Consideration of Transient Stream/Aquifer Interaction with the Nonlinear Boussinesq Equation using HPM

DEFF Research Database (Denmark)

Ganji, S. S.; Barari, Amin; Sfahani, M. G.

2011-01-01

of time. The differential equations were solved using the method of Homotopy Perturbation. The simplicity and accuracy of the approximation are compared with “exact” solution and illustrated numerically and graphically. The results reveal that the HPM is very effective and simple and provides highly...... accurate solutions for nonlinear differential equations.......The phenomenon of stream–aquifer interaction was investigated via mathematical modeling using the Boussinesq equation. A new approximate solution of the one-dimensional Boussinesq equation is presented for a semi-infinite aquifer when the hydraulic head at the source is an arbitrary function...

New methodology to investigate potential contaminant mass fluxes at the stream-aquifer interface by combining integral pumping tests and streambed temperatures

International Nuclear Information System (INIS)

Kalbus, E.; Schmidt, C.; Bayer-Raich, M.; Leschik, S.; Reinstorf, F.; Balcke, G.U.; Schirmer, M.

2007-01-01

The spatial pattern and magnitude of mass fluxes at the stream-aquifer interface have important implications for the fate and transport of contaminants in river basins. Integral pumping tests were performed to quantify average concentrations of chlorinated benzenes in an unconfined aquifer partially penetrated by a stream. Four pumping wells were operated simultaneously for a time period of 5 days and sampled for contaminant concentrations. Streambed temperatures were mapped at multiple depths along a 60 m long stream reach to identify the spatial patterns of groundwater discharge and to quantify water fluxes at the stream-aquifer interface. The combined interpretation of the results showed average potential contaminant mass fluxes from the aquifer to the stream of 272 μg m -2 d -1 MCB and 71 μg m -2 d -1 DCB, respectively. This methodology combines a large-scale assessment of aquifer contamination with a high-resolution survey of groundwater discharge zones to estimate contaminant mass fluxes between aquifer and stream. - We provide a new methodology to quantify the potential contaminant mass flux from an aquifer to a stream

The interaction between the unsaturated zone, aquifer, and stream during a period of groundwater withdrawal

DEFF Research Database (Denmark)

Poulsen, Søren Erbs; Christensen, Steen; Rasmussen, Keld Rømer

2011-01-01

drainage responses to water-table drawdown. The responses can be sufficiently modeled by estimating the specific yield and five exponential time constants of a Moench/Boulton type model of delayed drainage. The average specific yield is thus estimated to 0.24 which is in agreement with previous small scale......; in the second case the estimate (0.17) is in better agreement with core and previous estimates (0.24). The analysis indicates that relatively fast drainage, and the existence of two drawdown dependent sources of groundwater recharge (the storage and the stream), complicates pumping test design to obtain unique...... parameter estimation. The analysis supports that an essential factor in parameter estimation by pumping test analysis for (at least some) unconfined aquifers is the use of a model that accounts for time-varying drainage from the vadose zone. Finally, when predicting stream depletion beyond 1. day of pumping...

New Module to Simulate Groundwater-Surface Water Interactions in Small-Scale Alluvial Aquifer System.

Science.gov (United States)

Flores, L.

2017-12-01

Streamflow depletion can occur when groundwater pumping wells lower water table elevations adjacent to a nearby stream. Being able to accurately model the severity of this process is of critical importance in semi-arid regions where groundwater-surface water interactions affect water rights and the sustainability of water resource practices. The finite-difference flow model MODFLOW is currently the standard for estimating groundwater-surface water interactions in many regions in the western United States. However, certain limitations of the model persist when highly-resolved spatial scales are used to represent the stream-aquifer system, e.g. when the size of computational grid cells is much less than the river width. In this study, an external module is developed and linked with MODFLOW that (1) allows for multiple computational grid cells over the width of the river; (2) computes streamflow and stream stage along the length of the river using the one-dimensional (1D) steady (over a stress period) shallow water equations, which allows for more accurate stream stages when normal flow cannot be assumed or a rating curve is not available; and (3) incorporates a process for computing streamflow loss when an unsaturated zone develops under the streambed. Use of the module not only provides highly-resolved estimates of streamflow depletion, but also of streambed hydraulic conductivity. The new module is applied to the stream-aquifer alluvial system along the South Platte River south of Denver, Colorado, with results tested against field-measured groundwater levels, streamflow, and streamflow depletion.

Stream-aquifer relations and the potentiometric surface of the Upper Floridan aquifer in the lower Apalachicola-Chattahoochee-Flint River basin in parts of Georgia, Florida, and Alabama, 1999-2000

Science.gov (United States)

Mosner, Melinda S.

2002-01-01

The Upper Floridan aquifer is the principal source of water for domestic and agricultural use in the lower Apalachicola-Chattahoochee-Flint (ACF) River Basin. Recent drought and increased water use have made understanding surface- and ground-water relations a priority for water-resource managers in the region. From July 1999 through August 2000, less than normal precipitation reduced streamflow in the area to less than 12 percent of average mean-daily streamflow and ground-water levels reached record or near-record lows. Effects of drought on stream-aquifer interactions in the basin were evaluated using baseflow estimation, ground-water seepage calculations, and potentiometric-surface maps. Ground-water discharge to streams, or baseflow, was estimated using three methods: field measurements, hydrograph separation, and linear regression analysis. Results were evaluated seasonally -- October 1999, April 2000, and August 2000 -- and for the period of record at four surface-water stations located on Kinchafoonee, Spring, Muckalee, and Turkey Creeks. Estimates of baseflow also were compared annually; ground-water discharge during the drought years, 1999 - 2000, was compared with ground-water discharge during a relatively wet year, 1994. Hydrograph separation indicated decreased base-flow of streams as the water level in the Upper Floridan aquifer declined. Mean-annual baseflow for Kinchafoonee, Spring, Muckalee, and Turkey Creeks ranged from 36 to 71 percent of total streamflow during the period of record. In 1994 baseflow accounted for only 37 to 56 percent of total streamflow, in 1999 baseflow comprised from 60 to 73 percent of total streamflow, and in 2000 baseflow comprised from 56 to 76 percent of streamflow. The percentage of total streamflow attributed to ground water increased during the drought, whereas other components of streamflow decreased (overland flow, interflow, and channel precipitation). Even though relative ground-water contributions were increased

Hydrogeologic data for the Big River-Mishnock River stream-aquifer system, central Rhode Island

Science.gov (United States)

Craft, P.A.

2001-01-01

Hydrogeology, ground-water development alternatives, and water quality in the BigMishnock stream-aquifer system in central Rhode Island are being investigated as part of a long-term cooperative program between the Rhode Island Water Resources Board and the U.S. Geological Survey to evaluate the ground-water resources throughout Rhode Island. The study area includes the Big River drainage basin and that portion of the Mishnock River drainage basin upstream from the Mishnock River at State Route 3. This report presents geologic data and hydrologic and water-quality data for ground and surface water. Ground-water data were collected from July 1996 through September 1998 from a network of observation wells consisting of existing wells and wells installed for this study, which provided a broad distribution of data-collection sites throughout the study area. Streambed piezometers were used to obtain differences in head data between surface-water levels and ground-water levels to help evaluate stream-aquifer interactions throughout the study area. The types of data presented include monthly ground-water levels, average daily ground-water withdrawals, drawdown data from aquifer tests, and water-quality data. Historical water-level data from other wells within the study area also are presented in this report. Surface-water data were obtained from a network consisting of surface-water impoundments, such as ponds and reservoirs, existing and newly established partial-record stream-discharge sites, and synoptic surface-water-quality sites. Water levels were collected monthly from the surface-water impoundments. Stream-discharge measurements were made at partial-record sites to provide measurements of inflow, outflow, and internal flow throughout the study area. Specific conductance was measured monthly at partial-record sites during the study, and also during the fall and spring of 1997 and 1998 at 41 synoptic sites throughout the study area. General geologic data, such as

Instream flow assessment of streams draining the Arbuckle-Simpson Aquifer

Science.gov (United States)

Seilheimer, Titus S.; Fisher, William L.

2008-01-01

The availability of high quality water is critical to both humans and ecosystems. A recent proposal was made by rapidly expanding municipalities in central Oklahoma to begin transferring groundwater from the Arbuckle-Simpson aquifer, a sensitive sole-source aquifer in south-central Oklahoma. Concerned citizens and municipalities living on and getting their drinking water from the Arbuckle-Simpson lobbied the legislature to pass a temporary moratorium on groundwater transfer to allow for a comprehensive study of the aquifer and its ecosystems. We conducted an instream flow assessment using Physical Habitat Simulation (PHABSIM) on springs and streams with four spring-dependent species: two minnows, southern redbelly dace (Phoxinus erthyrogaster) and redspot chub (Nocomis asper); and two darters, least darter (Etheostoma microperca) and orangethroat darter (Etheostoma spectabile). Spring habitats are unique compared to other river habitats because they have constant flow and temperature, small and isolated habitat patches, and a general lack of predators. Our study sites included two spring-fed streams, one larger stream with high groundwater inputs, and a river with both groundwater and surface water inputs that is adjacent to the small spring-fed streams. These habitats meet the criteria for groundwater dependent ecosystems because they would not exist without the surface expression of groundwater. A total of 99 transects in all four sites were surveyed for channel elevation, and three sets of water surface elevation and water velocity were measured. Habitat suitability criteria were derived for the species at each site using nonparametric confidence limits based on underwater observations made by snorkelers. Simulations of flow were focused on declines in discharge, which is the expected effect of the proposed groundwater diversion. Our results show that only a small proportion of the total available area in each habitat is considered to be preferred habitat

Arsenic mobilization and attenuation by mineral-water interactions: implications for managed aquifer recharge.

Science.gov (United States)

Neil, Chelsea W; Yang, Y Jeffrey; Jun, Young-Shin

2012-07-01

Managed aquifer recharge (MAR) has potential for addressing deficits in water supplies worldwide. It is also widely used for preventing saltwater intrusion, maintaining the groundwater table, and augmenting ecological stream flows, among many other beneficial environmental applications. However, field MAR sites have experienced arsenic mobilization from aquifer formation minerals due to induced changes in groundwater chemistry. To address this environmental concern, it is crucial to understand the potential sources and sinks impacting arsenic mobilization. This paper outlines important mineral-water interactions that can occur at MAR sites. Detailed information on minerals of concern, physiochemical processes for arsenic mobilization or attenuation, and the potential impact of microbial activity and hydrology on these processes is provided. Based on these mineral-water interactions, guidelines for predicting arsenic mobility are presented, and recommendations are made concerning MAR site monitoring. The review emphasizes important aspects in correlating interfacial reactions to reactive transport modeling and elucidating future challenges, a first step toward developing safer and more sustainable MAR operations.

Using SWAT-MODFLOW to simulate groundwater flow and groundwater-surface water interactions in an intensively irrigated stream-aquifer system

Science.gov (United States)

Wei, X.; Bailey, R. T.

2017-12-01

Agricultural irrigated watersheds in semi-arid regions face challenges such as waterlogging, high soil salinity, reduced crop yield, and leaching of chemical species due to extreme shallow water tables resulting from long-term intensive irrigation. Hydrologic models can be used to evaluate the impact of land management practices on water yields and groundwater-surface water interactions in such regions. In this study, the newly developed SWAT-MODFLOW, a coupled surface/subsurface hydrologic model, is applied to a 950 km2 watershed in the Lower Arkansas River Valley (southeastern Colorado). The model accounts for the influence of canal diversions, irrigation applications, groundwater pumping, and earth canal seepage losses. The model provides a detailed description of surface and subsurface flow processes, thereby enabling detailed description of watershed processes such as runoff, infiltration, in-streamflow, three-dimensional groundwater flow in a heterogeneous aquifer system with sources and sinks (e.g. pumping, seepage to subsurface drains), and spatially-variable surface and groundwater exchange. The model was calibrated and tested against stream discharge from 5 stream gauges in the Arkansas River and its tributaries, groundwater levels from 70 observation wells, and evapotranspiration (ET) data estimated from satellite (ReSET) data during the 1999 to 2007 period. Since the water-use patterns within the study area are typical of many other irrigated river valleys in the United States and elsewhere, this modeling approach is transferable to other regions.

Development of a stream-aquifer numerical flow model to assess river water management under water scarcity in a Mediterranean basin.

Science.gov (United States)

Mas-Pla, Josep; Font, Eva; Astui, Oihane; Menció, Anna; Rodríguez-Florit, Agustí; Folch, Albert; Brusi, David; Pérez-Paricio, Alfredo

2012-12-01

Stream flow, as a part of a basin hydrological cycle, will be sensible to water scarcity as a result of climate change. Stream vulnerability should then be evaluated as a key component of the basin water budget. Numerical flow modeling has been applied to an alluvial formation in a small mountain basin to evaluate the stream-aquifer relationship under these future scenarios. The Arbúcies River basin (116 km(2)) is located in the Catalan Inner Basins (NE Spain) and its lower reach, which is related to an alluvial aquifer, usually becomes dry during the summer period. This study seeks to determine the origin of such discharge losses whether from natural stream leakage and/or induced capture due to groundwater withdrawal. Our goal is also investigating how discharge variations from the basin headwaters, representing potential effects of climate change, may affect stream flow, aquifer recharge, and finally environmental preservation and human supply. A numerical flow model of the alluvial aquifer, based on MODFLOW and especially in the STREAM routine, reproduced the flow system after the usual calibration. Results indicate that, in the average, stream flow provides more than 50% of the water inputs to the alluvial aquifer, being responsible for the amount of stored water resources and for satisfying groundwater exploitation for human needs. Detailed simulations using daily time-steps permit setting threshold values for the stream flow entering at the beginning of the studied area so surface discharge is maintained along the whole watercourse and ecological flow requirements are satisfied as well. The effects of predicted rainfall and temperature variations on the Arbúcies River alluvial aquifer water balance are also discussed from the outcomes of the simulations. Finally, model results indicate the relevance of headwater discharge management under future climate scenarios to preserve downstream hydrological processes. They also point out that small mountain basins

H(+) - O(+) two-stream interaction on auroral field lines

International Nuclear Information System (INIS)

Bergmann, R.

1990-01-01

Upflowing beams of hydrogen, oxygen, and minor ion species, and downward accelerated electrons have been observed above several thousand kilometers altitude on evening auroral field lines. The mechanism for electron and ion acceleration is generally accepted to be the presence of a quasi-static electric field with a component parallel to the earth's magnetic field. The thermal energy of the observed beams is much larger than ionospheric ion temperatures indicating that the beams have been heated as they are accelerated upward. This heating is probably due to a two-stream interaction between beams of different mass ions. The beams gain equal energy in the potential drop and so have different average velocities. Their relative streaming initiates an ion-ion two-stream interaction which then mediates a transfer of energy and momentum between the beams and causes thermalization of each beam. The qualitative evidence that supports this scenario is reviewed. Properties of the two-stream instability are presented in order to demonstrate that a calculation of the evolution of ion beams requires a model that includes field-aligned spatial structure. 26 refs

Report Assesses Nutrient Pollution in U.S. Streams and Aquifers

Science.gov (United States)

Showstack, Randy

2010-10-01

Concentrations of nutrients in many U.S. streams and aquifers have remained the same or have increased since the early 1990s, according to a new decadal assessment entitled “Nutrients in the nation's streams and groundwater, 1992-2004,” released by the U.S. Geological Survey (USGS) on 24 September. “Despite improvements in water quality made by reducing point sources of nutrients, our data show that nonpoint sources of nutrients have resulted in concentrations of both nitrogen and phosphorus far above criteria recommended by [the U.S. Environmental Protection Agency] for the protection of aquatic life,” Neil Dubrovsky, project chief for USGS's National Water-Quality Assessment (NAWQA) Program, said at a briefing when the report was released. While USGS continues to sample for nutrient concentrations, the report assessment period concluded in 2004.

Redox reaction rates in shallow aquifers: Implications for nitrate transport in groundwater and streams

Science.gov (United States)

Tesoriero, Anthony J.

2012-01-01

Groundwater age and water chemistry data along flow paths from recharge areas to streams were used to evaluate the trends and transformations of agricultural chemicals. Results from this analysis indicate that median nitrate recharge concentrations in these agricultural areas have increased markedly over the last 50 years from 4 mg N/L in samples collected prior to 1983 to 7.5 mg N/L in samples collected since 1983. The effect that nitrate accumulation in shallow aquifers will have on drinking water quality and stream ecosystems is dependent on the rate of redox reactions along flow paths and on the age distribution of nitrate discharging to supply wells and streams.

Accounting for intracell flow in models with emphasis on water table recharge and stream-aquifer interaction: 1. Problems and concepts

Science.gov (United States)

Jorgensen, Donald G.; Signor, Donald C.; Imes, Jeffrey L.

1989-01-01

Intracell flow is important in modeling cells that contain both sources and sinks. Special attention is needed if recharge through the water table is a source. One method of modeling multiple sources and sinks is to determine the net recharge per cell. For example, for a model cell containing both a sink and recharge through the water table, the amount of recharge should be reduced by the ratio of the area of influence of the sink within the cell to the area of the cell. The reduction is the intercepted portion of the recharge. In a multilayer model this amount is further reduced by a proportion factor, which is a function of the depth of the flow lines from the water table boundary to the internal sink. A gaining section of a stream is a typical sink. The aquifer contribution to a gaining stream can be conceptualized as having two parts; the first part is the intercepted lateral flow from the water table and the second is the flow across the streambed due to differences in head between the water level in the stream and the aquifer below. The amount intercepted is a function of the geometry of the cell, but the amount due to difference in head across the stream bed is largely independent of cell geometry. A discharging well can intercept recharge through the water table within a model cell. The net recharge to the cell would be reduced in proportion to the area of influence of the well within the cell. The area of influence generally changes with time. Thus the amount of intercepted recharge and net recharge may not be constant with time. During periods when the well is not discharging there will be no intercepted recharge even though the area of influence from previous pumping may still exist. The reduction of net recharge per cell due to internal interception of flow will result in a model-calculated mass balance less than the prototype. Additionally the “effective transmissivity” along the intercell flow paths may be altered when flow paths are occupied by

Case studies of groundwater- surface water interactions and scale relationships in small alluvial aquifers

NARCIS (Netherlands)

Love, Dave; de Hamer, Wouter; Owen, Richard J.S.; Booij, Martijn J.; Uhlenbrook, Stefan; Hoekstra, Arjen Ysbert; van der Zaag, Pieter

2007-01-01

An alluvial aquifer can be described as a groundwater system, generally unconfined, that is hosted in laterally discontinuous layers of gravel, sand, silt and clay, deposited by a river in a river channel, banks or flood plain. In semi-arid regions, streams that are associated with alluvial aquifers

Arsenic transport in groundwater, surface water, and the hyporheic zone of a mine-influenced stream-aquifer system

OpenAIRE

Brown, Brendan

2005-01-01

We investigated the transport of dissolved arsenic in groundwater, surface water and the hyporheic zone in a stream-aquifer system influenced by an abandoned arsenopyrite mine. Mine tailing piles consisting of a host of arsenic-bearing minerals including arsenopyrite and scorodite remain adjacent to the stream and represent a continuous source of arsenic. Arsenic loads from the stream, springs, and groundwater were quantified at the study reach on nine dates from January to August 2005 and ...

Flow-Through Stream Modeling with MODFLOW and MT3D: Certainties and Limitations.

Science.gov (United States)

Ben Simon, Rose; Bernard, Stéphane; Meurville, Charles; Rebour, Vincent

2015-01-01

This paper aims to assess MODFLOW and MT3D capabilities for simulating the spread of contaminants from a river exhibiting an unusual relationship with an alluvial aquifer, with the groundwater head higher than the river head on one side and lower on the other (flow-through stream). A series of simulation tests is conducted using a simple hypothetical model so as to characterize and quantify these limitations. Simulation results show that the expected contaminant spread could be achieved with a specific configuration composed of two sets of parameters: (1) modeled object parameters (hydraulic groundwater gradient, hydraulic conductivity values of aquifer and streambed), and (2) modeling parameters (vertical discretization of aquifer, horizontal refinement of stream modeled with River [RIV] package). The influence of these various parameters on simulation results is investigated, and potential complications and errors are identified. Contaminant spread from stream to aquifer is not always reproduced by MT3D due to the RIV package's inability to simulate lateral exchange fluxes between stream and aquifer. This paper identifies the need for a MODFLOW streamflow package allowing lateral stream-aquifer interactions and streamflow routine calculations. Such developments could be of particular interest for modeling contaminated flow-through streams. © 2015, National Ground Water Association.

Hydrochemical processes in a shallow coal seam gas aquifer and its overlying stream–alluvial system: implications for recharge and inter-aquifer connectivity

International Nuclear Information System (INIS)

Duvert, Clément; Raiber, Matthias; Owen, Daniel D.R.; Cendón, Dioni I.; Batiot-Guilhe, Christelle; Cox, Malcolm E.

2015-01-01

Highlights: • Major ions and isotopes used to study inter-aquifer mixing in a shallow CSG setting. • Considerable heterogeneity in the water composition of the coal-bearing aquifer. • Rapid recharge of the coal-bearing aquifer through highly fractured igneous rocks. • Potential mixing between the coal-bearing aquifer and downstream alluvial aquifer. • Need to consider the seasonal influences on inter-aquifer mixing in CSG settings. - Abstract: In areas of potential coal seam gas (CSG) development, understanding interactions between coal-bearing strata and adjacent aquifers and streams is of highest importance, particularly where CSG formations occur at shallow depth. This study tests a combination of hydrochemical and isotopic tracers to investigate the transient nature of hydrochemical processes, inter-aquifer mixing and recharge in a catchment where the coal-bearing aquifer is in direct contact with the alluvial aquifer and surface drainage network. A strong connection was observed between the main stream and underlying alluvium, marked by a similar evolution from fresh Ca–Mg–HCO 3 waters in the headwaters towards brackish Ca–Na–Cl composition near the outlet of the catchment, driven by evaporation and transpiration. In the coal-bearing aquifer, by contrast, considerable site-to-site variations were observed, although waters generally had a Na–HCO 3 –Cl facies and high residual alkalinity values. Increased salinity was controlled by several coexisting processes, including transpiration by plants, mineral weathering and possibly degradation of coal organic matter. Longer residence times and relatively enriched carbon isotopic signatures of the downstream alluvial waters were suggestive of potential interactions with the shallow coal-bearing aquifer. The examination of temporal variations in deuterium excess enabled detection of rapid recharge of the coal-bearing aquifer through highly fractured igneous rocks, particularly at the catchment

Development of a cross-section based stream package for MODFLOW

Science.gov (United States)

Ou, G.; Chen, X.; Irmak, A.

2012-12-01

Accurate simulation of stream-aquifer interactions for wide rivers using the streamflow routing package in MODFLOW is very challenging. To better represent a wide river spanning over multiple model grid cells, a Cross-Section based streamflow Routing (CSR) package is developed and incorporated into MODFLOW to simulate the interaction between streams and aquifers. In the CSR package, a stream segment is represented as a four-point polygon instead of a polyline which is traditionally used in streamflow routing simulation. Each stream segment is composed of upstream and downstream cross-sections. A cross-section consists of a number of streambed points possessing coordinates, streambed thicknesses and streambed hydraulic conductivities to describe the streambed geometry and hydraulic properties. The left and right end points are used to determine the locations of the stream segments. According to the cross-section geometry and hydraulic properties, CSR calculates the new stream stage at the cross-section using the Brent's method to solve the Manning's Equation. A module is developed to automatically compute the area of the stream segment polygon on each intersected MODFLOW grid cell as the upstream and downstream stages change. The stream stage and streambed hydraulic properties of model grids are interpolated based on the streambed points. Streambed leakage is computed as a function of streambed conductance and difference between the groundwater level and stream stage. The Muskingum-Cunge flow routing scheme with variable parameters is used to simulate the streamflow as the groundwater (discharge or recharge) contributes as lateral flows. An example is used to illustrate the capabilities of the CSR package. The result shows that the CSR is applicable to describing the spatial and temporal variation in the interaction between streams and aquifers. The input data become simple due to that the internal program automatically interpolates the cross-section data to each

PLASMA EMISSION BY COUNTER-STREAMING ELECTRON BEAMS

Energy Technology Data Exchange (ETDEWEB)

Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, MD (United States); Pavan, J., E-mail: luiz.ziebell@ufrgs.br, E-mail: yoonp@umd.edu, E-mail: joel.pavan@ufpel.edu.br [Instituto de Física e Matemática, UFPel, Pelotas, RS (Brazil)

2016-02-10

The radiation emission mechanism responsible for both type-II and type-III solar radio bursts is commonly accepted as plasma emission. Recently Ganse et al. suggested that type-II radio bursts may be enhanced when the electron foreshock geometry of a coronal mass ejection contains a double hump structure. They reasoned that the counter-streaming electron beams that exist between the double shocks may enhance the nonlinear coalescence interaction, thereby giving rise to more efficient generation of radiation. Ganse et al. employed a particle-in-cell simulation to study such a scenario. The present paper revisits the same problem with EM weak turbulence theory, and show that the fundamental (F) emission is not greatly affected by the presence of counter-streaming beams, but the harmonic (H) emission becomes somewhat more effective when the two beams are present. The present finding is thus complementary to the work by Ganse et al.

Self-focusing relativistic electron streams in plasmas

International Nuclear Information System (INIS)

Cox, J.L. Jr.

1975-01-01

A relativistic electron stream propagating through a dense plasma induces current and charge densities which determine how the stream can self-focus. Magnetic self-focusing is possible because stream-current neutralization, although extensive, is not complete. Electric self-focusing can occur because the stream charge becomes overneutralized when the net current is smaller than a critical value. Under some circumstances, the latter process can cause the stream to focus into a series of electron bunches

Arsenic mobilization and attenuation by mineral–water interactions: implications for managed aquifer recharge

Science.gov (United States)

Managed aquifer recharge (MAR) has a potential for addressing deficits in water supplies worldwide. It is also widely used for preventing saltwater intrusion, maintaining the groundwater table, and augmenting ecological stream flows among many beneficial environmental application...

Fluid aspects of electron streaming instability in electron-ion plasmas

International Nuclear Information System (INIS)

Jao, C.-S.; Hau, L.-N.

2014-01-01

Electrons streaming in a background electron and ion plasma may lead to the formation of electrostatic solitary wave (ESW) and hole structure which have been observed in various space plasma environments. Past studies on the formation of ESW are mostly based on the particle simulations due to the necessity of incorporating particle's trapping effects. In this study, the fluid aspects and thermodynamics of streaming instabilities in electron-ion plasmas including bi-streaming and bump-on-tail instabilities are addressed based on the comparison between fluid theory and the results from particle-in-cell simulations. The energy closure adopted in the fluid model is the polytropic law of d(pρ −γ )/dt=0 with γ being a free parameter. Two unstable modes are identified for the bump-on-tail instability and the growth rates as well as the dispersion relation of the streaming instabilities derived from the linear theory are found to be in good agreement with the particle simulations for both bi-streaming and bump-on-tail instabilities. At the nonlinear saturation, 70% of the electrons are trapped inside the potential well for the drift velocity being 20 times of the thermal velocity and the pρ −γ value is significantly increased. Effects of ion to electron mass ratio on the linear fluid theory and nonlinear simulations are also examined

Testing a community water supply well located near a stream for susceptibility to stream contamination and low-flows.

Science.gov (United States)

Stewart-Maddox, N. S.; Tysor, E. H.; Swanson, J.; Degon, A.; Howard, J.; Tsinnajinnie, L.; Frisbee, M. D.; Wilson, J. L.; Newman, B. D.

2014-12-01

A community well is the primary water supply to the town of El Rito. This small rural town in is located in a semi-arid, mountainous portion of northern New Mexico where water is scarce. The well is 72 meters from a nearby intermittent stream. Initial tritium sampling suggests a groundwater connection between the stream and well. The community is concerned with the sustainability and future quality of the well water. If this well is as tightly connected to the stream as the tritium data suggests, then the well is potentially at risk due to upstream contamination and the impacts of extended drought. To examine this, we observed the well over a two-week period performing pump and recovery tests, electrical resistivity surveys, and physical observations of the nearby stream. We also collected general chemistry, stable isotope and radon samples from the well and stream. Despite the large well diameter, our pump test data exhibited behavior similar to a Theis curve, but the rate of drawdown decreased below the Theis curve late in the test. This decrease suggests that the aquifer is being recharged, possibly through delayed yield, upwelling of groundwater, or from the stream. The delayed yield hypothesis is supported by our electrical resistivity surveys, which shows very little change in the saturated zone over the course of the pump test, and by low values of pump-test estimated aquifer storativity. Observations of the nearby stream showed no change in stream-water level throughout the pump test. Together this data suggests that the interaction between the stream and the well is low, but recharge could be occurring through other mechanisms such as delayed yield. Additional pump tests of longer duration are required to determine the exact nature of the aquifer and its communication with the well.

Investigation of plasma stream collision produced by thin films irradiated by powerful pulsed electron beam

International Nuclear Information System (INIS)

Efremov, V P; Demidov, B A; Ivkin, M V; Mescheryakov, A N; Petrov, V A; Potapenko, A I

2006-01-01

Collision of fast plasma streams in vacuum is investigated. Plasma streams were produced by irradiation of thin foils with a powerful pulsed electron beam. Interaction of the plasma flows was studied by using frame and streak cameras. One-dimensional numerical simulation was carried out. Application of this method for porous ICF targets and high-energy physics is discussed

Simulating selenium and nitrogen fate and transport in coupled stream-aquifer systems of irrigated regions

Science.gov (United States)

Shultz, Christopher D.; Bailey, Ryan T.; Gates, Timothy K.; Heesemann, Brent E.; Morway, Eric D.

2018-01-01

Elevated levels of selenium (Se) in aqueous environments can harm aquatic life and endanger livestock and human health. Although Se occurs naturally in the rocks and soils of many alluvial aquifers, mining and agricultural activities can increase its rate of mobilization and transport to surface waters. Attention is given here to regions where nonpoint source return flows from irrigated lands carry pollutant loads to aquifers and streams, contributing to concentrations that violate regulatory and performance standards. Of particular concern is the heightened level and mobilization of Se influenced by nitrate (NO3), a harmful pollutant in its own right. We present a numerical model that simulates the reactive transport of Se and nitrogen (N) species in a coupled groundwater-surface water system. Building upon a conceptual model that incorporates the major processes affecting Se and NO3 transport in an irrigated watershed, the model links the finite-difference models MODFLOW, UZF-RT3D, and OTIS, to simulate flow and reactive transport of multiple chemical species in both the aquifer and a stream network, with mass exchange between the two. The capability of the new model is showcased by calibration, testing, and application to a 500 km2 region in Colorado’s Lower Arkansas River Valley using a rich data set gathered over a 10-yr period. Simulation of spatial and temporal distributions of Se concentration reveals conditions that exceed standards in groundwater for approximately 20% of the area. For the Arkansas River, standards are exceeded by 290%–450%. Simulation indicates that river concentrations of NO3 alone are near the current interim standard for the total of all dissolved N species. These results indicate the need for future use of the developed model to investigate the prospects for land and water best management practices to decrease pollutant levels.

Simulating selenium and nitrogen fate and transport in coupled stream-aquifer systems of irrigated regions

Science.gov (United States)

Shultz, Christopher D.; Bailey, Ryan T.; Gates, Timothy K.; Heesemann, Brent E.; Morway, Eric D.

2018-05-01

Elevated levels of selenium (Se) in aqueous environments can harm aquatic life and endanger livestock and human health. Although Se occurs naturally in the rocks and soils of many alluvial aquifers, mining and agricultural activities can increase its rate of mobilization and transport to surface waters. Attention is given here to regions where nonpoint source return flows from irrigated lands carry pollutant loads to aquifers and streams, contributing to concentrations that violate regulatory and performance standards. Of particular concern is the heightened level and mobilization of Se influenced by nitrate (NO3), a harmful pollutant in its own right. We present a numerical model that simulates the reactive transport of Se and nitrogen (N) species in a coupled groundwater-surface water system. Building upon a conceptual model that incorporates the major processes affecting Se and NO3 transport in an irrigated watershed, the model links the finite-difference models MODFLOW, UZF-RT3D, and OTIS, to simulate flow and reactive transport of multiple chemical species in both the aquifer and a stream network, with mass exchange between the two. The capability of the new model is showcased by calibration, testing, and application to a 500 km2 region in Colorado's Lower Arkansas River Valley using a rich data set gathered over a 10-yr period. Simulation of spatial and temporal distributions of Se concentration reveals conditions that exceed standards in groundwater for approximately 20% of the area. For the Arkansas River, standards are exceeded by 290%-450%. Simulation indicates that river concentrations of NO3 alone are near the current interim standard for the total of all dissolved N species. These results indicate the need for future use of the developed model to investigate the prospects for land and water best management practices to decrease pollutant levels.

Study of tungsten surface interaction with plasma streams at DPF-1000U

Directory of Open Access Journals (Sweden)

Ladygina Marina S.

2015-06-01

Full Text Available In this note experimental studies of tungsten (W samples irradiated by intense plasma-ion streams are reported. Measurements were performed using the modified plasma focus device DPF-1000U equipped with an axial gas-puffing system. The main diagnostic tool was a Mechelle®900 optical spectrometer. The electron density of a freely propagating plasma stream (i.e., the plasma stream observed without any target inside the vacuum chamber was estimated on the basis of the half-width of the Dβ spectral line, taking into account the linear Stark effect. For a freely propagating plasma stream the maximum electron density amounted to about 1.3 × 1017 cm−3 and was reached during the maximum plasma compression. The plasma electron density depends on the initial conditions of the experiments. It was thus important to determine first the plasma flow characteristics before attempting any target irradiation. These data were needed for comparison with plasma characteristics after an irradiation of the investigated target. In fact, spectroscopic measurements performed during interactions of plasma streams with the investigated W samples showed many WI and WII spectral lines. The surface erosion was determined from mass losses of the irradiated samples. Changes on the surfaces of the irradiated samples were also investigated with an optical microscope and some sputtering and melting zones were observed.

Electron surfing acceleration by the electron two-stream instability in a weak magnetic field

International Nuclear Information System (INIS)

Dieckmann, M E; Shukla, P K

2006-01-01

The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here

Electron surfing acceleration by the electron two-stream instability in a weak magnetic field

Energy Technology Data Exchange (ETDEWEB)

Dieckmann, M E; Shukla, P K [Institut fuer Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2006-10-15

The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here.

Air-electron stream interactions during magnetic resonance IGRT. Skin irradiation outside the treatment field during accelerated partial breast irradiation

International Nuclear Information System (INIS)

Park, Jong Min; Shin, Kyung Hwan; Wu, Hong-Gyun; Kim, Jung-in; Park, So-Yeon; Kim, Jin Ho; Jeon, Seung Hyuck; Choi, Noorie

2018-01-01

To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. A 1 cm thick bolus was placed in front of the patient's jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3 films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated. For a single fraction delivery, the average areas of the measured isodoses of 14% (0.54 Gy), 12% (0.46 Gy), and 10% (0.39 Gy) at the front of the boluses were as large as 3, 10.4, and 21.4 cm 2 , respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times. During radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field. (orig.) [de

Quantifying and modelling the contribution of streams that recharge the Querença-Silves aquifer in the south of Portugal

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N. Salvador

2012-11-01

Full Text Available The water balance of the mesocenozoic aquifers of the Algarve, in the south of Portugal has traditionally been estimated considering only direct ("autogenic" recharge from rainfall occurring in the area of the aquifers. Little importance has been attributed to so-called allogenic recharge, originating from streambed infiltration from runoff generated outside the aquifers, particularly in the Palaeozoic rocks to the north where runoff is high. The Querença-Silves (QS aquifer is the most important aquifer of the region both for irrigation and public water supply. Several important and sensitive surface/groundwater ecotones and associated groundwater dependent ecosystems exist at the springs of the natural discharge areas of the aquifer system. A numerical flow model has been in constant development over the last few years and currently is able to reproduce the aquifer's responses to estimated direct recharge and abstraction for the years 2001–2010. However, recharge calculations for the model do not take into account allogenic recharge infiltration along influent reaches of streams. The quantification of allogenic recharge may further improve the assessment of water availability and exploitation risks. In this paper an attempt is made to quantify the average annual contribution of allogenic recharge to the QS aquifer, based on monitoring data of the principal water courses that cross the aquifer system. Significant uncertainties related to surface runoff generated within the aquifer area, as well as areal recharge were identified and the consequences for the optimization of spatial distribution of transmissivity in the groundwater flow model are also addressed.

Long-distance electron transfer by cable bacteria in aquifer sediments

DEFF Research Database (Denmark)

Müller, Hubert; Bosch, Julian; Griebler, Christian

2016-01-01

recycling of sulfate by electron transfer over 1–2-cm distance. Sediments were taken from a hydrocarbon-contaminated aquifer, amended with iron sulfide and saturated with water, leaving the sediment surface exposed to air. Steep geochemical gradients developed in the upper 3 cm, showing a spatial separation...... recently been discovered in marine sediments to couple spatially separated redox half reactions over centimeter scales. Here we provide primary evidence that such sulfur-oxidizing cable bacteria can also be found at oxic–anoxic interfaces in aquifer sediments, where they provide a means for the direct...

Hysteresis, regime shifts, and non-stationarity in aquifer recharge-storage-discharge systems

Science.gov (United States)

Klammler, Harald; Jawitz, James; Annable, Michael; Hatfield, Kirk; Rao, Suresh

2016-04-01

Based on physical principles and geological information we develop a parsimonious aquifer model for Silver Springs, one of the largest karst springs in Florida. The model structure is linear and time-invariant with recharge, aquifer head (storage) and spring discharge as dynamic variables at the springshed (landscape) scale. Aquifer recharge is the hydrological driver with trends over a range of time scales from seasonal to multi-decadal. The freshwater-saltwater interaction is considered as a dynamic storage mechanism. Model results and observed time series show that aquifer storage causes significant rate-dependent hysteretic behavior between aquifer recharge and discharge. This leads to variable discharge per unit recharge over time scales up to decades, which may be interpreted as a gradual and cyclic regime shift in the aquifer drainage behavior. Based on field observations, we further amend the aquifer model by assuming vegetation growth in the spring run to be inversely proportional to stream velocity and to hinder stream flow. This simple modification introduces non-linearity into the dynamic system, for which we investigate the occurrence of rate-independent hysteresis and of different possible steady states with respective regime shifts between them. Results may contribute towards explaining observed non-stationary behavior potentially due to hydrological regime shifts (e.g., triggered by gradual, long-term changes in recharge or single extreme events) or long-term hysteresis (e.g., caused by aquifer storage). This improved understanding of the springshed hydrologic response dynamics is fundamental for managing the ecological, economic and social aspects at the landscape scale.

The impact of poplar tree plantations for biomass production on the aquifer water budget and base flow in a Mediterranean basin

Energy Technology Data Exchange (ETDEWEB)

Folch, Albert, E-mail: folch.hydro@gmail.com [Hydrogeology Group (UPC-CSIC), Department of Geotechnical Engineering and Geo-sciences, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona (Spain); Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra (Spain); Ferrer, Núria [Hydrogeology Group (UPC-CSIC), Department of Geotechnical Engineering and Geo-sciences, Universitat Politècnica de Catalunya-BarcelonaTech, Barcelona (Spain)

2015-08-15

Poplar plantations are used for biomass production in many countries. These plantations are often located in areas where the tree roots can reach the water table of shallow aquifers to reduce irrigation costs and increase evapotranspiration, mainly during the summer. This study aims to assess the effects of these plantations on an aquifer water budget and on the stream flow of a Mediterranean basin (Santa Coloma River, 321.3 km{sup 2} NE Spain). A numerical flow model was constructed to simulate shallow aquifers and to simulate the stream–aquifer interaction for a period of 9 years. Once the model was calibrated, different land use scenarios, such as deciduous forests, dry farming and irrigated farming, were simulated for comparison. The mass balance shows that poplar extracts an average of 2.40 hm{sup 3} from the aquifer, i.e., approximately 18% of the average recharge of the modelled area. This effect reduces the groundwater flow to the main stream and increases the infiltration from the stream to the aquifer. As a result, there is an average reduction in the main stream flow by 46% during the summer, when the lowest flow occurs and when the river is most sensitive. The results indicate that these impacts should be considered in basin management plans and in evaluating the benefits of this type of biomass production. - Highlights: • Poplar plantations can evapotranspirate aquifer groundwater in semiarid areas • A groundwater flow model is presented to quantify poplars’ impact on the water budget • 20% of the aquifer recharge is consumed by poplars • The main stream flow is reduced up to 46% during summer due to plantations uptake • Biomass production impacts must be considered for evaluating water resources planning.

Review of analytical models to stream depletion induced by pumping: Guide to model selection

Science.gov (United States)

Huang, Ching-Sheng; Yang, Tao; Yeh, Hund-Der

2018-06-01

Stream depletion due to groundwater extraction by wells may cause impact on aquatic ecosystem in streams, conflict over water rights, and contamination of water from irrigation wells near polluted streams. A variety of studies have been devoted to addressing the issue of stream depletion, but a fundamental framework for analytical modeling developed from aquifer viewpoint has not yet been found. This review shows key differences in existing models regarding the stream depletion problem and provides some guidelines for choosing a proper analytical model in solving the problem of concern. We introduce commonly used models composed of flow equations, boundary conditions, well representations and stream treatments for confined, unconfined, and leaky aquifers. They are briefly evaluated and classified according to six categories of aquifer type, flow dimension, aquifer domain, stream representation, stream channel geometry, and well type. Finally, we recommend promising analytical approaches that can solve stream depletion problem in reality with aquifer heterogeneity and irregular geometry of stream channel. Several unsolved stream depletion problems are also recommended.

Solar wind stream interaction regions throughout the heliosphere

Science.gov (United States)

Richardson, Ian G.

2018-01-01

This paper focuses on the interactions between the fast solar wind from coronal holes and the intervening slower solar wind, leading to the creation of stream interaction regions that corotate with the Sun and may persist for many solar rotations. Stream interaction regions have been observed near 1 AU, in the inner heliosphere (at ˜ 0.3-1 AU) by the Helios spacecraft, in the outer and distant heliosphere by the Pioneer 10 and 11 and Voyager 1 and 2 spacecraft, and out of the ecliptic by Ulysses, and these observations are reviewed. Stream interaction regions accelerate energetic particles, modulate the intensity of Galactic cosmic rays and generate enhanced geomagnetic activity. The remote detection of interaction regions using interplanetary scintillation and white-light imaging, and MHD modeling of interaction regions will also be discussed.

Spatio-temporal variation of stream-aquifer interaction: Effect of a weir construction in Korea

Science.gov (United States)

Lee, Hyeonju; Koo, Min-Ho; Kim, Kisu; Kim, Yongcheol

2015-04-01

The Four Major Rivers Restoration Project was conducted to secure sufficient water resources, introduce comprehensive flood control measures, and improve water quality while restore the river ecosystem in Korea. The dredging of river bed and the installation of 16 weirs were done in Han, Geum, Yeongsan, and Nakdong rivers from late 2010 to early 2012 as a part of the project. Groundwater data obtained from 213 groundwater monitoring wells near the four major rivers were used to analyze the impacts of weir construction on the nearby groundwater flow system. The groundwater level and chemical characteristics were analyzed to investigate how the groundwater flow system and water quality changed after the weir construction. The results showed that groundwater level rose immediately following the rise of stream stage after the weir construction. Also, the hydrologic condition of the stream in some upland of the weirs was changed from a gaining to a losing stream. Consequently, the direction of groundwater flow was changed from perpendicular to parallel to the stream, and it swapped the groundwater in the downstream of the weir for the water recharged from the stream. Considering the results, some groundwater quality is expected to be changed and become similar to that of the stream, although the change has been not observed yet. Therefore, both further monitoring of the groundwater quality and hydrogeochemical analysis are required for quantitatively evaluating the effect of the weir.

Air-electron stream interactions during magnetic resonance IGRT : Skin irradiation outside the treatment field during accelerated partial breast irradiation.

Science.gov (United States)

Park, Jong Min; Shin, Kyung Hwan; Kim, Jung-In; Park, So-Yeon; Jeon, Seung Hyuck; Choi, Noorie; Kim, Jin Ho; Wu, Hong-Gyun

2018-01-01

To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. A 1 cm thick bolus was placed in front of the patient's jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3 films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated. For a single fraction delivery, the average areas of the measured isodoses of 14% (0.54 Gy), 12% (0.46 Gy), and 10% (0.39 Gy) at the front of the boluses were as large as 3, 10.4, and 21.4 cm 2 , respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times. During radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field.

Regional groundwater-flow model of the Redwall-Muav, Coconino, and alluvial basin aquifer systems of northern and central Arizona

Science.gov (United States)

Pool, D.R.; Blasch, Kyle W.; Callegary, James B.; Leake, Stanley A.; Graser, Leslie F.

2011-01-01

A numerical flow model (MODFLOW) of the groundwater flow system in the primary aquifers in northern Arizona was developed to simulate interactions between the aquifers, perennial streams, and springs for predevelopment and transient conditions during 1910 through 2005. Simulated aquifers include the Redwall-Muav, Coconino, and basin-fill aquifers. Perennial stream reaches and springs that derive base flow from the aquifers were simulated, including the Colorado River, Little Colorado River, Salt River, Verde River, and perennial reaches of tributary streams. Simulated major springs include Blue Spring, Del Rio Springs, Havasu Springs, Verde River headwater springs, several springs that discharge adjacent to major Verde River tributaries, and many springs that discharge to the Colorado River. Estimates of aquifer hydraulic properties and groundwater budgets were developed from published reports and groundwater-flow models. Spatial extents of aquifers and confining units were developed from geologic data, geophysical models, a groundwater-flow model for the Prescott Active Management Area, drill logs, geologic logs, and geophysical logs. Spatial and temporal distributions of natural recharge were developed by using a water-balance model that estimates recharge from direct infiltration. Additional natural recharge from ephemeral channel infiltration was simulated in alluvial basins. Recharge at wastewater treatment facilities and incidental recharge at agricultural fields and golf courses were also simulated. Estimates of predevelopment rates of groundwater discharge to streams, springs, and evapotranspiration by phreatophytes were derived from previous reports and on the basis of streamflow records at gages. Annual estimates of groundwater withdrawals for agriculture, municipal, industrial, and domestic uses were developed from several sources, including reported withdrawals for nonexempt wells, estimated crop requirements for agricultural wells, and estimated per

Anomalous electron streaming due to electrostatic modes in tokamak plasmas

International Nuclear Information System (INIS)

Schultz, S.D.; Bers, A.; Ram, A.K.

1993-01-01

The motion of circulating electrons in a tokamak interacting with electrostatic waves (such as lower-hybrid waves) is given by a guiding center Hamiltonian and studied by numerical integration. The unperturbed motion of electron guiding centers is first shown to be integrable, and, in a manner similar to that used in previous works, a set of action-angle coordinates for the orbits are derived which take into account finite aspect ratio and noncircular plasma cross section. Electrostatic modes in the low-frequency, long-wavelength limit are treated as a perturbation to the guiding center Hamiltonian. The waves are generated with low integral values of the toroidal and poloidal mode numbers n and m and satisfy the approximate lower-hybrid dispersion relation k perpendicular /k parallel ∼ ω pe /ω ∼ 10 1.5 . If the number of modes is greater than three, the electron motion parallel to the magnetic field is observed to be stochastic in the phase-space region where v parallel is near the wave parallel phase velocity. On surfaces with rational values of the safety factor q, superposition of modes with degenerate values of the parallel mode number n + (m/q) is shown to result in electron streaming perpendicular to the magnetic field. The speed and direction of this radial motion are observed to have sinusoidal dependence on the poloidal angle. For models including finite magnetic-field shear, the authors find a limit to the extent of the radial streaming of the electrons. Results for the speed of the electron radial motion for typical tokamak parameters are presented

Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations

Directory of Open Access Journals (Sweden)

B. Lavraud

2010-01-01

Full Text Available Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs in the vicinity of corotating interaction regions (CIRs during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used, but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream, as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1 the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2 that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to

Stream-Groundwater Interaction Buffers Seasonal Changes in Urban Stream Water Quality

Science.gov (United States)

Ledford, S. H.; Lautz, L. K.

2013-12-01

Urban streams in the northeastern United States have large road salt inputs during winter, increased nonpoint sources of inorganic nitrogen, and decreased short-term and permanent storage of nutrients. Meadowbrook Creek, a first order stream in Syracuse, New York, flows along a negative urbanization gradient, from a channelized and armored stream running through the middle of a roadway to a pool-riffle stream meandering through a broad, vegetated floodplain with a riparian aquifer. In this study we investigated how reconnection to groundwater and introduction of riparian vegetation impacted surface water chemistry by making bi-weekly longitudinal surveys of stream water chemistry in the creek from May 2012 until June 2013. Chloride concentrations in the upstream, urban reach of Meadowbrook Creek were strongly influenced by discharge of road salt to the creek during snow melt events in winter and by the chemistry of water draining an upstream retention basin in summer. Chloride concentrations ranged from 161.2 mg/L in August to 2172 mg/L in February. Chloride concentrations in the downstream, 'connected' reach had less temporal variation, ranging from 252.0 mg/L in August to 1049 mg/L in January, and were buffered by groundwater discharge, as the groundwater chloride concentrations during the sampling period ranged from 84.0 to 655.4 mg/L. Groundwater discharge resulted in higher chloride concentrations in summer and lower concentrations in winter in the connected reach relative to the urban reach, minimizing annual variation. In summer, there was little-to-no nitrate in the urban reach due to a combination of limited sources and high primary productivity. In contrast, during the summer, nitrate concentrations reached over 1 mg N/L in the connected reach due to the presence of riparian vegetation and lower nitrate uptake due to cooler temperatures and shading. During the winter, when temperatures fell below freezing, nitrate concentrations in the urban reach

Use of radon as tracer for identification of aquifer discharge along the Matinha stream, MG, Brazil

International Nuclear Information System (INIS)

Chagas, Claudio Jose

2017-01-01

Within the framework of 'Nuclear Techniques' is the use of natural and artificial isotopes as tracers for the study of the environment. The use of natural tracers in hydrology is a very useful tool that has been used in several scenarios. One such tracer is the isotope of radon, "2"2"2Rn, a noble gas from natural sources as a consequence of alpha decay of "2"2"6Ra. Radon can be found, to a greater or lesser degree, in all groundwater, as well as in soils and rocks from where it exudes into the atmosphere through spaces arising from fissures and or nanopores present. It can emerge into the water bodies by the leaching of water or other liquids through these interstices. In this research, the "2"2"2Rn gas diluted naturally by the leaching of the water that infiltrated the soils and rocks of the aquifers was used as a tracer in order to identify sections of discharge of these aquifers along the Stream of Matinha. The study area is about 70 km from Belo Horizonte and is in the city of Itauna, MG. The Matinha stream is about 2,200 m in length and is part of the network of tributaries of the water reservoir called Serra Azul, in the Juatuba River Basin, MG. The results presented express the studies that occurred between the second half of 2014 and the first half of 2016, in ten campaigns for water sampling, flow and natural gamma radiation measurements. Water samples were collected near the bottom and very close to the thalweg in the watercourse using syringe and or peristaltic suction pump at low flow to avoid gas leakage. The "2"2"2Rn analyzes were performed in the field during the collections and in the laboratory of the CDTN - Centro de Desenvolvimento da Tecnologia Nuclear, all of which were carried out with the radon detector RAD 7. The flow measurements counted on the use of the fluorescent tracer's technique: rhodamine and fluorescein were used for injection at points upstream and downstream of sections with higher "2"2"2Rn activities. The fluorimeter used to

Unravelling aquifer-wetland interaction using CSAMT and gravity methods: the Mollina-Camorra aquifer and the Fuente de Piedra playa-lake, southern Spain

Science.gov (United States)

Pedrera, A.; Martos-Rosillo, S.; Galindo-Zaldívar, J.; Rodríguez-Rodríguez, M.; Benavente, J.; Martín-Rodríguez, J. F.; Zúñiga-López, M. I.

2016-06-01

The hydrological regime of Fuente de Piedra playa-lake (Málaga, southern Spain) has been significantly affected by the intensive exploitation of groundwater in the area. The playa-lake is situated above clays, marls, and gypsum, and under unaltered conditions received surface-subsurface runoff within the watershed as well as groundwater discharge from two carbonate aquifers. We have analyzed the structure of the main one, the Mollina-Camorra carbonate aquifer, by combining controlled source audio magnetotellurics (CSAMT), gravity prospecting, and time-domain electromagnetic (TDEM) soundings. This geophysical information, together with new structural and hydrogeological data, was gathered to develop a new conceptual hydrogeological model. This model allows the hydrological linkage of the carbonate aquifer with the playa-lake system to be established. Moreover, the intensive exploitation in the carbonate aquifer, even outside the watershed of the playa-lake, has affected the hydrological regime of the system. This multidisciplinary work demonstrates the potential of geophysical methods for understanding wetland-aquifer interaction, having important groundwater management implications.

Estimating Groundwater Mounding in Sloping Aquifers for Managed Aquifer Recharge.

Science.gov (United States)

Zlotnik, Vitaly A; Kacimov, Anvar; Al-Maktoumi, Ali

2017-11-01

Design of managed aquifer recharge (MAR) for augmentation of groundwater resources often lacks detailed data, and simple diagnostic tools for evaluation of the water table in a broad range of parameters are needed. In many large-scale MAR projects, the effect of a regional aquifer base dip cannot be ignored due to the scale of recharge sources (e.g., wadis, streams, reservoirs). However, Hantush's (1967) solution for a horizontal aquifer base is commonly used. To address sloping aquifers, a new closed-form analytical solution for water table mound accounts for the geometry and orientation of recharge sources at the land surface with respect to the aquifer base dip. The solution, based on the Dupiuit-Forchheimer approximation, Green's function method, and coordinate transformations is convenient for computing. This solution reveals important MAR traits in variance with Hantush's solution: mounding is limited in time and space; elevation of the mound is strongly affected by the dip angle; and the peak of the mound moves over time. These findings have important practical implications for assessment of various MAR scenarios, including waterlogging potential and determining proper rates of recharge. Computations are illustrated for several characteristic MAR settings. © 2017, National Ground Water Association.

Streaming energetic electrons in earth's magnetotail - Evidence for substorm-associated magnetic reconnection

Science.gov (United States)

Bieber, J. W.; Stone, E. C.

1980-01-01

This letter reports the results of a systematic study of streaming greater than 200 keV electrons observed in the magnetotail with the Caltech Electron/Isotope Spectrometers aboard IMP-7 and IMP-8. A clear statistical association of streaming events with southward magnetic fields, often of steep inclination, and with substorms as evidenced by the AE index is demonstrated. These results support the interpretation that streaming energetic electrons are indicative of substorm-associated magnetic reconnection in the near-earth plasma sheet.

Ultrashort electromagnetic clusters formation by two-stream superheterodyne free electron lasers

DEFF Research Database (Denmark)

Kulish, Viktor V.; Lysenko, Alexander V.; Volk, Iurii I.

2016-01-01

A cubic nonlinear self-consistent theory of multiharmonic two-stream superheterodyne free electron lasers (TSFEL) of a klystron type, intended to form powerful ultrashort clusters of an electromagnetic field is constructed. Plural three-wave parametric resonant interactions of wave harmonics have...... been taken into account. An amplitude, phase and spectral analyses of the processes occurring in such devices have been carried out. The conditions necessary for the forming of the ultrashort clusters of an electromagnetic field have been found out. The possibility of the ultrashort electromagnetic...

On the Relationship Between High Speed Solar Wind Streams and Radiation Belt Electron Fluxes

Science.gov (United States)

Zheng, Yihua

2011-01-01

Both past and recent research results indicate that solar wind speed has a close connection to radiation belt electron fluxes [e.g., Paulikas and Blake, 1979; Reeves et aI., 2011]: a higher solar wind speed is often associated with a higher level of radiation electron fluxes. But the relationship can be very complex [Reeves et aI., 2011]. The study presented here provides further corroboration of this viewpoint by emphasizing the importance of a global perspective and time history. We find that all the events during years 2010 and 2011 where the >0.8 MeV integral electron flux exceeds 10(exp 5) particles/sq cm/sr/s (pfu) at GEO orbit are associated with the high speed streams (HSS) following the onset of the Stream Interaction Region (SIR), with most of them belonging to the long-lasting Corotating Interaction Region (CIR). Our preliminary results indicate that during HSS events, a maximum speed of 700 km/s and above is a sufficient but not necessary condition for the > 0.8 MeV electron flux to reach 10(exp 5) pfu. But in the exception cases of HSS events where the electron flux level exceeds the 10(exp 5) pfu value but the maximum solar wind speed is less than 700 km/s, a prior impact can be noted either from a CME or a transient SIR within 3-4 days before the arrival of the HSS - stressing the importance of time history. Through superposed epoch analysis and studies providing comparisons with the CME events and the HSS events where the flux level fails to reach the 10(exp 5) pfu, we will present the quantitative assessment of behaviors and relationships of various quantities, such as the time it takes to reach the flux threshold value from the stream interface and its dependence on different physical parameters (e.g., duration of the HSS event, its maximum or average of the solar wind speed, IMF Bz, Kp). The ultimate goal is to apply what is derived to space weather forecasting.

