Characterization of DNAPL Source Zone Architecture and Prediction of Associated Plume Response: Progress and Perspectives

Science.gov (United States)

Abriola, L. M.; Pennell, K. D.; Ramsburg, C. A.; Miller, E. L.; Christ, J.; Capiro, N. L.; Mendoza-Sanchez, I.; Boroumand, A.; Ervin, R. E.; Walker, D. I.; Zhang, H.

2012-12-01

It is now widely recognized that the distribution of contaminant mass will control both the evolution of aqueous phase plumes and the effectiveness of many source zone remediation technologies at sites contaminated by dense nonaqueous phase liquids (DNAPLs). Advances in the management of sites containing DNAPL source zones, however, are currently hampered by the difficulty associated with characterizing subsurface DNAPL 'architecture'. This presentation provides an overview of recent research, integrating experimental and mathematical modeling studies, designed to improve our ability to characterize DNAPL distributions and predict associated plume response. Here emphasis is placed on estimation of the most information-rich DNAPL architecture metrics, through a combination of localized in situ tests and more readily available plume transect concentration observations. Estimated metrics will then serve as inputs to an upscaled screening model for prediction of long term plume response. Machine learning techniques were developed and refined to identify a variety of source zone metrics and associated confidence intervals through the processing of down gradient concentration data. Estimated metrics include the volumes and volume percentages of DNAPL in pools and ganglia, as well as their ratio (pool fraction). Multiphase flow and transport simulations provided training data for model development and assessment that are representative of field-scale DNAPL source zones and their evolving plumes. Here, a variety of release and site heterogeneity (sequential Gaussian permeability) conditions were investigated. Push-pull tracer tests were also explored as a means to provide localized in situ observations to refine these metric estimates. Here, two-dimensional aquifer cell experiments and mathematical modeling were used to quantify upscaled interphase mass transfer rates and the interplay between injection and extraction rates, local source zone architecture, and tracer

Numerical modeling of continental lithospheric weak zone over plume

Science.gov (United States)

Perepechko, Y. V.; Sorokin, K. E.

2011-12-01

The work is devoted to the development of magmatic systems in the continental lithosphere over diffluent mantle plumes. The areas of tension originating over them are accompanied by appearance of fault zones, and the formation of permeable channels, which are distributed magmatic melts. The numerical simulation of the dynamics of deformation fields in the lithosphere due to convection currents in the upper mantle, and the formation of weakened zones that extend up to the upper crust and create the necessary conditions for the formation of intermediate magma chambers has been carried out. Thermodynamically consistent non-isothermal model simulates the processes of heat and mass transfer of a wide class of magmatic systems, as well as the process of strain localization in the lithosphere and their influence on the formation of high permeability zones in the lower crust. The substance of the lithosphere is a rheologic heterophase medium, which is described by a two-velocity hydrodynamics. This makes it possible to take into account the process of penetration of the melt from the asthenosphere into the weakened zone. The energy dissipation occurs mainly due to interfacial friction and inelastic relaxation of shear stresses. The results of calculation reveal a nonlinear process of the formation of porous channels and demonstrate the diversity of emerging dissipative structures which are determined by properties of both heterogeneous lithosphere and overlying crust. Mutual effect of a permeable channel and the corresponding filtration process of the melt on the mantle convection and the dynamics of the asthenosphere have been studied. The formation of dissipative structures in heterogeneous lithosphere above mantle plumes occurs in accordance with the following scenario: initially, the elastic behavior of heterophase lithosphere leads to the formation of the narrow weakened zone, though sufficiently extensive, with higher porosity. Further, the increase in the width of

Fate of organic contaminants in the redox zones of a landfill leachate pollution plume (Vejen, Denmark)

DEFF Research Database (Denmark)

Lyngkilde, John; Christensen, Thomas Højlund

1992-01-01

Samples from 75 sample locations in a landfill leachate pollution plume reveal a significant disappearance of specific organic compounds (SOC's) within the first 100 m of the plume. Only the herbicide Mecoprop® (MCPP) migrates further. Since sorption and dilution cannot account for the decreasing...... concentrations, degradation is considered to be the governing process. Non-volatile organic carbon shows a corresponding fate probably acting as a substrate for the microbial processes. The first 20 m of the plume are methanogenic/sulfidogenic, judged on the chemistry of the groundwater, followed...... by a significant ferrogenic zone exhibiting a substantial capacity to degrade the SOC's. The presence of intermediary products (here an oxidized camphor compound) supports the concept of degradation within the ferrogenic zone. This investigation draws the attention to the significant natural attenuation of organic...

Effects of crude oil on water and tracer movement in the unsaturated and saturated zones.

Science.gov (United States)

Delin, Geoffrey N; Herkelrath, William N

2017-05-01

A tracer test was conducted to aid in the investigation of water movement and solute transport at a crude-oil spill site near Bemidji, Minnesota. Time of travel was measured using breakthrough curves for rhodamine WT and bromide tracers moving from the soil surface through oil-contaminated and oil-free unsaturated zones to the saturated zone. Results indicate that the rates of tracer movement were similar in the oil-free unsaturated and saturated zones compared to the oily zones. These results are somewhat surprising given the oil contamination in the unsaturated and saturated zones. Rhodamine tracer breakthrough in the unsaturated and saturated zones in general was delayed in comparison to bromide tracer breakthrough. Peak tracer concentrations for the lysimeters and wells in the oily zone were much greater than at the corresponding depths in the oil-free zone. Water and tracer movement in the oily zone was complicated by soil hydrophobicity and decreased oil saturations toward the periphery of the oil. Preferential flow resulted in reduced tracer interaction with the soil, adsorption, and dispersion and faster tracer movement in the oily zone than expected. Tracers were freely transported through the oily zone to the water table. Recharge calculations support the idea that the oil does not substantially affect recharge in the oily zone. This is an important result indicating that previous model-based assumptions of decreased recharge beneath the oil were incorrect. Results have important implications for modeling the fate and transport of dissolved contaminants at hydrocarbon spill sites. Published by Elsevier B.V.

Formation of mantle "lone plumes" in the global downwelling zone - A multiscale modelling of subduction-controlled plume generation beneath the South China Sea

Science.gov (United States)

Zhang, Nan; Li, Zheng-Xiang

2018-01-01

It has been established that almost all known mantle plumes since the Mesozoic formed above the two lower mantle large low shear velocity provinces (LLSVPs). The Hainan plume is one of the rare exceptions in that instead of rising above the LLSVPs, it is located within the broad global mantle downwelling zone, therefore classified as a "lone plume". Here, we use the Hainan plume example to investigate the feasibility of such lone plumes being generated by subducting slabs in the mantle downwelling zone using 3D geodynamic modelling. Our geodynamic model has a high-resolution regional domain embedded in a relatively low resolution global domain, which is set up in an adaptive-mesh-refined, 3D mantle convection code ASPECT (Advanced Solver for Problems in Earth's ConvecTion). We use a recently published plate motion model to define the top mechanical boundary condition. Our modelling results suggest that cold slabs under the present-day Eurasia, formed from the Mesozoic subduction and closure of the Tethys oceans, have prevented deep mantle hot materials from moving to the South China Sea from regions north or west of the South China Sea. From the east side, the Western Pacific subduction systems started to promote the formation of a lower-mantle thermal-chemical pile in the vicinity of the future South China Sea region since 70 Ma ago. As the top of this lower-mantle thermal-chemical pile rises, it first moved to the west, and finally rested beneath the South China Sea. The presence of a thermochemical layer (possible the D″ layer) in the model helps stabilizing the plume root. Our modelling is the first implementation of multi-scale mesh in the regional model. It has been proved to be an effective way of modelling regional dynamics within a global plate motion and mantle dynamics background.

Saturated Zone In-Situ Testing

International Nuclear Information System (INIS)

Reimus, P. W.; Umari, M. J.

2003-01-01

The purpose of this scientific analysis is to document the results and interpretations of field experiments that have been conducted to test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain. The test interpretations provide estimates of flow and transport parameters that are used in the development of parameter distributions for Total System Performance Assessment (TSPA) calculations. These parameter distributions are documented in the revisions to the SZ flow model report (BSC 2003 [ 162649]), the SZ transport model report (BSC 2003 [ 162419]), the SZ colloid transport report (BSC 2003 [162729]), and the SZ transport model abstraction report (BSC 2003 [1648701]). Specifically, this scientific analysis report provides the following information that contributes to the assessment of the capability of the SZ to serve as a barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvium Testing Complex (ATC), which is located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and

Saturated Zone In-Situ Testing

Energy Technology Data Exchange (ETDEWEB)

P. W. Reimus; M. J. Umari

2003-12-23

The purpose of this scientific analysis is to document the results and interpretations of field experiments that have been conducted to test and validate conceptual flow and radionuclide transport models in the saturated zone (SZ) near Yucca Mountain. The test interpretations provide estimates of flow and transport parameters that are used in the development of parameter distributions for Total System Performance Assessment (TSPA) calculations. These parameter distributions are documented in the revisions to the SZ flow model report (BSC 2003 [ 162649]), the SZ transport model report (BSC 2003 [ 162419]), the SZ colloid transport report (BSC 2003 [162729]), and the SZ transport model abstraction report (BSC 2003 [1648701]). Specifically, this scientific analysis report provides the following information that contributes to the assessment of the capability of the SZ to serve as a barrier for waste isolation for the Yucca Mountain repository system: (1) The bases for selection of conceptual flow and transport models in the saturated volcanics and the saturated alluvium located near Yucca Mountain. (2) Results and interpretations of hydraulic and tracer tests conducted in saturated fractured volcanics at the C-wells complex near Yucca Mountain. The test interpretations include estimates of hydraulic conductivities, anisotropy in hydraulic conductivity, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, matrix diffusion coefficients, fracture apertures, and colloid transport parameters. (3) Results and interpretations of hydraulic and tracer tests conducted in saturated alluvium at the Alluvium Testing Complex (ATC), which is located at the southwestern corner of the Nevada Test Site (NTS). The test interpretations include estimates of hydraulic conductivities, storativities, total porosities, effective porosities, longitudinal dispersivities, matrix diffusion mass transfer coefficients, and

Heterogeneous hyporheic zone dechlorination of a TCE groundwater plume discharging to an urban river reach.

Science.gov (United States)

Freitas, Juliana G; Rivett, Michael O; Roche, Rachel S; Durrant Neé Cleverly, Megan; Walker, Caroline; Tellam, John H

2015-02-01

The typically elevated natural attenuation capacity of riverbed-hyporheic zones is expected to decrease chlorinated hydrocarbon (CHC) groundwater plume discharges to river receptors through dechlorination reactions. The aim of this study was to assess physico-chemical processes controlling field-scale variation in riverbed-hyporheic zone dechlorination of a TCE groundwater plume discharge to an urban river reach. The 50-m long pool-riffle-glide reach of the River Tame in Birmingham (UK) studied is a heterogeneous high energy river environment. The shallow riverbed was instrumented with a detailed network of multilevel samplers. Freeze coring revealed a geologically heterogeneous and poorly sorted riverbed. A chlorine number reduction approach provided a quantitative indicator of CHC dechlorination. Three sub-reaches of contrasting behaviour were identified. Greatest dechlorination occurred in the riffle sub-reach that was characterised by hyporheic zone flows, moderate sulphate concentrations and pH, anaerobic conditions, low iron, but elevated manganese concentrations with evidence of sulphate reduction. Transient hyporheic zone flows allowing input to varying riverbed depths of organic matter are anticipated to be a key control. The glide sub-reach displayed negligible dechlorination attributed to the predominant groundwater baseflow discharge condition, absence of hyporheic zone, transition to more oxic conditions and elevated sulphate concentrations expected to locally inhibit dechlorination. The tail-of-pool-riffle sub-reach exhibited patchy dechlorination that was attributed to sub-reach complexities including significant flow bypass of a low permeability, high organic matter, silty unit of high dechlorination potential. A process-based conceptual model of reach-scale dechlorination variability was developed. Key findings of practitioner relevance were: riverbed-hyporheic zone CHC dechlorination may provide only a partial, somewhat patchy barrier to CHC

Driver behavior and accident frequency in school zones: Assessing the impact of sign saturation.

Science.gov (United States)

Strawderman, Lesley; Rahman, Md Mahmudur; Huang, Yunchen; Nandi, Apurba

2015-09-01

Based on the models of human information processing, if a driver observes too many of the same signs, he or she may no longer pay attention to those signs. In the case of school zones, this expected effect may lead to non-compliance to posted speeds, negatively impacting safety around nearby schools. This study aims to investigate the effect of the number of nearby school zones on driver behavior (vehicle speed and compliance) and accident frequency. As a measure of the density of school zones, this study introduced and defined a new term sign saturation and presented a methodology to calculate sign saturation for school zones. Results found a significant effect of sign saturation on vehicle speed, compliance, and accident frequency. This study also examined the speeding behavior in school zones for different time of the day and day of the week. Results found that speeding was more prevalent in the early mornings and during the weekends. Copyright © 2015 Elsevier Ltd. All rights reserved.

Vertical Variability in Saturated Zone Hydrochemistry Near Yucca Mountain, Nevada

International Nuclear Information System (INIS)

G. Patterson; P. Striffler

2007-01-01

The differences in the saturated zone hydrochemistry with depth at borehole NC-EWDP-22PC reflect the addition of recharge along Fortymile Wash. The differences in water chemistry with depth at borehole NC-EWDP-19PB appear to indicate that other processes are involved. Water from the lower part of NC-EWDP-19PB possesses chemical characteristics that clearly indicate that it has undergone cation exchange that resulted in the removal of calcium and magnesium and the addition of sodium. This water is very similar to water from the Western Yucca Mountain facies that has previously been thought to flow west of NC-EWDP-19PB. Water from the lower zone in NC-EWDP-19PB also could represent water from the Eastern Yucca Mountain facies that has moved through clay-bearing or zeolitized aquifer material resulting in the altered chemistry. Water chemistry from the upper part of the saturated zone at NC-EWDP-19PB, both zones at NC-EWDP-22PC, and wells in the Fortymile Wash facies appears to be the result of recharge through the alluvium south of Yucca Mountain and within the Fortymile Wash channel

The use of sparge curtains for contaminant plume control

International Nuclear Information System (INIS)

Molnaa, B.; Dablow, J.

1994-01-01

Contamination by petroleum hydrocarbons and organic solvents represents a major impact to soil and groundwater. Following recent research and development, several technologies have evolved to treat saturated zone adsorbed- and dissolved-phase contaminants in situ. These technologies include bioremediation and air sparging. Funnel and gate approaches have been developed at the Waterloo Center for Groundwater Research to control contaminant plume migration and treat dissolved-phase contaminants before allowing migration downgradient and off site. The process consists of using low hydraulic conductivity cutoff walls to funnel groundwater flow through gates that contain in situ bioreactors. These systems can maintain hydraulic control and treat dissolved-phase contaminants at the downgradient margins of plumes, while minimizing, or in some cases eliminating, the need for groundwater pumping. Sparge curtains can be applied to treat dissolved-phase contaminants and prevent downgradient, off-site migration of contaminated groundwater

Phytoplankton response to a plume front in the northern South China Sea

Science.gov (United States)

Li, Qian P.; Zhou, Weiwen; Chen, Yinchao; Wu, Zhengchao

2018-04-01

Due to a strong river discharge during April-June 2016, a persistent salinity front, with freshwater flushing seaward on the surface but seawater moving landward at the bottom, was formed in the coastal waters west of the Pearl River estuary (PRE) over the northern South China Sea (NSCS) shelf. Hydrographic measurements revealed that the salinity front was influenced by both the river plume and coastal upwelling. On shipboard nutrient-enrichment experiments with size-fractionation chlorophyll a measurements were taken on both sides of the front as well as in the frontal zone to diagnose the spatial variations of phytoplankton physiology across the frontal system. We also assessed the size-fractionated responses of phytoplankton to the treatment of plume water at the frontal zone and the sea side of the front. The biological impact of vertical mixing or upwelling was further examined by the response of surface phytoplankton to the addition of local bottom water. Our results suggested that there was a large variation in phytoplankton physiology on the sea side of the front, driven by dynamic nutrient fluxes, although P limitation was prevailing on the shore side of the front and at the frontal zone. The spreading of plume water at the frontal zone would directly improve the growth of microphytoplankton, while nano- and picophytoplankton growths could have become saturated at high percentages of plume water. Also, the mixing of bottom water would stimulate the growth of surface phytoplankton on both sides of the front by altering the surface N/P ratio to make it closer to the Redfield stoichiometry. In summary, phytoplankton growth and physiology could be profoundly influenced by the physical dynamics in the frontal system during the spring-summer of 2016.

On predicting mantle mushroom plumes

Directory of Open Access Journals (Sweden)

Ka-Kheng Tan

2011-04-01

Top cooling may produce plunging plumes of diameter of 585 km and at least 195 Myr old. The number of cold plumes is estimated to be 569, which has not been observed by seismic tomography or as cold spots. The cold plunging plumes may overwhelm and entrap some of the hot rising plumes from CMB, so that together they may settle in the transition zone.

On the nature of the frontal zone of the Choctawhatchee Bay plume in the Gulf of Mexico

Science.gov (United States)

Huguenard, K. D.; Bogucki, D. J.; Ortiz-Suslow, D. G.; Laxague, N. J. M.; MacMahan, J. H.; Özgökmen, T. M.; Haus, B. K.; Reniers, A. J. H. M.; Hargrove, J.; Soloviev, A. V.; Graber, H.

2016-02-01

River plumes often feature turbulent processes in the frontal zone and interfacial region at base of the plume, which ultimately impact spreading and mixing rates with the ambient coastal ocean. The degree to which these processes govern overall plume mixing is yet to be quantified with microstructure observations. A field campaign was conducted in a river plume in the northeast Gulf of Mexico in December 2013, in order to assess mixing processes that could potentially impact transport and dispersion of surface material near coastal regions. Current velocity, density, and Turbulent Kinetic Energy Values, ɛ, were obtained using an Acoustic Doppler Current Profiler (ADCP), a Conductivity Temperature Depth (CTD) profiler, a Vertical Microstructure Profiler (VMP), and two Acoustic Doppler Velocimeters (ADVs). The frontal region contained ɛ values on the order of 10-5 m2 s-3, which were markedly larger than in the ambient water beneath (O 10-9 m2 s-3). An energetic wake of moderate ɛ values (O 10-6 m2 s-3) was observed trailing the frontal edge. The interfacial region of an interior section of the plume featured opposing horizontal velocities and a ɛ value on the order of 10-6 m2 s-3. A simplified mixing budget was used under significant assumptions to compare contributions from wind, tides, and frontal regions of the plume. The results from this order of magnitude analysis indicated that frontal processes (59%) dominated in overall mixing. This emphasizes the importance of adequate parameterization of river plume frontal processes in coastal predictive models.

Biofilter design for effective nitrogen removal from stormwater - influence of plant species, inflow hydrology and use of a saturated zone.

Science.gov (United States)

Payne, Emily G I; Pham, Tracey; Cook, Perran L M; Fletcher, Tim D; Hatt, Belinda E; Deletic, Ana

2014-01-01

The use of biofilters to remove nitrogen and other pollutants from urban stormwater runoff has demonstrated varied success across laboratory and field studies. Design variables including plant species and use of a saturated zone have large impacts upon performance. A laboratory column study of 22 plant species and designs with varied outlet configuration was conducted across a 1.5-year period to further investigate the mechanisms and influences driving biofilter nitrogen processing. This paper presents outflow concentrations of total nitrogen from two sampling events across both 'wet' and 'dry' frequency dosing, and from sampling across two points in the outflow hydrograph. All plant species were effective under conditions of frequent dosing, but extended drying increased variation between species and highlighted the importance of a saturated zone in maintaining biofilter function. The saturated zone also effectively treated the volume of stormwater stored between inflow events, but this extended detention provided no additional benefit alongside the rapid processing of the highest performing species. Hence, the saturated zone reduced performance differences between plant species, and potentially acts as an 'insurance policy' against poor sub-optimal plant selection. The study shows the importance of biodiversity and inclusion of a saturated zone in protecting against climate variability.

A strategy for validation a concept model for radionuclide migration in the saturated zone beneath Yucca Mountain

International Nuclear Information System (INIS)

Robinson, B.A.

1994-01-01

A conceptual model for radionuclide migration in the saturated zone beneath Yucca Mountain is presented. The available hydrologic data from the site is compiled to present a qualitative picture of transport of radionuclides horizontally within the first 100-200 m of the saturated zone. The transport model consists of flow within fractures and interchange of dissolved species between the fractures and surrounding matrix blocks via molecular diffusion. A parametric study illustrates that at the groundwater conditions expected to exist in the saturated zone, radionuclide will have ample time to diffuse fully within the matrix blocks. The result is a predicted solute transport time several orders of magnitude greater than the groundwater travel time (GWTT). To validate this model, a suite of interwell tracer tests are proposed at various flow rates and with conservative and sorbing species. Numerical simulations show that these tests will allow us to discriminate between a matrix diffusion model and a more conventional continuum transport model. (author) 8 figs., tabs., 35 refs

Effects of Faulted Stratigraphy on Saturated Zone Flow Beneath Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Cohen, Andrew J.B.; Oldenburg, Curtis M.

1999-01-01

The S 4 Z Model (''sub-site-scale saturated zone'') is a 3-D TOUGH2 model that was developed to study the saturated zone (SZ) at Yucca Mountain, Nevada, and to aid in the design and analysis of hydrologic tests. Yucca Mountain is the proposed site for a nuclear waste repository for the United States. The model covers an area of approximately 100 km 2 around Yucca Mountain, as shown in Figure 1. The proposed repository is located in the unsaturated zone, immediately above the area of equidimensional gridblocks east of Solitario Canyon fault, which defines the crest of Yucca Mountain. The finely discretized region near the center of the domain corresponds to the area near a cluster of boreholes used for hydraulic and tracer testing. This discretization facilitates simulation of tests conducted there. The hydrogeologic structure beneath the mountain is comprised of dipping geologic units of variable thickness which are offset by faults. One of the primary objectives of the S 4 Z modeling effort is to study the potential effects of the faulted structure on flow. Therefore, replication of the geologic structure in the model mesh is necessary. This paper summarizes (1) the mesh discretization used to capture the faulted geologic structure, and (2) a model simulation that illustrates the significance of the geologic structure on SZ flow and the resulting macrodispersion

Numerical study of the structure of thermal plume in a vertical channel: Effect of the height of canal

Directory of Open Access Journals (Sweden)

Jouini Belgacem

2016-01-01

Full Text Available In this paper we propose to study numerically, by means of a software Named Calculation FDS, a thermal plume evolve from a source at the entrance to of a vertical channel. In the literature, there are researchers who interested in the interaction of plume with his the confinement medium. These studies are based on the determination of the global structure of plume confined. They found that this plume consists of three distinct zones. A first zone near source (instability zone followed by a second zone, such as the development of plume, and a third zone which is the zone of turbulence, Comparing the overall structure of the plume confined to that of the free plume, we can identify the presence of a third zone (zone of instability. The aim is firstly to determine the height of the instability zone located above of source, and secondly, to make a spectral study frequencies exhaust. Thus, effects of the geometrical parameters on frequencies of these escapements and the height an instability zone. The final aim is to establish correlations between the dimensionless numbers of Strouhal and Grashof.

Yucca Mountain Area Saturated Zone Dissolved Organic Carbon Isotopic Data

International Nuclear Information System (INIS)

Thomas, James; Decker, David; Patterson, Gary; Peterman, Zell; Mihevc, Todd; Larsen, Jessica; Hershey, Ronald

2007-01-01

groundwater ages. The DIC calculated groundwater ages were compared with DOC calculated groundwater ages and both of these ages were compared to travel times developed in ground-water flow and transport models. If nuclear waste is stored in Yucca Mountain, the saturated zone is the final barrier against the release of radionuclides to the environment. The most recent rendition of the TSPA takes little credit for the presence of the saturated zone and is a testament to the inadequate understanding of this important barrier. If radionuclides reach the saturated zone beneath Yucca Mountain, then there is a travel time before they would leave the Yucca Mountain area and flow down gradient to the Amargosa Valley area. Knowing how long it takes groundwater in the saturated zone to flow from beneath Yucca Mountain to down gradient areas is critical information for potential radionuclide transport. Radionuclide transport in groundwater may be the quickest pathway for radionuclides in the proposed Yucca Mountain repository to reach land surface by way of groundwater pumped in Amargosa Valley. An alternative approach to ground-water flow and transport models to determine the travel time of radionuclides from beneath Yucca Mountain to down gradient areas in the saturated zone is by carbon-14 dating of both inorganic and organic carbon dissolved in the groundwater. A standard method of determining ground-water ages is to measure the carbon-13 and carbon-14 of DIC in the groundwater and then correct the measured carbon-14 along a flow path for geochemical reactions that involve carbon containing phases. These geochemical reactions are constrained by carbon-13 and isotopic fractionations. Without correcting for geochemical reactions, the ground-water ages calculated from only the differences in carbon-14 measured along a flow path (assuming the decrease in carbon-14 is due strictly to radioactive decay) could be tens of thousands of years too old. The computer program NETPATH, developed by

Numerical modeling for saturated-zone groundwater travel time analysis at Yucca Mountain

International Nuclear Information System (INIS)

Arnold, B.W.; Barr, G.E.

1996-01-01

A three-dimensional, site-scale numerical model of groundwater flow in the saturated zone at Yucca Mountain was constructed and linked to particle tracking simulations to produce an estimate of the distribution of groundwater travel times from the potential repository to the boundary of the accessible environment. This effort and associated modeling of groundwater travel times in the unsaturated zone were undertaken to aid in the evaluation of compliance of the site with 10CFR960. These regulations stipulate that pre-waste-emplacement groundwater travel time to the accessible environment shall exceed 1,000 years along any path of likely and significant radionuclide travel

Paducah Gaseous Diffusion Plant Northwest Plume interceptor system evaluation

International Nuclear Information System (INIS)

Laase, A.D.; Clausen, J.L.

1998-01-01

The Paducah Gaseous Diffusion Plant (PGDP) recently installed an interceptor system consisting of four wells, evenly divided between two well fields, to contain the Northwest Plume. As stated in the Northwest Plume Record of Decision (ROD), groundwater will be pumped at a rate to reduce further contamination and initiate control of the northwest contaminant plume. The objective of this evaluation was to determine the optimum (minimal) well field pumping rates required for plume hotspot containment. Plume hotspot, as defined in the Northwest Plume ROD and throughout this report, is that portion of the plume with trichloroethene (TCE) concentrations greater than 1,000 microg/L. An existing 3-dimensional groundwater model was modified and used to perform capture zone analyses of the north and south interceptor system well fields. Model results suggest that the plume hotspot is not contained at the system design pumping rate of 100 gallons per minute (gal/min) per well field. Rather, the modeling determined that north and south well field pumping rates of 400 and 150 gal/min, respectively, are necessary for plume hotspot containment. The difference between the design and optimal pumping rates required for containment can be attributed to the discovery of a highly transmissive zone in the vicinity of the two well fields

Calibration of the Site-Scale Saturated Zone Flow Model

International Nuclear Information System (INIS)

Zyvoloski, G. A.

2001-01-01

The purpose of the flow calibration analysis work is to provide Performance Assessment (PA) with the calibrated site-scale saturated zone (SZ) flow model that will be used to make radionuclide transport calculations. As such, it is one of the most important models developed in the Yucca Mountain project. This model will be a culmination of much of our knowledge of the SZ flow system. The objective of this study is to provide a defensible site-scale SZ flow and transport model that can be used for assessing total system performance. A defensible model would include geologic and hydrologic data that are used to form the hydrogeologic framework model; also, it would include hydrochemical information to infer transport pathways, in-situ permeability measurements, and water level and head measurements. In addition, the model should include information on major model sensitivities. Especially important are those that affect calibration, the direction of transport pathways, and travel times. Finally, if warranted, alternative calibrations representing different conceptual models should be included. To obtain a defensible model, all available data should be used (or at least considered) to obtain a calibrated model. The site-scale SZ model was calibrated using measured and model-generated water levels and hydraulic head data, specific discharge calculations, and flux comparisons along several of the boundaries. Model validity was established by comparing model-generated permeabilities with the permeability data from field and laboratory tests; by comparing fluid pathlines obtained from the SZ flow model with those inferred from hydrochemical data; and by comparing the upward gradient generated with the model with that observed in the field. This analysis is governed by the Office of Civilian Radioactive Waste Management (OCRWM) Analysis and Modeling Report (AMR) Development Plan ''Calibration of the Site-Scale Saturated Zone Flow Model'' (CRWMS M and O 1999a)

Constraining local 3-D models of the saturated-zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Barr, G.E.; Shannon, S.A.

1994-01-01

A qualitative three-dimensional analysis of the saturated zone flow system was performed for a 8 km x 8 km region including the potential Yucca Mountain repository site. Certain recognized geologic features of unknown hydraulic properties were introduced to assess the general response of the flow field to these features. Two of these features, the Solitario Canyon fault and the proposed fault in Drill Hole Wash, appear to constrain flow and allow calibration

SATURATED ZONE FLOW AND TRANSPORT MODEL ABSTRACTION

International Nuclear Information System (INIS)

B.W. ARNOLD

2004-01-01

The purpose of the saturated zone (SZ) flow and transport model abstraction task is to provide radionuclide-transport simulation results for use in the total system performance assessment (TSPA) for license application (LA) calculations. This task includes assessment of uncertainty in parameters that pertain to both groundwater flow and radionuclide transport in the models used for this purpose. This model report documents the following: (1) The SZ transport abstraction model, which consists of a set of radionuclide breakthrough curves at the accessible environment for use in the TSPA-LA simulations of radionuclide releases into the biosphere. These radionuclide breakthrough curves contain information on radionuclide-transport times through the SZ. (2) The SZ one-dimensional (I-D) transport model, which is incorporated in the TSPA-LA model to simulate the transport, decay, and ingrowth of radionuclide decay chains in the SZ. (3) The analysis of uncertainty in groundwater-flow and radionuclide-transport input parameters for the SZ transport abstraction model and the SZ 1-D transport model. (4) The analysis of the background concentration of alpha-emitting species in the groundwater of the SZ

Plume persistence caused by back diffusion from thin clay layers in a sand aquifer following TCE source-zone hydraulic isolation.

Science.gov (United States)

Parker, Beth L; Chapman, Steven W; Guilbeault, Martin A

2008-11-14

This paper concludes that back diffusion from one or a few thin clayey beds in a sand aquifer can cause contaminant persistence above MCLs in a sand aquifer long after the source zone initially causing the plume is isolated or removed. This conclusion is based on an intensive case study of a TCE contaminated site in Florida, with the processes evaluated using numerical modeling. At this site, the TCE DNAPL zone formed decades ago, and was hydraulically isolated by means of an innovative system performing groundwater extraction, treatment and re-injection. Treated water is re-injected in a row of injection wells situated a short distance downgradient of the extraction wells, creating a clean-water displacement front to efficiently flush the downgradient plume. This scheme avoids the creation of stagnation zones typical of most groundwater pump-and-treat systems, thereby minimizing the time for aquifer flushing and therefore downgradient cleanup. The system began operation in August 2002 and although the performance monitoring shows substantial declines in concentrations, detectable levels of TCE and degradation products persist downgradient of the re-injection wells, long after the TCE should have disappeared based on calculations assuming a nearly homogenous sand aquifer. Three hypotheses were assessed for this plume persistence: 1) incomplete source-zone capture, 2) DNAPL occurrence downgradient of the re-injection wells, and 3) back diffusion from one or more thin clay beds in the aquifer. After careful consideration, the first two hypotheses were eliminated, leaving back diffusion as the only plausible hypothesis, supported by detailed measurements of VOC concentrations within and near the clay beds and also by numerical model simulations that closely represent the field site hydrogeologic conditions. The model was also used to simulate a more generalized, hypothetical situation where more thin clayey beds occur in a sand aquifer with an underlying aquitard

On moistening of ash particles in smoke plumes of industrial sources

International Nuclear Information System (INIS)

Geints, Yu.E.; Zemlyanov, A.A.

1992-01-01

Moistening of ash particles occurring in the humid atmosphere is one of the main factors decreasing the accuracy of the lidar measurements of thickness of smoke emissions. Theoretical investigation of the growth of water coating of smoke particles under different meteorological conditions within the zone of emission has been carried out based on the Gaussian model of smoke plume with slant axis and its parameters. Numerical calculations have shown that in the case of high initial moisture content of the emissions near the source in the smoke plume the zone appears in which water vapor is supersaturated and the effect of particle moistening is significant. Seasonal trends and diurnal variations in temperature and humidity in the surface layer of the atmosphere also substantially affect moistening. Length of the zone of moistening of ash particles is maximum at night in winter under conditions of light breeze. The possibility of retrieving the initial mass concentration of the dry aerosol in the smoke plume has been shown based on lidar measurements of the scattering coefficient within the zone of maximum degree of moistening of smoke plume. 10 refs., 5 figs

Seismic images of the transition zone: is Hawaiian volcanism produced by a secondary plume from the top of the lower mantle?

Science.gov (United States)

Cao, Q.; van der Hilst, R. D.; Shim, S.; De Hoop, M. V.

2011-12-01

The Hawaiian hotspot is often attributed to hot material rising from depth in the mantle, but efforts to detect a thermal plume seismically have been inconclusive. Most tomographic models reveal anomalously low wavespeeds beneath Hawaii, but the depth extent of this structure is not well known. S or P data used in traveltime inversions are associated with steep rays to distant sources, which degrades depth resolution, and surface wave dispersion does not have sufficient sensitivity at the depths of interest. To investigate pertinent thermal anomalies we mapped depth variations of upper mantle discontinuities using precursors of the surface-reflected SS wave. Instead of stacking the data over geographical bins, which leads to averaging of topography and hence loss of spatial resolution, we used a generalized Radon transform (GRT) to detect and map localized elasticity contrasts in the transition zone (Cao et al., PEPI, 2010). We apply the GRT to produce 3D image volumes beneath a large area of the Pacific Ocean, including Hawaii and the Hawaii-Emperor seamount chain (Cao et al., Science, 2011). The 3D image volumes reveal laterally continuous interfaces near 410 and 660 km depths, that is, the traditional boundaries of the transition zone, but also suggest (perhaps intermittent) scatter horizons near 300-350, 520-550, and 800-1000 km depth. The upper mantle appears generally hot beneath Hawaii, but the most conspicuous topographic (and probably thermal) anomalies are found west of Hawaii. The GRT images reveal a 800 km wide uplift of the 660 discontinuity just west of Hawaii, but there is no evidence for a corresponding localized depression of the 410 discontinuity. This expression of the 410 and 660 km topographies is consistent with some existed geodynamical modeling results, in which a deep-rooted mantle plume impinging on the transition zone, creating a broad pond of hot material underneath endothermic phase change at 660 km depth, and with secondary plumes

Seismic Imaging of Mantle Plumes

Science.gov (United States)

Nataf, Henri-Claude

The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

Turbulent structure of thermal plume. Velocity field

International Nuclear Information System (INIS)

Guillou, B.; Brahimi, M.; Doan-kim-son

1986-01-01

An experimental investigation and a numerical study of the dynamics of a turbulent plume rising from a strongly heated source are described. This type of flow is met in thermal effluents (air, vapor) from, e.g., cooling towers of thermal power plants. The mean and fluctuating values of the vertical component of the velocity were determined using a Laser-Doppler anemometer. The measurements allow us to distinguish three regions in the plume-a developing region near the source, an intermediate region, and a self-preserving region. The characteristics of each zone have been determined. In the self-preserving zone, especially, the turbulence level on the axis and the entrainment coefficient are almost twice of the values observed in jets. The numerical model proposed takes into account an important phenomenon, the intermittency, observed in the plume. This model, established with the self-preserving hypothesis, brings out analytical laws. These laws and the predicted velocity profile are in agreement with the experimental evolutions [fr

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

Influence of the tension-saturated zone on contaminant migration in shallow water-table regimes

International Nuclear Information System (INIS)

Gillham, R.W.

1982-01-01

Groundwater discharge represents a major pathway for the return to the biosphere of contaminants that are released to the subsurface environment. An understanding of the transport processes in groundwater discharge zones is therefore an important consideration in pathway analyses associated with the environmental assessment of proposed waste-management facilities. Shallow water tables are a common characteristic of groundwater discharge zones, particularly in humid climatic regions. In this paper, the results of field tests, laboratory tests and numerical simulations are used to show that under shallow water-table conditions, the zone of tension saturation can result in a rapid and highly disproportionate water-table response to precipitation. It is further shown that this response can result in complex migration patterns that would not be predicted by the classical approaches to solute transport modelling and that the response could result in large and highly transient inputs to surface water

Experiments on Plume Spreading by Engineered Injection and Extraction

Science.gov (United States)

Mays, D. C.; Jones, M.; Tigera, R. G.; Neupauer, R.

2014-12-01

The notion that groundwater remediation is transport-limited emphasizes the coupling between physical (i.e., hydrodynamic), geochemical, and microbiological processes in the subsurface. Here we leverage this coupling to promote groundwater remediation using the approach of engineered injection and extraction. In this approach, inspired by the literature on chaotic advection, uncontaminated groundwater is injected and extracted through a manifold of wells surrounding the contaminated plume. The potential of this approach lies in its ability to actively manipulate the velocity field near the contaminated plume, generating plume spreading above and beyond that resulting from aquifer heterogeneity. Plume spreading, in turn, promotes mixing and reaction by chemical and biological processes. Simulations have predicted that engineered injection and extraction generates (1) chaotic advection whose characteristics depend on aquifer heterogeneity, and (2) faster rates and increased extent of groundwater remediation. This presentation focuses on a complimentary effort to experimentally demonstrate these predictions experimentally. In preparation for future work using refractive index matched (RIM) porous media, the experiments reported here use a Hele-Shaw apparatus containing silicone oil. Engineered injection and extraction is used to manipulate the geometry of an initially circular plume of black pigment, and photographs record the plume geometry after each step of injection of extraction. Image analysis, using complimentary Eulerian and Lagrangian approaches, reveals the thickness and variability of the dispersion zone surrounding the deformed plume of black pigment. The size, shape, and evolution of this dispersion zone provides insight into the interplay between engineered injection and extraction, which generates plume structure, and dispersion (here Taylor dispersion), which destroys plume structure. These experiments lay the groundwork for application of engineered

Biogeochemistry of landfill leachate plumes

DEFF Research Database (Denmark)

Christensen, Thomas Højlund; Kjeldsen, Peter; Bjerg, Poul Løgstrup

2001-01-01

are relatively narrow and do not in terms of width exceed the width of the landfill. The concept of redox zones being present in the plume has been confirmed by the reported composition of the leachate contaminated groundwater at several landfills and constitutes an important framework for understanding...... the behavior of the contaminants in the plume as the leachate migrates away from the landfill. Diverse microbial communities have been identified in leachate plumes and are believed to be responsible for the redox processes. Dissolved organic C in the leachate, although it appears to be only slowly degradable...... to be subject to anaerobic oxidation, but the mechanisms are not yet understood. Heavy metals do not seem to constitute a significant pollution problem at landfills, partly because the heavy metal concentrations in the leachate often are low, and partly because of strong attenuation by sorption...

Regional groundwater modeling of the saturated zone in the vicinity of Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Ahola, M.; Sagar, B.

1992-10-01

Results of groundwater modeling of the saturated zone in the vicinity of Yucca Mountain are presented. Both a regional (200 x 200 km) and subregional (50 x 50 km) model were used in the analyses. Simulations were conducted to determine the impact of various disruptive that might take place over the life span of a proposed Yucca Mountain geologic conditions repository on the groundwater flow field, as well as changes in the water-table elevations. These conditions included increases in precipitation and groundwater recharge within the regional model, changes in permeability of existing hydrogeologic barriers, a:nd the vertical intrusion of volcanic dikes at various orientations through the saturated zone. Based on the regional analysis, the rise in the water-table under Yucca Mountain due to various postulated conditions ranged from only a few meters to 275 meters. Results of the subregional model analysis, which was used to simulate intrusive dikes approximately 4 kilometers in length in the vicinity of Yucca Mountain, showed water-table rises ranging from a few meters to as much as 103 meters. Dikes oriented approximately north-south beneath Yucca Mountain produced the highest water-table rises. The conclusions drawn from this analysis are likely to change as more site-specific data become available and as the assumptions in the model are improved

A mantle plume model for the Equatorial Highlands of Venus

Science.gov (United States)

Kiefer, Walter S.; Hager, Bradford H.

1991-01-01

The possibility that the Equatorial Highlands are the surface expressions of hot upwelling mantle plumes is considered via a series of mantle plume models developed using a cylindrical axisymmetric finite element code and depth-dependent Newtonian rheology. The results are scaled by assuming whole mantle convection and that Venus and the earth have similar mantle heat flows. The best model fits are for Beta and Atla. The common feature of the allowed viscosity models is that they lack a pronounced low-viscosity zone in the upper mantle. The shape of Venus's long-wavelength admittance spectrum and the slope of its geoid spectrum are also consistent with the lack of a low-viscosity zone. It is argued that the lack of an asthenosphere on Venus is due to the mantle of Venus being drier than the earth's mantle. Mantle plumes may also have contributed to the formation of some smaller highland swells, such as the Bell and Eistla regions and the Hathor/Innini/Ushas region.

Surface Intermediate Zone of Submerged Turbulent Buoyant Jet in Current

DEFF Research Database (Denmark)

Chen, H. B.; Larsen, Torben

1995-01-01

This paper deals with the intermediate zone between the jet and plume stages of a submerged buoyant discharge from sea outfall in current. The stability criteria, plume width and height after the intermediate zone and the dilution within the intermediate region have been studied theoretically and...

A mega Ultra Low Velocity Zone at the Base of the Iceland Plume: a Target for Tomographic Telescope Implementation

Science.gov (United States)

Romanowicz, Barbara; Yuan, Kaiqing; Masson, Yder; Adourian, Sevan

2017-04-01

We have recently constructed the first global whole mantle radially anisotropic shear wave velocity model based on time domain full waveform inversion and numerical wavefield computations using the Spectral Element Method (French et al., 2013; French and Romanowicz, 2014). This model's most salient features are broad chimney-like low velocity conduits, rooted within the large-low-shear-velocity provinces (LLSVPs) at the base of the mantle, and extending from the core-mantle boundary up through most of the lower mantle, projecting to the earth's surface in the vicinity of major hotspots. The robustness of these features is confirmed through several non-linear synthetic tests, which we present here, including several iterations of inversion using a different starting model than that which served for the published model. The roots of these not-so-classical "plumes" are regions of more pronounced low shear velocity. While the detailed structure is not yet resolvable tomographically, at least two of them contain large (>800 km diameter) ultra-low-velocity zones (ULVZs), one under Hawaii (Cottaar and Romanowicz, 2012) and the other one under Samoa (Thorne et al., 2013). Through 3D numerical forward modelling of Sdiff phases down to 10s period, using data from broadband arrays illuminating the base of the Iceland plume from different directions, we show that such a large ULVZ also exists at the root of this plume, embedded within a taller region of moderately reduced low shear velocity, such as proposed by He et al. (2015). We also show that such a wide, but localized ULVZ is unique in a broad region around the base of the Iceland Plume. Because of the intense computational effort required for forward modelling of trial structures, to first order this ULVZ is represented by a cylindrical structure of diameter 900 km, height 20 km and velocity reduction 20%. To further refine the model, we have developed a technique which we call "tomographic telescope", in which we are

Atmospheric ice nuclei: No detectable effects from a coal-fired powerplant plume

International Nuclear Information System (INIS)

Schnell, R.C.; Van Valin, C.C.; Pueschel, R.F.

1976-01-01

Atmospheric ice nuclei were measured upwind and within the effluent plume of a coalfired powerplant during February 1976. Aerosol particles were captured on two types of membrane filters (Nuclepore and Millipore) and processed in two different thermal diffusion chambers, one calibrated to produce a 100% saturation relative to water and the other to produce a slight supersaturation relative to water. Consequently, the ice nuclei measured were active in the modes that are dominant in diffusion chambers, viz., deposition nucleation and condensation-followed-by-freezing nucleation. Results indicate that plume particles do not act as ice nuclei between the temperatures of -10 and -20degreeC, nor do combustion gases in the plume deactivate natural ice nuclei

Biotransformation of pesticides in saturated-zone materials

Science.gov (United States)

Hoyle, Blythe L.; Arthur, Ellen L.

Many studies have been conducted to evaluate pesticide contamination of groundwater in the United States, but investigations of pesticide biotransformation in saturated zones are much less numerous than in surface soils. Because results of studies using soils are not directly applicable to the subsurface, the purpose of this paper is to illustrate examples of pesticide biotransformation in saturated-zone materials. Although it must be considered with caution, the US Environmental Protection Agency's (EPA) "Pesticides in Ground Water Database" was used to focus the discussion on the biotransformation potential of dibromoethane (EDB), atrazine, acetanilide herbicides, and aldicarb, all of which have been detected in groundwater in the United States. Results of more than two dozen studies indicate that a biotransformation potential for these pesticides exists in saturated-zone materials, although for any given pesticide substantial differences in biotransformation occurred. These variations were due both to differences in experimental methods and to heterogeneities in the subsurface materials under investigation. However, because biotransformation mechanisms were not well investigated, it is generally not possible to extrapolate predictions of biotransformation potential beyond the specific sites investigated. These results highlight the need to better understand microbial genetic regulation of biotransformation processes so that genetic information may be effectively incorporated into future investigations of biotransformation potential in the subsurface. Résumé De nombreuses études ont été réalisées pour évaluer le degré de pollution des aquifères par les pesticides aux États-Unis, mais les recherches concernant la biotransformation des pesticides dans les eaux souterraines sont beaucoup moins nombreuses que dans les sols. Du fait que les résultats des études concernant les sols ne sont pas directement applicables au milieu souterrain, le propos de cet

Characterization of the vadose zone above a shallow aquifer contaminated with gas condensate hydrocarbons

International Nuclear Information System (INIS)

Sublette, K.; Duncan, K.; Thoma, G.; Todd, T.

2002-01-01

A gas production site in the Denver Basin near Ft. Lupton, Colorado has leaked gas condensate hydrocarbons from an underground concrete tank used to store produced water. The leak has contaminated a shallow aquifer. Although the source of pollution has been removed, a plume of hydrocarbon contamination still remains for nearly 46 m from the original source. An extensive monitoring program was conducted in 1993 of the groundwater and saturated sediments. The objective was to determine if intrinsic aerobic or anaerobic bioremediation of hydrocarbons occurred at the site at a rate that would support remediation. Geochemical indicators of hydrogen biodegradation by microorganisms in the saturated zone included oxygen depletion, increased alkalinity, sulfate depletion, methane production and Fe2+ production associated with hydrogen contamination. The presence of sulfate-reducing bacteria and methanogens was also much higher in the contaminated sediments. Degraded hydrocarbon metabolites were found in contaminated groundwater. An extensive characterization of the vadose zone was conducted in which the vadose zone was sample in increments of 15 cm from the surface to the water table at contaminated and non contaminated sites. The samples were tested for individual C3+ hydrocarbons, methane, CO2, total organic carbon, total inorganic carbon, and total petroleum hydrocarbons. The vadose zone consisted of an active and aerobic bioreactor fueled by condensate hydrocarbons transported into the unsaturated zone by evaporation of hydrocarbons at the water table. It was concluded that the unsaturated zone makes an important contribution to the natural attenuation of gas condensate hydrocarbons in the area. 17 refs., 2 tabs., 28 figs

A saturated zone site-scale flow model for Yucca mountain

Energy Technology Data Exchange (ETDEWEB)

Eddebbarh, Al Aziz [Los Alamos National Laboratory

2008-01-01

A saturated zone site-scale flow model (YMSZFM) was developed for licensing requirements for the Yucca Mountain nuclear waste repository to incorporate recent data and analyses including recent stratigraphic and water-level data from Nye County wells, single-and multiple-well hydraulic testing data, and recent hydrochemistry data. Analyses include use of data from the 2004 transient Death Valley Regional (ground-water) Flow System (DVRFS) model, the 2003 unsaturated zone flow model, and the latest hydrogeologic framework model (HFM). This model includes: (1) the latest understanding of SZ flow, (2) enhanced model validation and uncertainty analyses, (3) improved locations and definitions of fault zones, (4) refined grid resolution (500-to 250-m grid spacing), and (5) use of new data. The flow model was completed using the three-dimensional, Finite-Element Heat and Mass Transfer computer code (FEHM). The SZ site-scale flow model was calibrated with the commercial parameter estimation code, PEST to achieve a minimum difference between observed water levels and predicted water levels, and also between volumetric/mass flow rates along specific boundary segments as supplied by the DVRFS. A total of 161 water level and head measurements with varied weights were used for calibration. A comparison between measured water-level data and the potentiometric surface yielded an RMSE of 20.7 m (weighted RMSE of 8.8 m). The calibrated model was used to generate flow paths and specific discharge predictions. Model confidence was built by comparing: (l) calculated to observed hydraulic heads, and (2) calibrated to measured permeabilities (and therefore specific discharge). In addition, flowpaths emanating from below the repository footprint are consistent with those inferred both from gradients of measured head and from independent water-chemistry data. Uncertainties in the SZ site-scale flow model were quantified because all uncertainty contributes to inaccuracy in system

A saturated zone site-scale flow model for Yucca Mountain

International Nuclear Information System (INIS)

Eddebbarh, Al Aziz

2008-01-01

A saturated zone site-scale flow model (YMSZFM) was developed for licensing requirements for the Yucca Mountain nuclear waste repository to incorporate recent data and analyses including recent stratigraphic and water-level data from Nye County wells, single-and multiple-well hydraulic testing data, and recent hydrochemistry data. Analyses include use of data from the 2004 transient Death Valley Regional (ground-water) Flow System (DVRFS) model, the 2003 unsaturated zone flow model, and the latest hydrogeologic framework model (HFM). This model includes: (1) the latest understanding of SZ flow, (2) enhanced model validation and uncertainty analyses, (3) improved locations and definitions of fault zones, (4) refined grid resolution (500-to 250-m grid spacing), and (5) use of new data. The flow model was completed using the three-dimensional, Finite-Element Heat and Mass Transfer computer code (FEHM). The SZ site-scale flow model was calibrated with the commercial parameter estimation code, PEST to achieve a minimum difference between observed water levels and predicted water levels, and also between volumetric/mass flow rates along specific boundary segments as supplied by the DVRFS. A total of 161 water level and head measurements with varied weights were used for calibration. A comparison between measured water-level data and the potentiometric surface yielded an RMSE of 20.7 m (weighted RMSE of 8.8 m). The calibrated model was used to generate flow paths and specific discharge predictions. Model confidence was built by comparing: (l) calculated to observed hydraulic heads, and (2) calibrated to measured permeabilities (and therefore specific discharge). In addition, flowpaths emanating from below the repository footprint are consistent with those inferred both from gradients of measured head and from independent water-chemistry data. Uncertainties in the SZ site-scale flow model were quantified because all uncertainty contributes to inaccuracy in system

Hydrogeologic Framework Model for the Saturated Zone Site Scale flow and Transport Model

Energy Technology Data Exchange (ETDEWEB)

T. Miller

2004-11-15

The purpose of this report is to document the 19-unit, hydrogeologic framework model (19-layer version, output of this report) (HFM-19) with regard to input data, modeling methods, assumptions, uncertainties, limitations, and validation of the model results in accordance with AP-SIII.10Q, Models. The HFM-19 is developed as a conceptual model of the geometric extent of the hydrogeologic units at Yucca Mountain and is intended specifically for use in the development of the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]). Primary inputs to this model report include the GFM 3.1 (DTN: MO9901MWDGFM31.000 [DIRS 103769]), borehole lithologic logs, geologic maps, geologic cross sections, water level data, topographic information, and geophysical data as discussed in Section 4.1. Figure 1-1 shows the information flow among all of the saturated zone (SZ) reports and the relationship of this conceptual model in that flow. The HFM-19 is a three-dimensional (3-D) representation of the hydrogeologic units surrounding the location of the Yucca Mountain geologic repository for spent nuclear fuel and high-level radioactive waste. The HFM-19 represents the hydrogeologic setting for the Yucca Mountain area that covers about 1,350 km2 and includes a saturated thickness of about 2.75 km. The boundaries of the conceptual model were primarily chosen to be coincident with grid cells in the Death Valley regional groundwater flow model (DTN: GS960808312144.003 [DIRS 105121]) such that the base of the site-scale SZ flow model is consistent with the base of the regional model (2,750 meters below a smoothed version of the potentiometric surface), encompasses the exploratory boreholes, and provides a framework over the area of interest for groundwater flow and radionuclide transport modeling. In depth, the model domain extends from land surface to the base of the regional groundwater flow model (D'Agnese et al. 1997 [DIRS 100131], p 2). For the site

Hydrogeologic Framework Model for the Saturated Zone Site Scale flow and Transport Model

International Nuclear Information System (INIS)

Miller, T.

2004-01-01

The purpose of this report is to document the 19-unit, hydrogeologic framework model (19-layer version, output of this report) (HFM-19) with regard to input data, modeling methods, assumptions, uncertainties, limitations, and validation of the model results in accordance with AP-SIII.10Q, Models. The HFM-19 is developed as a conceptual model of the geometric extent of the hydrogeologic units at Yucca Mountain and is intended specifically for use in the development of the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]). Primary inputs to this model report include the GFM 3.1 (DTN: MO9901MWDGFM31.000 [DIRS 103769]), borehole lithologic logs, geologic maps, geologic cross sections, water level data, topographic information, and geophysical data as discussed in Section 4.1. Figure 1-1 shows the information flow among all of the saturated zone (SZ) reports and the relationship of this conceptual model in that flow. The HFM-19 is a three-dimensional (3-D) representation of the hydrogeologic units surrounding the location of the Yucca Mountain geologic repository for spent nuclear fuel and high-level radioactive waste. The HFM-19 represents the hydrogeologic setting for the Yucca Mountain area that covers about 1,350 km2 and includes a saturated thickness of about 2.75 km. The boundaries of the conceptual model were primarily chosen to be coincident with grid cells in the Death Valley regional groundwater flow model (DTN: GS960808312144.003 [DIRS 105121]) such that the base of the site-scale SZ flow model is consistent with the base of the regional model (2,750 meters below a smoothed version of the potentiometric surface), encompasses the exploratory boreholes, and provides a framework over the area of interest for groundwater flow and radionuclide transport modeling. In depth, the model domain extends from land surface to the base of the regional groundwater flow model (D'Agnese et al. 1997 [DIRS 100131], p 2). For the site-scale SZ flow model, the HFM

Fossil plume head beneath the Arabian lithosphere?

Science.gov (United States)

Stein, Mordechai; Hofmann, Albrecht W.

1992-12-01

Phanerozoic alkali basalts from Israel, which have erupted over the past 200 Ma, have isotopic compositions similar to PREMA ("prevalent mantle") with narrow ranges of initial ɛ Nd(T) = +3.9-+5.9; 87Sr/ 86Sr(T)= 0.70292-0.70334; 206Pb/ 204Pb(T)= 18.88-19.99; 207Pb/ 204Pb(T)= 15.58-15.70; and 208Pb/ 204Pb(T)= 38.42-39.57. Their Nb/U(43 ± 9) and Ce/Pb(26 ± 6) ratios are identical to those of normal oceanic basalts, demonstrating that the basalts are essentially free of crustal contamination. Overall, the basalts are chemically and isotopically indistinguishable from many ordinary plume basalts, but no plume track can be identified. We propose that these and other, similar, magmas from the Arabian plate originated from a "fossilized" head of a mantle plume, which was unable to penetrate the continental lithosphere and was therefore trapped and stored beneath it. The plume head was emplaced some time between the late Proterozoic crust formation and the initiation of the Phanerozoic magmatic cycles. Basalts from rift environments in other continental localities show similar geochemistry to that of the Arabian basalts and their sources may also represent fossil plume heads trapped below the continents. We suggest that plume heads are, in general, characterized by the PREMA isotopic mantle signature, because the original plume sources (which may have HIMU or EM-type composition) have been diluted by overlying mantle material, which has been entrained by the plume heads during ascent. On the Arabian plate, rifting and thinning of the lithosphere caused partial melting of the stored plume, which led to periodic volcanism. In the late Cenozoic, the lithosphere broke up and the Red Sea opened. N-MORB tholeiites are now erupting in the central trough of the Red Sea, where the lithosphere has moved apart and the fossil plume has been exhausted, whereas E-MORBs are erupting in the northern and southern troughs, still tapping the plume reservoir. Fossil plumes, which are

Quantifying mantle structure and dynamics using plume tracing in seismic tomography

Science.gov (United States)

O'Farrell, K. A.; Eakin, C. M.; Jackson, M. G.; Jones, T. D.; Lekic, V.; Lithgow-Bertelloni, C. R.

2017-12-01

Directly linking deep mantle processes with surface features and dynamics is a complex problem. Hotspot volcanism gives us surface observables of mantle signatures, but the depth and source of the mantle plumes feeding these hotspots are highly debated. To address these issues, it is necessary to consider the entire journey of a plume through the mantle. By analyzing the behavior of mantle plumes we can constrain the vigor of mantle convection, the net rotation of the mantle and the role of thermal versus chemical anomalies as well as the bulk physical properties such as the viscosity profile. To do this, we developed a new algorithm to trace plume-like features in shear-wave (Vs) seismic tomography models based on picking local minima in the velocity and searching for continuous features with depth. We applied this method to recent tomographic models and find 60+ continuous plume conduits that are > 750 km long. Approximately a third of these can be associated with known hotspots at the surface. We analyze the morphology of these continuous conduits and infer large scale mantle flow patterns and properties. We find the largest lateral deflections in the conduits occur near the base of the lower mantle and in the upper mantle (near the thermal boundary layers). The preferred orientation of the plume deflections show large variability at all depths and indicate no net mantle rotation. Plate by plate analysis shows little agreement in deflection below particular plates, indicating these deflected features might be long lived and not caused by plate shearing. Changes in the gradient of plume deflection are inferred to correspond with viscosity contrasts in the mantle and found below the transition zone as well as at 1000 km depth. From this inferred viscosity structure, we explore the dynamics of a plume through these viscosity jumps. We also retrieve the Vs profiles for the conduits and compare with the velocity profiles predicted for different mantle adiabat

Giant hydrogen sulfide plume in the oxygen minimum zone off Peru supports chemolithoautotrophy.

Directory of Open Access Journals (Sweden)

Harald Schunck

Full Text Available In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ. OMZs can sporadically accumulate hydrogen sulfide (H2S, which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2, which contained ∼2.2×10(4 tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with ∼440 km(3 the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct γ-, δ- and ε-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as ∼30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that

Scaling behavior of microbubbles rising in water-saturated porous media

Science.gov (United States)

Kong, X.; Ma, Y.; Scheuermann, A.; Bringemeier, D.; Galindo-Torres, S. A.; Saar, M. O.; Li, L.

2015-12-01

Gas transport in the form of discrete microbubbles in saturated porous media is of importance in a number of processes relevant to many geo-environmental and engineering systems such as bubbling of greenhouse gases in river and sea beds, hydrocarbon gas migration in coal cleats and rock fractures, and air sparging for remediation of soil contaminated with volatile organic compounds. Under the assumption of no or minor volume expansion during gravity-driven migration, the transport of a single microbubble can be well described using various drag force models. However, not enough attention has been paid to the collective behavior of microbubbles during their ascend as a plume through the saturated porous medium, involving dynamic interactions between individual bubbles, bubbles and the ambient fluid, as well as bubbles and the solid matrix. With our quasi-2D, lab-scale microbubble migration experiments, where bubbles are continuously released from a diffuser at the bottom of a porous bed of hydrated gel beads, we establish a scaling relationship between the gas (bubble) release rate and various characteristic parameters of the bubble plume, such as plume tip velocity, plume width, and breakthrough time of the plume front. We find that the characteristic width of the bubble plume varies as a power of both the gas release rate and the bed thickness, with exponents of 0.2 and 0.4, respectively. Moreover, the characteristic breakthrough time also scales with both the gas release rate and the bed thickness with power-law exponents of -0.4 and 1.2, respectively. The mean pore-water velocity of the circulating ambient water also follows a power-law relationship with the gas release rate being an exponent of 0.6 of the gas release rate. This can be quantitatively proven using a simplified momentum exchange model together with the above power-law exponents for the bubble plume. These analyses on the experimental results are carried out on the basis of non

Tracking stormwater discharge plumes and water quality of the Tijuana River with multispectral aerial imagery

Science.gov (United States)

Svejkovsky, Jan; Nezlin, Nikolay P.; Mustain, Neomi M.; Kum, Jamie B.

2010-04-01

Spatial-temporal characteristics and environmental factors regulating the behavior of stormwater runoff from the Tijuana River in southern California were analyzed utilizing very high resolution aerial imagery, and time-coincident environmental and bacterial sampling data. Thirty nine multispectral aerial images with 2.1-m spatial resolution were collected after major rainstorms during 2003-2008. Utilizing differences in color reflectance characteristics, the ocean surface was classified into non-plume waters and three components of the runoff plume reflecting differences in age and suspended sediment concentrations. Tijuana River discharge rate was the primary factor regulating the size of the freshest plume component and its shorelong extensions to the north and south. Wave direction was found to affect the shorelong distribution of the shoreline-connected fresh plume components much more strongly than wind direction. Wave-driven sediment resuspension also significantly contributed to the size of the oldest plume component. Surf zone bacterial samples collected near the time of each image acquisition were used to evaluate the contamination characteristics of each plume component. The bacterial contamination of the freshest plume waters was very high (100% of surf zone samples exceeded California standards), but the oldest plume areas were heterogeneous, including both polluted and clean waters. The aerial imagery archive allowed study of river runoff characteristics on a plume component level, not previously done with coarser satellite images. Our findings suggest that high resolution imaging can quickly identify the spatial extents of the most polluted runoff but cannot be relied upon to always identify the entire polluted area. Our results also indicate that wave-driven transport is important in distributing the most contaminated plume areas along the shoreline.

