mike B.; Peterson, John E.

    2002-11-05

    To effectively clean up many contaminated sites there is a need for information on heterogeneities at scales ranging from one centimeter to tens of meters, as these features can alter contaminant transport significantly. At the Department of Energy's Hanford, Washington site heterogeneities of interest can range from localized phenomena such as silt or gravel lenses, fractures, clastic dikes, to large-scale lithologic discontinuities. In the vadose zone it is critical to understand the parameters controlling flow. These features have been suspected of leading to funneling and fingering, additional physical mechanisms that could alter and possibly accelerate the transport of contaminants to underlying groundwater. For example, it has been observed from the studies to date that over relatively short distances there are heterogeneities in the physical structure of the porous medium and structural differences between repacked soil cores and the field site from which the materials initially came (Raymond and Shdo, 1966). Analysis of cores taken from the vadose zone (i.e., soil surface to water table) has been useful in identifying localized zones of contamination. Unfortunately, these analyses are sparse (limited to a few boreholes) and extremely expensive. The high levels of radioactivity at many of the contaminated sites increase drilling and sample costs and analysis time. Cost of drilling and core analysis for the SX tank farm has exceeded $1M per borehole (50 meter deep) for sampling. The inability to track highly mobile species through the vadose zone highlights an important need: the need for methods to describe the complete vadose zone plume and to determine processes controlling accelerated contamination of groundwater at Hanford. A combination of surface and crosswell (i.e. borehole) geophysical measurements is one means to provide this information. The main questions addressed with the radar methods in this study are: (1) What parts of the vadose zone

  14. Geochemical Processes Controlling Chromium Transport in the Vadose Zone and Regional Aquifer, Los Alamos, New Mexico

    Science.gov (United States)

    Longmire, P.; Ding, M.; Rearick, M.; Vaniman, D.; Katzman, D.

    2008-12-01

    The environmental aqueous geochemistry of Cr is of considerable interest to physical scientists and toxicologists in quantifying the fate and transport of this metal in surface and subsurface environments. Chromium(VI) solutions were released from cooling towers to a stream channel within Sandia Canyon at Los Alamos National Laboratory, NM from 1956 to 1971. These solutions have migrated 293 m depth through the vadose zone, containing several saturated zones, to the regional water table. Concentrations of total dissolved Cr, mainly as Cr(VI), in the regional aquifer range between 0.17 to 8.46 mM. The regional aquifer is characterized by calcium-sodium-bicarbonate solution, contains dissolved oxygen (0.09 to 0.22 mM), and has a circumneutral pH (6.8 to 8.3). Geochemical processes controlling the fate and transport of Cr in groundwater at Los Alamos include a combination of adsorption and precipitation reactions within aquifer systems. Vadose zone material containing hydrous ferric oxide, smectite, silica glass, and calcite widely range in their ability to adsorb Cr(VI) under basic pH conditions. Overall, the vadose zone at Los Alamos is relatively oxidizing, however, basalt flows are locally reducing with respect to Fe. Ferrous iron concentrated within the Cerros del Rio basalt has been shown through batch experiments to reduce Cr(VI) to Cr(III) resulting in precipitation of chromium(III) hydroxide. Regional aquifer material, consisting of silicates, oxides, and calcite, vary in the amount of Fe(II) available in reactive minerals to effectively reduce Cr(VI) to Cr(III). The results of our studies (1) directly assess the relationship between mineralogical characterization and transport behavior of Cr using site-specific hydrogeologic material and (2) provide site-specific adsorption and precipitation parameters obtained through the experiments to refine the fate and transport modeling of Cr within the vadose zone and regional aquifer. Natural attenuation of Cr at Los

  15. Effect of soil moisture on the sorption of trichloroethene vapor to vadose-zone soil at picatinny arsenal, New Jersey

    Science.gov (United States)

    Smith, J.A.; Chiou, C.T.; Kammer, J.A.; Kile, D.E.

    1990-01-01

    This report presents data on the sorption of trichloroethene (TCE) vapor to vadose-zone soil above a contaminated water-table aquifer at Picatinny Arsenal in Morris County, NJ. To assess the impact of moisture on TCE sorption, batch experiments on the sorption of TCE vapor by the field soil were carried out as a function of relative humidity. The TCE sorption decreases as soil moisture content increases from zero to saturation soil moisture content (the soil moisture content in equilibrium with 100% relative humidity). The moisture content of soil samples collected from the vadose zone was found to be greater than the saturation soil-moisture content, suggesting that adsorption of TCE by the mineral fraction of the vadose-zone soil should be minimal relative to the partition uptake by soil organic matter. Analyses of soil and soil-gas samples collected from the field indicate that the ratio of the concentration of TCE on the vadose-zone soil to its concentration in the soil gas is 1-3 orders of magnitude greater than the ratio predicted by using an assumption of equilibrium conditions. This apparent disequilibrium presumably results from the slow desorption of TCE from the organic matter of the vadose-zone soil relative to the dissipation of TCE vapor from the soil gas.

  16. Vertical Extent of 100 Area Vadose Zone Contamination of Metals at the Hanford Site

    Science.gov (United States)

    Khaleel, R.; Mehta, S.

    2012-12-01

    The 100 Area is part of the U.S. Department of Energy Hanford Site in southeastern Washington and borders the Columbia River. The primary sources of contamination in the area are associated with the operation of nine former production reactors, the last one shutting down in 1988. The area is undergoing a CERCLA remedial investigation (RI) that will provide data to support final cleanup decisions. During reactor operations, cooling water contaminated with radioactive and hazardous chemicals was discharged to both the adjacent Columbia River and infiltration cribs and trenches. Contaminated solid wastes were disposed of in burial grounds; the estimated Lead-Cadmium used as "reactor poison" and disposed of in 100 Area burial grounds is 1103 metric tons, of which up to 1059 metric tons are Lead and 44 metric tons are Cadmium. We summarize vadose zone site characterization data for the recently drilled boreholes, including the vertical distribution of concentration profiles for metals (i.e., Lead, Arsenic and Mercury) under the near neutral pH and oxygenated conditions. The deep borehole measurements targeted in the RI work plan were identified with a bias towards locating contaminants throughout the vadose zone and targeted areas at or near the waste sites; i.e., the drilling as well as the sampling was biased towards capturing contamination within the "hot spots." Unlike non-reactive contaminants such as tritium, Arsenic, Mercury and Lead are known to have a higher distribution coefficient (Kd), expected to be relatively immobile, and have a long residence time within the vadose zone. However, a number of sediment samples located close to the water table exceed the background concentrations for Lead and Arsenic. Three conceptual models are postulated to explain the deeper than expected penetration for the metals.

  17. The Use of Radar Methods to Determine Moisture Content in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Rosemary Knight

    2003-12-28

    Water content is a critical parameter affecting both liquid-phase and vapor-phase contaminant transport in the vadose zone. This means that accurate estimates of in situ water content must be obtained in order to design for the appropriate handling or remediation of a contaminated region of the vadose zone. Traditional methods of sampling the subsurface by drilling and/or direct sampling are very time consuming, limited in terms of spatial coverage, and have the associated risk of contacting and increasing the size of the contaminated area. One solution is to use geophysical methods which can provide a high-resolution, non-invasive means of sampling or imaging the subsurface. The overall objective of our research, defined at the start of this project, was to advance the usefulness of radar methods (ground-based and borehole) as a means of characterizing water content in the vadose zone. We have met this objective by providing research results that can be used to (1) improve the accuracy of water content estimates from radar measurements; (2) provide estimates of the potential error in water content estimates from radar measurements; (3) improve the clarity of radar images; (4) develop large-scale models of the subsurface ''architecture'' using radar images; (5) develop ways of quantifying the spatial heterogeneity of the subsurface through analysis of radar images. We have also been able to identify the critical areas where more research is needed in order to be able to use radar methods most effectively as an accurate means of subsurface characterization.

  18. Vadose zone characterization project at the Hanford Tank Farms: U Tank Farm Report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-05-01

    The U.S. Department of Energy Grand Junction Office (DOE-GJO) was tasked by the DOE Richland Operations Office (DOE-RL) to perform a baseline characterization of the gamma-ray-emitting radionuclides that are distributed in the vadose zone sediments beneath and around the single-shell tanks (SSTs) at the Hanford Site. The intent of this characterization is to determine the nature and extent of the contamination, to identify contamination sources when possible, and to develop a baseline of the contamination distribution that will permit future data comparisons. This characterization work also allows an initial assessment of the impacts of the vadose zone contamination as required by the Resource Conservation and Recovery Act (RCRA). This characterization project involves acquiring information regarding vadose zone contamination with borehole geophysical logging methods and documenting that information in a series of reports. This information is presently limited to detection of gamma-emitting radionuclides from both natural and man-made sources. Data from boreholes surrounding each tank are compiled into individual Tank Summary Data Reports. The data from each tank in a tank farm are then compiled and summarized in a Tank Farm Report. This document is the Tank Farm Report for the U Tank Farm. Logging operations used high-purity germanium detection systems to acquire laboratory-quality assays of the gamma-emitting radionuclides in the sediments around and below the tanks. These assays were acquired in 59 boreholes that surround the U Tank Farm tanks. Logging of all boreholes was completed in December 1995, and the last Tank Summary Data Report for the U Tank Farm was issued in September 1996.

  19. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Baolin Deng; Edward Thornton; Kirk Cantrell; Khris Olsen; James Amonette

    2004-01-11

    Immobilization of toxic and radioactive metals in the vadose zone by In Situ Gaseous Reduction (ISGR) using hydrogen sulfide (H2S) is a promising technology for soil remediation. Earlier laboratory and field studies have shown that Cr(VI) can be effectively immobilized by treatment with dilute gaseous H2S. The objective of this project is to characterize the interactions among H2S, the metal contaminants, and soil components. Understanding these interactions is needed to assess the long-term effectiveness of the technology and to optimize the remediation system.

  20. Impact of Groundwater Level on Nitrate Nitrogen Accumulation in the Vadose Zone Beneath a Cotton Field

    Directory of Open Access Journals (Sweden)

    Xiyun Jiao

    2017-02-01

    Full Text Available In this study, the impacts of groundwater level on nitrate nitrogen accumulation in the vadose zone of a cotton field were investigated. Experiments were conducted in a cotton field at the CAS Ecological Agricultural Experiment Station in Nanpi from 2008 to 2010. A vertical observation well was drilled, and time-domain reflectometry probes and soil solution extractors were installed every 50 cm in the walls of the well to a depth of 5 m. The soil water content was monitored, and soil solution samples were obtained and analyzed every six days throughout the growing seasons during the three studied years. Additionally, a water consumption experiment was conducted, and the topsoil water content and leaf area index were measured in the cotton field. The resulting data were used to estimate parameters for use in a soil hydraulic and nitrate nitrogen movement model, and cotton evapotranspiration was calculated using the Penman–Monteith method. Groundwater level increases and decreases of ±4 m were simulated during a ten-year period using HYDRUS-1D. The results showed significant nitrate nitrogen accumulation in the vadose zone when the groundwater level remained unchanged or decreased, with increased accumulation as the groundwater depth increased. Additionally, increased precipitation and a deeper groundwater level resulted in greater nitrate nitrogen leaching in the cotton root zone. Therefore, irrigation and fertilization strategies should be adjusted based on precipitation conditions and groundwater depth.

  1. Multiple lines of evidence to demonstrate vinyl chloride aerobic biodegradation in the vadose zone, and factors controlling rates

    Science.gov (United States)

    Patterson, B. M.; Aravena, R.; Davis, G. B.; Furness, A. J.; Bastow, T. P.; Bouchard, D.

    2013-10-01

    A field-based investigation was conducted at a contaminated site where the vadose zone was contaminated with a range of chlorinated hydrocarbons. The investigation consisted of groundwater and multilevel soil-gas monitoring of a range of contaminants and gases, along with isotope measurements and microbiology studies. The investigation provided multiple lines of evidence that demonstrated aerobic biodegradation of vinyl chloride (VC) was occurring in the vadose zone (i) above the on-site source zone, and (ii) above the downgradient off-site groundwater plume location. Data from both the on-site and off-site locations were consistent in showing substantially greater (an order of magnitude greater) rates of VC removal from the aerobic vadose zone compared to more recalcitrant contaminants trichloroethene (TCE) and tetrachloroethene (PCE). Soil gas VC isotope analysis showed substantial isotopic enrichment of VC (δ13C - 5.2 to - 10.9‰) compared to groundwater (δ13C - 39.5‰) at the on-site location. Soil gas CO2 isotope analysis at both locations showed that CO2 was highly isotopically depleted (δ13C - 28.8 to - 33.3‰), compared to soil gas CO2 data originating from natural sediment organic matter (δ13C = - 14.7 to - 21.3‰). The soil gas CO2 δ13C values were consistent with near-water table VC groundwater δ13C values (- 36.8 to - 39.5‰), suggesting CO2 originating from aerobic biodegradation of VC. Bacteria that had functional genes (ethene monooxygenase (etnC) and epoxyalkane transferase (etnE) involved in ethene metabolism and VC oxidation were more abundant at the source zone where oxygen co-existed with VC. The distribution of VC and oxygen vadose zone vapour plumes, together with long-term changes in soil gas CO2 concentrations and temperature, provided information to elucidate the factors controlling aerobic biodegradation of VC in the vadose zone. Based on the overlapping VC and oxygen vadose zone vapour plumes, aerobic vapour biodegradation

  2. Multiple lines of evidence to demonstrate vinyl chloride aerobic biodegradation in the vadose zone, and factors controlling rates.

    Science.gov (United States)

    Patterson, B M; Aravena, R; Davis, G B; Furness, A J; Bastow, T P; Bouchard, D

    2013-10-01

    A field-based investigation was conducted at a contaminated site where the vadose zone was contaminated with a range of chlorinated hydrocarbons. The investigation consisted of groundwater and multilevel soil-gas monitoring of a range of contaminants and gases, along with isotope measurements and microbiology studies. The investigation provided multiple lines of evidence that demonstrated aerobic biodegradation of vinyl chloride (VC) was occurring in the vadose zone (i) above the on-site source zone, and (ii) above the downgradient off-site groundwater plume location. Data from both the on-site and off-site locations were consistent in showing substantially greater (an order of magnitude greater) rates of VC removal from the aerobic vadose zone compared to more recalcitrant contaminants trichloroethene (TCE) and tetrachloroethene (PCE). Soil gas VC isotope analysis showed substantial isotopic enrichment of VC (δ¹³C -5.2 to -10.9‰) compared to groundwater (δ¹³C -39.5‰) at the on-site location. Soil gas CO₂ isotope analysis at both locations showed that CO₂ was highly isotopically depleted (δ¹³C -28.8 to -33.3‰), compared to soil gas CO₂ data originating from natural sediment organic matter (δ¹³C= -14.7 to -21.3‰). The soil gas CO2 δ¹³C values were consistent with near-water table VC groundwater δ¹³C values (-36.8 to -39.5‰), suggesting CO₂ originating from aerobic biodegradation of VC. Bacteria that had functional genes (ethene monooxygenase (etnC) and epoxyalkane transferase (etnE)) involved in ethene metabolism and VC oxidation were more abundant at the source zone where oxygen co-existed with VC. The distribution of VC and oxygen vadose zone vapour plumes, together with long-term changes in soil gas CO₂ concentrations and temperature, provided information to elucidate the factors controlling aerobic biodegradation of VC in the vadose zone. Based on the overlapping VC and oxygen vadose zone vapour plumes, aerobic vapour

  3. Vadose zone attenuation of organic compounds at a crude oil spill site - Interactions between biogeochemical reactions and multicomponent gas transport

    Science.gov (United States)

    Molins, S.; Mayer, K.U.; Amos, R.T.; Bekins, B.A.

    2010-01-01

    Contaminant attenuation processes in the vadose zone of a crude oil spill site near Bemidji, MN have been simulated with a reactive transport model that includes multicomponent gas transport, solute transport, and the most relevant biogeochemical reactions. Dissolution and volatilization of oil components, their aerobic and anaerobic degradation coupled with sequential electron acceptor consumption, ingress of atmospheric O2, and the release of CH4 and CO2 from the smear zone generated by the floating oil were considered. The focus of the simulations was to assess the dynamics between biodegradation and gas transport processes in the vadose zone, to evaluate the rates and contributions of different electron accepting processes towards vadose zone natural attenuation, and to provide an estimate of the historical mass loss. Concentration distributions of reactive (O2, CH4, and CO2) and non-reactive (Ar and N2) gases served as key constraints for the model calibration. Simulation results confirm that as of 2007, the main degradation pathway can be attributed to methanogenic degradation of organic compounds in the smear zone and the vadose zone resulting in a contaminant plume dominated by high CH4 concentrations. In accordance with field observations, zones of volatilization and CH4 generation are correlated to slightly elevated total gas pressures and low partial pressures of N2 and Ar, while zones of aerobic CH4 oxidation are characterized by slightly reduced gas pressures and elevated concentrations of N2 and Ar. Diffusion is the most significant transport mechanism for gases in the vadose zone; however, the simulations also indicate that, despite very small pressure gradients, advection contributes up to 15% towards the net flux of CH4, and to a more limited extent to O2 ingress. Model calibration strongly suggests that transfer of biogenically generated gases from the smear zone provides a major control on vadose zone gas distributions and vadose zone carbon

  4. Application of Vadose Zone Monitoring Technology for Characterization of Leachate Generation in Landfills

    Science.gov (United States)

    aharoni, imri; dahan, ofer

    2016-04-01

    Ground water contamination due to landfill leachate percolation is considered the most severe environmental threat related to municipal solid waste landfills. Natural waste degradation processes in landfills normally produce contaminated leachates up to decades after the waste has been buried. Studies have shown that understanding the mechanisms which govern attenuation processes and the fate of pollutants in the waste and in the underlying unsaturated zone is crucial for evaluation of environmental risks and selection of a restoration strategy. This work focuses on a closed landfill in the coastal plain of Israel that was active until 2002 without any lining infrastructure. A vadose zone monitoring system (VMS) that was implemented at the site enables continuous measurements across the waste body (15 m thick) and underlying sandy vadose zone (16 m thick). Data collected by the VMS included continuous measurements of water content as well as chemical composition of the leachates across the entire waste and vadose zone cross section. Results indicated that winter rain percolated through the waste, generating wetting waves which were observed across the waste and unsaturated sediment from land surface until groundwater at 31 m bls. Quick percolation and high fluxes were observed in spite of the clay cover that was implemented at the site as part of the rehabilitation scheme. The results show that the flow pattern is controlled by a preferential mechanism within the waste body. Specific sections showed rapid fluxes in response to rain events, while other sections remained unaffected. In the underlying sandy vadose zone the flow pattern exhibited characteristics of matrix flow. Yet, some sections received higher fluxes due to the uneven discharge of leachates from the overlying waste body. Water samples collected from the waste layer indicate production of highly polluted leachates over 14 years after the landfill was closed. The chemical composition within the waste

  5. Characterization of Vadose Zone Sediments from C Waste Management Area: Investigation of the C-152 Transfer Line Leak

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Serne, R. Jeffrey; Bjornstad, Bruce N.; Valenta, Michelle M.; Lanigan, David C.; Vickerman, Tanya S.; Clayton, Ray E.; Geiszler, Keith N.; Iovin, Cristian; Clayton, Eric T.; Kutnyakov, Igor V.; Baum, Steven R.; Lindberg, Michael J.; Orr, Robert D.

    2008-09-11

    The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in January 2007. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc., tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within waste management area (WMA) C. Specifically, this report contains all the geologic, geochemical, and selected physiochemical characterization data compiled on vadose zone sediment recovered from direct-push samples collected around the site of an unplanned release (UPR), UPR-200-E-82, adjacent to the 241-C-152 Diversion Box located in WMA C.

  6. In situ bioremediation of nitrate and perchlorate in vadose zone soil for groundwater protection using gaseous electron donor injection technology.

    Science.gov (United States)

    Evans, Patrick J; Trute, Mary M

    2006-12-01

    When present in the vadose zone, potentially toxic nitrate and perchlorate anions can be persistent sources of groundwater contamination. Gaseous electron donor injection technology (GEDIT), an anaerobic variation of petroleum hydrocarbon bioventing, involves injecting electron donor gases, such as hydrogen or ethyl acetate, into the vadose zone, to stimulate biodegradation of nitrate and perchlorate. Laboratory microcosm studies demonstrated that hydrogen and ethanol promoted nitrate and perchlorate reduction in vadose zone soil and that moisture content was an important factor. Column studies demonstrated that transport of particular electron donors varied significantly; ethyl acetate and butyraldehyde were transported more rapidly than butyl acetate and ethanol. Nitrate removal in the column studies, up to 100%, was best promoted by ethyl acetate. Up to 39% perchlorate removal was achieved with ethanol and was limited by insufficient incubation time. The results demonstrate that GEDIT is a promising remediation technology warranting further validation.

  7. Potential of arid zone vegetation as a source of substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bassham, J.A.

    1977-11-01

    Three aspects of the potential of vegetation in arid zones as a source of substrates are discussed. The first includes the limitations on efficiency of conversion of solar energy to the stored chemical energy of biomass in green plants, and the subsequent biochemical pathways of carbon dioxide fixation and biosynthesis. Second is the potential of plants endogenous to arid zones. Finally, the use of covered agriculture or controlled environmental agriculture (CEA) is considered both in its present form and in terms of possible extenion to the large scale production of stable crops. (JGB)

  8. Deep Vadose Zone Treatability Test for the Hanford Central Plateau: Interim Post-Desiccation Monitoring Results, Fiscal Year 2014

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Strickland, Christopher E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clayton, Ray E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chronister, Glen B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    Over decades of operation, the U.S. Department of Energy (DOE) and its predecessors have released nearly 2 trillion L (450 billion gal.) of liquid into the vadose zone at the Hanford Site. Much of this discharge of liquid waste into the vadose zone occurred in the Central Plateau, a 200 km2 (75 mi2) area that includes approximately 800 waste sites. Some of the inorganic and radionuclide contaminants in the deep vadose zone at the Hanford Site are at depths below the limit of direct exposure pathways, but may need to be remediated to protect groundwater. The Tri-Party Agencies (DOE, U.S. Environmental Protection Agency, and Washington State Department of Ecology) established Milestone M 015 50, which directed DOE to submit a treatability test plan for remediation of technetium-99 (Tc-99) and uranium in the deep vadose zone. These contaminants are mobile in the subsurface environment and have been detected at high concentrations deep in the vadose zone, and at some locations have reached groundwater. Testing technologies for remediating Tc-99 and uranium will also provide information relevant for remediating other contaminants in the vadose zone. A field test of desiccation is being conducted as an element of the DOE test plan published in March 2008 to meet Milestone M 015 50. The active desiccation portion of the test has been completed. Monitoring data have been collected at the field test site during the post-desiccation period and are reported herein. This is an interim data summary report that includes about 3 years of post-desiccation monitoring data. The DOE field test plan proscribes a total of 5 years of post-desiccation monitoring.

  9. Flow and Transport in the Hanford 300 Area Vadose Zone-Aquifer-River System

    Energy Technology Data Exchange (ETDEWEB)

    Waichler, Scott R.; Yabusaki, Steven B.

    2005-07-13

    Contaminant migration in the 300 Area unconfined aquifer is strongly coupled to fluctuations in the Columbia River stage. To better understand the interaction between the river, aquifer, and vadose zone, a 2-D saturated-unsaturated flow and transport model was developed for a vertical cross-section aligned west-east across the Hanford Site 300 Area, nearly perpendicular to the river. The model was used to investigate water flow and tracer transport in the vadose zone-aquifer-river flow system, in support of the ongoing study of the 300 Area uranium plume. The STOMP simulator was used to model 1-year from 3/1/92 to 2/28/93, a period when hourly data were available for both groundwater and river levels. Net water flow to the river (per 1-meter width of shoreline) was 182 m3/y in the base case, but the cumulative exchange or total flow back and forth across the riverbed was 30 times greater. The low river case had approximately double the net water and Groundwater tracer flux into the river as compared to the base case.

  10. The effect of subsurface military detonations on vadose zone hydraulic conductivity, contaminant transport and aquifer recharge

    Science.gov (United States)

    Lewis, Jeffrey; Burman, Jan; Edlund, Christina; Simonsson, Louise; Berglind, Rune; Leffler, Per; Qvarfort, Ulf; Thiboutot, Sonia; Ampleman, Guy; Meuken, Denise; Duvalois, Willem; Martel, Richard; Sjöström, Jan

    2013-03-01

    Live fire military training involves the detonation of explosive warheads on training ranges. The purpose of this experiment is to evaluate the hydrogeological changes to the vadose zone caused by military training with high explosive ammunition. In particular, this study investigates artillery ammunition which penetrates underground prior to exploding, either by design or by defective fuze mechanisms. A 105 mm artillery round was detonated 2.6 m underground, and hydraulic conductivity measurements were taken before and after the explosion. A total of 114 hydraulic conductivity measurements were obtained within a radius of 3 m from the detonation point, at four different depths and at three different time periods separated by 18 months. This data was used to produce a three dimensional numerical model of the soil affected by the exploding artillery round. This model was then used to investigate potential changes to aquifer recharge and contaminant transport caused by the detonating round. The results indicate that an exploding artillery round can strongly affect the hydraulic conductivity in the vadose zone, increasing it locally by over an order of magnitude. These variations, however, appear to cause relatively small changes to both local groundwater recharge and contaminant transport.

  11. Implementation Plan for the Deep Vadose Zone-Applied Field Research Center

    Energy Technology Data Exchange (ETDEWEB)

    Wellman, Dawn M.; Truex, Michael J.; Freshley, Mark D.; Gephart, Roy E.; Triplett, Mark B.; Johnson, Timothy C.

    2011-02-11

    The Long-Range Deep Vadose Zone Program Plan was published in October 2010. It summarized the U.S. Department of Energy’s (DOE’s) state-of-knowledge about the contaminant remediation challenges facing the deep vadose zone (DVZ) beneath the Central Plateau of the Hanford Site and their approach to solving those challenges. Developing an implementation plan is the next step to address the knowledge and capabilities required to solve DVZ challenges when needed. This multi-year plan (FY-11 through FY-20) identifies the short to long-term research, management, and execution plans required to solve those problems facing the DVZ-Applied Field Research Center (DVZ-AFRC). The schedule supporting implementation overlies existing activities and milestones from Hanford’s DOE-Environmental Management (EM) end-user projects. Success relies upon multi-project teams focused on coordinated subsurface projects undertaken across the DOE Complex combined with facilitated, problem-focused, research investments implemented through the DVZ-AFRC.

  12. Analysis of Radionuclide Migration Through a 200-m Vadose Zone Following a 16-Year Infiltration Event

    Energy Technology Data Exchange (ETDEWEB)

    Tompson, A F B; Smith, D K; Hudson, G B

    2002-01-31

    The CAMBRIC nuclear test was conducted beneath Frenchman Flat at the Nevada Test Site on May 14, 1965. The nuclear device was emplaced in heterogeneous alluvium, approximately 70 m beneath the ambient water table, which is itself 220 m beneath the ground surface. Approximately 10 years later, groundwater adjacent to the test was pumped steadily for 16 years to elicit information on radionuclide migration in the saturated zone. The pumping well effluent--containing mostly soluble radionuclides such as tritium, {sup 14}C, {sup 36}Cl, {sup 85}Kr, {sup 129}I, and {sup 106}Ru--was monitored, discharged to an unlined ditch, and allowed to flow towards Frenchman Lake just over one kilometer away. Water discharged into the ditch infiltrated into the ground during flow along the ditch. This created an unexpected and remarkable second experiment in which the migration of the effluent through the 220 meters of unsaturated media, or ''vadose zone'', back to the water table, could be studied. In this paper, the pumping and effluent data are being utilized in conjunction with a series of geologic data, new radionuclide measurements, isotopic age-dating estimates, and vadose zone flow and transport models to better understand the movement of radionuclides between the ditch and the water table. Measurements of radionuclide concentrations in water samples produced from a water table monitoring well 100m away from the ditch indicate rising levels of tritium since 1993. The detection of tritium in the monitoring well occurs approximately 16 years after its initial discharge into the ditch. Modeling and tritium age dating have suggested 3 to 5 years of this 16-year transit time occurred solely in the vadose zone. They also suggest considerable recirculation of the pumping well discharge back into the original pumping well. Surprisingly, no {sup 14}C was observed at the water table, suggesting its preferential retention, possibly due to precipitation or other

  13. Monitoring water storage variations in the vadose zone with gravimeters - quantifying the influence of observatory buildings

    Science.gov (United States)

    Reich, Marvin; Güntner, Andreas; Mikolaj, Michal; Blume, Theresa

    2016-04-01

    Time-lapse ground-based measurements of gravity have been shown to be sensitive to water storage variations in the surroundings of the gravimeter. They thus have the potential to serve as an integrative observation of storage changes in the vadose zone. However, in almost all cases of continuous gravity measurements, the gravimeter is located within a building which seals the soil beneath it from natural hydrological processes like infiltration and evapotranspiration. As water storage changes in close vicinity of the gravimeter have the strongest influence on the measured signal, it is important to understand the hydrology in the unsaturated soil zone just beneath the impervious building. For this reason, TDR soil moisture sensors were installed in several vertical profiles up to a depth of 2 m underneath the planned new gravimeter building at the Geodetic Observatory Wettzell (southeast Germany). In this study, we assess the influence of the observatory building on infiltration and subsurface flow patterns and thus the damping effect on gravimeter data in a two-way approach. Firstly, soil moisture time series of sensors outside of the building area are correlated with corresponding sensors of the same depth beneath the building. The resulting correlation coefficients, time lags and signal to noise relationships are used to find out how and where infiltrating water moves laterally beneath the building and towards its centre. Secondly, a physically based hydrological model (HYDRUS) with high discretization in space and time is set up for the 20 by 20 m area around and beneath the gravimeter building. The simulated spatial distribution of soil moisture in combination with the observed point data help to identify where and to what extent water storage changes and thus mass transport occurs beneath the building and how much this differs to the dynamics of the surroundings. This allows to define the umbrella space, i.e., the volume of the vadose zone where no mass

  14. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA; Co-Principal Investigator: Jeff Terry, Illinois Institute of Technology, Chicago, IL

    2008-05-12

    There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of the most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H{sub 2}S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H{sub 2}S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H{sub 2}S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H{sub 2}S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The

  15. Vadose zone process that control landslide initiation and debris flow propagation

    Science.gov (United States)

    Sidle, Roy C.

    2015-04-01

    Advances in the areas of geotechnical engineering, hydrology, mineralogy, geomorphology, geology, and biology have individually advanced our understanding of factors affecting slope stability; however, the interactions among these processes and attributes as they affect the initiation and propagation of landslides and debris flows are not well understood. Here the importance of interactive vadose zone processes is emphasized related to the mechanisms, initiation, mode, and timing of rainfall-initiated landslides that are triggered by positive pore water accretion, loss of soil suction and increase in overburden weight, and long-term cumulative rain water infiltration. Both large- and small-scale preferential flow pathways can both contribute to and mitigate instability, by respectively concentrating and dispersing subsurface flow. These mechanisms are influenced by soil structure, lithology, landforms, and biota. Conditions conducive to landslide initiation by infiltration versus exfiltration are discussed relative to bedrock structure and joints. The effects of rhizosphere processes on slope stability are examined, including root reinforcement of soil mantles, evapotranspiration, and how root structures affect preferential flow paths. At a larger scale, the nexus between hillslope landslides and in-channel debris flows is examined with emphasis on understanding the timing of debris flows relative to chronic and episodic infilling processes, as well as the episodic nature of large rainfall and related stormflow generation in headwater streams. The hydrogeomorphic processes and conditions that determine whether or not landslides immediately mobilize into debris flows is important for predicting the timing and extent of devastating debris flow runout in steep terrain. Given the spatial footprint of individual landslides, it is necessary to assess vadose zone processes at appropriate scales to ascertain impacts on mass wasting phenomena. Articulating the appropriate

  16. Vadose-zone moisture dynamics under radiation boundary conditions during a drying process

    Institute of Scientific and Technical Information of China (English)

    韩江波; 周志芳; 傅志敏; 王锦国

    2014-01-01

    In order to better understand the soil moisture dynamics during a drying process, a soil column experiment is conducted in the laboratory, followed by the numerical modeling with consideration of the coupled liquid water, water vapor and heat transport in the vadose zone. Results show that there are three distinct subzones above the water table according to the temporally dynamic variation of the water content profiles. Zone 1 sees a decrease in the water contents in the upper profiles (0 m-0.05 m) due to a negative net water flux in this zone where the upward isothermal water vapor flux becomes the main flow mechanism in the soils. In contrast, the water content within Zone 2 in the depth ranging from 0.05 m to 0.37 m sees an apparent increase over time, resulting from the positive net thermal water-vapor and isothermal liquid-water fluxes into this layer. Zone 3 (0.37 m-0.65 m) also sees an apparent decrease in the water content since the isothermal liquid water flux carries the liquid water either upward out of this region for vaporization or downward to the water table as a recharge to the groundwater.

  17. Conceptual Model of Uranium in the Vadose Zone for Acidic and Alkaline Wastes Discharged at the Hanford Site Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Serne, R. Jeffrey [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    Historically, uranium was disposed in waste solutions of varying waste chemistry at the Hanford Site Central Plateau. The character of how uranium was distributed in the vadose zone during disposal, how it has continued to migrate through the vadose zone, and the magnitude of potential impacts on groundwater are strongly influenced by geochemical reactions in the vadose zone. These geochemical reactions can be significantly influenced by the disposed-waste chemistry near the disposal location. This report provides conceptual models and supporting information to describe uranium fate and transport in the vadose zone for both acidic and alkaline wastes discharged at a substantial number of waste sites in the Hanford Site Central Plateau. The conceptual models include consideration of how co-disposed acidic or alkaline fluids influence uranium mobility in terms of induced dissolution/precipitation reactions and changes in uranium sorption with a focus on the conditions near the disposal site. This information, when combined with the extensive information describing uranium fate and transport at near background pH conditions, enables focused characterization to support effective fate and transport estimates for uranium in the subsurface.

  18. Data analysis for preliminary conceptual model design, Vadose Zone Monitoring System (VZMS), McClellan AFB. 1997 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.T.; Oldenburg, C.M.

    1998-01-05

    Vadose zone investigations are being performed at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) is being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature. Although each individual data set is useful in improving the characterization of this contaminated site, the overall purpose of data collection is to provide input for the conceptual and numerical modeling of VOC transport in the vadose zone and the exchange of contaminants between the vadose zone and groundwater. In this report the authors submit a summary and preliminary analysis of the data collected through the end of 1997 and present it in the context of input for the impending modeling. This report merges findings from both the first and second half of 1997 and is presented as an annual report in lieu of two semi-annual reports, due to the fact that insufficient data had been collected up to mid June to allow a meaningful analysis.

  19. Coupled effects of solution chemistry and hydrodynamics on the mobility and transport of quantum dot nanomaterials in the Vadose Zone

    Science.gov (United States)

    To investigate the coupled effects of solution chemistry and vadose zone processes on the mobility of quantum dot (QD) nanoparticles, laboratory scale transport experiments were performed. The complex coupled effects of ionic strength, size of QD aggregates, surface tension, contact angle, infiltrat...

  20. Effects of Lime and Concrete Waste on Vadose Zone Carbon Cycling

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jessen, Søren; Postma, D.

    2014-01-01

    In this work we investigate how lime and crushed concrete waste (CCW) affect carbon cycling in the vadose zone and explore whether these amendments could be employed to mitigate climate change by increasing the transport of CO2 from the atmosphere to the groundwater. We use a combination...... of experimental and modeling tools to determine ongoing biogeochemical processes. Our results demonstrate that lime and CCW amendments to acid soil contribute to the climate forcing by largely increasing the soil CO2 efflux to the atmosphere. In a series of mesocosm experiments, with barley (Hordeum vulgare L...... and lime treatments increased the dissolved inorganic carbon (DIC) percolation flux by about 150 and 100%, respectively,compared to the controls. However, concurrent increases in the CO2 efflux to the atmosphere (ER) were more than one order of magnitude higher than increases in the DIC percolation flux...

  1. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jacques, D.; Jessen, S.;

    2014-01-01

    mechanisms. Carbon dioxide partial pressure in the soil gas (pCO(2)), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO(2), alkalinity and the water flux...... percolation flux was more than one-third of the flux during growth. The R-s was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO(2) and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during......The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying...

  2. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    DEFF Research Database (Denmark)

    Thaysen, Eike Marie; Jacques, D.; Jessen, S.

    2014-01-01

    mechanisms. Carbon dioxide partial pressure in the soil gas (pCO(2)), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO(2), alkalinity and the water flux......The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying...... at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO(2) gradients...

  3. Spectroscopic Evidence for Uranium Bearing Precipitates in Vadose Zone Sediments at the Hanford 300-Area Site

    Energy Technology Data Exchange (ETDEWEB)

    Arai, Yuji [Clemson Univ., SC (United States); Marcus, Matthew A. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tamura, Nobumichi [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Davis, James A. [United States Geological Survey, Menlo Park, CA (United States); Zachara, John M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2007-07-01

    Uranium(U) solid-state speciation in vadose zone sediments collected beneath the former North Process Pond (NPP) in the 300-Area of the Hanford site (WA, USA) was investigated using multi-scale techniques. In 30-day batch experiments, only a small fraction of total U (~7.4%) was released to artificial groundwater solutions equilibrated with 1% pCO2. Synchrotron-based micro X-ray fluorescence spectroscopy analyses showed that U was distributed among at least two types of species: 1) U discrete grains associated with Cu, and 2) areas with intermediate U concentrations on grains and grain coatings. Metatorbernite (Cu[UO2]2[PO4]2•8H2O) and uranophane (Ca[UO2]2[SiO3(OH)]2•5H2O) at some U discrete grains, and muscovite at U intermediate concentration areas were identified in synchrotron-based micro X-ray diffraction. SEM/EDS analyses revealed 8-10 µm size metatorbernite particles that were embedded in C-, Al-, and Si-rich coatings on quartz and albite grains. In μ- and bulk-X-ray Absorption Structure (μ-XAS and XAS) spectroscopy analyses, the structure of metatorbernite with additional U-C and U-U coordination environments were consistently observed at U discrete grains with high U concentrations. The consistency of the μ- and bulk-XAS analyses suggests that metatorbernite may comprise a significant fraction of the total U in the sample. The entrapped, micron-sized metatorbernite particles in C, Al, and Si rich coatings, along with the more soluble precipitated uranyl carbonates and uranophane, likely control the long-term release of U to water associated with the vadose zone sediments.

  4. T-TY Tank Farm Interim Surface Barrier Demonstration—Vadose Zone Monitoring Plan

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Strickland, Christopher E.; Field, Jim G.; Parker, Danny L.

    2010-09-27

    The Hanford Site has 149 underground single-shell tanks that store hazardous radioactive waste. Many of these tanks and their associated infrastructure (e.g., pipelines, diversion boxes) have leaked. Some of the leaked waste has entered the groundwater. The largest known leak occurred from the T-106 Tank of the 241-T Tank Farm in 1973. Five tanks are assumed to have leaked in the TY Farm. Many of the contaminants from those leaks still reside within the vadose zone within the T and TY Tank Farms. The Department of Energy’s Office of River Protection seeks to minimize the movement of these contaminant plumes by placing interim barriers on the ground surface. Such barriers are expected to prevent infiltrating water from reaching the plumes and moving them further. The soil water regime is monitored to determine the effectiveness of the interim surface barriers. Soil-water content and water pressure are monitored using off-the-shelf equipment that can be installed by the hydraulic hammer technique. Four instrument nests were installed in the T Farm in fiscal year (FY) 2006 and FY2007; two nests were installed in the TY Farm in FY2010. Each instrument nest contains a neutron probe access tube, a capacitance probe, and four heat-dissipation units. A meteorological station has been installed at the north side of the fence of the T Farm. This document summarizes the monitoring methods, the instrument calibration and installation, and the vadose zone monitoring plan for interim barriers in T farm and TY Farm.

  5. Vadose Zone Characterization and Monitoring Beneath Waste Disposal Pits Using Horizontal Boreholes

    Science.gov (United States)

    McLin, S. G.; Newman, B. D.; Broxton, D. E.

    2004-12-01

    Vadose zone characterization and monitoring immediately below landfills using horizontal boreholes is an emerging technology. However, this topic has received little attention in the peer-reviewed literature. The value of this approach is that activities are conducted below the waste, providing clear and rapid verification of containment. Here we report on two studies that examined the utility of horizontal boreholes for environmental characterization and monitoring under radioactive waste disposal pits. Both studies used core sample analyses to determine the presence of various radionuclides, organics, or metals. At one borehole site, water content and pore-water chloride concentrations were also used to interpret vadose zone behavior. At another site, we examined the feasibility of using flexible membrane liners in uncased boreholes for periodic monitoring. For this demonstration, these retrievable liners were air-injected into boreholes on multiple occasions carrying different combinations of environmental surveillance equipment. Instrument packages included a neutron logging device to measure volumetric water at regular intervals, high-absorbency collectors that wicked available water from borehole walls, or vent tubes that were used to measure air permeability and collect air samples. The flexible and retrievable liner system was an effective way to monitor water content and collect air permeability data. The high-absorbency collectors were efficient at extracting liquid water for contaminant analyses even at volumetric water contents below 10 percent, and revealed vapor-phase tritium migration at one disposal pit. Both demonstration studies proved that effective characterization and periodic monitoring in horizontal boreholes is both feasible and adaptable to many waste disposal problems and locations.

  6. As transport characterization in the vadose zone of the soil : a combined study between field and laboratory experiments

    OpenAIRE

    Michel, Julien; Rollin, Claire

    2011-01-01

    Heavy metals are major soil pollutants since a lot of former industrial soils are polluted by these contaminants. In the context of risk assessment of contaminated sites, they are of particular concerns because of their toxicity toward human beings. Nevertheless, the vadose zone of the soil is not taken into consideration in this kind of studies though this is where the pollution enters the soil. That is why mechanisms responsible for trace element release in the unsaturated zone of the soil ...

  7. Real-time monitoring of nitrate transport in the deep vadose zone under a crop field - implications for groundwater protection

    Science.gov (United States)

    Turkeltaub, Tuvia; Kurtzman, Daniel; Dahan, Ofer

    2016-08-01

    Nitrate is considered the most common non-point pollutant in groundwater. It is often attributed to agricultural management, when excess application of nitrogen fertilizer leaches below the root zone and is eventually transported as nitrate through the unsaturated zone to the water table. A lag time of years to decades between processes occurring in the root zone and their final imprint on groundwater quality prevents proper decision-making on land use and groundwater-resource management. This study implemented the vadose-zone monitoring system (VMS) under a commercial crop field. Data obtained by the VMS for 6 years allowed, for the first time known to us, a unique detailed tracking of water percolation and nitrate migration from the surface through the entire vadose zone to the water table at 18.5 m depth. A nitrate concentration time series, which varied with time and depth, revealed - in real time - a major pulse of nitrate mass propagating down through the vadose zone from the root zone toward the water table. Analysis of stable nitrate isotopes indicated that manure is the prevalent source of nitrate in the deep vadose zone and that nitrogen transformation processes have little effect on nitrate isotopic signature. The total nitrogen mass calculations emphasized the nitrate mass migration towards the water table. Furthermore, the simulated pore-water velocity through analytical solution of the convection-dispersion equation shows that nitrate migration time from land surface to groundwater is relatively rapid, approximately 5.9 years. Ultimately, agricultural land uses, which are constrained to high nitrogen application rates and coarse soil texture, are prone to inducing substantial nitrate leaching.

  8. Characterization Activities to Determine the Extent of DNAPL in the Vadose Zone at the A-014 Outfall of A/M Area

    Energy Technology Data Exchange (ETDEWEB)

    Jackson, D.G.

    2000-09-05

    The purpose of this investigation was to perform characterization activities necessary to confirm the presence and extent of DNAPL in the shallow vadose zone near the headwaters of the A-014 Outfall. Following the characterization, additional soil vapor extraction wells and vadose monitoring probes were installed to promote and monitor remediation activities in regions of identified DNAPL.

  9. Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Dresel, P. Evan; Qafoku, Nikolla; McKinley, James P.; Fruchter, Jonathan S.; Ainsworth, Calvin C.; Liu, Chongxuan; Ilton, Eugene S.; Phillips, J. L.

    2008-07-16

    The major objectives of the proposed study were to: 1.) determine the leaching characteristics of hexavalent chromium [Cr(VI)] from contaminated sediments collected from 100 Area spill sites; 2.) elucidate possible Cr(VI) mineral and/or chemical associations that may be responsible for Cr(VI) retention in the Hanford Site 100 Areas through the use of i.) macroscopic leaching studies and ii.) microscale characterization of contaminated sediments; and 3.) provide information to construct a conceptual model of Cr(VI) geochemistry in the Hanford 100 Area vadose zone. In addressing these objectives, additional benefits accrued were: (1) a fuller understanding of Cr(VI) entrained in the vadose zone that will that can be utilized in modeling potential Cr(VI) source terms, and (2) accelerating the Columbia River 100 Area corridor cleanup by providing valuable information to develop remedial action based on a fundamental understanding of Cr(VI) vadose zone geochemistry. A series of macroscopic column experiments were conducted with contaminated and uncontaminated sediments to study Cr(VI) desorption patterns in aged and freshly contaminated sediments, evaluate the transport characteristics of dichromate liquid retrieved from old pipelines of the 100 Area; and estimate the effect of strongly reducing liquid on the reduction and transport of Cr(VI). Column experiments used the < 2 mm fraction of the sediment samples and simulated Hanford groundwater solution. Periodic stop-flow events were applied to evaluate the change in elemental concentration during time periods of no flow and greater fluid residence time. The results were fit using a two-site, one dimensional reactive transport model. Sediments were characterized for the spatial and mineralogical associations of the contamination using an array of microscale techniques such as XRD, SEM, EDS, XPS, XMP, and XANES. The following are important conclusions and implications. Results from column experiments indicated that most

  10. T-TY Tank Farm Interim Surface Barrier Demonstration - Vadose Zone Monitoring FY10 Report

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Strickland, Christopher E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Field, Jim G. [Washington River Protection Solutions, Inc., Richland, WA (United States); Parker, Danny L. [Washington River Protection Solutions, Inc., Richland, WA (United States)

    2011-01-01

    The U.S. Department of Energy’s Office of River Protection has constructed interim surface barriers over a portion of the T and TY tank farms as part of the Interim Surface Barrier Demonstration Project. The interim surface barriers (hereafter referred to as the surface barriers or barriers) are designed to minimize the infiltration of precipitation into the soil zones containing radioactive contaminants and minimize the movement of the contaminants. As part of the demonstration effort, vadose zone moisture is being monitored to assess the effectiveness of the barriers at reducing soil moisture. Solar-powered systems were installed to continuously monitor soil water conditions at four locations in the T (i.e., instrument Nests TA, TB, TC, and TD) and the TY (i.e., instrument Nests TYA and TYB) Farms beneath the barriers and outside the barrier footprint as well as site meteorological conditions. Nests TA and TYA are placed in the area outside the barrier footprint and serve as controls, providing subsurface conditions outside the influence of the surface barriers. Nest TB provides subsurface measurements to assess surface-barrier edge effects. Nests TC, TD, and TYB are used to assess changes in soil-moisture conditions beneath the interim surface barriers.

  11. Interpretation of vadose zone monitoring system data near engineered trench 1

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Whiteside, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-12-12

    The E-Area Vadose Zone Monitoring System (VZMS) includes lysimeter sampling points at many locations alongside and angling beneath the Engineered Trench #1 (ET1) disposal unit footprint. The sampling points for ET1 were selected for this study because collectively they showed consistently higher tritium (H-3) concentrations than lysimeters associated with other trench units. The VZMS tritium dataset for ET1 from 2001 through 2015 comprises concentrations at or near background levels at approximately half of locations through time, concentrations up to about 600 pCi/mL at a few locations, and concentrations at two locations that have exceeded 1000 pCi/mL. The highest three values through 2015 were 6472 pCi/mL in 2014 and 4533 pCi/mL in 2013 at location VL-17, and 3152 pCi/mL in 2007 at location VL-15. As a point of reference, the drinking water standard for tritium and a DOE Order 435.1 performance objective in the saturated zone at the distant 100-meter facility perimeter is 20 pCi/mL. The purpose of this study is to assess whether these elevated concentrations are indicative of a general trend that could challenge 2008 E-Area Performance Assessment (PA) conclusions, or are isolated perturbations that when considered in the context of an entire disposal unit would support PA conclusions.

  12. A modular subsurface borehole-tower for deep vadose zone monitoring

    Science.gov (United States)

    Breitenstein, Daniel; Or, Dani

    2016-04-01

    Some of the most urgent contemporary societal challenges ranging from climate change to ecosystem services and food security are strongly linked to processes taking place in the vadose zone. The growing interest in this critical zone prompted a massive deployment of eco-hydrological networks (TERENO, CZO, and more) focusing on long term and highly resolved monitoring of key variables such as soil moisture, pressure, temperature, gas fluxes and more. A challenge in all these endeavors remains the reliable and consistent acquisition of variables to depths of eco-hydrological interest (a few meters in some cases), especially soil moisture. In the absence of off-the-shelf sensor systems capable of vertically resolved acquisition of these variables, we developed a prototype of a modular borehole-based tower for simultaneous monitoring of water content, temperature, oxygen and CO2 gas concentrations, and potentially other variables (relative humidity, capillary pressure). The modular tower is made up of 1.5 m sections of 75 mm PVC tubing with TDR waveguides mounted on outer walls. Each paired waveguides (0.15 m in length) were installed on two opposing sides of inflatable sections along the modular unit to ensure contact with the borehole walls. Oxygen and CO2 are measured using solid-state and optical gas sensors that could be periodically calibrated for potential drift. A prototype that could be extended to 6 m depth and preliminary calibration results will be presented (as a potential design for future CZO's). We welcome suggestions for expansion and improvements.

  13. Integrated Field, Laboratory, and Modeling Studies to Determine the Effects of Linked Microbial and Physical Spatial Heterogeneity on Engineered Vadose Zone Bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    Fred Brokman; John Selker; Mark Rockhold

    2004-01-26

    While numerous techniques exist for remediation of contaminant plumes in groundwater or near the soil surface, remediation methods in the deep vadose zone are less established due to complex transport dynamics and sparse microbial populations. There is a lack of knowledge on how physical and hydrologic features of the vadose zone control microbial growth and colonization in response to nutrient delivery during bioremediation. Yet pollution in the vadose zone poses a serious threat to the groundwater resources lying deeper in the sediment. While the contaminants may be slowly degraded by native microbial communities, microbial degradation rates rarely keep pace with the spread of the pollutant. It is crucial to increase indigenous microbial degradation in the vadose zone to combat groundwater contamination.

  14. Integrated Field, Laboratory, and Modeling Studies to Determine the Effects of Linked Microbial and Physical Spatial Heterogeneity on Engineered Vadose Zone Bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    Brockman, Fred J.; Selker, John S.; Rockhold, Mark L.

    2004-10-31

    Executive Summary - While numerous techniques exist for remediation of contaminant plumes in groundwater or near the soil surface, remediation methods in the deep vadose zone are less established due to complex transport dynamics and sparse microbial populations. There is a lack of knowledge on how physical and hydrologic features of the vadose zone control microbial growth and colonization in response to nutrient delivery during bioremediation. Yet pollution in the vadose zone poses a serious threat to the groundwater resources lying deeper in the sediment. While the contaminants may be slowly degraded by native microbial communities, microbial degradation rates rarely keep pace with the spread of the pollutant. It is crucial to increase indigenous microbial degradation in the vadose zone to combat groundwater contamination...

  15. CO2 migration in the vadose zone: experimental and numerical modelling of controlled gas injection

    Science.gov (United States)

    gasparini, andrea; credoz, anthony; grandia, fidel; garcia, david angel; bruno, jordi

    2014-05-01

    The mobility of CO2 in the vadose zone and its subsequent transfer to the atmosphere is a matter of concern in the risk assessment of the geological storage of CO2. In this study the experimental and modelling results of controlled CO2 injection are reported to better understanding of the physical processes affecting CO2 and transport in the vadose zone. CO2 was injected through 16 micro-injectors during 49 days of experiments in a 35 m3 experimental unit filled with sandy material, in the PISCO2 facilities at the ES.CO2 centre in Ponferrada (North Spain). Surface CO2 flux were monitored and mapped periodically to assess the evolution of CO2 migration through the soil and to the atmosphere. Numerical simulations were run to reproduce the experimental results, using TOUGH2 code with EOS7CA research module considering two phases (gas and liquid) and three components (H2O, CO2, air). Five numerical models were developed following step by step the injection procedure done at PISCO2. The reference case (Model A) simulates the injection into a homogeneous soil(homogeneous distribution of permeability and porosity in the near-surface area, 0.8 to 0.3 m deep from the atmosphere). In another model (Model B), four additional soil layers with four specific permeabilities and porosities were included to predict the effect of differential compaction on soil. To account for the effect of higher soil temperature, an isothermal simulation called Model C was also performed. Finally, the assessment of the rainfall effects (soil water saturation) on CO2 emission on surface was performed in models called Model D and E. The combined experimental and modelling approach shows that CO2 leakage in the vadose zone quickly comes out through preferential migration pathways and spots with the ranges of fluxes in the ground/surface interface from 2.5 to 600 g·m-2·day-1. This gas channelling is mainly related to soil compaction and climatic perturbation. This has significant implications to

  16. Notice of Construction for Tank Waste Remediation System Vadose Zone Characterization

    Energy Technology Data Exchange (ETDEWEB)

    HILL, J.S.

    2000-03-08

    The following description and any attachments and references are provided to the Washington State Department of Health (WDOH), Division of Radiation Protection, Air Emissions & Defense Waste Section as a notice of construction (NOC) in accordance with Washington Administrative Code (WAC) 246-247, Radiation Protection--Air Emissions. The WAC 246-247-060, ''Applications, registration, and licensing'', states ''This section describes the information requirements for approval to construct, modify, and operate an emission unit. Any NOC requires the submittal of information listed in Appendix A,'' Appendix A (WAC 246-247-1 10) lists the requirements that must be addressed. The original NOC was submitted in May of 1999 as DOE/TU-99-34. Additionally, the following description, attachments and references are provided to the U.S. Environmental Protection Agency (EPA) as an NOC, in accordance with Title 40 Code of Federal Regulations (CFR), Part 61, ''National Emission Standards for Hazardous Air Pollutants.'' The information required for submittal to the EPA is specified in 40 CFR 61.07. The potential emissions from this activity are estimated to provide less than 0.1 millirem/year total effective dose equivalent (TEDE) to the hypothetical offsite maximally exposed individual (MEI), and commencement is needed within a short time frame. Therefore, this application is also intended to provide notification of the anticipated date of initial startup in accordance with the requirement listed in 40 CFR 61.09(axl), and it is requested that approval of this application will also constitute EPA acceptance of this initial start-up notification. Written notification of the actual date of initial startup, in accordance with the requirement listed in 40 CFR 61.09(a)(2) will be provided at a later date. This NOC covers the activities associated with vadose zone characterization within the Single-Shell Tank Farms located in the

  17. Notice of Construction for Tank Waste Remediation System Vadose Zone Characterization

    Energy Technology Data Exchange (ETDEWEB)

    HILL, J.S.

    2000-04-20

    The following description and any attachments and references are provided to the Washington State Department of Health (WDOH), Division of Radiation Protection, Air Emissions and Defense Waste Section as a notice of construction (NOC) in accordance with Washington Administrative Code (WAC) 246-247, Radiation Protection-Air Emissions. The WAC 246-247-060, ''Applications, registration, and licensing'', states ''This section describes the information requirements for approval to construct, modify, and operate an emission unit. Any NOC requires the submittal of information listed in Appendix A.'' Appendix A (WAC 246-247-1 10) lists the requirements that must be addressed. The original NOC was submitted in May of 1999 as DOm-99-34. Additionally, the following description, attachments and references are provided to the U.S. Environmental Protection Agency (EPA) as an NOC, in accordance with Title 40 Code of Federal Regulations (CFR), Part 61, ''National Emission Standards for Hazardous Air Pollutants.'' The information required for submittal to the EPA is specified in 40 CFR 61.07. The potential emissions from this activity are estimated to provide less than 0.1 milliredyear total effective dose equivalent (TEDE) to the hypothetical offsite maximally exposed individual (MEI), and commencement is needed within a short time frame. Therefore, this application is also intended to provide notification of the anticipated date of initial start-up in accordance with the requirement listed in 40 CFR 61.09(a)(1), and it is requested that approval of this application will also constitute EPA acceptance of this initial start-up notification. Written notification of the actual date of initial startup, in accordance with the requirement listed in 40 CFR 61.09(a)(2) will be provided at a later date. This NOC covers the activities associated with vadose zone characterization within the Single-Shell Tank Farms located in the 200

  18. Chromium speciation and mobility in a high level nuclear waste vadose zone plume

    Science.gov (United States)

    Zachara, John M.; Ainsworth, Calvin C.; Brown, Gordon E.; Catalano, Jeffrey G.; McKinley, James P.; Qafoku, Odeta; Smith, Steven C.; Szecsody, James E.; Traina, Sam J.; Warner, Jeffrey A.