Relativistic electron beam - plasma interaction with intense self-fields

International Nuclear Information System (INIS)

Davidson, R.C.

1984-01-01

The major interest in the equilibrium, stability and radiation properties of relativistic electron beams and in beam-plasma interactions originates from several diverse research areas. It is well known that a many-body collection of charged particles in which there is not overall charge neutrality and/or current neutrality can be characterized by intense self-electric fields and/or self-magnetic fields. Moreover, the intense equilibrium self-fields associated with the lack of charge neutrality and/or current neutrality can have a large effect on particle trajectories and on detailed equilibrium and stability behavior. The main emphasis in Sections 9.1.2-9.1.5 of this chapter is placed on investigations of the important influence of self-fields on the equilibrium and stability properties of magnetically confined electron beam-plasma systems. Atomic processes and discrete particle interactions (binary collisions) are omitted from the analysis, and collective processes are assumed to dominate on the time and length scales of interest. Moreover, both macroscopic (Section 9.1.2) and kinetic (Sections 9.1.3-9.1.5) theoretical models are developed and used to investigate equilibrium and stability properties in straight cylindrical geometry. Several of the classical waves and instabilities characteristic of nonneutral plasmas and beam-plasma systems are analyzed in Sections 9.1.2-9.1.5, including stable surface oscillation on a nonneutral electron beam, the ion resonance instability, the diocotron instability, two-stream instabilities between beam electrons and plasma electrons and between beam electrons and plasma ions, the filamentation instability, the modified two-stream instability, etc

Coronal mass ejection and stream interaction region characteristics and their potential geomagnetic effectiveness

International Nuclear Information System (INIS)

Lindsay, G.M.; Russell, C.T.; Luhmann, J.G.

1995-01-01

Previous studies have indicated that the largest geomagnetic storms are caused by extraordinary increases in the solar wind velocity and/or southward interplanetary magnetic field (IMF) produced by coronal mass ejections (CMEs) and their associated interplanetary shocks. However, much more frequent small to moderate increases in solar wind velocity and compressions in the IMF can be caused by either coronal mass ejections or fast/slow stream interactions. This study examines the relative statistics of the magnitudes of disturbances associated with the passage of both interplanetary coronal mass ejections and stream interaction regions, using an exceptionally continuous interplanetary database from the Pioneer Venus Orbiter at 0.7 AU throughout most of solar cycle 21. It is found that both stream interaction and CMEs produce magnetic fields significantly larger than the nominal IMF. Increases in field magnitude that are up to 2 and 3 times higher than the ambient field are observed for stream interaction regions and CMEs, respectively. Both stream interactions and CMEs produce large positive and negative Β z components at 0.7 AU, but only CMEs produce Β z magnitudes greater than 35 nT. CMEs are often associated with sustained periods of positive or negative Β z whereas stream interaction regions are more often associated with fluctuating Β z . CMEs tend to produce larger solar wind electric fields than stream interactions. Yet stream interactions tend to produce larger dynamic pressures than CMEs. Dst predictions based on solar wind duskward electric field and dynamic pressure indicate that CMEs produce the largest geomagnetic disturbances while the low-speed portion of stream interaction regions are least geomagnetically effective. Both stream interaction regions and CMEs contribute to low and moderate levels of activity with relative importance determined by their solar-cycle-dependent occurrence rates

Effect of irrigation pumpage during drought on karst aquifer systems in highly agricultural watersheds: example of the Apalachicola-Chattahoochee-Flint river basin, southeastern USA

Science.gov (United States)

Mitra, Subhasis; Srivastava, Puneet; Singh, Sarmistha

2016-09-01

In the Apalachicola-Chattahoochee-Flint (ACF) river basin in Alabama, Georgia, and Florida (USA), population growth in the city of Atlanta and increased groundwater withdrawal for irrigation in southwest Georgia are greatly affecting the supply of freshwater to downstream regions. This study was conducted to understand and quantify the effect of irrigation pumpage on the karst Upper Floridan Aquifer and river-aquifer interactions in the lower ACF river basin in southwest Georgia. The groundwater MODular Finite-Element model (MODFE) was used for this study. The effect of two drought years, a moderate and a severe drought year, were simulated. Comparison of the results of the irrigated and non-irrigated scenarios showed that groundwater discharge to streams is a major outflow from the aquifer, and irrigation can cause as much as 10 % change in river-aquifer flux. The results also show that during months with high irrigation (e.g., June 2011), storage loss (34 %), the recharge and discharge from the upper semi-confining unit (30 %), and the river-aquifer flux (31 %) are the major water components contributing towards the impact of irrigation pumpage in the study area. A similar scenario plays out in many river basins throughout the world, especially in basins in which underlying karst aquifers are directly connected to a nearby stream. The study suggests that improved groundwater withdrawal strategies using climate forecasts needs to be developed in such a way that excessive withdrawals during droughts can be reduced to protect streams and river flows.

Simulation of the interaction of karstic lakes Magnolia and Brooklyn with the upper Floridan Aquifer, southwestern Clay County, Florida

Science.gov (United States)

Merritt, M.L.

2001-01-01

The stage of Lake Brooklyn, in southwestern Clay County, Florida, has varied over a range of 27 feet since measurements by the U.S. Geological Survey began in July 1957. The large stage changes have been attributed to the relation between highly transient surface-water inflow to the lake and subsurface conduits of karstic origin that permit a high rate of leakage from the lake to the Upper Floridan aquifer. After the most recent and severe stage decline (1990-1994), the U.S. Geological Survey began a study that entailed the use of numerical ground-water flow models to simulate the interaction of the lake with the Upper Floridan aquifer and the large fluctuations of stage that were a part of that process. A package (set of computer programs) designed to represent lake/aquifer interaction in the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model (MODFLOW-96) and the Three-Dimensional Method-of-Characteristics Solute-Transport Model (MOC3D) simulators was prepared as part of this study, and a demonstration of its capability was a primary objective of the study. (Although the official names are Brooklyn Lake and Magnolia Lake (Florida Geographic Names), in this report the local names, Lake Brooklyn and Lake Magnolia, are used.) In the simulator of lake/aquifer interaction used in this investigation, the stage of each lake in a simulation is updated in successive time steps by a budget process that takes into account ground-water seepage, precipitation upon and evaporation from the lake surface, stream inflows and outflows, overland runoff inflows, and augmentation or depletion by artificial means. The simulator was given the capability to simulate both the division of a lake into separate pools as lake stage falls and the coalescence of several pools into a single lake as the stage rises. This representational capability was required to simulate Lake Brooklyn, which can divide into as many as 10 separate pools at sufficiently low stage. In the

Interactive real-time media streaming with reliable communication

Science.gov (United States)

Pan, Xunyu; Free, Kevin M.

2014-02-01

Streaming media is a recent technique for delivering multimedia information from a source provider to an end- user over the Internet. The major advantage of this technique is that the media player can start playing a multimedia file even before the entire file is transmitted. Most streaming media applications are currently implemented based on the client-server architecture, where a server system hosts the media file and a client system connects to this server system to download the file. Although the client-server architecture is successful in many situations, it may not be ideal to rely on such a system to provide the streaming service as users may be required to register an account using personal information in order to use the service. This is troublesome if a user wishes to watch a movie simultaneously while interacting with a friend in another part of the world over the Internet. In this paper, we describe a new real-time media streaming application implemented on a peer-to-peer (P2P) architecture in order to overcome these challenges within a mobile environment. When using the peer-to-peer architecture, streaming media is shared directly between end-users, called peers, with minimal or no reliance on a dedicated server. Based on the proposed software pɛvμa (pronounced [revma]), named for the Greek word meaning stream, we can host a media file on any computer and directly stream it to a connected partner. To accomplish this, pɛvμa utilizes the Microsoft .NET Framework and Windows Presentation Framework, which are widely available on various types of windows-compatible personal computers and mobile devices. With specially designed multi-threaded algorithms, the application can stream HD video at speeds upwards of 20 Mbps using the User Datagram Protocol (UDP). Streaming and playback are handled using synchronized threads that communicate with one another once a connection is established. Alteration of playback, such as pausing playback or tracking to a

Nonlinear two-stream interaction between a cold, relativistic electron beam and a collisional plasma-Astron experiment

International Nuclear Information System (INIS)

Newberger, B.S.; Thode, L.E.

1979-05-01

Experiments on the two-stream instability of a relativistic electron beam propagating through a neutral gas, carried out with the Lawrence Livermore Laboratory Astron beam, have been analyzed using a nonlinear saturation model for a cold beam. The behavior of the observed microwave emission due to the instability is in good agreement with that of the beam energy loss. Collisions on the plasma electrons weaken the nonlinear state of the instability but do not stabilize the mode. The beam essentially acts as if it were cold, a result substantiated by linear theory for waves propagating along the beam. In order to predict the effect of both beam momentum scatter and plasma electron collisions on the stability of the mode in future experiments a full two-dimensional linear theory must be developed

A theory of two-stream instability in two hollow relativistic electron beams

International Nuclear Information System (INIS)

Uhm, H.S.

1993-01-01

Stability properties of two-stream instability of two hollow electron beams are investigated. The equilibrium configuration consists of two intense relativistic hollow electron beams propagating through a grounded conducting cylinder. Analysis of the longitudinal two-stream instability is carried out within the framework of the linearized Vlasov--Maxwell equations for the equilibrium distribution function, in which beam electrons have a Lorentzian distribution in the axial momentum. Dispersion relation of the longitudinal two-stream instability is derived. Stability criteria from this dispersion relation indicate that the normalized velocity difference Δβ between the beams should be within a certain range of value to be unstable. Growth rate of the instability is a substantial fraction of the real frequency, thereby indicating that the longitudinal two-stream instability is an effective means of beam current modulation. Transverse instability of hollow electron beams is also investigated. Dispersion relation of the coupled transverse oscillation of the beams is derived and numerical investigation of this dispersion relation is carried out. Growth rate of the kink instability is a substantial fraction of the diocotron frequency, which may pose a serious threat to the two-stream klystron

Evolution and interaction of large interplanetary streams

International Nuclear Information System (INIS)

Whang, Y.C.; Burlaga, L.F.

1985-02-01

A computer simulation for the evolution and interaction of large interplanetary streams based on multi-spacecraft observations and an unsteady, one-dimensional MHD model is presented. Two events, each observed by two or more spacecraft separated by a distance of the order of 10 AU, were studied. The first simulation is based on the plasma and magnetic field observations made by two radially-aligned spacecraft. The second simulation is based on an event observed first by Helios-1 in May 1980 near 0.6 AU and later by Voyager-1 in June 1980 at 8.1 AU. These examples show that the dynamical evolution of large-scale solar wind structures is dominated by the shock process, including the formation, collision, and merging of shocks. The interaction of shocks with stream structures also causes a drastic decrease in the amplitude of the solar wind speed variation with increasing heliocentric distance, and as a result of interactions there is a large variation of shock-strengths and shock-speeds. The simulation results shed light on the interpretation for the interaction and evolution of large interplanetary streams. Observations were made along a few limited trajectories, but simulation results can supplement these by providing the detailed evolution process for large-scale solar wind structures in the vast region not directly observed. The use of a quantitative nonlinear simulation model including shock merging process is crucial in the interpretation of data obtained in the outer heliosphere

Seasonal Influences on Ground-Surface Water Interactions in an Arsenic-Affected Aquifer in Cambodia

Science.gov (United States)

Richards, L. A.; Magnone, D.; Van Dongen, B.; Bryant, C.; Boyce, A.; Ballentine, C. J.; Polya, D. A.

2015-12-01

Millions of people in South and Southeast Asia consume drinking water daily which contains dangerous levels of arsenic exceeding health-based recommendations [1]. A key control on arsenic mobilization in aquifers in these areas has been controversially identified as the interaction of 'labile' organic matter contained in surface waters with groundwaters and sediments at depth [2-4], which may trigger the release of arsenic from the solid- to aqueous-phase via reductive dissolution of iron-(hyr)oxide minerals [5]. In a field site in Kandal Province, Cambodia, which is an arsenic-affected area typical to others in the region, there are strong seasonal patterns in groundwater flow direction, which are closely related to monsoonal rains [6] and may contribute to arsenic release in this aquifer. The aim of this study is to explore the implications of the high susceptibility of this aquifer system to seasonal changes on potential ground-surface water interactions. The main objectives are to (i) identify key zones where there are likely ground-surface water interactions, (ii) assess the seasonal impact of such interactions and (iii) quantify the influence of interactions using geochemical parameters (such as As, Fe, NO3, NH4, 14C, 3T/3He, δ18O, δ2H). Identifying the zones, magnitude and seasonal influence of ground-surface water interactions elucidates new information regarding potential locations/pathways of arsenic mobilization and/or transport in affected aquifers and may be important for water management strategies in affected areas. This research is supported by NERC (NE/J023833/1) to DP, BvD and CJB and a NERC PhD studentship (NE/L501591/1) to DM. References: [1] World Health Organization, 2008. [2] Charlet & Polya (2006), Elements, 2, 91-96. [3] Harvey et al. (2002), Science, 298, 1602-1606. [4] Lawson et al. (2013), Env. Sci. Technol. 47, 7085 - 7094. [5] Islam et al. (2004), Nature, 430, 68-71. [6] Benner et al. (2008) Appl. Geochem. 23(11), 3072 - 3087.

Conceptual and numerical modeling approach of the Guarani Aquifer System

Science.gov (United States)

Rodríguez, L.; Vives, L.; Gomez, A.

2013-01-01

In large aquifers, relevant for their considerable size, regional groundwater modeling remains challenging given geologic complexity and data scarcity in space and time. Yet, it may be conjectured that regional scale groundwater flow models can help in understanding the flow system functioning and the relative magnitude of water budget components, which are important for aquifer management. The Guaraní Aquifer System is the largest transboundary aquifer in South America. It contains an enormous volume of water; however, it is not well known, being difficult to assess the impact of exploitation currently used to supply over 25 million inhabitants. This is a sensitive issue because the aquifer is shared by four countries. Moreover, an integrated groundwater model, and therefore a global water balance, were not available. In this work, a transient regional scale model for the entire aquifer based upon five simplified, equally plausible conceptual models represented by different hydraulic conductivity parametrizations is used to analyze the flow system and water balance components. Combining an increasing number of hydraulic conductivity zones and an appropriate set of boundary conditions, the hypothesis of a continuous sedimentary unit yielded errors within the calibration target in a regional sense. The magnitude of the water budget terms resulted very similar for all parametrizations. Recharge and stream/aquifer fluxes were the dominant components representing, on average, 84.2% of total inflows and 61.4% of total outflows, respectively. However, leakage was small compared to stream discharges of main rivers. For instance, the simulated average leakage for the Uruguay River was 8 m3 s-1 while the observed absolute minimum discharge was 382 m3 s-1. Streams located in heavily pumped regions switched from a gaining condition in early years to a losing condition over time. Water is discharged through the aquifer boundaries, except at the eastern boundary. On average

Geochemistry of the Arbuckle-Simpson Aquifer

Science.gov (United States)

Christenson, Scott; Hunt, Andrew G.; Parkhurst, David L.; Osborn, Noel I.

2009-01-01

The Arbuckle-Simpson aquifer in south-central Oklahoma provides water for public supply, farms, mining, wildlife conservation, recreation, and the scenic beauty of springs, streams, and waterfalls. A new understanding of the aquifer flow system was developed as part of the Arbuckle-Simpson Hydrology Study, done in 2003 through 2008 as a collaborative research project between the State of Oklahoma and the Federal government. The U.S. Geological Survey collected 36 water samples from 32 wells and springs in the Arbuckle-Simpson aquifer in 2004 through 2006 for geochemical analyses of major ions, trace elements, isotopes of oxygen and hydrogen, dissolved gases, and dating tracers. The geochemical analyses were used to characterize the water quality in the aquifer, to describe the origin and movement of ground water from recharge areas to discharge at wells and springs, and to determine the age of water in the aquifer.

Deciphering interaction of regional aquifers in Southern Tunisia using hydrochemistry and isotopic tools

International Nuclear Information System (INIS)

Abid, Kamel; Dulinski, Marek; Ammar, Friha Hadj; Rozanski, Kazimierz; Zouari, Kamel

2012-01-01

Groundwater is the most important source of water supply in southern Tunisia. Previous hydrogeologic and isotopic studies carried out in this region revealed the existence of two major aquifer systems: the “Complex Terminal” (CT) and the “Continental Intercalaire” (CI). Turonian carbonates constitute one of the major aquifer levels of the CT multilayered aquifer. It extends over most of southern Tunisia, and its hydrodynamic regime is largely influenced by tectonics, lithology and recharge conditions. Forty-eight groundwater samples from the CI and Turonian aquifers were collected between January and April 2004 for chemical and isotopic analyses. Hydrochemistry and isotopic tools were combined to get an insight into the processes controlling chemical composition of groundwater and wide-scale interaction of these two aquifer systems. Analysis of the dissolved constituents revealed that several processes control the observed chemical composition: (i) incongruent dissolution of carbonate minerals, (ii) dissolution of evaporitic minerals, and (iii) cation exchange. Dissolution alone cannot account for the observed high supersaturation states of groundwater with respect to calcite and dolomite. The observed supersaturation is most probably linked to geogenic CO 2 entering water-bearing horizons of the CT and CI aquifers via deep tectonic faults and discontinuities and subsequent degassing in the exploitation wells. Presence of geogenic CO 2 in the investigated region was confirmed by C isotope data of the DIC reservoir. The radiocarbon content of the Turonian samples varied between 9.5 and 43 pmc. For CI samples generally lower values were recorded, between 3.8 and 22.5 pmc. Stable isotope composition of Turonian groundwater samples varied from −8.3 to −5.3‰ for δ 18 O and from −60 to −25‰ for δ 2 H. The corresponding ranges of δ values for the Continental Intercalaire samples were from −8.9‰ to −6.9‰ for δ 18 O and from −68.2‰ to �

Modelling of stormwater infiltration for stream restoration. Beder (Aarhus) case study

DEFF Research Database (Denmark)

Locatelli, Luca; Bockhorn, Britta; Klint, K. E.

to assess the impact of stormwater runoff infiltration on (1) the water balance; (2) stream flow of the local stream Hovedgrøften; and (3) the risk of polluting the primary aquifer. The hydrogeological model was developed in a deterministic groundwater model (MIKE SHE) which was coupled dynamically...... carried out by developing a hydrogeological model of the Beder area in Aarhus, Denmark. The model area is characterized by the presence of a secondary unconfined aquifer that partly contributes baseflow to the local streams and partly to recharge to the underlying primary aquifer. The model was applied...... to a hydrodynamic 1-D river model (MIKE 11). Geological data based on spear mapping, geophysical data and lithology from local boreholes were used to set up the geological model. Groundwater observation and stream flow measurements were used for model calibration and validation.Different scenarios were analyzed...

Evaluating connection of aquifers to springs and streams, Great Basin National Park and vicinity, Nevada

Science.gov (United States)

Prudic, David E.; Sweetkind, Donald S.; Jackson, Tracie R.; Dotson, K. Elaine; Plume, Russell W.; Hatch, Christine E.; Halford, Keith J.

2015-12-22

Federal agencies that oversee land management for much of the Snake Range in eastern Nevada, including the management of Great Basin National Park by the National Park Service, need to understand the potential extent of adverse effects to federally managed lands from nearby groundwater development. As a result, this study was developed (1) to attain a better understanding of aquifers controlling groundwater flow on the eastern side of the southern part of the Snake Range and their connection with aquifers in the valleys, (2) to evaluate the relation between surface water and groundwater along the piedmont slopes, (3) to evaluate sources for Big Springs and Rowland Spring, and (4) to assess groundwater flow from southern Spring Valley into northern Hamlin Valley. The study focused on two areas—the first, a northern area along the east side of Great Basin National Park that included Baker, Lehman, and Snake Creeks, and a second southern area that is the potential source area for Big Springs. Data collected specifically for this study included the following: (1) geologic field mapping; (2) drilling, testing, and water quality sampling from 7 test wells; (3) measuring discharge and water chemistry of selected creeks and springs; (4) measuring streambed hydraulic gradients and seepage rates from 18 shallow piezometers installed into the creeks; and (5) monitoring stream temperature along selected reaches to identify places of groundwater inflow.

Protocols for collection of streamflow, water-quality, streambed-sediment, periphyton, macroinvertebrate, fish, and habitat data to describe stream quality for the Hydrobiological Monitoring Program, Equus Beds Aquifer Storage and Recovery Program, city of Wichita, Kansas

Science.gov (United States)

Stone, Mandy L.; Rasmussen, Teresa J.; Bennett, Trudy J.; Poulton, Barry C.; Ziegler, Andrew C.

2012-01-01

The city of Wichita, Kansas uses the Equus Beds aquifer, one of two sources, for municipal water supply. To meet future water needs, plans for artificial recharge of the aquifer have been implemented in several phases. Phase I of the Equus Beds Aquifer Storage and Recovery (ASR) Program began with injection of water from the Little Arkansas River into the aquifer for storage and subsequent recovery in 2006. Construction of a river intake structure and surface-water treatment plant began as implementation of Phase II of the Equus Beds ASR Program in 2010. An important aspect of the ASR Program is the monitoring of water quality and the effects of recharge activities on stream conditions. Physical, chemical, and biological data provide the basis for an integrated assessment of stream quality. This report describes protocols for collecting streamflow, water-quality, streambed-sediment, periphyton, macroinvertebrate, fish, and habitat data as part of the city of Wichita's hydrobiological monitoring program (HBMP). Following consistent and reliable methods for data collection and processing is imperative for the long-term success of the monitoring program.

Steady-state groundwater recharge in trapezoidal-shaped aquifers: A semi-analytical approach based on variational calculus

Science.gov (United States)

Mahdavi, Ali; Seyyedian, Hamid

2014-05-01

This study presents a semi-analytical solution for steady groundwater flow in trapezoidal-shaped aquifers in response to an areal diffusive recharge. The aquifer is homogeneous, anisotropic and interacts with four surrounding streams of constant-head. Flow field in this laterally bounded aquifer-system is efficiently constructed by means of variational calculus. This is accomplished by minimizing a properly defined penalty function for the associated boundary value problem. Simple yet demonstrative scenarios are defined to investigate anisotropy effects on the water table variation. Qualitative examination of the resulting equipotential contour maps and velocity vector field illustrates the validity of the method, especially in the vicinity of boundary lines. Extension to the case of triangular-shaped aquifer with or without an impervious boundary line is also demonstrated through a hypothetical example problem. The present solution benefits from an extremely simple mathematical expression and exhibits strictly close agreement with the numerical results obtained from Modflow. Overall, the solution may be used to conduct sensitivity analysis on various hydrogeological parameters that affect water table variation in aquifers defined in trapezoidal or triangular-shaped domains.

Influence of two-stream relativistic electron beam parameters on the space-charge wave with broad frequency spectrum formation

Science.gov (United States)

Alexander, LYSENKO; Iurii, VOLK

2018-03-01

We developed a cubic non-linear theory describing the dynamics of the multiharmonic space-charge wave (SCW), with harmonics frequencies smaller than the two-stream instability critical frequency, with different relativistic electron beam (REB) parameters. The self-consistent differential equation system for multiharmonic SCW harmonic amplitudes was elaborated in a cubic non-linear approximation. This system considers plural three-wave parametric resonant interactions between wave harmonics and the two-stream instability effect. Different REB parameters such as the input angle with respect to focusing magnetic field, the average relativistic factor value, difference of partial relativistic factors, and plasma frequency of partial beams were investigated regarding their influence on the frequency spectrum width and multiharmonic SCW saturation levels. We suggested ways in which the multiharmonic SCW frequency spectrum widths could be increased in order to use them in multiharmonic two-stream superheterodyne free-electron lasers, with the main purpose of forming a powerful multiharmonic electromagnetic wave.

Interactive collision detection for deformable models using streaming AABBs.

Science.gov (United States)

Zhang, Xinyu; Kim, Young J

2007-01-01

We present an interactive and accurate collision detection algorithm for deformable, polygonal objects based on the streaming computational model. Our algorithm can detect all possible pairwise primitive-level intersections between two severely deforming models at highly interactive rates. In our streaming computational model, we consider a set of axis aligned bounding boxes (AABBs) that bound each of the given deformable objects as an input stream and perform massively-parallel pairwise, overlapping tests onto the incoming streams. As a result, we are able to prevent performance stalls in the streaming pipeline that can be caused by expensive indexing mechanism required by bounding volume hierarchy-based streaming algorithms. At runtime, as the underlying models deform over time, we employ a novel, streaming algorithm to update the geometric changes in the AABB streams. Moreover, in order to get only the computed result (i.e., collision results between AABBs) without reading back the entire output streams, we propose a streaming en/decoding strategy that can be performed in a hierarchical fashion. After determining overlapped AABBs, we perform a primitive-level (e.g., triangle) intersection checking on a serial computational model such as CPUs. We implemented the entire pipeline of our algorithm using off-the-shelf graphics processors (GPUs), such as nVIDIA GeForce 7800 GTX, for streaming computations, and Intel Dual Core 3.4G processors for serial computations. We benchmarked our algorithm with different models of varying complexities, ranging from 15K up to 50K triangles, under various deformation motions, and the timings were obtained as 30 approximately 100 FPS depending on the complexity of models and their relative configurations. Finally, we made comparisons with a well-known GPU-based collision detection algorithm, CULLIDE [4] and observed about three times performance improvement over the earlier approach. We also made comparisons with a SW-based AABB

Water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine salt domes, northeast Texas salt-dome basin

International Nuclear Information System (INIS)

Carr, J.E.; Halasz, S.J.; Liscum, F.

1980-11-01

This report contains water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine Salt Domes in the northeast Texas salt-dome basin. Water-quality data were compiled for aquifers in the Wilcox Group, the Carrizo Sand, and the Queen City Sand. The data include analyses for dissolved solids, pH, temperature, hardness, calcium, magnesium, sodium, bicarbonate, chloride, and sulfate. Water-quality and streamflow data were obtained from 63 surface-water sites in the vicinity of the domes. These data include water discharge, specific conductance, pH, water temperature, and dissolved oxygen. Samples were collected at selected sites for analysis of principal and selected minor dissolved constituents

Vegetation dynamics induced by phreatophyte--aquifer interactions.

Science.gov (United States)

Ridolfi, Luca; D'Odorico, Paolo; Laio, Francesco

2007-09-21

The dynamics of phreatophyte vegetation are strongly coupled to those of the shallow phreatic aquifers from which phreatophytes extract water. Vegetation is able to influence the depth of the water table, which, in turn, can induce stress in vegetation. These interactions are likely to affect the composition and structure of phreatophyte plant communities, as well as their successional dynamics. Despite the environmental and economical value of many wetland plant ecosystems around the world, the impact of vegetation-water table interactions on ecosystem succession and interspecies competition in phreatophyte plant communities remains poorly understood. This study develops a minimalistic modelling framework to investigate the dynamics of two phreatophyte species, and their interactions with the water table. In spite of its simplicity, the model exhibits a remarkable variety of dynamical behaviors, especially when the water table depth is forced by external drivers. It is shown that, even when one of the two species is dominant with respect to the other, these two species can coexist showing periodic, quasi-periodic, and chaotic dynamics. Moreover, in the presence of a random environmental forcing, noise-induced coexistence may emerge.

Conceptual and numerical modeling approach of the Guarani Aquifer System

Directory of Open Access Journals (Sweden)

L. Rodríguez

2013-01-01

Full Text Available In large aquifers, relevant for their considerable size, regional groundwater modeling remains challenging given geologic complexity and data scarcity in space and time. Yet, it may be conjectured that regional scale groundwater flow models can help in understanding the flow system functioning and the relative magnitude of water budget components, which are important for aquifer management. The Guaraní Aquifer System is the largest transboundary aquifer in South America. It contains an enormous volume of water; however, it is not well known, being difficult to assess the impact of exploitation currently used to supply over 25 million inhabitants. This is a sensitive issue because the aquifer is shared by four countries. Moreover, an integrated groundwater model, and therefore a global water balance, were not available. In this work, a transient regional scale model for the entire aquifer based upon five simplified, equally plausible conceptual models represented by different hydraulic conductivity parametrizations is used to analyze the flow system and water balance components. Combining an increasing number of hydraulic conductivity zones and an appropriate set of boundary conditions, the hypothesis of a continuous sedimentary unit yielded errors within the calibration target in a regional sense. The magnitude of the water budget terms resulted very similar for all parametrizations. Recharge and stream/aquifer fluxes were the dominant components representing, on average, 84.2% of total inflows and 61.4% of total outflows, respectively. However, leakage was small compared to stream discharges of main rivers. For instance, the simulated average leakage for the Uruguay River was 8 m³ s⁻¹ while the observed absolute minimum discharge was 382 m³ s⁻¹. Streams located in heavily pumped regions switched from a gaining condition in early years to a losing condition over time. Water is discharged through

Electron Fluid Description of Wave-Particle Interactions in Strong Buneman Turbulence

Science.gov (United States)

Che, Haihong

2013-10-01

To understand the nature of anomalous resistivity in magnetic reconnection, we investigate turbulence-induced momentum transport and energy dissipation associated with electron heating in Buneman instability. Using 3D particle-in-cell simulations, we find that the macroscopic effects generated by wave-particle interactions can be described by a set of electron fluid equations. These equations show that the energy dissipation and momentum transports in Buneman instability are locally quasi-static but globally non-static and irreversible. Turbulence drag dissipates both the bulk energy of electron streams and the associated magnetic energy. The decrease of magnetic field maintains an inductive electric field that re-accelerates electrons. The net loss of streaming energy is converted into electron heat and increases the electron Boltzmann entropy. The growth of self-sustained Buneman waves satisfies a Bernoulli-like equation which relates the turbulence-induced convective momentum transport and thermal momentum transport. Electron trapping and de-trapping drives local momentum transports, while phase mixing converts convective momentum into thermal momentum.These two local momentum transports sustain the Buneman waves and act as the micro-macro link in the anomalous heating process. This research is supported by the NASA Postdoctoral Program at NASA/GSFC administered by Oak Ridge Associated Universities through a contract with NASA.

The quality of our Nation's waters: water quality in the Upper Floridan aquifer and overlying surficial aquifers, southeastern United States, 1993-2010

Science.gov (United States)

Berndt, Marian P.; Katz, Brian G.; Kingsbury, James A.; Crandall, Christy A.

2015-01-01

About 10 million people rely on groundwater from the Upper Floridan and surficial aquifers for drinking water. The Upper Floridan aquifer also is of primary importance to the region as a source of water for irrigation and as a source of crystal clear water that discharges to springs and streams providing recreational and tourist destinations and unique aquatic habitats. The reliance of the region on the Upper Floridan aquifer for drinking water and for the tourism and agricultural economies highlights the importance of long-term management to sustain the availability and quality of these resources.

Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

Science.gov (United States)

Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

2015-12-01

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons

Energy Technology Data Exchange (ETDEWEB)

Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)

2015-12-15

Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)

Ground-water flow directions and estimation of aquifer hydraulic properties in the lower Great Miami River Buried Valley aquifer system, Hamilton Area, Ohio

Science.gov (United States)

Sheets, Rodney A.; Bossenbroek, Karen E.

2005-01-01

The Great Miami River Buried Valley Aquifer System is one of the most productive sources of potable water in the Midwest, yielding as much as 3,000 gallons per minute to wells. Many water-supply wells tapping this aquifer system are purposely placed near rivers to take advantage of induced infiltration from the rivers. The City of Hamilton's North Well Field consists of 10 wells near the Great Miami River, all completed in the lower Great Miami River Buried Valley Aquifer System. A well-drilling program and a multiple-well aquifer test were done to investigate ground-water flow directions and to estimate aquifer hydraulic properties in the lower part of the Great Miami River Buried Valley Aquifer System. Descriptions of lithology from 10 well borings indicate varying amounts and thickness of clay or till, and therefore, varying levels of potential aquifer confinement. Borings also indicate that the aquifer properties can change dramatically over relatively short distances. Grain-size analyses indicate an average bulk hydraulic conductivity value of aquifer materials of 240 feet per day; the geometric mean of hydraulic conductivity values of aquifer material was 89 feet per day. Median grain sizes of aquifer material and clay units were 1.3 millimeters and 0.1 millimeters, respectively. Water levels in the Hamilton North Well Field are affected by stream stage in the Great Miami River and barometric pressure. Bank storage in response to stream stage is evident. Results from a multiple-well aquifer test at the well field indicate, as do the lithologic descriptions, that the aquifer is semiconfined in some areas and unconfined in others. Transmissivity and storage coefficient of the semiconfined part of the aquifer were 50,000 feet squared per day and 5x10-4, respectively. The average hydraulic conductivity (450 feet per day) based on the aquifer test is reasonable for glacial outwash but is higher than calculated from grain-size analyses, implying a scale effect

Evaluation of groundwater and surface-water interactions in the Caddo Nation Tribal Jurisdictional Area, Caddo County, Oklahoma, 2010-13

Science.gov (United States)

Mashburn, Shana L.; Smith, S. Jerrod

2014-01-01

Streamflows, springs, and wetlands are important natural and cultural resources to the Caddo Nation. Consequently, the Caddo Nation is concerned about the vulnerability of the Rush Springs aquifer to overdrafting and whether the aquifer will continue to be a viable source of water to tribal members and other local residents in the future. Interest in the long-term viability of local water resources has resulted in ongoing development of a comprehensive water plan by the Caddo Nation. As part of a multiyear project with the Caddo Nation to provide information and tools to better manage and protect water resources, the U.S. Geological Survey studied the hydraulic connection between the Rush Springs aquifer and springs and streams overlying the aquifer. The Caddo Nation Tribal Jurisdictional Area is located in southwestern Oklahoma, primarily in Caddo County. Underlying the Caddo Nation Tribal Jurisdictional Area is the Permian-age Rush Springs aquifer. Water from the Rush Springs aquifer is used for irrigation, public, livestock and aquaculture, and other supply purposes. Groundwater from the Rush Springs aquifer also is withdrawn by domestic (self-supplied) wells, although domestic use was not included in the water-use summary in this report. Perennial streamflow in many streams and creeks overlying the Rush Springs aquifer, such as Cobb Creek, Lake Creek, and Willow Creek, originates from springs and seeps discharging from the aquifer. This report provides information on the evaluation of groundwater and surface-water resources in the Caddo Nation Jurisdictional Area, and in particular, information that describes the hydraulic connection between the Rush Springs aquifer and springs and streams overlying the aquifer. This report also includes data and analyses of base flow, evidence for groundwater and surface-water interactions, locations of springs and wetland areas, groundwater flows interpreted from potentiometric-surface maps, and hydrographs of water levels

Groundwater declines are linked to changes in Great Plains stream fish assemblages.

Science.gov (United States)

Perkin, Joshuah S; Gido, Keith B; Falke, Jeffrey A; Fausch, Kurt D; Crockett, Harry; Johnson, Eric R; Sanderson, John

2017-07-11

Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950-2010) and prospective (2011-2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish assemblages associated with groundwater pumping from the United States High Plains Aquifer. We modeled the relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes. Scaling down to subwatersheds revealed consistent transformations in fish assemblage structure among western subwatersheds with increasing depths to groundwater. Although transformations occurred in the absence of barriers, barriers along mainstem rivers isolate depauperate western fish assemblages from relatively intact eastern fish assemblages. Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater. Our work illustrates the shrinking of streams and homogenization of Great Plains stream fish assemblages related to groundwater pumping, and we predict similar transformations worldwide where local and regional aquifer depletions occur.

Nonlinear magnetic electron tripolar vortices in streaming plasmas.

Science.gov (United States)

Vranjes, J; Marić, G; Shukla, P K

2000-06-01

Magnetic electron modes in nonuniform magnetized and unmagnetized streaming plasmas, with characteristic frequencies between the ion and electron plasma frequencies and at spatial scales of the order of the collisionless skin depth, are studied. Two coupled equations, for the perturbed (in the case of magnetized plasma) or self-generated (for the unmagnetized plasma case) magnetic field, and the temperature, are solved in the strongly nonlinear regime and stationary traveling solutions in the form of tripolar vortices are found.

Interaction of streaming and attention in human auditory cortex.

Science.gov (United States)

Gutschalk, Alexander; Rupp, André; Dykstra, Andrew R

2015-01-01

Serially presented tones are sometimes segregated into two perceptually distinct streams. An ongoing debate is whether this basic streaming phenomenon reflects automatic processes or requires attention focused to the stimuli. Here, we examined the influence of focused attention on streaming-related activity in human auditory cortex using magnetoencephalography (MEG). Listeners were presented with a dichotic paradigm in which left-ear stimuli consisted of canonical streaming stimuli (ABA_ or ABAA) and right-ear stimuli consisted of a classical oddball paradigm. In phase one, listeners were instructed to attend the right-ear oddball sequence and detect rare deviants. In phase two, they were instructed to attend the left ear streaming stimulus and report whether they heard one or two streams. The frequency difference (ΔF) of the sequences was set such that the smallest and largest ΔF conditions generally induced one- and two-stream percepts, respectively. Two intermediate ΔF conditions were chosen to elicit bistable percepts (i.e., either one or two streams). Attention enhanced the peak-to-peak amplitude of the P1-N1 complex, but only for ambiguous ΔF conditions, consistent with the notion that automatic mechanisms for streaming tightly interact with attention and that the latter is of particular importance for ambiguous sound sequences.

Characterizing pharmaceutical, personal care product, and hormone contamination in a karst aquifer of southwestern Illinois, USA, using water quality and stream flow parameters.

Science.gov (United States)

Dodgen, L K; Kelly, W R; Panno, S V; Taylor, S J; Armstrong, D L; Wiles, K N; Zhang, Y; Zheng, W

2017-02-01

Karst aquifers are drinking water sources for 25% of the global population. However, the unique geology of karst areas facilitates rapid transfer of surficial chemicals to groundwater, potentially contaminating drinking water. Contamination of karst aquifers by nitrate, chloride, and bacteria have been previously observed, but little knowledge is available on the presence of contaminants of emerging concern (CECs), such as pharmaceuticals. Over a 17-month period, 58 water samples were collected from 13 sites in the Salem Plateau, a karst region in southwestern Illinois, United States. Water was analyzed for 12 pharmaceutical and personal care products (PPCPs), 7 natural and synthetic hormones, and 49 typical water quality parameters (e.g., nutrients and bacteria). Hormones were detected in only 23% of samples, with concentrations of 2.2-9.1ng/L. In contrast, PPCPs were quantified in 89% of groundwater samples. The two most commonly detected PPCPs were the antimicrobial triclocarban, in 81% of samples, and the cardiovascular drug gemfibrozil, in 57%. Analytical results were combined with data of local stream flow, weather, and land use to 1) characterize the extent of aquifer contamination by CECs, 2) cluster sites with similar PPCP contamination profiles, and 3) develop models to describe PPCP contamination. Median detection in karst groundwater was 3 PPCPs at a summed concentration of 4.6ng/L. Sites clustered into 3 subsets with unique contamination models. PPCP contamination in Cluster I sites was related to stream height, manganese, boron, and heterotrophic bacteria. Cluster II sites were characterized by groundwater temperature, specific conductivity, sodium, and calcium. Cluster III sites were characterized by dissolved oxygen and barium. Across all sites, no single or small set of water quality factors was significantly predictive of PPCP contamination, although gemfibrozil concentrations were strongly related to the sum of PPCPs in karst groundwater

Estimated hydrologic budgets of kettle-hole ponds in coastal aquifers of southeastern Massachusetts

Science.gov (United States)

Walter, Donald A.; Masterson, John P.

2011-01-01

Kettle-hole ponds in southeastern Massachusetts are in good hydraulic connection to an extensive coastal aquifer system that includes the Plymouth-Carver aquifer system on the mainland and aquifers underlying Cape Cod. The ponds receive water from, and contribute water to, the underlying glacial aquifer; ponds also receive water from precipitation and lose water to evaporation from the pond surface. Some ponds are connected to surface-water drainage systems and receive water from or contribute water to streams or adjacent wetlands. The Massachusetts Department of Environmental Protection currently (2011) is developing Total Maximum Daily Loads of phosphorus for the freshwater ponds in the region to maintain the health of pond ecosystems; the amounts and sources of water fluxes into and out of the ponds are important factors in determining the amount of phosphorus that can be assimilated into a pond. To assist in this effort, the U.S. Geological Survey used groundwater-flow models of the coastal aquifer system to estimate hydrologic budgets-including inflows and outflows from the aquifer system and adjacent streams and wetlands, and recharge from precipitation-for 425 ponds in southeastern Massachusetts.

SP@CE - An SP-based programming model for consumer electronics streaming applications

NARCIS (Netherlands)

Varbanescu, Ana Lucia; Nijhuis, Maik; Escribano, Arturo González; Sips, Henk; Bos, Herbert; Bal, Henri

2007-01-01

Efficient programming of multimedia streaming applications for Consumer Electronics (CE) devices is not trivial. As a solution for this problem, we present SP@CE, a novel programming model designed to balance the specific requirements of CE streaming applications with the simplicity and efficiency

Development of A Mississippi River Alluvial Aquifer Groundwater Model

Science.gov (United States)

Karakullukcu, R. E.; Tsai, F. T. C.; Bhatta, D.; Paudel, K.; Kao, S. C.

2017-12-01

The Mississippi River Alluvial Aquifer (MRAA) underlies the Mississippi River Valley of the northeastern Louisiana, extending from the north border of Louisiana and Arkansas to south central of Louisiana. The MRAA has direct contact with the Mississippi River. However, the interaction between the Mississippi River and the alluvial aquifer is largely unknown. The MRAA is the second most used groundwater source in Louisiana's aquifers with about 390 million gallons per day, which is about 25% of all groundwater withdrawals in Louisiana. MRAA is the major water source to agriculture in the northeastern Louisiana. The groundwater withdrawals from the MRAA increases annually for irrigation. High groundwater pumping has caused significant groundwater level decline and elevated salinity in the aquifer. Therefore, dealing with agricultural irrigation is the primary purpose for managing the MRAA. The main objective of this study is to develop a groundwater model as a tool for the MRAA groundwater management. To do so, a hydrostratigraphy model of the MRAA was constructed by using nearly 8,000 drillers' logs and electric logs collected from Louisiana Department of Natural Resources. The hydrostratigraphy model clearly shows that the Mississippi River cuts into the alluvial aquifer. A grid generation technique was developed to convert the hydrostratigraphy model into a MODFLOW model with 12 layers. A GIS-based method was used to estimate groundwater withdrawals for irrigation wells based on the crop location and acreage from the USDACropScape - Cropland Data Layer. Results from the Variable Infiltration Capacity (VIC) model were used to determine potential recharge. NHDPlusV2 data was used to determine water level for major streams for the MODFLOW River Package. The groundwater model was calibrated using groundwater data between 2004 and 2015 to estimate aquifer hydraulic conductivity, specific yield, specific storage, river conductance, and surficial recharge.

Descriptions and characterizations of water-level data and groundwater flow for the Brewster Boulevard and Castle Hayne Aquifer Systems and the Tarawa Terrace Aquifer

Science.gov (United States)

Faye, Robert E.; Jones, L. Elliott; Suárez-Soto, René J.

2013-01-01

This supplement of Chapter A (Supplement 3) summarizes results of analyses of groundwater-level data and describes corresponding elements of groundwater flow such as vertical hydraulic gradients useful for groundwater-flow model calibration. Field data as well as theoretical concepts indicate that potentiometric surfaces within the study area are shown to resemble to a large degree a subdued replica of surface topography. Consequently, precipitation that infiltrates to the water table flows laterally from highland to lowland areas and eventually discharges to streams such as Northeast and Wallace Creeks and New River. Vertically downward hydraulic gradients occur in highland areas resulting in the transfer of groundwater from shallow relatively unconfined aquifers to underlying confined or semi-confined aquifers. Conversely, in the vicinity of large streams such as Wallace and Frenchs Creeks, diffuse upward leakage occurs from underlying confined or semi-confined aquifers. Point water-level data indicating water-table altitudes, water-table altitudes estimated using a regression equation, and estimates of stream levels determined from a digital elevation model (DEM) and topographic maps were used to estimate a predevelopment water-table surface in the study area. Approximate flow lines along hydraulic gradients are shown on a predevelopment potentiometric surface map and extend from highland areas where potentiometric levels are greatest toward streams such as Wallace Creek and Northeast Creek. The distribution of potentiometric levels and corresponding groundwater-flow directions conform closely to related descriptions of the conceptual model.

Hydrodynamical simulations of the stream-core interaction in the slow merger of massive stars

Science.gov (United States)

Ivanova, N.; Podsiadlowski, Ph.; Spruit, H.

2002-08-01

We present detailed simulations of the interaction of a stream emanating from a mass-losing secondary with the core of a massive supergiant in the slow merger of two stars inside a common envelope. The dynamics of the stream can be divided into a ballistic phase, starting at the L1 point, and a hydrodynamical phase, where the stream interacts strongly with the core. Considering the merger of a 1- and 5-Msolar star with a 20-Msolar evolved supergiant, we present two-dimensional hydrodynamical simulations using the PROMETHEUS code to demonstrate how the penetration depth and post-impact conditions depend on the initial properties of the stream material (e.g. entropy, angular momentum, stream width) and the properties of the core (e.g. density structure and rotation rate). Using these results, we present a fitting formula for the entropy generated in the stream-core interaction and a recipe for the determination of the penetration depth based on a modified Bernoulli integral.

Hydrogeology and simulation of groundwater flow in the Arbuckle-Simpson aquifer, south-central Oklahoma

Science.gov (United States)

Christenson, Scott; Osborn, Noel I.; Neel, Christopher R.; Faith, Jason R.; Blome, Charles D.; Puckette, James; Pantea, Michael P.

2011-01-01

The Arbuckle-Simpson aquifer in south-central Oklahoma provides water for public supply, farms, mining, wildlife conservation, recreation, and the scenic beauty of springs, streams, and waterfalls. Proposed development of water supplies from the aquifer led to concerns that large-scale withdrawals of water would cause decreased flow in rivers and springs, which in turn could result in the loss of water supplies, recreational opportunities, and aquatic habitat. The Oklahoma Water Resources Board, in collaboration with the Bureau of Reclamation, the U.S. Geological Survey, Oklahoma State University, and the University of Oklahoma, studied the aquifer to provide the Oklahoma Water Resources Board the scientific information needed to determine the volume of water that could be withdrawn while protecting springs and streams. The U.S. Geological Survey, in coopertion with the Oklahoma Water Resources Board, did a study to describe the hydrogeology and simulation of groundwater flow of the aquifer.

Architecture of portable electronic medical records system integrated with streaming media.

Science.gov (United States)

Chen, Wei; Shih, Chien-Chou

2012-02-01

Due to increasing occurrence of accidents and illness during business trips, travel, or overseas studies, the requirement for portable EMR (Electronic Medical Records) has increased. This study proposes integrating streaming media technology into the EMR system to facilitate referrals, contracted laboratories, and disease notification among hospitals. The current study encoded static and dynamic medical images of patients into a streaming video format and stored them in a Flash Media Server (FMS). Based on the Taiwan Electronic Medical Record Template (TMT) standard, EMR records can be converted into XML documents and used to integrate description fields with embedded streaming videos. This investigation implemented a web-based portable EMR interchanging system using streaming media techniques to expedite exchanging medical image information among hospitals. The proposed architecture of the portable EMR retrieval system not only provides local hospital users the ability to acquire EMR text files from a previous hospital, but also helps access static and dynamic medical images as reference for clinical diagnosis and treatment. The proposed method protects property rights of medical images through information security mechanisms of the Medical Record Interchange Service Center and Health Certificate Authorization to facilitate proper, efficient, and continuous treatment of patients.

Effects of non-Maxwellian electron velocity distribution function on two-stream instability in low-pressure discharges

International Nuclear Information System (INIS)

Sydorenko, D.; Smolyakov, A.; Kaganovich, I.; Raitses, Y.

2007-01-01

Electron emission from discharge chamber walls is important for plasma maintenance in many low-pressure discharges. The electrons emitted from the walls are accelerated by the sheath electric field and are injected into the plasma as an electron beam. Penetration of this beam through the plasma is subject to the two-stream instability, which tends to slow down the beam electrons and heat the plasma electrons. In the present paper, a one-dimensional particle-in-cell code is used to simulate these effects both in a collisionless plasma slab with immobile ions and in a cross-field discharge of a Hall thruster. The two-stream instability occurs if the total electron velocity distribution function of the plasma-beam system is a nonmonotonic function of electron speed. Low-pressure plasmas can be depleted of electrons with energy above the plasma potential. This study reveals that under such conditions the two-stream instability depends crucially on the velocity distribution function of electron emission. It is shown that propagation of the secondary electron beams in Hall thrusters may be free of the two-stream instability if the velocity distribution of secondary electron emission is a monotonically decaying function of speed. In this case, the beams propagate between the walls with minimal loss of the beam current and the secondary electron emission does not affect the thruster plasma properties

Device interactions in reducing the cost of tidal stream energy

International Nuclear Information System (INIS)

Vazquez, A.; Iglesias, G.

2015-01-01

Highlights: • Numerical modelling is used to estimate the levelised cost of tidal stream energy. • As a case study, a model of Lynmouth (UK) is implemented and successfully validated. • The resolution of the model allows the demarcation of individual devices on the model grid. • Device interactions reduce the available tidal resource and the cost increases significantly. - Abstract: The levelised cost of energy takes into account the lifetime generated energy and the costs associated with a project. The objective of this work is to investigate the effects of device interactions on the energy output and, therefore, on the levelised cost of energy of a tidal stream project, by means of numerical modelling. For this purpose, a case study is considered: Lynmouth (North Devon, UK), an area in the Bristol Channel in which the first tidal stream turbine was installed − a testimony of its potential as a tidal energy site. A state-of-the-art hydrodynamics model is implemented on a high-resolution computational grid, which allows the demarcation of the individual devices. The modification to the energy output resulting from interaction between turbines within the tidal farm is thus resolved for each individual turbine. The results indicate that significant changes in the levelised cost of energy values, of up to £0.221 kW h −1 , occur due to the aforementioned modifications, which should not be disregarded if the cost of tidal stream energy is to be minimised

Development of a stream–aquifer numerical flow model to assess river water management under water scarcity in a Mediterranean basin

International Nuclear Information System (INIS)

Mas-Pla, Josep; Font, Eva; Astui, Oihane; Menció, Anna; Rodríguez-Florit, Agustí; Folch, Albert; Brusi, David; Pérez-Paricio, Alfredo

2012-01-01

Stream flow, as a part of a basin hydrological cycle, will be sensible to water scarcity as a result of climate change. Stream vulnerability should then be evaluated as a key component of the basin water budget. Numerical flow modeling has been applied to an alluvial formation in a small mountain basin to evaluate the stream–aquifer relationship under these future scenarios. The Arbúcies River basin (116 km 2 ) is located in the Catalan Inner Basins (NE Spain) and its lower reach, which is related to an alluvial aquifer, usually becomes dry during the summer period. This study seeks to determine the origin of such discharge losses whether from natural stream leakage and/or induced capture due to groundwater withdrawal. Our goal is also investigating how discharge variations from the basin headwaters, representing potential effects of climate change, may affect stream flow, aquifer recharge, and finally environmental preservation and human supply. A numerical flow model of the alluvial aquifer, based on MODFLOW and especially in the STREAM routine, reproduced the flow system after the usual calibration. Results indicate that, in the average, stream flow provides more than 50% of the water inputs to the alluvial aquifer, being responsible for the amount of stored water resources and for satisfying groundwater exploitation for human needs. Detailed simulations using daily time-steps permit setting threshold values for the stream flow entering at the beginning of the studied area so surface discharge is maintained along the whole watercourse and ecological flow requirements are satisfied as well. The effects of predicted rainfall and temperature variations on the Arbúcies River alluvial aquifer water balance are also discussed from the outcomes of the simulations. Finally, model results indicate the relevance of headwater discharge management under future climate scenarios to preserve downstream hydrological processes. They also point out that small mountain basins

Evaluation of karstic aquifers contribution to streams by the statistical ...

Indian Academy of Sciences (India)

and water budget balance, have been applied to assess ... Keywords. Recession curve; karstic aquifer; western Mediterranean Basin–Turkey; data analysis; hydrology; modelling. .... on the solution of the general differential equa- tion of the ...

Implications of Kali–Hindon inter-stream aquifer water balance for ...

Indian Academy of Sciences (India)

evaporation from the water table, discharge from the aquifer to rivers and horizontal subsurface outflows were also ... and their future supply potential in order to predict possible conflicts ..... losses via evaporation losses and horizontal subsur-.

Substrate interactions of benzene, toluene, and para-xylene during microbial degradation by pure cultures and mixed culture aquifer slurries

International Nuclear Information System (INIS)

Alvarez, P.J.J.; Vogel, T.M.

1991-01-01

Release of petroleum hydrocarbons in the environment is a widespread occurrence. One particular concern is the contamination of drinking water sources by the toxic, water-soluble, and mobile petroleum components benzene, toluene, and xylene (BTX). Benzene, toluene, and p-xylene (BTX) were degraded by indigenous mixed cultures in sandy aquifer material and by two pure cultures isolated from the same site. Although BTX compounds have a similar chemical structure, the fate of individual BTX compounds differed when the compounds were fed to each pure culture and mixed culture aquifer slurries. The identification of substrate interactions aided the understanding of this behavior. Beneficial substrate interactions included enhanced degradation of benzene-dependent degradation of toluene and p-xylene by Arthrobacter sp. strain HCB. Detrimental substrate interactions included retardation in benzene and toluene degradation by the presence of p-xylene in both aquifer slurries and Pseudomonas incubations. The catabolic diversity of microbes in the environment precludes generalizations about the capacity of individual BTX compounds to enhance or inhibit the degradation of other BTX compounds

A framework to preserve the privacy of electronic health data streams.

Science.gov (United States)

Kim, Soohyung; Sung, Min Kyoung; Chung, Yon Dohn

2014-08-01

The anonymization of health data streams is important to protect these data against potential privacy breaches. A large number of research studies aiming at offering privacy in the context of data streams has been recently conducted. However, the techniques that have been proposed in these studies generate a significant delay during the anonymization process, since they concentrate on applying existing privacy models (e.g., k-anonymity and l-diversity) to batches of data extracted from data streams in a period of time. In this paper, we present delay-free anonymization, a framework for preserving the privacy of electronic health data streams. Unlike existing works, our method does not generate an accumulation delay, since input streams are anonymized immediately with counterfeit values. We further devise late validation for increasing the data utility of the anonymization results and managing the counterfeit values. Through experiments, we show the efficiency and effectiveness of the proposed method for the real-time release of data streams. Copyright © 2014 Elsevier Inc. All rights reserved.

Using hydraulic head, chloride and electrical conductivity data to distinguish between mountain-front and mountain-block recharge to basin aquifers

Science.gov (United States)

Bresciani, Etienne; Cranswick, Roger H.; Banks, Eddie W.; Batlle-Aguilar, Jordi; Cook, Peter G.; Batelaan, Okke

2018-03-01

Numerous basin aquifers in arid and semi-arid regions of the world derive a significant portion of their recharge from adjacent mountains. Such recharge can effectively occur through either stream infiltration in the mountain-front zone (mountain-front recharge, MFR) or subsurface flow from the mountain (mountain-block recharge, MBR). While a thorough understanding of recharge mechanisms is critical for conceptualizing and managing groundwater systems, distinguishing between MFR and MBR is difficult. We present an approach that uses hydraulic head, chloride and electrical conductivity (EC) data to distinguish between MFR and MBR. These variables are inexpensive to measure, and may be readily available from hydrogeological databases in many cases. Hydraulic heads can provide information on groundwater flow directions and stream-aquifer interactions, while chloride concentrations and EC values can be used to distinguish between different water sources if these have a distinct signature. Such information can provide evidence for the occurrence or absence of MFR and MBR. This approach is tested through application to the Adelaide Plains basin, South Australia. The recharge mechanisms of this basin have long been debated, in part due to difficulties in understanding the hydraulic role of faults. Both hydraulic head and chloride (equivalently, EC) data consistently suggest that streams are gaining in the adjacent Mount Lofty Ranges and losing when entering the basin. Moreover, the data indicate that not only the Quaternary aquifers but also the deeper Tertiary aquifers are recharged through MFR and not MBR. It is expected that this finding will have a significant impact on the management of water resources in the region. This study demonstrates the relevance of using hydraulic head, chloride and EC data to distinguish between MFR and MBR.

Geochemistry of silicate-rich rocks can curtail spreading of carbon dioxide in subsurface aquifers.

Science.gov (United States)

Cardoso, S S S; Andres, J T H

2014-12-11

Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We show that, while in carbonate rocks the streaming of dissolved carbon dioxide persists, the chemical interactions in silicate-rich rocks may curb this transport drastically and even inhibit it altogether. These results challenge our view of carbon sequestration and dissolution rates in the subsurface, suggesting that pooled carbon dioxide may remain in the shallower regions of the formation for hundreds to thousands of years. The deeper regions of the reservoir can remain virtually carbon free.