Groundwater contaminant plume maps and volumes, 100-K and 100-N Areas, Hanford Site, Washington

Science.gov (United States)

Johnson, Kenneth H.

2016-09-27

extents are shown graphically and in tabular form for comparison to previous estimates. Plume data also were interpolated to a finer grid (10 × 10 m) for some processing, particularly to estimate volumes of contaminated groundwater. However, hydrogeologic transport modeling was not considered for the interpolation. The compilation of plume extents for each contaminant also allowed estimates of overlap of the plumes or areas with more than one contaminant above regulatory standards.A mapping of saturated aquifer thickness also was derived across the 100-K and 100–N study area, based on the vertical difference between the groundwater level (water table) at the top and the altitude of the top of the Ringold Upper Mud geologic unit, considered the bottom of the uppermost unconfined aquifer. Saturated thickness was calculated for each cell in the finer (10 × 10 m) grid. The summation of the cells’ saturated thickness values within each polygon of plume regulatory exceedance provided an estimate of the total volume of contaminated aquifer, and the results also were checked using a SURFER® volumetric integration procedure. The total volume of contaminated groundwater in each plume was derived by multiplying the aquifer saturated thickness volume by a locally representative value of porosity (0.3).Estimates of the uncertainty of the plume delineation also are presented. “Upper limit” plume delineations were calculated for each contaminant using the same procedure as the “average” plume extent except with values at each well that are set at a 95-percent upper confidence limit around the log-normally transformed mean concentrations, based on the standard error for the distribution of the mean value in that well; “lower limit” plumes are calculated at a 5-percent confidence limit around the geometric mean. These upper- and lower-limit estimates are considered unrealistic because the statistics were increased or decreased at each well simultaneously and were not

A Plume Scale Model of Chlorinated Ethene Degradation

DEFF Research Database (Denmark)

Murray, Alexandra Marie; Broholm, Mette Martina; Badin, Alice

leaked from a dry cleaning facility, and a 2 km plume extends from the source in an unconfined aquifer of homogenous fluvio-glacial sand. The area has significant iron deposits, most notably pyrite, which can abiotically degrade chlorinated ethenes. The source zone underwent thermal (steam) remediation...

Combining different frequencies for electrical heating of saturated and unsaturated soil zones

Energy Technology Data Exchange (ETDEWEB)

Roland, U.; Holzer, F.; Kopinke, F.D. [Helmholtz Centre for Environmental Research - UFZ, Department of Environmental Engineering, Leipzig (Germany)

2011-10-15

In situ electrical heating of soil was studied applying different frequencies: low-frequency energy for resistive heating and radio-frequency energy for dielectric heating. Steep temperature gradients were observed for each heating mode under the condition of the coexistence of saturated and unsaturated soil zones. By combining the two heating modes, this undesired effect can be avoided, thus allowing efficient soil remediation especially when organic phases are accumulated at the capillary fringe. A parallel application of both frequencies was demonstrated as the most suitable method to reduce temperature gradients. By using electronic filters, both electric fields can be established by only one electrode array. This innovative concept is especially applicable for optimizing thermal remediation of light non-aqueous phase liquid contaminations or realizing thermally-enhanced electrokinetic removal of heavy metals. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A satellite view of riverine turbidity plumes on the NE-E Brazilian coastal zone

Directory of Open Access Journals (Sweden)

Eduardo Negri de Oliveira

2012-09-01

Full Text Available Turbidity plumes of São Francisco, Caravelas, Doce, and Paraiba do Sul river systems, located along the NE/E Brazilian coast, are analyzed for their dispersal patterns of Total Suspended Solids (TSS concentration using Landsat images and a logarithmic algorithm proposed by Tassan (1987 to convert satellite reflectance values to TSS. The TSS results obtained were compared to in situ collected TSS data. The analysis of the satellite image data set revealed that each river system exhibits a distinct turbidity plume dispersal pattern. The behavior, dimension and degree of turbidity of the São Francisco River plume have been greatly altered by the construction of a cascade of hydroelectric dam reservoirs in its hydrological basin. The plume has lost its typical unimodal seasonal pattern of material dispersion and its turbidity has decreased due to the regulation of river flow by the dams and TSS retainance by the reservoirs. In contrast, the Doce and Paraíba do Sul river plumes are still subject to seasonal pulsations and show more turbid conditions than the SF plume, as dams are less numerous, set in the middle river sections and the natural river flow has been maintained. The Caravelas Coastal System river plume is restricted to near shore shallow waters dominated by resuspension processes. During austral spring and summer when NE-E winds prevail, all plumes generally disperse southward. Short-term northward reversals may occur in winter with the passage of atmospheric cold fronts. The São Francisco and Doce river plumes tend to disperse obliquely to the coast and transport materials further offshore, while the Caravelas and Paraíba do Sul plumes tend to disperse mainly parallel to the coast, enhancing TSS retention nearshore.O presente estudo analisa as plumas de turbidez dos sistemas dos rios São Francisco, Caravelas, Doce, e Paraiba do Sul localizados na costa NE/E do Brasil utilizando imagens Landsat e o algoritmo logarítmico para Total

Rapid intrinsic biodegradation of benzene, toluene, and xylenes at the boundary of a gasoline-contaminated plume under natural attenuation

Energy Technology Data Exchange (ETDEWEB)

Takahata, Yoh; Hoaki, Toshihiro [Taisei Corp., Yokohama (Japan). Civil Engineering Research Inst.; Kasai, Yuki; Watanabe, Kazuya [Marine Biotechnology Institute, Kamaishi (Japan)

2006-12-15

A groundwater plume contaminated with gasoline constituents [mainly benzene, toluene, and xylenes (BTX)] had been treated by pumping and aeration for approximately 10 years, and the treatment strategy was recently changed to monitored natural attenuation (MNA). To gain information on the feasibility of using MNA to control the spread of BTX, chemical and microbiological parameters in groundwater samples obtained inside and outside the contaminated plume were measured over the course of 73 weeks. The depletion of electron acceptors (i.e., dissolved oxygen, nitrate, and sulfate) and increase of soluble iron were observed in the contaminated zone. Laboratory incubation tests revealed that groundwater obtained immediately outside the contaminated zone (the boundary zone) exhibited much higher potential for BTX degradation than those in the contaminated zone and in uncontaminated background zones. The boundary zone was a former contaminated area where BTX were no longer detected. Denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified bacterial 16S rRNA gene fragments revealed that DGGE profiles for groundwater samples obtained from the contaminated zone were clustered together and distinct from those from uncontaminated zones. In addition, unique bacterial rRNA types were observed in the boundary zone. These results indicate that the boundary zone in the contaminant plumes served as a natural barrier for preventing the BTX contamination from spreading out. (orig.)

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

International Nuclear Information System (INIS)

Tucci, P.

2001-01-01

This Analysis/Model Report (AMR) documents an updated analysis of water-level data performed to provide the saturated-zone, site-scale flow and transport model (CRWMS M and O 2000) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for model calibration. The previous analysis was presented in ANL-NBS-HS-000034, Rev 00 ICN 01, Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model (USGS 2001). This analysis is designed to use updated water-level data as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain. The objectives of this revision are to develop computer files containing (1) water-level data within the model area (DTN: GS010908312332.002), (2) a table of known vertical head differences (DTN: GS0109083 12332.003), and (3) a potentiometric-surface map (DTN: GS010608312332.001) using an alternate concept from that presented in ANL-NBS-HS-000034, Rev 00 ICN 01 for the area north of Yucca Mountain. The updated water-level data include data obtained from the Nye County Early Warning Drilling Program (EWDP) and data from borehole USW WT-24. In addition to being utilized by the SZ site-scale flow and transport model, the water-level data and potentiometric-surface map contained within this report will be available to other government agencies and water users for ground-water management purposes. The potentiometric surface defines an upper boundary of the site-scale flow model, as well as provides information useful to estimation of the magnitude and direction of lateral ground-water flow within the flow system. Therefore, the analysis documented in this revision is important to SZ flow and transport calculations in support of total system performance assessment

Emplacement of zero-valent metal for remediation of deep contaminant plumes

International Nuclear Information System (INIS)

Hubble, D.W.; Gillham, R.W.; Cherry, J.A.

1997-01-01

Some groundwater plumes containing chlorinated solvent contaminants are found to be so deep that current in situ remediation technologies cannot be economically applied. Also, source zones are often found to be too deep for removal or inaccessible due to surface features. Plumes emanating from these sources require containment or treatment. Containment technologies are available for shallow sites (< 15 m) and are being developed for greater depths. However, it is important to advance the science of reactive treatment - both for cut off of plumes and to contain and treat source zones. Zero-valent metal technology has been used for remediation of solvent plumes at sites in Canada, the UK and at several industrial and military sites in the USA. To date, all of the plumes treated with zero-valent metal (granular iron) have been at depths less than 15 m. This paper gives preliminary results of research into methods to emplace granular iron at depths in the range of 15 to 60 m. The study included review of available and emerging methods of installing barrier or reactive material and the selection, preliminary design and costing of several methods. The design of a treatment system for a 122 m wide PCE plume that, immediately down gradient from its source, extends from a depth of 24 to 37 m below the ground surface is used as a demonstration site. Both Permeable Reactive Wall and Funnel-and-Gate trademark systems were considered. The emplacement methods selected for preliminary design and costing were slurry wall, driven/vibrated beam, deep soil mixing and hydrofracturing injection. For each of these methods, the iron must be slurried for ease of pumping and placement using biodegradable polymer viscosifiers that leave the iron reactive

Moment analysis description of wetting and redistribution plumes in wettable and water-repellent soils

Science.gov (United States)

Xiong, Yunwu; Furman, Alex; Wallach, Rony

2012-02-01

SummaryWater repellency has a significant impact on water flow patterns in the soil profile. Transient 2D flow in wettable and natural water-repellent soils was monitored in a transparent flow chamber. The substantial differences in plume shape and spatial water content distribution during the wetting and subsequent redistribution stages were related to the variation of contact angle while in contact with water. The observed plumes shape, internal water content distribution in general and the saturation overshoot behind the wetting front in particular in the repellent soils were associated with unstable flow. Moment analysis was applied to characterize the measured plumes during the wetting and subsequent redistribution. The center of mass and spatial variances determined for the measured evolving plumes were fitted by a model that accounts for capillary and gravitational driving forces in a medium of temporally varying wettability. Ellipses defined around the stable and unstable plumes' centers of mass and whose semi-axes represented a particular number of spatial variances were used to characterize plume shape and internal moisture distribution. A single probability curve was able to characterize the corresponding fractions of the total added water in the different ellipses for all measured plumes, which testify the competence and advantage of the moment analysis method.

Modeling the influence of coupled mass transfer processes on mass flux downgradient of heterogeneous DNAPL source zones.

Science.gov (United States)

Yang, Lurong; Wang, Xinyu; Mendoza-Sanchez, Itza; Abriola, Linda M

2018-04-01

Sequestered mass in low permeability zones has been increasingly recognized as an important source of organic chemical contamination that acts to sustain downgradient plume concentrations above regulated levels. However, few modeling studies have investigated the influence of this sequestered mass and associated (coupled) mass transfer processes on plume persistence in complex dense nonaqueous phase liquid (DNAPL) source zones. This paper employs a multiphase flow and transport simulator (a modified version of the modular transport simulator MT3DMS) to explore the two- and three-dimensional evolution of source zone mass distribution and near-source plume persistence for two ensembles of highly heterogeneous DNAPL source zone realizations. Simulations reveal the strong influence of subsurface heterogeneity on the complexity of DNAPL and sequestered (immobile/sorbed) mass distribution. Small zones of entrapped DNAPL are shown to serve as a persistent source of low concentration plumes, difficult to distinguish from other (sorbed and immobile dissolved) sequestered mass sources. Results suggest that the presence of DNAPL tends to control plume longevity in the near-source area; for the examined scenarios, a substantial fraction (43.3-99.2%) of plume life was sustained by DNAPL dissolution processes. The presence of sorptive media and the extent of sorption non-ideality are shown to greatly affect predictions of near-source plume persistence following DNAPL depletion, with plume persistence varying one to two orders of magnitude with the selected sorption model. Results demonstrate the importance of sorption-controlled back diffusion from low permeability zones and reveal the importance of selecting the appropriate sorption model for accurate prediction of plume longevity. Large discrepancies for both DNAPL depletion time and plume longevity were observed between 2-D and 3-D model simulations. Differences between 2- and 3-D predictions increased in the presence of

Modeling the influence of coupled mass transfer processes on mass flux downgradient of heterogeneous DNAPL source zones

Science.gov (United States)

Yang, Lurong; Wang, Xinyu; Mendoza-Sanchez, Itza; Abriola, Linda M.

2018-04-01

Sequestered mass in low permeability zones has been increasingly recognized as an important source of organic chemical contamination that acts to sustain downgradient plume concentrations above regulated levels. However, few modeling studies have investigated the influence of this sequestered mass and associated (coupled) mass transfer processes on plume persistence in complex dense nonaqueous phase liquid (DNAPL) source zones. This paper employs a multiphase flow and transport simulator (a modified version of the modular transport simulator MT3DMS) to explore the two- and three-dimensional evolution of source zone mass distribution and near-source plume persistence for two ensembles of highly heterogeneous DNAPL source zone realizations. Simulations reveal the strong influence of subsurface heterogeneity on the complexity of DNAPL and sequestered (immobile/sorbed) mass distribution. Small zones of entrapped DNAPL are shown to serve as a persistent source of low concentration plumes, difficult to distinguish from other (sorbed and immobile dissolved) sequestered mass sources. Results suggest that the presence of DNAPL tends to control plume longevity in the near-source area; for the examined scenarios, a substantial fraction (43.3-99.2%) of plume life was sustained by DNAPL dissolution processes. The presence of sorptive media and the extent of sorption non-ideality are shown to greatly affect predictions of near-source plume persistence following DNAPL depletion, with plume persistence varying one to two orders of magnitude with the selected sorption model. Results demonstrate the importance of sorption-controlled back diffusion from low permeability zones and reveal the importance of selecting the appropriate sorption model for accurate prediction of plume longevity. Large discrepancies for both DNAPL depletion time and plume longevity were observed between 2-D and 3-D model simulations. Differences between 2- and 3-D predictions increased in the presence of

Partial nitrification enhances natural attenuation of nitrogen in a septic system plume.

Science.gov (United States)

Caschetto, M; Robertson, W; Petitta, M; Aravena, R

2018-06-01

Natural attenuation of nitrogen (N) was investigated in a well characterized septic system plume at a campground in Ontario, Canada. Total inorganic N (TIN) concentrations in deeper portions of the plume were about one third of the septic tank value of 40.7mgL -1 . NH 4 + and NO 3 - isotopic characterization were used to provide insight into potential attenuation processes. Concentrations of NH 4 + and NO 3 - were highly variable in the plume, but approached the septic tank TIN value in some shallow zones and exhibited δ 15 N values like the tank value of +6‰. However, isotopic enrichment (up to +24‰ for NH 4 + and +45‰ for NO 3 - ) and declining TIN concentrations in the deeper zones indicated that anaerobic ammonium oxidation contributed to the TIN attenuation. The degree of isotopic enrichment increased at lower NH 4 + concentrations and was consistent with Rayleigh-type distillation with an enrichment factor (Ɛ) of -5.1‰. Additionally, decreasing DOC values with depth and the concomitant enrichment of δ 15 N NO3 and δ 18 O NO3 , suggested that denitrification was also active. The N attenuation observed in the Killarney plume was partly due to incomplete nitrification that occurred because of the shallow water table, which varied from only 0.2-0.7m below the tile bed infiltration pipes. Moreover, some of the monitoring locations with the shallowest water table distances from the infiltration pipes, had the highest degree of TIN attenuation (70-90%) in the plume. This behavior suggests that controlling water table distance from the infiltration pipes could be a useful mechanism for enhancing N attenuation in septic system plumes. Copyright © 2017 Elsevier B.V. All rights reserved.

Wet plume atop of the flattening slab: Insight into intraplate volcanism in East Asia

Science.gov (United States)

He, Lijuan

2017-08-01

Geophysical observations imply the intraplate volcanism in East Asia is related to dehydration of slab stagnating in the transition zone. To better understand the dynamics of such process, a thermochemical mantle convection model is constructed to simulate numerically the thermal evolution of slab and the transportation of water in the process of slab downgoing, flattening and stagnation. Equation of water transfer is included, and water effects on density and viscosity are considered. Model results indicate the warming of slab by surrounding mantle is rather slow. Water could be successfully dragged into the transition zone if the reference viscosity of the hydrous layer (with initial water of 2 wt%) is higher than 1017 Pa s and that of mantle is 1021 Pa s. Wet plumes could then originate in the flat-lying part of the slab, relatively far from the trench. Generally, the viscosity of the hydrous layer governs the initiation of wet plume, whereas the viscosity of the overlying mantle wedge controls the activity of the ascending wet plumes - they are more active in the weaker wedge. The complex fluid flow superposed by corner flow and free thermal convection influences greatly the water transport pattern in the upper mantle. Modeling results together with previous modeling infer three stages of water circulation in the big mantle wedge: 1) water is brought into the mantle transition zone by downward subducting slab under some specific thermo-rheological conditions, otherwise water is released at shallow depth near wedge tip; 2) wet plume generates from surface of the flattening slab warmed by surrounding mantle, and 3) water spreads over the big mantle wedge. Wet plume from the flattening Pacific Plate arrives at the lithospheric base and induces melting, which can explain the intraplate Cenozoic volcanoes in East Asia.

Independent Technical Review Of The Focused Feasibility Study And Proposed Plan For Designated Solid Waste Management Units Contributing To The Southwest Groundwater Plume At The Paducah Gaseous Diffusion Plant

International Nuclear Information System (INIS)

Looney, B.; Eddy-Dilek, C.; Amidon, M.; Rossabi, J.; Stewart, L.

2011-01-01

The U. S. Department of Energy (DOE) is currently developing a Proposed Plan (PP) for remediation of designated sources of chlorinated solvents that contribute contamination to the Southwest (SW) Groundwater Plume at the Paducah Gaseous Diffusion Plant (PGDP), in Paducah, KY. The principal contaminants in the SW Plume are trichloroethene (TCE) and other volatile organic compounds (VOCs); these industrial solvents were used and disposed in various facilities and locations at PGDP. In the SW plume area, residual TCE sources are primarily in the fine-grained sediments of the Upper Continental Recharge System (UCRS), a partially saturated zone that delivers contaminants downward into the coarse-grained Regional Gravel Aquifer (RGA). The RGA serves as the significant lateral groundwater transport pathway for the plume. In the SW Plume area, the four main contributing TCE source units are: (1) Solid Waste Management Unit (SWMU) 1 / Oil Landfarm; (2) C-720 Building TCE Northeast Spill Site (SWMU 211A); (3) C-720 Building TCE Southeast Spill Site (SWMU 211B); and (4) C-747 Contaminated Burial Yard (SWMU 4). The PP presents the Preferred Alternatives for remediation of VOCs in the UCRS at the Oil Landfarm and the C-720 Building spill sites. The basis for the PP is documented in a Focused Feasibility Study (FFS) (DOE, 2011) and a Site Investigation Report (SI) (DOE, 2007). The SW plume is currently within the boundaries of PGDP (i.e., does not extend off-site). Nonetheless, reasonable mitigation of the multiple contaminant sources contributing to the SW plume is one of the necessary components identified in the PGDP End State Vision (DOE, 2005). Because of the importance of the proposed actions DOE assembled an Independent Technical Review (ITR) team to provide input and assistance in finalizing the PP.

INDEPENDENT TECHNICAL REVIEW OF THE FOCUSED FEASIBILITY STUDY AND PROPOSED PLAN FOR DESIGNATED SOLID WASTE MANAGEMENT UNITS CONTRIBUTING TO THE SOUTHWEST GROUNDWATER PLUME AT THE PADUCAH GASEOUS DIFFUSION PLANT

Energy Technology Data Exchange (ETDEWEB)

Looney, B.; Eddy-Dilek, C.; Amidon, M.; Rossabi, J.; Stewart, L.

2011-05-31

The U. S. Department of Energy (DOE) is currently developing a Proposed Plan (PP) for remediation of designated sources of chlorinated solvents that contribute contamination to the Southwest (SW) Groundwater Plume at the Paducah Gaseous Diffusion Plant (PGDP), in Paducah, KY. The principal contaminants in the SW Plume are trichloroethene (TCE) and other volatile organic compounds (VOCs); these industrial solvents were used and disposed in various facilities and locations at PGDP. In the SW plume area, residual TCE sources are primarily in the fine-grained sediments of the Upper Continental Recharge System (UCRS), a partially saturated zone that delivers contaminants downward into the coarse-grained Regional Gravel Aquifer (RGA). The RGA serves as the significant lateral groundwater transport pathway for the plume. In the SW Plume area, the four main contributing TCE source units are: (1) Solid Waste Management Unit (SWMU) 1 / Oil Landfarm; (2) C-720 Building TCE Northeast Spill Site (SWMU 211A); (3) C-720 Building TCE Southeast Spill Site (SWMU 211B); and (4) C-747 Contaminated Burial Yard (SWMU 4). The PP presents the Preferred Alternatives for remediation of VOCs in the UCRS at the Oil Landfarm and the C-720 Building spill sites. The basis for the PP is documented in a Focused Feasibility Study (FFS) (DOE, 2011) and a Site Investigation Report (SI) (DOE, 2007). The SW plume is currently within the boundaries of PGDP (i.e., does not extend off-site). Nonetheless, reasonable mitigation of the multiple contaminant sources contributing to the SW plume is one of the necessary components identified in the PGDP End State Vision (DOE, 2005). Because of the importance of the proposed actions DOE assembled an Independent Technical Review (ITR) team to provide input and assistance in finalizing the PP.

River Plumes in Sunglint, Sarawak, Borneo

Science.gov (United States)

1991-01-01

The sunglint pattern along the coast of Sarawak (3.0N, 111.5E) delineates the boundry of fresh water river plumes as they flow into the South China Sea. The fresh water lens (boundry between fresh and sea water) overides the saline and more dense sea water and oils, both natural and man made, collect along the convergence zones and dampen wave action. As a result, the smoother sea surface appears bright in the sunglint pattern.

Sulfate Reduction Remediation of a Metals Plume Through Organic Injection

International Nuclear Information System (INIS)

Phifer, M.A.

2003-01-01

Laboratory testing and a field-scale demonstration for the sulfate reduction remediation of an acidic/metals/sulfate groundwater plume at the Savannah River Site has been conducted. The laboratory testing consisted of the use of anaerobic microcosms to test the viability of three organic substrates to promote microbially mediated sulfate reduction. Based upon the laboratory testing, soybean oil and sodium lactate were selected for injection during the subsequent field-scale demonstration. The field-scale demonstration is currently ongoing. Approximately 825 gallons (3,123 L) of soybean oil and 225 gallons (852 L) of 60 percent sodium lactate have been injected into an existing well system within the plume. Since the injections, sulfate concentrations in the injection zone have significantly decreased, sulfate-reducing bacteria concentrations have significantly increased, the pH has increased, the Eh has decreased, and the concentrations of many metals have decreased. Microbially mediated sulfate reduction has been successfully promoted for the remediation of the acidic/metals/sulfate plume by the injection of soybean oil and sodium lactate within the plume

A review of possible origins of the uranium 'plume' in the aquifer under the EPIC site in the Chernobyl Exclusion Zone

Energy Technology Data Exchange (ETDEWEB)

Simonucci, C.; Van Meir, N.; Courbet, C. [Institute for Radioprotection and Nuclear Safety, PRP-DGE/SRTG/LETIS, POB 17, F-92262, Fontenay-aux-Roses Cedex (France); Roux, C. [Institute for Radioprotection and Nuclear Safety, PRP-DGE/SRTG/LETIS, POB 17, F-92262, Fontenay-aux-Roses Cedex (France); Aix-Marseille University, CNRS, IRD, CEREGE UM34, 13545 Aix en Provence (France); Le Gal La Salle, C.; Verdoux, P.; Lancelot, J.C. [Nimes University, Laboratoire de Geochimie Isotopique (GIS), 150 rue George Besse, 30035 Nimes (France); Ruas, A. [CEA, Nuclear Energy Division, RadioChemistry and Processes Department, F-30207, Bagnols-sur-Ceze (France); Bassot, S. [Institute for Radioprotection and Nuclear Safety, PRP-DGE/SRTG/LAME, POB 17, F-92262, Fontenay-aux-Roses Cedex (France); Bugai, D. [Institute of Geological Sciences, 55-b, Gonchara Str., Kiev 01054 (Ukraine); Levchuk, S.; Kashparov, V. [Ukrainian Institute of Agricultural Radiology, UIAR NUBiP of Ukraine, Mashinobudivnykiv str. 7, Chabany, Kyiv-Svjatoshin (Ukraine)

2013-07-01

The uniqueness of the Chernobyl accident lies in the fact that so much radioactive material was discharged to the atmosphere as solid fuel particles from the reactor core. Between the 26 April and the 6 May 1986 more than 6 tons of small particles of highly radioactive uranium oxide fuel were discharged to the atmosphere and were responsible for more than 75 % of the radioactive contamination on the ground in the exclusion zone. In 1987, about 800 trenches had been dug in the exclusion zone to prevent re-suspension and to protect workers from contamination. In 1999, the IRSN, in collaboration with IGS and UIAR, equipped trench 22 (CPS) in order to monitor radionuclide migration in the environment (water, soil, plants). At the EPIC site high uranium concentrations were observed in the groundwater downstream from trench 22. We discuss the possible origins of this uranium 'plume'. (authors)

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995

Energy Technology Data Exchange (ETDEWEB)

Luckey, R.R.; Tucci, P.; Faunt, C.C.; Ervin, E.M. [and others

1996-12-31

Yucca Mountain, which is being studied extensively because it is a potential site for a high-level radioactive-waste repository, consists of a thick sequence of volcanic rocks of Tertiary age that are underlain, at least to the southeast, by carbonate rocks of Paleozoic age. Stratigraphic units important to the hydrology of the area include the alluvium, pyroclastic rocks of Miocene age (the Timber Mountain Group; the Paintbrush Group; the Calico Hills Formation; the Crater Flat Group; the Lithic Ridge Tuff; and older tuffs, flows, and lavas beneath the Lithic Ridge Tuff), and sedimentary rocks of Paleozoic age. The saturated zone generally occurs in the Calico Hills Formation and stratigraphically lower units. The saturated zone is divided into three aquifers and two confining units. The flow system at Yucca Mountain is part of the Alkali Flat-Furnace Creek subbasin of the Death Valley groundwater basin. Variations in the gradients of the potentiometric surface provided the basis for subdividing the Yucca Mountain area into zones of: (1) large hydraulic gradient where potentiometric levels change at least 300 meters in a few kilometers; (2) moderate hydraulic gradient where potentiometric levels change about 45 meters in a few kilometers; and (3) small hydraulic gradient where potentiometric levels change only about 2 meters in several kilometers. Vertical hydraulic gradients were measured in only a few boreholes around Yucca Mountain; most boreholes had little change in potentiometric levels with depth. Limited hydraulic testing of boreholes in the Yucca Mountain area indicated that the range in transmissivity was more than 2 to 3 orders of magnitude in a particular hydrogeologic unit, and that the average values for the individual hydrogeologic units generally differed by about 1 order of magnitude. The upper volcanic aquifer seems to be the most permeable hydrogeologic unit, but this conclusion was based on exceedingly limited data.

Status of understanding of the saturated-zone ground-water flow system at Yucca Mountain, Nevada, as of 1995

International Nuclear Information System (INIS)

Luckey, R.R.; Tucci, P.; Faunt, C.C.; Ervin, E.M.

1996-01-01

Yucca Mountain, which is being studied extensively because it is a potential site for a high-level radioactive-waste repository, consists of a thick sequence of volcanic rocks of Tertiary age that are underlain, at least to the southeast, by carbonate rocks of Paleozoic age. Stratigraphic units important to the hydrology of the area include the alluvium, pyroclastic rocks of Miocene age (the Timber Mountain Group; the Paintbrush Group; the Calico Hills Formation; the Crater Flat Group; the Lithic Ridge Tuff; and older tuffs, flows, and lavas beneath the Lithic Ridge Tuff), and sedimentary rocks of Paleozoic age. The saturated zone generally occurs in the Calico Hills Formation and stratigraphically lower units. The saturated zone is divided into three aquifers and two confining units. The flow system at Yucca Mountain is part of the Alkali Flat-Furnace Creek subbasin of the Death Valley groundwater basin. Variations in the gradients of the potentiometric surface provided the basis for subdividing the Yucca Mountain area into zones of: (1) large hydraulic gradient where potentiometric levels change at least 300 meters in a few kilometers; (2) moderate hydraulic gradient where potentiometric levels change about 45 meters in a few kilometers; and (3) small hydraulic gradient where potentiometric levels change only about 2 meters in several kilometers. Vertical hydraulic gradients were measured in only a few boreholes around Yucca Mountain; most boreholes had little change in potentiometric levels with depth. Limited hydraulic testing of boreholes in the Yucca Mountain area indicated that the range in transmissivity was more than 2 to 3 orders of magnitude in a particular hydrogeologic unit, and that the average values for the individual hydrogeologic units generally differed by about 1 order of magnitude. The upper volcanic aquifer seems to be the most permeable hydrogeologic unit, but this conclusion was based on exceedingly limited data

Mantle roots of the Emeishan plume: an evaluation based on teleseismic P-wave tomography

Directory of Open Access Journals (Sweden)

C. He

2017-11-01

Full Text Available The voluminous magmatism associated with large igneous provinces (LIPs is commonly correlated to upwelling plumes from the core–mantle boundary (CMB. Here we analyse seismic tomographic data from the Emeishan LIP in southwestern China. Our results reveal vestiges of delaminated crustal and/or lithospheric mantle, with an upwelling in the upper mantle beneath the Emeishan LIP rather than a plume rooted in the CMB. We suggest that the magmatism and the Emeishan LIP formation might be connected with the melting of delaminated lower crustal and/or lithospheric components which resulted in plume-like upwelling from the upper mantle or from the mantle transition zone.

Contrasted continental rifting via plume-craton interaction: Applications to Central East African Rift

Directory of Open Access Journals (Sweden)

Alexander Koptev

2016-03-01

Full Text Available The East African Rift system (EARS provides a unique system with the juxtaposition of two contrasting yet simultaneously formed rift branches, the eastern, magma-rich, and the western, magma-poor, on either sides of the old thick Tanzanian craton embedded in a younger lithosphere. Data on the pre-rift, syn-rift and post-rift far-field volcanic and tectonic activity show that the EARS formed in the context of the interaction between a deep mantle plume and a horizontally and vertically heterogeneous lithosphere under far-field tectonic extension. We bring quantitative insights into this evolution by implementing high-resolution 3D thermo-mechanical numerical deformation models of a lithosphere of realistic rheology. The models focus on the central part of the EARS. We explore scenarios of plume-lithosphere interaction with plumes of various size and initial position rising beneath a tectonically pre-stretched lithosphere. We test the impact of the inherited rheological discontinuities (suture zones along the craton borders, of the rheological structure, of lithosphere plate thickness variations, and of physical and mechanical contrasts between the craton and the embedding lithosphere. Our experiments indicate that the ascending plume material is deflected by the cratonic keel and preferentially channeled along one of its sides, leading to the formation of a large rift zone along the eastern side of the craton, with significant magmatic activity and substantial melt amount derived from the mantle plume material. We show that the observed asymmetry of the central EARS, with coeval amagmatic (western and magmatic (eastern branches, can be explained by the splitting of warm material rising from a broad plume head whose initial position is slightly shifted to the eastern side of the craton. In that case, neither a mechanical weakness of the contact between the craton and the embedding lithosphere nor the presence of second plume are required to

Evaluating Ecosystem Services for Reducing Groundwater Nitrate Contamination: Nitrate Attenuation in the Unsaturated and Saturated Zones

Science.gov (United States)

Wang, J.

2013-12-01

Nitrates are the most common type of groundwater contamination in agricultural regions. Environmental policies targeting nitrates have focused on input control (e.g., restricted fertilizer application), intermediate loads control (e.g., reduce nitrate leached from crop fields), and final loads control (e.g., reduce catchment nitrate loads). Nitrate loads can be affected by hydrological processes in both unsaturated and saturated zones. Although many of these processes have been extensively investigated in literature, they are commonly modeled as exogenous to farm management. A couple of recent studies by scientists from the Lawrence Livermore National Laboratory show that in some situations nitrate attenuation processes in the unsaturated/saturated zone, particularly denitrification, can be intensified by certain management practices to mitigate nitrate loads. Therefore, these nitrate attenuation processes can be regarded as a set of ecosystem services that farmers can take advantage of to reduce their cost of complying with environmental policies. In this paper, a representative California dairy farm is used as a case study to show how such ecosystem attenuation services can be framed within the farm owner's decision-making framework as an option for reducing groundwater nitrate contamination. I develop an integrated dynamic model, where the farmer maximizes discounted net farm profit over multiple periods subject to environmental regulations. The model consists of three submodels: animal-waste-crop, hydrologic, and economic model. In addition to common choice variables such as irrigation, fertilization, and waste disposal options, the farmer can also endogenously choose from three water sources: surface water, deep groundwater (old groundwater in the deep aquifer that is not affected by farm effluent in the short term), and shallow groundwater (drainage water that can be recycled via capture wells at the downstream end of the farm). The capture wells not only

Impact of radionuclide spatial variability on groundwater quality downstream from a shallow waste burial in the Chernobyl Exclusion Zone

Science.gov (United States)

Nguyen, H. L.; de Fouquet, C.; Courbet, C.; Simonucci, C. A.

2016-12-01

The effects of spatial variability of hydraulic parameters and initial groundwater plume localization on the possible extent of groundwater pollution plumes have already been broadly studied. However, only a few studies, such as Kjeldsen et al. (1995), take into account the effect of source term spatial variability. We explore this question with the 90Sr migration modeling from a shallow waste burial located in the Chernobyl Exclusion Zone to the underlying sand aquifer. Our work is based upon groundwater sampled once or twice a year since 1995 until 2015 from about 60 piezometers and more than 3,000 137Cs soil activity measurements. These measurements were taken in 1999 from one of the trenches dug after the explosion of the Chernobyl nuclear power plant, the so-called "T22 Trench", where radioactive waste was buried in 1987. The geostatistical analysis of 137Cs activity data in soils from Bugai et al. (2005) is first reconsidered to delimit the trench borders using georadar data as a covariable and to perform geostatistical simulations in order to evaluate the uncertainties of this inventory. 90Sr activity in soils is derived from 137Cs/154Eu and 90Sr/154Eu activity ratios in Chernobyl hot fuel particles (Bugai et al., 2003). Meanwhile, a coupled 1D non saturated/3D saturated transient transport model is constructed under the MELODIE software (IRSN, 2009). The previous 90Sr transport model developed by Bugai et al. (2012) did not take into account the effect of water table fluctuations highlighted by Van Meir et al. (2007) which may cause some discrepancies between model predictions and field observations. They are thus reproduced on a 1D vertical non saturated model. The equiprobable radionuclide localization maps produced by the geostatistical simulations are selected to illustrate different heterogeneities in the radionuclide inventory and are implemented in the 1D model. The obtained activity fluxes from all the 1D vertical models are then injected in a 3D

Benchmarking of the saturated-zone module associated with three risk assessment models: RESRAD, MMSOILS, and MEPAS

International Nuclear Information System (INIS)

Whelan, Gene; Mcdonald, J P.; Gnanapragasam, Emmanuel K.; Laniak, Gerard F.; Lew, Christine S.; Mills, William B.; Yu, C

1998-01-01

A comprehensive benchmarking is being performed between three multimedia risk assessment models: RESRAD, MMSOILS, and MEPAS. Each multimedia model is comprised of a suite of modules (e.g., groundwater, air, surface water, exposure, and risk/hazard), all of which can impact the estimation of human-health risk. As a component of the comprehensive benchmarking exercise, the saturated-zone modules of each model were applied to an environmental release scenario, where uranium-234 was released from the waste site to a saturated zone. Uranium-234 time-varying emission rates exiting from the source and concentrations at three downgradient locations (0 m, 150 m, and 1500 m) are compared for each multimedia model. Time-Varying concentrations for uranium-234 decay products (i.e., thorium-230, radium-226, and lead-210) at the 1500-m location are also presented. Different results are reported for RESRAD, MMSOILS, and MEPAS, which are solely due to the assumptions and mathematical constructs inherently built into each model, thereby impacting the potential risks predicted by each model. Although many differences were identified between the models, differences that impacted these benchmarking results the most are as follows: (1) RESRAD transports its contaminants by pure translation, and MMSOILS and MEPAS solve the one-dimensional advective, three-dimensional dispersive equation. (2) Due to the manner in which the retardation factor is defined, RESRAD contaminant velocities will always be faster than MMSOILS or MEPAS. (3) RESRAD uses a dilution factor to account for a withdrawal well; MMSOILS and MEPAS were designed to calculate in-situ concentrations at a receptor location. (4) RESRAD allows for decay products to travel at different velocities, while MEPAS assumes the decay products travel at the same speed as their parents. MMSOILS does not account for decay products and assumes degradation/decay only in the aqueous phase

Changing compositions in the Iceland plume; Isotopic and elemental constraints from the Paleogene Faroe flood basalts

DEFF Research Database (Denmark)

Søager, Nina; Holm, Paul Martin

2011-01-01

Elemental and Sr, Nd, Hf and high precision Pb isotopic data are presented from 59 low-Ti and high-Ti lavas from the syn-break up part of the Faroe Flood Basalt Province. The depleted MORB-like low-Ti lavas erupted in the rift zone between the Faroe Islands and central East Greenland around......-type component similar in geochemistry to the Icelandic Öræfajökull lavas. This component is believed to be recycled pelagic sediments in the plume but it can alternatively be a local crustal or lithospheric mantle component. The enriched Faroe high-Ti lavas erupted inland from the rift have isotopic...... compositions very similar to the enriched Icelandic neo-volcanics and these lava suites apparently share the two enriched plume end-members IE1 and IE2 (Geochim. Cosmochim. Acta 68, 2, 2004). The lack of mixing between high and low-Ti melts at the time of break up, is explained by a zoned plume where only low...

Reactive transport modeling of processes controlling the distribution and natural attenuation of phenolic compounds in a deep sandstone aquifer

Science.gov (United States)

Mayer, K. U.; Benner, S. G.; Frind, E. O.; Thornton, S. F.; Lerner, D. N.

2001-12-01

Reactive solute transport modeling was utilized to evaluate the potential for natural attenuation of a contaminant plume containing phenolic compounds at a chemical producer in the West Midlands, UK. The reactive transport simulations consider microbially mediated biodegradation of the phenolic compounds (phenols, cresols, and xylenols) by multiple electron acceptors. Inorganic reactions including hydrolysis, aqueous complexation, dissolution of primary minerals, formation of secondary mineral phases, and ion exchange are considered. One-dimensional (1D) and three-dimensional (3D) simulations were conducted. Mass balance calculations indicate that biodegradation in the saturated zone has degraded approximately 1-5% of the organic contaminant plume over a time period of 47 years. Simulations indicate that denitrification is the most significant degradation process, accounting for approximately 50% of the organic contaminant removal, followed by sulfate reduction and fermentation reactions, each contributing 15-20%. Aerobic respiration accounts for less than 10% of the observed contaminant removal in the saturated zone. Although concentrations of Fe(III) and Mn(IV) mineral phases are high in the aquifer sediment, reductive dissolution is limited, producing only 5% of the observed mass loss. Mass balance calculations suggest that no more than 20-25% of the observed total inorganic carbon (TIC) was generated from biodegradation reactions in the saturated zone. Simulations indicate that aerobic biodegradation in the unsaturated zone, before the contaminant entered the aquifer, may have produced the majority of the TIC observed in the plume. Because long-term degradation is limited to processes within the saturated zone, use of observed TIC concentrations to predict the future natural attenuation may overestimate contaminant degradation by a factor of 4-5.

Modeling of geochemical processes in the submarine discharge zone of hydrothermal solutions

Directory of Open Access Journals (Sweden)

С. М. Судариков

2017-06-01

Full Text Available The paper reviews the main methods and analyzes modeling results for geochemical processes in the submarine discharge zone of hydrothermal solutions of mid-ocean ridges. Initial data for modeling have been obtained during several marine expeditions, including Russian-French expedition SERPENTINE on the research vessel «Pourquoi Рas?» (2007. Results of field observations, laboratory experiments and theoretical developments are supported by the analysis of regression model of mixing between hydrothermal solutions and sea water. Verification of the model has been carried out and the quality of chemical analysis has been assessed; degree and character of participation of solution components in the hydrothermal process have been defined; the content of end members has been calculated basing on reverse forecasting of element concentration, depending on regression character; data for thermodynamic modeling have been prepared. Regression model of acid-base properties and chloridity of mineralizing thermal springs confirms adequacy of the model of double-diffusive convection for forming the composition of hydrothermal solutions.  Differentiation of solutions according to concentrations of chloride-ion, depending on temperature and pH indicator within this model, is associated with phase conversions and mixing of fluids from two convection cells, one of which is a zone of brine circulation. In order to carry out computer thermodynamic modeling, hydro-geochemical and physicochemical models of hydrothermal discharge zone have been created. Verification of the model has been carried out basing on changes of Mn concentration in the hydrothermal plume. Prevailing forms of Mn migration in the plume are Mn2+, MnCl+, MnCl2. Two zones have been identified in the geochemical structure of the plume: 1 high-temperature zone (350-100 °С with prevalence of chloride complexes – ascending plume; 2 low-temperature zone (100-2 °С, where predominant form of

On the validity of a Fickian diffusion model for the spreading of liquid infiltration plumes in partially saturated heterogeneous media

International Nuclear Information System (INIS)

Pruess, K.

1994-01-01

Localized infiltration of aqueous and -non-aqueous phase liquids (NAPLs) occurs in many circumstances. Examples include leaky underground pipelines and storage tanks, landfill and disposal sites, and surface spills. Because of ever-present heterogeneities on different scales such infiltration plumes are expected to disperse transversally and longitudinally. This paper examines recent suggestions that liquid plumes are being dispersed from medium heterogeneities in a manner that is analogous to Fickian diffusion. Numerical simulation experiments on liquid infiltration in heterogeneous media are performed to study the dispersive effects of small-scale heterogeneity. It is found that plume spreading indeed tends to be diffusive. Our results suggest that, as far as infiltration of liquids is concerned, broad classes of heterogeneous media behave as dispersive media with locally homogeneous (albeit anisotropic) permeability

Damping Effect of an Unsaturated-Saturated System on Tempospatial Variations of Pressure Head and Specific Flux

Science.gov (United States)

Yang, C.; Zhang, Y. K.; Liang, X.

2014-12-01

Damping effect of an unsaturated-saturated system on tempospatialvariations of pressurehead and specificflux was investigated. The variance and covariance of both pressure head and specific flux in such a system due to a white noise infiltration were obtained by solving the moment equations of water flow in the system and verified with Monte Carlo simulations. It was found that both the pressure head and specific flux in this case are temporally non-stationary. The variance is zero at early time due to a deterministic initial condition used, then increases with time, and approaches anasymptotic limit at late time.Both pressure head and specific flux arealso non-stationary in space since the variance decreases from source to sink. The unsaturated-saturated systembehavesasa noise filterand it damps both the pressure head and specific flux, i.e., reduces their variations and enhances their correlation. The effect is stronger in upper unsaturated zone than in lower unsaturated zone and saturated zone. As a noise filter, the unsaturated-saturated system is mainly a low pass filter, filtering out the high frequency components in the time series of hydrological variables. The damping effect is much stronger in the saturated zone than in the saturated zone.

Modelling of transport and biogeochemical processes in pollution plumes: Vejen landfill, Denmark

DEFF Research Database (Denmark)

Brun, A.; Engesgaard, Peter Knudegaard; Christensen, Thomas Højlund

2002-01-01

A biogeochemical transport code is used to simulate leachate attenuation. biogeochemical processes. and development of redox zones in a pollution plume downstream of the Vejen landfill in Denmark. Calibration of the degradation parameters resulted in a good agreement with the observed distribution...

Numerical model simulation of atmospheric coolant plumes

International Nuclear Information System (INIS)

Gaillard, P.

1980-01-01

The effect of humid atmospheric coolants on the atmosphere is simulated by means of a three-dimensional numerical model. The atmosphere is defined by its natural vertical profiles of horizontal velocity, temperature, pressure and relative humidity. Effluent discharge is characterised by its vertical velocity and the temperature of air satured with water vapour. The subject of investigation is the area in the vicinity of the point of discharge, with due allowance for the wake effect of the tower and buildings and, where application, wind veer with altitude. The model equations express the conservation relationships for mometum, energy, total mass and water mass, for an incompressible fluid behaving in accordance with the Boussinesq assumptions. Condensation is represented by a simple thermodynamic model, and turbulent fluxes are simulated by introduction of turbulent viscosity and diffusivity data based on in-situ and experimental water model measurements. The three-dimensional problem expressed in terms of the primitive variables (u, v, w, p) is governed by an elliptic equation system which is solved numerically by application of an explicit time-marching algorithm in order to predict the steady-flow velocity distribution, temperature, water vapour concentration and the liquid-water concentration defining the visible plume. Windstill conditions are simulated by a program processing the elliptic equations in an axisymmetrical revolution coordinate system. The calculated visible plumes are compared with plumes observed on site with a view to validate the models [fr

Broad plumes rooted at the base of the Earth's mantle beneath major hotspots.

Science.gov (United States)

French, Scott W; Romanowicz, Barbara

2015-09-03

Plumes of hot upwelling rock rooted in the deep mantle have been proposed as a possible origin of hotspot volcanoes, but this idea is the subject of vigorous debate. On the basis of geodynamic computations, plumes of purely thermal origin should comprise thin tails, only several hundred kilometres wide, and be difficult to detect using standard seismic tomography techniques. Here we describe the use of a whole-mantle seismic imaging technique--combining accurate wavefield computations with information contained in whole seismic waveforms--that reveals the presence of broad (not thin), quasi-vertical conduits beneath many prominent hotspots. These conduits extend from the core-mantle boundary to about 1,000 kilometres below Earth's surface, where some are deflected horizontally, as though entrained into more vigorous upper-mantle circulation. At the base of the mantle, these conduits are rooted in patches of greatly reduced shear velocity that, in the case of Hawaii, Iceland and Samoa, correspond to the locations of known large ultralow-velocity zones. This correspondence clearly establishes a continuous connection between such zones and mantle plumes. We also show that the imaged conduits are robustly broader than classical thermal plume tails, suggesting that they are long-lived, and may have a thermochemical origin. Their vertical orientation suggests very sluggish background circulation below depths of 1,000 kilometres. Our results should provide constraints on studies of viscosity layering of Earth's mantle and guide further research into thermochemical convection.

Potential for saturated ground-water system contamination at the Lawrence Livermore National Laboratory

International Nuclear Information System (INIS)

Stone, R.; Ruggieri, M.R.; Rogers, L.L.; Emerson, D.O.; Buddemeier, R.W.

1982-01-01

A program of hydrogeologic investigation has been carried out to determine the likelihood of contaminant movement to the saturated zone from near the ground surface at Lawrence Livermore National Laboratory (LLNL). A companion survey of potential contaminant sources was also conducted at the LLNL. Water samples from selected LLNL wells were analyzed to test the water quality in the uppermost part of the saturated zone, which is from 14 to 48 m (45 to 158 ft) beneath the surface. Only nitrate and tritium were found in concentrations above natural background. In one well, the nitrate was slightly more concentrated than the drinking water limit. The nitrate source has not been found. The tritium in all ground-water samples from wells was found far less concentrated than the drinking water limit. The extent of infiltration of surface water was traced with environmental tritium. The thickness and stratigraphy of the unsaturated zone beneath the LLNL, and nearby area, was determined with specially constructed wells and boreholes. Well hydrograph analysis indicated where infiltration of surface water reached the saturated ground-water system. The investigation indicates that water infiltrating from the surface, through alluvial deposits, reaches the saturated zone along the course of Arroyo Seco, Arroyo Las Positas, and from the depression near the center of the site where seasonal water accumulates. Several potential contaminant sources were identified, and it is likely that contaminants could move from near the ground surface to the saturated zone beneath LLNL. Additional ground-water sampling and analysis will be performed and ongoing investigations will provide estimates of the speed with which potential contaminants can flow laterally in the saturated zone beneath LLNL. 34 references, 61 figures, 16 tables

Identifying key controls on the behavior of an acidic-U(VI) plume in the Savannah River Site using reactive transport modeling.

Science.gov (United States)

Bea, Sergio A; Wainwright, Haruko; Spycher, Nicolas; Faybishenko, Boris; Hubbard, Susan S; Denham, Miles E

2013-08-01

Acidic low-level waste radioactive waste solutions were discharged to three unlined seepage basins at the F-Area of the Department of Energy (DOE) Savannah River Site (SRS), South Carolina, USA, from 1955 through 1989. Despite many years of active remediation, the groundwater remains acidic and contaminated with significant levels of U(VI) and other radionuclides. Monitored Natural Attenuation (MNA) is a desired closure strategy for the site, based on the premise that regional flow of clean background groundwater will eventually neutralize the groundwater acidity, immobilizing U(VI) through adsorption. An in situ treatment system is currently in place to accelerate this in the downgradient portion of the plume and similar measures could be taken upgradient if necessary. Understanding the long-term pH and U(VI) adsorption behavior at the site is critical to assess feasibility of MNA along with the in-situ remediation treatments. This paper presents a reactive transport (RT) model and uncertainty quantification (UQ) analyses to explore key controls on the U(VI)-plume evolution and long-term mobility at this site. Two-dimensional numerical RT simulations are run including the saturated and unsaturated (vadose) zones, U(VI) and H(+) adsorption (surface complexation) onto sediments, dissolution and precipitation of Al and Fe minerals, and key hydrodynamic processes are considered. UQ techniques are applied using a new open-source tool that is part of the developing ASCEM reactive transport modeling and analysis framework to: (1) identify the complex physical and geochemical processes that control the U(VI) plume migration in the pH range where the plume is highly mobile, (2) evaluate those physical and geochemical parameters that are most controlling, and (3) predict the future plume evolution constrained by historical, chemical and hydrological data. The RT simulation results show a good agreement with the observed historical pH and concentrations of U(VI), nitrates

Enhancement of the complete autotrophic nitrogen removal over nitrite process in a modified single-stage subsurface vertical flow constructed wetland: Effect of saturated zone depth.

Science.gov (United States)

Huang, Menglu; Wang, Zhen; Qi, Ran

2017-06-01

This study was conducted to explore enhancement of the complete autotrophic nitrogen removal over nitrite (CANON) process in a modified single-stage subsurface vertical flow constructed wetland (VSSF) with saturated zone, and nitrogen transformation pathways in the VSSF treating digested swine wastewater were investigated at four different saturated zone depths (SZDs). SZD significantly affected nitrogen transformation pathways in the VSSF throughout the experiment. As the SZD was 45cm, the CANON process was enhanced most effectively in the system owing to the notable enhancement of anammox. Correspondingly, the VSSF had the best TN removal performance [(76.74±7.30)%] and lower N 2 O emission flux [(3.50±0.22)mg·(m 2 ·h) - 1 ]. It could be concluded that autotrophic nitrogen removal via CANON process could become a primary route for nitrogen removal in the VSSF with optimized microenvironment that developed as a result of the appropriate SZD. Copyright © 2017 Elsevier Ltd. All rights reserved.

Observational evidence for turbulent effects on total suspended matter within the Pearl River plume

Science.gov (United States)

Chunhua, Qiu; Danyi, Su; Huabin, Mao; Jiaxue, Wu; Yongsheng, Cui; Dongxiao, Wang

2017-12-01

We observed the structure of the Pearl River plume and its turbulent characteristics, and investigated the turbulent effect on total suspended matter (TSM) within its ;far-field; region, based on in situ and satellite data collected in June 2015. A significant northeastward plume was created under southern monsoonal conditions. The in situ data provided the width, depth, and velocity of the plume, as inferred by salinity. Weaker turbulence occurred at the front surface position than in the plume zone. Stronger turbulence induced greater turbidity in the bottom boundary layer; however, the surface mixed layer differed. By estimating the turbidity budget, we found the lateral fluxes term was the largest term in the plume, turbulent fluxes comprised the second largest term, and the settling terms comprised the smallest term. We quantified the turbulent mechanisms and found that stronger river discharge induced greater TSM turbidity. Tidal and buoyancy fluxes had minor regulatory effects on TSM. Our observations suggest that TSM in the ;far field; region originated from the Pearl River and the coastal region.

Prediction of a Visible Plume from a Dry and Wet Combined Cooling Tower and Its Mechanism of Abatement

Directory of Open Access Journals (Sweden)

Kazutaka Takata

2016-04-01

Full Text Available Heated moist air from a cooling tower forms a visible plume and needs to be predicted, not only for the performance design of the cooling tower, but also for environmental impact assessments. In this study, a computational fluid dynamics analysis is conducted to predict the scale of a visible plume rising from a cross flow cooling tower with mechanical draft (provided by a rotating fan. The results of computational fluid dynamics analysis are verified by comparing predictions with an actual observed plume. The results show that the predicted visible plume represents the observed plume in an error range of 15%–20%, which is permissible for designing a cooling tower. Additionally, the mixing condition of heated dry air and moist air under dry and wet combined operation is examined, and the condition is thought to affect the scale of the visible plume. It is found that, in the case of a mechanical-draft cooling tower, the fan has a mixing function which performs the complete mixing of wet and dry air, and this suggests that the generation of the plume can be determined by the intersection of the operation line and saturation line. Additionally, the effect of external wind on the scale of the visible plume is large, especially for dry and wet combined operation.

Numerical Modeling of Water Thermal Plumes Emitted by Thermal Power Plants

Directory of Open Access Journals (Sweden)

Azucena Durán-Colmenares

2016-10-01

Full Text Available This work focuses on the study of thermal dispersion of plumes emitted by power plants into the sea. Wastewater discharge from power stations causes impacts that require investigation or monitoring. A study to characterize the physical effects of thermal plumes into the sea is carried out here by numerical modeling and field measurements. The case study is the thermal discharges of the Presidente Adolfo López Mateos Power Plant, located in Veracruz, on the coast of the Gulf of Mexico. This plant is managed by the Federal Electricity Commission of Mexico. The physical effects of such plumes are related to the increase of seawater temperature caused by the hot water discharge of the plant. We focus on the implementation, calibration, and validation of the Delft3D-FLOW model, which solves the shallow-water equations. The numerical simulations consider a critical scenario where meteorological and oceanographic parameters are taken into account to reproduce the proper physical conditions of the environment. The results show a local physical effect of the thermal plumes within the study zone, given the predominant strong winds conditions of the scenario under study.

Water saturation in shaly sands: logging parameters from log-derived values

International Nuclear Information System (INIS)

Miyairi, M.; Itoh, T.; Okabe, F.

1976-01-01

The methods are presented for determining the relation of porosity to formation factor and that of true resistivity of formation to water saturation, which were investigated through the log interpretation of one of the oil and gas fields of northern Japan Sea. The values of the coefficients ''a'' and ''m'' in porosity-formation factor relation are derived from cross-plot of porosity and resistivity of formation corrected by clay content. The saturation exponent ''n'' is determined from cross-plot of porosity and resistivity index on the assumption that the product of porosity and irreducible water saturation is constant. The relation of porosity to irreducible water saturation is also investigated from core analysis. The new logging parameters determined from the methods, a = 1, m = 2, n = 1.4, improved the values of water saturation by 6 percent in average, and made it easy to distinguish the points which belong to the productive zone and ones belonging to the nonproductive zone

CFD investigation of balcony spill plumes in atria

International Nuclear Information System (INIS)

McCartney, C.J.; Lougheed, G.D.; Weckman, E.J.

2004-01-01

Smoke management in buildings during fire events often uses mechanical ventilation systems to maintain smoke layer elevation above a safe evacuation path. Design of these systems requires accurate correlations for the smoke production rate of the buoyant fire plume. One design issue is the smoke production rate of fire plumes which spill out from a fire compartment, under a balcony and up through an atrium or other large volume. Current engineering correlations for these balcony spill plumes are based on a combination of one-tenth scale test data and theoretical analysis. Questions have arisen over the suitability of these correlations for real-scale designs. A combined program of full-scale experimentation and CFD modeling is being conducted to analyze the accuracy of these correlations. A full-scale experimental facility was constructed with a 5 m by 5 m by 15 m fire compartment connected to a four-story atrium. Propane fires in the compartment produce balcony spill plumes which form steady-state smoke layers in the atrium. Experimental variables include fire size, compartment opening width, balcony depth and compartment fascia depth. A variable exhaust system was used to achieve various smoke layer heights for each of 100 compartment configurations. Temperature, smoke obscuration and gas concentrations were measured in the compartment, atrium and exhaust system. The experimental data was used to determine the atrium smoke layer elevation and balcony spill plume smoke production rate for each configuration and fire size. Comparison of this data with zone model results and design correlations for atrium smoke management systems will be performed to evaluate their accuracy. A CFD model of the experimental facility was implemented using the Fire Dynamics Simulator software (Version 3). Large-eddy simulations of the flow were performed with a constant radiative fraction and an infinitely fast mixture fraction combustion model. A grid sensitivity analysis was

Heat flow study of the Emeishan large igneous province region: Implications for the geodynamics of the Emeishan mantle plume

Science.gov (United States)

Jiang, Qiang; Qiu, Nansheng; Zhu, Chuanqing

2018-01-01

The Emeishan large igneous province (ELIP) is widely considered to be a consequence of a mantle plume. The supporting evidence includes rapid emplacement, voluminous flood basalt eruptions, and high mantle potential temperature estimates. Several studies have suggested that there was surface uplift prior to the eruption of the Emeishan flood basalts. Additionally, the plume's lateral extent is hard to constrain and has been variously estimated to be 800-1400 km in diameter. In this study, we analyzed present-day heat flow data and reconstructed the Permian paleo-heat flow using vitrinite reflectance and zircon (U-Th)/He thermochronology data in the ELIP region and discussed implications for the geodynamics of the Emeishan mantle plume. The present-day heat flow is higher in the inner and intermediate zones than in the outer zone, with a decrease of average heat flow from 76 mW/m2 to 51 mW/m2. Thermal history modeling results show that an abnormal high paleo-heat flow of 90-110 mW/m2 was caused by the Emeishan mantle plume activity. Based on the present-day heat flow data, we can calculate that there is lithospheric thinning in the central ELIP region, which may be due to the destruction of the lithosphere by mantle plume upwelling and magmatic underplating. The Permian paleo-heat flow anomaly implies that there was a temperature anomaly in the mantle. The ascending high-temperature mantle plume and the thinned lithosphere may have induced the large-scale uplift in the ELIP region. According to the range of the surface heat flow anomaly, it can be estimated that the diameter of the flattened head of the Emeishan mantle plume could have reached 1600-1800 km. Our research provides new insights into the geodynamics of the Emeishan mantle plume through study of heat flow.

Resistivity and self-potential tomography applied to groundwater remediation and contaminant plumes: Sandbox and field experiments

Science.gov (United States)

Mao, D.; Revil, A.; Hort, R. D.; Munakata-Marr, J.; Atekwana, E. A.; Kulessa, B.

