Science.gov

Sample records for affecting contaminant transport

  1. Benthic processes affecting contaminant transport in Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Carlson, Rick A; Parchaso, Francis; Fend, Steven V.; Stauffer-Olsen, Natalie; Manning, Andrew J.; Land, Jennie M.

    2016-09-30

    Executive SummaryMultiple sampling trips during calendar years 2013 through 2015 were coordinated to provide measurements of interdependent benthic processes that potentially affect contaminant transport in Upper Klamath Lake (UKL), Oregon. The measurements were motivated by recognition that such internal processes (for example, solute benthic flux, bioturbation and solute efflux by benthic invertebrates, and physical groundwater-surface water interactions) were not integrated into existing management models for UKL. Up until 2013, all of the benthic-flux studies generally had been limited spatially to a number of sites in the northern part of UKL and limited temporally to 2–3 samplings per year. All of the benthic invertebrate studies also had been limited to the northern part of the lake; however, intensive temporal (weekly) studies had previously been completed independent of benthic-flux studies. Therefore, knowledge of both the spatial and temporal variability in benthic flux and benthic invertebrate distributions for the entire lake was lacking. To address these limitations, we completed a lakewide spatial study during 2013 and a coordinated temporal study with weekly sampling of benthic flux and benthic invertebrates during 2014. Field design of the spatially focused study in 2013 involved 21 sites sampled three times as the summer cyanobacterial bloom developed (that is, May 23, June 13, and July 3, 2013). Results of the 27-week, temporally focused study of one site in 2014 were summarized and partitioned into three periods (referred to herein as pre-bloom, bloom and post-bloom periods), each period involving 9 weeks of profiler deployments, water column and benthic sampling. Partitioning of the pre-bloom, bloom, and post-bloom periods were based on water-column chlorophyll concentrations and involved the following date intervals, respectively: April 15 through June 10, June 17 through August 13, and August 20 through October 16, 2014. To examine

  2. Benthic processes affecting contaminant transport in Upper Klamath Lake, Oregon

    USGS Publications Warehouse

    Kuwabara, James S.; Topping, Brent R.; Carter, James L.; Carlson, Rick A; Parchaso, Francis; Fend, Steven V.; Stauffer-Olsen, Natalie; Manning, Andrew J.; Land, Jennie M.

    2016-09-30

    Executive SummaryMultiple sampling trips during calendar years 2013 through 2015 were coordinated to provide measurements of interdependent benthic processes that potentially affect contaminant transport in Upper Klamath Lake (UKL), Oregon. The measurements were motivated by recognition that such internal processes (for example, solute benthic flux, bioturbation and solute efflux by benthic invertebrates, and physical groundwater-surface water interactions) were not integrated into existing management models for UKL. Up until 2013, all of the benthic-flux studies generally had been limited spatially to a number of sites in the northern part of UKL and limited temporally to 2–3 samplings per year. All of the benthic invertebrate studies also had been limited to the northern part of the lake; however, intensive temporal (weekly) studies had previously been completed independent of benthic-flux studies. Therefore, knowledge of both the spatial and temporal variability in benthic flux and benthic invertebrate distributions for the entire lake was lacking. To address these limitations, we completed a lakewide spatial study during 2013 and a coordinated temporal study with weekly sampling of benthic flux and benthic invertebrates during 2014. Field design of the spatially focused study in 2013 involved 21 sites sampled three times as the summer cyanobacterial bloom developed (that is, May 23, June 13, and July 3, 2013). Results of the 27-week, temporally focused study of one site in 2014 were summarized and partitioned into three periods (referred to herein as pre-bloom, bloom and post-bloom periods), each period involving 9 weeks of profiler deployments, water column and benthic sampling. Partitioning of the pre-bloom, bloom, and post-bloom periods were based on water-column chlorophyll concentrations and involved the following date intervals, respectively: April 15 through June 10, June 17 through August 13, and August 20 through October 16, 2014. To examine

  3. BIOPLUME MODEL FOR CONTAMINANT TRANSPORT AFFECTED BY OXYGEN LIMITED BIODEGRADATION

    EPA Science Inventory

    Many of the organic pollutants entering ground water are potentially biodegradable in the subsurface. This potential has been demonstrated in aquifers contaminated by wood-creosoting process wastes. The persistence of many of these organic compounds in the subsurface indicated ...