Distribution of aquifers, liquid-waste impoundments, and municipal water-supply sources, Massachusetts

Science.gov (United States)

Delaney, David F.; Maevsky, Anthony

1980-01-01

Impoundments of liquid waste are potential sources of ground-water contamination in Massachusetts. The map report, at a scale of 1 inch equals 4 miles, shows the idstribution of aquifers and the locations of municipal water-supply sources and known liquid-waste impoundments. Ground water, an important source of municipal water supply, is produced from shallow sand and gravel aquifers that are generally unconfined, less than 200 feet thick, and yield less than 2,000 gallons per minute to individual wells. These aquifers commonly occupy lowlands and stream valleys and are most extensive in eastern Massachusetts. Surface impoundments of liquid waste are commonly located over these aquifers. These impoundments may leak and allow waste to infiltrate underlying aquifers and alter their water quality. (USGS)

Charaterising water-rock interaction in a mixed carbonate-evaporite karstified aquifer system, Qatar

Science.gov (United States)

Thirathititham, R.; Whitaker, F.

2017-12-01

Qatar is an arid country, most of the rainfall (80 mm/yr) occurring during intense storms. Surface runoff is endorheic and recharge is facilitated by karst features developed over an extended (c.30 Ma) period of exposure of the carbonate bedrock. In December 2016, we sampled a rare intense rainfall event (41 mm over 3 days), after which waters ponded within low-relief terminal depressions prior to infiltration. We compare the chemistry of these recharge waters with that of ground waters from 76 wells distributed across Qatar to understand the nature and spatial distribution of water-rock interaction. Using Cl- as a conservative tracer for seawater mixing, we calculate concentrations of rock-derived Ca2+, Mg2+ and SO42-. During surface detention, rain chemistry is modified by evaporation and interaction with clays and the surface bedrock over days to weeks. However, groundwater chemistry is dominated by subsurface interaction between recharge waters and the karstified Tertiary aquifers. These include the largely dolomitic Paleocene to Lower Eocene Umm er Radhuma (UER) and overlying Lower Eocene Rus, with the Middle Eocene Abarug limestone forming a locally important aquifer in the south west. Away from coastal areas which show clear evidence of salinisation, TDS of groundwaters in the interior of the peninsula increases from north to south. All groundwaters are significantly enriched in SO42-, but this enrichment is marked greater in the south. This likely reflects the presence of a unit of middle Rus gypsum that in the south of the country confines the Lower Rus and UER aquifers, whilst in the north either gypsum was not deposited or has been dissolved. Waters in the Abarug limestone show limited sulfate enrichment and a 1:1 molar ratio of rock-derived SO42-: Ca2+, but across much of the country both SO42- enrichment and SO42-: Ca2+ molar ratio are significantly higher, the latter reaching 2:1 and suggesting an additional sink for Ca2+. The dolomite aquifer waters

Interaction between stream temperature, streamflow, and groundwater exchanges in alpine streams

Science.gov (United States)

Constantz, James E.

1998-01-01

Four alpine streams were monitored to continuously collect stream temperature and streamflow for periods ranging from a week to a year. In a small stream in the Colorado Rockies, diurnal variations in both stream temperature and streamflow were significantly greater in losing reaches than in gaining reaches, with minimum streamflow losses occurring early in the day and maximum losses occurring early in the evening. Using measured stream temperature changes, diurnal streambed infiltration rates were predicted to increase as much as 35% during the day (based on a heat and water transport groundwater model), while the measured increase in streamflow loss was 40%. For two large streams in the Sierra Nevada Mountains, annual stream temperature variations ranged from 0° to 25°C. In summer months, diurnal stream temperature variations were 30–40% of annual stream temperature variations, owing to reduced streamflows and increased atmospheric heating. Previous reports document that one Sierra stream site generally gains groundwater during low flows, while the second Sierra stream site may lose water during low flows. For August the diurnal streamflow variation was 11% at the gaining stream site and 30% at the losing stream site. On the basis of measured diurnal stream temperature variations, streambed infiltration rates were predicted to vary diurnally as much as 20% at the losing stream site. Analysis of results suggests that evapotranspiration losses determined diurnal streamflow variations in the gaining reaches, while in the losing reaches, evapotranspiration losses were compounded by diurnal variations in streambed infiltration. Diurnal variations in stream temperature were reduced in the gaining reaches as a result of discharging groundwater of relatively constant temperature. For the Sierra sites, comparison of results with those from a small tributary demonstrated that stream temperature patterns were useful in delineating discharges of bank storage following

Plasma behavior during energetic electron streaming events: Further evidence for substorm-associated magnetic reconnection

International Nuclear Information System (INIS)

Bieber, J.W.; Stone, E.C.; Hones, E.W. Jr.; Baker, D.N.; Bame, S.J.

1982-01-01

A recent study showed that streaming energetic (>200 keV) electrons in Earth's magnetotail are statistically associated with southward magnetic fields and with enhancements of the AE index. It is shown here that the streaming electrons characteristically are preceded by aapprox.15 minute period of tailward plasma flow and followed by a dropout of the plasma sheet, thus demonstrating a clear statistical association between substorms and the classical signatures of magnetic reconnection and plasmoid formation. Additionally, a brief upward surge of mean electron energy preceded plasma dropout in several of the events studied, providing direct evidence of localized, reconnection-associated heating processes

Groundwater flow and mixing in a wetland–stream system

DEFF Research Database (Denmark)

Karan, Sachin; Engesgaard, Peter Knudegaard; Zibar, Majken Caroline Looms

2013-01-01

steady-state groundwater model that was calibrated against average head observations. The model results were tested against groundwater fluxes determined from streambed temperature measurements. Discharge varied up to one order of magnitude across the stream and the model was successful in capturing...... in the top of the aquifer and immediately underneath the streambed no NO3- was detected deeper within the aquifer. An inverse relationship between NO3- and SO42- suggests that pyrite oxidation takes place in the deeper parts of the aquifer. Simulated flow path lines showed very different origins for deeper...

Interplay between electron-phonon and electron-electron interactions

International Nuclear Information System (INIS)

Roesch, O.; Gunnarsson, O.; Han, J.E.; Crespi, V.H.

2005-01-01

We discuss the interplay between electron-electron and electron-phonon interactions for alkali-doped fullerides and high temperature superconductors. Due to the similarity of the electron and phonon energy scales, retardation effects are small for fullerides. This raises questions about the origin of superconductivity, since retardation effects are believed to be crucial for reducing effects of the Coulomb repulsion in conventional superconductors. We demonstrate that by treating the electron-electron and electron-phonon interactions on an equal footing, superconductivity can be understood in terms of a local pairing. The Jahn-Teller character of the important phonons in fullerides plays a crucial role for this result. To describe effects of phonons in cuprates, we derive a t-J model with phonons from the three-band model. Using exact diagonalization for small clusters, we find that the anomalous softening of the half-breathing phonon as well as its doping dependence can be explained. By comparing the solution of the t-J model with the Hartree-Fock approximation for the three-band model, we address results obtained in the local-density approximation for cuprates. We find that genuine many-body results, due to the interplay between the electron-electron and electron-phonon interactions, play an important role for the the results in the t-J model. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Electron-electron interactions in disordered systems

CERN Document Server

Efros, AL

1985-01-01

``Electron-Electron Interactions in Disordered Systems'' deals with the interplay of disorder and the Coulomb interaction. Prominent experts give state-of-the-art reviews of the theoretical and experimental work in this field and make it clear that the interplay of the two effects is essential, especially in low-dimensional systems.

Hydrological connectivity of perched aquifers and regional aquifers in semi-arid environments: a case study from Namibia

Science.gov (United States)

Hamutoko, J. T.; Wanke, H.

2017-12-01

Integrated isotopic and hydrological tracers along with standard hydrological data are used to understand complex dry land hydrological processes on different spatial and temporal scales. The objective of this study is to analyse the relationship between the perched aquifers and the regional aquifer using hydrochemical data and isotopic composition in the Cuvelai-Etosha Basin in Namibia. This relation between the aquifers will aid in understanding groundwater recharge processes and flow dynamics. Perched aquifers are discontinuous shallow aquifers with water level ranging from 0 to 30 meters below ground level. The regional aquifer occurs in semi-consolidated sandstone at depths between about 60 and 160 meters below ground level. Water samples were collected from both aquifers in 10 villages and were analysed for major ions and stable isotopes. The results show overlapping hydrochemistry and isotopic compositions of both aquifers in 8 villages which suggest the possibility of perched aquifer water infiltrating into the regional aquifer. In two villages the hydrochemistry and isotopic composition of the aquifers are totally different and this suggests that there is no interaction between this aquifers. Areas where perched aquifers are connected to regional aquifers maybe recharge zones. These finding have important implications for groundwater resource management.

Anomalous conductivity and electron heating in a plasma unstable to the two-stream instability

International Nuclear Information System (INIS)

Clark, W.H.M.; Hamberger, S.M.

1979-01-01

An experiment to excite the electron-ion two-stream instability in a cylindrical Q-machine plasma column is described. The mechanism for establishing a large pulsed electron drift velocity in the plasma by applying a potential difference between the end electrodes is discussed. The pulsed current-voltage characteristic of the plasma column and the temporal evolution of the electron density, drift velocity and thermal velocity are measured. In contrast with the behaviour of some computer simulations of the two-stream instability, the plasma exhibits a constant conductivity and the electron thermal velocity increases to values far in excess of the drift velocity. The electrical dissipation is consistent with the increase of the electron thermal energy, both indicating an anomalous conductivity of the same order as an empirical scaling found in earlier experiments on a toroidal discharge. (author)

Electron: Cluster interactions

International Nuclear Information System (INIS)

Scheidemann, A.A.; Knight, W.D.

1994-02-01

Beam depletion spectroscopy has been used to measure absolute total inelastic electron-sodium cluster collision cross sections in the energy range from E ∼ 0.1 to E ∼ 6 eV. The investigation focused on the closed shell clusters Na 8 , Na 20 , Na 40 . The measured cross sections show an increase for the lowest collision energies where electron attachment is the primary scattering channel. The electron attachment cross section can be understood in terms of Langevin scattering, connecting this measurement with the polarizability of the cluster. For energies above the dissociation energy the measured electron-cluster cross section is energy independent, thus defining an electron-cluster interaction range. This interaction range increases with the cluster size

Interactions between deep bedrock aquifers and surface water in function of recharge and topography: a numerical study

Science.gov (United States)

Goderniaux, P.; Davy, P.; Le Borgne, T.; Bresciani, E.; Jimenez-Martinez, J.

2011-12-01

In crystalline rock regions, such as Brittany (France), important reserves of groundwater into deep fractured aquifers are increasingly used and provide high quality water compared to shallow aquifers which can be subject to agricultural contamination. However, recharge processes of these deep aquifers and interactions with surface water are not yet fully understood. In some areas, intensive pumping is carried out without guarantee of the resource quantity and quality. Understanding these processes is crucial for sustainable management of the resource. In this study, we study how deep groundwater fluxes, pathways, ages, and river-aquifer interactions vary according to recharge. We assume that water flowing from the ground surface is distributed between shallow more permeable layers and deep layers. This repartition mostly depends on recharge rates. With high recharge, groundwater levels are high and subsurface streamlines are relatively short between recharge areas and existing draining rivers, which constitutes a very dense network. Therefore, most of the groundwater fluxes occur through the more permeable shallow layers. With low recharge, groundwater levels are lower, and river and shallow permeable levels are partly disconnected from each other. This induces a general increase of the groundwater streamlines length from the recharge areas to more sporadic discharge areas, and more fluxes occur through the deep layers. Recharge conditions and river-aquifer interactions have changed over the last thousands of years, due to change in precipitation, temperatures, existence of permafrost, etc. They have strongly influenced deep groundwater fluxes and can explain current groundwater age and flux distribution. To study these interactions, a regional-scale finite difference flow model was implemented. The model covers an area of 1400 km 2 , a depth of 1 km, and the topography is characteristic of Brittany. As rivers are mainly fed by groundwater drainage, seepages faces

CROSS-CORRELATION MODELLING OF SURFACE WATER – GROUNDWATER INTERACTION USING THE EXCEL SPREADSHEET APPLICATION

Directory of Open Access Journals (Sweden)

Kristijan Posavec

2017-01-01

Full Text Available Modelling responses of groundwater levels in aquifer systems, which occur as a reaction to changes in aquifer system boundary conditions such as river or stream stages, is commonly being studied using statistical methods, namely correlation, cross-correlation and regression methods. Although correlation and regression analysis tools are readily available in Microsoft Excel, a widely applied spreadsheet industry standard, the cross-correlation analysis tool is missing. As a part of research of groundwater pressure propagation into alluvial aquifer systems of the Sava and Drava/Danube River catchments following river stages rise, focused on estimating groundwater pressure travel times in aquifers, an Excel spreadsheet data analysis application for cross-correlation modelling has been designed and used in modelling surface water – groundwater interaction. Examples of fi eld data from the Zagreb aquifer system and the Kopački rit Nature Park aquifer system are used to illustrate the usefulness of the cross-correlation application.

Wave mode instabilities in a two-stream free-electron laser with a background plasma

International Nuclear Information System (INIS)

Nadrifard, Shabnam; Maraghechi, B; Mohsenpour, T

2013-01-01

A theory is presented for a two-stream free-electron laser (FEL) with a background plasma. A dispersion relation (DR) for the unstable couplings of wave modes is derived using fluid formulation. This DR is solved numerically to find the unstable modes and their growth rate. The effect of the velocity difference of the two electron beams as well as the background plasma on the FEL resonance and the two-stream instability is studied. It is shown that their separate as well as combined effects can increase the growth rates. (paper)

To what extent do long-duration high-volume dam releases influence river-aquifer interactions? A case study in New South Wales, Australia

Science.gov (United States)

Graham, P. W.; Andersen, M. S.; McCabe, M. F.; Ajami, H.; Baker, A.; Acworth, I.

2015-03-01

Long-duration high-volume dam releases are unique anthropogenic events with no naturally occurring equivalents. The impact from such dam releases on a downstream Quaternary alluvial aquifer in New South Wales, Australia, is assessed. It is observed that long-duration (>26 days), high-volume dam releases (>8,000 ML/day average) result in significant variations in river-aquifer interactions. These variations include a flux from the river to the aquifer up to 6.3 m3/day per metre of bank (at distances of up to 330 m from the river bank), increased extent and volume of recharge/bank storage, and a long-term (>100 days) reversal of river-aquifer fluxes. In contrast, during lower-volume events (bank. A groundwater-head prediction model was constructed and river-aquifer fluxes were calculated; however, predicted fluxes from this method showed poor correlation to fluxes calculated using actual groundwater heads. Long-duration high-volume dam releases have the potential to skew estimates of long-term aquifer resources and detrimentally alter the chemical and physical properties of phreatic aquifers flanking the river. The findings have ramifications for improved integrated management of dam systems and downstream aquifers.

Shallow aquifer storage and recovery (SASR): Initial findings from the Willamette Basin, Oregon

Science.gov (United States)

Neumann, P.; Haggerty, R.

2012-12-01

A novel mode of shallow aquifer management could increase the volumetric potential and distribution of groundwater storage. We refer to this mode as shallow aquifer storage and recovery (SASR) and gauge its potential as a freshwater storage tool. By this mode, water is stored in hydraulically connected aquifers with minimal impact to surface water resources. Basin-scale numerical modeling provides a linkage between storage efficiency and hydrogeological parameters, which in turn guides rulemaking for how and where water can be stored. Increased understanding of regional groundwater-surface water interactions is vital to effective SASR implementation. In this study we (1) use a calibrated model of the central Willamette Basin (CWB), Oregon to quantify SASR storage efficiency at 30 locations; (2) estimate SASR volumetric storage potential throughout the CWB based on these results and pertinent hydrogeological parameters; and (3) introduce a methodology for management of SASR by such parameters. Of 3 shallow, sedimentary aquifers in the CWB, we find the moderately conductive, semi-confined, middle sedimentary unit (MSU) to be most efficient for SASR. We estimate that users overlying 80% of the area in this aquifer could store injected water with greater than 80% efficiency, and find efficiencies of up to 95%. As a function of local production well yields, we estimate a maximum annual volumetric storage potential of 30 million m3 using SASR in the MSU. This volume constitutes roughly 9% of the current estimated summer pumpage in the Willamette basin at large. The dimensionless quantity lag #—calculated using modeled specific capacity, distance to nearest in-layer stream boundary, and injection duration—exhibits relatively high correlation to SASR storage efficiency at potential locations in the CWB. This correlation suggests that basic field measurements could guide SASR as an efficient shallow aquifer storage tool.

A quasi-one-dimensional velocity regime of super-thermal electron stream propagation through the solar corona

International Nuclear Information System (INIS)

Levin, B.N.

1984-01-01

The propagation of an inhomogeneous stream of fast electrons through the corona - the type III radio burst source - is considered. It is shown, that the angular spectrum width of plasma waves excited by the stream is defined both by Landau damping by particles of the diffuse component and by damping (in the region of large phase velocities) by particles of the stream itself having large pitch angles. The regime of quasi-one-dimensional diffusion in the velocity space is realized only in the presence of a sufficiently dense diffuse component of super-thermal particles and only for a sufficiently large inhomogeneity scale of the stream. A large scale of the stream space profile is formed, evidently, close to the region of injection of super-thermal particles. It is the result of 'stripping' of part of the electrons from the stream front to its slower part due to essential non-one-dimensionality of the particle diffusion in velocity space. Results obtained may explain, in particular, the evolution of a stream particle angular spectrum in the generation region of type III radio bursts observed by spacecrafts (Lin et al., 1981). For the relatively low energetic part of the stream, the oblique plasma wave stabilization by a diffuse component results in a quasi-one-dimensional regime of diffusion. The latter conserves the beam-like structure of this part of the stream. (orig.)

Evaluating the rate of migration of an uranium deposition front within the Uitenhage Aquifer

CSIR Research Space (South Africa)

Vogel

1999-07-01

Full Text Available of Geochemical Exploration 66 (1999) 269?276 www.elsevier.com/locate/jgeoexp Evaluating the rate of migration of an uranium deposition front within the Uitenhage Aquifer J.C. Vogel a,A.S.Talmaa, T.H.E. Heaton b, J. Kronfeld c,* a Quaternary Dating Research Unit... stream_source_info vogel_1999.pdf.txt stream_content_type text/plain stream_size 18078 Content-Encoding ISO-8859-1 stream_name vogel_1999.pdf.txt Content-Type text/plain; charset=ISO-8859-1 ELSEVIER Journal...

Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas.

Science.gov (United States)

Musgrove, MaryLynn; Opsahl, Stephen P.; Mahler, Barbara J.; Herrington, Chris; Sample, Thomas; Banta, John

2016-01-01

Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO3−) loading to surface and groundwater. We investigate variability and sources of NO3− in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO3− stable isotopes (δ15N and δ18O). These data were augmented by historical data collected from 1937 to 2007. NO3− concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO3− concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO3− concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO3−. These results highlight the vulnerability of karst aquifers to NO3− contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO3−than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a previously

Electron-molecule interactions and their applications

CERN Document Server

Christophorou, L G

1984-01-01

Electron-Molecule Interactions and Their Applications, Volume 2 provides a balanced and comprehensive account of electron-molecule interactions in dilute and dense gases and liquid media. This book consists of six chapters. Chapter 1 deals with electron transfer reactions, while Chapter 2 discusses electron-molecular positive-ion recombination. The electron motion in high-pressure gases and electron-molecule interactions from single- to multiple-collision conditions is deliberated in Chapter 3. In Chapter 4, knowledge on electron-molecule interactions in gases is linked to that on similar proc

Evaluation of long-term water-level declines in basalt aquifers near Mosier, Oregon

Science.gov (United States)

Burns, Erick R.; Morgan, David S.; Lee, Karl K.; Haynes, Jonathan V.; Conlon, Terrence D.

2012-01-01

are not sustainable, (2) well construction practices that have resulted in leakage from aquifers into springs and streams, and (3) reduction in aquifer recharge resulting from long-term climate variations. Historical well construction practices, specifically open, unlined, uncased boreholes that result in cross-connecting (or commingling) multiple aquifers, allow water to flow between these aquifers. Water flowing along the path of least resistance, through commingled boreholes, allows the drainage of aquifers that previously stored water more efficiently. The study area is in the eastern foothills of the Cascade Range in north central Oregon in a transitional zone between the High Cascades to the west and the Columbia Plateau to the east. The 78-square mile (mi2) area is defined by the drainages of three streams - Mosier Creek (51.8 mi2), Rock Creek (13.9 mi2), and Rowena Creek (6.9 mi2) - plus a small area that drains directly to the Columbia River.The three major components of the study are: (1) a 2-year intensive data collection period to augment previous streamflow and groundwater-level measurements, (2) precipitation-runoff modeling of the watersheds to determine the amount of recharge to the aquifer system, and (3) groundwater-flow modeling and analysis to evaluate the cause of groundwater-level declines and to evaluate possible water resource management strategies. Data collection included the following: 1. Water-level measurements were made in 37 wells. Bi-monthly or quarterly measurements were made in 30 wells, and continuous water-level monitoring instruments were installed in 7 wells. The measurements principally were made to capture the seasonal patterns in the groundwater system, and to augment the available long-term record. 2. Groundwater pumping was measured, reported, or estimated from irrigation, municipal and domestic wells. Flowmeters were installed on 74 percent of all high-capacity irrigation wells in the study area. 3. Borehole geophysical data

Groundwater availability in the Crouch Branch and McQueen Branch aquifers, Chesterfield County, South Carolina, 1900-2012

Science.gov (United States)

Campbell, Bruce G.; Landmeyer, James E.

2014-01-01

, totaled about 1,117 square miles. Major types of data used as input to the model included groundwater levels, groundwater-use data, and hydrostratigraphic data, along with estimates and measurements of stream base flows made specifically for this study. The groundwater-flow model was calibrated to groundwater-level and stream base-flow conditions from 1900 to 2012 using 39 stress periods. The model was calibrated with an automated parameter-estimation approach using the computer program PEST, and the model used regularized inversion and pilot points. The groundwater-flow model was calibrated using field data that included groundwater levels that had been collected between 1940 and 2012 from 239 wells and base-flow measurements from 44 locations distributed within the study area. To better understand recharge and inter-aquifer interactions, seven wells were equipped with continuous groundwater-level recording equipment during the course of the study, between 2008 and 2012. These water levels were included in the model calibration process. The observed groundwater levels were compared to the simulated ones, and acceptable calibration fits were achieved. Root mean square error for the simulated groundwater levels compared to all observed groundwater levels was 9.3 feet for the Crouch Branch aquifer and 8.6 feet for the McQueen Branch aquifer. The calibrated groundwater-flow model was then used to calculate groundwater budgets for the entire study area and for two sub-areas. The sub-areas are the Alligator Rural Water and Sewer Company well field near McBee, South Carolina, and the Carolina Sandhills National Wildlife Refuge acquisition boundary area. For the overall model area, recharge rates vary from 56 to 1,679 million gallons per day (Mgal/d) with a mean of 737 Mgal/d over the simulation period (1900–2012). The simulated water budget for the streams and rivers varies from 653 to 1,127 Mgal/d with a mean of 944 Mgal/d. The simulated “storage-in term” ranges from 0

RF-driven ion source with a back-streaming electron dump

Science.gov (United States)

Kwan, Joe; Ji, Qing

2014-05-20

A novel ion source is described having an improved lifetime. The ion source, in one embodiment, is a proton source, including an external RF antenna mounted to an RF window. To prevent backstreaming electrons formed in the beam column from striking the RF window, a back streaming electron dump is provided, which in one embodiment is formed of a cylindrical tube, open at one end to the ion source chamber and capped at its other end by a metal plug. The plug, maintained at the same electrical potential as the source, captures these backstreaming electrons, and thus prevents localized heating of the window, which due to said heating, might otherwise cause window damage.

To what extent do long-duration high-volume dam releases influence river–aquifer interactions? A case study in New South Wales, Australia

KAUST Repository

Graham, Peter W.

2014-11-20

Long-duration high-volume dam releases are unique anthropogenic events with no naturally occurring equivalents. The impact from such dam releases on a downstream Quaternary alluvial aquifer in New South Wales, Australia, is assessed. It is observed that long-duration (>26 days), high-volume dam releases (>8,000 ML/day average) result in significant variations in river–aquifer interactions. These variations include a flux from the river to the aquifer up to 6.3 m3/day per metre of bank (at distances of up to 330 m from the river bank), increased extent and volume of recharge/bank storage, and a long-term (>100 days) reversal of river–aquifer fluxes. In contrast, during lower-volume events (<2,000 ML/day average) the flux was directed from the aquifer to the river at rates of up to 1.6 m3/day per metre of bank. A groundwater-head prediction model was constructed and river–aquifer fluxes were calculated; however, predicted fluxes from this method showed poor correlation to fluxes calculated using actual groundwater heads. Long-duration high-volume dam releases have the potential to skew estimates of long-term aquifer resources and detrimentally alter the chemical and physical properties of phreatic aquifers flanking the river. The findings have ramifications for improved integrated management of dam systems and downstream aquifers.

Electron-excited molecule interactions

International Nuclear Information System (INIS)

Christophorou, L.G.; Tennessee Univ., Knoxville, TN

1991-01-01

In this paper the limited but significant knowledge to date on electron scattering from vibrationally/rotationally excited molecules and electron scattering from and electron impact ionization of electronically excited molecules is briefly summarized and discussed. The profound effects of the internal energy content of a molecule on its electron attachment properties are highlighted focusing in particular on electron attachment to vibrationally/rotationally and to electronically excited molecules. The limited knowledge to date on electron-excited molecule interactions clearly shows that the cross sections for certain electron-molecule collision processes can be very different from those involving ground state molecules. For example, optically enhanced electron attachment studies have shown that electron attachment to electronically excited molecules can occur with cross sections 10 6 to 10 7 times larger compared to ground state molecules. The study of electron-excited molecule interactions offers many experimental and theoretical challenges and opportunities and is both of fundamental and technological significance. 54 refs., 15 figs

The nitrogen cycle in highly urbanized tropical regions and the effect of river-aquifer interactions: The case of Jakarta and the Ciliwung River

Science.gov (United States)

Costa, Diogo; Burlando, Paolo; Priadi, Cindy; Shie-Yui, Liong

2016-09-01

Groundwater is extensively used in Jakarta to compensate for the limited public water supply network. Recent observations show a rise in nitrate (NO3-) levels in the shallow aquifer, thus pointing at a potential risk for public health. The detected levels are still below national and international regulatory limits for drinking water but a strategy is necessary to contain the growing problem. We combine 3 years of available data in the Ciliwung River, the major river flowing through Jakarta, with a distributed river-aquifer interaction model to characterise the impact of urbanisation on the N-cycle of both surface and groundwater systems. Results show that the N-cycle in the river-aquifer system is heterogeneous in space, seasonal dependent (i.e. flow regime) and strongly affected by urban pollution. Results suggest also that although the main sources of N related groundwater pollution are leaking septic tanks, the aquifer interaction with the Ciliwung River may locally have a strong effect on the concentrations. In the general context of pollution control in urban areas, this study demonstrates how advanced process-based models can be efficiently used in combination with field measurements to bring new insights into complex contamination problems. These are essential for more effective and integrated management of water quality in river-aquifer systems.

Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

Energy Technology Data Exchange (ETDEWEB)

Musgrove, M., E-mail: mmusgrov@usgs.gov [U.S. Geological Survey, 1505 Ferguson Lane, Austin, TX 78754 (United States); Opsahl, S.P. [U.S. Geological Survey, 5563 DeZavala, Ste. 290, San Antonio, TX 78249 (United States); Mahler, B.J. [U.S. Geological Survey, 1505 Ferguson Lane, Austin, TX 78754 (United States); Herrington, C. [City of Austin Watershed Protection Department, Austin, TX 78704 (United States); Sample, T.L. [U.S. Geological Survey, 19241 David Memorial Dr., Ste. 180, Conroe, TX 77385 (United States); Banta, J.R. [U.S. Geological Survey, 5563 DeZavala, Ste. 290, San Antonio, TX 78249 (United States)

2016-10-15

Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO{sub 3}{sup −}) loading to surface and groundwater. We investigate variability and sources of NO{sub 3}{sup −} in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO{sub 3}{sup −} stable isotopes (δ{sup 15}N and δ{sup 18}O). These data were augmented by historical data collected from 1937 to 2007. NO{sub 3}{sup −} concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO{sub 3}{sup −} concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO{sub 3}{sup −} concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO{sub 3}{sup −}. These results highlight the vulnerability of karst aquifers to NO{sub 3}{sup −} contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO{sub 3}{sup −} than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates

Source, variability, and transformation of nitrate in a regional karst aquifer: Edwards aquifer, central Texas

International Nuclear Information System (INIS)

Musgrove, M.; Opsahl, S.P.; Mahler, B.J.; Herrington, C.; Sample, T.L.; Banta, J.R.

2016-01-01

Many karst regions are undergoing rapid population growth and expansion of urban land accompanied by increases in wastewater generation and changing patterns of nitrate (NO 3 − ) loading to surface and groundwater. We investigate variability and sources of NO 3 − in a regional karst aquifer system, the Edwards aquifer of central Texas. Samples from streams recharging the aquifer, groundwater wells, and springs were collected during 2008–12 from the Barton Springs and San Antonio segments of the Edwards aquifer and analyzed for nitrogen (N) species concentrations and NO 3 − stable isotopes (δ 15 N and δ 18 O). These data were augmented by historical data collected from 1937 to 2007. NO 3 − concentrations and discharge data indicate that short-term variability (days to months) in groundwater NO 3 − concentrations in the Barton Springs segment is controlled by occurrence of individual storms and multi-annual wet-dry cycles, whereas the lack of short-term variability in groundwater in the San Antonio segment indicates the dominance of transport along regional flow paths. In both segments, longer-term increases (years to decades) in NO 3 − concentrations cannot be attributed to hydrologic conditions; rather, isotopic ratios and land-use change indicate that septic systems and land application of treated wastewater might be the source of increased loading of NO 3 − . These results highlight the vulnerability of karst aquifers to NO 3 − contamination from urban wastewater. An analysis of N-species loading in recharge and discharge for the Barton Springs segment during 2008–10 indicates an overall mass balance in total N, but recharge contains higher concentrations of organic N and lower concentrations of NO 3 − than does discharge, consistent with nitrification of organic N within the aquifer and consumption of dissolved oxygen. This study demonstrates that subaqueous nitrification of organic N in the aquifer, as opposed to in soils, might be a

Air-electron stream interactions during magnetic resonance IGRT. Skin irradiation outside the treatment field during accelerated partial breast irradiation

Energy Technology Data Exchange (ETDEWEB)

Park, Jong Min [Seoul National University Hospital, Department of Radiation Oncology, Seoul (Korea, Republic of); Seoul National University Hospital, Biomedical Research Institute, Seoul (Korea, Republic of); Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Advanced Institutes of Convergence Technology, Robotics Research Laboratory for Extreme Environments, Suwon (Korea, Republic of); Shin, Kyung Hwan; Wu, Hong-Gyun [Seoul National University Hospital, Department of Radiation Oncology, Seoul (Korea, Republic of); Seoul National University Hospital, Biomedical Research Institute, Seoul (Korea, Republic of); Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University College of Medicine, Department of Radiation Oncology, Seoul (Korea, Republic of); Kim, Jung-in; Park, So-Yeon; Kim, Jin Ho [Seoul National University Hospital, Department of Radiation Oncology, Seoul (Korea, Republic of); Seoul National University Hospital, Biomedical Research Institute, Seoul (Korea, Republic of); Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Jeon, Seung Hyuck [Seoul National University Hospital, Department of Radiation Oncology, Seoul (Korea, Republic of); Choi, Noorie [Seoul National University College of Medicine, Department of Radiation Oncology, Seoul (Korea, Republic of)

2018-01-15

To investigate and to prevent irradiation outside the treatment field caused by an electron stream in the air generated by the magnetic field during magnetic resonance image-guided accelerated partial breast irradiation (APBI). In all, 20 patients who received APBI with a magnetic resonance image-guided radiation therapy (MR-IGRT) system were prospectively studied. The prescription dose was 38.5 Gy in 10 fractions of 3.85 Gy and delivered with a tri-cobalt system (the ViewRay system). For each patient, primary plans were delivered for the first five fractions and modified plans with different gantry angles from those of the primary plan (in-treatment plans) were delivered for the remaining five fractions to reduce the skin dose. A 1 cm thick bolus was placed in front of the patient's jaw, ipsilateral shoulder, and arm to shield them from the electron stream. Radiochromic EBT3 films were attached to the front (towards the breast) and back (towards the head) of the bolus during treatment. Correlations between the measured values and the tumor locations, treatment times, and tumor sizes were investigated. For a single fraction delivery, the average areas of the measured isodoses of 14% (0.54 Gy), 12% (0.46 Gy), and 10% (0.39 Gy) at the front of the boluses were as large as 3, 10.4, and 21.4 cm{sup 2}, respectively, whereas no significant dose could be measured at the back of the boluses. Statistically significant but weak correlations were observed between the measured values and the treatment times. During radiotherapy for breast cancer with an MR-IGRT system, the patient must be shielded from electron streams in the air generated by the interaction of the magnetic field with the beams of the three-cobalt treatment unit to avoid unwanted irradiation of the skin outside the treatment field. (orig.) [German] Beim Einsatz eines Magnetresonanztomographie(MRT)-gefuehrten Bestrahlungsgeraets kann durch die Wechselwirkung von Magnetfeld und Strahlenquelle unerwuenscht

Research on interactions of plasma streams with CFC targets in the Rod Plasma Injector facility

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Zaloga Dobromil R.

2016-06-01

Full Text Available This paper present results of optical spectroscopy studies of interactions of intense plasma streams with a solid target made of carbon fibre composite (CFC. The experiments were carried out within the Rod Plasma Injector (RPI IBIS facility. The optical measurements were performed first for a freely propagating plasma stream in order to determine the optimal operational parameters of this facility. Optical emission spectra (OES were recorded for different operational modes of the RPI IBIS device, and spectral lines were identified originating from the working gas (deuterium as well as some lines from the electrode material (molybdenum. Subsequently, optical measurements of plasma interacting with the CFC target were performed. In the optical spectra recorded with the irradiated CFC samples, in addition to deuterium and molybdenum lines, many carbon lines, which enabled to estimate erosion of the investigated targets, were recorded. In order to study changes in the irradiated CFC samples, their surfaces were analysed (before and after several plasma discharges by means of scanning electron microscope (SEM and energy dispersive spectroscopy (EDS techniques. The analysis of the obtained SEM images showed that the plasma irradiation induces noticeable changes in the surface morphology, for example vaporisation of some carbon fibres and formation of microcracks. The obtained EDS images showed that upon the irradiated target surface, some impurity ions are also deposited, particularly molybdenum ions from the applied electrodes.

Aquifer/aquitard interfaces: mixing zones that enhance biogeochemical reactions

Science.gov (United States)

McMahon, P. B.

2001-01-01

Several important biogeochemical reactions are known to occur near the interface between aquifer and aquitard sediments. These reactions include O2 reduction; denitrification; and Fe3+, SO42-, and CO2 (methanogenesis) reduction. In some settings, these reactions occur on the aquitard side of the interface as electron acceptors move from the aquifer into the electron-donor-enriched aquitard. In other settings, these reactions occur on the aquifer side of the interface as electron donors move from the aquitard into the electron-acceptor-enriched, or microorganism-enriched, aquifer. Thus, the aquifer/aquitard interface represents a mixing zone capable of supporting greater microbial activity than either hydrogeologic unit alone. The extent to which biogeochemical reactions proceed in the mixing zone and the width of the mixing zone depend on several factors, including the abundance and solubility of electron acceptors and donors on either side of the interface and the rate at which electron acceptors and donors react and move across the interface. Biogeochemical reactions near the aquifer/aquitard interface can have a substantial influence on the chemistry of water in aquifers and on the chemistry of sediments near the interface. Résumé. Il se produit au voisinage de l'interface entre les aquifères et les imperméables plusieurs réactions biogéochimiques importantes. Il s'agit des réactions de réduction de l'oxygène, de la dénitrification et de la réduction de Fe3+, SO42- et CO2 (méthanogenèse). Dans certaines situations, ces réactions se produisent du côté imperméable de l'interface, avec des accepteurs d'électrons qui vont de l'aquifère vers l'imperméable riche en donneurs d'électrons. Dans d'autres situations, ces réactions se produisent du côté aquifère de l'interface, avec des donneurs d'électrons qui se déplacent de l'imperméable vers l'aquifère riche en accepteurs d'électrons ou en microorganismes. Ainsi, l'interface aquif

Interaction between counter-streaming ion-acoustic solitons and the Langmuir waves

International Nuclear Information System (INIS)

Basovich, A.Ya.; Gromov, E.M.; Talanov, V.I.

1984-01-01

The interaction between strong counter-streaming ion-acoustic solitons and the Langmuir waves is considered. At first the Langmuir waves spectrum transformation by counter-streaming ion-acoustic solutions of a preset amplitude e has been found. An increase in the frequency and number of the Langmuir waves due to the Doppler effect in the course of multiple reflection from the f front soliton slope has been determined and the wave number range in which the confinement of the Langmuir waves by counter-streaning solitons is possible has s been found. It is shown that the time of the Langmuir wave transformation into the short-wave region under the effect of the counter-streaming soliton may y be short as compared with the time of the Langmuir wave diffusion into the Landau damping region under the effect of random fields of ion-acoustic waves. In the adiabatic fpproximation changes in the counter-streaming ion acoustic parameters of solitons owing to the Langmuir waves have been

Detectability of weakly interacting massive particles in the Sagittarius dwarf tidal stream

International Nuclear Information System (INIS)

Freese, Katherine; Gondolo, Paolo; Newberg, Heidi Jo

2005-01-01

Tidal streams of the Sagittarius dwarf spheroidal galaxy (Sgr) may be showering dark matter onto the solar system and contributing ∼(0.3-23)% of the local density of our galactic halo. If the Sagittarius galaxy contains dark matter in the form of weakly interacting massive particles (WIMPs), the extra contribution from the stream gives rise to a steplike feature in the energy recoil spectrum in direct dark matter detection. For our best estimate of stream velocity (300 km/s) and direction (the plane containing the Sgr dwarf and its debris), the count rate is maximum on June 28 and minimum on December 27 (for most recoil energies), and the location of the step oscillates yearly with a phase opposite to that of the count rate. In the CDMS experiment, for 60 GeV WIMPs, the location of the step oscillates between 35 and 42 keV, and for the most favorable stream density, the stream should be detectable at the 11σ level in four years of data with 10 keV energy bins. Planned large detectors like XENON, CryoArray, and the directional detector DRIFT may also be able to identify the Sgr stream

Electron-electron interaction in p-SiGe/Ge quantum wells

International Nuclear Information System (INIS)

Roessner, Benjamin; Kaenel, Hans von; Chrastina, Daniel; Isella, Giovanni; Batlogg, Bertram

2005-01-01

The temperature dependent magnetoresistance of high mobility p-SiGe/Ge quantum wells is studied with hole densities ranging from 1.7 to 5.9 x 10 11 cm -2 . At magnetic fields below the onset of quantum oscillations that reflect the high mobility values (up to 75000 cm 2 /Vs), we observe the clear signatures of electron-electron interaction. We compare our experiment with the theory of electron-electron interaction including the Zeeman band splitting. The observed magnetoresistance is well explained as a superposition of band structure induced positive magnetoresistance and the negative magntoresistance due to the electron-electron interaction effect

Modeling Groundwater-Surface Water Interaction and Contaminant Transport of Chlorinated Solvent Contaminated Site

Science.gov (United States)

Yimer Ebrahim, Girma; Jonoski, Andreja; van Griensven, Ann; Dujardin, Juliette; Baetelaan, Okke; Bronders, Jan

2010-05-01

Chlorinated-solvent form one of the largest groups of environmental chemicals. Their use and misuse in industry have lead to a large entry of these chemicals into the environment, resulting in widespread dissemination and oftentimes environmental contamination. Chlorinated solvent contamination of groundwater resources has been widely reported. For instance, there has been much interest in the assessment of these contaminant levels and their evolutions with time in the groundwater body below the Vilvoorde-Machelen industrial area (Belgium). The long industrial history of the area has lead to complex patterns of pollution from multiple sources and the site has been polluted to the extent that individual plumes are not definable any more. Understanding of groundwater/surface water interaction is a critical component for determining the fate of contaminant both in streams and ground water due to the fact that groundwater and surface water are in continuous dynamic interaction in the hydrologic cycle. The interaction has practical consequences in the quantity and quality of water in either system in the sense that depletion and/or contamination of one of the system will eventually affect the other one. The transition zone between a stream and its adjacent aquifer referred to as the hyporheic zone plays a critical role in governing contaminant exchange and transformation during water exchange between the two water bodies. The hyporheic zone of Zenne River ( the main receptor ) is further complicated due to the fact that the river banks are artificially trained with sheet piles along its reach extending some 12 m below the surface. This study demonstrates the use of MODFLOW, a widely used modular three-dimensional block-centred finite difference, saturated flow model for simulating the flow and direction of movement of groundwater through aquifer and stream-aquifer interaction and the use of transport model RT3D, a three-dimensional multi-species reactive transport model

Volcanic aquifers of Hawai‘i—Hydrogeology, water budgets, and conceptual models

Science.gov (United States)

Izuka, Scot K.; Engott, John A.; Rotzoll, Kolja; Bassiouni, Maoya; Johnson, Adam G.; Miller, Lisa D.; Mair, Alan

2016-06-13

Hawai‘i’s aquifers have limited capacity to store fresh groundwater because each island is small and surrounded by saltwater. Saltwater also underlies much of the fresh groundwater. Fresh groundwater resources are, therefore, particularly vulnerable to human activity, short-term climate cycles, and long-term climate change. Availability of fresh groundwater for human use is constrained by the degree to which the impacts of withdrawal—such as lowering of the water table, saltwater intrusion, and reduction in the natural discharge to springs, streams, wetlands, and submarine seeps—are deemed acceptable. This report describes the hydrogeologic framework, groundwater budgets (inflows and outflows), conceptual models of groundwater occurrence and movement, and the factors limiting groundwater availability for the largest and most populated of the Hawaiian Islands—Kaua‘i, O‘ahu, Maui, and Hawai‘i Island.The bulk of each of Hawai‘i’s islands is built of many thin lava flows erupted from shield volcanoes; the great piles of lava flows form highly permeable aquifers. In some areas, low-permeability dikes cutting across the lava flows, or low-permeability ash and soil horizons interlayered with the lava flows, can substantially alter groundwater flow. On some islands, sedimentary rocks form thick semiconfining coastal-plain deposits, locally known as caprock, that impede natural groundwater discharge to the ocean. In some regions, thick lava flows that ponded in preexisting depressions form aquifers that are much less permeable than aquifers formed by thin lava flows.Fresh groundwater inflow to Hawai‘i’s aquifers comes from recharge. For predevelopment conditions (1870), estimates of groundwater recharge from this study are 871, 675, 1,279, and 5,291 million gallons per day (Mgal/d) for Kaua‘i, O‘ahu, Maui, and Hawai‘i Island, respectively. Estimates of recharge for recent conditions (2010 land cover and 1978–2007 rainfall for Kaua‘i, O�

Karst connections between unconfined aquifers and the Upper Floridan aquifer in south Georgia: geophysical evidence and hydrogeological models

Science.gov (United States)

Thieme, D. M.; Denizman, C.

2011-12-01

Buried karst features in sedimentary rocks of the south Georgia Coastal Plain present a challenge for hydrogeological models of recharge and confined flow within the underlying Upper Floridan aquifer. The Withlacoochee River, the trunk stream for the area, frequently disappears into subsurface caverns as it makes its way south to join the Suwannee River in northern Florida. The Withlacoochee also receives inputs from small ponds and bays which in turn receive spring and seep groundwater inputs. We have mapped karst topography at the "top of rock" using ground-penetrating radar (GPR). Up to seven meters of relief is indicated for the paleotopography on Miocene to Pliocene rocks, contrasting with the more subdued relief of the modern landscape. Current stratigraphic and hydrogeological reconstructions do not incorporate this amount of relief or lateral variation in the confining beds. One "pipe" which is approximately four meters in diameter is being mapped in detail. We have field evidence at this location for rapid movement of surficial pond and river water with a meteoric signature through several separate strata of sedimentary rock into an aquifer in the Hawthorn formation. We use our geophysical and hydrological field evidence to constrain quantitative hydrogeological models for the flow rates into and out of both this upper aquifer and the underlying Upper Floridan aquifer, which is generally considered to be confined by the clays of the Hawthorn.

Mechanism and rate of denitrification in an agricultural watershed: Electron and mass balance along groundwater flow paths

Science.gov (United States)

Tesoriero, Anthony J.; Liebscher, Hugh; Cox, Stephen E.

2000-01-01

The rate and mechanism of nitrate removal along and between groundwater flow paths were investigated using a series of well nests screened in an unconfined sand and gravel aquifer. Intensive agricultural activity in this area has resulted in nitrate concentrations in groundwater often exceeding drinking water standards. Both the extent and rate of denitrification varied depending on the groundwater flow path. While little or no denitrification occurred in much of the upland portions of the aquifer, a gradual redox gradient is observed as aerobic upland groundwater moves deeper in the aquifer. In contrast, a sharp shallow redox gradient is observed adjacent to a third‐order stream as aerobic groundwater enters reduced sediments. An essentially complete loss of nitrate concurrent with increases in excess N2 provide evidence that denitrification occurs as groundwater enters this zone. Electron and mass balance calculations suggest that iron sulfide (e.g., pyrite) oxidation is the primary source of electrons for denitrification. Denitrification rate estimates were based on mass balance calculations using nitrate and excess N2 coupled with groundwater travel times. Travel times were determined using a groundwater flow model and were constrained by chlorofluorocarbon‐based age dates. Denitrification rates were found to vary considerably between the two areas where denitrification occurs. Denitrification rates in the deep, upland portions of the aquifer were found to range from from 1.0 to 2.7 mM of N per year. Potential denitrification rates in groundwater adjacent to the stream may be much faster, with rates up to 140 mM per year based on an in situ experiment conducted in this zone.

Using hydraulic head, chloride and electrical conductivity data to distinguish between mountain-front and mountain-block recharge to basin aquifers

Directory of Open Access Journals (Sweden)

E. Bresciani

2018-03-01

Full Text Available Numerous basin aquifers in arid and semi-arid regions of the world derive a significant portion of their recharge from adjacent mountains. Such recharge can effectively occur through either stream infiltration in the mountain-front zone (mountain-front recharge, MFR or subsurface flow from the mountain (mountain-block recharge, MBR. While a thorough understanding of recharge mechanisms is critical for conceptualizing and managing groundwater systems, distinguishing between MFR and MBR is difficult. We present an approach that uses hydraulic head, chloride and electrical conductivity (EC data to distinguish between MFR and MBR. These variables are inexpensive to measure, and may be readily available from hydrogeological databases in many cases. Hydraulic heads can provide information on groundwater flow directions and stream–aquifer interactions, while chloride concentrations and EC values can be used to distinguish between different water sources if these have a distinct signature. Such information can provide evidence for the occurrence or absence of MFR and MBR. This approach is tested through application to the Adelaide Plains basin, South Australia. The recharge mechanisms of this basin have long been debated, in part due to difficulties in understanding the hydraulic role of faults. Both hydraulic head and chloride (equivalently, EC data consistently suggest that streams are gaining in the adjacent Mount Lofty Ranges and losing when entering the basin. Moreover, the data indicate that not only the Quaternary aquifers but also the deeper Tertiary aquifers are recharged through MFR and not MBR. It is expected that this finding will have a significant impact on the management of water resources in the region. This study demonstrates the relevance of using hydraulic head, chloride and EC data to distinguish between MFR and MBR.

Estimation of Hydraulic Parameters and Aquifer Properties for a Managed Aquifer Recharge Pilot Study in The Lower Mississippi River Basin

Science.gov (United States)

Ozeren, Y.; Rigby, J.; Holt, R. M.

2017-12-01

Mississippi River Valley Alluvial Aquifer (MRVAA) is the major irrigation water resource in the in the lower Mississippi River basin. MRVAA has been significantly depleted in the last two decades due to excessive pumping. A wide range of measures to ensure sustainable groundwater supply in the region is currently under investigation. One of the possible solution under consideration is to use Managed Aquifer Recharge (MAR) by artificial recharge. The proposed artificial recharge technique in this study is to collect water through bank filtration, transfer water via pipeline to the critically low groundwater areas by a set of injection wells. A pilot study in the area is underway to investigate the possibility of artificial recharge in the area. As part of this study, a pumping test was carried out on an existing irrigation well along banks of Tallahatchie River near Money, MS. Geophysical surveys were also carried out in the pilot study area. Hydraulic response of the observation wells was used to determine stream bed conductance and aquifer parameters. The collected hydraulic parameters and aquifer properties will provide inputs for small-scale, high-resolution engineering model for abstraction-injection hydraulics along river. Here, preliminary results of the pilot study is presented.

Influence of geometry of the discharge interval on distribution of ion and electron streams at surface of the Penning source cathode

International Nuclear Information System (INIS)

Egiazaryan, G.A.; Khachatrian, Zh.B.; Badalyan, E.S.; Ter-Gevorgyan, E.I.; Hovhannisyan, V.N.

2006-01-01

In the discharge of oscillating electrons, the mechanism of the processes, which controls the distribution of the ion and electron streams over the cathode surface, is investigated experimentally. The influence of the length of the discharge interval on value and distribution of the ion and electron streams is analyzed. The distribution both of ion and electron streams at the cathode surface is determined at different conditions of the discharge. It is shown that for given values of the anode diameter d a =31 mm and the gas pressure P=5x10 -5 Torr, the intensive stream of positive ions falls entirely on the cathode central area in the whole interval of the anode length variation (l a =1-11 cm). At the cathode, the ion current reaches the maximal value at a certain (optimal) value of the anode length that, in turn, depends on the anode voltage U a . The intensive stream of longitudinal electrons forms in the short anodes only (l a =2.5-3.5 cm) and depending on the choice of the discharge regime, may fall both on central and middle parts of the cathode

Combined phenomena of beam-beam and beam-electron cloud interactionsin circular e^{+}e^{-} colliders

Directory of Open Access Journals (Sweden)

Kazuhito Ohmi

2002-10-01

Full Text Available An electron cloud causes various effects in high intensity positron storage rings. The positron beam and the electron cloud can be considered a typical two-stream system with a certain plasma frequency. Beam-beam interaction is another important effect for high luminosity circular colliders. Colliding two beams can be considered as a two-stream system with another plasma frequency. We study the combined phenomena of the beam-electron cloud and beam-beam interactions from a viewpoint of two complex two-stream effects with two plasma frequencies.

Biotic interactions modify multiple-stressor effects on juvenile brown trout in an experimental stream food web.

Science.gov (United States)

Bruder, Andreas; Salis, Romana K; Jones, Peter E; Matthaei, Christoph D

2017-09-01

Agricultural land use results in multiple stressors affecting stream ecosystems. Flow reduction due to water abstraction, elevated levels of nutrients and chemical contaminants are common agricultural stressors worldwide. Concurrently, stream ecosystems are also increasingly affected by climate change. Interactions among multiple co-occurring stressors result in biological responses that cannot be predicted from single-stressor effects (i.e. synergisms and antagonisms). At the ecosystem level, multiple-stressor effects can be further modified by biotic interactions (e.g. trophic interactions). We conducted a field experiment using 128 flow-through stream mesocosms to examine the individual and combined effects of water abstraction, nutrient enrichment and elevated levels of the nitrification inhibitor dicyandiamide (DCD) on survival, condition and gut content of juvenile brown trout and on benthic abundance of their invertebrate prey. Flow velocity reduction decreased fish survival (-12% compared to controls) and condition (-8% compared to initial condition), whereas effects of nutrient and DCD additions and interactions among these stressors were not significant. Negative effects of flow velocity reduction on fish survival and condition were consistent with effects on fish gut content (-25% compared to controls) and abundance of dominant invertebrate prey (-30% compared to controls), suggesting a negative metabolic balance driving fish mortality and condition decline, which was confirmed by structural equation modelling. Fish mortality under reduced flow velocity increased as maximal daily water temperatures approached the upper limit of their tolerance range, reflecting synergistic interactions between these stressors. Our study highlights the importance of indirect stressor effects such as those transferred through trophic interactions, which need to be considered when assessing and managing fish populations and stream food webs in multiple-stressor situations

The effect of electron-electron interaction induced dephasing on electronic transport in graphene nanoribbons

Energy Technology Data Exchange (ETDEWEB)

Kahnoj, Sina Soleimani; Touski, Shoeib Babaee [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Pourfath, Mahdi, E-mail: pourfath@ut.ac.ir, E-mail: pourfath@iue.tuwien.ac.at [School of Electrical and Computer Engineering, University of Tehran, P.O. Box 14395-515, Tehran (Iran, Islamic Republic of); Institute for Microelectronics, TU Wien, Gusshausstrasse 27–29/E360, 1040 Vienna (Austria)

2014-09-08

The effect of dephasing induced by electron-electron interaction on electronic transport in graphene nanoribbons is theoretically investigated. In the presence of disorder in graphene nanoribbons, wavefunction of electrons can set up standing waves along the channel and the conductance exponentially decreases with the ribbon's length. Employing the non-equilibrium Green's function formalism along with an accurate model for describing the dephasing induced by electron-electron interaction, we show that this kind of interaction prevents localization and transport of electrons remains in the diffusive regime where the conductance is inversely proportional to the ribbon's length.

Effective electron-electron and electron-phonon interactions in the Hubbard-Holstein model

International Nuclear Information System (INIS)

Aprea, G.; Di Castro, C.; Grilli, M. . E-mail marco.grilli@roma1.infn.it; Lorenzana, J.

2006-01-01

We investigate the interplay between the electron-electron and the electron-phonon interaction in the Hubbard-Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron-phonon effective coupling and, conversely, the effect of phonons in the effective electron-electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron-electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed

Hydrology of aquifer systems in the Memphis area, Tennessee

Science.gov (United States)

Criner, James H.; Sun, P-C. P.; Nyman, Dale J.

1964-01-01

. The average rate of depletion of storage in each aquifer since pumping began is about 1 mgd. Most of the recharge to the '500-foot' and '1,400-foot' sands occurs in outcrop areas about 30-80 miles east of Memphis. Also, water leaks from the terrace deposits to the '500-foot' sand in some places, and there may be some leakage from streams where the confining clay is thin or is breached by faults or streams. The quality of water from both the principal aquifers is very good. Iron, carbon dioxide, and hydrogen sulfide are the only constituents found in undesirable quantities. Water from the terrace deposits is hard but generally contains less iron and carbon dioxide than water from either of the principal aquifers. The hydraulic characteristics of both aquifers were determined by pumping tests and by applying the knowledge of the geology o# the area; these characteristics indicate that the aquifers are capable of producing more water than is currently being pumped from them. The '500-foot' sand will produce more water per unit decline of water level than will the '1,400-foot' sand. There appears to be no reason why the development of water supplies from both aquifers should not continue, but well spacing will remain a factor which could affect future development. Greater well spacing will tend to prolong the useful life of a well and the aquifers.

Stream seepage and groundwater levels, Wood River Valley, south-central Idaho, 2012-13

Science.gov (United States)

Bartolino, James R.

2014-01-01

Stream discharge and water levels in wells were measured at multiple sites in the Wood River Valley, south-central Idaho, in August 2012, October 2012, and March 2013, as a component of data collection for a groundwater-flow model of the Wood River Valley aquifer system. This model is a cooperative and collaborative effort between the U.S. Geological Survey and the Idaho Department of Water Resources. Stream-discharge measurements for determination of seepage were made during several days on three occasions: August 27–28, 2012, October 22–24, 2012, and March 27–28, 2013. Discharge measurements were made at 49 sites in August and October, and 51 sites in March, on the Big Wood River, Silver Creek, their tributaries, and nearby canals. The Big Wood River generally gains flow between the Big Wood River near Ketchum streamgage (13135500) and the Big Wood River at Hailey streamgage (13139510), and loses flow between the Hailey streamgage and the Big Wood River at Stanton Crossing near Bellevue streamgage (13140800). Shorter reaches within these segments may differ in the direction or magnitude of seepage or may be indeterminate because of measurement uncertainty. Additional reaches were measured on Silver Creek, the North Fork Big Wood River, Warm Springs Creek, Trail Creek, and the East Fork Big Wood River. Discharge measurements also were made on the Hiawatha, Cove, District 45, Glendale, and Bypass Canals, and smaller tributaries to the Big Wood River and Silver Creek. Water levels in 93 wells completed in the Wood River Valley aquifer system were measured during October 22–24, 2012; these wells are part of a network established by the U.S. Geological Survey in 2006. Maps of the October 2012 water-table altitude in the unconfined aquifer and the potentiometric-surface altitude of the confined aquifer have similar topology to those on maps of October 2006 conditions. Between October 2006 and October 2012, water-table altitude in the unconfined aquifer rose by

Availability of streamflow for recharge of the basal aquifer in the Pearl Harbor area, Hawaii

Science.gov (United States)

Hirashima, George Tokusuke

1971-01-01

The Pearl Harbor area is underlain by an extensive basal aquifer that contains large supplies of fresh water. Because of the presence of a cap rock composed of sedimentary material that is less permeable than the basaltic lava of the basal aquifer, seaward movement of ground water is retarded. The cap rock causes the basal water to stand at a high level; thus, the lens of fresh water that floats on sea water is thick. Discharge from the basal ground-water body, which includes pumpage from wells and shafts, averaged 250 million gallons per day during 1931-65. Because the water level in the basal aquifer did not decline progressively, recharge to the ground-water body must have been approximately equal to discharge. Although pumping for agricultural use has decreased since 1931, net ground-water discharge has increased because of a large increase in pumping for urban use. Substitution of ground water for surface water in the irrigation of sugarcane has also contributed to a net increase in ground-water discharge. The development of Mililani Town will further increase discharge. The increase in ground-water discharge may cause an increase in chloride content of the water pumped from wells near the shore of Pearl Harbor unless the increased discharge is balanced by increased recharge to the local aquifer. The aquifer is recharged by direct infiltration and deep percolation of rain, principally in the high forested area, by infiltration and percolation of irrigation water applied in excess of plant requirements, by seepage of water through streambeds, and possibly by ground-water inflow from outside the area. Recharge is greatest in the uplands, where rainfall is heavy and where much infiltration takes place before rainwater collects in the middle and lower reaches of stream channels. Once water collects in and saturates the alluvium of stream channels, additional inflow to the streams will flow out to sea, only slightly decreased by seepage. Average annual direct

Role of electron-electron interactions in the RKKY theory of magnetism

International Nuclear Information System (INIS)

Cooke, J.F.