    2004-01-01

    Radioactive core samples containing elevated concentrations of Cr from a high level nuclear waste plume in the Hanford vadose zone were studied to asses the future mobility of Cr. Cr(VI) is an important subsurface contaminant at the Hanford Site. The plume originated in 1969 by leakage of self-boiling supernate from a tank containing REDOX process waste. The supernate contained high concentrations of alkali (NaOH ≈ 5.25 mol/L), salt (NaNO 3/NaNO 2 >10 mol/L), aluminate [Al(OH) 4- = 3.36 mol/L], Cr(VI) (0.413 mol/L), and 137Cs + (6.51 × 10 -5 mol/L). Water and acid extraction of the oxidized subsurface sediments indicated that a significant portion of the total Cr was associated with the solid phase. Mineralogic analyses, Cr valence speciation measurements by X-ray adsorption near edge structure (XANES) spectroscopy, and small column leaching studies were performed to identify the chemical retardation mechanism and leachability of Cr. While X-ray diffraction detected little mineralogic change to the sediments from waste reaction, scanning electron microscopy (SEM) showed that mineral particles within 5 m of the point of tank failure were coated with secondary, sodium aluminosilicate precipitates. The density of these precipitates decreased with distance from the source (e.g., beyond 10 m). The XANES and column studies demonstrated the reduction of 29-75% of the total Cr to insoluble Cr(III), and the apparent precipitation of up to 43% of the Cr(VI) as an unidentified, non-leachable phase. Both Cr(VI) reduction and Cr(VI) precipitation were greater in sediments closer to the leak source where significant mineral alteration was noted by SEM. These and other observations imply that basic mineral hydrolysis driven by large concentrations of OH - in the waste stream liberated Fe(II) from the otherwise oxidizing sediments that served as a reductant for CrO 42-. The coarse-textured Hanford sediments contain silt-sized mineral phases (biotite, clinochlore, magnetite, and

  19. DNAPL Surface Chemistry: Its Impact on DNAPL Distribution in the Vadose Zone and its Manipulation to Enhance Remediation

    Energy Technology Data Exchange (ETDEWEB)

    Suan Power; Stefan Grimberg; Miles Denham

    2003-06-16

    The remediation of DNAPLs in subsurface environments is often limited by the heterogeneous distribution of the organic fluid. The fraction of DNAPL that is in the high conductivity regions of the subsurface can often be recovered relatively easily, although DNAPL in lower conductivity regions is much more difficult to extract, either through direct pumping or remediation measures based on interface mass transfer. The distribution of DNAPL within the vadose zone is affected by a complex interplay of heterogeneities in the porous matrix and the interfacial properties defining the interactions among all fluid and solid phases. Decreasing the interfacial tension between a DNAPL and water in the vadose zone could change the spreading of the DNAPL, thereby increase the surface area for mass transfer and the effectiveness of soil vapor extraction remediation.

  20. Geochemical Characterization Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J.; Brown, Christopher F.; Serne, R. Jeffrey; Krupka, Kenneth M.

    2008-01-07

    This data package discusses the geochemistry of vadose zone sediments beneath the single-shell tank (SST) farms at the U.S. Department of Energy’s (DOE’s) Hanford Site. The purpose of the report is to provide a review of the most recent and relevant geochemical information available for the vadose zone beneath the SST farms and the Integrated Disposal Facility (IDF).

  1. Deep Vadose Zone Treatability Test for the Hanford Central Plateau. Interim Post-Desiccation Monitoring Results, Fiscal Year 2015

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Strickland, Christopher E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Oostrom, Martinus [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Christian D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tartakovsky, Guzel D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clayton, Ray E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chronister, Glen B. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-09-01

    A field test of desiccation is being conducted as an element of the Deep Vadose Zone Treatability Test Program. The active desiccation portion of the test has been completed. Monitoring data have been collected at the field test site during the post-desiccation period and are reported herein. This is an interim data summary report that includes about 4 years of post-desiccation monitoring data. The DOE field test plan proscribes a total of 5 years of post-desiccation monitoring.

  2. Seasonal Variability in Vadose zone biodegradation at a crude oil pipeline rupture site

    Science.gov (United States)

    Sihota, Natasha J.; Trost, Jared J.; Bekins, Barbara; Berg, Andrew M.; Delin, Geoffrey N.; Mason, Brent E.; Warren, Ean; Mayer, K. Ulrich

    2016-01-01

    Understanding seasonal changes in natural attenuation processes is critical for evaluating source-zone longevity and informing management decisions. The seasonal variations of natural attenuation were investigated through measurements of surficial CO2 effluxes, shallow soil CO2 radiocarbon contents, subsurface gas concentrations, soil temperature, and volumetric water contents during a 2-yr period. Surficial CO2 effluxes varied seasonally, with peak values of total soil respiration (TSR) occurring in the late spring and summer. Efflux and radiocarbon data indicated that the fractional contributions of natural soil respiration (NSR) and contaminant soil respiration (CSR) to TSR varied seasonally. The NSR dominated in the spring and summer, and CSR dominated in the fall and winter. Subsurface gas concentrations also varied seasonally, with peak values of CO2 and CH4 occurring in the fall and winter. Vadose zone temperatures and subsurface CO2 concentrations revealed a correlation between contaminant respiration and temperature. A time lag of 5 to 7 mo between peak subsurface CO2 concentrations and peak surface efflux is consistent with travel-time estimates for subsurface gas migration. Periods of frozen soils coincided with depressed surface CO2 effluxes and elevated CO2 concentrations, pointing to the temporary presence of an ice layer that inhibited gas transport. Quantitative reactive transport simulations demonstrated aspects of the conceptual model developed from field measurements. Overall, results indicated that source-zone natural attenuation (SZNA) rates and gas transport processes varied seasonally and that the average annual SZNA rate estimated from periodic surface efflux measurements is 60% lower than rates determined from measurements during the summer.

  3. Transit times of water particles in the vadose zone across catchment states and catchments functional units

    Science.gov (United States)

    Sprenger, Matthias; Weiler, Markus

    2014-05-01

    Understanding the water movement in the vadose zone and its associated transport of solutes are of major interest to reduce nutrient leaching, pollution transport or other risks to water quality. Soil physical models are widely used to asses such transport processes, while the site specific parameterization of these models remains challenging. Inverse modeling is a common method to adjust the soil physical parameters in a way that the observed water movement or soil water dynamics are reproduced by the simulation. We have shown that the pore water stable isotope concentration can serve as an additional fitting target to simulate the solute transport and water balance in the unsaturated zone. In the presented study, the Mualem- van Genuchten parameters for the Richards equation and diffusivity parameter for the convection-dispersion equation have been parameterized using the inverse model approach with Hydrus-1D for 46 experimental sites of different land use, topography, pedology and geology in the Attert basin in Luxembourg. With the best parameter set we simulated the transport of a conservative solute that was introduced via a pulse input at different points in time. Thus, the transit times in the upper 2 m of the soil for different catchment states could be inferred for each location. It has been shown that the time a particle needs to pass the -2 m depth plane highly varies from the systems state and the systems forcing during and after infiltration of that particle. Differences in transit times among the study sites within the Attert basin were investigated with regards to its governing factors to test the concept of functional units. The study shows the potential of pore water stable isotope concentration for residence times and transport analyses in the unsaturated zone leading to a better understanding of the time variable subsurface processes across the catchment.

  4. Compositional evolution of the emplaced fuel source in the vadose zone field experiment at airbase Vaerlose, Denmark

    DEFF Research Database (Denmark)

    Broholm, Mette Martina; Christophersen, Mette; Maier, U.;

    2005-01-01

    A field experiment was performed in a sandy vadose zone, studying the fate of an emplaced fuel-NAPL source, composed of 13 hydrocarbons and a tracer. The UNIFAC model was used to test the nonideal behavior of the source, and the numerical model MIN3P was used for assessing the effect of biodegrad......A field experiment was performed in a sandy vadose zone, studying the fate of an emplaced fuel-NAPL source, composed of 13 hydrocarbons and a tracer. The UNIFAC model was used to test the nonideal behavior of the source, and the numerical model MIN3P was used for assessing the effect...... of biodegradation on source evolution. The diffusive loss to the surrounding vadose zone and the atmosphere created temporary gradients in mole fractions of the individual compounds within the source NAPL. The evolution of the source composition corresponded in general with expectations based on Raoult's Law....... Positive deviations were calculated for the aromatic compounds. The effect of biodegradation on source depletion, evaluated by numerical modeling, was greater for the aromatic as compared to the aliphatic compounds. Hence, the faster depletion of the aromatic relative to aliphatic compounds of similar...

  5. Characterization of Vadose Zone Sediment: Slant Borehole SX-108 in the S-SX Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Last, George V.; Schaef, Herbert T.; Lanigan, David C.; Lindenmeier, Clark W.; Ainsworth, Calvin C.; Clayton, Ray E.; Legore, Virginia L.; O' Hara, Matthew J.; Brown, Christopher F.; Orr, Robert D.; Kutnyakov, Igor V.; Wilson, Teresa C.; Wagnon, Kenneth B.; Williams, Bruce A.; Burke, Deborah S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.17. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is the fourth in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from a slant borehole installed beneath tank SX-108 (or simply SX-108 slant borehole).

  6. Characterization of Vadose Zone Sediment: Borehole 41-09-39 in the S-SX Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Last, George V.; Schaef, Herbert T.; Lanigan, David C.; Lindenmeier, Clark W.; Ainsworth, Calvin C.; Clayton, Ray E.; Legore, Virginia L.; O' Hara, Matthew J.; Brown, Christopher F.; Orr, Robert D.; Kutnyakov, Igor V.; Wilson, Teresa C.; Wagnon, Kenneth B.; Williams, Bruce A.; Burke, Deborah S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Table 5.15. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the S-SX Waste Management Area. This report is one in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 41-09-39 installed adjacent to tank SX-109.

  7. Waste storage in the vadose zone affected by water vapor condensation and leaching

    Energy Technology Data Exchange (ETDEWEB)

    Cary, J.W.; Gee, G.W.; Whyatt, G.A.

    1990-08-01

    One of the major concerns associated with waste storage in the vadose zone is that toxic materials may somehow be leached and transported by advecting water down to the water table and reach the accessible environment through either a well or discharge to a river. Consequently, care is taken to provide barriers over and around the storage sites to reduce contact between infiltrating water and the buried waste form. In some cases, it is important to consider the intrusion of water vapor as well as water in the liquid phase. Water vapor diffuses through porous material along vapor pressure gradients. A slightly low temperature, or the presence of water-soluble components in the waste, favors water condensation resulting in leaching of the waste form and advection of water-soluble components to the water table. A simple analysis is presented that allows one to estimate the rate of vapor condensation as a function of waste composition and backfill materials. An example using a waste form surrounded by concrete and gravel layers is presented. The use of thermal gradients to offset condensation effects of water-soluble components in the waste form is discussed. Thermal gradients may be controlled by design factors that alter the atmospheric energy exchange across the soil surface or that interrupt the geothermal heat field. 7 refs., 2 figs., 1 tab.

  8. Use of Gas Transported Reactants for Uranium Remediation in Vadose Zone Sediments

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Zhong, Lirong; Truex, Michael J.; Resch, Charles T.; Williams, Mark D.

    2010-03-10

    This laboratory-scale investigation is focused on decreasing mobility of uranium in subsurface contaminated sediments in the vadose zone by in situ geochemical manipulation at low water content. This geochemical manipulation of the sediment surface phases included reduction, pH change (acidic and alkaline), and additions of chemicals (phosphate, ferric iron) to form specific precipitates. Reactants were advected into 1-D columns packed with Hanford 200 area U-contaminated sediment as a reactive gas (for CO2, NH3, H2S, SO2), with a 0.1% water content mist (for NaOH, Fe(III), HCl, PO4) and with a 1% water content foam (for PO4). Because uranium is present in the sediment in multiple phases, changes in U surface phases were evaluated with a series of liquid extractions that dissolve progressively less soluble phases and electron microbe identification of mineral phases. In terms of the short-term decrease in U mobility (in decreasing order), NH3, NaOH mist, CO2, HCl mist, and Fe(III) mist showed 20% to 35% change in U surface phases. The two reductive gas treatments (H2S and SO2) showed little change. For long-term decrease in U transport, mineral phases created that had low solubility (phosphates, silicates) were desired, so NH3, phosphates (mist and foam delivered), and NaOH mist showed the greatest formation of these minerals.

  9. Physical modeling of shrink-swell cycles and cracking in a clayey vadose zone

    CERN Document Server

    Chertkov, V Y

    2014-01-01

    Physical understanding of the crack origin and quantitative physical prediction of the crack volume variation far from the clay soil surface are necessary to protect the underlying aquifers from pollutants. The basis of this work is an available physical model for predicting the shrinkage and swelling curves in the maximum water content range (the primary curves) and crack volume variation. The objective of the work is to generalize this model to the conditions of the deep layer of a clayey vadose zone with the overburden pressure, multiple shrinkage-swelling, and variation of water content in a small range. We aim to show that the scanning shrinkage and swelling curves, and steady shrink-swell cycles existing in such conditions, inevitably lead to the occurrence of cracks and a hysteretic crack volume. The generalization is based on the transition to the increasingly complex soil medium from the contributive clay, through the intra-aggregate matrix and aggregated soil with no cracking, to the soil with crack...

  10. Characterization and Potential Remediation Approaches for Vadose Zone Contamination at Hanford 241-SX Tank Farm

    Energy Technology Data Exchange (ETDEWEB)

    Eberlein, Susan J.; Sydnor, Harold A.; Parker, Danny L.; Glaser, Danney R.

    2013-01-10

    Unplanned releases of radioactive and hazardous wastes have occurred at the 241-SX Tank Farm on the U.S. Department of Energy Hanford Site in southeast Washington State. Interim and long-term mitigation efforts are currently under evaluation for 241-SX Tank Farm. Two contiguous interim surface barriers have been designed for deployment at 241-SX Tank Farm to reduce future moisture infiltration; however, construction of the surface barriers has been deferred to allow testing of alternative technologies for soil moisture reduction and possibly contaminant source term reduction. Previous tests performed by other organizations at the Hanford Site have demonstrated that: vadose zone desiccation using large diameter (greater than 4 inch) boreholes is feasible; under certain circumstances, mobile contaminants may be removed in addition to water vapor; and small diameter (approximately 2 inch) boreholes (such as those placed by the direct push hydraulic hammer) can be used to perform vapor extractions. Evaluation of the previous work combined with laboratory test results have led to the design of a field proof-of-principle test to remove water and possibly mobile contaminants at greater depths, using small boreholes placed with the direct push unit.

  11. Flow dynamics and potential for Biodegradation of Organic Contaminants in Fractured Rock Vadose Zones

    Energy Technology Data Exchange (ETDEWEB)

    Geller, J.T.; Holman, H.-Y.; Su, T.-S.; Liou, M.S.; Conrad, M.S.; Pruess, K.; Hunter-Devera, J.C.

    1998-12-01

    We present an experimental approach for investigating the potential for bioremediation of volatile organic chemicals (VOCs) in fractured-rock vadose zones. This approach is based on the coupling of fluid flow dynamics and biotransformation processes. Fluid flow and distribution within fracture networks may be a significant factor in the ability of microorganisms to degrade VOCs, as they affect the availability of substrate, moisture and nutrients. Biological activity can change liquid surface tension and generate biofilms that may change the nettability of solid surfaces, locally alter fracture permeability and redirect infiltrating liquids. Our approach has four components: (1) establishing a conceptual model for fluid and contaminant distribution in the geologic matrix of interest; (2) physical and numerical experiments of liquid seepage in the fracture plane; (3) non-destructive monitoring of biotransformations on rock surfaces at the micron-scale; and, (4) integration of flow and biological activity in natural rock ''geocosms''. Geocosms are core-scale flow cells that incorporate some aspects of natural conditions, such as liquid seepage in the fracture plane and moisture content. The experimental work was performed with rock samples and indigenous microorganisms from the site of the US Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL), located in a basalt flow basin where VOC contamination threatens the Snake River Aquifer. The insights gained from this approach should contribute to the design of techniques to monitor and stimulate naturally occurring biological activity and control the spread of organic contaminants.

  12. Summary of Uranium Solubility Studies in Concrete Waste Forms and Vadose Zone Environments

    Energy Technology Data Exchange (ETDEWEB)

    Golovich, Elizabeth C.; Wellman, Dawn M.; Serne, R. Jeffrey; Bovaird, Chase C.

    2011-09-30

    One of the methods being considered for safely disposing of Category 3 low-level radioactive wastes is to encase the waste in concrete. Concrete encasement would contain and isolate the waste packages from the hydrologic environment and act as an intrusion barrier. The current plan for waste isolation consists of stacking low-level waste packages on a trench floor, surrounding the stacks with reinforced steel, and encasing these packages in concrete. These concrete-encased waste stacks are expected to vary in size with maximum dimensions of 6.4 m long, 2.7 m wide, and 4 m high. The waste stacks are expected to have a surrounding minimum thickness of 15 cm of concrete encasement. These concrete-encased waste packages are expected to withstand environmental exposure (solar radiation, temperature variations, and precipitation) until an interim soil cover or permanent closure cover is installed and to remain largely intact thereafter. Any failure of concrete encasement may result in water intrusion and consequent mobilization of radionuclides from the waste packages. This report presents the results of investigations elucidating the uranium mineral phases controlling the long-term fate of uranium within concrete waste forms and the solubility of these phases in concrete pore waters and alkaline, circum-neutral vadose zone environments.

  13. T Tank Farm Interim Surface Barrier Demonstration--Vadose Zone Monitoring Plan

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Keller, Jason M.; Strickland, Christopher E.

    2007-04-01

    The Hanford Site has 149 underground single-shell tanks that store hazardous radioactive waste. Many of these tanks and their associated infrastructure (e.g., pipelines, diversion boxes) have leaked. Some of the leaked waste has entered the groundwater. The largest known leak occurred from the T-106 Tank in 1973. Many of the contaminants from that leak still reside within the vadose zone beneath the T Tank Farm. CH2M Hill Hanford Group, Inc. seeks to minimize movement of this residual contaminant plume by placing an interim barrier on the surface. Such a barrier is expected to prevent infiltrating water from reaching the plume and moving it further. A plan has been prepared to monitor and determine the effectiveness of the interim surface barrier. Soil water content and water pressure will be monitored using off-the-shelf equipment that can be installed by the hydraulic hammer technique. In fiscal year 2006, two instrument nests were installed. Each instrument nest contains a neutron probe access tube, a capacitance probe, four heat-dissipation units, and a drain gauge to measure soil water flux. A meteorological station has been installed outside of the fence. In fiscal year 2007, two additional instrument nests are planned to be installed beneath the proposed barrier.

  14. Introduction: Assessing non-point source pollution in the vadose zone with advanced information technologies

    Science.gov (United States)

    Corwin, Dennis L.; Loague, Keith; Ellsworth, Timothy R.

    The information age has ushered in a global awareness of complex environmental problems that do not respect political or physical boundaries: climatic change, ozone layer depletion, deforestation, desertification, and non-point source (NPS) pollution. Among these global environmental problems, NPS pollutants represent a perfect example of a complex multidisciplinary problem that exists over multiple scales with tremendous spatial and temporal complexity. To address the NPS problem, specific to the vadose zone, advanced information technologies must be applied in a spatial context. An integrated system of advanced information technologies (i.e., global positioning, geographic information system, geostatistics, remote sensing, solute transport modeling, neural networks, transfer functions, fuzzy logic, hierarchical theory, and uncertainty analysis) provides a framework from which real-time and/or simulated assessments of NPS pollution can be made. The ability to accurately assess present and future NPS-pollution impacts on ecosystems ranging from local to global scales provides a powerful tool for environmental stewardship and guiding future human activities.

  15. Vadose zone monitoring system installation report for McClellan AFB

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.; Faybishenko, B.; James, A.; Freifeld, B.; Salve, R.

    1996-10-31

    Two vadose zone monitoring systems (VZMS) have been installed at Site S-7, in Investigation Cluster 34 (IC 34), in Operable Unit A (OU A) of McClellan AFB. The two boreholes, VZMS-A and VZMS-B were instrumented at depths ranging from approximately 6 ft to 113 ft. Instruments were installed in clusters using a custom-made stainless steel cage with a spring-loaded mechanism allowing instruments to be in contact with the well bore wall once in place. Each cluster contains a tensiometer, suction lysimeter, soil gas probe and thermistor for measuring hydraulic potential, liquid- and gas-phase pressure, temperature of the formation and for collecting samples for chemical analyses in both the liquid and gas phases. Neutron probe logging is performed in two separate, smaller borings, VZMS-NP-1 and VZMS-NP-2, to obtain soil moisture content data. Preliminary details of soil gas analyses, laboratory field testing of soil samples, particle size analyses and neutron probe data are presented.

  16. Quantifying Deep Vadose Zone Soil Water Potential Changes At A Waste Disposal Site

    Energy Technology Data Exchange (ETDEWEB)

    Joel M. Hubbell; Deborah L. McElroy

    2007-10-01

    Recent advances in moisture monitoring using tensiometers has allowed long-duration, high quality data sets from within the deep vadose zone. A network of about 30 advanced tensiometers in 18 wells provided field-scale data to monitor moisture conditions and movement in the subsurface in and around a mixed waste disposal site at depths ranging from 6 to over 67 m below land surface (bls). Sensors are located in both sediments and fractured rock within the geologic profile and some have been in operation for over 10 years. The moisture monitoring was able to detect long term declines in moisture content presumably in response to lower than normal precipitation and resultant infiltration over the time period from 2000 to 2004. This trend was reversed in 2005 and 2006 in more than half of the monitoring sites over the 6 to 33 m depth interval and in several monitoring sites from 33 to 67 m, in response to normal to above normal precipitation. This tensiometer data can be used to evaluate the appropriateness of the current conceptual model of flow at this site. It also shows that a moisture monitoring system should be effective to rapidly validate that a proposed remedial action (such as placement of an ET cover) would be effective in reducing the moisture movement to levels similar to those in undisturbed sites outside of the disposal area. This paper will describe the instrument design, how the instruments were installed, and the resultant data from this monitoring system.

  17. Quantifying Deep Vadose Zone Soil Water Potential Changes at a Waste Disposal Site

    Energy Technology Data Exchange (ETDEWEB)

    Joel M. Hubbell; Deborah L. McElroy

    2007-08-01

    Recent advances in moisture monitoring using tensiometers has resulted in long-duration, high quality data sets from within the deep vadose zone. A network of about 30 advanced tensiometers in 18 wells provided field-scale data to monitor soil water potential conditions and movement in the subsurface in and around a mixed waste disposal site at depths ranging from 6 to over 67 m below land surface (bls). Sensors are located in both sediments and fractured rock within the geologic profile and some have been in operation for over 10 years. The moisture monitoring was able to detect long term declines in soil water potential in response to lower than normal precipitation and resultant infiltration over the time period from 2000 to 2004. This trend was reversed in 2005 and 2006 in more than half of the monitoring sites over the 6 to 33 m depth interval and in several monitoring sites from 33 to 67 m, in response to above normal precipitation. These tensiometer data have the potential to effectively and rapidly validate that a remedial action such as placement of an ET cover would be successful in reducing the water moisture movement inside the disposal area to levels similar to those in undisturbed sites outside of the disposal area. This paper will describe the instrument design, how the instruments were installed, and the resultant data from this monitoring system.

  18. Leaf protein concentrate as food supplement from arid zone plants.

    Science.gov (United States)

    Rathore, Mala

    2010-06-01

    In arid and semi-arid areas where prevalence of droughts and famines is a recurring feature, forest cover can in general make valuable contributions to food security and provide income to the rural poor. Protein and calorie malnutrition is widespread in these areas leading to high child mortality rate. Plant species can play an important role in overcoming this by being used as a source of leaf protein concentrate (LPC), a highly nutritious food. LPC should be considered seriously as it can serve as an additional protein source in the case of non-ruminants and man, especially in drought prone areas. The use of LPC in developing countries as an alternative protein source to fishmeal in broiler diet holds tremendous promise as it can substantially lower high cost of fishmeal and eventually the acute shortage of animal protein supply. Potential tropical plants for LPC production have been evaluated and selected for further research by United States Department of Agriculture. The present study was aimed to determine the potential of arid zone plants for preparation of LPC. Extraction characteristics of the several plant species have been studied and the quality of LPC prepared from them was investigated. Different fractions, chloroplastic and cytoplasmic proteins, were analyzed for their crude protein contents. Analysis of LPC shows considerable differences in their protein contents, which was found to range from 13.7 to 88.9%. Based on this, Achyranthes aspera and Tephrosia purpurea were found to be the best suited plants for LPC preparation.

  19. Vadose Zone VOC Mass Transfer Testing At The SRS Miscellaneous Chemical Basin

    Energy Technology Data Exchange (ETDEWEB)

    Riha, B

    2005-10-30

    Active remedial activities have been ongoing since 1996 to address low levels of solvent contamination at the Miscellaneous Chemical Basin at SRS. Contaminant levels in the subsurface may be approaching levels where mass transfer limitations are impacting the efficiency of the remedial action. Rate limited mass transfer effects have been observed at other sites in the vadose zone at the SRS, however, detailed measurements and evaluation has not been undertaken. Anecdotal evidence suggests that the mass transfer rates are very slow from the fine grain sediments. This conclusion is based on the observation that measured soil gas concentrations tend to be low in permeable zones relative to the higher concentrations found in fine grain zones. Decreasing soil gas concentration with depth below the ''upland unit'' at several areas at SRS is also evidence of slow diffusion rates. In addition, due to the length of time since disposal ceased at the MCB, we hypothesize that mobile solvents have migrated downward, and the solvent remaining in the upper fine grain zone (''upland unit'') are trapped in fine grain material and are primarily released by gas diffusion (Riha and Rossabi 2004). Natural weathering and other chemical solutions disposed with the solvents can further enhance this effect by increasing the micro-porosity in the clays (kaolinite). This microporosity can result in increased entrapment of water and solvents by capillary forces (Powers, et. al., 2003). Also supporting this conclusion is the observation that active SVE has proven ineffective on VOC removal from the fine grain zones at the SRS. Adsorption and the very slow release phenomenon have been documented similarly in the literature especially for old solvent spills such as at the SRS (Pavlostathis and Mathavan 1992; Oostrom and Lenhard 2003). Mass transfer relationships need to be developed in order to optimize remediation activities and to determine actual

  20. Coupled effects of solution chemistry and hydrodynamics on the mobility and transport of quantum dot nanomaterials in the vadose zone

    Science.gov (United States)

    Uyusur, Burcu; Darnault, Christophe J. G.; Snee, Preston T.; Kokën, Emre; Jacobson, Astrid R.; Wells, Robert R.

    2010-11-01

    To investigate the coupled effects of solution chemistry and hydrodynamics on the mobility of quantum dot (QD) nanoparticles in the vadose zone, laboratory scale transport experiments involving single and/or sequential infiltrations of QDs in unsaturated and saturated porous media, and computations of total interaction and capillary potential energies were performed. As ionic strength increased, QD retention in the unsaturated porous media increased; however, this retention was significantly suppressed in the presence of a non-ionic surfactant in the infiltration suspensions as indicated by surfactant enhanced transport of QDs. In the vadose zone, the non-ionic surfactant limited the formation of QD aggregates, enhanced QD mobility and transport, and lowered the solution surface tension, which resulted in a decrease in capillary forces that not only led to a reduction in the removal of QDs, but also impacted the vadose zone flow processes. When chemical transport conditions were favorable (ionic strength of 5 × 10 -4 M and 5 × 10 -3 M, or ionic strengths of 5 × 10 -2 M and 0.5 M with surfactant), the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were meso-scale processes, where infiltration by preferential flow results in the rapid transport of QDs. When chemical transport conditions were unfavorable (ionic strength of 5 × 10 -2 M and 0.5 M) the dominating phenomena controlling the mobility and transport of QDs in the vadose zone were pore-scale processes governed by gas-water interfaces (GWI) that impact the mobility of QDs. The addition of surfactant enhanced the transport of QDs both in favorable and unfavorable chemical transport conditions. The mobility and retention of QDs was controlled by interaction and capillary forces, with the latter being the most influential. GWI were found to be the dominant mechanism and site for QD removal compared with solid-water interfaces (SWI) and pore straining. Additionally

  1. Dependence of shear wave seismoelectrics on soil textures: a numerical study in the vadose zone

    Science.gov (United States)

    Zyserman, F. I.; Monachesi, L. B.; Jouniaux, L.

    2017-02-01

    In this work, we study seismoelectric conversions generated in the vadose zone, when this region is traversed by a pure SH wave. We assume that the soil is a 1-D partially saturated lossy porous medium and we use the van Genuchten's constitutive model to describe the water saturation profile. Correspondingly, we extend Pride's formulation to deal with partially saturated media. In order to evaluate the influence of different soil textures we perform a numerical analysis considering, among other relevant properties, the electrokinetic coupling, coseismic responses and interface responses (IRs). We propose new analytical transfer functions for the electric and magnetic field as a function of the water saturation, modifying those of Bordes et al. and Garambois & Dietrich, respectively. Further, we introduce two substantially different saturation-dependent functions into the electrokinetic (EK) coupling linking the poroelastic and the electromagnetic wave equations. The numerical results show that the electric field IRs markedly depend on the soil texture and the chosen EK coupling model, and are several orders of magnitude stronger than the electric field coseismic ones. We also found that the IRs of the water table for the silty and clayey soils are stronger than those for the sandy soils, assuming a non-monotonous saturation dependence of the EK coupling, which takes into account the charged air-water interface. These IRs have been interpreted as the result of the jump in the viscous electric current density at the water table. The amplitude of the IR is obtained using a plane SH wave, neglecting both the spherical spreading and the restriction of its origin to the first Fresnel zone, effects that could lower the predicted values. However, we made an estimation of the expected electric field IR amplitudes detectable in the field by means of the analytical transfer functions, accounting for spherical spreading of the SH seismic waves. This prediction yields a value

  2. Fate of trace organic compounds during vadose zone soil treatment in an onsite wastewater system

    Science.gov (United States)

    Conn, K.E.; Siegrist, R.L.; Barber, L.B.; Meyer, M.T.

    2010-01-01

    During onsite wastewater treatment, trace organic compounds are often present in the effluents applied to subsurface soils for advanced treatment during vadose zone percolation and groundwater recharge. The fate of the endocrine-disrupting surfactant metabolites 4-nonylphenol (NP), 4-nonylphenolmonoethoxylate (NP1EO), and 4-nonylphenolmonoethoxycarboxylate (NP1EC), metal-chelating agents ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA), antimicrobial agent triclosan, stimulant caffeine, and antibiotic sulfamethoxazole during transport through an unsaturated sandy loam soil was studied at a field-scale test site. To assess the effects of effluent quality and hydraulic loading rate (HLR) on compound fate in the soil profile, two effluents (septic tank or textile biofilter) were applied at two design HLRs (2 or 8 cm/d). Chemical concentrations were determined in the two effluents and soil pore water at 60, 120, and 240 cm below the soil infiltrative surface. Concentrations of trace organic compounds in septic tank effluent were reduced by more than 90% during transport through 240 cm (often within 60 cm) of soil, likely due to sorption and biotransformation. However, the concentration of NP increased with depth in the shallow soil profile. Additional treatment of anaerobic septic tank effluent with an aerobic textile biofilter reduced effluent concentrations of many compounds, but generally did not affect any changes in pore water concentrations. The soil profile receiving septic tank effluent (vs. textile biofilter effluent) generally had greater percent removal efficiencies. EDTA, NP, NP1EC, and sulfamethoxazole were measured in soil pore water, indicating the ability of some trace organic compounds to reach shallow groundwater. Risk is highly dependent on the degree of further treatment in the saturated zone and the types and proximity of uses for the receiving groundwater environment. ?? 2009 SETAC.

  3. Review of several problems on the study of eco-hydrological processes in arid zones

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Ecosystem degradation is a common and cardinal environmental problem in arid zones. The change in the eco-hydrological processes is the basic cause responsible for such a problem. The study on the eco-hydrological processes in arid zones has become a forefront and focus of the eco-environmental research. Recent studies on eco-hydrological processes in arid zones show that the primary vegetation pattern and its eco-hydrological effect are of the most stable state of the ecosystem in arid zones. Special water absorption ways of plants in arid zones and the hydraulic lift and reverse hydraulic lift functions of some plants are the key mechanisms to maintain the stability of the ecosystem in arid zones. In the case of water shortage, ensuring ecological water requirement and maintaining proper ecological ground- water table are the prerequisite to keep healthful operation of the ecosystem in arid zones. The paper reviews some advances in the study of eco-hydrological processes in arid zones. It puts forward the concepts of critical ecological water requirement, optimal ecological water requirement and saturated ecological water requirement, and discusses their determination methods. It also emphasizes that the studies on natural vegetation pattern and eco-hydrological effect, on plants with hydraulic lift function, on water sources for plant absorption, on ecological water requirement and ecological groundwater table for different plant species should be strengthened to determine the species composition and pattern suitable for the restoration and reestablishment of vegetation in different arid zones in China.

  4. Antibacterial and Antifungal Potential of some Arid Zone Plants.

    Science.gov (United States)

    Jain, S C; Pancholi, B; Singh, R; Jain, R

    2010-07-01

    Sequential extracts of some medicinally important arid zone plants of Rajasthan, viz. Lepidagathis trinervis Nees., Polycarpea corymbosa Lam. and Sericostoma pauciflorum Stocks. ex Wight. were tested against six bacterial (Gram +ve and Gram -ve) and five fungal strains using agar well diffusion method. Ethyl acetate extract of L. trinervis showed maximum activity against Bacillus subtilis, Enterobactor aerogenes, Pseudomonas aeruginosa, Aspergillus flavus and Trichophyton rubrum (inhibition zone 16.00±0.81, 13.33±0.66, 14.33±1.85, 14.30±0.34 and 23.00±0.00 mm) at varied minimum inhibitory concentrations of 82, 20, 41, 41 and 20 μg/ml, respectively.

  5. Antibacterial and antifungal potential of some arid zone plants

    Directory of Open Access Journals (Sweden)

    Jain S

    2010-01-01

    Full Text Available Sequential extracts of some medicinally important arid zone plants of Rajasthan, viz. Lepidagathis trinervis Nees., Polycarpea corymbosa Lam. and Sericostoma pauciflorum Stocks. ex Wight. were tested against six bacterial (Gram +ve and Gram -ve and five fungal strains using agar well diffusion method. Ethyl acetate extract of L. trinervis showed maximum activity against Bacillus subtilis, Enterobactor aerogenes, Pseudomonas aeruginosa, Aspergillus flavus and Trichophyton rubrum (inhibition zone 16.00±0.81, 13.33±0.66, 14.33±1.85, 14.30±0.34 and 23.00±0.00 mm at varied minimum inhibitory concentrations of 82, 20, 41, 41 and 20 μg/ml, respectively.

  6. Reactant Carrier Microfoam Technology for In-Situ Remediation of Radionuclide and Metallic Contaminants in Deep Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Mattigod, Shas V.; Zhong, Lirong; Jansik, Danielle P.; Foote, Martin; Hart, Andrea T.; Wellman, Dawn M.

    2010-07-01

    The U.S. Department of Energy (DOE) is currently developing advanced remedial technologies for addressing metal and radionuclide (Cr, Tc, and U) contamination in deep vadose zone environments. One of the transformational technology alternatives being considered by the DOE Office of Environmental Management, is the use of Reactant Carrier Microfoams (RCM) as a minimally invasive method for delivery and emplacement of reagents for in-situ immobilization of contaminants. Penetration of low permeability zones deep within the subsurface for Enhance Oil Recovery (EOR) has been well-established. Use of surfactant foams have also been explored for mobilizing DNAPL from sediments. So far, the concept of using RCM for immobilizing labile metal and long-lived radionuclide contaminants in the deep vadose zone has not been explored. We, at the Pacific Northwest National Laboratory (PNNL), conducted studies to develop stable foams as a means to deliver reductive and/or precipitating reactants to the deep subsurface. To test the feasibility of this approach, we developed a preliminary foam formulation consisting of a mixture of an anionic and a nonionic surfactant with a reactant consisting of a 9:1 blend of tripoly- and orthophosphate. The MSE Technology Applications, Inc (MSE) in collaboration with PNNL, conducted a scale-up test to evaluate the efficacy of this reactant carrier foam for in-situ immobilization of U containing sediment zones in a heterogenous sediment matrix. The data indicated that successful immobilization of U contamination is feasible using specifically tailored reactant carrier foam injection technology. Studies are continuing for developing more robust optimized RCM for highly mobile contaminants such as Cr (VI), Tc (VII) in the deep vadose zone.

  7. Multiobjective Optimization of Effective Soil Hydraulic Properties on a Lysimeter from a Layered, Gravelly Vadose Zone

    Science.gov (United States)

    Werisch, Stefan; Lennartz, Franz

    2013-04-01

    Estimation of effective soil hydraulic parameters for characterization of the vadose zone properties is important for many applications from prediction of solute and pesticide transport to water balance modeling in small catchments. Inverse modeling has become a common approach to infer the parameters of the water retention and hydraulic conductivity functions from dynamic experiments under varying boundary conditions. To gain further inside into to the water transport behavior of an agricultural field site with a layered, gravelly vadose zone, a lysimeter was taken and equipped with a total of 48 sensors (24 tensiometers and 24 water content probes). The sensors were arranged in 6 vertical arrays consisting of 4 sensor pairs, respectively. Pressure heads and water contents were measured in four depths in each of the arrays allowing for the estimation of the soil hydraulic properties of the three individual soil layers by inverse modeling. For each of the soil horizons, a separate objective function was defined to fit the model to the observation. We used the global multiobjective multimethod search algorithm AMALGAM (Vrugt et al., 2007) in combination with the water flow and solute transport model Hydrus1D (Šimúnek et al., 2008) to estimate the soil hydraulic properties of the Mualem van Genuchten model (van Genuchten, 1980). This experimental design served for the investigation of two important questions: a) do effective soil hydraulic properties at the lysimeter scale exist, more specifically: can a single representative parameter set be found which describes the hydraulic behavior in each of the arrays with acceptable performance? And b) which degree of freedom is necessary or required for an accurate description of the one dimensional water flow at each of the arrays? Effective soil hydraulic parameters were obtained for each of the sensor arrays individually, resulting in good agreement between the model predictions and the observations for the individual

  8. Remediation of Technetium in Vadose Zone Sediments Using Ammonia and Hydrogen Sulfide Gases

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); McKinley, James P. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lee, Brady D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Saurey, Sabrina D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2015-04-17

    The feasibility of applying a combination of H2S and NH3 gases for Tc-99 remediation in vadose zone sediments evaluated in laboratory experiments showed a significant mobility decrease from 75 to 95% leachable Tc-99 in untreated sediments to 15 to 48% leachable Tc-99 after gas treatment. Individual H2S or NH3 gas treatment of sediments had little lasting effect. For the combined gas treatment, the H2S gas created reducing conditions at the pore water/mineral interface that pertechnetate was temporarily reduced/precipitated. The NH3 gas created alkaline pore water, which induces some mineral dissolution and subsequent aluminosilicate precipitation as the pH neutralizes, which may coat Tc-99 surface phases and render them less mobile. Surface phase analysis showed Tc-99 associated with weathered basalt clasts and sulfur, possibly from the precipitation of TcSx. Treatment performance was nearly the same at different Tc-99 concentration (34 to 6500 pCi/g), water content (1 to 8%), and gas injection rate, but was sensitive to gas concentrations. Low gas concentrations (< 3%) had insufficient reductant or slower mineral dissolution. High gas concentrations (>30%) formed NH4SH precipitate. The 15 - 23% mobile Tc-99 remaining after gas treatment may be caused by limited time for aluminosilicates to precipitate in experiments. Nitrogen species concentrations showed no nitrate or nitrite production and a significant decrease in the sediment microbial population over three months, suggesting nitrification of added ammonia was inhibited. Overall, this study showed that combined H2S and NH3 gas treatment of low water content sediments was a robust technology to significantly decrease Tc-99 mobility.

  9. Numerical modeling of the effect of variation of boundary conditions on vadose zone hydraulic properties

    Directory of Open Access Journals (Sweden)

    Tairone Paiva Leão

    2011-02-01

    Full Text Available An accurate estimation of hydraulic fluxes in the vadose zone is essential for the prediction of water, nutrient and contaminant transport in natural systems. The objective of this study was to simulate the effect of variation of boundary conditions on the estimation of hydraulic properties (i.e. water content, effective unsaturated hydraulic conductivity and hydraulic flux in a one-dimensional unsaturated flow model domain. Unsaturated one-dimensional vertical water flow was simulated in a pure phase clay loam profile and in clay loam interlayered with silt loam distributed according to the third iteration of the Cantor Bar fractal object Simulations were performed using the numerical model Hydrus 1D. The upper and lower pressure heads were varied around average values of -55 cm for the near-saturation range. This resulted in combinations for the upper and lower constant head boundary conditions, respectively, of -50 and -60 cm, -40 and -70 cm, -30 and -80 cm, -20 and -90 cm, and -10 and -100 cm. For the drier range the average head between the upper and lower boundary conditions was set to -550 cm, resulting in the combinations -500 and -600 cm, -400 and -700 cm, -300 and -800 cm, -200 and -900 cm, and -100 and -1,000 cm, for upper and lower boundary conditions, respectively. There was an increase in water contents, fluxes and hydraulic conductivities with the increase in head difference between boundary conditions. Variation in boundary conditions in the pure phase and interlayered one-dimensional profiles caused significant deviations in fluxes, water contents and hydraulic conductivities compared to the simplest case (a head difference between the upper and lower constant head boundaries of 10 cm in the wetter range and 100 cm in the drier range.

  10. Flow dynamics and potential for biodegradation of organic contaminants in fractured rock vadose zones

    Science.gov (United States)

    Geller, J. T.; Holman, H.-Y.; Su, G.; Conrad, M. E.; Pruess, K.; Hunter-Cevera, J. C.

    2000-04-01

    We present an experimental approach for investigating the potential for bioremediation of volatile organic compounds (VOCs) in fractured rock vadose zones. The experimental work was performed with rock samples and indigenous microorganisms from the site of the United States Department of Energy's Idaho National Engineering and Environmental Laboratory (INEEL), located in a basalt flow basin where VOC contamination threatens the Snake River Aquifer. Our approach has four components: (1) establishing a conceptual model for fluid and contaminant distribution in the geologic matrix of interest; (2) identification of important features of liquid distribution by means of seepage experiments in the fracture plane; (3) identification of the presence and activity of microorganisms by non-destructive monitoring of biotransformations on rock surfaces at the micron-scale; and (4) integration of flow and biological activity in natural rock "geocosms". Geocosms are core-scale flow cells that incorporate some aspects of natural conditions, such as liquid seepage in the fracture plane and moisture content. Fluid flow and distribution within fracture networks may be a significant factor in the ability of microorganisms to degrade VOCs, as they affect the availability of substrate, moisture and nutrients. Flow visualization and tracer breakthrough curves in transparent fracture replicas for unsaturated inlet conditions exhibited the channelized and intermittent nature of liquid seepage. The seepage of water and non-aqueous phase liquids (NAPLs) of varying physical and chemical properties into an initially dry replica showed only subtle differences in liquid distribution. In contrast, the seepage of a NAPL into the fracture replica containing residual water resulted in complex trapping of NAPL along the solid/water/air contact lines and diversion of NAPL to previously dry parts of the fracture. We found that a mixed culture of viable bacteria exists on the natural rock surfaces

  11. Impacts of Climate Anomalies on the Vegetation Patterns in the Arid and Semi-Arid Zones of Uzbekistan

    Science.gov (United States)

    Dildora, Aralova; Toderich, Kristina; Dilshod, Gafurov

    2016-08-01

    Steadily rising temperature anomalies in last decades are causing changes in vegetation patterns for sensitive to climate change in arid and semi-arid dryland ecosystems. After desiccation of the Aral Sea, Uzbekistan has been left with the challenge to develop drought and heat stress monitoring system and tools (e.g., to monitor vegetation status and/crop pattern dynamics) with using remote sensing technologies in broad scale. This study examines several climate parameters, NDVI and drought indexes within geostatistical method to predict further vegetation status in arid and semi-arid zones of landscapes. This approaches aimed to extract and utilize certain variable environmental data (temperature and precipitation) for assessment and inter-linkages of vegetation cover dynamics, specifically related to predict degraded and recovered zones or desertification process in the drylands due to scarcity of water resources and high risks of climate anomalies in fragile ecosystem of Uzbekistan.

  12. Linking river, floodplain, and vadose zone hydrology to improve restoration of a coastal river affected by saltwater intrusion.

    Science.gov (United States)

    Kaplan, D; Muñoz-Carpena, R; Wan, Y; Hedgepeth, M; Zheng, F; Roberts, R; Rossmanith, R

    2010-01-01

    Floodplain forests provide unique ecological structure and function, which are often degraded or lost when watershed hydrology is modified. Restoration of damaged ecosystems requires an understanding of surface water, groundwater, and vadose (unsaturated) zone hydrology in the floodplain. Soil moisture and porewater salinity are of particular importance for seed germination and seedling survival in systems affected by saltwater intrusion but are difficult to monitor and often overlooked. This study contributes to the understanding of floodplain hydrology in one of the last bald cypress [Taxodium distichum (L.) Rich.] floodplain swamps in southeast Florida. We investigated soil moisture and porewater salinity dynamics in the floodplain of the Loxahatchee River, where reduced freshwater flow has led to saltwater intrusion and a transition to salt-tolerant, mangrove-dominated communities. Twenty-four dielectric probes measuring soil moisture and porewater salinity every 30 min were installed along two transects-one in an upstream, freshwater location and one in a downstream tidal area. Complemented by surface water, groundwater, and meteorological data, these unique 4-yr datasets quantified the spatial variability and temporal dynamics of vadose zone hydrology. Results showed that soil moisture can be closely predicted based on river stage and topographic elevation (overall Nash-Sutcliffe coefficient of efficiency = 0.83). Porewater salinity rarely exceeded tolerance thresholds (0.3125 S m(-1)) for bald cypress upstream but did so in some downstream areas. This provided an explanation for observed vegetation changes that both surface water and groundwater salinity failed to explain. The results offer a methodological and analytical framework for floodplain monitoring in locations where restoration success depends on vadose zone hydrology and provide relationships for evaluating proposed restoration and management scenarios for the Loxahatchee River.

  13. Influence of colloids on the attenuation and transport of phosphorus in alluvial gravel aquifer and vadose zone media.

    Science.gov (United States)

    Pang, Liping; Lafogler, Mark; Knorr, Bastian; McGill, Erin; Saunders, Darren; Baumann, Thomas; Abraham, Phillip; Close, Murray

    2016-04-15

    Phosphorous (P) leaching (e.g., from effluents, fertilizers) and transport in highly permeable subsurface media can be an important pathway that contributes to eutrophication of receiving surface waters as groundwater recharges the base-flow of surface waters. Here we investigated attenuation and transport of orthophosphate-P in gravel aquifer and vadose zone media in the presence and absence of model colloids (Escherichia coli, kaolinite, goethite). Experiments were conducted using repacked aquifer media in a large column (2m long, 0.19m in diameter) and intact cores (0.4m long, 0.24m in diameter) of vadose zone media under typical field flow rates. In the absence of the model colloids, P was readily traveled through the aquifer media with little attenuation (up to 100% recovery) and retardation, and P adsorption was highly reversible. Conversely, addition of the model colloids generally resulted in reduced P concentration and mass recovery (down to 28% recovery), and increased retardation and adsorption irreversibility in both aquifer and vadose zone media. The degree of colloid-assisted P attenuation was most significant in the presence of fine material and Fe-containing colloids at low flow rate but was least significant in the presence of coarse gravels and E. coli at high flow rate. Based on the experimental results, setback distances of 49-53m were estimated to allow a reduction of P concentrations in groundwater to acceptable levels in the receiving water. These estimates were consistent with field observations in the same aquifer media. Colloid-assisted P attenuation can be utilized to develop mitigation strategies to better manage effluent applications in gravelly soils. To efficiently retain P within soil matrix and reduce P leaching to groundwater, it is recommended to select soils that are rich in iron oxides, to periodically disturb soil preferential flow paths by tillage, and to apply a low irrigation rate.

  14. Estimation of percolating water dynamics through the vadose zone of the Postojna cave on the basis of isotope composition

    Directory of Open Access Journals (Sweden)

    Janja Kogovšek

    2007-12-01

    Full Text Available Within the scope of monitoring water percolation through the 100-m thick vadose zone in the area of Postojnska jama continuous measurements of precipitation were carried out on the surface, and continuous measurements of water flowandphysicalandchemicalparametersof selected water trickles were performed under the surface. Occasional samples of percolating waters were taken for the analysis of water oxygen isotope composition. An exponential model of groundwater flowwaselaborated,bymeansofwhichtheretentiontime of water in individual trickles was estimated. Modelled retention times of groundwater range from 2.5 months to over one year.

  15. Monitoring and data analysis for the Vadose Zone Monitoring System (VZMS), McClellan AFB. Quarterly status report

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.T.; Salve, R.; Freifeld, B. [and others

    1997-05-28

    This report contains information on field and laboratory work performed between January and May 15th 1997 at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) is currently being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature. Due to delays in the completion of the above-ground installations, data collection did not commence until mid-February. As a result, the data presented in this report is preliminary.

  16. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    Directory of Open Access Journals (Sweden)

    E. M. Thaysen

    2014-03-01

    Full Text Available The efflux of carbon dioxide (CO2 from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated. Carbon dioxide partial pressure in the soil gas (pCO2, alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley mesocosms. The dissolved inorganic carbon (DIC percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn emanation rates and soil air Rn concentration profiles, and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modelled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol carbon (C m−2 s−1, respectively, and largely exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m−2 s−1. Post-harvest soil respiration (Rs was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Plant biomass and soil pCO2 were high in the mesocosms as compared to a standard field situation. Our results indicate no change of the cropland C balance under elevated atmospheric CO2 in a warmer future climate, in which plant biomass and soil pCO2 are expected to increase.

  17. Inorganic carbon fluxes across the vadose zone of planted and unplanted soil mesocosms

    Science.gov (United States)

    Thaysen, E. M.; Jacques, D.; Jessen, S.; Andersen, C. E.; Laloy, E.; Ambus, P.; Postma, D.; Jakobsen, I.

    2014-12-01

    The efflux of carbon dioxide (CO2) from soils influences atmospheric CO2 concentrations and thereby climate change. The partitioning of inorganic carbon (C) fluxes in the vadose zone between emission to the atmosphere and to the groundwater was investigated to reveal controlling underlying mechanisms. Carbon dioxide partial pressure in the soil gas (pCO2), alkalinity, soil moisture and temperature were measured over depth and time in unplanted and planted (barley) mesocosms. The dissolved inorganic carbon (DIC) percolation flux was calculated from the pCO2, alkalinity and the water flux at the mesocosm bottom. Carbon dioxide exchange between the soil surface and the atmosphere was measured at regular intervals. The soil diffusivity was determined from soil radon-222 (222Rn) emanation rates and soil air Rn concentration profiles and was used in conjunction with measured pCO2 gradients to calculate the soil CO2 production. Carbon dioxide fluxes were modeled using the HP1 module of the Hydrus 1-D software. The average CO2 effluxes to the atmosphere from unplanted and planted mesocosm ecosystems during 78 days of experiment were 0.1 ± 0.07 and 4.9 ± 0.07 μmol C m-2 s-1, respectively, and grossly exceeded the corresponding DIC percolation fluxes of 0.01 ± 0.004 and 0.06 ± 0.03 μmol C m-2 s-1. Plant biomass was high in the mesocosms as compared to a standard field situation. Post-harvest soil respiration (Rs) was only 10% of the Rs during plant growth, while the post-harvest DIC percolation flux was more than one-third of the flux during growth. The Rs was controlled by production and diffusivity of CO2 in the soil. The DIC percolation flux was largely controlled by the pCO2 and the drainage flux due to low solution pH. Modeling suggested that increasing soil alkalinity during plant growth was due to nutrient buffering during root nitrate uptake.

  18. Characterization of Vadose Zone Sediment: Borehole 299-E33-45 Near BX-102 in the B-BX-BY Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Last, George V.; Gee, Glendon W.; Schaef, Herbert T.; Lanigan, David C.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Orr, Robert D.; Kutnyakov, Igor V.; Baum, Steven R.; Geiszler, Keith N.; Brown, Christopher F.; Valenta, Michelle M.; Vickerman, Tanya S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.22. The data was removed due to potential contamination introduced during the acid extraction process. The remaining text is unchanged from the original report issued in 2002. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area B-BX-BY. This report is the first in a series of four reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole 299-E33-45 installed northeast of tank BX-102.

  19. Analysis of vadose zone inhomogeneity toward distinguishing recharge rates: Solving the nonlinear interface problem with Newton method

    Science.gov (United States)

    Steward, David R.

    2016-11-01

    Recharge from surface to groundwater is an important component of the hydrological cycle, yet its rate is difficult to quantify. Percolation through two-dimensional circular inhomogeneities in the vadose zone is studied where one soil type is embedded within a uniform background, and nonlinear interface conditions in the quasilinear formulation are solved using Newton's method with the Analytic Element Method. This numerical laboratory identifies detectable variations in pathline and pressure head distributions that manifest due to a shift in recharge rate through in a heterogeneous media. Pathlines either diverge about or converge through coarser and finer grained materials with inverse patterns forming across lower and upper elevations; however, pathline geometry is not significantly altered by recharge. Analysis of pressure head in lower regions near groundwater identifies a new phenomenon: its distribution is not significantly impacted by an inhomogeneity soil type, nor by its placement nor by recharge rate. Another revelation is that pressure head for coarser grained inhomogeneities in upper regions is completely controlled by geometry and conductivity contrasts; a shift in recharge generates a difference Δp that becomes an additive constant with the same value throughout this region. In contrast, shifts in recharge for finer grained inhomogeneities reveal patterns with abrupt variations across their interfaces. Consequently, measurements aimed at detecting shifts in recharge in a heterogeneous vadose zone by deciphering the corresponding patterns of change in pressure head should focus on finer grained inclusions well above a groundwater table.

  20. A resolution analysis of two geophysical imaging methods for characterizing and monitoring hydrologic conditions in the Vadose zone.

    Energy Technology Data Exchange (ETDEWEB)

    Brainard, James Robert; Hammond, Gary.; Alumbaugh, David L. (University of Wisconsin-Madison, Madison, WI); La Brecque, D.J. (Multi-Phase Technologies, LLC, Sparks, NV)

    2007-06-01

    This research project analyzed the resolution of two geophysical imaging techniques, electrical resistivity tomography (ERT) and cross-borehole ground penetrating radar (XBGPR), for monitoring subsurface flow and transport processes within the vadose zone. The study was based on petrophysical conversion of moisture contents and solute distributions obtained from unsaturated flow forward modeling. This modeling incorporated boundary conditions from a potable water and a salt tracer infiltration experiment performed at the Sandia-Tech Vadose Zone (STVZ) facility, and high-resolution spatial grids (6.25-cm spacing over a 1700-m domain) and incorporated hydraulic properties measured on samples collected from the STVZ. The analysis process involved petrophysical conversion of moisture content and solute concentration fields to geophysical property fields, forward geophysical modeling using the geophysical property fields to obtain synthetic geophysical data, and finally, inversion of this synthetic data. These geophysical property models were then compared to those derived from the conversion of the hydrologic forward modeling to provide an understanding of the resolution and limitations of the geophysical techniques.

  1. Review of Techniques to Characterize the Distribution of Chromate Contamination in the Vadose Zone of the 100 Areas at the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Dresel, P. Evan; Truex, Michael J.; Sweeney, Mark D.

    2007-09-01

    The purpose of this report is to identify and evaluate the state-of-the-art techniques for characteriza¬tion of chromate contamination in the vadose zone of the 100 Areas at the Hanford Site. The techniques include direct techniques for analysis of chromium in the subsurface as well as indirect techniques to identify contamination through geophysical properties, soil moisture, or co-contaminants. Characteri¬zation for the distribution of chromium concentration in the vadose zone is needed to assess potential sources for chromate contamination plumes in groundwater at the 100-D, 100-K, and 100-B/C Areas.

  2. Geochemical Processes Data Package for the Vadose Zone in the Single-Shell Tank Waste Management Areas at the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J.; Zachara, John M.; Dresel, P. Evan; Krupka, Kenneth M.; Serne, R. Jeffrey

    2007-09-28

    This data package discusses the geochemistry of vadose zone sediments beneath the single-shell tank farms at the U.S. Department of Energy’s (DOE’s) Hanford Site. The purpose of the report is to provide a review of the most recent and relevant geochemical process information available for the vadose zone beneath the single-shell tank farms and the Integrated Disposal Facility. Two companion reports to this one were recently published which discuss the geology of the farms (Reidel and Chamness 2007) and groundwater flow and contamination beneath the farms (Horton 2007).

  3. Rainwater harvesting in arid and semi-arid zones (repr. 1997)

    NARCIS (Netherlands)

    Boers, Th.M.

    1994-01-01

    In arid and semi-arid regions, the scarcity of water can be alleviated by rainwater harvesting, which is defined as a method of inducing, collecting, storing, and conserving local surface runoff for agriculture. Rainwater harvesting can be applied with different systems, and this dissertation deals

  4. Geochemical Characterization of Chromate Contamination in the 100 Area Vadose Zone at the Hanford Site - Part 2

    Energy Technology Data Exchange (ETDEWEB)

    Qafoku, Nikolla; Dresel, P. Evan; McKinley, James P.; Ilton, Eugene S.; Um, Wooyong; Resch, Charles T.; Kukkadapu, Ravi K.; Petersen, Scott W.