  4. Arctic seabirds transport marine-derived contaminants.

    PubMed

    Blais, Jules M; Kimpe, Lynda E; McMahon, Dominique; Keatley, Bronwyn E; Mallory, Mark L; Douglas, Marianne S V; Smol, John P

    2005-07-15

    Long-range atmospheric transport of pollutants is generally assumed to be the main vector for arctic contamination, because local pollution sources are rare. We show that arctic seabirds, which occupy high trophic levels in marine food webs, are the dominant vectors for the transport of marine-derived contaminants to coastal ponds. The sediments of ponds most affected by seabirds had 60 times higher DDT, 25 times higher mercury, and 10 times higher hexachlorobenzene concentrations than nearby control sites. Bird guano greatly stimulates biological productivity in these extreme environments but also serves as a major source of industrial and agricultural pollutants in these remote ecosystems.

  5. MODELING CONTAMINANT TRANSPORT THROUGH SUBSURFACE SYSTEMS

    EPA Science Inventory

    Modeling of contaminant transport through soil to groundwater to a receptor requires that consideration be given to the many processes which control the transport and fate of chemical constituents in the subsurface environment. These processes include volatilization, degradation,...

  6. Verification tests for contaminant transport codes

    SciTech Connect

    Rowe, R.K.; Nadarajah, P.

    1996-12-31

    The importance of verifying contaminant transport codes and the techniques that may be used in this verification process are discussed. Commonly used contaminant transport codes are characterized as belonging to one of several types or classes of solution, such as analytic, finite layer, boundary element, finite difference and finite element. Both the level of approximation and the solution methodology should be verified for each contaminant transport code. One powerful method that may be used in contaminant transport code verification is cross-checking (benchmarking) with other codes. This technique is used to check the results of codes from one solution class with the results of codes from another solution class. In this paper cross-checking is performed for three classes of solution; these are, analytic, finite layer, and finite element.

  7. Subsurface Flow and Contaminant Transport

    2000-09-19

    FACT is a transient three-dimensional, finite element code for simulating isothermal groundwater flow, moisture movement, and solute transport in variably and/or fully saturated subsurface porous media. Both single and dual-domain transport formulations are available. Transport mechanisms considered include advection, hydrodynamic dispersion, linear adsorption, mobile/immobile mass transfer and first-order degradation. A wide range of acquifier conditions and remediation systems commonly encountered in the field can be simulated. Notable boundary condition (BC) options include, a combined rechargemore » and drain BC for simulating recirculation wells, and a head dependent well BC that computes flow based on specified drawdown. The code is designed to handle highly heterogenous, multi-layer, acquifer systems in a numerically efficient manner. Subsurface structure is represented with vertically distorted rectangular brick elements in a Cartesian system. The groundwater flow equation is approximated using the Bubnov-Galerkin finite element method in conjunction with an efficient symmetric Preconditioned Conjugate Gradient (PCG) ICCG matrix solver. The solute transport equation is approximated using an upstream weighted residual finite element method designed to alleviate numerical oscillation. An efficient asymmetric PCG (ORTHOMIN) matrix solver is employed for transport. For both the flow and transport equations, element matrices are computed from either influence coefficient formulas for speed, or two point Gauss-Legendre quadrature for accuracy. Non-linear flow problems can be solved using either Newton-Ralphson linearization or Picard iteration, with under-relaxation formulas to further enhance convergence. Dynamic memory allocation is implemented using Fortran 90 constructs. FACT coding is clean and modular.« less

  8. Hydrogeology, Water Chemistry, and Factors Affecting the Transport of Contaminants in the Zone of Contribution of a Public-Supply Well in Modesto, Eastern San Joaquin Valley, California

    USGS Publications Warehouse

    Jurgens, Bryant C.; Burow, Karen R.; Dalgish, Barbara A.; Shelton, Jennifer L.