1978-10-01

The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional perturbation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode

Role of electron-electron interactions in the RKKY theory of magnetism

International Nuclear Information System (INIS)

Cooke, J.F.

1979-01-01

The theory of magnetism in heavy rare earth metals is based on the RKKY theory. In this formalism the indirect exchange interaction between the local 4f spins is mediated by the conduction electrons. When carried to second order in the 4f-conduction electron interaction, traditional pertubation theory leads to a Heisenberg-like interaction between the local spins which depends on the electronic energy bands and 4f-conduction electron exchange matrix elements. This derivation neglects the detailed behavior of electron-electron interaction within the conduction band, which is known to be important in metallic systems. By using an equation of motion method, an expression for the inelastic neutron scattering cross-section has been derived which includes, in an approximate way, this electron-electron interaction. The results of this calculation indicate that spin-wave peaks can be broadened and shifted if the spin-wave band lies near the conduction electron Stoner continuum. The origin of this effect is similar to that found in itinerant electron systems where the spin-wave band actually intersects the Stoner continuum, resulting in the disappearance of the spin-wave mode

Water-Rock Interactions in the Peridotite Aquifer of the Oman-UAE Ophiolite: Strontium Isotopic Ratio and Geochemical Evolution of Groundwater

Science.gov (United States)

Bompard, Nicolas; Matter, Juerg; Teagle, Damon

2016-04-01

The peridotite aquifer in Wadi Tayin, Sultanate of Oman, is a perfect example of natural carbonation of ultramafic rocks. In situ mineral carbonation is considered the most safest and permanent option of CO2 Capture and Sequestration (CCS). However, the process itself is yet to be characterised and a better understanding of the mechanisms involved in natural mineral carbonation is needed before geo-engineering it. We used the 87Sr/86Sr system to follow the water-rock interactions along the groundwater flowpath in the peridotite aquifer and to determine the sources of divalent cations (Mg2+, Ca2+) required for mineral carbonation. The Sr-isotope data of groundwater show that the aquifer rocks are the main source for divalent cations (Mg2+, Ca2+ and Sr2+) and secondary carbonates are their main sink. The groundwater 87Sr/86Sr ratio evolves with its pH: from 87Sr/86Sr = 0.7087 (n=3) to 0.7082 (n=8) between pH 7 and 8, and from 0.7086 (n=6) at pH 9 to 0.07075 (n=9) at pH 11. This evolution seems to support a two-step model for the water-rock interactions in the peridotite aquifer. From pH 7 to 8, secondary Ca-carbonate precipitation buffers the pH rise resulting from peridotite serpentinisation. From pH 9 to 11, peridotite serpentinisation drives the pH to alkaline condition. The change from a Mg-rich to a Ca-rich groundwater at pH 9 seems to confirm the two-step model.

A stable production of intense electron beam plasma with ion back stream

International Nuclear Information System (INIS)

Uramoto, Johshin.

1975-12-01

An intense electron beam is extracted without space charge limit from a dc plasma source along a magnetic field. The beam space charge is neutralized stably through back streaming of self-ionized ions from the beam extracting anode region where a neutral gas is fed locally. In Appendix I, a space charge free electron gun is designed under this neutralization method. In Appendix II, a dynamic discharge through a series resistance is described, where an operative mechanism of the well-known TP-D plasma is clarified. (auth.)

Dispersion relation and growth in a two-stream free electron laser with helical wiggler and ion channel guiding

International Nuclear Information System (INIS)

Mehdian, Hassan; Abbasi, Negar

2008-01-01

A linear theory of two-stream free electron laser (FEL) with helical wiggler and ion channel guiding is presented. The dispersion relation is obtained with the help of fluid theory and the growth rate is analyzed through the numerical solutions. The considerable enhancement of the growth rate is demonstrated due to the two-stream instability and continuous tuning of peak growth rate ratio, two-stream FEL compared to single-stream FEL, in terms of varying the ion channel frequency is illustrated

Hydrogeology and water quality of the stratified-drift aquifer in the Pony Hollow Creek Valley, Tompkins County, New York

Science.gov (United States)

Bugliosi, Edward F.; Miller, Todd S.; Reynolds, Richard J.

2014-01-01

The lithology, areal extent, and the water-table configuration in stratified-drift aquifers in the northern part of the Pony Hollow Creek valley in the Town of Newfield, New York, were mapped as part of an ongoing aquifer mapping program in Tompkins County. Surficial geologic and soil maps, well and test-boring records, light detection and ranging (lidar) data, water-level measurements, and passive-seismic surveys were used to map the aquifer geometry, construct geologic sections, and determine the depth to bedrock at selected locations throughout the valley. Additionally, water-quality samples were collected from selected streams and wells to characterize the quality of surface and groundwater in the study area. Sedimentary bedrock underlies the study area and is overlain by unstratified drift (till), stratified drift (glaciolacustrine and glaciofluvial deposits), and recent post glacial alluvium. The major type of unconsolidated, water-yielding material in the study area is stratified drift, which consists of glaciofluvial sand and gravel, and is present in sufficient amounts in most places to form an extensive unconfined aquifer throughout the study area, which is the source of water for most residents, farms, and businesses in the valleys. A map of the water table in the unconfined aquifer was constructed by using (1) measurements made between the mid-1960s through 2010, (2) control on the altitudes of perennial streams at 10-foot contour intervals from lidar data collected by Tompkins County, and (3) water surfaces of ponds and wetlands that are hydraulically connected to the unconfined aquifer. Water-table contours indicate that the direction of groundwater flow within the stratified-drift aquifer is predominantly from the valley walls toward the streams and ponds in the central part of the valley where groundwater then flows southwestward (down valley) toward the confluence with the Cayuta Creek valley. Locally, the direction of groundwater flow is radially

Groundwater Discharge along a Channelized Coastal Plain Stream

Energy Technology Data Exchange (ETDEWEB)

LaSage, Danita M [Ky Dept for natural resources, Div of Mine Permits; Sexton, Joshua L [JL Sexton and Son; Mukherjee, Abhijit [Univ of Tx, Jackson School of Geosciences, Bur of Econ. Geology; Fryar, Alan E [Univ of KY, Dept of Earth and Geoligical Sciences; Greb, Stephen F [Univ of KY, KY Geological Survey

2015-10-01

In the Coastal Plain of the southeastern USA, streams have commonly been artificially channelized for flood control and agricultural drainage. However, groundwater discharge along such streams has received relatively little attention. Using a combination of stream- and spring-flow measurements, spring temperature measurements, temperature profiling along the stream-bed, and geologic mapping, we delineated zones of diffuse and focused discharge along Little Bayou Creek, a channelized, first-order perennial stream in western Kentucky. Seasonal variability in groundwater discharge mimics hydraulic-head fluctuations in a nearby monitoring well and spring-discharge fluctuations elsewhere in the region, and is likely to reflect seasonal variability in recharge. Diffuse discharge occurs where the stream is incised into the semi-confined regional gravel aquifer, which is comprised of the Mounds Gravel. Focused discharge occurs upstream where the channel appears to have intersected preferential pathways within the confining unit. Seasonal fluctuations in discharge from individual springs are repressed where piping results in bank collapse. Thereby, focused discharge can contribute to the morphological evolution of the stream channel.

Interactions of diffuse and focused allogenic recharge in an eogenetic karst aquifer (Florida, USA)

Science.gov (United States)

Langston, Abigail L.; Screaton, Elizabeth J.; Martin, Jonathan B.; Bailly-Comte, Vincent

2012-06-01

The karstic upper Floridan aquifer in north-central Florida (USA) is recharged by both diffuse and allogenic recharge. To understand how recharged water moves within the aquifer, water levels and specific conductivities were monitored and slug tests were conducted in wells installed in the aquifer surrounding the Santa Fe River Sink and Rise. Results indicate that diffuse recharge does not mix rapidly within the aquifer but instead flows horizontally. Stratification may be aided by the high matrix porosity of the eogenetic karst aquifer. Purging wells for sample collection perturbed conductivity for several days, reflecting mixing of the stratified water and rendering collection of representative samples difficult. Interpretive numerical simulations suggest that diffuse recharge impacts the intrusion of allogenic water from the conduit by increasing hydraulic head in the surrounding aquifer and thereby reducing influx to the aquifer from the conduit. In turn, the increase of head within the conduits affects flow paths of diffuse recharge by moving newly recharged water vertically as the water table rises and falls. This movement may result in a broad vertical zone of dissolution at the water table above the conduit system, with thinner and more focused water-table dissolution at greater distance from the conduit.

Localization of electrons by electron-electron interaction in an Anderson model

International Nuclear Information System (INIS)

Ritala, R.K.; Kurkijaervi, J.

1981-01-01

We study the effect of attractive Hubbard interaction on disordered electron system. We map the interacting system back to noninteracting one and determine self-consistently the disorder change due to interaction in the system. (author)

Changing Groundwater-Surface Water Interactions Impact Stream Chemistry and Ecology at the Arctic-Boreal Transition in Western Alaska

Science.gov (United States)

Koch, J. C.; Carey, M.; O'Donnell, J.; Sjoberg, Y.; Zimmerman, C. E.

2016-12-01

The arctic-boreal transition zone of Alaska is experiencing rapid change related to unprecedented warming and subsequent loss of permafrost. These changes in turn may affect groundwater-surface water (GW-SW) interactions, biogeochemical cycling, and ecosystem processes. While recent field and modeling studies have improved our understanding of hydrology in watersheds underlain by thawing permafrost, little is known about how these hydrologic shifts will impact bottom-up controls on stream food webs. To address this uncertainty, we are using an integrative experimental design to link GW-SW interactions to stream biogeochemistry and biota in 10 first-order streams in northwest Alaska. These study streams drain watersheds that span several gradients, including elevation, aspect, and vegetation (tundra vs. forest). We have developed a robust, multi-disciplinary data set to characterize GW-SW interactions and to mechanistically link GW-SW dynamics to water quality and the stream ecosystem. Data includes soil hydrology and chemistry; stream discharge, temperature, and inflow rates; water chemistry (including water isotopes, major ions, carbon concentration and isotopes, nutrients and chlorophyll-a), and invertebrate and fish communities. Stream recession curves indicate a decreasing rate later in the summer in some streams, consistent with seasonal thaw in lower elevation and south-facing catchments. Base cation and water isotope chemistry display similar impacts of seasonal thaw and also suggest the dominance of groundwater in many streams. Coupled with estimates of GW-SW exchange at point, reach, and catchment scales, these results will be used to predict how hydrology and water quality are likely to impact fish habitat and growth given continued warming at the arctic-boreal transition.

Electron-electron interactions in artificial graphene

Science.gov (United States)

Rasanen, Esa

2013-03-01

Recent advances in the creation and modulation of graphenelike systems are introducing a science of ``designer Dirac materials.'' In its original definition, artificial graphene is a man-made nanostructure that consists of identical potential wells (quantum dots) arranged in an adjustable honeycomb lattice in the two-dimensional electron gas. As our ability to control the quality of artificial graphene samples improves, so grows the need for an accurate theory of its electronic properties, including the effects of electron-electron interactions. Here we determine those effects on the band structure and on the emergence of Dirac points, and discuss future investigations and challenges in this field.

Processes of water rock interaction in the Turonian aquifer of Oum Er-Rabia Basin, Morocco

Science.gov (United States)

Ettazarini, Said

2005-12-01

Possible water rock interaction processes, in the Moroccan basin of Oum Er-Rabia, were discussed by a geochemical study of groundwater from the Turonian limestone aquifer, the most important water resource in the region. Different types of water according to the classification of Piper were defined. Waters have shown an evolution from dominant CHO3 Ca Mg type through mixed to SO4 Cl Ca Mg type. The use of geochemical diagrams and chemical speciation modeling method has shown that water rock interaction is mainly controlled by carbonate and anhydrite dissolution, ion exchange and reverse ion exchange processes. Water rock equilibrium conditions are favorable for the precipitation of calcite, dolomite, kaolinite and magnesian smectite.

Delineating groundwater/surface water interaction in a karst watershed: Lower Flint River Basin, southwestern Georgia, USA

Directory of Open Access Journals (Sweden)

Kathleen Rugel

2016-03-01

Full Text Available Study region: Karst watershed in Lower Flint River Basin (LFRB, southwestern Georgia, USA. Study focus: Baseflow discharges in the LFRB have declined for three decades as regional irrigation has increased; yet, the location and nature of connectivity between groundwater and surface water in this karstic region are poorly understood. Because growing water demands will likely be met by further development of regional aquifers, an important management concern is the nature of interactions between groundwater and surface water components under natural and anthropogenic perturbations. We conducted coarse and fine-scale stream sampling on a major tributary of the Lower Flint River (Ichawaynochaway Creek in southwestern Georgia, USA, to identify locations and patterns of enhanced hydrologic connectivity between this stream and the Upper Floridan Aquifer. New hydrological insights for the region: Prior water resource studies in the LFRB were based on regional modeling that neglected local heterogeneities in groundwater/surface water connectivity. Our results demonstrated groundwater inputs were concentrated around five of fifty sampled reaches, evidenced by increases in multiple groundwater indicators at these sites. These five reaches contributed up to 42% of the groundwater detected along the entire 50-km sampling section, with ∼24% entering through one groundwater-dominated tributary, Chickasawhatchee Creek. Intermittent flows occurred in two of these upstream reaches during extreme drought and heavy groundwater pumping, suggesting reach-scale behaviors should be considered in resource management and policy. Keywords: Karst hydrogeology, Hydrologic connectivity, Groundwater/surface water interaction, Upper Floridan Aquifer, Groundwater Irrigation

Theoretical study of the interplay of electron-electron interaction and disorder

International Nuclear Information System (INIS)

Brezini, A.; Behilil, S.

1988-10-01

A disordered Hubbard model with diagonal disorder is used to investigate the electron localization effects associated with both disorder and electron-electron interaction. Extensive results are reported on the ground state properties and compared to other theories. Two regimes have been found: when the electron-electron interaction u is greater than the disorder parameter w and when u < w. (author). 18 refs, 4 figs

Potential interaction between transport and stream networks over the lowland rivers in Eastern India.

Science.gov (United States)

Roy, Suvendu; Sahu, Abhay Sankar

2017-07-15

Extension of transport networks supports good accessibility and associated with the development of a region. However, transport lines have fragmented the regional landscape and disturbed the natural interplay between rivers and their floodplains. Spatial analysis using multiple buffers provides information about the potential interaction between road and stream networks and their impact on channel morphology of a small watershed in the Lower Gangetic Plain. Present study is tried to understand the lateral and longitudinal disconnection in headwater stream by rural roads with the integration of geoinformatics and field survey. Significant (p development, delineation of stream corridor, regular monitoring and engineering efficiency for the construction of road and road-stream crossing might be effective in managing river geomorphology and riverine landscape. Copyright © 2017 Elsevier Ltd. All rights reserved.

StreamMap: Smooth Dynamic Visualization of High-Density Streaming Points.

Science.gov (United States)

Li, Chenhui; Baciu, George; Han, Yu

2018-03-01

Interactive visualization of streaming points for real-time scatterplots and linear blending of correlation patterns is increasingly becoming the dominant mode of visual analytics for both big data and streaming data from active sensors and broadcasting media. To better visualize and interact with inter-stream patterns, it is generally necessary to smooth out gaps or distortions in the streaming data. Previous approaches either animate the points directly or present a sampled static heat-map. We propose a new approach, called StreamMap, to smoothly blend high-density streaming points and create a visual flow that emphasizes the density pattern distributions. In essence, we present three new contributions for the visualization of high-density streaming points. The first contribution is a density-based method called super kernel density estimation that aggregates streaming points using an adaptive kernel to solve the overlapping problem. The second contribution is a robust density morphing algorithm that generates several smooth intermediate frames for a given pair of frames. The third contribution is a trend representation design that can help convey the flow directions of the streaming points. The experimental results on three datasets demonstrate the effectiveness of StreamMap when dynamic visualization and visual analysis of trend patterns on streaming points are required.

Partitioning Hydrologic and Biological Drivers of Discharge Loss in Arctic Headwater Streams

Science.gov (United States)

Koch, J. C.; Carey, M.; O'Donnell, J. A.; Records, M. K.; Sjoberg, Y.; Zimmerman, C. E.

2017-12-01

The Arctic-Boreal transition (ABT) zone of Alaska is experiencing unprecedented warming, leading to permafrost thaw and vegetation change. Both of these processes are likely to affect streams and stream ecosystems, but there is little direct empirical evidence regarding the magnitude of these effects and their relative importance. To understand how permafrost thaw and vegetation are affecting streams at the ABT, we monitored 8 first-order streams that drain catchments varying in elevation, aspect, and vegetation cover. Data were obtained from meteorological stations, continuous stream discharge, seepage runs, and stream tracer experiments. Hydrograph analysis indicated that runoff ratios in south-facing catchments were lower than north-facing catchments and decreased over the season. Seepage runs indicated that south-facing catchments lost a large portion of water (up to 50% per km stream reach) in the late summer, while north-facing catchments were gaining water. All streams displayed diel variability in discharge, but with different daily and seasonal trends related to aspect and elevation. South-facing, forested catchment streams showed diel discharge timing consistent with cycles in evapotranspiration rates, while the signal in north-facing catchments and those dominated by tundra was more consistent with thermal controls on water viscosity and groundwater discharge to streams. Together, these signals indicate that the warmer, south-facing catchments are losing a large portion of water to a combination of infiltration and evapotranspiration. The seasonal trends are consistent with higher infiltration rates beneath south-facing streams as the ground thaws over the summer. The magnitude and seasonal dynamics of the diel signatures help separate biological (i.e. evapotranspiration) vs. physical controls (i.e. frozen ground hydrology) on stream-catchment interactions, which vary depending on aspect, elevation, and vegetation cover. Warming, and subsequent increases

Groundwater and surface-water interaction and effects of pumping in a complex glacial-sediment aquifer, phase 2, east-central Massachusetts

Science.gov (United States)

Eggleston, Jack R.; Zarriello, Phillip J.; Carlson, Carl S.

2015-12-31

The U.S. Geological Survey, in cooperation with the Town of Framingham, Massachusetts, has investigated the potential of proposed groundwater withdrawals at the Birch Road well site to affect nearby surface water bodies and wetlands, including Lake Cochituate, the Sudbury River, and the Great Meadows National Wildlife Refuge in east-central Massachusetts. In 2012, the U.S. Geological Survey developed a Phase 1 numerical groundwater model of a complex glacial-sediment aquifer to synthesize hydrogeologic information and simulate potential future pumping scenarios. The model was developed with MODFLOW-NWT, an updated version of a standard USGS numerical groundwater flow modeling program that improves solution of unconfined groundwater flow problems. The groundwater model and investigations of the aquifer improved understanding of groundwater–surface-water interaction and the effects of groundwater withdrawals on surface-water bodies and wetlands in the study area. The initial work also revealed a need for additional information and model refinements to better understand this complex aquifer system.

The Maryland Coastal Plain Aquifer Information System: A GIS-based tool for assessing groundwater resources

Science.gov (United States)

Andreasen, David C.; Nardi, Mark R.; Staley, Andrew W.; Achmad, Grufron; Grace, John W.

2016-01-01

Groundwater is the source of drinking water for ∼1.4 million people in the Coastal Plain Province of Maryland (USA). In addition, groundwater is essential for commercial, industrial, and agricultural uses. Approximately 0.757 × 109 L d–1 (200 million gallons/d) were withdrawn in 2010. As a result of decades of withdrawals from the coastal plain confined aquifers, groundwater levels have declined by as much as 70 m (230 ft) from estimated prepumping levels. Other issues posing challenges to long-term groundwater sustainability include degraded water quality from both man-made and natural sources, reduced stream base flow, land subsidence, and changing recharge patterns (drought) caused by climate change. In Maryland, groundwater supply is managed primarily by the Maryland Department of the Environment, which seeks to balance reasonable use of the resource with long-term sustainability. The chief goal of groundwater management in Maryland is to ensure safe and adequate supplies for all current and future users through the implementation of appropriate usage, planning, and conservation policies. To assist in that effort, the geographic information system (GIS)–based Maryland Coastal Plain Aquifer Information System was developed as a tool to help water managers access and visualize groundwater data for use in the evaluation of groundwater allocation and use permits. The system, contained within an ESRI ArcMap desktop environment, includes both interpreted and basic data for 16 aquifers and 14 confining units. Data map layers include aquifer and ­confining unit layer surfaces, aquifer extents, borehole information, hydraulic properties, time-series groundwater-level data, well records, and geophysical and lithologic logs. The aquifer and confining unit layer surfaces were generated specifically for the GIS system. The system also contains select groundwater-quality data and map layers that quantify groundwater and surface-water withdrawals. The aquifer

The interactive effects of climate change, riparian management, and a nonnative predator on stream-rearing salmon.

Science.gov (United States)

Lawrence, David J; Stewart-Koster, Ben; Olden, Julian D; Ruesch, Aaron S; Torgersen, Christian E; Lawler, Joshua J; Butcher, Don P; Crown, Julia K

2014-06-01

Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use-related reductions in riparian shading have caused changes in stream thermal regimes, and additional warming from projected climate change may result in significant losses of coldwater fish habitat over the next century. Predatory, nonnative smallmouth bass have also been introduced into many northwestern streams, and their range is likely to expand as streams warm, presenting an additional challenge to the persistence of threatened Pacific salmon. The goal of this work was to forecast the interactive effects of climate change, riparian management, and nonnative species on stream-rearing salmon and to evaluate the capacity of restoration to mitigate these effects. We intersected downscaled global climate forecasts with a local-scale water temperature model to predict mid- and end-of-century temperatures in streams in the Columbia River basin. We compared one stream that is thermally impaired due to the loss of riparian vegetation and another that is cooler and has a largely intact riparian corridor. Using the forecasted stream temperatures in conjunction with fish-habitat models, we predicted how stream-rearing chinook salmon and bass distributions would change as each stream warmed. In the highly modified stream, end-of-century warming may cause near total loss of chinook salmon-rearing habitat and a complete invasion of the upper watershed by bass. In the less modified stream, bass were thermally restricted from the upstream-most areas. In both systems, temperature increases resulted in higher predicted spatial overlap between stream-rearing chinook salmon and potentially predatory bass in the early summer (two- to fourfold increase) and greater abundance of

Geosynchronous Relativistic Electron Events Associated with High-Speed Solar Wind Streams in 2006

Directory of Open Access Journals (Sweden)

Sungeun Lee

2009-12-01

Full Text Available Recurrent enhancements of relativistic electron events at geosynchronous orbit (GREEs were observed in 2006. These GREE enhancements were associated with high-speed solar wind streams coming from the same coronal hole. For the first six months of 2006, the occurrence of GREEs has 27 day periodicity and the GREEs were enhanced with various flux levels. Several factors have been studied to be related to GREEs: (1 High speed stream, (2 Pc5 ULF wave activity, (3 Southward IMF Bz, (4 substorm occurrence, (5 Whistler mode chorus wave, and (6 Dynamic pressure. In this paper, we have examined the effectiveness about those parameters in selected periods.

Features of solar wind streams on June 21-28, 2015 as a result of interactions between coronal mass ejections and recurrent streams from coronal holes

Science.gov (United States)

Shugay, Yu. S.; Slemzin, V. A.; Rod'kin, D. G.

2017-11-01

Coronal sources and parameters of solar wind streams during a strong and prolonged geomagnetic disturbance in June 2015 have been considered. Correspondence between coronal sources and solar wind streams at 1 AU has been determined using an analysis of solar images, catalogs of flares and coronal mass ejections, solar wind parameters including the ionic composition. The sources of disturbances in the considered period were a sequence of five coronal mass ejections that propagated along the recurrent solar wind streams from coronal holes. The observed differences from typical in magnetic and kinetic parameters of solar wind streams have been associated with the interactions of different types of solar wind. The ionic composition has proved to be a good additional marker for highlighting components in a mixture of solar wind streams, which can be associated with different coronal sources.

Electron-electron interaction in Multiple Quantum Wells

Science.gov (United States)

Zybert, M.; Marchewka, M.; Tomaka, G.; Sheregii, E. M.

2012-07-01

The complex investigation of the magneto-transport effects in structures containing multiple quantum well (MQWs) based on the GaAs/AlGaAs-heterostructures has been performed. The MQWs investigated have different electron densities in QWs. The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH) observed at low temperatures (0.6-4.2 K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D. Płoch et al., Phys. Rev. B 79 (2009) 195434) including the screening of this interaction. The IQHE and SdH observed in these multilayer structures with the third degree of freedom for electrons are interpreted from this.

Benzene dynamics and biodegradation in alluvial aquifers affected by river fluctuations.

Science.gov (United States)

Batlle-Aguilar, J; Morasch, B; Hunkeler, D; Brouyère, S

2014-01-01

The spatial distribution and temporal dynamics of a benzene plume in an alluvial aquifer strongly affected by river fluctuations was studied. Benzene concentrations, aquifer geochemistry datasets, past river morphology, and benzene degradation rates estimated in situ using stable carbon isotope enrichment were analyzed in concert with aquifer heterogeneity and river fluctuations. Geochemistry data demonstrated that benzene biodegradation was on-going under sulfate reducing conditions. Long-term monitoring of hydraulic heads and characterization of the alluvial aquifer formed the basis of a detailed modeled image of aquifer heterogeneity. Hydraulic conductivity was found to strongly correlate with benzene degradation, indicating that low hydraulic conductivity areas are capable of sustaining benzene anaerobic biodegradation provided the electron acceptor (SO4 (2-) ) does not become rate limiting. Modeling results demonstrated that the groundwater flux direction is reversed on annual basis when the river level rises up to 2 m, thereby forcing the infiltration of oxygenated surface water into the aquifer. The mobilization state of metal trace elements such as Zn, Cd, and As present in the aquifer predominantly depended on the strong potential gradient within the plume. However, infiltration of oxygenated water was found to trigger a change from strongly reducing to oxic conditions near the river, causing mobilization of previously immobile metal species and vice versa. MNA appears to be an appropriate remediation strategy in this type of dynamic environment provided that aquifer characterization and targeted monitoring of redox conditions are adequate and electron acceptors remain available until concentrations of toxic compounds reduce to acceptable levels. © 2013, National Ground Water Association.

Hydrogeology and water quality of the Nanticoke Creek stratified-drift aquifer, near Endicott, New York

Science.gov (United States)

Kreitinger, Elizabeth A.; Kappel, William M.

2014-01-01

The Village of Endicott, New York, is seeking an alternate source of public drinking water with the potential to supplement their current supply, which requires treatment due to legacy contamination. The southerly-draining Nanticoke Creek valley, located north of the village, was identified as a potential water source and the local stratified-drift (valley fill) aquifer was investigated to determine its hydrogeologic and water-quality characteristics. Nanticoke Creek and its aquifer extend from the hamlet of Glen Aubrey, N.Y., to the village of Endicott, a distance of about 15 miles, where it joins the Susquehanna River and its aquifer. The glacial sediments that comprise the stratified-drift aquifer vary in thickness and are generally underlain by glacial till over Devonian-aged shale and siltstone. Groundwater is more plentiful in the northern part of the aquifer where sand and gravel deposits are generally more permeable than in the southern part of the aquifer where less-permeable unconsolidated deposits are found. Generally there is enough groundwater to supply most homeowner wells and in some cases, supply small public-water systems such as schools, mobile-home parks, and small commercial/industrial facilities. The aquifer is recharged by precipitation, runoff, and tributary streams. Most tributary streams flowing across alluvial deposits lose water to the aquifer as they flow off of their bedrock-lined channels and into the more permeable alluvial deposits at the edges of the valley. The quality of both surface water and groundwater is generally good. Some water wells do have water-quality issues related to natural constituents (manganese and iron) and several homeowners noted either the smell and (or) taste of hydrogen sulfide in their drinking water. Dissolved methane concentrations from five drinking-water wells were well below the potentially explosive value of 28 milligrams per liter. Samples from surface and groundwater met nearly all State and Federal

Groundwater level responses to precipitation variability in Mediterranean insular aquifers

Science.gov (United States)

Lorenzo-Lacruz, Jorge; Garcia, Celso; Morán-Tejeda, Enrique

2017-09-01

Groundwater is one of the largest and most important sources of fresh water on many regions under Mediterranean climate conditions, which are exposed to large precipitation variability that includes frequent meteorological drought episodes, and present high evapotranspiration rates and water demand during the dry season. The dependence on groundwater increases in those areas with predominant permeable lithologies, contributing to aquifer recharge and the abundance of ephemeral streams. The increasing pressure of tourism on water resources in many Mediterranean coastal areas, and uncertainty related to future precipitation and water availability, make it urgent to understand the spatio-temporal response of groundwater bodies to precipitation variability, if sustainable use of the resource is to be achieved. We present an assessment of the response of aquifers to precipitation variability based on correlations between the Standardized Precipitation Index (SPI) at various time scales and the Standardized Groundwater Index (SGI) across a Mediterranean island. We detected three main responses of aquifers to accumulated precipitation anomalies: (i) at short time scales of the SPI (24 months). The differing responses were mainly explained by differences in lithology and the percentage of highly permeable rock strata in the aquifer recharge areas. We also identified differences in the months and seasons when aquifer storages are more dependent on precipitation; these were related to climate seasonality and the degree of aquifer exploitation or underground water extraction. The recharge of some aquifers, especially in mountainous areas, is related to precipitation variability within a limited spatial extent, whereas for aquifers located in the plains, precipitation variability influence much larger areas; the topography and geological structure of the island explain these differences. Results indicate large spatial variability in the response of aquifers to precipitation in

Groundwater/surface-water interaction in central Sevier County, Tennessee, October 2015–2016

Science.gov (United States)

Carmichael, John K.; Johnson, Gregory C.

2017-12-14

The U.S. Geological Survey evaluated the interaction of groundwater and surface water in the central part of Sevier County, Tennessee, from October 2015 through October 2016. Stream base flow was surveyed in December 2015 and in July and October 2016 to evaluate losing and gaining stream reaches along three streams in the area. During a July 2016 synoptic survey, groundwater levels were measured in wells screened in the Cambrian-Ordovician aquifer to define the potentiometric surface in the area. The middle and lower reaches of the Little Pigeon River and the middle reaches of Middle Creek and the West Prong Little Pigeon River were gaining streams at base-flow conditions. The lower segments of the West Prong Little Pigeon River and Middle Creek were losing reaches under base-flow conditions, with substantial flow losses in the West Prong Little Pigeon River and complete subsurface diversion of flow in Middle Creek through a series of sinkholes that developed in the streambed and adjacent flood plain beginning in 2010. The potentiometric surface of the Cambrian-Ordovician aquifer showed depressed water levels in the area where loss of flow occurred in the lower reaches of West Prong Little Pigeon River and Middle Creek. Continuous dewatering activities at a rock quarry located in this area appear to have lowered groundwater levels by as much as 180 feet, which likely is the cause of flow losses observed in the two streams, and a contributing factor to the development of sinkholes at Middle Creek near Collier Drive.

Changes in the Regional Groundwater Aquifer and Potential Impacts on Surface Waters in Central Zealand, Denmark

DEFF Research Database (Denmark)

Thorn, Paul

The regional, confined aquifer on the island of Zealand, in eastern Denmark, is the primary aquifer used for large-scale abstraction for the supplies of all larger cities, including Roskilde and the greater Copenhagen metropolitan area. Large-scale groundwater abstraction from this aquifer...... in the area near Lejre Denmark (approximately 15km to the SW of Roskilde) began in 1937, exporting approximately 18 million m3 of water per year to supply the city of Copenhagen. After abstraction began, streams in the area were observed to go dry after extended periods without precipitation, where......, wetlands and lakes in the area. The results show that there was a significant impact on the regional groundwater aquifer in the Langvad river catchment, with groundwater as much as 17m lower in 1987 from 1936 (pre-abstraction). However, in the Elverdam river catchment, the levels remained virtually...

Biogeochemistry at a wetland sediment-alluvial aquifer interface in a landfill leachate plume

Science.gov (United States)

Lorah, M.M.; Cozzarelli, I.M.; Böhlke, J.K.

2009-01-01

stoichiometrically balanced increase in magnesium concentration with decreasing ammonium and potassium concentrations indicated that cation exchange was the sorption mechanism in the slough porewater. Only a partial mass balance could be determined for cations exchanged for ammonium and potassium in the aquifer, indicating that some irreversible sorption may be occurring. Although wetlands commonly are expected to decrease fluxes of contaminants in riparian environments, enhanced attenuation of the leachate contaminants in the slough sediment porewater compared to the aquifer was not observed in this study. The lack of enhanced attenuation can be attributed to the fact that the anoxic plume, comprised largely of recalcitrant DOC and reduced inorganic constituents, interacted with anoxic slough sediments and porewaters, rather than encountering a change in redox conditions that could cause transformation reactions. Nevertheless, the attenuation processes in the narrow zone of groundwater/surface-water interaction were effective in reducing ammonium concentrations by a factor of about 3 during lateral transport across the slough and by a factor of 2 to 10 before release to the surface water. Slough porewater geochemistry also indicated that the slough could be a source of sulfate in dry conditions, potentially providing a terminal electron acceptor for natural attenuation of organic compounds in the leachate plume.

Interaction of counter-streaming plasma flows in dipole magnetic field

OpenAIRE

Shaikhislamov, I F; Posukh, V G; Melekhov, A V; Prokopov, P A; Boyarintsev, E L; Zakharov, Yu P; Ponomarenko, A G

2017-01-01

Transient interaction of counter-streaming super-sonic plasma flows in dipole magnetic dipole is studied in laboratory experiment. First quasi-stationary flow is produced by teta-pinch and forms a magnetosphere around the magnetic dipole while laser beams focused at the surface of the dipole cover launch second explosive plasma expanding from inner dipole region outward. Laser plasma is energetic enough to disrupt magnetic field and to sweep through the background plasma for large distances. ...

The quality of our Nation's waters-Nutrients in the Nation's streams and groundwater, 1992-2004

Science.gov (United States)

Dubrovsky, N.M.; Burow, K.R.; Clark, G.M.; Gronberg, J.M.; Hamilton, P.A.; Hitt, K.J.; Mueller, D.K.; Munn, M.D.; Nolan, B.T.; Puckett, L.J.; Rupert, M.G.; Short, T.M.; Spahr, N.E.; Sprague, L.A.; Wilber, W.G.

2010-01-01

National Findings and Their Implications Although the use of artificial fertilizer has supported increasing food production to meet the needs of a growing population, increases in nutrient loadings from agricultural and, to a lesser extent, urban sources have resulted in nutrient concentrations in many streams and parts of aquifers that exceed standards for protection of human health and (or) aquatic life, often by large margins. Do NAWQA findings substantiate national concerns for aquatic and human health? National Water-Quality Assessment (NAWQA) findings indicate that nutrient concentrations in streams and groundwater in basins with significant agricultural or urban development are substantially greater than naturally occurring or ?background? levels. For example, median concentrations of total nitrogen and phosphorus in agricultural streams are about 6 times greater than background levels. Findings also indicate that concentrations in streams routinely were 2 to 10 times greater than regional nutrient criteria recommended by the U.S. Environmental Protection Agency (USEPA) to protect aquatic life. Such large differences in magnitude suggest that significant reductions in sources of nutrients, as well as greater use of land management strategies to reduce the transport of nutrients to streams, are needed to meet recommended criteria for streams draining areas with significant agricultural and urban development. Nitrate concentrations above the Federal drinking-water standard-or Maximum Contaminant Level (MCL)-of 10 milligrams per liter (mg/L, as nit-ogen) are relatively uncommon in samples from streams used for drinking water or from relatively deep aquifers; the MCL is exceeded, however, in more than 20 percent of shallow (less than 100 feet below the water table) domestic wells in agricultural areas. This finding raises concerns for human health in rural agricultural areas where shallow groundwater is used for domestic supply and may warn of future

Impacts of groundwater metal loads from bedrock fractures on water quality of a mountain stream.

Science.gov (United States)

Caruso, Brian S; Dawson, Helen E

2009-06-01

Acid mine drainage and metal loads from hardrock mines to surface waters is a significant problem in the western USA and many parts of the world. Mines often occur in mountain environments with fractured bedrock aquifers that serve as pathways for metals transport to streams. This study evaluates impacts from current and potential future groundwater metal (Cd, Cu, and Zn) loads from fractures underlying the Gilt Edge Mine, South Dakota, on concentrations in Strawberry Creek using existing flow and water quality data and simple mixing/dilution mass balance models. Results showed that metal loads from bedrock fractures to the creek currently contribute water quality is achieved upstream in Strawberry Creek, fracture metal loads would be water quality standards exceedances once groundwater with elevated metals concentrations in the aquifer matrix migrates to the fractures and discharges to the stream. Potential future metal loads from an upstream fracture would contribute a small proportion of the total load relative to current loads in the stream. Cd has the highest stream concentrations relative to standards. Even if all stream water was treated to remove 90% of the Cd, the standard would still not be achieved. At a fracture farther downstream, the Cd standard can only be met if the upstream water is treated achieving a 90% reduction in Cd concentrations and the median stream flow is maintained.

Attractive electron correlation in wide band gap semiconductors by electron-photon interaction

International Nuclear Information System (INIS)

Takeda, Hiroyuki; Yoshino, Katsumi

2004-01-01

We theoretically demonstrate attractive electron correlation in wide band gap semiconductors by electron-photon interaction. At low temperature, wavevectors of electromagnetic waves absorbed in wide band gap semiconductors cannot be neglected for wavevectors of electron waves; that is, electromagnetic waves affect the movements of electrons. In particular, attractive interaction occurs between two electrons when one electron changes from a valence band to a conduction band and the other electron changes from a conduction band to a valence band

Spin Relaxation in GaAs: Importance of Electron-Electron Interactions

Directory of Open Access Journals (Sweden)

Gionni Marchetti

2014-04-01

Full Text Available We study spin relaxation in n-type bulk GaAs, due to the Dyakonov–Perel mechanism, using ensemble Monte Carlo methods. Our results confirm that spin relaxation time increases with the electronic density in the regime of moderate electronic concentrations and high temperature. We show that the electron-electron scattering in the non-degenerate regime significantly slows down spin relaxation. This result supports predictions by Glazov and Ivchenko. Most importantly, our findings highlight the importance of many-body interactions for spin dynamics: we show that only by properly taking into account electron-electron interactions within the simulations, results for the spin relaxation time—with respect to both electron density and temperature—will reach good quantitative agreement with corresponding experimental data. Our calculations contain no fitting parameters.

Tunable Electron-Electron Interactions in LaAlO_{3}/SrTiO_{3} Nanostructures

Directory of Open Access Journals (Sweden)

Guanglei Cheng

2016-12-01

Full Text Available The interface between the two complex oxides LaAlO_{3} and SrTiO_{3} has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of “sketched” quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a single-electron (Andreev bound state tunneling regime where the interactions become repulsive. The electron-electron interaction sign change is associated with a Lifshitz transition where the d_{xz} and d_{yz} bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.

Electron-positron interactions

International Nuclear Information System (INIS)

Wiik, B.; Wolf, G.

1979-01-01

This book is an introduction into the physics of electron-positron interactions. After a description of electron-positron storage rings pure electromagnetic e + e - interactions, and the total cross section are considered. Then low energy processes, the production of the J/psi and psi' particles including their radiative decay as well as the search for other narrow vector states are described. Then after the quark model interpretation of J/psi and psi' charmed mesons, the heavy lepton t, and the upsilon resonances are described. Thereafter inclusive hadron production and jet formation is discussed. Finally the next generation of e + e - colliding rings is described, and the first results from PETRA are presented. This book is suited for all physicists, who want to get a general review about e + e - physics. (HSI) 891 HSI/HSI 892 RKD

Effects of electron-electron interactions on electronic transport in disordered systems

International Nuclear Information System (INIS)

Foley, Simon Timothy

2002-01-01

This thesis is concerned with the role of electron-electron interactions on electronic transport in disordered systems. We first consider a novel non-linear sigma model in order to microscopically treat the effects of disorder and electronic interaction. We successfully reproduce the perturbative results for the zero-bias anomaly and the interaction correction to the conductivity in a weakly disordered system, and discuss possible directions for future work. Secondly we consider the fluctuations of the dephasing rate for a closed diffusive and quantum dot system. Using the Keldysh technique we derive an expression for the inelastic scattering rate with which we self-consistently obtain the fluctuations in the dephasing rate. For the diffusive regime we find the relative fluctuations is given by F ∼ (L φ /L) 2 /g 2 , where g is the dimensionless conductance, L φ is the dephasing length and L is the sample size. For the quantum dot regime we find a perturbative divergence due to the presence of the zero mode. By mapping divergent diagrams to those for the two-level correlation function, we conjecture the existence of an exact relation between the two. Finally we discuss the consequences of this relation. (author)

Geochemical orientation survey of stream sediment, stream water, and ground water near uranium prospects, Monticello area, New York. National Uranium Resource Evaluation Program

International Nuclear Information System (INIS)

Rose, A.W.; Smith, A.T.; Wesolowski, D.

1982-08-01

A detailed geochemical test survey has been conducted in a 570 sq km area around six small copper-uranium prospects in sandstones of the Devonian Catskill Formation near Monticello in southern New York state. This report summarizes and interprets the data for about 500 stream sediment samples, 500 stream water samples, and 500 ground water samples, each analyzed for 40 to 50 elements. The groundwater samples furnish distinctive anomalies for uranium, helium, radon, and copper near the mineralized localities, but the samples must be segregated into aquifers in order to obtain continuous well-defined anomalies. Two zones of uranium-rich water (1 to 16 parts per billion) can be recognized on cross sections; the upper zone extends through the known occurrences. The anomalies in uranium and helium are strongest in the deeper parts of the aquifers and are diluted in samples from shallow wells. In stream water, copper and uranium are slightly anomalous, as in an ore factor derived from factor analysis. Ratios of copper, uranium, and zinc to conductivity improve the resolution of anomalies. In stream sediment, extractable uranium, copper, niobium, vanadium, and an ore factor furnish weak anomalies, and ratios of uranium and copper to zinc improve the definition of anomalies. The uranium/thorium ratio is not helpful. Published analyses of rock samples from the nearby stratigraphic section show distinct anomalies in the zone containing the copper-uranium occurrences. This report is being issued without the normal detailed technical and copy editing, to make the data available to the public before the end of the National Uranium Reconnaissance Evaluation program

Geochemical orientation survey of stream sediment, stream water, and ground water near uranium prospects, Monticello area, New York. National Uranium Resource Evaluation Program

Energy Technology Data Exchange (ETDEWEB)

Rose, A. W.; Smith, A. T.; Wesolowski, D.

1982-08-01

A detailed geochemical test survey has been conducted in a 570 sq km area around six small copper-uranium prospects in sandstones of the Devonian Catskill Formation near Monticello in southern New York state. This report summarizes and interprets the data for about 500 stream sediment samples, 500 stream water samples, and 500 ground water samples, each analyzed for 40 to 50 elements. The groundwater samples furnish distinctive anomalies for uranium, helium, radon, and copper near the mineralized localities, but the samples must be segregated into aquifers in order to obtain continuous well-defined anomalies. Two zones of uranium-rich water (1 to 16 parts per billion) can be recognized on cross sections; the upper zone extends through the known occurrences. The anomalies in uranium and helium are strongest in the deeper parts of the aquifers and are diluted in samples from shallow wells. In stream water, copper and uranium are slightly anomalous, as in an ore factor derived from factor analysis. Ratios of copper, uranium, and zinc to conductivity improve the resolution of anomalies. In stream sediment, extractable uranium, copper, niobium, vanadium, and an ore factor furnish weak anomalies, and ratios of uranium and copper to zinc improve the definition of anomalies. The uranium/thorium ratio is not helpful. Published analyses of rock samples from the nearby stratigraphic section show distinct anomalies in the zone containing the copper-uranium occurrences. This report is being issued without the normal detailed technical and copy editing, to make the data available to the public before the end of the National Uranium Reconnaissance Evaluation program.

Modelling high Reynolds number wall-turbulence interactions in laboratory experiments using large-scale free-stream turbulence.

Science.gov (United States)

Dogan, Eda; Hearst, R Jason; Ganapathisubramani, Bharathram

2017-03-13

A turbulent boundary layer subjected to free-stream turbulence is investigated in order to ascertain the scale interactions that dominate the near-wall region. The results are discussed in relation to a canonical high Reynolds number turbulent boundary layer because previous studies have reported considerable similarities between these two flows. Measurements were acquired simultaneously from four hot wires mounted to a rake which was traversed through the boundary layer. Particular focus is given to two main features of both canonical high Reynolds number boundary layers and boundary layers subjected to free-stream turbulence: (i) the footprint of the large scales in the logarithmic region on the near-wall small scales, specifically the modulating interaction between these scales, and (ii) the phase difference in amplitude modulation. The potential for a turbulent boundary layer subjected to free-stream turbulence to 'simulate' high Reynolds number wall-turbulence interactions is discussed. The results of this study have encouraging implications for future investigations of the fundamental scale interactions that take place in high Reynolds number flows as it demonstrates that these can be achieved at typical laboratory scales.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'. © 2017 The Author(s).

Cell for studying electron-adsorbed gas interactions; Cellule d'etudes des interactions electron-gaz adsorbe

Energy Technology Data Exchange (ETDEWEB)

Golowacz, H; Degras, D A [Commissariat a l' Energie Atomique, 91 - Saclay (France). Centre d' Etudes Nucleaires, Deptartement de Physique des Plasmas et de la Fusion Controlee, Service de Physique Appliquee, Service de Physique des Interractions Electroniques, Section d' Etude des Interactions Gaz-Solides

1967-07-01

The geometry and the technology of a cell used for investigations on electron-adsorbed gas interactions are described. The resonance frequencies of the surface ions which are created by the electron impact on the adsorbed gas are predicted by simplified calculations. The experimental data relative to carbon monoxide and neon are in good agreement with these predictions. (authors) [French] Les caracteristiques geometriques et technologiques generales d'une cellule d'etude des interactions entre un faisceau d'electrons et un gaz adsorbe sont donnees. Un calcul simplifie permet de prevoir les frequences de resonance des ions de surface crees par l'impact des electrons sur le gaz adsorbe. Les donnees experimentales sur l'oxyde de carbone et le neon confirment les previsions du calcul. (auteurs)

The interactive effects of climate change, riparian management, and a non-native predators on stream-rearing salmon

Science.gov (United States)

Lawrence, David J.; Stewart-Koster, Ben; Olden, Julian D.; Ruesch, Aaron S.; Torgersen, Christian E.; Lawler, Joshua J.; Butcher, Don P.; Crown, Julia K.

2014-01-01

Predicting how climate change is likely to interact with myriad other stressors that threaten species of conservation concern is an essential challenge in aquatic ecosystems. This study provides a framework to accomplish this task in salmon-bearing streams of the northwestern United States, where land-use related reductions in riparian shading have caused changes in stream thermal regimes, and additional warming from projected climate change may result in significant losses of coldwater fish habitat over the next century. Predatory non-native smallmouth bass have also been introduced into many northwestern streams and their range is likely to expand as streams warm, presenting an additional challenge to the persistence of threatened Pacific salmon. The goal of this work was to forecast the interactive effects of climate change, riparian management, and non-native species on stream-rearing salmon, and to evaluate the capacity of restoration to mitigate these effects. We intersected downscaled global climate forecasts with a local-scale water temperature model to predict mid- and end-of-century temperatures in streams in the Columbia River basin; we compared one stream that is thermally impaired due to the loss of riparian vegetation and another that is cooler and has a largely intact riparian corridor. Using the forecasted stream temperatures in conjunction with fish-habitat models, we predicted how stream-rearing Chinook salmon and bass distributions would change as each stream warmed. In the highly modified stream, end-of-century warming may cause near total loss of Chinook salmon rearing habitat and a complete invasion of the upper watershed by bass. In the less modified stream, bass were thermally restricted from the upstream-most areas. In both systems, temperature increases resulted in higher predicted spatial overlap between stream-rearing Chinook salmon and potentially predatory bass in the early summer (2-4-fold increase) and greater abundance of bass. We

Relativistic Electron Response to the Combined Magnetospheric Impact of a Coronal Mass Ejection Overlapping with a High-Speed Stream: Van Allen Probes Observations

Science.gov (United States)

Kanekal, S. G.; Baker, D. N.; Henderson, M. G.; Li, W.; Fennell, J. F.; Zheng, Y.; Richardson, I. G.; Jones, A.; Ali, A. F.; Elkington, S. R.;

Scalable Stream Coding for Adaptive Foveation Enhanced Percept Multimedia Information Communication for Interactive Medical Applications

National Research Council Canada - National Science Library

Khan, Javed

2003-01-01

.... The demonstrated systems include interactive perceptual transcoding where real-time eye-tracker data fuses with a passing stream, the active subnet diffusion coding-- where multiple active nodes...

Assessment of groundwater availability in the Northern Atlantic Coastal Plain aquifer system From Long Island, New York, to North Carolina

Science.gov (United States)

Masterson, John P.; Pope, Jason P.; Fienen, Michael N.; Monti, Jr., Jack; Nardi, Mark R.; Finkelstein, Jason S.

2016-08-31

Executive SummaryThe U.S. Geological Survey began a multiyear regional assessment of groundwater availability in the Northern Atlantic Coastal Plain (NACP) aquifer system in 2010 as part of its ongoing regional assessments of groundwater availability of the principal aquifers of the Nation. The goals of this national assessment are to document effects of human activities on water levels and groundwater storage, explore climate variability effects on the regional water budget, and provide consistent and integrated information that is useful to those who use and manage the groundwater resource. As part of this nationwide assessment, the USGS evaluated available groundwater resources within the NACP aquifer system from Long Island, New York, to northeastern North Carolina.The northern Atlantic Coastal Plain physiographic province depends heavily on groundwater to meet agricultural, industrial, and municipal needs. The groundwater assessment of the NACP aquifer system included an evaluation of how water use has changed over time; this evaluation primarily used groundwater budgets and development of a numerical modeling tool to assess system responses to stresses from future human uses and climate trends.This assessment focused on multiple spatial and temporal scales to examine changes in groundwater pumping, storage, and water levels. The regional scale provides a broad view of the sources and demands on the system with time. The sub-regional scale provides an evaluation of the differing response of the aquifer system across geographic areas allowing for closer examination of the interaction between different aquifers and confining units and the changes in these interactions under pumping and recharge conditions in 2013 and hydrologic stresses as much as 45 years in the future. By focusing on multiple scales, water-resource managers may utilize this study to understand system response to changes as they affect the system as a whole.The NACP aquifer system extends from

Experimental study of simulant melt stream-water thermal interaction in pool and narrow geometries

International Nuclear Information System (INIS)

Narayanan, K.S.; Jasmin Sudha, A.; Murthy, S.S.; Rao, E.H.V.M.; Lydia, G.; Das, S.K.; Harvey, J.; Kannan, S.E.

2005-01-01

Full text of publication follows: Small scale experiments were carried out to investigate the thermal interaction characteristics of a few kilograms of Sn Pb, Bi and Zn as hot melt, in the film boiling region of water in an attempt to simulate a coherent fuel coolant interaction during a postulated severe accident in a nuclear reactor. Melt stream solidification and detached debris generation were studied with different melt superheat up to 200 deg. C, at different coolant temperatures of 30 deg. C, 50 deg. C, 70 deg. C, 90 deg. C, in pool geometry and in long narrow coolant column. The material was heated in an Alumina crucible and poured through a hot stainless steel funnel with a nozzle diameter of 7.7 mm, into the coolant. A stainless steel plate was used to collect the solidified mass after the interaction. Temperature monitoring was done in the coolant column close to the melt stream. The melt stream movement inside the coolant was imaged using a video camera at 25 fps. Measured melt stream entry velocity was around 1.5 m/sec. For low melt superheat and low coolant temperature, solidified porous tree like structure extended from the collector plate up to the melt release point. For water temperature of 70 deg. C, the solidified bed height at the center was found to decrease with increase in the melt superheat up to 150 deg. C. Fragmentation was found to occur when the melt superheat exceeded 200 deg. C. Particle size distribution was obtained for the fragmented debris. In 1D geometry, with 50 deg. C superheat, columnar solidification was observed with no fine debris. The paper gives the details of the results obtained in the experiments and highlights the role of Rayleigh-Taylor, Kelvin-Helmholtz instabilities and the melt physical properties on the fragmentation kinetics. (authors)

Estimation of the recharge area contributing water to a pumped well in a glacial-drift, river-valley aquifer

Science.gov (United States)

Morrissey, Daniel J.

1989-01-01

The highly permeable, unconfined, glacial-drift aquifers that occupy most New England river valleys constitute the principal source of drinking water for many of the communities that obtain part or all of their public water supply from ground water. Recent events have shown that these aquifers are highly susceptible to contamination that results from a number of sources, such as seepage from wastewater lagoons, leaking petroleum-product storage tanks, and road salting. To protect the quality of water pumped from supply wells in these aquifers, it is necessary to ensure that potentially harmful contaminants do not enter the ground in the area that contributes water to the well. A high degree of protection can be achieved through the application of appropriate land-use controls within the contributing area. However, the contributing areas for most supply wells are not known. This report describes the factors that affect the size and shape of contributing areas to public supply wells and evaluates several methods that may be used to delineate contributing areas of wells in glacial-drift, river-valley aquifers. Analytical, two-dimensional numerical, and three-dimensional numerical models were used to delineate contributing areas. These methods of analysis were compared by applying them to a hypothetical aquifer having the dimensions and geometry of a typical glacial-drift, river-valley aquifer. In the model analyses, factors that control the size and shape of a contributing area were varied over ranges of values common to glacial-drift aquifers in New England. The controlling factors include the rate of well discharge, rate of recharge to the aquifer from precipitation and from adjacent till and bedrock uplands, distance of a pumping well from a stream or other potential source of induced recharge, degree of hydraulic connection of the aquifer with a stream, horizontal hydraulic conductivity of the aquifer, ratio of horizontal to vertical hydraulic conductivity, and

Physical and Chemical Connectivity of Streams and Riparian Wetlands to Downstream Waters: A Synthesis

Science.gov (United States)

Streams, riparian areas, floodplains, alluvial aquifers, and downstream waters (e.g., large rivers, lakes, and oceans) are interconnected by longitudinal, lateral, and vertical fluxes of water, other materials, and energy. Collectively, these interconnected waters are called fluv...

Landfill leachate effects on sorption of organic micropollutants onto aquifer materials

DEFF Research Database (Denmark)

Larsen, Thomas; Christensen, Thomas Højlund; Pfeffer, Fred M.

1992-01-01

The effect of dissolved organic carbon as present in landfill leachate, on the sorption of organic micropollutants in aquifer materials was studied by laboratory batch and column experiments involving 15 non-polar organic chemicals, 5 landfill leachates and 4 aquifer materials of low organic carbon......, the effect of landfill leachate on retardation of organic micropollutants in aquifer material seems limited....... content. The experiments showed that hydrophobic organic micropollutants do partition into dissolved organic carbon found in landfill leachate potentially increasing their mobility. However, landfill leachate interacted with aquifer materials apparently increases the sorbent affinity for the hydrophobic...

Stream flow - its estimation, uncertainty and interaction with groundwater and floodplains

DEFF Research Database (Denmark)

Poulsen, Jane Bang

, floodplain hydraulics and sedimentation patterns has been investigated along a restored channel section of Odense stream, Denmark. Collected samples of deposited sediment, organic matter and phosphorus on the floodplain were compared with results from a 2D dynamic flow model. Three stage dependent flow...... regimes were predicted by the flow model with shifting primary overbank flow and zones of flow confluence. These dynamic flow patterns were found to correlate with the spatial deposition of total phosphorus (11.4 g m-2), organic matter (0.65 kg m-2) and sediment (4.72 kg m-2), and zones of major total...... sediment deposition coincided with the flow confluence zones. The revealed complex spatially and temporally changing floodplain flow pattern was found to play a decisive role for the deposition processes. The interaction between stream flow and groundwater from catchment to point scale has been...