    2011-01-04

    At the Hanford Site, chromate was used throughout the 100 Areas (100-B, 100-C, 100-D/DR, 100-F, 100-H, and 100 K) as a corrosion inhibitor in reactor cooling water. Chromate was delivered in rail cars, tanker trucks, barrels, and local pipelines as dichromate granular solid or stock solution. In many occasions, chromate was inevitably discharged to surface or near-surface ground through spills during handling, pipeline leaks, or during disposal to cribs. The composition of the liquids that were discharged is not known and it is quite possible that Cr(VI) fate and transport in the contaminated sediments would be a function of the chemical composition of the waste fluids. The major objectives of this investigation which was limited in scope by the financial resources available, were to 1) determine the leaching characteristics of hexavalent chromium [Cr(VI)] from contaminated sediments collected from 100-D Area spill sites; 2) elucidate possible Cr(VI) mineral and/or chemical associations that may be responsible for Cr(VI) retention in the Hanford Site 100 Areas through the use of macroscopic leaching studies, and microscale characterization of contaminated sediments; and 3) provide information to construct a conceptual model of Cr(VI) geochemistry in the Hanford 100 Area vadose zone that can be used for developing options for environmental remediation. The information gathered from this research effort will help to further improve our understanding of Cr(VI) behavior in the vadose zone and will also help in accelerating the 100 Area Columbia River Corridor cleanup by providing valuable information to develop remedial action based on a fundamental understanding of Cr(VI) vadose zone geochemistry. A series of column experiments were conducted with contaminated sediments to study Cr(VI) desorption patterns. Column experiments used the field size fraction of the sediment samples and a simulated Hanford Site groundwater solution. Periodic stop flow events were applied to

  5. Characterization of Vadose Zone Sediments Below the C Tank Farm: Borehole C4297 and RCRA Borehole 299-E27-22

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Serne, R. Jeffrey; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Clayton, Ray E.; Valenta, Michelle M.; Vickerman, Tanya S.; Kutnyakov, Igor V.; Geiszler, Keith N.; Baum, Steven R.; Parker, Kent E.; Lindberg, Michael J.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.7 and 4.25. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in September 2006. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at the Hanford Site. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory (PNNL) to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) C. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physiochemical characterization data collected on vadose zone sediment recovered from borehole C4297, installed adjacent to tank C-105, and from borehole 299-E27-22, installed directly north of the C Tank Farm. This report also presents the interpretation of data in the context of sediment types, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone below the C Tank Farm. The information presented in this report supports the WMA A-AX, C, and U field investigation report in preparation by CH2M HILL Hanford Group, Inc.

  6. A BENCHMARKING ANALYSIS FOR FIVE RADIONUCLIDE VADOSE ZONE MODELS (CHAIN, MULTIMED_DP, FECTUZ, HYDRUS, AND CHAIN 2D) IN SOIL SCREENING LEVEL CALCULATIONS

    Science.gov (United States)

    Five radionuclide vadose zone models with different degrees of complexity (CHAIN, MULTIMED_DP, FECTUZ, HYDRUS, and CHAIN 2D) were selected for use in soil screening level (SSL) calculations. A benchmarking analysis between the models was conducted for a radionuclide (99Tc) rele...

  7. Solute transport processes in a karst vadose zone characterized by long-term tracer tests (the cave system of Postojnska Jama, Slovenia)

    Science.gov (United States)

    Kogovsek, Janja; Petric, Metka

    2014-11-01

    The processes influencing the solute transport in the karst vadose zone were studied by long-term tracer tests with artificial tracers. The results of three successive tracer tests with different modes of injection were compared. Tracer breakthrough curves were monitored at three drips of different hydrological types inside one of the cave galleries of the system of Postojnska Jama over several years. Comparison of the results indicates the highly significant influence of preceding hydrological conditions (dry vs wet), injection mode (artificial flushing vs natural infiltration by subsequent rainfall, and on a bare rock vs on an overlying layer) and geologic heterogeneities within the vadose zone on solute transport in the karst vadose zone. Injection with artificial flushing resulted in rapid infiltration and the tracer traversed almost one hundred meters of bedrock in hours. However, the majority of tracer can be stored within less permeable parts of the vadose zone and then gradually flushed out after additional abundant and intensive precipitation in the period of several years. Long-continued sampling in each of the tests proved to be important for reliable characterization of the long-term solute transport dynamics.

  8. Monitoring and data analysis for the Vadose Zone Monitoring System (VZMS), McClellan AFB. Quarterly status report, August 15, 1997--November 15, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.T.; Mountford, H.S.; Dahlquist, R.; Rodriguez, S.J.; Salve, R.

    1997-12-05

    This report contains information on field and laboratory work performed between August 15th and November 15th at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) (LBNL, 1996) is currently being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature.

  9. Recommendations for computer code selection of a flow and transport code to be used in undisturbed vadose zone calculations for TWRS immobilized environmental analyses

    Energy Technology Data Exchange (ETDEWEB)

    VOOGD, J.A.

    1999-04-19

    An analysis of three software proposals is performed to recommend a computer code for immobilized low activity waste flow and transport modeling. The document uses criteria restablished in HNF-1839, ''Computer Code Selection Criteria for Flow and Transport Codes to be Used in Undisturbed Vadose Zone Calculation for TWRS Environmental Analyses'' as the basis for this analysis.

  10. A comparison of the spatial distribution of vadose zone water in forested and agricultural floodplains a century after harvest.

    Science.gov (United States)

    Kellner, Elliott; Hubbart, Jason A

    2016-01-15

    To improve quantitative understanding of the long-term impact of historic forest removal on floodplain vadose zone water regime, a study was implemented in fall 2010, in the Hinkson Creek Watershed, Missouri, USA. Automated, continuously logging capacitance-frequency probes were installed in a grid-like formation (n=6) and at depths of 15, 30, 50, 75, and 100 cm within a historic agricultural field (Ag) and a remnant bottomland hardwood forest (BHF). Data were logged at thirty minute intervals for the duration of the 2011, 2012, and 2013 hydrologic years. Results showed volumetric water content (VWC) to be significantly different between sites (pagricultural systems, and point to the value of reestablishing floodplain forests for fresh water routing, water quality, and flood mitigation in mixed-land-use watersheds.

  11. A Resolution Analysis of Two Geophysical Imaging Methods For Characterizing and Monitoring Hydrologic Conditions in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Alumbaugh, D. [Univ. of Wisconsin, Madison, WI (United States). Geological Engineering Program; LaBreque, D. [Multi-Phase Technologies, LLC, Sparks, NV (United States); Brainard, J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Hammond, G. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2006-08-02

    The objective of this research project was to analyze the resolution of two geophysical imaging techniques: electrical resistivity tomography (ERT) and cross-borehole ground penetrating radar (XBGPR) for monitoring subsurface flow and transport processes within the vadose zone. This was accomplished through a coupled approach involving very fine-scale unsaturated flow forward modeling, conversion of the resultant flow and solute fields to geophysical property models, forward geophysical modeling using the property model obtained from the last step to obtain synthetic geophysical data, and finally inversion of this synthetic data. These geophysical property models were then compared to those derived from the conversion of the hydrologic forward modeling to provide an understanding of the resolution and limitations of the geophysical techniques.

  12. Modeling vadose zone processes during land application of food-processing waste water in California's Central Valley.

    Science.gov (United States)

    Miller, Gretchen R; Rubin, Yoram; Mayer, K Ulrich; Benito, Pascual H

    2008-01-01

    Land application of food-processing waste water occurs throughout California's Central Valley and may be degrading local ground water quality, primarily by increasing salinity and nitrogen levels. Natural attenuation is considered a treatment strategy for the waste, which often contains elevated levels of easily degradable organic carbon. Several key biogeochemical processes in the vadose zone alter the characteristics of the waste water before it reaches the ground water table, including microbial degradation, crop nutrient uptake, mineral precipitation, and ion exchange. This study used a process-based, multi-component reactive flow and transport model (MIN3P) to numerically simulate waste water migration in the vadose zone and to estimate its attenuation capacity. To address the high variability in site conditions and waste-stream characteristics, four food-processing industries were coupled with three site scenarios to simulate a range of land application outcomes. The simulations estimated that typically between 30 and 150% of the salt loading to the land surface reaches the ground water, resulting in dissolved solids concentrations up to sixteen times larger than the 500 mg L(-1) water quality objective. Site conditions, namely the ratio of hydraulic conductivity to the application rate, strongly influenced the amount of nitrate reaching the ground water, which ranged from zero to nine times the total loading applied. Rock-water interaction and nitrification explain salt and nitrate concentrations that exceed the levels present in the waste water. While source control remains the only method to prevent ground water degradation from saline wastes, proper site selection and waste application methods can reduce the risk of ground water degradation from nitrogen compounds.

  13. Characteristics and laws of MODS coupling relation in arid zone under global change

    Institute of Scientific and Technical Information of China (English)

    WANG Ranghui; ZHANG Huizhi; HUANG Qing

    2006-01-01

    Global change has influenced the distribution pattern and spatio-temporal changes of resources in arid zone, and has restrained the land use and land cover change, which is shown by water-heat state, landscape structure, climate effect, and human activities. The above-mentioned characteristics have a close coupling relation with the mountain-oasisdesert system (MODS). The climate in Central Asia arid zone is warm and wet, which is different from that in northern China which takes a tendency of aridity, and the mechanism has restricted the characteristics and laws of MODS. Systematic interface characteristics and process, especially the formation,transformation and consumption laws of water resource reflect directly MODS's response to global change in arid zone. Spatio-temporal pattern, dynamic change, scale change and coupling mode of MODS reflect the ecology mechanism between the systems and within the systems.

  14. The vadose zone as a geoindicator of environmental change and groundwater quality in water-scarce areas

    Science.gov (United States)

    Edmunds, W. M.; Baba Goni, I.; Gaye, C. B.; Jin, L.

    2013-12-01

    Inert and reactive tracers in moisture profiles provide considerable potential for the vadose zone to be used as an indicator of rapid environmental change. This indicator is particularly applicable in areas of water stress where long term (decade to century) scale records may be found in deep unsaturated zones in low rainfall areas and provide insights into recent recharge, climate variation and water-rock interactions which generate groundwater quality. Unsaturated zone Cl records obtained by elutriation of moisture are used widely for estimating recharge and water balance studies; isotope profiles (3H, δ2H, δ18O) from total water extraction procedures are used for investigation of residence times and hydrological processes. Apart from water taken using lysimeters, little work has been conducted directly on the geochemistry of pore fluids. This is mainly due to the difficulties of extraction of moisture from unsaturated material with low water contents (typically 2-6 wt%) and since dilution methods can create artifacts. Using immiscible liquid displacement techniques it is now possible to directly investigate the geochemistry of moisture from unsaturated zone materials. Profiles up to 35m from Quaternary sediments from dryland areas of the African Sahel (Nigeria, Senegal) as well as Inner Mongolia, China are used to illustrate the breadth of information obtainable from vadose zone profiles. Using pH, major and trace elements and comparing with isotopic data, a better understanding is gained of timescales of water movement, aquifer recharge, environmental records and climate history as well as water-rock interaction and contaminant behaviour. The usefulness of tritium as residence time indicator has now expired following cessation of atmospheric thermonuclear testing and through radioactive decay. Providing the rainfall Cl, moisture contents and bulk densities of the sediments are known, then Cl accumulation can be substituted to estimate timescales. Profiles

  15. T Tank Farm Interim Surface Barrier Demonstration - Vadose Zone Monitoring FY09 Report

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Strickland, Christopher E.; Field, Jim G.; Parker, Danny L.

    2010-01-01

    DOE’s Office of River Protection constructed a temporary surface barrier over a portion of the T Tank Farm as part of the T Farm Interim Surface Barrier Demonstration Project. As part of the demonstration effort, vadose zone moisture is being monitored to assess the effectiveness of the barrier at reducing soil moisture. A solar-powered system was installed to continuously monitor soil water conditions at four locations (i.e., instrument Nests A, B, C, and D) beneath the barrier and outside the barrier footprint as well as site meteorological conditions. Nest A is placed in the area outside the barrier footprint and serves as a control, providing subsurface conditions outside the influence of the surface barrier. Nest B provides subsurface measurements to assess surface-barrier edge effects. Nests C and D are used to assess changes in soil-moisture conditions beneath the interim surface barrier. Each instrument nest is composed of a capacitance probe (CP) with multiple sensors, multiple heat-dissipation units (HDUs), and a neutron probe (NP) access tube. The monitoring results in FY09 are summarized below. The solar panels functioned normally and could provide sufficient power to the instruments. The CP in Nest C after September 20, 2009, was not functional. The CP sensors in Nest B after July 13 and the 0.9-m CP sensor in Nest D before June 10 gave noisy data. Other CPs were functional normally. All the HDUs were functional normally but some pressure-head values measured by HDUs were greater than the upper measurement-limit. The higher-than-upper-limit values might be due to the very wet soil condition and/or measurement error but do not imply the malfunction of the sensors. Similar to FY07 and FY08, in FY09, the soil under natural conditions (Nest A) was generally recharged during the winter period (October-March) and discharged during the summer period (April-September). Soil water conditions above about 1.5-m to 2-m depth from all three types of measurements

  16. Characterization of Vadose Zone Sediments from C Waste Management Area: Investigation of the C-152 Transfer Line Leak

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F; Serne, R JEFFREY; Bjornstad, Bruce N; Valenta, Michelle M; Lanigan, David C; Vickerman, Tanya S; Clayton, Ray E; Geiszler, Keith N; Iovin, Cristian; Clayton, Eric T; Kutynakov, I V; Baum, Steven R; Lindberg, Michael J; Orr, Robert D

    2007-02-05

    A geologic/geochemical investigation in the vicinity of UPR-200-E-82 was performed using pairs of cone-penetrometer probe holes. A total of 41 direct-push cone-penetrometer borings (19 pairs to investigate different high moisture zones in the same sampling location and 3 individual) were advanced to characterize vadose zone moisture and the distribution of contaminants. A total of twenty sample sets, containing up to two split-spoon liners and one grab sample, were delivered to the laboratory for characterization and analysis. The samples were collected around the documented location of the C-152 pipeline leak, and created an approximately 120-ft diameter circle around the waste site. UPR-200-E-82 was a loss of approximately 2,600 gallons of Cs-137 Recovery Process feed solution containing an estimated 11,300 Ci of cesium-137 and 5 Ci of technetium-99. Several key parameters that are used to identify subsurface contamination were measured, including: water extract pH, electrical conductivity, nitrate, technetium-99, sodium, and uranium concentrations and technetium-99 and uranium concentrations in acid extracts. All of the parameters, with the exception of electrical conductivity, were elevated in at least some of the samples analyzed as part of this study. Specifically, soil pH was elevated (from 8.69 to 9.99) in five samples collected northeast and southwest of the C-152 pipeline leak. Similarly, samples collected from these same cone-pentrometer holes contained significantly more water-extractable sodium (more than 50 g/g of dry sediment), uranium (as much as 7.66E-01 g/g of dry sediment), nitrate (up to 30 g/g of dry sediment), and technetium-99 (up to 3.34 pCi/g of dry sediment). Most of the samples containing elevated concentrations of water-extractable sodium also had decreased levels of water extractable calcium and or magnesium, indicating that tank-related fluids that were high in sodium did seep into the vadose zone near these probe holes. Several of the

  17. Ion association in water solution of soil and vadose zone of chestnut saline solonetz as a driver of terrestrial carbon sink

    Science.gov (United States)

    Batukaev, Abdul-Malik A.; Endovitsky, Anatoly P.; Andreev, Andrey G.; Kalinichenko, Valery P.; Minkina, Tatiana M.; Dikaev, Zaurbek S.; Mandzhieva, Saglara S.; Sushkova, Svetlana N.

    2016-03-01

    The assessment of soil and vadose zone as the drains for carbon sink and proper modeling of the effects and extremes of biogeochemical cycles in the terrestrial biosphere are the key components to understanding the carbon cycle, global climate system, and aquatic and terrestrial system uncertainties. Calcium carbonate equilibrium causes saturation of solution with CaCO3, and it determines its material composition, migration and accumulation of salts. In a solution electrically neutral ion pairs are formed: CaCO30, CaSO40, MgCO30, and MgSO40, as well as charged ion pairs CaHCO3+, MgHCO3+, NaCO3-, NaSO4-, CaOH+, and MgOH+. The calcium carbonate equilibrium algorithm, mathematical model and original software to calculate the real equilibrium forms of ions and to determine the nature of calcium carbonate balance in a solution were developed. This approach conducts the quantitative assessment of real ion forms of solution in solonetz soil and vadose zone of dry steppe taking into account the ion association at high ionic strength of saline soil solution. The concentrations of free and associated ion form were calculated according to analytical ion concentration in real solution. In the iteration procedure, the equations were used to find the following: ion material balance, a linear interpolation of equilibrium constants, a method of ionic pairs, the laws of initial concentration preservation, operating masses of equilibrium system, and the concentration constants of ion pair dissociation. The coefficient of ion association γe was determined as the ratio of ions free form to analytical content of ion γe = Cass/Can. Depending on soil and vadose zone layer, concentration and composition of solution in the ionic pair's form are 11-52 % Ca2+; 22.2-54.6 % Mg2+; 1.1-10.5 % Na+; 3.7-23.8 HCO3-, 23.3-61.6 % SO42-, and up to 85.7 % CO32-. The carbonate system of soil and vadose zone water solution helps to explain the evolution of salted soils, vadose and saturation zones, and

  18. Conceptual Models for Migration of Key Groundwater Contaminants Through the Vadose Zone and Into the Upper Unconfined Aquifer Below the B-Complex

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Keller, Jason M.; Thorne, Paul D.; Lanigan, David C.; Christensen, J. N.; Thomas, Gregory S.

    2010-07-01

    The B-Complex contains 3 major crib and trench disposal sites and 3 SST farms that have released nearly 346 mega-liters of waste liquids containing the following high groundwater risk drivers: ~14,000 kg of CN, 29,000 kg of Cr, 12,000 kg of U and 145 Ci of Tc-99. After a thorough review of available vadose zone sediment and pore water, groundwater plume, field gamma logging, field electrical resistivity studies, we developed conceptual models for which facilities have been the significant sources of the contaminants in the groundwater and estimated the masses of these contaminants remaining in the vadose zone and currently present in the groundwater in comparison to the totals released. This allowed us to make mass balance calculations on how consistent our knowledge is on the current deep vadose zone and groundwater distribution of contaminants. Strengths and weaknesses of the conceptual models are discussed as well as implications on future groundwater and deep vadose zone remediation alternatives. Our hypothesized conceptual models attribute the source of all of the cyanide and most of the Tc-99 currently in the groundwater to the BY cribs. The source of the uranium is the BX-102 tank overfill event and the source of most of the chromium is the B-7-A&B and B-8 cribs. Our mass balance estimates suggest that there are much larger masses of U, CN, and Tc remaining in the deep vadose zone within ~20 ft of the water table than is currently in the groundwater plumes below the B-Complex. This hypothesis needs to be carefully considered before future remediation efforts are chosen. The masses of these groundwater risk drivers in the the groundwater plumes have been increasing over the last decade and the groundwater plumes are migrating to the northwest towards the Gable Gap. The groundwater flow rate appears to flucuate in response to seasonal changes in hydraulic gradient. The flux of contaminants out of the deep vadose zone from the three proposed sources also

  19. Influence of lithology on tracer movement in the vadose zone of the Calcaire de Beauce aquifer (France).

    Science.gov (United States)

    Viel, Emélie; Coquet, Yves; Dedewanou, Myriam; Binet, Stéphane

    2016-04-01

    The "Calcaire de Beauce" aquifer is contaminated by nitrate and pesticides mostly coming from agricultural activities. In this region the saturated part of the aquifer is relatively well known compared to the unsaturated (vadose) zone. This unsaturated zone can extend to more than 20 m in depth, and may play a significant role in the retention and/or release of pollutants or in the rate of nitrate transfer to wells. In order to improve knowledge on the dispersion of contaminants in the vadose zone, a tracer experiment took place at the Lycée de la Saussaye near Chartres. A pit, 4 meter in width, 1.60 meter deep and 1 meter large was excavated in a Beauce limestone, giving access to the vadose zone. The surface organic soil layer (40 cm) was excavated. Thirty Liters of brilliant blue (FCF) at a concentration of 6 g/L have been applied to the surface at a rate of 0.14 L/h/m² with automatic sprinklers during 66 h. The pit has then cut successively in four vertical profiles at 0, 33, 66, 100 cm from the edge. A RGB-photo and a lithological description was taken for each vertical profile. Image processing (ratio red canal /green canal) was applied to picture the plume of brilliant blue (BB). Areas filled with BB were converted into polygons using ArcGIS and compared with the lithological description. The proportion of tracer filled area at a given depth was used to evaluate the dispersion of the tracer with depth. The lithology present within the 4 profiles was very heterogeneous from fine ocher limestone to clay. Some profils are structured with tilt around 120° to the right in the (x,z) plane. Dye maps showed irregular plume dispersion with fast flows. A "fingered" front of BB was observed and was oriented according a tilt of 110-120° in the (x,z) plane. This distribution appears to be controlled by the lithology, with tracer moving around the low permeable lithologies. Fast flow distribution and lithological observation showed the same tilt, indicating a link

  20. Scale-Up Information for Gas-Phase Ammonia Treatment of Uranium in the Vadose Zone at the Hanford Site Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Szecsody, James E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zhong, Lirong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Thomle, Jonathan N. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Johnson, Timothy C. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2014-09-01

    Uranium is present in the vadose zone at the Hanford Central Plateau and is of concern for protection of groundwater. The Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau identified gas-phase treatment and geochemical manipulation as potentially effective treatment approaches for uranium and technetium in the Hanford Central Plateau vadose zone. Based on laboratory evaluation, use of ammonia vapor was selected as the most promising uranium treatment candidate for further development and field testing. While laboratory tests have shown that ammonia treatment effectively reduces the mobility of uranium, additional information is needed to enable deployment of this technology for remediation. Of importance for field applications are aspects of the technology associated with effective distribution of ammonia to a targeted treatment zone, understanding the fate of injected ammonia and its impact on subsurface conditions, and identifying effective monitoring approaches. In addition, information is needed to select equipment and operational parameters for a field design. As part of development efforts for the ammonia technology for remediation of vadose zone uranium contamination, field scale-up issues were identified and have been addressed through a series of laboratory and modeling efforts. This report presents a conceptual description for field application of the ammonia treatment process, engineering calculations to support treatment design, ammonia transport information, field application monitoring approaches, and a discussion of processes affecting the fate of ammonia in the subsurface. The report compiles this information from previous publications and from recent research and development activities. The intent of this report is to provide technical information about these scale-up elements to support the design and operation of a field test for the ammonia treatment technology.

  1. Conceptual Model of the Geometry and Physics of Water Flow in a Fractured Basalt Vadose Zone: Box Canyon Site, Idaho

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Doughty, Christine [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Steiger, Michael [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Long, Jane C.S. [Univ. of Nevada, Reno, NV (US). Mackay School of Mines; Wood, Tom [Parsons Engineering, Inc., Idaho Falls, ID (United States); Jacobsen, Janet [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lore, Jason [Stanford Univ., CA (United States); Zawislanski, Peter T. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    1999-03-01

    A conceptual model of the geometry and physics of water flow in a fractured basalt vadose zone was developed based on the results of lithological studies and a series of ponded infiltration tests conducted at the Box Canyon site near the Idaho National Engineering and Environmental Laboratory (INEEL) in Idaho. The infiltration tests included one two-week test in 1996, three two-day tests in 1997, and one four-day test in 1997. For the various tests, initial infiltration rates ranged from 4.1 cm/day to 17.7 cm/day and then decreased with time, presumably due to mechanical or microbiological clogging of fractures and vesicularbasalt in the near-surface zone, as well as the effect of entrapped air. The subsurface moisture redistribution was monitored with tensiometers, neutron logging, time domain reflectrometry and ground penetrating radar. A conservative tracer, potassium bromide, was added to the pond water at a concentration of 3 g/L to monitor water flow with electrical resistivity probes and water sampling. Analysis of the data showed evidence of preferential flow rather than the propagation of a uniform wetting front. We propose a conceptual model describing the saturation-desaturation behavior of the basalt, in which rapid preferential flow through vertical column-bounding fractures occurs from the surface to the base of the basalt flow. After the rapid wetting of column-bounding fractures, a gradual wetting of other fractures and the basalt matrix occurs. Fractures that are saturated early in the tests may become desaturated thereafter, which we attribute to the redistribution of water between fractures and matrix. Lateral movement of water was also observed within a horizontal central fracture zone and rubble zone, which could have important implications for contaminant accumulation at contaminated sites.

  2. Bayesian Markov-Chain-Monte-Carlo inversion of time-lapse crosshole GPR data to characterize the vadose zone at the Arrenaes Site, Denmark

    DEFF Research Database (Denmark)

    Scholer, Marie; Irving, James; Zibar, Majken Caroline Looms

    2012-01-01

    We examined to what extent time-lapse crosshole ground-penetrating radar traveltimes, measured during a forced infiltration experiment at the Arreneas field site in Denmark, could help to quantify vadose zone hydraulic properties and their corresponding uncertainties using a Bayesian Markov......-chain-Monte-Carlo inversion approach with different priors. The ground-penetrating radar (GPR) geophysical method has the potential to provide valuable information on the hydraulic properties of the vadose zone because of its strong sensitivity to soil water content. In particular, recent evidence has suggested...... that the stochastic inversion of crosshole GPR traveltime data can allow for a significant reduction in uncertainty regarding subsurface van Genuchten–Mualem (VGM) parameters. Much of the previous work on the stochastic estimation of VGM parameters from crosshole GPR data has considered the case of steady...

  3. Perched-Water Evaluation for the Deep Vadose Zone Beneath the B, BX, and BY Tank Farms Area of the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Oostrom, Martinus; Carroll, KC; Chronister, Glen B.

    2013-06-28

    Perched-water conditions have been observed in the vadose zone above a fine-grained zone that is located a few meters above the water table within the B, BX, and BY Tank Farms area. The perched water contains elevated concentrations of uranium and technetium-99. This perched-water zone is important to consider in evaluating the future flux of contaminated water into the groundwater. The study described in this report was conducted to examine the perched-water conditions and quantitatively evaluate 1) factors that control perching behavior, 2) contaminant flux toward groundwater, and 3) associated groundwater impact.

  4. Calibrating vadose zone models with time-lapse gravity data: a forced infiltration experiment

    DEFF Research Database (Denmark)

    Christiansen, Lars; Hansen, Allan Bo; Zibar, Majken Caroline Looms

    in the unsaturated zone. These results are confirmed by field measurements of gravity and georadar data at a forced infiltration experiment conducted over 14 days on a grassland area of 10 m by 10 m. An unsaturated zone infiltration model can be calibrated using the gravity data with good agreement to the field data...

  5. Characterization of Vadose Zone Sediments Below the TX Tank Farm: Boreholes C3830, C3831, C3832 and RCRA Borehole 299-W10-27

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Orr, Robert D.; Kutnyakov, Igor V.; Baum, Steven R.; Geiszler, Keith N.; Valenta, Michelle M.; Vickerman, Tanya S.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.8, 4.28,4.43, and 4.59. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in April 2004. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) T-TX-TY. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from boreholes C3830, C3831, and C3832 in the TX Tank Farm, and from borehole 299-W-10-27 installed northeast of the TY Tank Farm.

  6. Characterization of Vadose Zone Sediments Below the T Tank Farm: Boreholes C4104, C4105, 299-W10-196, and RCRA Borehole 299-W11-39

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Schaef, Herbert T.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Geiszler, Keith N.; Baum, Steven R.; Valenta, Michelle M.; Kutnyakov, Igor V.; Vickerman, Tanya S.; Orr, Robert D.; Brown, Christopher F.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.8, 4.28, and 4.52. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in September 2004. The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) T-TX-TY. This report is the second of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from boreholes C4104 and C4105 in the T Tank Farm, and from borehole 299-W-11-39 installed northeast of the T Tank Farm. Finally, the measurements on sediments from borehole C4104 are compared with a nearby borehole drilled in 1993, 299- W10-196, through the tank T-106 leak plume.

  7. Characterization of Vadose Zone Sediment: Borehole 299-E33-46 Near B 110 in the B BX-BY Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Gee, Glendon W.; Schaef, Herbert T.; Lanigan, David C.; mccain, r. G.; Lindenmeier, Clark W.; Orr, Robert D.; Legore, Virginia L.; Clayton, Ray E.; Lindberg, Michael J.; Kutynakov, I. V.; Baum, Steven R.; Geiszler, Keith N.; Valenta, Michelle M.; Vickerman, Tanya S.; Royack, Lisa J.

    2008-09-11

    This report was revised in September 2008 to remove acid-ectractable sodium data from Table 4.17. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in December 2002. The overall goal of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities. To meet this goal, CH2M HILL Hanford Group, Inc., asked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediment from within the B-BX-BY Waste Management Area. This report is the third in a series of three reports to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from a borehole installed approximately 4.5 m (15 ft) northeast of tank B- 110 (borehole 299-E33-46).

  8. Spectroscopic and Microscopic Characterization of Contaminant Uptake and Retention by Carbonates in the Soil and Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Richard J. Reeder; Nicholas S. Fisher; Wayne P. Hess; Kenneth M. Beck

    2003-04-15

    The research focus of this previous EMSP grant was assessment of the role that carbonate minerals play in the uptake and sequestration of metal and radionuclide contaminants in soils and the vadose zone for conditions relevant to the Hanford Site and other sites in the DOE Complex. The project was a collaboration among researchers at SUNY-Stony Brook and EMSL/PNNL. Carbonates, particularly calcite, are present in the Hanford subsurface as grain coatings, disseminated particles, and dense caliche layers. Calcite is also predicted to be forming beneath leaking tanks. A range of metal and radionuclide species that pose risks at Hanford and othe DOE istes were considered, including u(VI), Cr(CV), Cs, Pb(II), and selected lanthanides (as models for trivalent actinides). Batch sorption and co-precipitation experiments of these metals with pre-equilibrated calcite and selected uptake experiments on natural caliche formed the basis to determine the mechanisms of metal/radionuclide binding and to assess the effect on the stability of the sorbed species and the potential for remobilization. Our results provide ne information that can benefit DOE clean-up methodology and potentially provide new approaches for uptake of selected heavy metals

  9. Experimental Plan: 300 Area Treatability Test: In Situ Treatment of the Vadose Zone and Smear Zone Uranium Contamination by Polyphosphate Infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Wellman, Dawn M.; Pierce, Eric M.; Oostrom, Mart; Fruchter, Jonathan S.

    2007-08-31

    The overall objectives of the treatability test is to evaluate and optimize polyphosphate remediation technology for infiltration either from ground surface, or some depth of excavation, providing direct stabilization of uranium within the deep vadose and capillary fringe above the 300 Area aquifer. Expected result from this experimental plan is a data package that includes: 1) quantification of the retardation of polyphosphate, 2) the rate of degradation and the retardation of degradation products as a function of water content, 3) an understanding of the mechanism of autunite formation via the reaction of solid phase calcite-bound uranium and aqueous polyphosphate remediation technology, 4) an understanding of the transformation mechanism, identity of secondary phases, and the kinetics of the reaction between uranyl-carbonate and –silicate minerals with the polyphosphate remedy under solubility-limiting conditions, 5) quantification of the extent and rate of uranium released and immobilized based on the infiltration rate of the polyphosphate remedy and the effect of and periodic wet-dry cycling on the efficacy of polyphosphate remediation for uranium in the vadose zone and capillary fringe, and 6) quantification of reliable equilibrium solubility values for autunite under hydraulically unsaturated conditions allowing accurate prediction of the long-term stability of autunite. Moreover, results of intermediate scale testing will quantify the transport of polyphosphate and degradation products, and yield degradation rates, at a scale that is bridging the gap between the small-scale UFA studies and the field scale. These results will be used to test and verify a site-specific, variable saturation, reactive transport model and to aid in the design of a pilot-scale field test of this technology. In particular, the infiltration approach and monitoring strategy of the pilot test would be primarily based on results from intermediate-scale testing. Results from this

  10. Characterization of Vadose Zone Sediments Below the TX Tank Farm: Probe Holes C3830, C3831, C3832 and 299-W10-27

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R JEFFREY.; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; LeGore, Virginia L.; Orr, Robert D.; Kutnyakov, Igor V.; Baum, Steven R.; Geiszler, Keith N.; Valenta, Michelle M.; Vickerman, Tanya S.

    2004-04-01

    Pacific Northwest National Laboratory performed detailed analyses on vadose zone sediments from within Waste Management Area T-TX-TY. This report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from three probe holes (C3830, C3831, and C3832) in the TX Tank Farm, and from borehole 299-W-10-27. Sediments from borehole 299-W-10-27 are considered to be uncontaminated sediments that can be compared with contaminated sediments. This report also presents our interpretation of the sediment lithologies, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone and groundwater below the TX Tank Farm. Sediment from the probe holes was analyzed for: moisture, radionuclide and carbon contents;, one-to-one water extracts (soil pH, electrical conductivity, cation, trace metal, and anion data), and 8 M nitric acid extracts. Overall, our analyses showed that common ion exchange is a key mechanism that influences the distribution of contaminants within that portion of the vadose zone affected by tank liquor. We did not observe significant indications of caustic alteration of the sediment mineralogy or porosity, or significant zones of slightly elevated pH values in the probe holes. The sediments do show that sodium-, nitrate-, and sulfate-dominated fluids are present. The fluids are more dilute than tank fluids observed below tanks at the SX and BX Tank Farms. Three primary stratigraphic units were encountered in each probe hole: (1) backfill material, (2) the Hanford formation, and (3) the Cold Creek unit. Each of the probe holes contain thin fine-grained layers in the Hanford H2 stratigraphic unit that may impact the flow of leaked fluids and effect irregular and horizontal flow. The probe holes could not penetrate below the enriched calcium carbonate strata of the Cold Creek lower subunit; therefore, we did not

  11. Factors Effecting the Fate and Transport of CL-20 in the Vadose Zone and Groundwater: Final Report 2002 - 2004 SERDP Project CP-1255

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Riley, Robert G.; Devary, Brooks J.; Girvin, Donald C.; Resch, Charles T.; Campbell, James A.; Fredrickson, Herbert L.; Thompson, Karen T.; Crocker, Fiona H.; Qasim, Mohammad M.; Gamerdinger, Amy P.; Lemond, Luke A.

    2005-06-01

    This SERDP-funded project was initiated to investigate the fate of CL-20 in the subsurface environment, with a focus on identification and quantification of geochemical and microbial reactions of CL-20. CL-20 can be released to the surface and subsurface terrestrial environment by: a) manufacturing processes, b) munition storage, and c) use with low order detonation or unexploded ordnance. The risk of far-field subsurface migration was assessed through labora-tory experiments with a variety of sediments and subsurface materials to quantify processes that control CL-20 sorption-limited migration and degradation. Results of this study show that CL-20 will exhibit differing behavior in the subsurface terrestrial environment: 1. CL-20 on the sediment surface will photodegrade and interact with plants/animals (described in other SERDP projects CU 1254, 1256). CL-20 will exhibit greater sorption in humid sediments to organic matter. Transport will be solubility limited (i.e., low CL-20 aqueous solubility). 2. CL-20 infiltration into soils (<2 m) from spills will be subject to sorption to soil organic matter (if present), and low to high biodegradation rates (weeks to years) depending on the microbial population (greater in humid environment). 3. CL-20 in the vadose zone (>2 m) will be, in most cases, subject to low sorption and low degradation rates, so would persist in the subsurface environment and be at risk for deep migration. Low water content in arid regions will result in a decrease in both sorption and the degradation rate. Measured degradation rates in unsaturated sediments of years would result in significant subsurface migration distances. 4. CL-20 in groundwater will be subject to some sorption but likely very slow degradation rates. CL-20 sorption will be greater than RDX. Most CL-20 degradation will be abiotic (ferrous iron and other transition metals), because most deep subsurface systems have extremely low natural microbial populations. Degradation rates

  12. The ecohydrology of the soil-vegetation system restoration in arid zones: a review

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Arid zones, which cover approximately 40 percent of the earth’s land surface, support complicated and widely varied ecological systems. As such, arid zones are an important composition of the global terrestrial ecosystem, and water is the key and abiotic lim-ited factor in ecosystem-driven processes in these areas. Ecohydrology is a new cross discipline that provides, in an objective and comprehensive manner, novel ideas and approaches to the evaluation of the interaction and feedback mechanisms involved in the soil-vegetation systems in arid zones. In addition, ecohydrology provides a theoretical basis of ecological restoration that is cen-tered on vegetation construction. In this paper, long-term monitoring and local observations in the transitional belt between a de-sertified steppe and a steppified desert at the Shapotou Desert Research and Experiment Station, Tengger Desert, in northern China, were evaluated. The primary achievements and related research progress regarding ecohydrology in arid zones were analyzed and summarized, as a keystone, and the response of soil ecohydrological processes to the changes in the species composition, structure, and function of sandland vegetation was discussed. Meanwhile, the long-term ecological effects and mechanism of regulation of vegetation on soil habitat and on water-cycling were considered. As a vital participant in the ecohydrological processes of soil-vegetation systems, the studies on biological soil crusts was also summarized, and related theoretical models of restoration based on the water balance was reviewed.

  13. Remediation of Uranium in the Hanford Vadose Zone Using Gas-Transported Reactants: Laboratory Scale Experiments in Support of the Deep Vadose Zone Treatability Test Plan for the Hanford Central Plateau

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Truex, Michael J.; Zhong, Lirong; Williams, Mark D.; Resch, Charles T.; McKinley, James P.

    2010-01-04

    This laboratory-scale investigation is focused on decreasing mobility of uranium in subsurface contaminated sediments in the vadose zone by in situ geochemical manipulation at low water content. This geochemical manipulation of the sediment surface phases included reduction, pH change (acidic and alkaline), and additions of chemicals (phosphate, ferric iron) to form specific precipitates. Reactants were advected into 1-D columns packed with Hanford 200 area U-contaminated sediment as a reactive gas (for CO2, NH3, H2S, SO2), with a 0.1% water content mist (for NaOH, Fe(III), HCl, PO4) and with a 1% water content foam (for PO4). Uranium is present in the sediment in multiple phases that include (in decreasing mobility): aqueous U(VI) complexes, adsorbed U, reduced U(IV) precipitates, rind-carbonates, total carbonates, oxides, silicates, phosphates, and in vanadate minerals. Geochemical changes were evaluated in the ability to change the mixture of surface U phases to less mobile forms, as defined by a series of liquid extractions that dissolve progressively less soluble phases. Although liquid extractions provide some useful information as to the generalized uranium surface phases (and are considered operational definitions of extracted phases), positive identification (by x-ray diffraction, electron microprobe, other techniques) was also used to positively identify U phases and effects of treatment. Some of the changes in U mobility directly involve U phases, whereas other changes result in precipitate coatings on U surface phases. The long-term implication of the U surface phase changes to alter U mass mobility in the vadose zone was then investigated using simulations of 1-D infiltration and downward migration of six U phases to the water table. In terms of the short-term decrease in U mobility (in decreasing order), NH3, NaOH mist, CO2, HCl mist, and Fe(III) mist showed 20% to 35% change in U surface phases. Phosphate addition (mist or foam advected) showed

  14. Sampling vadose-zone water for a volatile organic compound at Picatinny Arsenal, New Jersey

    Science.gov (United States)

    Smith, James A.; Cho, H. Jean; Jaffe, Peter R.; MacLeod, Cecilia L.; Koehnlein, Susan A.

    1992-01-01

    A new method of collecting samples of unsaturated-zone water for quantitative analysis for a volatile organic compound, trichloroethene (TCE), was compared to three other, previously described sampling methodologies in the laboratory and in the field. In the laboratory, prepared water samples containing TCE in a known concentration (20 µg/L) were sampled repeatedly by using each of the four methods to quantify method precision and accuracy. To compare the four methods in the field, unsaturated-zone water above a TCE-contaminated water-table aquifer was transferred from a depth of 2 m to land surface with 0.15-m-long suction lysimeters attached to 1.85-m lengths of stainless-steel tubing. Statistical analyses of the laboratory and field data indicate that the new method, which involves collecting the water samples in gas-tight glass syringes, is superior to the other three methods for the quantitative sampling and analysis of TCE on the basis of its high precision and accuracy and ease of use. This method was used to collect additional samples from the field site to quantify the spatial variability of TCE concentrations in the unsaturated-zone water. Results of analysis of variance of the data indicate that the spatial concentration variability is important, and that differences in TCE concentration are statistically significant for horizontal distances less than 3.6 m.

  15. Diffusive transport and evaporation to the atmosphere from a NAPL source in the vadose zone

    DEFF Research Database (Denmark)

    Holtegaard, L.E.; Bjerre, T.; Christophersen, Mette;

    2002-01-01

    To evaluate the risks concerned with the presence of volatile organic compounds in the unsaturated zone it is important to know how the compounds are transported in the soil. In this project the effective diffusion coefficient of 3-methylpentane, hexane, methyl-cyclopentane, iso-octane and methyl......-cyclo-hexane has been measured in-situ using a diffusive tracer test (DTT). Furthermore the flux from a NAPL source has been measured in flux chambers. From these results the effective diffusion coefficient has been calculated for CFC113, methyl-cyclo-pentane, benzene, iso-octane, and methyl...

  16. Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Szecsody, James E.; Truex, Michael J.; Zhong, Lirong; Qafoku, Nikolla; Williams, Mark D.; McKinley, James P.; Wang, Zheming; Bargar, John; Faurie, Danielle K.; Resch, Charles T.; Phillips, Jerry L.

    2010-12-01

    This investigation is focused on refining an in situ technology for vadose zone remediation of uranium by the addition of ammonia (NH3) gas. Objectives are to: a) refine the technique of ammonia gas treatment of low water content sediments to minimize uranium mobility by changing uranium surface phases (or coat surface phases), b) identify the geochemical changes in uranium surface phases during ammonia gas treatment, c) identify broader geochemical changes that occur in sediment during ammonia gas treatment, and d) predict and test injection of ammonia gas for intermediate-scale systems to identify process interactions that occur at a larger scale and could impact field scale implementation.Overall, NH3 gas treatment of low-water content sediments appears quite effective at decreasing aqueous, adsorbed uranium concentrations. The NH3 gas treatment is also fairly effective for decreasing the mobility of U-carbonate coprecipitates, but shows mixed success for U present in Na-boltwoodite. There are some changes in U-carbonate surface phases that were identified by surface phase analysis, but no changes observed for Na-boltwoodite. It is likely that dissolution of sediment minerals (predominantly montmorillonite, muscovite, kaolinite) under the alkaline conditions created and subsequent precipitation as the pH returns to natural conditions coat some of the uranium surface phases, although a greater understanding of these processes is needed to predict the long term impact on uranium mobility. Injection of NH3 gas into sediments at low water content (1% to 16% water content) can effectively treat a large area without water addition, so there is little uranium mobilization (i.e., transport over cm or larger scale) during the injection phase.

  17. Enhanced biogeochemical cycling and subsequent reduction of hydraulic conductivity associated with soil-layer interfaces in the vadose zone.

    Science.gov (United States)

    Hansen, David J; McGuire, Jennifer T; Mohanty, Binayak P

    2011-01-01

    Biogeochemical dynamics in the vadose zone are poorly understood due to the transient nature of chemical and hydrologic conditions but are nonetheless critical to understanding chemical fate and transport. This study explored the effects of a soil layer on linked geochemical, hydrological, and microbiological processes. Three laboratory soil columns were constructed: a homogenized medium-grained sand, a homogenized organic-rich loam, and a sand-over-loam layered column. Upward and downward infiltration of water was evaluated during experiments to simulate rising water table and rainfall events, respectively. In situ collocated probes measured soil water content, matric potential, and Eh. Water samples collected from the same locations were analyzed for Br, Cl, NO, SO, NH, Fe, and total sulfide. Compared with homogeneous columns, the presence of a soil layer altered the biogeochemistry and water flow of the system considerably. Enhanced biogeochemical cycling was observed in the layered column over the texturally homogeneous soil columns. Enumerations of iron- and sulfate-reducing bacteria showed 1 to 2 orders of magnitude greater community numbers in the layered column. Mineral and soil aggregate composites were most abundant near the soil-layer interface, the presence of which likely contributed to an observed order-of-magnitude decrease in hydraulic conductivity. These findings show that quantifying coupled hydrologic-biogeochemical processes occurring at small-scale soil interfaces is critical to accurately describing and predicting chemical changes at the larger system scale. These findings also provide justification for considering soil layering in contaminant fate and transport models because of its potential to increase biodegradation or to slow the rate of transport of contaminants.

  18. Part 1: Vadose-zone column studies of toluene (enhanced bioremediation) in a shallow unconfined aquifer

    Science.gov (United States)

    Tindall, J.A.; Friedel, M.J.; Szmajter, R.J.; Cuffin, S.M.

    2005-01-01

    The objectives of the laboratory study described in this paper were (1) to determine the effectiveness of four nutrient solutions and a control in stimulating the microbial degradation of toluene in the unsaturated zone as an alternative to bioremediation methodologies such as air sparging, in situ vitrification, or others (Part I), and (2) to compare the effectiveness of the addition of the most effective nutrient solution from Part I (modified Hoagland type, nitrate-rich) and hydrogen peroxide (H2O2) on microbial degradation of toluene for repeated, simulated spills in the unsaturated zone (Part II). For Part 1, fifteen columns (30-cm diameter by 150-cm height), packed with air-dried, 0.25-mm, medium-fine sand, were prepared to simulate shallow unconfined aquifer conditions. Toluene (10 mL) was added to the surface of each column, and soil solution and soil gas samples were collected from the columns every third day for 21 days. On day 21, a second application of toluene (10 mL) was made, and the experiment was run for another 21 days. Solution 4 was the most effective for microbial degradation in Part I. For Part II, three columns were designated nutrient-rich 3-day toluene columns and received toluene injections every 3 days; three columns were designated as nutrient-rich 7-day columns and received toluene injections every 7 days; and two columns were used as controls to which no nutrient was added. As measured by CO2 respiration, the initial benefits for aerobic organisms from the O2 enhancement were sustained by the bacteria for only a short period of time (about 8 days). Degradation benefits from the nutrient solution were sustained throughout the experiment. The O2 and nutrient-enhanced columns degraded significantly more toluene than the control columns when simulating repeated spills onto the unsaturated zone, and demonstrated a potentially effective in situ bioremediation technology when used immediately or within days after a spill. The combined usage

  19. Hanford Tank Farms Vadose Zone, Addendum to the BX Tank Farm Report

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, A.W.

    2000-07-01

    This addendum to the BX Tank Farm Report (GJO-98-40-TARA, GJO-HAN-19) published in August 1998 incorporates the results of high-rate and repeat logging activities along with shape factor analysis of the logging data. A high-rate logging system was developed and deployed in the BX Tank Farm to measure cesium-137 concentration levels in high gamma flux zones where the spectral gamma logging system was unable to collect usable data because of high dead times and detector saturation. This report presents additional data and revised visualizations of subsurface contaminant distribution in the BX Tank Farm at the DOE Hanford Site in the state of Washington.

  20. Modeling the air-soil transport pathway of perfluorooctanoic acid in the mid-Ohio Valley using linked air dispersion and vadose zone models

    Science.gov (United States)

    Shin, Hyeong-Moo; Ryan, P. Barry; Vieira, Verónica M.; Bartell, Scott M.

    2012-05-01

    As part of an extensive modeling effort on the air-soil-groundwater transport pathway of perfluorooctanoic acid (PFOA), this study was designed to compare the performance of different air dispersion modeling systems (AERMOD vs. ISCST3), and different approaches to handling incomplete meteorological data using a data set with substantial soil measurements and a well characterized point source for air emissions. Two of the most commonly used EPA air dispersion models, AERMOD and ISCST3, were linked with the EPA vadose zone model PRZM-3. Predicted deposition rates from the air dispersion model were used as input values for the vadose zone model to estimate soil concentrations of PFOA at different depths. We applied 34 years of meteorological data including hourly surface measurements from Parkersburg Airport and 5 years of onsite wind direction and speed to the air dispersion models. We compared offsite measured soil concentrations to predictions made for the corresponding sampling depths, focusing on soil rather than air measurements because the offsite soil samples were less likely to be influenced by short-term variability in emission rates and meteorological conditions. PFOA concentrations in surface soil (0-30 cm depth) were under-predicted and those in subsurface soil (>30 cm depth) were over-predicted compared to observed concentrations by both linked air and vadose zone model. Overall, the simulated values from the linked modeling system were positively correlated with those observed in surface soil (Spearman's rho, Rsp = 0.59-0.70) and subsurface soil (Rsp = 0.46-0.48). This approach provides a useful modeling scheme for similar exposure and risk analyses where the air-soil-groundwater transport is a primary contamination pathway.

  1. Characterization of Vadose Zone Sediments Below the C Tank Farm: Borehole C4297 and RCRA Borehole 299-E27-22

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Serne, R. JEFFREY; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Clayton, Ray E.; Valenta, Michelle M.; Vickerman, Tanya S.; Kutnyakov, Igor V.; Geiszler, Keith N.; Baum, Steven R.; Parker, Kent E.; Lindberg, Michael J.

    2006-10-18

    The overall goal of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., is to define risks from past and future single-shell tank farm activities at Hanford. To meet this goal, CH2M HILL Hanford Group, Inc. tasked scientists from Pacific Northwest National Laboratory to perform detailed analyses on vadose zone sediments from within Waste Management Area (WMA) C. This report is the first of two reports written to present the results of these analyses. Specifically, this report contains all the geologic, geochemical, and selected physical characterization data collected on vadose zone sediment recovered from borehole C4297, installed adjacent to Tank C-105, and from borehole 299-E27-22, installed directly north of the C Tank Farm. Sediments from borehole 299-E27-22 were considered to be background uncontaminated sediments against which to compare contaminated sediments for the C Tank Farm characterization effort. This report also presents our interpretation of the data in the context of sediment types, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone and groundwater below the C Tank Farm. The information presented in this report supports the A-AX, C and U Waste Management Area field investigation report(a) in preparation by CH2M HILL Hanford Group, Inc. A core log was generated for both boreholes and a geologic evaluation of all core samples was performed at the time of opening. Aliquots of sediment from the borehole core samples were analyzed and characterized in the laboratory for the following parameters: moisture content, gamma-emitting radionuclides, one-to-one water extracts (which provide soil pH, electrical conductivity, cation, trace metal, and anion data), total carbon and inorganic carbon content, and 8 M nitric acid extracts (which provide a measure of the total leachable sediment content of contaminants). Two key radiocontaminants

  2. Assessing the impact of dairy waste lagoons on groundwater quality using a spatial analysis of vadose zone and groundwater information in a coastal phreatic aquifer.

    Science.gov (United States)

    Baram, S; Kurtzman, D; Ronen, Z; Peeters, A; Dahan, O

    2014-01-01

    Dairy waste lagoons are considered to be point sources of groundwater contamination by chloride (Cl(-)), different nitrogen-species and pathogens/microorganisms. The objective of this work is to introduce a methodology to assess the past and future impacts of such lagoons on regional groundwater quality. The method is based on a spatial statistical analysis of Cl(-) and total nitrogen (TN) concentration distributions in the saturated and the vadose (unsaturated) zones. The method provides quantitative data on the relation between the locations of dairy lagoons and the spatial variability in Cl(-) and TN concentrations in groundwater. The method was applied to the Beer-Tuvia region, Israel, where intensive dairy farming has been practiced for over 50 years above the local phreatic aquifer. Mass balance calculations accounted for the various groundwater recharge and abstraction sources and sinks in the entire region. The mass balances showed that despite the small surface area covered by the dairy lagoons in this region (0.8%), leachates from lagoons have contributed 6.0% and 12.6% of the total mass of Cl(-) and TN (mainly as NO3(-)-N) added to the aquifer. The chemical composition of the aquifer and vadose zone water suggested that irrigated agricultural activity in the region is the main contributor of Cl(-) and TN to the groundwater. A low spatial correlation between the Cl(-) and NO3(-)-N concentrations in the groundwater and the on-land location of the dairy farms strengthened this assumption, despite the dairy waste lagoon being a point source for groundwater contamination by Cl(-) and NO3(-)-N. Mass balance calculations, for the vadose zone of the entire region, indicated that drying of the lagoons would decrease the regional groundwater salinization process (11% of the total Cl(-) load is stored under lagoons). A more considerable reduction in the groundwater contamination by NO3(-)-N is expected (25% of the NO3(-)-N load is stored under lagoons). Results

  3. Site S-7 VOC Transport modeling for the Vadose Zone Monitoring System (VZMS), McClellan AFB - 1999 Semi-Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Doughty, Christine; Oldenburg, Curtis M.; James, April L.

    1999-06-15

    Enhanced data analysis is continuing for the Vadose Zone Monitoring System (VZMS) installed at site S-7 in IC 34 at McClellan AFB. Air temperatures along with data from the four highest levels of thermistors in VZMS-A and B are used with an analytical solution for the heat conduction equation to show that heat transfer in the shallow vadose zone at S-7 is conduction-dominated. This analysis is extended to reveal that stiace temperature, i.e., the temperature of the concrete slab at S-7, is significantly higher in summer than the surrounding air temperature. These high temperatures in the shallow vadose zone can lead to increased volatilization of VOCS. Seasonal temperature reversals can cause upward buoyant gas flow in the uppermost 30 feet of the vadose zone in the winter. Data on gas-phase VOC concentrations in VZMS-A and B show highest concentrations in the shallow subsurface, low concentrations between depths of 30-70 feet, and slightly higher concentrations near the water table. Modeling VOC flow and transport subject to the constraints of data collected by the VZMS requires extension of the one-dimensional site-representative model used previously. Conceptual models broadly consistent with these data include (1) a diffusion-only model; (2) a preferential flow model; or (3) two- and three-dimensional flow models where the VOC plume undergoes lateral migration. Simulations of VOC transport suggest that there are VOCS at depths shallower than 6 feet, that significant NAPL is unlikely to be present, and that a source of VOCS may be provided by lateral flow in the gravel layer between two concrete layers present at the site. The conceptual models upon which VOC transport modeling is based require further development and testing. Prior Vapour-T modeling results for the S-7 site based on cis-1,2-DCE concentrations in well SS7SB08 are not substantiated by VZMS data, but these data are localized whereas VapourT results are generalized for the S-7 site as a whole

  4. Role of the sedimentary structure of the urban vadose zone (URVAZO) on the transfer of heavy metals of an urban stormwater basin

    Science.gov (United States)

    Angulo-Jaramillo, R.; Winiarski, T.; Goutaland, D.; Lassabatere, L.

    2009-12-01

    Stormwater infiltration basins have become a common alternative practice to traditional stormwater pipe networks in urban areas. They are often built in permeable subsurface soils (Urban Vadose Zone, URVAZO), such as alluvial deposits. These sedimentary deposits are highly heterogeneous and generate preferential flow paths that may cause either rapid or non-uniform transport of contaminants at great depths. The understanding of how subsurface vadose zone heterogeneities transfer contaminant and fluid flow to the aquifer still remains a challenge in urban hydrology. Indeed, urban stormwater may contain pollutants that can contaminate either soil or groundwater. The aim of this study is to evaluate the role of the lithological heterogeneity of a glaciofluvial deposit underlying an urban infiltration basin on the link between water flow and heavy metals retention. A trench wall (14m length x 3m depth) was exposed by excavating the glaciofluvial formation. By a hydrogeophysical approach based on a sedimentary structural units and in situ hydraulic characterization (Beerkan tests), a realistic hydrostratigraphic 2D model was defined. The trench was sampled on nine vertical sections of 1.5m length, with ten samples per vertical section following each lithofacies. A total of 90 samples were analyzed. Coarse (mechanical sieving) and fine (laser diffraction) particle size distribution analysis, as well as the concentration of three replicates of Pb, Cu, Zn and organic matter (OM) was measured for each sample. The principal component analysis shows a strong correlation between metal concentration and the lithofacies. This hydrostratigraphic model was implemented in the finite element program Hydrus2D. The soil heterogeneity exerts an impact on the heterogeneity of the water content field under slightly saturated conditions, as they induce capillary barrier effects. These capillary barrier effects may generate water accumulation in some lithofacies overlying matrix

  5. Monitoring and data analysis for the Vadose Zone Monitoring System (VZMS), McClellan AFB. Quarterly status report, May 15, 1997--August 15, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.T.; Salve, R.; Freifeld, B. [and others

    1997-08-01

    This report contains information on field and laboratory work performed between May 15th and August 15th 1997 at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) is currently being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature. This report describes: (1) re-calibration of pressure transducers; (2) moisture content changes, based on neutron logging; (3) gas-phase VOC concentrations; (4) aqueous-phase VOC concentrations; (5) temperature profiles; and (6) pressure readings.

  6. Monitoring and Data Analysis for the Vadose Zone Monitoring System (VZMS), McClellan AFB. Quarterly Status Report (2/20/98 - 5/20/98)

    Energy Technology Data Exchange (ETDEWEB)

    Zawislanski, P.T.; Mountford, H.S.Monitoring and Data Analysis; for the Vadose Zone Monitoring System; Mountford, H.S.; Dahlquist, R.; Rodriguez, S.J.

    1998-06-18

    This report contains information on field and laboratory work performed between February 20th, 1998 and May 20th, 1998, at site S-7 in IC 34, at McClellan AFB. At this location, a Vadose Zone Monitoring System (VZMS) (LBNL, 1996) is currently being used to collect subsurface data including hydraulic potential, soil gas pressure, moisture content, water chemistry, gas chemistry, and temperature. This report describes: moisture content changes, based on neutron logging; gas-phase VOC concentrations; aqueous-phase VOC concentrations; temperature profiles; and installation of new instrument cluster.

  7. 300 Area Treatability Test: Laboratory Development of Polyphosphate Remediation Technology for In Situ Treatment of Uranium Contamination in the Vadose Zone and Capillary Fringe

    Energy Technology Data Exchange (ETDEWEB)

    Wellman, Dawn M.; Pierce, Eric M.; Bacon, Diana H.; Oostrom, Martinus; Gunderson, Katie M.; Webb, Samuel M.; Bovaird, Chase C.; Cordova, Elsa A.; Clayton, Eric T.; Parker, Kent E.; Ermi, Ruby M.; Baum, Steven R.; Vermeul, Vincent R.; Fruchter, Jonathan S.