    2008-01-01

    Ground-water chemistry in the zone of contribution of a public-supply well in Modesto, California, was studied by the U.S. Geological Survey National Water Quality Assessment (NAWQA) Program's topical team for Transport of Anthropogenic and Natural Contaminants (TANC) to supply wells. Twenty-three monitoring wells were installed in Modesto to record baseline hydraulic information and to collect water-quality samples. The monitoring wells were divided into four categories that represent the chemistry of different depths and volumes of the aquifer: (1) water-table wells were screened between 8.5 and 11.7 m (meter) (28 and 38.5 ft [foot]) below land surface (bls) and were within 5 m (16 ft) of the water table; (2) shallow wells were screened between 29 and 35 m (95 and 115 ft) bls; (3) intermediate wells were screened between 50.6 and 65.5 m (166 and 215 ft) bls; and (4) deep wells are screened between 100 to 106 m (328 and 348 ft) bls. Inorganic, organic, isotope, and age-dating tracers were used to characterize the geochemical conditions in the aquifer and understand the mechanisms of mobilization and movement of selected constituents from source areas to a public-supply well. The ground-water system within the study area has been significantly altered by human activities. Water levels in monitoring wells indicated that horizontal movement of ground water was generally from the agricultural areas in the northeast towards a regional water-level depression within the city in the southwest. However, intensive pumping and irrigation recharge in the study area has caused large quantities of ground water to move vertically downward within the regional and local flow systems. Analysis of age tracers indicated that ground-water age varied from recent recharge at the water table to more than 1,000 years in the deep part of the aquifer. The mean age of shallow ground water was determined to be between 30 and 40 years. Intermediate ground water was determined to be a mixture

  9. Contaminant transport in organophilic waste deposit liners

    SciTech Connect

    Stockmeyer, M.R.; Madsen, F.T.; Kahr, G.

    1995-12-31

    The advective transport and diffusive transport of phenol through a soil liner material improve with organophilic bentonites was studied. The results were compared with the transport of phenol through the unimproved soil, a silty sand with a natural clay minerals content of approximately 5%, and through samples which were blended with a common calcium bentonite. With an increasing amount of added organophilic bentonite the adsorption capacity of the liner material and the contaminant retention increase. The diffusive transport of phenol is significantly retarded in the presence of organophilic bentonites, whereas the addition of a common hydrophilic calcium bentonite to the liner material only reduces the hydraulic permeability. There is little contaminant retention due to a low adsorption capacity for phenol of the hydrophilic bentonite. The diffusion is independent on the permeability of a liner material. In the appendix, the significance and the velocity of the hydraulic and diffusive contaminant transport of phenol as an organic test compound in a mineral sealing layer were studied. In a natural, hydrophilic, 1 m-thick liner, diffusion was calculated to be the faster transport mechanism. In the presence of organophilic bentonites the diffusive transport of phenol was found to be considerably hindered. 17 refs., 8 figs., 5 tabs.

  10. Nearshore transport processes affecting the dilution and fate of energy-related contaminants. Progress report, October 1, 1979-September 30, 1980

    SciTech Connect

    Blanton, J. O.

    1980-07-15

    Research was conducted on physical oceanograhic processes off the Georgia Coast. Spatral variations in momentum and salt flux were measured to determine their importance in generating flow and salt transport. Analyses of data are presently underway.

  11. TNT transport and fate in contaminated soil

    SciTech Connect

    Comfort, S.D.; Shea, P.J.; Hundal, L.S.