2015-11-01

Geophysical methods can be used to remotely characterize contaminated sites and monitor in situ enhanced remediation processes. We have conducted one sandbox experiment and one contaminated field investigation to show the robustness of electrical resistivity tomography and self-potential (SP) tomography for these applications. In the sandbox experiment, we injected permanganate in a trichloroethylene (TCE)-contaminated environment under a constant hydraulic gradient. Inverted resistivity tomograms are able to track the evolution of the permanganate plume in agreement with visual observations made on the side of the tank. Self-potential measurements were also performed at the surface of the sandbox using non-polarizing Ag-AgCl electrodes. These data were inverted to obtain the source density distribution with and without the resistivity information. A compact horizontal dipole source located at the front of the plume was obtained from the inversion of these self-potential data. This current dipole may be related to the redox reaction occurring between TCE and permanganate and the strong concentration gradient at the front of the plume. We demonstrate that time-lapse self-potential signals can be used to track the kinetics of an advecting oxidizer plume with acceptable accuracy and, if needed, in real time, but are unable to completely resolve the shape of the plume. In the field investigation, a 3D resistivity tomography is used to characterize an organic contaminant plume (resistive domain) and an overlying zone of solid waste materials (conductive domain). After removing the influence of the streaming potential, the identified source current density had a magnitude of 0.5 A m-2. The strong source current density may be attributed to charge movement between the neighboring zones that encourage abiotic and microbially enhanced reduction and oxidation reactions. In both cases, the self-potential source current density is located in the area of strong resistivity

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

International Nuclear Information System (INIS)

K. Rehfeldt

2004-01-01

This report is an updated analysis of water-level data performed to provide the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]) (referred to as the saturated zone (SZ) site-scale flow model or site-scale SZ flow model in this report) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for calibration of groundwater flow models. This report also contains an expanded discussion of uncertainty in the potentiometric-surface map. The analysis of the potentiometric data presented in Revision 00 of this report (USGS 2001 [DIRS 154625]) provides the configuration of the potentiometric surface, target heads, and hydraulic gradients for the calibration of the SZ site-scale flow model (BSC 2004 [DIRS 170037]). Revision 01 of this report (USGS 2004 [DIRS 168473]) used updated water-level data for selected wells through the year 2000 as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain based on an alternative interpretation of perched water conditions. That revision developed computer files containing: Water-level data within the model area (DTN: GS010908312332.002); A table of known vertical head differences (DTN: GS010908312332.003); and A potentiometric-surface map (DTN: GS010608312332.001) using an alternative concept from that presented by USGS (2001 [DIRS 154625]) for the area north of Yucca Mountain. The updated water-level data presented in USGS (2004 [DIRS 168473]) include data obtained from the Nye County Early Warning Drilling Program (EWDP) Phases I and II and data from Borehole USW WT-24. This document is based on Revision 01 (USGS 2004 [DIRS 168473]) and expands the discussion of uncertainty in the potentiometric-surface map. This uncertainty assessment includes an analysis of the impact of more recent water-level data and the impact of adding data from the EWDP Phases III and IV wells. In addition to being utilized

Recharge and Lateral Groundwater Flow Boundary Conditions for the Saturated Zone Site-Scale Flow and Transport Model

Energy Technology Data Exchange (ETDEWEB)

B. Arnold; T. Corbet

2001-12-18

The purpose of the flow boundary conditions analysis is to provide specified-flux boundary conditions for the saturated zone (SZ) site-scale flow and transport model. This analysis is designed to use existing modeling and analysis results as the basis for estimated groundwater flow rates into the SZ site-scale model domain, both as recharge at the upper (water table) boundary and as underflow at the lateral boundaries. The objective is to provide consistency at the boundaries between the SZ site-scale flow model and other groundwater flow models. The scope of this analysis includes extraction of the volumetric groundwater flow rates simulated by the SZ regional-scale flow model to occur at the lateral boundaries of the SZ site-scale flow model and the internal qualification of the regional-scale model for use in this analysis model report (AMR). In addition, the scope includes compilation of information on the recharge boundary condition taken from three sources: (1) distributed recharge as taken from the SZ regional-scale flow model, (2) recharge below the area of the unsaturated zone (UZ) site-scale flow model, and (3) focused recharge along the Fortymile Wash channel.

Solar Coronal Plumes

Directory of Open Access Journals (Sweden)

Giannina Poletto

2015-12-01

Full Text Available Polar plumes are thin long ray-like structures that project beyond the limb of the Sun polar regions, maintaining their identity over distances of several solar radii. Plumes have been first observed in white-light (WL images of the Sun, but, with the advent of the space era, they have been identified also in X-ray and UV wavelengths (XUV and, possibly, even in in situ data. This review traces the history of plumes, from the time they have been first imaged, to the complex means by which nowadays we attempt to reconstruct their 3-D structure. Spectroscopic techniques allowed us also to infer the physical parameters of plumes and estimate their electron and kinetic temperatures and their densities. However, perhaps the most interesting problem we need to solve is the role they cover in the solar wind origin and acceleration: Does the solar wind emanate from plumes or from the ambient coronal hole wherein they are embedded? Do plumes have a role in solar wind acceleration and mass loading? Answers to these questions are still somewhat ambiguous and theoretical modeling does not provide definite answers either. Recent data, with an unprecedented high spatial and temporal resolution, provide new information on the fine structure of plumes, their temporal evolution and relationship with other transient phenomena that may shed further light on these elusive features.

Dispersal of suspended sediments in the turbid and highly stratified Red River plume

Science.gov (United States)

van Maren, D. S.; Hoekstra, P.

2005-03-01

The Red River, annually transporting 100 million tons of sediment, flows into a shallow shelf sea where it rapidly deposits most of its sediment on a prograding delta front. Oceanographic cruises were carried out in February-March and July-August 2000 to determine the vertical structure of the Ba Lat river plume and sediment transport patterns on the delta front. The surface waters in the coastal zone were strongly stratified with a low density and high sediment concentration during the larger part of the wet season, caused by low mixing rates of river plumes with ambient water. The river plume is advected to the south by a well-developed coastal current which originates from the river plumes that enter the Gulf of Tonkin North of the Ba Lat and are deflected southward by the Coriolis force. Sediment predominantly leaves the surface plume by settling from suspension and less by mixing of fresh and marine water. A one-dimensional model for plume deposition valid for fair weather conditions indicates that most sediment is deposited within 10 km and southward of the river mouth. Of prime importance for this depositional pattern is the phase relation between river outflow and tidal currents, in combination with the southward surface flow; alongshore advection is very low during outflow of the turbid river plume. The agreement of modeled plume sedimentation patterns with long-term bathymetric changes strongly suggests that fair weather depositional processes determine delta front development. This may be related to the fact that reworking of sediment mainly occurs several months after the peak deposition period; in the meantime sediment compaction and consolidation have increased the shear strength of deposited sediments.

Radionuclide inventories for the F- and H-area seepage basin groundwater plumes

Energy Technology Data Exchange (ETDEWEB)

Hiergesell, Robert A [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Kubilius, Walter P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2016-05-01

Within the General Separations Areas (GSA) at the Savannah River Site (SRS), significant inventories of radionuclides exist within two major groundwater contamination plumes that are emanating from the F- and H-Area seepage basins. These radionuclides are moving slowly with groundwater migration, albeit more slowly due to interaction with the soil and aquifer matrix material. The purpose of this investigation is to quantify the activity of radionuclides associated with the pore water component of the groundwater plumes. The scope of this effort included evaluation of all groundwater sample analyses obtained from the wells that have been established by the Environmental Compliance & Area Completion Projects (EC&ACP) Department at SRS to monitor groundwater contamination emanating from the F- and H-Area Seepage Basins. Using this data, generalized groundwater plume maps for the radionuclides that occur in elevated concentrations (Am-241, Cm-243/244, Cs-137, I-129, Ni-63, Ra-226/228, Sr-90, Tc-99, U-233/234, U-235 and U-238) were generated and utilized to calculate both the volume of contaminated groundwater and the representative concentration of each radionuclide associated with different plume concentration zones.

Entrainment by turbulent plumes

Science.gov (United States)

Parker, David; Burridge, Henry; Partridge, Jamie; Linden, Paul

2017-11-01

Plumes are of relevance to nature and real consequence to industry. While the Morton, Taylor & Turner (1956) plume model is able to estimate the mean physical flux parameters, the process of entrainment is only parametrised in a time-averaged sense and a deeper understanding is key to understanding how they evolve. Various flow configurations, resulting in different entrainment values, are considered; we perform simultaneous PIV and plume-edge detection on saline plumes in water resulting from a point source, a line source and a line source where a vertical wall is placed immediately adjacent. Of particular interest is the effect the large scale eddies, forming at the edge of the plume and engulfing ambient fluid, have on the entrainment process. By using velocity statistics in a coordinate system based on the instantaneous scalar edge of the plume the significance of this large scale engulfment is quantified. It is found that significant mass is transported outside the plumes, in particular in regions where large scale structures are absent creating regions of relatively high-momentum ambient fluid. This suggests that the large scale processes, whereby ambient fluid is engulfed into the plume, contribute significantly to the entrainment.

Capturing volcanic plumes in 3D with UAV-based photogrammetry at Yasur Volcano - Vanuatu

Science.gov (United States)

Gomez, C.; Kennedy, B.

2018-01-01

As a precise volume of volcanic ash-plume is essential to understand the dynamic of gas emission, exchanges and the eruptive dynamics, we have measured in 3D using photogrammetry a small-size volcanic plume at the summit of Yasur Volcano, Vanuatu. The objective was to collect the altitude and planform shape of the plume as well as the vertical variations of the shape and size. To reach this objective, the authors have used the Structure from Motion photogrammetric method applied to a series of photographs captured in a very short period of time around and above the plume. A total of 146 photographs at 3000 × 4000 pixel were collected as well as the geolocation, the pitch, tilt and orientation of the cameras. The results revealed a "mushroom"-like shape of the plume with a narrow ascending column topped by a turbulent mixing zone. The volume of the plume was calculated to be 13,430 m3 ± 512 m3 (with the error being the cube of the linear error from the Ground Control Points) for a maximum height above the terrain of 63 m. The included error was also kept high because of the irregular distribution of the Ground Control Points that could not be collected in dangerous areas due to the ongoing eruption. Based on this research, it is therefore worth investigating the usage of multiple cameras to capture plumes in 3D over time and the method is also a good complement to the recent development of photogrammetry from space, which can tackle larger-scale eruption plumes.

Heard Island and McDonald Islands Acoustic Plumes: Split-beam Echo sounder and Deep Tow Camera Observations of Gas Seeps on the Central Kerguelen Plateau

Science.gov (United States)

Watson, S. J.; Spain, E. A.; Coffin, M. F.; Whittaker, J. M.; Fox, J. M.; Bowie, A. R.

2016-12-01

Heard and McDonald islands (HIMI) are two active volcanic edifices on the Central Kerguelen Plateau. Scientists aboard the Heard Earth-Ocean-Biosphere Interactions voyage in early 2016 explored how this volcanic activity manifests itself near HIMI. Using Simrad EK60 split-beam echo sounder and deep tow camera data from RV Investigator, we recorded the distribution of seafloor emissions, providing the first direct evidence of seabed discharge around HIMI, mapping >244 acoustic plume signals. Northeast of Heard, three distinct plume clusters are associated with bubbles (towed camera) and the largest directly overlies a sub-seafloor opaque zone (sub-bottom profiler) with >140 zones observed within 6.5 km. Large temperature anomalies did not characterize any of the acoustic plumes where temperature data were recorded. We therefore suggest that these plumes are cold methane seeps. Acoustic properties - mean volume backscattering and target strength - and morphology - height, width, depth to surface - of plumes around McDonald resembled those northeast of Heard, also suggesting gas bubbles. We observed no bubbles on extremely limited towed camera data around McDonald; however, visibility was poor. The acoustic response of the plumes at different frequencies (120 kHz vs. 18 kHz), a technique used to classify water column scatterers, differed between HIMI, suggestiing dissimilar target size (bubble radii) distributions. Environmental context and temporal characteristics of the plumes differed between HIMI. Heard plumes were concentrated on flat, sediment rich plains, whereas around McDonald plumes emanated from sea knolls and mounds with hard volcanic seafloor. The Heard plumes were consistent temporally, while the McDonald plumes varied temporally possibly related to tides or subsurface processes. Our data and analyses suggest that HIMI acoustic plumes were likely caused by gas bubbles; however, the bubbles may originate from two or more distinct processes.

Simulation of plume rise: Study the effect of stably stratified turbulence layer on the rise of a buoyant plume from a continuous source by observing the plume centroid

Science.gov (United States)

Bhimireddy, Sudheer Reddy; Bhaganagar, Kiran

2016-11-01

Buoyant plumes are common in atmosphere when there exists a difference in temperature or density between the source and its ambience. In a stratified environment, plume rise happens until the buoyancy variation exists between the plume and ambience. In a calm no wind ambience, this plume rise is purely vertical and the entrainment happens because of the relative motion of the plume with ambience and also ambient turbulence. In this study, a plume centroid is defined as the plume mass center and is calculated from the kinematic equation which relates the rate of change of centroids position to the plume rise velocity. Parameters needed to describe the plume are considered as the plume radius, plumes vertical velocity and local buoyancy of the plume. The plume rise velocity is calculated by the mass, momentum and heat conservation equations in their differential form. Our study focuses on the entrainment velocity, as it depicts the extent of plume growth. This entrainment velocity is made up as sum of fractions of plume's relative velocity and ambient turbulence. From the results, we studied the effect of turbulence on the plume growth by observing the variation in the plume radius at different heights and the centroid height reached before loosing its buoyancy.

Joint application of Geoelectrical Resistivity and Ground Penetrating Radar techniques for the study of hyper-saturated zones. Case study in Egypt

Directory of Open Access Journals (Sweden)

Hany S. Mesbah

2017-06-01

Full Text Available This paper presents the results of the application of the Geoelectrical Resistivity Sounding (GRS and Ground Penetrating Radar (GPR for outlining and investigating of surface springing out (flow of groundwater to the base of an service building site, and determining the reason(s for the zone of maximum degree of saturation; in addition to provide stratigraphic information for this site. The studied economic building is constructed lower than the ground surface by about 7 m. A Vertical Electrical Sounding (VES survey was performed at 12 points around the studied building in order to investigate the vertical and lateral extent of the subsurface sequence, three VES's were conducted at each side of the building at discrete distances. And a total of 9 GPR profiles with 100- and 200-MHz antennae were conducted, with the objective of evaluating the depth and the degree of saturation of the subsurface layers. The qualitative and quantitative interpretation of the acquired VES's showed easily the levels of saturations close to and around the studied building. From the interpretation of GPR profiles, it was possible to locate and determine the saturated layers. The radar signals are penetrated and enabled the identification of the subsurface reflectors. The results of GPR and VES showed a good agreement and the integrated interpretations were supported by local geology. Finally, the new constructed geoelectrical resistivity cross-sections (in contoured-form, are easily clarifying the direction of groundwater flow toward the studied building.

Fire analog: a comparison between fire plumes and energy center cooling tower plumes

Energy Technology Data Exchange (ETDEWEB)

Orgill, M.M.

1977-10-01

Thermal plumes or convection columns associated with large fires are compared to thermal plumes from cooling towers and proposed energy centers to evaluate the fire analog concept. Energy release rates of mass fires are generally larger than for single or small groups of cooling towers but are comparable to proposed large energy centers. However, significant physical differences exist between cooling tower plumes and fire plumes. Cooling tower plumes are generally dominated by ambient wind, stability and turbulence conditions. Fire plumes, depending on burning rates and other factors, can transform into convective columns which may cause the fire behavior to become more violent. This transformation can cause strong inflow winds and updrafts, turbulence and concentrated vortices. Intense convective columns may interact with ambient winds to create significant downwind effects such as wakes and Karman vortex streets. These characteristics have not been observed with cooling tower plumes to date. The differences in physical characteristics between cooling tower and fire plumes makes the fire analog concept very questionable even though the approximate energy requirements appear to be satisfied in case of large energy centers. Additional research is suggested in studying the upper-level plume characteristics of small experimental fires so this information can be correlated with similar data from cooling towers. Numerical simulation of fires and proposed multiple cooling tower systems could also provide comparative data.

Modeling investigation of the nutrient and phytoplankton variability in the Chesapeake Bay outflow plume

Science.gov (United States)

Jiang, Long; Xia, Meng

2018-03-01

The Chesapeake Bay outflow plume (CBOP) is the mixing zone between Chesapeake Bay and less eutrophic continental shelf waters. Variations in phytoplankton distribution in the CBOP are critical to the fish nursery habitat quality and ecosystem health; thus, an existing hydrodynamic-biogeochemical model for the bay and the adjacent coastal ocean was applied to understand the nutrient and phytoplankton variability in the plume and the dominant environmental drivers. The simulated nutrient and chlorophyll a distribution agreed well with field data and real-time satellite imagery. Based on the model calculation, the net dissolved inorganic nitrogen (DIN) and phosphorus (DIP) flux at the bay mouth was seaward and landward during 2003-2012, respectively. The CBOP was mostly nitrogen-limited because of the relatively low estuarine DIN export. The highest simulated phytoplankton biomass generally occurred in spring in the near field of the plume. Streamflow variations could regulate the estuarine residence time, and thus modulate nutrient export and phytoplankton biomass in the plume area; in comparison, changing nutrient loading with fixed streamflow had a less extensive impact, especially in the offshore and far-field regions. Correlation analyses and numerical experiments revealed that southerly winds on the shelf were effective in promoting the offshore plume expansion and phytoplankton accumulation. Climate change including precipitation and wind pattern shifts is likely to complicate the driving mechanisms of phytoplankton variability in the plume region.

Geochemical characteristics of Antarctic magmatism connected with Karoo-Maud and Kerguelen mantle plumes

Science.gov (United States)

Sushchevskaya, Nadezhda; Krymsky, Robert; Belyatsky, Boris; Antonov, Anton; Migdisova, Natalya

2013-04-01

Emplacement (130-115 m.y. ago) of dikes and sills of alkaline-ultrabasic composition within Jetty oasis (East Antarctica) is suggested as a later appearance of plume magmatism within the East-Antarctic Shield [Andronikov et al., 1993, 2001; Laiba et al., 1987]. This region is located opposite Kerguelen Islands and possibly could be properly connected with activity of the Kerguelen-plume [Foley et al., 2001, 2006]. Jurassic-Cretaceous dykes, stocks and sills of alkaline-ultrabasic rocks, relatively close to kimberlite-type, are exposed within Jetty oasis and on the southern shore of the Raddock Lake. This alkaline-ultrabasic magmatism has appeared to be connected with the main Mesozoic stage of the evolution of the Lambert and Amery glaciers riftogenic structure [Kurinin et al., 1980, 1988]. The alkaline-ultrabasic dikes and sills within Jetty oasis cut the rocks of the Beaver complex, Permo-Triassic terrigeneous successions of the Amery complex, and late Paleozoic low-alkaline basic dikes as well. Dashed chain of 6 stock bodies spread out on 15 km along the eastern shore of the Beaver Lake, marked their allocation with submeridianal zone of the deep cracks, boarded of the eastern side of the Beaver Lake trough. At the same time, new data upon Quaternary magmatism of the mountain Gaussberg has confirmed the unique features of ultra-potassium alkaline magmatism (up to 14-17% K2O) formed under exclusively continental conditions [Murphy et al., 2002]. Volcanic cone is located at the continuation of Gaussberg rift zone which is possibly a part of Lambert fracture zone. Its formation is connected with the early stages of Gondwana development, perhaps, reactivated in different Precambrian events and according to numerous data is a single rift zone which is traced Indian inland (Indrani graben, [Golynsky, 2011]). The time of lamproitic magmas eruption is estimated at 56000±5000 yeas ago [Tingey et al., 1983]. Earlier it had been shown the Mesozoic (about 170 Ma) basaltic

Geodynamics of rift-plume interaction in Iceland as constrained by new 40Ar/ 39Ar and in situ U-Pb zircon ages

Science.gov (United States)

Martin, E.; Paquette, J. L.; Bosse, V.; Ruffet, G.; Tiepolo, M.; Sigmarsson, O.

2011-11-01

The interaction between a rift zone and a mantle plume leads to exceptional situations in Iceland where the island is 1.5 wider than expected, given the North-Atlantic spreading rate. In order to give a better idea of the timeframe of this evolution, we present 32 new 40Ar/ 39Ar and in-situ U-Pb dating on zircon from 16 volcanic systems located from the west to east coasts of Iceland. The North Iceland Rift Zone (NIRZ) was initiated at least 12 Ma ago. Furthermore, during these last 12 Ma, the NIRZ half spreading rate was between 0.7 and 1.2 cm/yr and it propagated to the south at a rate of 1.0-1.2 cm/yr. The excess width of Iceland can thus not be explained by faster spreading rate in the past. Here we discuss a model that explains the ~ 200 km 'excess' of crust, taking into account the eastward relocation of the rift zone and corresponding older crustal capture over the course of Iceland's geological history. The most recent rift relocation is dated at approximately 6 Ma at Snæfellsnes Peninsula in the west, whereas the oldest volcanic systems (15-13 Ma) from the extreme north east of Iceland were most likely generated at the Kolbeinsey ridge north of Iceland rather than in the NIRZ itself. The need for rift relocations and crustal capture to explain the width of Iceland strongly suggests that during rift-plume interaction the mantle plume plays an active role. It forces the active rift zone to be frequently relocated by rift jumps above its center leaving inactive rift zones as older synclines in the geological record. This result in an eastward position of the rift zone in Iceland relative to the North Atlantic ridge, and it can be predicted that in a few tens of millions of years the Mid-Atlantic ridge and the Icelandic plume may become decoupled.

Subduction, Extension, and a Mantle Plume in the Pacific Northwest

Science.gov (United States)

Hawley, W. B.; Allen, R. M.; Richards, M. A.

2016-12-01

Subduction zones are some of the most important systems that control the dynamics and evolution of the earth. The Cascadia Subduction Zone offers a unique natural laboratory for understanding the subduction process, and how subduction interacts with other large-scale geodynamical phenomena. The small size of the Juan de Fuca (JdF) plate and the proximity of the system to the Yellowstone Hotspot and the extensional Basin and Range province allow for detailed study of the effects these important systems have on each other. We present both a P-wave and an S-wave tomographic model of the Pacific Northwestern United States using regional seismic arrays, including the amphibious Cascadia Initiative. These models share important features, such as the Yellowstone plume, the subducting JdF slab, a gap in the subducting slab, and a low-velocity feature beneath the shallowest portions of the slab. But subtle differences in these features between the models—the size of the gap in the subducting JdF slab and the shape of the Yellowstone plume shaft above the transition zone, for example—provide physical insight into the interpretation of these models. The physics that we infer from our seismic tomography and other studies of the region will refine our understanding of subduction zones worldwide, and will help to identify targets for future amphibious seismic array studies. The discovery of a pronounced low-velocity feature beneath the JdF slab as it subducts beneath the coastal Pacific Northwest is, thus far, the most surprising result from our imaging work, and implies a heretofore unanticipated regime of dynamical interaction between the sublithospheric oceanic asthenosphere and the subduction process. Such discoveries are made possible, and rendered interpretable, by ever-increasing resolution that the Cascadia Initiative affords seismic tomography models.

The effect of limestone aggregate porosity and saturation degree on the interfacial zone

International Nuclear Information System (INIS)

Nguyen, T.D.; Le Saout, G.; Devillers, P.; Garcia-Diaz, E.

2015-01-01

The recycling of concrete wastes concerns the nuclear industry as many nuclear facilities will have to be dismantled and the reduction and reuse of the decommissioning concrete wastes in order to minimize the total waste volume is a key issue. The recycled aggregates have the potential to replace natural resources however it is necessary to assess the effect of recycled aggregates on the final concrete. One important issue to be addressed to achieve the required mechanical properties is the water absorption of the recycled aggregates. As a first step, we have used in this study limestone aggregates with different porosities (total porosity from 2 to 20 %) and have investigated the influence of the porosity and the initial saturation degree of these aggregates on the porosity of the interfacial transition zone (ITZ) using scanning electron microscope. The equation of Feret for the strength-porosity relationship of our mortars was applied σ = K(100-p) 2 where σ is the compressive strength in MPa, p is the capillary pore volume in % and K a constant. Aggregates with lower porosity follow the same law characterized by a K value higher than the value for the more porous aggregate law. The K parameter is not dependent of the humidity degree of the aggregate: for a given aggregate, family mortars made with dry and wet aggregate follow the same law. But for porous aggregates as the meso-porosity of the ITZ for a given time of hydration is higher for mortars made with wet aggregates, the compressive strength of these mortars is less than those of mortars made with dry aggregates. Contrary to the low porous aggregate, it was not possible for porous limestone aggregates, and with a calculation based on the saturated surface dry state as reference state to obtain the same net water to cement ratio with wet and dry aggregates. This study reflects the difficulty to control the amount of efficient water in concrete when using porous aggregates and its influence on compressive

Integrated characterization of natural attenuation of a PCE plume after thermal remediation of the source zone - incl. dual isotope and microbial techniques

DEFF Research Database (Denmark)

Broholm, Mette Martina

dechlorination 1-1.5 km downstream the source area, where the plume descends into more reduced groundwater. The objective of the new (2014) study is to evaluate how the source remediation has impacted the plume and in particular the natural attenuation within the plume. A large monitoring campaign including...... down-gradient which co-inside with the reduction in redox conditions. The findings document a significant increase in cDCE degradation without accumulation of VC. This reduces the risk posed by the contaminant plume to the drinking water resource. This project is unique in the integrated...... area, resulted in the release of dissolved organic matter and some geochemical changes. This has had an effect on redox conditions and biodegradation by reductive dechlorination particularly in the near source area. However, also in the further downstream area of the plume redox and contaminant levels...

Impact of Reservoir Fluid Saturation on Seismic Parameters: Endrod Gas Field, Hungary

Science.gov (United States)

El Sayed, Abdel Moktader A.; El Sayed, Nahla A.

2017-12-01

Outlining the reservoir fluid types and saturation is the main object of the present research work. 37 core samples were collected from three different gas bearing zones in the Endrod gas field in Hungary. These samples are belonging to the Miocene and the Upper - Lower Pliocene. These samples were prepared and laboratory measurements were conducted. Compression and shear wave velocity were measured using the Sonic Viewer-170-OYO. The sonic velocities were measured at the frequencies of 63 and 33 kHz for compressional and shear wave respectively. All samples were subjected to complete petrophysical investigations. Sonic velocities and mechanical parameters such as young’s modulus, rigidity, and bulk modulus were measured when samples were saturated by 100%-75%-0% brine water. Several plots have been performed to show the relationship between seismic parameters and saturation percentages. Robust relationships were obtained, showing the impact of fluid saturation on seismic parameters. Seismic velocity, Poisson’s ratio, bulk modulus and rigidity prove to be applicable during hydrocarbon exploration or production stages. Relationships among the measured seismic parameters in gas/water fully and partially saturated samples are useful to outline the fluid type and saturation percentage especially in gas/water transitional zones.

Water-Level Data Analysis for the Saturated Zone Site-Scale Flow and Transport Model

Energy Technology Data Exchange (ETDEWEB)

K. Rehfeldt

2004-10-08

This report is an updated analysis of water-level data performed to provide the ''Saturated Zone Site-Scale Flow Model'' (BSC 2004 [DIRS 170037]) (referred to as the saturated zone (SZ) site-scale flow model or site-scale SZ flow model in this report) with the configuration of the potentiometric surface, target water-level data, and hydraulic gradients for calibration of groundwater flow models. This report also contains an expanded discussion of uncertainty in the potentiometric-surface map. The analysis of the potentiometric data presented in Revision 00 of this report (USGS 2001 [DIRS 154625]) provides the configuration of the potentiometric surface, target heads, and hydraulic gradients for the calibration of the SZ site-scale flow model (BSC 2004 [DIRS 170037]). Revision 01 of this report (USGS 2004 [DIRS 168473]) used updated water-level data for selected wells through the year 2000 as the basis for estimating water-level altitudes and the potentiometric surface in the SZ site-scale flow and transport model domain based on an alternative interpretation of perched water conditions. That revision developed computer files containing: Water-level data within the model area (DTN: GS010908312332.002); A table of known vertical head differences (DTN: GS010908312332.003); and A potentiometric-surface map (DTN: GS010608312332.001) using an alternative concept from that presented by USGS (2001 [DIRS 154625]) for the area north of Yucca Mountain. The updated water-level data presented in USGS (2004 [DIRS 168473]) include data obtained from the Nye County Early Warning Drilling Program (EWDP) Phases I and II and data from Borehole USW WT-24. This document is based on Revision 01 (USGS 2004 [DIRS 168473]) and expands the discussion of uncertainty in the potentiometric-surface map. This uncertainty assessment includes an analysis of the impact of more recent water-level data and the impact of adding data from the EWDP Phases III and IV wells. In

On the offshore dispersal of the Amazon's Plume in the North Atlantic: Comments on the paper by A. Longhurst, ``Seasonal cooling and blooming in tropical oceans''

Science.gov (United States)

Muller-Karger, F. E.; Richardson, P. L.; Mcgillicuddy, D.

1995-11-01

Coastal Zone Color Scanner (CZCS) satellite images show extensive plumes of discolored water extending from South America into the western tropical Atlantic. The most conspicuous plumes originate at the mouths of the Amazon and Orinoco Rivers, and plumes originating at smaller rivers can also be seen from space. In a recent paper by Longhurst (1993), the plume associated with the Amazon River was attributed to phytoplankton blooms stimulated by nutrients supplied via eddy upwelling. We revisit the argument that this plume is of riverine origin, and offer evidence that material present near continental margins can be advected offshore and trace circulation patterns in the adjacent ocean.

High Resolution Seismic Images of Transition Zone Discontinuities beneath the Hawaii-Emperor Seamount Chain

Science.gov (United States)

Cao, Q.; Wang, P.; van der Hilst, R. D.; Shim, S.

2009-12-01

Taking advantage of the abundance of natural sources (earthquakes) in western Pacific subduction zones and the many seismograph stations in the Americas, we use inverse scattering - a generalized Radon transform - of SS precursors to image the transition zone discontinuities underneath Hawaii and the Hawaii-Emperor seamount chain. The GRT makes use of scattering theory and extracts structural information from broad band data windows that include precursors to SS (which are the specular reflections at the discontinuities that form the main arrivals) as well as non-specular scattered energy (which is often discarded as noise). More than 150,000 seismograms (from the IRIS Data Management Center) are used to form a 3-D image of the transition zone discontinuities beneath the central Pacific. In addition to clear signals near 410, 520, and 660 km depth, the data also reveal scatter interfaces near 370 km dept and between 800-1000 km depth, which may be regional, laterally intermittent scatter horizons. Our images reveal a conspicuous uplift of the 660 discontinuity in a region of 800km in diameter to the west of the active volcanoes of Hawaii. No correspondent localized depression of the 410 discontinuity is found. Instead, we find a smaller scale anomaly suggesting that the 410 discontinuity is locally elevated in the same region. This may indicate the presence of melt or minor chemical constitutes. The lack of correlation between and differences in lateral length scale of the topographies of the 410 and 660 km discontinuities are also consistent with a deep-mantle plume impinging on the transition zone, creating a pond of hot material underneath 660 discontinuity, and with secondary plumes connecting to the present-day hotspot at Earth’s surface. Our observations suggest that more complicated plume morphology and plume dynamics within the Earth's mantle should be taken into account to describe the plumes and, in particular, mass transport across the transition zone

Explosion Amplitude Reduction due to Fractures in Water-Saturated and Dry Granite

Science.gov (United States)

Stroujkova, A. F.; Leidig, M.; Bonner, J. L.

2013-12-01

Empirical observations made at the Semipalatinsk Test Site suggest that nuclear tests in the fracture zones left by previous explosions ('repeat shots') show reduced seismic amplitudes compared to the nuclear tests in virgin rocks. Likely mechanisms for the amplitude reduction in the repeat shots include increased porosity and reduced strength and elastic moduli, leading to pore closing and frictional sliding. Presence of pore water significantly decreases rock compressibility and strength, thus affecting seismic amplitudes. A series of explosion experiments were conducted in order to define the physical mechanism responsible for the amplitude reduction and to quantify the degree of the amplitude reduction in fracture zones of previously detonated explosions. Explosions in water-saturated granite were conducted in central New Hampshire in 2011 and 2012. Additional explosions in dry granite were detonated in Barre, VT in 2013. The amplitude reduction is different between dry and water-saturated crystalline rocks. Significant reduction in seismic amplitudes (by a factor of 2-3) in water-saturated rocks was achieved only when the repeat shot was detonated in the extensive damage zone created by a significantly larger (by a factor of 5) explosion. In case where the first and the second explosions were similar in yield, the amplitude reduction was relatively modest (5-20%). In dry rocks the amplitude reduction reached a factor of 2 even in less extensive damage zones. In addition there are differences in frequency dependence of the spectral amplitude ratios between explosions in dry and water-saturated rocks. Thus the amplitude reduction is sensitive to the extent of the damage zone as well as the pore water content.

Ion Formation Resulting from Freezing, Thawing, and Collisional Processes in Plumes Emitted from Planetary Bodies: Implications for Plume Chemistry and the Detection of Trace Organics Present in Enceladus Geysers

Science.gov (United States)

Beauchamp, J. L.; Wiley, J. S.; Thomas, D. A.

2014-12-01

Icy plumes emitted into space from Enceladus and other planetary bodies offer the intriguing possibility of sampling the composition of subsurface liquid reservoirs that may comprise habitable zones of particular astrobiological significance in our solar system. Mass spectrometric sampling of plume materials enables the detection of molecules that facilitate an assessment of the extent of chemical and biological evolution that may have occurred in a subsurface sea. In laboratory experiments we have investigated the physical and chemical processes that occur in the complex plume environment that lead to ionization of trace organic constituents, both as a result of the freezing of liquid droplets and the thawing of icy particles. We also demonstrate that collisions between icy particles lead to triboelectric charging. Subsequent discharges between oppositely charged particles result not only in the ionization of trace organics but to chemical reactions between molecular components present in the particles. For example, nitriles react with water to form amides and acids. In particular, icy particles doped with small amounts of aminoacetonitrile and water lead to the formation of the simplest amino acid glycine. The implications which these observations may have for sampling plume composition from orbit in a future mission to Enceladus will be discussed.

Acoustical Survey of Methane Plumes on North Hydrate Ridge: Constraining Temporal and Spatial Characteristics.

Science.gov (United States)

Kannberg, P. K.; Trehu, A. M.

2008-12-01

While methane plumes associated with hydrate formations have been acoustically imaged before, little is known about their temporal characteristics. Previous acoustic surveys have focused on determining plume location, but as far as we know, multiple, repeated surveys of the same plume have not been done prior to the survey presented here. In July 2008, we acquired sixteen identical surveys within 19 hours over the northern summit of Hydrate Ridge in the Cascadia accretionary complex using the onboard 3.5 and 12 kHz echosounders. As in previous studies, the plumes were invisible to the 3.5 kHz echosounder and clearly imaged with 12 kHz. Seafloor depth in this region is ~600 m. Three distinct plumes were detected close to where plumes were located by Heeschen et al. (2003) a decade ago. Two of the plumes disappeared at ~520 m water depth, which is the depth of the top of the gas hydrate stability as determined from CTD casts obtained during the cruise. This supports the conclusion of Heeschen et al. (2003) that the bubbles are armored by gas hydrate and that they dissolve in the water column when they leave the hydrate stability zone. One of the plumes near the northern summit, however, extended through this boundary to at least 400 m (the shallowest depth recorded). A similar phenomenon was observed in methane plumes in the Gulf of Mexico, where the methane was found to be armored by an oil skin. In addition to the steady plumes, two discrete "burps" were observed. One "burp" occurred approximately 600 m to the SSW of the northern summit. This was followed by a second strong event 300m to the north an hour later. To evaluate temporal and spatial patterns, we summed the power of the backscattered signal in different depth windows for each survey. We present the results as a movie in which the backscatter power is shown in map view as a function of time. The surveys encompassed two complete tidal cycles, but no correlation between plume location or intensity and tides

Field-scale forward and back diffusion through low-permeability zones

Science.gov (United States)

Yang, Minjune; Annable, Michael D.; Jawitz, James W.

2017-07-01

Understanding the effects of back diffusion of groundwater contaminants from low-permeability zones to aquifers is critical to making site management decisions related to remedial actions. Here, we combine aquifer and aquitard data to develop recommended site characterization strategies using a three-stage classification of plume life cycle based on the solute origins: aquifer source zone dissolution, source zone dissolution combined with back diffusion from an aquitard, and only back diffusion. We use measured aquitard concentration profile data from three field sites to identify signature shapes that are characteristic of these three stages. We find good fits to the measured data with analytical solutions that include the effects of advection and forward and back diffusion through low-permeability zones, and linearly and exponentially decreasing flux resulting from source dissolution in the aquifer. Aquifer contaminant time series data at monitoring wells from a mature site were well described using analytical solutions representing the combined case of source zone and back diffusion, while data from a site where the source had been isolated were well described solely by back diffusion. The modeling approach presented in this study is designed to enable site managers to implement appropriate remediation technologies at a proper timing for high- and low-permeability zones, considering estimated plume life cycle.

The paleohydrology of unsaturated and saturated zones at Yucca Mountain, Nevada, and vicinity

Science.gov (United States)

Paces, James B.; Whelan, Joseph F.; Stuckless, John S.

2012-01-01

Surface, unsaturated-zone, and saturated-zone hydrologic conditions at Yucca Mountain responded to past climate variations and are at least partly preserved by sediment, fossil, and mineral records. Characterizing past hydrologic conditions in surface and subsurface environments helps to constrain hydrologic responses expected under future climate conditions and improve predictions of repository performance. Furthermore, these records provide a better understanding of hydrologic processes that operate at time scales not readily measured by other means. Pleistocene climates in southern Nevada were predominantly wetter and colder than the current interglacial period. Cyclic episodes of aggradation and incision in Fortymile Wash, which drains the eastern slope of Yucca Mountain, are closely linked to Pleistocene climate cycles. Formation of pedogenic cement is favored under wetter Pleistocene climates, consistent with increased soil moisture and vegetation, higher chemical solubility, and greater evapotranspiration relative to Holocene soil conditions. The distribution and geochemistry of secondary minerals in subsurface fractures and cavities reflect unsaturated-zone hydrologic conditions and the response of the hydrogeologic system to changes in temperature and percolation flux over the last 12.8 m.y. Physical and fluid-inclusion evidence indicates that secondary calcite and opal formed in air-filled cavities from fluids percolating downward through connected fracture pathways in the unsaturated zone. Oxygen, strontium, and carbon isotope data from calcite are consistent with a descending meteoric water source but also indicate that water compositions and temperatures evolved through time. Geochronological data indicate that secondary mineral growth rates are less than 1–5 mm/m.y., and have remained approximately uniform over the last 10 m.y. or longer. These data are interpreted as evidence for hydrological stability despite large differences in surface moisture

Remediating Contaminant Plumes in Groundwater with Shallow Excavations Containing Coarse Reactive Media.

Science.gov (United States)

Hudak, Paul F

2018-02-01

A groundwater flow and mass transport model tested the capability of shallow excavations filled with coarse, reactive media to remediate a hypothetical unconfined aquifer with a maximum saturated thickness of 5 m. Modeled as contaminant sinks, the rectangular excavations were 10 m downgradient of an initial contaminant plume originating from a source at the top of the aquifer. The initial plume was approximately 259 m long, 23 m wide, and 5 m thick, with a downgradient tip located approximately 100 m upgradient of the site boundary. The smallest trench capable of preventing offsite migration was 11 m long (measured perpendicular to groundwater flow), 4 m wide (measured parallel to groundwater flow), and 3 m deep. Results of this study suggest that shallow trenches filled with coarse filter media that partially penetrate unconfined aquifers may be a viable alternative for remediating contaminated groundwater at some sites.

A buoyant plume adjacent to a headland-Observations of the Elwha River plume

Science.gov (United States)

Warrick, J.A.; Stevens, A.W.

2011-01-01

Small rivers commonly discharge into coastal settings with topographic complexities - such as headlands and islands - but these settings are underrepresented in river plume studies compared to more simplified, straight coasts. The Elwha River provides a unique opportunity to study the effects of coastal topography on a buoyant plume, because it discharges into the Strait of Juan de Fuca on the western side of its deltaic headland. Here we show that this headland induces flow separation and transient eddies in the tidally dominated currents (O(100. cm/s)), consistent with other headlands in oscillatory flow. These flow conditions are observed to strongly influence the buoyant river plume, as predicted by the "small-scale" or "narrow" dynamical classification using Garvine's (1995) system. Because of the transient eddies and the location of the river mouth on the headland, flow immediately offshore of the river mouth is directed eastward twice as frequently as it is westward. This results in a buoyant plume that is much more frequently "bent over" toward the east than the west. During bent over plume conditions, the plume was attached to the eastern shoreline while having a distinct, cuspate front along its westernmost boundary. The location of the front was found to be related to the magnitude and direction of local flow during the preceding O(1. h), and increases in alongshore flow resulted in deeper freshwater mixing, stronger baroclinic anomalies, and stronger hugging of the coast. During bent over plume conditions, we observed significant convergence of river plume water toward the frontal boundary within 1. km of the river mouth. These results show how coastal topography can strongly influence buoyant plume behavior, and they should assist with understanding of initial coastal sediment dispersal pathways from the Elwha River during a pending dam removal project. ?? 2010.

Modelling thermal plume impacts - Kalpakkam approach

International Nuclear Information System (INIS)

Rao, T.S.; Anup Kumar, B.; Narasimhan, S.V.

2002-01-01

A good understanding of temperature patterns in the receiving waters is essential to know the heat dissipation from thermal plumes originating from coastal power plants. The seasonal temperature profiles of the Kalpakkam coast near Madras Atomic Power Station (MAPS) thermal out fall site are determined and analysed. It is observed that the seasonal current reversal in the near shore zone is one of the major mechanisms for the transport of effluents away from the point of mixing. To further refine our understanding of the mixing and dilution processes, it is necessary to numerically simulate the coastal ocean processes by parameterising the key factors concerned. In this paper, we outline the experimental approach to achieve this objective. (author)

Characteristics of bubble plumes, bubble-plume bubbles and waves from wind-steepened wave breaking

NARCIS (Netherlands)

Leifer, I.; Caulliez, G.; Leeuw, G. de

2007-01-01

Observations of breaking waves, associated bubble plumes and bubble-plume size distributions were used to explore the coupled evolution of wave-breaking, wave properties and bubble-plume characteristics. Experiments were made in a large, freshwater, wind-wave channel with mechanical wind-steepened

Measurements at cooling tower plumes. Part 3. Three-dimensional measurements at cooling tower plumes

International Nuclear Information System (INIS)

Fortak, H.

An extended field experiment is described in which cooling tower plumes were studied by means of three-dimensional in situ measurements. The goal was to obtain input data for numerical models of cooling tower plumes. Of special interest were data for testing or developing assumptions for sub-grid parametrizations. Utilizing modern systems for high-resolution aerology and small aircraft, four measuring campaigns were conducted: two campaigns (1974) at the cooling towers of the RWE power station Neurath and also two (1975) at the single cooling tower of the RWE power station Meppen. Because of the broad spectrum of weather situations it can be assumed that the results are representative with regard to the interrelationship between structure of cooling tower plume and large-scale meteorological situation. A large number of flights with a powered glider crossing the plumes on orthogonal tracks was performed. All flights showed that the plume could be identified up to large downwind distances by discontinuous jumps of temperature and vapor pressure. Therefore, a definite geometry of the plume could always be defined. In all cross sections a vertical circulation could be observed. At the boundary, which could be defined by the mentioned jumps of temperature and vapor pressure, a maximum of downward vertical motion could be observed in most cases. Entrainment along the boundary of a cross section seems to be very small, except at the lower part of the plume. There, the mass entrainment is maximum and is responsible for plume rise as well as for enlargement of the cross section. The visible part of the plume (cloud) was only a small fraction of the whole plume. High-resolution aerology is necessary in order to explain the structure and behavior of such plumes. This is especially the case in investigations regarding the dynamic break-through of temperature inversions. Such cases were observed frequently under various meteorological conditions and are described

The 2016 Case for Mantle Plumes and a Plume-Fed Asthenosphere (Augustus Love Medal Lecture)

Science.gov (United States)

Morgan, Jason P.

2016-04-01

The process of science always returns to weighing evidence and arguments for and against a given hypothesis. As hypotheses can only be falsified, never universally proved, doubt and skepticism remain essential elements of the scientific method. In the past decade, even the hypothesis that mantle plumes exist as upwelling currents in the convecting mantle has been subject to intense scrutiny; from geochemists and geochronologists concerned that idealized plume models could not fit many details of their observations, and from seismologists concerned that mantle plumes can sometimes not be 'seen' in their increasingly high-resolution tomographic images of the mantle. In the place of mantle plumes, various locally specific and largely non-predictive hypotheses have been proposed to explain the origins of non-plate boundary volcanism at Hawaii, Samoa, etc. In my opinion, this debate has now passed from what was initially an extremely useful restorative from simply 'believing' in the idealized conventional mantle plume/hotspot scenario to becoming an active impediment to our community's ability to better understand the dynamics of the solid Earth. Having no working hypothesis at all is usually worse for making progress than having an imperfect and incomplete but partially correct one. There continues to be strong arguments and strong emerging evidence for deep mantle plumes. Furthermore, deep thermal plumes should exist in a mantle that is heated at its base, and the existence of Earth's (convective) geodynamo clearly indicates that heat flows from the core to heat the mantle's base. Here I review recent seismic evidence by French, Romanowicz, and coworkers that I feel lends strong new observational support for the existence of deep mantle plumes. I also review recent evidence consistent with the idea that secular core cooling replenishes half the mantle's heat loss through its top surface, e.g. that the present-day mantle is strongly bottom heated. Causes for

Effect of percolation rate on water-travel time in deep, partially saturated zones

International Nuclear Information System (INIS)

Peters, R.R.; Gauthier, J.H.; Dudley, A.L.

1986-02-01

The Nevada Nuclear Waste Storage Investigations (NNWSI) project is investigating Yucca Mountain, Nye county, Nevada, as a prospective site for a radioactive-waste repository. The Yucca Mountain site is unique among those currently being investigated by the US Department of Energy (DOE) in that the prospective repository location is in the unsaturated zone, approximately 300 m above the water table. The rock units at Yucca Mountain can be grouped into three types: (1) vitric tuffs with high matrix conductivity and few fractures; (2) zeolitized tuffs with low matrix conductivity and few fractures; and (3) densely welded tuffs with low matrix conductivities and many fractures. The prospective repository zone is in densely welded tuff; the units between it and the water table are of types 1 and 2. Current percolation rates through Yucca Mountain, and those that are currently postulated under future climatic conditions, are thought to be of the order of the saturated matrix conductivity of some of the units. Although it is probable that there is now little or no water movement in fracture, it is necessary to investigate the potential for fracture flow, especially that which could be initiated under future climatic conditions. Significant fracture flow, if present, could reduce the water travel time between the repository and the water table. A composite-porosity, continuum model was developed to model flow in a fractured, porous medium. Simulations using data from the Yucca Mountain site and this model in the one-dimensional code TOSPAC indicate that current estimates of the percolation rate result in water movement confined to the matrix and that the water-travel time from the repository to the water table is on the order of hundreds of thousands of years. this result is sensitive to the percolation rate; an increase in percolation rate of a factor of 10 many initiate water movement in the fractures, reducing the travel time significantly

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume.

Science.gov (United States)

Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M

2017-09-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011-2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich "iron curtain," associated with the anoxic-suboxic transition zone, migrated 30m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter. Copyright © 2017 Elsevier B.V. All rights reserved.

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume

Science.gov (United States)

Ziegler, Brady A.; Schreiber, Madeline E.; Cozzarelli, Isabelle M.

2017-01-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011–2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich “iron curtain,” associated with the anoxic-suboxic transition zone, migrated 30 m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter.

Thermal plumes in ventilated rooms

DEFF Research Database (Denmark)

Kofoed, Peter; Nielsen, Peter V.

1990-01-01

The design of a displacement ventilation system involves determination of the flow rate in the thermal plumes. The flow rate in the plumes and the vertical temperature gradient influence each other, and they are influenced by many factors. This paper shows some descriptions of these effects. Free...... above a point heat source cannot be used. This is caused either by the way of generating the plume including a long intermediate region or by the environmental conditions where vertical temperature gradients are present. The flow has a larger angle of spread and the entrainment factor is greather than...... turbulent plumes from different heated bodies are investigated. The measurements have taken place in a full-scale test room where the vertical temperature gradient have been changed. The velocity and the temperature distribution in the plume are measured. Large scale plume axis wandering is taken...

Life Cycle of Mantle Plumes: A perspective from the Galapagos Plume (Invited)

Science.gov (United States)

Gazel, E.; Herzberg, C. T.

2009-12-01

Hotspots are localized sources of heat and magmatism considered as modern-day evidence of mantle plumes. Some hotspots are related to massive magmatic production that generated Large Igneous Provinces (LIPS), an initial-peak phase of plume activity with a mantle source hotter and more magmatically productive than present-day hotspots. Geological mapping and geochronological studies have shown much lower eruption rates for OIB compared to lavas from Large Igneous Provinces LIPS such as oceanic plateaus and continental flood provinces. Our study is the first quantitative petrological comparison of mantle source temperatures and extent of melting for OIB and LIP sources. The wide range of primary magma compositions and inferred mantle potential temperatures for each LIP and OIB occurrence suggest that this rocks originated form a hotspot, a spatially localized source of heat and magmatism restricted in time. Extensive outcrops of basalt, picrite, and sometimes komatiite with circa 65-95 Ma ages occupy portions of the pacific shore of Central and South America included in the Caribbean Large Igneous Province (CLIP). There is general consensus of a Pacific-origin of CLIP and most studies suggest that it was produced by melting in the Galapagos mantle plume. The Galapagos connection is consistent with isotopic and geochemical similarities with lavas from the present-day Galapagos hotspot. A Galapagos link for rocks in South American oceanic complexes (eg. the island of Gorgona) is more controversial and requires future work. The MgO and FeO contents of lavas from the Galapagos related lavas and their primary magmas have decreased since the Cretaceous. From petrological modeling we infer that these changes reflect a cooling of the Galapagos mantle plume from a potential temperature of 1560-1620 C in the Cretaceous to 1500 C at the present time. These temperatures are higher than 1350 C for ambient mantle associated with oceanic ridges, and provide support for the mantle

Scaling for turbulent viscosity of buoyant plumes in stratified fluids: PIV measurement with implications for submarine hydrothermal plume turbulence

Science.gov (United States)

Zhang, Wei; He, Zhiguo; Jiang, Houshuo

2017-11-01

Time-resolved particle image velocimetry (PIV) has been used to measure instantaneous two-dimensional velocity vector fields of laboratory-generated turbulent buoyant plumes in linearly stratified saltwater over extended periods of time. From PIV-measured time-series flow data, characteristics of plume mean flow and turbulence have been quantified. To be specific, maximum plume penetration scaling and entrainment coefficient determined from the mean flow agree well with the theory based on the entrainment hypothesis for buoyant plumes in stratified fluids. Besides the well-known persistent entrainment along the plume stem (i.e., the 'plume-stem' entrainment), the mean plume velocity field shows persistent entrainment along the outer edge of the plume cap (i.e., the 'plume-cap' entrainment), thereby confirming predictions from previous numerical simulation studies. To our knowledge, the present PIV investigation provides the first measured flow field data in the plume cap region. As to measured plume turbulence, both the turbulent kinetic energy field and the turbulence dissipation rate field attain their maximum close to the source, while the turbulent viscosity field reaches its maximum within the plume cap region; the results also show that maximum turbulent viscosity scales as νt,max = 0.030(B/N)1/2, where B is source buoyancy flux and N is ambient buoyancy frequency. These PIV data combined with previously published numerical simulation results have implications for understanding the roles of hydrothermal plume turbulence, i.e. plume turbulence within the cap region causes the 'plume-cap' entrainment that plays an equally important role as the 'plume-stem' entrainment in supplying the final volume flux at the plume spreading level.

Comparing plume characteristics inferred from cross-borehole geophysical data

DEFF Research Database (Denmark)

Haarder, Eline Bojsen; Binley, Andrew; Zibar, Majken Caroline Looms

2012-01-01

significantly influences results of the moment analysis. We compare results of three cross-borehole geophysical approaches for imaging tracer migration arising from a point injection of water in the unsaturated zone: three-dimensional electrical resistivity tomography (ERT), two-dimensional ground......-penetrating radar (GPR) tomography and quasi-three-dimensional GPR tomography. In the studied field experiment, a tracer was injected for a period of 5 d and was monitored both during injection and for 5 d during the subsequent redistribution. The three methods show similar characteristics of the plume development...

Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

Science.gov (United States)

Wang, Xiujuan; Hutchinson, Deborah R.; Wu, Shiguo; Yang, Shengxiong; Guo, Yiqun

2011-01-01

Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

Predicted and observed cooling tower plume rise and visible plume length at the John E. Amos power plant

Energy Technology Data Exchange (ETDEWEB)

Hanna, S R

1976-01-01

A one-dimensional numerical cloud growth model and several empirical models for plume rise and cloud growth are compared with twenty-seven sets of observations of cooling tower plumes from the 2900 MW John E. Amos power plant in West Virginia. The three natural draft cooling towers are 200 m apart. In a cross wind, the plumes begin to merge at a distance of about 500 m downwind. In calm conditions, with reduced entrainment, the plumes often do not merge until heights of 1000 m. The average plume rise, 750 m, is predicted well by the models, but day-to-day variations are simulated with a correlation coefficient of about 0.5. Model predictions of visible plume length agree, on the average, with observations for visible plumes of short to moderate length (less than about 1 km). The prediction of longer plumes is hampered by our lack of knowledge of plume spreading after the plumes level off. Cloud water concentrations predicted by the numerical model agree with those measured in natural cumulus clouds (about 0.1 to 1 g kg/sup -1/).

Turbulent buoyant jets and plumes

CERN Document Server

Rodi, Wolfgang

The Science & Applications of Heat and Mass Transfer: Reports, Reviews, & Computer Programs, Volume 6: Turbulent Buoyant Jets and Plumes focuses on the formation, properties, characteristics, and reactions of turbulent jets and plumes. The selection first offers information on the mechanics of turbulent buoyant jets and plumes and turbulent buoyant jets in shallow fluid layers. Discussions focus on submerged buoyant jets into shallow fluid, horizontal surface or interface jets into shallow layers, fundamental considerations, and turbulent buoyant jets (forced plumes). The manuscript then exami

An Updated Site Scale Saturated Zone Ground Water Transport Model For Yucca Mountain

International Nuclear Information System (INIS)

S. Kelkar; H. Viswanathan; A. Eddebbarrh; M. Ding; P. Reimus; B. Robinson; B. Arnold; A. Meijer

2006-01-01

The Yucca Mountain site scale saturated zone transport model has been revised to incorporate the updated flow model based on a hydrogeologic framework model using the latest lithology data, increased grid resolution that better resolves the geology within the model domain, updated Kd distributions for radionuclides of interest, and updated retardation factor distributions for colloid filtration. The resulting numerical transport model is used for performance assessment predictions of radionuclide transport and to guide future data collection and modeling activities. The transport model results are validated by comparing the model transport pathways with those derived from geochemical data, and by comparing the transit times from the repository footprint to the compliance boundary at the accessible environment with those derived from 14 C-based age estimates. The transport model includes the processes of advection, dispersion, fracture flow, matrix diffusion, sorption, and colloid-facilitated transport. The transport of sorbing radionuclides in the aqueous phase is modeled as a linear, equilibrium process using the Kd model. The colloid-facilitated transport of radionuclides is modeled using two approaches: the colloids with irreversibly embedded radionuclides undergo reversible filtration only, while the migration of radionuclides that reversibly sorb to colloids is modeled with modified values for sorption coefficient and matrix diffusion coefficients. Model breakthrough curves for various radionuclides at the compliance boundary are presented along with their sensitivity to various parameters

Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer

Science.gov (United States)

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2010-07-01

We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten-Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten-Mualem parameters with laboratory values obtained for similar materials in the area.

The effect of vadose zone heterogeneities on vapor phase migration and aquifer contamination by volatile organics

Energy Technology Data Exchange (ETDEWEB)

Seneviratne, A.; Findikakis, A.N. [Bechtel Corporation, San Francisco, CA (United States)

1995-03-01

Organic vapors migrating through the vadose zone and inter-phase transfer can contribute to the contamination of larger portions of aquifers than estimated by accounting only for dissolved phase transport through the saturated zone. Proper understanding of vapor phase migration pathways is important for the characterization of the extent of both vadose zone and the saturated zone contamination. The multiphase simulation code T2VOC is used to numerically investigate the effect of heterogeneties on the vapor phase migration of chlorobenzene at a hypothetical site where a vapor extraction system is used to remove contaminants. Different stratigraphies consisting of alternate layers of high and low permeability materials with soil properties representative of gravel, sandy silt and clays are evaluated. The effect of the extent and continuity of low permeability zones on vapor migration is evaluated. Numerical simulations are carried out for different soil properties and different boundary conditions. T2VOC simulations with zones of higher permeability were made to assess the role of how such zones in providing enhanced migration pathways for organic vapors. Similarly, the effect of the degree of saturation of the porous medium on vapor migration was for a range of saturation values. Increased saturation reduces the pore volume of the medium available for vapor diffusion. Stratigraphic units with higher aqueous saturation can retard the vapor phase migration significantly.

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.

Effect of Anisotropy Structure on Plume Entropy and Reactive Mixing in Helical Flows

DEFF Research Database (Denmark)

Ye, Yu; Chiogna, Gabriele; Lu, Chunhui

2018-01-01

Plume dilution and reactive mixing can be considerably enhanced by helical flows occurring in three-dimensional anisotropic porous media. In this study, we perform conservative and reactive transport simulations considering different anisotropy structures of a single inclusion with the objective...... of exploring the effect of the inclusion’s geometry and orientation on the patterns of twisted streamlines and on the overall dilution and reaction of solute plumes. We analyzed 100 different scenarios by varying key parameters such as the angle of the anisotropic structures with respect to the average flow...... velocity, the spacing between alternated heterogeneous zones of coarse and fine materials, the permeability contrast between such matrices, and the magnitude of the seepage velocity. Entropy conservation equations and entropy-based metrics for both conservative and reactive species were adopted to quantify...

Plume rise from multiple sources

International Nuclear Information System (INIS)

Briggs, G.A.

1975-01-01

A simple enhancement factor for plume rise from multiple sources is proposed and tested against plume-rise observations. For bent-over buoyant plumes, this results in the recommendation that multiple-source rise be calculated as [(N + S)/(1 + S)]/sup 1/3/ times the single-source rise, Δh 1 , where N is the number of sources and S = 6 (total width of source configuration/N/sup 1/3/ Δh 1 )/sup 3/2/. For calm conditions a crude but simple method is suggested for predicting the height of plume merger and subsequent behavior which is based on the geometry and velocity variations of a single buoyant plume. Finally, it is suggested that large clusters of buoyant sources might occasionally give rise to concentrated vortices either within the source configuration or just downwind of it

Suspended matter and nutrient gradients of a small-scale river plume in Sepetiba Bay, SE-Brazil

Directory of Open Access Journals (Sweden)

Raphael Paiva Rodrigues

2009-04-01

Full Text Available Coastal river plumes represent one of the final stages of material transport across the land-sea interface. Most studies, however have focused on the behavior of medium to large sized river plumes of coastal-shelf waters, whereas small sized river plumes acting within estuaries have been neglected. This study addressed the behavior of suspended particulate matter (SPM, dissolved inorganic nutrients (DIN, DIP and DSi and Chlorophyll a (Chl. a of a small sized river plume derived from the closely lain São Francisco and Guandú river channels, set in the Sepetiba Bay estuary, SE-Brazil. Two surface water sampling campaigns were conducted, one in January 2003 (humid summer conditions and the other in June 2003 (dry winter conditions. On both occasions, the plumes dispersed in a SE direction towards the inner portion of the bay. The "wet" event plume was more turbid, nutrient rich and dispersed beyond nearshore waters, whereas the "dry" event plume proliferated as a narrow, less turbid and more nutrient poor film alongshore. Both exhibited a marked degree of patchiness, induced by the differential input of materials from the river sources and resuspension processes from the shallow nearshore bottom. The São Francisco river channel was the main source of freshwater, SPM and nutrients, except for ammonia (NH4+-N derived from domestic effluents of the Guandú river. The mesohaline portion of the estuarine mixing zone of the plumes behaved as a slight source for SPM, DSi and DIP, due to bottom resuspension processes. N:P molar ratios ranged between 80:1 and 20:1 along the estuarine gradient, being higher in the summer than in the winter event, indicating that DIP was the potential nutrient limiting primary production. Chl. a concentrations increased at the outer premises of the plume, suggesting that the short residence times and turbidity of the plume waters, hampered primary production nearshore, particularly during the summer occasion. The small

Experimental Plan: Uranium Stabilization Through Polyphosphate Injection 300 Area Uranium Plume Treatability Demonstration Project

Energy Technology Data Exchange (ETDEWEB)

Wellman, Dawn M.; Fruchter, Jonathan S.; Vermeul, Vince R.

2006-09-20

This Test Plan describes a laboratory-testing program to be performed at Pacific Northwest National Laboratory (PNNL) in support of the 300-FF-5 Feasibility Study (FS). The objective of the proposed treatability test is to evaluate the efficacy of using polyphosphate injections to treat uranium contaminated groundwater in situ. This study will be used to: (1) Develop implementation cost estimates; (2) Identify implementation challenges; and (3) Investigate the technology's ability to meet remedial objectives These activities will be conducted in parallel with a limited field investigation, which is currently underway to more accurately define the vertical extent of uranium in the vadose zone, and in the capillary fringe zone laterally throughout the plume. The treatability test will establish the viability of the method and, along with characterization data from the limited field investigation, will provide the means for determining how best to implement the technology in the field. By conducting the treatability work in parallel with the ongoing Limited Field Investigation, the resulting Feasibility Study (FS) will provide proven, site-specific information for evaluating polyphosphate addition and selecting a suitable remediation strategy for the uranium plume within the FS time frame at an overall cost savings.

Time scales for dissolution of calcite fracture fillings and implications for saturated zone radionuclide transport at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Winterle, J.R.; Murphy, W.M.