    2008-09-30

    This report presents results from bench-scale treatability studies conducted under site-specific conditions to optimize the polyphosphate amendment for implementation of a field-scale technology demonstration to stabilize uranium within the 300 Area vadose and smear zones of the Hanford Site. The general treatability testing approach consisted of conducting studies with site sediment and under site conditions, to develop an effective chemical formulation and infiltration approach for the polyphosphate amendment under site conditions. Laboratory-scale dynamic column tests were used to 1) quantify the retardation of polyphosphate and its degradation products as a function of water content, 2) determine the rate of polyphosphate degradation under unsaturated conditions, 3) develop an understanding of the mechanism of autunite formation via the reaction of solid phase calcite-bound uranium and aqueous polyphosphate remediation technology, 4) develop an understanding of the transformation mechanism, the identity of secondary phases, and the kinetics of the reaction between uranyl-carbonate and -silicate minerals with the polyphosphate remedy under solubility-limiting conditions, and 5) quantify the extent and rate of uranium released and immobilized based on the infiltration rate of the polyphosphate remedy and the effect of and periodic wet-dry cycling on the efficacy of polyphosphate remediation for uranium in the vadose zone and smear zone.

  8. L'économie de la gestion des risques en zone semi-aride

    NARCIS (Netherlands)

    Dijk, van J.W.M.; Tielekes, E.; Schlecht, E.; Hiernaux, P.

    2001-01-01

    Toute forme de gestion ou d'aménagement des ressources fourragères pour les éleveurs dans la zone semi-aride au Sahel commence obligatoirement par l'appréciation d'un certain nombre de variables et notamment leur variabilité dans l'espace et dans le temps. Cette variabilité est la source d'une vaste

  9. Characterization of Direct-Push Vadose Zone Sediments from the 241-B and 241-BX Tank Farms

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Christopher F.; Icenhower, Jonathan P.; Um, Wooyong; Bjornstad, Bruce N.; Valenta, Michelle M.; Iovin, Cristian; Lanigan, David C.; Clayton, Ray E.; Geiszler, Keith N.; Clayton, Eric T.; Kutnyakov, Igor V.; Baum, Steven R.; Lindberg, Michael J.; Orr, Robert D.

    2007-12-21

    Geochemical tests provide evidence for the transit of a plume of caustic waste solution through the sediment column at the Hanford 241-B and -BX Tank Farms. Direct-push samples recovered from boreholes surrounding Tanks 241-B-110 and 241-BX-102 and related waste transfer lines and diversion boxes included sediments typical of those previously recovered from other localities on the Hanford Site. The Hanford formation sediments are dominantly quartzo-feldspathic sands strewn with lithic fragments, displaying a range of particle size distributions and sorting characteristics. Some moderately well-sorted, fine-grained lithologies are interpreted as lenticular bodies irregularly dispersed in coarser-grained, more poorly sorted sediments. Tier I tests conducted on the vadose zone sediments revealed an inverse correlation between moisture content and sediment size fraction (i.e., there is greater moisture content in finer-grained sediments). The Tier I tests also showed that the pore water solutions were likely sodium-rich, moderately saline, and possessed higher pH values than background (untainted) sediments. These data are characteristic of sediments that have encountered sodium-rich, saline, caustic waste solution, as documented in other reports at other suspect contamination sites around Hanford. Analyses of solutions from 1:1 water extracts reveal relatively balanced cation and anion concentrations, indicating that most of the geochemical species have been accounted for. The water extract data for affected sediments also indicate unusually high concentrations of aluminum, iron, and phosphorus. The relatively high concentrations of aluminum and iron may be the result of dissolution of secondary amorphous phases that precipitated after a reactive plume partially dissolved aluminum- and iron-bearing phases as it migrated through the sediment column. On the other hand, the presence of elevated concentrations of phosphorous may be the tell-tale signature of wastes

  10. Utilizing High-Performance Computing to Investigate Parameter Sensitivity of an Inversion Model for Vadose Zone Flow and Transport

    Science.gov (United States)

    Fang, Z.; Ward, A. L.; Fang, Y.; Yabusaki, S.

    2011-12-01

    High-resolution geologic models have proven effective in improving the accuracy of subsurface flow and transport predictions. However, many of the parameters in subsurface flow and transport models cannot be determined directly at the scale of interest and must be estimated through inverse modeling. A major challenge, particularly in vadose zone flow and transport, is the inversion of the highly-nonlinear, high-dimensional problem as current methods are not readily scalable for large-scale, multi-process models. In this paper we describe the implementation of a fully automated approach for addressing complex parameter optimization and sensitivity issues on massively parallel multi- and many-core systems. The approach is based on the integration of PNNL's extreme scale Subsurface Transport Over Multiple Phases (eSTOMP) simulator, which uses the Global Array toolkit, with the Beowulf-Cluster inspired parallel nonlinear parameter estimation software, BeoPEST in the MPI mode. In the eSTOMP/BeoPEST implementation, a pre-processor generates all of the PEST input files based on the eSTOMP input file. Simulation results for comparison with observations are extracted automatically at each time step eliminating the need for post-process data extractions. The inversion framework was tested with three different experimental data sets: one-dimensional water flow at Hanford Grass Site; irrigation and infiltration experiment at the Andelfingen Site; and a three-dimensional injection experiment at Hanford's Sisson and Lu Site. Good agreements are achieved in all three applications between observations and simulations in both parameter estimates and water dynamics reproduction. Results show that eSTOMP/BeoPEST approach is highly scalable and can be run efficiently with hundreds or thousands of processors. BeoPEST is fault tolerant and new nodes can be dynamically added and removed. A major advantage of this approach is the ability to use high-resolution geologic models to preserve

  11. Modeling non-steady state radioisotope transport in the vadose zone--A case study using uranium isotopes at Pena Blanca, Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Ku, T. L.; Luo, S.; Goldstein, S. J.; Murrell, M. T.; Chu, W. L.; Dobson, P. F.

    2009-06-01

    Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leads to a linear relationship between reciprocal U concentration and {sup 234}U/{sup 238}U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and {alpha}-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Pena Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced {sup 234}U/{sup 238}U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using {sup 234}U/{sup 238}U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.

  12. Modeling non-steady state radioisotope transport in the vadose zone - A case study using uranium isotopes at Peña Blanca, Mexico

    Science.gov (United States)

    Ku, T. L.; Luo, S.; Goldstein, S. J.; Murrell, M. T.; Chu, W. L.; Dobson, P. F.

    2009-10-01

    Current models using U- and Th-series disequilibria to study radioisotope transport in groundwater systems mostly consider a steady-state situation. These models have limited applicability to the vadose zone (UZ) where the concentration and migratory behavior of radioisotopes in fluid are often transitory. We present here, as a first attempt of its kind, a model simulating the non-steady state, intermittent fluid transport in vadose layers. It provides quantitative constraints on in-situ migration of dissolved and colloidal radioisotopes in terms of retardation factor and rock-water interaction (or water transit) time. For uranium, the simulation predicts that intermittent flushing in the UZ leads to a linear relationship between reciprocal U concentration and 234U/ 238U ratio in percolating waters, with the intercept and slope bearing information on the rates of dissolution and α-recoil of U isotopes, respectively. The general validity of the model appears to be borne out by the measurement of uranium isotopes in UZ waters collected at various times over a period during 1995-2006 from a site in the Peña Blanca mining district, Mexico, where the Nopal I uranium deposit is located. Enhanced 234U/ 238U ratios in vadose-zone waters resulting from lengthened non-flushing time as prescribed by the model provide an interpretative basis for using 234U/ 238U in cave calcites to reconstruct the regional changes in hydrology and climate. We also provide a theoretical account of the model's potential applications using radium isotopes.

  13. SOIL DESICCATION TECHNIQUES STRATEGIES FOR IMMOBILIZATION OF DEEP VADOSE CONTAMINANTS AT THE HANFORD CENTRAL PLATEAU

    Energy Technology Data Exchange (ETDEWEB)

    BENECKE MW; CHRONISTER GB; TRUEX MJ

    2012-01-30

    Deep vadose zone contamination poses some of the most difficult remediation challenges for the protection of groundwater at the Hanford Site where processes and technologies are being developed and tested for use in the on-going effort to remediate mobile contamination in the deep vadose zone, the area deep beneath the surface. Historically, contaminants were discharged to the soil along with significant amounts of water, which continues to drive contaminants deeper in the vadose zone toward groundwater. Soil desiccation is a potential in situ remedial technology well suited for the arid conditions and the thick vadose zone at the Hanford Site. Desiccation techniques could reduce the advance of contaminants by removing the pore water to slow the rate of contaminants movement toward groundwater. Desiccation technologies have the potential to halt or slow the advance of contaminants in unsaturated systems, as well as aid in reduction of contaminants from these same areas. Besides reducing the water flux, desiccation also establishes capillary breaks that would require extensive rewetting to resume pore water transport. More importantly, these techniques have widespread application, whether the need is to isolate radio nuclides or address chemical contaminant issues. Three different desiccation techniques are currently being studied at Hanford.

  14. Characterization of Vadose Zone Sediment: RCRA Borehole 299-E33-338 Located Near the B-BX-BY Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Lindenmeier, Clark W.; Serne, R. Jeffrey; Bjornstad, Bruce N.; Gee, Glendon W.; Schaef, Herbert T.; Lanigan, David C.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Kutnyakov, Igor V.; Baum, Steven R.; Geiszler, Keith N.; Brown, Christopher F.; Valenta, Michelle M.; Vickerman, Tanya S.; Royack, Lisa J.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Table 4.8. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in June 2003. The overall goals of the of the Tank Farm Vadose Zone Project, led by CH2M HILL Hanford Group, Inc., are: 1) to define risks from past and future single-shell tank farm activities, 2) to identify and evaluate the efficacy of interim measures, and 3) to aid via collection of geotechnical information and data, future decisions that must be made by the U.S. Department of Energy (DOE) regarding the near-term operations, future waste retrieval, and final closure activities for the single-shell tank waste management areas. For a more complete discussion of the goals of the Tank Farm Vadose Zone Project, see the overall work plan, Phase 1 RCRA Facility Investigation/Corrective Measures Study Work Plan for the Single-Shell Tank Waste Management Areas (DOE 1999). Specific details on the rationale for activities performed at the B-BX-BY tank farm waste management area are found in CH2M HILL (2000).

  15. Processes controlling the migration and biodegradation of Non-aqueous phase liquids (NAPLs) within fractured rocks in the vadose zone FY97 annual report

    Energy Technology Data Exchange (ETDEWEB)

    Geller, J.T.; Holman, Hoi-Ying; Conrad, M. [and others

    1998-02-01

    Subsurface contamination from volatile organic compounds (VOCs) has been found at many Department of Energy (DOE), Department of Defense (DoD) and industrial sites due to the widespread use of organic solvents and hydrocarbon fuels. At ambient pressures and temperatures in the shallow subsurface, these substances are liquids that are immiscible with water; hence they are commonly designated as non-aqueous phase liquids (NAPLs). At some DOE sites, NAPLs are the presumed source of groundwater contamination in fractured rocks, such as basalts (at Hanford and Idaho National Engineering and Environmental Laboratory (INEEL)), shales (Oak Ridge Y-12 Plant), and welded tuffs (Los Alamos National Laboratory (LANL)). The flow, transport and biodegradation processes controlling NAPL behavior in the vadose zone must be understood in order to establish the possible extent of contamination, the risk to groundwater supplies, and appropriate remediation action. This is particularly important in and sites with deep water tables (such as at Hanford, INEEL and LANL). In fractured rock aquifers, NAPL migration is likely to be dominated by the highly permeable pathways provided by rock fractures and joints. Two- and three-phase fluid phases may be present in vadose zone fractures, including NAPL-gas, NAPL-water (in regions of perched water) and NAPL-water-gas.

  16. VAMOS: The verification and monitoring options study: Current research options for in-situ monitoring and verification of contaminant remediation and containment within the vadose zone

    Energy Technology Data Exchange (ETDEWEB)

    Betsill, J.D. [Sandia National Labs., Albuquerque, NM (United States); Gruebel, R.D. [Tech Reps., Inc., Albuquerque, NM (United States)

    1995-09-01

    The Verification and Monitoring Options Study Project (VAMOS) was established to identify high-priority options for future vadose-zone environmental research in the areas of in-situ remediation monitoring, post-closure monitoring, and containment emplacement and verification monitoring. VAMOS examined projected needs not currently being met with applied technology in order to develop viable monitoring and verification research options. The study emphasized a compatible systems approach to reinforce the need for utilizing compatible components to provide user friendly site monitoring systems. To identify the needs and research options related to vadose-zone environmental monitoring and verification, a literature search and expert panel forums were conducted. The search included present drivers for environmental monitoring technology, technology applications, and research efforts. The forums included scientific, academic, industry, and regulatory environmental professionals as well as end users of environmental technology. The experts evaluated current and future monitoring and verification needs, methods for meeting these needs, and viable research options and directions. A variety of high-priority technology development, user facility, and technology guidance research options were developed and presented as an outcome of the literature search and expert panel forums.

  17. Site S-7 Representative Model and Application for the Vadose Zone Monitoring System (VZMS) McClellan AFB - 1998 Semi-Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    James, A.L.; Oldenburg, C.M.

    1998-12-01

    Vadose zone data collection and enhanced data analysis are continuing for the Vadose Zone Monitoring System (VZMS) installed at site S-7 in IC 34 at McClellan MB. Data from core samples from boreholes drilled in 1998 and from VZMS continuous monitoring are evaluated and compared to previously collected data and analyses. The suite of data collected to date is used to develop and constrain a spatially averaged, one-dimensional site S-7 representative model that is implemented into T2VOC. Testing of the conceptual model under conditions of recharge of 100 mm/yr produces plausible moisture contents relative to data from several sources. Further scoping calculations involving gas-phase TCE transport in the representative model were undertaken. We investigate the role of recharge on TCE transport as well as the role of ion- and gas-phase flow driven by density and barometric pumping effects. This report provides the first example of the application of the site S-7 representative model in th e investigation of subsurface VOC movement.

  18. Long-term tillage and crop rotation effects on residual nitrate in the crop root zone and nitrate accumulation in the intermediate vadose zone

    Science.gov (United States)

    Katupitiya, A.; Eisenhauer, D.E.; Ferguson, R.B.; Spalding, R.F.; Roeth, F.W.; Bobier, M.W.

    1997-01-01

    Tillage influences the physical and biological environment of soil. Rotation of crops with a legume affects the soil N status. A furrow irrigated site was investigated for long-term tillage and crop rotation effects on leaching of nitrate from the root zone and accumulation in the intermediate vadose zone (IVZ). The investigated tillage systems were disk-plant (DP), ridge-till (RT) and slot-plant (SP). These tillage treatments have been maintained on the Hastings silt loam (Udic Argiustoll) and Crete silt loam (Pachic Argiustoll) soils since 1976. Continuous corn (CC) and corn soybean (CS) rotations were the subtreatments. Since 1984, soybeans have been grown in CS plots in even calendar years. All tillage treatments received the same N rate. The N rate varied annually depending on the root zone residual N. Soybeans were not fertilized with N-fertilizer. Samples for residual nitrate in the root zone were taken in 8 of the 15 year study while the IVZ was only sampled at the end of the study. In seven of eight years, root zone residual soil nitrate-N levels were greater with DP than RT and SP. Residual nitrate-N amounts were similar in RT and SP in all years. Despite high residual nitrate-N with DP and the same N application rate, crop yields were higher in RT and SP except when DP had an extremely high root zone nitrate level. By applying the same N rates on all tillage treatments, DP may have been fertilized in excess of crop need. Higher residual nitrate-N in DP was most likely due to a combination of increased mineralization with tillage and lower yield compared to RT and SP. Because of higher nitrate availability with DP, the potential for nitrate leaching from the root zone was greater with DP as compared to the RT and SP tillage systems. Spring residual nitrate-N contents of DP were larger than RT and SP in both crop rotations. Ridge till and SP systems had greater nitrate-N with CS than CC rotations. Nitrate accumulation in IVZ at the upstream end of the

  19. Parallel inversion of a massive ERT data set to characterize deep vadose zone contamination beneath former nuclear waste infiltration galleries at the Hanford Site B-Complex (Invited)

    Science.gov (United States)

    Johnson, T.; Rucker, D. F.; Wellman, D.

    2013-12-01

    The Hanford Site, located in south-central Washington, USA, originated in the early 1940's as part of the Manhattan Project and produced plutonium used to build the United States nuclear weapons stockpile. In accordance with accepted industrial practice of that time, a substantial portion of relatively low-activity liquid radioactive waste was disposed of by direct discharge to either surface soil or into near-surface infiltration galleries such as cribs and trenches. This practice was supported by early investigations beginning in the 1940s, including studies by Geological Survey (USGS) experts, whose investigations found vadose zone soils at the site suitable for retaining radionuclides to the extent necessary to protect workers and members of the general public based on the standards of that time. That general disposal practice has long since been discontinued, and the US Department of Energy (USDOE) is now investigating residual contamination at former infiltration galleries as part of its overall environmental management and remediation program. Most of the liquid wastes released into the subsurface were highly ionic and electrically conductive, and therefore present an excellent target for imaging by Electrical Resistivity Tomography (ERT) within the low-conductivity sands and gravels comprising Hanford's vadose zone. In 2006, USDOE commissioned a large scale surface ERT survey to characterize vadose zone contamination beneath the Hanford Site B-Complex, which contained 8 infiltration trenches, 12 cribs, and one tile field. The ERT data were collected in a pole-pole configuration with 18 north-south trending lines, and 18 east-west trending lines ranging from 417m to 816m in length. The final data set consisted of 208,411 measurements collected on 4859 electrodes, covering an area of 600m x 600m. Given the computational demands of inverting this massive data set as a whole, the data were initially inverted in parts with a shared memory inversion code, which

  20. Characterization of Vadose Zone Sediment: Borehole C3103 Located in the 216-B-7A Crib Near the B Tank Farm

    Energy Technology Data Exchange (ETDEWEB)

    Lindenmeier, Clark W.; Serne, R JEFFREY.; Bjornstad, Bruce N.; Last, George V.; Lanigan, David C.; Lindberg, Michael J.; Clayton, Ray E.; Legore, Virginia L.; Kutnyakov, Igor V.; Baum, Steven R.; Geiszler, Keith N.; Valenta, Michelle M.; Vickerman, Tanya S.

    2002-12-01

    This report summarizes data collected from samples in borehole C3103. Borehole C3103 was completed to further characterize the nature and extent of vadose zone contaminants supplied by intentional liquid discharges into the crib 216-B7A/7B between 1954 and 1967. These cribs received dilute waste streams from the bismuth phosphate fuel reprocessing program in the 1950's and decontamination waste in the 1960's. Elevated concentrations of several constituents were primarily measured at different depth intervals. The primary radionuclides present in this borehole are cesium-137 and uranium near the top of the borehole. Chemical characteristics attributed to wastewater-soil interaction at different locations within this zone are elevated pH, sodium, fluoride, carbonate nitrate, and sulphate

  1. Are Advecting Processes in the Vadose Zone of the Albuquerque Basin Altering the Conductive Heat Transfer Signal From Surface Temperature Change ?

    Science.gov (United States)

    Reiter, M. A.

    2004-12-01

    Temperature measurements ( T logs ) in the deep vadose zone ( about 60m to 120m depth ) of the Albuquerque Basin have been repeated over the past year at four piezometer nests. The measurements were made with a very fast time response thermistor, which allowed data to be taken every meter going down hole. This depth resolution of temperature data permits a rather detailed observation of the thermal regime in the vadose zone. At one site ( Lincoln Middle School ) the temperature profile below 20m clearly shows a conductive profile resulting from surface temperature change due to urbanization and nearby ( about 10m ) asphalt pavement. At the other three sites the cause of non-linearity in the T log is less certain. Temperature records suggest about 1 deg C increase in near surface air temperature over the past thirty years at the Albuquerque airport; although this data may also be affected by urbanization. The Tome and 98th Street sites are being approached by paved roads and urbanization. At the Tome site expressions representing horizontal advection are the statistically preferred fit to the T log from about 25m to 58m ( F statistic ). At the 98th Street site an expression representing a surface temperature step best fits the T log from 20m to about 75m; however, the temperature step (about 1 deg C to 2 deg C, 3 to 15 yr ago ) is variable between logs, and the profile of the T log with abrupt discontinuities may suggest other than just conductive heat transfer. The fourth piezometer nest at the Mesa del Sol site is the most remote of the sites considered, with as little nearby surface disturbance as might be expected for a drilling location. At depths between 30m and 70m the expressions representing surface temperature change, horizontal advection, and vertical advection, all fit the T log reasonably well. The temperature step expression suggests about 1 deg C to 1.8 deg C surface temperature increase about 13 yr to 28 yr ago. Deeper in the vadose zone, from about

  2. Computer code selection criteria for flow and transport code(s) to be used in undisturbed vadose zone calculations for TWRS environmental analyses

    Energy Technology Data Exchange (ETDEWEB)

    Mann, F.M.

    1998-01-26

    The Tank Waste Remediation System (TWRS) is responsible for the safe storage, retrieval, and disposal of waste currently being held in 177 underground tanks at the Hanford Site. In order to successfully carry out its mission, TWRS must perform environmental analyses describing the consequences of tank contents leaking from tanks and associated facilities during the storage, retrieval, or closure periods and immobilized low-activity tank waste contaminants leaving disposal facilities. Because of the large size of the facilities and the great depth of the dry zone (known as the vadose zone) underneath the facilities, sophisticated computer codes are needed to model the transport of the tank contents or contaminants. This document presents the code selection criteria for those vadose zone analyses (a subset of the above analyses) where the hydraulic properties of the vadose zone are constant in time the geochemical behavior of the contaminant-soil interaction can be described by simple models, and the geologic or engineered structures are complicated enough to require a two-or three dimensional model. Thus, simple analyses would not need to use the fairly sophisticated codes which would meet the selection criteria in this document. Similarly, those analyses which involve complex chemical modeling (such as those analyses involving large tank leaks or those analyses involving the modeling of contaminant release from glass waste forms) are excluded. The analyses covered here are those where the movement of contaminants can be relatively simply calculated from the moisture flow. These code selection criteria are based on the information from the low-level waste programs of the US Department of Energy (DOE) and of the US Nuclear Regulatory Commission as well as experience gained in the DOE Complex in applying these criteria. Appendix table A-1 provides a comparison between the criteria in these documents and those used here. This document does not define the models (that

  3. VOCs in Arid soils: Technology summary

    Energy Technology Data Exchange (ETDEWEB)

    1994-02-01

    The Volatile Organic Compounds In Arid Soils Integrated Demonstration (VOC-Arid ID) focuses on technologies to clean up volatile organic compounds and associated contaminants in soil and groundwater at arid sites. The initial host site is the 200 West Area at DOE`s Hanford site in southeastern Washington state. The primary VOC contaminant is carbon tetrachloride, in association with heavy metals and radionuclides. An estimated 580--920 metric tons of carbon tetrachloride were disposed of between 1955 and 1973, resulting in extensive soil and groundwater contamination. The VOC-Arid ID schedule has been divided into three phases of implementation. The phased approach provides for: rapid transfer of technologies to the Environmental Restoration (EM-40) programs once demonstrated; logical progression in the complexity of demonstrations based on improved understanding of the VOC problem; and leveraging of the host site EM-40 activities to reduce the overall cost of the demonstrations. During FY92 and FY93, the primary technology demonstrations within the ID were leveraged with an ongoing expedited response action at the Hanford 200 West Area, which is directed at vapor extraction of VOCs from the vadose (unsaturated) zone. Demonstration efforts are underway in the areas of subsurface characterization including: drilling and access improvements, off-gas and borehole monitoring of vadose zone VOC concentrations to aid in soil vapor extraction performance evaluation, and treatment of VOC-contaminated off-gas. These current demonstration efforts constitute Phase 1 of the ID and, because of the ongoing vadose zone ERA, can result in immediate transfer of successful technologies to EM-40.

  4. Electrical Resistivity Correlation to Vadose Zone Sediment and Pore-Water Composition for the BC Cribs and Trenches Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Ward, Anderson L.; Um, Wooyong; Bjornstad, Bruce N.; Rucker, Dale F.; Lanigan, David C.; Benecke, Mark W.

    2009-06-01

    This technical report documents the results of geochemical and soil resistivity characterization of sediment obtained from four boreholes drilled in the BC Cribs and Trench area. Vadose zone sediment samples were obtained at a frequency of about every 2.5 ft from approximately 5 ft bgs to borehole total depth. In total, 505 grab samples and 39 six-inch long cores were obtained for characterization. The pore-water chemical composition data, laboratory-scale soil resistivity and other ancillary physical and hydrologic measurements and analyses described in this report are designed to provide a crucial link between direct measurements on sediments and the surface-based electrical-resistivity information obtained via field surveys. A second goal of the sediment characterization was to measure the total and water-leachable concentrations of key contaminants of concern as a function of depth and distance from the footprints of inactive disposal facilities. The total and water-leachable concentrations of key contaminants will be used to update contaminant distribution conceptual models and to provide more data for improving base-line risk predictions and remedial alternative selections. The ERC “ground truthing” exercise for the individual boreholes showed mixed results. In general, the high concentrations of dissolved salts in the pore waters of sediments from C5923, C5924 and C4191 produced a low resistivity “target” in the processed resistivity field surveys, and variability could be seen in the resistivity data that could relate to the variability in pore- water concentrations but the correlations (regression R2 were mediocre ranging from 0.2 to 0.7 at best; where perfect correlation is 1.0). The field-based geophysical data also seemed to suffer from a sort of vertigo, where looking down from the ground surface, the target (e.g., maximum pore-water salt concentration) depth was difficult to resolve. The best correlations between the field electrical

  5. Hydrologic and geochemical dynamics of vadose zone recharge in a mantled karst aquifer: Results of monitoring drip waters in Mystery Cave, Minnesota

    Science.gov (United States)

    Doctor, Daniel H.; Alexander, E. Calvin; Jameson, Roy A.; Alexander, Scott C.

    2015-01-01

    Caves provide direct access to flows through the vadose zone that recharge karst aquifers. Although many recent studies have documented the highly dynamic processes associated with vadose zone flows in karst settings, few have been conducted in mantled karst settings, such as that of southeastern Minnesota. Here we present some results of a long-term program of cave drip monitoring conducted within Mystery Cave, Minnesota. In this study, two perennial ceiling drip sites were monitored between 1997 and 2001. The sites were located about 90 m (300 ft) apart along the same cave passage approximately 18 m (60 ft) below the surface; 7 to 9 m (20 to 30 ft) of loess and 12 m (40 ft) of flat-lying carbonate bedrock strata overlie the cave. Records of drip rate, electrical conductivity, and water temperature were obtained at 15 minute intervals, and supplemented with periodic sampling for major ion chemistry and water stable isotopes. Patterns in flow and geochemistry emerged at each of the two drip sites that were repeated year after year. Although one site responded relatively quickly (within 2-7 hours) to surface recharge events while the other responded more slowly (within 2-5 days), thresholds of antecedent moisture needed to be overcome in order to produce a discharge response at both sites. The greatest amount of flow was observed at both sites during the spring snowmelt period. Rainfall events less than 10 mm (0.4 in) during the summer months generally did not produce a drip discharge response, yet rapid drip responses were observed following intense storm events after periods of prolonged rainfall. The chemical data from both sites indicate that reservoirs of vadose zone water with distinct chemical signatures mixed during recharge events, and drip chemistry returned to a baseline composition during low flow periods. A reservoir with elevated chloride and sulfate concentrations impacts the slow-response drip site with each recharge event, but does not similarly

  6. Deep Vadose Zone–Applied Field Research Initiative Fiscal Year 2012 Annual Report

    Energy Technology Data Exchange (ETDEWEB)

    Wellman, Dawn M.; Truex, Michael J.; Johnson, Timothy C.; Bunn, Amoret L.; Golovich, Elizabeth C.

    2013-03-14

    This annual report describes the background of the Deep Vadose Zone-Applied Field Research Initiative, and some of the programmatic approaches and transformational technologies in groundwater and deep vadose zone remediation developed during fiscal year 2012.

  7. Evaluating the role of soil variability on groundwater pollution and recharge at regional scale by integrating a process-based vadose zone model in a stochastic approach

    Science.gov (United States)

    Coppola, Antonio; Comegna, Alessandro; Dragonetti, Giovanna; Lamaddalena, Nicola; Zdruli, Pandi

    2013-04-01

    Interpreting and predicting the evolution of water resources and soils at regional scale are continuing challenges for natural scientists. Examples include non-point source (NPS) pollution of soil and surface and subsurface water from agricultural chemicals and pathogens, as well as overexploitation of groundwater resources. The presence and build up of NPS pollutants may be harmful for both soil and groundwater resources. The accumulation of salts and trace elements in soils can significantly impact crop productivity, while loading of salts, nitrates, trace elements and pesticides into groundwater supplies can deteriorate a source of drinking and irrigation water. Consequently, predicting the spatial distribution and fate of NPS pollutants in soils at applicative scales is now considered crucial for maintaining the fragile balance between crop productivity and the negative environmental impacts of NPS pollutants, which is a basis of sustainable agriculture. Soil scientists and hydrologists are regularly asked to assist state agencies to understand these critical environmental issues. The most frequent inquiries are related to the development of mathematical models needed for analyzing the impacts of alternative land-use and best management use and management of soil and water resources. Different modelling solutions exist, mainly differing on the role of the vadose zone and its horizontal and vertical variability in the predictive models. The vadose zone (the region from the soil surface to the groundwater surface) is a complex physical, chemical and biological ecosystem that controls the passage of NPS pollutants from the soil surface where they have been deposited or accumulated due to agricultural activities, to groundwater. Physically based distributed hydrological models require the internal variability of the vadose zone be explored at a variety of scales. The equations describing fluxes and storage of water and solutes in the unsaturated zone used in these

  8. Molecular phylogeography and systematics of the arid-zone members of the Egernia whitii (Lacertilia: Scincidae) species group.

    Science.gov (United States)

    Chapple, David G; Keogh, J Scott; Hutchinson, Mark N

    2004-12-01

    We assembled a molecular phylogeny for the arid-zone members of the Egernia whitii species group to test Pianka's [Zoogeography and speciation of Australian desert lizards: an ecological perspective, Copeia (1972) 127-145] hypothesis that habitat specificity to the three major arid-zone vegetation communities is the primary cause of lizard speciation within the arid interior of Australia. This hypothesis predicts that species should exhibit phylogeographic structuring concordant with the major arid-zone vegetation types. Sequence data were obtained from four of the five arid-zone members of the E. whitii species group, and from across the ranges of the ecologically generalized E. inornata and E. multiscutata and the more specialized E. striata. We targeted a fragment (696 base pair (bp)) of the mitochondrial genome comprising the 3' half of the ND4 gene. We analysed the data using parsimony, maximum likelihood and Bayesian methods. Our phylogeny confirms the monophyly of the arid-zone members of the species group, although the phylogenetic relationships among species were not fully resolved. Although our topology does not support the recognition of the existing subspecies within E. multiscutata, there is a substantial phylogeographic break between South Australian/Victorian (Clade 1) and Western Australian (Clade 2) populations. We found considerable phylogeographic structure within E. inornata, with six major clades identified. However, these clades were not concordant with the distribution of habitat types in the arid-zone. Phylogeographic structure was also observed in the more specialized E. striata, although our analysis revealed close phylogenetic affinities between the sympatric species E. striata and E. kintorei. Shimodaira-Hasegawa topology tests were equivocal in regard to whether the phylogeographic structure within E. striata was in accordance with Pianka's predictions. Although our data failed to provide strong support for the suggestion that

  9. System-Scale Model of Aquifer, Vadose Zone, and River Interactions for the Hanford 300 Area - Application to Uranium Reactive Transport

    Energy Technology Data Exchange (ETDEWEB)

    Rockhold, Mark L.; Bacon, Diana H.; Freedman, Vicky L.; Parker, Kyle R.; Waichler, Scott R.; Williams, Mark D.

    2013-10-01

    This report represents a synthesis and integration of basic and applied research into a system-scale model of the Hanford 300 Area groundwater uranium plume, supported by the U.S. Department of Energy’s Richland Operations (DOE-RL) office. The report integrates research findings and data from DOE Office of Science (DOE-SC), Office of Environmental Management (DOE-EM), and DOE-RL projects, and from the site remediation and closure contractor, Washington Closure Hanford, LLC (WCH). The three-dimensional, system-scale model addresses water flow and reactive transport of uranium for the coupled vadose zone, unconfined aquifer, and Columbia River shoreline of the Hanford 300 Area. The system-scale model of the 300 Area was developed to be a decision-support tool to evaluate processes of the total system affecting the groundwater uranium plume. The model can also be used to address “what if” questions regarding different remediation endpoints, and to assist in design and evaluation of field remediation efforts. For example, the proposed cleanup plan for the Hanford 300 Area includes removal, treatment, and disposal of contaminated sediments from known waste sites, enhanced attenuation of uranium hot spots in the vadose and periodically rewetted zone, and continued monitoring of groundwater with institutional controls. Illustrative simulations of polyphosphate infiltration were performed to demonstrate the ability of the system-scale model to address these types of questions. The use of this model in conjunction with continued field monitoring is expected to provide a rigorous basis for developing operational strategies for field remediation and for defining defensible remediation endpoints.

  10. A method of characterizing land-cover swap changes in the arid zone of China

    Institute of Scientific and Technical Information of China (English)

    Yecheng YUAN; Baolin LI; Xizhang GAO; Haijiang LIU; Lili XU; Chenghu ZHOU

    2016-01-01

    Net area change analysis can dramatically underestimate total change of land cover,even sometimes seriously misinterpret ecological processes of the ecosystem,especially in arid or semiarid zones.In this paper,a suite of indices are presented to characterize land-cover swaps that may seriously damage the ecosystem in arid or semiarid zones,based on swap-change areas extracted from remotely sensed images.First,swap percentage of total area and swap intensity of total changes were used to determine the status of land-cover swap change in an area.Then,dominated swap category and individual swapchange intensity for a land-cover category were used to determine flagged land-cover swap-change categories.Finally,swap-change mode and Pielou's index were used to determine the land-cover swap-change processes of dominant categories.A case study is conducted using this approach,based on two land-cover maps in the 1980s and 2000 in Naiman Qi,Tongliao City,Inner Mongolia,China.This study shows that the approach can clearly quantify the severity and flagged classes of land-cover swap-change and reveal their relationship with ecological processes of the ecosystem.These results indicate that the approach can give deep insights into swap change,which can be very valuable to land-cover policy making and management.

  11. Untangling a species complex of arid zone grasses (Triodia) reveals patterns congruent with co-occurring animals.

    Science.gov (United States)

    Anderson, Benjamin M; Barrett, Matthew D; Krauss, Siegfried L; Thiele, Kevin

    2016-08-01

    The vast Australian arid zone formed over the last 15million years, and gradual aridification as well as more extreme Pliocene and Pleistocene climate shifts have impacted the evolution of its biota. Understanding the evolutionary history of groups of organisms or regional biotas such as the Australian arid biota requires clear delimitation of the units of biodiversity (taxa). Here we integrate evidence from nuclear (ETS and ITS) and chloroplast (rps16-trnK spacer) regions and morphology to clarify taxonomic boundaries in a species complex of Australian hummock grasses (Triodia) to better understand the evolution of Australian arid zone plants and to evaluate congruence in distribution patterns with co-occurring organisms. We find evidence for multiple new taxa in the T. basedowii species complex, but also incongruence between data sets and indications of hybridization that complicate delimitation. We find that the T. basedowii complex has high lineage diversity and endemism in the biologically important Pilbara region of Western Australia, consistent with the region acting as a refugium. Taxa show strong geographic structure in the Pilbara, congruent with recent work on co-occurring animals and suggesting common evolutionary drivers across the biota. Our findings confirm recognition of the Pilbara as an important centre of biodiversity in the Australian arid zone, and provide a basis for future taxonomic revision of the T. basedowii complex and more detailed study of its evolutionary history and that of arid Australia.

  12. GEOPHYSICS AND SITE CHARACTERIZATION AT THE HANFORD SITE THE SUCCESSFUL USE OF ELECTRICAL RESISTIVITY TO POSITION BOREHOLES TO DEFINE DEEP VADOSE ZONE CONTAMINATION - 11509

    Energy Technology Data Exchange (ETDEWEB)

    GANDER MJ; LEARY KD; LEVITT MT; MILLER CW

    2011-01-14

    Historic boreholes confirmed the presence of nitrate and radionuclide contaminants at various intervals throughout a more than 60 m (200 ft) thick vadose zone, and a 2010 electrical resistivity survey mapped the known contamination and indicated areas of similar contaminants, both laterally and at depth; therefore, electrical resistivity mapping can be used to more accurately locate characterization boreholes. At the Hanford Nuclear Reservation in eastern Washington, production of uranium and plutonium resulted in the planned release of large quantities of contaminated wastewater to unlined excavations (cribs). From 1952 until 1960, the 216-U-8 Crib received approximately 379,000,000 L (100,000,000 gal) of wastewater containing 25,500 kg (56,218 lb) uranium; 1,029,000 kg (1,013 tons) of nitrate; 2.7 Ci of technetium-99; and other fission products including strontium-90 and cesium-137. The 216-U-8 Crib reportedly holds the largest inventory of waste uranium of any crib on the Hanford Site. Electrical resistivity is a geophysical technique capable of identifying contrasting physical properties; specifically, electrically conductive material, relative to resistive native soil, can be mapped in the subsurface. At the 216-U-8 Crib, high nitrate concentrations (from the release of nitric acid [HNO{sub 3}] and associated uranium and other fission products) were detected in 1994 and 2004 boreholes at various depths, such as at the base of the Crib at 9 m (30 ft) below ground surface (bgs) and sporadically to depths in excess of 60 m (200 ft) bgs. These contaminant concentrations were directly correlative with the presence of observed low electrical resistivity responses delineated during the summer 2010 geophysical survey. Based on this correlation and the recently completed mapping of the electrically conductive material, additional boreholes are planned for early 2011 to identify nitrate and radionuclide contamination: (a) throughout the entire vertical length of the

  13. Systematic revision of the marbled velvet geckos (Oedura marmorata species complex, Diplodactylidae) from the Australian arid and semi-arid zones.

    Science.gov (United States)

    Oliver, Paul M; Doughty, Paul

    2016-03-08

    Lizards restricted to rocky habitats often comprise numerous deeply divergent lineages, reflecting the disjunct nature of their preferred habitat and the capacity of rocky habitats to function as evolutionary refugia. Here we review the systematics and diversity of the predominantly saxicoline Australian marbled velvet geckos (genus Oedura) in the Australian arid and semi-arid zones using newly-gathered morphological data and previously published genetic data. Earlier work showed that four largely allopatric and genetically divergent lineages are present: Western (Pilbara and Gascoyne regions), Gulf (west and south of the Gulf of Carpentaria), Central (central ranges) and Eastern (Cooper and Darling Basins). None of these four populations are conspecific with true O. marmorata, a seperate species complex that is restricted to the Top End region of the Northern Territory. Top End forms share a short, bulbous tail whereas the other four lineages treated here possess a long, tapering tail. Morphological differences among the arid and semi-arid lineages include smaller body size, tapering lamellae and a shorter tail for the Gulf population, and a partially divided rostral scale in the Western population compared to the Central and Eastern populations. Accordingly, we resurrect O. cincta de Vis from synonymy for the Central and Eastern lineages, and regard this species as being comprised of two evolutionary significant units. We also describe the Gulf and Western lineages as new species: Oedura bella sp. nov. and O. fimbria sp. nov., respectively. We note that a predominantly arboreal lineage (the Eastern lineage of O. cincta) is more widely distributed than the other lineages and is phylogenetically nested within a saxicoline clade, but tends to have a deeper head and shorter limbs, consistent with morphological variation observed in other lizard radiations including both saxicoline and arboreal taxa.

  14. Characterization of Vadose Zone Sediment: Borehole 299-W23-19 [SX-115] in the S-SX Waste Management Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Bjornstad, Bruce N.; Lanigan, David C.; Gee, Glendon W.; Lindenmeier, Clark W.; Clayton, Ray E.; Legore, Virginia L.; O' Hara, Matthew J.; Brown, Christopher F.; Last, George V.; Kutnyakov, Igor V.; Burke, Deborah S.; Wilson, Teresa C.; Williams, Bruce A.

    2008-09-11

    This report was revised in September 2008 to remove acid-extractable sodium data from Tables 4.15 and 4.19. The sodium data was removed due to potential contamination introduced during the acid extraction process. The rest of the text remains unchanged from the original report issued in February 2002. The Tank Farm Vadose Zone Project is led by CH2M HILL Hanford Group, Inc. Their goals include defining risks from past and future single-shell tank farm activities, identifying and evaluating the efficacy of interim measures, and collecting geotechnical information and data. The purpose of these activities is to support future decisions made by the U.S. Department of Energy (DOE) regarding near-term operations, future waste retrieval, and final closure activities for the single-shell tank Waste Management Areas. To help in this effort, CH2M HILL Hanford Group, Inc. contracted with scientists at Pacific Northwest National Laboratory to analyze sediment samples collected from borehole 299-W23-19.

  15. Enhanced data analysis for the VZMS: Conceptual model design and initial application for the Vadose Zone Monitoring System (VZMS), McClellan AFB. 1998 semi-annual report

    Energy Technology Data Exchange (ETDEWEB)

    James, A.L.; Oldenburg, C.M.

    1998-06-14

    The VZMS project at McClellan AFB involves both vadose zone data collection as well as enhanced data analysis. The purpose of enhanced data analysis is to develop conceptual models to carry out model validation and evaluation, as well as sensitivity and predictive modeling studies. Enhanced data analysis consists primarily of T2VOC forward simulations and ITOUGH2 inverse modeling. The methodology the authors employ in the VZMS project involves developing a conceptual model and iteratively updating it based on the agreement between model results and VZMS data. They demonstrate the development of an initial T2VOC conceptual model for the S-7 site based on data from instrument cluster VZMS-B. Lithologic data from the drilling logs along with empirical relations for estimating permeability and sediment moisture retention characteristics are used to define the layering of four different sediment types. The authors adjusted the layering of the sediments manually until the sediment moisture content profile from the T2VOC simulation of the gravity-capillary equilibrium agreed well with observed neutron probe data. Using this updated conceptual model, they performed inverse modeling using ITOUGH2 to find bet-fit absolute permeability values based on the minimization of differences between simulated and actual soil-gas pressure measurements.

  16. Influence of Wetting and Mass Transfer Properties of Organic Chemical Mixtures in Vadose Zone Materials on Groundwater Contamination by Nonaqueous Phase Liquids

    Energy Technology Data Exchange (ETDEWEB)

    Charles J Werth; Albert J Valocchi, Hongkyu Yoon

    2011-05-21

    Previous studies have found that organic acids, organic bases, and detergent-like chemicals change surface wettability. The wastewater and NAPL mixtures discharged at the Hanford site contain such chemicals, and their proportions likely change over time due to reaction-facilitated aging. The specific objectives of this work were to (1) determine the effect of organic chemical mixtures on surface wettability, (2) determine the effect of organic chemical mixtures on CCl4 volatilization rates from NAPL, and (3) accurately determine the migration, entrapment, and volatilization of organic chemical mixtures. Five tasks were proposed to achieve the project objectives. These are to (1) prepare representative batches of fresh and aged NAPL-wastewater mixtures, (2) to measure interfacial tension, contact angle, and capillary pressure-saturation profiles for the same mixtures, (3) to measure interphase mass transfer rates for the same mixtures using micromodels, (4) to measure multiphase flow and interphase mass transfer in large flow cell experiments, all using the same mixtures, and (5) to modify the multiphase flow simulator STOMP in order to account for updated P-S and interphase mass transfer relationships, and to simulate the impact of CCl4 in the vadose zone on groundwater contamination. Results and findings from these tasks and summarized in the attached final report.

  17. Arthropods in Natural Communities in Mescal Agave (Agave durangensis Gentry in an Arid Zone

    Directory of Open Access Journals (Sweden)

    Maria P. Gonzalez-Castillo

    2011-01-01

    Full Text Available Problem statement: The arthropods have a very important role in the arid zones due to their interactions with many organism and because they constituted an important element in the structure of the plant community. Nevertheless their importance there are few knowledge about the community of arthropods associated to vegetation in arid zones in the North of Mexico. The present study had the objective of determining the abundance, richness and diversity of arthropods in three localities where there are natural populations of mescal agave in the State of Durango, Mexico. Approach: In order to know the structure community of the arthropods associated to the mescal agave, we perform a sampling schedule during March 2008 to November 2010 by direct collection, using transects in three different localities with the presence of mescal agave. The relative abundance, species richness, Shannon’s diversity index, Pielou’s Index of evenness, Jaccard’s similitude and Simpson’s dominance indexes were determined. Results: A total of 4665 individual arthropods associated to mescal agave corresponding to 39 species were found. El Mezquital had the highest abundance and relative abundance (44.1% with 29 species. The mean species abundance was not significantly different between localities using Turkey’s test. The highest density per unit of area was found in El Mezquital (La Brena had the highest species diversity (1.89, evenness (0.61 and dominance (0.78. At the taxon level, Hymenoptera had the highest number of species represented (14, followed by Coleoptera (9 and hemiptera (5, with the remaining taxons with four, two and one species each. Conclusion: The greatest similitude was observed between La Brena and El Mezquital (46% which shared seven taxons, while the least similitude was observed between El Venado and La Brena (29%. Dominance/diversity curves are presented for each locality. The species Caulotops sp., Acutaspis agavis, Chilorus sp

  18. Bayesian Markov chain Monte Carlo Inversion of Time-Lapse Geophysical Data To Characterize the Vadose Zone

    DEFF Research Database (Denmark)

    Scholer, Marie; Irving, James; Zibar, Majken Caroline Looms;

    Geophysical methods have the potential to provide valuable information on hydrological properties in the unsaturated zone. In particular, time-lapse geophysical data, when coupled with a hydrological model and inverted stochastically, may allow for the effective estimation of subsurface hydraulic...

  19. ENVIRONMENTALMANAGEMENT SCIENCE PROGRAM PROJECT NUMBER 87016 CO-PRECIPITATION OF TRACEMETALS INGROUNDWATER AND VADOSE ZONE CALCITE: IN SITU CONTAINMENT AND STABILIZATION OF STRONTIUM-90 ANDOTHER DIVALENT METALS AND RADIONUCLIDES AT ARIDWESTERN DOE SITES

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, F. Grant; Fujita, Yoshiko; Smith, Robert W.; Cosgrove, Donna M.; Colwell, F. S.

    2004-06-15

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) weapons complex. In situ containment and stabilization of these contaminants in vadose zones or groundwater is a cost-effective treatment strategy. Our facilitated approach relies upon the hydrolysis of introduced urea to cause the acceleration of calcium carbonate precipitation (and trace metal coprecipitation) by increasing groundwater pH and alkalinity (Fujita et al., 2000; Warren et al., 2001). Subsurface urea hydrolysis is catalyzed by the urease enzyme, which may be either introduced with the urea or produced in situ by ubiquitous subsurface urea hydrolyzing microorganisms. Because the precipitation processes are irreversible and many western aquifers are saturated with respect to calcite, the co-precipitated metals and radionuclides will be effectively removed from groundwater. The rate at which trace metals are incorporated into calcite is a function of calcite precipitation kinetics, adsorption interactions between the calcite surface and the trace metal in solution (Zachara et al., 1991), solid solution properties of the trace metal in calcite (Tesoriero and Pankow, 1996), and also the surfaces upon which the calcite is precipitating. A fundamental understanding of the coupling of calcite precipitation and trace metal partitioning, and how this occurs in aquifers and vadose environments is lacking. This report summarizes work undertaken during the second year of this project.

  20. Different responses of MODIS-derived NDVI to root-zone soil moisture in semi-arid and humid regions

    Science.gov (United States)

    Wang, Xianwei; Xie, Hongjie; Guan, Huade; Zhou, Xiaobing

    2007-06-01

    SummarySurface representation of the root-zone soil moisture is investigated so that feasibility of using optical remote sensing techniques to indirectly map root-zone soil moisture is assessed. Specifically, covariation of root-zone soil moisture with the normalized difference of vegetation index (NDVI) from Moderate Resolution Imaging Spectroradiometer (MODIS) is studied at three sites (New Mexico, Arizona, and Texas) selected from the Soil Climate Analysis Network (SCAN). The three sites represent two types of vegetation (shrub and grass) and two types of climate conditions: semi-arid (New Mexico and Arizona) and humid (Texas). Collocated deseasonalized time series of soil moistures at five depths (5 cm, 10 cm, 20 cm, 50 cm, and 100 cm) and NDVI (8-day composite in 250 m resolution) during the period of February 2000 through April 2004 were used for correlation analysis. Similar analysis was also conducted for the raw time series for comparison purposes. The linear regression of both the deseasonalized time series and the raw time series was used to estimate root-zone soil moisture. Results show that (1) the deseasonalized time series results in consistent and significant correlation (0.46-0.55) between NDVI and root-zone soil moisture at the three sites; (2) vegetation (NDVI) at the humid site needs longer time (10 days) to respond to soil moisture change than that at the semi-arid sites (5 days or less); (3) the time-series of root-zone soil moisture estimated by a linear regression model based on deseasonalized time series accounts for 42-71% of the observed soil moisture variations for the three sites; and (4) in the semi-arid region, root-zone soil moisture of shrub-vegetated area can be better estimated using NDVI than that of grass-vegetated area.

  1. Prevalence of peste des petits ruminants in the arid zone in the Republic of Niger

    Directory of Open Access Journals (Sweden)

    Souaibou Farougou

    2013-03-01

    Full Text Available The study aimed to determine the prevalence of peste des petits ruminants in the arid zone (Niamey, Tillabéry and Tahoua of the Republic of Niger. A serological survey was conducted and 519 serum samples were collected from 253 unvaccinated sheep and 266 unvaccinated goats. The sample included 340 female animals (168 sheep and 172 goats and 160 kids and lambs (78 lambs and 82 kids. A competitive enzyme-linked immunosorbent assay yielded an overall seroprevalence of 45.0%. The prevalence in sheep was 42.0% compared with 47.9% in goats. The seroprevalence observed amongst small ruminants in Tahoua (49.8% and Tillabéry (46.6% was significantly higher (p = 0.001 than that observed in animals from Niamey (25.1%. It was also higher (p = 0.04 in sheep younger than two years (51.8% than in adults (37.6%. Conversely, the seroprevalence showed no significant difference between male animals (35.8% in sheep; 50.1% in goats and female animals (45.1% in sheep; 46.4% in goats. The prevalence of the disease observed amongst the sheep and goat populations confirms the continued danger of this disease in the areas studied. It is therefore necessary to develop strategies such as improving livestock services, providing effective vaccines and implementing a vaccination programme for an effective control of the disease in sub-Saharan Africa.

  2. Energy use pattern in production agriculture of a typical village in arid zone India: Pt. 2

    Energy Technology Data Exchange (ETDEWEB)

    Singh, H.; Mishra, D.; Nahar, N.M.; Ranjan, Mohnot [Central Arid Zone Research Inst., Div. of Agricultural Engineering and Energy, Rajasthan (India)

    2003-05-01

    The Indian hot arid zone, occupying an area of 31.71 Mha, spreads over Western Rajasthan, North Gujrat, South West Haryana and Punjab, some parts of Andhra Pradesh and Karnataka State, but the major part of it (61.8%) lies in the western part of Rajasthan, covering 12 districts commonly known as 'Thar Desert' and characterized by harsh climatic conditions with active dunal activities. To add to the misery, there is continuous occurrence of severe drought in the region since the last 2-3 years (1997-98 and 1999-2000). Data on the energy input for cultivating different selective crops for 1999-2000 (drought year) were collected, analysed and presented for the village 'Siwas' district, Pali (Zone-IV, rainfall >400 mm/yr). Owing to the drought, farmers of the village have grown kharif crops (being rainfed) by providing life saving irrigation. The maximum energy is required for raising the cotton crop, followed by wheat, mustard, maize and cluster bean. There is more non-renewable form of energy input (73.2%) than renewable form (26.8%) in all the crops. Further, more non-renewable energy is required for cultivating rabi crops compared to kharif. Among the kharif crops, the energy ratio varied from 3.4 to 7.0, suggesting that cotton, having an energy ratio 7.0, is most profitable compared to other crops. However, among the rabi crops, mustard is found most profitable. The crop yield can be correlated with energy input in the form of a second degree polynomial. During a drought period, by providing life saving irrigation, the yields of kharif crops were in agreement with the average yield obtained during a normal rainfall year. (Author)

  3. Environmental resilience of rangeland ecosystems: assessment drought indices and vegetation trends on arid and semi-arid zones of Central Asia

    Science.gov (United States)

    Aralova, Dildora; Toderich, Kristina; Jarihani, Ben; Gafurov, Dilshod; Gismatulina, Liliya; Osunmadewa, Babatunde A.; Rahamtallah Abualgasim, Majdaldin

    2016-10-01

    The Central Asian (CA) rangelands is a part of the arid and semi-arid ecological zones and spatial extent of drylands in CA (Tajikistan, Kazakhstan, Uzbekistan, Kyrgyzstan, and Turkmenistan) is vast. Projections averaged across a suite of climate models, as measured between 1950-2012 by Standardised Precipitation-Evapotranspiration Index (SPEI) estimated a progressively increasing drought risks across rangelands (Turkmenistan, Tajikistan and Uzbekistan) especially during late summer and autumn periods, another index: Potential Evapotranspiration (PET) indicated drought anomalies for Turkmenistan and partly in Uzbekistan (between 1950-2000). On this study, we have combined a several datasets of drought indices ( SPIE, PET, temperature_T°C and precipitation_P) for better estimation of resilience/non-resilience of the ecosystems after warming the temperature in the following five countries, meanwhile, warming of climate causing of increasing rating of degradations and extension of desertification in the lowland and foothill zones of the landscape and consequently surrounding experienced of a raising balance of evapotranspiration (ET0). The study concluded, increasing drought anomalies which is closely related with raising (ET0) in the lowland and foothill zones of CA indicated on decreasing of NDVI indices with occurred sandy and loamy soils it will resulting a loss of vegetation diversity (endangered species) and raising of wind speeds in lowlands of CA, but on regional level especially towards agricultural intensification (without rotation) it indicated no changes of greenness index. It was investigated to better interpret how vegetation feedback modifies the sensitivity of drought indices associated with raising tendency of air temperature and changes of cold and hot year seasons length in the territory of CA.

  4. The affect and importance of the Lichens in the Arid zone conservation and protection of water resource

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-liang; ZHANG Yuan-ming; Adil Abdulla; Anwar Tumur; Abdulla Abbas

    2004-01-01

    Desertification has already become the global social problem. On the Arid zone it has closer relation with the frail ecotope. The system of the arid zone mountain belongs to crisscross between the farming ,forestry and husbandry . The frailty of the ecosystem manifests on the internal frailty, depends on the plant ,intensity of the contradictory between the landscape transitional and natural reservation area,physical weathering strong,the development of the soil surface is slowly but the erode of the rain ,soil erosion very grave. Lichens not only rein force the intensity and depth of the weathering of rocks and formation ,accelerate of the mineral weathering making and accumulating the organic compound, at the same time lichens have strongly water protection abilities and inestimable role in the prevent soil erosion. In this paper we were according to on-the-spot investigation and analysis of the laboratory from 1985 to now on the middle and west of the Mt . Tianshan and Mt. Altay kanas where mainly probe into the significance of the protection water and conservation water resources of the Arid zone. This research works will be provide scientific basis and reference of the government for put into effect ,improving environment of the mountain region ,major construction oasis ecotope and make great efforts for protection desert ecotope.

  5. Characterization of Vadose Zone Sediments Below the T Tank Farm: Boreholes C4104, C4105, 299-W10-196 and RCRA Borehole 299-W11-39

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R JEFFREY.; Bjornstad, Bruce N.; Horton, Duane G.; Lanigan, David C.; Lindenmeier, Clark W.; Lindberg, Michael J.; Clayton, Ray E.; LeGore, Virginia L.; Geiszler, Keith N.; Baum, Steven R.; Valenta, Michelle M.; Kutnyakov, Igor V.; Vickerman, Tanya S.; Orr, Robert D.; Brown, Christopher F.

    2004-09-01

    This report contains geologic, geochemical, and physical characterization data collected on sediment recovered from boreholes C4104 and C4105 in the T Tank Farm, and 299-W-11-39 installed northeast of the T Tank Farm. The measurements on sediments from borehole C4104 are compared to a nearby borehole 299-W10-196 placed through the plume from the 1973 T-106 tank leak. This report also presents the data in the context of sediment types, the vertical extent of contamination, the migration potential of the contaminants, and the likely source of the contamination in the vadose zone and groundwater below the T Tank Farm. Sediment samples were characterized for: moisture content, gamma-emission radionuclides, one-to-one water extracts (which provide soil pH, electrical conductivity, cation, trace metal, radionuclide and anion data), total carbon and inorganic carbon content, and 8 M nitric acid extracts (which provide a measure of the total leachable sediment content of contaminants). Overall, our analyses showed that common ion exchange is a key mechanism that influences the distribution of contaminants within that portion of the vadose zone affected by tank liquor. We observed slight elevated pH values in samples from borehole C4104. The sediments from the three boreholes, C4104, C4105, and 299-W10-196 do show that sodium-, nitrate-, and sulfate-dominated fluids are present below tank T-106 and have formed a salt plume. The fluids are more dilute than tank fluids observed below tanks at the SX and BX Tank Farms and slightly less than those from the most saline porewater found in contaminated TX tank farm sediments. The boreholes could not penetrate below the gravel-rich strata of the Ringold Formation Wooded Island member (Rwi) (refusal was met at about 130 ft bgs); therefore, we could not identify the maximum vertical penetration of the tank related plumes. The moisture content, pH, electrical conductivity, nitrate, and technetium-99 profiles versus depth in the three

  6. Transitions in Land Use Architecture under Multiple Human Driving Forces in a Semi-Arid Zone

    Directory of Open Access Journals (Sweden)

    Issa Ouedraogo

    2015-07-01

    Full Text Available The present study aimed to detect the main shifts in land-use architecture and assess the factors behind the changes in typical tropical semi-arid land in Burkina Faso. Three sets of time-series LANDSAT data over a 23-year period were used to detect land use changes and their underpinning drivers in multifunctional but vulnerable ecologies. Group discussions in selected villages were organized for mapping output interpretation and collection of essential drivers of change as perceived by local populations. Results revealed profound changes and transitions during the study period. During the last decade, shrub and wood savannahs exhibited high net changes (39% and −37% respectively with a weak net positive change for cropland (only 2%, while cropland and shrub savannah exhibited high swap (8% and 16%. This suggests that the area of cropland remained almost unchanged but was subject to relocation, wood savannah decreased drastically, and shrub savannah increased exponentially. Cropland exhibited a null net persistence while shrub and wood savannahs exhibited positive and negative net persistence (1.91 and −10.24, respectively, indicating that there is movement toward agricultural intensification and wood savannah tended to disappear to the benefit of shrub savannah. Local people are aware of the changes that have occurred and support the idea that illegal wood cutting and farming are inappropriate farming practices associated with immigration; absence of alternative cash generation sources, overgrazing and increasing demand for wood energy are driving the changes in their ecosystems. Policies that integrate restoration and conservation of natural ecosystems and promote sustainable agroforestry practices in the study zone are highly recommended.