    1995-11-01

    Past disposal practices at munitions production plants have contaminated terrestrial and aquatk ecosystems with 2,4,6-trinitrotoluene (TNT). We determined TNT transport, degradation, and long-term sorption characteristics in soil. Transport experiments were conducted with repacked, unsaturated soil columns containing uncontaminated soil or layers of contaminated and uncontaminated soil. Uncontaminated soil columns received multiple pore volumes (22-50) of a TNT-{sup 3}H{sub 2}O pulse, containing 70 or 6.3 mg TNT L{sup -1} at a constant pore water velocity. TNT breakthrough curves (BTCs) never reached initial solute pulse concentrations. Apex concentrations (C/C{sub o}) were between 0.6 and 0.8 for an initial pulse of 70 mg TNT L{sup -1} and 0.2 to 0.3 for the 6.3 mg TNT L{sup -1} pulse. Earlier TNT breakthrough was observed at the higher pulse concentration. This mobility difference was predicted from the nonlinear adsorption isotherm determined for TNT sorption. In all experiments, a significant fraction of added TNT was recovered as amino degradates of TNT. Mass balance estimates indicated 81% of the added TNT was recovered (as TNT and amino degradates) from columns receiving the 70 mg TNT L{sup -1} pulse compared to 35% from columns receiving the 6.3 mg TNT L{sup -1} pulse. Most of the unaccountable TNT was hypothesized to be unextractable. This was supported by a 168-d sorption experiment, which found that within 14d, 80% of {sup 14}C activity (added as {sup 14}C-TNT) was adsorbed and roughly 40% unextractable. Our observations illustrate that TNT sorption and degradation are concentration-dependent and the assumptions of linear adsorption and adsorption-desorption singularity commonly used in transport modeling, may not be valid for predicting TNT transport in munitions-contaminated soils. 29 refs., 6 figs., 7 tabs.

  12. Modelling contaminant transport for pumping wells in riverbank filtration systems.

    PubMed

    Mustafa, Shaymaa; Bahar, Arifah; Aziz, Zainal Abdul; Suratman, Saim

    2016-01-01

    Analytical study of the influence of both the pumping well discharge rate and pumping time on contaminant transport and attenuation is significant for hydrological and environmental science applications. This article provides an analytical solution for investigating the influence of both pumping time and travelling time together for one-dimensional contaminant transport in riverbank filtration systems by using the Green's function approach. The basic aim of the model is to understand how the pumping time and pumping rate, which control the travelling time, can affect the contaminant concentration in riverbank filtration systems. Results of analytical solutions are compared with the results obtained using a MODFLOW numerical model. Graphically, it is found that both analytical and numerical solutions have almost the same behaviour. Additionally, the graphs indicate that any increase in the pumping rate or simulation pumping time should increase the contamination in groundwater. The results from the proposed analytical model are well matched with the data collected from a riverbank filtration site in France. After this validation, the model is then applied to the first pilot project of a riverbank filtration system conducted in Malaysia. Sensitivity analysis results highlight the importance of degradation rates of contaminants on groundwater quality, for which higher utilization rates lead to the faster consumption of pollutants.

  13. Can contaminant transport models predict breakthrough?

    USGS Publications Warehouse

    Peng, Wei-Shyuan; Hampton, Duane R.; Konikow, Leonard F.; Kambham, Kiran; Benegar, Jeffery J.

    2000-01-01

    A solute breakthrough curve measured during a two-well tracer test was successfully predicted in 1986 using specialized contaminant transport models. Water was injected into a confined, unconsolidated sand aquifer and pumped out 125 feet (38.3 m) away at the same steady rate. The injected water was spiked with bromide for over three days; the outflow concentration was monitored for a month. Based on previous tests, the horizontal hydraulic conductivity of the thick aquifer varied by a factor of seven among 12 layers. Assuming stratified flow with small dispersivities, two research groups accurately predicted breakthrough with three-dimensional (12-layer) models using curvilinear elements following the arc-shaped flowlines in this test. Can contaminant transport models commonly used in industry, that use rectangular blocks, also reproduce this breakthrough curve? The two-well test was simulated with four MODFLOW-based models, MT3D (FD and HMOC options), MODFLOWT, MOC3D, and MODFLOW-SURFACT. Using the same 12 layers and small dispersivity used in the successful 1986 simulations, these models fit almost as accurately as the models using curvilinear blocks. Subtle variations in the curves illustrate differences among the codes. Sensitivities of the results to number and size of grid blocks, number of layers, boundary conditions, and values of dispersivity and porosity are briefly presented. The fit between calculated and measured breakthrough curves degenerated as the number of layers and/or grid blocks decreased, reflecting a loss of model predictive power as the level of characterization lessened. Therefore, the breakthrough curve for most field sites can be predicted only qualitatively due to limited characterization of the hydrogeology and contaminant source strength.