1999-01-01

An analysis was performed to estimate time scales for dissolution of calcite fracture fillings in the fractured tuff aquifer that underlies Yucca Mountain (YM), Nevada, where groundwater is chemically undersaturated with respect to calcite. The impetus for this analysis originates from speculation that undissolved calcite in the saturated zone is evidence for limited diffusive exchange between fracture and matrix waters. Assuming that matrix diffusion is the rate-limiting process, the time scale for dissolution of calcite fracture fillings depends on the amount of calcite initially deposited, the distance between flowing fractures, the degree of chemical disequilibrium, and the rate of diffusion. Assuming geochemistry of J-13 well water in free-flowing fractures, estimated time scales for complete dissolution of matrix-entrapped calcite range from about 10 4 yr for a 2 mm-thick deposit located 1 m from a flowing fracture, to over 10 7 yr for a 2 cm-thick deposit located 100 m from a flowing fracture. The authors conclude that, given the geochemical and hydrologic characteristics observed at YM, the persistence of calcite minerals over geologic time scales in aquifers where flowing water is under-saturated with calcite does not necessarily preclude matrix diffusion as a dilution mechanism. However, the model suggests that the effective spacing between flowing fractures may be large enough to diminish the overall benefit of matrix diffusion to proposed high-level waste repository performance

Origin of VC-only plumes from naturally enhanced dechlorination in a peat-rich hydrogeologic setting

Science.gov (United States)

Filippini, Maria; Amorosi, Alessandro; Campo, Bruno; Herrero-Martìn, Sara; Nijenhuis, Ivonne; Parker, Beth L.; Gargini, Alessandro

2016-09-01

The occurrence of vinyl chloride (VC) is often a main concern at sites contaminated with chlorinated solvents due to its high degree of toxicity and carcinogenicity. VC occurrence in aquifers is most often related to the degradation of higher chlorinated ethenes or ethanes and it is generally detected in plumes along with parent contaminants. However, specific combination of stratigraphic, hydrogeologic and geochemical conditions can enhance the degradation of parents and lead to the formation of plumes almost entirely composed of VC (i.e. VC-only plumes). This paper investigates the causes of VC-only plumes in the aquifers below the city of Ferrara (northern Italy) by combining multiple lines of evidence. The City of Ferrara is located on an alluvial lowland, built by the River Po, and is made up of alternating unconsolidated sandy aquifer and silt-clay aquitard deposits of fluvial origin. This region has been strongly impacted by prior industrial activities, with the occurrence of chlorinated compounds at several sites. VC-only plumes with uncertain source location were found at two contaminated sites. The source zone of a third plume composed of chloroethenes from PCE to VC was investigated for high resolution depositional facies architecture and contaminant distribution (contaminant concentration and Compound Specific Isotope Analysis - CSIA). The investigation suggested that degradation of PCE and TCE takes place during contaminant migration through peat-rich (swamp) layers related to the Holocene transgression, which locally act as a ;reactor; for stimulating degradation with the accumulation of VC in the strongly reducing environment of the peat. Regional-scale stratigraphic architecture showed the ubiquitous occurrence of swamp layers at distinct stratigraphic levels in the investigated system and their apparent linkage to the in situ creation of the VC-only plumes.

THE PROGNOSTIC AND DIAGNOSTIC VALUE OF REPEATED TRANSRECTAL PROSTATE SATURATION BIOPSY

Directory of Open Access Journals (Sweden)

M. A. Kurdzhiev

2014-08-01

Full Text Available Objective: to determine the rate of prostate cancer (PC development after repeated transrectal saturation prostate biopsy (RTRSPB, to study the characteristics of diagnosed tumors, and to estimate their clinical significance from the data of radical retropubic prostatectomy (RRP.Materials and methods. The results of RTRSPB were analyzed in 226 patients with a later evaluation of a tumor from the results of RRP. All the patients underwent at least 2 prostate biopsies (mean 2.4. The average number of biopsy cores was 26.7 (range 24—30. The average value of total prostate-specific antigen before saturation biopsy was 7.5 (range 7.5 to 28.6 ng/ml. The mean age of patients was 62 years (range 53 to 70.  Results. PC was diagnosed in 14.6% of cases (33/226. An isolated lesion of the prostatic transition zone was in 12.1% of cases. If this zone had been excluded from the biopsy scheme, the detection rate of PC during saturation biopsy should be reduced by 13.8%. Better PC detectability during repeated saturation biopsy generally occurred due to the localized forms of the disease (93.3%. The agreement of Gleason tumor grading in the biopsy and prostatectomy specimens was noted in 66.7% of cases.Conclusion. Saturation biopsy allows prediction of a pathological stage of PC, Gleason grade of a tumor and its site localization with a greater probability. Most tumors detectable by saturation biopsy were clinically significant, which makes it possible to recommend RTRSPB to some cohort of high PC-risk patients 

Shearing of saturated clays in rock joints at high confining pressures

International Nuclear Information System (INIS)

Wang, C.; Mao, N.

1979-01-01

Saturated clays are sheared between rock joints at various pore water pressures and at confining pressures up to 3 kb (300 Mpa). Sliding on these joints is stable. For a given clay, the shear stress required to initiate sliding increases linearly with the effective normal stress across the sliding surface, with a slope of 0.08 +- 0.01 for joints filled with saturated montmorillonite, 0.12 +- 0.01 with saturated chlorite, 0.15 +- 0.01 with saturated kaolinite, and 0.22 +- 0.02 with saturated silty illite. Thus at high confining pressures the shear stress required to initiate sliding on joints filled with saturated clays are very much smaller than that required to initiate sliding on clean rock joints or on joints filled with dry gouge materials. In the crust, saturation of gouge materials along active faults would greatly lower the frictional resistance to faulting and would stabilize fault movement. Different fault behaviors such as stable creep along some faults and intermittent but sudden slip along others may reflect in part different degrees of saturation of fault zones at depth

Evaluation of plume potential and plume abatement of evaporative cooling towers in a subtropical region

International Nuclear Information System (INIS)

Xu Xinhua; Wang Shengwei; Ma Zhenjun

2008-01-01

Hong Kong is a typical subtropical region with frequently high humidity in late spring and summer seasons. Plume from evaporative cooling towers, which service air-conditioning systems of civil buildings, has aroused public concerns since 2000 when the fresh water evaporative cooling towers were allowed to be used for high energy efficiency and environmental issues. This paper presents the evaluation of the plume potential and its effect on the sizing of the plume abatement system in a large commercial office building in Hong Kong for practical application. This evaluation was conducted based on a dynamic simulation platform using the typical meteorological year of Hong Kong since the occurrence of the plume heavily depends on the state conditions of the exhaust air from cooling towers and the ambient air, while the state condition of the exhaust air is determined by the total building cooling load and the control strategies of cooling towers employed mainly for improving energy efficiency. The results show that the control strategies have a significant effect on the plume potential and further affect the system design and sizing of the plume abatement system

A review and assessment of variable density ground water flow effects on plume formation at UMTRA project sites

International Nuclear Information System (INIS)

1995-01-01

A standard assumption when evaluating the migration of plumes in ground water is that the impacted ground water has the same density as the native ground water. Thus density is assumed to be constant, and does not influence plume migration. This assumption is valid only for water with relatively low total dissolved solids (TDS) or a low difference in TDS between water introduced from milling processes and native ground water. Analyses in the literature suggest that relatively minor density differences can significantly affect plume migration. Density differences as small as 0.3 percent are known to cause noticeable effects on the plume migration path. The primary effect of density on plume migration is deeper migration than would be expected in the arid environments typically present at Uranium Mill Tailings Remedial Action (UMTRA) Project sites, where little or no natural recharge is available to drive the plume into the aquifer. It is also possible that at some UMTRA Project sites, a synergistic affect occurred during milling operations, where the mounding created by tailings drainage (which created a downward vertical gradient) and the density contrast between the process water and native ground water acted together, driving constituents deeper into the aquifer than either process would alone. Numerical experiments were performed with the U.S. Geological Survey saturated unsaturated transport (SUTRA) model. This is a finite-element model capable of simulating the effects of variable fluid density on ground water flow and solute transport. The simulated aquifer parameters generally are representative of the Shiprock, New Mexico, UMTRA Project site where some of the highest TDS water from processing has been observed

Contaminant plume configuration and movement: an experimental model

Science.gov (United States)

Alencoao, A.; Reis, A.; Pereira, M. G.; Liberato, M. L. R.; Caramelo, L.; Amraoui, M.; Amorim, V.

2009-04-01

The relevance of Science and Technology in our daily routines makes it compulsory to educate citizens who have both scientific literacy and scientific knowledge. These will allow them to be intervening citizens in a constantly changing society. Thus, physical and natural sciences are included in school curricula, both in primary and secondary education, with the fundamental aim of developing in the students the skills, attitudes and knowledge needed for the understanding of the planet Earth and its real problems. On the other hand, teaching in Geosciences is more and more based on practical methodologies which use didactic material, sustaining teachers' pedagogical practices and facilitating students' learning tasks suggested on the syllabus defined for each school level. Themes related to exploring the different components of the Hydrological Cycle and themes related to natural environment protection and preservation, namely water resources and soil contamination by industrial and urban sewage are examples of subject matters included on the Portuguese syllabus. These topics motivated the conception and construction of experimental models for the study of the propagation of pollutants on a porous medium. The experimental models allow inducing a horizontal flux of water though different kinds of permeable substances (e.g. sand, silt), with contamination spots on its surface. These experimental activities facilitate the student to understand the flow path of contaminating substances on the saturated zone and to observe the contaminant plume configuration and movement. The activities are explored in a teaching and learning process perspective where the student builds its own knowledge through real question- problem based learning which relate Science, Technology and Society. These activities have been developed in the framework of project ‘Water in the Environment' (CV/PVI/0854) of the POCTI Program (Programa Operacional "Ciência, Tecnologia, Inovação") financed

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A.G.; Stordal, F.; Knudsen, S. [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P. [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1997-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

Chemistry in aircraft plumes

Energy Technology Data Exchange (ETDEWEB)

Kraabol, A G; Stordal, F; Knudsen, S [Norwegian Inst. for Air Research, Kjeller (Norway); Konopka, P [Deutsche Forschungsanstalt fuer Luft- und Raumfahrt e.V. (DLR), Wessling (Germany). Inst. fuer Physik der Atmosphaere

1998-12-31

An expanding plume model with chemistry has been used to study the chemical conversion of NO{sub x} to reservoir species in aircraft plumes. The heterogeneous conversion of N{sub 2}O{sub 5} to HNO{sub 3}(s) has been investigated when the emissions take place during night-time. The plume from an B747 has been simulated. During a ten-hour calculation the most important reservoir species was HNO{sub 3} for emissions at noon. The heterogeneous reactions had little impact on the chemical loss of NO{sub x} to reservoir species for emissions at night. (author) 4 refs.

The Alberta smoke plume observation study

Directory of Open Access Journals (Sweden)

K. Anderson

2018-02-01

Full Text Available A field project was conducted to observe and measure smoke plumes from wildland fires in Alberta. This study used handheld inclinometer measurements and photos taken at lookout towers in the province. Observations of 222 plumes were collected from 21 lookout towers over a 6-year period from 2010 to 2015. Observers reported the equilibrium and maximum plume heights based on the plumes' final levelling heights and the maximum lofting heights, respectively. Observations were tabulated at the end of each year and matched to reported fires. Fire sizes at assessment times and forest fuel types were reported by the province. Fire weather conditions were obtained from the Canadian Wildland Fire Information System (CWFIS. Assessed fire sizes were adjusted to the appropriate size at plume observation time using elliptical fire-growth projections. Though a logical method to collect plume observations in principle, many unanticipated issues were uncovered as the project developed. Instrument limitations and environmental conditions presented challenges to the investigators, whereas human error and the subjectivity of observations affected data quality. Despite these problems, the data set showed that responses to fire behaviour conditions were consistent with the physical processes leading to plume rise. The Alberta smoke plume observation study data can be found on the Canadian Wildland Fire Information System datamart (Natural Resources Canada, 2018 at http://cwfis.cfs.nrcan.gc.ca/datamart.

The Alberta smoke plume observation study

Science.gov (United States)

Anderson, Kerry; Pankratz, Al; Mooney, Curtis; Fleetham, Kelly

2018-02-01

A field project was conducted to observe and measure smoke plumes from wildland fires in Alberta. This study used handheld inclinometer measurements and photos taken at lookout towers in the province. Observations of 222 plumes were collected from 21 lookout towers over a 6-year period from 2010 to 2015. Observers reported the equilibrium and maximum plume heights based on the plumes' final levelling heights and the maximum lofting heights, respectively. Observations were tabulated at the end of each year and matched to reported fires. Fire sizes at assessment times and forest fuel types were reported by the province. Fire weather conditions were obtained from the Canadian Wildland Fire Information System (CWFIS). Assessed fire sizes were adjusted to the appropriate size at plume observation time using elliptical fire-growth projections. Though a logical method to collect plume observations in principle, many unanticipated issues were uncovered as the project developed. Instrument limitations and environmental conditions presented challenges to the investigators, whereas human error and the subjectivity of observations affected data quality. Despite these problems, the data set showed that responses to fire behaviour conditions were consistent with the physical processes leading to plume rise. The Alberta smoke plume observation study data can be found on the Canadian Wildland Fire Information System datamart (Natural Resources Canada, 2018) at http://cwfis.cfs.nrcan.gc.ca/datamart.

Electric conductivity for laboratory and field monitoring of induced partial saturation (IPS) in sands

Science.gov (United States)

Kazemiroodsari, Hadi

Liquefaction is loss of shear strength in fully saturated loose sands caused by build-up of excess pore water pressure, during moderate to large earthquakes, leading to catastrophic failures of structures. Currently used liquefaction mitigation measures are often costly and cannot be applied at sites with existing structures. An innovative, practical, and cost effective liquefaction mitigation technique titled "Induced Partial Saturation" (IPS) was developed by researchers at Northeastern University. The IPS technique is based on injection of sodium percarbonate solution into fully saturated liquefaction susceptible sand. Sodium percarbonate dissolves in water and breaks down into sodium and carbonate ions and hydrogen peroxide which generates oxygen gas bubbles. Oxygen gas bubbles become trapped in sand pores and therefore decrease the degree of saturation of the sand, increase the compressibility of the soil, thus reduce its potential for liquefaction. The implementation of IPS required the development and validation of a monitoring and evaluation technique that would help ensure that the sands are indeed partially saturated. This dissertation focuses on this aspect of the IPS research. The monitoring system developed was based on using electric conductivity fundamentals and probes to detect the transport of chemical solution, calculate degree of saturation of sand, and determine the final zone of partial saturation created by IPS. To understand the fundamentals of electric conductivity, laboratory bench-top tests were conducted using electric conductivity probes and small specimens of Ottawa sand. Bench-top tests were used to study rate of generation of gas bubbles due to reaction of sodium percarbonate solution in sand, and to confirm a theory based on which degree of saturation were calculated. In addition to bench-top tests, electric conductivity probes were used in a relatively large sand specimen prepared in a specially manufactured glass tank. IPS was

Linking carbon and hydrologic fluxes in the critical zone: Observations from high-frequency monitoring of a weathered bedrock vadose zone

Science.gov (United States)

Tune, A. K.; Druhan, J. L.; Wang, J.; Cargill, S.; Murphy, C.; Rempe, D. M.

2017-12-01

A principle challenge in quantifying feedbacks between continental weathering and atmospheric CO2 is to improve understanding of how biogeochemical processes in the critical zone influence the distribution and mobility of organic and inorganic carbon. In particular, in landscapes characterized by thin soils and heterogeneous weathered and fractured bedrock, little data exist to inform and constrain predictive models for carbon dynamics. Here, we present the results of an intensive water and gas sampling campaign across an 18 m thick, variably saturated argillite weathering profile in the Eel River CZO. We monitor water content in situ and regularly collect samples of freely-draining water, tightly-held water, and gas through wet and dry seasons using a novel Vadose-zone Monitoring System (VMS) consisting of sensors and samplers distributed across a 20 m long inclined borehole. This novel approach facilitates the interception of gas and water during transport across the entire variably saturated weathering profile. The data demonstrate that seasonal changes in saturation control the vertical distribution and mobility of carbon in the fractured critical zone. Concentrations of gaseous CO2, O2, and dissolved organic and inorganic carbon fluctuate significantly and repeatably with seasonal additions of water infiltrating the weathered bedrock. A persistent vertical structure in the concentrations of dissolved phases and gas concentrations broadly corresponds to depths associated with unsaturated, seasonally saturated, and chronically saturated zones. Associated variations in the vertical structure of mineralogy and elemental composition, including solid phase organic carbon content, are observed in core obtained during drilling. Together, our observations indicate significant respiration of organic carbon at depths greater than the base of the soil, and thus motivate further investigation of the role of heterogeneous weathered, bedrock environments, which are needed to

Unveiling CO2 heterogeneous freezing plumes during champagne cork popping.

Science.gov (United States)

Liger-Belair, Gérard; Cordier, Daniel; Honvault, Jacques; Cilindre, Clara

2017-09-14

Cork popping from clear transparent bottles of champagne stored at different temperatures (namely, 6, 12, and 20 °C) was filmed through high-speed video imaging in the visible light spectrum. During the cork popping process, a plume mainly composed of gaseous CO 2 with traces of water vapour freely expands out of the bottleneck through ambient air. Most interestingly, for the bottles stored at 20 °C, the characteristic grey-white cloud of fog classically observed above the bottlenecks of champagne stored at lower temperatures simply disappeared. It is replaced by a more evanescent plume, surprisingly blue, starting from the bottleneck. We suggest that heterogeneous freezing of CO 2 occurs on ice water clusters homogeneously nucleated in the bottlenecks, depending on the saturation ratio experienced by gas-phase CO 2 after adiabatic expansion (indeed highly bottle temperature dependent). Moreover, and as observed for the bottles stored at 20 °C, we show that the freezing of only a small portion of all the available CO 2 is able to pump the energy released through adiabatic expansion, thus completely inhibiting the condensation of water vapour found in air packages adjacent to the gas volume gushing out of the bottleneck.

Aquatic dispersion modelling of a tritium plume in Lake Ontario

International Nuclear Information System (INIS)

Klukas, M.H.; Moltyaner, G.L.

1996-05-01

Approximately 2900 kg of tritiated water, containing 2.3E+15 Bq of tritium, were released to Lake Ontario via the cooling water discharge when a leak developed in a moderator heat exchanger in Unit 1 at the Pickering Nuclear Generating Station (PNGS) on 1992 August 2. The release provided the opportunity to study the dispersion of a tritium plume in the coastal zone of Lake Ontario. Current direction over the two-week period following the release was predominantly parallel to the shore, and elevated tritium concentrations were observed up to 20 km east and 85 km west of the PNGS. Predictions of the tritium plume movement were made using current velocity measurements taken at 8-m depth, 2.5 km offshore from Darlington and using a empirical relationship where alongshore current speed is assumed to be proportional to the alongshore component of the wind speed. The tritium migration was best described using current velocity measurements. The tritium plume dispersion is modelled using the one-dimensional advection-dispersion equation. Transport parameters are the alongshore current speed and longitudinal dispersion coefficient. Longitudinal dispersion coefficients, estimated by fitting the solution of the advection-dispersion equation to measured concentration distance profiles ranged from 3.75 to 10.57 m 2 s -1 . Simulations using the fitted values of the dispersion coefficient were able to describe maximum tritium concentrations measured at water supply plants located within 25 km of Pickering to within a factor of 3. The dispersion coefficient is a function of spatial and temporal variability in current velocity and the fitted dispersion coefficients estimated here may not be suitable for predicting tritium plume dispersion under different current conditions. The sensitivity of the dispersion coefficient to variability in current conditions should be evaluated in further field experiments. (author). 13 refs., 7 tabs., 12 figs

In-situ gas hydrate hydrate saturation estimated from various well logs at the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Science.gov (United States)

Lee, M.W.; Collett, T.S.

2011-01-01

In 2006, the U.S. Geological Survey (USGS) completed detailed analysis and interpretation of available 2-D and 3-D seismic data and proposed a viable method for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area of northern Alaska. To validate the predictions of the USGS and to acquire critical reservoir data needed to develop a long-term production testing program, a well was drilled at the Mount Elbert prospect in February, 2007. Numerous well log data and cores were acquired to estimate in-situ gas hydrate saturations and reservoir properties.Gas hydrate saturations were estimated from various well logs such as nuclear magnetic resonance (NMR), P- and S-wave velocity, and electrical resistivity logs along with pore-water salinity. Gas hydrate saturations from the NMR log agree well with those estimated from P- and S-wave velocity data. Because of the low salinity of the connate water and the low formation temperature, the resistivity of connate water is comparable to that of shale. Therefore, the effect of clay should be accounted for to accurately estimate gas hydrate saturations from the resistivity data. Two highly gas hydrate-saturated intervals are identified - an upper ???43 ft zone with an average gas hydrate saturation of 54% and a lower ???53 ft zone with an average gas hydrate saturation of 50%; both zones reach a maximum of about 75% saturation. ?? 2009.

Saturated-unsaturated flow to a partially penetrating well with storage in a compressible aquifer

Science.gov (United States)

Mishra, P. K.; Neuman, S. P.

2010-12-01

Mishra and Neuman [2010] developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or the unsaturated zone. We extend their solution to the case of a finite diameter pumping well with storage. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten - Mualem constitutive model; and use our solution to analyze drawdown data from a pumping test conducted at the Borden site in Ontario, Canada.

Development of upwelling on pathway and freshwater transport of Pearl River plume in northeastern South China Sea

Science.gov (United States)

Chen, Zhaoyun; Jiang, Yuwu; Liu, James T.; Gong, Wenping

2017-08-01

In situ observations, satellite images, and numerical modeling results have shown that the Pearl River plume axis extends alongshore and passes through two separate upwelling regions—one off the Guangdong and Fujian coasts (the Yuedong upwelling) and the other in the Taiwan Bank during the initial and medium stages of the Yuedong upwelling, while it is directed offshore when the Yuedong upwelling is strong. Model experiments are conducted to examine the effects of wind strength and baroclinicity on the upwelling and the corresponding pathway and freshwater transport of the Pearl River plume. The baroclinic effect is important to intensifying the horizontal velocity at the upwelling front and freshwater transport in the northeastern South China Sea. The freshwater transport flux is further decomposed into advection, vertical shear, and tidal pumping components, and advection is the dominant contributor. As the Yuedong upwelling develops, the zone with a relatively high-pressure gradient moves offshore due to offshore Ekman transport and the shift in the upwelling front, which is responsible for the offshore transport of the river plume. When the river plume is transported to the outer-shelf, sometimes it can be further entrained into eddies, allowing its export to the open sea.

Liquid Booster Module (LBM) plume flowfield model

Science.gov (United States)

Smith, S. D.

1981-01-01

A complete definition of the LBM plume is important for many Shuttle design criteria. The exhaust plume shape has a significant effect on the vehicle base pressure. The LBM definition is also important to the Shuttle base heating, aerodynamics and the influence of the exhaust plume on the launch stand and environment. For these reasons a knowledge of the LBM plume characteristics is necessary. A definition of the sea level LBM plume as well as at several points along the Shuttle trajectory to LBM, burnout is presented.

Measurements on cooling tower plumes. Pt. 3

International Nuclear Information System (INIS)

Fortak, H.

1975-11-01

In this paper an extended field experiment is described in which cooling tower plumes were investigated by means of three-dimensional in situ measurements. The goal of this program was to obtain input data for numerical models of cooling tower plumes. Data for testing or developing assumptions for sub-grid parametrizations were of special interest. Utilizing modern systems for high-resolution aerology and small aircraft, four measuring campaigns were conducted: two campaigns (1974) at the cooling towers of the RWE power station at Neurath and also two (1975) at the single cooling tower of the RWE power station at Meppen. Because of the broad spectrum of weather situations, it can be assumed that the results are representative with regard to the interrelationship between the structure of cooling tower plumes and the large-scale meteorological situation. A large number of flights with a powered glider ASK 16 (more than 100 flight hours) crossing the plumes on orthogonal tracks was performed. All flights showed that the plume could be identified up to large downwind distances by discontinuous jumps of temperature and vapour pressure. Therefore a definite geometry of the plume could always be defined. In all cross sections a vertical circulation could be observed. At the plumes boundaries, which could be defined by the mentioned jumps of temperature and vapour pressure, a maximum of downward vertical motion was observed in most cases. Entrainment along the boundary of a cross section seems to be very small, except at the lower part of the plume. There, the mass entrainment is maximum and is responsible for plume rise as well as for enlargement of the cross section. The visible part of the plume (cloud) was only a small fraction of the whole plume. The discontinuities of temperature and vapour pressure show that the plume fills the space below the visible plume down to the ground. However, all effects decrease rapidly towards the ground. It turned out that high

The earliest low and high δ18O caldera-forming eruptions of the Yellowstone plume: Implications for the 30–40 Ma Oregon calderas and speculations on plume-triggered delaminations

Directory of Open Access Journals (Sweden)

Angela Nicole Seligman

2014-11-01

Full Text Available We present new isotopic and trace element data for four eruptive centers in Oregon: Wildcat Mountain (40 Ma, Crooked River (32–28 Ma, Tower Mountain (32 Ma, and Mohawk River (32 Ma. The first three calderas are located too far east to be sourced through renewed subduction of the Farallon slab following accretion of the Yellowstone-produced Siletzia terrane at ~50 Ma. Basalts of the three eastern eruptive centers yield high Nb/Yb and Th/Yb ratios, indicating an enriched sublithospheric mantle source, while Mohawk River yields trace element and isotopic (δ18O and εHf values that correlate with its location above a subduction zone. The voluminous rhyolitic tuffs and lavas of Crooked River (41 x 27 km have δ18Ozircon values that include seven low δ18Ozircon units (1.8–4.5 ‰, one high δ18Ozircon unit (7.4–8.8 ‰, and two units with heterogeneous zircons (2.0–9.0 ‰, similar to younger Yellowstone-Snake River Plain rhyolites. In order to produce these low δ18O values, a large heat source, widespread hydrothermal circulation, and repeated remelting are all required. In contrast, Wildcat Mountain and Tower Mountain rocks yield high δ18Ozircon values (6.4–7.9 ‰ and normal to low εHfi values (5.2–12.6, indicating crustal melting of high-δ18O supracrustal rocks. We propose that these calderas were produced by the first appearance of the Yellowstone plume east of the Cascadia subduction zone, which is supported by plate reconstructions that put the Yellowstone plume under Crooked River at 32–28 Ma. Given the eastern location of these calderas along the suture of the accreted Siletzia terrane and North America, we suggest that the Yellowstone hotspot is directly responsible for magmatism at Crooked River, and for plume-assisted delamination of portions of the edge of the Blue Mountains that produced the Tower Mountain magmas, while the older Wildcat Mountain magmas are related to suture zone instabilities that were created

Radioactive Plumes Monitoring Simulator

International Nuclear Information System (INIS)

Kapelushnik, I.; Sheinfeld, M.; Avida, R.; Kadmon, Y.; Ellenbogen, M.; Tirosh, D.

1999-01-01

The Airborne Radiation Monitoring System (ARMS) monitors air or ground radioactive contamination. The contamination source can be a radioactive plume or an area contaminated with radionuclides. The system is based on two major parts, an airborne unit carried by a helicopter and a ground station carried by a truck. The system enables real time measurement and analysis of radioactive plumes as well as post flight processing. The Radioactive Plumes Monitoring Simulator purpose is to create a virtual space where the trained operators experience full radiation field conditions, without real radiation hazard. The ARMS is based on a flying platform and hence the simulator allows a significant reduction of flight time costs

Investigation of Balcony Plume Entrainment

OpenAIRE

Liu, F.; Nielsen, Peter V.; Heiselberg, Per; Brohus, Henrik; Li, B. Z.

2009-01-01

An investigation on the scenarios of the spill plume and its equation was presented in this paper. The study includes two aspects, i.e., the small-scale experiment and the numerical simulation. Two balcony spill plume models are assessed by comparing with the FDS (Fire Dynamic Simulation) and small scale model experiment results. Besides validating the spill model by experiments, the effect of different fire location on balcony plume is also discussed.The results show that the balcony equatio...

Are splash plumes the origin of minor hotspots?

Science.gov (United States)

Davies, J. H.; Bunge, H.-P.

2006-05-01

It has been claimed that focused hot cylindrical upwelling plumes cause many of the surface volcanic hotspots on Earth. It has also been argued that they must originate from thermal boundary layers. In this paper, we present spherical simulations of mantle circulation at close to Earth-like vigor with significant internal heating. These show, in addition to thermal boundary layer plumes, a new class of plumes that are not rooted in thermal boundary layers. These plumes develop as instabilities from the edge of bowls of hot mantle, which are produced by cold downwelling material deforming hot sheets of mantle. The resulting bowl and plume structure can look a bit like the “splash” of a water droplet. These splash plumes might provide an explanation for some hotspots that are not underlain by thermal boundary layer sourced plumes and not initiated by large igneous provinces. We suggest that in Earth's mantle, lithospheric instabilities or small pieces of subducting slab could play the role of the model downwelling material in initiating splash plumes. Splash plumes would have implications for interpreting ocean-island basalt geochemistry, plume fixity, excess plume temperature, and estimating core heat flux. Improved seismic imaging will ultimately test this hypothesis.

Partially to fully saturated flow through smooth, clean, open fractures: qualitative experimental studies

Science.gov (United States)

Jones, Brendon R.; Brouwers, Luke B.; Dippenaar, Matthys A.

2018-05-01

Fractures are both rough and irregular but can be expressed by a simple model concept of two smooth parallel plates and the associated cubic law governing discharge through saturated fractures. However, in natural conditions and in the intermediate vadose zone, these assumptions are likely violated. This paper presents a qualitative experimental study investigating the cubic law under variable saturation in initially dry free-draining discrete fractures. The study comprised flow visualisation experiments conducted on transparent replicas of smooth parallel plates with inlet conditions of constant pressure and differing flow rates over both vertical and horizontal inclination. Flow conditions were altered to investigate the influence of intermittent and continuous influx scenarios. Findings from this research proved, for instance, that saturated laminar flow is not likely achieved, especially in nonhorizontal fractures. In vertical fractures, preferential flow occupies the minority of cross-sectional area despite the water supply. Movement of water through the fractured vadose zone therefore becomes a matter of the continuity principle, whereby water should theoretically be transported downward at significantly higher flow rates given the very low degree of water saturation. Current techniques that aim to quantify discrete fracture flow, notably at partial saturation, are questionable. Inspired by the results of this study, it is therefore hypothetically improbable to achieve saturation in vertical fractures under free-draining wetting conditions. It does become possible under extremely excessive water inflows or when not free-draining; however, the converse is not true, as a wet vertical fracture can be drained.

Partially to fully saturated flow through smooth, clean, open fractures: qualitative experimental studies

Science.gov (United States)

Jones, Brendon R.; Brouwers, Luke B.; Dippenaar, Matthys A.

2017-11-01

Fractures are both rough and irregular but can be expressed by a simple model concept of two smooth parallel plates and the associated cubic law governing discharge through saturated fractures. However, in natural conditions and in the intermediate vadose zone, these assumptions are likely violated. This paper presents a qualitative experimental study investigating the cubic law under variable saturation in initially dry free-draining discrete fractures. The study comprised flow visualisation experiments conducted on transparent replicas of smooth parallel plates with inlet conditions of constant pressure and differing flow rates over both vertical and horizontal inclination. Flow conditions were altered to investigate the influence of intermittent and continuous influx scenarios. Findings from this research proved, for instance, that saturated laminar flow is not likely achieved, especially in nonhorizontal fractures. In vertical fractures, preferential flow occupies the minority of cross-sectional area despite the water supply. Movement of water through the fractured vadose zone therefore becomes a matter of the continuity principle, whereby water should theoretically be transported downward at significantly higher flow rates given the very low degree of water saturation. Current techniques that aim to quantify discrete fracture flow, notably at partial saturation, are questionable. Inspired by the results of this study, it is therefore hypothetically improbable to achieve saturation in vertical fractures under free-draining wetting conditions. It does become possible under extremely excessive water inflows or when not free-draining; however, the converse is not true, as a wet vertical fracture can be drained.

Diffuse Volcanism at the Young End of the Walvis Ridge - Tristan - Gough Seamount Province: Geochemical Sampling and Constraints on Plume Dynamics

Science.gov (United States)

Class, C.; Koppers, A. A. P.; Sager, W. W.; Schnur, S.

2014-12-01

The Walvis Ridge-Tristan/Gough seamount province in the South Atlantic represents 130 Myr of continuous intra-plate volcanism that can be connected to the once conjunct Parana-Etendeka flood basalt province. With this it represents one of the few primary hotspots consistent with the thermal plume model. However, around 60 Ma, the morphological expression of the Walvis Ridge changed drastically from a robust 200 km wide aseismic ridge into a 400 km wide region of diffuse and diminished volcanism. As a result, this part of the plume trail has been described by two subtracks, one ending at Tristan da Cunha and another at Gough Island more than 400 km to the SSE. Where the Walvis Ridge forks into these two tracks there is a center prong. There is also the 39.5°S lineament of seamounts between, but oblique to, the two subtracks, which is parallel to the local fracture zone directions. All these features are at odds with the classical definition of a narrow hotspot track although Rohde et al. (2013) showed that the Tristan and Gough subtracks retain a distinct geochemical signature over 70 Myr and are consistent with a zoned, deep-seated plume. The first Sr-Nd-Hf-Pb isotopic and trace element analyses from the detailed dredge sampling cruise MV1203 show that samples from two prominent seamounts at the western end of the 39.5°S lineament have a Gough-type signature, which makes an upper mantle source for this lineament unlikely but rather indicates that the Gough-type source stretches some 200 km NNW from Gough. Tristan track seamount samples are comparable with published data, however, one new sample has a Gough-type composition suggesting leakage of this component into the Tristan-type plume zone. Seamounts on the middle prong of the Walvis Ridge fork have compositions intermediate to Gough and Tristan domains, suggesting mixing between sources or melts of the two domains. Thus, the Gough-component in the last 60 Myr of plume activity is volumetrically much more

Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?

Science.gov (United States)

Morgan, J. P.; Shi, C.; Hasenclever, J.

2010-12-01

An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels

Modelling the fate of the Tijuana River discharge plume

Science.gov (United States)

van Ormondt, M.; Terrill, E.; Hibler, L. F.; van Dongeren, A. R.

2010-12-01

After rainfall events, the Tijuana River discharges excess runoff into the ocean in a highly turbid plume. The runoff waters contain large suspended solids concentrations, as well as high levels of toxic contaminants, bacteria, and hepatitis and enteroviruses. Public health hazards posed by the effluent often result in beach closures for several kilometers northward along the U.S. shoreline. A Delft3D model has been set up to predict the fate of the Tijuana River plume. The model takes into account the effects of tides, wind, waves, salinity, and temperature stratification. Heat exchange with the atmosphere is also included. The model consists of a relatively coarse outer domain and a high-resolution surf zone domain that are coupled with Domain Decomposition. The offshore boundary conditions are obtained from the larger NCOM SoCal model (operated by the US Navy) that spans the entire Southern California Bight. A number of discharge events are investigated, in which model results are validated against a wide range of field measurements in the San Diego Bight. These include HF Radar surface currents, REMUS tracks, drifter deployments, satellite imagery, as well as current and temperature profile measurements at a number of locations. The model is able to reproduce the observed current and temperature patterns reasonably well. Under calm conditions, the model results suggest that the hydrodynamics in the San Diego Bight are largely governed by internal waves. During rainfall events, which are typically accompanied by strong winds and high waves, wind and wave driven currents become dominant. An analysis will be made of what conditions determine the trapping and mixing of the plume inside the surfzone and/or the propagation of the plume through the breakers and onto the coastal shelf. The model is now also running in operational mode. Three day forecasts are made every 24 hours. This study was funded by the Office of Naval Research.

Submarine Alkalic Lavas Around the Hawaiian Hotspot; Plume and Non-Plume Signatures Determined by Noble Gases

Science.gov (United States)

Hanyu, T.; Clague, D. A.; Kaneoka, I.; Dunai, T. J.; Davies, G. R.

2004-12-01

Noble gas isotopic ratios were determined for submarine alkalic volcanic rocks distributed around the Hawaiian islands to constrain the origin of such alkalic volcanism. Samples were collected by dredging or using submersibles from the Kauai Channel between Oahu and Kauai, north of Molokai, northwest of Niihau, Southwest Oahu, South Arch and North Arch volcanic fields. Sites located downstream from the center of the hotspot have 3He/4He ratios close to MORB at about 8 Ra, demonstrating that the magmas erupted at these sites had minimum contribution of volatiles from a mantle plume. In contrast, the South Arch, located upstream of the hotspot on the Hawaiian Arch, has 3He/4He ratios between 17 and 21 Ra, indicating a strong plume influence. Differences in noble gas isotopic characteristics between alkalic volcanism downstream and upstream of the hotspot imply that upstream volcanism contains incipient melts from an upwelling mantle plume, having primitive 3He/4He. In combination with lithophile element isotopic data, we conclude that the most likely source of the upstream magmatism is depleted asthenospheric mantle that has been metasomatised by incipient melt from a mantle plume. After major melt extraction from the mantle plume during production of magmas for the shield stage, the plume material is highly depleted in noble gases and moderately depleted in lithophile elements. Partial melting of the depleted mantle impregnated by melts derived from this volatile depleted plume source may explain the isotopic characteristics of the downstream alkalic magmatism.

Modeling variably saturated subsurface solute transport with MODFLOW-UZF and MT3DMS

Science.gov (United States)

Morway, Eric D.; Niswonger, Richard G.; Langevin, Christian D.; Bailey, Ryan T.; Healy, Richard W.

2013-01-01

The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated-zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume-averaged approach in which Lagrangian-based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF-MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably-Saturated Two-Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two- and three-dimensional simulations also were investigated to ensure unsaturated-saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large-scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF-MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three-dimensional variably saturated flow and transport simulations revealed UZF-MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide-spread use of both MODFLOW and MT3DMS, the added capability of unsaturated-zone transport in this familiar modeling framework stands to benefit a broad user-ship.

Assessing geotechnical centrifuge modelling in addressing variably saturated flow in soil and fractured rock.

Science.gov (United States)

Jones, Brendon R; Brouwers, Luke B; Van Tonder, Warren D; Dippenaar, Matthys A

2017-05-01

The vadose zone typically comprises soil underlain by fractured rock. Often, surface water and groundwater parameters are readily available, but variably saturated flow through soil and rock are oversimplified or estimated as input for hydrological models. In this paper, a series of geotechnical centrifuge experiments are conducted to contribute to the knowledge gaps in: (i) variably saturated flow and dispersion in soil and (ii) variably saturated flow in discrete vertical and horizontal fractures. Findings from the research show that the hydraulic gradient, and not the hydraulic conductivity, is scaled for seepage flow in the geotechnical centrifuge. Furthermore, geotechnical centrifuge modelling has been proven as a viable experimental tool for the modelling of hydrodynamic dispersion as well as the replication of similar flow mechanisms for unsaturated fracture flow, as previously observed in literature. Despite the imminent challenges of modelling variable saturation in the vadose zone, the geotechnical centrifuge offers a powerful experimental tool to physically model and observe variably saturated flow. This can be used to give valuable insight into mechanisms associated with solid-fluid interaction problems under these conditions. Findings from future research can be used to validate current numerical modelling techniques and address the subsequent influence on aquifer recharge and vulnerability, contaminant transport, waste disposal, dam construction, slope stability and seepage into subsurface excavations.

Lithosphere erosion atop mantle plumes

Science.gov (United States)

Agrusta, R.; Arcay, D.; Tommasi, A.

2012-12-01

Mantle plumes are traditionally proposed to play an important role in lithosphere erosion. Seismic images beneath Hawaii and Cape Verde show a lithosphere-asthenosphere-boundary (LAB) up to 50 km shallower than the surroundings. However, numerical models show that unless the plate is stationary the thermo-mechanical erosion of the lithosphere does not exceed 30 km. We use 2D petrological-thermo-mechanical numerical models based on a finite-difference method on a staggered grid and marker in cell method to study the role of partial melting on the plume-lithosphere interaction. A homogeneous peridotite composition with a Newtonian temperature- and pressure-dependent viscosity is used to simulate both the plate and the convective mantle. A constant velocity, ranging from 5 to 12.5 cm/yr, is imposed at the top of the plate. Plumes are created by imposing a thermal anomaly of 150 to 350 K on a 50 km wide domain at the base of the model (700 km depth); the plate right above the thermal anomaly is 40 Myr old. Partial melting is modeled using batch-melting solidus and liquidus in anhydrous conditions. We model the progressive depletion of peridotite and its effect on partial melting by assuming that the melting degree only strictly increases through time. Melt is accumulated until a porosity threshold is reached and the melt in excess is then extracted. The rheology of the partially molten peridotite is determined using viscous constitutive relationship based on a contiguity model, which enables to take into account the effects of grain-scale melt distribution. Above a threshold of 1%, melt is instantaneously extracted. The density varies as a function of partial melting degree and extraction. Besides, we analyze the kinematics of the plume as it impacts a moving plate, the dynamics of time-dependent small-scale convection (SSC) instabilities developing in the low-viscosity layer formed by spreading of hot plume material at the lithosphere base, and the resulting thermal

Turbulent forces within river plumes affect spread

Science.gov (United States)

Bhattacharya, Atreyee

2012-08-01

When rivers drain into oceans through narrow mouths, hydraulic forces squeeze the river water into buoyant plumes that are clearly visible in satellite images. Worldwide, river plumes not only disperse freshwater, sediments, and nutrients but also spread pollutants and organisms from estuaries into the open ocean. In the United States, the Columbia River—the largest river by volume draining into the Pacific Ocean from North America—generates a plume at its mouth that transports juvenile salmon and other fish into the ocean. Clearly, the behavior and spread of river plumes, such as the Columbia River plume, affect the nation's fishing industry as well as the global economy.

Plume rise measurements at Turbigo

Energy Technology Data Exchange (ETDEWEB)

Anfossi, D

1982-01-01

This paper presents analyses of plume measurements obtained during that campaign by the ENEL ground-based Lidar. The five stacks of Turbigo Power Plant have different heights and emission parameters and their plumes usually combine, so a model for multiple sources was used to predict the plume rises. These predictions are compared with the observations. Measurements of sigma/sub v/ and sigma/sub z/ over the first 1000 m are compared with the curves derived from other observations in the Po Valley, using the no-lift balloon technique over the same range of downwind distance. Skewness and kurtosis distributions are shown, both along the vertical and the horizontal directions. In order to show the plume structure in more detail, we present two examples of Lidar-derived cross sections and the corresponding vertically and horizontally integrated concentration profiles.

Redox zones of a landfill leachate pollution plume (Vejen, Denmark)

DEFF Research Database (Denmark)

Lyngkilde, John; Christensen, Thomas Højlund

1992-01-01

Downgradient from an old municipal landfill allowing leachate, rich in dissolved organic carbon, to enter a shallow sandy aerobic aquifer, a sequence of redoxe zones is identified from groundwater chemical analysis. Below the landfill, methanogenic conditions prevail, followed by sulfidogenic...... the fate of reactive pollutants leached from the landfill....

Plume meander and dispersion in a stable boundary layer

Science.gov (United States)

Hiscox, April L.; Miller, David R.; Nappo, Carmen J.

2010-11-01

Continuous lidar measurements of elevated plume dispersion and corresponding micrometeorology data are analyzed to establish the relationship between plume behavior and nocturnal boundary layer dynamics. Contrasting nights of data from the JORNADA field campaign in the New Mexico desert are analyzed. The aerosol lidar measurements were used to separate the plume diffusion (plume spread) from plume meander (displacement). Mutiresolution decomposition was used to separate the turbulence scale (90 s). Durations of turbulent kinetic energy stationarity and the wind steadiness were used to characterize the local scale and submesoscale turbulence. Plume meander, driven by submesoscale wind motions, was responsible for most of the total horizontal plume dispersion in weak and variable winds and strong stability. This proportion was reduced in high winds (i.e., >4 m s-1), weakly stable conditions but remained the dominant dispersion mechanism. The remainder of the plume dispersion in all cases was accounted for by internal spread of the plume, which is a small eddy diffusion process driven by turbulence. Turbulence stationarity and the wind steadiness are demonstrated to be closely related to plume diffusion and plume meander, respectively.

Characterization of thermal, hydraulic, and gas diffusion properties in variably saturated sand grades

DEFF Research Database (Denmark)

Deepagoda Thuduwe Kankanamge Kelum, Chamindu; Smits, Kathleen; Ramirez, Jamie

2016-01-01

porous media transport properties, key transport parameters such as thermal conductivity and gas diffusivity are particularly important to describe temperature-induced heat transport and diffusion-controlled gas transport processes, respectively. Despite many experimental and numerical studies focusing...... transport models (thermal conductivity, saturated hydraulic conductivity, and gas diffusivity). An existing thermal conductivity model was improved to describe the distinct three-region behavior in observed thermal conductivity–water saturation relations. Applying widely used parametric models for saturated......Detailed characterization of partially saturated porous media is important for understanding and predicting vadose zone transport processes. While basic properties (e.g., particle- and pore-size distributions and soil-water retention) are, in general, essential prerequisites for characterizing most...

On Fluid and Thermal Dynamics in a Heterogeneous CO2 Plume Geothermal Reservoir

Directory of Open Access Journals (Sweden)

Tianfu Xu

2017-01-01

Full Text Available CO2 is now considered as a novel heat transmission fluid to extract geothermal energy. It can achieve both the energy exploitation and CO2 geological sequestration. The migration pathway and the process of fluid flow within the reservoirs affect significantly a CO2 plume geothermal (CPG system. In this study, we built three-dimensional wellbore-reservoir coupled models using geological and geothermal conditions of Qingshankou Formation in Songliao Basin, China. The performance of the CPG system is evaluated in terms of the temperature, CO2 plume distribution, flow rate of production fluid, heat extraction rate, and storage of CO2. For obtaining a deeper understanding of CO2-geothermal system under realistic conditions, heterogeneity of reservoir’s hydrological properties (in terms of permeability and porosity is taken into account. Due to the fortissimo mobility of CO2, as long as a highly permeable zone exists between the two wells, it is more likely to flow through the highly permeable zone to reach the production well, even though the flow path is longer. The preferential flow shortens circulation time and reduces heat-exchange area, probably leading to early thermal breakthrough, which makes the production fluid temperature decrease rapidly. The analyses of flow dynamics of CO2-water fluid and heat may be useful for future design of a CO2-based geothermal development system.

Is the track of the Yellowstone hotspot driven by a deep mantle plume? -- Review of volcanism, faulting, and uplift in light of new data

Science.gov (United States)

Pierce, Kenneth L.; Morgan, Lisa A.

2009-01-01

Geophysical imaging of a tilted mantle plume extending at least 500 km beneath the Yellowstone caldera provides compelling support for a plume origin of the entire Yellowstone hotspot track back to its inception at 17 Ma with eruptions of flood basalts and rhyolite. The widespread volcanism, combined with a large volume of buoyant asthenosphere, supports a plume head as an initial phase. Estimates of the diameter of the plume head suggest it completely spanned the upper mantle and was fed from sources beneath the transition zone, We consider a mantle–plume depth to at least 1,000 km to best explain the large scale of features associated with the hotspot track. The Columbia River–Steens flood basalts form a northward-migrating succession consistent with the outward spreading of a plume head beneath the lithosphere. The northern part of the inferred plume head spread (pancaked) upward beneath Mesozoic oceanic crust to produce flood basalts, whereas basalt melt from the southern part intercepted and melted Paleozoic and older crust to produce rhyolite from 17 to 14 Ma. The plume head overlapped the craton margin as defined by strontium isotopes; westward motion of the North American plate has likely "scraped off" the head from the plume tail. Flood basalt chemistries are explained by delamination of the lithosphere where the plume head intersected this cratonic margin. Before reaching the lithosphere, the rising plume head apparently intercepted the east-dipping Juan de Fuca slab and was deflected ~ 250 km to the west; the plume head eventually broke through the slab, leaving an abruptly truncated slab. Westward deflection of the plume head can explain the anomalously rapid hotspot movement of 62 km/m.y. from 17 to 10 Ma, compared to the rate of ~ 25 km/m.y. from 10 to 2 Ma.

Experimental investigation of bubble plume structure instability

Energy Technology Data Exchange (ETDEWEB)

Marco Simiano; Robert Zboray; Francois de Cachard [Thermal-Hydraulics Laboratory, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Djamel Lakehal; George Yadigaroglu [Institute of Energy Technology, Swiss Federal Institute of Technology, ETH-Zentrum/CLT, 8092 Zurich (Switzerland)

2005-07-01

Full text of publication follows: The hydrodynamic properties of a 3D bubble plume in a large water pool are investigated experimentally. Bubble plumes are present in various industrial processes, including chemical plants, stirred reactors, and nuclear power plants, e.g. in BWR suppression pools. In these applications, the main issue is to predict the currents induced by the bubbles in the liquid phase, and to determine the consequent mixing. Bubble plumes, especially large and unconfined ones, present strong 3D effects and a superposition of different characteristic length scales. Thus, they represent relevant test cases for assessment and verification of 3D models in thermal-hydraulic codes. Bubble plumes are often unsteady, with fluctuations in size and shape of the bubble swarm, and global movements of the plume. In this case, local time-averaged data are not sufficient to characterize the flow. Additional information regarding changes in plume shape and position is required. The effect of scale on the 3D flow structure and stability being complex, there was a need to conduct studies in a fairly large facility, closer to industrial applications. Air bubble plumes, up to 30 cm in base diameter and 2 m in height were extensively studied in a 2 m diameter water pool. Homogeneously sized bubbles were obtained using a particular injector. The main hydrodynamic parameters. i.e., gas and liquid velocities, void fraction, bubble shape and size, plume shape and position, were determined experimentally. Photographic and image processing techniques were used to characterize the bubble shape, and double-tip optical probes to measure bubble size and void fraction. Electromagnetic probes measured the recirculation velocity in the pool. Simultaneous two-phase flow particle image velocimetry (STPFPIV) in a vertical plane containing the vessel axis provided instantaneous velocity fields for both phases and therefore the relative velocity field. Video recording using two CCD

Chesapeake Bay plume dynamics from LANDSAT

Science.gov (United States)

Munday, J. C., Jr.; Fedosh, M. S.

1981-01-01

LANDSAT images with enhancement and density slicing show that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

PLUME-MoM 1.0: A new integral model of volcanic plumes based on the method of moments

Science.gov (United States)

de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

2015-08-01

In this paper a new integral mathematical model for volcanic plumes, named PLUME-MoM, is presented. The model describes the steady-state dynamics of a plume in a 3-D coordinate system, accounting for continuous variability in particle size distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. A proper description of such a multi-particle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows for a description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of parameters of the continuous size distribution of the particles. This is achieved by formulation of fundamental transport equations for the multi-particle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows for the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables the investigation of the response of four key output variables (mean and standard deviation of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and standard deviation) characterizing the

Buoyant plume calculations

International Nuclear Information System (INIS)

Penner, J.E.; Haselman, L.C.; Edwards, L.L.

1985-01-01

Smoke from raging fires produced in the aftermath of a major nuclear exchange has been predicted to cause large decreases in surface temperatures. However, the extent of the decrease and even the sign of the temperature change, depend on how the smoke is distributed with altitude. We present a model capable of evaluating the initial distribution of lofted smoke above a massive fire. Calculations are shown for a two-dimensional slab version of the model and a full three-dimensional version. The model has been evaluated by simulating smoke heights for the Hamburg firestorm of 1943 and a smaller scale oil fire which occurred in Long Beach in 1958. Our plume heights for these fires are compared to those predicted by the classical Morton-Taylor-Turner theory for weakly buoyant plumes. We consider the effect of the added buoyancy caused by condensation of water-laden ground level air being carried to high altitude with the convection column as well as the effects of background wind on the calculated smoke plume heights for several fire intensities. We find that the rise height of the plume depends on the assumed background atmospheric conditions as well as the fire intensity. Little smoke is injected into the stratosphere unless the fire is unusually intense, or atmospheric conditions are more unstable than we have assumed. For intense fires significant amounts of water vapor are condensed raising the possibility of early scavenging of smoke particles by precipitation. 26 references, 11 figures

PLUME and research sotware

Science.gov (United States)

Baudin, Veronique; Gomez-Diaz, Teresa

2013-04-01

The PLUME open platform (https://www.projet-plume.org) has as first goal to share competences and to value the knowledge of software experts within the French higher education and research communities. The project proposes in its platform the access to more than 380 index cards describing useful and economic software for this community, with open access to everybody. The second goal of PLUME focuses on to improve the visibility of software produced by research laboratories within the higher education and research communities. The "development-ESR" index cards briefly describe the main features of the software, including references to research publications associated to it. The platform counts more than 300 cards describing research software, where 89 cards have an English version. In this talk we describe the theme classification and the taxonomy of the index cards and the evolution with new themes added to the project. We will also focus on the organisation of PLUME as an open project and its interests in the promotion of free/open source software from and for research, contributing to the creation of a community of shared knowledge.

Characterization of redox conditions in pollution plumes

DEFF Research Database (Denmark)

Christensen, Thomas Højlund; Bjerg, Poul Løgstrup; Banwart, Steven A.

2000-01-01

Evalution of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few...

Plume-stagnant slab-lithosphere interactions: Origin of the late Cenozoic intra-plate basalts on the East Eurasia margin

Science.gov (United States)

Kimura, Jun-Ichi; Sakuyama, Tetsuya; Miyazaki, Takashi; Vaglarov, Bogdan S.; Fukao, Yoshio; Stern, Robert J.

2018-02-01

Intra-plate basalts of 35-0 Ma in East Eurasia formed in a broad backarc region above the stagnant Pacific Plate slab in the mantle transition zone. These basalts show regional-scale variations in Nd-Hf isotopes. The basalts with the most radiogenic Nd-Hf center on the Shandong Peninsula with intermediate Nd-Hf at Hainan and Datong. The least radiogenic basalts occur in the perimeters underlain by the thick continental lithosphere. Shandong basalts possess isotopic signatures of the young igneous oceanic crust of the subducted Pacific Plate. Hainan and Datong basalts have isotopic signatures of recycled subduction materials with billions of years of storage in the mantle. The perimeter basalts have isotopic signatures similar to pyroxenite xenoliths from the subcontinental lithospheric mantle beneath East Eurasia. Hainan basalts exhibit the highest mantle potential temperature (Tp), while the Shandong basalts have the lowest Tp. We infer that a deep high-Tp plume interacted with the subducted Pacific Plate slab in the mantle transition zone to form a local low-Tp plume by entraining colder igneous oceanic lithosphere. We infer that the subducted Izanagi Plate slab, once a part of the Pacific Plate mosaic, broke off from the Pacific Plate slab at 35 Ma to sink into the lower mantle. The sinking Izanagi slab triggered the plume that interacted with the stagnant Pacific slab and caused subcontinental lithospheric melting. This coincided with formation of the western Pacific backarc marginal basins due to Pacific Plate slab rollback and stagnation.

Geodynamics of oceanic plateau and plume head accretion and their role in Phanerozoic orogenic systems of China

Directory of Open Access Journals (Sweden)

Peter G. Betts

2015-01-01

Full Text Available We present three 3D numerical models of deep subduction where buoyant material from an oceanic plateau and a plume interact with the overriding plate to assess the influence on subduction dynamics, trench geometry, and mechanisms for plateau accretion and continental growth. Transient instabilities of the convergent margin are produced, resulting in: contorted trench geometry; trench migration parallel with the plate margin; folding of the subducting slab and orocline development at the convergent margin; and transfer of the plateau to the overriding plate. The presence of plume material beneath the oceanic plateau causes flat subduction above the plume, resulting in a “bowed” shaped subducting slab. In plateau-only models, plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction is re-established directly behind the trailing edge of the plateau. The plateau shortens and some plateau material subducts. The presence of buoyant plume material beneath the oceanic plateau has a profound influence on the behaviour of the convergent margin. In the plateau + plume model, plateau accretion causes rapid trench advance. Plate convergence is accommodated by shearing at the base of the plateau and shortening in the overriding plate. The trench migrates around the edge of the plateau and subduction is re-established well behind the trailing edge of the plateau, effectively embedding the plateau into the overriding plate. A slab window forms beneath the accreted plateau and plume material is transferred from the subducting plate to the overriding plate through the window. In all of the models, the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate. The models provide a dynamic context for plateau and plume accretion in Phanerozoic accretionary orogenic systems such as the East China Orogen and the Central Asian

Hydrogeologic Framework Model for the Saturated-Zone Site-Scale Flow

Energy Technology Data Exchange (ETDEWEB)

Z. Peterman

2003-03-05

Yucca Mountain is being evaluated as a potential site for development of a geologic repository for the permanent disposal of spent nuclear fuel and high-level radioactive waste. Ground water is considered to be the principal means for transporting radionuclides that may be released from the potential repository to the accessible environment, thereby possibly affecting public health and safety. The ground-water hydrology of the region is a result of both the arid climatic conditions and the complex geology. Ground-water flow in the Yucca Mountain region generally can be described as consisting of two main components: a series of relatively shallow and localized flow paths that are superimposed on deeper regional flow paths. A significant component of the regional ground-water flow is through a thick, generally deep-lying, Paleozoic carbonate rock sequence. Locally within the potential repository area, the flow is through a vertical sequence of welded and nonwelded tuffs that overlie the carbonate aquifer. Downgradient from the site, these tuffs terminate in basin fill deposits that are dominated by alluvium. Throughout the system, extensive and prevalent faults and fractures may control ground-water flow. The purpose of this Analysis/Modeling Report (AMR) is to document the three-dimensional (3D) hydrogeologic framework model (HFM) that has been constructed specifically to support development of a site-scale ground-water flow and transport model. Because the HFM provides the fundamental geometric framework for constructing the site-scale 3D ground-water flow model that will be used to evaluate potential radionuclide transport through the saturated zone (SZ) from beneath the potential repository to down-gradient compliance points, the HFM is important for assessing potential repository system performance. This AMR documents the progress of the understanding of the site-scale SZ ground-water flow system framework at Yucca Mountain based on data through July 1999. The

Io Pele plume

Science.gov (United States)

2000-01-01

Voyager 1 took this narrow-angle camera image on 5 March 1979 from a distance of 450,000 kilometers. At this geometry, the camera looks straight down through a volcanic plume at one of Io's most active volcanos, Pele. The large heart-shaped feature is the region where Pele's plume falls to the surface. At the center of the 'heart' is the small dark fissure that is the source of the eruption. The Voyager Project is managed by the Jet Propulsion Laboratory for NASA's Office of Space Science.

Io's Active Eruption Plumes: Insights from HST

Science.gov (United States)

Jessup, K. L.; Spencer, J. R.

2011-10-01

Taking advantage of the available data, we recently [10] completed a detailed analysis of the spectral signature of Io's Pele-type Tvashtar plume as imaged by the HST Wide Field and Planetary Camera 2 (HST/WFPC2) via absorption during Jupiter transit and via reflected sunlight in 2007, as well as HST/WFPC2 observations of the 1997 eruption of Io's Prometheus-type Pillan plume (Fig. 1). These observations were obtained in the 0.24-0.42 μm range, where the plumes gas absorption and aerosol scattering properties are most conspicuous. By completing a detailed analysis of these observations, several key aspects of the reflectance and the absorption properties of the two plumes have been revealed. Additionally, by considering the analysis of the HST imaging data in light of previously published spectral analysis of Io's Prometheus and Pele-type plumes several trends in the plume properties have been determined, allowing us to define the relative significance of each plume on the rate of re-surfacing occurring on Io and providing the measurements needed to better assess the role the volcanoes play in the stability of Io's tenuous atmosphere.

Fate of mercury species in the coastal plume of the Adour River estuary (Bay of Biscay, SW France)

Energy Technology Data Exchange (ETDEWEB)

Sharif, Abubaker; Monperrus, Mathilde; Tessier, Emmanuel; Bouchet, Sylvain; Pinaly, Hervé; Rodriguez-Gonzalez, Pablo [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Matériaux, UMR 5254 CNRS, Université de Pau et des Pays de l' Adour, Hélioparc Pau Pyrénées, 2 av. P. Angot, 64053 Pau cedex 9 (France); Maron, Philippe [Laboratoire des Sciences de l' Ingénieur Appliquées à la Mécanique et au Génie Electrique, Institut Supérieur Aquitain du Bâtiment et des Travaux Publics, Université de Pau et des Pays de l' Adour, Allée du Parc Montaury, 64600 Anglet (France); Amouroux, David, E-mail: david.amouroux@univ-pau.fr [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Matériaux, UMR 5254 CNRS, Université de Pau et des Pays de l' Adour, Hélioparc Pau Pyrénées, 2 av. P. Angot, 64053 Pau cedex 9 (France)

2014-10-15

Because mercury (Hg) undergoes significant biogeochemical processes along the estuarine-coastal continuum, the objective of this work was to investigate the distribution and reactivity of methylmercury (MeHg), inorganic mercury (Hg(II)) and gaseous Hg (DGM) in plume waters of the Adour River estuary (Bay of Biscay). Vertical profiles, spatial and tidal variability of Hg species concentrations were evaluated during two campaigns (April 2007 and May 2010) characterized by significant plume extents over the coastal zone. Incubations with isotopically enriched tracers were performed on bulk and filtered waters under sunlight or dark conditions to investigate processes involved in Hg methylation, demethylation and reduction rates. Total Hg(II) concentrations were more dispersed in April 2007 (5.2 ± 4.9 pM) than in May 2010 (2.5 ± 1.1 pM) while total MeHg concentrations were similar for both seasons and averaged 0.13 ± 0.07 and 0.18 ± 0.11 pM, respectively. DGM concentrations were also similar between the two campaigns, averaging 0.26 ± 0.10 and 0.20 ± 0.09 pM, respectively. Methylation yields remained low within the estuarine plume (< 0.01–0.4% day{sup −1}) while MeHg was efficiently demethylated via both biotic and abiotic pathways (2.3–55.3% day{sup −1}), mainly photo-induced. Hg reduction was also effective in these waters (0.3–43.5% day{sup −1}) and was occurring in both light and dark conditions. The results suggest that the plume is overall a sink for MeHg with integrated net demethylation rates, ranging from 2.0–3.7 g (Hg) d{sup −1}, in the same range than the estimated MeHg inputs from the estuary (respectively, 0.9 and 3.5 g (Hg) d{sup −1}). The large evasion of DGM from the plume waters to the atmosphere (8.8–26.9 g (Hg) d{sup −1}) may also limit Hg{sub T} inputs to coastal waters (33–69 g (Hg) d{sup −1}). These processes are thus considered to be most significant in controlling the fate of Hg transferred from the river to the

Fate of mercury species in the coastal plume of the Adour River estuary (Bay of Biscay, SW France)

International Nuclear Information System (INIS)

Sharif, Abubaker; Monperrus, Mathilde; Tessier, Emmanuel; Bouchet, Sylvain; Pinaly, Hervé; Rodriguez-Gonzalez, Pablo; Maron, Philippe; Amouroux, David

2014-01-01

Because mercury (Hg) undergoes significant biogeochemical processes along the estuarine-coastal continuum, the objective of this work was to investigate the distribution and reactivity of methylmercury (MeHg), inorganic mercury (Hg(II)) and gaseous Hg (DGM) in plume waters of the Adour River estuary (Bay of Biscay). Vertical profiles, spatial and tidal variability of Hg species concentrations were evaluated during two campaigns (April 2007 and May 2010) characterized by significant plume extents over the coastal zone. Incubations with isotopically enriched tracers were performed on bulk and filtered waters under sunlight or dark conditions to investigate processes involved in Hg methylation, demethylation and reduction rates. Total Hg(II) concentrations were more dispersed in April 2007 (5.2 ± 4.9 pM) than in May 2010 (2.5 ± 1.1 pM) while total MeHg concentrations were similar for both seasons and averaged 0.13 ± 0.07 and 0.18 ± 0.11 pM, respectively. DGM concentrations were also similar between the two campaigns, averaging 0.26 ± 0.10 and 0.20 ± 0.09 pM, respectively. Methylation yields remained low within the estuarine plume (< 0.01–0.4% day −1 ) while MeHg was efficiently demethylated via both biotic and abiotic pathways (2.3–55.3% day −1 ), mainly photo-induced. Hg reduction was also effective in these waters (0.3–43.5% day −1 ) and was occurring in both light and dark conditions. The results suggest that the plume is overall a sink for MeHg with integrated net demethylation rates, ranging from 2.0–3.7 g (Hg) d −1 , in the same range than the estimated MeHg inputs from the estuary (respectively, 0.9 and 3.5 g (Hg) d −1 ). The large evasion of DGM from the plume waters to the atmosphere (8.8–26.9 g (Hg) d −1 ) may also limit Hg T inputs to coastal waters (33–69 g (Hg) d −1 ). These processes are thus considered to be most significant in controlling the fate of Hg transferred from the river to the coastal zone. - Highlights: �

Small rocket exhaust plume data

Science.gov (United States)

Chirivella, J. E.; Moynihan, P. I.; Simon, W.