  7. Part 2: A field study of enhanced remediation of Toluene in the vadose zone using a nutrient solution

    Science.gov (United States)

    Tindall, J.A.; Weeks, E.P.; Friedel, M.

    2005-01-01

    The objective of this study was to test the effectiveness of a nitrate-rich nutrient solution and hydrogen peroxide (H2O2) to enhance in-situ microbial remediation of toluene in the unsaturated zone. Three sand-filled plots were tested in three phases (each phase lasting approximately 2 weeks). During the control phase, toluene was applied uniformly via sprinkler irrigation. Passive remediation was allowed to occur during this phase. A modified Hoagland nutrient solution, concentrated in 150 L of water, was tested during the second phase. The final phase involved addition of 230 moles of H2O2 in 150 L of water to increase the available oxygen needed for aerobic biodegradation. During the first phase, measured toluene concentrations in soil gas were reduced from 120 ppm to 25 ppm in 14 days. After the addition of nutrients during the second phase, concentrations were reduced from 90 ppm to about 8 ppm within 14 days, and for the third phase (H 2O2), toluene concentrations were about 1 ppm after only 5 days. Initial results suggest that this method could be an effective means of remediating a contaminated site, directly after a BTEX spill, without the intrusiveness and high cost of other abatement technologies such as bioventing or soil-vapor extraction. However, further tests need to be completed to determine the effect of each of the BTEX components. ?? Springer 2005.

  8. A chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1997 progress report and presentations at the annual meeting, Ernest Orlando Lawrence Berkeley National Laboratory, December 3--4, 1997

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, B.; Doughty, C.; Geller, J. [and others

    1998-07-01

    Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to develop a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies. View-graphs from ten presentations made at the annual meeting held December 3--4, 1997 are included in an appendix to this report.

  9. Design parameters of a non-air-conditioned cinema hall for thermal comfort under arid-zone climatic conditions

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, G.N. (Indian Inst. of Tech., New Delhi (India). Centre for Energy Studies); Lugani, N. (Indian Inst. of Tech., New Delhi (India). Centre for Energy Studies); Singh, A.K. (Indian Inst. of Tech., New Delhi (India). Centre for Energy Studies)

    1993-01-01

    In this communication, a design of a cinema hall suitable for climatic conditions in an arid zone has been presented. The various cooling techniques, namely evaporative cooling, wind tower, ventilation/infiltration and natural cooling, have been incorporated in the design to achieve thermal comfort during the period of operation. The design parameters have been optimized on the basis of numerical computations after establishing an energy balance for each component of a cinema hall. It is observed that cooling treatment, i.e., a wind tower with a cooling pool on the roof provides reasonable thermal comfort inside the enclosure. (orig.)

  10. Energy use pattern in production agriculture of a typical village in arid zone - Part III

    Energy Technology Data Exchange (ETDEWEB)

    Singh, H. E-mail: hsingh11@rediffmail.com; Mishra, D.; Nahar, N.M

    2004-09-01

    India has 31.71 Mha of hot arid areas, of which 61.8% is in Western Rajasthan, commonly known as the 'Thar Desert'. A detailed study of the energy use pattern in production agriculture for a representative village, Pemasar, district Bikaner of zone II (200 mm/yr {<=} annual rainfall < 300 mm/yr) has been conducted. Out of the total geographical area (945.7 ha) of the village, 693.6 ha is cultivable land. The main crops grown in the village are cluster bean, moth bean, groundnut, green gram (Kharif), wheat, mustard, gram, barley and rocket salad (Rabi). In general, Kharif crops are grown as rain fed crops, but due to low rainfall in the zone and the presence of the Indira Gandhi Canal, even Kharif crops are raised under irrigated conditions. However, the area covered under irrigation is meagre as the availability of canal water is very much limited and uncertain. Operation wise, the total energy consumed for rain fed Kharif crops is minimum (1187.6 MJ/ha) for moth bean and maximum (1261.9 MJ/ha) for cluster bean, while for irrigated crops, it is minimum (2847.3 MJ/ha) for moth bean, and maximum (12,809.6 MJ/ha) for groundnut. The average specific energy for cultivation of cluster bean (rain fed), cluster bean (irrigated), moth bean (rain fed), moth bean (irrigated) and groundnut were 11.7, 7.5, 7.7, 7.4 and 11.2 MJ/ha, respectively. Operation wise, the energy consumed for Rabi crops is minimum (3855.6 MJ/ha) for rocket salad followed by 4779.4 MJ/ha for mustard, 4845.2 MJ/ha for gram and maximum (7953.2 MJ/ha) for wheat. The average specific energy for cultivation of wheat, gram, mustard and rocket salad were 11.4, 16.5, 13.2 and 13.7 MJ/ha, respectively. The average values of estimated energy ratio for cluster bean (rain fed), cluster bean (irrigated), moth bean (rain fed), moth bean (irrigated) and groundnut were 2.1, 0.5, 3.4, 3.5 and 3.0, respectively. This suggests that the moth bean crop is more remunerating to the farmers in Kharif as compared to

  11. Vadose zone measurement and modeling

    OpenAIRE

    Hopmans, J.W.; V. Clausnitzer; K.I. Kosugi; Nielsen,D.R.; Somma, F.

    1997-01-01

    The following treatise is a summary of some of the ongoing research activities in the soil physics program at the University of California in Davis. Each of the four listed areas win be presented at the Workshop on special topics on soil physics and crop modeling in Piracicaba at the University of Sao Paulo. We limited ourselves to a general overview of each area, but will present a more thorough discussion with examples at the Workshop.

  12. Water and Carbon Fluxes in a Semi-Arid Region Floodplain: Multiple Approaches to Constrain Estimates of Seasonal- and Depth Dependent Fluxes at Rifle, Colorado

    Science.gov (United States)

    Tokunaga, T. K.; Wan, J.; Dong, W.; Kim, Y.; Williams, K. H.; Conrad, M. E.; Christensen, J. N.; Bill, M.; Faybishenko, B.; Hobson, C.; Dayvault, R.; Long, P. E.; Hubbard, S. S.

    2014-12-01

    The importance of floodplains as links between watersheds and rivers highlights the need to understand water and carbon fluxes within floodplain profiles, from their surface soil, through the vadose zone and underlying groundwater. Here, we present results of field and laboratory measurements conducted to quantify fluxes at a remediated uranium/vanadium mill tailings site on a floodplain at Rifle, Colorado. This semi-arid site has a vegetated, locally derived fill soil that replaced the original milling-contaminated soil to a depth of about 1.5 m. The fill soil overlies about 4.5 m of native sandy and cobbly alluvium containing the shallow aquifer. The aquifer generally drains into the Colorado River and is underlain by low permeability Wasatch Formation shale. Within this system, key issues being investigated include water and carbon fluxes between the vadose zone and aquifer, and CO2 fluxes through the vadose zone soil out to the atmosphere. Magnitudes of these fluxes are typically low, thus challenging to measure, yet increasingly important to quantify given the expansion of arid and semi-arid regions under changing climate. The results of field investigations demonstrated that the annual water table rise and fall are driven by snowmelt runoff into the Colorado River in late spring to early summer. Tensiometer data indicate that net recharge from the deeper part of the vadose zone into groundwater occurs later in summer, after water table decline. The effectiveness of summer evapotranspiration in limiting groundwater recharge is reflected in water potentials decreasing to as low as -3 MPa within the upper 1.5 m of the vadose zone. Examination of the historical precipitation record further indicates that net recharge only occurs in years with above-average precipitation during winter and spring. These short intervals of net recharge also facilitate C transport into groundwater because of higher organic C concentrations in the vadose zone. Fluxes of CO2 measured

  13. Variations of the aerosol concentration and chemical composition over the arid steppe zone of Southern Russia in summer

    Science.gov (United States)

    Artamonova, M. S.; Gubanova, D. P.; Iordanskii, M. A.; Lebedev, V. A.; Maksimenkov, L. O.; Minashkin, V. M.; Obvintsev, Y. I.; Chketiani, O. G.

    2016-12-01

    Variations in the surface aerosol over the arid steppe zone of Southern Russia have been measured. The parameters of atmospheric aerosol (mass concentration, both dispersed and elemental compositions) and meteorological parameters were measured in Tsimlaynsk raion (Rostov oblast). The chemical composition of aerosol particles in the atmospheric surface layer has been determined, and the coefficients of enrichment of elements with respect to clarkes in the Earth's crust have been calculated. It is shown that, in summer, arid aerosols are transported from both alkaline and sandy soils of Kalmykia to the air basin over the observation zone. Aerosol particles in the surface air layer over this region have been found to contain the products of combustion of oil, coal, and ethylized fuel. These combustion products make a small contribution to the total mass concentration of atmospheric aerosol; however, they are most hazardous to the health of people because of their sizes and heavy-metal contents. A high concentration of submicron sulfur-containing aerosol particles of chemocondensation nature has been recorded. Sources of aerosol of both natural and anthropogenic origins in southern Russia are discussed.

  14. Functional traits drive the contribution of solar radiation to leaf litter decomposition among multiple arid-zone species.

    Science.gov (United States)

    Pan, Xu; Song, Yao-Bin; Liu, Guo-Fang; Hu, Yu-Kun; Ye, Xue-Hua; Cornwell, William K; Prinzing, Andreas; Dong, Ming; Cornelissen, Johannes H C

    2015-08-18

    In arid zones, strong solar radiation has important consequences for ecosystem processes. To better understand carbon and nutrient dynamics, it is important to know the contribution of solar radiation to leaf litter decomposition of different arid-zone species. Here we investigated: (1) whether such contribution varies among plant species at given irradiance regime, (2) whether interspecific variation in such contribution correlates with interspecific variation in the decomposition rate under shade; and (3) whether this correlation can be explained by leaf traits. We conducted a factorial experiment to determine the effects of solar radiation and environmental moisture for the mass loss and the decomposition constant k-values of 13 species litters collected in Northern China. The contribution of solar radiation to leaf litter decomposition varied significantly among species. Solar radiation accelerated decomposition in particular in the species that already decompose quickly under shade. Functional traits, notably specific leaf area, might predict the interspecific variation in that contribution. Our results provide the first empirical evidence for how the effect of solar radiation on decomposition varies among multiple species. Thus, the effect of solar radiation on the carbon flux between biosphere and atmosphere may depend on the species composition of the vegetation.

  15. Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones

    Science.gov (United States)

    Gil-Sotres, F.; Miralles, I.; Canton-Castilla, Y.; Domingo, F.; Leiros, M. C.; Trasar-Cepeda, C.

    2012-04-01

    Influence of biological soil crusts at different successional stages in the implantation of biogeochemical cycles in arid and semiarid zones I. Miralles1, F. Gil-Sotres2, Y. Cantón-Castilla3, F. Domingo1, M.C. Leirós2, C. Trasar-Cepeda4 1 Experimental Estation of Arid Zones (CSIC), E-04230 La Cañada de San Urbano, Almería, Spain. 2 Departamento Edafología y Química Agrícola, Grupo de Evaluación de la Calidad del Suelo, Unidad Asociada CSIC, Facultad de Farmacia, Universidad de Santiago de Compostela, E-15782 Santiago de Compostela, Spain. 3 University of Almería, Departamento de Edafología y Química Agrícola, E-04230-La Cañada de San Urbano, Almería, Spain. 4 Departamento Bioquímica del Suelo, IIAG-CSIC, Apartado 122, E-15708 Santiago de Compostela, Spain. Crusts (BSCs) are formed by a close association between soil particles and cyanobacteria, algae, lichens, bryophytes and microfungi in varying proportions. Their habitat is within or immediately on top of the uppermost millimetres of the soil and are the predominant surface cover in arid and semiarid zones. Among the diverse functions developed by BSCs in the ecosystem (hydrology, erosion, soil properties, etc.), one of the most important is its role in nutrient cycling. Within arid and semiarid environments, BSCs have been termed 'mantles of fertility' being considered hotspots of biogeochemical inputs, fixing C, N and P above- and below-ground. However, there are differences in N and C fixation rates between BSCs types. Early successional BSCs, dominated by cyanobacterial species, fix lower quantities of C and N than mature BSCs dominated by lichens. Although the positive effects of BSCs on biogeochemical soil cycles are widely accepted, no previous studies have evaluated the activities of the enzymes involved in C, N and P cycles of BSCs and how they are affected by the successional stage of the BSC. In this work, performed in the Tabernas desert (SE Spain), we studied the hydrolase enzymes

  16. Human response and adaptation to drought in the arid zone: lessons from southern Africa

    OpenAIRE

    W. R.J. Dean; S. J. Milton; P.J. O'Farrell; P. M.L. Anderson

    2009-01-01

    Human adaptation and response to drought is primarily through evasion or endurance. A review of historical agricultural practices in southern Africa demonstrates evidence of drought evasion response strategies in well-established transhumance routes, where herders move livestock on a seasonal basis in order to exploit resources subject to different climatic regimes. European settlers to the arid regions of South Africa quickly recognised the necessity of these evasion options to survive droug...

  17. Rodent middens, a new method for Quaternary research in arid zones of South America

    Science.gov (United States)

    Betancourt, J.L.; Saavedra, B.

    2002-01-01

    In arid and semi-arid regions of South America, historical evidence for climate and vegetation change is scarce despite its importance for determining reference conditions and rates of natural variability in areas susceptible to modern desertification. Normal lines of evidence, such as pollen stratigraphies from lakes, are either rare or unobtainable in deserts; studies of late Quaternary vegetation history are few and generally inconclusive. This gap in knowledge may be corrected with discovery and development of fossil rodent middens in rocky environments throughout arid South America. These middens, mostly the work of Lagidium, Phyllotis, Abrocoma and Octodontomys, are rich in readily identifiable plant macrofossils, cuticles and pollen, as well as vertebrate and insect remains. In the North American deserts, more than 2,500 woodrat (Neotoma) middens analyzed since 1960 have yielded a detailed history of environmental change during the past 40,000 years. Preliminary work in the pre-puna, Monte and Patagonian Deserts of western Argentina, the Atacama Desert of northern Chile/southern Peru, the Mediterranean matorral of central Chile, and the Puna of the Andean altiplano suggest a similar potential for rodent middens in South America. Here we borrow from the North American experience to synthesize methodologies and approaches, summarize preliminary work, and explore the potential of rodent midden research in South America.

  18. Macropores in Vadose Zone of Well Vegetated Slopes%植被发育斜坡非饱和带大孔隙

    Institute of Scientific and Technical Information of China (English)

    张家明; 徐则民; 裴银鸽

    2012-01-01

    In warm and humid landslide prone area,root channels,faunal tunnels,shrinkage cracks,pipes and inter aggregate porosity are common in vadose zones of hillslopes. By using microscopic observation, chemical analysis and field experiment method, combining the existing research achievements in relative fields, the definitions of macropores, the types of macropores and controlling factors, the three dimensional spatial structure of macropores and the temporal stability of macropores in well vegetated slope were analyzed. The differences between different measurement methods and the temporal and spatial variability of macropores density are causes of no consensus for the definition of macropores. Macropores size alone is not a sufficient criterion for the definition of a macropore, and then three dimensional geometry morphology of macropores must be take into consideration. The formation and the type of macropores are controlled by several factors. Root channels, shrinkage cracks and inter aggregate porosity makes a significant contribution to preferential flow. The spatial structure of macropores needs to be further investigated from two aspects of three dimensional geometry and topology. Litters protect the soil beneath from rainfall impact and filter out the fine particles that may clog macropores, but water transfer between macropores domain and the surrounding soil matrix domain have negative effects. An indepth research of above questions is important for the improvement and development of preferential flow model of well vegetated slopes.%在气候温湿的滑坡灾害易发区,根系通道、动物通道、干裂缝、管道及团聚体间的结构性孔隙等大孔隙普遍存在于斜坡非饱和带中.采用微观观察、化学分析和现场试验方法并结合相关学科的研究成果,分析大孔隙界定、大孔隙类型和主控因素、大孔隙三维空间结构及大孔隙时效稳定.不同测量方法的差异和大孔隙密度时空变异性是

  19. Transport of elemental mercury in the unsaturated zone from a waste disposal site in an arid region

    Science.gov (United States)

    Walvoord, M.A.; Andraski, B.J.; Krabbenhoft, D.P.; Striegl, R.G.

    2008-01-01

    Mercury contained in buried landfill waste may be released via upward emission to the atmosphere or downward leaching to groundwater. Data from the US Geological Survey's Amargosa Desert Research Site (ADRS) in arid southwestern Nevada reveal another potential pathway of Hg release: long-distance (102 m) lateral migration of elemental Hg (Hg0) through the unsaturated zone. Gas collected from multiple depths from two instrumented boreholes that sample the entire 110-m unsaturated zone thickness and are located 100 and 160 m away from the closest waste burial trench exhibit gaseous Hg concentrations of up to 33 and 11 ng m-3, respectively. The vertical distribution of gaseous Hg in the borehole closest to the disposal site shows distinct subsurface peaks in concentration at depths of 1.5 and 24 m that cannot be explained by radial diffusive transport through a heterogeneous layered unsaturated zone. The inability of current models to explain gaseous Hg distribution at the ADRS highlights the need to advance the understanding of gas-phase contaminant transport in unsaturated zones to attain a comprehensive model of landfill Hg release.

  20. Analysis and environmental diagnosis of rural habitat in arid zones of the Province of San Juan, Argentina

    Directory of Open Access Journals (Sweden)

    María Guillermina Re

    2015-03-01

    Full Text Available This paper presents the environmental analysis on rural communities on arid zones of the province of San Juan. The objective of this research is to perform a diagnosis and to develop proposals for future improvements on this region. The analysis was carried out at two different scales: one on the natural environment (macro scale, and another one, on the humanized environment (micro scale, represented by the productive farms, considered as the core of the rural domestic and productive habitat. This research allowed a characterization of the environment and an understanding of the rules that structure the rural habitat in San Juan, and also to perform an evaluation and diagnosis of this type of rural habitat.

  1. An effect of spatial resolution of remotely sensed data for vegetation analysis over an arid zone

    Science.gov (United States)

    Oguro, Y.; Tsuchiya, K.; Setoguchi, R.

    1997-05-01

    One of the recent trends in the development of an optical sensor of earth observation satellite is a great importance of spatial resolution and the order of 1 - 2 meter resolution sensor is under development. To cope with this trend analyses are made on the effect of extremely fine spatial resolution of land cover classification accuracy utilizing spatial resolution of 20 cm and 1 meter aerial multi-sensor data of an arid reddish land where desertification is taking place in small spatial scale. Applied methods are supervised classification with combination of multi-level slice(pallarelpiped classification) and the Mahalanobis distance. The result of analysis indicates that the difference is within several percentage for 3 categories of bare land, vegetation and shadow. It was also found that small dried sparse grass land which can be recognized in 20 cm resolution image is difficult to extract in 1 meter resolution image.

  2. Richness and diversity of Leguminosae in an altitudinal gradient in the tropical semi-arid zone of Brazil

    Institute of Scientific and Technical Information of China (English)

    Jacira R.LIMA; Vidal F.MANSANO; Francisca S.ARA(U)JO

    2012-01-01

    Many studies are based on the premise that,on a local scale,diversity is the result of ecological processes,whereas on a regional scale factors such as the topography,geology,hydrology,and historical and evolutionary events would influence this control.The Baturité Mountain Range (Ceará state),located in the Brazilian semi-arid zone,is considered an area of extreme importance for conservation with its vegetation varying with the altitude and slope (windward vs.leeward).On the windward (wet) slope,rainforest dominates,whereas the leeward (dry) slope is dominated by seasonal forests and thorny woodland.The aim of this study was to contribute to the knowledge of the patterns of richness and diversity of the family Leguminosae on a local scale (Baturité Mountain Range) as well as a regional scale (northeastern Brazil).The two slopes present quite distinct floras.The dry slope presents higher richness and diversity indices for Leguminosae than the wet slope.The highest diversity of Leguminosae in the dry areas did not corroborate the ideas of other studies carried out in neotropical forests (total flora) that the higher species richness was predicted for wet areas.The present study indicates that the historical and evolutionary processes influence the diversity patterns on a local scale (Baturité Mountain Range),as well as on a regional scale (Brazilian semi-arid).Our results reinforce the uniqueness of each portion of this area and its importance for conservation.

  3. Urban Market Gardening and Rodent-Borne Pathogenic Leptospira in Arid Zones: A Case Study in Niamey, Niger.

    Directory of Open Access Journals (Sweden)

    Gauthier Dobigny

    Full Text Available Leptospirosis essentially affects human following contact with rodent urine-contaminated water. As such, it was mainly found associated with rice culture, recreational activities and flooding. This is also the reason why it has mainly been investigated in temperate as well as warm and humid regions, while arid zones have been only very occasionally monitored for this disease. In particular, data for West African countries are extremely scarce. Here, we took advantage of an extensive survey of urban rodents in Niamey, Niger, in order to look for rodent-borne pathogenic Leptospira species presence and distribution across the city. To do so, we used high throughput bacterial 16S-based metabarcoding, lipL32 gene-targeting RT-PCR, rrs gene sequencing and VNTR typing as well as GIS-based multivariate spatial analysis. Our results show that leptospires seem absent from the core city where usual Leptospira reservoir rodent species (namely R. rattus and M. natalensis are yet abundant. On the contrary, L. kirschneri was detected in Arvicanthis niloticus and Cricetomys gambianus, two rodent species that are restricted to irrigated cultures within the city. Moreover, the VNTR profiles showed that rodent-borne leptospires in Niamey belong to previously undescribed serovars. Altogether, our study points towards the importance of market gardening in maintain and circulation of leptospirosis within Sahelian cities. In Africa, irrigated urban agriculture constitutes a pivotal source of food supply, especially in the context of the ongoing extensive urbanization of the continent. With this in mind, we speculate that leptospirosis may represent a zoonotic disease of concern also in arid regions that would deserve to be more rigorously surveyed, especially in urban agricultural settings.

  4. Urban Market Gardening and Rodent-Borne Pathogenic Leptospira in Arid Zones: A Case Study in Niamey, Niger.

    Science.gov (United States)

    Dobigny, Gauthier; Garba, Madougou; Tatard, Caroline; Loiseau, Anne; Galan, Max; Kadaouré, Ibrahima; Rossi, Jean-Pierre; Picardeau, Mathieu; Bertherat, Eric

    2015-01-01

    Leptospirosis essentially affects human following contact with rodent urine-contaminated water. As such, it was mainly found associated with rice culture, recreational activities and flooding. This is also the reason why it has mainly been investigated in temperate as well as warm and humid regions, while arid zones have been only very occasionally monitored for this disease. In particular, data for West African countries are extremely scarce. Here, we took advantage of an extensive survey of urban rodents in Niamey, Niger, in order to look for rodent-borne pathogenic Leptospira species presence and distribution across the city. To do so, we used high throughput bacterial 16S-based metabarcoding, lipL32 gene-targeting RT-PCR, rrs gene sequencing and VNTR typing as well as GIS-based multivariate spatial analysis. Our results show that leptospires seem absent from the core city where usual Leptospira reservoir rodent species (namely R. rattus and M. natalensis) are yet abundant. On the contrary, L. kirschneri was detected in Arvicanthis niloticus and Cricetomys gambianus, two rodent species that are restricted to irrigated cultures within the city. Moreover, the VNTR profiles showed that rodent-borne leptospires in Niamey belong to previously undescribed serovars. Altogether, our study points towards the importance of market gardening in maintain and circulation of leptospirosis within Sahelian cities. In Africa, irrigated urban agriculture constitutes a pivotal source of food supply, especially in the context of the ongoing extensive urbanization of the continent. With this in mind, we speculate that leptospirosis may represent a zoonotic disease of concern also in arid regions that would deserve to be more rigorously surveyed, especially in urban agricultural settings.

  5. Performance of Jatropha curcas L. in Semi-arid Zone: Seed Germination, Seedling Growth and Early Field Growth

    Directory of Open Access Journals (Sweden)

    Sharif AHAMAD

    2013-05-01

    Full Text Available There is a lack of information on basic agronomic properties of Jatropha curcas L. (jatropha cultivation on the marginal lands in the semi-arids. Evaluation of agronomic performance of identified elite strains of J. curcas in marginal lands would be of paramount importance for addressing gap areas in their agronomic properties and subsequently for harnessing their optimum economic potentials. The present study undertook the task of analysing the growth performance of a high oil bearing elite strain of J. curcas–DARL-2 in degraded land in semi-arid zone of Deccan Plateau, India. While undertaking the assessment of growth performance of elite strain DARL-2, two other native (wild strains (namely AHN-1 and AHN-2 of J. curcas were also considered so that a comparative evaluation could be carried out. The role of gypsum was also investigated on J. curcas in the nursery stage as well its carry over effects on growth performance of transplanted trees in the field. Two types of substrates, gypsum-treated soil (GS and untreated soil (SL were used for growing seedlings of all the three jatropha strains. Seedlings (120-days-old of DARL-2 exhibited greater plant height, collar diameter and number of branches but root length was greater in the local strains. In the second year of field transplantation, DARL-2 strain exhibited significantly (p<0.05 greater plant height and number of branches/plant. No carry over effects of gypsum treatment were observed in field transplanted plants as none of the growth parameters significantly varied among the substrate types.

  6. Fishery Resources in Arid Zone Mangroves in Gulf of Kachchh, Gujarat, Northwest Coast of India

    Institute of Scientific and Technical Information of China (English)

    A. Saravanakumar; M. Rajkumar; J. Sesh Serebiah; G. A. Thivakaran

    2009-01-01

    The finfish and shellfish resources were assessed quantitatively and qualitatively in regard to their abundance in creek waters at three sites within a period of two years, from January 1999 to December 2000, in the western mangrove areas of Kachchh.The catch rate varied from 0.69 to 6.99 kg h-1. It was low during monsoon (July to October), which could be due to the freshwater-flow-induced salinity reduction in all the sites. Among 38 species recorded, 5 were shellfish and 33 were finfish. The spawning period of fishes was found to be during summer and early monsoon period (May to August). Surface water temperatures varied from 17 ℃ to 37 ℃. Salinity values varied from 34 to 44 and the pH ranged between 7 and 8.9. Variation in dissolved oxygen content was from 3.42 to 5.85 mLL-1. The high fishery densities in these semi arid mangrove creek areas were recorded during monsoon and early winter season.

  7. Human response and adaptation to drought in the arid zone: lessons from southern Africa

    Directory of Open Access Journals (Sweden)

    W. R.J. Dean

    2009-12-01

    Full Text Available Human adaptation and response to drought is primarily through evasion or endurance. A review of historical agricultural practices in southern Africa demonstrates evidence of drought evasion response strategies in well-established transhumance routes, where herders move livestock on a seasonal basis in order to exploit resources subject to different climatic regimes. European settlers to the arid regions of South Africa quickly recognised the necessity of these evasion options to survive drought, and adopted the transhumance practices of indigenous farmers. Areas of geographically diverse resource bases became hotly contested by settlers and indigenous farmers. The success of evasion systems are shown to hinge on good social and institutional support structures. When movement is not an option, drought endurance is pursued by attempting to limit the damage to the natural resource base. This is through a number of means such as forage conservation, varying livestock types and numbers, water and soil conservation and taking up alternative livelihood options. State responses to drought over the last century reflect the general South African pattern of racially divided and unjust policies relating to resource access. Historically the state provided considerable support to white commercial farmers. This support was frequently contradictory in its aims and generally was inadequate to enable farmers to cope with drought. Since the advent of democracy in 1994, the state has intervened less, with some support extended to previously disadvantaged and poor communal farmers. Climate change predictions suggest an increase in drought, suggesting that the adoption of mitigating strategies should be a matter of urgency. To do this South Africa needs to build social and institutional capacity, strive for better economic and environmental sustainability, embed drought-coping mechanisms into land restitution policy to ensure the success of this programme, and

  8. Ajustement de la courbe de lactation de la chèvre locale dans les zones arides Tunisiennes

    Directory of Open Access Journals (Sweden)

    Ilyes Mekki

    2011-10-01

    Full Text Available Les performances laitières de la chèvre locale dans les zones arides tunisiennes dépendent des capacités génétiques de l’effet des conditions du milieu et du mode de conduite des troupeaux. L’objectif de cette étude est d’analyser les performances laitières de la chèvre locale en fonction de ces facteurs à travers l’ajustement de la courbe de lactation. De telles connaissances sont indispensables pour planifier la gestion raisonnable de cette ressource animale rustique dans des conditions naturelles difficiles. Les données utilisées pour cette étude sont issues de 10 campagnes de contrôle laitier réalisé au niveau d’un troupeau caprin expérimental conduit dans les régions arides. Suite à l’élaboration des données, l’application des procédures de régression non linéaire a identifié le modèle de Wood comme le plus adaptée pour l’ajustement de la courbe de lactation de la chèvre locale. Ce modèle a été appliqué pour estimer les paramètres de la lactation individuelle et l’étude des facteurs de variation. Les résultats d’ajustements des données montrent que la lactation de la chèvre locale évolue après la mise bas selon une trajectoire assez aplatie. Les performances de la chèvre locale sont assez réduites et similaires à celles observées pour des populations élevées dans des zones difficiles tunisiennes de point de vue climatique et pastorale. La moyenne de production initiale observée est de 720 g/j, le pic de lactation est observé au 17ème jour lorsqu’une chèvre produit en moyenne 980g/j. La réduction des potentialités laitières de la chèvre locale illustre les effets du processus de sélection naturelle qui a favorisé l’adaptation aux conditions difficiles des régions arides. Les résultats contribuent à la caractérisation de la chèvre locale et à la planification de son amélioration comme étant une ressource génétique locale et rustique.

  9. Marine isolates of Trichoderma spp. as potential halotolerant agents of biological control for arid-zone agriculture.

    Science.gov (United States)

    Gal-Hemed, Inbal; Atanasova, Lea; Komon-Zelazowska, Monika; Druzhinina, Irina S; Viterbo, Ada; Yarden, Oded

    2011-08-01

    The scarcity of fresh water in the Mediterranean region necessitates the search for halotolerant agents of biological control of plant diseases that can be applied in arid-zone agriculture irrigated with saline water. Among 29 Trichoderma strains previously isolated from Mediterranean Psammocinia sp. sponges, the greatest number of isolates belong to the Trichoderma longibrachiatum-Hypocrea orientalis species pair (9), H. atroviridis/T. atroviride (9), and T. harzianum species complex (7), all of which are known for high mycoparasitic potential. In addition, one isolate of T. asperelloides and two putative new species, Trichoderma sp. O.Y. 14707 and O.Y. 2407, from Longibrachiatum and Strictipilosa clades, respectively, have been identified. In vitro salinity assays showed that the ability to tolerate increasing osmotic pressure (halotolerance) is a strain- or clade-specific property rather than a feature of a species. Only a few isolates were found to be sensitive to increased salinity, while others either were halotolerant or even demonstrated improved growth in increasingly saline conditions. In vitro antibiosis assays revealed strong antagonistic activity toward phytopathogens due to the production of both soluble and volatile metabolites. Two marine-derived Trichoderma isolates, identified as T. atroviride and T. asperelloides, respectively, effectively reduced Rhizoctonia solani damping-off disease on beans and also induced defense responses in cucumber seedlings against Pseudomonas syringae pv. lachrimans. This is the first inclusive evaluation of marine fungi as potential biocontrol agents.

  10. Impact of climate change on surface water resource and tendency in the future in the arid zone of northwestern China

    Institute of Scientific and Technical Information of China (English)

    施雅风; 张祥松

    1995-01-01

    The surface water resource in the arid zone of northwestern China is pregnant in the 6great mountain systems induding snow covers,glaciers,rivers and lakes.Though the climate fluctuates,becoming warmer and drier,and the water resource trends to wither during the 20th century,it is evident thatin the Holocene Megathermal there would be a more plentiful water resource.During the Little Ice Age,theglacier area and the amount of runoff and lake water were also higher than those at present.It is estimated thatthe temperature in mountains of western China would be 1℃ warmer by 2030 A.D.,when the precipitationand evaporation would be some higher,the snow cover would be lower in plains and higher in mountains,gla-ciers would retreat further,many small glacier would disappear,river runoff would increase with a highervariability,most of the lakes would be in a negative balance state and would wither further.

  11. Tritium plume dynamics in the shallow unsaturated zone in an arid environment

    Science.gov (United States)

    Maples, S.R.; Andraski, B.J.; Stonestrom, D.A.; Cooper, C.A.; Pohll, G.; Michel, R.L.

    2014-01-01

    The spatiotemporal variability of a tritium plume in the shallow unsaturated zone and the mechanisms controlling its transport were evaluated during a 10-yr study. Plume movement was minimal and its mass declined by 68%. Upward-directed diffusive-vapor tritium fluxes and radioactive decay accounted for most of the observed plume-mass declines. Effective isolation of tritium (3H) and other contaminants at waste-burial facilities requires improved understanding of transport processes and pathways. Previous studies documented an anomalously widespread (i.e., theoretically unexpected) distribution of 3H (>400 m from burial trenches) in a dry, sub-root-zone gravelly layer (1–2-m depth) adjacent to a low-level radioactive waste (LLRW) burial facility in the Amargosa Desert, Nevada, that closed in 1992. The objectives of this study were to: (i) characterize long-term, spatiotemporal variability of 3H plumes; and (ii) quantify the processes controlling 3H behavior in the sub-root-zone gravelly layer beneath native vegetation adjacent to the facility. Geostatistical methods, spatial moment analyses, and mass flux calculations were applied to a spatiotemporally comprehensive, 10-yr data set (2001–2011). Results showed minimal bulk-plume advancement during the study period and limited Fickian spreading of mass. Observed spreading rates were generally consistent with theoretical vapor-phase dispersion. The plume mass diminished more rapidly than would be expected from radioactive decay alone, indicating net efflux from the plume. Estimates of upward 3H efflux via diffusive-vapor movement were >10× greater than by dispersive-vapor or total-liquid movement. Total vertical fluxes were >20× greater than lateral diffusive-vapor fluxes, highlighting the importance of upward migration toward the land surface. Mass-balance calculations showed that radioactive decay and upward diffusive-vapor fluxes contributed the majority of plume loss. Results indicate that plume losses

  12. Antimicrobial activities of endophytic fungi obtained from the arid zone invasive plant Opuntia dillenii and the isolation of equisetin, from endophytic Fusarium sp.

    OpenAIRE

    Ratnaweera, Pamoda B.; de Silva, E. Dilip; Williams, David E.; Andersen, Raymond J

    2015-01-01

    Background Opuntia dillenii is an invasive plant well established in the harsh South-Eastern arid zone of Sri Lanka. Evidence suggests it is likely that the endophytic fungal populations of O. dillenii assist the host in overcoming biotic and abiotic stress by producing biologically active metabolites. With this in mind there is potential to discover novel natural products with useful biological activities from this hitherto poorly investigated source. Consequently, an investigation of the an...

  13. Effects of temperature on embryonic and larval development and growth in the natterjack toad (Bufo calamita in a semi-arid zone

    Directory of Open Access Journals (Sweden)

    Sanuy, D.

    2008-06-01

    Full Text Available Temperature affects the duration of embryonic and larval periods in amphibians. Plasticity in time to metamorphosis is especially important in amphibian populations of Mediterranean semi-arid zones where temperatures are high and precipitation is low, increasing the rate of pond desiccation. In order to test the influence of water temperature on the larval development and growth of the natterjack toad (Bufo calamita, we collected two spawns in a semi¿arid zone at Balaguer (Lleida, NE Iberian peninsula. Approximately 50 (+/-10 eggs (stage 14-16 were raised in the lab at different temperature conditions: 10, 15, 20, 22.5 and 25ºC with 12:12 photoperiod. The results show a lengthening of development time with decreasing temperatures and a better survival performance of B. calamita to high temperatures. However, mean size at metamorphosis was not different across treatments, thus, suggesting that this population of B. calamita requires a minimum size to complete the metamorphosis. This study is the first approach to examine the effects that climatic factors have on the growth and development of B. calamita in semi-arid zones.

  14. Field test of moisture migration in vadose zone under heterogeneity%非均质条件下河流包气带水分运移的原位试验

    Institute of Scientific and Technical Information of China (English)

    李永涛; 王文科; 肖建英; 杨晓婷

    2012-01-01

    围绕非均质条件下河流包气带水分运移,选择渭河河漫滩开展原位试验.在渭河原位试验点开挖7m×1 m×2.8m的探坑,以一侧剖面为研究面,刨光成垂直平面并对剖面做保护工作,方便观测.在不同层位按不同深度、在不同岩性的层位上打孔,分别安装MP-917时域反射仪与水银压力计,监测含水率及地下水压力势,并采用自制Bauwer渗水仪做持续5d的有压入渗试验,研究非均质条件下河流包气带水分运移规律及人渗速度与水头高度的关系.结果表明,包气带介质含水率分布与包气带结构有关,受岩性渗透系数制约,其中弱透水层的存在阻滞了水分的运移,包气带很难达到饱和,在弱透水层以上形成上层滞水并以非饱和流形式人渗.入渗速度随水层的厚度增大而增大,且入渗速度与水头高度呈对数关系.%The paper is engaged in a field test of moisture migration in vadose zone under the heterogeneous condition in the Weihe(Shaanx-i) flood-plain. The reason why we have chosen the topic is that the evolution of a river may exert serious consequential effects on the groundwater change, the water quality and even the ecological environment along the entire river reach. It is for such purposes, we have dug up some measuring pits as large as 7 m × 1 m×2.8m and taken them as our study profile. For the convenience of observation, we have installed a MP - 917 Time Domain Reflectometry (TDR) and a mercury manometer to observe the potential pressure and the moisture content in correspondence with the different properties of lithology and depth respectively. And, then, we have done a five-day infiltration test by using our own-made Bauwer Ooze water meter. Though it is difficult to understand the infiltration mechanism for its complexity with the unsaturated zone being heterogeneous with compacted sandwich structure, the field test is comparatively simple about the moisture migration in vadose zone

  15. Tritium Plume Dynamics in the Shallow Unsaturated Zone Adjacent to an Arid Waste Disposal Facility

    Science.gov (United States)

    Maples, S.; Andraski, B. J.; Stonestrom, D. A.; Cooper, C. A.; Michel, R. L.; Pohll, G. M.

    2012-12-01

    Previous studies at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS) in southern Nevada have documented two plumes of tritiated water-vapor (3HHOg) adjacent to a closed, commercial low-level radioactive waste disposal facility. Wastes were disposed on-site from 1962-92. Tritium has moved long distances (> 400 m) through a shallow (1-2-m depth) dry gravelly layer—orders of magnitude further than anticipated by standard transport models. Geostatistical methods, spatial moment analyses and tritium flux calculations were applied to assess shallow plume dynamics. A grid-based plant-water sampling method was utilized to infer detailed, field-scale 3HHOg concentrations at 5-yr intervals during 2001-11. Results indicate that gravel-layer 3HHOg mass diminished faster than would be expected from radioactive decay (~70% in 10 yr). Both plumes exhibited center-of-mass stability, suggesting that bulk-plume movement is minimal during the period of study. Nonetheless, evidence of localized lateral advancement along some margins, combined with increases in the spatial covariance of concentration distribution, indicates intra-plume mass redistribution is ongoing. Previous studies have recognized that vertical movement of tritiated water from sub-root-zone gravel into the root-zone contributes to atmospheric release via evapotranspiration. Estimates of lateral and vertical tritium fluxes during the study period indicate (1) vertical tritiated water fluxes were dominated by diffusive-vapor fluxes (> 90%), and (2) vertical diffusive-vapor fluxes were roughly an order of magnitude greater than lateral diffusive-vapor fluxes. This behavior highlights the importance of the atmosphere as a tritium sink. Estimates of cumulative vertical diffusive-vapor flux and radioactive decay with time were comparable to observed declines in total shallow plume mass with time. This suggests observed changes in plume mass may (1) be attributed, in considerable part, to these removal

  16. ANTI- MICROBAL EFFICACY OF MEDICINALLY IMPORTANT PLANTS (C. PHLOMIDIS USED IN FOLKARIC MEDICINES IN ARID ZONE

    Directory of Open Access Journals (Sweden)

    Chahal Jasvinder Kaur

    2012-05-01

    Full Text Available The present investigation was undertaken to evaluate in vivo antimicrobial activity of different extracts (Methanol, Benzene and Aqueous of Clerodendrum phlomidis plants parts. In vivo antimicrobial efficacy of various extracts of Clerodendrum phlomidis was assessed by disc diffusion method against Gram positive - Bacillus subtilis (ATCC 6633, Staphylococcus aureus (ATCC 25923 Gram negative- Escherichia coli (ATCC 25922, Psedomaonas aeruginosa (ATCC 27853 and fungal strains Aspergillus niger (ATCC 16404, Aspergillus flavus (ATCC 9807, Candida albicans (ATCC 5027 and Candida glabrata (ATCC 66032. The methanol leaf extract exhibited highest zone of inhibition against the bacterial stain in S. aureus (15.6±0.6mm with low MIC values (0.078 mg/ml and in the case of fungal strains C. albicans (14.0±0.0mm with low MIC values (0.156 mg/ml.However, none of activity is shown by aqueous extract against pathogenic bacteria. Result of the present investigation indicates that Clerodendrum phlomidis possess compounds with antimicrobial properties and hence can be exploited for future natural plant based antimicrobial agents.

  17. Plant species effects on soil nutrients and chemistry in arid ecological zones.

    Science.gov (United States)

    Johnson, Brittany G; Verburg, Paul S J; Arnone, John A

    2016-09-01

    The presence of vegetation strongly influences ecosystem function by controlling the distribution and transformation of nutrients across the landscape. The magnitude of vegetation effects on soil chemistry is largely dependent on the plant species and the background soil chemical properties of the site, but has not been well quantified along vegetation transects in the Great Basin. We studied the effects of plant canopy cover on soil chemistry within five different ecological zones, subalpine, montane, pinyon-juniper, sage/Mojave transition, and desert shrub, in the Great Basin of Nevada all with similar underlying geology. Although plant species differed in their effects on soil chemistry, the desert shrubs Sarcobatus vermiculatus, Atriplex spp., Coleogyne ramosissima, and Larrea tridentata typically exerted the most influence on soil chemistry, especially amounts of K(+) and total nitrogen, beneath their canopies. However, the extent to which vegetation affected soil nutrient status in any given location was not only highly dependent on the species present, and presumably the nutrient requirements and cycling patterns of the plant species, but also on the background soil characteristics (e.g., parent material, weathering rates, leaching) where plant species occurred. The results of this study indicate that the presence or absence of a plant species, especially desert shrubs, could significantly alter soil chemistry and subsequently ecosystem biogeochemistry and function.

  18. Energy use pattern in production agriculture of a typical village in arid zone. Pt. 3

    Energy Technology Data Exchange (ETDEWEB)

    Singh, H.; Mishra, D.; Nahar, N.M. [Central Arid Zone Research Institute, Rajasthan (India). Div. of Agricultural Engineering and Energy

    2004-09-01

    India has 31.71 Mha of hot and areas, of which 61.8% is in Western Rajasthan, commonly known as the ''Thar Desert''. A detailed study of the energy use pattern in production agriculture for a representative village, Pemasar, district Bikaner of zone II (200 mm/yr {<=} annual rainfall < 300 mm/yr) has been conducted. Out of the total geographical area (945.7 ha) of the village, 693.6 ha is cultivable land. The main crops grown in the village are cluster bean, moth bean, groundnut, green gram (Kharif), wheat, mustard, gram, barley and rocket salad (Rabi). In general, Kharif crops are grown as rain fed crops, but due to low rainfall in the zone and the presence of the Indira Gandhi Canal, even Kharif crops are raised under irrigated conditions. However, the area covered under irrigation is meagre as the availability of canal water is very much limited and uncertain. Operation wise, the total energy consumed for rain fed Kharif crops is minimum (1187.6 MJ/ha) for moth bean and maximum (1261.9 MJ/ha) for cluster bean, while for irrigated crops, it is minimum (2847.3 MJ/ha) for moth bean, and maximum (12,809.6 MJ/ha) for groundnut. The average specific energy for cultivation of cluster bean (rain fed), cluster bean (irrigated), moth bean (rain fed), moth bean (irrigated) and groundnut were 11.7, 7.5, 7.7, 7.4 and 11.2 MJ/ha, respectively. Operation wise, the energy consumed for Rabi crops is minimum (3855.6 MJ/ha) for rocket salad followed by 4779.4 MJ/ha for mustard, 4845.2 MJ/ha for gram and maximum (7953.2 MJ/ha) for wheat. The average specific energy for cultivation of wheat, gram, mustard and rocket salad were 11.4, 16.5, 13.2 and 13.7 MJ/ha, respectively. The average values of estimated energy ratio for cluster bean (rain fed), cluster bean (irrigated), moth bean (rain fed), moth bean (irrigated) and groundnut were 2.1, 0.5, 3.4, 3.5 and 3.0, respectively. This suggests that the moth bean crop is more remunerating to the farmers in Kharif as

  19. Bacterial community structure and nitrogen transformation in hyporheic zones of arid-land streams

    Science.gov (United States)

    Zeglin, L. H.; Crenshaw, C. L.; Dahm, C. N.; Takacs-Vesbach, C.

    2007-12-01

    Hyporheic zones of desert streams can be areas of high biological activity and consequent nutrient transformation, particularly where land use change increases nutrient concentrations in a stream. Does hyporheic bacterial community composition vary, and does this biotic heterogeneity covary with water and nutrient supply? Bromide (Br-) and 15N-NO3- was injected for 24 hr in six streams (three "natural" reference streams, three streams in agricultural/urbanized catchments) in New Mexico and Arizona, USA. Four transects of 3 to 4 wells were placed along a longitudinal gradient within the study reach, and from these hyporheic water and gas samples were collected during and after each experiment. Gas samples were analyzed for O2, 15N2O, and 15N2. Hyporheic water samples were analyzed for major cations and anions, DOC, 15NO3- and 15NH4+. Bacterial diversity of hyporheic water was assessed using Denaturing Gradient Gel Electrophoresis (DGGE). There was high spatial and temporal variability in hyporheic bacterial community structure, connection with surface water and nutrient concentrations both within and among streams. For example, mean subsurface DGGE band richness per stream ranged from 9 to 21, and surface water comprised between 0 to 100 percent of hyporheic water in each well. There were strong differences in bacterial richness between streams (ANOVA, p nutrient concentration. 15NH4+ levels were higher in modified stream than reference stream subsurface waters, suggesting dissimilatory nitrate reduction to ammonium (DNRA) may be an important process in these hyporheic sediments. Our results to date suggest that though hyporheic microbial community structure is highly heterogeneous, this biological variability may be due to different factors than variability in stream nitrogen cycling function. Further work will identify dominant sequences within these bacterial communities and investigate within-stream heterogeneity.

  20. Paleomagnetism of Basaltic Lava Flows in Coreholes ICPP 213, ICPP-214, ICPP-215, and USGS 128 Near the Vadose Zone Research Park, Idaho Nuclear Technology and Engineering Center, Idaho National Engineering and Environmental Laboratory, Idaho

    Science.gov (United States)

    Champion, Duane E.; Herman, Theodore C.

    2003-01-01

    A paleomagnetic study was conducted on basalt from 41 lava flows represented in about 2,300 ft of core from coreholes ICPP-213, ICPP-214, ICPP-215, and USGS 128. These wells are in the area of the Idaho Nuclear Technology and Engineering Center (INTEC) Vadose Zone Research Park within the Idaho National Engineering and Environmental Laboratory (INEEL). Paleomagnetic measurements were made on 508 samples from the four coreholes, which are compared to each other, and to surface outcrop paleomagnetic data. In general, subhorizontal lines of correlation exist between sediment layers and between basalt layers in the area of the new percolation ponds. Some of the basalt flows and flow sequences are strongly correlative at different depth intervals and represent important stratigraphic unifying elements. Some units pinch out, or thicken or thin even over short separation distances of about 1,500 ft. A more distant correlation of more than 1 mile to corehole USGS 128 is possible for several of the basalt flows, but at greater depth. This is probably due to the broad subsidence of the eastern Snake River Plain centered along its topographic axis located to the south of INEEL. This study shows this most clearly in the oldest portions of the cored sections that have differentially subsided the greatest amount.

  1. 干旱区对降水变化响应的研究进展%Progress in the Study on Response of Arid Zones to Precipitation Change

    Institute of Scientific and Technical Information of China (English)

    朱雅娟; 吴波; 卢琦

    2012-01-01

    水分是干旱区的主要限制因子之一,降水是干旱区最重要的水分来源.根据气候变化研究的预测,未来我国干旱区的降水格局会改变,包括降水量、降水频率和降水强度等.降水变化会影响干旱区的土壤变化,植被变化,土地荒漠化和水文变化等方面.我国极端干旱区和干旱区的降水有总体增加趋势,而部分半干旱区和亚湿润干旱区的降水则出现减少趋势.降水的增加能够促进生物土壤结皮的发育,改善土壤水分状况,促进植物生长,提高植被盖度,促使荒漠植被向草原植被方向发展,有利于土地荒漠化的逆转;另外,降水增加会增加河流的径流量和湖泊水量,促进洪水的发生,降水减少则具有相反的效应.这些研究有助于人们预测干旱区在未来降水格局改变之后可能发生的变化,对于天然植被保育以及荒漠化防治等实践工作等具有重要的理论指导意义.未来的研究需要加强实验,如增雨、升温、模拟氮沉降和CO2浓度增加等对干旱区的土壤、植被、荒漠化和水文等方面的影响,才能获得更有说服力的结果.%The pattern of precipitation, including precipitation amount, frequency and intensity, may change in the future according to the prediction of climate change. In arid zones, the soil dynamics, plant growth and vegetation change, desertification and hydrology might be affected by precipitation change. In general, the precipitation in extreme arid zone and arid zone showed an increase tendency whereas the precipitation in some area in semi-arid zone and sub-humid arid zone showed a decrease tendency. The increase of precipitation could enhance the growth of biological soil crust, improve soil water status, promote plant growth, increase vegetation coverage, facilitate the change from desert vegetation to grassland vegetation, and it is benefit to the reversion of land desertification. In addition, the increase of

  2. WEATHER CONDITIONS OF MAIZE VEGETATION IN CONNECTION WITH THE PLANTING DATES IN THE ARID ZONE OF CENTRAL CISCAUCASUSIA

    Directory of Open Access Journals (Sweden)

    Kravchenko R. V.

    2016-02-01

    Full Text Available There were reviewed the results of the study of the dependence of main phenological phases of development of corn hybrids of different maturity groups of the selection of Krasnodar Research Institute of Agriculture named after P.P. Lukyanenko in the arid zone of Central Ciscaucasia (Ross 199, Ross 299, Krasnodar 382 and Krasnodar 410 and the AllRussian Research Institute of Corn (Mashuk 170, Newton, RIC 345 and Eric, as well as early-middle Rossiyskaya 1 from the changes of average daily air temperature of planting dates and preplant seed treatment by the preparation "TMTD-plus", containing the growth promoter called Krezatsin in its composition. The studies were conducted in accordance with the thematic plan of scientific researches of the department of crop and forage production of Stavropol State Agrarian University. The technology of maize growing on the experimental plot corresponds to the standard technology for this area and culture. The sowing was performed in three stages. The first (early sowing period was at t = + 7 ... +8 ° C. The second (recommended – was at t = + 10 ... + 12 ° C. The third (later sowing period was at t = +15 ° C. There was identified a high inverse correlation between the average daily air temperature and the duration of the intraphase periods of maize propagation. Thus, at the shifting of maize sowing dates with the second half of May on the second half of April we have optimization of heat regime in the generative period and rising of the efficiency of use of thermal resources of the region. There was marked the acceleration of development of corn seedlings when the average daily air temperatures was up to 12 ° C at the samples with the application of the disinfectant TMTD-plus

  3. Breeding habitat selection of an endangered species in an arid zone: the case of Alytes dickhilleni Arntzen & García-París, 1995

    Directory of Open Access Journals (Sweden)

    Andrés Egea-Serrano

    2006-11-01

    Full Text Available The influence of environmental variables on the selection of a particular water body as breeding habitat by Alytes dickhilleni was studied in the southeastern and most arid zone of its distribution range. From November 2002 to October 2003, 50 water bodies were monitored in the south east of the Iberian Peninsula. Environmental data were submitted to a stepwise logistic regression analysis at macrohabitat, water body typology and microhabitat scales in order to establish the main factors influencing the use of a given water body as breeding habitat by this species. Statistical analysis showed that the reproduction of Alytes dickhilleni is associated with the macrohabitat variable topography, and the water body typology. This species breeds mainly in permanent water bodies located in mountainous topography in the study area. These results should be taken into account when populations of this species are subjected to management and/or recovery programmes in arid areas.

  4. Evaporation and concentration gradients created by episodic river recharge in a semi-arid zone aquifer: Insights from Cl-, δ18O, δ2H, and 3H

    Science.gov (United States)

    Meredith, K. T.; Hollins, S. E.; Hughes, C. E.; Cendón, D. I.; Chisari, R.; Griffiths, A.; Crawford, J.

    2015-10-01

    This study has significantly advanced our understanding of the origin of groundwater recharge in a semi-arid zone region of the Darling River catchment, Australia. The generally accepted hypothesis in arid zone environments in Australia that river water forms the primary groundwater recharge source has proven difficult to monitor. This is due to the time lags between large floods, the remoteness and expense of studying these hydrologically complex systems in detail. In addition, the highly episodic nature of dryland rivers complicates the interpretation of the groundwater signal. A range of hydrochemical tracers (chloride, oxygen-18, deuterium and tritium) measured in rain, river water, soil water and groundwater were used in this multi-year study to trace the pathways of groundwater recharge under wet and dry climatic conditions. The evaporation and Cl concentrations observed in the unsaturated zone confirmed that small volumetric inputs from periodic rainfall were not the major recharge mechanism. Sampling which included an overbank flooding event in March 2012 provided firm evidence for groundwater originating from high flow episodic river recharge. The use of long-term environmental data to understand how economically important water resources respond to climate change with increasing temperatures is considered essential for future sustainability.

  5. Biogeochemical anomaly above oil-containing structures in an arid zone. [Growth stimulation of plants by sodium naphthenate used for prospecting

    Energy Technology Data Exchange (ETDEWEB)

    Grishchenko, O.M.

    1983-01-01

    Visual biological anomalies above the oil-containing structures are characterized by bright green coloring of the vegetation cover, gigantism of the plants, extended vegetation period of the plants, deformity of the plants, etc. Biological anomalies are associated with geological features and are observed only above the zone of fault disorders of the earth's crust, above deep faults. A conclusion is drawn about the presence above the oil-bearing structures in the arid zone of a biogeochemical anomaly whose origin is explained by the biological activity of oil and its derivatives. The petroleum growth matter is the sodium salt of naphthene acid, a growth stimulator of plants and animals. The oils of the USSR contain 0.8-4.8% naphthene acids, which effuse through the faults into the root area levels of the soil. As a result of stimulation of growth and development by the petroleum growth matter, the vegetation period of the plants is prolonged. Under the influence of natural petroleum growth substances, the height and productivity of the anomalous plants increases 2-3-fold. Formation and manifestation of signs of biogeochemical anomalies above the oil-bearing structures in the arid zone predetermine the following conditions: presence of fault disorders of the earth's crust; salinity of the root area of the soil layer necessary for neutralization of the naphthene acids with subsequent formation of the biologically active naphthenates; aridity of the desert landscape; plain relief excluding color diversity in vegetation cover because of nonuniform wetting, etc. The established biogeochemical anomaly can be used in prospecting and exploration of oil, gas and bitumen, and also in determining the fault disorders of the earth's crust.

  6. 北京典型地区灌溉条件下包气带水分运移特征研究%Research on the Characteristics of Water Movement under Irrigation Condition in Vadose Zone in the Typical Area of Beijing

    Institute of Scientific and Technical Information of China (English)

    刘颖超; 邢国章; 刘凯; 谢振华

    2015-01-01

    以张家湾包气带水盐运移试验场灌溉试验资料为依据,运用土壤水分能量观点,分析了灌溉条件下包气带水分运移特征。试验结果表明,在一定灌溉量下包气带水分运移具有明显的分带特征以及灌溉水明显运移到达的深度;在一定灌溉量条件下,灌溉后地下水位上升微小,灌溉补给地下水量较小,并通过非饱和水流达西定律计算了向下入渗补给量。%Base on the irrigation experiment of moisture and salt content migration of the vadose zones in-situ in the Zhangjiawan area, the paper analyzes the migration characteristics of moisture movement of unsaturated zones from the view of moisture energy. It shows that moisture migration of vadose zones can be roughly divided into three zones and the process of groundwater recharge under irrigation, the deep of the moisture migration. The ground water level rises very low under the condition of irrigation and the irrigation recharge quantity was very little, which was calculated by unsaturated lfow Darcy's law.