  14. Packaging and transportation of radioactively contaminated lead

    SciTech Connect

    Gleason, Eugene; Holden, Gerard

    2007-07-01

    Under the management of the Nuclear Decommissioning Authority (NDA) the government of the United Kingdom has launched an ambitious program to remediate the nation's nuclear waste legacy. Over a twenty-five year period NDA plans to decommission several first generation nuclear power plants and other radioactive facilities. The use innovative, safe 'fit for purpose' technologies will be a major part of this complex program. This paper will present a case study of a recently completed project undertaken in support of the nuclear decommissioning activities at the Sellafield site in the United Kingdom. The focus is on an innovative application of new packaging technology developed for the safe transportation of radioactively contaminated lead objects. Several companies collaborated on the project and contributed to its safe and successful conclusion. These companies include British Nuclear Group, Gravatom Engineering, W. F. Bowker Transport, Atlantic Container Lines, MHF Logistical Solutions and Energy Solutions. New containers and a new innovative inter-modal packaging system to transport the radioactive lead were developed and demonstrated during the project. The project also demonstrated the potential contribution of international nuclear recycling activities as a safe, economic and feasible technical option for nuclear decommissioning in the United Kingdom. (authors)

  15. Biologically mediated transport of contaminants to aquatic systems.

    PubMed

    Blais, Jules M; Macdonald, Robie W; Mackay, Donald; Webster, Eva; Harvey, Colin; Smol, John P

    2007-02-15

    The prevailing view is that long-range transport of semivolatile contaminants is primarily conducted by the physical system (e.g., winds, currents), and biological transport is typically ignored. Although this view may be correct in terms of bulk budgets and fluxes, it neglects the potential of animals to focus contaminants into foodwebs due to their behaviors and lifecycles. In particular, gregarious animals that biomagnify and bioaccumulate certain contaminants and then migrate and congregate can become the predominant pathway for contaminants in many circumstances. Fish and birds provide prominent examples for such behavior. This review examines the potential for biovector transport to expose populations to contaminants. In addition, we apply a modeling approach to compare the potential of biovector transport to other physical transport pathways for a hypothetical lake receiving large numbers of fish. We conclude that biovector transport should not be neglected when considering environmental risks of biomagnifying contaminants.

  16. Shielding analysis of the long length contaminated equipment transportation package

    SciTech Connect

    Nelson, J.V., Westinghouse Hanford

    1996-05-10

    A shielding analysis of a potential long length contaminated equipment transportation package was completed. The analysis was performed to support the design of the transportation package and external shielding.

  17. Feed gas contaminant removal in ion transport membrane systems

    DOEpatents

    Underwood, Richard Paul; Makitka, III, Alexander; Carolan, Michael Francis

    2012-04-03

    An oxygen ion transport membrane process wherein a heated oxygen-containing gas having one or more contaminants is contacted with a reactive solid material to remove the one or more contaminants. The reactive solid material is provided as a deposit on a support. The one or more contaminant compounds in the heated oxygen-containing gas react with the reactive solid material. The contaminant-depleted oxygen-containing gas is contacted with a membrane, and oxygen is transported through the membrane to provide transported oxygen.

  18. FACILITATED TRANSPORT OF INORGANIC CONTAMINANTS IN GROUNDWATER: PART II. COLLOIDAL TRANSPORT

    EPA Science Inventory

    This project consisted of both field and laboratory components. Field studies evaluated routine sampling procedures for determination of aqueous inorganicgeochemistry and assessment of contaminant transport by colloidal mobility. Research at three different metal-contaminated sit...

  19. Generation of long-term record of contaminant transport

    SciTech Connect

    Solo-Gabriele, H.M.