The electrical conductivity of an interacting electron gas

International Nuclear Information System (INIS)

Kojima, D.Y.

1977-01-01

A manybody theory by the propagator method developed by Montroll and Ward for the equilibrium statistical mechanics, is reformulated to describe the electrical conductivity for an electron gas system containing impurity. The theory includes electron-impurity interaction to the infinite order and electron-electron interaction to the first order exchange effect. The propagator used by Montroll and Ward is separated into two propagators, each of which satisfies either Bloch or Schroedinger equation, to utilize the perturbation method. Correct counting of graphs are presented. Change in the relaxation time due to the electron-electron interaction is explicity shown and compared with recent works [pt

Interaction of surface water and groundwater in the Nile River basin: isotopic and piezometric evidence

Science.gov (United States)

Kebede, Seifu; Abdalla, Osman; Sefelnasr, Ahmed; Tindimugaya, Callist; Mustafa, Osman

2017-05-01

Past discussions around water-resources management and development in the River Nile basin disregard groundwater resources from the equation. There is an increasing interest around factoring the groundwater resources as an integral part of the Nile Basin water resources. This is hampered by knowledge gap regarding the groundwater resources dynamics (recharge, storage, flow, quality, surface-water/groundwater interaction) at basin scale. This report provides a comprehensive analysis of the state of surface-water/groundwater interaction from the headwater to the Nile Delta region. Piezometric and isotopic (δ18O, δ2H) evidence reveal that the Nile changes from a gaining stream in the headwater regions to mostly a loosing stream in the arid lowlands of Sudan and Egypt. Specific zones of Nile water leakage to the adjacent aquifers is mapped using the two sources of evidence. Up to 50% of the surface-water flow in the equatorial region of the Nile comes from groundwater as base flow. The evidence also shows that the natural direction and rate of surface-water/groundwater interaction is largely perturbed by human activities (diversion, dam construction) particularly downstream of the Aswan High Dam in Egypt. The decrease in discharge of the Nile River along its course is attributed to leakage to the aquifers as well as to evaporative water loss from the river channel. The surface-water/groundwater interaction occurring along the Nile River and its sensitivity to infrastructure development calls for management strategies that account groundwater as an integral part of the Nile Basin resources.

Multi-scale interactions affecting transport, storage, and processing of solutes and sediments in stream corridors (Invited)

Science.gov (United States)

Harvey, J. W.; Packman, A. I.

2010-12-01

Surface water and groundwater flow interact with the channel geomorphology and sediments in ways that determine how material is transported, stored, and transformed in stream corridors. Solute and sediment transport affect important ecological processes such as carbon and nutrient dynamics and stream metabolism, processes that are fundamental to stream health and function. Many individual mechanisms of transport and storage of solute and sediment have been studied, including surface water exchange between the main channel and side pools, hyporheic flow through shallow and deep subsurface flow paths, and sediment transport during both baseflow and floods. A significant challenge arises from non-linear and scale-dependent transport resulting from natural, fractal fluvial topography and associated broad, multi-scale hydrologic interactions. Connections between processes and linkages across scales are not well understood, imposing significant limitations on system predictability. The whole-stream tracer experimental approach is popular because of the spatial averaging of heterogeneous processes; however the tracer results, implemented alone and analyzed using typical models, cannot usually predict transport beyond the very specific conditions of the experiment. Furthermore, the results of whole stream tracer experiments tend to be biased due to unavoidable limitations associated with sampling frequency, measurement sensitivity, and experiment duration. We recommend that whole-stream tracer additions be augmented with hydraulic and topographic measurements and also with additional tracer measurements made directly in storage zones. We present examples of measurements that encompass interactions across spatial and temporal scales and models that are transferable to a wide range of flow and geomorphic conditions. These results show how the competitive effects between the different forces driving hyporheic flow, operating at different spatial scales, creates a situation

Rock–water interactions and pollution processes in the volcanic aquifer system of Guadalajara, Mexico, using inverse geochemical modeling

International Nuclear Information System (INIS)

Morán-Ramírez, J.; Ledesma-Ruiz, R.; Mahlknecht, J.; Ramos-Leal, J.A.

2016-01-01

In order to understand and mitigate the deterioration of water quality in the aquifer system underlying Guadalajara metropolitan area, an investigation was performed developing geochemical evolution models for assessment of groundwater chemical processes. The models helped not only to conceptualize the groundwater geochemistry, but also to evaluate the relative influence of anthropogenic inputs and natural sources of salinity to the groundwater. Mixing processes, ion exchange, water–rock–water interactions and nitrate pollution and denitrification were identified and confirmed using mass-balance models constraint by information on hydrogeology, groundwater chemistry, lithology and stability of geochemical phases. The water–rock interactions in the volcanic setting produced a dominant Na−HCO_3 water type, followed by Na−Mg−Ca−HCO_3 and Na−Ca−HCO_3. For geochemical evolution modeling, flow sections were selected representing recharge and non-recharge processes and a variety of mixing conditions. Recharge processes are dominated by dissolution of soil CO_2 gas, calcite, gypsum, albite and biotite, and Ca/Na exchange. Non-recharge processes show that the production of carbonic acid and Ca/Na exchange are decreasing, while other minerals such as halite and amorphous SiO_2 are precipitated. The origin of nitrate pollution in groundwater are fertilizers in rural plots and wastewater and waste disposal in the urban area. This investigation may help water authorities to adequately address and manage groundwater contamination. - Highlights: • The Inverse geochemical modeling was used to study to processes occurring in a volcanic aquifer. • Three flow sections were selected to apply inverse hydrogeochemical modeling. • Three main groundwater flows were identified: a local, intermediate and regional flow. • The models show that in the study area that groundwater is mixed with local recharge. • In the south, the aquifer has thermal influence.

Analytical local electron-electron interaction model potentials for atoms

International Nuclear Information System (INIS)

Neugebauer, Johannes; Reiher, Markus; Hinze, Juergen

2002-01-01

Analytical local potentials for modeling the electron-electron interaction in an atom reduce significantly the computational effort in electronic structure calculations. The development of such potentials has a long history, but some promising ideas have not yet been taken into account for further improvements. We determine a local electron-electron interaction potential akin to those suggested by Green et al. [Phys. Rev. 184, 1 (1969)], which are widely used in atom-ion scattering calculations, electron-capture processes, and electronic structure calculations. Generalized Yukawa-type model potentials are introduced. This leads, however, to shell-dependent local potentials, because the origin behavior of such potentials is different for different shells as has been explicated analytically [J. Neugebauer, M. Reiher, and J. Hinze, Phys. Rev. A 65, 032518 (2002)]. It is found that the parameters that characterize these local potentials can be interpolated and extrapolated reliably for different nuclear charges and different numbers of electrons. The analytical behavior of the corresponding localized Hartree-Fock potentials at the origin and at long distances is utilized in order to reduce the number of fit parameters. It turns out that the shell-dependent form of Green's potential, which we also derive, yields results of comparable accuracy using only one shell-dependent parameter

Carbonate aquifers

Science.gov (United States)

Cunningham, Kevin J.; Sukop, Michael; Curran, H. Allen

2012-01-01

Only limited hydrogeological research has been conducted using ichnology in carbonate aquifer characterization. Regardless, important applications of ichnology to carbonate aquifer characterization include its use to distinguish and delineate depositional cycles, correlate mappable biogenically altered surfaces, identify zones of preferential groundwater flow and paleogroundwater flow, and better understand the origin of ichnofabric-related karst features. Three case studies, which include Pleistocene carbonate rocks of the Biscayne aquifer in southern Florida and Cretaceous carbonate strata of the Edwards–Trinity aquifer system in central Texas, demonstrate that (1) there can be a strong relation between ichnofabrics and groundwater flow in carbonate aquifers and (2) ichnology can offer a useful methodology for carbonate aquifer characterization. In these examples, zones of extremely permeable, ichnofabric-related macroporosity are mappable stratiform geobodies and as such can be represented in groundwater flow and transport simulations.

Uranium series geochemistry in aquifers: quantification of transport mechanisms of uranium and daughter products: the chalk aquifer (Champagne, France)

International Nuclear Information System (INIS)

Hubert, A.

2005-09-01

With the increase of contaminant flux of radionuclides in surface environment (soil, river, aquifer...), there is a need to understand and model the processes that control the distribution of uranium and its daughter products during transport within aquifers. We have used U-series disequilibria as an analogue for the transport of uranium and its daughter products in aquifer to understand such mechanisms. The measurements of uranium ( 234 U et 238 U), thorium ( 230 Th et 232 Th), 226 Ra and 222 Rn isotopes in the solid and liquid phases of the chalk aquifer in Champagne (East of France) allows us to understand the processes responsible for fractionation within the uranium decay chain. Fractionations are induced by physical and chemical properties of the elements (leaching, adsorption) but also by radioactive properties (recoil effect during α-decay). For the first time a comprehensive sampling of the solid phase has been performed, allowing quantifying mechanisms responsible for the long term evolution of the aquifer. A non steady state 1D model has been developed which takes into account leaching, adsorption processes as well as radioactive filiation and α-recoil effect. Retardation coefficients have been calculated for uranium, thorium and radium. The aquifer is characterised by a double porosity, and the contribution of fracture and matrix porosity on the water/rock interaction processes has been estimated. (author)

Noncovalent Interactions in Organic Electronic Materials

KAUST Repository

Ravva, Mahesh Kumar

2017-06-29

In this chapter, we provide an overview of how noncovalent interactions, determined by the chemical structure of π-conjugated molecules and polymers, govern essential aspects of the electronic, optical, and mechanical characteristics of organic semiconductors. We begin by describing general aspects of materials design, including the wide variety of chemistries exploited to control the electronic and optical properties of these materials. We then discuss explicit examples of how the study of noncovalent interactions can provide deeper chemical insights that can improve the design of new generations of organic electronic materials.

Motion of shocks through interplanetary streams

International Nuclear Information System (INIS)

Burlaga, L.F.; Scudder, J.D.

1975-01-01

A model for the motion of flare-generated shocks through interplanetary streams is presented, illustrating the effects of a stream-shock interaction on the shock strength and geometry. It is a gas dynamic calculation based on Whitham's method and on an empirical approximation for the relevant characteristics of streams. The results show that the Mach number of a shock can decrease appreciably to near unity in the interaction region ahead of streams and that the interaction of a spherically symmetric shock with a spiral-shaped corotating stream can cause significant distortions of the initial shock front geometry. The geometry of the February 15--16, 1967, shock discussed by Lepping and Chao (1972) is qualitatively explained by this model

Interaction of Aquifer and River-Canal Network near Well Field.

Science.gov (United States)

Ghosh, Narayan C; Mishra, Govinda C; Sandhu, Cornelius S S; Grischek, Thomas; Singh, Vikrant V

2015-01-01

The article presents semi-analytical mathematical models to asses (1) enhancements of seepage from a canal and (2) induced flow from a partially penetrating river in an unconfined aquifer consequent to groundwater withdrawal in a well field in the vicinity of the river and canal. The nonlinear exponential relation between seepage from a canal reach and hydraulic head in the aquifer beneath the canal reach is used for quantifying seepage from the canal reach. Hantush's (1967) basic solution for water table rise due to recharge from a rectangular spreading basin in absence of pumping well is used for generating unit pulse response function coefficients for water table rise in the aquifer. Duhamel's convolution theory and method of superposition are applied to obtain water table position due to pumping and recharge from different canal reaches. Hunt's (1999) basic solution for river depletion due to constant pumping from a well in the vicinity of a partially penetrating river is used to generate unit pulse response function coefficients. Applying convolution technique and superposition, treating the recharge from canal reaches as recharge through conceptual injection wells, river depletion consequent to variable pumping and recharge is quantified. The integrated model is applied to a case study in Haridwar (India). The well field consists of 22 pumping wells located in the vicinity of a perennial river and a canal network. The river bank filtrate portion consequent to pumping is quantified. © 2014, National GroundWater Association.

Interactions between hyporheic flow produced by stream meanders, bars, and dunes

Science.gov (United States)

Stonedahl, Susa H.; Harvey, Judson W.; Packman, Aaron I.

2013-01-01

Stream channel morphology from grain-scale roughness to large meanders drives hyporheic exchange flow. In practice, it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers. As a result, many studies only characterize isolated exchange processes at a single spatial scale. In this work, we simulated hyporheic flows induced by a range of geomorphic features including meanders, bars and dunes in sand bed streams. Twenty cases were examined with 5 degrees of river meandering. Each meandering river model was run initially without any small topographic features. Models were run again after superimposing only bars and then only dunes, and then run a final time after including all scales of topographic features. This allowed us to investigate the relative importance and interactions between flows induced by different scales of topography. We found that dunes typically contributed more to hyporheic exchange than bars and meanders. Furthermore, our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to, but not linearly additive. These findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers.

Hydrogeologic appraisal of a stratified-drift aquifer near Smyrna, Chenango County, New York

Science.gov (United States)

Reynolds, R.J.; Brown, G.A.

1984-01-01

A broad, Y-shaped valley near Smyrna, New York, contains extensive water-table and confined aquifers that are largely hydraulically separated from the nearby Chenango River to the east. Accordingly, ground-water withdrawals from this valley would not appreciably decrease streamflow in the Chenango River by induced infiltration and could be used for specialized needs. The aquifers in the valley are capable of sustaining a long-term total withdrawal of about 12.7 million gallons per day during prolonged drought conditions. Larger withdrawals could be made on a short-term basis or during periods of normal or above-normal precipitation. Saturated thickness of undifferentiated stratified-drift deposits in the valley ranges from 20 feet in the northwestern part of the valley to more than 300 feet at its southern end. Direct areal recharge accounts for about 56 percent of the total recharge to the valley aquifer infiltration from streams accounts for 24 percent, and runoff from the adjacent till-mantled hillsides accounts for 20 percent. The water-table and confined aquifers within the valley hold at least 19.6 billion gallons of usable ground water in storage. (USGS)

Terahertz electron cyclotron maser interactions with an axis-encircling electron beam

Science.gov (United States)

Li, G. D.; Kao, S. H.; Chang, P. C.; Chu, K. R.

2015-04-01

To generate terahertz radiation via the electron cyclotron maser instability, harmonic interactions are essential in order to reduce the required magnetic field to a practical value. Also, high-order mode operation is required to avoid excessive Ohmic losses. The weaker harmonic interaction and mode competition associated with an over-moded structure present challenging problems to overcome. The axis-encircling electron beam is a well-known recipe for both problems. It strengthens the harmonic interaction, as well as minimizing the competing modes. Here, we examine these advantages through a broad data base obtained for a low-power, step-tunable, gyrotron oscillator. Linear results indicate far more higher-harmonic modes can be excited with an axis-encircling electron beam than with an off-axis electron beam. However, multi-mode, time-dependent simulations reveal an intrinsic tendency for a higher-harmonic mode to switch over to a lower-harmonic mode at a high beam current or upon a rapid current rise. Methods are presented to identify the narrow windows in the parameter space for stable harmonic interactions.

Terahertz electron cyclotron maser interactions with an axis-encircling electron beam

International Nuclear Information System (INIS)

Li, G. D.; Kao, S. H.; Chang, P. C.; Chu, K. R.

2015-01-01

To generate terahertz radiation via the electron cyclotron maser instability, harmonic interactions are essential in order to reduce the required magnetic field to a practical value. Also, high-order mode operation is required to avoid excessive Ohmic losses. The weaker harmonic interaction and mode competition associated with an over-moded structure present challenging problems to overcome. The axis-encircling electron beam is a well-known recipe for both problems. It strengthens the harmonic interaction, as well as minimizing the competing modes. Here, we examine these advantages through a broad data base obtained for a low-power, step-tunable, gyrotron oscillator. Linear results indicate far more higher-harmonic modes can be excited with an axis-encircling electron beam than with an off-axis electron beam. However, multi-mode, time-dependent simulations reveal an intrinsic tendency for a higher-harmonic mode to switch over to a lower-harmonic mode at a high beam current or upon a rapid current rise. Methods are presented to identify the narrow windows in the parameter space for stable harmonic interactions

Functional trait composition of aquatic plants can serve to disentangle multiple interacting stressors in lowland streams

Energy Technology Data Exchange (ETDEWEB)

Baattrup-Pedersen, Annette, E-mail: abp@bios.au.dk [Department of Bioscience, Aarhus University, Vejlsøvej 25, P.O. Box 314, DK-8600 Silkeborg (Denmark); Göthe, Emma [Department of Bioscience, Aarhus University, Vejlsøvej 25, P.O. Box 314, DK-8600 Silkeborg (Denmark); Riis, Tenna [Department of Bioscience, Aarhus University, Ole Worms Allé 1, Building 1135, Room 217, DK-8000 Aarhus C (Denmark); O' Hare, Matthew T. [Centre for Ecology and Hydrology, Bush Estate, Penicuik EH26 0QB (United Kingdom)

2016-02-01

Historically, close attention has been paid to negative impacts associated with nutrient loads to streams and rivers, but today hydromorphological alterations are considered increasingly implicated when lowland streams do not achieve good ecological status. Here, we explore if trait-abundance patterns of aquatic plants change along gradients in hydromorphological degradation and eutrophication in lowland stream sites located in Denmark. Specifically, we hypothesised that: i) changes in trait-abundance patterns occur along gradients in hydromorphological degradation and ii) trait-abundance patterns can serve to disentangle effects of eutrophication and hydromorphological degradation in lowland streams reflecting that the mechanisms behind changes differ. We used monitoring data from a total of 147 stream reaches with combined data on aquatic plant species abundance, catchment land use, hydromorphological alterations (i.e. planform, cross section, weed cutting) and water chemistry parameters. Traits related to life form, dispersal, reproduction and survival together with ecological preference values for nutrients and light (Ellenberg N and L) were allocated to 41 species representing 79% of the total species pool. We found clear evidence that habitat degradation (hydromorphological alterations and eutrophication) mediated selective changes in the trait-abundance patterns of the plant community. Specific traits could distinguish hydromorphological degradation (free-floating, surface; anchored floating leaves; anchored heterophylly) from eutrophication (free-floating, submerged; leaf area). We provide a conceptual framework for interpretation of how eutrophication and hydromorphological degradation interact and how this is reflected in trait-abundance patterns in aquatic plant communities in lowland streams. Our findings support the merit of trait-based approaches in biomonitoring as they shed light on mechanisms controlling structural changes under environmental

Functional trait composition of aquatic plants can serve to disentangle multiple interacting stressors in lowland streams

International Nuclear Information System (INIS)

Baattrup-Pedersen, Annette; Göthe, Emma; Riis, Tenna; O'Hare, Matthew T.

2016-01-01

Historically, close attention has been paid to negative impacts associated with nutrient loads to streams and rivers, but today hydromorphological alterations are considered increasingly implicated when lowland streams do not achieve good ecological status. Here, we explore if trait-abundance patterns of aquatic plants change along gradients in hydromorphological degradation and eutrophication in lowland stream sites located in Denmark. Specifically, we hypothesised that: i) changes in trait-abundance patterns occur along gradients in hydromorphological degradation and ii) trait-abundance patterns can serve to disentangle effects of eutrophication and hydromorphological degradation in lowland streams reflecting that the mechanisms behind changes differ. We used monitoring data from a total of 147 stream reaches with combined data on aquatic plant species abundance, catchment land use, hydromorphological alterations (i.e. planform, cross section, weed cutting) and water chemistry parameters. Traits related to life form, dispersal, reproduction and survival together with ecological preference values for nutrients and light (Ellenberg N and L) were allocated to 41 species representing 79% of the total species pool. We found clear evidence that habitat degradation (hydromorphological alterations and eutrophication) mediated selective changes in the trait-abundance patterns of the plant community. Specific traits could distinguish hydromorphological degradation (free-floating, surface; anchored floating leaves; anchored heterophylly) from eutrophication (free-floating, submerged; leaf area). We provide a conceptual framework for interpretation of how eutrophication and hydromorphological degradation interact and how this is reflected in trait-abundance patterns in aquatic plant communities in lowland streams. Our findings support the merit of trait-based approaches in biomonitoring as they shed light on mechanisms controlling structural changes under environmental

Regeneration of a confined aquifer after redevelopment and decommission of artesian wells, example from Grafendorf aquifer (Styria, Austria)

Science.gov (United States)

Mehmedovski, Nudzejma; Winkler, Gerfried

2016-04-01

Water is essential for life and it is therefore necessary to protect drinking water sustainably. Compared to shallow groundwater, deeper groundwater is especially important due to its characteristic tendency to remain extensively unaffected by environmental impacts. Thus, the uncontrolled waste of this valuable resource has to be avoided. A lot of artesian wells have been established in Grafendorf bei Hartberg (Styria, Austria). Almost all wells were not state-of-the art. As a result the different aquifer horizons began to intermix. Additionally some of the artesian wells had a permanent free overflow and the water was not even used. Consequently, since 1950, where the mean discharge of 37 wells was 0,334 l/s per well, the discharge has decreased to 0,090 l/s until 2013, which means a decline of about 75 %. As a reaction to these declines a decommissioning campaign was conducted where 69 artesian wells have been closed by injecting a cement-bentonite suspension (ratio 3:1). The Grafendorf aquifer is situated in the Styrian Basin and consists of 5 separated artesian horizons in Neogene sediments. These artesian horizons range from 42 m (1st horizon) to 176 m (5th horizon) and mostly consist of sand, partly of fine/medium/coarse gravel and partially with minor clay content. In order to analyse the reaction of the Grafendorf aquifer to these redevelopments, 5 monitoring wells could be used for the analysis. Some monitoring wells include different aquifer horizons and hydraulically short cut them. Thus, in this work the analysis focus on the general trend of the whole aquifer system neglecting the individual interactions between the different aquifers. In a first investigation step the hydraulic properties of the aquifer system has been determined using pumping tests which were analysed with different analytical solutions with the software AQTESOLV. Overall the pumping test solutions hardly differ in the transmissivity and hydraulic conductivity. On the contrary the

Effects of self-fields on electron trajectory and gain in two-stream electromagnetically pumped free-electron laser with ion channel guiding

International Nuclear Information System (INIS)

Saviz, S.; Ghorannevis, M.; Aghamir, Farzin M.; Mehdian, H.

2011-01-01

A theory for the two-stream free-electron laser with an electromagnetic wiggler (EMW) and an ion channel guiding is developed. In the analysis, the effects of self-fields have been taken into account. The electron trajectories and the small signal gain are derived. The stability of the trajectories, the characteristics of the linear gain and the normalized maximum gain are studied numerically. The dependence of the normalized frequency ω-circumflex corresponding to the maximum gain on the ion-channel frequency is presented. The results show that there are seven groups of orbits in the presence of the self-fields, which are similar to those reported in the absence of the self-fields. It is also shown that the normalized gains of 2 groups decrease while the rest increase with the increasing normalized ion-channel frequency. Furthermore, it is found that the two-stream instability and the self-field lead to a decrease in the maximum gain except for group 4. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Non-uniform groundwater discharge across a stream bed: Heat as a tracer

DEFF Research Database (Denmark)

Jensen, Jannick Kolbjørn; Engesgaard, Peter Knudegaard

2011-01-01

Time series analysis of conO nuous streambed temperature during a period of 47 d revealed that discharge to a stream is nonuniform, with strongly increasing verO cal fl uxes throughout the top 20 cm of the streambed–aquifer interface. An analyO cal soluO on to the transient heat transport equa...... near the streambed. Seepage meter measurements in the middle of the stream oO en resulted in highly variable fl ux esO - mates, which could have been caused by hyporheic fl ow due to the presence of a gravel layer. Discharge and recharge to the stream at the bank near the meadow was relaO vely steady...

The Guarani Aquifer System: estimation of recharge along the Uruguay-Brazil border

Science.gov (United States)

Gómez, Andrea A.; Rodríguez, Leticia B.; Vives, Luis S.

2010-11-01

The cities of Rivera and Santana do Livramento are located on the outcropping area of the sandstone Guarani Aquifer on the Brazil-Uruguay border, where the aquifer is being increasingly exploited. Therefore, recharge estimates are needed to address sustainability. First, a conceptual model of the area was developed. A multilayer, heterogeneous and anisotropic groundwater-flow model was built to validate the conceptual model and to estimate recharge. A field campaign was conducted to collect water samples and monitor water levels used for model calibration. Field data revealed that there exists vertical gradients between confining basalts and underlying sandstones, suggesting basalts could indirectly recharge sandstone in fractured areas. Simulated downward flow between them was a small amount within the global water budget. Calibrated recharge rates over basalts and over outcropping sandstones were 1.3 and 8.1% of mean annual precipitation, respectively. A big portion of sandstone recharge would be drained by streams. The application of a water balance yielded a recharge of 8.5% of average annual precipitation. The numerical model and the water balance yielded similar recharge values consistent with determinations from previous authors in the area and other regions of the aquifer, providing an upper bound for recharge in this transboundary aquifer.

Geohydrology of the valley-fill aquifer in the Endicott-Johnson City area, Broome County, New York

Science.gov (United States)

Holecek, Thomas J.; Randall, A.D.; Belli, J.L.; Allen, R.V.

1982-01-01

This report is the tenth in a series of 11 map sets depicting geohydrologic conditions in selected aquifers in upstate New York. Geohydrologic data are compiled on five maps at 1:24,000 scale. Together, the maps provide a comprehensive overview of a major valley-fill aquifer in southwestern Broome County. The maps include surficial geology, geologic sections, aquifer thickness, water-infiltration potential of soil zone, potentiometric-surface altitude, and land use. The valley-fill deposits consist of alluvial silt and sand, glacial outwash (sand and gravel), ice-contact sand and gravel, till, and lacustrine silt and clay. The sand and gravel beds have relatively high permeabilities whereas the till, silt, and clay deposits have relatively low permeabilities. Water-table conditions are found in unconfined sand and gravel, whereas artesian conditions prevail within sand and gravel confined by silty deposits. Recharge occurs over the entire surface of the aquifer, due to permeable land-surface conditions, but is greatest along the margin of the valley, where runoff from the hillsides is concentrated, and near streams. The use of land overlying the aquifer is predominantly commercial and residential with lesser amounts of agricultural and industrial uses. (USGS)

The Electron-Phonon Interaction in Strongly Correlated Systems

International Nuclear Information System (INIS)

Castellani, C.; Grilli, M.

1995-01-01

We analyze the effect of strong electron-electron repulsion on the electron-phonon interaction from a Fermi-liquid point of view and show that the electron-electron interaction is responsible for vertex corrections, which generically lead to a strong suppression of the electron-phonon coupling in the v F q/ω >>1 region, while such effect is not present when v F q/ω F is the Fermi velocity and q and ω are the transferred momentum and frequency respectively. In particular the e-ph scattering is suppressed in transport properties which are dominated by low-energy-high-momentum processes. On the other hand, analyzing the stability criterion for the compressibility, which involves the effective interactions in the dynamical limit, we show that a sizable electron-phonon interaction can push the system towards a phase-separation instability. Finally a detailed analysis of these ideas is carried out using a slave-boson approach for the infinite-U three-band Hubbard model in the presence of a coupling between the local hole density and a dispersionless optical phonon. (author)

Water resources of Rockland County, New York, 2005-07, with emphasis on the Newark Basin Bedrock Aquifer

Science.gov (United States)

Heisig, Paul M.

2011-01-01

Concerns over the state of water resources in Rockland County, NY, prompted an assessment of current (2005-07) conditions. The investigation included a review of all water resources but centered on the Newark basin aquifer, a fractured-bedrock aquifer over which nearly 300,000 people reside. Most concern has been focused on this aquifer because of (1) high summer pumping rates, with occasional entrained-air problems and an unexplained water-level decline at a monitoring well, (2) annual withdrawals that have approached or even exceeded previous estimates of aquifer recharge, and (3) numerous contamination problems that have caused temporary or long-term shutdown of production wells. Public water supply in Rockland County uses three sources of water in roughly equal parts: (1) the Newark basin sedimentary bedrock aquifer, (2) alluvial aquifers along the Ramapo and Mahwah Rivers, and (3) surface waters from Lake DeForest Reservoir and a smaller, new reservoir supply in the Highlands part of the county. Water withdrawals from the alluvial aquifer in the Ramapo River valley and the Lake DeForest Reservoir are subject to water-supply application permits that stipulate minimum flows that must be maintained downstream into New Jersey. There is a need, therefore, at a minimum, to prevent any loss of the bedrock-aquifer resource--to maintain it in terms of both sustainable use and water-quality protection. The framework of the Newark basin bedrock aquifer included characterization of (1) the structure and fracture occurrence associated with the Newark basin strata, (2) the texture and thickness of overlying glacial and alluvial deposits, (3) the presence of the Palisades sill and associated basaltic units on or within the Newark basin strata, and (4) the streams that drain the aquifer system. The greatest concern regarding sustainability of groundwater resources is the aquifer response to the seasonal increase in pumping rates from May through October (an average increase

Variability of streambed hydraulic conductivity in an intermittent stream reach regulated by Vented Dams: A case study

Science.gov (United States)

Naganna, Sujay Raghavendra; Deka, Paresh Chandra

2018-07-01

The hydro-geological properties of streambed together with the hydraulic gradients determine the fluxes of water, energy and solutes between the stream and underlying aquifer system. Dam induced sedimentation affects hyporheic processes and alters substrate pore space geometries in the course of progressive stabilization of the sediment layers. Uncertainty in stream-aquifer interactions arises from the inherent complex-nested flow paths and spatio-temporal variability of streambed hydraulic properties. A detailed field investigation of streambed hydraulic conductivity (Ks) using Guelph Permeameter was carried out in an intermittent stream reach of the Pavanje river basin located in the mountainous, forested tract of western ghats of India. The present study reports the spatial and temporal variability of streambed hydraulic conductivity along the stream reach obstructed by two Vented Dams in sequence. Statistical tests such as Levene's and Welch's t-tests were employed to check for various variability measures. The strength of spatial dependence and the presence of spatial autocorrelation among the streambed Ks samples were tested by using Moran's I statistic. The measures of central tendency and dispersion pointed out reasonable spatial variability in Ks distribution throughout the study reach during two consecutive years 2016 and 2017. The streambed was heterogeneous with regard to hydraulic conductivity distribution with high-Ks zones near the backwater areas of the vented dam and low-Ks zones particularly at the tail water section of vented dams. Dam operational strategies were responsible for seasonal fluctuations in sedimentation and modifications to streambed substrate characteristics (such as porosity, grain size, packing etc.), resulting in heterogeneous streambed Ks profiles. The channel downstream of vented dams contained significantly more cohesive deposits of fine sediment due to the overflow of surplus suspended sediment-laden water at low velocity

Effect of electron-photon interaction on the knight shift

International Nuclear Information System (INIS)

Tripathi, G.S.; Misra, C.M.; Tripathi, P.; Misra, P.K.

1990-01-01

The effect of electron-phonon interaction is considered on the spin (K s ), orbital (K o ) and spin-orbit (K so ) contributions to the Knight shift. In case of K s , it is found that the modifications caused due to the magnetic field dependence of electron self-energy in the presence of electron-phonon interaction is cancelled by the electron-phonon mass enhancement. However, in the presence of both electron-electron and electron-phonon interactions, the exchange enhancement parameter α is modified to α(1+γ) -1 where γ is the electron-phonon mass enhancement parameter. The orbital and spin-orbital contributions are mainly modified through the changes in the one-electron energies and wave functions. (orig.)

Electron emission during multicharged ion-metal surface interactions

International Nuclear Information System (INIS)

Zeijlmans van Emmichoven, P.A.; Havener, C.C.; Hughes, I.G.; Overbury, S.H.; Robinson, M.T.; Zehner, D.M.; Meyer, F.W.

1992-01-01

The electron emission during multicharged ion-metal surface interactions will be discussed. The interactions lead to the emission of a significant number of electrons. Most of these electrons have energies below 30 eV. For incident ions with innershell vacancies the emission of Auger electrons that fill these vacancies has been found to occur mainly below the surface. We will present recently measured electron energy distributions which will be used to discuss the mechanisms that lead to the emission of Auger and of low-energy electrons

Understanding the physical dynamics and ecological interactions in tidal stream energy environments

Science.gov (United States)

Fraser, Shaun; Williamson, Benjamin J.; Nikora, Vladimir; Scott, Beth E.

2017-04-01

Tidal stream energy devices are intended to operate in energetic physical environments characterised by high flows and extreme turbulence. These environments are often of ecological importance to a range of marine species. Understanding the physical dynamics and ecological interactions at fine scales in such sites is essential for device/array design and to understand environmental impacts. However, investigating fine scale characteristics requires high resolution field measurements which are difficult to attain and interpret, with data often confounded by interference related to turbulence. Consequently, field observations in tidal stream energy environments are limited and require the development of specialised analysis methods and so significant knowledge gaps are still present. The seabed mounted FLOWBEC platform is addressing these knowledge gaps using upward facing instruments to collect information from around marine energy infrastructure. Multifrequency and multibeam echosounder data provide detailed information on the distribution and interactions of biological targets, such as fish and diving seabirds, while simultaneously recording the scales and intensity of turbulence. Novel processing methodologies and instrument integration techniques have been developed which combine different data types and successfully separates signal from noise to reveal new evidence about the behaviour of mobile species and the structure of turbulence at all speeds of the tide and throughout the water column. Multiple platform deployments in the presence and absence of marine energy infrastructure reveal the natural characteristics of high energy sites, and enable the interpretation of the physical and biological impacts of tidal stream devices. These methods and results are relevant to the design and consenting of marine renewable energy technologies, and provide novel information on the use of turbulence for foraging opportunities in high energy sites by mobile species.

Aquifer storage and recovery: recent hydrogeological advances and system performance.

Science.gov (United States)

Maliva, Robert G; Guo, Weixing; Missimer, Thomas M

2006-12-01

Aquifer storage and recovery (ASR) is part of the solution to the global problem of managing water resources to meet existing and future freshwater demands. However, the metaphoric "ASR bubble" has been burst with the realization that ASR systems are more physically and chemically complex than the general conceptualization. Aquifer heterogeneity and fluid-rock interactions can greatly affect ASR system performance. The results of modeling studies and field experiences indicate that more sophisticated data collection and solute-transport modeling are required to predict how stored water will migrate in heterogeneous aquifers and how fluid-rock interactions will affect the quality of stored water. It has been well-demonstrated, by historic experience, that ASR systems can provide very large volumes of storage at a lesser cost than other options. The challenges moving forward are to improve the success rate of ASR systems, optimize system performance, and set expectations appropriately.

Metal particle emissions in the exhaust stream of diesel engines: an electron microscope study.

Science.gov (United States)

Liati, Anthi; Schreiber, Daniel; Dimopoulos Eggenschwiler, Panayotis; Arroyo Rojas Dasilva, Yadira

2013-12-17

Scanning electron microscopy and transmission electron microscopy were applied to investigate the morphology, mode of occurrence and chemical composition of metal particles (diesel ash) in the exhaust stream of a small truck outfitted with a typical after-treatment system (a diesel oxidation catalyst (DOC) and a downstream diesel particulate filter (DPF)). Ash consists of Ca-Zn-P-Mg-S-Na-Al-K-phases (lube-oil related), Fe, Cr, Ni, Sn, Pb, Sn (engine wear), and Pd (DOC coating). Soot agglomerates of variable sizes (1-5 μm, exceptionally 13 μm), rarely engine wear and escape into the atmosphere.

Electron interactions with nuclei: Progress report

International Nuclear Information System (INIS)

1988-08-01

This paper contains information on the following topics: inclusive electron scattering; electroexcitation of Δ in nuclei; longitudinal and transverse response in the quasi-elastic region; electron scattering at MIT-Bates; detector development at LEGS; electron scattering at Saclay; intermediate energy nuclear interactions; research and development at CEBAF; and computing facilities

Electron spin from self interaction

International Nuclear Information System (INIS)

Spavieri, G.

1992-01-01

The author explores the possibility that the electron self-interaction is the origin of the spin and of the radiative effects of QED. The electron is conceived as a charged, massless, point particle with a quantum or stochastic, internal motion about its center of mass and bound by a self-interaction potential. The hydrodynamic equations of motion describing the electron in its center of mass frame are related to non-Markovian stochastic equations recently used to derive the Schroedinger equation. By averaging over this stochastic internal motion and identifying the energy with the rest mass energy, the angular momentum exhibits properties characteristic of spin. The electromagnetic self-interactions added to the Hamiltonian of the particle correct the g factor to yield the anomalous value (g-2)/2 ∼ 1159.7(2.3) X 10 -6 in agreement with experiment. Calculations of other open-quotes radiativeclose quotes effects including the Lamb shift are presented. The results obtained are finite and suggest that the QED corrections attributed to radiative effects could be obtained classically, i.e., without second quantization and renormalization, by complementing the Dirac theory with this self-interaction mechanism. The g factor dependence on the external magnetic field of this and other spin models is compared with that of QED, showing that these theories can be tested by the present precision measurements of the g factor. 33 refs., 2 tabs

Vertical variability of arsenic concentrations under the control of iron-sulfur-arsenic interactions in reducing aquifer systems

Science.gov (United States)

Pi, Kunfu; Wang, Yanxin; Postma, Dieke; Ma, Teng; Su, Chunli; Xie, Xianjun

2018-06-01

High spatial variability of arsenic (As) concentration in geogenic As-contaminated groundwater has been commonly observed worldwide, but the underlying reasons remain not well understood. Selecting a sulfate-containing, As-affected aquifer at the Datong Basin, northern China as the study area and combining hydrogeochemical investigation and sediment extraction with reactive transport modeling, this work elucidated the roles of Fe-S-As interactions in regulating the vertical variation of As concentration in the groundwater. Dissolved As concentration varied between 0.05 and 18 μmol/L, but generally increased in the depth of 20-25 m and then decreased in 25-30 m. The high-As groundwater contained low Fe(II) (groundwater devoid of sulfate reduction. The reductive dissolution of As-bearing Fe(III) oxides coupled to the degradation of organic matter with an estimated maximum rate of 0.22 mmol C/L/yr, mainly accounted for the depth-dependent increase of As concentration in the upper part of the shallow aquifer (groundwater but also probably co-precipitated As to prompt As decrease in the depth of 25-30 m. Arsenite adsorbed on remaining Fe(III) oxides and newly-formed Fe(II) sulfides is another important pool of As in the aquifer, which varies in response to the extents of Fe(III)-oxide and sulfate reduction and consequently alters As distribution coefficient between the solid and the aqueous phases. This study highlights the importance of coupled geochemical cycling of Fe, S and As for As mobilization and reveals how it regulates As partitioning between groundwater and sediments.

Drought-sensitive aquifer settings in southeastern Pennsylvania

Science.gov (United States)

Zimmerman, Tammy M.; Risser, Dennis W.

2005-01-01

This report describes the results of a study conducted by the U.S. Geological Survey, in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey, to determine drought-sensitive aquifer settings in southeastern Pennsylvania. Because all or parts of southeastern Pennsylvania have been in drought-warning or drought-emergency status during 6 of the past 10 years from 1994 through 2004, this information should aid well owners, drillers, and water-resource managers in guiding appropriate well construction and sustainable use of Pennsylvania's water resources. 'Drought-sensitive' aquifer settings are defined for this study as areas unable to supply adequate quantities of water to wells during drought. Using information from previous investigations and a knowledge of the hydrogeology and topography of the study area, drought-sensitive aquifer settings in southeastern Pennsylvania were hypothesized as being associated with two factors - a water-table decline (WTD) index and topographic setting. The WTD index is an estimate of the theoretical water-table decline at the ground-water divide for a hypothetical aquifer with idealized geometry. The index shows the magnitude of ground-water decline after cessation of recharge is a function of (1) distance from stream to divide, (2) ground-water recharge rate, (3) transmissivity, (4) specific yield, and (5) duration of the drought. WTD indices were developed for 39 aquifers that were subsequently grouped into categories of high, moderate, and low WTD index. Drought-sensitive settings determined from the hypothesized factors were compared to locations of wells known to have been affected (gone dry, replaced, or deepened) during recent droughts. Information collected from well owners, drillers, and public agencies identified 2,016 wells affected by drought during 1998-2002. Most of the available data on the location of drought-affected wells in the study area were

Geochemical Investigation of the Arbuckle-Simpson Aquifer, South-Central Oklahoma, 2004-06

Science.gov (United States)

Christenson, Scott; Hunt, Andrew G.; Parkhurst, David L.

2009-01-01

dolomite. The major ion chemistry for these 34 samples is consistent with a set of water-rock interactions. Rainfall infiltrates the soil zone, where the host rock, limestone or dolomite, dissolves as a result of uptake of carbon dioxide gas. Some continued dissolution of dolomite and precipitation of calcite occur as the water flows through the saturated zone. The major ion chemistry of the two samples from wells completed in the confined part of the aquifer indicates the water is a sodium chloride type. Geochemical inverse modeling determined that mixing of calcite-saturated recharge water with brine and dissolving calcite, dolomite, and gypsum accounts for the water composition of these two samples. One of the two samples, collected at Vendome Well in Chickasaw National Recreation Area, had a mixing fraction of brine of about 1 percent. The brine component of the sample at Vendome Well is likely to account for the relatively large concentrations of many of the trace elements (potassium, fluoride, bromide, iodide, ammonia, arsenic, boron, lithium, selenium, and strontium) measured in the water sample. Carbon-14, helium-3/tritium, and chlorofluorocarbons were used to calculate ground-water ages, recharge temperatures, and mixtures of ground water in the Arbuckle-Simpson aquifer. Thirty four of 36 water samples recharged the aquifer after 1950, indicating that water is moving quickly from recharge areas to discharge at streams and springs. Two exceptions to this classification were noted in samples 6 and 15 (Vendome Well). Ground-water ages determined for these two samples by using carbon-14 are 34,000 years (site 6) and 10,500 years (site 15). Concentrations of dissolved argon, neon, and xenon in water samples were used to determine the temperature of the water when it recharged the aquifer. The mean annual air temperature at Ada, Oklahoma, is 16 degrees Celsius (C) and the median temperature of the 30 reconnaissance water samples was 18.1 C. The av

Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

DEFF Research Database (Denmark)

Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

2015-01-01

We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

Born-Oppenheimer Dynamics, Electronic Friction, and the Inclusion of Electron-Electron Interactions

Science.gov (United States)

Dou, Wenjie; Miao, Gaohan; Subotnik, Joseph E.

2017-07-01

We present a universal expression for the electronic friction as felt by a set of classical nuclear degrees of freedom (DOFs) coupled to a manifold of quantum electronic DOFs; no assumptions are made regarding the nature of the electronic Hamiltonian and electron-electron repulsions are allowed. Our derivation is based on a quantum-classical Liouville equation for the coupled electronic-nuclear motion, followed by an adiabatic approximation whereby electronic transitions are assumed to equilibrate faster than nuclear movement. The resulting form of friction is completely general, but does reduce to previously published expressions for the quadratic Hamiltonian (i.e., Hamiltonians without electronic correlation). At equilibrium, the second fluctuation-dissipation theorem is satisfied and the frictional matrix is symmetric. To demonstrate the importance of electron-electron correlation, we study electronic friction within the Anderson-Holstein model, where a proper treatment of electron-electron interactions shows signatures of a Kondo resonance and a mean-field treatment is completely inadequate.

Ground-water-quality assessment of the Central Oklahoma Aquifer, Oklahoma: geochemical and geohydrologic investigations

Science.gov (United States)

Parkhurst, David L.; Christenson, Scott C.; Breit, George N.

1993-01-01

-capacity data. The transmissivities of the Permian geologic units depend largely on the percentage of sandstone; the percentage is greatest in the central part of the aquifer and decreases in all directions from this central part. Because of large mudstone and siltstone contents, the Hennessey Group and the Vanoss Formation are assumed to be confining units above and below the aquifer. The Cimarron and Canadian Rivers are defined to be the northern and southern extent of the aquifer because of decreases in transmissivity beyond the rivers and because there is no indication of ground-water underflow at these rivers. The eastern boundary of the aquifer is the limit of the outcrop of the Chase, Council Grove, and Admire Groups. The presence of brines in the western part of the study unit and below the aquifer indicate the extent of the freshwater flow system in these directions.Regional ground-water flow is west to east; the Deep Fork is a major discharge area for the regional flow system. Local flow systems are present within the unconfined part of the study unit. Most streams are gaining streams, and very few losing streams are evident.Median values of aquifer properties were estimated as follows: recharge to the saturated zone, 1.6 inches per year; evapotranspiration of water that never reaches the saturated zone, 25 to 30 inches per year; porosity, 0.22; storage coefficient, 0.0002; transmissivity, 260 to 450 feet squared per day; horizontal hydraulic conductivity, 4.5 feet per day; and the ratio of horizontal to vertical hydraulic conductivity, 10,000. Reported ground-water withdrawals peaked in 1985 at 13,900 million gallons but had decreased to 7,860 million gallons by 1989. Unreported domestic withdrawals were estimated to be 1,685 million gallons in 1980.The flow system in the aquifer can be considered to have three major components: (1) A shallow, local flow system in the unconfined part of the aquifer, (2) a deep, regional flow system in the unconfined part of the

Current and high-β sheets in CIR streams: statistics and interaction with the HCS and the magnetosphere

Science.gov (United States)

Potapov, A. S.

2018-04-01

Thirty events of CIR streams (corotating interaction regions between fast and slow solar wind) were analyzed in order to study statistically plasma structure within the CIR shear zones and to examine the interaction of the CIRs with the heliospheric current sheet (HCS) and the Earth's magnetosphere. The occurrence of current layers and high-beta plasma sheets in the CIR structure has been estimated. It was found that on average, each of the CIR streams had four current layers in its structure with a current density of more than 0.12 A/m2 and about one and a half high-beta plasma regions with a beta value of more than five. Then we traced how and how often the high-speed stream associated with the CIR can catch up with the heliospheric current sheet (HCS) and connect to it. The interface of each fourth CIR stream coincided in time within an hour with the HCS, but in two thirds of cases, the CIR connection with the HCS was completely absent. One event of the simultaneous observation of the CIR stream in front of the magnetosphere by the ACE satellite in the vicinity of the L1 libration point and the Wind satellite in the remote geomagnetic tail was considered in detail. Measurements of the components of the interplanetary magnetic field and plasma parameters showed that the overall structure of the stream is conserved. Moreover, some details of the fine structure are also transferred through the magnetosphere. In particular, the so-called "magnetic hole" almost does not change its shape when moving from L1 point to a neighborhood of L2 point.

Characterisation of organic matter associated with groundwater arsenic in reducing aquifers of southwestern Taiwan

Energy Technology Data Exchange (ETDEWEB)

Al Lawati, Wafa M. [School of Earth, Atmospheric and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester (United Kingdom); Higher College of Technology, Ministry of Manpower, Muscat (Oman); Jean, Jiin-Shuh [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Kulp, Thomas R. [Department of Earth Sciences and Environmental Studies, State University of New York, Binghamton, NY (United States); Lee, Ming-Kuo [Department of Geology and Geography, Auburn University, Auburn, AL (United States); Polya, David A. [School of Earth, Atmospheric and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester (United Kingdom); Liu, Chia-Chuan [Department of Earth Sciences, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan (China); Dongen, Bart E. van, E-mail: Bart.vanDongen@manchester.ac.uk [School of Earth, Atmospheric and Environmental Sciences, Williamson Research Centre for Molecular Environmental Science, University of Manchester, Manchester (United Kingdom)

2013-11-15

Highlights: ► First lipid analysis of Taiwanese aquifer sediments from groundwater As-prone region. ► Both plant-derived terrestrial and mature hydrocarbon lipid sources identified. ► Organic matter sources similar to those of other high As groundwater aquifers. ► Groundwater arsenic at depth controlled by biotic As mobilisation processes. ► Biotic As mobilisation not controlled by a specific source of analysed organic matter. -- Abstract: Arsenic (As) in groundwaters extensively used by people across the world constitutes a serious public health threat. The importance of organic matter (OM) as an electron donor in microbially-mediated reduction of As(V) or Fe(III)-bearing As-host minerals leading to mobilisation of solid-phase arsenic is widely recognised. Notwithstanding this, there are few studies characterising OM in such aquifers and, in particular, there is a dearth of data from the classic arsenic bearing aquifers in southwestern Taiwan. Organic geochemical analyses of sediments from a known groundwater arsenic hot-spot in southwestern Taiwan revealed contributions of thermally mature and plant derived origin, consistent with OM sources in all other Asian groundwater aquifer sediments analysed to date, indicating comparable sources and routes of OM transfer. The combined results of amended As(V) reduction assays with the organic geochemical analysis revealed that the microbiological process of dissimilatory As(V) reduction is active in this aquifer, but it is not controlled by a specific source of analysed OM. These indicate that (i) part of the OM that was considered to be less bio-available could still be used as an electron donor or (ii) other electron donors, not analysed in present study, could be controlling the rate of As release.

Characterisation of organic matter associated with groundwater arsenic in reducing aquifers of southwestern Taiwan

International Nuclear Information System (INIS)

Al Lawati, Wafa M.; Jean, Jiin-Shuh; Kulp, Thomas R.; Lee, Ming-Kuo; Polya, David A.; Liu, Chia-Chuan; Dongen, Bart E. van

2013-01-01

Highlights: ► First lipid analysis of Taiwanese aquifer sediments from groundwater As-prone region. ► Both plant-derived terrestrial and mature hydrocarbon lipid sources identified. ► Organic matter sources similar to those of other high As groundwater aquifers. ► Groundwater arsenic at depth controlled by biotic As mobilisation processes. ► Biotic As mobilisation not controlled by a specific source of analysed organic matter. -- Abstract: Arsenic (As) in groundwaters extensively used by people across the world constitutes a serious public health threat. The importance of organic matter (OM) as an electron donor in microbially-mediated reduction of As(V) or Fe(III)-bearing As-host minerals leading to mobilisation of solid-phase arsenic is widely recognised. Notwithstanding this, there are few studies characterising OM in such aquifers and, in particular, there is a dearth of data from the classic arsenic bearing aquifers in southwestern Taiwan. Organic geochemical analyses of sediments from a known groundwater arsenic hot-spot in southwestern Taiwan revealed contributions of thermally mature and plant derived origin, consistent with OM sources in all other Asian groundwater aquifer sediments analysed to date, indicating comparable sources and routes of OM transfer. The combined results of amended As(V) reduction assays with the organic geochemical analysis revealed that the microbiological process of dissimilatory As(V) reduction is active in this aquifer, but it is not controlled by a specific source of analysed OM. These indicate that (i) part of the OM that was considered to be less bio-available could still be used as an electron donor or (ii) other electron donors, not analysed in present study, could be controlling the rate of As release

Characterizing groundwater/surface-water interactions in the interior of Jianghan Plain, central China

Science.gov (United States)

Du, Yao; Ma, Teng; Deng, Yamin; Shen, Shuai; Lu, Zongjie

2018-01-01

Quantifying groundwater/surface-water interactions is essential for managing water resources and revealing contaminant fate. There has been little concern on the exchange between streams and aquifers through an extensive aquitard thus far. In this study, hydrogeologic calculation and tritium modeling were jointly applied to characterize such interactions through an extensive aquitard in the interior of Jianghan Plain, an alluvial plain of Yangtze River, China. One groundwater simulation suggested that the lateral distance of influence from the river was about 1,000 m; vertical flow in the aquitard followed by lateral flow in the aquifer contributed significantly more ( 90%) to the aquifer head change near the river than lateral bank storage in the aquitard followed by infiltration. The hydrogeologic calculation produced vertical fluxes of the order 0.01 m/day both near and farther from the river, suggesting that similar shorter-lived (half-monthly) vertical fluxes occur between the river and aquitard near the river, and between the surface end members and aquitard farther from the river. Tritium simulation based on the OTIS model produced an average groundwater residence time of about 15 years near the river and a resulting vertical flux of the order 0.001 m/day. Another tritium simulation based on a dispersion model produced a vertical flux of the order 0.0001 m/day away from the river, coupled with an average residence time of around 90 years. These results suggest an order of magnitude difference for the longer-lived (decadal) vertical fluxes between surface waters and the aquifer near and away from the river.

Electron-electron interaction and transfer ionization in fast ion-atom collisions

International Nuclear Information System (INIS)

Voitkiv, A B

2008-01-01

Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.

Analytic approach to auroral electron transport and energy degradation

International Nuclear Information System (INIS)

Stamnes, K.

1980-01-01

The interaction of a beam of auroral electrons with the atmosphere is described by the linear transport equation, encompassing discrete energy loss, multiple scattering, and secondary electrons. A solution to the transport equation provides the electron intensity as a function of altitude, pitch angle (with respect to the geomagnetic field) and energy. A multi-stream (discrete ordinate) approximation to the transport equation is developed. An analytic solution is obtained in this approximation. The computational scheme obtained by combining the present transport code with the energy degradation method of Swartz (1979) conserves energy identically. The theory provides a framework within which angular distributions can be easily calculated and interpreted. Thus, a detailed study of the angular distributions of 'non-absorbed' electrons (i.e., electrons that have lost just a small fraction of their incident energy) reveals a systematic variation with incident angle and energy, and with penetration depth. The present approach also gives simple yet accurate solutions in low order multi-stream approximations. The accuracy of the four-stream approximation is generally within a few per cent, whereas two-stream results for backscattered mean intensities and fluxes are accurate to within 10-15%. (author)

On the wake structure in streaming complex plasmas

International Nuclear Information System (INIS)

Ludwig, Patrick; Kählert, Hanno; Bonitz, Michael; Miloch, Wojciech J

2012-01-01

The theoretical description of complex (dusty) plasmas requires multiscale concepts that adequately incorporate the correlated interplay of streaming electrons and ions, neutrals and dust grains. Knowing the effective dust-dust interaction, the multiscale problem can be effectively reduced to a one-component plasma model of the dust subsystem. The goal of this paper is a systematic evaluation of the electrostatic potential distribution around a dust grain in the presence of a streaming plasma environment by means of two complementary approaches: (i) a high-precision computation of the dynamically screened Coulomb potential from the dynamic dielectric function and (ii) full 3D particle-in-cell simulations, which self-consistently include dynamical grain charging and nonlinear effects. The range of applicability of these two approaches is addressed. (paper)

Interaction of electrons with light metal hydrides in the transmission electron microscope.

Science.gov (United States)

Wang, Yongming; Wakasugi, Takenobu; Isobe, Shigehito; Hashimoto, Naoyuki; Ohnuki, Somei

2014-12-01

Transmission electron microscope (TEM) observation of light metal hydrides is complicated by the instability of these materials under electron irradiation. In this study, the electron kinetic energy dependences of the interactions of incident electrons with lithium, sodium and magnesium hydrides, as well as the constituting element effect on the interactions, were theoretically discussed, and electron irradiation damage to these hydrides was examined using in situ TEM. The results indicate that high incident electron kinetic energy helps alleviate the irradiation damage resulting from inelastic or elastic scattering of the incident electrons in the TEM. Therefore, observations and characterizations of these materials would benefit from increased, instead decreased, TEM operating voltage. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Structured multi-stream command language

International Nuclear Information System (INIS)

Glad, A.S.

1982-12-01

A multi-stream command language was implemented to provide the sequential and decision-making operations necessary to run the neutral-beam ion sources connected to the Doublet III tokamak fusion device. A multi-stream command language was implemented in Pascal on a Classic 7870 running under MAX IV. The purpose of this paper is threefold. First, to provide a brief description of the programs comprising the command language including the operating system interaction. Second, to give a description of the language syntax and commands necessary to develop a procedure stream. Third, to provide a description of the normal operating procedures for executing either the sequential or interactive streams

Coupling a three-dimensional subsurface flow and transport model with a land surface model to simulate stream-aquifer-land interactions (CP v1.0)

Science.gov (United States)

Bisht, Gautam; Huang, Maoyi; Zhou, Tian; Chen, Xingyuan; Dai, Heng; Hammond, Glenn E.; Riley, William J.; Downs, Janelle L.; Liu, Ying; Zachara, John M.

2017-12-01

A fully coupled three-dimensional surface and subsurface land model is developed and applied to a site along the Columbia River to simulate three-way interactions among river water, groundwater, and land surface processes. The model features the coupling of the Community Land Model version 4.5 (CLM4.5) and a massively parallel multiphysics reactive transport model (PFLOTRAN). The coupled model, named CP v1.0, is applied to a 400 m × 400 m study domain instrumented with groundwater monitoring wells along the Columbia River shoreline. CP v1.0 simulations are performed at three spatial resolutions (i.e., 2, 10, and 20 m) over a 5-year period to evaluate the impact of hydroclimatic conditions and spatial resolution on simulated variables. Results show that the coupled model is capable of simulating groundwater-river-water interactions driven by river stage variability along managed river reaches, which are of global significance as a result of over 30 000 dams constructed worldwide during the past half-century. Our numerical experiments suggest that the land-surface energy partitioning is strongly modulated by groundwater-river-water interactions through expanding the periodically inundated fraction of the riparian zone, and enhancing moisture availability in the vadose zone via capillary rise in response to the river stage change. Meanwhile, CLM4.5 fails to capture the key hydrologic process (i.e., groundwater-river-water exchange) at the site, and consequently simulates drastically different water and energy budgets. Furthermore, spatial resolution is found to significantly impact the accuracy of estimated the mass exchange rates at the boundaries of the aquifer, and it becomes critical when surface and subsurface become more tightly coupled with groundwater table within 6 to 7 meters below the surface. Inclusion of lateral subsurface flow influenced both the surface energy budget and subsurface transport processes as a result of river-water intrusion into the

Arsenic release from shallow aquifers of the Hetao basin, Inner Mongolia: evidence from bacterial community in aquifer sediments and groundwater.