1972-01-01

During recent cryodeposit tests with an 0.18-N thruster, the mass flux in the plume back field was measured for the first time for nitrogen, carbon dioxide, and a mixture of nitrogen, hydrogen, and ammonia at various inlet pressures. This mixture simulated gases that would be generated by a hydrazine plenum attitude propulsion system. The measurements furnish a base upon which to build a mathematical model of plume back flow that will be used in predicting the mass distribution in the boundary region of other plumes. The results are analyzed and compared with existing analytical predictions.

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

Directory of Open Access Journals (Sweden)

Thomas Ohde

Full Text Available We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area. The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone

Seasonal and annual variability of coastal sulphur plumes in the northern Benguela upwelling system.

Science.gov (United States)

Ohde, Thomas; Dadou, Isabelle

2018-01-01

We investigated the seasonal and annual variability of surface sulphur plumes in the northern Benguela upwelling system off Namibia because of their significant impacts on the marine ecosystem, fishing industry, aquaculture farming and tourism due to their toxic properties. We identified the sulphur plumes in ocean colour satellite data of the medium resolution imaging spectrometer (MERIS) for the 2002-2012 time period using the differences in the spectral properties of Namibian Benguela optical water types. The sulphur events have a strong seasonal cycle with pronounced main and off-seasons forced by local and remote-driven processes. The main peak season is in late austral summer and early austral autumn at the beginning of the annual upwelling cycle caused by increasing equatorwards alongshore winds. The sulphur plume activity is high between February and April during the seasonal oxygen minimum associated with the seasonal reduction of cross-shore ventilation of the bottom waters, the seasonal southernmost position of the Angola Benguela Frontal Zone, the seasonal maximum of water mass fractions of South Atlantic and Angola Gyre Central Waters as well as the seasonal arrival of the downwelling coastal trapped waves. The off-season is in austral spring and early austral summer during increased upwelling intensity and enhanced oxygen supply. The annual variability of sulphur events is characterized by very high activities in years 2004, 2005 and 2010 interrupted by periods of lower activity in years 2002 to 2003, 2006 to 2009 and 2011 to 2012. This result can be explained by the relative contributions or adding effects of local and remote-driven forces (from the equatorial area). The probability for the occurrence of sulphur plumes is enhanced in years with a lower annual mean of upwelling intensity, decreased oxygen supply associated with decreased lateral ventilation of bottom waters, more southern position of the Angola Benguela Frontal Zone, increased mass

Seismic structure of the lithosphere beneath NW Namibia: Impact of the Tristan da Cunha mantle plume

Science.gov (United States)

Yuan, Xiaohui; Heit, Benjamin; Brune, Sascha; Steinberger, Bernhard; Geissler, Wolfram H.; Jokat, Wilfried; Weber, Michael

2017-01-01

Northwestern Namibia, at the landfall of the Walvis Ridge, was affected by the Tristan da Cunha mantle plume during continental rupture between Africa and South America, as evidenced by the presence of the Etendeka continental flood basalts. Here we use data from a passive-source seismological network to investigate the upper mantle structure and to elucidate the Cretaceous mantle plume-lithosphere interaction. Receiver functions reveal an interface associated with a negative velocity contrast within the lithosphere at an average depth of 80 km. We interpret this interface as the relic of the lithosphere-asthenosphere boundary (LAB) formed during the Mesozoic by interaction of the Tristan da Cunha plume head with the pre-existing lithosphere. The velocity contrast might be explained by stagnated and "frozen" melts beneath an intensively depleted and dehydrated peridotitic mantle. The present-day LAB is poorly visible with converted waves, indicating a gradual impedance contrast. Beneath much of the study area, converted phases of the 410 and 660 km mantle transition zone discontinuities arrive 1.5 s earlier than in the landward plume-unaffected continental interior, suggesting high velocities in the upper mantle caused by a thick lithosphere. This indicates that after lithospheric thinning during continental breakup, the lithosphere has increased in thickness during the last 132 Myr. Thermal cooling of the continental lithosphere alone cannot produce the lithospheric thickness required here. We propose that the remnant plume material, which has a higher seismic velocity than the ambient mantle due to melt depletion and dehydration, significantly contributed to the thickening of the mantle lithosphere.

Hydrogeological modeling constraints provided by geophysical and geochemical mapping of a chlorinated ethenes plume in northern France

Science.gov (United States)

Razafindratsima, Stephen; Guérin, Roger; Bendjoudi, Hocine; de Marsily, Ghislain

2014-09-01

A methodological approach is described which combines geophysical and geochemical data to delineate the extent of a chlorinated ethenes plume in northern France; the methodology was used to calibrate a hydrogeological model of the contaminants' migration and degradation. The existence of strong reducing conditions in some parts of the aquifer is first determined by measuring in situ the redox potential and dissolved oxygen, dissolved ferrous iron and chloride concentrations. Electrical resistivity imaging and electromagnetic mapping, using the Slingram method, are then used to determine the shape of the pollutant plume. A decreasing empirical exponential relation between measured chloride concentrations in the water and aquifer electrical resistivity is observed; the resistivity formation factor calculated at a few points also shows a major contribution of chloride concentration in the resistivity of the saturated porous medium. MODFLOW software and MT3D99 first-order parent-daughter chain reaction and the RT3D aerobic-anaerobic model for tetrachloroethene (PCE)/trichloroethene (TCE) dechlorination are finally used for a first attempt at modeling the degradation of the chlorinated ethenes. After calibration, the distribution of the chlorinated ethenes and their degradation products simulated with the model approximately reflects the mean measured values in the observation wells, confirming the data-derived image of the plume.

Flow and fracture in water-saturated, unconstrained granular beds

Directory of Open Access Journals (Sweden)

Germán eVaras

2015-06-01

Full Text Available The injection of gas in a liquid-saturated granular bed gives rise to a wide variety of invasion patterns. Many studies have focused on constrained porous media, in which the grains are fixed in the bed and only the interstitial fluid flows when the gas invades the system. With a free upper boundary, however, the grains can be entrained by the ascending gas or fluid motion, and the competition between the upward motion of grains and sedimentation leads to new patterns. We propose a brief review of the experimental investigation of the dynamics of air rising through a water-saturated, unconstrained granular bed, in both two and three dimensions. After describing the invasion pattern at short and long time, a tentative regime-diagram is proposed. We report original results showing a dependence of the fluidized zone shape, at long times, on the injection flow rate and grain size. A method based on image analysis makes it possible to detect not only the fluidized zone profile in the stationary regime, but also to follow the transient dynamics of its formation. Finally, we describe the degassing dynamics inside the fluidized zone, in the stationary regime. Depending on the experimental conditions, regular bubbling, continuous degassing, intermittent regime or even spontaneous flow-to-fracture transition are observed.

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

Thermal Plumes in Ventilated Rooms

DEFF Research Database (Denmark)

Kofoed, Peter; Nielsen, Peter V.

The design of a displacement ventilation system involves determination of the flow rate in the thermal plumes. The flow rate in the plumes and the vertical temperature gradient influence each other, and they are influenced by many factors. This paper shows some descriptions of these effects....

Deciduous Forest Zone of Ghana

African Journals Online (AJOL)

carbon, nitrogen and phosphorus contents, soil reaction and base saturation with highest values in the topsoil due to the .... These soils occur extensively in the. Zone ... tion with 6M sulphuric acid. .... which will lead to removal of topsoil litter,.

Galileo observations of volcanic plumes on Io

Science.gov (United States)

Geissler, P.E.; McMillan, M.T.

2008-01-01

Io's volcanic plumes erupt in a dazzling variety of sizes, shapes, colors and opacities. In general, the plumes fall into two classes, representing distinct source gas temperatures. Most of the Galileo imaging observations were of the smaller, more numerous Prometheus-type plumes that are produced when hot flows of silicate lava impinge on volatile surface ices of SO2. Few detections were made of the giant, Pele-type plumes that vent high temperature, sulfur-rich gases from the interior of Io; this was partly because of the insensitivity of Galileo's camera to ultraviolet wavelengths. Both gas and dust spout from plumes of each class. Favorably located gas plumes were detected during eclipse, when Io was in Jupiter's shadow. Dense dust columns were imaged in daylight above several Prometheus-type eruptions, reaching heights typically less than 100 km. Comparisons between eclipse observations, sunlit images, and the record of surface changes show that these optically thick dust columns are much smaller in stature than the corresponding gas plumes but are adequate to produce the observed surface deposits. Mie scattering calculations suggest that these conspicuous dust plumes are made up of coarse grained “ash” particles with radii on the order of 100 nm, and total masses on the order of 106 kg per plume. Long exposure images of Thor in sunlight show a faint outer envelope apparently populated by particles small enough to be carried along with the gas flow, perhaps formed by condensation of sulfurous “snowflakes” as suggested by the plasma instrumentation aboard Galileo as it flew through Thor's plume [Frank, L.A., Paterson, W.R., 2002. J. Geophys. Res. (Space Phys.) 107, doi:10.1029/2002JA009240. 31-1]. If so, the total mass of these fine, nearly invisible particles may be comparable to the mass of the gas, and could account for much of Io's rapid resurfacing.

Rise of a cold plume

International Nuclear Information System (INIS)

Kakuta, Michio

1977-06-01

The rise of smoke from the stacks of two research reactors in normal operation was measured by photogrametric method. The temperature of effluent gas is less than 20 0 C higher than that of the ambient air (heat emission of the order 10 4 cal s -1 ), and the efflux velocity divided by the wind speed is between 0.5 and 2.8 in all 16 smoke runs. The field data obtained within downwind distance of 150m are compared with those by plume rise formulas presently available. Considering the shape of bending-over plume, the Briggs' formula for 'jet' gives a reasonable explanation of the observed plume rise. (auth.)

PLUME-MoM 1.0: a new 1-D model of volcanic plumes based on the method of moments

Science.gov (United States)

de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

2015-05-01

In this paper a new mathematical model for volcanic plumes, named PlumeMoM, is presented. The model describes the steady-state 1-D dynamics of the plume in a 3-D coordinate system, accounting for continuous variability in particle distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. Proper description of such a multiparticle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of properties of the continuous size-distribution of the particles. This is achieved by formulation of fundamental transport equations for the multiparticle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables investigation of the response of four key output variables (mean and standard deviation (SD) of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and SD) characterizing the pyroclastic mixture at the base of the plume

Ocean acidification and calcium carbonate saturation states in the coastal zone of the West Antarctic Peninsula

NARCIS (Netherlands)

Jones, Elizabeth M.; Fenton, Mairi; Meredith, Michael P.; Clargo, Nicola M.; Ossebaar, Sharyn; Ducklow, Hugh W.; Venables, Hugh J.; de Baar, Henricus

The polar oceans are particularly vulnerable to ocean acidification; the lowering of seawater pH and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide (CO2). High spatial variability in surface water pH and saturation states (Omega) for two biologically-important

Coastal Zone Color Scanner studies

Science.gov (United States)

Elrod, J.

1988-01-01

Activities over the past year have included cooperative work with a summer faculty fellow using the Coastal Zone Color Scanner (CZCS) imagery to study the effects of gradients in trophic resources on coral reefs in the Caribbean. Other research included characterization of ocean radiances specific to an acid-waste plume. Other activities include involvement in the quality control of imagery produced in the processing of the global CZCS data set, the collection of various other data global sets, and the subsequent data comparison and analysis.

Using electrical resistivity tomography to assess the effectiveness of managed aquifer recharge in a salinized coastal aquifer.

Science.gov (United States)

García-Menéndez, Olga; Ballesteros, Bruno J; Renau-Pruñonosa, Arianna; Morell, Ignacio; Mochales, Tania; Ibarra, Pedro I; Rubio, Félix M

2018-01-27

Over 40 years, the detrital aquifer of the Plana de Castellón (Spanish Mediterranean coast) has been subjected to seawater intrusion because of long dry periods combined with intensive groundwater exploitation. Against this backdrop, a managed artificial recharge (MAR) scheme was implemented to improve the groundwater quality. The large difference between the electrical conductivity (EC) of the ambient groundwater (brackish water due to marine intrusion) and the recharge water (freshwater) meant that there was a strong contrast between the resistivities of the brackish water saturated zone and the freshwater saturated zone. Electrical resistivity tomography (ERT) can be used for surveying similar settings to evaluate the effectiveness of artificial recharge schemes. By integrating geophysical data with lithological information, EC logs from boreholes, and hydrochemical data, we can interpret electrical resistivity (ER) with groundwater EC values and so identify freshwater saturated zones. Using this approach, ERT images provided a high-resolution spatial characterization and an accurate picture of the shape and extent of the recharge plume of the MAR site. After 5 months of injection, a freshwater plume with an EC of 400-600 μS/cm had formed that extended 400 m in the W-E direction, 250 m in the N-S direction, and to a depth of 40 m below piezometric level. This study also provides correlations between ER values with different lithologies and groundwater EC values that can be used to support other studies.

Ocean acidification and calcium carbonate saturation states in the coastal zone of the West Antarctic Peninsula

NARCIS (Netherlands)

Jones, E.M.; Fenton, M.; Meredith, M.P.; Clargo, N.M.; Ossebaar, S.; Ducklow, H.W.; Venables, H.J.; De Baar, H.J.W.

2017-01-01

The polar oceans are particularly vulnerable to ocean acidification; the lowering of seawater pH and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide (CO2). High spatial variability in surface water pH and saturation states (Ω) for two biologically-important calcium

Uranium migration in a podzol. The role of colloids in the non-saturated zone and the phreatic water: application to the Landes de Gascogne area

International Nuclear Information System (INIS)

Crancon, P.

2001-01-01

The non-saturated zone of a soil represents the interface between the atmosphere and the phreatic water. The confinement efficiency of the non-saturated zone above the phreatic water depends on the fastness of water transfers and on the type of pollutant transport mechanisms. Uranium (VI) can combine with humid acids to form very stable complexes. The aggregates of the absorbing complex are highly sensible to the variations of the ionic force of the environment. This sensitiveness can be at the origin of a strong remobilization of the colloid humic compounds of the soil, and of their migration towards the underground water. In this situation, the uranium complexed by humic compounds can rapidly migrate in the soil. The comparative reactive transport of the total uranium and its isotopes has been studied in a site, the Landes de Gascogne podzol (SW France), where metallic uranium has been sprinkled on the surface of the soil. The field study has been completed with an experimental column transport study using uranium isotopes tracer techniques. The field study shows that most of uranium is trapped in the very first cm of the soil. However, anomalous high uranium concentrations are observed in underground waters, more than 2 km away from the contaminated areas. This demonstrates that a fast and long distance transport process exists for uranium in the unsaturated zone. In the sandy soil of the study area, natural argillo-humic colloids migrate with the velocity of water but can be delayed when the ionic force of the underground waters increases. It is shown that uranium is strongly linked with the thin grain size fraction ( 233 U allows to discriminate between the uranium transported through the sand in a non-reactive way, and the uranium desorbed from the argillo-humic aggregates and the sand grain coatings. A fast reduction of the ionic force of the environment during the tests shows an important remobilization of uranium from the soil. When the complex relations

A numerical study of the Magellan Plume

Science.gov (United States)

Palma, Elbio D.; Matano, Ricardo P.

2012-05-01

In this modeling study we investigate the dynamical mechanisms controlling the spreading of the Magellan Plume, which is a low-salinity tongue that extends along the Patagonian Shelf. Our results indicate that the overall characteristics of the plume (width, depth, spreading rate, etc.) are primarily influenced by tidal forcing, which manifests through tidal mixing and tidal residual currents. Tidal forcing produces a homogenization of the plume's waters and an offshore displacement of its salinity front. The interaction between tidal and wind-forcing reinforces the downstream and upstream buoyancy transports of the plume. The influence of the Malvinas Current on the Magellan Plume is more dominant north of 50°S, where it increases the along-shelf velocities and generates intrusions of saltier waters from the outer shelf, thus causing a reduction of the downstream buoyancy transport. Our experiments also indicate that the northern limit of the Magellan Plume is set by a high salinity discharge from the San Matias Gulf. Sensitivity experiments show that increments of the wind stress cause a decrease of the downstream buoyancy transport and an increase of the upstream buoyancy transport. Variations of the magnitude of the discharge produce substantial modifications in the downstream penetration of the plume and buoyancy transport. The Magellan discharge generates a northeastward current in the middle shelf, a recirculation gyre south of the inlet and a region of weak currents father north.

Ocean outfall plume characterization using an Autonomous Underwater Vehicle.

Science.gov (United States)

Rogowski, Peter; Terrill, Eric; Otero, Mark; Hazard, Lisa; Middleton, William

2013-01-01

A monitoring mission to map and characterize the Point Loma Ocean Outfall (PLOO) wastewater plume using an Autonomous Underwater Vehicle (AUV) was performed on 3 March 2011. The mobility of an AUV provides a significant advantage in surveying discharge plumes over traditional cast-based methods, and when combined with optical and oceanographic sensors, provides a capability for both detecting plumes and assessing their mixing in the near and far-fields. Unique to this study is the measurement of Colored Dissolved Organic Matter (CDOM) in the discharge plume and its application for quantitative estimates of the plume's dilution. AUV mission planning methodologies for discharge plume sampling, plume characterization using onboard optical sensors, and comparison of observational data to model results are presented. The results suggest that even under variable oceanic conditions, properly planned missions for AUVs equipped with an optical CDOM sensor in addition to traditional oceanographic sensors, can accurately characterize and track ocean outfall plumes at higher resolutions than cast-based techniques.

Role of the unsaturated zone in radioactive and hazardous waste disposal

International Nuclear Information System (INIS)

Mercer, J.W.; Marine, I.W.; Rao, P.S.C.

1983-01-01

The problems of hazardous and low-level radioactive waste disposal caused by the physical and chemical processes active in the unsaturated zone are explored in this book. The focus is on the use of laboratory analyses, field observations, and numerical and analytical calculations to create a clear picture of both problems and potential solutions. Topics include policy modeling, statistical techniques, liners, and field applications. Contents include: Modeling of Moisture Movement through Layered Trench Covers; Role of Partially Saturated Soil in Liner Design for Hazardous Waste Disposal Sites; Field Experiments to Determine Saturated Hydraulic Conductivity in the Vadose Zone; Role of Desaturation on Transport through Fractured Rock; Nuclear Waste Isolation in the Unsaturated Zone of Arid Regions

Prediction uncertainty of plume characteristics derived from a small number of measuring points

Science.gov (United States)

French, H. K.; van der Zee, S. E. A. T. M.; Leijnse, A.

A small number of measuring points may inflict a bias on the characterisation of flow and transport based on field experiments in the unsaturated zone. Simulation of pure advective transport of a Gaussian plume through a setup of 30 regularly placed measuring points revealed regular temporal fluctuations about the real spatial moments. An irregular setup predicted both irregular fluctuations and larger discrepancies from the real value. From these considerations, a regular setup is recommended. Spatial moments were sensitive to the plume size relative to the distance between individual measuring points. To reduce prediction errors of the variance, the distance between the measuring points should be less than twice the standard deviation of the examined plume. The total size of the setup should cover several standard deviations of the plume to avoid mass being lost from the monitored area. Numerical simulations of a dispersing plume (comparing calculations based on 9000 nodes with 30 measuring points) revealed that vertical and horizontal centres of mass were predicted well at all degrees of heterogeneity, and the same was the case for horizontal variances. Vertical variances were more susceptible to prediction errors, but estimates were of the same order of magnitude as the real values. Résumé Lorsque l'on cherche à caractériser l'écoulement et le transport à partir d'expériences de terrain dans la zone saturée, il arrive qu'un petit nombre de points introduisent un biais. La simulation d'un transport purement advectif d'un panache gaussien au travers d'un ensemble de 30 points de mesures espacés régulièrement fait apparaître des variations temporelles régulières autour des moments spatiaux réels. Un ensemble irrégulier conduit à prédire à la fois des variations irrégulières et de plus grandes divergences par rapport à la valeur réelle. A partir de ces constations, un ensemble régulier est recommandé. Les moments spatiaux sont apparus

The evolution of photochemical smog in a power plant plume

Science.gov (United States)

Luria, Menachem; Valente, Ralph J.; Tanner, Roger L.; Gillani, Noor V.; Imhoff, Robert E.; Mueller, Stephen F.; Olszyna, Kenneth J.; Meagher, James F. Present address: Aeronomy Laboratory, NOAA, 325 Broadway, Boulder CO 80303, USA.)

The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism.

The evolution of photochemical smog in a power plant plume

International Nuclear Information System (INIS)

Luria, M.; The Hebrew University, Jerusalem; Valente, R.J.; Tanner, R.L.; Imhoff, R.E.; Mueller, S.F.; Olszyna, K.J.; Meagher, J.F.; Gillani, N.V.; University of Alabama, Huntsville, AL

1999-01-01

The evolution of photochemical smog in a plant plume was investigated with the aid of an instrumented helicopter. Air samples were taken in the plume of the Cumberland Power Plant, located in central Tennessee, during the afternoon of 16 July 1995 as part of the Southern Oxidants Study - Nashville Middle Tennessee Ozone Study. Twelve cross-wind air sampling traverses were made at six distance groups from 35 to 116 km from the source. During the sampling period the winds were from the west-northwest and the plume drifted towards the city of Nashville TN. Ten of the traverses were made upwind of the city, where the power plant plume was isolated, and two traverses downwind of the city when the plumes were possibly mixed. The results revealed that even six hours after the release, excess ozone production was limited to the edges of the plume. Only when the plume was sufficiently dispersed, but still upwind of Nashville, was excess ozone (up to 109 ppbv, 50-60 ppbv above background levels) produced in the center of the plume. The concentrations image of the plume and a Lagrangian particle model suggests that portions of the power plant plume mixed with the urban plume. The mixed urban power plant plume began to regenerate O 3 that peaked at 120 ppbv at a short distance (15-25 km) downwind of Nashville. Ozone productivity (the ratio of excess O 3 to NO y and NO z ) in the isolated plume was significantly lower compared with that found in the city plume. The production of nitrate, a chain termination product, was significantly higher in the power plant plume compared to the mixed plume, indicating shorter chain length of the photochemical smog chain reaction mechanism. (author)

Driver speed limit compliance in school zones : assessing the impact of sign saturation.

Science.gov (United States)

2013-10-01

School zones are often viewed as an effective way to reduce driving speeds and thereby improve : safety near our nations schools. The effect of school zones on reducing driving speeds, however, is : minimal at best. Studies have shown that over 90...

Plume structure in high-Rayleigh-number convection

Science.gov (United States)

Puthenveettil, Baburaj A.; Arakeri, Jaywant H.

2005-10-01

Near-wall structures in turbulent natural convection at Rayleigh numbers of 10^{10} to 10^{11} at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR= 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. the mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log normal probability distribution function, independent of the rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-rayleigh-number turbulent natural convection are likely to be laminar mixed convection type.

3-D spectral IP imaging: Non-invasive characterization of contaminant plumes. 1998 annual progress report

International Nuclear Information System (INIS)

Lesmes, D.; Morgan, F.D.; Rodi, W.

1998-01-01

'The overall objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth''s subsurface using field measurements of induced polarization (IP) effects. Three specific objectives towards this end are: (1) understanding IP at the laboratory level through measurements of complex resistivity as a function of frequency in rock and soil samples with varying pore geometries, pore fluid conductivities and saturations, and contaminant chemistries and concentrations; (2) developing effective data acquisition techniques for measuring the critical IP responses (time domain or frequency domain) in the field; (3) developing modeling and inversion algorithms that permit the interpretation of field IP data in terms of subsurface geology and contaminant plume properties. The authors laboratory experiments to date are described in Appendices A and B, which consist of two papers submitted to the annual SAGEEP conference (Frye et al., 1998; Sturrock et al., 1998). The experiments involved measurements of complex resistivity vs. frequency on a suite of brine saturated sandstone samples. In one set of experiments, the fluid chemistry (pH, ionic strength, and cation type) was varied. In a second set of experiments, the microgeometry of the rock matrix was varied. The experiments showed that spectral IP responses are sensitive to subtle variations in both the solution chemistry and rock microgeometry. The results demonstrate that spectral IP responses have the potential of being sensitive indicators of in-situ chemistry and microgeometry, the latter of which may be related to the hydraulic properties. Data Acquisition The authors have been looking in some detail at the effects of electromagnetic coupling and how to practically deal with it. In this area, the results to date are summarized in Vandiver (1998). The progress in the development of modeling and inversion algorithms for IP is described in Appendix C, a paper submitted to the

FLASH: A finite element computer code for variably saturated flow

International Nuclear Information System (INIS)

Baca, R.G.; Magnuson, S.O.

1992-05-01

A numerical model was developed for use in performance assessment studies at the INEL. The numerical model, referred to as the FLASH computer code, is designed to simulate two-dimensional fluid flow in fractured-porous media. The code is specifically designed to model variably saturated flow in an arid site vadose zone and saturated flow in an unconfined aquifer. In addition, the code also has the capability to simulate heat conduction in the vadose zone. This report presents the following: description of the conceptual frame-work and mathematical theory; derivations of the finite element techniques and algorithms; computational examples that illustrate the capability of the code; and input instructions for the general use of the code. The FLASH computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of Energy Order 5820.2A

Delineation of contaminant plume for an inorganic contaminated site using electrical resistivity tomography: comparison with direct-push technique.

Science.gov (United States)

Liao, Qing; Deng, Yaping; Shi, Xiaoqing; Sun, Yuanyuan; Duan, Weidong; Wu, Jichun

2018-03-03

Precise delineation of contaminant plume distribution is essential for effective remediation of contaminated sites. Traditional in situ investigation methods like direct-push (DP) sampling are accurate, but are usually intrusive and costly. Electrical resistivity tomography (ERT) method, as a non-invasive geophysical technique to map spatiotemporal changes in resistivity of the subsurface, is becoming increasingly popular in environmental science. However, the resolution of ERT for delineation of contaminant plumes still remains controversial. In this study, ERT and DP technique were both conducted at a real inorganic contaminated site. The reliability of the ERT method was validated by the direct comparisons of their investigation results that the resistivity acquired by ERT method is in accordance with the total dissolved solid concentration in groundwater and the overall variation of the total iron content in soil obtained by DP technique. After testifying the applicability of ERT method for contaminant identification, the extension of contaminant plume at the study site was revealed by supplementary ERT surveys conducted subsequently in the surrounding area of the contaminant source zone.

DSMC Simulations of Io's Pele Plume

Science.gov (United States)

McDoniel, William; Goldstein, D.; Varghese, P.; Trafton, L.

2012-10-01

Io’s Pele plume rises over 300km in altitude and leaves a deposition ring 1200km across on the surface of the moon. Material emerges from an irregularly-shaped vent, and this geometry gives rise to complex 3D flow features. The Direct Simulation Monte Carlo method is used to model the gas flow in the rarefied plume, demonstrating how the geometry of the source region is responsible for the asymmetric structure of the deposition ring and illustrating the importance of very small-scale vent geometry in explaining large observed features of interest. Simulations of small particles in the plume and comparisons to the black “butterfly wings” seen at Pele are used to constrain particle sizes and entrainment mechanisms. Preliminary results for the effects of plasma energy and momentum transfer to the plume will also be presented.

Cage-rotor induction motor inter-turn short circuit fault detection with and without saturation effect by MEC model.

Science.gov (United States)

Naderi, Peyman

2016-09-01

The inter-turn short fault for the Cage-Rotor-Induction-Machine (CRIM) is studied in this paper and its local saturation is taken into account. However, in order to observe the exact behavior of machine, the Magnetic-Equivalent-Circuit (MEC) and nonlinear B-H curve are proposed to provide an insight into the machine model and saturation effect respectively. The electrical machines are generally operated near to their saturation zone due to some design necessities. Hence, when the machine is exposed to a fault such as short circuit or eccentricities, it is operated within its saturation zone and thus, time and space harmonics are integrated and as a result, current and torque harmonics are generated which the phenomenon cannot be explored when saturation is dismissed. Nonetheless, inter-turn short circuit may lead to local saturation and this occurrence is studied in this paper using MEC model. In order to achieve the mentioned objectives, two and also four-pole machines are modeled as two samples and the machines performances are analyzed in healthy and faulty cases with and without saturation effect. A novel strategy is proposed to precisely detect inter-turn short circuit fault according to the stator׳s lines current signatures and the accuracy of the proposed method is verified by experimental results. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Simulating Fine-Scale Marine Pollution Plumes for Autonomous Robotic Environmental Monitoring

Directory of Open Access Journals (Sweden)

Muhammad Fahad

2018-05-01

Full Text Available Marine plumes exhibit characteristics such as intermittency, sinuous structure, shape and flow field coherency, and a time varying concentration profile. Due to the lack of experimental quantification of these characteristics for marine plumes, existing work often assumes marine plumes exhibit behavior similar to aerial plumes and are commonly modeled by filament based Lagrangian models. Our previous field experiments with Rhodamine dye plumes at Makai Research Pier at Oahu, Hawaii revealed that marine plumes show similar characteristics to aerial plumes qualitatively, but quantitatively they are disparate. Based on the field data collected, this paper presents a calibrated Eulerian plume model that exhibits the qualitative and quantitative characteristics exhibited by experimentally generated marine plumes. We propose a modified model with an intermittent source, and implement it in a Robot Operating System (ROS based simulator. Concentration time series of stationary sampling points and dynamic sampling points across cross-sections and plume fronts are collected and analyzed for statistical parameters of the simulated plume. These parameters are then compared with statistical parameters from experimentally generated plumes. The comparison validates that the simulated plumes exhibit fine-scale qualitative and quantitative characteristics similar to experimental plumes. The ROS plume simulator facilitates future evaluations of environmental monitoring strategies by marine robots, and is made available for community use.

Reservoir Characterization and CO2 Plume Migration Modeling Based on Bottom-hole Pressure Data: An Example from the AEP Mountaineer Geological Storage Project

Science.gov (United States)

Mishra, Srikanta; Kelley, Mark; Oruganti, YagnaDeepika; Bhattacharya, Indra; Spitznogle, Gary

2014-05-01

We present an integrated approach for formation permeability estimation, front tracking, reservoir model calibration, and plume migration modeling based on injection rate and down-hole pressure data from CO2 geologic sequestration projects. The data are taken from the 20 MW CO2 capture and storage project at American Electric Power's Mountaineer Plant in West Virginia, USA. The Mountaineer CO2 injection system consists of two injection wells - one in the Copper Ridge Dolomite formation and one in the Rose Run sandstone formation, and three deep observation wells that were operational between October 2009 and May 2011. Approximately 27000 MT and 10000 MT were injected into the Copper Ridge dolomite formation and Rose Run sandstone formation, respectively. A wealth of pressure and rate data from injection and observation wells is available covering a series of injection and pressure falloff events. The methodology developed and applied for interpreting and integrating the data during reservoir analysis and modeling from the Rose Run formation is the subject of this paper. For the analysis of transient pressure data at the injection and observation wells, the CO2 storage reservoir is conceptualized as a radial composite system, where the inner (invaded) zone consists of both supercritical CO2 and brine, and the outer (uninvaded) zone consists of undisturbed brine. Using established analytical solutions for analyzing fluid injection problems in the petroleum reservoir engineering literature, we show how the late-time pressure derivative response from both injection and observation wells will be identical - reflecting the permeability-thickness product of the undisturbed brine-filled formation. We also show how the expanding CO2 plume affects the "effective" compressibility that can be estimated by history matching injection-falloff data and how this can be used to develop a relationship between the plume radius and "effective" compressibility. This provides a novel non

Determination of residual oil saturation from time-lapse pulsed neutron capture logs in a large sandstone reservoir

International Nuclear Information System (INIS)

Syed, E.V.; Salaita, G.N.; McCaffery, F.G.

1991-01-01

Cased hole logging with pulsed neutron tools finds extensive use for identifying zones of water breakthrough and monitoring oil-water contacts in oil reservoirs being depleted by waterflooding or natural water drive. Results of such surveys then find direct use for planning recompletions and water shutoff treatments. Pulsed neutron capture (PNC) logs are useful for estimating water saturation changes behind casing in the presence of a constant, high-salinity environment. PNC log surveys run at different times, i.e., in a time-lapse mode, are particularly amenable to quantitative analysis. The combined use of the original open hole and PNC time-lapse log information can then provide information on remaining or residual oil saturations in a reservoir. This paper reports analyses of historical pulsed neutron capture log data to assess residual oil saturation in naturally water-swept zones for selected wells from a large sandstone reservoir in the Middle East. Quantitative determination of oil saturations was aided by PNC log information obtained from a series of tests conducted in a new well in the same field

Analysis of dissolved benzene plumes and methyl tertiary butyl ether (MTBE) plumes in ground water at leaking underground fuel tank (LUFT) sites

International Nuclear Information System (INIS)

Happel, A.M.; Rice, D.; Beckenbach, E.; Savalin, L.; Temko, H.; Rempel, R.; Dooher, B.

1996-11-01

The 1990 Clean Air Act Amendments mandate the addition of oxygenates to gasoline products to abate air pollution. Currently, many areas of the country utilize oxygenated or reformulated fuel containing 15- percent and I I-percent MTBE by volume, respectively. This increased use of MTBE in gasoline products has resulted in accidental point source releases of MTBE containing gasoline products to ground water. Recent studies have shown MTBE to be frequently detected in samples of shallow ground water from urban areas throughout the United States (Squillace et al., 1995). Knowledge of the subsurface fate and transport of MTBE in ground water at leaking underground fuel tank (LUFT) sites and the spatial extent of MTBE plumes is needed to address these releases. The goal of this research is to utilize data from a large number of LUFT sites to gain insights into the fate, transport, and spatial extent of MTBE plumes. Specific goals include defining the spatial configuration of dissolved MTBE plumes, evaluating plume stability or degradation over time, evaluating the impact of point source releases of MTBE to ground water, and attempting to identify the controlling factors influencing the magnitude and extent of the MTBE plumes. We are examining the relationships between dissolved TPH, BTEX, and MTBE plumes at LUFT sites using parallel approaches of best professional judgment and a computer-aided plume model fitting procedure to determine plume parameters. Here we present our initial results comparing dissolved benzene and MTBE plumes lengths, the statistical significance of these results, and configuration of benzene and MTBE plumes at individual LUFT sites

Lu-Hf isotope constraints on plume-lithosphere interaction during emplacement of the Bushveld Large Igneous Province at 2.06 Ga: Implications for the structure and evolution of the Kaapvaal Craton's lithospheric mantle

Science.gov (United States)

Zirakparvar, N. A.; Mathez, E. A.; Rajesh, H.; Vervoort, J. D.; Choe, S.

2016-12-01

The Bushveld Large Igneous Province (B-LIP) comprises a diverse array of >30 magma bodies that intruded the Kaapvaal Craton at 2.06 Ga. In this talk we use zircon and bulk-rock Lu-Hf isotope data to show that the B-LIP formed in response to the arrival of a plume(s) from the deep mantle. New zircon Hf isotope compositions for four B-LIP bodies yield intrusion-specific average ɛHf (2.06 Ga) values that range from -20.7 ± 2.8 to -2.7 ± 2.8, largely consistent with literature zircon data for other B-LIP intrusions. Bulk-rock solution ɛHf (2.06 Ga) values for a variety of B-LIP intrusions range from -2.1 ± 0.2 to -10.6 ± 0.2. Because the most radiogenic Hf isotope compositions across the entire B-LIP are nearly primordial with an ɛHf (2.06 Ga) close to 0, it is likely that the heat source of the B-LIP was a plume(s) from deep mantle. The Hf isotope data further suggests that individual intrusions in the B-LIP can be grouped into four categories based on their ultimate sources: 1) melts generated in subduction and plume modified continental lithospheric mantle; 2) melts generated by melting of a mafic-ultramafic reservoir composed of older ( 2.7 Ga) plume-related material trapped in the Kaapvaal lithosphere; 3) melts generated in the mid- to upper crust; and 4) melts generated from the 2.06 Ga mantle plume itself. The presence of 2.7 Ga mafic-ultramafic material in the Kaapvaal lithosphere may have acted to strengthen the lithosphere so that it was able to resist being dispered by the arrival of the B-LIP plume at 2.06 Ga. Because the B-LIP extends into a 2.7 Ga aged suture zone between the Kaapvaal and Zimbabwe cratons, it is also possible to understand the role of the lithospheric mantle in producing the Lu-Hf signatures observed in the various B-LIP intrusions as a function of two different types of the continental lithosphere: The very old lithosphere comprising the Kaapvaal Craton and the somewhat younger lithosphere comprising the suture zone. A basic

Identification and assessment of water pollution as a consequence of a leachate plume migration from a municipal landfill site (Tucumán, Argentina).

Science.gov (United States)

Fernández, Diego S; Puchulu, María E; Georgieff, Sergio M

2014-06-01

Landfills constitute potential sources of different pollutants that could generate human health and environmental problems. While some landfills currently work under the protection of a bottom liner with leachate collection, it was demonstrated that migration could take place even yet with these cautions. The purpose of this paper is to assess the pollution caused by a leachate plume from a municipal landfill that is affecting both groundwater and surface waters. The research was carried out at Pacará Pintado landfill in northwestern Argentina. Analysis of water samples indicates that leachate is affecting groundwater under the landfill area and an abandoned river channel hydraulically connected. In the center of the landfill area, the plume is anoxic and sulfate, nitrate, iron and manganese reduction zones were identified. Leachate plume presented high concentration of organic matter, Fe, Mn, NH(4)(+), Cl(-) and Cr reaching an extension of 900 m. The presence of a leachate plume in a landfill site with a single liner system implies that the use of this groundwater pollution control method alone is not enough especially if permeable sediments are present below.

Follow the plume: the habitability of Enceladus.

Science.gov (United States)

McKay, Christopher P; Anbar, Ariel D; Porco, Carolyn; Tsou, Peter

2014-04-01

The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost flyby mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus mission are more advanced than for any other Solar System body. The goals of such a mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved in situ investigations and a sample return.

The Late Jurassic Panjeh submarine volcano in the northern Sanandaj-Sirjan Zone, northwest Iran: Mantle plume or active margin?

Science.gov (United States)

Azizi, Hossein; Lucci, Federico; Stern, Robert J.; Hasannejad, Shima; Asahara, Yoshihiro

2018-05-01

The tectonic setting in which Jurassic igneous rocks of the Sanandaj-Sirjan Zone (SaSZ) of Iran formed is controversial. SaSZ igneous rocks are mainly intrusive granodiorite to gabbroic bodies, which intrude Early to Middle Jurassic metamorphic basement; Jurassic volcanic rocks are rare. Here, we report the age and petrology of volcanic rocks from the Panjeh basaltic-andesitic rocks complex in the northern SaSZ, southwest of Ghorveh city. The Panjeh magmatic complex consists of pillowed and massive basalts, andesites and microdioritic dykes and is associated with intrusive gabbros; the overall sequence and relations with surrounding sediments indicate that this is an unusually well preserved submarine volcanic complex. Igneous rocks belong to a metaluminous sub-alkaline, medium-K to high-K calc-alkaline mafic suite characterized by moderate Al2O3 (13.7-17.6 wt%) and variable Fe2O3 (6.0-12.6 wt%) and MgO (0.9-11.1 wt%) contents. Zircon U-Pb ages (145-149 Ma) define a Late Jurassic (Tithonian) age for magma crystallization and emplacement. Whole rock compositions are enriched in Th, U and light rare earth elements (LREEs) and are slightly depleted in Nb, Ta and Ti. The initial ratios of 87Sr/86Sr (0.7039-0.7076) and εNd(t) values (-1.8 to +4.3) lie along the mantle array in the field of ocean island basalts and subcontinental metasomatized mantle. Immobile trace element (Ti, V, Zr, Y, Nb, Yb, Th and Co) behavior suggests that the mantle source was enriched by fluids released from a subducting slab (i.e. deep-crustal recycling) with some contribution from continental crust for andesitic rocks. Based the chemical composition of Panjeh mafic and intermediate rocks in combination with data for other gabbroic to dioritic bodies in the Ghorveh area we offer two interpretations for these (and other Jurassic igneous rocks of the SaSZ) as reflecting melts from a) subduction-modified OIB-type source above a Neo-Tethys subduction zone or b) plume or rift tectonics involving

Contrasting Inherent Optical Properties and Carbon Metabolism Between Five Northeastern (USA) Estuary-plume Systems

Science.gov (United States)

Vandemark, Doug; Salisbury, Joe; Hunt, Chris; McGillis, Wade R.

2004-01-01

We have recently developed the ability to rapidly assess Surface inherent optical properties (IOP), oxygen concentration and pCO2 in estuarine-plume systems using flow-through instrumentation. During the summer of 2004, several estuarine-plume systems were surveyed which include the Pleasant (ME), Penobscot (ME), Kennebec-Androscoggin (ME), Merrimack (NH-MA) and Hudson (NY). Continuous measurements of surface chlorophyll and colored dissolved organic carbon (CDOM) fluorescence, beam attenuation, temperature, salinity, oxygen and pC02 were taken at each system along a salinity gradient from fresh water to near oceanic endmembers. CTD and IOP profiles were also taken at predetermined surface salinity intervals. These were accompanied by discrete determinations of chlorophyll (HPLC and fluorometric), total suspended solids (TSS), dissolved organic carbon (DOC) and alkalinity. IOP data were calibrated using chlorophyll, DOC and TSS data to enable the retrieval of these constituents from IOP data. Considerable differences in the data sets were observed between systems. These ranged from the DOC-enriched, strongly heterotrophic Pleasant River System to the high-chlorophyll autotrophic Merrimack River System. Using pCO2 and oxygen saturation measurements as proxies for water column metabolism, distinct relationships were found between trophic status and inherent optical properties. The nature of these relationships varies between systems and is likely a function of watershed and estuarine attributes including carbon and nutrient loading, in-situ production and related autochthonous inputs of DOC and alkalinity. Our results suggest that IOP data may contain significant information about the trophic status of estuarine and plume systems.

A new method for calculating gas saturation of low-resistivity shale gas reservoirs

Directory of Open Access Journals (Sweden)

Jinyan Zhang

2017-09-01

Full Text Available The Jiaoshiba shale gas field is located in the Fuling area of the Sichuan Basin, with the Upper Ordovician Wufeng–Lower Silurian Longmaxi Fm as the pay zone. At the bottom of the pay zone, a high-quality shale gas reservoir about 20 m thick is generally developed with high organic contents and gas abundance, but its resistivity is relatively low. Accordingly, the gas saturation calculated by formulas (e.g. Archie using electric logging data is often much lower than the experiment-derived value. In this paper, a new method was presented for calculating gas saturation more accurately based on non-electric logging data. Firstly, the causes for the low resistivity of shale gas reservoirs in this area were analyzed. Then, the limitation of traditional methods for calculating gas saturation based on electric logging data was diagnosed, and the feasibility of the neutron–density porosity overlay method was illustrated. According to the response characteristics of neutron, density and other porosity logging in shale gas reservoirs, a model for calculating gas saturation of shale gas was established by core experimental calibration based on the density logging value, the density porosity and the difference between density porosity and neutron porosity, by means of multiple methods (e.g. the dual-porosity overlay method by optimizing the best overlay coefficient. This new method avoids the effect of low resistivity, and thus can provide normal calculated gas saturation of high-quality shale gas reservoirs. It works well in practical application. This new method provides a technical support for the calculation of shale gas reserves in this area. Keywords: Shale gas, Gas saturation, Low resistivity, Non-electric logging, Volume density, Compensated neutron, Overlay method, Reserves calculation, Sichuan Basin, Jiaoshiba shale gas field

Birth, life, and death of a solar coronal plume

Energy Technology Data Exchange (ETDEWEB)

Pucci, Stefano; Romoli, Marco [Department of Physics and Astronomy, University of Firenze, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Poletto, Giannina [INAF-Arcetri Astrophysical Observatory, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Sterling, Alphonse C., E-mail: stpucci@arcetri.astro.it [Space Science Office, NASA/MSFC, Huntsville, AL 35812 (United States)

2014-10-01

We analyze a solar polar-coronal-hole (CH) plume over its entire ≈40 hr lifetime, using high-resolution Solar Dynamic Observatory Atmospheric Imaging Assembly (AIA) data. We examine (1) the plume's relationship to a bright point (BP) that persists at its base, (2) plume outflows and their possible contribution to the solar wind mass supply, and (3) the physical properties of the plume. We find that the plume started ≈2 hr after the BP first appeared and became undetectable ≈1 hr after the BP disappeared. We detected radially moving radiance variations from both the plume and from interplume regions, corresponding to apparent outflow speeds ranging over ≈(30-300) km s{sup –1} with outflow velocities being higher in the 'cooler' AIA 171 Å channel than in the 'hotter' 193 Å and 211 Å channels, which is inconsistent with wave motions; therefore, we conclude that the observed radiance variations represent material outflows. If they persist into the heliosphere and plumes cover ≈10% of a typical CH area, these flows could account for ≈50% of the solar wind mass. From a differential emission measure analysis of the AIA images, we find that the average electron temperature of the plume remained approximately constant over its lifetime, at T {sub e} ≈ 8.5 × 10{sup 5} K. Its density, however, decreased with the age of the plume, being about a factor of three lower when the plume faded compared to when it was born. We conclude that the plume died due to a density reduction rather than to a temperature decrease.

Multi-pollutant interactions in hyporheic zones

Science.gov (United States)

Krause, S.; Weatherill, J.; Bonet, B.; Blaen, P.; Khamis, K.; Cassidy, N. J.; Hannah, D. M.; Rivett, M. O.; Lynch, I.; Ullah, S.

2017-12-01

Hyporheic zones represent hotspots of biogeochemical reactivity, with the potential to attenuate pollutants and ameliorate their impact on ecosystem functioning. Sources and types of pollutants in streambed environments are manifold, with legacy industry contaminants, agricultural pollution and emerging pollutants such as pharmaceuticals or engineered nanoparticles entering hyporheic zones along different flow paths where they mix and potentially react with each other. Current conceptualizations of drivers and controls of biogeochemical turnover in hyporheic zones highlight primarily the role of transport and reaction times but do not account for potential interactions between different pollutants. This study presents two case studies of multi-pollutant interactions to illustrate the need to consider interferences between different pollutants, their transport and reaction pathways for adequate impact assessment. We discuss in the first instance how the natural attenuation of a Trichloroethylene (TCE) groundwater plume in an agricultural catchment is limited by high riparian and hyporheic nitrate concentrations. As nitrate outcompeted TCE in its reaction with organic carbon as electron donor, TCE attenuation was in this case limited to hyporheic denitrification hotspots. Hence any pollution control measures to reduce the impact of this TCE plume require a reduction of agricultural nitrate loads, highlighting the connectedness of legacy (TCE) and more recent (nitrate) pollution problems. In the second case, we investigate how the labile organic carbon content of streambed sediments as main control of hyporheic respiration is overridden by exposure to different silver nanoparticle concentrations, representing emerging pollutants in many of our rivers. Also in this case, the impacts of different stressors (nanoparticle exposure) and drivers (availability of organic matter, water temperature) are interacting in their impacts on hyporheic zone functioning. We argue that

Synthesis of Fe3O4 nanostructures by backward plume deposition and influence of ambient gas pressure on their morphology

International Nuclear Information System (INIS)

Lin, J J; Mahmood, S; Zhang, T; Hassan, S M; White, T; Ramanujan, R V; Lee, P; Rawat, R S

2007-01-01

Iron oxide nanostructures with significantly fewer droplets were successfully synthesized by pulsed laser deposition using a special target-substrate geometry, which is coined backward plume deposition. The morphology of deposited nanostructures for backward plume deposition is found to be strongly controlled by the ambient gas pressure and changes from a thin film to an assemble of nanoclusters to nanoclusters with loosely bound floccule-like network with the increase in ambient gas pressure. The post-annealing considerably changes the structural properties of deposited materials, which were determined to be magnetite FCC-Fe 3 O 4 . It also causes the relaxation of long range stress in the film and hence leads to an increase in the saturation magnetization. The coercivity is found to decrease upon annealing due to the growth of randomly oriented Fe 3 O 4 nanocrystallite as well as the relaxation of internal stress

Multi-temporal dynamics of suspended particulate matter in a macro-tidal river Plume (the Gironde) as observed by satellite data

Science.gov (United States)

Constantin, Sorin; Doxaran, David; Derkacheva, Anna; Novoa, Stéfani; Lavigne, Héloïse

2018-03-01

The Gironde River plume area is unique in terms of Suspended Particulate Matter (SPM) dynamics. Multiple factors contribute to the variations of SPM at multiple time scales, from river outputs to wind stress, currents and tidal cycles. The formation and evolution of the Maximum Turbidity Zone (MTZ) inside the estuary also plays a significant role. Thus, detailed analyses and monitoring of the region is important for better understanding the mechanisms governing the turbid plume dynamics, for proper future management and monitoring of SPM export from the estuary to the coastal ocean. In this study we use an unprecedented volume of satellite data to capture and better understand the dynamics of the river plume. We combine two types of satellite information in order to achieve these goals: data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Spinning Enhanced Visible and Infrared Imager (SEVIRI) sensors. The integrated information allows accounting for multiple time scales, i.e. from seasonal to diurnal cycles. We show and parameterize the overall effects of river discharge rates over the plume extension. Seasonal variations are also analyzed and an overall relationship between river discharge rates and plume magnitude is computed. For the first time, we clearly observe and explain the diurnal cycle of SPM dynamics in the river plume. Despite the limited capabilities of the SEVIRI sensor, geostationary data was successfully used to derive such information and results similar to in-situ datasets were obtained. The same patterns are observed, with significant increase in SPM plume during spring/ebb tide periods. Results from our study can be further used to refine sediment transport models and to gain a better perspective on the ecological implications of the sediment output in the continental shelf area.

Smoke plumes: Emissions and effects

Science.gov (United States)

Susan O' Neill; Shawn Urbanski; Scott Goodrick; Sim Larkin

2017-01-01

Smoke can manifest itself as a towering plume rising against the clear blue sky-or as a vast swath of thick haze, with fingers that settle into valleys overnight. It comes in many forms and colors, from fluffy and white to thick and black. Smoke plumes can rise high into the atmosphere and travel great distances across oceans and continents. Or smoke can remain close...

Evapotranspiration And Geochemical Controls On Groundwater Plumes At Arid Sites: Toward Innovative Alternate End-States For Uranium Processing And Tailings Facilities

International Nuclear Information System (INIS)

Looney, Brian B.; Denham, Miles E.; Eddy-Dilek, Carol A.; Millings, Margaret R.; Kautsky, Mark

2014-01-01

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 and 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 and 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

New Age and Geochemical Data From Seamounts in the Canary and Madeira Volcanic Provinces: A Contribution to the "Great Plume Debate"

Science.gov (United States)

Geldmacher, J.; Hoernle, K.; van den Bogaard, P.; Duggen, S.; Werner, R.

2004-12-01

The role of hotspots (mantle plumes) in the formation of intraplate volcanic island and seamount groups is being increasingly questioned, in particular concerning the abundant and somewhat irregularly distributed island and seamount volcanoes off the coast of northwest Africa. However, new 40Ar/39Ar ages and Sr-Nd-Pb isotope geochemistry of volcanic rocks from two seamounts northeast of the Canary Islands and two northeast of the Madeira Islands provide new support for the plume hypothesis. The oldest ages of shield stage volcanism from seamounts and islands northeast of the Canary and Madeira Islands confirm progressions of increasing age to the northeast for both island/seamount chains consistent with northeast directed plate motion. Calculated angular velocities for the average movement of the African plate in both regions gave similar values of about 0.45\\deg plus/minus 0.05\\deg/Ma around a rotation pole located north of the Azores Islands. Furthermore, the curvature of the chains clearly deviates from the E-W orientation of fracture zones in the East Atlantic. A local control of surface volcanism by lithospheric zones of weakness, however, is likely for some E-W elongated seamounts and islands. The isotope geochemistry additionally confirms that the two volcanic provinces are derived from distinct sources, consistent with distinct mantle plumes having formed both volcanic groups. Conventional hotspot models, however, cannot easily explain the wide distribution of seamounts in the Canary region and the long history of volcanic activity at single volcanic centers (e.g. Dacia seamount, 47-4 Ma; Selvagen Islands, 30-3 Ma). A possible explanation could involve interaction of a Canary mantle plume with small-scale upper mantle processes such as edge driven convection at the edge of the NW African craton (e.g. King and Ritsema, 2000, Science 290, 1137-1140).

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.

Plume Splitting in a Two-layer Stratified Ambient Fluid

Science.gov (United States)

Ma, Yongxing; Flynn, Morris; Sutherland, Bruce

2017-11-01

A line-source plume descending into a two-layer stratified ambient fluid in a finite sized tank is studied experimentally. Although the total volume of ambient fluid is fixed, lower- and upper-layer fluids are respectively removed and added at a constant rate mimicking marine outfall through diffusers and natural and hybrid ventilated buildings. The influence of the plume on the ambient depends on the value of λ, defined as the ratio of the plume buoyancy to the buoyancy loss of the plume as it crosses the ambient interface. Similar to classical filling-box experiments, the plume can always reach the bottom of the tank if λ > 1 . By contrast, if λ < 1 , an intermediate layer eventually forms as a result of plume splitting. Eventually all of the plume fluid spreads within the intermediate layer. The starting time, tv, and the ending time, tt, of the transition process measured from experiments correlate with the value of λ. A three-layer ambient fluid is observed after transition, and the mean value of the measured densities of the intermediate layer fluid is well predicted using plume theory. Acknowledgments: Funding for this study was provided by NSERC.

Teaching the Mantle Plumes Debate

Science.gov (United States)

Foulger, G. R.

2010-12-01

There is an ongoing debate regarding whether or not mantle plumes exist. This debate has highlighted a number of issues regarding how Earth science is currently practised, and how this feeds into approaches toward teaching students. The plume model is an hypothesis, not a proven fact. And yet many researchers assume a priori that plumes exist. This assumption feeds into teaching. That the plume model is unproven, and that many practising researchers are skeptical, may be at best only mentioned in passing to students, with most teachers assuming that plumes are proven to exist. There is typically little emphasis, in particular in undergraduate teaching, that the origin of melting anomalies is currently uncertain and that scientists do not know all the answers. Little encouragement is given to students to become involved in the debate and to consider the pros and cons for themselves. Typically teachers take the approach that “an answer” (or even “the answer”) must be taught to students. Such a pedagogic approach misses an excellent opportunity to allow students to participate in an important ongoing debate in Earth sciences. It also misses the opportunity to illustrate to students several critical aspects regarding correct application of the scientific method. The scientific method involves attempting to disprove hypotheses, not to prove them. A priori assumptions should be kept uppermost in mind and reconsidered at all stages. Multiple working hypotheses should be entertained. The predictions of a hypothesis should be tested, and unpredicted observations taken as weakening the original hypothesis. Hypotheses should not be endlessly adapted to fit unexpected observations. The difficulty with pedagogic treatment of the mantle plumes debate highlights a general uncertainty about how to teach issues in Earth science that are not yet resolved with certainty. It also represents a missed opportunity to let students experience how scientific theories evolve, warts

Simultaneous fingering, double-diffusive convection, and thermal plumes derived from autocatalytic exothermic reaction fronts

Science.gov (United States)

Eskew, Matthew W.; Harrison, Jason; Simoyi, Reuben H.

2016-11-01

Oxidation reactions of thiourea by chlorite in a Hele-Shaw cell are excitable, autocatalytic, exothermic, and generate a lateral instability upon being triggered by the autocatalyst. Reagent concentrations used to develop convective instabilities delivered a temperature jump at the wave front of 2.1 K. The reaction zone was 2 mm and due to normal cooling after the wave front, this generated a spike rather than the standard well-studied front propagation. The reaction front has solutal and thermal contributions to density changes that act in opposite directions due to the existence of a positive isothermal density change in the reaction. The competition between these effects generates thermal plumes. The fascinating feature of this system is the coexistence of plumes and fingering in the same solution which alternate in frequency as the front propagates, generating hot and cold spots within the Hele-Shaw cell, and subsequently spatiotemporal inhomogeneities. The small ΔT at the wave front generated thermocapillary convection which competed effectively with thermogravitational forces at low Eötvös Numbers. A simplified reaction-diffusion-convection model was derived for the system. Plume formation is heavily dependent on boundary effects from the cell dimensions. This work was supported by Grant No. CHE-1056366 from the NSF and a Research Professor Grant from the University of KwaZulu-Natal.

Lidar sounding of volcanic plumes

Science.gov (United States)

Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

2013-10-01

Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

Plume collimation for laser ablation electrospray ionization mass spectrometry

Science.gov (United States)

Vertes, Akos; Stolee, Jessica A.

2014-09-09

In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

Mount Etna-Iblean volcanism caused by rollback-induced upper mantle upwelling around the Ionian slab edge : An alternative to the plume model

NARCIS (Netherlands)

Schellart, W. P.

Volcanism in Sicily (Italy) at Mount Etna (0.5 Ma to present) and the Iblean Plateau (ca. 7.0-1.1 Ma) remains enigmatic, because it is located in close proximity to, but is laterally offset from, the Calabrian subduction zone. Previous work suggests that the volcanism results from a plume or from

Minerals in fractures of the saturated zone from drill core USW G-4, Yucca Mountain, Nye County, Nevada

International Nuclear Information System (INIS)

Carlos, B.A.

1987-04-01

The minerals in fractures in drill core USW G-4, from the static water level (SWL) at 1770 ft to the base of the hole at 3000 ft, were studied to determine their identity and depositional sequence and to compare them with those found above the SWL in the same drill hole. There is no change in mineralogy or mineral morphology across the SWL. The significant change in mineralogy and relationship to the host rock occurs at 1381 ft, well above the present water table. Below 1381 ft clinoptilolite appears in the fractures and rock matrix instead of heulandite, and the fracture mineralogy correlates with the host rock mineralogy. Throughout most of the saturated zone (below the SWL) in USW G-4, zeolites occur in fractures only in zeolitic tuff; however, zeolites persist in fracture below the base of the deepest zeolitic tuff interval. Nonzeolitic intervals of tuff have fewer fractures, and many of these have no coatings; a few have quartz and feldspar coatings. One interval in zeolitic tuff (2125-2140 ft) contains abundant crisobalite coatings in the fractures. Calcite occurs in fractures from 2575 to 2660 ft, usually with the manganese mineral hollandite, and from 2750 to 2765 ft, usually alone. Manganese minerals occur in several intervals. The spatial correlation of zeolites in fractures with zeolitic host rock suggests that both may have been zeolitized at the same time, possibly by water moving laterally through more permeable zones in the tuff. The continuation of zeolites in fractures below the lowest zeolitic interval in this hole suggests that vertical fracture flow may have been important in the deposition of these coatings. Core from deeper intervals in another hole will be examined to determine if that relationship continues. 17 refs., 19 figs

Saharan dust plume charging observed over the UK

Science.gov (United States)

Harrison, R. Giles; Nicoll, Keri A.; Marlton, Graeme J.; Ryder, Claire L.; Bennett, Alec J.

2018-05-01

A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s‑1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (‑8.0 ± 3.3) nC m‑2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

High rates of organic carbon processing in the hyporheic zone of intermittent streams.