    1998-07-01

    A long-term record (1900--1993) of streamflow, sediment, and metal transport was simulated for an urbanized watershed, the Aberjona River watershed, located near Boston, Mass. The approach is an innovative procedure that includes the use of a watershed-specific contaminant transport model. The input to the program is hourly precipitation; the output is hourly streamflow, sediment, and metal fluxes. Hourly precipitation was available for part of the record. For time periods for which only daily precipitation data were available, the data were disaggregated into hourly values. The effects of urbanization on streamflow were simulated by adjusting the timing of river flood routing and the area contributing to different flow components. Variations in industrial water withdrawals were also considered. Sediment core data were utilized to estimate changes in source metal concentrations in time. The long-term record that was generated confirms that urbanization can account for a flashier river response including larger peaks in streamflow and sediment transport. Metal transport was affected by changes in metal source characteristics as well as hydrologic factors.

  20. Chemical contaminants in the Wadden Sea: Sources, transport, fate and effects

    NASA Astrophysics Data System (ADS)

    Laane, R. W. P. M.; Vethaak, A. D.; Gandrass, J.; Vorkamp, K.; Köhler, A.; Larsen, M. M.; Strand, J.

    2013-09-01

    The Wadden Sea receives contaminants from various sources and via various transport routes. The contaminants described in this overview are various metals (Cd, Cu, Hg, Pb and Zn) and various organic contaminants (polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and lindane (hexachlorocyclohexane, γ-HCH)). In addition, information is presented about other and emerging contaminants such as antifouling biocides (e.g. TBT and Irgarol), brominated flame retardants (BFRs), poly- and perfluorinated compounds (PFCs) and pharmaceutical and personal care products (PPCPs). Special attention is given to biogeochemical processes that contribute to the mobilization of contaminants in the surface sediments of the Wadden Sea. Finally, the effects on organisms of contaminants are reviewed and discussed. The main source of contaminants in the Wadden Sea are the rivers Rhine (via de Dutch coastal zone), Elbe and Weser. The Wadden Sea is not a sink for contaminants and adsorbed contaminants are transported from east to west. The surface sediments of the Wadden Sea are an important source for contaminants to the water above. The input and concentration of most contaminants have significantly decreased in water, sediments, organisms (e.g., mussel, flounder and bird eggs) in various parts of the Wadden Sea in the last three decades. Remarkably, the Cd concentration in mussels is increasing the last decades. In recent decades, the effects of contaminants on organisms (e.g., flounder, seal) have fallen markedly. Most of the affected populations have recovered, except for TBT induced effects in snails. Little is known about the concentration and effects of most emerging contaminants and the complex environmental mixtures of contaminants. It is recommended to install an international coordinated monitoring programme for contaminants and their effects in the whole Wadden Sea and to identify the chemical contaminants that really cause the effect.

  1. Preliminary study of niobium alloy contamination by transport through helium

    NASA Technical Reports Server (NTRS)

    Scheuermann, C. M.; Moore, T. J.; Wheeler, D. R.

    1987-01-01

    Transport of gaseous contaminants through the working fluid to or from sensitive refractory alloys is theoretically possible during long time operation of Brayton and Stirling space power generation systems which use a gas as the working fluid. A test was designed which could give an answer to whether transport of contaminants through the working fluid was a potential major problem. The findings of that preliminary study are summarized.

  2. Small agricultural impoundments affect pollutant transport

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-03-01

    Reservoirs created by dams intercept runoff from upslope areas and thus are often sinks for fertilizers and other pollutants that would otherwise flow downstream. Most studies of solute transport through impoundments have focused on large, long-lived systems. However, small impoundments, such as those created for irrigation or livestock watering, are common in agricultural regions, and their total global surface area is comparable to that of large reservoirs. As these small systems mature, the impoundments fill with sediment, creating ecosystems with wetland-like characteristics. Because dams that create these small impoundments are more likely to be degraded, poorly maintained, or removed by their owners, it is important to understand how changes in such systems may affect pollutant transport.