Science.gov (United States)

Li, Yuan; Guo, Huaming; Hao, Chunbo

2014-12-01

Indigenous microbes play crucial roles in arsenic mobilization in high arsenic groundwater systems. Databases concerning the presence and the activity of microbial communities are very useful in evaluating the potential of microbe-mediated arsenic mobilization in shallow aquifers hosting high arsenic groundwater. This study characterized microbial communities in groundwaters at different depths with different arsenic concentrations by DGGE and one sediment by 16S rRNA gene clone library, and evaluated arsenic mobilization in microcosm batches with the presence of indigenous bacteria. DGGE fingerprints revealed that the community structure changed substantially with depth at the same location. It indicated that a relatively higher bacterial diversity was present in the groundwater sample with lower arsenic concentration. Sequence analysis of 16S rRNA gene demonstrated that the sediment bacteria mainly belonged to Pseudomonas, Dietzia and Rhodococcus, which have been widely found in aquifer systems. Additionally, NO3(-)-reducing bacteria Pseudomonas sp. was the largest group, followed by Fe(III)-reducing, SO4(2-)-reducing and As(V)-reducing bacteria in the sediment sample. These anaerobic bacteria used the specific oxyanions as electron acceptor and played a significant role in reductive dissolution of Fe oxide minerals, reduction of As(V), and release of arsenic from sediments into groundwater. Microcosm experiments, using intact aquifer sediments, showed that arsenic release and Fe(III) reduction were microbially mediated in the presence of indigenous bacteria. High arsenic concentration was also observed in the batch without amendment of organic carbon, demonstrating that the natural organic matter in sediments was the potential electron donor for microbially mediated arsenic release from these aquifer sediments.

Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range

Science.gov (United States)

Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.

2006-01-01

The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.

Response of groundwater level and surface-water/groundwater interaction to climate variability: Clarence-Moreton Basin, Australia

Science.gov (United States)

Cui, Tao; Raiber, Matthias; Pagendam, Dan; Gilfedder, Mat; Rassam, David

2018-03-01

Understanding the response of groundwater levels in alluvial and sedimentary basin aquifers to climatic variability and human water-resource developments is a key step in many hydrogeological investigations. This study presents an analysis of groundwater response to climate variability from 2000 to 2012 in the Queensland part of the sedimentary Clarence-Moreton Basin, Australia. It contributes to the baseline hydrogeological understanding by identifying the primary groundwater flow pattern, water-level response to climate extremes, and the resulting dynamics of surface-water/groundwater interaction. Groundwater-level measurements from thousands of bores over several decades were analysed using Kriging and nonparametric trend analysis, together with a newly developed three-dimensional geological model. Groundwater-level contours suggest that groundwater flow in the shallow aquifers shows local variations in the close vicinity of streams, notwithstanding general conformance with topographic relief. The trend analysis reveals that climate variability can be quickly reflected in the shallow aquifers of the Clarence-Moreton Basin although the alluvial aquifers have a quicker rainfall response than the sedimentary bedrock formations. The Lockyer Valley alluvium represents the most sensitively responding alluvium in the area, with the highest declining (-0.7 m/year) and ascending (2.1 m/year) Sen's slope rates during and after the drought period, respectively. Different surface-water/groundwater interaction characteristics were observed in different catchments by studying groundwater-level fluctuations along hydrogeologic cross-sections. The findings of this study lay a foundation for future water-resource management in the study area.

Multiple drivers, scales, and interactions influence southern Appalachian stream salamander occupancy

Science.gov (United States)

Cecala, Kristen K.; Maerz, John C.; Halstead, Brian J.; Frisch, John R.; Gragson, Ted L.; Hepinstall-Cymerman, Jeffrey; Leigh, David S.; Jackson, C. Rhett; Peterson, James T.; Pringle, Catherine M.

2018-01-01

Understanding how factors that vary in spatial scale relate to population abundance is vital to forecasting species responses to environmental change. Stream and river ecosystems are inherently hierarchical, potentially resulting in organismal responses to fine‐scale changes in patch characteristics that are conditional on the watershed context. Here, we address how populations of two salamander species are affected by interactions among hierarchical processes operating at different scales within a rapidly changing landscape of the southern Appalachian Mountains. We modeled reach‐level occupancy of larval and adult black‐bellied salamanders (Desmognathus quadramaculatus) and larval Blue Ridge two‐lined salamanders (Eurycea wilderae) as a function of 17 different terrestrial and aquatic predictor variables that varied in spatial extent. We found that salamander occurrence varied widely among streams within fully forested catchments, but also exhibited species‐specific responses to changes in local conditions. While D. quadramaculatus declined predictably in relation to losses in forest cover, larval occupancy exhibited the strongest negative response to forest loss as well as decreases in elevation. Conversely, occupancy of E. wilderae was unassociated with watershed conditions, only responding negatively to higher proportions of fast‐flowing stream habitat types. Evaluation of hierarchical relationships demonstrated that most fine‐scale variables were closely correlated with broad watershed‐scale variables, suggesting that local reach‐scale factors have relatively smaller effects within the context of the larger landscape. Our results imply that effective management of southern Appalachian stream salamanders must first focus on the larger scale condition of watersheds before management of local‐scale conditions should proceed. Our findings confirm the results of some studies while refuting the results of others, which may indicate that

Electron cyclotron harmonic wave acceleration

Science.gov (United States)

Karimabadi, H.; Menyuk, C. R.; Sprangle, P.; Vlahos, L.

1987-01-01

A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts.

Electron cyclotron harmonic wave acceleration

International Nuclear Information System (INIS)

Karimabadi, H.; Menyuk, C.R.; Sprangle, P.; Vlahos, L.; Salonika Univ., Greece)

1987-01-01

A nonlinear analysis of particle acceleration in a finite bandwidth, obliquely propagating electromagnetic cyclotron wave is presented. It has been suggested by Sprangle and Vlahos in 1983 that the narrow bandwidth cyclotron radiation emitted by the unstable electron distribution inside a flaring solar loop can accelerate electrons outside the loop by the interaction of a monochromatic wave propagating along the ambient magnetic field with the ambient electrons. It is shown here that electrons gyrating and streaming along a uniform, static magnetic field can be accelerated by interacting with the fundamental or second harmonic of a monochromatic, obliquely propagating cyclotron wave. It is also shown that the acceleration is virtually unchanged when a wave with finite bandwidth is considered. This acceleration mechanism can explain the observed high-energy electrons in type III bursts. 31 references

In-stream contaminant interaction and transport

International Nuclear Information System (INIS)

Whelan, G.

1983-07-01

In order to assess contaminant exposure levels in biotic and abiotic pathways from waste-disposal sites, a comprehensive Multimedia Contaminant Environmental Exposure Assessment (MCEA) methodology using several mathematical models is being developed. Prior to a full development of the proposed methodology, a scaled-down version involving terrestrial plants, overland, and in-stream compartments was applied to an actual shallow land waste-disposal site. The purpose was to evaluate and demonstrate the attributes of the methodology. The in-stream component of the abbreviated methodology as it relates to Mortandad Canyon in Los Alamos, New Mexico is discussed herein. A two-year period was simulated consisting of six major runoff events which possessed a variety of distributions and magnitudes. The in-stream component of the methodology was composed of two models integrated to simulate the migration of radionuclides: DKWAV and TODAM. DKWAV is an unsteady, one-dimensional, second-order, explicit, finite difference, channel flow code which simulates the hydrodynamics in dendritric river systems and includes point and/or continuous lateral inflow and channel seepage. TODAM is an unsteady, one-dimensional, finite element, sediment-contaminant transport code which simulates the migration and fate of sediment and radionuclides in their dissolved and particulate phases by solving the general advection/diffusion equation with sink and source terms

Characterising aquifer treatment for pathogens in managed aquifer recharge.

Science.gov (United States)

Page, D; Dillon, P; Toze, S; Sidhu, J P S

2010-01-01

In this study the value of subsurface treatment of urban stormwater during Aquifer Storage Transfer Recovery (ASTR) is characterised using quantitative microbial risk assessment (QMRA) methodology. The ASTR project utilizes a multi-barrier treatment train to treat urban stormwater but to date the role of the aquifer has not been quantified. In this study it was estimated that the aquifer barrier provided 1.4, 2.6, >6.0 log(10) removals for rotavirus, Cryptosporidium and Campylobacter respectively based on pathogen diffusion chamber results. The aquifer treatment barrier was found to vary in importance vis-à-vis the pre-treatment via a constructed wetland and potential post-treatment options of UV-disinfection and chlorination for the reference pathogens. The risk assessment demonstrated that the human health risk associated with potable reuse of stormwater can be mitigated (disability adjusted life years, DALYs aquifer is integrated with suitable post treatment options into a treatment train to attenuate pathogens and protect human health.

Propagation of seasonal temperature signals into an aquifer upon bank infiltration.

Science.gov (United States)

Molina-Giraldo, Nelson; Bayer, Peter; Blum, Philipp; Cirpka, Olaf A

2011-01-01

Infiltrating river water carries the temperature signal of the river into the adjacent aquifer. While the diurnal temperature fluctuations are strongly dampened, the seasonal fluctuations are much less attenuated and can be followed into the aquifer over longer distances. In one-dimensional model with uniform properties, this signal is propagated with a retarded velocity, and its amplitude decreases exponentially with distance. Therefore, time shifts in seasonal temperature signals between rivers and groundwater observation points may be used to estimate infiltration rates and near-river groundwater velocities. As demonstrated in this study, however, the interpretation is nonunique under realistic conditions. We analyze a synthetic test case of a two-dimensional cross section perpendicular to a losing stream, accounting for multi-dimensional flow due to a partially penetrating channel, convective-conductive heat transport within the aquifer, and heat exchange with the underlying aquitard and the land surface. We compare different conceptual simplifications of the domain in order to elaborate on the importance of different system elements. We find that temperature propagation within the shallow aquifer can be highly influenced by conduction through the unsaturated zone and into the underlying aquitard. In contrast, regional groundwater recharge has no major effect on the simulated results. In our setup, multi-dimensionality of the flow field is important only close to the river. We conclude that over-simplistic analytical models can introduce substantial errors if vertical heat exchange at the aquifer boundaries is not accounted for. This has to be considered when using seasonal temperature fluctuations as a natural tracer for bank infiltration. Copyright © 2010 The Author(s). Journal compilation © 2010 National Ground Water Association.

The Ozark Plateaus Regional Aquifer Study—Documentation of a groundwater-flow model constructed to assess water availability in the Ozark Plateaus

Science.gov (United States)

Clark, Brian R.; Richards, Joseph M.; Knierim, Katherine J.

2018-03-30

Recent short-term drought conditions have emphasized the need to better understand the delicate balance between abundance, sustainability, and scarcity of groundwater in the Ozark Plateaus aquifer system. In 2014, the U.S. Geological Survey began construction of a groundwater-flow model as a tool for the assessment of groundwater availability in the Ozark Plateaus aquifer system. The model was developed to benefit concurrent and future investigations involving groundwater-pumping scenarios, optimization, particle transport, and groundwater-monitoring network analysis.The groundwater model simulates 116 years (1900–2015) of hydrologic conditions and the response of the groundwater system to changes in stress including changes in recharge and groundwater pumping for water supply. Semiseasonal stress periods were simulated from the later part of 1991 to 2015 and represent higher demand and lower recharge in the spring and summer months and lower demand and higher recharge in the fall and winter months. Groundwater pumping increases throughout the simulation period with a maximum rate of about 600 million gallons per day (Mgal/d).The process of matching historical hydrologic data for the Ozark Plateaus aquifer system model was accomplished by a combination of manual changes to parameter values and automated calibration methods. Observation data used in the development and evaluation of the model included 19,045 hydraulic-head observations from 6,683 wells within the model area. Observation data also included stream leakage estimates summed to calculate a net gain or net loss value for approximately 81 named streams.The majority (mean of over 95 percent) of the recharge component is discharged through streams simulated in the model. The total simulated discharge to streams fluctuates seasonally between 7,500 and 17,500 Mgal/d with a mean outflow of 11,500 Mgal/d. Much of the remaining balance between modeled recharge inflows and stream outflows is made up by water

Groundwater salinity in coastal aquifer of Karachi, Pakistan

International Nuclear Information System (INIS)

Mashiatullah, A.; Qureshi, R.M.; Ahmad, E.; Tasneem, M.A.; Sajjad, M.I.; Khan, H.A.

2002-01-01

Potable groundwater salinity has become a problem of great concern in the Karachi Metropolis, which is not only the most populous and biggest industrial base but also the largest coastal dwelling of Pakistan. Stable isotope techniques [O/sup 18/ content of Oxygen in the water molecular and C/sup 13/ content of the Total Dissolved Inorganic Carbon (TDIC)] have been used, in conjunction with physiochemical tools (temperature, dissolved oxygen, pH, redox electrical conductivity, salinity), to examine the quality of potable water and the source of salinity. Surface water samples (12 No.) were collected from polluted streams, namely: Layeri River, Malir River; Hub River/Hub Lake and the Indus River. Shallow groundwater samples (7 No. ) were collected from operating dug wells. Relatively deep groundwater samples (12 No.) were collected from operating dug wells, relatively deep groundwater samples (12 No.) were collected from pumping wells/tube-wells. Physicochemical analysis of water samples was completed in the field. In the laboratory, water samples were analyzed for O/sup 18/ content of oxygen in the water molecule and C/sup 13/ content of the TDIC, using specific gas extraction systems and a modified GD-150 gas source mass spectrometer. It is concluded from this preliminary investigation that the potable aquifer system in coastal Karachi hosts a mixture of precipitation (rainwater only) from hinterlands, trapped seawater in relatively deep aquifer system, as well as intruded seawater under natural infiltration conditions and/or induced recharge conditions (in shallow aquifers). (author)

Interactions of solutes and streambed sediment: 1. An experimental analysis of cation and anion transport in a mountain stream

Science.gov (United States)

Bencala, Kenneth E.; Kennedy, Vance C.; Zellweger, Gary W.; Jackman, Alan P.; Avanzino, Ronald J.

1984-01-01

An experimental injection was performed to study the transport of stream water solutes under conditions of significant interaction with streambed sediments in a mountain pool-and-riffle stream. Experiments were conducted in Little Lost Man Creek, Humboldt County, California, in a period of low flow duringwhich only a part of the bank-full channel held active surface flow. The injection of chloride and several trace cations lasted 20 days. In this report we discuss the results of the first 24 hours of the injection and survey the results of the first 10 days. Solute-streambed interactions of two types were observed. First, the physical transport of the conservative tracer, chloride, was affected by intergravel flow and stagnant watt, zones created by the bed relief. Second, the transport of the cations (strontium, potassium, and lithium) was appreciably modified by sorption onto streambed sediment. In the stream the readily observable consequence of the solute-streambed interactions was an attenuation of the dissolved concentration of each of the tracers. The attenuation in the stream channel occurred concurrently with the storage of tracers in the streambed via both physical and chemical processes. All tracers were subsequently present in shallow wells dug several meters from the wetted part of the channel. Sediment samples collected approximately 3 weeks after the start of the injection contained increased concentrations of the injected cations.

Topics in electron-positron interactions

International Nuclear Information System (INIS)

Soeding, P.

1983-01-01

This chapter investigates the collision of an electron and a positron in a high energy storage ring in which a large energy Q=W=√s=2 E /SUB beam/ is dumped into a tiny region of space-time. If the electron and positron annihilate each other almost all of this energy becomes concentrated in a single field quantum. Points out 3 consequences: 1) all flavored particles existing in nature are expected to be pair-produced provided their mass is not larger than W/2; 2) the pair production process acts as an effective ''filter'' for fundamental (i.e. pointlike) particles; and 3) particles without flavor (i.e. the gluons) are not directly pair-produced in e - e + interactions. Discusses basic processes; probing QED and lepton structure; hadron production at high energies; resonances; e - e + storage rings; detectors; electroweak interaction and new particles (leptons, quarks); restrictions on a more general weak interaction scenario; limits on pair production of scalar particles; and jets and QCD tests

Alluvial Aquifer

Data.gov (United States)

Kansas Data Access and Support Center — This coverage shows the extents of the alluvial aquifers in Kansas. The alluvial aquifers consist of unconsolidated Quaternary alluvium and contiguous terrace...

Re-Meandering of Lowland Streams

DEFF Research Database (Denmark)

Pedersen, Morten Lauge; Kristensen, Klaus Kevin; Friberg, Nikolai

2014-01-01

We evaluated the restoration of physical habitats and its influence on macroinvertebrate community structure in 18 Danish lowland streams comprising six restored streams, six streams with little physical alteration and six channelized streams. We hypothesized that physical habitats...... and macroinvertebrate communities of restored streams would resemble those of natural streams, while those of the channelized streams would differ from both restored and near-natural streams. Physical habitats were surveyed for substrate composition, depth, width and current velocity. Macroinvertebrates were sampled...... along 100 m reaches in each stream, in edge habitats and in riffle/run habitats located in the center of the stream. Restoration significantly altered the physical conditions and affected the interactions between stream habitat heterogeneity and macroinvertebrate diversity. The substrate in the restored...

Use of radon as tracer for identification of aquifer discharge along the Matinha stream, MG, Brazil; O uso do radonio como tracador para identificacao de descarga de aquiferos ao longo do corrego da Matinha, MG

Energy Technology Data Exchange (ETDEWEB)

Chagas, Claudio Jose

2017-11-01

Within the framework of 'Nuclear Techniques' is the use of natural and artificial isotopes as tracers for the study of the environment. The use of natural tracers in hydrology is a very useful tool that has been used in several scenarios. One such tracer is the isotope of radon, {sup 222}Rn, a noble gas from natural sources as a consequence of alpha decay of {sup 226}Ra. Radon can be found, to a greater or lesser degree, in all groundwater, as well as in soils and rocks from where it exudes into the atmosphere through spaces arising from fissures and or nanopores present. It can emerge into the water bodies by the leaching of water or other liquids through these interstices. In this research, the {sup 222}Rn gas diluted naturally by the leaching of the water that infiltrated the soils and rocks of the aquifers was used as a tracer in order to identify sections of discharge of these aquifers along the Stream of Matinha. The study area is about 70 km from Belo Horizonte and is in the city of Itauna, MG. The Matinha stream is about 2,200 m in length and is part of the network of tributaries of the water reservoir called Serra Azul, in the Juatuba River Basin, MG. The results presented express the studies that occurred between the second half of 2014 and the first half of 2016, in ten campaigns for water sampling, flow and natural gamma radiation measurements. Water samples were collected near the bottom and very close to the thalweg in the watercourse using syringe and or peristaltic suction pump at low flow to avoid gas leakage. The {sup 222}Rn analyzes were performed in the field during the collections and in the laboratory of the CDTN - Centro de Desenvolvimento da Tecnologia Nuclear, all of which were carried out with the radon detector RAD 7. The flow measurements counted on the use of the fluorescent tracer's technique: rhodamine and fluorescein were used for injection at points upstream and downstream of sections with higher {sup 222}Rn

Inferring Groundwater Age in an Alluvial Aquifer from Tracer Concentrations in the Stream - Little Wind River, Wyoming

Science.gov (United States)

Goble, D.; Gardner, W. P.; Naftz, D. L.; Solder, J. E.

2017-12-01

We use environmental tracers: CFC's, SF6, and 222Rn measured in stream water to determine volume and mean age of groundwater discharging to the Little Wind River, near Riverton, Wyoming. Samples of 222Rn were collected every 200 m along a 2 km reach, surrounding a known groundwater discharge zone. Nearby groundwater wells, in-stream piezometers and seepage meters were sampled for 222Rn, CFC's and SF6. Tracer concentrations measured in groundwater and in-stream piezometers were used to estimate the mean age of the subsurface system. High resolution 222Rn samples were used to determine the location and volume of groundwater inflow using a model of instream transport that includes radioactive decay and gas exchange with the atmosphere. The age of groundwater entering the stream was then estimated from in-stream measured CFC and SF6 concentrations using a new coupled stream transport and lumped-parameter groundwater age model. Ages derived from in-stream measurements were then compared to the age of subsurface water measured in piezometers, seepage meters, and groundwater wells. We then asses the ability of groundwater age inferred from in-stream samples to provide constraint on the age of the subsurface discharge to the stream. The ability to asses groundwater age from in-stream samples can provide a convenient method to constrain the regional distribution of groundwater circulation rates when groundwater sampling is challenging or wells are not in place.

The study of the interactions between groundwater and Sava River water in the Ljubljansko polje aquifer system (Slovenia)

Science.gov (United States)

Vrzel, Janja; Solomon, D. Kip; Blažeka, Željko; Ogrinc, Nives

2018-01-01

River basin aquifers are common sites for drinking water wells as bank filtration can be a cost effective pretreatment technology. A groundwater vulnerability to pollution depends on a groundwater mean residence time and on a relative contribution of river water versus local precipitation to groundwater. Environmental isotopes of oxygen and hydrogen (δ18O and δ2H), tritium (3H) and concentrations of nitrate (NO3-) were used to investigate hydrological pathways, mean residence time and interactions between surface water and groundwater in the Ljubljansko polje aquifer system in Slovenia. δ18O and δ2H values indicate a spatial variability of the influence of individual groundwater sources inside the aquifer - local precipitation and the Sava River water. Fractions of river water in groundwater depend on the depth of perforated screens in the pumping wells and their distance from the Sava River. It was estimated that groundwater at wells Kleče 11, Hrastje 3, and Hrastje 8 is mostly composed of recently infiltrated local precipitation, while the Sava River is the dominant source of groundwater at the well Jarški prod 1. Groundwater at wells Kleče 8, Kleče 12, and Jarški prod 3 contains on average between 41% and 48% of the Sava River water. The 3H and 3H/3He methods indicate short mean residence time of groundwater present at Jarški prod (2-7 years) and Hrastje (7-8 years). A small fraction (pollution.

Whimsicality of multi-mode Hasegawa space-charge waves in a complex plasma containing collision-dominated electrons and streaming ions

Science.gov (United States)

Lee, Myoung-Jae; Jung, Young-Dae

2017-09-01

The influence of collision-dominated electrons on multi-mode Hasegawa space-charge waves are investigated in a complex plasma containing streaming ions. The dispersion relation for the multi-mode Hasegawa space-charge wave propagating in a cylindrical waveguide filled with dusty plasma containing collision-dominated electrons and streaming ions is derived by using the fluid equations and Poisson’s equation which lead to a Bessel equation. By the boundary condition, the roots of the Bessel function would characterize the property of space-charge wave propagation. It is found that two solutions exist for wave frequency, which are affected by the radius of waveguide and the roots of the Bessel function. The damping and growing modes are found to be enhanced by an increase of the radius. However, an increase of electron collision frequency would suppress the damping and the growing modes of the propagating space-charge wave in a cylindrical waveguide plasma.

Groundwater vulnerability assessment in karstic aquifers using COP method.

Science.gov (United States)

Bagherzadeh, Somayeh; Kalantari, Nasrollah; Nobandegani, Amir Fadaei; Derakhshan, Zahra; Conti, Gea Oliveri; Ferrante, Margherita; Malekahmadi, Roya

2018-05-02

Access to safe and reliable drinking water is amongst the important indicators of development in each society, and water scarcity is one of the challenges and limitations affecting development at national and regional levels and social life and economic activity areas. Generally, there are two types of drinking water sources: the first type is surface waters, including lakes, rivers, and streams and the second type is groundwaters existing in aquifers. Amongst aquifers, karst aquifers play an important role in supplying water sources of the world. Therefore, protecting these aquifers from pollution sources is of paramount importance. COP method is amongst the methods to investigate the intrinsic vulnerability of this type of aquifers, so that areas susceptible to contamination can be determined before being contaminated and these sources can be protected. In the present study, COP method was employed in order to spot the regions that are prone to contamination in the region. This method uses the properties of overlying geological layers above the water table (O factor), the concentration of flow (C factor), and precipitation (P factor) over the aquifer, as the parameters to assess the intrinsic vulnerability of groundwater resources. In this regard, geographical information system (GIS) and remote sensing (RS) were utilized to prepare the mentioned factors and the intrinsic vulnerability map was obtained. The results of COP method indicated that the northwest and the west of the region are highly and very vulnerable. This study indicated that regions with low vulnerability were observed in eastern areas, which accounted for 15.6% of the area. Moderate vulnerability was 40% and related to the northeast and southeast of the area. High vulnerability was 38.2% and related to western and southwestern regions. Very high vulnerability was 6.2% and related to the northwest of the area. By means of the analysis of sensitivity of the model, it was determined that the focus

Three-dimensional semi-analytical solution to groundwater flow in confined and unconfined wedge-shaped aquifers

Science.gov (United States)

Sedghi, Mohammad Mahdi; Samani, Nozar; Sleep, Brent

2009-06-01

The Laplace domain solutions have been obtained for three-dimensional groundwater flow to a well in confined and unconfined wedge-shaped aquifers. The solutions take into account partial penetration effects, instantaneous drainage or delayed yield, vertical anisotropy and the water table boundary condition. As a basis, the Laplace domain solutions for drawdown created by a point source in uniform, anisotropic confined and unconfined wedge-shaped aquifers are first derived. Then, by the principle of superposition the point source solutions are extended to the cases of partially and fully penetrating wells. Unlike the previous solution for the confined aquifer that contains improper integrals arising from the Hankel transform [Yeh HD, Chang YC. New analytical solutions for groundwater flow in wedge-shaped aquifers with various topographic boundary conditions. Adv Water Resour 2006;26:471-80], numerical evaluation of our solution is relatively easy using well known numerical Laplace inversion methods. The effects of wedge angle, pumping well location and observation point location on drawdown and the effects of partial penetration, screen location and delay index on the wedge boundary hydraulic gradient in unconfined aquifers have also been investigated. The results are presented in the form of dimensionless drawdown-time and boundary gradient-time type curves. The curves are useful for parameter identification, calculation of stream depletion rates and the assessment of water budgets in river basins.

Electron beam interaction with space plasmas

International Nuclear Information System (INIS)

Krafft, C.; Volokitin, A.S.

1999-01-01

Active space experiments involving the controlled injection of electron beams and the formation of artificially generated currents can provide in many cases a calibration of natural phenomena connected with the dynamic interaction of charged particles with fields. They have a long history beginning from the launches of small rockets with electron guns in order to map magnetic fields lines in the Earth's magnetosphere or to excite artificial auroras. Moreover, natural beams of charged particles exist in many space and astrophysical plasmas and were identified in situ by several satellites; a few examples are beams connected with solar bursts, planetary foreshocks or suprathermal fluxes traveling in planetary magnetospheres. Many experimental and theoretical works have been performed in order to interpret or plan space experiments involving beam injection as well as to understand the physics of wave-particle interaction, as wave radiation, beam dynamics and background plasma modification. Recently, theoretical studies of the nonlinear evolution of a thin monoenergetic electron beam injected in a magnetized plasma and interacting with a whistler wave packet have led to new results. The influence of an effective dissipation process connected with whistler wave field leakage out of the beam volume to infinity (that is, effective radiation outside the beam) on the nonlinear evolution of beam electrons distribution in phase space has been studied under conditions relevant to active space experiments and related laboratory modelling. The beam-waves system's evolution reveals the formation of stable nonlinear structures continuously decelerated due to the effective friction imposed by the strongly dissipated waves. The nonlinear interaction between the electron bunches and the wave packet are discussed in terms of dynamic energy exchange, particle trapping, slowing down of the beam, wave dissipation and quasi-linear diffusion. (author)

Electron-phonon interaction in Chevrel-phase compounds

International Nuclear Information System (INIS)

Rainer, D.; Pobell, F.

1981-03-01

Experiments on the electron-phonon interaction in Chevrel-phase compounds (CPC) and a theoretical discussion of their results are presented. The authors particularly discuss measurements of the isotope effect of the transition temperature in Mo 6 Se 8 and SnMo 6 S 8 and tunneling spectroscopy experiments on Cu 1 . 8 Mo 6 S 8 and PbMo 6 S 8 . These investigations have been performed to get information about the strength of the electron-phonon interaction in CPC, and about the question whether there are phonon modes which couple particularly strongly to the electrons in these compounds. (orig./GSCH)

Geology, Streamflow, and Water Chemistry of the Talufofo Stream Basin, Saipan, Northern Mariana Islands

Science.gov (United States)

Izuka, Scot K.; Ewart, Charles J.

1995-01-01

A study of the geology, streamflow, and water chemistry of Talufofo Stream Basin, Saipan, Commonwealth of the Northern Mariana Islands, was undertaken to determine the flow characteristics of Talufofo Stream and the relation to the geology of the drainage basin. The Commonwealth government is exploring the feasibility of using water from Talufofo Stream to supplement Saipan's stressed municipal water supply. Streamflow records from gaging stations on the principal forks of Talufofo Stream indicate that peak streamflows and long-term average flow are higher at the South Fork gaging station than at the Middle Fork gaging station because the drainage area of the South Fork gaging station is larger, but persistent base flow from ground-water discharge during dry weather is greater in the Middle Fork gaging station. The sum of the average flows at the Middle Fork and South Fork gaging stations, plus an estimate of the average flow at a point in the lower reaches of the North Fork, is about 2.96 cubic feet per second or 1.91 million gallons per day. Although this average represents the theoretical maximum long-term draft rate possible from the Talufofo Stream Basin if an adequate reservoir can be built, the actual amount of surface water available will be less because of evaporation, leaks, induced infiltration, and reservoir-design constraints. Base-flow characteristics, such as stream seepage and spring discharge, are related to geology of the basin. Base flow in the Talufofo Stream Basin originates as discharge from springs near the base of limestones located in the headwaters of Talufofo Stream, flows over low-permeability volcanic rocks in the middle reaches, and seeps back into the high-permeability limestones in the lower reaches. Water sampled from Talufofo Stream during base flow had high dissolved-calcium concentrations (between 35 and 98 milligrams per liter), characteristic of water from a limestone aquifer. Concentrations of potassium, sodium, and chloride

Impact of electron-electron Coulomb interaction on the high harmonic generation process in graphene

Science.gov (United States)

Avetissian, H. K.; Mkrtchian, G. F.

2018-03-01

Generation of high harmonics in a monolayer graphene initiated by a strong coherent radiation field, taking into account electron-electron Coulomb interaction, is investigated. A microscopic theory describing the nonlinear optical response of graphene is developed. The Coulomb interaction of electrons is treated in the scope of dynamic Hartree-Fock approximation. The closed set of integrodifferential equations for the single-particle density matrix of a graphene quantum structure is solved numerically. The obtained solutions show the significance of many-body Coulomb interaction on the high harmonic generation process in graphene.

Insights on surface-water/groundwater exchange in the upper Floridan aquifer, north-central Florida (USA), from streamflow data and numerical modeling

Science.gov (United States)

Sutton, James E.; Screaton, Elizabeth J.; Martin, Jonathan B.

2015-03-01

Surface-water/groundwater exchange impacts water quality and budgets. In karst aquifers, these exchanges also play an important role in dissolution. Five years of river discharge data were analyzed and a transient groundwater flow model was developed to evaluate large-scale temporal and spatial variations of exchange between an 80-km stretch of the Suwannee River in north-central Florida (USA) and the karstic upper Floridan aquifer. The one-layer transient groundwater flow model was calibrated using groundwater levels from 59 monitoring wells, and fluxes were compared to the exchange calculated from discharge data. Both the numerical modeling and the discharge analysis suggest that the Suwannee River loses water under both low- and high-stage conditions. River losses appear greatest at the inside of a large meander, and the former river water may continue across the meander within the aquifer rather than return to the river. In addition, the numerical model calibration reveals that aquifer transmissivity is elevated within this large meander, which is consistent with enhanced dissolution due to river losses. The results show the importance of temporal and spatial variations in head gradients to exchange between streams and karst aquifers and dissolution of the aquifers.

Studying electron-PAG interactions using electron-induced fluorescence

Science.gov (United States)

Narasimhan, Amrit; Grzeskowiak, Steven; Ostrander, Jonathan; Schad, Jonathon; Rebeyev, Eliran; Neisser, Mark; Ocola, Leonidas E.; Denbeaux, Gregory; Brainard, Robert L.

2016-03-01

In extreme ultraviolet (EUV) lithography, 92 eV photons are used to expose photoresists. Typical EUV resists are organic-based and chemically amplified using photoacid generators (PAGs). Upon exposure, PAGs produce acids which catalyze reactions that result in changes in solubility. In EUV lithography, photo- and secondary electrons (energies of 10- 80 eV) play a large role in PAG acid-production. Several mechanisms for electron-PAG interactions (e.g. electron trapping, and hole-initiated chemistry) have been proposed. The aim of this study is to explore another mechanism - internal excitation - in which a bound PAG electron can be excited by receiving energy from another energetic electron, causing a reaction that produces acid. This paper explores the mechanism of internal excitation through the analogous process of electron-induced fluorescence, in which an electron loses energy by transferring that energy to a molecule and that molecule emits a photon rather than decomposing. We will show and quantify electron-induced fluorescence of several fluorophores in polymer films to mimic resist materials, and use this information to refine our proposed mechanism. Relationships between the molecular structure of fluorophores and fluorescent quantum yield may aid in the development of novel PAGs for EUV lithography.

Electron-phonon interactions in correlated systems

International Nuclear Information System (INIS)

Wysokinski, K.I.

1996-01-01

There exist attempts to describe the superconducting mechanism operating in HTS as based on antiferromagnetic fluctuations. It is not our intention to dwell on the superconducting mechanism, even though this is very a important issue. The main aim is to discuss the problem of interplay between electron-phonon and electron-electron interactions in correlated systems. We believe such analysis can be of importance for various materials and not only HTS'S. We shall however mainly refer to experiments on this last class of superconductors. Severe complications are to be expected by studying the problem. As is well known electron correlations are very important in narrow band systems, where the relevant electronic scale E F is quite small. In those circumstances, the phonon energy scale ω D is of comparable magnitude, with the ratio ω D /E F of order 1 signalling a possible break down of the Migdal - Eliashberg description of the electron-phonon interaction in metals. Here we shall assume the validity of the Migdal-Eliashberg approximation and concentrate on the mutual influence of electron and phonon subsystems. In the next section we shall discuss experimental motivation for and theoretical work related to the present problem. Section 3 contains a brief discussion of our theory. It is a self-consistent theory a la Migdal with strong correlations treated with an auxiliary boson technique. We conclude with results and their discussion. (orig.)

Novel Insights Linking Ecological Health to Biogeochemical Hotspots across the Groundwater-Surface Water Interface in Mixed Land Use Stream Systems

Science.gov (United States)

McKnight, U. S.; Sonne, A. T.; Rasmussen, J. J.; Rønde, V.; Traunspurger, W.; Höss, S.; Bjerg, P. L.

2017-12-01

Increasing modifications in land use and water management have resulted in multiple stressors impacting freshwater ecosystems globally. Chemicals with the potential to impact aquatic habitats are still often evaluated individually for their adverse effects on ecosystem health. This may lead to critical underestimations of the combined impact caused by interactions occurring between stressors not typically evaluated together, e.g. xenobiotic groundwater pollutants and trace metals. To address this issue, we identified sources and levels of chemical stressors along a 16-km groundwater-fed stream corridor (Grindsted, Denmark), representative for a mixed land use stream system. Potential pollution sources included two contaminated sites (factory, landfill), aquaculture, wastewater/industrial discharges, and diffuse sources from agriculture and urban areas. Ecological status was determined by monitoring meiobenthic and macrobenthic invertebrate communities.The stream was substantially impaired by both geogenic and anthropogenic sources of metals throughout the investigated corridor, with concentrations close to or above threshold values for barium, copper, lead, nickel and zinc in the stream water, hyporheic zone and streambed sediment. The groundwater plume from the factory site caused elevated concentrations of chlorinated ethenes, benzene and pharmaceuticals in both the hyporheic zone and stream, persisting for several km downstream. Impaired ecological conditions, represented by a lower abundance of meiobenthic individuals, were found in zones where the groundwater plume discharges to the stream. The effect was only pronounced in areas characterized by high xenobiotic organic concentrations and elevated dissolved iron and arsenic levels - linked to the dissolution of iron hydroxides caused by the degradation of xenobiotic compounds in the plume. The results thus provide ecological evidence for the interaction of organic and inorganic chemical stressors, which may

Water exchange and pressure transfer between conduits and matrix and their influence on hydrodynamics of two karst aquifers with sinking streams

Science.gov (United States)

Bailly-Comte, Vincent; Martin, Jonathan B.; Jourde, Hervé; Screaton, Elizabeth J.; Pistre, Séverin; Langston, Abigail

2010-05-01

SummaryKarst aquifers are heterogeneous media where conduits usually drain water from lower permeability volumes (matrix and fractures). For more than a century, various approaches have used flood recession curves, which integrate all hydrodynamic processes in a karst aquifer, to infer physical properties of the movement and storage of groundwater. These investigations typically only consider flow to the conduits and thus have lacked quantitative observations of how pressure transfer and water exchange between matrix and conduit during flooding could influence recession curves. We present analyses of simultaneous discharge and water level time series of two distinctly different karst systems, one with low porosity and permeability matrix rocks in southern France, and one with high porosity and permeability matrix rocks in north-central Florida (USA). We apply simple mathematical models of flood recession using time series representations of recharge, storage, and discharge processes in the karst aquifer. We show that karst spring hydrographs can be interpreted according to pressure transfer between two distinct components of the aquifer, conduit and matrix porosity, which induce two distinct responses at the spring. Water exchange between conduits and matrix porosity successively control the flow regime at the spring. This exchange is governed by hydraulic head differences between conduits and matrix, head gradients within conduits, and the contrast of permeability between conduits and matrix. These observations have consequences for physical interpretations of recession curves and modeling of karst spring flows, particularly for the relative magnitudes of base flow and quick flow from karst springs. Finally, these results suggest that similar analyses of recession curves can be applied to karst aquifers with distinct physical characteristics utilizing well and spring hydrograph data, but information must be known about the hydrodynamics and physical properties of

Software packages for simulating groundwater flow and the spreading of soluble and insoluble admixtures in aquifers

International Nuclear Information System (INIS)

Roshal, A.A.; Klein, I.S.; Svishchov, A.M.

1993-01-01

Software programs are described designed for solving hydrogeological and environmental problems related to the analysis and prediction of groundwater flow and the spreading of solutes and insolubles in the saturated zones. The software package GWFS (Ground Water Flow Simulation) allows for simulating steady-state and unsteady-state flow in confined, unconfined, and confined-unconfined multi-layer and quasi-3D isotropic and anisotropic aquifer systems. Considered are intra-layer sources and sinks, infiltration, inter-layer leakages, the interrelationships with surface reservoirs and streams, interrelationships with the drains, aquifer discharge to surface sources. The MTS (Mass Transport Simulation) package is designed for solving solute transport problems. Taken into account is convective transport, hydrodynamic dispersion and diffusion, linear equilibrium sorption. The method of characteristics is being implemented here using the ''particles-in-cells'' scheme in which the transport is modeled with the help of tracers. The software package OWFS (Oil-Water Flow Simulation) is designed for the simulation of hydrocarbon (oil-water) migration in aquifers

Brown trout and food web interactions in a Minnesota stream

Science.gov (United States)

Zimmerman, J.K.H.; Vondracek, B.

2007-01-01

1. We examined indirect, community-level interactions in a stream that contained non-native brown trout (Salmo trutta Linnaeus), native brook trout (Salvelinus fontinalis Mitchill) and native slimy sculpin (Cottus cognatus Richardson). Our objectives were to examine benthic invertebrate composition and prey selection of fishes (measured by total invertebrate dry mass, dry mass of individual invertebrate taxa and relative proportion of invertebrate taxa in the benthos and diet) among treatments (no fish, juvenile brook trout alone, juvenile brown trout alone, sculpin with brook trout and sculpin with brown trout). 2. We assigned treatments to 1 m2 enclosures/exclosures placed in riffles in Valley Creek, Minnesota, and conducted six experimental trials. We used three designs of fish densities (addition of trout to a constant number of sculpin with unequal numbers of trout and sculpin; addition of trout to a constant number of sculpin with equal numbers of trout and sculpin; and replacement of half the sculpin with an equal number of trout) to investigate the relative strength of interspecific versus intraspecific interactions. 3. Presence of fish (all three species, alone or in combined-species treatments) was not associated with changes in total dry mass of benthic invertebrates or shifts in relative abundance of benthic invertebrate taxa, regardless of fish density design. 4. Brook trout and sculpin diets did not change when each species was alone compared with treatments of both species together. Likewise, we did not find evidence for shifts in brown trout or sculpin diets when each species was alone or together. 5. We suggest that native brook trout and non-native brown trout fill similar niches in Valley Creek. We did not find evidence that either species had an effect on stream communities, potentially due to high invertebrate productivity in Valley Creek. ?? 2007 Blackwell Publishing Ltd.

Characterisation of organic matter associated with groundwater arsenic in reducing aquifers of southwestern Taiwan.

Science.gov (United States)

Al Lawati, Wafa M; Jean, Jiin-Shuh; Kulp, Thomas R; Lee, Ming-Kuo; Polya, David A; Liu, Chia-Chuan; van Dongen, Bart E

2013-11-15

Arsenic (As) in groundwaters extensively used by people across the world constitutes a serious public health threat. The importance of organic matter (OM) as an electron donor in microbially-mediated reduction of As(V) or Fe(III)-bearing As-host minerals leading to mobilisation of solid-phase arsenic is widely recognised. Notwithstanding this, there are few studies characterising OM in such aquifers and, in particular, there is a dearth of data from the classic arsenic bearing aquifers in southwestern Taiwan. Organic geochemical analyses of sediments from a known groundwater arsenic hot-spot in southwestern Taiwan revealed contributions of thermally mature and plant derived origin, consistent with OM sources in all other Asian groundwater aquifer sediments analysed to date, indicating comparable sources and routes of OM transfer. The combined results of amended As(V) reduction assays with the organic geochemical analysis revealed that the microbiological process of dissimilatory As(V) reduction is active in this aquifer, but it is not controlled by a specific source of analysed OM. These indicate that (i) part of the OM that was considered to be less bio-available could still be used as an electron donor or (ii) other electron donors, not analysed in present study, could be controlling the rate of As release. Copyright © 2012 Elsevier B.V. All rights reserved.

Comparison of aquifer characteristics derived from local and regional aquifer tests.

Science.gov (United States)

Randolph, R.B.; Krause, R.E.; Maslia, M.L.

1985-01-01

A comparison of the aquifer parameter values obtained through the analysis of a local and a regional aquifer test involving the same area in southeast Georgia is made in order to evaluate the validity of extrapolating local aquifer-test results for use in large-scale flow simulations. Time-drawdown and time-recovery data were analyzed by using both graphical and least-squares fitting of the data to the Theis curve. Additionally, directional transmissivity, transmissivity tensor, and angle of anisotropy were computed for both tests. -from Authors Georgia drawdown transmissivity regional aquifer tests

Analytical solution of groundwater waves in unconfined aquifers with ...

Indian Academy of Sciences (India)

Selva Balaji Munusamy

2017-07-29

Jul 29, 2017 ... higher-order Boussinesq equation. The homotopy perturbation solution is derived using a virtual perturbation .... reality, seepage face formation is common for tide–aquifer interaction problems. To simplify the complexity of the.

Strontium isotope geochemistry of groundwater in the central part of the Dakota (Great Plains) aquifer, USA

International Nuclear Information System (INIS)

Gosselin, David C.; Edwin Harvey, F.; Frost, Carol; Stotler, Randy; Allen Macfarlane, P.

2004-01-01

The Dakota aquifer of the central and eastern Great Plains of the United States is an important source of water for municipal supplies, irrigation and industrial use. Although the regional flow system can be characterized generally as east to northeasterly from the Rocky Mountains towards the Missouri River, locally the flow systems are hydrologically complex. This study uses Sr isotopic data from groundwater and leached aquifer samples to document the complex subsystems within the Dakota aquifer in Nebraska and Kansas. The interaction of groundwater with the geologic material through which it flows has created spatial patterns in the isotopic measurements that are related to: long-term water-rock interaction, during which varying degrees of isotopic equilibrium between water and rock has been achieved; and the alteration of NaCl fluids by water-rock interaction. Specifically, Sr isotopic data distinguish brines from Kansas and western Nebraska from those in eastern Nebraska: the former are interpreted to reflect interaction with Permian rocks, whereas the latter record interaction with Pennsylvanian rocks. The Sr isotopic composition of groundwater from other parts of Nebraska and Kansas are a function of the dynamic interaction between groundwater and unlithified sediments (e.g., glacial till and loess), followed by interaction with oxidized and unoxidized sediments within the Dakota Formation. This study illustrates the power of combining Sr chemistry with more conventional geochemical data to obtain a more complete understanding of groundwater flow systems within regional aquifer systems where extensive monitoring networks do not exist

Aquifer Storage Recovery (ASR) of chlorinated municipal drinking water in a confined aquifer

Science.gov (United States)

Izbicki, John A.; Petersen, Christen E.; Glotzbach, Kenneth J.; Metzger, Loren F.; Christensen, Allen H.; Smith, Gregory A.; O'Leary, David R.; Fram, Miranda S.; Joseph, Trevor; Shannon, Heather

2010-01-01

About 1.02 x 106 m3 of chlorinated municipal drinking water was injected into a confined aquifer, 94-137 m below Roseville, California, between December 2005 and April 2006. The water was stored in the aquifer for 438 days, and 2.64 x 106 m3 of water were extracted between July 2007 and February 2008. On the basis of Cl data, 35% of the injected water was recovered and 65% of the injected water and associated disinfection by-products (DBPs) remained in the aquifer at the end of extraction. About 46.3 kg of total trihalomethanes (TTHM) entered the aquifer with the injected water and 37.6 kg of TTHM were extracted. As much as 44 kg of TTHMs remained in the aquifer at the end of extraction because of incomplete recovery of injected water and formation of THMs within the aquifer by reactions with freechlorine in the injected water. Well-bore velocity log data collected from the Aquifer Storage Recovery (ASR) well show as much as 60% of the injected water entered the aquifer through a 9 m thick, high-permeability layer within the confined aquifer near the top of the screened interval. Model simulations of ground-water flow near the ASR well indicate that (1) aquifer heterogeneity allowed injected water to move rapidly through the aquifer to nearby monitoring wells, (2) aquifer heterogeneity caused injected water to move further than expected assuming uniform aquifer properties, and (3) physical clogging of high-permeability layers is the probable cause for the observed change in the distribution of borehole flow. Aquifer heterogeneity also enhanced mixing of native anoxic ground water with oxic injected water, promoting removal of THMs primarily through sorption. A 3 to 4-fold reduction in TTHM concentrations was observed in the furthest monitoring well 427 m downgradient from the ASR well, and similar magnitude reductions were observed in depth-dependent water samples collected from the upper part of the screened interval in the ASR well near the end of the extraction

Interactions of electrons with biologically important molecules

International Nuclear Information System (INIS)

Pisklova, K.; Papp, P.; Stano, M.

2012-01-01

For the study of interactions of low-energy electrons with the molecules in the gas phase, the authors used electron-molecule cross-beam apparatus. The experiment is carried out in high vacuum, where molecules of the tested compound are inducted through a capillary. For purposes of this experiment the sample was electrically heated to 180 Deg C., giving a bundle of GlyGly molecules into the gas phase. The resulting signals can be evaluated in two different modes: mass spectrum - at continuous electron energy (e.g. 100 eV) they obtained the signal of intensity of the ions according to their mass to charge ratio; ionization and resonance spectra - for selected ion mass when the authors received the signal of intensity of the ions, depending on the energy of interacting electron.

Groundwater nitrate pollution and climate change: learnings from a water balance-based analysis of several aquifers in a western Mediterranean region (Catalonia).

Science.gov (United States)

Mas-Pla, Josep; Menció, Anna

2018-04-11

Climate change will affect the dynamics of the hydrogeological systems and their water resources quality; in particular nitrate, which is herein taken as a paradigmatic pollutant to illustrate the effects of climate change on groundwater quality. Based on climatic predictions of temperature and precipitation for the horizon of 2021 and 2050, as well as on land use distribution, water balances are recalculated for the hydrological basins of distinct aquifer systems in a western Mediterranean region as Catalonia (NE Spain) in order to determine the reduction of available water resources. Besides the fact that climate change will represent a decrease of water availability, we qualitatively discuss the modifications that will result from the future climatic scenarios and their impact on nitrate pollution according to the geological setting of the selected aquifers. Climate effects in groundwater quality are described according to hydrological, environmental, socio-economic, and political concerns. Water reduction stands as a major issue that will control stream-aquifer interactions and subsurface recharge, leading to a general modification of nitrate in groundwater as dilution varies. A nitrate mass balance model provides a gross estimation of potential nitrate evolution in these aquifers, and it points out that the control of the fertilizer load will be crucial to achieve adequate nitrate content in groundwater. Reclaimed wastewater stands as local reliable resource, yet its amount will only satisfy a fraction of the loss of available resources due to climate change. Finally, an integrated management perspective is necessary to avoid unplanned actions from private initiatives that will jeopardize the achievement of sustainable water resources exploitation under distinct hydrological scenarios.

Intra-Wellbore Head Losses in a Horizontal Well with both Kinematic and Frictional Effects in an Anisotropic Confined Aquifer between Two Streams

Science.gov (United States)

Wang, Q.; Zhan, H.

2017-12-01

Horizontal drilling becomes an appealing technology for water exploration or aquifer remediation in recent decades, due to the decreasing operational cost and many technical advantages over the vertical wells. However, many previous studies on the flow into horizontal wells were based on the uniform flux boundary condition (UFBC) for treating horizontal wells, which could not reflect the physical processes of flow inside the well accurately. In this study, we investigated transient flow into a horizontal well in an anisotropic confined aquifer between two streams for three types of boundary conditions of treating the horizontal well, including UFBC, uniform head boundary condition (UHBC), and mixed-type boundary condition (MTBC). The MTBC model considered both kinematic and frictional effects inside the horizontal well, in which the kinematic effect referred to the accelerational and fluid inflow effects. The new solution of UFBC was derived by superimposing the point sink/source solutions along the axis of the horizontal well with a uniform strength. The solutions of UHBC and MTBC were obtained by a hybrid analytical-numerical method, and an iterative method was proposed to determine the minimum well segment number required to yield sufficiently accurate answer. The results showed that the differences among the UFBC, UHBC, MTBCFriction and MTBC solutions were obvious, in which MTBCFriction represented the solutions considering the frictional effect but ignoring the kinematic effect. The MTBCFriction and MTBC solutions were sensitive to the flow rate, and the difference of these two solutions increases with the flow rate, suggesting that the kinematic effect could not be ignored for studying flow to a horizontal well, especially when the flow rate is great. The well specific inflow (WSI) (which is the inflow per unit screen length at a specified location of the horizontal well) increased with the distance along the wellbore for the MTBC model at early stage, while

Hydrology of the Claiborne aquifer and interconnection with the Upper Floridan aquifer in southwest Georgia

Science.gov (United States)

Gordon, Debbie W.; Gonthier, Gerard

2017-04-24

The U.S. Geological Survey conducted a study, in cooperation with the Georgia Environmental Protection Division, to define the hydrologic properties of the Claiborne aquifer and evaluate its connection with the Upper Floridan aquifer in southwest Georgia. The effort involved collecting and compiling hydrologic data from the aquifer in subarea 4 of southwestern Georgia. Data collected for this study include borehole geophysical logs in 7 wells, and two 72-hour aquifer tests to determine aquifer properties.The top of the Claiborne aquifer extends from an altitude of about 200 feet above the North American Vertical Datum of 1988 (NAVD 88) in Terrell County to 402 feet below NAVD 88 in Decatur County, Georgia. The base of the aquifer extends from an altitude of about 60 feet above NAVD 88 in eastern Sumter County to about 750 feet below NAVD 88 in Decatur County. Aquifer thickness ranges from about 70 feet in eastern Early County to 400 feet in Decatur County.The transmissivity of the Claiborne aquifer, determined from two 72-hour aquifer tests, was estimated to be 1,500 and 700 feet squared per day in Mitchell and Early Counties, respectively. The storage coefficient was estimated to be 0.0006 and 0.0004 for the same sites, respectively. Aquifer test data from Mitchell County indicate a small amount of leakage occurred during the test. Groundwater-flow models suggest that the source of the leakage was the underlying Clayton aquifer, which produced about 2.5 feet of drawdown in response to pumping in the Claiborne aquifer. The vertical hydraulic conductivity of the confining unit between the Claiborne and Clayton aquifers was simulated to be about 0.02 foot per day.Results from the 72-hour aquifer tests run for this study indicated no interconnection between the Claiborne and overlying Upper Floridan aquifers at the two test sites. Additional data are needed to monitor the effects that increased withdrawals from the Claiborne aquifer may have on future water resources.

Nitrogen Dynamics Along a Headwater Stream Draining a Fen, Swamp, and Marsh in a Fractured Dolomite Watershed

Science.gov (United States)

Duval, T. P.; Waddington, J. M.

2009-05-01

Stream-wetland interaction has been shown to have a significant effect on nutrient cycling and downstream water quality. Additionally, connection to regional groundwater systems can dilute or enrich stream water with a number of dissolved constituents. This study demonstrates the resultant downstream change in dissolved nitrogen species as a hardwater stream emerges from a calcareous aquifer and traverses a calcareous fen, a cedar swamp, and a cattail marsh over two growing seasons, a very dry 2006 and a very wet 2007. Upon emergence at a number of groundwater seeps, the water contained appreciable nitrate levels averaging 2.72±0.42 mg NO3-N L-1, minimal organic nitrogen, and ammonium below detectable levels. Through the gently sloping calcareous fen, with a stream residence time of ~ 5 hours, NO3-N concentration decreases of 0.35 mg L-1 were observed. Concomitantly, stream recharge into the dolomite bedrock depressed stream discharge values significantly, further removing nitrate from the stream system. This resulted in the fen-bedrock system acting as an estimated net sink of 432 kg of NO3-N in the early summer of 2007, for example. In contrast, the hydrological-biogeochemical systems became decoupled through the swamp during the same period, where concentrations increased from 2.58±0.34 mg L-1 entering the swamp to 2.65±0.58 mg L-1 exiting, but streamflow decreased in general by 5 L s- 1. This resulted in the swamp, with its large depression storage, acting as a small net sink of nitrate (75 kg through the early summer), which would not be detected simply from concentration changes. The concentration-discharge relation realigned through the marsh, where significant groundwater entered the wetland, increasing both concentration and discharge, yielding a small export of 93 kg over the same time period. A series of tracer injections in each wetland type will be presented to compare the streamflow- concentration patterns with the measured nutrient spiralling

Geohydrology and water quality of the stratified-drift aquifers in Upper Buttermilk Creek and Danby Creek Valleys, Town of Danby, Tompkins County, New York

Science.gov (United States)

Miller, Todd S.

2015-11-20

In 2006, the U.S. Geological Survey, in cooperation with the Town of Danby and the Tompkins County Planning Department, began a study of the stratified-drift aquifers in the upper Buttermilk Creek and Danby Creek valleys in the Town of Danby, Tompkins County, New York. In the northern part of the north-draining upper Buttermilk Creek valley, there is only one sand and gravel aquifer, a confined basal unit that overlies bedrock. In the southern part of upper Buttermilk Creek valley, there are as many as four sand and gravel aquifers, two are unconfined and two are confined. In the south-draining Danby Creek valley, there is an unconfined aquifer consisting of outwash and kame sand and gravel (deposited by glacial meltwaters during the late Pleistocene Epoch) and alluvial silt, sand, and gravel (deposited by streams during the Holocene Epoch). In addition, throughout the study area, there are several small local unconfined aquifers where large tributaries deposited alluvial fans in the valley.

Electron-Electron and Electron-Phonon interactions effects on the tunnel electronic spectrum of PbS quantum dots

Science.gov (United States)

Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Mottaghizadeh, Alireza; Ulysse, Christian; Zimmers, Alexandre; Dubertret, Benoit; Aubin, Herve

2015-03-01

We present a tunnel spectroscopy study of the electronic spectrum of single PbS Quantum Dots (QDs) trapped between nanometer-spaced electrodes, measured at low temperature T=5 K. The carrier filling of the QD can be controlled either by the drain voltage in the shell filling regime or by a gate voltage. In the empty QD, the tunnel spectrum presents the expected signature of the 8x degenerated excited levels. In the drain controlled shell filling regime, the levels degeneracies are lifted by the global electrostatic Coulomb energy of the QD; in the gate controlled shell filling regime, the levels degeneracies are lifted by the intra-Coulomb interactions. In the charged quantum dot, electron-phonons interactions lead to the apparition of Franck-Condon side bands on the single excited levels and possibly Franck Condon blockade at low energy. The sharpening of excited levels at higher gate voltage suggests that the magnitude of electron-phonon interactions is decreased upon increasing the electron filling in the quantum dot. This work was supported by the French ANR Grants 10-BLAN-0409-01, 09-BLAN-0388-01, by the Region Ile-de-France in the framework of DIM Nano-K and by China Scholarship Council.