  7. Tailoring conservation agriculture technologies to West Africa semi-arid zones: Building on traditional local practices for soil restoration

    NARCIS (Netherlands)

    Lahmar, R.; Bationo, B.A.; Lamso, N.D.; Guéro, Y.; Tittonell, P.A.

    2012-01-01

    Low inherent fertility of tropical soils and degradation, nutrient deficiency and water stress are the key factors that hamper rainfed agriculture in semi-arid West Africa. Conservation Agriculture (CA) is currently promoted in the region as a technology to reduce soil degradation, mitigate the effe

  8. Water quality assessment of highly polluted rivers in a semi-arid Mediterranean zone Oued Fez and Sebou River (Morocco)

    OpenAIRE

    2014-01-01

    Oued Fez (one of the Sebou River tributaries - Morocco) allowed us to study and quantify the effect of the lack of wastewater treatment on surface water quality in semi-arid hydrological context. The analysis is based on field data collected from June 2009 to December 2011. Concentration and load patterns of nitrogen, phosphorus and chromium (used in the processing of leather) are compared in stable hydrological conditions during low flow and high flow periods in an eight-location sampling ne...

  9. Effects of land use/land cover and climate changes on surface runoff in a semi-humid and semi-arid transition zone in northwest China

    Science.gov (United States)

    Yin, Jing; He, Fan; Jiu Xiong, Yu; Qiu, Guo Yu

    2017-01-01

    Water resources, which are considerably affected by land use/land cover (LULC) and climate changes, are a key limiting factor in highly vulnerable ecosystems in arid and semi-arid regions. The impacts of LULC and climate changes on water resources must be assessed in these areas. However, conflicting results regarding the effects of LULC and climate changes on runoff have been reported in relatively large basins, such as the Jinghe River basin (JRB), which is a typical catchment (> 45 000 km2) located in a semi-humid and arid transition zone on the central Loess Plateau, northwest China. In this study, we focused on quantifying both the combined and isolated impacts of LULC and climate changes on surface runoff. We hypothesized that under climatic warming and drying conditions, LULC changes, which are primarily caused by intensive human activities such as the Grain for Green Program, will considerably alter runoff in the JRB. The Soil and Water Assessment Tool (SWAT) was adopted to perform simulations. The simulated results indicated that although runoff increased very little between the 1970s and the 2000s due to the combined effects of LULC and climate changes, LULC and climate changes affected surface runoff differently in each decade, e.g., runoff increased with increased precipitation between the 1970s and the 1980s (precipitation contributed to 88 % of the runoff increase). Thereafter, runoff decreased and was increasingly influenced by LULC changes, which contributed to 44 % of the runoff changes between the 1980s and 1990s and 71 % of the runoff changes between the 1990s and 2000s. Our findings revealed that large-scale LULC under the Grain for Green Program has had an important effect on the hydrological cycle since the late 1990s. Additionally, the conflicting findings regarding the effects of LULC and climate changes on runoff in relatively large basins are likely caused by uncertainties in hydrological simulations.

  10. Integrating variations in the soil chloride profile and evaporativity for in-situ estimation of evaporation in arid zones: an application in south-eastern Morocco

    Science.gov (United States)

    Bouhlassa, Saïdati; Ammary, Bouchaib; Paré, Samuel; Safsaf, Naima

    2016-11-01

    In arid regions, knowledge of the evaporation rate from the water table is essential for appropriate management of scarce resources and to prevent land degradation. Soil chloride profiles in the unsaturated zone of a bare soil in an arid area of south-eastern Morocco were used to assess the evaporation flux, using chloride inventories in conjunction with evaporative demand. Moisture fluxes were calculated from measured chloride concentrations on the basis of a steady-state flow model. The chloride profiles displayed large variations in concentrations and had (1) low chloride concentrations near the soil surface, (2) maximum chloride concentrations at depths of 11-14 cm beneath the soil surface, respectively in July and February, and (3) gradually decreasing chloride concentrations while depth increased below these peaks. Evaporative demands were found to be inversely proportional to the depth of evaporation fronts and proportional to evaporation fluxes. In addition, the evaporation along the profiles seems to be controlled by the soil composition and texture. The investigation of chloride profiles in February and July enabled the determination of a value for annual evaporation (˜30 mm), which is in good agreement with the value estimated by the Allison-Barnes type model (˜32 mm).

  11. Integrating variations in the soil chloride profile and evaporativity for in-situ estimation of evaporation in arid zones: an application in south-eastern Morocco

    Science.gov (United States)

    Bouhlassa, Saïdati; Ammary, Bouchaib; Paré, Samuel; Safsaf, Naima

    2016-06-01

    In arid regions, knowledge of the evaporation rate from the water table is essential for appropriate management of scarce resources and to prevent land degradation. Soil chloride profiles in the unsaturated zone of a bare soil in an arid area of south-eastern Morocco were used to assess the evaporation flux, using chloride inventories in conjunction with evaporative demand. Moisture fluxes were calculated from measured chloride concentrations on the basis of a steady-state flow model. The chloride profiles displayed large variations in concentrations and had (1) low chloride concentrations near the soil surface, (2) maximum chloride concentrations at depths of 11-14 cm beneath the soil surface, respectively in July and February, and (3) gradually decreasing chloride concentrations while depth increased below these peaks. Evaporative demands were found to be inversely proportional to the depth of evaporation fronts and proportional to evaporation fluxes. In addition, the evaporation along the profiles seems to be controlled by the soil composition and texture. The investigation of chloride profiles in February and July enabled the determination of a value for annual evaporation (˜30 mm), which is in good agreement with the value estimated by the Allison-Barnes type model (˜32 mm).

  12. Thixotropic gel for vadose zone remediation

    Science.gov (United States)

    Rhia, Brian D.

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  13. Vadose zone monitoring for hazardous waste sites

    Energy Technology Data Exchange (ETDEWEB)

    Singley, J.E.; Beaudet, B.A.; Markey, P.H.; De Berry, D.W.; Kidwell, J.R.; Malish, D.A.

    1985-01-01

    The corrosion of water treatment and supply systems is a very significant concern. Not only does it affect the aesthetic quality of the water but it also has an economic impact and poses adverse health implications. Corrosion by-products containing materials such as lead and cadmium have been associated with serious risks to the health of consumers of drinking water. In addition, corrosion-related contaminants commonly include compounds such as zinc, iron, and copper, which adversely affect the aesthetic aspects of the water. This book presents a guidance manual for corrosion control with sections on how and why corrosion occurs and how best to handle it. It also reviews the various materials used in the water works industry and their corrosion characteristics, as well as monitoring and detection techniques. Emphasis is placed on assessing the conditions and water quality characteristics due to the corrosion or deterioration of each of these materials.

  14. Thixotropic gel for vadose zone remediation

    Energy Technology Data Exchange (ETDEWEB)

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  15. Study on the Method of Measuring Denitrification Strength of Vadose Zone Soil%包气带土层的反硝化强度测定方法研究

    Institute of Scientific and Technical Information of China (English)

    张云; 张胜; 刘长礼; 宋超; 王秀艳; 彭玉荣; 王俊坤

    2011-01-01

    The impact factor of denitrification of vadose zone soil is complex. Currently there is no good method to be applied directly to measuring the denitrification strength. After comparing a variety of relevant methods, this paper chose "to increase the permeability of soil substrate disappearance balance method " as a guide and tried to use the way of applying a certain nitrate liquid manure to the situ permeability soil box of the field, with the simultaneous test of soil organic nitrogen mineralization, mi-crobial retention of inorganic nitrogen,and ammonia volatilization, crop uptake of nitrogen value , etc. And then with the soil net nitrate input, background value, final value and changes in value of ammonia nitrogen involved in calculating equilibrium, solving the value of soil denitrification ("improvement balance method "for short), so as to make a study on the determination of strength of denitrification for different soil quality, thickness, soil organic matter consumption, permeability soil box or soil column under soil water potential. The results showed that different thickness, soil organic matter consumption, permeability soil box and sandy soil or mild clay column under soil water potential as mentioned above produced a range of 8. 07~16. 54 mg. M-3 and 6. 23 ~ 26. 4 mg · M-3 of NO3-N removal, compared with the original method of determination of a range of 7. 29~ 11. 42 mg · M-3 and 5. 38 ~ 18. 1 mg. M-3's removal to a certain extent increased. This is "mainly due to the improved method reflecting complementally the effect of soil organic nitrogen mineralization. It eliminated some deficiencies in the original method, and not only revealed the soil denitrification phenomenon, but also described a more comprehensive picture of environmental factors on soil denitrification consequences. The method is more suitable for protection against the vadose zone soil contamination of groundwater denitrification measured, so as to provide services for

  16. An Evaluation of Unsaturated Flow Models in an Arid Climate

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, J. [Univ. of Nevada, Las Vegas, NV (United States)

    1999-12-01

    The objective of this study was to evaluate the effectiveness of two unsaturated flow models in arid regions. The area selected for the study was the Area 5 Radioactive Waste Management Site (RWMS) at the Nevada Test Site in Nye County, Nevada. The two models selected for this evaluation were HYDRUS-1D [Simunek et al., 1998] and the SHAW model [Flerchinger and Saxton, 1989]. Approximately 5 years of soil-water and atmospheric data collected from an instrumented weighing lysimeter site near the RWMS were used for building the models with actual initial and boundary conditions representative of the site. Physical processes affecting the site and model performance were explored. Model performance was based on a detailed sensitivity analysis and ultimately on storage comparisons. During the process of developing descriptive model input, procedures for converting hydraulic parameters for each model were explored. In addition, the compilation of atmospheric data collected at the site became a useful tool for developing predictive functions for future studies. The final model results were used to evaluate the capacities of the HYDRUS and SHAW models for predicting soil-moisture movement and variable surface phenomena for bare soil conditions in the arid vadose zone. The development of calibrated models along with the atmospheric and soil data collected at the site provide useful information for predicting future site performance at the RWMS.

  17. Climate variability, precipitation trends, and impacts on surface processes in humid to arid climate transition zones of the NW Argentine Andes (24° S, 65° W)

    Science.gov (United States)

    Castino, Fabiana; Bookhagen, Bodo; Strecker, Manfred

    2015-04-01

    In the Andes of NW Argentina the distribution and amount of rainfall and associated surface processes are intimately correlated with pronounced topographic gradients and relief contrasts that intercept easterly moisture-bearing winds related to the South American Monsoon System. These conditions have led to a pronounced elevation-dependent distribution of rainfall, which involves areally limited transition zones between the humid eastern flanks of the orogen (eastern foreland and eastern flanks of the E Cordillera) and the arid orogen interior (Puna Plateau). At interannual scales rainfall patterns in this area can be modulated by different atmospheric disturbances, such as the South Atlantic Convergent Zone and the El Niño Southern Oscillation, resulting in drought or flooding events. During the last two decades, field observations document fluvial aggradation in many intermontane valleys along the eastern flanks of the orogen. This may be related to changing overall climatic conditions, impacting hillslope erosion processes at high elevation, but contemporaneously overwhelming the fluvial system and reducing transport capacity, leading to transient sediment storage. We analyzed rainfall trends in the humid to arid climatic transition zone in the NW Argentine Andes over different time periods to characterize the spatiotemporal variability of rainfall patterns during the last five decades. We relied on both daily ground station (40 stations, 1956-2012) and three-hourly remote sensing rainfall data (3B42 V7 TRMM data, 1998-2014). Seasonal total anomalies analysis shows a complex rainfall pattern, reflected both in station data and remote sensing observations with clear positive (negative) statistically significant trends in the northern Puna Plateau and in the northern part of the foreland basin (southern part of the eastern foreland basin) of up to +20mm/yr (-20mm/yr). Quantile regression of three-hourly and daily data furthermore shows that, on average

  18. Habitat Fragmentation in Arid Zones: A Case Study of Linaria nigricans Under Land Use Changes (SE Spain)

    Science.gov (United States)

    Peñas, Julio; Benito, Blas; Lorite, Juan; Ballesteros, Miguel; Cañadas, Eva María; Martinez-Ortega, Montserrat

    2011-07-01

    Habitat fragmentation due to human activities is one of the most important causes of biodiversity loss. In Mediterranean areas the species have co-evolved with traditional farming, which has recently been replaced for more severe and aggressive practices. We use a methodological approach that enables the evaluation of the impact that agriculture and land use changes have for the conservation of sensitive species. As model species, we selected Linaria nigricans, a critically endangered plant from arid and semiarid ecosystems in south-eastern Spain. A chronosequence of the evolution of the suitable habitat for the species over more than 50 years has been reconstructed and several geometrical fragmentation indices have been calculated. A new index called fragmentation cadence (FC) is proposed to quantify the historical evolution of habitat fragmentation regardless of the habitat size. The application of this index has provided objective forecasting of the changes of each remnant population of L. nigricans. The results indicate that greenhouses and construction activities (mainly for tourist purposes) exert a strong impact on the populations of this endangered species. The habitat depletion showed peaks that constitute the destruction of 85% of the initial area in only 20 years for some populations of L. nigricans. According to the forecast established by the model, a rapid extinction could take place and some populations may disappear as early as the year 2030. Fragmentation-cadence analysis can help identify population units of primary concern for its conservation, by means of the adoption of improved management and regulatory measures.

  19. Water quality assessment of highly polluted rivers in a semi-arid Mediterranean zone Oued Fez and Sebou River (Morocco)

    Science.gov (United States)

    Perrin, J. L.; Raïs, N.; Chahinian, N.; Moulin, P.; Ijjaali, M.

    2014-03-01

    Oued Fez (one of the Sebou River tributaries - Morocco) allowed us to study and quantify the effect of the lack of wastewater treatment on surface water quality in semi-arid hydrological context. The analysis is based on field data collected from June 2009 to December 2011. Concentration and load patterns of nitrogen, phosphorus and chromium (used in the processing of leather) are compared in stable hydrological conditions during low flow and high flow periods in an eight-location sampling network. The Oued Fez and the Sebou River are characterised by severe pollution downstream from the city of Fez, particularly TN (mainly NH4 and Norg), TP (mainly Ppart) and TCr. The most polluted sites are those directly under the influence of domestic and industrial waste water inputs, particularly tannery effluents. Obviously, the concentrations measured at these locations are above all environmental quality standards. Pollutant loads are very heavy in the Sebou River and can contaminate the river course for kilometres. Moreover, as the water of the Sebou River is used for the irrigation of vegetables, serious problems of public health could arise. A better understanding of contaminant dynamics and self-purifying processes in these rivers will help implement actions and steps aimed at improving water quality in the Sebou River, which is the primary water supply source in Morocco and is used for agricultural and industrials purposes as well as for drinking water.

  20. Linking chloride mass balance infiltration rates with chlorofluorocarbon and SF6 groundwater dating in semi-arid settings: potential and limitations.

    Science.gov (United States)

    Stadler, Susanne; Osenbruck, Karsten; Duijnisveld, Wilhelmus H M; Schwiede, Martin; Bottcher, Jurgen

    2010-09-01

    In the framework of the investigation of enrichment processes of nitrate in groundwater of the Kalahari of Botswana near Serowe, recharge processes were investigated. The thick unsaturated zone extending to up to 100 m of mostly unconsolidated sediments and very low recharge rates pose a serious challenge to study solute transport related to infiltration and recharge processes, as this extends past the conventional depths of soil scientific investigations and is difficult to describe using evidence from the groundwater due to the limitations imposed by available tracers. To determine the link between nitrate in the vadose zone and in the uppermost groundwater, sediment from the vadose zone was sampled up to a depth of 15-20 m (in one case also to 65 m) on several sites with natural vegetation in the research area. Among other parameters, sediment and water were analysed to determine chloride and nitrate concentration depth profiles. Using the chloride mass balance method, an estimation of groundwater infiltration rates produced values of 0.2-4 mm a(-1). The uncertainty of these values is, however, high. Because of the extreme thickness of the vadose zone, the travel time in the unsaturated zone might reach extreme values of up to 500 years and more. For investigations using groundwater, we applied the chlorofluorocarbons CFC-113, CFC-12, sulphur hexafluoride (SF(6)) and tritium to identify potential recharge, and found indications for some advective transport of the CFCs and SF(6), which we accounted for as constituting potential active localised recharge. In our contribution, we show the potential and limitations of the applied methods to determine groundwater recharge and coupled solute transport in semi-arid settings, and compare travel time ranges derived from soil science and groundwater investigations.

  1. Evolution of chemical and isotopic composition of inorganic carbon in a complex semi-arid zone environment: Consequences for groundwater dating using radiocarbon

    Science.gov (United States)

    Meredith, K. T.; Han, L. F.; Hollins, S. E.; Cendón, D. I.; Jacobsen, G. E.; Baker, A.

    2016-09-01

    Estimating groundwater age is important for any groundwater resource assessment and radiocarbon (14C) dating of dissolved inorganic carbon (DIC) can provide this information. In semi-arid zone (i.e. water-limited environments), there are a multitude of reasons why 14C dating of groundwater and traditional correction models may not be directly transferable. Some include; (1) the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer(s), (2) the varied sources, origins and ages of organic matter in the unsaturated zone and (3) high evaporation rates. These all influence the evolution of DIC and are not easily accounted for in traditional correction models. In this study, we determined carbon isotope data for; DIC in water, carbonate minerals in the sediments, sediment organic matter, soil gas CO2 from the unsaturated zone, and vegetation samples. The samples were collected after an extended drought, and again after a flood event, to capture the evolution of DIC after varying hydrological regimes. A graphical method (Han et al., 2012) was applied for interpretation of the carbon geochemical and isotopic data. Simple forward mass-balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data. High values of DIC and δ13CDIC, and low 14CDIC could not be explained by a simple carbonate mineral-CO2 gas dissolution process. Instead it is suggested that during extended drought, water-sediment interaction leads to ion exchange processes within the top ∼10-20 m of the aquifer which promotes greater calcite dissolution in saline groundwater. This process was found to contribute more than half of the DIC, which is from a mostly 'dead' carbon source. DIC is also influenced by carbon exchange between DIC in water and carbonate minerals found in the top 2 m of the unsaturated zone. This process occurs because of repeated dissolution/precipitation of carbonate that is dependent on

  2. Breeding habitat selection of an endangered species in an arid zone: the case of Alytes dickhilleni Arntzen & García-París, 1995

    OpenAIRE

    2006-01-01

    The influence of environmental variables on the selection of a particular water body as breeding habitat by Alytes dickhilleni was studied in the southeastern and most arid zone of its distribution range. From November 2002 to October 2003, 50 water bodies were monitored in the south east of the Iberian Peninsula. Environmental data were submitted to a stepwise logistic regression analysis at macrohabitat, water body typology and microhabitat scales in order to establish the ma...

  3. Effect of Wetting-Drying Cycles on Redistribution of Lead in Some Semi-Arid Zone Soils Spiked with a Lead Salt

    Institute of Scientific and Technical Information of China (English)

    H.KHODAVERDILOO; M.RAHMANIAN; S.REZAPOUR; S.GHORBANI DASHTAKI; H.HADI; F.X.HAN

    2012-01-01

    Mobility and bioavailability of lead (Pb) could be affected considerably by soil physicochemical properties; however,less is known about the effect of Pb levels and aging time.This study was conducted to evaluate the effects of Pb levels and wetting-drying (WD) cycles on distribution and bioavailability of Pb in three semi-arid zone soils treated with different levels of Pb(NO3)2.Wetting-drying cycles simulated the actual field irrigation in the semi-arid soils.A soil with a long history of Pb contamination was also taken as a reference soil.The soils were spiked with various levels of Pb and incubated under WD cycles for 160 d.Sequential extractions and batch sorption experiments were performed to assess the fractionation of Pb in the spiked soils.Redistribution index (Uts) and reduced partitioning parameter (IR) were applied to semi-quantify the distribution of Pb in the spiked soils.A small amount of Pb sorbed was desorbed by the soils,indicating a strong and irreversible binding of Pb in the studied soils.Contribution of carbonate-bound (Car) and residual (Res) Pb fractions to the total Pb of the soils was more than 97%.The Car,soluble plus exchangeable (SE),and organic matter-bound (OMB) fractions of Pb were transferred to the Res fraction under the WD cycles.The IR and Uts values were influenced by Pb loading levels and WD; therefore,the Pb lability and/or redistribution pattern could semi-quantitatively be assessed via these parameters.At the end of the experiment,the IR and Uts values for the Pb salt-spiked soils did not show the quasiequilibrium state.The lability of Pb in the soils decreased with increasing incubation time and showed a strong dependence on Pb levels and soil chemical composition.WD cycles significantly affected the overall lability of Pb in soils through influencing the redistribution of Pb among solid-phase components.

  4. Influence of climate variability on water partitioning and effective energy and mass transfer in a semi-arid critical zone

    Science.gov (United States)

    Zapata-Rios, Xavier; Brooks, Paul D.; Troch, Peter A.; McIntosh, Jennifer; Rasmussen, Craig

    2016-03-01

    The critical zone (CZ) is the heterogeneous, near-surface layer of the planet that regulates life-sustaining resources. Previous research has demonstrated that a quantification of the influxes of effective energy and mass transfer (EEMT) to the CZ can predict its structure and function. In this study, we quantify how climate variability in the last 3 decades (1984-2012) has affected water availability and the temporal trends in EEMT. This study takes place in the 1200 km2 upper Jemez River basin in northern New Mexico. The analysis of climate, water availability, and EEMT was based on records from two high-elevation SNOTEL stations, PRISM data, catchment-scale discharge, and satellite-derived net primary productivity (MODIS). Results from this study indicated a decreasing trend in water availability, a reduction in forest productivity (4 g C m-2 per 10 mm of reduction in precipitation), and decreasing EEMT (1.2-1.3 MJ m2 decade-1). Although we do not know the timescales of CZ change, these results suggest an upward migration of CZ/ecosystem structure on the order of 100 m decade-1, and that decadal-scale differences in EEMT are similar to the differences between convergent/hydrologically subsidized and planar/divergent landscapes, which have been shown to be very different in vegetation and CZ structure.

  5. An integrated assessment of the impact of precipitation and groundwater on vegetation growth in arid and semiarid areas

    CERN Document Server

    Zhu, Lin; Dai, Zhenxue; Xu, Tingbao; Su, Xiaosi

    2014-01-01

    Increased demand for water resources together with the influence of climate change has degraded water conditions which support vegetation in many parts of the world, especially in arid and semiarid areas. This study develops an integrated framework to assess the impact of precipitation and groundwater on vegetation growth in the Xiliao River Plain of northern China. The integrated framework systematically combines remote sensing technology with water flow modeling in the vadose zone and field data analysis. The vegetation growth is quantitatively evaluated with the remote sensing data by the Normalized Difference Vegetation Index (NDVI) and the simulated plant water uptake rates. The correlations among precipitation, groundwater depth and NDVI are investigated by using Pearson correlation equations. The results provide insights for understanding interactions between precipitation and groundwater and their contributions to vegetation growth. Strong correlations between groundwater depth, plant water uptake and...

  6. Tritium Fluxes through the Shallow Unsaturated Zone adjacent to a Radioactive Waste Disposal Facility in an Arid Environment

    Science.gov (United States)

    Maples, S.; Andraski, B. J.; Stonestrom, D. A.; Cooper, C. A.; Pohll, G.

    2011-12-01

    Studies at the U.S. Geological Survey's Amargosa Desert Research Site (ADRS) in southern Nevada have documented long-distance (>400-m) tritium (3H) transport adjacent to a commercial, low-level radioactive waste disposal facility. Transport at this scale is orders of magnitude greater than anticipated; however, lateral 3H fluxes through the shallow unsaturated zone (UZ) have not been investigated in detail. The objective of this study is to estimate and compare lateral and vertical tritiated water-vapor (3HHOg) fluxes in the shallow UZ and their relation to the observed plume migration. Previous studies have recognized two distinct plumes of 3H emanating from the facility. Shallow (0.5 and 1.5-m depth) soil-water vapor samples were collected yearly along 400-m long transects through both plumes from 2003-09. Within the south plume, 3H concentrations at 1.5-m depth have decreased by 44 ± 0.3% during this period, and plume advancement there has effectively ceased (i.e., rate of advance equals rate of decay). During the same period, the west plume showed a net decrease in concentration of 34 ± 0.9% within 100-m of the facility; however, plume advancement is observed at the leading edge of the plume, and concentrations 200-300-m from the facility show an increase in 3H concentration of 64 ± 28.4%. Lateral and vertical diffusive fluxes within both plumes were calculated using 3HHOg concentrations from 2006. Lateral 3HHOg diffusive fluxes within both plumes have been estimated 25-300-m from the facility at 1.5-m depth. Mean lateral 3HHOg diffusive fluxes are 10-14 g m-2 yr-1 within the south plume, and 10-13 g m-2 yr-1 within the west plume. Mean lateral fluxes in the south plume are an order of magnitude lower than in the west plume. This behavior corresponds with the observed relative immobility of the south plume, while the elevated west plume fluxes agree with the plume advancement seen there. Shallow, upward directed, mean vertical 3HHOg fluxes 25-300-m from the

  7. Timing and causes of gully erosion in the riparian zone of the semi-arid tropical Victoria River, Australia: Management implications

    Science.gov (United States)

    McCloskey, G. L.; Wasson, R. J.; Boggs, G. S.; Douglas, M.

    2016-08-01

    Gully erosion in the seasonally wet tropics of Australia is a major source of sediment in rivers. Stabilization of gullies to reduce impacts on aquatic ecosystems and water storages is a focus for management. However, the cause of the gully erosion is poorly understood and so a critical context for soil conservation is missing. It is uncertain if they are the result of post-European cattle grazing or are they much older and related to non-human factors. The causes of riparian gully erosion along a reach of the Victoria River in the semi-arid tropics of Australia were investigated using several methods. Gully complexes were described and characterised by two major components: a Flood Drainage Channel (FDC) and upslope of this an Outer Erosion Feature (OEF) characterised by badlands set within an amphitheatre. The OEF is likely to be a major source of sediment that appears to be of recent origin. A review of historical records, combined with Optically Stimulated Luminescence (OSL) dating, showed that the FDCs were well established prior to the introduction of domestic stock. It also showed that the badlands began to develop about 90 years ago; that is, about 40 years after the arrival of domestic stock. In addition, an analysis of aerial photos coupled with an on-ground survey and analysis of fallout radionuclides revealed that erosion processes are still active within the gully complexes. While the FDCs are natural drainage channels, cattle grazing probably triggered the badland formation, with the expansion aided by increased rainfall in the past 40 years. Therefore, the OEFs are of human origin and protection from grazing of the riparian zone should slow badland erosion and reduce sediment input to the river.

  8. FEATURES OF THE DEVELOPMENT OF CORN HYBRIDS DEPENDING ON THE TERMS OF PLANTING AND TMTD-PLUS DISINFECTANT IN THE ARID ZONE CENTRAL CISCAUCASIA

    Directory of Open Access Journals (Sweden)

    Kravchenko R. V.

    2015-11-01

    Full Text Available There was given the review of the results of the study in the arid zone of Central Ciscaucasia, the influence of planting terms and presowing seed treatment by the drug called "TMTD-plus", containing the growth stimulator Krezatsin in its composition, on the development of corn hybrids of different maturity groups of the selection of Krasnodar Research Institute of Agriculture named after P.P. Lukyanenko (Ross 199, Ross 299, Krasnodar 382 and Krasnodar 410 and the All-Russian Research Institute of Corn (Mashuk 170, Newton, RIC 345 and Eric, as well as middlematurity population Rossiyskaya 1. The studies were conducted in accordance with the thematic plan of scientific researches of the chair of crop and forage production of the Stavropol State Agrarian University. The soil surface was presented as southern black earth. The technology of growing of maize on the experimental plot corresponds to the standard one for the present area and cultivar. The predecessor is winter wheat. Sowing was performed in three terms. The first (early sowing term was carried out at t = + 7 ... +8 ° C. The second (recommended - when t = + 10 ... + 12 ° C. The third (later sowing time was carried out at t = +15 ° C. The plant density: early-maturing hybrids – 70 thousand pieces/ha, is mid-maturing ones – 60 thousand pieces/ha, middle-ripe – 50 thousand piece/ha, middle-later ones – 45 thousand pieces/ha. The scheme is single-row, with spacing of 70 cm. The application of the studied drug TMTD-plus helped to reduce the growing season of maize plants for one - two days. Thus, changing the sowing terms of maize hybrids and populations, we can largely control the development of plants changing the length of the growing season to two weeks and form a harvesting conveyor, thereby reducing the intensity of field work

  9. Facteurs décisionnels dans la gestion des ressources hydriques par les éleveurs et agro-éleveurs dans une zone semi-aride du Burkina Faso

    Directory of Open Access Journals (Sweden)

    Zongo, BIN.

    2006-01-01

    Full Text Available Decisional Factors in the Water Resources Management by the Livestock Keepers and the Agropastoralist in a Semi-arid Zone of Burkina Faso. A survey was carried out in a semi-arid zone of Burkina Faso in order to determine the factors influencing water management by allochthonous livestock keepers and native agro-pastoralists. The results of the study showed that the availability of water and grazing land as well as some other factors influence the livestock keepers on the place where to settle in a zone. The village and the geographical origin of the producers can influence the utilisation of the different types of watering points. The study shows also that easy access, easy drawing of water and proximity influence their choices. These factors explain why livestock keepers and agropastoralists used on a rather high level (56 to 94% surface water to water cattle and sheep, and boreholes (41.1 to 76.9% to water sheep and goats. Surface water attracts farmers if the distance to cover does not exceed 4 km. The factors determining the behaviours of livestock keepers and agro-pastoralists in water management were similar. The type of watering point, the distance and the animal species influence their choices. They however present differences in the levels of using watering points.

  10. Isotherms and kinetic study of dihydrogen and hydrogen phosphate ions (H{2}PO{4}- and HPO{4}2-) adsorption onto crushed plant matter of the semi-arid zones of Morocco: Asphodelus microcarpus, Asparagus albus and Senecio anthophorbium

    Science.gov (United States)

    Chiban, M.; Benhima, H.; Saadi, B.; Nounah, A.; Sinan, F.

    2005-03-01

    In the present work H{2}PO4- and HPO42- ions adsorption onto organic matter (OM) obtained from ground dried three plants growing in arid zones of Morocco has been studied. The adsorption process is affected by various parameters such as contact time, particle size and initial concentration of phosphate solution (Ci ≤ 30 mg/l). The uptake of both ions is increased by increasing the concentration of them selves. The retention of phosphate ions by Asphodelus microcarpus, Asparagus albus are well defined by several isotherms such as the Langmuir, Temkin and Freundlich.

  11. An analytical model for predicting transport in a coupled vadose/phreatic system

    Energy Technology Data Exchange (ETDEWEB)

    Tomasko, D.

    1997-05-01

    A simple analytical model is presented for predicting the transport of a contaminant in both the unsaturated (vadose) and saturated (phreatic) zones following a surficial spill. The model incorporates advection, dispersion, adsorption, and first-order decay in both zones and couples the transport processes at the water table. The governing equation is solved by using the method of Laplace transforms, with numerical inversion of the Laplace space equation for concentration. Because of the complexity of the functional form for the Laplace space solution, a numerical methodology using the real and imaginary parts of a Fourier series was implemented. To reduce conservatism in the model, dilution at the water table was also included. Verification of the model is demonstrated by its ability to reproduce the source history at the surface and to replicate appropriate one-dimensional transport through either the vadose or phreatic zone. Because of its simplicity and lack of detailed input data requirements, the model is recommended for scoping calculations.

  12. Evapotranspiration And Geochemical Controls On Groundwater Plumes At Arid Sites: Toward Innovative Alternate End-States For Uranium Processing And Tailings Facilities

    Energy Technology Data Exchange (ETDEWEB)

    Looney, Brian B.; Denham, Miles E.; Eddy-Dilek, Carol A.; Millings, Margaret R.; Kautsky, Mark

    2014-01-08

    Management of legacy tailings/waste and groundwater contamination are ongoing at the former uranium milling site in Tuba City AZ. The tailings have been consolidated and effectively isolated using an engineered cover system. For the existing groundwater plume, a system of recovery wells extracts contaminated groundwater for treatment using an advanced distillation process. The ten years of pump and treat (P&T) operations have had minimal impact on the contaminant plume – primarily due to geochemical and hydrological limits. A flow net analysis demonstrates that groundwater contamination beneath the former processing site flows in the uppermost portion of the aquifer and exits the groundwater as the plume transits into and beneath a lower terrace in the landscape. The evaluation indicates that contaminated water will not reach Moenkopi Wash, a locally important stream. Instead, shallow groundwater in arid settings such as Tuba City is transferred into the vadose zone and atmosphere via evaporation, transpiration and diffuse seepage. The dissolved constituents are projected to precipitate and accumulate as minerals such as calcite and gypsum in the deep vadose zone (near the capillary fringe), around the roots of phreatophyte plants, and near seeps. The natural hydrologic and geochemical controls common in arid environments such as Tuba City work together to limit the size of the groundwater plume, to naturally attenuate and detoxify groundwater contaminants, and to reduce risks to humans, livestock and the environment. The technical evaluation supports an alternative beneficial reuse (“brownfield”) scenario for Tuba City. This alternative approach would have low risks, similar to the current P&T scenario, but would eliminate the energy and expense associated with the active treatment and convert the former uranium processing site into a resource for future employment of local citizens and ongoing benefit to the Native American Nations.

  13. Diarrhea in Pre-Weaned Calves: Relative Risk Rates for Morbidity and Mortality in 13 Commercial Farms of Hot Arid Zone

    OpenAIRE

    M. A. Razzaque; Al-Mutawa, T; S.A. MOHAMMED

    2010-01-01

    Problem statement: In many hot arid countries, pregnant Holstein Friesian heifers are imported for herd replacement. The calves obtained from exotic cows are exposed to adverse climate in feedlot system resulting in very high morbidity and mortality rates. Diarrhea, dehydration and deaths are causing a major loss to the producers. This study examines the Risk Rates (RR) for morbidity and mortality in pre-weaned calves. Approach: Thirteen commercial dairy farms of small, me...

  14. Seepage weathering impacts on erosivity of arid stream banks: A new conceptual model

    Science.gov (United States)

    Nachshon, Uri

    2016-05-01

    Field observations have indicated the formation of horizontal, pipe shape cavities, along gully and dry stream channel banks in the semi-arid region of the northern Negev Desert, Israel. Piping is a well-known phenomenon in humid regions due to subsurface water flow and seepage weathering. However, in dry environments where rain events are scarce and subsurface water flow is rare, it is proposed here that capillary flow of saline water in the vadose zone leads to similar processes. It is suggested that where saline and shallow ground water persists, capillary flow may result in salt accumulation and precipitation at the top of the capillary fringe, consequently rendering this zone to be more susceptible to erosion. A conceptual model is presented and field observations, laboratory experiments, and a physically-based model are used to prove the feasibility of the proposed conceptual model and to explain why salts accumulate at the top of the capillary fringe, even though evaporation acts all along the vertical stream channel or gully banks. It is suggested that the low evaporative flux, in comparison to the liquid water flux, disables salt accumulation along the profile to the top of the capillary fringe where the liquid water flux is minimal. The presented findings strengthen the conceptual model, but thorough field studies are needed to estimate the impact of the proposed mechanism on erosion processes on a field scale.

  15. RECOMMEND OF HIGH-YIELDING HYBRID MILLET DEVELOPMENT IN CENTRAL ARID ZONE OF NINGXIA%宁夏中部干旱带发展高产杂交谷子产业的建议

    Institute of Scientific and Technical Information of China (English)

    马力文; 刘静; 周斌; 刘维斌; 杨立文; 席国术

    2016-01-01

    Ningxia is a severe water scarcity province in China. Under the background of global warming, the drought on central arid zone has intensified, the contradiction between water supply and demand is increasingly prominent, and food production is low and long-term instability. Ecological migrants faced enormous pressure to get rid of poverty, and survival and development problems became prominent. Since 2010, Ningxia meteorological department successfully introduced a series of hybrid millet varieties in the central arid zone, carried out a large se-ries of hybrid millet experimental study, and promoted the planting areas to nearly 667hm2 . In this paper, under the very dry year of 2011 , the comparative cost-effectiveness and prospects of high-yielding hybrid millet with local mainly cultivars was analyzed. The results showed that the cultivation of hybrid millet can save water resources, re-sist heavy drought, and increase more than double yield comparing with the traditional local millet yields. Due to the high price of small grains, farmers' income was generally higher than that planting other crops. Based on the Zhang hybrid millet experiment and demonstration, combined with the distribution of agricultural climate resources, the Ningxia Zhang hybrid millet cultivated climatic suitability zoning map was obtained. Different areas suitable va-rieties for cultivation, methods and planting risks were analyzed. It recommended to actively and steadily develop hybrid millet cultivation in the central arid zone of Ningxia,strengthen hybrid millet yield cultivation and water-saving technology training, and establish millet cultivation-processing-marketing service system becoming a new way for the central arid zone farmers to get rich.%宁夏水资源严重匮乏,在全球气候变暖背景下,中部干旱带干旱有所加剧,水资源供需矛盾日益突出,粮食产量长期低而不稳,生态移民脱贫压力大,生存与发展问题突出.2010

  16. Ecological opportunity and the evolution of habitat preferences in an arid-zone bird: implications for speciation in a climate-modified landscape.

    Science.gov (United States)

    Norman, Janette A; Christidis, Les

    2016-01-20

    Bioclimatic models are widely used to investigate the impacts of climate change on species distributions. Range shifts are expected to occur as species track their current climate niche yet the potential for exploitation of new ecological opportunities that may arise as ecosystems and communities remodel is rarely considered. Here we show that grasswrens of the Amytornis textilis-modestus complex responded to new ecological opportunities in Australia's arid biome through shifts in habitat preference following the development of chenopod shrublands during the late Plio-Pleistocene. We find evidence of spatially explicit responses to climatically driven landscape changes including changes in niche width and patterns of population growth. Conservation of structural and functional aspects of the ancestral niche appear to have facilitated recent habitat shifts, while demographic responses to late Pleistocene climate change provide evidence for the greater resilience of populations inhabiting the recently evolved chenopod shrubland communities. Similar responses could occur under future climate change in species exposed to novel ecological conditions, or those already occupying spatially heterogeneous landscapes. Mechanistic models that consider structural and functional aspects of the niche along with regional hydro-dynamics may be better predictors of future climate responses in Australia's arid biome than bioclimatic models alone.

  17. Effet du biotope sur la diversité floristique et le polymorphisme phénotypique des groupements à Tamarix africana Poir. dans les zones arides de la région de Khenchela (Est Algerien

    Directory of Open Access Journals (Sweden)

    Khabtane Abdelhamid

    2012-12-01

    Full Text Available RESUME Le genre Tamarix (Tamaricaceae regroupe plus de 80 espèces, parmi eux le Tamarix africana Poir. qui représente une très grande ubiquité en Algérie, soit du point de vue climatique (humidité et sécheresse, édaphique (sols salés et calcaires; où il représente l’espèce  à caractère typique des plantes thermo xérophytes. Pour contribuer à la connaissance de cette espèce et de son comportement nous avons essayé de suivre le comportement  phytosociologique ainsi que sa variabilité morphologique (l’hauteur, le recouvrement basale, nombre des ramifications à la base.. dans trois biotopes, extrêmement différents du point de vue climatique et édaphique,  dans les zones steppiques arides de la région de Khenchela (Est Algérien et qui sont  choisis  selon un transect Nord - Sud. Les résultats révèlent que les groupements à Tamarix africana Poir. représentent une richesse floristique importante, qui se diffère d’un site à l’autre, avec un polymorphisme phénotypique adaptée aux conditions spécifiques à chacun des trois sites et qui lui permet d’être l’espèce à forme arbustive  la plus adaptée pour la réhabilitation des écosystèmes dégradés dans les zones de transitions Désert-NordMots clés Tamarix africana P. - ubiquité- thermo xérophytes-  régions arides- halophytes- polymorphisme phénotypique

  18. Disentangling the impacts of climate and human colonization on the flora and fauna of the Australian arid zone over the past 100 ka using stable isotopes in avian eggshell

    Science.gov (United States)

    Miller, Gifford H.; Fogel, Marilyn L.; Magee, John W.; Gagan, Michael K.

    2016-11-01

    Throughout the Quaternary, the flora and fauna of Australia evolved and adapted to the high-amplitude, low- and high-frequency climate changes that characterized the ice-age cycles. However, during the last glacial cycle, between ∼120 and 15 ka, unprecedented irreversible changes in flora and fauna occurred, and in that same interval modern humans established their first firm presence in the landscape. Disentangling the impacts of the first-order trend toward a colder, drier planet through the Late Quaternary from the impacts of human colonization has been challenging, from both the chronological and paleoenvironmental perspectives. We utilize the stable isotopes of carbon and oxygen preserved in near-continuous time series of Dromaius (emu) eggshell from five regions across Australia to provide independent reconstructions of ecosystem status and climate over the past 100 ka. Carbon isotopes are determined by the diet consumed by the female bird, whereas oxygen isotopes record the status of local moisture balance in the months prior to breeding. Together, δ13C and δ18O provide ecosystem status and climate from the same dated sample, reducing correlation uncertainties between proxies. Combined with recent improvements in the chronologies of Late Quaternary shorelines fringing inland lake basins and deflation during arid times, these data collectively reaffirm that Australia generally became increasingly, albeit irregularly, drier from the last interglaciation through to the last glacial maximum. Dromaius eggshell δ18O documents peak aridity between 30 and 15 ka, but shows no evidence of exceptional climate change between 60 and 40 ka. In contrast, Dromaius δ13Cdiet documents an irreversible loss of the majority of palatable summer-rainfall-related C4 grasses across the Australian arid zone between 50 and 45 ka, about the same time that the giant megafaunal bird, Genyornis, became extinct, and coincident with human dispersal across the continent. Our data

  19. Spatial assessment of soil organic carbon and physicochemical properties in a horticultural orchard at arid zone of India using geostatistical approaches.

    Science.gov (United States)

    Singh, Akath; Santra, Priyabrata; Kumar, Mahesh; Panwar, Navraten; Meghwal, P R

    2016-09-01

    Soil organic carbon (SOC) is a major indicator of long-term sustenance of agricultural production system. Apart from sustaining productivity, SOC plays a crucial role in context of climate change. Keeping in mind these potentials, spatial variation of SOC contents of a fruit orchard comprising several arid fruit plantations located at arid region of India is assessed in this study through geostatistical approaches. For this purpose, surface and subsurface soil samples from 175 locations from a fruit orchard spreading over 14.33 ha area were collected along with geographical coordinates. SOC content and soil physicochemical properties of collected soil samples were determined followed by geostatistical analysis for mapping purposes. Average SOC stock density of the orchard was 14.48 Mg ha(-1) for 0- to 30-cm soil layer ranging from 9.01 Mg ha(-1) in Carissa carandas to 19.52 Mg ha(-1) in Prosopis cineraria block. Range of spatial variation of SOC content was found about 100 m, while two other soil physicochemical properties, e.g., pH and electrical conductivity (EC) also showed similar spatial trend. This indicated that minimum sampling distance for future SOC mapping programme may be kept lower than 100 m for better accuracy. Ordinary kriging technique satisfactorily predicted SOC contents (in percent) at unsampled locations with root-mean-squared residual (RMSR) of 0.35-0.37. Co-kriging approach was found slightly superior (RMSR = 0.26-0.28) than ordinary kriging for spatial prediction of SOC contents because of significant correlations of SOC contents with pH and EC. Uncertainty of SOC estimation was also presented in terms of 90 % confidence interval. Spatial estimates of SOC stock through ordinary kriging or co-kriging approach were also found with low uncertainty of estimation than non-spatial estimates, e.g., arithmetic averaging approach. Among different fruit block plantations of the orchard, the block with Prosopis cineraria ('khejri') has

  20. Effect of meteorologic conditions on total suspended particulate (TSP) levels and elemental concentration of aerosols in a semi-arid zone (Beer-Sheva, Israel)

    Energy Technology Data Exchange (ETDEWEB)

    Kushelevsky, A.; Shani, G.; Haccoun, A. (Ben-Gurion Univ. of the Negev, Beersheba (Israel). Dept. of Nuclear Engineering)

    1983-02-01

    The total suspended particulate (TSP) levels in Beer-Sheva, situated in a semi-arid area with winds bringing in dust from the surrounding deserts, was measured 41 times between June 1977 and May 1978. The TSP levels are correlated with climatic conditions. High TSP levels (890 +- 250 ..mu..g m-/sup 3/) were found during Sharav conditions and sandstorms (hot, dry weather, typical to this region). Low TSP levels (59 +- 28 ..mu..g m-/sup 3/) were found in the winter following rain. Usual TSP levels were found to be 140 +- 20 ..mu..g m-/sup 3/ occurring during normal weather conditions. The elemental composition of the Beer-Sheva aerosols were determined using instrumental neutron activation analysis (INNA) and X-ray Fluorescence (XRF). The concentrations of the following elements Fe, Na, Br, K, Sm, Au, Sb, Ga, La, Yb, Lu, Se, Hg, Cr, Sc, Rb, Co, Ta and Zn were determined by INNA and Ca, Si, S, Ti, Cl, Pb, Fe, V, Ni and Mn by XRF. Their relative abundances were found to depend on the prevailing TSP level.

  1. Tracer-based studies of soil water movement in semi-arid forests of New Mexico

    Science.gov (United States)

    Newman, Brent D.; Campbell, Andrew R.; Wilcox, Bradford P.

    1997-09-01

    The related issues of water movement and contaminant transport in arid and semi-arid environments have generated considerable interest and concern in the last few decades. Essential to understanding these issues is knowledge of how water moves through the soils that form the uppermost part of the vadose zone. The use of tracers, both natural and artificially introduced, is proving to be an effective method for gaining such knowledge in dry regions, where investigation by other means is difficult. In this study, natural stable-isotope and chloride tracers were used to investigate water movement in the soils of a piñon-juniper woodland and of a ponderosa pine forest on the Pajarito Plateau in northern New Mexico. The objectives were to (1) estimate and compare near-surface flux rates and evaluate the importance of evaporation in the two communities, and (2) determine to what extent differences in flux rates and evaporation are due to differences in plant cover and/or soil hydraulic properties. The results of this study will aid in evaluating the potential for contaminant mobility in semi-arid systems such as the Pajarito Plateau and, in addition, will increase understanding of nutrient distributions and plant water use in semi-arid environments. The stable-isotope data indicate a similarity between the piñon-juniper and ponderosa communities with respect to evaporation: in both, it is restricted mainly to the upper 10 cm of soil. Chloride profiles from the two communities, on the other hand, show a distinct difference with respect to downward fluxes: in the ponderosa pine forest, these fluxes (≈0.02 cm year -1) are an order of magnitude lower than those in the piñon-juniper woodland (≈0.2 cm year -1), even though total precipitation is about 4 cm year -1 higher in the ponderosa pine forest. This difference, however, appears to be related not to plant cover, but to differences in soil hydraulic properties. The soils of the ponderosa pine forest contain clay

  2. 宁夏中部干旱带天然草地气候生产潜力研究%Potential Climatic Productivity of Natural Grassland in the Middle Arid Zone of Ningxia

    Institute of Scientific and Technical Information of China (English)

    马甜; 王俊波; 张治华; 徐秀梅

    2013-01-01

    The annual potential productivity of grassland in the middle arid zone of Ningxia during 1975 to 2006 was estimated according to the ten-day period temperature and precipitation of these years (1975 - 2010) recorded by 10 meteorological observatories using Miami model and Thornthwaite Memorial model. The objects were to analyze the change regulation of the potential climatic productivity and provide a theoretical basis for improving grassland and increasing vegetation. Results showed that the climate in the middle arid zone of Ningxia had a change tendency toward "warm dry". The inter-annual variation range of the grassland potential climatic productivity was 2668. 56~7499. 53 kg · hm-2 · a-1 and the potentiality was large. The grassland potential climatic productivity increased or decreased 58. 68 kg · hm-2 · a-1 with the maximum temperature increasing or decreasing 1℃. The grassland potential climatic productivity increased or decreased 18. 64 kg · hm-2 · a-1 with the annual precipitation increasing or decreasing 1 mm. The annual precipitation and potential climatic productivity in the middle arid zone of Ningxia had an extremely significant linear correlation and the correlation coefficient was 0. 984 ~0. 997, whereas the average annual temperature and potential climatic productivity did not have a significant correlation. Therefore, the natural tolerance, namely potential climatic productivity of the natural grassland of the area, should be considered when planting.%依据宁夏中部干旱带同心县、盐池县等10个代表性气象台站36年(1975-2010年)逐旬气温、降水资料,基于Miami模型和Thornthwaite Memorial模型对宁夏中部干旱带1975-2006年间草地生产潜力作估算,并分析其变化规律,旨在为改良草地、植被恢复提供理论依据.结果表明:宁夏中部干旱带气候具有向“暖干化”变化的趋势,草地气候生产潜力年际变化范围为2668.56~7499.53kg·hm-2·a-1,气候生产潜力较

  3. Diarrhea in Pre-Weaned Calves: Relative Risk Rates for Morbidity and Mortality in 13 Commercial Farms of Hot Arid Zone

    Directory of Open Access Journals (Sweden)

    M. A. Razzaque

    2010-01-01

    Full Text Available Problem statement: In many hot arid countries, pregnant Holstein Friesian heifers are imported for herd replacement. The calves obtained from exotic cows are exposed to adverse climate in feedlot system resulting in very high morbidity and mortality rates. Diarrhea, dehydration and deaths are causing a major loss to the producers. This study examines the Risk Rates (RR for morbidity and mortality in pre-weaned calves. Approach: Thirteen commercial dairy farms of small, medium and large sizes were surveyed using 1,280 newborn calves. A survey was conducted for calves from their birth to weaning at 90 day. Parameters of the study were birth weights, colostrum feeding, growth rate, incidences of diseases, clinical symptoms, post-mortem findings and results of laboratory investigations of samples obtained from sick and dead calves. Calf housing and feeding management of 13 farms were investigated. Results: RR for morbidity and mortality ranged from 0.3-1.00 and being highest during the first week. Most common disease was diarrhea representing 90.6% of the total calves affected. Common pathogens causing diarrhea were E. coli, Salmonella sp. Klebsiella, Pasturella and rotavirus. Relationship between calf management and morbidity RR for diarrhea was significant (r2 = 627, p = 0.01 and the growth rate was positively correlated (r2 = 0.761, p = 0.1. Diarrhea caused a significant negative impact on gross margins of the calf enterprises. Conclusion: Colostrum feeding and housing management were the key factors for causing a high RR for morbidity and mortality. Gross margin loss was significantly influenced by morbidity and mortality RR of calves.

  4. The International Workshop on Environmental Changes and Sustainable Development in Arid and Semi-arid Regions

    Institute of Scientific and Technical Information of China (English)

    Xiaoping Yang; Arthur Conacher

    2007-01-01

    @@ Arid regions,dominated by deserts,are characterized by a severe shortage of moisture,and a lack of perennial and integrated systems of drainage.Distributed over a very large range of temperatures,from the very hot to the very cold zones,arid regions cover about one third of the world's land surface and occur in every continent,including Antarctica.

  5. Biodegradation of Petroleum Hydrocarbon Vapors in the Vadose Zone

    Science.gov (United States)

    The current state of practice to estimate the risk from intrusion of vapors of petroleum hydrocarbons from spills of gasoline is to measure the concentration of the chemical of concern in ground water under the spill, use Henry’s Law to estimate a concentration of the chemical ...

  6. SUMMARY PAPER: IN SITU BIOREMEDIATION OF CONTAMINATED VADOSE ZONE SOIL

    Science.gov (United States)

    The Robert S. Kerr Environmental Research Laboratory (RSKERL) has developed a number of Issue Papers and Briefing Documents which are designed to exchange up-to-date information related to the remediation of contaminated soil and ground water at hazardous waste sites. In an attem...

  7. In Situ Bioremediation of Perchlorate in Vadose Zone Source Areas

    Science.gov (United States)

    2011-01-01

    Metal_ RL IDL Alwunum 200 28 Antimony 6 . 0 1. 4 Arsenl.c 3 . 0 1.2 San.um 200 Beryl lium 1.0 . 1 Boron 100 1.5 Cadmium 4 . 0 . 4 Calc1.um...QC Lunit s: result < RL Tl.me : Samp le I O: Metal_ RL IDL Alwunum 200 28 Antimony 6 . 0 1. 4 Arsenl.c 3 . 0 1.2 San.um 200 Beryl lium 1.0...Arsenl.c 3 . 0 1.2 San.um 200 Beryl lium 1.0 . 1 Boron 100 1.5 Cadmium 4 . 0 . 4 Ca lc1.um 5000 31 Chr omium 10 . 3 Cobalt 50 . 3 Copper 25

  8. OPTIMIZING BIOVENTING IN SHALLOW VADOSE ZONES AND COLD CLIMATES

    Science.gov (United States)

    This paper describes a bioventing study design and initial activities applied to a JP-4 jet fuel spill at Eielson Air Force Base, Alaska. The primary objectives of the project were to investigate the feasibility of using bioventing technology to remediate JP-4 jet fuel contaminat...

  9. Relationship between the Salt Accumulation and the Drought Resistance in Several Woody Plants in Arid Zone%干旱区木本植物盐分积累与其耐旱性的关系

    Institute of Scientific and Technical Information of China (English)

    柏新富; 朱建军; 王仲礼; 谭永芹; 刘林德

    2012-01-01

    The plants in arid zones tend to accumulate more salt because the evaporation is much higher than the rainfall in arid environment, and because the selective uptake of water by plant roots results in the rise of salt concentration in solutions in the rhizosphere. In this study, parameters such as the Na+ and K+ concentrations, as well as the water status and photosynthesis were measured and analyzed. The results showed that H. ammodendron and T. ramosissima were able to absorb and accumulate more Na+ than H. scoparium and E. angustifolia. In accordance, H. scoparium and T. ramosissima also had lower water potentials and osmotic potentials in their tissues, as well as lower transpiration and larger range of water potential for effective photosynthesis than H. scoparium and E. angustifolia. There was a negative correlation between the Na+ concentration and the water/osmotic potentials of the plants, a negative correlation between the Na+ concentration and the transpirational water loss; but a positive correlation between the Na+ concentration and the range of water potential for effective photosynthesis. It is therefore concluded that the salt accumulation could decrease the osmotic potential and water potential of plant tissues, enhance the driving force of water absorption, and reduce the transpiration of the plants, which was beneficial for the plants to retain a relatively higher photosynthesis, implying that salt accumulation in plants could enhance the drought resistance of the plant species in arid zone.%通过对干旱区4种木本植物体内Na+,K+浓度和水分、光合等指标的测定、比较,分析盐分积累与其耐旱性的关系.结果表明:梭梭和柽柳能够吸收、积累较多的Na+,而花棒和沙枣组织Na+浓度相对较低;与花棒和沙枣相比,梭梭和柽柳具有较低的组织水势和渗透势、较小的蒸腾失水量和较大光合作用有效水势范围.表现为植株水势、渗透势和蒸腾失水量与其组织Na

  10. Simulation analysis on the regulation of overflow ecological water consumption in arid areas——A case study in the Canmrik ecological area of the mainstream zone of the Tarim River

    Institute of Scientific and Technical Information of China (English)

    CHEN Xi; HUANG Yue; QIAN Jing; LIU HaiLong; FENG XianWei; LIU Ying; BAO AnMing; WANG WeiSheng

    2007-01-01

    After analyzing the regulation of overflow ecological water consumption in the Canmrik ecological area of mainstream zone of the Tarim River, in this paper a model of ecological bifurcation is developed, the dynamic overflow process of ecological bifurcation is simulated, and the quantitative relationships between the volume of ecological water consumption and the ecological conservation extent and overflow time are analyzed using GIS, advance of freshet and RS means. The results reveal that the effects of discharge and time of ecological bifurcation on the efficiency of ecological water consumption are significant, there is a geometrical exponential relationship between the efficiency of ecological bifurcation and the water supply with different discharges and different times under the same ecological water consumption, hypsography plays an important role in ecological water consumption, the regulation of ecological water consumption cannot be equated with the ordinary farming irrigation system, a serious water waste will result and the prospective ecological benefits will not be able to be achieved if an ordinary ecological bifurcation is implemented. The efficiency of ecological water consumption can be increased by 30% by selecting the bifurcation schemes in an optimized way, which is of the utmost importance for arid areas with shortage of water resources.

  11. Fluid inclusions in vadose cement with consistent vapor to liquid ratios, Pleistocene Miami Limestone, southeastern Florida

    Science.gov (United States)

    Barker, C.E.; Halley, R.B.