  3. The new potential for understanding groundwater contaminant transport.

    PubMed

    Hadley, Paul W; Newell, Charles

    2014-01-01

    The groundwater remediation field has been changing constantly since it first emerged in the 1970s. The remediation field has evolved from a dissolved-phase centric conceptual model to a DNAPL-dominated one, which is now being questioned due to a renewed appreciation of matrix diffusion effects on remediation. Detailed observations about contaminant transport have emerged from the remediation field, and challenge the validity of one of the mainstays of the groundwater solute transport modeling world: the concept of mechanical dispersion (Payne et al. 2008). We review and discuss how a new conceptual model of contaminant transport based on diffusion (the usurper) may topple the well-established position of mechanical dispersion (the status quo) that is commonly used in almost every groundwater contaminant transport model, and evaluate the status of existing models and modeling studies that were conducted using advection-dispersion models.

  4. Conditions and processes affecting radionuclide transport

    USGS Publications Warehouse

    Simmons, Ardyth M.; Neymark, Leonid A.

    2012-01-01

    Understanding of unsaturated-zone transport is based on laboratory and field-scale experiments. Fractures provide advective transport pathways. Sorption and matrix diffusion may contribute to retardation of radionuclides. Conversely, sorption onto mobile colloids may enhance radionuclide transport.

  5. Transport of trace contaminants through porous media

    NASA Technical Reports Server (NTRS)

    Madey, R.

    1975-01-01

    Research accomplishments in the following areas are discussed: (1) the calibration of the gas chromatograph for acetaldehyde and ethanol; (2) the development of data reduction and analysis methods; (3) the generation and analysis of experimental data for the transport of 100 ppm acetaldehyde through a cylindrical bed packed with activated carbon granules; (4) the generation and analysis of experimental data for the transport of 100 ppm ethanol through a cylindrical bed packed with activated carbon granules; and (5) a comparison of the volume adsorption capacity of activated carbon for 100 ppm concentrations of acetaldehyde, ethanol, and acetone. Activities in progress and planned activities are reviewed.

  6. Preliminary study of niobium alloy contamination by transport through helium

    NASA Technical Reports Server (NTRS)

    Scheuermann, Coulson M.; Moore, Thomas J.; Wheeler, Donald R.

    1987-01-01

    Preliminary tests were conducted to determine if interstitial element transport through a circulating helium working fluid was a potential problem in Brayton and Stirling space power systems. Test specimens exposed to a thermal gradient for up to 3000-hr included Nb-1%Zr, a Sm-Co alloy (referred to as SmCo in this paper), Hiperco 50 steel, and alumina to simulate various engine components of the Brayton and Stirling systems. Results indicate that helium transport of interstitial contaminants can be minimized over a 7-yr life with a monometallic Nb-1%Zr design. Exposure with other materials indicated a potential for interstitial contaminant transport. Determination of contamination kinetics and the effects on structural integrity will require additional testing.

  7. Contaminant transport from Elliott and Commencement Bays. Technical memo

    SciTech Connect

    Curl, H.C.; Baker, E.T.; Bates, T.S.; Cannon, G.A.; Feely, R.A.

    1988-04-01

    Contaminant transport from Elliott and Commencement Bays to the main basin of the Puget Sound was investigated by the Pacific Marine Environmental Laboratory during the spring and summer of 1985 and January of 1986. Distributions of water properties (salinity, suspended particulate matter, and toxic trace metals and organics) were mapped during periods of high river runoff and during combined sewer outflow after heavy rainfall. Results indicate that: (1) dissolved contaminants remain in the very thin, fresh-water plume and are transported through the bays into the main basin quite rapidly; (2) PCB and DDT isomers were undetectable in either bay; and (3) there was no evidence that resuspension and transport of contaminated bottom sediments was taking place in Elliot Bay. These results must be qualified due to the short periods during which measurements were taken.

  8. Simultaneous parameter estimation and contaminant source characterization for coupled groundwater flow and contaminant transport modelling

    USGS Publications Warehouse

    Wagner, B.J.