Science.gov (United States)

Burrows, Ryan M; Rutlidge, Helen; Bond, Nick R; Eberhard, Stefan M; Auhl, Alexandra; Andersen, Martin S; Valdez, Dominic G; Kennard, Mark J

2017-10-16

Organic carbon cycling is a fundamental process that underpins energy transfer through the biosphere. However, little is known about the rates of particulate organic carbon processing in the hyporheic zone of intermittent streams, which is often the only wetted environment remaining when surface flows cease. We used leaf litter and cotton decomposition assays, as well as rates of microbial respiration, to quantify rates of organic carbon processing in surface and hyporheic environments of intermittent and perennial streams under a range of substrate saturation conditions. Leaf litter processing was 48% greater, and cotton processing 124% greater, in the hyporheic zone compared to surface environments when calculated over multiple substrate saturation conditions. Processing was also greater in more saturated surface environments (i.e. pools). Further, rates of microbial respiration on incubated substrates in the hyporheic zone were similar to, or greater than, rates in surface environments. Our results highlight that intermittent streams are important locations for particulate organic carbon processing and that the hyporheic zone sustains this fundamental process even without surface flow. Not accounting for carbon processing in the hyporheic zone of intermittent streams may lead to an underestimation of its local ecological significance and collective contribution to landscape carbon processes.

Polyphosphate Amendments for In-Situ Immobilization of Uranium Plumes

International Nuclear Information System (INIS)

Wellman, Dawn M.; Icenhower, Jonathan P.; Pierce, Eric M.; McNamara, Bruce K.; Burton, Sarah D.; Geiszler, Keith N.; Baum, Steven R.; Butler, Bart C.; R.F. Olfenbuttel; P.J. White

2005-01-01

A multi-faceted approach has been taken to address basic science questions with regards to the efficacy of utilizing phosphate amendments for subsurface immobilization of uranium plumes. Hydraulically saturated and unsaturated column tests demonstrate the ability of polyphosphate compounds to control the precipitation kinetics of insoluble phosphate minerals and optimize conditions for controlled application of phosphate amendments for subsurface remediation. X-Ray micro-focus tomography results illustrate long-term effects of phosphate mineralization on hydraulic conductivity. 31P NMR has been utilized to quantify the effect of sedimentary and aqueous components on the in-situ hydrolysis kinetics of condensed polyphosphates. Single-pass flow-through (SPFT) tests have been conducted to evaluate the longevity and quantify the effects of aqueous organic material on the dissolution kinetics of autunite minerals, X1-2[(UO2)(PO4)]2nH2O. Preliminary results indicate: (1) autunite minerals will precipitate within 1-2 months given a 0.05 M phosphate concentration and 10-6 M aqueous uranium concentration, under hydraulically saturated conditions; (2) polyphosphate chain lengths can be optimized for specific site conditions, given thorough knowledge of the subsurface environment; (3) the release of uranium from autunite minerals appears to be 6-7 order of magnitude slower than uranium (UO2) minerals formed by iron barrier reduction; and (4) understanding secondary uranyl-phase formation is necessary for predicting the long-term fate of uranium in the environment

Proceedings of plumes, plates and mineralisation symposium: an introduction

CSIR Research Space (South Africa)

Hatton, CJ

1997-12-01

Full Text Available of plume-theory. Mechanisms of magma formation are identified and plume positions and distances to their surface expression considered. Mantle plumes are considered as a heat and fluid source for the Witwatersrand gold deposits....

Simplified scheme or radioactive plume calculations

International Nuclear Information System (INIS)

Gibson, T.A.; Montan, D.N.

1976-01-01

A simplified mathematical scheme to estimate external whole-body γ radiation exposure rates from gaseous radioactive plumes was developed for the Rio Blanco Gas Field Nuclear Stimulation Experiment. The method enables one to calculate swiftly, in the field, downwind exposure rates knowing the meteorological conditions and γ radiation exposure rates measured by detectors positioned near the plume source. The method is straightforward and easy to use under field conditions without the help of mini-computers. It is applicable to a wide range of radioactive plume situations. It should be noted that the Rio Blanco experiment was detonated on May 17, 1973, and no seep or release of radioactive material occurred

Hubble Captures Volcanic Eruption Plume From Io

Science.gov (United States)

1997-01-01

The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through the plume and is

Assessment of attenuation processes in a chlorinated ethene plume by use of stream bed Passive Flux Meters, streambed Point Velocity Probes and contaminant mass balances

DEFF Research Database (Denmark)

Rønde, Vinni Kampman; McKnight, Ursula S.; Annable, Michael

, however studies contradicting this have also been reported. Since dilution commonly reduces contaminant concentrations in streams to below quantification limits, use of mass balances along the pathway from groundwater to stream is unusual. Our study is conducted at the low-land Grindsted stream, Denmark......Chlorinated ethenes (CE) are abundant groundwater contaminants and pose risk to both groundwater and surface water bodies, as plumes can migrate through aquifers to streams. After release to the environment, CE may undergo attenuation. The hyporheic zone is believed to enhance CE attenuation......, which is impacted by a contaminant plume. CE have been observed in the stream water; hence our study site provides an unusual opportunity to study attenuation processes in a CE plume as it migrates through the groundwater at the stream bank, through the stream bed and further to the point of fully mixed...

Predicting DNAPL Source Zone and Plume Response Using Site-Measured Characteristics

Science.gov (United States)

2017-05-19

Losses must be considered such as complete degradation, changes in hydro -stratigraphy, and remediation. c. Use of Extraction Wells Changes in...coal tar is polyparameter linear free energy relationships which uses a mechanistic description of the intermolecular interactions. Final Report ER...used to identify zones of contamination. There were three electric conductivity logging tools tested: the flame ionization detector (FID), the

Assessment of chloroethene degradation rates based on ratios of daughter/parent compounds in groundwater plumes

Science.gov (United States)

Höhener, Patrick

2014-05-01

Chlorinated solvent spills at industrial and urban sites create groundwater plumes where tetrachloro- and trichloroethene may degrade to their daughter compounds, dichloroethenes, vinyl chloride and ethane. The assessment of degradation and natural attenuation at such sites may be based on the analysis and inverse modelling of concentration data, on the calculation of mass fluxes in transsects, and/or on the analysis of stable isotope ratios in the ethenes. Relatively few work has investigated the possibility of using ratio of concentrations for gaining information on degradation rates. The use of ratios bears the advantage that dilution of a single sample with contaminant-free water does not matter. It will be shown that molar ratios of daughter to parent compounds measured along a plume streamline are a rapid and robust mean of determining whether degradation rates increase or decrease along the degradation chain, and allow furthermore a quantitation of the relative magnitude of degradation rates compared to the rate of the parent compound. Furthermore, ratios of concentration will become constant in zones where degradation is absent, and this allows to sketching the extension of actively degrading zones. The assessment is possible for pure sources and also for mixed sources. A quantification method is proposed in order to estimate first-order degradation rates in zones of constant degradation activity. This quantification method includes corrections that are needed due to longitudinal and transversal dispersivity. The method was tested on a number of real field sites from literature. At the majority of these sites, the first-order degradation rates were decreasing along the degradation chain from tetrachloroethene to vinyl chloride, meaning that the latter was often reaching important concentrations. This is bad news for site owners due to the increased toxicity of vinyl chloride compared to its parent compounds.

An integral model of plume rise from high explosive detonations

International Nuclear Information System (INIS)

Boughton, B.A.; De Laurentis, J.M.

1987-01-01

A numerical model has been developed which provides a complete description of the time evolution of both the physical and thermodynamic properties of the cloud formed when a high explosive is detonated. This simulation employs the integral technique. The model equations are derived by integrating the three-dimensional conservation equations of mass, momentum and energy over the plume cross section. Assumptions are made regarding (a) plume symmetry; (b) the shape of profiles of velocity, temperature, etc. across the plume; and (c) the methodology for simulating entrainment and the effects of the crossflow induced pressure drag force on the plume. With these assumptions, the integral equations can be reduced to a set of ordinary differential equations on the plume centerline variables. Only the macroscopic plume characteristics, e.g., plume radius, centerline height, temperature and density, are predicted; details of the plume intrastructure are ignored. The model explicitly takes into account existing meteorology and has been expanded to consider the alterations in plume behavior which occur when aqueous foam is used as a dispersal mitigating material. The simulation was tested by comparison with field measurements of cloud top height and diameter. Predictions were within 25% of field observations over a wide range of explosive yield and atmospheric stability

The controversy over plumes: Who is actually right?

Science.gov (United States)

Puchkov, V. N.

2009-01-01

The current state of the theory of mantle plumes and its relation to classic plate tectonics show that the “plume” line of geodynamic research is in a period of serious crisis. The number of publications criticizing this concept is steadily increasing. The initial suggestions of plumes’ advocates are disputed, and not without grounds. Questions have been raised as to whether all plumes are derived from the mantle-core interface; whether they all have a wide head and a narrow tail; whether they are always accompanied by uplifting of the Earth’s surface; and whether they can be reliably identified by geochemical signatures, e.g., by the helium-isotope ratio. Rather convincing evidence indicates that plumes cannot be regarded as a strictly fixed reference frame for moving lithospheric plates. More generally, the very existence of plumes has become the subject of debate. Alternative ideas contend that all plumes, or hot spots, are directly related to plate-tectonic mechanisms and appear as a result of shallow tectonic stress, subsequent decompression, and melting of the mantle enriched in basaltic material. Attempts have been made to explain the regular variation in age of volcanoes in ocean ridges by the crack propagation mechanism or by drift of melted segregations of enriched mantle in a nearly horizontal asthenospheric flow. In the author’s opinion, the crisis may be overcome by returning to the beginnings of the plume concept and by providing an adequate specification of plume attributes. Only mantle flows with sources situated below the asthenosphere should be referred to as plumes. These flows are not directly related to such plate-tectonic mechanisms as passive rifting and decompression melting in the upper asthenosphere and are marked by time-progressive volcanic chains; their subasthenospheric roots are detected in seismic tomographic images. Such plumes are mostly located at the margins of superswells, regions of attenuation of seismic waves at the

Integrating wildfire plume rises within atmospheric transport models

Science.gov (United States)

Mallia, D. V.; Kochanski, A.; Wu, D.; Urbanski, S. P.; Krueger, S. K.; Lin, J. C.

2016-12-01

Wildfires can generate significant pyro-convection that is responsible for releasing pollutants, greenhouse gases, and trace species into the free troposphere, which are then transported a significant distance downwind from the fire. Oftentimes, atmospheric transport and chemistry models have a difficult time resolving the transport of smoke from these wildfires, primarily due to deficiencies in estimating the plume injection height, which has been highlighted in previous work as the most important aspect of simulating wildfire plume transport. As a result of the uncertainties associated with modeled wildfire plume rise, researchers face difficulties modeling the impacts of wildfire smoke on air quality and constraining fire emissions using inverse modeling techniques. Currently, several plume rise parameterizations exist that are able to determine the injection height of fire emissions; however, the success of these parameterizations has been mixed. With the advent of WRF-SFIRE, the wildfire plume rise and injection height can now be explicitly calculated using a fire spread model (SFIRE) that is dynamically linked with the atmosphere simulated by WRF. However, this model has only been tested on a limited basis due to computational costs. Here, we will test the performance of WRF-SFIRE in addition to several commonly adopted plume parameterizations (Freitas, Sofiev, and Briggs) for the 2013 Patch Springs (Utah) and 2012 Baker Canyon (Washington) fires, for both of which observations of plume rise heights are available. These plume rise techniques will then be incorporated within a Lagrangian atmospheric transport model (STILT) in order to simulate CO and CO2 concentrations during NASA's CARVE Earth Science Airborne Program over Alaska during the summer of 2012. Initial model results showed that STILT model simulations were unable to reproduce enhanced CO concentrations produced by Alaskan fires observed during 2012. Near-surface concentrations were drastically

CALIOP-based Biomass Burning Smoke Plume Injection Height

Science.gov (United States)

Soja, A. J.; Choi, H. D.; Fairlie, T. D.; Pouliot, G.; Baker, K. R.; Winker, D. M.; Trepte, C. R.; Szykman, J.

2017-12-01

Carbon and aerosols are cycled between terrestrial and atmosphere environments during fire events, and these emissions have strong feedbacks to near-field weather, air quality, and longer-term climate systems. Fire severity and burned area are under the control of weather and climate, and fire emissions have the potential to alter numerous land and atmospheric processes that, in turn, feedback to and interact with climate systems (e.g., changes in patterns of precipitation, black/brown carbon deposition on ice/snow, alteration in landscape and atmospheric/cloud albedo). If plume injection height is incorrectly estimated, then the transport and deposition of those emissions will also be incorrect. The heights to which smoke is injected governs short- or long-range transport, which influences surface pollution, cloud interaction (altered albedo), and modifies patterns of precipitation (cloud condensation nuclei). We are working with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) science team and other stakeholder agencies, primarily the Environmental Protection Agency and regional partners, to generate a biomass burning (BB) plume injection height database using multiple platforms, sensors and models (CALIOP, MODIS, NOAA HMS, Langley Trajectory Model). These data have the capacity to provide enhanced smoke plume injection height parameterization in regional, national and international scientific and air quality models. Statistics that link fire behavior and weather to plume rise are crucial for verifying and enhancing plume rise parameterization in local-, regional- and global-scale models used for air quality, chemical transport and climate. Specifically, we will present: (1) a methodology that links BB injection height and CALIOP air parcels to specific fires; (2) the daily evolution of smoke plumes for specific fires; (3) plumes transport and deposited on the Greenland Ice Sheet; and (4) compare CALIOP-derived smoke plume injection

On the relative motions of long-lived Pacific mantle plumes.

Science.gov (United States)

Konrad, Kevin; Koppers, Anthony A P; Steinberger, Bernhard; Finlayson, Valerie A; Konter, Jasper G; Jackson, Matthew G

2018-02-27

Mantle plumes upwelling beneath moving tectonic plates generate age-progressive chains of volcanos (hotspot chains) used to reconstruct plate motion. However, these hotspots appear to move relative to each other, implying that plumes are not laterally fixed. The lack of age constraints on long-lived, coeval hotspot chains hinders attempts to reconstruct plate motion and quantify relative plume motions. Here we provide 40 Ar/ 39 Ar ages for a newly identified long-lived mantle plume, which formed the Rurutu hotspot chain. By comparing the inter-hotspot distances between three Pacific hotspots, we show that Hawaii is unique in its strong, rapid southward motion from 60 to 50 Myrs ago, consistent with paleomagnetic observations. Conversely, the Rurutu and Louisville chains show little motion. Current geodynamic plume motion models can reproduce the first-order motions for these plumes, but only when each plume is rooted in the lowermost mantle.

Volcanic eruption plumes on Io

International Nuclear Information System (INIS)

Strom, R.G.; Terrile, R.J.; Masursky, H.; Hansen, C.

1979-01-01

The detection of an umbrella-shaped plume extending about 280 km above the bright limb of Io was one of the most important discoveries made during the Voyager 1 encounter with the jovian system. This discovery proves that Io is volcanically active at present, and the number and magnitude of these eruptions indicate that Io is the most volcanically active body so far discovered in the Solar System. Preliminary analyses of these eruptive plumes are presented. (U.K.)

Analysis of plasmaspheric plumes: CLUSTER and IMAGE observations

Directory of Open Access Journals (Sweden)

F. Darrouzet

2006-07-01

Full Text Available Plasmaspheric plumes have been routinely observed by CLUSTER and IMAGE. The CLUSTER mission provides high time resolution four-point measurements of the plasmasphere near perigee. Total electron density profiles have been derived from the electron plasma frequency identified by the WHISPER sounder supplemented, in-between soundings, by relative variations of the spacecraft potential measured by the electric field instrument EFW; ion velocity is also measured onboard these satellites. The EUV imager onboard the IMAGE spacecraft provides global images of the plasmasphere with a spatial resolution of 0.1 RE every 10 min; such images acquired near apogee from high above the pole show the geometry of plasmaspheric plumes, their evolution and motion. We present coordinated observations of three plume events and compare CLUSTER in-situ data with global images of the plasmasphere obtained by IMAGE. In particular, we study the geometry and the orientation of plasmaspheric plumes by using four-point analysis methods. We compare several aspects of plume motion as determined by different methods: (i inner and outer plume boundary velocity calculated from time delays of this boundary as observed by the wave experiment WHISPER on the four spacecraft, (ii drift velocity measured by the electron drift instrument EDI onboard CLUSTER and (iii global velocity determined from successive EUV images. These different techniques consistently indicate that plasmaspheric plumes rotate around the Earth, with their foot fully co-rotating, but with their tip rotating slower and moving farther out.

River plume patterns and dynamics within the Southern California Bight

Science.gov (United States)

Warrick, J.A.; DiGiacomo, P.M.; Weisberg, S.B.; Nezlin, N.P.; Mengel, M.; Jones, B.H.; Ohlmann, J.C.; Washburn, L.; Terrill, E.J.; Farnsworth, K.L.

2007-01-01

Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r2=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r2=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.

Characterization of redox conditions in groundwater contaminant plumes

Science.gov (United States)

Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

2000-10-01

Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

Analytical theory relating the depth of the sulfate-methane transition to gas hydrate distribution and saturation

Science.gov (United States)

Bhatnagar, Gaurav; Chatterjee, Sayantan; Chapman, Walter G.; Dugan, Brandon; Dickens, Gerald R.; Hirasaki, George J.

2011-03-01

We develop a theory that relates gas hydrate saturation in marine sediments to the depth of the sulfate-methane transition (SMT) zone below the seafloor using steady state, analytical expressions. These expressions are valid for systems in which all methane transported into the gas hydrate stability zone (GHSZ) comes from deeper external sources (i.e., advective systems). This advective constraint causes anaerobic oxidation of methane to be the only sulfate sink, allowing us to link SMT depth to net methane flux. We also develop analytical expressions that define the gas hydrate saturation profile based on SMT depth and site-specific parameters such as sedimentation rate, methane solubility, and porosity. We evaluate our analytical model at four drill sites along the Cascadia Margin where methane sources from depth dominate. With our model, we calculate average gas hydrate saturations across GHSZ and the top occurrence of gas hydrate at these sites as 0.4% and 120 mbsf (Site 889), 1.9% and 70 mbsf (Site U1325), 4.7% and 40 mbsf (Site U1326), and 0% (Site U1329), mbsf being meters below seafloor. These values compare favorably with average saturations and top occurrences computed from resistivity log and chloride data. The analytical expressions thus provide a fast and convenient method to calculate gas hydrate saturation and first-order occurrence at a given geologic setting where vertically upward advection dominates the methane flux.

Using satellite imagery for qualitative evaluation of plume transport in modeling the effects of the Kuwait oil fire smoke plumes

International Nuclear Information System (INIS)

Bass, A.; Janota, P.

1992-01-01

To forecast the behavior of the Kuwait oil fire smoke plumes and their possible acute or chronic health effects over the Arabian Gulf region, TASC created a comprehensive health and environmental impacts modeling system. A specially-adapted Lagrangian puff transport model was used to create (a) short-term (multiday) forecasts of plume transport and ground-level concentrations of soot and SO 2 ; and (b) long-term (seasonal and longer) estimates of average surface concentrations and depositions. EPA-approved algorithms were used to transform exposures to SO 2 and soot (as PAH/BaP) into morbidity, mortality and crop damage risks. Absent any ground truth, satellite imagery from the NOAA Polar Orbiter and the ESA Geostationary Meteosat offered the only opportunity for timely qualitative evaluation of the long-range plume transport and diffusion predictions. This paper shows the use of actual satellite images (including animated loops of hourly Meteosat images) to evaluate plume forecasts in near-real-time, and to sanity-check the meso- and long-range plume transport projections for the long-term estimates. Example modeled concentrations, depositions and health effects are shown

Field experimental observations of highly graded sediment plumes

DEFF Research Database (Denmark)

Hjelmager Jensen, Jacob; Saremi, Sina; Jimenez, Carlos

2015-01-01

A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes......-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages...... are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model....

On the development of a three-dimensional finite-element groundwater flow model of the saturated zone, Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Czarnecki, J.B.; Faunt, C.C.; Gable, C.W.; Zyvoloski, G.A.

1996-01-01

Development of a preliminary three-dimensional model of the saturated zone at Yucca Mountain, the potential location for a high-level nuclear waste repository, is presented. The development of the model advances the technology of interfacing: (1)complex three-dimensional hydrogeologic framework modeling; (2) fully three-dimensional, unstructured, finite-element mesh generation; and (3) groundwater flow, heat, and transport simulation. The three-dimensional hydrogeologic framework model is developed using maps, cross sections, and well data. The framework model data are used to feed an automated mesh generator, designed to discretize irregular three-dimensional solids,a nd to assign materials properties from the hydrogeologic framework model to the tetrahedral elements. The mesh generator facilitated the addition of nodes to the finite-element mesh which correspond to the exact three-dimensional position of the potentiometric surface based on water-levels from wells. A ground water flow and heat simulator is run with the resulting finite- element mesh, within a parameter-estimation program. The application of the parameter-estimation program is designed to provide optimal values of permeability and specified fluxes over the model domain to minimize the residual between observed and simulated water levels

Simulation of consolidation in partially saturated soil materials

International Nuclear Information System (INIS)

Narasimhan, T.N.

1982-03-01

Partially saturated soil materials undergo consolidation, heave, collapse and failure due to changes in pore fluid pressure. The precise nature of the mechanics of such deformations is only poorly understood at present. Experimental evidence has shown that the volume change behavior of unsaturated soils cannot be adequately explained through changes in effective stress, even when a saturation dependent parameter is incorporated into the definition of effective stress. Two independent stress-state variables, involving combinations of total stress, pore air pressure and pore water pressure, are required to characterize volume changes and saturation changes in the partially saturated state. In general, two coupled conservation equations, one for the water-phase and the other for the air-phase need to be solved in order to predict the deformation behavior of unsaturated soils. If directional displacements and changes in the stress-field are required, then the conservation equations are to be integrated with an additional set of multi-dimensional force balance equations. For lack of a sufficient understanding of elastic constants such as Poisson's Ratio and Lame's constants as applied to unsaturated soils, little has been achieved so far in integrating the conservation equations and the force balance equations. For the long-term modeling of consolidation with respect to uranium mill tailings, it may be acceptable and economical to solve a single conservation equation for water, assuming that the air-phase is continuous and is at atmospheric pressure everywhere in the soil. The greatest challenge to modeling consolidation in the unsaturated zone at the presnt time is to develop enough experimental data defining the variation of void ratio and saturation with reference to the two chosen stress-state variables

Volcanic Plume Measurements with UAV (Invited)

Science.gov (United States)

Shinohara, H.; Kaneko, T.; Ohminato, T.

2013-12-01

Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

Calculation of doses received while crossing a plume of radioactive material

International Nuclear Information System (INIS)

Scherpelz, R.I.; Desrosiers, A.E.

1981-04-01

A method has been developed for determining the dose received by a person while crossing a plume of radioactive material. The method uses a Gaussian plume model to arrive at a dose rate on the plume centerline at the position of the plume crossing. This dose rate may be due to any external or internal dose pathway. An algebraic formula can then be used to convert the plume centerline dose rate to a total dose integrated over the total time of plume crossing. Correction factors are presented for dose pathways in which the dose rate is not normally distributed about the plume centerline. The method is illustrated by a study done at the Pacific Northwest Laboratory, and results of this study are presented

Argonne National Laboratory's thermal plume measurements: instruments and techniques

International Nuclear Information System (INIS)

Van Loon, L.S.; Frigo, A.A.; Paddock, R.A.

1977-12-01

Instrumentation and techniques were developed at Argonne National Laboratory for measuring the three-dimensional temperature structure of thermal plumes from power plants, along with the limnological, meteorological, and plant operating conditions affecting their behavior. The equipment and procedures were designed to provide field data for use in evaluating predictive models that describe thermal plume behavior, and over 100 sets of these data have been collected. The instrument systems and techniques employed in a typical thermal discharge survey are highly integrated. Continuous monitoring of ambient and plant conditions is coupled with plume mapping from a moving survey boat. The instantaneous location of the boat together with subsurface temperature measurements from a towed thermistor chain provide a quasisynoptic view of the plume structure. Real-time, onboard display of the boat path and vertical temperatures supply feedback to investigators for determining the extent and spatial resolution of measurements required. The unique design, reliability, accuracy, calibration, and historical development of the components of these integrated systems are described. Survey system interfaces with data handling and processing techniques are also explained. Special supportive studies to investigate plume dynamics, values of eddy diffusivities, time-temperature histories of water parcels in thermal plumes, and rapid changes in plume shape are also described along with instrumentation used

Building Conceptual Models of Field-Scale Uranium Reactive Transport in a Dynamic Vadose Zone-Aquifer-River System

International Nuclear Information System (INIS)

Yabusaki, Steven B.; Fang, Yilin; Waichler, Scott R.

2008-01-01

Subsurface simulation is being used to build, test, and couple conceptual process models to better understand controls on a 0.4 km by 1.0 km uranium plume that has persisted above the drinking water standard in the groundwater of the Hanford 300 Area over the last 15 years. At this site, uranium-contaminated sediments in the vadose zone and aquifer are subject to significant variations in water levels and velocities driven by the diurnal, weekly, seasonal, and episodic Columbia River stage dynamics. Groundwater flow reversals typically occur twice a day with significant exchange of river water and groundwater in the near-river aquifer. Mixing of the dilute solution chemistry of the river with the groundwater complicates the uranium sorption behavior as the mobility of U(VI) has been shown experimentally to be a function of pH, carbonate, calcium, and uranium. Furthermore, uranium mass transfer between solid and aqueous phases has been observed to be rate-limited in the context of the high groundwater velocities resulting from the river stage fluctuations and the highly transmissive sediments (hydraulic conductivities ∼1500 m/d). One- and two-dimensional vertical cross-sectional simulations of variably-saturated flow and reactive transport, based on laboratory-derived models of distributed rate mass transfer and equilibrium multicomponent surface complexation, are used to assess uranium transport at the dynamic vadose zone aquifer interface as well as changes to uranium mobility due to incursions of river water into the aquifer

Problems of saturation of the excitation and creation of irreversible changes in solid after laser irradiation

International Nuclear Information System (INIS)

Sakhnyuk, L.A.; Trokhimchuck, P.P.

2009-01-01

The problem of modeling of processes of the irreversible interaction light and solid is discussed. This problem is connected with the processes of the saturation the excitation of respective scattering centers. The possible cascades of these processes are analyzed. The correlation between nonequilibrium and irreversible phenomena are analyzed. Two-dimensional sphalerite lattice of InSb was used for the kinetic modeling of the hierarchic processes of saturation of the excitation respective chemical bonds. The cascade characteristics of these processes were estimated for the cylindrical form of 'zone of energy scattering' of photon. The comparative analyses these results with results, which were received with the help straight method and method the spherical form of 'zone of energy scattering' of photon, is represented too. The good concordance of experimental and theoretical data was received. (authors)

Comparison of Radiofrequency Ablation with Saturated Saline Preinjection and Renal Artery Occlusion: In Vivo Study in Canine Kidneys Preinjection and Renal Artery Occlusion: In Vivo Study in Canine Kidneys

Energy Technology Data Exchange (ETDEWEB)

Shin, Byung Seok; Ahn, Moon Sang [Chungnam National University Hospital, Daejeon (Korea, Republic of); Park, Mi Hyun [Dept. of Radiology, Dankook University Hospital, Cheonan (Korea, Republic of); Jeon, Gyeong Sik [Dept. of Radiology, CHA Bundang Medical Center, CHA University College of Medicine, Seongnam (Korea, Republic of); Lee, Byung Mo [Dept. of Surgery, Paik Hospital, Inje University College of Medicine, Seoul (Korea, Republic of); Lee, Ki Chang [Dept. of Veterinary Radiology, Chonbuk National University College of VeterinaryMedicine, Seoul (Korea, Republic of); Kim, Ho Jun [Dept. of Radiology, Konyang University Hospital, Daejeon (Korea, Republic of); Ohm, Joon Young [Dept. of Radiology, Bucheon St. Mary Hospital, The Catholic University of Korea College of Medicine, Bucheon (Korea, Republic of)

2012-04-15

To compare the ablation zone after radiofrequency ablation (RFA) with saturated saline preinjection and renal artery occlusion in canine kidneys. RFA was induced in the kidneys of six mongrel dogs. A total of 24 ablation zones were induced using a 1-cm tip internally cooled needle electrode in three groups: RFA (Control group), RFA with 0.5 mL saturated saline preinjection (SS group), and RFA with renal artery occlusion by atraumatic vascular clamp (Occlusion group). Ablation zone diameters were measured along transverse and longitudinal sections of the needle axis, and volumes were calculated. Temperature, applied voltage, current, and impedance during RFA were recorded automatically. The RFA zone volume was the largest in the SS group (1.33 {+-} 0.34 cm{sup 3}), followed by the Occlusion group (1.07 {+-} 0.38 cm{sup 3}) and then the Control group (0.62 {+-} 0.09 cm{sup 3}). Volumes for the SS and Occlusion groups were significantly larger than those for the Control group (p = 0.001, p = 0.012). There was no significant difference in volumes between the SS and Occlusion groups (p = 0.178). Saturated saline preinjection is as effective as renal arterial occlusion for expanding the ablation zone. RFA with saturated saline preinjection could help to treat large renal tumors.

Comparison of Radiofrequency Ablation with Saturated Saline Preinjection and Renal Artery Occlusion: In Vivo Study in Canine Kidneys Preinjection and Renal Artery Occlusion: In Vivo Study in Canine Kidneys

International Nuclear Information System (INIS)

Shin, Byung Seok; Ahn, Moon Sang; Park, Mi Hyun; Jeon, Gyeong Sik; Lee, Byung Mo; Lee, Ki Chang; Kim, Ho Jun; Ohm, Joon Young

2012-01-01

To compare the ablation zone after radiofrequency ablation (RFA) with saturated saline preinjection and renal artery occlusion in canine kidneys. RFA was induced in the kidneys of six mongrel dogs. A total of 24 ablation zones were induced using a 1-cm tip internally cooled needle electrode in three groups: RFA (Control group), RFA with 0.5 mL saturated saline preinjection (SS group), and RFA with renal artery occlusion by atraumatic vascular clamp (Occlusion group). Ablation zone diameters were measured along transverse and longitudinal sections of the needle axis, and volumes were calculated. Temperature, applied voltage, current, and impedance during RFA were recorded automatically. The RFA zone volume was the largest in the SS group (1.33 ± 0.34 cm 3 ), followed by the Occlusion group (1.07 ± 0.38 cm 3 ) and then the Control group (0.62 ± 0.09 cm 3 ). Volumes for the SS and Occlusion groups were significantly larger than those for the Control group (p = 0.001, p = 0.012). There was no significant difference in volumes between the SS and Occlusion groups (p = 0.178). Saturated saline preinjection is as effective as renal arterial occlusion for expanding the ablation zone. RFA with saturated saline preinjection could help to treat large renal tumors.

Pressure and fluid saturation prediction in a multicomponent reservoir, using combined seismic and electromagnetic imaging

International Nuclear Information System (INIS)

Hoversten, G.M.; Gritto, Roland; Washbourne, John; Daley, Tom

2002-01-01

This paper presents a method for combining seismic and electromagnetic measurements to predict changes in water saturation, pressure, and CO 2 gas/oil ratio in a reservoir undergoing CO 2 flood. Crosswell seismic and electromagnetic data sets taken before and during CO 2 flooding of an oil reservoir are inverted to produce crosswell images of the change in compressional velocity, shear velocity, and electrical conductivity during a CO 2 injection pilot study. A rock properties model is developed using measured log porosity, fluid saturations, pressure, temperature, bulk density, sonic velocity, and electrical conductivity. The parameters of the rock properties model are found by an L1-norm simplex minimization of predicted and observed differences in compressional velocity and density. A separate minimization, using Archie's law, provides parameters for modeling the relations between water saturation, porosity, and the electrical conductivity. The rock-properties model is used to generate relationships between changes in geophysical parameters and changes in reservoir parameters. Electrical conductivity changes are directly mapped to changes in water saturation; estimated changes in water saturation are used along with the observed changes in shear wave velocity to predict changes in reservoir pressure. The estimation of the spatial extent and amount of CO 2 relies on first removing the effects of the water saturation and pressure changes from the observed compressional velocity changes, producing a residual compressional velocity change. This velocity change is then interpreted in terms of increases in the CO 2 /oil ratio. Resulting images of the CO 2 /oil ratio show CO 2 -rich zones that are well correlated to the location of injection perforations, with the size of these zones also correlating to the amount of injected CO 2 . The images produced by this process are better correlated to the location and amount of injected CO 2 than are any of the individual

Sample dimensions effect on prediction of soil water retention curve and saturated hydraulic conductivity

Science.gov (United States)

Soil water retention curve (SWRC) and saturated hydraulic conductivity (SHC) are key hydraulic properties for unsaturated zone hydrology and groundwater. Not only are the SWRC and SHC measurements time-consuming, their results are scale dependent. Although prediction of the SWRC and SHC from availab...

Initial site characterisation of a dissolved hydrocarbon groundwater plume discharging to a surface water environment

International Nuclear Information System (INIS)

Westbrook, S.J.; Commonwealth Scientific and Industrial Research Organisation Land and Water, Wembley, WA; Davis, G.B.; Rayner, J.L.; Fisher, S.J.; Clement, T.P.

2000-01-01

Preliminary characterisation of a dissolved hydrocarbon groundwater plume flowing towards a tidally- and seasonally-forced estuarine system has been completed at a site in Perth, Western Australia. Installation and sampling of multiport boreholes enabled fine scale (0.5-m) vertical definition of hydrocarbon concentrations. Vertical electrical conductivity profiles from multiport and spear probe sampling into the river sediments indicated that two groundwater/river water interfaces or dispersion zones are present: (a) an upper dispersion zone between brackish river water and groundwater, and (b) a lower interface between groundwater and deeper saline water. On-line water level loggers show that near-shore groundwater levels are also strongly influence by tidal oscillation. Results from the initial site characterisation will be used to plan further investigations of contaminated groundwater/surface water interactions and the biodegradation processes occurring at the site

Geophysical Responses of Hydrocarbon-impacted Zones at the Various Contamination Conditions

Science.gov (United States)

Kim, C.; Ko, K.; Son, J.; Kim, J.

2008-12-01

One controlled experiment and two field surveys were conducted to investigate the geoelectrical responses of hydrocarbon-contaminated zones, so called smeared zone, on the geophysical data at the hydrocarbon- contaminated sites with various conditions. One controlled physical model experiment with GPR using fresh gasoline and two different 3-D electrical resistivity investigations at the aged sites. One field site (former military facilities for arms maintenance) was mainly contaminated with lubricating oils and the other (former gas station) was contaminated with gasoline and diesel, respectively. The results from the physical model experiment show that GPR signals were enhanced when LNAPL was present as a residual saturation in the water-saturated system due to less attenuation of the electromagnetic energy through the soil medium of the hydrocarbon-impacted zone (no biodegradation), compared to when the medium was saturated with only water (no hydrocarbon impaction). In the former gas station site, 3-D resistivity results demonstrate that the highly contaminated zones were imaged with low resistivity anomalies since the biodegradation of petroleum hydrocarbons has been undergone for many years, causing the drastic increase in the TDS at the hydrocarbon-impacted zones. Finally, 3-D resistivity data obtained from the former military maintenance site show that the hydrocarbon-contaminated zones show high resistivity anomalies since the hydrocarbons such as lubricating oils at the contaminated soils were not greatly influenced by microbial degradation and has relatively well kept their original physical properties of high electrical resistivity. The results of the study illustrated that the hydrocarbon-impacted zones under various contamination conditions yielded various geophysical responses which include (1) enhanced GPR amplitudes at the fresh LNAPL (Gasoline to middle distillates) spill sites, (2) low electrical resistivity anomalies due to biodegradation at the

Io with Loki Plume on Bright Limb

Science.gov (United States)

1990-01-01

Voyager 1 image of Io showing active plume of Loki on limb. Heart-shaped feature southeast of Loki consists of fallout deposits from active plume Pele. The images that make up this mosaic were taken from an average distance of approximately 490,000 kilometers (340,000 miles).

Implementation of Solute Transport in the Vadose Zone into the `HYDRUS Package for MODFLOW'

Science.gov (United States)

Simunek, J.; Beegum, S.; Szymkiewicz, A.; Sudheer, K. P.

2017-12-01

The 'HYDRUS package for MODFLOW' was developed by Seo et al. (2007) and Twarakavi et al. (2008) to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package, which is based on the HYDRUS-1D model (Šimůnek et al., 2016) simulating unsaturated water flow in the vadose zone, was incorporated into MODFLOW (Harbaugh et al., 2000) simulating saturated groundwater flow. The HYDRUS package in the coupled model can be used to represent the effects of various unsaturated zone processes, including infiltration, evaporation, root water uptake, capillary rise, and recharge in homogeneous or layered soil profiles. The coupled model is effective in addressing spatially-variable saturated-unsaturated hydrological processes at the regional scale, allowing for complex layering in the unsaturated zone, spatially and temporarily variable water fluxes at the soil surface and in the root zone, and with alternating recharge and discharge fluxes (Twarakavi et al., 2008). One of the major limitations of the coupled model was that it could not be used to simulate at the same time solute transport. However, solute transport is highly dependent on water table fluctuations due to temporal and spatial variations in groundwater recharge. This is an important concern when the coupled model is used for analyzing groundwater contamination due to transport through the unsaturated zone. The objective of this study is to integrate the solute transport model (the solute transport part of HYDRUS-1D for the unsaturated zone and MT3DMS (Zheng and Wang, 1999; Zheng, 2009) for the saturated zone) into an existing coupled water flow model. The unsaturated zone component of the coupled model can consider solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption (Šimůnek and van Genuchten, 2008

Modeling of time-lapse multi-scale seismic monitoring of CO2 injected into a fault zone to enhance the characterization of permeability in enhanced geothermal systems

Science.gov (United States)

Zhang, R.; Borgia, A.; Daley, T. M.; Oldenburg, C. M.; Jung, Y.; Lee, K. J.; Doughty, C.; Altundas, B.; Chugunov, N.; Ramakrishnan, T. S.

2017-12-01

Subsurface permeable faults and fracture networks play a critical role for enhanced geothermal systems (EGS) by providing conduits for fluid flow. Characterization of the permeable flow paths before and after stimulation is necessary to evaluate and optimize energy extraction. To provide insight into the feasibility of using CO2 as a contrast agent to enhance fault characterization by seismic methods, we model seismic monitoring of supercritical CO2 (scCO2) injected into a fault. During the CO2 injection, the original brine is replaced by scCO2, which leads to variations in geophysical properties of the formation. To explore the technical feasibility of the approach, we present modeling results for different time-lapse seismic methods including surface seismic, vertical seismic profiling (VSP), and a cross-well survey. We simulate the injection and production of CO2 into a normal fault in a system based on the Brady's geothermal field and model pressure and saturation variations in the fault zone using TOUGH2-ECO2N. The simulation results provide changing fluid properties during the injection, such as saturation and salinity changes, which allow us to estimate corresponding changes in seismic properties of the fault and the formation. We model the response of the system to active seismic monitoring in time-lapse mode using an anisotropic finite difference method with modifications for fracture compliance. Results to date show that even narrow fault and fracture zones filled with CO2 can be better detected using the VSP and cross-well survey geometry, while it would be difficult to image the CO2 plume by using surface seismic methods.

Laser-generated plasma plume expansion: Combined continuous-microscopic modeling

Science.gov (United States)

Itina, Tatiana E.; Hermann, Jörg; Delaporte, Philippe; Sentis, Marc

2002-12-01

The physical phenomena involved in the interaction of a laser-generated plasma plume with a background gas are studied numerically. A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas. The proposed approach takes advantages of both continuous and microscopic descriptions. The simulation technique is suitable for the simulation of high-rate laser ablation for a wide range of background pressure. The model takes into account the mass diffusion and the energy exchange between the ablated and background species, as well as the collective motion of the ablated species and the background-gas particles. The developed approach is used to investigate the influence of the background gas on the expansion dynamics of the plume obtained during the laser ablation of aluminum. At moderate pressures, both plume and gas compressions are weak and the process is mainly governed by the diffusive mixing. At higher pressures, the interaction is determined by the plume-gas pressure interplay, the plume front is strongly compressed, and its center exhibits oscillations. In this case, the snowplough effect takes place, leading to the formation of a compressed gas layer in front of the plume. The background pressure needed for the beginning of the snowplough effect is determined from the plume and gas density profiles obtained at various pressures. Simulation results are compared with experimentally measured density distributions. It is shown that the calculations suggest localized formation of molecules during reactive laser ablation.

Laser-generated plasma plume expansion: Combined continuous-microscopic modeling

International Nuclear Information System (INIS)

Itina, Tatiana E.; Hermann, Joerg; Delaporte, Philippe; Sentis, Marc

2002-01-01

The physical phenomena involved in the interaction of a laser-generated plasma plume with a background gas are studied numerically. A three-dimensional combined model is developed to describe the plasma plume formation and its expansion in vacuum or into a background gas. The proposed approach takes advantages of both continuous and microscopic descriptions. The simulation technique is suitable for the simulation of high-rate laser ablation for a wide range of background pressure. The model takes into account the mass diffusion and the energy exchange between the ablated and background species, as well as the collective motion of the ablated species and the background-gas particles. The developed approach is used to investigate the influence of the background gas on the expansion dynamics of the plume obtained during the laser ablation of aluminum. At moderate pressures, both plume and gas compressions are weak and the process is mainly governed by the diffusive mixing. At higher pressures, the interaction is determined by the plume-gas pressure interplay, the plume front is strongly compressed, and its center exhibits oscillations. In this case, the snowplough effect takes place, leading to the formation of a compressed gas layer in front of the plume. The background pressure needed for the beginning of the snowplough effect is determined from the plume and gas density profiles obtained at various pressures. Simulation results are compared with experimentally measured density distributions. It is shown that the calculations suggest localized formation of molecules during reactive laser ablation

Turbulence and wave particle interactions in solar-terrestrial plasmas. Annual Status Report, 1 July 1983-30 June 1984

International Nuclear Information System (INIS)

Dulk, G.A.; Goldman, M.V.; Toomre, J.

1985-01-01

Activities in the following study areas are reported: (1) particle and wave processes in solar flares; (2) solar convection zone turbulence; and (3) solar radiation emission. To investigate the amplification of cyclotron maser radiation in solar flares, a radio frequency. (RF) heating model was developed for the corona surrounding the energy release site. Then nonlinear simulations of compressible convection display prominent penetration by plumes into regions of stable stratification at the base of the solar convection zone, leading to the excitation of internal gravity waves there. Lastly, linear saturation of electron-beam-driven Langmuir waves by ambient density fluctuations, nonlinear saturation by strong turbulence processes, and radiation emission mechanisms are examined. An additional section discusses solar magnetic fields and hydromagnetic waves in inhomogeneous media, and the effect of magnetic fields on stellar oscillation

Field experimental observations of highly graded sediment plumes.

Science.gov (United States)

Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis

2015-06-15

A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. Copyright © 2015 Elsevier Ltd. All rights reserved.

Heterogeneity and Scaling in Geologic Media: Applications to Transport in the Vadose and Saturated Zones

Energy Technology Data Exchange (ETDEWEB)

Brown, Stephen R.

2003-06-01

Heterogeneity and Scaling in Geologic Media: Applications to Transport in the Vadose and Saturated Zones Stephen Brown, Gregory Boitnott, and Martin Smith New England Research In rocks and soils, the bulk geophysical and transport properties of the matrix and of fracture systems are determined by the juxtaposition of geometric features at many length scales. For sedimentary materials the length scales are: the pore scale (irregularities in grain surface roughness and cementation), the scale of grain packing faults (and the resulting correlated porosity structures), the scale dominated by sorting or winnowing due to depositional processes, and the scale of geomorphology at the time of deposition. We are studying the heterogeneity and anisotropy in geometry, permeability, and geophysical response from the pore (microscopic), laboratory (mesoscopic), and backyard field (macroscopic) scales. In turn these data are being described and synthesized for development of mathematical models. Eventually, we will perform parameter studies to explore these models in the context of transport in the vadose and saturated zones. We have developed a multi-probe physical properties scanner which allows for the mapping of geophysical properties on a slabbed sample or core. This device allows for detailed study of heterogeneity at those length scales most difficult to quantify using standard field and laboratory practices. The measurement head consists of a variety of probes designed to make local measurements of various properties, including: gas permeability, acoustic velocities (compressional and shear), complex electrical impedance (4 electrode, wide frequency coverage), and ultrasonic reflection (ultrasonic impedance and permeability). We can thus routinely generate detailed geophysical maps of a particular sample. With the exception of the acoustic velocity, we are testing and modifying these probes as necessary for use on soil samples. As a baseline study we have been

Benchmarking variable-density flow in saturated and unsaturated porous media

Science.gov (United States)

Guevara Morel, Carlos Roberto; Cremer, Clemens; Graf, Thomas

2015-04-01

In natural environments, fluid density and viscosity can be affected by spatial and temporal variations of solute concentration and/or temperature. These variations can occur, for example, due to salt water intrusion in coastal aquifers, leachate infiltration from waste disposal sites and upconing of saline water from deep aquifers. As a consequence, potentially unstable situations may exist in which a dense fluid overlies a less dense fluid. This situation can produce instabilities that manifest as dense plume fingers that move vertically downwards counterbalanced by vertical upwards flow of the less dense fluid. Resulting free convection increases solute transport rates over large distances and times relative to constant-density flow. Therefore, the understanding of free convection is relevant for the protection of freshwater aquifer systems. The results from a laboratory experiment of saturated and unsaturated variable-density flow and solute transport (Simmons et al., Transp. Porous Medium, 2002) are used as the physical basis to define a mathematical benchmark. The HydroGeoSphere code coupled with PEST are used to estimate the optimal parameter set capable of reproducing the physical model. A grid convergency analysis (in space and time) is also undertaken in order to obtain the adequate spatial and temporal discretizations. The new mathematical benchmark is useful for model comparison and testing of variable-density variably saturated flow in porous media.

Plume rise from stacks with scrubbers: a state-of-the-art review

International Nuclear Information System (INIS)

Schatzmann, M.; Policastro, A.J.

1984-01-01

The state of the art of predicting plume rise from stacks with scrubbers is evaluated critically. The significant moisture content of the scrubbed plume upon exit leads to important thermodynamic effects during plume rise that are unaccounted for in the usual dry plume rise theories. For example, under conditionally unstable atmospheres, a wet scrubbed plume treated as completely dry acts as if the atmosphere were stable, whereas in reality the scrubbed plume behaves instead as if the atmosphere were unstable. Even the use of moist plume models developed for application to cooling tower plume rise is not valid since these models 1) employ the Boussinesq approximation, 2) use a number of additional simplifying approximations that require small exit temperature differences between tower exit and ambient temperatures, and 3) are not calibrated to stack data

Diagnostics of laser ablated plasma plumes

DEFF Research Database (Denmark)

Amoruso, S.; Toftmann, B.; Schou, Jørgen

2004-01-01

The effect of an ambient gas on the expansion dynamics of laser ablated plasmas has been studied for two systems by exploiting different diagnostic techniques. First, the dynamics of a MgB2 laser produced plasma plume in an Ar atmosphere has been investigated by space-and time-resolved optical...... of the laser ablated plasma plume propagation in a background gas. (C) 2003 Elsevier B.V All rights reserved....

Mantle plumes on Venus revisited

Science.gov (United States)

Kiefer, Walter S.

1992-01-01

The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not

Saturated-unsaturated flow to a well with storage in a compressible unconfined aquifer

Science.gov (United States)

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2011-05-01

Mishra and Neuman (2010) developed an analytical solution for flow to a partially penetrating well of zero radius in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from responses recorded in the saturated and/or unsaturated zones. Their solution accounts for horizontal as well as vertical flows in each zone. It represents unsaturated zone constitutive properties in a manner that is at once mathematically tractable and sufficiently flexible to provide much improved fits to standard constitutive models. In this paper we extend the solution of [2010] to the case of a finite diameter pumping well with storage; investigate the effects of storage in the pumping well and delayed piezometer response on drawdowns in the saturated and unsaturated zones as functions of position and time; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the [1980]- [1976] model; use our solution to analyze 11 transducer-measured drawdown records from a seven-day pumping test conducted by University of Waterloo researchers at the Canadian Forces Base Borden in Ontario, Canada; validate our parameter estimates against manually-measured drawdown records in 14 other piezometers at Borden; and compare (a) our estimates of aquifer parameters with those obtained on the basis of all these records by [2008], (b) on the basis of 11 transducer-measured drawdown records by [2007], (c) our estimates of van Genuchten-Mualem parameters with those obtained on the basis of laboratory drainage data from the site by [1992], and (d) our corresponding prediction of how effective saturation varies with elevation above the initial water table under static conditions with a profile based on water contents measured in a neutron access tube at a radial distance of about 5 m from the center of the pumping well. We also use our solution to analyze 11 transducer-measured drawdown

Bio-Physical Coupling of Seabirds and Prey with a Dynamic River Plume

Science.gov (United States)

Phillips, E. M.; Horne, J. K.; Zamon, J. E.; Adams, J.

2016-02-01

Freshwater plumes and plume density fronts are important regions of bio-physical coupling. On the west coast of North America, discharge from the Columbia River into the northern California Current creates a large, dynamic plume and multiple plume fronts. These nutrient-rich, productive waters fuel primary and secondary production, supporting a wide variety of small pelagic prey fish, large populations of Pacific salmon, seabirds, and marine mammals. To determine the influence of the Columbia River plume on marine predators, we analyzed at-sea seabird counts, in situ environmental data, surface trawl densities of prey fish, and acoustic backscatter measurements collected from research vessels in May and June 2010-2012. Concurrent distribution patterns of satellite-tagged sooty shearwaters (Puffinus griseus) and common murres (Uria aalge) were compared with seabird counts from ship surveys. To evaluate plume use by satellite-tagged birds, daily surface salinity values from SELFE hindcast models were extracted at each tag location. Both seabird species occurred in plume waters disproportionate to the total surveyed area, concentrating in the river plume when river flow and plume volume decreased. Murres were consistently within 20 km of the geographic mean center of the river plume. In contrast, shearwaters consistently occurred 100 km to the north of the plume center, where high densities of prey fish occur. Although acoustically detected prey also occurred in greater densities within the plume when volume decreased, surface catches of prey in the plume did not vary with changing plume conditions. Geographic indices of colocation (GIC) were low between murres and prey species caught in surface trawls, whereas GICs were >0.5 between shearwaters and prey species including squid (Loligo opalescens), juvenile Chinook salmon (Oncorhynchus tshawytscha), and coho (O. kisutch) salmon. We conclude that the river plume and associated fronts are identifiable, predictable, and

ALOFT-PC a smoke plume trajectory model for personal computers

International Nuclear Information System (INIS)

Walton, W.D.; McGrattan, K.B.; Mullin, J.V.

1996-01-01

A computer model, named ALOFT-PC, was developed for use during in-situ burning of oil spills to predict smoke plume trajectory. The downwind distribution of smoke particulate is a complex function of fire parameters, meteorological conditions, and topographic features. Experimental burns have shown that the downwind distribution of smoke is not Gaussian and simple smoke plume models do not capture the observed plume features. ALOFT-PC consists of the Navier-Stokes equations using an eddy viscosity over a uniform grid that spans the smoke plume and its surroundings. The model inputs are wind speed and variability, atmospheric temperature profile, and fire parameters and the output is the average of the plume. 7 refs., 3 tabs

Loire and Gironde turbid plumes: Characterization and influence on thermohaline properties

Science.gov (United States)

Costoya, X.; Fernández-Nóvoa, D.; deCastro, M.; Gómez-Gesteira, M.

2017-12-01

Knowledge and predictability of turbid river plumes is of great importance because they modulate the properties of the seawater adjacent to river mouths. The Loire and Gironde Rivers form the most important plumes in the Bay of Biscay, as they provide > 75% of total runoff. The development of the turbid plume under the influence of its main drivers was analyzed using Moderate Resolution Imaging Spectroradiometer satellite data from the period 2003-2015. River discharge was found to be the main driver, followed by wind, which also had an important effect in modulating the turbid plume during periods of high river discharge. Seaward and upwelling favorable winds enhanced the dispersion of plumes on seawater, whereas landward and downwelling favorable winds limited mixing with the adjacent ocean water. The maximum extension of the turbid plume was reached under landward winds. In addition, the spatio-temporal evolution of the East Atlantic pattern and the North Atlantic Oscillation was observed to affect the dynamics of plumes: positive values of both indices favored a greater extension of the plume. Thermohaline properties differed inside and outside the area affected by both rivers. In particular, these rivers maintain winter stratification inside the turbid plume, which results in a different warming ratio when compared with the adjacent ocean.

When interflow also percolates: downslope travel distances and hillslope process zones.

Energy Technology Data Exchange (ETDEWEB)

Jackson, C. Rhett [Warnell School of Forestry and Natural Resources, University of Georgia, GA 30602 Athens USA; Bitew, Menberu [Warnell School of Forestry and Natural Resources, University of Georgia, GA 30602 Athens USA; Du, Enhao [Climate Science Department, Lawrence Berkeley National Laboratory, CA 94720 Berkeley USA

2014-02-17

In hillslopes with soils characterized by deep regoliths, such as Ultisols,Oxisols, and Alfisols, interflow occurs episodically over impeding layers near and parallel to the soil surface such as low-conductivity B horizons (e.g.Newman et al., 1998; Buttle andMcDonald, 2002; Du et al., In Review), till layers (McGlynn et al., 1999; Bishop et al., 2004), hardpans (McDaniel et al., 2008), C horizons (Detty and McGuire, 2010), and permeable bedrock (Tromp van Meerveld et al., 2007). As perched saturation develops within and above these impeding but permeable horizons, flow moves laterally downslope, but the perched water also continues to percolate through the impeding horizon to the unsaturated soils and saprolite below. Perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon. In such flow situations, only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm.farther up the slope, lateral flow within the zone of perched saturation. will act mainly to shift the point of percolation (location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer) down the hillslope from the point of infiltration. In flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers, lateral flow distances will be negligible.

Investigations of the unsaturated zone at two radioactive waste disposal sites in Lithuania.

Science.gov (United States)

Skuratovič, Žana; Mažeika, Jonas; Petrošius, Rimantas; Martma, Tõnu

2016-01-01

The unsaturated zone is an important part of the water cycle, governed by many hydrological and hydrogeological factors and processes and provide water and nutrients to the terrestrial ecosystem. Besides, the soils of the unsaturated zone are regarded as the first natural barrier to a large extent and are able to limit the spread of contaminants depending on their properties. The unsaturated zone provides a linkage between atmospheric moisture, groundwater, and seepage of groundwater to streams, lakes, or other surface water bodies. The major difference between water flow in saturated and unsaturated soils is that the hydraulic conductivity, which is conventionally assumed to be a constant in saturated soils, is a function of the degree of saturation or matrix suction in the unsaturated soils. In Lithuania, low and intermediate level radioactive wastes generated from medicine, industry and research were accumulated at the Maisiagala radioactive waste repository. Short-lived low and intermediate levels radioactive waste, generated during the operation of the Ignalina Nuclear Power Plant (INPP) and arising after the INPP decommissioning will be disposed of in the near surface repository close to the INPP (Stabatiske site). Extensive data sets of the hydraulic properties and water content attributed to unsaturated zone soil profiles of the two radioactive waste disposal sites have been collected and summarized. Globally widespread radionuclide tritium ((3)H) and stable isotope ratio ((18)O/(16)O and (2)H/(1)H) distribution features were determined in precipitation, unsaturated zone soil moisture profiles and groundwater.

The Green Propellant Infusion Mission Thruster Performance Testing for Plume Diagnostics

Science.gov (United States)

Deans, Matthew C.; Reed, Brian D.; Arrington, Lynn A.; Williams, George J.; Kojima, Jun J.; Kinzbach, McKenzie I.; McLean, Christopher H.

2014-01-01

The Green Propellant Infusion Mission (GPIM) is sponsored by NASA's Space Technology Mission Directorate (STMD) Technology Demonstration Mission (TDM) office. The goal of GPIM is to advance the technology readiness level of a green propulsion system, specifically, one using the monopropellant, AF-M315E, by demonstrating ground handling, spacecraft processing, and on-orbit operations. One of the risks identified for GPIM is potential contamination of sensitive spacecraft surfaces from the effluents in the plumes of AF-M315E thrusters. NASA Glenn Research Center (GRC) is conducting activities to characterize the effects of AF-M315E plume impingement and deposition. GRC has established individual plume models of the 22-N and 1-N thrusters that will be used on the GPIM spacecraft. The model simulations will be correlated with plume measurement data from Laboratory and Engineering Model 22-N, AF-M315E thrusters. The thrusters are currently being tested in a small rocket, altitude facility at NASA GRC. A suite of diagnostics, including Raman spectroscopy, Rayleigh spectroscopy, and Schlieren imaging are being used to acquire plume measurements of AF-M315E thrusters. Plume data will include temperature, velocity, relative density, and species concentration. The plume measurement data will be compared to the corresponding simulations of the plume model. The GRC effort will establish a data set of AF-M315E plume measurements and a plume model that can be used for future AF-M315E applications.

Sample and plume luminescence in fast heavy ion induced desorption

International Nuclear Information System (INIS)

Tuszynski, W.; Koch, K.; Hilf, E.R.

1996-01-01

The luminescence arising in 252 Cf-fission fragment induced desorption events has been measured using the time-correlated single photon counting technique. Photons emitted from the sample have been guided from a plasma desorption ion source to a photodetector by an optical fibre. Spectra and decay functions have been obtained using thin layers of Coronene or POPOP as samples. The results are strongly dependent on the acceleration field applied for ion extraction. Approximately 10 photons per fission fragment have been produced when applying no accelerating voltage. The results clearly show that these photons come from radiative electronic relaxations of molecules in the solid sample. Considerably more photons per fission fragment have been produced when applying a positive acceleration voltage. The intensity increases almost linearly for acceleration fields below 10 kV/cm and saturates at a nearly 10-fold higher value when compared to no acceleration. The intensity is also affected by the homogeneity of the accelerating field. These additional photons are attributed to radiative electronic relaxations of desorbed neutral molecules in the plume excited by inelastic collisions with accelerated positive ions. No additional photons have been observed when extracting negative ions. The negative ions produced do obviously not hit and/or excite desorbed neutral molecules, presumably due to their specific desorption characteristics. The experimental data have been analyzed by comparing with the cw and time-resolved sample luminescence obtained by optical excitation. The findings demonstrate that valuable information on ion-solid interactions, on specific desorption quantities and on processes in the plume can be obtained by measuring and analyzing the luminescence induced by the impact of high energy primary ions. (orig.)

Biodegradation at Dynamic Plume Fringes: Mixing Versus Reaction Control

Science.gov (United States)

Cirpka, O. A.; Eckert, D.; Griebler, C.; Haberer, C.; Kürzinger, P.; Bauer, R.; Mellage, A.

2014-12-01

Biodegradation of continuously emitted plumes is known to be most pronounced at the plume fringe, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. Under steady-state conditions, physical mixing of contaminant and electron acceptor by transverse dispersion was shown to be the major bottleneck for biodegradation, with plume lengths scaling inversely with the bulk transverse dispersivity in quasi two-dimensional settings. Under these conditions, the presence of suitable microbes is essential but the biokinetic parameters do not play an important role. When the location of the plume shifts (caused, e.g., by a fluctuating groundwater table), however, the bacteria are no more situated at the plume fringe and biomass growth, decay, activation and deactivation determine the time lag until the fringe-controlled steady state is approached again. During this time lag, degradation is incomplete. The objective of the presented study was to analyze to which extent flow and transport dynamics diminish effectiveness of fringe-controlled biodegradation and which microbial processes and related biokinetic parameters determine the system response in overall degradation to hydraulic fluctuations. We performed experiments in quasi-two-dimensional flow through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth and maintenance (often subsumed as "biomass decay") microbial dormancy (that is, change into a metabolically inactive state) and

The Entrainment Rate for Buoyant Plumes in a Crossflow

Science.gov (United States)

Devenish, B. J.; Rooney, G. G.; Webster, H. N.; Thomson, D. J.

2010-03-01

We consider large-eddy simulations (LES) of buoyant plumes from a circular source with initial buoyancy flux F 0 released into a stratified environment with constant buoyancy frequency N and a uniform crossflow with velocity U. We make a systematic comparison of the LES results with the mathematical theory of plumes in a crossflow. We pay particular attention to the limits {tilde{U}≪1} and {tilde{U}≫ 1}, where {tilde{U}=U/(F_0 N)^{1/4}}, for which analytical results are possible. For {tilde{U}≫ 1}, the LES results show good agreement with the well-known two-thirds law for the rise in height of the plume. Sufficiently far above the source, the centreline vertical velocity of the LES plumes is consistent with the analytical z -1/3 and z -1/2 scalings for respectively {tilde{U}≪ 1} and {tilde{U}≫ 1}. In the general case, where the entrainment is assumed to be the sum of the contributions from the horizontal and vertical velocity components, we find that the discrepancy between the LES data and numerical solutions of the plume equations is largest for {tilde{U}=O(1)}. We propose a modified additive entrainment assumption in which the contributions from the horizontal and vertical velocity components are not equally weighted. We test this against observations of the plume generated by the Buncefield fire in the U.K. in December 2005 and find that the results compare favourably. We also show that the oscillations of the plume as it settles down to its final rise height may be attenuated by the radiation of gravity waves. For {tilde{U}≪ 1} the oscillations decay rapidly due to the transport of energy away from the plume by gravity waves. For {tilde{U}>rsim 1} the gravity waves travel in the same direction and at the same speed as the flow. In this case, the oscillations of the plume do not decay greatly by radiation of gravity waves.