Distribution of polychlorinated biphenyls in the Housatonic River and adjacent aquifer, Massachusetts

Science.gov (United States)

Gay, Frederick B.; Frimpter, Michael H.

1985-01-01

Polychlorinated biphenyls (PCB's) are sorbed to the fine-grained stream-bottom sediments along the Housatonic River from Pittsfield, Massachusetts, southward to the Massachusetts-Connecticut boundary. The highest PCB concentrations, up to 140,000 micrograms per kilogram, were found in samples of bottom material from a reach of the river between Pittsfield and Woods Pond Dam in Lee, Massachusetts. Sediments in Woods Pond have been estimated to contain about 11,000 pounds of PCB's. Approximately 490 pounds per year of PCB's have also been estimated to move past the Housatonic River gaging station at Great Barrington. The distribution of hydraulic heads, water temperatures, and concentrations of dissolved oxygen, ammonia, nitrate, iron, and manganese in ground water shows that industrial water-supply wells in a sand and gravel aquifer adjacent to a stretch of the river called Woods Pond have been inducing ground-water recharge through the PCB-contaminated bottom sediments of the pond since late 1956. These data indicate that, at one location along the shore of the pond, the upper 40 feet of the aquifer contains water derived from induced infiltration. However, this induced recharge has not moved PCB's from the bottom sediments into a vertical section of the aquifer located 5 feet downgradient from the edge of Woods Pond. Samples taken at selected intervals in this section showed that no PCB's sorbed to the aquifer material or dissolved in the ground water within the detection limits of the chemical analyses.

An evaluation of aquifer intercommunication between the unconfined and Rattlesnake Ridge aquifers on the Hanford Site

International Nuclear Information System (INIS)

Jensen, E.J.

1987-10-01

During 1986, Pacific Northwest Laboratory conducted a study of a portion of the Rattlesnake Ridge aquifer (confined aquifer) that lies beneath the B Pond - Gable Mountain Pond area of the Hanford Site. The purpose was to determine the extent of intercommunication between the unconfined aquifer and the uppermost regionally extensive confined aquifer, referred to as the Rattlesnake Ridge aquifer. Hydraulic head data and chemical data were collected from the ground water in the study area during December 1986. The hydraulic head data were used to determine the effects caused by water discharged to the ground from B Pond on both the water table of the unconfined aquifer and the potentiometric surface of the confined aquifer. The chemical data were collected to determine the extent of chemical constituents migrating from the unconfined aquifer to the confined aquifer. Analysis of chemical constituents in the Rattlesnake Ridge aquifer demonstrated that communication between the unconfined and confined aquifers had occurred. However, the levels of contaminants found in the Rattlesnake Ridge aquifer during this study were below the DOE Derived Concentration Guides

Effects of projected climate (2011–50) on karst hydrology and species vulnerability—Edwards aquifer, south-central Texas, and Madison aquifer, western South Dakota

Science.gov (United States)

Mahler, Barbara J.; Stamm, John F.; Poteet, Mary F.; Symstad, Amy J.; Musgrove, MaryLynn; Long, Andrew J.; Norton, Parker A.

2015-12-22

Karst aquifers—formed by the dissolution of soluble rocks such as limestone—are critical groundwater resources in North America, and karst springs, caves, and streams provide habitat for unique flora and fauna. Springflow and groundwater levels in karst terrane can change greatly over short time scales, and therefore are likely to respond rapidly to climate change. How might the biological communities and ecosystems associated with karst respond to climate change and accompanying changes in groundwater levels and springflow? Sites in two central U.S. regions—the Balcones Escarpment of south-central Texas and the Black Hills of western South Dakota (fig. 1)—were selected to study climate change and its potential effects on the local karst hydrology and ecosystem. The ecosystems associated with the Edwards aquifer (Balcones Escarpment region) and Madison aquifer (Black Hills region) support federally listed endangered and threatened species and numerous State-listed species of concern, including amphibians, birds, insects, and plants. Full results are provided in Stamm and others (2014), and are summarized in this fact sheet.

Diagnosis of the Ghiss Nekor aquifer in order to elaborate the aquifer contract

Science.gov (United States)

Baite, Wissal; Boukdir, A.; Zitouni, A.; Dahbi, S. D.; Mesmoudi, H.; Elissami, A.; Sabri, E.; Ikhmerdi, H.

2018-05-01

The Ghiss-Nekor aquifer, located in the north-east of the action area of the ABHL, plays a strategic role in the drinkable water supply of the city of Al Hoceima and of the neighboring urban areas. It also participates in the irrigation of PMH. However, this aquifer has problems such as over-exploitation and pollution. In the face of these problems, the only Solution is the establishment of a new mode of governance, which privileges the participation, the involvement and the responsibility of the actors concerned in a negotiated contractual framework, namely the aquifer contract. The purpose of this study is to diagnose the current state of the Ghiss Nekor aquifer, the hydrogeological characterization of the aquifer, the use of the waters of the aquifer, the Problem identification and the introduction of the aquifer contract, which aims at the participatory and sustainable management of underground water resources in the Ghiss- Nekor plain, to ensure sustainable development.

Interaction between shallow and deep aquifers in the Tivoli Plain (Central Italy) enhanced by groundwater extraction: A multi-isotope approach and geochemical modeling

International Nuclear Information System (INIS)

Carucci, Valentina; Petitta, Marco; Aravena, Ramon

2012-01-01

In the Tivoli Plain (Rome, Central Italy) the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using isotopic and chemical tracers. A conceptual model of the groundwater flowpaths has been developed and verified by geochemical modeling. A combined hydrogeochemical and isotopic investigation using ion relationships such as DIC/Cl − , Ca/(Ca + Mg)/SO 4 /(SO 4 + HCO 3 ), and environmental isotopes (δ 18 O, δ 2 H, 87 Sr/ 86 Sr, δ 34 S and δ 13 C) was carried out in order to determine the sources of recharge of the aquifer, the origin of solutes and the mixing processes in groundwater of Tivoli Plain. Multivariate statistical methods such as principal component analysis and Cluster analyses have confirmed the existence of different geochemical facies and the role of mixing in the chemical composition of the groundwater. Results indicate that the hydrochemistry of groundwater is characterized by mixing between end-members coming directly from carbonate recharge areas and to groundwater circulating in a deeply buried Meso-Cenozoic carbonate sequence. The travertine aquifer is fed by both flow systems, but a local contribution by direct input in the Plain has also been recognized. The stable isotope data ( 18 O, 2 H, 13 C and 34 S) supports the flow system conceptual model inferred from the geochemical data and represents key data to quantify the geochemical mixing in the different groundwaters of the Plain. The results of numerical modeling (PHREEQC) are consistent with the flowpaths derived from the hydrogeochemical conceptual model. The inverse models performed generated the main geochemical processes occurring in the groundwater flow system, which also included mixing. Geochemical and isotope modeling demonstrate an increasing influence of groundwater from the deeply buried aquifer in the travertine aquifer, enhanced by lowering of the travertine aquifer water table due to quarry pumping.

Coherent counter-steaming electrostatic wave Raman interaction system utilizing opposing electron beams for the production of coherent microwaves in plasmas

International Nuclear Information System (INIS)

Leiby, C.C. Jr.; Prasad, B.

1977-01-01

The generation of controlled, electromagnetic, coherent, microwave radiation from a warm, uniform plasma at approximately twice the electron plasma frequency by means of two oppositely directed streams of high energy electrons and the coupling of the resulting coherent, electromagnetic radiation from a cavity resonator into external circuitry, wherein the two opposing streams of high energy electrons directed into the warm, uniform plasma result in a conversion of electron beam and plasma energies into transverse electromagnetic radiation from 10 to 100 times that which is possible with a single electron beam-plasma system. 7 claims, 4 figures

Potentiometric Surface of the Alluvial Aquifer and Hydrologic Conditions in the Juana Diaz area, Puerto Rico, June 29 - July 1, 2005

Science.gov (United States)

Rodriguez, Jose M.; Santigo-Rivera, Luis; Gómez-Gómez, Fernando

2006-01-01

A synoptic survey of the hydrologic conditions in the Juana Diaz area, Puerto Rico, was conducted between June 29 and July 1, 2005, to define the spatial distribution of the potentiometric surface of the alluvial aquifer. The study area encompasses 21 square miles of the more extensive South Coastal Plain Alluvial Aquifer system and is bounded along the north by foothills of the Cordillera Central mountain chain, to the south by the Caribbean Sea, the east by the Rio Descalabrado and to the west by the Rio Inabon. Ground water in the Juana Diaz area is in the Quaternary-age alluvial deposits and the middle-Tertiary age Ponce Limestone and Juana Diaz Formation (Giusti, 1968). The hydraulic properties of the Ponce Limestone in the Juana Diaz area are unknown, and the Juana Diaz Formation is a unit of poor permeability due to its high clay content. Consequently, the Ponce Limestone and the Juana Diaz Formation are generally considered to be the base of the alluvial aquifer in the Juana Diaz area with ground-water flow occurring primarily within the alluvial deposits. The potentiometric-surface map of the alluvial aquifer was delineated using ground-water level measurements taken at existing wells. The water-level measurements were taken at wells that were either not pumping during the survey or were shut down for a brief period. In the latter case, a recovery period of 30 minutes was allowed for the drawdown in the wellbore to achieve a near static level position representative of the aquifer at the measurement point. Land-surface altitude from U.S. Geological Survey (USGS) 1:20,000 scale topographic maps (Playa de Ponce, Ponce, Rio Descalabrado, and Santa Isabel) were used to refer ground-water levels to mean sea level datum (National Geodetic Vertical Datum of 1929). In addition to the ground-water level measurements, the potentiometricsurface contours were delineated using hydrologic features, such as drainage ditches and saturated intermittent streams that were

Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada

Science.gov (United States)

Davis, Kyle W.; Long, Andrew J.

2018-05-31

Hills aquifer. The numerical model was constructed using a uniform grid with square cells that are about 1 mile (1,600 meters) on each side with a total of about 657,000 active cells.Model calibration was completed by linking Parameter ESTimation (PEST) software with MODFLOW–NWT. The PEST software uses statistical parameter estimation techniques to identify an optimum set of input parameters by adjusting individual model input parameters and assessing the differences, or residuals, between observed (measured or estimated) data and simulated values. Steady-state model calibration consisted of attempting to match mean simulated values to measured or estimated values of (1) hydraulic head, (2) hydraulic head differences between model layers, (3) stream infiltration, and (4) discharge to streams. Calibration of the transient model consisted of attempting to match simulated and measured temporally distributed values of hydraulic head changes, stream base flow, and groundwater discharge to artesian flowing wells. Hydraulic properties estimated through model calibration included hydraulic conductivity, vertical hydraulic conductivity, aquifer storage, and riverbed hydraulic conductivity in addition to groundwater recharge and well skin.The ability of the numerical model to accurately simulate groundwater flow in the Williston Basin was assessed primarily by its ability to match calibration targets for hydraulic head, stream base flow, and flowing well discharge. The steady-state model also was used to assess the simulated potentiometric surfaces in the upper Fort Union aquifer, the lower Fort Union aquifer, and the Fox Hills aquifer. Additionally, a previously estimated regional groundwater-flow budget was compared with the simulated steady-state groundwater-flow budget for the Williston Basin. The simulated potentiometric surfaces typically compared well with the estimated potentiometric surfaces based on measured hydraulic head data and indicated localized groundwater

Hydrogeology and simulation of groundwater flow and analysis of projected water use for the Canadian River alluvial aquifer, western and central Oklahoma

Science.gov (United States)

Ellis, John H.; Mashburn, Shana L.; Graves, Grant M.; Peterson, Steven M.; Smith, S. Jerrod; Fuhrig, Leland T.; Wagner, Derrick L.; Sanford, Jon E.

2017-02-13

This report describes a study of the hydrogeology and simulation of groundwater flow for the Canadian River alluvial aquifer in western and central Oklahoma conducted by the U.S. Geological Survey in cooperation with the Oklahoma Water Resources Board. The report (1) quantifies the groundwater resources of the Canadian River alluvial aquifer by developing a conceptual model, (2) summarizes the general water quality of the Canadian River alluvial aquifer groundwater by using data collected during August and September 2013, (3) evaluates the effects of estimated equal proportionate share (EPS) on aquifer storage and streamflow for time periods of 20, 40, and 50 years into the future by using numerical groundwater-flow models, and (4) evaluates the effects of present-day groundwater pumping over a 50-year period and sustained hypothetical drought conditions over a 10-year period on stream base flow and groundwater in storage by using numerical flow models. The Canadian River alluvial aquifer is a Quaternary-age alluvial and terrace unit consisting of beds of clay, silt, sand, and fine gravel sediments unconformably overlying Tertiary-, Permian-, and Pennsylvanian-age sedimentary rocks. For groundwater-flow modeling purposes, the Canadian River was divided into Reach I, extending from the Texas border to the Canadian River at the Bridgeport, Okla., streamgage (07228500), and Reach II, extending downstream from the Canadian River at the Bridgeport, Okla., streamgage (07228500), to the confluence of the river with Eufaula Lake. The Canadian River alluvial aquifer spans multiple climate divisions, ranging from semiarid in the west to humid subtropical in the east. The average annual precipitation in the study area from 1896 to 2014 was 34.4 inches per year (in/yr).A hydrogeologic framework of the Canadian River alluvial aquifer was developed that includes the areal and vertical extent of the aquifer and the distribution, texture variability, and hydraulic properties of

Multiple stressors in agricultural streams: a mesocosm study of interactions among raised water temperature, sediment addition and nutrient enrichment.

Directory of Open Access Journals (Sweden)

Jeremy J Piggott

Full Text Available Changes to land use affect streams through nutrient enrichment, increased inputs of sediment and, where riparian vegetation has been removed, raised water temperature. We manipulated all three stressors in experimental streamside channels for 30 days and determined the individual and pair-wise combined effects on benthic invertebrate and algal communities and on leaf decay, a measure of ecosystem functioning. We added nutrients (phosphorus+nitrogen; high, intermediate, natural and/or sediment (grain size 0.2 mm; high, intermediate, natural to 18 channels supplied with water from a nearby stream. Temperature was increased by 1.4°C in half the channels, simulating the loss of upstream and adjacent riparian shade. Sediment affected 93% of all biological response variables (either as an individual effect or via an interaction with another stressor generally in a negative manner, while nutrient enrichment affected 59% (mostly positive and raised temperature 59% (mostly positive. More of the algal components of the community responded to stressors acting individually than did invertebrate components, whereas pair-wise stressor interactions were more common in the invertebrate community. Stressors interacted often and in a complex manner, with interactions between sediment and temperature most common. Thus, the negative impact of high sediment on taxon richness of both algae and invertebrates was stronger at raised temperature, further reducing biodiversity. In addition, the decay rate of leaf material (strength loss accelerated with nutrient enrichment at ambient but not at raised temperature. A key implication of our findings for resource managers is that the removal of riparian shading from streams already subjected to high sediment inputs, or land-use changes that increase erosion or nutrient runoff in a landscape without riparian buffers, may have unexpected effects on stream health. We highlight the likely importance of intact or restored buffer

Application of Integral Pumping Tests to estimate the influence of losing streams on groundwater quality

Science.gov (United States)

Leschik, S.; Musolff, A.; Reinstorf, F.; Strauch, G.; Schirmer, M.

2009-05-01

Urban streams receive effluents of wastewater treatment plants and untreated wastewater during combined sewer overflow events. In the case of losing streams substances, which originate from wastewater, can reach the groundwater and deteriorate its quality. The estimation of mass flow rates Mex from losing streams to the groundwater is important to support groundwater management strategies, but is a challenging task. Variable inflow of wastewater with time-dependent concentrations of wastewater constituents causes a variable water composition in urban streams. Heterogeneities in the structure of the streambed and the connected aquifer lead, in combination with this variable water composition, to heterogeneous concentration patterns of wastewater constituents in the vicinity of urban streams. Groundwater investigation methods based on conventional point sampling may yield unreliable results under these conditions. Integral Pumping Tests (IPT) can overcome the problem of heterogeneous concentrations in an aquifer by increasing the sampled volume. Long-time pumping (several days) and simultaneous sampling yields reliable average concentrations Cav and mass flow rates Mcp for virtual control planes perpendicular to the natural flow direction. We applied the IPT method in order to estimate Mex of a stream section in Leipzig (Germany). The investigated stream is strongly influenced by combined sewer overflow events. Four pumping wells were installed up- and downstream of the stream section and operated for a period of five days. The study was focused on four inorganic (potassium, chloride, nitrate and sulfate) and two organic (caffeine and technical-nonylphenol) wastewater constituents with different transport properties. The obtained concentration-time series were used in combination with a numerical flow model to estimate Mcp of the respective wells. The difference of the Mcp's between up- and downstream wells yields Mex of wastewater constituents that increase

Temperature Dependence of the Spin-Hall Conductivity of a Two-Dimensional Impure Rashba Electron Gas in the Presence of Electron-Phonon and Electron-Electron Interactions

Science.gov (United States)

Yavari, H.; Mokhtari, M.; Bayervand, A.

2015-03-01

Based on Kubo's linear response formalism, temperature dependence of the spin-Hall conductivity of a two-dimensional impure (magnetic and nonmagnetic impurities) Rashba electron gas in the presence of electron-electron and electron-phonon interactions is analyzed theoretically. We will show that the temperature dependence of the spin-Hall conductivity is determined by the relaxation rates due to these interactions. At low temperature, the elastic lifetimes ( and are determined by magnetic and nonmagnetic impurity concentrations which are independent of the temperature, while the inelastic lifetimes ( and related to the electron-electron and electron-phonon interactions, decrease when the temperature increases. We will also show that since the spin-Hall conductivity is sensitive to temperature, we can distinguish the intrinsic and extrinsic contributions.

Event-Based Analysis of Rainfall-Runoff Response to Assess Wetland-Stream Interaction in the Prairie Pothole Region

Science.gov (United States)

Haque, M. A.; Ross, C.; Schmall, A.; Bansah, S.; Ali, G.

2016-12-01

Process-based understanding of wetland response to precipitation is needed to quantify the extent to which non-floodplain wetlands - such as Prairie potholes - generate flow and transmit that flow to nearby streams. While measuring wetland-stream (W-S) interaction is difficult, it is possible to infer it by examining hysteresis characteristics between wetland and stream stage during individual precipitation events. Hence, to evaluate W-S interaction, 10 intact and 10 altered/lost potholes were selected for study; they are located in Broughton's Creek Watershed (Manitoba, Canada) on both sides of a 5 km creek reach. Stilling wells (i.e., above ground wells) were deployed in the intact and altered wetlands to monitor surface water level fluctuations while water table wells were drilled below drainage ditches to a depth of 1 m to monitor shallow groundwater fluctuations. All stilling wells and water table wells were equipped with capacitance water level loggers to monitor fluctuations in surface water and shallow groundwater every 15 minutes. In 2013 (normal year) and 2014 (wet year), 15+ precipitation events were identified and scatter plots of wetland (x-axis) versus stream (y-axis) stage were built to identify W-S hysteretic dynamics. Initial data analysis reveals that in dry antecedent conditions, intact and altered wetlands show clockwise W-S relations, while drained wetlands show anticlockwise W-S hysteresis. However, in wetter antecedent conditions, all wetland types show anticlockwise hysteresis. Future analysis will target the identification of thresholds in antecedent moisture conditions that determine significant changes in event wetland response characteristics (e.g., the delay between the start of rainfall and stream stage, the maximum water level rise in each wetland during each event, the delay between the start of rainfall and peak wetland stage) as well as hysteresis properties (e.g., gradient and area of the hysteresis loop).

Dissociated repetition deficits in aphasia can reflect flexible interactions between left dorsal and ventral streams and gender-dimorphic architecture of the right dorsal stream.

Science.gov (United States)

Berthier, Marcelo L; Froudist Walsh, Seán; Dávila, Guadalupe; Nabrozidis, Alejandro; Juárez Y Ruiz de Mier, Rocío; Gutiérrez, Antonio; De-Torres, Irene; Ruiz-Cruces, Rafael; Alfaro, Francisco; García-Casares, Natalia

2013-01-01

CA patient showed a greater activation of these cortical areas than the TCMA patient, but these changes did not result in normal performance. Repetition of word triplet lists activated bilateral perisylvian cortices in both patients, but activation in the CA patient with very poor performance was restricted to small frontal and posterior temporal foci bilaterally. These findings suggest that dissociated repetition deficits in our cases are probably reliant on flexible interactions between left dorsal stream (spared segments, short tracts remains) and left ventral stream and on gender-dimorphic architecture of the right dorsal stream.

Electron cloud and ion effects

CERN Document Server

Arduini, Gianluigi

2002-01-01

The significant progress in the understanding and control of machine impedances has allowed obtaining beams with increasing brilliance. Dense positively charged beams generate electron clouds via gas ionization, photoemission and multipacting. The electron cloud in turn interacts with the beam and the surrounding environment originating fast coupled and single bunch instabilities, emittance blow-up, additional loads to vacuum and cryogenic systems, perturbation to beam diagnostics and feedbacks and it constitutes a serious limitation to machine performance. In a similar way high brilliance electron beams are mainly affected by positively charged ions produced by residual gas ionization. Recent observations of electron cloud build-up and its effects in present accelerators are reviewed and compared with theory and with the results of state-of-the-art computer simulations. Two-stream instabilities induced by the interaction between electron beams and ions are discussed. The implications for future accelerators ...

A Study of the Connection Among Basin-Fill Aquifers, Carbonate-Rock Aquifers, and Surface-Water Resources in Southern Snake Valley, Nevada

Science.gov (United States)

,

2008-01-01

The Secretary of the Interior through the Southern Nevada Public Lands Management Act approved funding for research to improve understanding of hydrologic systems that sustain numerous water-dependent ecosystems on Federal lands in Snake Valley, Nevada. Some of the streams and spring-discharge areas in and adjacent to Great Basin National Park have been identified as susceptible to ground-water withdrawals (Elliott and others, 2006) and research has shown a high potential for ground-water flow from southern Spring Valley into southern Snake Valley through carbonate rocks that outcrop along a low topographic divide known as the Limestone Hills (Welch and others, 2007). Comprehensive geologic, hydrologic, and chemical information will be collected and analyzed to assess the hydraulic connection between basin-fill aquifers and surface-water resources, water-dependent ecological features, and the regional carbonate-rock aquifer, the known source of many high-discharge springs. Understanding these connections is important because proposed projects to pump and export ground water from Spring and Snake Valleys in Nevada may result in unintended capture of water currently supplying springs, streams, wetlands, limestone caves, and other biologically sensitive areas (fig. 1). The methods that will be used in this study may be transferable to other areas in the Great Basin. The National Park Service, Bureau of Land Management, U.S. Fish and Wildlife Service, and U.S. Forest Service submitted the proposal for funding this research to facilitate science-based land management. Scientists from the U.S. Geological Survey (USGS) Water Resources and Geologic Disciplines, and the University of Nevada, Reno, will accomplish four research elements through comprehensive data collection and analysis that are concentrated in two distinct areas on the eastern and southern flanks of the Snake Range (fig. 2). The projected time line for this research is from July 2008 through September 2011.

The University of Minnesota aquifer thermal energy storage (ATES) field test facility -- system description, aquifer characterization, and results of short-term test cycles

Energy Technology Data Exchange (ETDEWEB)

Walton, M.; Hoyer, M.C.; Eisenreich, S.J.; Holm, N.L.; Holm, T.R.; Kanivetsky, R.; Jirsa, M.A.; Lee, H.C.; Lauer, J.L.; Miller, R.T.; Norton, J.L.; Runke, H. (Minnesota Geological Survey, St. Paul, MN (United States))

1991-06-01

Phase 1 of the Aquifer Thermal Energy Storage (ATES) Project at the University of Minnesota was to test the feasibility, and model, the ATES concept at temperatures above 100{degrees}C using a confined aquifer for the storage and recovery of hot water. Phase 1 included design, construction, and operation of a 5-MW thermal input/output field test facility (FTF) for four short-term ATES cycles (8 days each of heat injection, storage, and heat recover). Phase 1 was conducted from May 1980 to December 1983. This report describes the FTF, the Franconia-Ironton-Galesville (FIG) aquifer used for the test, and the four short-term ATES cycles. Heat recovery; operational experience; and thermal, chemical, hydrologic, and geologic effects are all included. The FTF consists of monitoring wells and the source and storage well doublet completed in the FIG aquifer with heat exchangers and a fixed-bed precipitator between the wells of the doublet. The FIG aquifer is highly layered and a really anisotropic. The upper Franconia and Ironton-Galesville parts of the aquifer, those parts screened, have hydraulic conductivities of {approximately}0.6 and {approximately}1.0 m/d, respectively. Primary ions in the ambient ground water are calcium and magnesium bicarbonate. Ambient temperature FIG ground water is saturated with respect to calcium/magnesium bicarbonate. Heating the ground water caused most of the dissolved calcium to precipitate out as calcium carbonate in the heat exchanger and precipitator. Silica, calcium, and magnesium were significantly higher in recovered water than in injected water, suggesting dissolution of some constituents of the aquifer during the cycles. Further work on the ground water chemistry is required to understand water-rock interactions.

Drivers and Effects of Groundwater-Surface Water Interaction in the Karstic Lower Flint River Basin, Southwestern Georgia, USA

Science.gov (United States)

Rugel, K.; Golladay, S. W.; Jackson, C. R.; Rasmussen, T. C.; Dowd, J. F.; Mcdowell, R. J.

2017-12-01

Groundwater provides the majority of global water resources for domestic and agricultural usage while contributing vital surface water baseflows which support healthy aquatic ecosystems. Understanding the extent and magnitude of hydrologic connectivity between groundwater and surface water components in karst watersheds is essential to the prudent management of these hydraulically-interactive systems. We examined groundwater and surface water connectivity between the Upper Floridan Aquifer (UFA) and streams in the Lower Flint River Basin (LFRB) in southwestern Georgia where development of agricultural irrigation intensified over the past 30 years. An analysis of USGS streamflow data for the pre- and post-irrigation period showed summer baseflows in some Lower Flint River tributaries were reduced by an order of magnitude in the post-irrigation period, reiterating the strong hydraulic connection between these streams and the underlying aquifer. Large and fine-scale monitoring of calcium, nitrate, specific conductance and stable isotopes (δ18O and δD) on 50 km of Ichawaynochaway Creek, a major tributary of the Lower Flint, detected discrete groundwater-surface water flow paths which accounted for 42% of total groundwater contributions in the 50 km study reach. This presentation will highlight a new analysis using the metadata EPA Reach File (1) and comparing stream reach and instream bedrock joint azimuths with stream geochemical results from previous field study. Our findings suggested that reaches with NNW bearing may be more likely to display enhanced groundwater-surface water connectivity. Our results show that local heterogeneity can significantly affect water budgets and quality within these watersheds, making the use of geomorphological stream attributes a valuable tool to water resource management for the prediction and protection of vulnerable regions of hydrologic connectivity in karst catchments.

Hydrologic and water-quality conditions in the lower Apalachicola-Chattahoochee-Flint and parts of the Aucilla-Suwannee-Ochlockonee River basins in Georgia and adjacent parts of Florida and Alabama during drought conditions, July 2011

Science.gov (United States)

Gordon, Debbie W.; Peck, Michael F.; Painter, Jaime A.

2012-01-01

As part of the U.S. Department of the Interior sustainable water strategy, WaterSMART, the U.S. Geological Survey documented hydrologic and water-quality conditions in the lower Apalachicola-Chattahoochee-Flint and western and central Aucilla-Suwannee-Ochlockonee River basins in Alabama, Florida, and Georgia during low-flow conditions in July 2011. Moderate-drought conditions prevailed in this area during early 2011 and worsened to exceptional by June, with cumulative rainfall departures from the 1981-2010 climate normals registering deficits ranging from 17 to 27 inches. As a result, groundwater levels and stream discharges measured below median daily levels throughout most of 2011. Water-quality field properties including temperature, dissolved oxygen, specific conductance, and pH were measured at selected surface-water sites. Record-low groundwater levels measured in 12 of 43 surficial aquifer wells and 128 of 312 Upper Floridan aquifer wells during July 2011 underscored the severity of drought conditions in the study area. Most wells recorded groundwater levels below the median daily statistic, and 7 surficial aquifer wells were dry. Groundwater-level measurements taken in July 2011 were used to determine the potentiometric surface of the Upper Floridan aquifer. Groundwater generally flows to the south and toward streams except in reaches where streams discharge to the aquifer. The degree of connection between the Upper Floridan aquifer and streams decreases east of the Flint River where thick overburden hydraulically separates the aquifer from stream interaction. Hydraulic separation of the Upper Floridan aquifer from streams located east of the Flint River is shown by stream-stage altitudes that differ from groundwater levels measured in close proximity to streams. Most streams located in the study area during 2011 exhibited below normal flows (streamflows less than the 25th percentile), substantiating the severity of drought conditions that year. Streamflow

Creating a monthly time series of the potentiometric surface in the Upper Floridan aquifer, Northern Tampa Bay area, Florida, January 2000-December 2009

Science.gov (United States)

Lee, Terrie M.; Fouad, Geoffrey G.

2014-01-01

In Florida’s karst terrain, where groundwater and surface waters interact, a mapping time series of the potentiometric surface in the Upper Floridan aquifer offers a versatile metric for assessing the hydrologic condition of both the aquifer and overlying streams and wetlands. Long-term groundwater monitoring data were used to generate a monthly time series of potentiometric surfaces in the Upper Floridan aquifer over a 573-square-mile area of west-central Florida between January 2000 and December 2009. Recorded groundwater elevations were collated for 260 groundwater monitoring wells in the Northern Tampa Bay area, and a continuous time series of daily observations was created for 197 of the wells by estimating missing daily values through regression relations with other monitoring wells. Kriging was used to interpolate the monthly average potentiometric-surface elevation in the Upper Floridan aquifer over a decade. The mapping time series gives spatial and temporal coherence to groundwater monitoring data collected continuously over the decade by three different organizations, but at various frequencies. Further, the mapping time series describes the potentiometric surface beneath parts of six regionally important stream watersheds and 11 municipal well fields that collectively withdraw about 90 million gallons per day from the Upper Floridan aquifer. Monthly semivariogram models were developed using monthly average groundwater levels at wells. Kriging was used to interpolate the monthly average potentiometric-surface elevations and to quantify the uncertainty in the interpolated elevations. Drawdown of the potentiometric surface within well fields was likely the cause of a characteristic decrease and then increase in the observed semivariance with increasing lag distance. This characteristic made use of the hole effect model appropriate for describing the monthly semivariograms and the interpolated surfaces. Spatial variance reflected in the monthly

Coulomb drag: a probe of electron interactions in coupled quantum wells

DEFF Research Database (Denmark)

Jauho, Antti-Pekka

1996-01-01

As semiconductor devices shrink in size and in dimensionality, interactions between charge carriers become more and more important. There is a simple physical reason behind this behavior: fewer carriers lead to less effective screening, and hence stronger effective interactions. A point in case...... are one-dimensional systems (quantum wires): there electron-electron interactions may lead to a behavior, which is qualitatively different from the standard Fermi liquid picture (Luttinger liquids). Electron-electron interactions also play a central role in the fractional quantum Hall effect, which...... be the study of quantum wires: there the interactions may lead to even more dramatic effects...

Plural three-wave resonances of space charge wave harmonics in transit section of klystron-type two-stream FEL with helical electron beam

DEFF Research Database (Denmark)

Lysenko, Alexander; Volk, Iurii; Serozhko, Anastasia

2017-01-01

We have carried out the research of plural three-wave resonances of space charge wave (SCW) harmonics in the transit section of the klystron type two-stream superheterodyne free-electron laser (TSFEL) with helical electron beam in cubic non-linear approximation. We have found out that two...

EPA Region 1 Sole Source Aquifers

Science.gov (United States)

This coverage contains boundaries of EPA-approved sole source aquifers. Sole source aquifers are defined as an aquifer designated as the sole or principal source of drinking water for a given aquifer service area; that is, an aquifer which is needed to supply 50% or more of the drinking water for the area and for which there are no reasonable alternative sources should the aquifer become contaminated.The aquifers were defined by a EPA hydrogeologist. Aquifer boundaries were then drafted by EPA onto 1:24000 USGS quadrangles. For the coastal sole source aquifers the shoreline as it appeared on the quadrangle was used as a boundary. Delineated boundaries were then digitized into ARC/INFO.

Sources, occurrence and predicted aquatic impact of legacy and contemporary pesticides in streams.

Science.gov (United States)

McKnight, Ursula S; Rasmussen, Jes J; Kronvang, Brian; Binning, Philip J; Bjerg, Poul L

2015-05-01

We couple current findings of pesticides in surface and groundwater to the history of pesticide usage, focusing on the potential contribution of legacy pesticides to the predicted ecotoxicological impact on benthic macroinvertebrates in headwater streams. Results suggest that groundwater, in addition to precipitation and surface runoff, is an important source of pesticides (particularly legacy herbicides) entering surface water. In addition to current-use active ingredients, legacy pesticides, metabolites and impurities are important for explaining the estimated total toxicity attributable to pesticides. Sediment-bound insecticides were identified as the primary source for predicted ecotoxicity. Our results support recent studies indicating that highly sorbing chemicals contribute and even drive impacts on aquatic ecosystems. They further indicate that groundwater contaminated by legacy and contemporary pesticides may impact adjoining streams. Stream observations of soluble and sediment-bound pesticides are valuable for understanding the long-term fate of pesticides in aquifers, and should be included in stream monitoring programs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Spin Relaxation in III-V Semiconductors in various systems: Contribution of Electron-Electron Interaction

Science.gov (United States)

Dogan, Fatih; Kesserwan, Hasan; Manchon, Aurelien

2015-03-01

In spintronics, most of the phenomena that we are interested happen at very fast time scales and are rich in structure in time domain. Our understanding, on the other hand, is mostly based on energy domain calculations. Many of the theoretical tools use approximations and simplifications that can be perceived as oversimplifications. We compare the structure, material, carrier density and temperature dependence of spin relaxation time in n-doped III-V semiconductors using Elliot-Yafet (EY) and D'yakanov-Perel'(DP) with real time analysis using kinetic spin Bloch equations (KSBE). The EY and DP theories fail to capture details as the system investigated is varied. KSBE, on the other hand, incorporates all relaxation sources as well as electron-electron interaction which modifies the spin relaxation time in a non-linear way. Since el-el interaction is very fast (~ fs) and spin-conserving, it is usually ignored in the analysis of spin relaxation. Our results indicate that electron-electron interaction cannot be neglected and its interplay with the other (spin and momentum) relaxation mechanisms (electron-impurity and electron-phonon scattering) dramatically alters the resulting spin dynamics. We use each interaction explicitly to investigate how, in the presence of others, each relaxation source behaves. We use GaAs and GaN for zinc-blend structure, and GaN and AlN for the wurtzite structure.

Writing an Electronic Astronomy Book with Interactive Curricular Material

Science.gov (United States)

Thompson, Kristen L.; Belloni, Mario; Christian, Wolfgang

2015-01-01

With the rise of tablets, the past few years have seen an increase in the demand for quality electronic textbooks. Unfortunately, most of the current offerings do not exploit the accessibility and interactivity that electronic books can deliver. In this poster, we discuss how we are merging our curriculum development projects (Physlets, Easy Java/JavaScript Simulations, and Open Source Physics) with the EPUB electronic book format to develop an interactive textbook for use in a one-semester introductory astronomy course. The book, Astronomy: An Interactive Introduction, combines the narrative, equations, and images of a traditional astronomy text with new JavaScript simulations.

StreamExplorer: A Multi-Stage System for Visually Exploring Events in Social Streams.

Science.gov (United States)

Wu, Yingcai; Chen, Zhutian; Sun, Guodao; Xie, Xiao; Cao, Nan; Liu, Shixia; Cui, Weiwei

2017-10-18

Analyzing social streams is important for many applications, such as crisis management. However, the considerable diversity, increasing volume, and high dynamics of social streams of large events continue to be significant challenges that must be overcome to ensure effective exploration. We propose a novel framework by which to handle complex social streams on a budget PC. This framework features two components: 1) an online method to detect important time periods (i.e., subevents), and 2) a tailored GPU-assisted Self-Organizing Map (SOM) method, which clusters the tweets of subevents stably and efficiently. Based on the framework, we present StreamExplorer to facilitate the visual analysis, tracking, and comparison of a social stream at three levels. At a macroscopic level, StreamExplorer uses a new glyph-based timeline visualization, which presents a quick multi-faceted overview of the ebb and flow of a social stream. At a mesoscopic level, a map visualization is employed to visually summarize the social stream from either a topical or geographical aspect. At a microscopic level, users can employ interactive lenses to visually examine and explore the social stream from different perspectives. Two case studies and a task-based evaluation are used to demonstrate the effectiveness and usefulness of StreamExplorer.Analyzing social streams is important for many applications, such as crisis management. However, the considerable diversity, increasing volume, and high dynamics of social streams of large events continue to be significant challenges that must be overcome to ensure effective exploration. We propose a novel framework by which to handle complex social streams on a budget PC. This framework features two components: 1) an online method to detect important time periods (i.e., subevents), and 2) a tailored GPU-assisted Self-Organizing Map (SOM) method, which clusters the tweets of subevents stably and efficiently. Based on the framework, we present Stream

Characterization of the lowland coastal aquifer of Comacchio (Ferrara, Italy): Hydrology, hydrochemistry and evolution of the system

Science.gov (United States)

Giambastiani, B. M. S.; Colombani, N.; Mastrocicco, M.; Fidelibus, M. D.

2013-09-01

This study delineates the actual hydrogeochemistry and the geological evolution of an unconfined coastal aquifer located in a lowland setting in order to understand the drivers of the groundwater salinization. Physical aquifer parameterization highlights a vertical hydraulic gradient due to the presence of a heavy drainage system, which controls the hydrodynamics of this coastal area, forcing groundwater to flow from the bottom toward the top of the aquifer. As a consequence, relict seawater in stable density stratification, preserved within low permeability sediments in the deepest portion of the aquifer, has been drawn upward. The hydrogeochemical investigations allow identifying the role of seepage and water-sediment interactions in the aquifer salinization process and in the modification of groundwater chemistry. Mixing between freshwater and saltwater occurs; however, it is neither the only nor the dominant process driving groundwater hydrochemistry. In the aquifer several concurring and competing water-sediment interactions - as NaCl solution, ion-exchange, calcite and dolomite dissolution/precipitation, oxidation of organic matter, and sulfate bacterial reduction - are triggered by or overlap freshwater-saltwater mixing The hyper-salinity found in the deepest portion of the aquifer cannot be associated with present seawater intrusion, but suggests the presence of salt water of marine origin, which was trapped in the inter-basin during the Holocene transgression. The results of this study contribute to a better understanding of groundwater dynamics and salinization processes in this lowland coastal aquifer.

Geochemical approach of the salinization mechanisms of coastal aquifers - 14C - 226Ra chronologies

International Nuclear Information System (INIS)

Barbecot, F.

1999-11-01

Through time, coastal aquifers which constitute a great part of available fresh water resources from sedimentary basins in France, were submitted to changes in hydraulic gradients and hydrodynamic properties mainly due to discharge/recharge phases in response to sea level variations and/or anthropic forcing. Performed in the framework of the European program PALAEAUX ('Management of coastal aquifers in Europe, paleo-waters and natural controls'), this work aimed to understand the salinization process originating from the recharge/discharge conditions and recognized in three study aquifers: the calcareous Dogger aquifers along the Channel (Caen area), and the Atlantic coast (Marais Poitevin), and the Astian sandy aquifer (Cap d'Agde). Besides the conventional hydrogeological and hydrochemical methods, the main tools used are those of isotope geochemistry. For the three sites, the modern, fresh groundwaters are marked by the anthropisation of the recharge area. The evolution of isotopic signatures along a flow path depending on the mineralogy of the aquifer matrix, is linked to water-rock interactions such as cation exchange, and equilibrium with aluminosilicates. For the three study sites, the modern fresh groundwaters are marked by the anthropisation of the recharge area. The evolution of isotopic signatures along a flow path depending on the mineralogy of the aquifer matrix, is linked to water-rock interactions such as cation exchange, and equilibrium with aluminosilicates. Residence times of these fresh groundwater are from Present (Atlantic site) up to the 14 C detection limit (Channel site). Groundwater of the Astian aquifer belongs to Holocene, as determined by both 14 C and 226 Ra. From Present to 3 ka, 14 C and 226 Ra ages are coherent. Beyond, the discrepancy observed can be associated to the under-estimation of in- situ 226 Ra production, but more likely, to the 'buffer' effect of the matrix with respect to the 14 C isotopic equilibration. The salty waters

Geomicrobial and Geochemical Redox Processes in a Landfill-Polluted Aquifer

DEFF Research Database (Denmark)

Ludvigsen, Liselotte; Heron, Gorm; Albrechtsen, Hans-Jørgen

1995-01-01

The distribution of different dominant microbial-mediated redox processes in a landfill leachate-polluted aquifer (Grindsted, Denmark) was investigated. The most probable number method was utilized for detecting bacteria able to use each of the electron acceptors, and unamended incubations were u...

Analytical Analyses of Spatial and Temporal Characteristics of Infiltrated Water for Managed Aquifer Recharge

Science.gov (United States)

Zlotnik, V. A.; Ledder, G.; Kacimov, A. R.

2014-12-01

Disposal of excessive runoff or treated sewage into wadis and ephemeral streams is a common practice and an important hydrological problem in many Middle Eastern countries. While chemical and biological properties of the injected treated wastewater may be different from those of the receiving aquifer, the density contrast between the two fluids can be small. Therefore, studies of the fluid interface for variable density fluids or water intrusion are not directly relevant in many Managed Aquifer Recharge (MAR) problems. Other factors, such as the transient nature of injection and lack of detailed aquifer information must be considered. The disposed water reaching the water table through the vadose zone creates groundwater mounds, deforms the original water table, and develops finite-size convex-concave lenses of treated water over receiving water. After cessation of infiltration, these mounds flatten, water levels become horizontal, and infiltrated water becomes fully embedded in the receiving aquifer. The shape of the treated water body is controlled by the aquifer parameters, the magnitude of ambient flow, and the duration, rate, and cyclicity of infiltration. In case of limited aquifer data, advective transport modeling offers the most appropriate tools for predicting plume shapes over time, but surprisingly little work has been done on this important 3D flow problem. We investigate the lateral and vertical spreading of infiltrated water combining techniques of spatial velocity analyses by Zlotnik and Ledder (1992, 1993) with particle tracking. This approach allows for evaluating the geometry of the plume and the protection zone, the flow development phases, and other temporal and spatial effects and results can be used in conditions of limited data availability and quality. (Funding was provided by the USAID, DAI Subcontract 1001624-12S-19745)

A Black Hills-Madison Aquifer origin for Dakota Aquifer groundwater in northeastern Nebraska.

Science.gov (United States)

Stotler, Randy; Harvey, F Edwin; Gosselin, David C

2010-01-01

Previous studies of the Dakota Aquifer in South Dakota attributed elevated groundwater sulfate concentrations to Madison Aquifer recharge in the Black Hills with subsequent chemical evolution prior to upward migration into the Dakota Aquifer. This study examines the plausibility of a Madison Aquifer origin for groundwater in northeastern Nebraska. Dakota Aquifer water samples were collected for major ion chemistry and isotopic analysis ((18)O, (2)H, (3)H, (14)C, (13)C, (34)S, (18)O-SO(4), (87)Sr, (37)Cl). Results show that groundwater beneath the eastern, unconfined portion of the study area is distinctly different from groundwater sampled beneath the western, confined portion. In the east, groundwater is calcium-bicarbonate type, with delta(18)O values (-9.6 per thousand to -12.4 per thousand) similar to local, modern precipitation (-7.4 per thousand to -10 per thousand), and tritium values reflecting modern recharge. In the west, groundwater is calcium-sulfate type, having depleted delta(18)O values (-16 per thousand to -18 per thousand) relative to local, modern precipitation, and (14)C ages 32,000 to more than 47,000 years before present. Sulfate, delta(18)O, delta(2)H, delta(34)S, and delta(18)O-SO(4) concentrations are similar to those found in Madison Aquifer groundwater in South Dakota. Thus, it is proposed that Madison Aquifer source water is also present within the Dakota Aquifer beneath northeastern Nebraska. A simple Darcy equation estimate of groundwater velocities and travel times using reported physical parameters from the Madison and Dakota Aquifers suggests such a migration is plausible. However, discrepancies between (14)C and Darcy age estimates indicate that (14)C ages may not accurately reflect aquifer residence time, due to mixtures of varying aged water.

Interactions between mobilized radionuclides and secondary phases in final repository-relevant formation aquifers. Final report; Wechselwirkung mobilisierter Radionuklide mit sekundaeren Phasen in endlagerrelevanten Formationswaessern. Abschlussbericht

Energy Technology Data Exchange (ETDEWEB)

Curtius, H.; Kaiser, G.; Paparigas, Z.; Hansen, B.; Neumann, A.; Klinkenberg, M.; Mueller, E.; Bruecher, H.; Bosbach, D.

2010-10-15

The report on interactions between mobilized radionuclides and secondary phases in final repository-relevant formation aquifers covers the following issues: scope of study, leaching experiments, secondary phases, incorporation and sorption studies, summary and prospects. The results show that the investigated spent fuels dissolve instantaneously in contact with the repository-relevant aquifers in presence of iron ions. For the elements Cs and Sr no re-immobilization was observed. These elements have to be considered as mobile species in the radionuclide source term. The secondary phases due to corrosion processes are radionuclide sinks, i.e. actinides are re-immobilized, the retention mechanisms were clarified. The studies with irradiated nuclear fuel show that the uranium/silicon containing phases effect the molar solubility of actinides.

Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

International Nuclear Information System (INIS)

Li, X. F.; Yu, Q.; Qu, J. F.; Kong, Q.; Gu, Y. J.; Ma, Y. Y.; Kawata, S.

2016-01-01

In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electrons is significant, especially to the peak photon energy.

Medium-energy electrons and heavy ions in Jupiter's magnetosphere - Effects of lower hybrid wave-particle interactions

Science.gov (United States)

Barbosa, D. D.

1986-01-01

A theory of medium-energy (about keV) electrons and heavy ions in Jupiter's magnetosphere is presented. Lower hybrid waves are generated by the combined effects of a ring instability of neutral wind pickup ions and the modified two-stream instability associated with transport of cool Iogenic plasma. The quasi-linear energy diffusion coefficient for lower hybrid wave-particle interactions is evaluated, and several solutions to the diffusion equation are given. Calculations based on measured wave properties show that the noise substantially modifies the particle distribution functions. The effects are to accelerate superthermal ions and electrons to keV energies and to thermalize the pickup ions on time scales comparable to the particle residence time. The S(2+)/S(+) ratio at medium energies is a measure of the relative contribution from Iogenic thermal plasma and neutral wind ions, and this important quantity should be determined from future measurements. The theory also predicts a preferential acceleration of heavy ions with an accleration time that scales inversely with the root of the ion mass. Electrons accelerated by the process contribute to further reionization of the neutral wind by electron impact, thus providing a possible confirmation of Alfven's critical velocity effect in the Jovian magnetosphere.

Experimental evidence for interactions between anions and electron-deficient aromatic rings.

Science.gov (United States)

Berryman, Orion B; Johnson, Darren W

2009-06-14

This feature article summarizes our research aimed at using electron-deficient aromatic rings to bind anions in the context of complementary research in this active field. Particular attention is paid to the different types of interactions exhibited between anions and electron-deficient arenes in solution. The 120+ references cited in this article underscore the flurry of recent activity by numerous researchers in this field, which was relatively nascent when our efforts began in 2005. While the interaction of anions with electron-deficient aromatic rings has recently garnered much attention by supramolecular chemists, the observation of these interactions is not a recent discovery. Therefore, we begin with a historical perspective on early examples of anions interacting with electron-deficient arenes. An introduction to recent (and not so recent) computational investigations concerning anions and electron-deficient aromatic rings as well as a brief structural survey of crystalline examples of this interaction are provided. Finally, the limited solution-based observations of anions interacting with electron-deficient aromatic rings are summarized to introduce our current investigations in this area. We highlight three different systems from our lab where anion-arene interactions have been investigated. First, we show that tandem hydrogen bonds and anion-arene interactions augment halide binding in solution. Second, a crystallographic and computational study highlights the multiple types of interactions possible between anions and electron-deficient arenes. Third, we summarize the first example of a class of designed receptors that emphasize the different types of anion-arene interactions possible in solution.

Application of hydrologic tools and monitoring to support managed aquifer recharge decision making in the Upper San Pedro River, Arizona, USA

Science.gov (United States)

Lacher, Laurel J.; Turner, Dale S.; Gungle, Bruce W.; Bushman, Brooke M.; Richter, Holly E.

2014-01-01

The San Pedro River originates in Sonora, Mexico, and flows north through Arizona, USA, to its confluence with the Gila River. The 92-km Upper San Pedro River is characterized by interrupted perennial flow, and serves as a vital wildlife corridor through this semiarid to arid region. Over the past century, groundwater pumping in this bi-national basin has depleted baseflows in the river. In 2007, the United States Geological Survey published the most recent groundwater model of the basin. This model served as the basis for predictive simulations, including maps of stream flow capture due to pumping and of stream flow restoration due to managed aquifer recharge. Simulation results show that ramping up near-stream recharge, as needed, to compensate for downward pumping-related stress on the water table, could sustain baseflows in the Upper San Pedro River at or above 2003 levels until the year 2100 with less than 4.7 million cubic meters per year (MCM/yr). Wet-dry mapping of the river over a period of 15 years developed a body of empirical evidence which, when combined with the simulation tools, provided powerful technical support to decision makers struggling to manage aquifer recharge to support baseflows in the river while also accommodating the economic needs of the basin.

Application of Hydrologic Tools and Monitoring to Support Managed Aquifer Recharge Decision Making in the Upper San Pedro River, Arizona, USA

Directory of Open Access Journals (Sweden)

Laurel J. Lacher

2014-11-01

Full Text Available The San Pedro River originates in Sonora, Mexico, and flows north through Arizona, USA, to its confluence with the Gila River. The 92-km Upper San Pedro River is characterized by interrupted perennial flow, and serves as a vital wildlife corridor through this semiarid to arid region. Over the past century, groundwater pumping in this bi-national basin has depleted baseflows in the river. In 2007, the United States Geological Survey published the most recent groundwater model of the basin. This model served as the basis for predictive simulations, including maps of stream flow capture due to pumping and of stream flow restoration due to managed aquifer recharge. Simulation results show that ramping up near-stream recharge, as needed, to compensate for downward pumping-related stress on the water table, could sustain baseflows in the Upper San Pedro River at or above 2003 levels until the year 2100 with less than 4.7 million cubic meters per year (MCM/yr. Wet-dry mapping of the river over a period of 15 years developed a body of empirical evidence which, when combined with the simulation tools, provided powerful technical support to decision makers struggling to manage aquifer recharge to support baseflows in the river while also accommodating the economic needs of the basin.

Determining Changes in Groundwater Quality during Managed Aquifer Recharge

Science.gov (United States)

Gambhir, T.; Houlihan, M.; Fakhreddine, S.; Dadakis, J.; Fendorf, S. E.

2016-12-01

Managed aquifer recharge (MAR) is becoming an increasingly prevalent technology for improving the sustainability of freshwater supply. However, recharge water can alter the geochemical conditions of the aquifer, mobilizing contaminants native to the aquifer sediments. Geochemical alterations on deep (>300 m) injection of highly treated recycled wastewater for MAR has received limited attention. We aim to determine how residual disinfectants used in water treatment processes, specifically the strong oxidants chloramine and hydrogen peroxide, affect metal mobilization within deep injection wells of the Orange County Water District. Furthermore, as the treated recharge water has very low ionic strength (44.6 mg L-1 total dissolved solids), we tested how differing concentrations of magnesium chloride and calcium chloride affected metal mobilization within deep aquifers. Continuous flow experiments were conducted on columns dry packed with sediments from a deep injection MAR site in Orange County, CA. The effluent was analyzed for shifts in water quality, including aqueous concentrations of arsenic, uranium, and chromium. Interaction between the sediment and oxic recharge solution causes naturally-occurring arsenopyrite to repartition onto iron oxides. The stability of arsenic on the newly precipitated iron oxides is dependent on pH changes during recharge.

Investigating Stream Metabolism and Nutrient Dynamics in Contrasting Ecosystems: The Role of Hydrologic Compartments

Science.gov (United States)

Gonzalez-Pinzon, R.; Riveros-Iregui, D. A.; Covino, T. P.

2015-12-01

The interactions between mobile and less mobile hydrologic compartments affect the quality and quantity of water in streams and aquifers, and the cycling of dissolved carbon and nutrients. As new laboratory and field techniques become available, new questions and challenges emerge, including: What do we measure, where, and for how long to fully characterize a system? and, What is the ideal cost-maintenance-benefit relationship that we should strive for to maximize knowledge gained in different field settings? We recently performed a series of field experiments to measure aquatic metabolism and nutrient dynamics in two highly contrasting hydrologic systems, i.e., 1) a wetland-stream alpine, tropical system in Colombia (South America) and 2) a dryland river continuum (1st - 5th stream orders) in New Mexico. In this presentation we discuss how multiple lines of evidence can support the analysis of key aquatic processes and how co-interpretation provides a more complete picture of stream complexity. For this analysis, we deployed YSI EXO2 and 6920 sondes, Turner Designs C-sense and C6 sensors, and Onset HOBO water quality data loggers. Parameters measured by these instruments include conductivity, temperature, dissolved oxygen, pH, turbidity, pCO2, chlorophyll-a, phycocyanin, fluorescein, CDOM, brighteners and water depth. We also injected conservative tracers (i.e., NaCl and NaBr) and the bioreactive tracer resazurin in both experimental sites, and NO3 in the dryland river continuum. NO3 was measured in-situ with Satlantic Submersible Ultraviolet Nitrate Analyzers (SUNA) sensors and in the laboratory using Ion Chromatograph techniques using stream grab samples. Our results highlight the role of both residence times and chemical fluxes in regulating the effective processing of carbon and nutrients. Our results also demonstrate that stream stimuli from controlled experiments are ideal for maximizing the information content derived from short (hours to days) and mid

Aquifer thermal-energy-storage modeling

Science.gov (United States)

Schaetzle, W. J.; Lecroy, J. E.

1982-09-01

A model aquifer was constructed to simulate the operation of a full size aquifer. Instrumentation to evaluate the water flow and thermal energy storage was installed in the system. Numerous runs injecting warm water into a preconditioned uniform aquifer were made. Energy recoveries were evaluated and agree with comparisons of other limited available data. The model aquifer is simulated in a swimming pool, 18 ft by 4 ft, which was filled with sand. Temperature probes were installed in the system. A 2 ft thick aquifer is confined by two layers of polyethylene. Both the aquifer and overburden are sand. Four well configurations are available. The system description and original tests, including energy recovery, are described.

Towards a First-Principles Determination of Effective Coulomb Interactions in Correlated Electron Materials: Role of Intershell Interactions.

Science.gov (United States)

Seth, Priyanka; Hansmann, Philipp; van Roekeghem, Ambroise; Vaugier, Loig; Biermann, Silke

2017-08-04

The determination of the effective Coulomb interactions to be used in low-energy Hamiltonians for materials with strong electronic correlations remains one of the bottlenecks for parameter-free electronic structure calculations. We propose and benchmark a scheme for determining the effective local Coulomb interactions for charge-transfer oxides and related compounds. Intershell interactions between electrons in the correlated shell and ligand orbitals are taken into account in an effective manner, leading to a reduction of the effective local interactions on the correlated shell. Our scheme resolves inconsistencies in the determination of effective interactions as obtained by standard methods for a wide range of materials, and allows for a conceptual understanding of the relation of cluster model and dynamical mean field-based electronic structure calculations.

A comparison of large-scale electron beam and bench-scale 60Co irradiations of simulated aqueous waste streams

Science.gov (United States)

Kurucz, Charles N.; Waite, Thomas D.; Otaño, Suzana E.; Cooper, William J.; Nickelsen, Michael G.

2002-11-01

The effectiveness of using high energy electron beam irradiation for the removal of toxic organic chemicals from water and wastewater has been demonstrated by commercial-scale experiments conducted at the Electron Beam Research Facility (EBRF) located in Miami, Florida and elsewhere. The EBRF treats various waste and water streams up to 450 l min -1 (120 gal min -1) with doses up to 8 kilogray (kGy). Many experiments have been conducted by injecting toxic organic compounds into various plant feed streams and measuring the concentrations of compound(s) before and after exposure to the electron beam at various doses. Extensive experimentation has also been performed by dissolving selected chemicals in 22,700 l (6000 gal) tank trucks of potable water to simulate contaminated groundwater, and pumping the resulting solutions through the electron beam. These large-scale experiments, although necessary to demonstrate the commercial viability of the process, require a great deal of time and effort. This paper compares the results of large-scale electron beam irradiations to those obtained from bench-scale irradiations using gamma rays generated by a 60Co source. Dose constants from exponential contaminant removal models are found to depend on the source of radiation and initial contaminant concentration. Possible reasons for observed differences such as a dose rate effect are discussed. Models for estimating electron beam dose constants from bench-scale gamma experiments are presented. Data used to compare the removal of organic compounds using gamma irradiation and electron beam irradiation are taken from the literature and a series of experiments designed to examine the effects of pH, the presence of turbidity, and initial concentration on the removal of various organic compounds (benzene, toluene, phenol, PCE, TCE and chloroform) from simulated groundwater.