    1988-01-01

    Vadose cements in the Late Pleistocene Miami Limestone contain regions with two-phase aqueous fluid inclusions that have consistent vapor to liquid (V-L) ratios. When heated, these seemingly primary inclusions homogenize to a liquid phase in a range between 75??C and 130??C (mean = 100??C) and have final melting temperatures between -0.3?? and 0.0??C. The original distribution of Th was broadened during measurements because of fluid inclusion reequilibration. The narrow range of Th in these fluid inclusions suggest unusually consistent V-L ratios. They occur with small, obscure, single phase liquid-filled inclusions, which infer a low temperature origin (less than 60??C), and contradict the higher temperature origin implied by the two phase inclusions. The diagenetic environment producing these seemingly primary fluid inclusions can be inferred from the origin of the host calcite enclosing them. The ??18O composition of these cements (-4 to-5.5%., PDB) and the fresh water in the fluid inclusions are consistent with precipitation from low-temperature meteoric water. The carbon-isotope composition of the vadose cements that contain only rare two-phase fluid inclusions are comparable to the host rock matrix (??13C between 0 and +4%., PDB). Cements that contain common two-phase fluid-inclusions have a distinctly lighter carbon isotopic composition of -3 to -5%.. The carbon isotope composition of cements that contain common two-phase inclusions are about 6%. lighter than those of other vadose cements; models of early meteoric diagenesis indicate that this is the result of precipitation from water that has been influenced by soil gas CO2. Our hypothesis is that the primary fluid inclusions, those with consistent V-L ratios and the single-phase liquid inclusions, form at near-surface temperature (25??C) and pressure when consistent proportions of soil gas and meteoric water percolating through the vadose zone are trapped within elongate vacuoles. This study corroborates

  12. 种植枸杞对干旱区荒漠缓冲带土壤质量的影响%Research on Soil Quality of Planting Lycium barbarum in Arid Desert Buffer Zone

    Institute of Scientific and Technical Information of China (English)

    牟宗江; 何学敏; 孙景鑫; 吕光辉

    2011-01-01

    [ Objective] A comparative analysis was conducted about the soil pH, organic matter, total soil N and C/N before and after planting Lycium barbarum in Arid Desert Buffer Zone of National Nature Reserve in the Ebinur Wetland and the condition of soil comprehensive quality changes was evaluated in order that the basis for protecting areas soil and water conservation and planting economic crops could be provided. [Method] Through artificial cultivation and indoor experiments, the physical and chemical properties and comprehensive quality status of soil samples before and after planting the Lycium barbarum and the surrounding natural control samples were evaluated and analyzed. [ Result ] Short - term weather changes insignificantly impacted on soil pH, total salt and total nitrogen, while the influence on surface soil organic matter was stronger; Effects of Artificial cultivation, planting and irrigation on soil physical and chemical properties were strong, such as reducing the soil pH and total salt, which was helpful to the improvement of soil salinization, while reducing soil organic matter and total nitrogen at the same time; The orders about integrated soil quality index of April, August, the experimental group and contrast group were that August test group < April < August contrast group. [ Conclusion ] Newly planted Lycium barbarum plantation played a certain role in the improvement of soil salinization in arid desert buffer zone, but exacerbated the soil poor degree. Under natural conditions, soil quality showed increasing trend from spring to summer, and Lycium barbarum cultivation reduced the soil quality to some extent.%[目的]对艾比湖湿地国家级自然保护区荒漠边缘缓冲带枸杞种植前后土壤的pH、总盐、有机质、全氮及C/N进行比较分析,评价其土壤综合质量变化情况,为保护区水土保持和经济作物种植提供依据.[方法]通过人工栽培和室内试验,对枸杞种植前后及周边自然对照土

  13. Occurrence and spatial distribution of emerging contaminants in the unsaturated zone. case study: Guadalete River basin (Cadiz, Spain).

    Science.gov (United States)

    Corada-Fernández, Carmen; Jiménez-Martínez, Joaquín; Candela, Lucila; González-Mazo, Eduardo; Lara-Martín, Pablo A

    2015-01-01

    Irrigation with reclaimed water is becoming a common practice in arid- and semi-arid regions as a consequence of structural water resource scarcity. This practice can lead to contamination of the vadose zone if sewage-derived contaminants are not removed properly. In the current work, we have characterized soils from the Guadalete River basin (SW Spain), which are often irrigated with reclaimed water from a nearby wastewater treatment plant and amended using sludge. Physico-chemical, mineralogical and hydraulic properties were measured in soil samples from this area (from surface up to 2 m depth). Emerging contaminants (synthetic surfactants and pharmaceutically active compounds, or PhACs) were also determined. Synthetic surfactants, widely used in personal care products (PCPs), were found in a wide range of concentrations: 73-1300 μg kg(-1) for linear alkylbenzene sulfonates (LAS), 120-496 μg kg(-1) for alkyl ethoxysulfates (AES), 19-1090 μg kg(-1) for alcohol polyethoxylates (AEOs), and 155-280 μg kg(-1) for nonylphenol polyethoxylates (NPEOs). The presence of surfactant homologues with longer alkyl chains was predominant due to their sorption capacity. A positive correlation was found between LAS and AEOs and soil organic carbon and clay content, respectively. Out of 64 PhACs analyzed, only 7 were detected occasionally (diclofenac, metoprolol, fenofibrate, carbamazepine, clarithromycin, famotidine and hydrochlorothiazide), always at very low concentrations (from 0.1 to 1.3 μg kg(-1)).

  14. Integrated approach to ecohydrology of semi-arid sites in areas of complex topography and biome transitions

    Science.gov (United States)

    Gutierrez, H. A.; Ivanov, V. Y.; Vivoni, E. R.; Bras, R. L.

    2005-05-01

    Vegetation constitutes an essential link in the hydrologic cycle at the land surface - atmosphere interface. Vegetation exerts a predominant control over the partition of rainfall into soil infiltration and evapotranspiration and determines to a great extent the water budget of entire regions. Conversely, water availability has a strong influence on the vegetation dynamics, including growth rates and overall health. In semiarid areas, changes in vegetation composition can follow slight variations in climate-derived moisture availability that, in turn, have a feedback effect on the surface water and energy balance. In this study, we present an integrated approach for studying the ecohydrology of semiarid regions characterized by complex topography and transitions between different vegetation life forms (grasses, shrubs, trees). We first present a set of hypotheses on the interaction between vegetation, landscape conditions, and climate variability in biome transitions zones. These hypotheses will be tested via the combination of numerical modeling and field data collection in the Sevilleta National Wildlife Refuge, central New Mexico. The field site is a first-order drainage basin consisting of two opposing hillslopes that differentially support a shrub-grass ecosystem and a conifer-grass community. Our modeling approaches consist of an ecohydrological module coupled to a 1-D vadose zone model as well as a more complex 3-D ecohydrological framework capable of simulating full vegetation dynamics at the watershed scale. The field instrumentation and model development efforts will be used synergistically to improve our understanding of the ecohydrology of semiarid complex watersheds. We then present an analysis of the ecohydrological model simulations driven by short- term meteorological data (~10 years) as well as by longer term, synthetically-generated climate scenarios. In particular, we will focus on the response of different vegetation communities to the

  15. 宁夏中部干旱区定位培肥对耕地土壤微生物的影响%Effect of Positioning Fertilization on Soil Microorganism in Middle Arid Zone of Ningxia

    Institute of Scientific and Technical Information of China (English)

    牛红霞; 马琨

    2015-01-01

    为了探明适宜宁夏中部干旱区的培肥方式,通过长期田间定位培肥,利用BIOLOG技术与田间试验相结合,研究了不同培肥方式对土壤微生物群落结构及功能的影响。结果表明:化肥配施羊粪能有效提高土壤有机质、全氮、速效磷和速效钾的含量,化肥配施生物有机肥提高了碱解氮和全磷含量;化肥配施黄腐酸钾能有效降低土壤中真菌的含量,提高土壤中细菌和放线菌的含量;化肥配施黄腐酸钾为土壤提供了丰富的碳源,可以提高土壤微生物活性,促进土壤微生物功能多样性,提高了土壤对氨基酸、芳香类化合物的利用率。综合分析认为,化肥配施黄腐酸钾对于改善土壤微生物群落结构及功能多样性效果最佳,其次为化肥配施羊粪。%In order to find the suitable soil fertilization approach for the Middle Arid Zone of Ningxia, the effects of different soil fertilization approaches on the structure and function of the soil microbial community were studied through long-term field positioning fertilization and combining the BIOLOG technology with field experiment. The results showed that using fer-tilizer together with sheep manure could upgrade the content of soil organic matter, total nitrogen, available phosphorus and available potassium effectively; using fertilizer together with biological organic fertilizer had improved the nitrogen and phos-phorus content; using fertilizer together with fulvic acid potassium could reduce the content of fungi in the soil, increase the content of bacteria and actinomycetes in the soil effectively; using fertilizer together with fulvic acid potassium provided a rich source of carbon and could improve the soil microbial activity, promote the microbial diversity and had improved the soil’s utilization rate of amino acids and aromatic compound. By comprehensive analysis, it is concluded that the effect of using fertilizer together with

  16. Modeling the distributed effects of forest thinning on the long-term water balance and streamflow extremes for a semi-arid basin in the southwestern US

    Science.gov (United States)

    Moreno, Hernan A.; Gupta, Hoshin V.; White, Dave D.; Sampson, David A.

    2016-03-01

    To achieve water resource sustainability in the water-limited southwestern US, it is critical to understand the potential effects of proposed forest thinning on the hydrology of semi-arid basins, where disturbances to headwater catchments can cause significant changes in the local water balance components and basinwise streamflows. In Arizona, the Four Forest Restoration Initiative (4FRI) is being developed with the goal of restoring 2.4 million acres of ponderosa pine along the Mogollon Rim. Using the physically based, spatially distributed triangulated irregular network (TIN)-based Real-time Integrated Basin Simulator (tRIBS) model, we examine the potential impacts of the 4FRI on the hydrology of Tonto Creek, a basin in the Verde-Tonto-Salt (VTS) system, which provides much of the water supply for the Phoenix metropolitan area. Long-term (20-year) simulations indicate that forest removal can trigger significant shifts in the spatiotemporal patterns of various hydrological components, causing increases in net radiation, surface temperature, wind speed, soil evaporation, groundwater recharge and runoff, at the expense of reductions in interception and shading, transpiration, vadose zone moisture and snow water equivalent, with south-facing slopes being more susceptible to enhanced atmospheric losses. The net effect will likely be increases in mean and maximum streamflow, particularly during El Niño events and the winter months, and chiefly for those scenarios in which soil hydraulic conductivity has been significantly reduced due to thinning operations. In this particular climate, forest thinning can lead to net loss of surface water storage by vegetation and snowpack, increasing the vulnerability of ecosystems and populations to larger and more frequent hydrologic extreme conditions on these semi-arid systems.

  17. Modeling the distributed effects of forest thinning on the long-term water balance and stream flow extremes for a semi-arid basin in the southwestern US

    Directory of Open Access Journals (Sweden)

    H. A. Moreno

    2015-10-01

    Full Text Available To achieve water resources sustainability in the water-limited Southwestern US, it is critical to understand the potential effects of proposed forest thinning on the hydrology of semi-arid basins, where disturbances to headwater catchments can cause significant changes in the local water balance components and basin-wise stream flows. In Arizona, the Four Forest Restoration Initiative (4FRI is being developed with the goal of restoring 2.4 million acres of ponderosa pine along the Mogollon Rim. Using the physically based, spatially distributed tRIBS model, we examine the potential impacts of the 4FRI on the hydrology of Tonto Creek, a basin in the Verde–Tonto–Salt (VTS system, which provides much of the water supply for the Phoenix Metropolitan Area. Long-term (20 year simulations indicate that forest removal can trigger significant shifts in the spatio-temporal patterns of various hydrological components, causing increases in net radiation, surface temperature, wind speed, soil evaporation, groundwater recharge, and runoff, at the expense of reductions in interception and shading, transpiration, vadose zone moisture and snow water equivalent, with south facing slopes being more susceptible to enhanced atmospheric losses. The net effect will likely be increases in mean and maximum stream flow, particularly during El Niño events and the winter months, and chiefly for those scenarios in which soil hydraulic conductivity has been significantly reduced due to thinning operations. In this particular climate, forest thinning can lead to net loss of surface water storage by vegetation and snow pack, increasing the vulnerability of ecosystems and populations to larger and more frequent hydrologic extreme conditions on these semi-arid systems.

  18. Entomological studies for surveillance and prevention of dengue in arid and semi-arid districts of Rajasthan, India

    Directory of Open Access Journals (Sweden)

    Anil Purohit

    2008-05-01

    Full Text Available Background & objectives: Rajasthan is one of the dengue endemic states of India. Very few studies have been published on entomological aspects of dengue in this state. Owing to water scarcity, inhabitants in desert areas overstore domestic water which leads to the persistence of dengue vectors within the domestic premises. Area specific knowledge on breeding, key containers and seasonal rhythms of vector population is essential for preparing an effective prevention plan against dengue. Present paper reports results of entomological investigations on dengue vectors in arid and semi-arid districts of Rajasthan. Methods: Longitudinal studies were undertaken during 2004–06 in one arid and two semi-arid dengue endemic districts of Rajasthan. Adult and larval Aedes were collected from the randomly selected houses in representative towns and villages with associated details of container types and water storage practices of inhabitants. Results: In urban areas during all the seasons adult house index (AHI of Aedes aegypti was maximum in desert zone (25 and least in semi-arid area with saline river III (1. The difference of AHI during three seasons was statistically significant (c2 = 16.1, p <0.01 for urban; and c2 = 50.71, p < 0.001 for rural. Breeding of Ae. aegypti among urban settings was maximum in desert zone. During all the seasons cement tanks were the key breeding habitats for Ae. aegypti in desert as well as semi-arid areas. Interpretation & conclusion: Water storage habits during summer season emerged to be the risk factor of vector abundance in urban areas of arid and semi-arid settings. A carefully designed study of key containers targeting cement tanks as the primary habitats of mosquito control may lead to commendable results for dengue prevention.

  19. Understanding the rapidity of subsurface storm flow response from a fracture-oriented shallow vadose through a new perspective

    Science.gov (United States)

    Zhao, Peng; Zhao, Pei; Liang, Chuan; Li, Tianyang; Zhou, Baojia

    2017-01-01

    Velocity and celerity in hydrologic systems are controlled by different mechanisms. Efforts were made through joint sample collection and the use of hydrographs and tracers to understand the rapidity of the subsurface flow response to rainstorms on hourly time scales. Three deep subsurface flows during four natural rainstorm events were monitored. The results show that (1) deeper discharge was observed early in responding rainfall events and yielded a high hydrograph amplitude; (2) a ratio index, k, reflecting the dynamic change of the rainfall perturbation intensity in subsurface flow, might reveal inner causal relationships between the flow index and the tracer signal index. Most values of k were larger than 1 at the perturbation stage but approximated 1 at the no-perturbation stage; and (3) for statistical analysis of tracer signals in subsurface flows, the total standard deviation was 17.2, 11.9, 7.4 and 3.5 at perturbation stages and 4.4, 2.5, 1.1, and 0.95 at the non-perturbation stage for observed events. These events were 3-7 times higher in the former rather than the later, reflecting that the variation of tracer signals primarily occurred under rainfall perturbation. Thus, we affirmed that the dynamic features of rainfall have a key effect on rapid processes because, besides the gravity, mechanical waves originating from dynamic rainfall features are another driving factor for conversion between different types of rainfall mechanical energy. A conceptual model for pressure wave propagation was proposed, in which virtual subsurface flow processes in a heterogeneous vadose zone under rainfall are analogous to the water hammer phenomenon in complex conduit systems. Such an analogy can allow pressure in a shallow vadose to increase and decrease and directly influence the velocity and celerity of the flow reflecting a mechanism for rapid subsurface hydrologic response processes in the shallow vadose zone.

  20. A new approach for studying prehistoric herd management in arid areas: intra-tooth isotopic analyses of archaeological caprine from IranUne nouvelle approche pour l'étude de la gestion préhistorique des troupeaux en zones arides: analyses isotopiques intra-dentaires de caprinés archéologiques d'Iran

    Science.gov (United States)

    Bocherens, Hervé; Mashkour, Marjan; Billiou, Daniel; Pellé, Eric; Mariotti, André

    2001-01-01

    Carbon and oxygen isotopic variations in archaeological tooth enamel from Iran have been used to investigate prehistoric herd management. Oxygen isotopic variations in domestic caprines are more important than in wild equids, indicating a seasonal consumption of 18O-depleted drinking water. Since the plants consumed at the same time were partly C 4, it is presumed that the access to this 18O-depleted water was controlled by humans, and that the water came from wells or underground canalisations. This methodology is expected to provide valuable information on herd management in the past in arid areas.

  1. 新疆干旱区湖泊演化及其气候水文特征%LAKE EVOLUTION AND CLIMATIC AND HYDROLOGICAL CHANGES IN ARID ZONE OF XINJIANG

    Institute of Scientific and Technical Information of China (English)

    吴敬禄; 马龙

    2011-01-01

    新疆干旱区湖泊水资源变化受自然和人类活动的共同影响,湖泊面积收缩与扩展幅度大而频繁,引起一系列的区域环境问题.然而,不同时期或不同类型的湖泊受这两种因素影响的强度并不一致.在人类活动前,湖泊受气候因素控制,湖泊波动表现出一定的规律性.约6.5~8.0 kaBP期间,艾比湖处于近一万年来的最高水位,湖面扩展,当时湖泊流域平均降水比现代高约22%,其他地区不同类型湖泊也处于高湖面时期.随后,在中世纪早期及小冰期前后也都出现了历时百年的气候湿润时期,艾比湖、罗布泊以及博斯腾湖等都处于相对较高的水位.人类活动影响以来,以20世纪六七十年代人为活动对湖泊水资源变化的影响最为强烈.新疆平原区湖泊出现大范围萎缩,艾比湖面积比1950s减少近400km2,罗布泊、台特玛湖以及玛纳斯湖等100km2以上的大湖快速干涸,而赛里木湖等山地湖泊变化相对稳定,受人类活动影响小,与相应的气候变化较一致.从长远分析,新疆湖泊水资源变化以自然因素影响为主,人类活动对湖泊的影响充当气候效应放大器的功能,即人类活动的结果放大了气候对湖泊变化的影响,使得湖泊的变化幅度加剧、频率增加.%Both natural and artificial factors bring effects to lake water resources in the arid zone of Xinjiang. The considerable and frequent shrinkage and expansion of lakes may cause a series of regional environmental problems. However, the influence intensity of the factors on lake variations changes with time.The lake variations were mainly controlled by climatic factors before human society. During the period between 6.5 and 8.0 kaBP, the Ebinur Lake had reached the highest water level in a time span of almost ten thousand years. The average precipitation of the Ebinur drainage area was about 22%, higher than that of the present, and the lakes in other regions were also

  2. Impact de l'érosion sur l'envasement des barrages, la recharge des nappes phréatiques côtières et les intrusions marines dans la zone semi-aride méditerranéenne : cas du barrage de Boukourdane (Algérie

    Directory of Open Access Journals (Sweden)

    Tadrist, N.

    2016-01-01

    Full Text Available Impact of erosion on the silting of dams, on the recharging groundwater and on coastal marine intrusion in the Mediterranean semi-arid area: Case of Boukourdane dam (Algeria. Description of the subject. Water erosion is a particularly important issue, especially in the Mediterranean and semi-arid zone. This zone is characterized by irregular rainfall patterns, which have a considerable influence on soil loss. In mountainous areas, water erosion phenomena are accentuated by steep slopes and low ground cover. The dams draining these areas undergo siltation linked to significant erosion. The silting of the dams drastically limits their capacity and thus their operating life. When used for recharging aquifers, the resuspension of fine particles may accumulate in the recharge areas and reduce infiltration capacity by clogging soil porosity. This leads to a significant reduction of groundwater levels. Additionally, groundwater situated in the coastal zone is submitted to intensive pumping. These two phenomena make groundwater particularly sensitive to marine intrusions. Objectives. This article aims, on the one hand to quantify the rate of siltation in the case of the Boukourdane dam (northern Algeria, which is used to recharge groundwater. On the other hand, the article also shows the reduction in permeability in the capturing field with the current management of releases. Method. Solid rates were set in relation to the liquid flow and sediment concentration occasionally taken from the wadi. The relation established made it possible to evaluate the solid contributions to the dam of Boukourdane. The impact of the releases on recharging the well field was evaluated by grouping wells and the well field mushrooms using heuristic k-means. Regressions were applied to the piezometric variations of each group. Results. This dam is fed by a catchment area of 156 km². Sediment transport was estimated from empirical formulas. The specific degradation rate was

  3. Erosion processes acting in semi-arid climate zone of the Ebro Basin (Bardenas Reales, NE of Spain); Procesos de erosion actuantes en una zona de clima semiarido de la Depresion del Ebro (Bardenas Reales, NE de Espana)

    Energy Technology Data Exchange (ETDEWEB)

    Marin, C.; Desir, G.

    2009-07-01

    Bardenas Reales is an erosive depression located in the central-western part of the Ebro Depression. May different erosion processes act on this zone: gullying, piping, mud slides and armoured mud balls among others that contribute to export great quantity of material outside the basin. Depending on lithology and physico-chemical properties erosion acting processes differ. The knowledge of that processes help us to understand the great amount of soil loss that take place on the studied zone, bigger than those recommended. (Author) 8 refs.

  4. Factores abióticos que influencian la germinación de seis especies herbáceas de la zona árida de Chile Abiotic factors effects influencing the germination of six herbaceous species of Chilean arid zone

    Directory of Open Access Journals (Sweden)

    Paola A Jara

    2006-09-01

    determinadas por las características ambientales del lugar de procedencia y de la época de germinación naturalThe arid zone of northern Chile has a dry climate that prevents the massive emergency of plant species. The exception to this general trend arises when scarce and irregular rainfall events occur, modify the environmental humidity, and stimulate the germination of seeds. The main external factors that modify the internal nature of the seeds are the hydration time, light, temperature and scarification. In this work two questions were addressed: (a is the germination of seeds of arid zones regulated by independent external factors or by a combined array of stimuli? and (b do exist correspondence between laboratory and in situ germinative conditions?. Seeds of six native and endemic herbaceous species of the north of Chile (Cistanthe salsoloides, Leucocoryne purpurea, Pasithea coerulea, Placea amoena, Schizanthus litoralis y Trichopetalum plumosum were subjected to two germination experiments, with factorial combinations of hydration time, temperature, light, dehydration and scarification. Schizanthus litoralis, was subjected to an aditional scarification-dehydration experiment (experiment 3. Results showed a common response of all the species in study to certain external factors. Maximum germination percentages were reached when exceeding a threshold of 96 h of hydration and at temperatures of 10 to 25 ºC. Light response was species-dependent. Agreement was found between the germinative conditions determined in laboratory and natural conditions of germination. Therefore, the seeds of plant species of arid zones display similar germinative thresholds and the techniques of germination in laboratory must be determined by the environmental characteristics of the place of origin and the time of natural germination

  5. Paleomadrigueras de roedores, un nuevo método para el estudio del Cuaternario en zonas áridas de Sudamérica Rodent middens, a new method for Quaternary research in arid zones of South America

    Directory of Open Access Journals (Sweden)

    Julio L. Betancourt

    2002-09-01

    formadores. Basados en la experiencia Norteamericana entregamos además, un resumen de los métodos existentes para la detección y análisis de dichos depósitos, los sesgos asociados, así como el aporte potencial que su análisis podría representar en futuros estudios paleoecológicos en las zonas áridas y semiáridas de SudaméricaIn arid and semi-arid regions of South America, historical evidence for climate and vegetation change is scarce despite its importance for determining reference conditions and rates of natural variability in areas susceptible to modern desertification. Normal lines of evidence, such as pollen stratigraphies from lakes, are either rare or unobtainable in deserts; studies of late Quaternary vegetation history are few and generally inconclusive. This gap in knowledge may be corrected with discovery and development of fossil rodent middens in rocky environments throughout arid South America. These middens, mostly the work of Lagidium, Phyllotis, Abrocoma and Octodontomys, are rich in readily identifiable plant macrofossils, cuticles and pollen, as well as vertebrate and insect remains. In the North American deserts, more than 2,500 woodrat (Neotoma middens analyzed since 1960 have yielded a detailed history of environmental change during the past 40,000 years. Preliminary work in the pre-puna, Monte and Patagonian Deserts of western Argentina, the Atacama Desert of northern Chile/southern Peru, the Mediterranean matorral of central Chile, and the Puna of the Andean altiplano suggest a similar potential for rodent middens in South America. Here we borrow from the North American experience to synthesize methodologies and approaches, summarize preliminary work, and explore the potential of rodent midden research in South America

  6. Determine the optimum spectral reflectance of juniper and pistachio in arid and semi-arid region

    Science.gov (United States)

    Fadaei, Hadi; Suzuki, Rikie

    2012-11-01

    Arid and semi-arid areas of northeast Iran cover about 3.4 million ha are populated by two main tree species, the broadleaf Pistacia vera. L (pistachio) and the conifer Juniperus excelsa ssp. polycarpos (Persian juniper). Natural stands of pistachio in Iran are not only environmentally important but genetically essential as seed sources for pistachio production in orchards. In this study, we estimated the optimum spectral reflectance of juniper forests and natural pistachio stands using remote sensing to help in the sustainable management and production of pistachio in Iran. In this research spectral reflectance are able to specify of multispectral from Advanced Land Observing Satellite (ALOS) that provided by JAXA. These data included PRISM is a panchromatic radiometer with a 2.5 m spatial resolution at nadir, has one band with a wavelength of 0.52-0.77 μm and AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones with a 10 m spatial resolution at nadir, has four multispectral bands: blue (0.42-0.50 μm), green (0.52-0.60 μm), red (0.61-0.69 μm), and near infrared (0.76-0.89 μm). Total ratio vegetation index (TRVI) of optimum spectral reflectance of juniper and pistachio have been evaluated. The result of TRVI for Pistachio and juniper were (R2= 0.71 and 0.55). I hope this research can provide decision of managers to helping sustainable management for arid and semi-arid regions in Iran.

  7. Changes in aridity in response to the global warming hiatus

    Science.gov (United States)

    Guan, Xiaodan; Huang, Jianping; Guo, Ruixia

    2017-02-01

    The global warming slowdown or warming hiatus, began around the year 2000 and has persisted for nearly 15 years. Most studies have focused on the interpretation of the hiatus in temperature. In this study, changes in a global aridity index (AI) were analyzed by using a newly developed dynamical adjustment method that can successfully identify and separate dynamically induced and radiatively forced aridity changes in the raw data. The AI and Palmer Drought Severity Index produced a wetting zone over the mid-to-high latitudes of the Northern Hemisphere in recent decades. The dynamical adjustment analysis suggested that this wetting zone occurred in response to the global warming hiatus. The dynamically induced AI (DAI) played a major role in the AI changes during the hiatus period, and its relationships with the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multi-decadal Oscillation (AMO) also indicated that different phases of the NAO, PDO, and AMO contributed to different performances of the DAI over the Northern Hemisphere. Although the aridity wetting over the mid-to-high latitudes may relieve long-term drying in certain regions, the hiatus is temporary, and so is the relief. Accelerated global warming will return when the NAO, PDO, and AMO revert to their opposite phases in the future, and the wetting zone is likely to disappear.

  8. Aridity modulates N availability in arid and semiarid Mediterranean grasslands.

    Directory of Open Access Journals (Sweden)

    Manuel Delgado-Baquerizo

    Full Text Available While much is known about the factors that control each component of the terrestrial nitrogen (N cycle, it is less clear how these factors affect total N availability, the sum of organic and inorganic forms potentially available to microorganisms and plants. This is particularly true for N-poor ecosystems such as drylands, which are highly sensitive to climate change and desertification processes that can lead to the loss of soil nutrients such as N. We evaluated how different climatic, abiotic, plant and nutrient related factors correlate with N availability in semiarid Stipa tenacissima grasslands along a broad aridity gradient from Spain to Tunisia. Aridity had the strongest relationship with N availability, suggesting the importance of abiotic controls on the N cycle in drylands. Aridity appeared to modulate the effects of pH, plant cover and organic C (OC on N availability. Our results suggest that N transformation rates, which are largely driven by variations in soil moisture, are not the direct drivers of N availability in the studied grasslands. Rather, the strong relationship between aridity and N availability could be driven by indirect effects that operate over long time scales (decades to millennia, including both biotic (e.g. plant cover and abiotic (e.g. soil OC and pH. If these factors are in fact more important than short-term effects of precipitation on N transformation rates, then we might expect to observe a lagged decrease in N availability in response to increasing aridity. Nevertheless, our results suggest that the increase in aridity predicted with ongoing climate change will reduce N availability in the Mediterranean basin, impacting plant nutrient uptake and net primary production in semiarid grasslands throughout this region.

  9. New crops for arid lands.

    Science.gov (United States)

    Hinman, C W

    1984-09-28

    Five plants are described that could be grown commercially under arid conditions. Once the most valuable component has been obtained from each plant (rubber from guayule; seed oil from jojoba, buffalo gourd, and bladderpod; and resin from gumweed), the remaining material holds potential for useful products as well as fuel. It is difficult to realize the full potential of arid land plants, however, because of the complexities of developing the necessary agricultural and industrial infrastructure simultaneously. To do so, multicompany efforts or cooperative efforts between government and the private sector will be required.

  10. A PROPOSED NEW VEGETATION INDEX, THE TOTAL RATIO VEGETATION INDEX (TRVI, FOR ARID AND SEMI-ARID REGIONS

    Directory of Open Access Journals (Sweden)

    H. Fadaei

    2012-07-01

    Full Text Available Vegetation indices that provide important key to predict amount vegetation in forest such as percentage vegetation cover, aboveground biomass, and leaf-area index. Arid and semi-arid areas are not exempt of this rule. Arid and semi-arid areas of northeast Iran cover about 3.4 million ha and are populated by two main tree species, the broadleaf Pistacia vera (pistachio and the conifer Juniperus excelsa ssp. polycarpos (Persian juniper. Natural stands of pistachio in Iran are not only environmentally important but also genetically essential as seed sources for pistachio production in orchards. We investigated the relationships between tree density and vegetation indices in the arid and semi-arid regions in the northeast of Iran by analysing Advanced Land Observing Satellite (ALOS data PRISM is a panchromatic radiometer with a 2.5 m spatial resolution at nadir, and has one band with a wavelength of 0.52–0.77 μm (JAXA EORC. AVNIR-2 is a visible and near infrared radiometer for observing land and coastal zones with a 10 m spatial resolution at nadir, and has four multispectral bands: blue (0.42–0.50 μm, green (0.52–0.60 μm, red (0.61–0.69 μm, and near infrared (0.76–0.89 μm (JAXA EORC. In this study, we estimated various vegetation indices using maximum filtering algorithm (5×5 and examined. This study carried out of juniper forests and natural pistachio stand using Advanced Land Observing Satellite (ALOS and field inventories. Have been compared linear regression model of vegetation indices and proposed new vegetation index for arid and semi-arid regions. Also, we estimated the densities of juniper forests and natural pistachio stands using remote sensing to help in the sustainable management and production of pistachio in Iran. We present a new vegetation index for arid and semi-arid regions with sparse forest cover, the Total Ratio Vegetation Index (TRVI, and we investigate the relationship of the new index to tree density by

  11. Stability measures in arid ecosystems

    Science.gov (United States)

    Nosshi, M. I.; Brunsell, N. A.; Koerner, S.

    2015-12-01

    Stability, the capacity of ecosystems to persist in the face of change, has proven its relevance as a fundamental component of ecological theory. Here, we would like to explore meaningful and quantifiable metrics to define stability, with a focus on highly variable arid and semi-arid savanna ecosystems. Recognizing the importance of a characteristic timescale to any definition of stability, our metrics will be focused scales from annual to multi-annual, capturing different aspects of stability. Our three measures of stability, in increasing order of temporal scale, are: (1) Ecosystem resistance, quantified as the degree to which the system maintains its mean state in response to a perturbation (drought), based on inter-annual variability in Normalized Difference Vegetation Index (NDVI). (2) An optimization approach, relevant to arid systems with pulse dynamics, that models vegetation structure and function based on a trade off between the ability to respond to resource availability and avoid stress. (3) Community resilience, measured as species turnover rate (β diversity). Understanding the nature of stability in structurally-diverse arid ecosystems, which are highly variable, yields theoretical insight which has practical implications.

  12. Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia

    Directory of Open Access Journals (Sweden)

    W. A. Timms

    2011-11-01

    in land use and a thick clay dominated vadose zone. This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

  13. Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia

    Directory of Open Access Journals (Sweden)

    W. A. Timms

    2012-04-01

    rainfall and large potential evapotranspiration, transient hydrological conditions after changes in land use and a thick clay dominated vadose zone.

    This is in contrast to regional groundwater modelling that assumes annual recharge of 0.5% of rainfall. Importantly, it was found that leaching from episodic deep drainage could not cause discharge of saline groundwater in the area, since the water table was several meters below the incised river bed.

  14. 70193-Influence of Clastic Dikes on Vertical Migration of Contaminants in the Vadose Zonde at Hanford

    Energy Technology Data Exchange (ETDEWEB)

    Christopher J Murray; Anderson L. Ward; John L. Wilson

    2004-04-07

    The purpose of this study was to examine the hypothesis that clastic dikes could form a preferential flow path through the vadose zone to the water table at the Hanford Site. Clastic dikes are subvertical structures that form within sedimentary sequences after deposition and cut across the original sedimentary layers. They are common throughout the Hanford Site, often occurring in organized polygonal networks. In the initial phase of the project, we analyzed the large-scale geometry of the clastic dikes and developed an algorithm for simulating their spatial distribution. This result will be useful in providing maps of the potential distribution of clastic dikes in areas where they are not exposed at the surface (e.g., where covered by windblown sand or construction of facilities like tank farms at the surface). In addition to the study of the large-scale distribution of the dikes, a major focus of the project was on field, laboratory, and modeling studies of the hydrogeological properties of the clastic dikes and the effect that they have on transport of water through the vadose zone. These studies were performed at two field locations at the Hanford Site. We performed an extensive series of field and laboratory measurements of a large number of samples from the clastic dikes, linked with infrared (IR) and visual imagery of the clastic dikes and surrounding matrix. We developed a series of correlations from the sample data that allowed us to estimate the unsaturated hydraulic conductivity of the dike and matrix at an extremely high resolution (approximately 1 mm). The resulting grids, each of which measured several meters on a side and included nearly four million grid nodes, were used to study the distribution of moisture between the clastic dike and surrounding matrix, as well as the relative velocities that moisture would have through the clastic dike and matrix for a number of different recharge scenarios. Results show the development of complex flow networks

  15. Annual plants in arid and semi-arid desert regions

    Institute of Scientific and Technical Information of China (English)

    Xuehua LI; Xiaolan LI; Deming JIANG; Zhimin LIU; Qinghe YU

    2008-01-01

    Annual plants are the main vegetation in arid and semi-arid desert regions.Because of their unique traits,they are the optimal experimental subjects for eco-logical studies.In this article,we summarize annual plants' seed germination strategies,seedling adaptability mechanism to environments,seed dispersal,and soil seed banks.We also discuss the biotic and abiotic factors affecting the composition and dynamics of annual plant populations and communities.Because annual plants have important ecological functions in desert vegetation systems,this study on annual plants will be of great bene-fit to the conservation and restoration of desert ecosys-tems,the rational utilization of resources,and the sustainable development of desert regions.

  16. In Situ Bioremediation of Perchlorate in Vadose Zone Soil Using Gaseous Electron Donors

    Science.gov (United States)

    2009-11-01

    12.1 CDM-CB9-50-120208 NA SW 1500 0.5 9.3 CDM-CB10-10-120208 NA GW 26000 0.1 10.5 CDM-CB10-20-120208 NA CL 11000 0.1 16.3 CDM-CB10-30-120208 NA GW 270...40-120308 NA ML 26000 0.5 13.3 CDM-CB11-50-120308 NA GW 11000 0.9 8.4 CDM-CB12-10-120308 NA CL 7500 0.5 31.1 CDM-CB12-20-120308 NA GM 7600 3.4 27.9 CDM...0.96 6.7% N 10.00 9.50 -5.0% N 2.00 1.80 -10.0% N * iso -butane used as standard. Low level was reported either as percent (0.9%) or percent of LEL (49

  17. Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

    Energy Technology Data Exchange (ETDEWEB)

    Ward, Andy L.; Gee, Glendon W.; Zhang, Z. F.; Keller, Jason M.

    2004-10-14

    The BC Cribs and Trenches, part of the 200 TW 1 OU waste sites, received about 30 Mgal of scavenged tank waste, with possibly the largest inventory of 99Tc ever disposed to the soil at Hanford and site remediation is being accelerated. The purpose of this work was to develop a conceptual model for contaminant fate and transport at the 216-B-26 Trench site to support identification and development and evaluation of remediation alternatives. Large concentrations of 99Tc high above the water table implicated stratigraphy in the control of the downward migration. The current conceptual model accounts for small-scale stratigraphy; site-specific changes soil properties; tilted layers; and lateral spreading. It assumes the layers are spatially continuous causing water and solutes to move laterally across the boundary if conditions permit. Water influx at the surface is assumed to be steady. Model parameters were generated with pedotransfer functions; these were coupled high resolution neutron moisture logs that provided information on the underlying heterogeneity on a scale of 3 inches. Two approaches were used to evaluate the impact of remedial options on transport. In the first, a 1-D convolution solution to the convective-dispersive equation was used, assuming steady flow. This model was used to predict future movement of the existing plume using the mean and depth dependent moisture content. In the second approach, the STOMP model was used to first predict the current plume distribution followed by its future migration. Redistribution of the 99Tc plume was simulated for the no-action alternative and on-site capping. Hypothetical caps limiting recharge to 1.0, 0.5, and 0.1 mm yr-1 were considered and assumed not to degrade in the long term. Results show that arrival time of the MCLs, the peak arrival time, and the arrival time of the center of mass increased with decreasing recharge rate. The 1-D convolution model is easy to apply and can easily accommodate initial contaminant inventory and water content depth distributions of any complexity. However, the results are somewhat conservative in that the model does not take credit for stratification and its dimensionality effects. Transient analysis shows transport to be controlled by small-scale stratification that resulted in laterally movement of contaminants and their failure to reach the ground water. Multiple discharges quickly merged into a single plume that migrated beyond the domain boundaries. However, it appears that this very feature that was effective in mitigating deep transport of the contaminants for almost 50 years now functions to confound expected barrier effects. Simulations suggest that a barrier provides no additional protection above the no-action alternative. Although continuous layers are assumed, in reality, there may be discontinuities that could lead to vertical movement. Episodic recharge events could also be conducive to downward movement. As more data becomes available, the conceptual model will be revised. Based on the analyses, capping appears to be no better than the no-action alternative. Projected 99Tc concentrations reaching the groundwater suggest that alternate source control actions may be necessary to reach soil screening levels. The benefits of active remediation are therefore readily apparent. Because none of the alternatives reduce soil concentrations, they effect no active reduction in the groundwater concentrations therefore the residual risk will remain high.

  18. Soil-atmosphere and vadose zone water fluxes at the Wagna - lysimeter: Workflow, models, and results

    Science.gov (United States)

    Fank, Johann

    2014-05-01

    A precise knowledge of the water fluxes between the soil-plant system and the atmosphere is of great importance for understanding and modeling water, solute and energy transfer in the soil-plant-atmosphere system. Weighing lysimeters are precise tools to allow the determination of the hydrological cycle components in very short time intervals. Lysimeters with controlled suction at the lower boundary allow estimation of capillary rise and deep water percolation on short time scales. Evapotranspiration, rainfall, and irrigation can be computed from weight changes. In the last decades resolution and precision of the weighing systems have been substantially improved, so that modern lysimeters, resting on weighing cells can reach resolutions of up to 0.01 mm. Nevertheless, a lot of external effects (e.g. from maintenance, surface treatment) and small mechanical disturbances (e.g. caused by wind) became visible in the data. Seepage mass data are affected by water sampling and the emptying process of the seepage water container. Increasing parts of corrected seepage mass data show deep water percolation, decreasing parts in dry weather periods can be interpreted as capillary rise. In the evaluation process of corrected lysimeter mass data every increase in system weight (lysimeter mass + cumulative seepage mass) might be interpreted as rainfall or irrigation, whereas every decrease in system weight is interpreted as evapotranspiration. To apply this concept correctly, the noise in both data sets has to be separated from signals using a filtering routine (e.g. Peters et al., 2013) which is appropriate for any event, including events with low disturbances as well as strong wind and heavy precipitation in small time intervals. Based on the data set from the "Wagna" lysimeter in Austria with a high resolution of the scale (~ 0,015 mm) and very low noise due to low wind velocities for the year 2010 a lysimeter data preparation workflow will be executed: (a) correction of the lysimeter mass data set, (b) correction of the seepage mass data set, (c) definition of periods with congruent analyzable data sets, (d) computing upper boundary fluxes, (e) filtering of seepage mass, (f) filtering of upper boundary fluxes, (g) definition of the time step for data evaluation (e. g. hourly values, daily values). For every time step in the analyzable periods the data evaluation workflow follows the scheme: (1) computing change of stored water volume S from lysimeter weight, (2) computing rainfall and/or irrigation R from increasing upper boundary fluxes, (3) computing capillary rise C from decreasing seepage mass, (4) calculation of percolation water P from mass change of seepage + C, (5) calculation of evapotranspiration ET using the water balance equation (ET = R - P + C - S). Based on the "Wagna" data set the accuracy of modern lysimeter measurements is shown as an effect of rime precipitation and rime evaporation on a cold winter day. Results are compared to the Penman-Monteith model for computing grass reference evapotranspiration. For January 27th 2010 rime precipitation was measured to 0.23 mm, evaporation was estimated to 0.33 mm. The estimation of ET was in a very good agreement with the Penman-Monteith computation of 0.34 mm. Results of lysimeter data evaluation (R, ET, P) using different time steps for the year 2010 are discussed. Estimation of R (1013.8 mm) is compared to measured precipitation using a tipping bucket (1013.6 mm) and a precipitation scale (900.4 mm) nearby the lysimeter. Peters, A., Nehls, T., Schonsky, H., and Wessolek, G.: Separating precipitation and evapotranspiration from noise - a new filter routine for high resolution lysimeter data, Hydrol. Earth Syst. Sci. Discuss., 10, 14645-14674, doi:10.5194/hessd-10-14645-2013, 2013.

  19. Modeling and Optimization of GEDIT for In Situ Contaminant Destruction in the Vadose Zone

    Science.gov (United States)

    2012-04-01

    40AT 41 10.9653E+000.1060E+010.1325E+00 A1 41A1 42 10.1060E+010.1164E+010.1458E+00 A2 41A2 42...030.2441E+031. A1 41A2 41 30.5000E-030.5000E+000.2951E+031. A2 41A3 41 30.5000E+000.5000E+000.2951E+031. A3 41A4 41

  20. A Catalog of Vadose Zone Hydraulic Properties for the Hanford Site

    Energy Technology Data Exchange (ETDEWEB)

    Freeman, Eugene J.; Khaleel, Raziuddin; Heller, Paula R.

    2002-09-30

    To predict contaminant release to the groundwater, it is necessary to understand the hydraulic properties of the material between the release point and the water table. Measurements of the hydraulic properties of the Hanford unsaturated sediments that buffer the water table are available from many areas of the site; however, the documentation is not well cataloged nor is it easily accessible. The purpose of this report is to identify what data is available for characterization of the unsaturated hydraulic properties at Hanford and Where these data can be found.

  1. Estimating the effect of shallow groundwater on diurnal heat transport in a vadose zone

    Science.gov (United States)

    Jiang, Jianmei; Zhao, Lin; Zhai, Zhe

    2016-09-01

    The influence of shallow groundwater on the diurnal heat transport of the soil profile was analyzed using a soil sensor automatic monitoring system that continuously measures temperature and water content of soil profiles to simulate heat transport based on the Philip and de Vries (PDV) model. Three experiments were conducted to measure soil properties at depths of 5 cm, 10 cm, 20 cm, and 30 cm when groundwater tables reached 10 cm, 30 cm, and 60 cm (Experiments I, II, and III). Results show that both the soil temperature near shallow groundwater and the soil water content were effectively simulated by the PDV model. The root mean square errors of the temperature at depths of 5 cm, 10 cm, and 20 cm were 1.018°C, 0.909°C, and 0.255°C, respectively. The total heat flux generated the convergent and divergent planes in space-time fields with valley values of-161.5W•m-2 at 7:30 and-234.6W•m-2 at 11:10 in Experiments II and III, respectively. The diurnal heat transport of the saturated soil occurred in five stages, while that of saturated-unsaturated and unsaturated soil profiles occurred in four stages because high moisture content led to high thermal conductivity, which hastened the heat transport.

  2. Using Nonlinear Dynamics for Environmental Management of the Vadose Zone and Groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Faybishenko, Boris

    2003-03-27

    The need to improve characterization and prediction methods for flow and transport in partially saturated and saturated heterogeneous soils and fractured rock has long been recognized. Such improvement would be specifically welcomed in the fields of environmental management, containment and remediation of contaminated sites. Until recently, flow and transport processes in heterogeneous soils and fractured rock (with oscillating irregularities) were assumed to be random and were analyzed using conventional stochastic and deterministic methods. In this presentation, I will present the results of laboratory and field investigations of flow and transport in unsaturated soils and fractured rock, applying the methods of nonlinear dynamics and deterministic chaos. I will discuss using these methods for the development of improved characterization and prediction methods as well as for the development of remediation technologies for contaminated soils and groundwater.

  3. Impact of Soil Water Flux on Vadose Zone Solute Transport Parameters

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The transport processes of solutes in two soil columns filled with undisturbed soil material collected from an unsaturated sandy aquifer formation in Belgium subjected to a variable upper boundary condition were identified from breakthrough curves measured by means of time domain refiectometry (TDR). Solute breakthrough was measured with 3 TDR probes inserted into each soil column at three different depths at a 10 minutes time interval. In addition, soil water content and pressure head were measured at 3 different depths. Analytical solute transport models were used to estimate the solute dispersion coefficient and average pore-water velocity from the observed breakthrough curves. The results showed that the analytical solutions were suitable in fitting the observed solute transport. The dispersion coefficient was found to be a function of the soil depth and average pore-water velocity, imposed by the soil water flux. The mobile moisture content on the other hand was not correlated with the average pore-water velocity and the dispersion coefficient.

  4. Role of air on local water retention behavior in the shallow heterogeneous vadose zone

    Science.gov (United States)

    Sakaki, T.; Limsuwat, A.; Illangasekare, T. H.

    2009-12-01

    In the presence of a subsurface source, air flowing through the unsaturated soil can transport toxic vapor into subsurface structures due to pressure gradients created by, e.g., a pressure drop within the building. Development of dynamic air pathways in the subsurface are largely controlled by the geological heterogeneity and the spatial and temporal distribution of soil moisture. To better understand how these air pathways are developed, it is crucial to know how water is retained in heterogeneous medium at spatial resolutions that are finer than those adopted in typical hydrologic and soil physics applications. Although methods for soil water pressure measurement can be readily found in literature, a technique for measuring “air pressure” in wet soil is not well-established or documented. Hydrophobic porous ceramic cups have been used to measure non-wetting NAPL phase pressure in two-phase systems. However, our preliminary tests using the hydrophobic ceramic cups installed in highly wet soil showed that under conditions of fast drainage of the wetting fluid that is replaced by air, it typically took some time before the cups responded to register the air pressure. Therefore, an attempt was made to develop a more robust method where the time lag is minimized. The tested materials were; 1) ceramic porous cups, 2) sintered stainless steel cups, 3) porous glass discs, and 4) non-woven PTFE fabric. The ceramic cups, sintered stainless steel cups and sintered porous glass discs required hydrophobic treatment, whereas the non-woven PTFE fabric is hydrophobic by itself. To treat the ceramic porous cups, the method proposed by Parker and Lenhard [1988] was adopted. The sintered porous stainless steel cups and porous glass discs were treated by a commercially available water repellant compound. For those four materials, contact angle, water entry pressure, and time lag to respond to an imposed pressure were measured. The best performing material was then tested in a simple heterogeneous column. The column was packed using two sands to form three layers where the coarser sand was sandwitched by two layers of a finer sand. In each layer, soil moisture, water pressure and air pressure were monitored. The soil was initially saturated and suction at the bottom was gradually increased to induce wetting fluid drainage, and followed by a wetting cycle. In the drainage cycle, the coarse middle layer did not drain until air front reached the bottom of the top fine layer. Once the air front reached the fine-coarse interface, air was quickly pulled into the coarse layer. The results showed that the newly developed hydrophobic material showed very small time lag and captured the abrupt air pressure change in the wet soil. In the wetting cycle, we observed positive air pressure which indicated entrapment of air and its compression as wetting proceeded. This behavior cannot be evaluated properly without the rapid measurement of air pressure. The method is currently being applied in a large 2D vertical aquifer with a structured heterogeneity to investigate how air pathways are formed under various flux/temperature conditions at the soil surface.

  5. Assessing tungsten transport in the vadose zone: from dissolution studies to soil columns.

    Science.gov (United States)

    Tuna, Gulsah Sen; Braida, Washington; Ogundipe, Adebayo; Strickland, David

    2012-03-01

    This study investigates the dissolution, sorption, leachability, and plant uptake of tungsten and alloying metals from canister round munitions in the presence of model, well characterized soils. The source of tungsten was canister round munitions, composed mainly of tungsten (95%) with iron and nickel making up the remaining fraction. Three soils were chosen for the lysimeter studies while four model soils were selected for the adsorption studies. Lysimeter soils were representatives of the typical range of soils across the continental USA; muck-peat, clay-loamy and sandy-quartzose soil. Adsorption equilibrium data on the four model soils were modeled with Langmuir and linear isotherms and the model parameters were obtained. The adsorption affinity of soils for tungsten follows the order: Pahokee peat>kaolinite>montmorillonite>illite. A canister round munition dissolution study was also performed. After 24 d, the measured dissolved concentrations were: 61.97, 3.56, 15.83 mg L(-1) for tungsten, iron and nickel, respectively. Lysimeter transport studies show muck peat and sandy quartzose soils having higher tungsten concentration, up to 150 mg kg(-1) in the upper layers of the lysimeters and a sharp decline with depth suggesting strong retardation processes along the soil profile. The concentrations of tungsten, iron and nickel in soil lysimeter effluents were very low in terms of posing any environmental concern; although no regulatory limits have been established for tungsten in natural waters. The substantial uptake of tungsten and nickel by ryegrass after 120 d of exposure to soils containing canister round munition suggests the possibility of tungsten and nickel entering the food chain.

  6. Tensiometer for shallow or deep measurements including vadose zone and aquifers

    Science.gov (United States)

    Faybishenko, Boris

    1999-01-01

    A two cell tensiometer is described in which water level in the lower cell is maintained at a relatively constant height, and in equilibrium with the water pressure of materials that surround the tensiometer. An isolated volume of air in the lower cell changes pressure proportionately to the changing water pressure of the materials that surround the tensiometer. The air pressure is measured remotely. The tensiometer can be used in drying as well as wetting cycles above and below the water table.

  7. FUTURE STUDIES AT PENA BLANCA: RADIONUCLIDE MIGRATION IN THE VADOSE ZONE OF AN ALLUVIAL FAN

    Energy Technology Data Exchange (ETDEWEB)

    P. Goodell; J. Walton; P.J. Rodriguez

    2005-07-11

    The pathway to the accessible environment at Yucca Mountain contains volcanic rocks and alluvial fill. Transport properties in alluvial fill, specifically retardation and dispersivity, may be significant in determining the overall performance of the repository. Prior relevant studies, with the exception of the Nye County Tracer Test, are almost entirely in bedrock material. The proposed study will provide field data on radionuclide migration in alluvial material. High grade uranium ore was mined at the Nopal I deposit. This mined ore (60,000 tons) was moved in 1994 to its present site as open piles on an alluvial fan in the Boquilla Colorada Microbasin. Precipitation is approximately 20 cm/year, and has caused migration of radionuclides into the subsurface. We propose partial removal of an ore pile, excavation into the alluvial fan, sampling, and determination of radionuclide mobilities from the uranium decay chain. The proposed research would be taking advantage of a unique opportunity with a known time frame for migration.

  8. Imaging on a Shoestring: Cost-Effective Technologies for Probing Vadose Zone Transport Processes

    Science.gov (United States)

    Corkhill, C.; Bridge, J. W.; Barns, G.; Fraser, R.; Romero-Gonzalez, M.; Wilson, R.; Banwart, S.

    2010-12-01

    Key barriers to the widespread uptake of imaging technology for high spatial resolution monitoring of porous media systems are cost and accessibility. X-ray tomography, magnetic resonance imaging (MRI), gamma and neutron radiography require highly specialised equipment, controlled laboratory environments and/or access to large synchrotron facilities. Here we present results from visible light, fluorescence and autoradiographic imaging techniques developed at low cost and applied in standard analytical laboratories, adapted where necessary at minimal capital expense. UV-visible time lapse fluorescence imaging (UV-vis TLFI) in a transparent thin bed chamber enabled microspheres labelled with fluorescent dye and a conservative fluorophore solute (disodium fluorescein) to be measured simultaneously in saturated, partially-saturated and actively draining quartz sand to elucidate empirical values for colloid transport and deposition parameters distributed throughout the flow field, independently of theoretical approximations. Key results include the first experimental quantification of the effects of ionic strength and air-water interfacial area on colloid deposition above a capillary fringe, and the first direct observations of particle mobilisation and redeposition by moving saturation gradients during drainage. UV-vis imaging was also used to study biodegradation and reactive transport in a variety of saturated conditions, applying fluorescence as a probe for oxygen and nitrate concentration gradients, pH, solute transport parameters, reduction of uranium, and mapping of two-dimensional flow fields around a model dipole flow borehole system to validate numerical models. Costs are low: LED excitation sources (< US 50), flow chambers (US 200) and detectors (although a complete scientific-grade CCD set-up costs around US$ 8000, robust datasets can be obtained using a commercial digital SLR camera) mean that set-ups can be flexible to meet changing experimental requirements. The critical limitations of UV-vis fluorescence imaging are the need for reliable fluorescent probes suited to the experimental objective, and the reliance on thin-bed (2D) transparent porous media. Autoradiographic techniques address some of these limitations permit imaging of key biogeochemical processes in opaque media using radioactive probes, without the need for specialised radiation sources. We present initial calibration data for the use of autoradiography to monitor transport parameters for radionuclides (99-technetium), and a novel application of a radioactive salt tracer as a probe for pore water content, in model porous media systems.

  9. Salinization of groundwater in arid and semi-arid zones: an example from Tajarak, western Iran

    Science.gov (United States)

    Jalali, Mohsen

    2007-06-01

    Study of the groundwater samples from Tajarak area, western Iran, was carried out in order to assess their chemical compositions and suitability for agricultural purposes. All of the groundwaters are grouped into two categories: relatively low mineralized of Ca-HCO3 and Na-HCO3 types and high mineralized waters of Na-SO4 and Na-Cl types. The chemical evolution of groundwater is primarily controlled by water-rock interactions mainly weathering of aluminosilicates, dissolution of carbonate minerals and cation exchange reactions. Calculated values of pCO2 for the groundwater samples range from 2.34 × 10-4 to 1.07 × 10-1 with a mean value of 1.41 × 10-2 (atm), which is above the pCO2 of the earth’s atmosphere (10-3.5). The groundwater is oversaturated with respect to calcite, aragonite and dolomite and undersaturated with respect to gypsum, anhydrite and halite. According to the EC and SAR the most dominant classes (C3-S1, C4-S1 and C4-S2) were found. With respect to adjusted SAR (adj SAR), the sodium (Na+) content in 90% of water samples in group A is regarded as low and can be used for irrigation in almost all soils with little danger of the development of harmful levels of exchangeable Na+, while in 40 and 37% of water samples in group B the intensity of problem is moderate and high, respectively. Such water, when used for irrigation will lead to cation exchange and Na+ is adsorbed on clay minerals while calcium (Ca2+) and magnesium (Mg2+) are released to the liquid phase. The salinity hazard is regarded as medium to high and special management for salinity control is required. Thus, the water quality for irrigation is low, providing the necessary drainage to avoid the build-up of toxic salt concentrations.

  10. Rapid warming accelerates tree growth decline in semi-arid forests of Inner Asia.

    Science.gov (United States)

    Liu, Hongyan; Park Williams, A; Allen, Craig D; Guo, Dali; Wu, Xiuchen; Anenkhonov, Oleg A; Liang, Eryuan; Sandanov, Denis V; Yin, Yi; Qi, Zhaohuan; Badmaeva, Natalya K

    2013-08-01

    Forests around the world are subject to risk of high rates of tree growth decline and increased tree mortality from combinations of climate warming and drought, notably in semi-arid settings. Here, we assess how climate warming has affected tree growth in one of the world's most extensive zones of semi-arid forests, in Inner Asia, a region where lack of data limits our understanding of how climate change may impact forests. We show that pervasive tree growth declines since 1994 in Inner Asia have been confined to semi-arid forests, where growing season water stress has been rising due to warming-induced increases in atmospheric moisture demand. A causal link between increasing drought and declining growth at semi-arid sites is corroborated by correlation analyses comparing annual climate data to records of tree-ring widths. These ring-width records tend to be substantially more sensitive to drought variability at semi-arid sites than at semi-humid sites. Fire occurrence and insect/pathogen attacks have increased in tandem with the most recent (2007-2009) documented episode of tree mortality. If warming in Inner Asia continues, further increases in forest stress and tree mortality could be expected, potentially driving the eventual regional loss of current semi-arid forests.

  11. Nutritive valve of some ingrediants from arid zone

    Energy Technology Data Exchange (ETDEWEB)

    Tejada de Hernadex, I.

    1976-01-01

    Vantress chickens 1 week old were given a standard diet of maize and soya or had 25 or 50% jojoba seed meal (Simondsia chinensis) from which most of the wax had been extracted, with lysine or methionine or both or neither. All diets had 20% protein. All chickens given jojoba for 1 week lost weight. For 3 weeks 15 male Wistar rats 28 days old had 30 or 15% guayule leaves (Parthenium argentatum) to replace lucerne meal wholly or partly. All given guayule lost weight and lesions of kidney, lung, liver and spleen were found. For 4 weeks 30 Wistar rats initially 30 days old got 35% of dietary energy from bastard saffron oil or with 25, 50, 75 or 100% of it replaced by oil from seeds of Yucca filifera. There was no difference in growth or feed conversion among groups.

  12. Multiphase Reactive Transport modeling of Stable Isotope Fractionation of Infiltrating Unsaturated Zone Pore Water and Vapor Using TOUGHREACT

    Energy Technology Data Exchange (ETDEWEB)

    Singleton, Michael J.; Sonnenthal, Eric L.; Conrad, Mark E.; DePaolo, Donald J.