The planet beyond the plume hypothesis

Science.gov (United States)

Smith, Alan D.; Lewis, Charles

1999-12-01

Acceptance of the theory of plate tectonics was accompanied by the rise of the mantle plume/hotspot concept which has come to dominate geodynamics from its use both as an explanation for the origin of intraplate volcanism and as a reference frame for plate motions. However, even with a large degree of flexibility permitted in plume composition, temperature, size, and depth of origin, adoption of any limited number of hotspots means the plume model cannot account for all occurrences of the type of volcanism it was devised to explain. While scientific protocol would normally demand that an alternative explanation be sought, there have been few challenges to "plume theory" on account of a series of intricate controls set up by the plume model which makes plumes seem to be an essential feature of the Earth. The hotspot frame acts not only as a reference but also controls plate tectonics. Accommodating plumes relegates mantle convection to a weak, sluggish effect such that basal drag appears as a minor, resisting force, with plates having to move themselves by boundary forces and continents having to be rifted by plumes. Correspondingly, the geochemical evolution of the mantle is controlled by the requirement to isolate subducted crust into plume sources which limits potential buffers on the composition of the MORB-source to plume- or lower mantle material. Crustal growth and Precambrian tectonics are controlled by interpretations of greenstone belts as oceanic plateaus generated by plumes. Challenges to any aspect of the plume model are thus liable to be dismissed unless a counter explanation is offered across the geodynamic spectrum influenced by "plume theory". Nonetheless, an alternative synthesis can be made based on longstanding petrological evidence for derivation of intraplate volcanism from volatile-bearing sources (wetspots) in conjunction with concepts dismissed for being incompatible or superfluous to "plume theory". In the alternative Earth, the sources for

[Models for quantification of fluid saturation in two-phase flow system by light transmission method and its application].

Science.gov (United States)

Zhang, Yan-Hong; Ye, Shu-Jun; Wu, Ji-Chun

2014-06-01

Based on light transmission method in quantification of liquid saturation and its application in two-phase flow system, two groups of sandbox experiments were set up to study the migration of gas or Dense Non-Aqueous Phase Liquids (DNAPLs) in water saturated porous media. The migration of gas or DNAPL was monitored in the study. Two modified Light Intensity-Saturation (LIS) models for water/gas two-phase system were applied and verified by the experiment data. Moreover two new LIS models for NAPL/water system were developed and applied to simulate the DNAPL infiltration experiment data. The gas injection experiment showed that gas moved upward to the top of the sandbox in the form of 'fingering' and finally formed continuous distribution. The results of DNAPL infiltration experiment showed that TCE mainly moved downward as the result of its gravity, eventually formed irregular plume and accumulated at the bottom of the sandbox. The outcomes of two LIS models for water/gas system (WG-A and WG-B) were consistent to the measured data. The results of two LIS models for NAPL/water system (NW-A and NW-B) fit well with the observations, and Model NW-A based on assumption of individual drainage gave better results. It could be a useful reference for quantification of NAPL/water saturation in porous media system.

On the coupled unsaturated–saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

Directory of Open Access Journals (Sweden)

X. Liang

2017-03-01

established with special consideration of the coupled unsaturated–saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace–finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant in unconfined aquifers affected from above by the unsaturated flow process.

Ablation plume dynamics in a background gas

DEFF Research Database (Denmark)

Amoruso, Salvatore; Schou, Jørgen; Lunney, James G.

2010-01-01

The expansion of a plume in a background gas of pressure comparable to that used in pulsed laser deposition (PLD) has been analyzed in terms of the model of Predtechensky and Mayorov (PM). This approach gives a relatively clear and simple description of the essential hydrodynamics during the expa......The expansion of a plume in a background gas of pressure comparable to that used in pulsed laser deposition (PLD) has been analyzed in terms of the model of Predtechensky and Mayorov (PM). This approach gives a relatively clear and simple description of the essential hydrodynamics during...... the expansion. The model also leads to an insightful treatment of the stopping behavior in dimensionless units for plumes and background gases of different atomic/molecular masses. The energetics of the plume dynamics can also be treated with this model. Experimental time-of-flight data of silver ions in a neon...... background gas show a fair agreement with predictions from the PM-model. Finally we discuss the validity of the model, if the work done by the pressure of the background gas is neglected....

Subsurface migration of petroleum hydrocarbons: A case study of immiscible migration and chromatographic separation

International Nuclear Information System (INIS)

Dawson, H.E.

1991-01-01

The subsurface distribution of a leaked crude oil illustrates the combined influence of both the chemical and physical properties of soil and free product on the migration of petroleum hydrocarbons. Immiscible phase behavior was observed, as well as chromatographic-like separation of the lighter constituents of the crude oil from the heavier constituents. After downward migration through approximately 50 ft of unsaturated, heterogeneous alluvial sediments, the crude oil formed a horizontal plume on top of a perched, saturated zone. Immiscible phase trapping is evident from the occurrence of very high concentration of hydrocarbons in both the vertical and horizontal plumes. Samples taken from the vertical zone of contamination indicate a transition from heavier hydrocarbons near the surface to lighter hydrocarbons at depth. This phenomenon is attributed to chromatographic-like separation of the heavier hydrocarbons by the soil, possibly due to preferential solubility of the lighter hydrocarbons in percolating ran water

Subsurface oil release field experiment - observations and modelling of subsurface plume behaviour

International Nuclear Information System (INIS)

Rye, H.; Brandvik, P.J.; Reed, M.

1996-01-01

An experiment was conducted at sea, in which oil was released from 107 metres depth, in order to study plume behaviour. The objective of the underwater release was to simulate a pipeline leakage without gas and high pressure and to study the behaviour of the rising plume. A numerical model for the underwater plume behaviour was used for comparison with field data. The expected path of the plume, the time expected for the plume to reach the sea surface and the width of the plume was modelled. Field data and the numerical model were in good agreement. 10 refs., 2 tabs., 9 figs

3-D spectral Induced Polarization (IP) imaging: Non-invasive characterization of contaminant plumes. Annual progress report, September 15, 1996 - September 14, 1997

International Nuclear Information System (INIS)

Frye, K.M.; Lesmes, D.P.; Morgan, F.D.; Rodi, W.; Shi, W.; Sturrock, J.

1997-01-01

'The objective of this project is to develop the scientific basis for characterizing contaminant plumes in the earth''s subsurface using field measurements of induced polarization (IP) effects. The first-year accomplishments are (1) laboratory experiments on fluid-saturated sandstones quantifying the dependence of spectral IP responses on solution chemistry and rock micro-geometry; (2) library research on the current understanding of electromagnetic coupling effects on IP data acquired in the field: and (3) development of prototype forward modeling and inversion algorithms for interpreting IP data in terms of 3-D models of complex resistivity.'

Observed rise of visible plumes from hyperbolic natural draft cooling towers

Energy Technology Data Exchange (ETDEWEB)

Brennan, P T [Smith-Singer Meteorologists, Inc., Amityville, NY; Seymour, D E; Butler, M J; Kramer, M L; Smith, M E; Frankenberg, T T

1976-01-01

The behavior of natural draft cooling tower plumes and related meteorological variables have been measured from aircraft near three major plants of the American Electric Power System. The rise of those plumes which persisted long enough to reach a stabilized height depended primarily upon the height of the capping inversion aloft. All such plumes rose to elevations of 425 m or more above grade. No significant relationships between plume rise and wind speed, plant load, or ambient temperature were found. We conclude that simple temperature humidity soundings in the vicinity of the towers would serve as effective predictors of plume rise and persistence.

Chasing Sources and Transports of Methane Plumes in the Northern Gulf of Mexico Using In Situ Sensors on Untethered Landers

Science.gov (United States)

Martens, C. S.; Mendlovitz, H.; Seim, H.; Lapham, L.; Magen, C.; Joye, S. B.; MacDonald, I. R.; Asper, V. L.; Diercks, A. R.

2016-02-01

In situ time-series measurements of light hydrocarbons, oxygen, temperature and bottom currents from landers and elevators in the benthic boundary layer (BBL) at multiple sites in the northern Gulf of Mexico reveal spatial and temporal variability in methane concentrations controlled by horizontal advection of methane-rich plumes originating from nearby natural oil and gas seeps. Multi-sensor systems deployed for several weeks within 1m of the seafloor at depths from 882 to 1622m revealed methane concentrations ranging from near atmospheric saturation (gas chromatography. Continuous laser sensor methane measurements from mini-landers deployed in September 2015 at our Horn Dome and Bush Hill sites featuring numerous gas seeps revealed methane concentrations ranging from data within the BBL and friction layer from untethered platforms provides important new opportunities for monitoring the impacts of natural seeps and accidental hydrocarbon releases. The instrumented approaches we have developed to simultaneously monitor methane sources and physical processes controlling plume development and transport will enable more effective responses to further accidental hydrocarbon releases.

NW Iberia Shelf Dynamics. Study of the Douro River Plume.

Directory of Open Access Journals (Sweden)

Isabel Iglesias

2014-06-01

Full Text Available River plumes are one of the most important mechanisms that transport the terrestrial materials to the coast and the ocean. Some examples of those materials are pollutants, essential nutrients, which enhance the phytoplankton productivity or sediments, which settle on the seabed producing modifications on the bathymetry affecting the navigation channels. The mixing between the riverine and the oceanic waters can induce instabilities, which might generate bulges, filaments, and buoyant currents over the continental shelf. Offshore, the buoyant riverine water could form a front with the oceanic waters often related with the occurrence of current-jets, eddies and strong mixing. The study and modelling of the river plumes is a key factor for the complete understanding of sediment transport mechanisms and patterns, and of coastal physics and dynamic processes. On this study the Douro River plume will be simulated. The Douro River is located on the north-west Iberian coast and its daily averaged freshwater discharge can range values from 0 to 13000 m3/s. This variability impacts the formation of the river plumes and its dispersion along the continental shelf. This study builds on the long-term objective of generate a Douro River plume forecasting system as part of the RAIA and RAIA.co projects. Satellite imagery was analyzed showing that the river Douro is one of the main sources of suspended particles, dissolved material and chlorophyll in the NW Iberian Shelf. The Regional Oceanic Modeling System (ROMS model was selected to reproduce scenarios of plume generation, retention and dispersion. Whit this model, three types of simulations were performed: (i schematic winds simulations with prescribed river flow, wind speed and direction; (ii multi-year climatological simulation, with river flow and temperature change for each month; (iii extreme case simulation, based on the Entre-os-Rios accident situation. The schematic wind case-studies suggest that the

Appearance property and mechanism of plume produced by pulsed ultraviolet laser ablating copper

International Nuclear Information System (INIS)

Huang Qingju; Li Fuquan; Wang Honghua

2008-01-01

Time-resolved measurements of plume emission spectra by pulsed ultraviolet laser ablating copper in neon were analyzed, and the photographs of plume from laser ablating copper were taken. The experimental results show that plume has different colours in different ranges. At low pressure the centre layer and middle layer colours of plume are mixed colour, and the outer layer colours of plume are yellow and green. At middle pressure the centre layer and middle layer colours of plume are white, and the outer layer colour of plume is pea green. At high pressure the centre layer and middle layer colours of plume are white, and the outer layer colour of plume is faintness green. The plume range is pressed with the rising of ambient gas pressure, and the range colour gets thin with the rising of ambient gas pressure. The plume excitation radiation mechanism in pulsed ultraviolet laser ablating copper was discussed. The primary excitation radiation mechanism in plume is electron collision energy transfer and atom collision energy transfer at low pressure and middle pressure, and it is electrons Bremsstrahlung and recombination excitation radiation of electron and ion at high pressure. The model can be used to explain the experimental result qualitatively. (authors)

Using Contaminant Transport Modeling to Determine Historical Discharges at the Surface

Science.gov (United States)

Fogwell, T. W.

2013-12-01

When it is determined that a contaminated site needs to be remediated, the issue of who is going to pay for that remediation is an immediate concern. This means that there needs to be a determination of who the responsible parties are for the existing contamination. Seldom is it the case that records have been made and kept of the surface contaminant discharges. In many cases it is possible to determine the relative amount of contaminant discharge at the surface of the various responsible parties by employing a careful analysis of the history of contaminant transport through the surface, through the vadose zone, and within the saturated zone. The process begins with the development of a dynamic conceptual site model that takes into account the important features of the transport of the contaminants through the vadose zone and in the groundwater. The parameters for this model can be derived from flow data available for the site. The resulting contaminant transport model is a composite of the vadose zone transport model, together with the saturated zone (groundwater) flow model. Any calibration of the model should be carefully employed in order to avoid using information about the conclusions of the relative discharge amounts of the responsible parties in determining the calibrated parameters. Determination of the leading edge of the plume is an important first step. It is associated with the first discharges from the surface of the site. If there were several discharging parties at the same time, then it is important to establish a chemical or isotopic signature of the chemicals that were discharged. The time duration of the first discharger needs to be determined as accurately as possible in order to establish the appropriate characterization of the leading portion of the resulting plume in the groundwater. The information about the first discharger and the resulting part of the plume associated with this discharger serves as a basis for the determination of the

Environmental controls on phytoplankton community composition in the Thames plume, U.K.

Science.gov (United States)

Weston, Keith; Greenwood, Naomi; Fernand, Liam; Pearce, David J.; Sivyer, David B.

2008-11-01

The aim of this study was to investigate controls on the phytoplankton community composition and biogeochemistry of the estuarine plume zone of the River Thames, U.K. using an instrumented moored buoy for in situ measurements and preserved sample collection, and laboratory-based measurements from samples collected at the same site. Instrumentation on the moored buoy enabled high frequency measurements of a suite of environmental variables including in situ chlorophyll, water-column integrated irradiance, macronutrients throughout an annual cycle for 2001 e.g. nitrate and silicate, and phytoplankton biomass and species composition. The Thames plume region acts as a conduit for fluvial nutrients into the wider southern North Sea with typical winter concentrations of 45 μM nitrate, 17 μM silicate and 2 μM phosphate measured. The spring bloom resulted from water-column integrated irradiance increasing above 60 W h m - 2 d - 1 and was initially dominated by a diatom bloom mainly composed of Nitzschia sp. and Odontella sinesis. The spring bloom then switched after ˜ 30 days to become dominated by the flagellate Phaeocystis reaching a maximum chlorophyll concentration of 37.8 μg L - 1 . During the spring bloom there were high numbers of the heterotrophic dinoflagellates Gyrodinium spirale and Katodinium glaucum that potentially grazed the phytoplankton bloom. This diatom-flagellate switch was predicted to be due to a combination of further increasing water-column integrated irradiance > 100 W h m - 2 d - 1 and/or silicate reaching potentially limiting concentrations (nutrient and phytoplankton processing and transport to the southern North Sea. The use of a combination of moorings and ship-based sampling was essential in understanding the factors influencing nutrient transport, phytoplankton biomass and species composition in this shelf sea plume region.

Observations of subauroral ionospheric dynamics during SED plume passage at Millstone Hill

Science.gov (United States)

Zhang, S.; Erickson, P. J.; Coster, A. J.

2017-12-01

Storm enhanced density (SED) is a characteristic ionospheric storm time structure, with a significant plasma density enhancement in a narrow zone. SED structures often (but not always) span the continental US with a base in the US northeast at the afternoon and dusk sector, extending westward or northwest into the high latitude dayside cusp region. It is a typical and repeatable space weather phenomenon occurring during the main phase of magnetic storms with intensity ranging from active to disturbed levels. Observations of stormtime ionospheric density enhancement at subauroral latitudes have a long history, and were termed the 'dusk effect' until relatively recently, when dense networks of GNSS receivers have allowed us to view this structure with much finer spatial and temporal resolution. The formation of a SED plume is a topic under intensive community investigation, but in general it is believed that stormtime ionospheric dynamics and processes within the coupling magnetosphere-ionosphere-thermosphere system are responsible. For instance, poleward and sunward plasma drifts at the edge of the expanded dusk sector high-latitude convection can be important. Subauroral polarization stream (SAPS) are often observed at the poleward edge of the SED plume where ionospheric conductivity is low. SAPS is a huge westward ion flow that can convect ionospheric plasma from the afternoon or evening sector where solar photoionization production is waning, creating low density or density troughs. Stormtime penetration electric fields also exist, creating enhanced low and mid latitude upward ion drifts that move ionospheric plasma upward from the low altitude region where they are produced. This provides another important ionization source to contribute to maintaining the SED plume. This paper will provide analysis of the relative strength of these factors by using joint datasets of current geospace storm events obtained with the Millstone Hill incoherent scatter radar, GNSS

Wireless Sensor Network Based Subsurface Contaminant Plume Monitoring

Science.gov (United States)

2012-04-16

Sensor Network (WSN) to monitor contaminant plume movement in naturally heterogeneous subsurface formations to advance the sensor networking based...time to assess the source and predict future plume behavior. This proof-of-concept research aimed at demonstrating the use of an intelligent Wireless

Can molecular diffusion explain Space Shuttle plume spreading?

Science.gov (United States)

Meier, R. R.; Plane, John M. C.; Stevens, Michael H.; Paxton, L. J.; Christensen, A. B.; Crowley, G.

2010-04-01

The satellite-borne Global Ultraviolet Imager (GUVI) has produced more than 20 images of NASA Space Shuttle main engine plumes in the lower thermosphere. These reveal atomic hydrogen and, by inference, water vapor transport over hemispherical-scale distances with speeds much faster than expected from models of thermospheric wind motions. Furthermore, the hydrogen plumes expand rapidly. We find rates that exceed the horizontal diffusion speed at nominal plume altitudes of 104-112 km. Kelley et al. (2009) have proposed a 2-D turbulence mechanism to explain the observed spreading rates (and rapid advection) of the plumes. But upon further investigation, we conclude that H atom diffusion can indeed account for the observed expansion rates by recognizing that vertical diffusion quickly conveys atoms to higher altitudes where horizontal diffusion is much more rapid. We also find evidence for H atom production directly during the Shuttle's main engine burn.

Review of the potential effects of alkaline plume migration from a cementitious repository for radioactive waste

International Nuclear Information System (INIS)

Savage, D.

1997-01-01

Extensive use of cement and concrete is envisaged in the construction of geological repositories for low and intermediate-level radioactive wastes, both for structural, and encapsulation and backfilling purposes. Saturation of these materials with groundwater may occur in the post-closure period of disposal, producing a hyperalkaline pore fluid with a pH in the range 10-13.5. These pore fluids have the potential to migrate from the repository according to local groundwater flow conditions and react chemically with the host rock. These chemical reactions may affect the rock's capacity to retard the migration of radionuclides released from the repository after the degradation of the waste packages. The effects of these chemical reactions on the behaviour of the repository rock as a barrier to waste migration need to be investigated for the purposes of assessing the safety of the repository design (so-called 'safety assessment' or 'performance assessment'). The objectives of the work reported here were to: identify those processes influencing radionuclide mobility in the geosphere which could be affected by plume migration; review literature relevant to alkali-rock reaction; contact organisations carrying out relevant research and summarise their current and future activities; and make recommendations how the effects of plume migration can be incorporated into models of repository performance assessment. (author)

Analysis of plume rise data from five TVA steam plants

International Nuclear Information System (INIS)

Anfossi, D.

1985-01-01

A large data set containing the measurements of the rise of plumes emitted by five TVA steam plants was examined. Particular attention was paid to the problem of the merging of the plumes emitted by adjacent stacks and to the role played by the wind angle in this respect. It was demonstrated that there is a noticeable rise enhancement of merged plumes with respect to single emissions, both in neutral and in stable conditions, as far as transversal and parallel plumes are concerned. For plumes advected normal to the row of the stacks the enhancement is noticeable only in the final stage of rise. The existence of a critical angle for merging suggested enhancement is noticeable only in the final stage of rise. The existence of a critical angle for merging suggested by Briggs was examined. Finally, a formula to describe plume rise in the transitional and in the final phase, both in neutral and stable conditions, is proposed; it was obtained by interpolation of two familiar Brigg's equations

Modelling suction instabilities in soils at varying degrees of saturation

Directory of Open Access Journals (Sweden)

Buscarnera Giuseppe

2016-01-01

Full Text Available Wetting paths imparted by the natural environment and/or human activities affect the state of soils in the near-surface, promoting transitions across different regimes of saturation. This paper discusses a set of techniques aimed at quantifying the role of hydrologic processes on the hydro-mechanical stability of soil specimens subjected to saturation events. Emphasis is given to the mechanical conditions leading to coupled flow/deformation instabilities. For this purpose, energy balance arguments for three-phase systems are used to derive second-order work expressions applicable to various regimes of saturation. Controllability analyses are then performed to relate such work input with constitutive singularities that reflect the loss of strength under coupled and/or uncoupled hydro-mechanical forcing. A suction-dependent plastic model is finally used to track the evolution of stability conditions in samples subjected to wetting, thus quantifying the growth of the potential for coupled failure modes upon increasing degree of saturation. These findings are eventually linked with the properties of the field equations that govern pore pressure transients, thus disclosing a conceptual link between the onset of coupled hydro-mechanical failures and the evolution of suction with time. Such results point out that mathematical instabilities caused by a non-linear suction dependent behaviour play an important role in the advanced constitutive and/or numerical tools that are commonly used for the analysis of geomechanical problems in the unsaturated zone, and further stress that the relation between suction transients and soil deformations is a key factor for the interpretation of runaway failures caused by intense saturation events.

Airborne Gamma-ray Measurements in the Chernobyl Plume

DEFF Research Database (Denmark)

Grasty, R. L.; Hovgaard, Jens; Multala, J.

1997-01-01

On 29 April 1986, the Geological Survey of Finland (GSF) survey aircraft with a gamma ray spectrometer flew through a radioactive plume from the Chernobyl nuclear accident. The aircraft became contaminated and the gamma spectrometer measured radioactivity in the plume as well as radioactivity...

EM Modelling of RF Propagation Through Plasma Plumes

Science.gov (United States)

Pandolfo, L.; Bandinelli, M.; Araque Quijano, J. L.; Vecchi, G.; Pawlak, H.; Marliani, F.

2012-05-01

Electric propulsion is a commercially attractive solution for attitude and position control of geostationary satellites. Hall-effect ion thrusters generate a localized plasma flow in the surrounding of the satellite, whose impact on the communication system needs to be qualitatively and quantitatively assessed. An electromagnetic modelling tool has been developed and integrated into the Antenna Design Framework- ElectroMagnetic Satellite (ADF-EMS). The system is able to guide the user from the plume definition phases through plume installation and simulation. A validation activity has been carried out and the system has been applied to the plume modulation analysis of SGEO/Hispasat mission.

Laser beam-plasma plume interaction during laser welding

Science.gov (United States)

Hoffman, Jacek; Moscicki, Tomasz; Szymanski, Zygmunt

2003-10-01

Laser welding process is unstable because the keyhole wall performs oscillations which results in the oscillations of plasma plume over the keyhole mouth. The characteristic frequencies are equal to 0.5-4 kHz. Since plasma plume absorbs and refracts laser radiation, plasma oscillations modulate the laser beam before it reaches the workpiece. In this work temporary electron densities and temperatures are determined in the peaks of plasma bursts during welding with a continuous wave CO2 laser. It has been found that during strong bursts the plasma plume over the keyhole consists of metal vapour only, being not diluted by the shielding gas. As expected the values of electron density are about two times higher in peaks than their time-averaged values. Since the plasma absorption coefficient scales as ~N2e/T3/2 (for CO2 laser radiation) the results show that the power of the laser beam reaching the metal surface is modulated by the plasma plume oscillations. The attenuation factor equals 4-6% of the laser power but it is expected that it is doubled by the refraction effect. The results, together with the analysis of the colour pictures from streak camera, allow also interpretation of the dynamics of the plasma plume.

DeepBlow - a Lagrangian plume model for deep water blowouts

International Nuclear Information System (INIS)

Johansen, Oeistein

2000-01-01

This paper presents a sub-sea blowout model designed with special emphasis on deep-water conditions. The model is an integral plume model based on a Lagrangian concept. This concept is applied to multiphase discharges in the formation of water, oil and gas in a stratified water column with variable currents. The gas may be converted to hydrate in combination with seawater, dissolved into the plume water, or leaking out of the plume due to the slip between rising gas bubbles and the plume trajectory. Non-ideal behaviour of the gas is accounted for by the introduction of pressure- and temperature-dependent compressibility z-factor in the equation of state. A number of case studies are presented in the paper. One of the cases (blowout from 100 m depth) is compared with observations from a field experiment conducted in Norwegian waters in June 1996. The model results are found to compare favourably with the field observations when dissolution of gas into seawater is accounted in the model. For discharges at intermediate to shallow depths (100-250 m), the two major processes limiting plume rise will be: (a) dissolution of gas into ambient water, or (b) bubbles rising out of the inclined plume. These processes tend to be self-enforcing, i.e., when a gas is lost by either of these processes, plume rise tends to slow down and more time will be available for dissolution. For discharges in deep waters (700-1500 m depth), hydrate formation is found to be a dominating process in limiting plume rise. (Author)

A study of space shuttle plumes in the lower thermosphere

Science.gov (United States)

Meier, R. R.; Stevens, Michael H.; Plane, John M. C.; Emmert, J. T.; Crowley, G.; Azeem, I.; Paxton, L. J.; Christensen, A. B.

2011-12-01

During the space shuttle main engine burn, some 350 t of water vapor are deposited at between 100 and 115 km. Subsequent photodissociation of water produces large plumes of atomic hydrogen that can expand rapidly and extend for thousands of kilometers. From 2002 to 2007, the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite imaged many of these hydrogen plumes at Lyman α (121.567 nm) while viewing in the nadir. The images reveal rapid plume expansion and occasional very fast transport to both north and south polar regions. Some plumes persist for up to 6 d. Near-simultaneous direct detections of water vapor were made with the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) instrument, also on TIMED. We compare the spreading of the hydrogen plume with a two-dimensional model that includes photodissociation as well as both vertical and horizontal diffusion. Molecular diffusion appears to be sufficient to account for the horizontal expansion, although wind shears and turbulent mixing may also contribute. We compare the bulk motion of the observed plumes with wind climatologies derived from satellite observations. The plumes can move much faster than predictions of wind climatologies. But dynamical processes not contained in wind climatologies, such as the quasi-two-day wave, can account for at least some of the high speed observations. The plume phenomena raise a number of important questions about lower thermospheric and mesospheric processes, ranging from dynamics and chemistry to polar mesospheric cloud formation and climatology.

Controls on deep drainage beneath the root soil zone in snowmelt-dominated environments

Science.gov (United States)

Hammond, J. C.; Harpold, A. A.; Kampf, S. K.

2017-12-01

Snowmelt is the dominant source of streamflow generation and groundwater recharge in many high elevation and high latitude locations, yet we still lack a detailed understanding of how snowmelt is partitioned between the soil, deep drainage, and streamflow under a variety of soil, climate, and snow conditions. Here we use Hydrus 1-D simulations with historical inputs from five SNOTEL snow monitoring sites in each of three regions, Cascades, Sierra, and Southern Rockies, to investigate how inter-annual variability on water input rate and duration affects soil saturation and deep drainage. Each input scenario was run with three different soil profiles of varying hydraulic conductivity, soil texture, and bulk density. We also created artificial snowmelt scenarios to test how snowmelt intermittence affects deep drainage. Results indicate that precipitation is the strongest predictor (R2 = 0.83) of deep drainage below the root zone, with weaker relationships observed between deep drainage and snow persistence, peak snow water equivalent, and melt rate. The ratio of deep drainage to precipitation shows a stronger positive relationship to melt rate suggesting that a greater fraction of input becomes deep drainage at higher melt rates. For a given amount of precipitation, rapid, concentrated snowmelt may create greater deep drainage below the root zone than slower, intermittent melt. Deep drainage requires saturation below the root zone, so saturated hydraulic conductivity serves as a primary control on deep drainage magnitude. Deep drainage response to climate is mostly independent of soil texture because of its reliance on saturated conditions. Mean water year saturations of deep soil layers can predict deep drainage and may be a useful way to compare sites in soils with soil hydraulic porosities. The unit depth of surface runoff often is often greater than deep drainage at daily and annual timescales, as snowmelt exceeds infiltration capacity in near-surface soil layers

Studies of the environmental impact of evaporative cooling tower plumes

International Nuclear Information System (INIS)

Thomson, D.W.

1978-01-01

This ongoing research program of the environmental impact of natural-draft evaporative cooling tower plumes consists principally of a comprehensive series of airborne measurements of a variety of the physical characteristics of the plumes and, to a lesser extent, of preliminary studies of remote sodar plume probing techniques and the development of simplified dynamical numerical models suitable for use in conducting field measurement programs. The PSU Doppler sodar was used at the Keystone Power Plant in southwestern Pennsylvania for an extended series of remote measurements of the characteristics of plume turbulent temperature and velocity fluctuations and results are discussed

Investigating the influence of DNAPL spill characteristics on source zone architecture and mass removal in pool-dominated source zones

Science.gov (United States)

Wallace, K. A.; Abriola, L.; Chen, M.; Ramsburg, A.; Pennell, K. D.; Christ, J.

2009-12-01

Multiphase, compositional simulators were employed to investigate the spill characteristics and subsurface properties that lead to pool-dominated, dense non-aqueous phase liquid (DNAPL) source zone architectures. DNAPL pools commonly form at textural interfaces where low permeability lenses restrict the vertical migration of DNAPL, allowing for DNAPL to accumulate, reaching high saturation. Significant pooling has been observed in bench-scale experiments and field settings. However, commonly employed numerical simulations rarely predict the pooling suspected in the field. Given the importance of pooling on the efficacy of mass recovery and the down-gradient contaminant signal, it is important to understand the predominant factors affecting the creation of pool-dominated source zones and their subsequent mass discharge. In this work, contaminant properties, spill characteristics and subsurface permeability were varied to investigate the factors contributing to the development of a pool-dominated source zone. DNAPL infiltration and entrapment simulations were conducted in two- and three-dimensional domains using the University of Texas Chemical Compositional (UTCHEM) simulator. A modified version of MT3DMS was then used to simulate DNAPL dissolution and mass discharge. Numerical mesh size was varied to investigate the importance of numerical model parameters on simulations results. The temporal evolution of commonly employed source zone architecture metrics, such as the maximum DNAPL saturation, first and second spatial moments, and fraction of DNAPL mass located in pools, was monitored to determine how the source zone architecture evolved with time. Mass discharge was monitored to identify the link between source zone architecture and down-gradient contaminant flux. Contaminant characteristics and the presence of extensive low permeability lenses appeared to have the most influence on the development of a pool-dominated source zone. The link between DNAPL mass

Soil Systems for Upscaling Saturated Hydraulic Conductivity (Ksat) for Hydrological Modeling in the Critical Zone

Science.gov (United States)

Successful hydrological model predictions depend on appropriate framing of scale and the spatial-temporal accuracy of input parameters describing soil hydraulic properties. Saturated soil hydraulic conductivity (Ksat) is one of the most important properties influencing water movement through soil un...

Fractal analysis: A new tool in transient volcanic ash plume characterization.

Science.gov (United States)

Tournigand, Pierre-Yves; Peña Fernandez, Juan Jose; Taddeucci, Jacopo; Perugini, Diego; Sesterhenn, Jörn

2017-04-01

Transient volcanic plumes are time-dependent features generated by unstable eruptive sources. They represent a threat to human health and infrastructures, and a challenge to characterize due to their intrinsic instability. Plumes have been investigated through physical (e.g. visible, thermal, UV, radar imagery), experimental and numerical studies in order to provide new insights about their dynamics and better anticipate their behavior. It has been shown experimentally that plume dynamics is strongly dependent to source conditions and that plume shape evolution holds key to retrieve these conditions. In this study, a shape evolution analysis is performed on thermal high-speed videos of volcanic plumes from three different volcanoes Sakurajima (Japan), Stromboli (Italy) and Fuego (Guatemala), recorded with a FLIR SC655 thermal camera during several field campaigns between 2012 and 2016. To complete this dataset, three numerical gas-jet simulations at different Reynolds number (2000, 5000 and 10000) have been used in order to set reference values to the natural cases. Turbulent flow shapes are well known to feature scale-invariant structures and a high degree of complexity. For this reason we characterized the bi-dimensional shape of natural and synthetic plumes by using a fractal descriptor. Such method has been applied in other studies on experimental turbulent jets as well as on atmospheric clouds and have shown promising results. At each time-step plume contour has been manually outlined and measured using the box-counting method. This method consists in covering the image with squares of variable sizes and counting the number of squares containing the plume outline. The negative slope of the number of squares in function of their size in a log-log plot gives the fractal dimension of the plume at a given time. Preliminary results show an increase over time of the fractal dimension for natural volcanic plume as well as for the numerically simulated ones, but at

Oceanic magmatic evolution during ocean opening under influence of mantle plume

Science.gov (United States)

Sushchevskaya, Nadezhda; Melanholina, Elena; Belyatsky, Boris; Krymsky, Robert; Migdisova, Natalya

2015-04-01

Petrology, geochemistry and geophysics as well as numerical simulation of spreading processes in plume impact environments on examples of Atlantic Ocean Iceland and the Central Atlantic plumes and Kerguelen plume in the Indian Ocean reveal: - under interaction of large plume and continental landmass the plume can contribute to splitting off individual lithosphere blocks, and their subsequent movement into the emergent ocean. At the same time enriched plume components often have geochemical characteristics of the intact continental lithosphere by early plume exposure. This is typical for trap magmatism in Antarctica, and for magmatism of North and Central Atlantic margins; - in the course of the geodynamic reconstruction under the whole region of the South Atlantic was formed (not in one step) metasomatized enriched sub-oceanic mantle with pyroxenite mantle geochemical characteristics and isotopic composition of enriched HIMU and EM-2 sources. That is typical for most of the islands in the West Antarctic. This mantle through spreading axes jumping involved in different proportions in the melting under the influence of higher-temperature rising asthenospheric lherzolite mantle; - CAP activity was brief enough (200 ± 2 Ma), but Karoo-Maud plume worked for a longer time and continued from 180 to 170 Ma ago in the main phase. Plume impact within Antarctica distributed to the South and to the East, leading to the formation of extended igneous provinces along the Transantarctic Mountains and along the east coast (Queen Maud Land province and Schirmacher Oasis). Moreover, this plume activity may be continued later on, after about 40 million years cessation, as Kerguelen plume within the newly-formed Indian Ocean, significantly affects the nature of the rift magmatism; - a large extended uplift in the eastern part of the Indian Ocean - Southeastern Indian Ridge (SEIR) was formed on the ancient spreading Wharton ridge near active Kerguelen plume. The strongest plume

Ozone production efficiency of a ship-plume: ITCT 2K2 case study.

Science.gov (United States)

Kim, Hyun S; Kim, Yong H; Han, Kyung M; Kim, Jhoon; Song, Chul H

2016-01-01

Ozone production efficiency (OPE) of ship plume was first evaluated in this study, based on ship-plume photochemical/dynamic model simulations and the ship-plume composition data measured during the ITCT 2K2 (Intercontinental Transport and Chemical Transformation 2002) aircraft campaign. The averaged instantaneous OPEs (OPE(i)‾) estimated via the ship-plume photochemical/dynamic modeling for the ITCT 2K2 ship-plume ranged between 4.61 and 18.92, showing that the values vary with the extent of chemical evolution (or chemical stage) of the ship plume and the stability classes of the marine boundary layer (MBL). Together with OPE(i)‾, the equivalent OPEs (OPE(e)‾) for the entire ITCT 2K2 ship-plume were also estimated. The OPE(e)‾ values varied between 9.73 (for the stable MBL) and 12.73 (for the moderately stable MBL), which agreed well with the OPE(e)‾ of 12.85 estimated based on the ITCT 2K2 ship-plume observations. It was also found that both the model-simulated and observation-based OPE(e)‾ inside the ship-plume were 0.29-0.38 times smaller than the OPE(e)‾ calculated/measured outside the ITCT 2K2 ship-plume. Such low OPEs insides the ship plume were due to the high levels of NO and non-liner ship-plume photochemistry. Possible implications of this ship-plume OPE study in the global chemistry-transport modeling are also discussed. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Apollo Video Photogrammetry Estimation Of Plume Impingement Effects

Science.gov (United States)

Immer, Christopher; Lane, John; Metzger, Philip T.; Clements, Sandra

2008-01-01

The Constellation Project's planned return to the moon requires numerous landings at the same site. Since the top few centimeters are loosely packed regolith, plume impingement from the Lander ejects the granular material at high velocities. Much work is needed to understand the physics of plume impingement during landing in order to protect hardware surrounding the landing sites. While mostly qualitative in nature, the Apollo Lunar Module landing videos can provide a wealth of quantitative information using modem photogrammetry techniques. The authors have used the digitized videos to quantify plume impingement effects of the landing exhaust on the lunar surface. The dust ejection angle from the plume is estimated at 1-3 degrees. The lofted particle density is estimated at 10(exp 8)- 10(exp 13) particles per cubic meter. Additionally, evidence for ejection of large 10-15 cm sized objects and a dependence of ejection angle on thrust are presented. Further work is ongoing to continue quantitative analysis of the landing videos.

Evaluating the Influence of Pore Architecture and Initial Saturation on Wettability and Relative Permeability in Heterogeneous, Shallow-Shelf Carbonates

Energy Technology Data Exchange (ETDEWEB)

Byrnes, Alan P.; Bhattacharya, Saibal; Victorine, John; Stalder, Ken

2007-09-30

Thin (3-40 ft thick), heterogeneous, limestone and dolomite reservoirs, deposited in shallow-shelf environments, represent a significant fraction of the reservoirs in the U.S. midcontinent and worldwide. In Kansas, reservoirs of the Arbuckle, Mississippian, and Lansing-Kansas City formations account for over 73% of the 6.3 BBO cumulative oil produced over the last century. For these reservoirs basic petrophysical properties (e.g., porosity, absolute permeability, capillary pressure, residual oil saturation to waterflood, resistivity, and relative permeability) vary significantly horizontally, vertically, and with scale of measurement. Many of these reservoirs produce from structures of less than 30-60 ft, and being located in the capillary pressure transition zone, exhibit vertically variable initial saturations and relative permeability properties. Rather than being simpler to model because of their small size, these reservoirs challenge characterization and simulation methodology and illustrate issues that are less apparent in larger reservoirs where transition zone effects are minor and most of the reservoir is at saturations near S{sub wirr}. These issues are further augmented by the presence of variable moldic porosity and possible intermediate to mixed wettability and the influence of these on capillary pressure and relative permeability. Understanding how capillary-pressure properties change with rock lithology and, in turn, within transition zones, and how relative permeability and residual oil saturation to waterflood change through the transition zone is critical to successful reservoir management and as advanced waterflood and improved and enhanced recovery methods are planned and implemented. Major aspects of the proposed study involve a series of tasks to measure data to reveal the nature of how wettability and drainage and imbibition oil-water relative permeability change with pore architecture and initial water saturation. Focus is placed on

Dynamics of vapor plume in transient keyhole during laser welding of stainless steel: Local evaporation, plume swing and gas entrapment into porosity

Science.gov (United States)

Pang, Shengyong; Chen, Xin; Shao, Xinyu; Gong, Shuili; Xiao, Jianzhong

2016-07-01

In order to better understand the local evaporation phenomena of keyhole wall, vapor plume swing above the keyhole and ambient gas entrapment into the porosity defects, the 3D time-dependent dynamics of the metallic vapor plume in a transient keyhole during fiber laser welding is numerically investigated. The vapor dynamical parameters, including the velocity and pressure, are successfully predicted and obtain good agreements with the experimental and literature data. It is found that the vapor plume flow inside the keyhole has complex multiple directions, and this various directions characteristic of the vapor plume is resulted from the dynamic evaporation phenomena with variable locations and orientations on the keyhole wall. The results also demonstrate that because of this dynamic local evaporation, the ejected vapor plume from the keyhole opening is usually in high frequency swinging. The results further indicate that the oscillation frequency of the plume swing angle is around 2.0-8.0 kHz, which is of the same order of magnitude with that of the keyhole depth (2.0-5.0 kHz). This consistency clearly shows that the swing of the ejected vapor plume is closely associated with the keyhole instability during laser welding. Furthermore, it is learned that there is usually a negative pressure region (several hundred Pa lower than the atmospheric pressure) of the vapor flow around the keyhole opening. This pressure could lead to a strong vortex flow near the rear keyhole wall, especially when the velocity of the ejected metallic vapor from the keyhole opening is high. Under the effect of this flow, the ambient gas is involved into the keyhole, and could finally be entrapped into the bubbles within a very short time (keyhole.

Plume expansion dynamics during laser ablation of manganates in oxygen atmosphere

International Nuclear Information System (INIS)

Amoruso, S.; Sambri, A.; Wang, X.

2007-01-01

The effect of ambient gas on the expansion dynamics of the plasma plume generated by excimer laser ablation of a LaMnO 3 target is investigated by using fast photography and optical emission spectroscopy. The plume propagation in an oxygen environment is examined with pressure ranging from vacuum to few hundreds Pa. Imaging analysis of the plume emission has allowed following the changes in the plume front dynamics as a function of time and pressure. The expansion dynamics of the plume front is examined by means of a theoretical description of plume evolution and shock-wave propagation in dimensionless variables. Optical emission spectroscopy analysis showed that the oxides are mainly formed in the gas-phase through reaction of the ablated atomic species with ambient oxygen. Moreover, we observed that the formation of oxides is strongly favoured at a pressure level where the formation of a shock-wave occurs

Tracing Mantle Plumes: Quantifying their Morphology and Behavior from Seismic Tomography

Science.gov (United States)

O'Farrell, K. A.; Eakin, C. M.; Jones, T. D.; Garcia, E.; Robson, A.; Mittal, T.; Lithgow-Bertelloni, C. R.; Jackson, M. G.; Lekic, V.; Rudolph, M. L.

2016-12-01

Hotspot volcanism provides a direct link between the deep mantle and the surface, but the location, depth and source of the mantle plumes that feed hotspots are highly controversial. In order to address this issue it is important to understand the journey along which plumes have travelled through the mantle. The general behavior of plumes in the mantle also has the potential to tell us about the vigor of mantle convection, net rotation of the mantle, the role of thermal versus chemical anomalies, and important bulk physical properties of the mantle such as the viscosity profile. To address these questions we developed an algorithm to trace plume-like features in shear-wave (Vs) seismic tomographic models based on picking local minima in velocity and searching for continuous features with depth. We apply this method to several of the latest tomographic models and can recover 30 or more continuous plume conduits that are >750 km long. Around half of these can be associated with a known hotspot at the surface. We study the morphology of these plume chains and find that the largest lateral deflections occur near the base of the lower mantle and in the upper mantle. We analyze the preferred orientation of the plume deflections and their gradient to infer large scale mantle flow patterns and the depth of viscosity contrasts in the mantle respectively. We also retrieve Vs profiles for our traced plumes and compare with velocity profiles predicted for different mantle adiabat temperatures. We use this to constrain the thermal anomaly associated with these plumes. This thermal anomaly is then converted to a density anomaly and an upwelling velocity is derived. We compare this to buoyancy fluxes calculated at the surface and use this in conjunction with our measured plume tilts/deflections to estimate the strength of the "mantle wind".

Saturated Switching Systems

CERN Document Server

Benzaouia, Abdellah

2012-01-01

Saturated Switching Systems treats the problem of actuator saturation, inherent in all dynamical systems by using two approaches: positive invariance in which the controller is designed to work within a region of non-saturating linear behaviour; and saturation technique which allows saturation but guarantees asymptotic stability. The results obtained are extended from the linear systems in which they were first developed to switching systems with uncertainties, 2D switching systems, switching systems with Markovian jumping and switching systems of the Takagi-Sugeno type. The text represents a thoroughly referenced distillation of results obtained in this field during the last decade. The selected tool for analysis and design of stabilizing controllers is based on multiple Lyapunov functions and linear matrix inequalities. All the results are illustrated with numerical examples and figures many of them being modelled using MATLAB®. Saturated Switching Systems will be of interest to academic researchers in con...

The Prototype Plume Busters Software: A New Tool for Exploring Issues Related to Environmental Policy in Undergraduate-level Earth and Environmental Science Courses

Science.gov (United States)

Macfarlane, P. A.

2006-12-01

Students seldom have an opportunity to explore the issues related to the environmental impact of contamination on water resources. With NSF support we have developed the prototype Plume Busters, in which students take on the role of an environmental consultant. The software consists of an interactive, Java application and accompanying HTML linked pages. Following a pipeline spill, the environmental consultant is hired by the pipeline owner to locate the resulting plume created by the spill and remediate the contaminated aquifer at minimum monetary and time cost. The contamination must be removed from the aquifer before it reaches the river and eventually a downstream public water supply. The application simulates movement of a plume from a pipeline break through a shallow alluvial aquifer towards the river upstream from a municipal water supply intake. To locate the plume, the student places observation wells on a gridded map of the study area and the simulation returns the contaminant concentrations at those locations on the appropriate sample dates. Once the plume is located, the student is able to site pumping and injection wells on the map for aquifer remediation using a simple pump-and-treat technique. The simulation then computes the movement of particles to the pumping wells and returns the cumulative mass removed by the production remediation well. Plume Busters also provides teachers with a means to initiate student exploration of a wide range of environmental issues, including (1) source-water assessment and ground-water and wellhead protection zones, (2) the impact of human activities and technology on the hydrosphere and the biosphere, (3) the role of technology in the resolution of environmental issues (4) legal, social, political, and economic implications of environmental issues, and (5) risk assessment resulting from human activities.

Dispersal of the Pearl River plume over continental shelf in summer

Science.gov (United States)

Chen, Zhaoyun; Gong, Wenping; Cai, Huayang; Chen, Yunzhen; Zhang, Heng

2017-07-01

Satellite images of turbidity were used to study the climatological, monthly, and typical snapshot distributions of the Pearl River plume over the shelf in summer from 2003 to 2016. These images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf. Eastward extension of the plume retreats from June to August. Monthly spatial variations of the plume are characterized by eastward spreading, westward spreading, or both. Time series of monthly plume area was quantified by applying the K-mean clustering method to identify the turbid plume water. Decomposition of the 14-year monthly turbidity data by the empirical orthogonal function (EOF) analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the Pearl River discharge, and the 2nd mode with out-of-phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction. Eight typical plume types were detected from the satellite snapshots. They are characterized by coastal jet, eastward offshore spreading, westward spreading, bidirectional spreading, bulge, isolated patch, offshore branch, and offshore filaments, respectively. Their possible mechanisms are discussed.

Hybrid cooling tower Neckarwestheim 2 cooling function, emission, plume dispersion

International Nuclear Information System (INIS)

Braeuning, G.; Ernst, G.; Maeule, R.; Necker, P.

1990-01-01

The fan-assisted hybrid cooling tower of the 1300 MW power plant Gemeinschafts-Kernkraftwerk Neckarwestheim 2 was designed and constructed based on results from theoretical and experimental studies and experiences from a smaller prototype. The wet part acts in counterflow. The dry part is arranged above the wet part. Each part contains 44 fans. Special attention was payed to the ducts which mix the dry into the wet plume. The cooling function and state, mass flow and contents of the emission were measured. The dispersion of the plume in the atmosphere was observed. The central results are presented in this paper. The cooling function corresponds to the predictions. The content of drifted cooling water in the plume is extremely low. The high velocity of the plume in the exit causes an undisturbed flow into the atmosphere. The hybrid operation reduces visible plumes strongly, especially in warmer and drier ambient air

Groundwater contaminant plume ranking

International Nuclear Information System (INIS)

1988-08-01

Containment plumes at Uranium Mill Tailings Remedial Action (UMTRA) Project sites were ranked to assist in Subpart B (i.e., restoration requirements of 40 CFR Part 192) compliance strategies for each site, to prioritize aquifer restoration, and to budget future requests and allocations. The rankings roughly estimate hazards to the environment and human health, and thus assist in determining for which sites cleanup, if appropriate, will provide the greatest benefits for funds available. The rankings are based on the scores that were obtained using the US Department of Energy's (DOE) Modified Hazard Ranking System (MHRS). The MHRS and HRS consider and score three hazard modes for a site: migration, fire and explosion, and direct contact. The migration hazard mode score reflects the potential for harm to humans or the environment from migration of a hazardous substance off a site by groundwater, surface water, and air; it is a composite of separate scores for each of these routes. For ranking the containment plumes at UMTRA Project sites, it was assumed that each site had been remediated in compliance with the EPA standards and that relict contaminant plumes were present. Therefore, only the groundwater route was scored, and the surface water and air routes were not considered. Section 2.0 of this document describes the assumptions and procedures used to score the groundwater route, and Section 3.0 provides the resulting scores for each site. 40 tabs

Plume tracer experiments at Hinkley Point 'A' [Nuclear Power Station] during 1987

International Nuclear Information System (INIS)

Foster, P.M.

1988-11-01

The results of the first part of a programme of plume dispersion measurements at the Hinkley Point Nuclear Power Station are described. Using SF 6 gas and pyrotechnic smoke tracer techniques developed during an earlier study at Oldbury, measurements of ground level plume behaviour out to about 4 km and elevated plume behaviour out to about 1 km have been made in a series of twelve 1 hour trials and one 15 minute trial. Whereas the Oldbury study considered passive emissions, attention in this study has been focussed on the behaviour of the buoyant shield cooling air emission. Data on plume rise and the degree of plume entrainment by the building wake and on the effects of entrainment and wind meander on plume width and concentration, are presented and discussed in relation to current modelling recommendations. A limited number of 10 minute averaged measurements of plume concentration and 41-Ar decay gamma count were also made at 2 km range and their correlation and variability examined. (author)

Studies of non-isothermal flow in saturated and partially saturated porous media

International Nuclear Information System (INIS)

Ho, C.K.; Maki, K.S.; Glass, R.J.

1993-01-01

Physical and numerical experiments have been performed to investigate the behavior of nonisothermal flow in two-dimensional saturated and partially saturated porous media. The physical experiments were performed to identify non-isothermal flow fields and temperature distributions in fully saturated, half-saturated, and residually saturated two-dimensional porous media with bottom heating and top cooling. Two counter-rotating liquid-phase convective cells were observed to develop in the saturated regions of all three cases. Gas-phase convection was also evidenced in the unsaturated regions of the partially saturated experiments. TOUGH2 numerical simulations of the saturated case were found to be strongly dependent on the assumed boundary conditions of the physical system. Models including heat losses through the boundaries of the test cell produced temperature and flow fields that were in better agreement with the observed temperature and flow fields than models that assumed insulated boundary conditions. A sensitivity analysis also showed that a reduction of the bulk permeability of the porous media in the numerical simulations depressed the effects of convection, flattening the temperature profiles across the test cell

Large-eddy simulation study of oil/gas plumes in stratified fluid with cross current

Science.gov (United States)

Yang, Di; Xiao, Shuolin; Chen, Bicheng; Chamecki, Marcelo; Meneveau, Charles

2017-11-01

Dynamics of the oil/gas plume from a subsea blowout are strongly affected by the seawater stratification and cross current. The buoyant plume entrains ambient seawater and lifts it up to higher elevations. During the rising process, the continuously increasing density difference between the entrained and ambient seawater caused by the stable stratification eventually results in a detrainment of the entrained seawater and small oil droplets at a height of maximum rise (peel height), forming a downward plume outside the rising inner plume. The presence of a cross current breaks the plume's axisymmetry and causes the outer plume to fall along the downstream side of the inner plume. The detrained seawater and oil eventually fall to a neutral buoyancy level (trap height), and disperse horizontally to form an intrusion layer. In this study, the complex plume dynamics is investigated using large-eddy simulation (LES). Various laboratory and field scale cases are simulated to explore the effect of cross current and stratification on the plume dynamics. Based on the LES data, various turbulence statistics of the plume are systematically quantified, leading to some useful insights for modeling the mean plume dynamics using integral plume models. This research is made possible by a RFP-V Grant from The Gulf of Mexico Research Initiative.

Characterizing Io’s Pele, Tvashtar and Pillan plumes: Lessons learned from Hubble

Science.gov (United States)

Jessup, Kandis Lea; Spencer, John R.

2012-03-01

Hubble Space Telescope/Wide Field and Planetary Camera 2 (HST/WFPC2) images of Io obtained between 1995 and 2007 between 0.24 and 0.42 μm led to the detection of the Pele plume in reflected sunlight in 1995 and 1999; imaging of the Pele plume via absorption of jovian light in 1996 and 1999; detection of the Prometheus-type Pillan plume in reflected sunlight in 1997; and detection of the 2007 Pele-type Tvashtar plume eruption in reflected sunlight and via absorption of jovian light. Based on a detailed analysis of these observations we characterize and compare the gas and dust properties of each of the detected plumes. In each case, the brightness of the plumes in reflected sunlight is less at 0.26 μm than at 0.33 μm. Mie scattering analysis of the wavelength dependence of each plume’s reflectance signature suggests that range of particle sizes within the plumes is quite narrow. Assuming a normal distribution of particle sizes, the range of mean particle sizes is ∼0.035-0.12 μm for the 1997 Pillan eruption, ∼0.05-0.08 μm for the 1999 Pele and 2007 Tvasthar plumes, and ∼0.05-0.11 μm for the 1995 Pele plume, and in each case the standard deviation in the particle size distribution is Pele eruption released ∼109 g of SO2 dust, the 1997 Pillan eruption released ∼1010 g of SO2 dust, and the 1995 Pele plume may have released ∼1010 g of SO2 dust. Analysis of the plume absorption signatures recorded in the F255W filter bandpass (0.24-0.28 μm) indicates that the opacity of the 2007 Tvashtar plume was 2× that of the 1996 and 1999 Pele plume eruptions. While the sulfur dust density estimated for the Tvashtar from the reflected sunlight data could have produced 61% of the observed plume opacity, Pele F255W plume opacity could have resulted from the SO2 dust detected in the eruption. Accounting for the remaining F255W opacity level of the Pele and Tvasthar plumes based on SO2 and S2 gas absorption, the SO2 and S2 gas density inferred for each plume is

Resonant Scattering of Relativistic Outer Zone Electrons by Plasmaspheric Plume Electromagnetic Ion Cyclotron Waves

International Nuclear Information System (INIS)

Zhen-Peng, Su; Hui-Nan, Zheng

2009-01-01

The bounce-averaged Fokker–Planck equation is solved to study the relativistic electron phase space density (PSD) evolution in the outer radiation belt due to resonant interactions with plasmaspheric plume electromagnetic ion cyclotron (EMIC) waves. It is found that the PSDs of relativistic electrons can be depleted by 1–3 orders of magnitude in 5h, supporting the previous finding that resonant interactions with EMIC waves may account for the frequently observed relativistic electron flux dropouts in the outer radiation belt during the main phase of a storm. The significant precipitation loss of ∼MeV electrons is primarily induced by the EMIC waves in H + and He + bands. The rapid remove of highly relativistic electrons (> 5 MeV) is mainly driven by the EMIC waves in O + band at lower pitch-angles, as well as the EMIC waves in H + and He + bands at larger pitch-angles. Moreover, a stronger depletion of relativistic electrons is found to occur over a wider pitch angle range when EMIC waves are centering relatively higher in the band

Morphological changes in ultrafast laser ablation plumes with varying spot size.

Science.gov (United States)

Harilal, S S; Diwakar, P K; Polek, M P; Phillips, M C

2015-06-15

We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 μm. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present results clearly show that the morphological changes in the plume with spot size are independent of laser pulse width.

Nighttime NOx Chemistry in Coal-Fired Power Plant Plumes

Science.gov (United States)

Fibiger, D. L.; McDuffie, E. E.; Dube, W. P.; Veres, P. R.; Lopez-Hilfiker, F.; Lee, B. H.; Green, J. R.; Fiddler, M. N.; Ebben, C. J.; Sparks, T.; Weinheimer, A. J.; Montzka, D.; Campos, T. L.; Cohen, R. C.; Bililign, S.; Holloway, J. S.; Thornton, J. A.; Brown, S. S.

2015-12-01

Nitrogen oxides (NOx = NO + NO2) play a key role in atmospheric chemistry. During the day, they catalyze ozone (O3) production, while at night they can react to form nitric acid (HNO3) and nitryl chloride (ClNO2) and remove O3 from the atmosphere. These processes are well studied in the summer, but winter measurements are more limited. Coal-fired power plants are a major source of NOx to the atmosphere, making up approximately 30% of emissions in the US (epa.gov). NOx emissions can vary seasonally, as well as plant-to-plant, with important impacts on the details of the plume chemistry. In particular, due to inefficient plume dispersion, nighttime NOx emissions from power plants are held in concentrated plumes, where rates of mixing with ambient O3 have a strong influence on plume evolution. We will show results from the aircraft-based WINTER campaign over the northeastern United States, where several nighttime intercepts of power plant plumes were made. Several of these intercepts show complete O3 titration, which can have a large influence on NOx lifetime, and thus O3 production, in the plume. When power plant NO emissions exceed background O3 levels, O3 is completely consumed converting NO to NO2. In the presence of O3, NO2 will be oxidized to NO3, which will then react with NO2 to form N2O5, which can then form HNO3 and/or ClNO2 and, ultimately, remove NOx from the atmosphere or provide next-day oxidant sources. If there is no O3 present, however, no further chemistry can occur and NO and NO2 will be transported until mixing with sufficient O3 for higher oxidation products. Modeling results of plume development and mixing, which can tell us more about this transport, will also be presented.

Hydrochemical investigations in characterizing the unsaturated zone at Yucca Mountain, Nevada

International Nuclear Information System (INIS)

Yang, I.C.; Rattray, G.W.; Ferarese, J.S.; Yu, P.; Ryan, J.N.

1998-01-01

Hydrochemical and isotopic investigations of ground water at Yucca Mountain, Nevada, site of a potential permanent national nuclear-waste repository, demonstrate that younger rocks are dominated by calcium-sulfate or calcium-chloride water and that older rocks contain sodium-carbonate or sodium-bicarbonate water. Furthermore, unsaturated-zone pore water has significantly larger concentrations of major ions and dissolved solids than does the saturated-zone water. Recharge of perched or saturated-zone water, therefore, requires rapid flow through fractures or permeable regions in the unsaturated zone to avoid mixing with the chemically concentrated water in the unsaturated zone. This conceptual model is consistent with observations of rapidly moved post-bomb (post-1954) tritium and chlorine-36 in the deep unsaturated zone at Yucca Mountain. Presence of post-bomb tritium in matrix water away from fracture zones further indicates that parts of the fast-flow water that moves through fractures have been diverted laterally into nonwelded units. Experimental data show that different lithologic units require specific water-extraction methods for stable-isotope analyses of hydrogen and oxygen to ensure accurate characterization. Vacuum-distillation and compression-extraction methods both can yield accurate data but must be used with specific lithologies. Column experiments demonstrate that percolating water can exchange with pore water of the core as well as water held in zeolite minerals in the core. Exchange rates range from days to months. Pore-water samples from core, therefore, reflect the most recently infiltrated water but do not reflect percolating water of the distant past

OClO and BrO observations in the volcanic plume of Mt. Etna - implications on the chemistry of chlorine and bromine species in volcanic plumes

Science.gov (United States)

Gliß, J.; Bobrowski, N.; Vogel, L.; Platt, U.

2014-10-01

Spatial and temporal profiles of chlorine dioxide (OClO), bromine monoxide (BrO) and sulphur dioxide (SO2) were measured in the plume of Mt. Etna, Italy, in September 2012 using Multi-Axis-Differential-Optical-Absorption-Spectroscopy (MAX-DOAS). OClO (BrO) was detected in 119 (452) individual measurements covering plume ages up to 6 (23) minutes. The retrieved slant column densities (SCDs) reached values up to 2.0 × 1014 molecules cm-2 (OClO) and 1.1 × 1015 molecules cm-2 (BrO). In addition, the spectra were analysed for signatures of IO, OIO and OBrO, none of these species could be detected. The corresponding detection limits for IO / SO2, OIO / SO2 and OBrO / SO2 were 1.8 × 10-6, 2.0 × 10-5 and 1.1 × 10-5 respectively. The measurements were performed at plume ages (τ) from zero to 23 min downwind the emission source. The chemical variability of BrO and OClO in the plume was studied analysing the OClO / SO2 and BrO / SO2-ratio. A marked increase of both ratios was observed in the young plume (τ 3 min) with mean abundances of 3.17 × 10-5 (OClO / SO2), 1.55 × 10-4 (BrO / SO2) and 0.16 (OClO / BrO). Furthermore, enhanced BrO/SO2-ratios were found at the plume edges (by ~30-37%) and a strong indication of enhanced OClO / SO2-ratios as well (~10-250%). A measurement performed in the early morning (05:20-06:20 UTC, sunrise: 04:40 UTC) showed an BrO / SO2-ratio increasing with time until 05:35 UTC and a constant ratio afterwards. Observing this increase was only possible due to a correction for stratospheric BrO signals in the plume spectra. The corresponding OClO / SO2-ratio showed a similar trend stabilising around 06:13 UTC, approximately 40 min later than BrO. This is another strong indication for the photochemical nature of the reactions involved in the formation of oxidised halogens in volcanic plumes. In particular, these findings support the current understanding of the underlying chemistry, namely, that BrO is formed in an autocatalytic reaction

Fumarole/plume and diffuse CO2 emission from Sierra Negra volcano, Galapagos archipelago

Science.gov (United States)

Padron, E.; Hernandez Perez, P. A.; Perez, N.; Theofilos, T.; Melian, G.; Barrancos, J.; Virgil, G.; Sumino, H.; Notsu, K.