A comparison of large-scale electron beam and bench-scale 60Co irradiations of simulated aqueous waste streams

International Nuclear Information System (INIS)

Kurucz, Charles N.; Waite, Thomas D.; Otano, Suzana E.; Cooper, William J.; Nickelsen, Michael G.

2002-01-01

The effectiveness of using high energy electron beam irradiation for the removal of toxic organic chemicals from water and wastewater has been demonstrated by commercial-scale experiments conducted at the Electron Beam Research Facility (EBRF) located in Miami, Florida and elsewhere. The EBRF treats various waste and water streams up to 450 l min -1 (120 gal min -1 ) with doses up to 8 kilogray (kGy). Many experiments have been conducted by injecting toxic organic compounds into various plant feed streams and measuring the concentrations of compound(s) before and after exposure to the electron beam at various doses. Extensive experimentation has also been performed by dissolving selected chemicals in 22,700 l (6000 gal) tank trucks of potable water to simulate contaminated groundwater, and pumping the resulting solutions through the electron beam. These large-scale experiments, although necessary to demonstrate the commercial viability of the process, require a great deal of time and effort. This paper compares the results of large-scale electron beam irradiations to those obtained from bench-scale irradiations using gamma rays generated by a 60 Co source. Dose constants from exponential contaminant removal models are found to depend on the source of radiation and initial contaminant concentration. Possible reasons for observed differences such as a dose rate effect are discussed. Models for estimating electron beam dose constants from bench-scale gamma experiments are presented. Data used to compare the removal of organic compounds using gamma irradiation and electron beam irradiation are taken from the literature and a series of experiments designed to examine the effects of pH, the presence of turbidity, and initial concentration on the removal of various organic compounds (benzene, toluene, phenol, PCE, TCE and chloroform) from simulated groundwater

Coulomb interactions in dense two-dimensional electron systems in a magnetic field

International Nuclear Information System (INIS)

Cheng, Szucheng.

1988-01-01

The simplest model of a two-dimensional system ignores the Coulomb interactions between the electrons. In this approximation, the electrons occupy the Landau levels, broadened by impurities and irregularities in the lattice. This independent electron approximation has usually been used to discuss observations for electron densities ρ and magnetic fields B where bar ν > 1 (bar ν triple-bond the number of Landau levels occupied). The most famous example is the theory of the integral Quantum Hall effect. However, when bar ν 1, electron-electron interactions should become important through the mixing of Landau levels. This thesis describes calculations for bar ν > 1 on phenomena which should be sensitive to electron-electron interactions: Wigner crystallization, the stability of the Landau levels under electron-electron interactions, the existence of quasiparticles and quasiholes, and the densities of states. The main results obtained concern: (1) The values of ρ and B where crystallization should occur when bar ν > 1. (2) The effect of electron-electron interactions in broadening the individual Landau levels, and in distributing the amplitudes for the excitation of independent electrons over many Landau levels. (3) The existence of quasiparticles and quasiholes whose lifetime is infinite near the Fermi level

The Electron Transport Chain: An Interactive Simulation

Science.gov (United States)

Romero, Chris; Choun, James

2014-01-01

This activity provides students an interactive demonstration of the electron transport chain and chemiosmosis during aerobic respiration. Students use simple, everyday objects as hydrogen ions and electrons and play the roles of the various proteins embedded in the inner mitochondrial membrane to show how this specific process in cellular…

Interaction effects in liquids with low electron densities

International Nuclear Information System (INIS)

Warren, W.W. Jr.

1987-01-01

The author discusses two complementary classes of systems in which strong electron-electron or electron-ion interactions appear at low electron densities. The first are the expanded liquid alkali metals (cesium) in which electron correlation effects have a profound effect on the magnetic properties on the metallic side of the metal-nonmetal transition. The second group are molten alkali halides containing low densities of localized electrons introduced, say, by dissolution of small amounts of excess metal. (Auth.)

Effects of electrostatic interactions on electron transfer reactions

International Nuclear Information System (INIS)

Hickel, B.

1987-01-01

The fast reactions of electron transfer are studied by pulse radiolysis. This technique allows the creation in about 10 -8 second radicals and radical ions with high redox potentials. For solvated electrons electrostatic interaction on the kinetics of reactions limited by diffusion is described by Debye's equation when ion mobility is known. Deviation from theory can occur in ion pairs formation. This is evidenced experimentally for anions by cation complexation with a cryptate. Relatively slow reactions are more sensitive to electrostatic interactions than limited by diffusion. If ion pairs are not formed kinetics constant depends on dielectric constant of solvent and reaction radius. Experimentally is studied the effect of electrostatic interaction on the rate constants of solvated electrons with anions and cations in water-ethanol mixtures where the dielectric constant change from 80 to 25 at room temperature. 17 refs

Yield and quality of ground water from stratified-drift aquifers, Taunton River basin, Massachusetts : executive summary

Science.gov (United States)

Lapham, Wayne W.; Olimpio, Julio C.

1989-01-01

Water shortages are a chronic problem in parts of the Taunton River basin and are caused by a combination of factors. Water use in this part of the Boston metropolitan area is likely to increase during the next decade. The Massachusetts Division of Water Resources projects that about 50% of the cities and towns within and on the perimeter of the basin may have water supply deficits by 1990 if water management projects are not pursued throughout the 1980s. Estimates of the long-term yield of the 26 regional aquifers indicate that the yields of the two most productive aquifers equal or exceed 11.9 and 11.3 cu ft/sec, 90% of the time, respectively, if minimum stream discharge is maintained at 99.5% flow duration. Eighteen of the 26 aquifers were pumped for public water supply during 1983. Further analysis of the yield characteristics of these 18 aquifers indicates that the 1983 pumping rate of each of these 18 aquifers can be sustained at least 70% of the time. Selected physical properties and concentrations of major chemical constituents in groundwater from the stratified-drift aquifers at 80 sampling sites were used to characterize general water quality in aquifers throughout the basin. The pH of the groundwater ranged from 5.4 to 7.0. Natural elevated concentrations of Fe and Mn in water in the stratified-drift aquifers are present locally in the basin. Natural concentrations of these two metals commonly exceed the limits of 0.3 mg/L for Fe and 0.05 mg/L for Mn recommended for drinking water. Fifty-one analyses of selected trace metals in groundwater samples from stratified-drift aquifers throughout the basin were used to characterize trace metal concentrations in the groundwater. Of the 10 constituents sampled that have US EPA limits recommended for drinking water, only the Pb concentration in water at one site (60 micrograms/L) exceeded the recommended limit of 50 micrograms/L. Analyses of selected organic compounds in water in the stratified-drift aquifers at 74

Photon-Electron Interaction and Condense Beams

International Nuclear Information System (INIS)

Chattopadhyay, S.

1998-01-01

We discuss beams of charged particles and radiation from multiple perspectives. These include fundamental acceleration and radiation mechanisms, underlying electron-photon interaction, various classical and quantum phase-space concepts and fluctuational interpretations

Interaction Between Electrons, Magnons and Phonons in Nickel. RCN Report

International Nuclear Information System (INIS)

Frikkee, E.

1971-02-01

By means of inelastic neutron scattering, a localized electron excitation was observed in Ni and (4% Fe). The excitation interacts with magnons and phonons, and is assumed to correspond with transitions between the nearly-degenerate electronstates Δ 6 ↑ and Δ 7 ↑ near X, which are situated just below the Fermi level.Selection rules for electron-phonon and electronmagnon scattering are determined by means of group theory. It is found that in particular the transverse (Δ 5 ) phonons in the [100] direction are perturbed. The observed neutron-electron scattering turns out to be an indirect process, which is only possible due to the interaction between the (Δ 6 , Δ 7 ) electrons and the lattice. The basic mechanism for the observed effects is the electron spin-orbit coupling, which establishes the interaction between the electron spin system and the lattice. (author)

Simulation and reconstruction of free-streaming data in CBM

International Nuclear Information System (INIS)

Friese, Volker

2011-01-01

The CBM experiment will investigate heavy-ion reactions at the FAIR facility at unprecedented interaction rates. This implies a novel read-out and data acquisition concept with self-triggered front-end electronics and free-streaming data. Event association must be performed in software on-line, and may require four-dimensional reconstruction routines. In order to study the problem of event association and to develop proper algorithms, simulations must be performed which go beyond the normal event-by-event processing as available from most experimental simulation frameworks. In this article, we discuss the challenges and concepts for the reconstruction of such free-streaming data and present first steps for a time-based simulation which is necessary for the development and validation of the reconstruction algorithms, and which requires modifications to the current software framework FAIRROOT as well as to the data model.

Electron-dislocation interaction at low temperatures. Progress report

International Nuclear Information System (INIS)

1976-01-01

Studies of the interaction of mobile dislocations with electrons have shown that dislocation motion can be, in part, described by treating the dislocation as an underdamped oscillator. In particular, studies in lead alloys have shown tht dislocation motion can be considered as the motion of string, slightly damped by electrons, without regard for any other lattice friction. In addition we have shown that silver solutes, in lead crystals, occupy, partially, interstitial sites. Finally, we have shown that dislocations in copper interact, unexpectedly, with electrons. This is shown by measuring the influence of a magnetic field on the flow stress of copper crystals at 4.2 0 K

Heat storage in the Hettangian aquifer in Berlin - results from a column experiment

Science.gov (United States)

Milkus, Chri(Sch)augott

2015-04-01

Aquifer Thermal Energy Storage (ATES) is a sustainable alternative for storage and seasonal availability of thermal energy. However, its impact on the subsurface flow regime is not well known. In Berlin (Germany), the Jurassic (Hettangian) sandstone aquifer with highly mineralized groundwater (TDS 27 g/L) is currently used for heat storage. The aim of this study was to examine the hydrogeochemical changes that are caused by the induced temperature shift and its effects on the hydraulic permeability of the aquifer. Column experiments were conducted, in which stainless steel columns were filled with sediment from the aquifer and flushed with native groundwater for several weeks. The initial temperature of the experiment was 20°C, comparable to the in-situ conditions within the aquifer. After reaching equilibrium between sediment and water, the temperature was increased to simulate heating of the aquifer. During the experiment, physical and chemical parameters (pH, ORP, dissolved oxygen and dissolved carbon dioxide) were measured at the outflow of the column and the effluent water was sampled. Using a Scanning Electron Microscope, the deposition of precipitated minerals and biofilm on sediment grains was analyzed. Changes in hydraulic properties of the sediment were studied by the use of tracer tests with Uranin.

Localized sulfate-reducing zones in a coastal plain aquifer

Science.gov (United States)

Brown, C.J.; Coates, J.D.; Schoonen, M.A.A.

1999-01-01

High concentrations of dissolved iron in ground water of coastal plain or alluvial aquifers contribute to the biofouling of public supply wells for which treatment and remediation is costly. Many of these aquifers, however, contain zones in which microbial sulfate reduction and the associated precipitation of iron-sulfide minerals decreases iron mobility. The principal water-bearing aquifer (Magothy Aquifer of Cretaceous age) in Suffolk County, New York, contains localized sulfate-reducing zones in and near lignite deposits, which generally are associated with clay lenses. Microbial analyses of core samples amended with [14C]-acetate indicate that microbial sulfate reduction is the predominant terminal-electron-accepting process (TEAP) in poorly permeable, lignite-rich sediments at shallow depths and near the ground water divide. The sulfate-reducing zones are characterized by abundant lignite and iron-sulfide minerals, low concentrations of Fe(III) oxyhydroxides, and by proximity to clay lenses that contain pore water with relatively high concentrations of sulfate and dissolved organic carbon. The low permeability of these zones and, hence, the long residence time of ground water within them, permit the preservation and (or) allow the formation of iron-sulfide minerals, including pyrite and marcasite. Both sulfate-reducing bacteria (SRB) and iron-reducing bacteria (IRB) are present beneath and beyond the shallow sulfate-reducing zones. A unique Fe(III)-reducing organism, MD-612, was found in core sediments from a depth of 187 m near the southern shore of Long Island. The distribution of poorly permeable, lignite-rich, sulfate-reducing zones with decreased iron concentration is varied within the principal aquifer and accounts for the observed distribution of dissolved sulfate, iron, and iron sulfides in the aquifer. Locating such zones for the placement of production wells would be difficult, however, because these zones are of limited aerial extent.

Noncovalent Interactions in Organic Electronic Materials

KAUST Repository

Ravva, Mahesh Kumar; Risko, Chad; Bredas, Jean-Luc

2017-01-01

In this chapter, we provide an overview of how noncovalent interactions, determined by the chemical structure of π-conjugated molecules and polymers, govern essential aspects of the electronic, optical, and mechanical characteristics of organic

Electromagnetically Interacting Dust Streams During Ulysses' Second Jupiter Encounter

International Nuclear Information System (INIS)

Krueger, H.; Forsyth, R.J.; Graps, A.L.; Gruen, E.

2005-01-01

The Jupiter system is a source of collimated burst-like streams of electrically charged 10-nm dust particles. In 2004 the Ulysses spacecraft had its second flyby at Jupiter and from late 2002 to early 2005 it measured a total of 24 dust streams between 0.8 and 3.4 AU from the planet. The grains show strong coupling to the interplanetary magnetic field: their impact directions correlate with the orientation and strength of the interplanetary magnetic field vector (namely its tangential and radial components) and they occur at 26 day intervals, closely matching the solar rotation period. Ulysses measured the dust streams over a large range in jovian latitude (+75 deg. to -35 deg.). Enhanced dust emission was measured along the jovian equator

Hydrogeology and hydrologic conditions of the Ozark Plateaus aquifer system

Science.gov (United States)

Hays, Phillip D.; Knierim, Katherine J.; Breaker, Brian K.; Westerman, Drew A.; Clark, Brian R.

2016-11-23

The hydrogeology and hydrologic characteristics of the Ozark Plateaus aquifer system were characterized as part of ongoing U.S. Geological Survey efforts to assess groundwater availability across the Nation. The need for such a study in the Ozark Plateaus physiographic province (Ozark Plateaus) is highlighted by increasing demand on groundwater resources by the 5.3 million people of the Ozark Plateaus, water-level declines in some areas, and potential impacts of climate change on groundwater availability. The subject study integrates knowledge gained through local investigation within a regional perspective to develop a regional conceptual model of groundwater flow in the Ozark Plateaus aquifer system (Ozark system), a key phase of groundwater availability assessment. The Ozark system extends across much of southern Missouri and northwestern and north-central Arkansas and smaller areas of southeastern Kansas and northeastern Oklahoma. The region is one of the major karst landscapes in the United States, and karst aquifers are predominant in the Ozark system. Groundwater flow is ultimately controlled by aquifer and confining unit lithologies and stratigraphic relations, geologic structure, karst development, and the character of surficial lithologies and regolith mantle. The regolith mantle is a defining element of Ozark Plateaus karst, affecting recharge, karst development, and vulnerability to surface-derived contaminants. Karst development is more advanced—as evidenced by larger springs, hydraulic characteristics, and higher well yields—in the Salem Plateau and in the northern part of the Springfield Plateau (generally north of the Arkansas-Missouri border) as compared with the southern part of the Springfield Plateau in Arkansas, largely due to thinner, less extensive regolith and purer carbonate lithology.Precipitation is the ultimate source of all water to the Ozark system, and the hydrologic budget for the Ozark system includes inputs from recharge

Aquifer test to determine hydraulic properties of the Elm aquifer near Aberdeen, South Dakota

Science.gov (United States)

Schaap, Bryan D.

2000-01-01

The Elm aquifer, which consists of sandy and gravelly glacial-outwash deposits, is present in several counties in northeastern South Dakota. An aquifer test was conducted northeast of Aberdeen during the fall of 1999 to determine the hydraulic properties of the Elm aquifer in that area. An improved understanding of the properties of the aquifer will be useful in the possible development of the aquifer as a water resource. Historical water-level data indicate that the saturated thickness of the Elm aquifer can change considerably over time. From September 1977 through November 1985, water levels at three wells completed in the Elm aquifer near the aquifer test site varied by 5.1 ft, 9.50 ft, and 11.1 ft. From June 1982 through October 1999, water levels at five wells completed in the Elm aquifer near the aquifer test site varied by 8.7 ft, 11.4 ft, 13.2 ft, 13.8 ft, and 19.7 ft. The water levels during the fall of 1999 were among the highest on record, so the aquifer test was affected by portions of the aquifer being saturated that might not be saturated during drier times. The aquifer test was conducted using five existing wells that had been installed prior to this study. Well A, the pumped well, has an operating irrigation pump and is centrally located among the wells. Wells B, C, D, and E are about 70 ft, 1,390 ft, 2,200 ft, and 3,100 ft, respectively, in different directions from Well A. Using vented pressure transducers and programmable data loggers, water-level data were collected at the five wells prior to, during, and after the pumping, which started on November 19, 1999, and continued a little over 72 hours. Based on available drilling logs, the Elm aquifer near the test area was assumed to be unconfined. The Neuman (1974) method theoretical response curves that most closely match the observed water-level changes at Wells A and B were calculated using software (AQTESOLV for Windows Version 2.13-Professional) developed by Glenn M. Duffield of Hydro

Hydrogeology and water quality of the Floridan aquifer system and effect of Lower Floridan aquifer withdrawals on the Upper Floridan aquifer at Barbour Pointe Community, Chatham County, Georgia, 2013

Science.gov (United States)

Gonthier, Gerard; Clarke, John S.

2016-06-02

Two test wells were completed at the Barbour Pointe community in western Chatham County, near Savannah, Georgia, in 2013 to investigate the potential of using the Lower Floridan aquifer as a source of municipal water supply. One well was completed in the Lower Floridan aquifer at a depth of 1,080 feet (ft) below land surface; the other well was completed in the Upper Floridan aquifer at a depth of 440 ft below land surface. At the Barbour Pointe test site, the U.S. Geological Survey completed electromagnetic (EM) flowmeter surveys, collected and analyzed water samples from discrete depths, and completed a 72-hour aquifer test of the Floridan aquifer system withdrawing from the Lower Floridan aquifer.Based on drill cuttings, geophysical logs, and borehole EM flowmeter surveys collected at the Barbour Pointe test site, the Upper Floridan aquifer extends 369 to 567 ft below land surface, the middle semiconfining unit, separating the two aquifers, extends 567 to 714 ft below land surface, and the Lower Floridan aquifer extends 714 to 1,056 ft below land surface.A borehole EM flowmeter survey indicates that the Upper Floridan and Lower Floridan aquifers each contain four water-bearing zones. The EM flowmeter logs of the test hole open to the entire Floridan aquifer system indicated that the Upper Floridan aquifer contributed 91 percent of the total flow rate of 1,000 gallons per minute; the Lower Floridan aquifer contributed about 8 percent. Based on the transmissivity of the middle semiconfining unit and the Floridan aquifer system, the middle semiconfining unit probably contributed on the order of 1 percent of the total flow.Hydraulic properties of the Upper Floridan and Lower Floridan aquifers were estimated based on results of the EM flowmeter survey and a 72-hour aquifer test completed in Lower Floridan aquifer well 36Q398. The EM flowmeter data were analyzed using an AnalyzeHOLE-generated model to simulate upward borehole flow and determine the transmissivity of

Magnetic impurity in a system of interacting electrons

International Nuclear Information System (INIS)

Huynh Thanh Duc; Nguyen Toan Thang

1999-04-01

The Kondo effect of the Anderson impurity in a correlated conduction electron system is studied within the slave boson mean-field theory. The interacting conduction electrons are described by a Hubbard model with an interaction of strength U. It is shown that the Kondo temperature T K decreases with an increase of U. In the intermediate regime at half-filling the exponential scale of the Kondo temperature T K is lost already at the saddle-point level of slave boson formulation. (author)

Relativistic electron beam interaction with a thin target

International Nuclear Information System (INIS)

Gazaix, M.

1981-03-01

This study is concerned with the increasing possibilities of electron energy deposition in thin targets. The thesis theoretical part studies the relativistic electron beam-plasma instability; the Buneman-Pierce instability in limited medium is also studied. In the experimental part, several questions are tentatively answered: - what is the spatial and temporal evolution of the anode material, in temperature and in density. - What sort of interaction is the beam-target interaction; more particularly questions about focusing and energy deposition are studied [fr

Stochastic Coulomb interactions in space charge limited electron emission

International Nuclear Information System (INIS)

Nijkerk, M.D.; Kruit, P.

2004-01-01

Emission models that form the basis of self-consistent field computations make use of the approximation that emitted electrons form a smooth space charge jelly. In reality, electrons are discrete particles that are subject to statistical Coulomb interactions. A Monte Carlo simulation tool is used to evaluate the influence of discrete space charge effects on self-consistent calculations of cathode-ray tube optics. We find that interactions in the space charge cloud affect the electron trajectories such that the velocity distribution is Maxwellian, regardless of the current density. Interactions near the emitter effectively conserve the Maxwellian distribution. The surprising result is that the width of the distribution of transversal velocities does not change. The distribution of longitudinal velocities does broaden, as expected from existing theories

Modulation of continuous electron beams in plasma wake-fields

International Nuclear Information System (INIS)

Rosenzweig, J.B.

1988-01-01

In this paper we discuss the interaction of a continuous electron beam with wake-field generated plasma waves. Using a one-dimensional two fluid model, a fully nonlinear analytical description of the interaction is obtained. The phenomena of continuous beam modulation and wave period shortening are discussed. The relationship between these effects and the two-stream instability is also examined. 12 refs., 1 fig

Analysis of electron interactions in dielectric gases

International Nuclear Information System (INIS)

Olivet, Aurelio; Duque, Daniel; Vega, Lourdes F.

2007-01-01

We present and discuss results concerning electron interactions processes of dielectric gases and their relationship with the macroscopic behavior of these gases, in particular, with their dielectric strength. Such analysis is based on calculating energies of reactions for molecular ionization, dissociative ionization, parent negative ion formation, and dissociative electron attachment processes. We hypothesize that the estimation of the required energy for a reduced number of processes that take place in electrically stressed gases could be related to the gas' capability to manage the electron flow during an electrical discharge. All calculations were done with semiempirical quantum chemistry methods, including an initial optimization of molecular geometry and heat of formation of the dielectric gases and all of species that appear during electron interaction reactions. The performance of semiempirical methods Austin model 1 and Parametric model 3 (PM3) was compared for several compounds, PM3 being superior in most cases. Calculations performed for a sample of nine dielectric gases show that electron attachment and detachment processes occur in different energy bands that do not overlap for any value of the dielectric strength. We have also analyzed the relationship between dielectric strength and two physical properties: electron affinity and ionization energy. Calculations performed for 43 dielectric gases show no clear correlation between them, although certain guidelines for the qualitative estimation of dielectric strength can still be assessed

Guarani aquifer hydrogeological synthesis of the Guarani aquifer system. Edicion bilingue

International Nuclear Information System (INIS)

2009-01-01

This work represents the synthesis of current knowledge of the Guarani Aquifer System, based on technical products made by different companies and consultants who participated in the framework of the Project for Environmental Protection and Sustainable Development of the Guarani Aquifer.

Arsenic in Holocene aquifers of the Red River floodplain, Vietnam: Effects of sediment-water interactions, sediment burial age and groundwater residence time

Science.gov (United States)

Sø, Helle Ugilt; Postma, Dieke; , Mai Lan, Vi; Pham, Thi Kim Trang; Kazmierczak, Jolanta; Dao, Viet Nga; Pi, Kunfu; Koch, Christian Bender; Pham, Hung Viet; Jakobsen, Rasmus

2018-03-01

Water-sediment interactions were investigated in arsenic contaminated Holocene aquifers of the Red River floodplain, Vietnam, in order to elucidate the origin of the spatial variability in the groundwater arsenic concentration. The investigated aquifers are spread over an 8 × 13 km field area with sediments that varied in burial age from V) redox couple was found in disequilibrium with the other redox couples. Using the pe calculated from the CH4/CO2 redox couple we show that the groundwater has a reducing potential towards Fe-oxides ranging from ferrihydrite to poorly crystalline goethite, but not for well crystalline goethite or hematite. Hematite and poorly crystalline goethite were identified as the Fe-oxides present in the sediments. Reductive dissolution experiments identify two phases releasing Fe(II); one rapidly dissolving that also contains As and a second releasing Fe(II) more slowly but without As. The initial release of Fe and As occurs at a near constant As/Fe ratio that varied from site to site between 1.2 and 0.1 mmol As/mol Fe. Siderite (FeCO3) is the main sink for Fe(II), based on saturation calculations as well as the identification of siderite in the sediment. Most of the carbonate incorporated in siderite originates from the dissolution of sedimentary CaCO3. Over time the CaCO3 content of the sediments diminishes and FeCO3 appears instead. No specific secondary phases that incorporate arsenite could be identified. Alternatively, the amount of arsenic mobilized during the dissolution of reactive phases can be contained in the pool of adsorbed arsenite. Combining groundwater age with aquifer sediment age allows the calculation of the total number of pore volumes flushed through the aquifer. Comparison with groundwater chemistry shows the highest arsenic concentration to be present within the first 200 pore volumes flushed through the aquifer. These results agree with reactive transport modeling combining a kinetic description of reductive

Electron-photon and electron-electron interactions in the presence of strong electromagnetic fields

International Nuclear Information System (INIS)

Surzhykov, A.; Fritzsche, S.; Stoehlker, Th.

2010-01-01

During the last decade, photon emission from highly-charged, heavy ions has been in the focus of intense studies at the GSI accelerator and storage ring facility in Darmstadt. These studies have revealed unique information about the electron-electron and electron-photon interactions in the presence of extremely strong nuclear fields. Apart from the radiative electron capture processes, characteristic photon emission following collisional excitation of projectile ions has also attracted much interest. In this contribution, we summarize the recent theoretical studies on the production of excited ionic states and their subsequent radiative decay. We will pay special attention to the angular and polarization properties of Kα emission from helium-like ions produced by means of dielectronic recombination. The results obtained for this (resonant) capture process will be compared with the theoretical predictions for the characteristic X-rays following Coulomb excitation and radiative recombination of few-electron, heavy ions. Work is supported by Helmholtz Association and GSl under the project VH-NG--421. (author)

Monitoring Aquifer Depletion from Space: Case Studies from the Saharan and Arabian Aquifers

Science.gov (United States)

Ahmed, M.; Sultan, M.; Wahr, J. M.; Yan, E.

2013-12-01

Access to potable fresh water resources is a human right and a basic requirement for economic development in any society. In arid and semi-arid areas, the characterization and understanding of the geologic and hydrologic settings of, and the controlling factors affecting, these resources is gaining increasing importance due to the challenges posed by increasing population. In these areas, there is immense natural fossil fresh water resources stored in large extensive aquifers, the transboundary aquifers. Yet, natural phenomena (e.g., rainfall patterns and climate change) together with human-related factors (e.g., population growth, unsustainable over-exploitation, and pollution) are threatening the sustainability of these resources. In this study, we are developing and applying an integrated cost-effective approach to investigate the nature (i.e., natural and anthropogenic) and the controlling factors affecting the hydrologic settings of the Saharan (i.e., Nubian Sandstone Aquifer System [NSAS], Northwest Sahara Aquifer System [NWSA]) and Arabian (i.e., Arabian Peninsula Aquifer System [APAS]) aquifer systems. Analysis of the Gravity Recovery and Climate Experiment (GRACE)-derived Terrestrial Water Storage (TWS) inter-annual trends over the NSAS and the APAS revealed two areas of significant TWS depletions; the first correlated with the Dakhla Aquifer System (DAS) in the NSAS and second with the Saq Aquifer System (SAS) in the APAS. Annual depletion rates were estimated at 1.3 × 0.66 × 109 m3/yr and 6.95 × 0.68 × 109 m3/yr for DAS and SAS, respectively. Findings include (1) excessive groundwater extraction, not climatic changes, is responsible for the observed TWS depletions ;(2) the DAS could be consumed in 350 years if extraction rates continue to double every 50 years and the APAS available reserves could be consumed within 60-140 years at present extraction (7.08 × 109 m3/yr) and depletion rates; and (3) observed depletions over DAS and SAS and their

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy.

Science.gov (United States)

Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan

2016-11-29

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Multiply excited molecules produced by photon and electron interactions

International Nuclear Information System (INIS)

Odagiri, T.; Kouchi, N.

2006-01-01

The photon and electron interactions with molecules resulting in the formation of multiply excited molecules and the subsequent decay are subjects of great interest because the independent electron model and Born-Oppenheimer approximation are much less reliable for the multiply excited states of molecules than for the ground and lower excited electronic states. We have three methods to observe and investigate multiply excited molecules: 1) Measurements of the cross sections for the emission of fluorescence emitted by neutral fragments in the photoexcitation of molecules as a function of incident photon energy [1-3], 2) Measurements of the electron energy-loss spectra tagged with the fluorescence photons emitted by neutral fragments [4], 3) Measurements of the cross sections for generating a pair of photons in absorption of a single photon by a molecule as a function of incident photon energy [5-7]. Multiply excited states degenerate with ionization continua, which make a large contribution in the cross section curve involving ionization processes. The key point of our methods is hence that we measure cross sections free from ionization. The feature of multiply excited states is noticeable in such a cross section curve. Recently we have measured: i) the cross sections for the emission of the Lyman- fluorescence in the photoexcitation of CH 4 as a function of incident photon energy in the range 18-51 eV, ii) the electron energy-loss spectrum of CH 4 tagged with the Lyman-photons at 80 eV incident electron energy and 10 electron scattering angle in the range of the energy loss 20-45 eV, in order to understand the formation and decay of the doubly excited methane in photon and electron interactions. [8] The results are summarized in this paper and the simultaneous excitation of two electrons by electron interaction is compared with that by photon interaction in terms of the oscillator strength. (authors)

Groundwater flow and water budget in the surficial and Floridan aquifer systems in east-central Florida

Science.gov (United States)

Sepulveda, Nicasio; Tiedeman, Claire; O'Reilly, Andrew M.; Davis, Jeffrey B.; Burger, Patrick

2012-01-01

A numerical transient model of the surficial and Floridan aquifer systems in east-central Florida was developed to (1) increase the understanding of water exchanges between the surficial and the Floridan aquifer systems, (2) assess the recharge rates to the surficial aquifer system from infiltration through the unsaturated zone and (3) obtain a simulation tool that could be used by water-resource managers to assess the impact of changes in groundwater withdrawals on spring flows and on the potentiometric surfaces of the hydrogeologic units composing the Floridan aquifer system. The hydrogeology of east-central Florida was evaluated and used to develop and calibrate the groundwater flow model, which simulates the regional fresh groundwater flow system. The U.S. Geological Survey three-dimensional groundwater flow model, MODFLOW-2005, was used to simulate transient groundwater flow in the surficial, intermediate, and Floridan aquifer systems from 1995 to 2006. The East-Central Florida Transient model encompasses an actively simulated area of about 9,000 square miles. Although the model includes surficial processes-rainfall, irrigation, evapotranspiration (ET), runoff, infiltration, lake water levels, and stream water levels and flows-its primary purpose is to characterize and refine the understanding of groundwater flow in the Floridan aquifer system. Model-independent estimates of the partitioning of rainfall into ET, streamflow, and aquifer recharge are provided from a water-budget analysis of the surficial aquifer system. The interaction of the groundwater flow system with the surface environment was simulated using the Green-Ampt infiltration method and the MODFLOW-2005 Unsaturated-Zone Flow, Lake, and Streamflow-Routing Packages. The model is intended to simulate the part of the groundwater system that contains freshwater. The bottom and lateral boundaries of the model were established at the estimated depths where the chloride concentration is 5,000 milligrams

Sources of water to wells in updip areas of the Wenonah-Mount Laurel aquifer, Gloucester and Camden Counties, New Jersey

Science.gov (United States)

Watt, Martha K.; Voronin, Lois M.

2006-01-01

Since 1996, when the New Jersey Department of Environmental Protection (NJDEP) restricted ground-water withdrawals from the Potomac-Raritan-Magothy aquifer system in the southern New Jersey Coastal Plain as a result of excessive drawdown, Coastal Plain communities have been interested in developing alternate sources of water supply for their residents. The use of ground water from areas near the updip parts of the overlying confined aquifers where withdrawals are not restricted is being considered to meet the demand for drinking water. Concerns have arisen, however, regarding the potential effects of increased withdrawals from these areas on ground-water flow to streams and wetlands as well as to the deeper, confined parts of the aquifers. Therefore, the U.S. Geological Survey, in cooperation with the NJDEP, conducted a study to investigate the sources of water to currently inactive wells in the updip part of the Wenonah-Mount Laurel aquifer in Gloucester and Camden Counties, New Jersey. Of particular interest is whether the primary source of the increased withdrawals is likely to be the aquifer outcrop or the downdip, confined part of the aquifer. The outcrop of the Wenonah-Mount Laurel aquifer covers nearly 8 mi2 (square miles), or about 46 percent of Deptford Township's 17.56-mi2 area. The Deptford Township Municipal Utilities Authority owns six currently (2005) inactive wells in the Wenonah-Mount Laurel aquifer at the southeastern boundary of Deptford Township, 1.25 mi (miles) from the outcrop. For the purposes of this study, an existing ground-water-flow model of the New Jersey Coastal Plain aquifers was used to simulate ground-water-flow conditions in Gloucester and Camden Counties in 1998. Two alternative withdrawal scenarios were superimposed on the results of the 1998 simulation. In the first (the 'full-allocation' scenario), full-allocation withdrawal rates established by the NJDEP were applied to 45 existing wells in the Deptford Township area. In the

Molecular Understanding of Fullerene - Electron Donor Interactions in Organic Solar Cells

KAUST Repository

Ryno, Sean

2016-09-13

Organic solar cells hold promise of providing low-cost, renewable power generation, with current devices providing up to 13% power conversion efficiency. The rational design of more performant systems requires an in-depth understanding of the interactions between the electron donating and electron accepting materials within the active layers of these devices. Here, we explore works that give insight into the intermolecular interactions between electron donors and electron acceptors, and the impact of molecular orientations and environment on these interactions. We highlight, from a theoretical standpoint, the effects of intermolecular interactions on the stability of charge carriers at the donor/acceptor interface and in the bulk and how these interactions influence the nature of the charge transfer states as wells as the charge separation and charge transport processes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydro-geochemical modeling of subalpine urbanized area: geochemical characterization of the shallow and deep aquifers of the urban district of Como (first results).

Science.gov (United States)

Terrana, Silvia; Brunamonte, Fabio; Frascoli, Francesca; Ferrario, Maria Francesca; Michetti, Alessandro Maria; Pozzi, Andrea; Gambillara, Roberto; Binda, Gilberto

2016-04-01

One of the greatest environmental and social-economics threats is climate change. This topic, in the next few years, will have a significant impact on the availability of water resources of many regions. This is compounded by the strong anthropization of water systems that shows an intensification of conflicts for water resource exploitation. Therefore, it is necessary a sustainable manage of natural resources thorough knowledge of the hosting territories. The development of investigation and data processing methods are essential to reduce costs for the suitable use and protection of resources. Identify a sample area for testing the best approach is crucial. This research aims to find a valid methodology for the characterization, modeling and management of subalpine urban aquifers, and the urban district of Como appears perfect. The city of Como is located at the southern end of the western sector of Lake Como (N Italy). It is a coastal town, placed on a small alluvial plain, therefore in close communication with the lake. The plain is drained by two streams, which are presently artificially buried, and have an underground flow path in the urban section till the mouth. This city area, so, is suitable for this project as it is intensely urbanized, its dimensions is not too extensive and it is characterized by two aquifers very important and little known. These are a shallow aquifer and a deep aquifer, which are important not only for any water supply, but also for the stability of the ground subsidence in the city. This research is also the opportunity to work in a particular well-known area with high scientific significance; however, there is complete absence of information regarding the deep aquifer. Great importance has also the chosen and used of the more powerful open source software for this type of area, such as PHREEQC, EnvironInsite, PHREEQE etc., used for geological and geochemical data processing. The main goal of this preliminary work is the

Magnetic impurity coupled to interacting conduction electrons

International Nuclear Information System (INIS)

Schork, T.

1996-01-01

We consider a magnetic impurity which interacts by hybridization with a system of weakly correlated electrons and determine the energy of the ground state by means of a 1/N f expansion. The correlations among the conduction electrons are described by a Hubbard Hamiltonian and are treated to the lowest order in the interaction strength. We find that their effect on the Kondo temperature, T K , in the Kondo limit is twofold: first, the position of the impurity level is shifted due to the reduction of charge fluctuations, which reduces T K . Secondly, the bare Kondo exchange coupling is enhanced as spin fluctuations are enlarged. In total, T K increases. Both corrections require intermediate states beyond the standard Varma-Yafet ansatz. This shows that the Hubbard interaction does not just provide quasiparticles, which hybridize with the impurity, but also renormalizes the Kondo coupling. copyright 1996 The American Physical Society

Interactions between stream fungi and bacteria associated with decomposing leaf litter at different levels of nutrient availability

Science.gov (United States)

Vladislav Gulis; Keller Suberkropp

2003-01-01

We examined the potential for interactions between aquatic hyphomycetes and bacteria isolated from leaves decaying in a headwater stream. In agar plate assays, culture filtrates of each of 28 aquatic hyphomycete isolates tested (5 species) inhibited bacterial growth (16 Gram-negative bacterial isolates belonging to 6 colony morphotypes were tested). Inhibition of...

Recharge and Aquifer Response: Manukan Island’s Aquifer, Sabah, Malaysia

Directory of Open Access Journals (Sweden)

Sarva Mangala Praveena

2010-01-01

Full Text Available Manukan Island is a small island located in North-West of Sabah, Malaysia was used as a case study area for numerical modeling of an aquifer response to recharge and pumping rates. The results in this study present the variations of recharge into the aquifer under the prediction simulations. The recharge rate increases the water level as indicated by hydraulic heads. This shows that it can alter groundwater of Manukan Island which has been suffering from an overexploration in its unconfined the aquifer. The increase in recharge rate (from 600 mm/year to 750 mm/year increases the water level indicated by hydraulic heads. A reduction in pumping rate (from 0.072 m3/day to 0.058 m3/day not only increases the amount of water levels in aquifer but also reduces the supply hence a deficit in supply. The increase in hydraulic heads depends on the percentage reduction of pumping and recharges rates. The well water has 1978.3 mg/L chloride with current pumping (0.072 m3/day and recharge rates (600 mm/year. However, with an increased of recharge rate and current pumping rate it has decreased about 1.13%. In addition, reduction in pumping rate made the chloride concentration decreased about 2.8%. In general, a reduction in pumping with an increase in recharge rate leads to a decreased in chloride concentrations within the vicinity of cone of depression. Next, to further develop the numerical model, the model should focus on climate change variables such as consequences of climate change are increase in air temperature, increase in sea surface temperature, and more extreme weather conditions. These parameters are considered critical parameters for climate change impact modeling in aquifers. The behavior of the aquifer and its sustainable pumping rate can be done by applying a computer modeling component.

Conceptual and numerical models of groundwater flow in the Ogallala aquifer in Gregory and Tripp Counties, South Dakota, water years 1985--2009

Science.gov (United States)

Davis, Kyle W.; Putnam, Larry D.

2013-01-01

smallest differences between simulated and observed values, within a given set of constraints. The potentiometric surface of the aquifer calculated during the 200-year initialization period established initial conditions for the transient simulation. Water levels for 38 observation wells were used to calibrate the 25-year simulation. Simulated hydraulic heads for the transient simulation were within plus or minus 20 feet of observed values for 95 percent of observation wells, and the mean absolute difference was 5.1 feet. Calibrated hydraulic conductivity ranged from 0.9 to 227 feet per day (ft/d). The annual recharge rates for the transient simulation (water years 1985–2009) ranged from 0.60 to 6.96 inches, with a mean of 3.68 inches for the Ogallala aquifer. This represents a mean recharge rate of 280.5 ft3/s for the model area. Discharge from the aquifer occurs through evapotranspiration, discharge to streams through river leakage and flow from springs and seeps, and well withdrawals. Water is withdrawn from wells for irrigation, public supply, domestic, and stock uses. Simulated mean discharge rates for water years 1985–2009 were about 185 cubic feet per second (ft3/s) for evapotranspiration, 66.7 ft3/s for discharge to streams, and 5.48 ft3/s for well withdrawals. Simulated annual evapotranspiration rates ranged from about 128 to 254 ft3/s, and outflow to streams ranged from 52.2 to 79.9 ft3/s. A sensitivity analysis was used to examine the response of the calibrated model to changes in model parameters for horizontal hydraulic conductivity, recharge, evapotranspiration, and spring and riverbed conductance. The model was most sensitive to recharge and maximum potential evapotranspiration and least sensitive to riverbed and spring conductances. Two potential future scenarios were simulated: a potential drought scenario and a potential increased pumping scenario. To simulate a potential drought scenario, a synthetic drought record was created, the mean of which was

Geothermal characterization of the coastal aquifer near Ravenna (Italy

Directory of Open Access Journals (Sweden)

M. Antonellini

2012-12-01

Full Text Available The coastal aquifer near Ravenna (Italy contains a large volume of groundwater (2,5x109 m3 whose quality has been compromised by sea-water intrusion. Today, the phreatic groundwater is mostly brackish with some lenses of freshwater floating on top of more saline water. This water, although impossible to use as drink-water or for irrigation, is still important to guarantee the health of wetland habitats and especially of the roman historical and coastal pine forests of Ravenna. With the objective of defining the flow pattern within the aquifer and the exchange between surface and ground water, we characterized the temperature distribution in the shallow subsurface by means of a dense network of piezometers. At the same time we had the opportunity to characterize the phreatic aquifer from the geothermal point of view, so that it could eventually be considered for use as a “low enthalpy” heat source. Heat pumps are able to extract heat during the winter and dissipate it during the summer. The temperature of the groundwater in the top layer of the aquifer (surficial zone is sensitive to the changes in atmospheric temperature throughout the year whereas the temperature of the deeper groundwater follows the geothermal gradient (geothermal zone. One of the scopes of the project is to discover at what depth is located the geothermal zone, so that the aquifer has a constant temperature throughout the year. A constant temperature is needed for storage of heat at low enthalpy. The thickness of the surficial zone and the temperature at the top of the geothermal zone are essentially related to land use, distance from the sea, sediment type, and amount of interaction between surface and groundwater. A knowledge of these factors allows to better exploit the geothermal potential of the aquifer when choosing the optimal placement of the heat pumps.

A General Solution for Groundwater Flow in Estuarine Leaky Aquifer System with Considering Aquifer Anisotropy

Science.gov (United States)

Chen, Po-Chia; Chuang, Mo-Hsiung; Tan, Yih-Chi

2014-05-01

In recent years the urban and industrial developments near the coastal area are rapid and therefore the associated population grows dramatically. More and more water demand for human activities, agriculture irrigation, and aquaculture relies on heavy pumping in coastal area. The decline of groundwater table may result in the problems of seawater intrusion and/or land subsidence. Since the 1950s, numerous studies focused on the effect of tidal fluctuation on the groundwater flow in the coastal area. Many studies concentrated on the developments of one-dimensional (1D) and two-dimensional (2D) analytical solutions describing the tide-induced head fluctuations. For example, Jacob (1950) derived an analytical solution of 1D groundwater flow in a confined aquifer with a boundary condition subject to sinusoidal oscillation. Jiao and Tang (1999) derived a 1D analytical solution of a leaky confined aquifer by considered a constant groundwater head in the overlying unconfined aquifer. Jeng et al. (2002) studied the tidal propagation in a coupled unconfined and confined costal aquifer system. Sun (1997) presented a 2D solution for groundwater response to tidal loading in an estuary. Tang and Jiao (2001) derived a 2D analytical solution in a leaky confined aquifer system near open tidal water. This study aims at developing a general analytical solution describing the head fluctuations in a 2D estuarine aquifer system consisted of an unconfined aquifer, a confined aquifer, and an aquitard between them. Both the confined and unconfined aquifers are considered to be anisotropic. The predicted head fluctuations from this solution will compare with the simulation results from the MODFLOW program. In addition, the solutions mentioned above will be shown to be special cases of the present solution. Some hypothetical cases regarding the head fluctuation in costal aquifers will be made to investigate the dynamic effects of water table fluctuation, hydrogeological conditions, and

ENERGETIC PHOTON AND ELECTRON INTERACTIONS WITH POSITIVE IONS

Energy Technology Data Exchange (ETDEWEB)

Phaneuf, Ronald A. [UNR

2013-07-01

The objective of this research is a deeper understanding of the complex multi-electron interactions that govern inelastic processes involving positive ions in plasma environments, such as those occurring in stellar cares and atmospheres, x-ray lasers, thermonuclear fusion reactors and materials-processing discharges. In addition to precision data on ionic structure and transition probabilities, high resolution quantitative measurements of ionization test the theoretical methods that provide critical input to computer codes used for plasma modeling and photon opacity calculations. Steadily increasing computational power and a corresponding emphasis on simulations gives heightened relevance to precise and accurate benchmark data. Photons provide a highly selective probe of the internal electronic structure of atomic and molecular systems, and a powerful means to better understand more complex electron-ion interactions.

Modeling of a Compact Terahertz Source based on the Two-Stream Instability

Energy Technology Data Exchange (ETDEWEB)

Svimonishvili, Tengiz [Univ. of New Mexico, Albuquerque, NM (United States)

2016-05-17

THz radiation straddles the microwave and infrared bands of the electromagnetic spectrum, thus combining the penetrating power of lower-frequency waves and imaging capabilities of higher-energy infrared radiation. THz radiation is employed in various elds such as cancer research, biology, agriculture, homeland security, and environmental monitoring. Conventional vacuum electronic sources of THz radiation (e.g., fast- and slow-wave devices) either require very small structures or are bulky and expensive to operate. Optical sources necessitate cryogenic cooling and are presently capable of producing milliwatt levels of power at THz frequencies. We propose a millimeter and sub-millimeter wave source based on a well-known phenomenon called the two-stream instability. The two-beam source relies on lowenergy and low-current electron beams for operation. Also, it is compact, simple in design, and does not contain expensive parts that require complex machining and precise alignment. In this dissertation, we perform 2-D particle-in-cell (PIC) simulations of the interaction region of the two-beam source. The interaction region consists of a beam pipe of radius ra and two electron beams of radius rb co-propagating and interacting inside the pipe. The simulations involve the interaction of unmodulated (no initial energy modulation) and modulated (energy-modulated, seeded at a given frequency) electron beams. In addition, both cold (monoenergetic) and warm (Gaussian) beams are treated.

2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012

Energy Technology Data Exchange (ETDEWEB)

McCusker, James [Michigan State Univ., East Lansing, MI (United States)

2012-08-10

The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

Comparative Study on Interaction of Form and Motion Processing Streams by Applying Two Different Classifiers in Mechanism for Recognition of Biological Movement

Science.gov (United States)

2014-01-01

Research on psychophysics, neurophysiology, and functional imaging shows particular representation of biological movements which contains two pathways. The visual perception of biological movements formed through the visual system called dorsal and ventral processing streams. Ventral processing stream is associated with the form information extraction; on the other hand, dorsal processing stream provides motion information. Active basic model (ABM) as hierarchical representation of the human object had revealed novelty in form pathway due to applying Gabor based supervised object recognition method. It creates more biological plausibility along with similarity with original model. Fuzzy inference system is used for motion pattern information in motion pathway creating more robustness in recognition process. Besides, interaction of these paths is intriguing and many studies in various fields considered it. Here, the interaction of the pathways to get more appropriated results has been investigated. Extreme learning machine (ELM) has been implied for classification unit of this model, due to having the main properties of artificial neural networks, but crosses from the difficulty of training time substantially diminished in it. Here, there will be a comparison between two different configurations, interactions using synergetic neural network and ELM, in terms of accuracy and compatibility. PMID:25276860

Comparative Study on Interaction of Form and Motion Processing Streams by Applying Two Different Classifiers in Mechanism for Recognition of Biological Movement

Directory of Open Access Journals (Sweden)

Bardia Yousefi

2014-01-01

Full Text Available Research on psychophysics, neurophysiology, and functional imaging shows particular representation of biological movements which contains two pathways. The visual perception of biological movements formed through the visual system called dorsal and ventral processing streams. Ventral processing stream is associated with the form information extraction; on the other hand, dorsal processing stream provides motion information. Active basic model (ABM as hierarchical representation of the human object had revealed novelty in form pathway due to applying Gabor based supervised object recognition method. It creates more biological plausibility along with similarity with original model. Fuzzy inference system is used for motion pattern information in motion pathway creating more robustness in recognition process. Besides, interaction of these paths is intriguing and many studies in various fields considered it. Here, the interaction of the pathways to get more appropriated results has been investigated. Extreme learning machine (ELM has been implied for classification unit of this model, due to having the main properties of artificial neural networks, but crosses from the difficulty of training time substantially diminished in it. Here, there will be a comparison between two different configurations, interactions using synergetic neural network and ELM, in terms of accuracy and compatibility.

Nutrient Removal during Stormwater Aquifer Storage and Recovery in an Anoxic Carbonate Aquifer.

Science.gov (United States)

Vanderzalm, Joanne L; Page, Declan W; Dillon, Peter J; Barry, Karen E; Gonzalez, Dennis

2018-03-01

Stormwater harvesting coupled to managed aquifer recharge (MAR) provides a means to use the often wasted stormwater resource while also providing protection of the natural and built environment. Aquifers can act as a treatment barrier within a multiple-barrier approach to harvest and use urban stormwater. However, it remains challenging to assess the treatment performance of a MAR scheme due to the heterogeneity of aquifers and MAR operations, which in turn influences water treatment processes. This study uses a probabilistic method to evaluate aquifer treatment performance based on the removal of total organic C (TOC), N, and P during MAR with urban stormwater in an anoxic carbonate aquifer. Total organic C, N, and P are represented as stochastic variables and described by probability density functions (PDFs) for the "injectant" and "recovery"; these injectant and recovery PDFs are used to derive a theoretical MAR removal efficiency PDF. Four long-term MAR sites targeting one of two tertiary carbonate aquifers (T1 and T2) were used to describe the nutrient removal efficiencies. Removal of TOC and total N (TN) was dominated by redox processes, with median removal of TOC between 50 and 60% at all sites and TN from 40 to 50% at three sites with no change at the fourth. Total P removal due to filtration and sorption accounted for median removal of 29 to 53%. Thus, the statistical method was able to characterize the capacity of the anoxic carbonate aquifer treatment barrier for nutrient removal, which highlights that aquifers can be an effective long-term natural treatment option for management of water quality, as well as storage of urban stormwater. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Assessment of groundwater recharge and water fluxes of the Guarani Aquifer System, Brazil

Science.gov (United States)

Rabelo, Jorge Luiz; Wendland, Edson

2009-11-01

The groundwater recharge and water fluxes of the Guarani Aquifer System in the state of Sao Paulo in Brazil were assessed through a numeric model. The study area (6,748 km2) comprises Jacaré-Guaçú and Jacaré-Pepira River watersheds, tributaries of the Tietê River in the central region of the state. GIS based tools were used in the storage, processing and analysis of data. Main hydrologic phenomena were selected, leading to a groundwater conceptual model, taking into account the significant outcrops occurring in the study area. Six recharge zones were related to the geologic formation and structures of the semi-confined and phreatic aquifer. The model was calibrated against the baseflows and static water levels of the wells. The results emphasize the strong interaction of groundwater flows between watersheds and the groundwater inflow into the rivers. It has been concluded that lateral groundwater exchanges between basins, the deep discharges to the regional system, and well exploitation were not significant aquifer outflows when compared to the aquifer recharge. The results have shown that the inflows from the river into the aquifer are significant and have the utmost importance since the aquifer is potentially more vulnerable in these places.

STREAMS - Technology Programme. Yearbook 2003

International Nuclear Information System (INIS)

2003-01-01

The STREAMS Technology Programme addresses municipal waste. Municipal waste is composed of waste from households and small businesses. The programme focuses on five areas Waste prevention, Collection, transportation, and management of waste streams, Waste treatment technologies, Waste recycling into raw materials and new products, Landfill technologies. The development projects of the STREAMS Programme utilize a number of different technologies, such as biotechnology, information technology, materials technology, measurement and analysis, and automation technology. Finnish expertise in materials recycling technologies and related electronics and information technology is extremely high on a worldwide scale even though the companies represent SMEs. Started in 2001, the STREAMS programme has a total volume of 27 million euros, half of which is funded by Tekes. The programme runs through the end of 2004. (author)

Sources, occurrence and predicted aquatic impact of legacy and contemporary pesticides in streams

International Nuclear Information System (INIS)

McKnight, Ursula S.; Rasmussen, Jes J.; Kronvang, Brian; Binning, Philip J.; Bjerg, Poul L.

2015-01-01

We couple current findings of pesticides in surface and groundwater to the history of pesticide usage, focusing on the potential contribution of legacy pesticides to the predicted ecotoxicological impact on benthic macroinvertebrates in headwater streams. Results suggest that groundwater, in addition to precipitation and surface runoff, is an important source of pesticides (particularly legacy herbicides) entering surface water. In addition to current-use active ingredients, legacy pesticides, metabolites and impurities are important for explaining the estimated total toxicity attributable to pesticides. Sediment-bound insecticides were identified as the primary source for predicted ecotoxicity. Our results support recent studies indicating that highly sorbing chemicals contribute and even drive impacts on aquatic ecosystems. They further indicate that groundwater contaminated by legacy and contemporary pesticides may impact adjoining streams. Stream observations of soluble and sediment-bound pesticides are valuable for understanding the long-term fate of pesticides in aquifers, and should be included in stream monitoring programs. - Highlights: • Findings comprised a range of contemporary and banned legacy pesticides in streams. • Groundwater is a significant pathway for some herbicides entering streams. • Legacy pesticides increased predicted aquatic toxicity by four orders of magnitude. • Sediment-bound insecticides were identified as the primary source for ecotoxicity. • Stream monitoring programs should include legacy pesticides to assess impacts. - Legacy pesticides, particularly sediment-bound insecticides were identified as the primary source for predicted ecotoxicity impacting benthic macroinvertebrates in headwater streams

Biophysical Interactions within Step-Pool Mountain Streams Following Wildfire

Science.gov (United States)

Parker, A.; Chin, A.; O'Dowd, A. P.

2014-12-01

Recovery of riverine ecosystems following disturbance is driven by a variety of interacting processes. Wildfires pose increasing disturbances to riverine landscapes, with rising frequencies and magnitudes owing to warming climates and increased fuel loads. The effects of wildfire include loss of vegetation, elevated runoff and flash floods, erosion and deposition, and changing biological habitats and communities. Understanding process interactions in post-fire landscapes is increasingly urgent for successful management and restoration of affected ecosystems. In steep channels, steps and pools provide prominent habitats for organisms and structural integrity in high energy environments. Step-pools are typically stable, responding to extreme events with recurrence intervals often exceeding 50 years. Once wildfire occurs, however, intensification of post-fire flood events can potentially overpower the inherent stability of these systems, with significant consequences for aquatic life and human well-being downstream. This study examined the short-term response of step-pool streams following the 2012 Waldo Canyon Fire in Colorado. We explored interacting feedbacks among geomorphology, hydrology, and ecology in the post-fire environment. At selected sites with varying burn severity, we established baseline conditions immediately after the fire with channel surveys, biological assessment using benthic macroinvertebrates, sediment analysis including pebble counts, and precipitation gauging. Repeat measurements after major storm events over several years enabled analysis of the interacting feedbacks among post-fire processes. We found that channels able to retain the step-pool structure changed less and facilitated recovery more readily. Step habitats maintained higher percentages of sensitive macroinvertebrate taxa compared to pools through post-fire floods. Sites burned with high severity experienced greater reduction in the percentage of sensitive taxa. The decimation of

High-field electron-photon interactions

International Nuclear Information System (INIS)

Hartemann, F V.

1999-01-01

Recent advances in novel technologies (including chirped-pulse amplification, femtosecond laser systems operating in the TW-PW range, high-gradient rf photoinjectors, and synchronized relativistic electron bunches with subpicosecond durations and THz bandwidths) allow experimentalists to study the interaction of relativistic electrons with ultrahigh-intensity photon fields. Ponderomotive scattering can accelerate these electrons with extremely high gradients in a three-dimensional vacuum laser focus. The nonlinear Doppler shift induced by relativistic radiation pressure in Compton backscattering is shown to yield complex nonlinear spectra which can be modified by using temporal laser pulse shaping techniques. Colliding laser pulses, where ponderomotive acceleration and Compton backscattering are combined, could also yield extremely short wavelength photons. Finally, one expects strong radiative corrections when the Doppler-upshifted laser wavelength approaches the Compton scale. These are discussed within the context of high-field classical electrodynamics, a new discipline borne out of the aforementioned innovations

The usefulness of multi-well aquifer tests in heterogeneous aquifers

International Nuclear Information System (INIS)

Young, S.C.; Benton, D.J.; Herweijer, J.C.; Sims, P.