    2003-08-28

    Numerical simulations of transport and isotope fractionation provide a method to quantitatively interpret vadose zone pore water stable isotope depth profiles based on soil properties, climatic conditions, and infiltration. We incorporate the temperature-dependent equilibration of stable isotopic species between water and water vapor, and their differing diffusive transport properties into the thermodynamic database of the reactive transport code TOUGHREACT. These simulations are used to illustrate the evolution of stable isotope profiles in semiarid regions where recharge during wet seasons disturbs the drying profile traditionally associated with vadose zone pore waters. Alternating wet and dry seasons lead to annual fluctuations in moisture content, capillary pressure, and stable isotope compositions in the vadose zone. Periodic infiltration models capture the effects of seasonal increases in precipitation and predict stable isotope profiles that are distinct from those observed under drying (zero infiltration) conditions. After infiltration, evaporation causes a shift to higher 18O and D values, which are preserved in the deeper pore waters. The magnitude of the isotopic composition shift preserved in deep vadose zone pore waters varies inversely with the rate of infiltration.

  13. Effect of Partial Root-zone Drying on Potato Water Utilization on Semi-arid Conditions in China%隔沟交替灌溉对我国半干旱地区马铃薯水分利用的影响

    Institute of Scientific and Technical Information of China (English)

    谢开云; 王晓雪; 张若芳; 巩秀峰; 张世彪; MARES Victor; GAVILAN Carla; POSADAS Adolfo; QUIROZ Roberto

    2012-01-01

    隔沟交替灌溉(Partialroot-zonedrying,PRD)被认为是一种节水灌溉的方法,它可以提高多种作物的水分利用率。本研究开展于我国甘肃与内蒙两个半干旱马铃薯种植区,比较常规灌溉与隔沟交替灌溉对马铃薯产量和水分利用率的影响。结果表明,由于两个试验点的气候条件与土壤条件不同,所以马铃薯产量存在显著的差异。但是在两试验点中,PRD。处理(隔沟交替灌溉,灌水量为经验灌水量的1/2)的产量与常规灌溉处理(c100,经验灌水量)的产量没有显著的差别,水分利用率却显著提高。研究显示,运用合理的灌溉方式,可以在保证产量不变的基础上节省用水量。另外,在易发生干旱的地区,选用适合的品种,同时采用覆膜技术对于增加马铃薯产量有着重要的作用。%Partial root-zone drying (PRD) irrigation method was considered as a water-saving irrigation method which could increase the water use efficiency for many crops. To compare the partial root-zone drying as an alternative to the conventional irrigation method used in semi-arid potato producing areas in China and its impact on tuber yield and water use efficiency, field trials were conducted in Gansu and in Inner Mongolia where water was the main constraint to potato production. Due to different soil types and rainfalls, the yield of potatoes in two locations varied remarkably. However, the yield of PRD using half amount of water as conventional irrigation was very close to the yields of the full conventional irrigation method in the two locations. The results showed that water could be dramatically reduced in Inner Mongolia and Gansu without affecting the tuber yields by proper irrigation management. Results also supported the fact that the use of plastic mulching and a variety selected for drought-prone environments could increase the potato yield.

  14. Study of the effect of the nature of aggregates on the mechanical behaviour of the concrete in hot and dry zones «Contribution of the curing» Etude de l’effet de la nature des granulats sur le comportement mécanique du béton en zones chaudes et arides «Contribution de la cure»

    Directory of Open Access Journals (Sweden)

    Bendjillali K.

    2012-09-01

    Full Text Available Laghouat est parmi les villes de l’Algérie riches en matériaux de différentes natures, tels que les roches calcaires massives et les matériaux alluvionnaires meubles siliceux et silico-calcaires. L’objectif premier de ce travail est d’établir une comparaison des performances mécaniques des bétons préparés avec de granulats de natures différentes. Nôtre second objectif est l’étude de l’influence de la cure sur la résistance à la compression et la résistance à la flexion des bétons étudiés. Les échantillons sont conservés sous un climat chaud et sec réel qui est le climat de Laghouat. Nous avons utilisé comme cure: le film plastique, la toile de jute mouillée et l’immersion dans l’eau. A travers ce travail expérimental, nous avons pu constater que les meilleures résistances à la compression sont obtenues dans les bétons à sable siliceux et celles à la flexion sont obtenues dans les bétons à granulats calcaires. La conservation du béton dans une ambiance aride sans protection augmente sa résistance mécanique à jeune âge, mais à long terme, cette dernière chute d’une façon significative. L’étude a mis en évidence la nécessité de l’emploi d’un super plastifiant et de l’application immédiate de la cure pour le bétonnage en climat chaud. Laghouat is among the cities of Algeria rich in materials of various natures, such as the massive limestone rocks and the natural river materials. The first objective of this work is to establish a comparison of the mechanical performances between concretes with aggregates of different natures. The second objective is to study the effect of curing on the compressive and the flexural strength of concretes. Samples are conserved under a real hot and dry climate which is the climate of Laghouat. We used as curing: plastic film, wet hessian and immersing in water. Through this work, we noticed that the best compressive strengths are obtained in concretes

  15. Aridity, desalination plants and tourism in the eastern Canary Islands

    Directory of Open Access Journals (Sweden)

    José-León García-Rodríguez

    2016-05-01

    Full Text Available The islands of Lanzarote and Fuerteventura are the easternmost of the Canary Islands, and are located on the southern edge of the temperate zone, in the subtropical anticyclone belt. With less than 150 mm of rainfall a year, they are classified as an arid zone. Their inhabitants have devised original agricultural systems to combat the aridity, although low yields have historically limited socio-economic development and population growth. These systems were used until the introduction of seawater desalination plants and the arrival of tourism in the last third of the twentieth century, which improved living standards for the local population but also led to a cultural transition. Nevertheless, these farming systems have left behind an important regional heritage, with an environmental and scenic value that has played an integral role in the latest phase of development. The systems have become a tourist attraction and have been central to the two islands being designated biosphere reserves by UNESCO. This article aims to analyse the main socioeconomic and land-use changes that have come about as a result of desalination technology.

  16. Quantifying macropore recharge: Examples from a semi-arid area

    Science.gov (United States)

    Wood, W.W.; Rainwater, K.A.; Thompson, D.B.

    1997-01-01

    The purpose of this paper is to illustrate the significantly increased resolution of determining macropore recharge by combining physical, chemical, and isotopic methods of analysis. Techniques for quantifying macropore recharge were developed for both small-scale (1 to 10 km2) and regional-scale areas in and semi-arid areas. The Southern High Plains region of Texas and New Mexico was used as a representative field site to test these methods. Macropore recharge in small-scale areas is considered to be the difference between total recharge through floors of topographically dosed basins and interstitial recharge through the same area. On the regional scale, macropore recharge was considered to be the difference between regional average annual recharge and interstitial recharge measured in the unsaturated zone. Stable isotopic composition of ground water and precipitation was used us an independent estimate of macropore recharge on the regional scale. Results of this analysis suggest that in the Southern High Plains recharge flux through macropores is between 60 and 80 percent of the total 11 mm/y. Between 15 and 35 percent of the recharge occurs by interstitial recharge through the basin floors. Approximately 5 percent of the total recharge occurs as either interstitial or matrix recharge between the basin floors, representing approximately 95 percent of the area. The approach is applicable to other arid and semi-arid areas that focus rainfall into depressions or valleys.The purpose of this paper is to illustrate the significantly increased resolution of determining macropore recharge by combining physical, chemical, and isotopic methods of analysis. Techniques for quantifying macropore recharge were developed for both small-scale (1 to 10 km2) and regional-scale areas in arid and semi-arid areas. The Southern High Plains region of Texas and New Mexico was used as a representative field site to test these methods. Macropore recharge in small-scale areas is considered

  17. Plant species diversity of wetland ecosystem in an arid and semi-arid region in northwest China

    Institute of Scientific and Technical Information of China (English)

    LI Rui; LIU Yunfang; ZHANG Kebin

    2007-01-01

    In order to study the changes of plant species diversity along the biotope gradient and its influencing factors in a wetland-add grassland ecosystem in the add and semi-arid regions of northwest China,four transect lines were set along the biotope gradient in four directions:east,northeast,west and northwest,and altogether 123 sample plots were investigated on species composition,density,foliage cover,height and biomass (calculated in fresh weight).The whole study area was divided into the Wetland zone,the ecotone and the arid grassland zone in terms of habitat characteristics and vegetation types.In this paper,we analyzed and compared the species diversity in the ecotone of a wetland-dry grassland ecosystem in Yanchi County,Ningxia Hui Autonomous Region,with the help of biodiversity software BioDiversity Pro and statistical software Microcal Origin,as well as the combined measurement of species diversity indices.The results revealed distinct differences between those three vegetation zones along each transect line.The ecotone had the highest richness indices (R) and comprehensive diversity indices (Y),reflecting the edge effect.The greatest evenness indices (E) were found in the add grassland zones.This result agreed with the phenomenon of desertification reversion,vegetation restoration and dominant communities' formation.As for the four transect lines,the east and the northeast scored higher in each diversity index than the others due to less human disturbance,gentler topography uplift and more intercepted materials and energies.The highest Simpson index value was found in the northeast transect line,which was 39.9% higher than the lowest in the Northwest.

  18. Vapour intrusion from the vadose zone—seven algorithms compared

    NARCIS (Netherlands)

    Provoost, J.; Bosman, A.; Reijnders, L.; Bronders, J.; Touchant, K.; Swartjes, F.

    2010-01-01

    Background, aim and scope: Vapours of volatile organic compounds (VOCs) emanating from contaminated soils may move through the unsaturated zone to the subsurface. VOC in the subsurface can be transported to the indoor air by convective air movement through openings in the foundation and basement. On

  19. Eco-epidemiologia de Haemonchus contortus bahienses, ecotipo presente en ovinos de zonas aridas de Venezuela Eco-epidemiologia de Haemonchus contortus bahiensis, ecotipo presente em ovinos de zonas áridas da Venezuela Ecoepidemiology of Haemonchus contortus bahiensis: ecotype present in sheep of Venezuelan arid zone

    Directory of Open Access Journals (Sweden)

    Gustavo Morales

    1987-09-01

    Full Text Available Haemonchus contortus bahiensis Grisi, 1974 parasita a los ovinos de zonas áridas de Venezuela. En las hembras de dicho ecotipo la distribución de frecuencias por nosotros observada fue de un 15,32% para el morfotipo con lengüeta supravulvar, de un 51,61% para el botonado y de un 33,07% para el liso. Correspondiéndole a dicho ecotipo un índice de diversidad de Shannon-Weaver de 1,44 bits. Las medidas corporales, el tamaño de los huevos y el symlophe son similares en los tres morfotipos. La disposición espacial tanto de los machos como de las hembras en el seno de la población de hospedadores es de tipo contagiosa siendo bien descrita por el parámetro K de la distibución binominal negativa. Se evidenció la existencia de una compleja interacción entre la abundancia, la agregación y la prevalencia de dicho ecotipo y se discute su importancia sobre el equilibrio hospedador-parásito.Nas fêmesas do dito ecotipo a distribuição de freqüência observada foi de 15,32% para o morfotipo com lingueta supra-vulvar, de 51,61% para o tipo com botão vulvare de 33,07% para o tipo liso. A esse ecotipo corresponde um índice de diversidade de Shannon-Weaver igual a 1,44 bits. As medidas corporais, o tamanho dos ovos e o número de estrias cuticulares longitudinais são semelhantes nos três morfotipos. A disposição espacial, tanto dos machos quanto das fêmeas na população de hospedeiros é do tipo contagiosa, sendo bem descrita pelo parâmetro K da distribuição binomial negativa. Se verificou a existência de uma complexa interação entre a abundância, a agregação e a prevalência do citado ecotipo, discutindo-se sua importância no equilíbrio hospedeiro-parasito.The frequency distribution of female Haemonchus contortus bahiensis Grisi, 1974 in sheep from Venezuelan arid zones is 15.32% for the type with vulvar flap, 51.6% for the vulvar-knob and 33.07% for smooth type. A Shannon-Weaver diversity index corresponding to 1.44 bits was

  20. Life at the hyperarid margin: novel bacterial diversity in arid soils of the Atacama Desert, Chile

    Science.gov (United States)

    Neilson, Julia W.; Quade, Jay; Ortiz, Marianyoly; Nelson, William M.; Legatzki, Antje; Tian, Fei; LaComb, Michelle; Betancourt, Julio L.; Wing, Rod A.; Soderlund, Carol A.; Maier, Raina M.

    2012-01-01

    Nearly half the earth's surface is occupied by dryland ecosystems, regions susceptible to reduced states of biological productivity caused by climate fluctuations. Of these regions, arid zones located at the interface between vegetated semiarid regions and biologically unproductive hyperarid zones are considered most vulnerable. The objective of this study was to conduct a deep diversity analysis of bacterial communities in unvegetated arid soils of the Atacama Desert, to characterize community structure and infer the functional potential of these communities based on observed phylogenetic associations. A 454-pyrotag analysis was conducted of three unvegetated arid sites located at the hyperarid-arid margin. The analysis revealed communities with unique bacterial diversity marked by high abundances of novel Actinobacteria and Chloroflexi and low levels of Acidobacteria and Proteobacteria, phyla that are dominant in many biomes. A 16S rRNA gene library of one site revealed the presence of clones with phylogenetic associations to chemoautotrophic taxa able to obtain energy through oxidation of nitrite, carbon monoxide, iron, or sulfur. Thus, soils at the hyperarid margin were found to harbor a wealth of novel bacteria and to support potentially viable communities with phylogenetic associations to non-phototrophic primary producers and bacteria capable of biogeochemical cycling.

  1. Impacts of climate change on nutrient cycling in semi-arid and arid ecosystems

    Energy Technology Data Exchange (ETDEWEB)

    Belnap, J. [National Biological Survey, Moab, UT (United States)

    1995-09-01

    Effective precipitation is a major factor in determining nutrient pathways in different ecosystems. Soil flora and fauna play a critical role in nutrient cycles of all ecosystems. Temperature, timing, and amounts of precipitation affect population composition, activity levels, biomass, and recovery rates from disturbance. Changes in these variables can result in very different inputs and outputs for different nutrients. As a result, areas with less effective precipitation have very different nutrient cycles than more mesic zones. Climate change, therefore, can profoundly affect the nutrient cycles of ecosystems. Nitrogen cycles may be especially sensitive to changes in temperature and to timing and amounts of precipitation. Rainfall contains varying amounts of nitrogen compounds. Changes in amounts of rainfall will change amounts of nitrogen available to these systems. Because rainfall is limited in semi-arid and regions, these systems tend to be more dependent on microbial populations for nitrogen input. Consequently, understanding the effects of climate change on these organisms is critical in understanding the overall effect on ecosystems.

  2. SCIENCES IN COLD AND ARID REGIONS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Aims and Scope Sciences in Cold and Arid Regions, an international Engiish-language journal, is devoted to publishing the latest research achievements on the process and the pattern of Earth surface system in cold and arid regions. Researches in cold regions 1) emphasize particularly on the cold-region-characterized physical, chemical and biological processes and their interactions, and on the response of Cryosphere to Global change and Human activities as well as its effect to environment and the acclimatizable

  3. Recent advances associated with soil water in the unsaturated zone

    Science.gov (United States)

    Sposito, Garrison

    1995-07-01

    Perhaps the most compelling theme to emerge in the discipline of vadose-zone hydrology during the past decade is the scale invariance of soil water behavior. The numerous practical hydrologic consequences of this type of symmetry were summarized recently in a volume edited by Hillel and Elrick [1990]. The vadose zone, i.e., the porous earth material below the land surface whose water saturation fluctuates, is spatially heterogeneous to a degree difficult to capture in routine measurements, and there is a need to reduce this complexity for purposes of prediction and management. Scale invariance offers a way to do that. One imagines a heterogeneous field soil to be the union of approximately homogeneous spatial domains, each of which can be associated with a small number of characteristic length scales that are related to the equilibrium properties and movement of water. Heterogeneity then simplifies into the spatial variability of these local length scales, while the generic functional relationships that describe soil water properties remain uniform. These generic functional relationships include not only the dependence of water content and hydraulic conductivity on matric potential (the analog of pressure head for water in the unsaturated zone), but also the partial differential equations of transport and the empirical flux laws they contain. Russo [1991] has summarized and illustrated this important simplifying approach in the context of stochastic models of nonsteady infiltration. Roth et al. [1990] have compiled both research practice and the practitioners' consensus on how scale-invariance assists in the quantification and modeling of vadose-zone hydrologic processes. Some of the same scaling issues, of course, arise in groundwater hydrology; their conceptual underpinnings were discussed in detail in a compilation of research position papers edited by Cushman [1990].

  4. Feeding behavior and physiological responses of sheep grazing in the semi-arid

    Directory of Open Access Journals (Sweden)

    Carolyny Batista Lima

    2014-01-01

    Full Text Available Sheep farming is an important social and economic support for the population living in semi-arid zones. These climatic conditions in these regions - a high radiant heat load, especially - may require adjustments in physiology and behavior of the animal to enable their survival. The increased respiratory rate and rectal temperature, with seeking behavioral patterns reduced grazing time and increased idle time are recurrent in the literature as the main physiological and behavioral responses of sheep grazing in high radiant heat load environments. The presence of shadow, natural or artificial, can encourage and facilitate thermolysis physiological adjustments sheep without harm, predominantly, your metabolism. Thus, the objective of compiling information on the main patterns of behavior, as well as major physiological responses of sheep grazing in semi-arid zones.

  5. Soil tillage and water infiltration in semi-arid Morocco: the role fo surface and sub-surface soil conditions

    NARCIS (Netherlands)

    Dimanche, P.H.; Hoogmoed, W.B.

    2002-01-01

    Production of cereals in a dryland farming system forms an important part of agricultural production in Morocco. Yield levels on the Saïs Plateau between Meknès and Fez in the semi-arid zone, however, remain low possibly because of sub-optimum water use due to inefficient tillage systems. A study wa

  6. Study on RS- and GIS-based ecological capital assessment in arid areas

    Institute of Scientific and Technical Information of China (English)

    ZHOU Kefa; CHEN Xi; ZHOU Huarong; ZHANG Qing; ZUO Qiting; ZHANG Haibo; YAN Jinfeng; CHEN Chuan

    2006-01-01

    Ecological capital assessment is currently one of the important research contents in the interdisciplinary field of ecology, resources economics, environmental economics and ecological economics. To scientifically assess ecological capital redounds to decision-makers to consider the ecological cost in economic development, and is also necessary for sustainable economic development in arid areas. Based on the theory of landscape ecology,in this paper the per unit area ecological capital values in arid areas are researched by using the Landsat TM data, CBERS satellite data, meteorological data, MODIS satellite data and other ecological data,and the RS- and GIS-based models of assessing ecological capital values in arid areas are developed.Moreover, based on the field-measured data, a case study on ecological capital assessment in the Manas River basin, Xinjiang in 2003 is carried out. The basin is divided into 4 ecological capital areas so as to quantitatively calculate the ecological capital values of the ecosystems, analyze the spatial distribution of ecological capital, and chart the maps of spatial distribution of ecological capital. The results show that the total ecological capital value of the ecosystems in the Manas River basin in 2003 was 1.49454×1011yuan RMB. In spatial distribution, the ecological capital decreases from the alpine zones to the plains and from the oases to the deserts, which accords with the distribution of vegetation zonality in this arid area.The assessed results can objectively reflect the ecological capital and its spatial distribution in the arid basin, and can also provide reference for roundly carrying out the assessment of ecological capital in arid areas.

  7. Mitigating Climate Change in the Arid Lands of Namibia

    Science.gov (United States)

    Schneider, Martin B.; Sorensen, Marten

    2014-05-01

    Mitigating Climate Change in the Arid Lands of Namibia Namibia is the most arid country south of the Sahara, with scarce rainfall and perennial rivers only at its borders, > 80% of the area relies solely on groundwater. This has had devastating economic effects limiting opportunities for sustainable rural livelihoods that keep the population majority living below the World Bank poverty line (IFAD, 2013). A primary example of climatic variability which affects agrarian productivity is increased bush encroachment of Namibia's arid grazing land. The result has been a severe biodiversity loss, increased desertification and diminished water-use efficiency and underground water tables. Given these factors, Namibia's arid lands provide a unique opportunity to assess and test innovative / appropriate adaptation and mitigation strategies. Working toward sustainable management, restoration, and maintenance of balanced, resilient arid ecosystems in Namibia will also be a means to support and expand economic sectors incl. opportunities for job creation and potentially provide a model for similar arid regions. Main vegetation zones are: desert (46%), savannah (37%), and dry woodlands and forests (17%), i.e. management strategies currently used by rural communities. 2. Capture and assess cultural and gender dimensions of management strategies within stakeholder groups using participatory approaches. 3. Determine science-based alternatives for adaptive land management strategies and test their acceptability to local communities and within the current policy framework. 4. Integrate identified indigenous knowledge with appropriate science and new emerging technologies to develop a training toolkit of effective strategies relevant to all stakeholders. 5. Utilize training sessions, education workshops, curriculum revisions, and appropriate information and communication technologies (ICTs) including social media outlets to disseminate the toolkit strategies. 6. Apply a modified logic

  8. Study of energy partitioning and its feedback on the micro climate over different surfaces in an arid zone%干旱区不同下垫面能量分配机理及对微气候反馈的研究∗

    Institute of Scientific and Technical Information of China (English)

    李宏宇; 符淙斌; 郭维栋; 马芳

    2015-01-01

    Model simulations show that land use and land cover changes(LUCC) may alter surface energy budget and influence surface microclimate, but up to now, it still lacks of sufficient observations for explaining the mechanism of climate change brought about by LUCC. Grasslands and shrub lands are typical land covers in the mid-latitude arid zone of the northern hemisphere. The data used in this paper was collected from four sites which are related to grassland, open shrubland, savanna and closed shrubland, and all located in New Mexico, USA. The four sites are near each other and have the same background in climate and weather. Thus, the difference in surface energy partitioning over the four surfaces is induced by different land processes, which was explained in our study. The paper also analyzed the feedbacks of different land surface parameters and energy partitioning for the surface microclimate. We find that the leaf area index(LAI) and surface roughness of the four sites increases from the desert grassland to the closed shrubland. The difference in vegetation structures and functions also affects aerodynamic resistance and surface resistance to heat transfer and the resistances exhibit larger over sparse surfaces. Generally, the sites with high vegetation cover have higher net radiation, sensible and latent heat fluxes, particularly in the growing season. In addition, the contributions of impacting factors to the turbulent fluxes are diagnosed by Penman-Monteith equation and a mathematical formula combining net radiation with Bowen ratio. Compared to the desert grassland, the variations in net radiation over other three surfaces indicate positive contributions to both sensible and latent heat fluxes and govern their changes. The variations in the aerodynamic resistance and the surface resistance lead to opposite contributions. Besides, both radiative surface temperature and surface air temperature over the sparse surfaces are significantly higher than that over the

  9. Farmers'Perception of Water Resource Shortage and Adaption in Continental River Basin of Arid Zone:A Case of the Middle-lower Reaches of the Shiyang River%干旱区内陆河流域农户对水资源紧缺的感知及适应——以石羊河中下游为例

    Institute of Scientific and Technical Information of China (English)

    赵雪雁; 薛冰

    2015-01-01

    内陆河流域水资源极为紧缺,理解农户对水资源紧缺的感知及适应策略选择倾向对于制定科学的水资源管理政策至关重要.以石羊河中下游为研究区,基于农户调查数据,分析了农户对水资源紧缺的感知及适应策略,并利用经济计量模型分析了农户的水资源紧缺性感知对其适应策略选择的影响.结果发现:① 农户感知到的水资源紧缺可能性、严重性、适应功效及适应成本均较高,但感知到的自我效能处于中等水平;② 水资源紧缺风险感知与适应功效感知、适应成本感知呈显著正相关,其与自我效能感知虽呈负相关,但并不显著;③ 农户的适应策略多样化指数达2.80,水资源紧缺严重性感知、适应功效感知、适应成本感知及自我效能感知与适应策略多样化指数呈显著正相关;④ 随着风险感知与适应功效感知的增强,农户首选收缩型策略的概率增大,但随着自我效能感知的增强,农户首选收缩型策略的概率降低.最后,提出了增强农户适应能力的对策建议及未来需进一步关注的问题.%In recent years, the farmer's perception of environment change and their adaption strategies has been the research focus of the adaptation domain. Water resource shortage is the most serious environmental prob-lem in the continental river basin of arid zone, it is badly in need of looking for the effective adaptation strate-gies in order to reduce the adverse impact of water resource shortage. Understanding the farmers'perception of water resource shortage and adaption strategy selection is very important to determine the proper adaptation strategy and make scientific water resource management policy. Selecting the middle-lower reaches of the Shi-yang River as the study case and through stratified random sampling survey, participatory rural appraisal and investigation of plots, 367 household are investigated and sampled. Based on the

  10. Influences on the stable oxygen and carbon isotopes in gerbillid rodent teeth in semi-arid and arid environments: Implications for past climate and environmental reconstruction

    Science.gov (United States)

    Jeffrey, Amy; Denys, Christiane; Stoetzel, Emmanuelle; Lee-Thorp, Julia A.

    2015-10-01

    mammal teeth strongly reflects moisture availability in semi-arid and arid environments and would provide an excellent record of palaeo-aridity in a terrestrial setting. The results illustrate that an understanding of an animal's physiology is essential for interpreting the animal's isotopic responses to external contexts, especially in arid zones.

  11. Cultural innovation and megafauna interaction in the early settlement of arid Australia

    Science.gov (United States)

    Hamm, Giles; Mitchell, Peter; Arnold, Lee J.; Prideaux, Gavin J.; Questiaux, Daniele; Spooner, Nigel A.; Levchenko, Vladimir A.; Foley, Elizabeth C.; Worthy, Trevor H.; Stephenson, Birgitta; Coulthard, Vincent; Coulthard, Clifford; Wilton, Sophia; Johnston, Duncan

    2016-11-01

    Elucidating the material culture of early people in arid Australia and the nature of their environmental interactions is essential for understanding the adaptability of populations and the potential causes of megafaunal extinctions 50-40 thousand years ago (ka). Humans colonized the continent by 50 ka, but an apparent lack of cultural innovations compared to people in Europe and Africa has been deemed a barrier to early settlement in the extensive arid zone. Here we present evidence from Warratyi rock shelter in the southern interior that shows that humans occupied arid Australia by around 49 ka, 10 thousand years (kyr) earlier than previously reported. The site preserves the only reliably dated, stratified evidence of extinct Australian megafauna, including the giant marsupial Diprotodon optatum, alongside artefacts more than 46 kyr old. We also report on the earliest-known use of ochre in Australia and Southeast Asia (at or before 49-46 ka), gypsum pigment (40-33 ka), bone tools (40-38 ka), hafted tools (38-35 ka), and backed artefacts (30-24 ka), each up to 10 kyr older than any other known occurrence. Thus, our evidence shows that people not only settled in the arid interior within a few millennia of entering the continent, but also developed key technologies much earlier than previously recorded for Australia and Southeast Asia.

  12. Identification of potential artificial groundwater recharge zones in Northwestern Saudi Arabia using GIS and Boolean logic

    Science.gov (United States)

    Zaidi, Faisal K.; Nazzal, Yousef; Ahmed, Izrar; Naeem, Muhammad; Jafri, Muhammad Kamran

    2015-11-01

    Identifying potential groundwater recharge zones is a pre-requisite for any artificial recharge project. The present study focuses on identifying the potential zones of Artificial Groundwater Recharge (AGR) in Northwestern Saudi Arabia. Parameters including slope, soil texture, vadose zone thickness, groundwater quality (TDS) and type of water bearing formation were integrated in a GIS environment using Boolean logic. The results showed that 17.90% of the total studied area is suitable for AGR. The identified zones were integrated with the land use/land cover map to avoid agricultural and inhabited lands which reduced the total potential area to 14.24%. Geomorphologically the wadi beds are the most suitable sites for recharge. On the basis of the potential AGR zones closeness to the available recharge water supply (rain water, desalinated sea water and treated waste water) the potential zones were classified as Category A (high priority) and Category B (low priority).

  13. Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd. Poir from Brazilian semi-arid

    Directory of Open Access Journals (Sweden)

    Tancredo Augusto Feitosa de Souza

    2016-06-01

    Full Text Available Abstract Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

  14. Arbuscular mycorrhizal fungi in Mimosa tenuiflora (Willd.) Poir from Brazilian semi-arid.

    Science.gov (United States)

    de Souza, Tancredo Augusto Feitosa; Rodriguez-Echeverría, Susana; de Andrade, Leonaldo Alves; Freitas, Helena

    2016-01-01

    Many plant species from Brazilian semi-arid present arbuscular mycorrhizal fungi (AMF) in their rhizosphere. These microorganisms play a key role in the establishment, growth, survival of plants and protection against drought, pathogenic fungi and nematodes. This study presents a quantitative analysis of the AMF species associated with Mimosa tenuiflora, an important native plant of the Caatinga flora. AMF diversity, spore abundance and root colonization were estimated in seven sampling locations in the Ceará and Paraíba States, during September of 2012. There were significant differences in soil properties, spore abundance, percentage of root colonization, and AMF diversity among sites. Altogether, 18 AMF species were identified, and spores of the genera Acaulospora, Claroideoglomus, Dentiscutata, Entrophospora, Funneliformis, Gigaspora, Glomus, Racocetra, Rhizoglomus and Scutellospora were observed. AMF species diversity and their spore abundance found in M. tenuiflora rhizosphere shown that this native plant species is an important host plant to AMF communities from Brazilian semi-arid region. We concluded that: (a) during the dry period and in semi-arid conditions, there is a high spore production in M. tenuiflora root zone; and (b) soil properties, as soil pH and available phosphorous, affect AMF species diversity, thus constituting key factors for the similarity/dissimilarity of AMF communities in the M. tenuiflora root zone among sites.

  15. Groundwater Diffuse Recharge and its Response to Climate Changes in Semi-Arid Northwestern China

    Directory of Open Access Journals (Sweden)

    Lin Deng

    2015-01-01

    Full Text Available Understanding the processes and rates of groundwater recharge in arid and semi-arid areas is crucial for utilizing and managing groundwater resources sustainably. We obtained three chloride profiles of the unsaturated-zone in the desert/loess transition zone of northwestern China and reconstructed the groundwater recharge variations over the last 11, 21, and 37 years, respectively, using the generalized chloride mass balance (GCMB method. The average recharge rates were 43.7, 43.5, and 45.1 mm yr-1, respectively, which are similar to those evaluated by the chloride mass balance (CMB or GCMB methods in other semi-arid regions. The results indicate that the annual recharge rates were not in complete linear proportion to the corresponding annual precipitations, although both exhibited descending tendencies on the whole. Comparisons between the daily precipitation aggregate at different intensity and recharge rates reveal that the occurrence of relatively heavy daily precipitation per year may contribute to such nonlinearity between annual precipitation and recharge. The possible influences of vegetation cover alterations following precipitation change cannot be excluded as well. The approximately negative correlation between the average annual recharge and temperature suggests that changes in temperature have had significant influences on recharge.

  16. Does aridity influence the morphology, distribution and accumulation of calcium oxalate crystals in Acacia (Leguminosae: Mimosoideae)?

    Science.gov (United States)

    Brown, Sharon L; Warwick, Nigel W M; Prychid, Christina J

    2013-12-01

    Calcium oxalate (CaOx) crystals are a common natural feature of many plant families, including the Leguminosae. The functional role of crystals and the mechanisms that underlie their deposition remain largely unresolved. In several species, the seasonal deposition of crystals has been observed. To gain insight into the effects of rainfall on crystal formation, the morphology, distribution and accumulation of calcium oxalate crystals in phyllodes of the leguminous Acacia sect. Juliflorae (Benth.) C. Moore & Betche from four climate zones along an aridity gradient, was investigated. The shapes of crystals, which include rare Rosanoffian morphologies, were constant between species from different climate zones, implying that morphology was not affected by rainfall. The distribution and accumulation of CaOx crystals, however, did appear to be climate-related. Distribution was primarily governed by vein density, an architectural trait which has evolved in higher plants in response to increasing aridity. Furthermore, crystals were more abundant in acacias from low rainfall areas, and in phyllodes containing high concentrations of calcium, suggesting that both aridity and soil calcium levels play important roles in the precipitation of CaOx. As crystal formation appears to be calcium-induced, we propose that CaOx crystals in Acacia most likely function in bulk calcium regulation.

  17. Cavity-based secondary mineralization in volcanic tuffs of Yucca Mountain, Nevada: a new type of the polymineral vadose speleothem, or a hydrothermal deposit?

    Directory of Open Access Journals (Sweden)

    Dublyansky Yuri V.

    2005-07-01

    Full Text Available Secondary minerals (calcite, chalcedony, quartz, opal, fluorite, heulandite, strontianite residing in open cavities in the Miocenerhyolite tuffs of Yucca Mountain, Nevada have been interpreted by some researchers as "speleothemic" formations, deposited as aresult of downward infiltration of meteoric waters (DOE, 2001, Whelan et al., 2002. The major mineral of the paragenesis, calcite,shows spectacular trend of the textural and crystal morphology change: from anhedral granular occurrences, through (optionalplatelet, bladed and scepter varieties, to euhedral blocky morphologies. The trend is consistent with the overall decrease in thesupesaturation of the mineral forming solution. Stable isotope properties of calcite evolve from 13C-enriched (δ13C = +4 to +9 ‰ PDBat early stages of growth to 13C-depleted (-5 to -10 ‰ at late stages. The non-cyclic character of the isotope record and extremevariations of isotopic values argue against the meteoric origin of mineral forming fluids. The δ13C >4 ‰ PDB require isotope partitioningbetween dissolved CO2 and CH4, which is only possible in reducing anoxic environment, but not in aerated vadose zone.Fluid inclusions studied in calcite, quartz and fluorite revealed that the minerals were deposited from thermal solutions. Thetemperatures were higher at early stages of mineral growth (60 to 85oC and declined with time. Most late-stage calcites containonly all-liquid inclusions, suggesting temperatures less than ca. 35-50oC. Minerals collected close to the major fault show the highesttemperatures. Gases trapped in fluid inclusions are dominated by CO2 and CH4; Raman spectrometry results suggest the presenceof aromatic/cyclic hydrocarbon gases. The gas chemistry, thus, also indicates reduced (anoxic character of the mineral formingfluids.Secondary minerals at Yucca Mountain have likely formed during the short-term invasion(s of the deep-seated aqueous fluidsinto the vadose zone. Following the invasion

  18. Conservation and restoration of degraded ecosystems in arid and semi-arid areas of northwest China

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In "West Development" of China, one of the most important activities is the Natural Forest Protection Program, designed to swiftly convert the focus of management and utilization of the natural forests from a timber orientation towards forest conservation, sustainable management and environmental protection. The project covered almost all the arid and semi-arid regions in Northwest region. Accompanying this great campaign this paper studied the conservation and restoration model of degraded ecosystems in arid and semi-arid lands in Northwest China. The past practices have resulted in considerably natural forest degradation and loss through land conversion (primarily for agriculture), over-harvesting, inadequate reforestation and lack of protection. The consequences have been the loss of soil and water resources, diminished timber production capacity on a sustainable basis, and environmental losses. This paper applied Aronson's restoration model and proposed the conservation, restoration, re-allocation and preservation program for the implementation of environmental improvement and natural forest conservation.

  19. Adaptation to drought in arid and semi-arid environments: Case of the Zambezi Valley, Zimbabwe

    OpenAIRE

    Emmanuel Mavhura; Desmond Manatsa; Terence Mushore

    2015-01-01

    Small-scale rain-fed agriculture is the main livelihood in arid to semi-arid regions of subSaharan Africa. The area is characterised by erratic rainfall and frequent droughts, making the capacity for coping with temporal water shortages essential for smallholder farmers. Focusing on the Zambezi Valley, Zimbabwe, this study investigates the impact of drought on food security and the strategies used by smallholder farmers to cope with drought. We used meteorological data and interviews to exami...

  20. Aridity and decomposition processes in complex landscapes

    Science.gov (United States)

    Ossola, Alessandro; Nyman, Petter

    2015-04-01

    Decomposition of organic matter is a key biogeochemical process contributing to nutrient cycles, carbon fluxes and soil development. The activity of decomposers depends on microclimate, with temperature and rainfall being major drivers. In complex terrain the fine-scale variation in microclimate (and hence water availability) as a result of slope orientation is caused by differences in incoming radiation and surface temperature. Aridity, measured as the long-term balance between net radiation and rainfall, is a metric that can be used to represent variations in water availability within the landscape. Since aridity metrics can be obtained at fine spatial scales, they could theoretically be used to investigate how decomposition processes vary across complex landscapes. In this study, four research sites were selected in tall open sclerophyll forest along a aridity gradient (Budyko dryness index ranging from 1.56 -2.22) where microclimate, litter moisture and soil moisture were monitored continuously for one year. Litter bags were packed to estimate decomposition rates (k) using leaves of a tree species not present in the study area (Eucalyptus globulus) in order to avoid home-field advantage effects. Litter mass loss was measured to assess the activity of macro-decomposers (6mm litter bag mesh size), meso-decomposers (1 mm mesh), microbes above-ground (0.2 mm mesh) and microbes below-ground (2 cm depth, 0.2 mm mesh). Four replicates for each set of bags were installed at each site and bags were collected at 1, 2, 4, 7 and 12 months since installation. We first tested whether differences in microclimate due to slope orientation have significant effects on decomposition processes. Then the dryness index was related to decomposition rates to evaluate if small-scale variation in decomposition can be predicted using readily available information on rainfall and radiation. Decomposition rates (k), calculated fitting single pool negative exponential models, generally

  1. Aridity under conditions of increased CO2

    Science.gov (United States)

    Greve, Peter; Roderick, Micheal L.; Seneviratne, Sonia I.

    2016-04-01

    A string of recent of studies led to the wide-held assumption that aridity will increase under conditions of increasing atmospheric CO2 concentrations and associated global warming. Such results generally build upon analyses of changes in the 'aridity index' (the ratio of potential evaporation to precipitation) and can be described as a direct thermodynamic effect on atmospheric water demand due to increasing temperatures. However, there is widespread evidence that contradicts the 'warmer is more arid' interpretation, leading to the 'global aridity paradox' (Roderick et al. 2015, WRR). Here we provide a comprehensive assessment of modeled changes in a broad set of dryness metrics (primarily based on a range of measures of water availability) over a large range of realistic atmospheric CO2 concentrations. We use an ensemble of simulations from of state-of-the-art climate models to analyse both equilibrium climate experiments and transient historical simulations and future projections. Our results show that dryness is, under conditions of increasing atmospheric CO2 concentrations and related global warming, generally decreasing at global scales. At regional scales we do, however, identify areas that undergo changes towards drier conditions, located primarily in subtropical climate regions and the Amazon Basin. Nonetheless, the majority of regions, especially in tropical and mid- to northern high latitudes areas, display wetting conditions in a warming world. Our results contradict previous findings and highlight the need to comprehensively assess all aspects of changes in hydroclimatological conditions at the land surface. Roderick, M. L., P. Greve, and G. D. Farquhar (2015), On the assessment of aridity with changes in atmospheric CO2, Water Resour. Res., 51, 5450-5463

  2. CHARACTERISTICS OF ARIDITY CONDITIONS IN SOUTH DOBRUDJA

    Directory of Open Access Journals (Sweden)

    A. TISCOVSCHI

    2013-04-01

    Full Text Available Characteristics of Aridity Conditions in South Dobrudja. For most people, the arid and semi-arid lands are those where precipitation is low (less than 200 mm per year, and yet enough for supplying streams capable of temporarily carrying the debris resulted from weathering, but insufficient for encouraging the development of a vegetal cover meant to protect the soil blanket against eroding agents. The drought is a major and permanent climatic risk for the Dobrudja territory as a whole and for South Dobrudja in particular, a territory where hydrographic network is underdeveloped, streams are ephemeral, and semi-endorheic areas are well developed. When the period of moisture deficiency lasts longer, it can bring about a significant water imbalance, which results in crop losses or restrictions in water consumption, thus leading to a number of economic problems. Under the circumstances, the risk of aridity expansion is significant, this being the reason why a better water management system in Romania is urgently needed. In the last decades, the numerous specialty studies undertaken in the area have emphasized an intensification of the process of dryness, because atmospheric and pedological droughts have become more and more serious. Romania is a member of the United Nations Convention to Combat Desertification (UNCCD and the World Meteorological Organization (WMO. It actively participates within the drought management network and the Drought Management Center for Southeastern Europe, which comprises 11 countries. The scope is to work together and exchange experience with the neighboring countries that have recorded positive results and acquired a rich experience in terms of drought management. The employment of appropriate pluvial indices in identifying the areas prone to aridity may prove to be convenient tool for finding practical solutions meant to mitigate the impact of this phenomenon on the local communities living in South Dobrudja.

  3. Analysis list: Arid1a [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Arid1a Adipocyte + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Arid1a....1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Arid1a.5.tsv http://dbarchive.biosciencedbc.jp/...kyushu-u/mm9/target/Arid1a.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Arid1a.Adipocyte.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Adipocyte.gml ...

  4. Water pulses and biogeochemical cycles in arid and semiarid ecosystems.

    Science.gov (United States)

    Austin, Amy T; Yahdjian, Laura; Stark, John M; Belnap, Jayne; Porporato, Amilcare; Norton, Urszula; Ravetta, Damián A; Schaeffer, Sean M

    2004-10-01

    The episodic nature of water availability in arid and semiarid ecosystems has significant consequences on belowground carbon and nutrient cycling. Pulsed water events directly control belowground processes through soil wet-dry cycles. Rapid soil microbial response to incident moisture availability often results in almost instantaneous C and N mineralization, followed by shifts in C/N of microbially available substrate, and an offset in the balance between nutrient immobilization and mineralization. Nitrogen inputs from biological soil crusts are also highly sensitive to pulsed rain events, and nitrogen losses, particularly gaseous losses due to denitrification and nitrate leaching, are tightly linked to pulses of water availability. The magnitude of the effect of water pulses on carbon and nutrient pools, however, depends on the distribution of resource availability and soil organisms, both of which are strongly affected by the spatial and temporal heterogeneity of vegetation cover, topographic position and soil texture. The 'inverse texture hypothesis' for net primary production in water-limited ecosystems suggests that coarse-textured soils have higher NPP than fine-textured soils in very arid zones due to reduced evaporative losses, while NPP is greater in fine-textured soils in higher rainfall ecosystems due to increased water-holding capacity. With respect to belowground processes, fine-textured soils tend to have higher water-holding capacity and labile C and N pools than coarse-textured soils, and often show a much greater flush of N mineralization. The result of the interaction of texture and pulsed rainfall events suggests a corollary hypothesis for nutrient turnover in arid and semiarid ecosystems with a linear increase of N mineralization in coarse-textured soils, but a saturating response for fine-textured soils due to the importance of soil C and N pools. Seasonal distribution of water pulses can lead to the accumulation of mineral N in the dry season

  5. HEIST: An event-scale model of cascading water and solute fronts through the vadose zone (Invited)

    Science.gov (United States)

    Harman, C. J.; Basu, N. B.; Rao, P. C.; Sivapalan, M.

    2009-12-01

    The transport of a sorbing, degrading solute (such as Atrazine) through the soil is largely driven by infiltrating water from storms or irrigation, and so depends on the interactions between the timing and characteristics of the rainfall or irrigation events, the properties of the solute, soil characteristics (e.g, porosity, macropore density etc.), and the antecedent soil moisture conditions. This interaction causes the time series inputs of the solute to be “filtered” prior to reaching the watertable, so that the timing, frequency and magnitude of output events is altered. While many previous studies have examined the movement of solutes through soils for a particular site, few have examined the nature of this filtering in more general terms. In this work we present an elegant 1-D model of solute transport through the soil, driven by infiltration events, that is designed to examine this filtering effect. A unique feature of this model is the event-scale time-stepping. By assuming that infiltration and redistribution processes occur instantaneously during an event, while degradation, mobilization, and evapotranspiration are the only important processes occurring between storms, analytical expressions can be derived for the event-to-event transformations of the input signal within the system. Solutes can be surface applied in recalcitrant and labile forms, with first-order mass transfer between the pools, and linear reversible sorption. Infiltrating water mobilizes the labile dissolved solute, generating a point load that moves through the soil with wetting fronts generated by storm events. The retardation and first-order decay of the point-loads eventually decouples them from the wetting fronts they first entered with, allowing solutes to concentrate in the profile. Because only one timestep is required per storm, the model runs very fast, allowing us to examine the effect of different parameter combinations on the filtering. The results show that, particularly in shallow soils, solute delivery events exhibit an intriguing clustering behavior both in time and in a phase space plot with solute inputs and initial conditions. This clustering is caused by events that flush significant amounts of solute from the system, which occur more rarely when soils are deeper, or degradation rates are higher. The results are interpreted in terms of their implications for ecosystem services and downstream ecosystem health.

  6. Vadose zone transport of natural and synthetic estrogen hormones at Penn State's "Living Filter" wastewater irrigation site

    Science.gov (United States)

    The increase in endocrine disrupting compounds (EDCs) in the environment has generated new research focused on the behavior of these compounds in natural soil and water ecosystems. To understand how estrogens behave in the soil environment as a result of 25+ years of wastewater irrigation, soils fro...

  7. Annual report to W-2188 multi-state research project "Characterizing Mass and Energy Transport at Different Vadose Zone Scales"

    Science.gov (United States)

    Results of our studies on soil water sensors were conveyed to manufacturers, including Acclima, Inc. and Decagon, Inc. Four invited presentations on soil water sensing for irrigation management were made to irrigation conferences in the Central and Southern High Plains (Nebraska and Texas). Eleven i...

  8. A two-dimensional simulation of tritium transport in the vadose zone at the Nevada Test site

    Energy Technology Data Exchange (ETDEWEB)

    Ross, W.C.; Wheatcraft, S.W.

    1994-09-01

    The site of a 0.75-kiloton underground nuclear explosion, the Cambric event, was selected for the study of radionuclide transport in the hydrologic environment. Water samples from RNM-2S, a well located 91 m from Cambric, have been analyzed for tritium and other radionuclides since the initiation of pumping. Water from RNM-2S flows to Frenchman Lake via an unlined canal. Flume data indicate canal transmission losses of approximately 2m{sup 3}/day/meter of canal. To determine if infiltrating canal water might be recirculated by RNM-2S, and therefore provide an additional radionuclide input to water samples collected at RNM-2S, a two-dimensional variably saturated solute transport computer model (SATURN, Huyakorn et al., 1983) was used to simulate the movement of tritium from the canal to the water table. Results indicate that recirculated canal water has not had a significant effect on the breakthrough of tritium at RNM-2S.

  9. Sorption and phase distribution of ethanol and butanol blended gasoline vapours in the vadose zone after release.

    Science.gov (United States)

    Ugwoha, Ejikeme; Andresen, John M

    2014-03-01

    The sorption and phase distribution of 20% ethanol and butanol blended gasoline (E20 and B20) vapours have been examined in soils with varying soil organic matter (SOM) and water contents via laboratory microcosm experiments. The presence of 20% alcohol reduced the sorption of gasoline compounds by soil as well as the mass distribution of the compounds to soil solids. This effect was greater for ethanol than butanol. Compared with the sorption coefficient (Kd) of unblended gasoline compounds, the Kd of E20 gasoline compounds decreased by 54% for pentane, 54% for methylcyclopentane (MCP) and 63% for benzene, while the Kd of B20 gasoline compounds decreased by 39% for pentane, 38% for MCP and 49% for benzene. The retardation factor (R) of E20 gasoline compounds decreased by 53% for pentane, 53% for MCP and 48% for benzene, while the R of B20 gasoline compounds decreased by 39% for pentane, 37% for MCP and 38% for benzene. For all SOM and water contents tested, the Kd and R of all gasoline compounds were in the order of unblended gasoline > B20 > E20, indicating that the use of high ethanol volume in gasoline to combat climate change could put the groundwater at greater risk of contamination.

  10. Coupled Vadose Zone and Atmospheric Surface-Layer Transport of CO2 from Geologic Carbon Sequestration Sites

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, Curtis M.; Unger, Andre J.A.

    2004-03-29

    Geologic carbon dioxide (CO{sub 2}) sequestration is being considered as a way to offset fossil-fuel-related CO{sub 2} emissions to reduce the rate of increase of atmospheric CO{sub 2} concentrations. The accumulation of vast quantities of injected carbon dioxide (CO{sub 2}) in geologic sequestration sites may entail health and environmental risks from potential leakage and seepage of CO{sub 2} into the near-surface environment. We are developing and applying a coupled subsurface and atmospheric surface-layer modeling capability built within the framework of the integral finite difference reservoir simulator TOUGH2. The overall purpose of modeling studies is to predict CO{sub 2} concentration distributions under a variety of seepage scenarios and geologic, hydrologic, and atmospheric conditions. These concentration distributions will provide the basis for determining above-ground and near-surface instrumentation needs for carbon sequestration monitoring and verification, as well as for assessing health, safety, and environmental risks. A key feature of CO{sub 2} is its large density ({rho} = 1.8 kg m{sup -3}) relative to air ({rho} = 1.2 kg m{sup -3}), a property that may allow small leaks to cause concentrations in air above the occupational exposure limit of 4 percent in low-lying and enclosed areas such as valleys and basements where dilution rates are low. The approach we take to coupled modeling involves development of T2CA, a TOUGH2 module for modeling the multicomponent transport of water, brine, CO{sub 2}, gas tracer, and air in the subsurface. For the atmospheric surface-layer advection and dispersion, we use a logarithmic vertical velocity profile to specify constant time-averaged ambient winds, and atmospheric dispersion approaches to model mixing due to eddies and turbulence. Initial simulations with the coupled model suggest that atmospheric dispersion quickly dilutes diffuse CO{sub 2} seepage fluxes to negligible concentrations, and that rainfall infiltration causes CO{sub 2} to return to the subsurface as a dissolved component in infiltrating rainwater.

  11. Gypsum effects on crop yield and chemistry of soil, crop tissue, and vadose zone water: A meta-analysis.

    Science.gov (United States)

    Gypsum has various potential benefits as a soil amendment, but data are lacking on gypsum effects on crop yields and on environmental impacts across diverse field sites. Gypsum studies were conducted in six states using a common design with three rates each of mined and flue gas desulfurization (FGD...

  12. Enhanced Remediation of Toluene in the Vadose Zone via a Nitrate-Rich Nutrient Solution: Field Study

    Science.gov (United States)

    Tindall, J. A.; Friedel, M. J.

    2003-12-01

    The objective of this study was to test the effectiveness of nitrate-rich nutrient solutions and hydrogen peroxide (H202) to enhance in-situ microbial remediation of toluene. Three sand filled plots (2 m2 surface area and 1.5 meters deep) were tested in three phases (each phase lasting approximately 2 weeks). During each phase, toluene (21.6 mol as an emulsion in 50L of water) was applied uniformly via sprinkler irrigation. Passive remediation was allowed to occur during the first (control) phase. A nutrient solution (modified Hoagland), concentrated in 40L of water, was tested during the second phase. The final phase involved addition of 230 moles of H202 in 50L of water to increase the available oxygen needed for aerobic biodegradation. During the first phase, toluene concentrations in soil gas were reduced from 120 ppm to 25 ppm in 14 days. After the addition of nutrients during the second phase, concentrations were reduced from 90 ppm to about 8 ppm within 14 days, and for the third phase (H202), toluene concentrations were about 1 ppm after only five days. Initial results suggest that this method could be an effective means of remediating a contaminated site, directly after a BTEX spill, without the intrusiveness and high cost of other abatement technologies such as bioventing and soil vapor extraction. However, further tests need to be completed to determine the effect of each of the BTEX components.

  13. Treatability Test Report: Characterization of Vadose Zone Carbon Tetrachloride Source Strength Using Tomographic Methods at the 216-Z-9 Site

    Energy Technology Data Exchange (ETDEWEB)

    Truex, Michael J.; Carroll, Kenneth C.; Rohay, Virginia J.; Mackley, Rob D.; Parker, Kyle R.

    2012-09-28

    A treatability test was conducted in 2011 at the 216-Z-9 Trench to evaluate methods for collecting characterization information that supports refined assessment of SVE performance goals based on impact to groundwater. The characterization information can also provide input to operational strategies for continued SVE operation and decisions regarding closure of the SVE system or transition to other remedies, if necessary.

  14. Appendix C -- Soil gas analysis of vadose zone monitoring system installation report for McClellan AFB

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-31

    This appendix compiles the data from gas chromatography/mass spectroscopy measurements of gas samples from McClellan AFB soils collected and analyzed in December, 1995. Compounds detected include: vinyl chloride, methylene chloride, chloroethanes, chloroethenes, benzene, chlorobenzenes, propylene, trimethylbenzenes, acetone, toluene, xylenes.

  15. Update on Research on the Impact of CO2 Intrusion into USDWs, the Vadose Zone, and Indoor Air

    Science.gov (United States)

    It is widely acknowledged that leakage through transmissive faults (and associated fractures) and well penetrations (operational, non-operational, and abandoned wells) are the most likely pathways for migration out of a storage formation at sites selected for geological sequestra...

  16. Vadose zone measurement and modeling Mensurações e modelagem na zona não saturada

    Directory of Open Access Journals (Sweden)

    J. W. Hopmans

    1997-06-01

    Full Text Available The following treatise is a summary of some of the ongoing research activities in the soil physics program at the University of California in Davis. Each of the four listed areas win be presented at the Workshop on special topics on soil physics and crop modeling in Piracicaba at the University of Sao Paulo. We limited ourselves to a general overview of each area, but will present a more thorough discussion with examples at the Workshop.O presente texto é o resumo das atuais atividades do programa de física do solo na Universidade da Califórnia, em Davis. As quatro áreas aqui relacionadas serão apresentadas no "Workshop on special topics about soil physics and crop modeling and simulation" na Universidade de São Paulo, em Piracicaba. O texto se restringe a urna abordagem geral de cada área, porém discussões e exemplos mais detalhados serão apresentados no Workshop.

  17. Zero-tension lysimeters: An improved design to monitor colloid-facilitated contaminant transport in the vadose zone

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, M.L.; Scharf, R.L.; Shang, C.

    1995-04-24

    There is increasing evidence that mobile colloids facilitate the long-distance transport of contaminants. The mobility of fine particles and macromolecules has been linked to the movement of actinides, organic contaminants, and heavy metals through soil. Direct evidence for colloid mobility includes the presence of humic materials in deep aquifers as well as coatings of accumulated clay, organic matter, or sesquioxides on particle or aggregate surfaces in subsoil horizons of many soils. The potential for colloid-facilitated transport of contaminants from hazardous-waste sites requires adequate monitoring before, during, and after in-situ remediation treatments. Zero-tension lysimeters (ZTLs) are especially appropriate for sampling water as it moves through saturated soil, although some unsaturated flow events may be sampled as well. Because no ceramic barrier or fiberglass wick is involved to maintain tension on the water (as is the case with other lysimeters), particles suspended in the water as well as dissolved species may be sampled with ZTLs. In this report, a ZTL design is proposed that is more suitable for monitoring colloid-facilitated contaminant migration. The improved design consists of a cylinder made of polycarbonate or polytetrafluoroethylene (PTFE) that is placed below undisturbed soil material. In many soils, a hydraulically powered tube may be used to extract an undisturbed core of soil before placement of the lysimeter. In those cases, the design has significant advantages over conventional designs with respect to simplicity and speed of installation. Therefore, it will allow colloid-facilitated transport of contaminants to be monitored at more locations at a given site.

  18. Rainfall Characterization In An Arid Area

    OpenAIRE

    Bazaraa, A. S.; Ahmed, Shamim

    1991-01-01

    The objective of this work is to characterize the rainfall in Doha which lies in an arid region. The rainfall data included daily rainfall depth since 1962 and the hyetographs of the individual storms since 1976. The rainfall is characterized by high variability and severe thunderstorms which are of limited geographical extent. Four probability distributions were used to fit the maximum rainfall in 24 hours and the annual rainfall depth. The extreme value distribution was found to have the be...

  19. Aridity increases below-ground niche breadth in grass communities

    Science.gov (United States)

    Butterfield, Bradley J.; Bradford, John B.; Munson, Seth M.; Gremer, Jennifer R.

    2017-01-01

    Aridity is an important environmental filter in the assembly of plant communities worldwide. The extent to which root traits mediate responses to aridity, and how they are coordinated with leaf traits, remains unclear. Here, we measured variation in root tissue density (RTD), specific root length (SRL), specific leaf area (SLA), and seed size within and among thirty perennial grass communities distributed along an aridity gradient spanning 190–540 mm of climatic water deficit (potential minus actual evapotranspiration). We tested the hypotheses that traits exhibited coordinated variation (1) among species, as well as (2) among communities varying in aridity, and (3) functional diversity within communities declines with increasing aridity, consistent with the “stress-dominance” hypothesis. Across communities, SLA and RTD exhibited a coordinated response to aridity, shifting toward more conservative (lower SLA, higher RTD) functional strategies with increasing aridity. The response of SRL to aridity was more idiosyncratic and was independent of variation in SLA and RTD. Contrary to the stress-dominance hypothesis, the diversity of SRL values within communities increased with aridity, while none of the other traits exhibited significant diversity responses. These results are consistent with other studies that have found SRL to be independent of an SLA–RTD axis of functional variation and suggest that the dynamic nature of soil moisture in arid environments may facilitate a wider array of resource capture strategies associated with variation in SRL.

  20. Arid sites stakeholder participation in evaluating innovative technologies: VOC-Arid Site Integrated Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, T.S.; McCabe, G.H.; Brockbank, B.R. [and others

    1995-