2009-12-01

The active shield-volcano Sierra Negra is part of the Galapagos hotspot. Sierra Negra is the largest shield volcano of Isabela Island, hosting a 10 km diameter caldera. Ten historic eruptions have occurred and some involved a frequently visited east caldera rim fissure zone called Volcan Chico. The last volcanic event occurred in October 2005 and lasted for about a week, covering approximately twenty percent of the eastern caldera floor. Sierra Negra volcano has experienced some significant changes in the chemical composition of its volcanic gas discharges after the 2005 eruption. This volcanic event produced an important SO2 degassing that depleted the magmatic content of this gas. Not significant changes in the MORB and plume-type helium contribution were observed after the 2005 eruption, with a 65.5 % of MORB and 35.5 % of plume contribution. In 2006 a visible and diffuse gas emission study was performed at the summit of Sierra Negra volcano, Galapagos, to evaluate degassing rate from this volcanic system. Diffuse degassing at Sierra Negra was mainly confined in three different DDS: Volcan Chico, the southern inner margin of the caldera, and Mina Azufral. These areas showed also visible degassing, which indicates highly fractured areas where volcano-hydrothermal fluids migrate towards surface. A total fumarole/plume SO2 emission of 11 ± 2 td-1 was calculated by mini-DOAS ground-based measurements at Mina Azufral fumarolic area. Molar ratios of major volcanic gas components were also measured in-situ at Mina Azufral with a portable multisensor. The results showed H2S/SO2, CO2/SO2 and H2O/SO2 molar ratios of 0.41, 52.2 and 867.9, respectively. Multiplying the observed SO2 emission rate times the observed (gas)i/SO2 mass ratio we have estimated other volatiles emission rates. The results showed that H2O, CO2 and H2S emission rates from Sierra Negra are 562, 394, and 2.4 t d-1, respectively. The estimated total output of diffuse CO2 emission from the summit of

Mobile Bay turbidity plume study

Science.gov (United States)

Crozier, G. F.

1976-01-01

Laboratory and field transmissometer studies on the effect of suspended particulate material upon the appearance of water are reported. Quantitative correlations were developed between remotely sensed image density, optical sea truth data, and actual sediment load. Evaluation of satellite image sea truth data for an offshore plume projects contours of transmissivity for two different tidal phases. Data clearly demonstrate the speed of change and movement of the optical plume for water patterns associated with the mouth of Mobile bay in which relatively clear Gulf of Mexico water enters the bay on the eastern side. Data show that wind stress in excess of 15 knots has a marked impact in producing suspended sediment loads.

Sewage outfall plume dispersion observations with an autonomous underwater vehicle.

Science.gov (United States)

Ramos, P; Cunha, S R; Neves, M V; Pereira, F L; Quintaneiro, I

2005-01-01

This work represents one of the first successful applications of Autonomous Underwater Vehicles (AUVs) for interdisciplinary coastal research. A monitoring mission to study the shape and estimate the initial dilution of the S. Jacinto sewage outfall plume using an AUV was performed on July 2002. An efficient sampling strategy enabling greater improvements in spatial and temporal range of detection demonstrated that the sewage effluent plume can be clearly traced using naturally occurring tracers in the wastewater. The outfall plume was found at the surface highly influenced by the weak stratification and low currents. Dilution varying with distance downstream was estimated from the plume rise over the outfall diffuser until a nearly constant value of 130:1, 60 m from the diffuser, indicating the near field end. Our results demonstrate that AUVs can provide high-quality measurements of physical properties of effluent plumes in a very effective manner and valuable considerations about the initial mixing processes under real oceanic conditions can be further investigated.

FY 2000 Annual Report for EMSP Project No.70108 - Effects of Fluid Distribution on Measured Geophysical Properties for Partially Saturated, Shallow Subsurface Conditions

International Nuclear Information System (INIS)

Berge, P.A.; Bonner, B.P.; Roberts, J.J.; Wildenschild, D.; Aracne-Ruddle, C.M.; Berryman, J.G.; Bertete-Aguirre, H.; Boro, C.O.; Carlberg, E.D.

2000-01-01

Our goal is to improve geophysical imaging of the vadose zone. We will achieve this goal by providing new methods to improve interpretation of field data. The purpose of this EMSP project is to develop relationships between laboratory measured geophysical properties and porosity, saturation, and fluid distribution, for partially saturated soils. Algorithms for relationships between soil composition, saturation, and geophysical measurements will provide new methods to interpret geophysical field data collected in the vadose zone at sites such as Hanford, WA. This report summarizes work after 10 months of a 3-year project. We have modified a laboratory ultrasonics apparatus developed in a previous EMSP project (No.55411) so that we can make velocity measurements for partially-saturated samples rather than fully-saturated or dry samples. We are testing the measurement apparatus using standard laboratory sand samples such as Ottawa sand samples. Preliminary results indicate that we can measure both compressional and shear velocities in these sand samples. We have received Hanford soil samples (sands from split-spoon cores from an uncontaminated site) and expect to make ultrasonic measurements on them also. We have used the LLNL x-ray facility to perform x-ray computed tomography (XCT) imaging for several partially-saturated Ottawa sand and Lincoln sand samples, and have also used the DOE Advance Photon Source at Argonne National Laboratory to make higher-resolution images of some sand samples. Preliminary results indicate that we can image amount and distribution of fluids in homogeneous sand samples. Continuing work from the previous EMSP project, we are testing a new data analysis method for seismic data that is expected to improve interpretation of seismic data from the vadose zone by showing how partial saturation affects seismic parameters. Our results suggest that the planned approach for this research is appropriate, that microstructure is an important factor

Radiatively-driven processes in forest fire and desert dust plumes

Energy Technology Data Exchange (ETDEWEB)

Weinzierl, Bernadett Barbara

2008-07-01

The absorption of solar radiation by atmospheric aerosol particles is important for the climate effects of aerosols. Absorption by aerosol particles heats atmospheric layers, even though the net effect for the entire atmospheric column may still be a cooling. Most experimental studies on absorbing aerosols so far focussed mainly on the aerosol properties and did not consider the influence of the aerosols on the thermodynamic structure of the atmosphere. In this study, data from two international aircraft field experiments, the Intercontinental Transport of Ozone and Precursors study (ITOP) 2004 and the Saharan Mineral Dust Experiment (SAMUM) 2006 are investigated. The ITOP data were collected before the work on this thesis started, while the logistics and the instrument preparation of the SAMUM campaign, the weather forecast during SAMUM and the in-situ aerosol measurements during SAMUM were done within this thesis. The experimental data are used to explore the impact of layers containing absorbing forest fire and desert dust aerosol particles on the atmospheric stability and the implications of a changed stability on the development of the aerosol microphysical and optical properties during long-range transport. For the first time, vertical profiles of the Richardson number Ri are used to assess the stability and mixing in forest fire and desert dust plumes. Also for the first time, the conclusions drawn from the observations of forest fire and desert dust aerosol, at first glance apparently quite different aerosol types, are discussed from a common perspective. Two mechanisms, the selfstabilising and the sealed ageing effect, acting in both forest fire and desert dust aerosol layers, are proposed to explain the characteristic temperature structure as well as the aerosol properties observed in lofted forest fire and desert dust plumes. The proposed effects impact on the ageing of particles within the plumes and reduce the plume dilution, therefore extending the

Spectrum Diagnosis for Fuchsia Plume of Hall Effect Thruster with Xenon as Propellant

International Nuclear Information System (INIS)

Yu Daren; Ding Jiapeng; Dai Jingmin

2006-01-01

The colour of the Hall effect thruster's plume is often light-green, and sometimes a fuchsia plume appears during experiments. Based on a spectrum and colour analysis, and a comparison with normal plumes, a conclusion is made that the density of the Xe ions and the temperature of electrons are low when the plume appears fuchsia. In this condition, most of the components of the plume are Xe atoms, and the ionization rate of the propellant is low

Using environmental tracers to determine the relative importance of travel times in the unsaturated and saturated zones for the delay of nitrate reduction measures

Science.gov (United States)

Gerber, Christoph; Purtschert, Roland; Hunkeler, Daniel; Hug, Rainer; Sültenfuss, Jürgen

2018-06-01

Groundwater quality in many regions with intense agriculture has deteriorated due to the leaching of nitrate and other agricultural pollutants. Modified agricultural practices can reduce the input of nitrate to groundwater bodies, but it is crucial to determine the time span over which these measures become effective at reducing nitrate levels in pumping wells. Such estimates can be obtained from hydrogeological modeling or lumped-parameter models (LPM) in combination with environmental tracer data. Two challenges in such tracer-based estimates are (i) accounting for the different modes of transport in the unsaturated zone (USZ), and (ii) assessing uncertainties. Here we extend a recently published Bayesian inference scheme for simple LPMs to include an explicit USZ model and apply it to the Dünnerngäu aquifer, Switzerland. Compared to a previous estimate of travel times in the aquifer based on a 2D hydrogeological model, our approach provides a more accurate assessment of the dynamics of nitrate concentrations in the aquifer. We find that including tracer measurements (3H/3He, 85Kr, 39Ar, 4He) reduces uncertainty in nitrate predictions if nitrate time series at wells are not available or short, but does not necessarily lead to better predictions if long nitrate time series are available. Additionally, the combination of tracer data with nitrate time series allows for a separation of the travel times in the unsaturated and saturated zone.

Study of the distribution of steam plumes in the PANDA facility using CFD code

Energy Technology Data Exchange (ETDEWEB)

Guo, Shuanshuan [School of Physics and Engineering, Sun Yat-sen University, Guangzhou (China); Cai, Jiejin, E-mail: chiven77@hotmail.com [Sino-French Institute of Nuclear Engineering & Technology, Sun Yat-sen University, Guangzhou (China); Zhang, Huiyong [China Nuclear Power Technology Research Institute, Shenzhen 518026 (China); Yin, Huaqiang; Yang, Xingtuan [Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education, Tsinghua University, Beijing 100084 (China)

2015-08-15

Highlights: • The standard k–ε model has been verified for gas plume simulation in the large-scale volume. • The k–k{sub l}–ω model has been improved for gas plume simulations. • The sensitivity analyses about the computational mesh, time step, Froude numbers have been carried out. - Abstract: During a postulated severe accident in light water reactor, a large amount of steam is injected into containment through the break. This would lead to the increases of pressure and temperature, and consequently threaten the integrity of the containment. In this study the light gas (saturated steam) distribution in a large-scale multi-compartment volume is simulated by using CFD code. Several turbulence models, including the standard k–ε model, the k–k{sub l}–ω model, the transitional SST model, and the improved k–k{sub l}–ω model with considering buoyancy effect are used for the simulation. The results show that both the standard k–ε model and the improved k–k{sub l}–ω model with considering the buoyancy effect can get good results comparing to the experimental results. The improved k–k{sub l}–ω model can get much better than the original k–k{sub l}–ω model without considering the buoyancy effect for predicting the steam distribution in vessels, and some characteristics in concerned region are predicted well. The sensitivity analyses about the computational mesh, time step, Froude numbers are also carried out.

The mantle-plume model, its feasibility and consequences

NARCIS (Netherlands)

Calsteren, van P.W.C.

1981-01-01

High beat-flow foci on the Earth have been named ‘hot-spots’ and are commonly correlated with ‘mantle-plumes’ in the deep. A mantle plume may be described as a portion of mantle material with a higher heat content than its surroundings. The intrusion of a mantle-plume is inferred to be similar to

Geochemical Processes Controlling Migration of High Level Wastes in Hanford's Vadose Zone

International Nuclear Information System (INIS)

Zachara, John M.; Serne, R. Jeffrey; Freshley, Mark D.; Mann, Frederick M.; Anderson, Frank J.; Wood, Marcus I.; Jones, Thomas E.; Myers, David A.

2007-01-01

High level nuclear wastes (HLW) from Hanford's plutonium reprocessing are stored in massive, buried, single-shell tanks in eighteen tank farms. The wastes were initially hot because of radioactive decay, and many exhibited extreme chemical character in terms of pH, salinity, and radionuclide concentration. At present, 67 of the 149 single shell tanks are suspected to have released over 1.9 million L of tank waste to the vadose zone, with most leak events occurring between 1950 and 1975. Boreholes have been placed through the largest vadose zone plumes to define the extent of contaminant migration, and to develop conceptual models of processes governing the transformation, retardation, and overall transport of tank waste residuals. Laboratory studies with sediments so collected have shown that ion exchange, precipitation and dissolution, and surface complexation reactions have occurred between the HLW and subsurface sediments moderating their chemical character, and retarding the migration of select contaminants. Processes suspected to facilitate the far-field migration of immobile radionuclides including stable aqueous complex formation and mobile colloids were found to be potentially operative, but unlikely to occur in the field, with the exception of cyanide-facilitated migration of 60Co. Fission product oxyanions are the most mobile of tank waste constituents because their adsorption is suppressed by large concentrations of waste anions; the vadose zone clay fraction is negative in surface charge; and, unlike Cr, their reduced forms are unstable in oxidizing environments. Reaction/process-based transport modeling is beginning to be used for predictions of future contaminant mobility and plume evolution

Eyjafjallajokull Volcano Plume Particle-Type Characterization from Space-Based Multi-angle Imaging

Science.gov (United States)

Kahn, Ralph A.; Limbacher, James

2012-01-01

The Multi-angle Imaging SpectroRadiometer (MISR) Research Aerosol algorithm makes it possible to study individual aerosol plumes in considerable detail. From the MISR data for two optically thick, near-source plumes from the spring 2010 eruption of the Eyjafjallaj kull volcano, we map aerosol optical depth (AOD) gradients and changing aerosol particle types with this algorithm; several days downwind, we identify the occurrence of volcanic ash particles and retrieve AOD, demonstrating the extent and the limits of ash detection and mapping capability with the multi-angle, multi-spectral imaging data. Retrieved volcanic plume AOD and particle microphysical properties are distinct from background values near-source, as well as for overwater cases several days downwind. The results also provide some indication that as they evolve, plume particles brighten, and average particle size decreases. Such detailed mapping offers context for suborbital plume observations having much more limited sampling. The MISR Standard aerosol product identified similar trends in plume properties as the Research algorithm, though with much smaller differences compared to background, and it does not resolve plume structure. Better optical analogs of non-spherical volcanic ash, and coincident suborbital data to validate the satellite retrieval results, are the factors most important for further advancing the remote sensing of volcanic ash plumes from space.

Plume Particle Collection and Sizing from Static Firing of Solid Rocket Motors

Science.gov (United States)

Sambamurthi, Jay K.

1995-01-01

Thermal radiation from the plume of any solid rocket motor, containing aluminum as one of the propellant ingredients, is mainly from the microscopic, hot aluminum oxide particles in the plume. The plume radiation to the base components of the flight vehicle is primarily determined by the plume flowfield properties, the size distribution of the plume particles, and their optical properties. The optimum design of a vehicle base thermal protection system is dependent on the ability to accurately predict this intense thermal radiation using validated theoretical models. This article describes a successful effort to collect reasonably clean plume particle samples from the static firing of the flight simulation motor (FSM-4) on March 10, 1994 at the T-24 test bed at the Thiokol space operations facility as well as three 18.3% scaled MNASA motors tested at NASA/MSFC. Prior attempts to collect plume particles from the full-scale motor firings have been unsuccessful due to the extremely hostile thermal and acoustic environment in the vicinity of the motor nozzle.

Vadose Zone Monitoring of Dairy Green Water Lagoons using Soil Solution Samplers.

Energy Technology Data Exchange (ETDEWEB)

Brainard, James R.; Coplen, Amy K

2005-11-01

Over the last decade, dairy farms in New Mexico have become an important component to the economy of many rural ranching and farming communities. Dairy operations are water intensive and use groundwater that otherwise would be used for irrigation purposes. Most dairies reuse their process/green water three times and utilize lined lagoons for temporary storage of green water. Leakage of water from lagoons can pose a risk to groundwater quality. Groundwater resource protection infrastructures at dairies are regulated by the New Mexico Environment Department which currently relies on monitoring wells installed in the saturated zone for detecting leakage of waste water lagoon liners. Here we present a proposal to monitor the unsaturated zone beneath the lagoons with soil water solution samplers to provide early detection of leaking liners. Early detection of leaking liners along with rapid repair can minimize contamination of aquifers and reduce dairy liability for aquifer remediation. Additionally, acceptance of vadose zone monitoring as a NMED requirement over saturated zone monitoring would very likely significantly reduce dairy startup and expansion costs. Acknowledgment Funding for this project was provided by the Sandia National Laboratories Small Business Assistance Program

The effect of sediments on turbulent plume dynamics in a stratified fluid

Science.gov (United States)

Stenberg, Erik; Ezhova, Ekaterina; Brandt, Luca

2017-11-01

We report large eddy simulation results of sediment-loaded turbulent plumes in a stratified fluid. The configuration, where the plume is discharged from a round source, provides an idealized model of subglacial discharge from a submarine tidewater glacier and is a starting point for understanding the effect of sediments on the dynamics of the rising plume. The transport of sediments is modeled by means of an advection-diffusion equation where sediment settling velocity is taken into account. We initially follow the experimental setup of Sutherland (Phys. Rev. Fluids, 2016), considering uniformly stratified ambients and further extend the work to pycnocline-type stratifications typical of Greenland fjords. Apart from examining the rise height, radial spread and intrusion of the rising plume, we gain further insights of the plume dynamics by extracting turbulent characteristics and the distribution of the sediments inside the plume.

Assessment of freeway work zone safety with improved cellular automata model

Directory of Open Access Journals (Sweden)

Guohua Liang

2014-08-01

Full Text Available To accurately assess the safety of freeway work zones, this paper investigates the safety of vehicle lane change maneuvers with improved cellular automata model. Taking the traffic conflict and standard deviation of operating speed as the evaluation indexes, the study evaluates the freeway work zone safety. With improved deceleration probability in car-following raies and the addition of lanechanging rules under critical state, the lane-changing behavior under critical state is defined as a conflict count. Through 72 schemes of simulation runs, the possible states of the traffic flow are carefully studied. The results show that under the condition of constant saturation traffic conflict count and vehicle speed standard deviation reach their maximums when the mixed rate of heave vehicles is 40%. Meanwhile, in the case of constant heavy vehicles mix, traffic conflict count and vehicle speed standard deviation reach maximum values when saturation rate is 0. 75. Integrating ail simulation results, it is known the traffic safety in freeway work zones is classified into four levels : safe, relatively safe, relatively dangerous, and dangerous.

Karst system vadose zone hydrodynamics highlighted by an integrative geophysical and hydrogeological monitoring

Science.gov (United States)

Watlet, A.; Van Camp, M. J.; Francis, O.; Poulain, A.; Hallet, V.; Rochez, G.; Kaufmann, O.

2015-12-01

The vadose zone of karst systems plays an important role on the water dynamics. In particular, temporary perched aquifers can appear in the subsurface due to changes of climate conditions, diminished evapotranspiration and differences of porosity relative to deeper layers. It is therefore crucial, but challenging, to separate the hydrological signature of the vadose zone from the one of the saturated zone for understanding hydrological processes that occur in the vadose zone. Although many difficulties are usually encountered when studying karst environments due to their heterogeneities, cave systems offer an outstanding opportunity to investigate vadose zone from the inside with various techniques. We present results covering two years of hydrogeological and geophysical monitoring at the Rochefort Cave Laboratory (RCL), located in the Variscan fold-and-thrust belt (Belgium), a region that shows many karstic networks within Devonian limestone units. Hydrogeological data such as flows and levels monitoring or tracer tests performed in both vadose and saturated zones bring valuable information on the hydrological context of the studied area. Combining those results with geophysical measurements allows validating and imaging them with more integrative techniques. A microgravimetric monitoring involves a superconducting gravimeter continuously measuring at the surface of the RCL. Early in 2015, a second relative gravimeter was installed in the underlying cave system located 35 meters below the surface. This set up allows highlighting vadose gravity changes. These relative measurements are calibrated using an absolute gravimeter. 12 additional stations (7 at the surface, 5 in the cave) are monitored on a monthly basis by a spring gravimeter. To complete these gravimetric measurements, the site has been equipped with a permanent Electrical Resistivity Tomography (ERT) monitoring system comprising an uncommon array of surface, borehole and cave electrodes. Although such

Understanding Fluid and Contaminant Movement in the Unsaturated Zone Using the INEEL Vadose Zone Monitoring System

International Nuclear Information System (INIS)

Hubbell, J. M.; Mattson, E. D.; Sisson, J. B.; Magnuson, S. O.

2002-01-01

DOE has hundreds of contaminated facilities and waste sites requiring cleanup and/or long-term monitoring. These contaminated sites reside in unsaturated soils (i.e. the vadose zone) above the water table. Some of these sites will require active remediation activities or removal while other sites will be placed under institutional controls. In either case, evaluating the effectiveness of the remediation strategy or institutional controls will require monitoring. Classical monitoring strategies implemented at RCRA/CERCLA sites require ground water sampling for 30 years following closure. The overall effectiveness of ground water sampling is diminished due to the fact that by the time you detect chemical transport from a waste site, a major contamination plume likely exists in the vadose zone and the aquifer. This paper suggests a more effective monitoring strategy through monitoring near the contaminant sites within the vadose zone. Vadose zone monitoring allows for quicker detection of potential contaminant transport. The INEEL Vadose Zone Monitoring System (VZMS) is becoming an accepted, cost effective monitoring technology for assessing contaminant transport at DOE facilities. This paper describes the technologies employed in the VZMS and describes how it was used at several DOE facilities. The INEEL VZMS has provided the information in developing and validating both conceptual and risk assessment models of contaminant transport at the Idaho National Engineering and Environmental Laboratory (INEEL), Oak Ridge National Laboratory (ORNL), Savannah River Site (SRS) and the Hanford site. These DOE sites exhibit a broad range of meteorologic, hydrologic and geologic conditions representative of various common geologic environments. The VZMS is comprised of advanced tensiometers, water content sensors, temperature sensors and soil and gas samplers. These instruments are placed at multiple depths in boreholes and allows for the detection of water movement in the

Tidally induced lateral dispersion of the Storfjorden overflow plume

Directory of Open Access Journals (Sweden)

F. Wobus

2013-10-01

Full Text Available We investigate the flow of brine-enriched shelf water from Storfjorden (Svalbard into Fram Strait and onto the western Svalbard Shelf using a regional set-up of NEMO-SHELF, a 3-D numerical ocean circulation model. The model is set up with realistic bathymetry, atmospheric forcing, open boundary conditions and tides. The model has 3 km horizontal resolution and 50 vertical levels in the sh-coordinate system which is specially designed to resolve bottom boundary layer processes. In a series of modelling experiments we focus on the influence of tides on the propagation of the dense water plume by comparing results from tidal and non-tidal model runs. Comparisons of non-tidal to tidal simulations reveal a hotspot of tidally induced horizontal diffusion leading to the lateral dispersion of the plume at the southernmost headland of Spitsbergen which is in close proximity to the plume path. As a result the lighter fractions in the diluted upper layer of the plume are drawn into the shallow coastal current that carries Storfjorden water onto the western Svalbard Shelf, while the dense bottom layer continues to sink down the slope. This bifurcation of the plume into a diluted shelf branch and a dense downslope branch is enhanced by tidally induced shear dispersion at the headland. Tidal effects at the headland are shown to cause a net reduction in the downslope flux of Storfjorden water into the deep Fram Strait. This finding contrasts previous results from observations of a dense plume on a different shelf without abrupt topography.

Plasma plume expansion dynamics in nanosecond Nd:YAG laserosteotome

Science.gov (United States)

Abbasi, Hamed; Rauter, Georg; Guzman, Raphael; Cattin, Philippe C.; Zam, Azhar

2018-02-01

In minimal invasive laser osteotomy precise information about the ablation process can be obtained with LIBS in order to avoid carbonization, or cutting of wrong types of tissue. Therefore, the collecting fiber for LIBS needs to be optimally placed in narrow cavities in the endoscope. To determine this optimal placement, the plasma plume expansion dynamics in ablation of bone tissue by the second harmonic of a nanosecond Nd:YAG laser at 532 nm has been studied. The laserinduced plasma plume was monitored in different time delays, from one nanosecond up to one hundred microseconds. Measurements were performed using high-speed gated illumination imaging. The expansion features were studied using illumination of the overall visible emission by using a gated intensified charged coupled device (ICCD). The camera was capable of having a minimum gate width (Optical FWHM) of 3 ns and the timing resolution (minimum temporal shift of the gate) of 10 ps. The imaging data were used to generate position-time data of the luminous plasma-front. Moreover, the velocity of the plasma plume expansion was studied based on the time-resolved intensity data. By knowing the plasma plume profile over time, the optimum position (axial distance from the laser spot) of the collecting fiber and optimal time delay (to have the best signal to noise ratio) in spatial-resolved and time-resolved laser-induced breakdown spectroscopy (LIBS) can be determined. Additionally, the function of plasma plume expansion could be used to study the shock wave of the plasma plume.

Oxidation of trichloroethylene, toluene, and ethanol vapors by a partially saturated permeable reactive barrier

Science.gov (United States)

Mahmoodlu, Mojtaba G.; Hassanizadeh, S. Majid; Hartog, Niels; Raoof, Amir

2014-08-01

The mitigation of volatile organic compound (VOC) vapors in the unsaturated zone largely relies on the active removal of vapor by ventilation. In this study we considered an alternative method involving the use of solid potassium permanganate to create a horizontal permeable reactive barrier for oxidizing VOC vapors. Column experiments were carried out to investigate the oxidation of trichloroethylene (TCE), toluene, and ethanol vapors using a partially saturated mixture of potassium permanganate and sand grains. Results showed a significant removal of VOC vapors due to the oxidation. We found that water saturation has a major effect on the removal capacity of the permeable reactive layer. We observed a high removal efficiency and reactivity of potassium permanganate for all target compounds at the highest water saturation (Sw = 0.6). A change in pH within the reactive layer reduced oxidation rate of VOCs. The use of carbonate minerals increased the reactivity of potassium permanganate during the oxidation of TCE vapor by buffering the pH. Reactive transport of VOC vapors diffusing through the permeable reactive layer was modeled, including the pH effect on the oxidation rates. The model accurately described the observed breakthrough curve of TCE and toluene vapors in the headspace of the column. However, miscibility of ethanol in water in combination with produced water during oxidation made the modeling results less accurate for ethanol. A linear relationship was found between total oxidized mass of VOC vapors per unit volume of permeable reactive layer and initial water saturation. This behavior indicates that pH changes control the overall reactivity and longevity of the permeable reactive layer during oxidation of VOCs. The results suggest that field application of a horizontal permeable reactive barrier can be a viable technology against upward migration of VOC vapors through the unsaturated zone.

Paleocene Picrites of Davis Strait: Products of a Plume or Plates?

Science.gov (United States)

Beutel, E. K.; Clarke, D. B.

2017-12-01

Voluminous, subaerial, ultra-depleted, 62 Ma, primary picritic lavas occur on both sides of Davis Strait separating Baffin Island and West Greenland. Temporally, the picrites are coeval with the initiation of sea-floor spreading in Labrador Sea and Baffin Bay around 62 Ma. Petrogenetically, the chemical characteristics of these picrites (MgO = 18-21 wt. %; K2O = 0.01-0.20 wt. %; 87Sr/86Sri ≈ 0.7030; ɛNdi ≈ +5.2-8.6; 3He/4He ≤ 49.5RA) demand only derivation by partial melting of highly depleted subcontinental lithospheric mantle (SCLM) at a pressure of 4 GPa, followed by rapid ascent to the surface, but do not necessarily require high temperatures or high degrees of partial melting. Tectonically, these picrites formed in thick Archean and Paleoproterozoic cratonic terranes during Paleogene rifting between Greenland and North America. Structurally, the picrites are related to the major intersection of a NNW suture zone under Baffin Bay and the E-W trending Paleoproterozoic Nagssugtoqidian Fold Belt. During the late Mesozoic, ENE extension created normal faulted basins quasi-parallel with the NNW suture and thinned the mantle lithosphere. Elastic finite element models and present day studies of crustal extension show that the thicker Nagssugtoqidian Fold Belt underwent less thinning and extension than the NNW suture zone in the Archean Rae craton. These extensional disparities occur at the orthogonal intersection of pre-existing E-W trending strike-slip faults in the thicker Nagssugtoqidian Fold Belt with the NNW thinned Archean suture zone, and likely resulted in the formation of one or more pull-apart basins. Because the strike-slip faults are ancient suture zones, trans-tension within these suture zones easily reached 120 km, creating not only decompression melting in the SCLM, but also a pathway for the picritic melts to rapidly reach the surface. Such a purely tectonic model requires no spatially or temporally improbable deep mantle plume for generation of

Novel plume deflection concept testing

Data.gov (United States)

National Aeronautics and Space Administration — The proposed effort will explore the feasibility and effectiveness of utilizing an electrically driven thermal shield for use as part of rocket plume deflectors. To...

Waves generated in the plasma plume of helicon magnetic nozzle

International Nuclear Information System (INIS)

Singh, Nagendra; Rao, Sathyanarayan; Ranganath, Praveen

2013-01-01

Experimental measurements have shown that the plasma plume created in a helicon plasma device contains a conical structure in the plasma density and a U-shaped double layer (US-DL) tightly confined near the throat where plasma begins to expand from the source. Recently reported two-dimensional particle-in-cell simulations verified these density and US-DL features of the plasma plume. Simulations also showed that the plasma in the plume develops non-thermal feature consisting of radial ion beams with large densities near the conical surface of the density structure. The plasma waves that are generated by the radial ion beams affecting the structure of the plasma plume are studied here. We find that most intense waves persist in the high-density regions of the conical density structure, where the transversely accelerated ions in the radial electric fields in the plume are reflected setting up counter-streaming. The waves generated are primarily ion Bernstein modes. The nonlinear evolution of the waves leads to magnetic field-aligned striations in the fields and the plasma near the conical surface of the density structure.

A cold plasma plume with a highly conductive liquid electrode

International Nuclear Information System (INIS)

Chen Guangliang; Chen Wenxing; Chen Shihua; Yang Size

2008-01-01

A cold dielectric barrier discharge (DBD) plasma plume with one highly conductive liquid electrode has been developed to treat thermally sensitive materials, and its preliminary discharging characteristics have been studied. The averaged electron temperature and density is estimated to be 0.6eV and 10 11 /cm 3 , respectively. The length of plasma plume can reach 5 cm with helium gas (He), and the conductivity of the outer electrode affects the plume length obviously. This plasma plume could be touched by bare hand without causing any burning or painful sensation, which may provide potential application for safe aseptic skin care. Moreover, the oxidative particles (e.g., OH, O * , O 3 ) in the downstream oxygen (O2) gas of the plume have been applied to treat the landfill leachate. The results show that the activated O 2 gas can degrade the landfill leachate effectively, and the chemical oxygen demand (COD), conductivity, biochemical oxygen demand (BOD), and suspended solid (SS) can be decreased by 52%, 57%, 76% and 92%, respectively. (fluids, plasmas and electric discharges)

Waves generated in the plasma plume of helicon magnetic nozzle

Energy Technology Data Exchange (ETDEWEB)

Singh, Nagendra; Rao, Sathyanarayan; Ranganath, Praveen [Department of Electrical and Computer Engineering, University of Alabama, Huntsville, Alabama 35899 (United States)

2013-03-15

Experimental measurements have shown that the plasma plume created in a helicon plasma device contains a conical structure in the plasma density and a U-shaped double layer (US-DL) tightly confined near the throat where plasma begins to expand from the source. Recently reported two-dimensional particle-in-cell simulations verified these density and US-DL features of the plasma plume. Simulations also showed that the plasma in the plume develops non-thermal feature consisting of radial ion beams with large densities near the conical surface of the density structure. The plasma waves that are generated by the radial ion beams affecting the structure of the plasma plume are studied here. We find that most intense waves persist in the high-density regions of the conical density structure, where the transversely accelerated ions in the radial electric fields in the plume are reflected setting up counter-streaming. The waves generated are primarily ion Bernstein modes. The nonlinear evolution of the waves leads to magnetic field-aligned striations in the fields and the plasma near the conical surface of the density structure.

Jet plume injection and combustion system for internal combustion engines

Science.gov (United States)

Oppenheim, Antoni K.; Maxson, James A.; Hensinger, David M.

1993-01-01

An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

Plume dynamics in TiC laser ablation

International Nuclear Information System (INIS)

D'Alessio, L.; Galasso, A.; Santagata, A.; Teghil, R.; Villani, A.R.; Villani, P.; Zaccagnino, M.

2003-01-01

In this work, the analysis of the gaseous phase, produced by pulsed laser ablation of a TiC target and performed by emission spectroscopy and intensified charge coupled device (ICCD) imaging is reported. In the case of laser fluence higher than 3 J/cm 2 , the front of the emitting plume is identified with the presence of Ti 2+ ions, while the presence of a double maximum is due to the neutral and ionized titanium particles traveling with different velocities. At a laser fluence lower than 3 J/cm 2 , the front is marked by C + emission and only one maximum is present. The results, compared with those obtained for other carbides of group 4, evidence that only in the plume produced from TiC targets there is the presence of a large amount of ions with high kinetic energy. In particular, the highly energetic M 2+ ions (M=Ti, Zr, Hf) are present only in the TiC plume. The different energy and concentration of ions in the different carbide plumes confirm the importance of the ionized part of the gaseous phase in the film growth mechanism. In fact only in the TiC films, we find a layered structure in contrast with the columnar structure found in the other carbides of the same group

Critical Magnetic Field Strengths for Unipolar Solar Coronal Plumes In Quiet Regions and Coronal Holes?

Science.gov (United States)

Avallone, Ellis; Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; Winebarger, Amy

2017-01-01

Coronal plumes are bright magnetic funnels that are found in quiet regions and coronal holes that extend high into the solar corona whose lifetimes can last from hours to days. The heating processes that make plumes bright involve the magnetic field at the base of the plume, but their intricacies remain mysterious. Raouafi et al. (2014) infer from observation that plume heating is a consequence of magnetic reconnection at the base, whereas Wang et al. (2016) infer that plume heating is a result of convergence of the magnetic flux at the plume's base, or base flux. Both papers suggest that the base flux in their plumes is of mixed polarity, but do not quantitatively measure the base flux or consider whether a critical magnetic field strength is required for plume production. To investigate the magnetic origins of plume heating, we track plume luminosity in the 171 Å wavelength as well as the abundance and strength of the base flux over the lifetimes of six unipolar coronal plumes. Of these, three are in coronal holes and three are in quiet regions. For this sample, we find that plume heating is triggered when convergence of the base flux surpasses a field strength of approximately 300 - 500 Gauss, and that the luminosity of both quiet region and coronal hole plumes respond similarly to the strength of the magnetic field in the base.

Microscopic analysis of saturable absorbers: Semiconductor saturable absorber mirrors versus graphene

Energy Technology Data Exchange (ETDEWEB)

Hader, J.; Moloney, J. V. [Nonlinear Control Strategies, Inc., 3542 N. Geronimo Ave., Tucson, Arizona 85705 (United States); College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Yang, H.-J.; Scheller, M. [College of Optical Sciences, University of Arizona, Tucson, Arizona 85721 (United States); Koch, S. W. [Department of Physics and Materials Sciences Center, Philipps Universität Marburg, Renthof 5, 35032 Marburg (Germany)

2016-02-07

Fully microscopic many-body calculations are used to study the influence of strong sub-picosecond pulses on the carrier distributions and corresponding optical response in saturable absorbers used for mode-locking—semiconductor (quantum well) saturable absorber mirrors (SESAMs) and single layer graphene based saturable absorber mirrors (GSAMs). Unlike in GSAMs, the saturation fluence and recovery time in SESAMs show a strong spectral dependence. While the saturation fluence in the SESAM is minimal at the excitonic bandgap, the optimal recovery time and least pulse distortion due to group delay dispersion are found for excitation higher in the first subband. For excitation near the SESAM bandgap, the saturation fluence is about one tenth of that in the GSAM. At energies above the bandgap, the fluences in both systems become similar. A strong dependence of the saturation fluence on the pulse width in both systems is caused by carrier relaxation during the pulse. The recovery time in graphene is found to be about two to four times faster than that in the SESAMs. The occurrence of negative differential transmission in graphene is shown to be caused by dopant related carriers. In SESAMs, a negative differential transmission is found when exciting below the excitonic resonance where excitation induced dephasing leads to an enhancement of the absorption. Comparisons of the simulation data to the experiment show a very good quantitative agreement.

Isotopically (δ13C and δ18O) heavy volcanic plumes from Central Andean volcanoes: a field study

Science.gov (United States)

Schipper, C. Ian; Moussallam, Yves; Curtis, Aaron; Peters, Nial; Barnie, Talfan; Bani, Philipson; Jost, H. J.; Hamilton, Doug; Aiuppa, Alessandro; Tamburello, Giancarlo; Giudice, Gaetano

2017-08-01

Stable isotopes of carbon and oxygen in volcanic gases are key tracers of volatile transfer between Earth's interior and atmosphere. Although important, these data are available for few volcanoes because they have traditionally been difficult to obtain and are usually measured on gas samples collected from fumaroles. We present new field measurements of bulk plume composition and stable isotopes (δ13CCO2 and δ18OH2O+CO2) carried out at three northern Chilean volcanoes using MultiGAS and isotope ratio infrared spectroscopy. Carbon and oxygen in magmatic gas plumes of Lastarria and Isluga volcanoes have δ13C in CO2 of +0.76‰ to +0.77‰ (VPDB), similar to slab carbonate; and δ18O in the H2O + CO2 system ranging from +12.2‰ to +20.7‰ (VSMOW), suggesting significant contributions from altered slab pore water and carbonate. The hydrothermal plume at Tacora has lower δ13CCO2 of -3.2‰ and δ18OH2O+CO2 of +7.0‰, reflecting various scrubbing, kinetic fractionation, and contamination processes. We show the isotopic characterization of volcanic gases in the field to be a practical complement to traditional sampling methods, with the potential to remove sampling bias that is a risk when only a few samples from accessible fumaroles are used to characterize a given volcano's volatile output. Our results indicate that there is a previously unrecognized, relatively heavy isotopic signature to bulk volcanic gas plumes in the Central Andes, which can be attributed to a strong influence from components of the subducting slab, but may also reflect some local crustal contamination. The techniques we describe open new avenues for quantifying the roles that subduction zones and arc volcanoes play in the global carbon cycle.

Multiphase CFD modeling of nearfield fate of sediment plumes

DEFF Research Database (Denmark)

Saremi, Sina; Hjelmager Jensen, Jacob

2014-01-01

Disposal of dredged material and the overflow discharge during the dredging activities is a matter of concern due to the potential risks imposed by the plumes on surrounding marine environment. This gives rise to accurately prediction of the fate of the sediment plumes released in ambient waters...

Busted Butte : final report on laboratory radionuclide migration experiments in non-welded tuff under unsaturated and saturated conditions

International Nuclear Information System (INIS)

Vandergraaf, T.T.; Drew, D.J.; Ticknor, K.V.; Hamon, C.J.

2004-01-01

Three blocks of non-welded tuff, one nominally one cubic foot (trial block) in volume and the other two, nominally one cubic meter (1 m 3 ) in volume, were excavated from the Busted Butte Test Facility on the Nevada Test Site in 1999 and transported to the Atomic Energy of Canada Limited Whiteshell Laboratories in Pinawa, Manitoba. The trial block and one of the 1-m 3 blocks were used for radionuclide migration experiments under unsaturated conditions; the remaining 1-m3 block was used for similar migration experiments under saturated conditions. After a vertical flow of synthetic transport solution was set up under unsaturated conditions, a suite of conservative and chemically reactive radionuclide tracers was injected at volumetric flow rates of 20 mL/hr in the trial block, and 10 mL/hr in two locations on the upper surface of the 1-m 3 block. These flow rates correspond to infiltration rates of about 120 cm/year and about 17 cm/year, respectively. The duration of the migration experiment in the trial block was 87 days, while the migration experiment in the 1-m3 block was performed for a period of 588 days. Results obtained from the migration experiment in the trial block showed that transport of 95m+99 Tc, injected as the pertechnetate (an)ion, was slightly faster than that of the transport solution, using tritiated water ( 3 H 2 0) as a flow indicator. Retardation of 237 Np was consistent with that predicted from results obtained in supporting static batch sorption studies. Post-migration analysis of the flow field in the trial block showed that the front of the 22 Na plume had migrated about half the distance through the block, and that 60 Co and 137 Cs had been retained near the inlet. This observation agrees qualitatively with that predicted from the results obtained in static batch sorption studies. In the larger-scale experiment, the transport behavior of Tc was also very similar to that of the transport solution. None of the other radionuclide tracers

Contaminant plumes containment and remediation focus area. Technology summary

International Nuclear Information System (INIS)

1995-06-01

EM has established a new approach to managing environmental technology research and development in critical areas of interest to DOE. The Contaminant Plumes Containment and Remediation (Plumes) Focus Area is one of five areas targeted to implement the new approach, actively involving representatives from basic research, technology implementation, and regulatory communities in setting objectives and evaluating results. This document presents an overview of current EM activities within the Plumes Focus Area to describe to the appropriate organizations the current thrust of the program and developing input for its future direction. The Plumes Focus Area is developing remediation technologies that address environmental problems associated with certain priority contaminants found at DOE sites, including radionuclides, heavy metals, and dense non-aqueous phase liquids (DNAPLs). Technologies for cleaning up contaminants of concern to both DOE and other federal agencies, such as volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), and other organics and inorganic compounds, will be developed by leveraging resources in cooperation with industry and interagency programs

Contaminant plumes containment and remediation focus area. Technology summary

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-06-01

EM has established a new approach to managing environmental technology research and development in critical areas of interest to DOE. The Contaminant Plumes Containment and Remediation (Plumes) Focus Area is one of five areas targeted to implement the new approach, actively involving representatives from basic research, technology implementation, and regulatory communities in setting objectives and evaluating results. This document presents an overview of current EM activities within the Plumes Focus Area to describe to the appropriate organizations the current thrust of the program and developing input for its future direction. The Plumes Focus Area is developing remediation technologies that address environmental problems associated with certain priority contaminants found at DOE sites, including radionuclides, heavy metals, and dense non-aqueous phase liquids (DNAPLs). Technologies for cleaning up contaminants of concern to both DOE and other federal agencies, such as volatile organic compounds (VOCs), polychlorinated biphenyls (PCBs), and other organics and inorganic compounds, will be developed by leveraging resources in cooperation with industry and interagency programs.

Multiscale Approach to Small River Plumes off California

Science.gov (United States)

Basdurak, N. B.; Largier, J. L.; Nidzieko, N.

2012-12-01

While larger scale plumes have received significant attention, the dynamics of plumes associated with small rivers typical of California are little studied. Since small streams are not dominated by a momentum flux, their plumes are more susceptible to conditions in the coastal ocean such as wind and waves. In order to correctly model water transport at smaller scales, there is a need to capture larger scale processes. To do this, one-way nested grids with varying grid resolution (1 km and 10 m for the parent and the child grid respectively) were constructed. CENCOOS (Central and Northern California Ocean Observing System) model results were used as boundary conditions to the parent grid. Semi-idealized model results for Santa Rosa Creek, California are presented from an implementation of the Regional Ocean Modeling System (ROMS v3.0), a three-dimensional, free-surface, terrain-following numerical model. In these preliminary results, the interaction between tides, winds, and buoyancy forcing in plume dynamics is explored for scenarios including different strengths of freshwater flow with different modes (steady and pulsed). Seasonal changes in transport dynamics and dispersion patterns are analyzed.

Tracking of smokestack and cooling tower plumes using wind measurements at different levels

International Nuclear Information System (INIS)

Miller, R.L.; Patrinos, A.A.N.

1980-08-01

Relationships between cooling tower and smokestack plumes at the Bowen Electric Generating Plant in northwestern Georgia and wind direction measurements at levels from the surface at 850 mb (approx. 1.5 km) are examined. The wind measurements play an important role in estimating plume directions which in turn are utilized to establish control and target (upwind and downwind) areas for a study of plant-induced precipitation modification. Fifty-two plume observations were made during a three week period in December 1979. Results indicate that a windset (4.5 km from the plant) mounted at a level approximating that of the cooling tower plume is a better predictor of plume direction than surface windsets (1.0 km from the plant) or 850 mb level winds. However, an apparent topographical influence on the wind direction measurements at the plume-level windset site somewhat limits its plume tracking capability, at least for ambient winds from the SW quadrant

Vapor plume oscillation mechanisms in transient keyhole during tandem dual beam fiber laser welding

Science.gov (United States)

Chen, Xin; Zhang, Xiaosi; Pang, Shengyong; Hu, Renzhi; Xiao, Jianzhong

2018-01-01

Vapor plume oscillations are common physical phenomena that have an important influence on the welding process in dual beam laser welding. However, until now, the oscillation mechanisms of vapor plumes remain unclear. This is primarily because mesoscale vapor plume dynamics inside a millimeter-scale, invisible, and time-dependent keyhole are difficult to quantitatively observe. In this paper, based on a developed three-dimensional (3D) comprehensive model, the vapor plume evolutions in a dynamical keyhole are directly simulated in tandem dual beam, short-wavelength laser welding. Combined with the vapor plume behaviors outside the keyhole observed by high-speed imaging, the vapor plume oscillations in dynamical keyholes at different inter-beam distances are the first, to our knowledge, to be quantitatively analyzed. It is found that vapor plume oscillations outside the keyhole mainly result from vapor plume instabilities inside the keyhole. The ejection velocity at the keyhole opening and dynamical behaviors outside the keyhole of a vapor plume both violently oscillate with the same order of magnitude of high frequency (several kHz). Furthermore, the ejection speed at the keyhole opening and ejection area outside the keyhole both decrease as the beam distance increases, while the degree of vapor plume instability first decreases and then increases with increasing beam distance from 0.6 to 1.0 mm. Moreover, the oscillation mechanisms of a vapor plume inside the dynamical keyhole irradiated by dual laser beams are investigated by thoroughly analyzing the vapor plume occurrence and flow process. The vapor plume oscillations in the dynamical keyhole are found to mainly result from violent local evaporations and severe keyhole geometry variations. In short, the quantitative method and these findings can serve as a reference for further understanding of the physical mechanisms in dual beam laser welding and of processing optimizations in industrial applications.

A mass balance approach to investigate arsenic cycling in a petroleum plume.

Science.gov (United States)

Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M; Crystal Ng, G-H

2017-12-01

Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simulating Irregular Source Geometries for Ionian Plumes

Science.gov (United States)

McDoniel, W. J.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Buchta, D. A.; Freund, J.; Kieffer, S. W.

2011-05-01

Volcanic plumes on Io respresent a complex rarefied flow into a near-vacuum in the presence of gravity. A 3D Direct Simulation Monte Carlo (DSMC) method is used to investigate the gas dynamics of such plumes, with a focus on the effects of source geometry on far-field deposition patterns. A rectangular slit and a semicircular half annulus are simulated to illustrate general principles, especially the effects of vent curvature on deposition ring structure. Then two possible models for the giant plume Pele are presented. One is a curved line source corresponding to an IR image of a particularly hot region in the volcano's caldera and the other is a large area source corresponding to the entire caldera. The former is seen to produce the features seen in observations of Pele's ring, but with an error in orientation. The latter corrects the error in orientation, but loses some structure. A hybrid simulation of 3D slit flow is also discussed.

Simulating Irregular Source Geometries for Ionian Plumes

International Nuclear Information System (INIS)

McDoniel, W. J.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Buchta, D. A.; Freund, J.; Kieffer, S. W.

2011-01-01

Volcanic plumes on Io respresent a complex rarefied flow into a near-vacuum in the presence of gravity. A 3D Direct Simulation Monte Carlo (DSMC) method is used to investigate the gas dynamics of such plumes, with a focus on the effects of source geometry on far-field deposition patterns. A rectangular slit and a semicircular half annulus are simulated to illustrate general principles, especially the effects of vent curvature on deposition ring structure. Then two possible models for the giant plume Pele are presented. One is a curved line source corresponding to an IR image of a particularly hot region in the volcano's caldera and the other is a large area source corresponding to the entire caldera. The former is seen to produce the features seen in observations of Pele's ring, but with an error in orientation. The latter corrects the error in orientation, but loses some structure. A hybrid simulation of 3D slit flow is also discussed.

Overview of NASA GRCs Green Propellant Infusion Mission Thruster Testing and Plume Diagnostics

Science.gov (United States)

Deans, Matthew C.; Reed, Brian D.; Yim, John T.; Arrington, Lynn A.; Williams, George J.; Kojima, Jun J.; McLean, Christopher H.

2014-01-01

The Green Propellant Infusion Mission (GPIM) is sponsored by NASA's Space Technology Mission Directorate (STMD) Technology Demonstration Mission (TDM) office. The goal of GPIM is to advance the technology readiness level of a green propulsion system, specifically, one using the monopropellant, AF-M315E, by demonstrating ground handling, spacecraft processing, and on-orbit operations. One of the risks identified for GPIM is potential contamination of sensitive spacecraft surfaces from the effluents in the plumes of AF-M315E thrusters. NASA Glenn Research Center (GRC) is conducting activities to characterize the effects of AF-M315E plume impingement and deposition. GRC has established individual plume models of the 22-N and 1-N thrusters that will be used on the GPIM spacecraft. The models describe the pressure, temperature, density, Mach number, and species concentration of the AF-M315E thruster exhaust plumes. The models are being used to assess the impingement effects of the AF-M315E thrusters on the GPIM spacecraft. The model simulations will be correlated with plume measurement data from Laboratory and Engineering Model 22-N, AF-M315E thrusters. The thrusters will be tested in a small rocket, altitude facility at NASA GRC. The GRC thruster testing will be conducted at duty cycles representatives of the planned GPIM maneuvers. A suite of laser-based diagnostics, including Raman spectroscopy, Rayleigh spectroscopy, Schlieren imaging, and physical probes will be used to acquire plume measurements of AFM315E thrusters. Plume data will include temperature, velocity, relative density, and species concentration. The plume measurement data will be compared to the corresponding simulations of the plume model. The GRC effort will establish a data set of AF-M315E plume measurements and a plume model that can be used for future AF-M315E applications.

The EtnaPlumeLab (EPL research cluster: advance the understanding of Mt. Etna plume, from source characterisation to downwind impact

Directory of Open Access Journals (Sweden)

Pasquale Sellitto

2017-01-01

Full Text Available In 2013, a multidisciplinary research cluster named EtnaPlumeLab (EPL was established, gathering experts from volcanology and atmospheric science communities. Target of EPL is to advance the understanding of Mt. Etna's gas and aerosol emissions and the related processes, from source to its regional climatic impact in the Mediterranean area. Here, we present the cluster and its three interacting modules: EPL-RADIO (Radioactive Aerosols and other source parameters for better atmospheric Dispersion and Impact estimatiOns, SMED (Sulfur MEditerranean Dispersion and Med-SuV (MEDiterranean SUpersite Volcanoes Work Package 5. Preliminary results have for the first time highlighted the relevance of Mt. Etna's plume impact at the Mediterranean regional scale. These results underline that further efforts need to be made to get insight into a synoptic volcanogenic-atmospheric chemistry/climatic understanding of volcanic plumes impact.

Modeling Smoke Plume-Rise and Dispersion from Southern United States Prescribed Burns with Daysmoke

Science.gov (United States)

G L Achtemeier; S L Goodrick; Y Liu; F Garcia-Menendez; Y Hu; M. Odman

2011-01-01

We present Daysmoke, an empirical-statistical plume rise and dispersion model for simulating smoke from prescribed burns. Prescribed fires are characterized by complex plume structure including multiple-core updrafts which makes modeling with simple plume models difficult. Daysmoke accounts for plume structure in a three-dimensional veering/sheering atmospheric...

Acid-base status of soils in groundwater discharge zones — relation to surface water acidification

Science.gov (United States)

Norrström, Ann Catrine

1995-08-01

Critical load calculations have suggested that groundwater at depth of 2 m in Sweden is very sensitive to acid load. As environmental isotope studies have shown that most of the runoff in streams has passed through the soil, there is a risk in the near future of accelerated acidification of surface waters. To assess the importance of the last soil horizon of contact before discharge, the upper 0-0.2m of soils in seven discharge zones were analysed for pools of base cations, acidity and base saturation. The sites were about 3-4 m 2 in size and selected from two catchments exposed to different levels of acid deposition. The soils in the seven sites had high concentrations of exchangeable base cations and consequently high base saturation. The high correlation ( r2 = 0.74) between base saturation in the soils of the discharge zones and mean pH of the runoff waters suggested that the discharge zone is important for surface water acidification. The high pool of exchangeable base cations will buffer initially against the acid load. As the cation exchange capacity (meq dm -3) and base saturation were lower in the sites from the catchment receiving lower deposition, these streams may be more vulnerable to acidification in the near future. The high concentration of base cations in non-exchangeable fractions may also buffer against acidification as it is likely that some of these pools will become exchangeable with time.

Experimental investigation of the hydrodynamics of confined bubble plumes in water and viscous media

International Nuclear Information System (INIS)

Brahma N Reddy Vanga; Martin A Lopez de Bertodano; Alexandr Zaruba; Eckhard Krepper; Horst-Michael Prasser

2005-01-01

Wire-mesh tomography measurements of void fraction and bubble size distribution in a rectangular bubble column 10 cm wide and 2 cm deep have been conducted. Experiments were performed in an air-water and ethylene glycol system with the column operating in the dispersed bubbly flow regime.Experiments were conducted for plumes with different aspect ratios between 2.2 to 13. The experiments also serve the purpose of studying the performance of wire-mesh sensors in batch flows. The behaviour of the long plumes (larger aspect ratio) was found to be significantly different than that of the short plumes (aspect ratios 2 to 4). The oscillating nature of the bubble plume is preserved over the entire height of the water column for the short plumes. The longer plumes are characterized by two distinct regions, the near injector oscillating region and a further downstream region where the bubbles rise in a string like motion. The void fraction distribution in the oscillating region of the plume exhibits a center-peak profile. A 'wall peak' has been observed in the measured void fraction profiles (for higher gas flow rates) in the downstream string-like region. The effect of column height and superficial gas velocity on the void distribution has been investigated. This paper presents the measurement principle and the experimental results for short and long plumes in an air-water system and for short plumes rising in viscous media. The results of the visualization experiment characterizing the structure of the bubble plume and the oscillation frequency of the bubble plumes are reported. (authors)

New method for calculation of integral characteristics of thermal plumes

DEFF Research Database (Denmark)

Zukowska, Daria; Popiolek, Zbigniew; Melikov, Arsen Krikor

2008-01-01

A method for calculation of integral characteristics of thermal plumes is proposed. The method allows for determination of the integral parameters of plumes based on speed measurements performed with omnidirectional low velocity thermoanemometers. The method includes a procedure for calculation...... of the directional velocity (upward component of the mean velocity). The method is applied for determination of the characteristics of an asymmetric thermal plume generated by a sitting person. The method was validated in full-scale experiments in a climatic chamber with a thermal manikin as a simulator of a sitting...

Delineating a road-salt plume in lakebed sediments using electrical resistivity, piezometers, and seepage meters at Mirror Lake, New Hampshire, U.S.A

Science.gov (United States)

Toran, Laura; Johnson, Melanie; Nyquist, Jonathan E.; Rosenberry, Donald O.

2010-01-01

Electrical-resistivity surveys, seepage meter measurements, and drive-point piezometers have been used to characterize chloride-enriched groundwater in lakebed sediments of Mirror Lake, New Hampshire, U.S.A. A combination of bottom-cable and floating-cable electrical-resistivity surveys identified a conductive zone (ohm-m)">(ohm-m)(ohm-m) overlying resistive bedrock (ohm-m)">(ohm-m)(ohm-m)beneath the lake. Shallow pore-water samples from piezometers in lakebed sediments have chloride concentrations of 200–1800μeq/liter">200–1800μeq/liter200–1800μeq/liter, and lake water has a chloride concentration of 104μeq/liter">104μeq/liter104μeq/liter. The extent of the plume was estimated and mapped using resistivity and water-sample data. The plume (20×35m">20×35m20×35m wide and at least 3m">3m3m thick) extends nearly the full length and width of a small inlet, overlying the top of a basin formed by the bedrock. It would not have been possible to mapthe plume's shape without the resistivity surveys because wells provided only limited coverage. Seepage meters were installed approximately 40m">40m40m from the mouth of a small stream discharging at the head of the inlet in an area where the resistivity data indicated lake sediments are thin. These meters recorded in-seepage of chloride-enriched groundwater at rates similar to those observed closer to shore, which was unexpected because seepage usually declines away from shore. Although the concentration of road salt in the northeast inlet stream is declining, the plume map and seepage data indicate the groundwater contribution of road salt to the lake is not declining. The findings demonstrate the benefit of combining geophysical and hydrologic data to characterize discharge of a plume beneath Mirror Lake. The extent of the plume in groundwater beneath the lake and stream indicate there will likely be a long-term source of chloride to the lake from groundwater.

Utilization of a hydraulic barrier to control migration of a uranium plume

International Nuclear Information System (INIS)

Brettschneider, D.J.; Simmons, R.A. Jr.; Kappa, J.D.; Stover, J.A.

1995-01-01

A uranium plume emanating from the U.S. Department of Energy's Fernald Environmental Management Project (FEMP) in Fernald, Ohio had migrated off site and the leading edge of the plume had already mixed with an organic and inorganic plume emanating from two industries south of the FEMP. A method was needed to prevent the further southern migration of the plume, minimize any impacts to the geometry, concentrations, distribution or flow patterns of the organic and inorganic plumes emanating from the off-site industries, while meeting the ultimate cleanup goals for the FEMP. This paper discusses the use of a hydraulic barrier created to meet these goals by pumping a five well recovery system and the problems associated with the disposition of over 2 million gallons per day of water with low concentrations of uranium

Isotope Investigations of Groundwater Movement in a Coarse Gravel Unsaturated Zone

Energy Technology Data Exchange (ETDEWEB)

Mali, N. [Geological Survey of Slovenia, Department of Hydrogeology, Ljubljana (Slovenia); Kozar-Logar, J. [Jozef Stefan Institute, Ljubljana (Slovenia); Leis, A. [Institute of Water Resources Management, Hydrogeology and Geophysics, Joanneum Research Forschungsgesellschaft mbH, Graz (Austria)

2013-07-15

The unsaturated zone above an aquifer serves as a water reservoir which discharges water and possible pollution to the saturated zone. This paper presents the application of oxygen-18 and tritium isotope methods in the study of groundwater transport processes in the unsaturated zone of Selniska Dobrava coarse gravel aquifer. The Selniska Dobrava gravel aquifer is an important water resource for Maribor and its surroundings, therefore the determination of transport processes in the unsaturated zone is important regarding its protection. Groundwater flow characteristics were estimated using isotopes and based on experimental work in a lysimeter. Tritium investigation results were compared with the results of long term oxygen-18 isotope investigation. In this paper the analytical approach, results and interpretation of {delta}{sup 18}O and tritium measurements in the unsaturated zone are presented. (author)

Field studies of submerged-diffuser thermal plumes with comparisons to predictive model results

International Nuclear Information System (INIS)

Frigo, A.A.; Paddock, R.A.; Ditmars, J.D.

1976-01-01

Thermal plumes from submerged discharges of cooling water from two power plants on Lake Michigan were studied. The system for the acquisition of water temperatures and ambient conditions permitted the three-dimensional structure of the plumes to be determined. The Zion Nuclear Power Station has two submerged discharge structures separated by only 94 m. Under conditions of flow from both structures, interaction between the two plumes resulted in larger thermal fields than would be predicted by the superposition of single non-interacting plumes. Maximum temperatures in the near-field region of the plume compared favorably with mathematical model predictions. A comparison of physical-model predictions for the plume at the D. C. Cook Nuclear Plant with prototype measurements indicated good agreement in the near-field region, but differences in the far-field occurred as similitude was not preserved there

Appearance and water quality of turbidity plumes produced by dredging in Tampa Bay, Florida

Science.gov (United States)

Goodwin, Carl R.; Michaelis, D.M.

1984-01-01

Turbidity plumes in Tampa Bay, Florida, produced during ship-channel dredging operations from February 1977 to August 1978, were monitored in order to document plume appearance and water quality, evaluate plume influence on the characteristics of Tampa Bay water, and provide a data base for comparison with other areas that have similar sediment, dredge, placement, containment, and tide conditions. The plumes investigated originated from the operation of one hopper dredge and three cutterhead-pipeline dredges. Composition of bottom sediment was found to vary from 85 percent sand and shell fragments to 60 percent silt and clay. Placement methods for dredged sediment included beach nourishment, stationary submerged discharge, oscillating surface discharge, and construction of emergent dikes. Tidal currents ranged from slack water to flow velocities of 0.60 meter per second. Plumes were monitored simultaneously by (1) oblique and vertical 35-millimeter aerial photography and (2) water-quality sampling to determine water clarity and concentrations of nutrients, metals, pesticides, and industrial compounds. Forty-nine photographs depict plumes ranging in length from a few tens of meters to several kilometers and ranging in turbidity level from hopper-dredge unloading operations also produced plumes of low visibility. Primary turbidity plumes were produced directly by dredging and placement operations; secondary plumes were produced indirectly by resuspension of previously deposited material. Secondary plumes were formed both by erosion, in areas of high-velocity tidal currents, and by turbulence from vessels passing over fine material deposited in shallow areas. Where turbidity barriers were not used, turbidity plumes visible at the surface were good indicators of the location of turbid water at depth. Where turbidity barriers were used, turbid bottom water was found at locations having no visible surface plumes. A region of rapidly accelerating then decelerating flow

Dynamics of Mantle Plume Controlled by both Post-spinel and Post-garnet Phase Transitions

Science.gov (United States)