    1992-01-01

    Parameter estimation and contaminant source characterization are key steps in the development of a coupled groundwater flow and contaminant transport simulation model. Here a methodologyfor simultaneous model parameter estimation and source characterization is presented. The parameter estimation/source characterization inverse model combines groundwater flow and contaminant transport simulation with non-linear maximum likelihood estimation to determine optimal estimates of the unknown model parameters and source characteristics based on measurements of hydraulic head and contaminant concentration. First-order uncertainty analysis provides a means for assessing the reliability of the maximum likelihood estimates and evaluating the accuracy and reliability of the flow and transport model predictions. A series of hypothetical examples is presented to demonstrate the ability of the inverse model to solve the combined parameter estimation/source characterization inverse problem. Hydraulic conductivities, effective porosity, longitudinal and transverse dispersivities, boundary flux, and contaminant flux at the source are estimated for a two-dimensional groundwater system. In addition, characterization of the history of contaminant disposal or location of the contaminant source is demonstrated. Finally, the problem of estimating the statistical parameters that describe the errors associated with the head and concentration data is addressed. A stage-wise estimation procedure is used to jointly estimate these statistical parameters along with the unknown model parameters and source characteristics. ?? 1992.

  9. Processes affecting the remediation of chromium-contaminated sites.

    PubMed Central

    Palmer, C D; Wittbrodt, P R

    1991-01-01

    The remediation of chromium-contaminated sites requires knowledge of the processes that control the migration and transformation of chromium. Advection, dispersion, and diffusion are physical processes affecting the rate at which contaminants can migrate in the subsurface. Heterogeneity is an important factor that affects the contribution of each of these mechanisms to the migration of chromium-laden waters. Redox reactions, chemical speciation, adsorption/desorption phenomena, and precipitation/dissolution reactions control the transformation and mobility of chromium. The reduction of CrVI to CrIII can occur in the presence of ferrous iron in solution or in mineral phases, reduced sulfur compounds, or soil organic matter. At neutral to alkaline pH, the CrIII precipitates as amorphous hydroxides or forms complexes with organic matter. CrIII is oxidized by manganese dioxide, a common mineral found in many soils. Solid-phase precipitates of hexavalent chromium such as barium chromate can serve either as sources or sinks for CrVI. Adsorption of CrVI in soils increases with decreasing chromium concentration, making it more difficult to remove the chromium as the concentration decreases during pump-and-treat remediation. Knowledge of these chemical and physical processes is important in developing and selecting effective, cost-efficient remediation designs for chromium-contaminated sites. PMID:1935849

  10. CONTAMINANT TRANSPORT IN PARALLEL FRACTURED MEDIA: SUDICKY AND FRIND REVISITED

    EPA Science Inventory

    This paper is concerned with a modified, nondimensional form of the parallel fracture, contaminant transport model of Sudicky and Frind (1982). The modifications include the boundary condition at the fracture wall, expressed by a parameter , and the power-law relationship betwe...

  11. CONTAMINANT TRANSPORT IN PARALLEL FRACTURED MEDIA: SUDICKY AND FRIND REVISITED

    EPA Science Inventory

    This paper is concerned with a modified, nondimensional form of the parallel fracture, contaminant transport model of Sudicky and Frind (1982). The modifications include the boundary condition at the fracture wall, expressed by a parameter, and the power-law relationship between...

  12. Chemical transport associated with discharge of contaminated fine particles to a steady open-channel flow

    NASA Astrophysics Data System (ADS)

    Ng, Chiu-On

    2000-01-01

    In this paper, an analytical study on the advective-dispersive transport of a chemical contaminant resulting from the discharge of contaminated fine solid particles into a two-dimensional, steady and uniform turbulent open-channel flow is presented. Because of sorptive exchange, the transport of the chemical cloud is affected by that of the suspended particulates. Such a relationship has so far not been explicitly established by intuitive arguments. The effective transport equations are formally derived by an extended method of homogenization. It is found that over a long time scale the fall velocity will delay the sediment advection, and the advection velocity and dispersion coefficient for the chemical transport will change with space and time according to the local sediment concentration. Numerical results confirm that the centers of mass of the sediment and dissolved phase clouds are not advancing at the same speed, and the dispersion of the chemical is enhanced by the local retardation factor.

  13. Contamination and restoration of an estuary affected by phosphogypsum releases.

    PubMed

    Villa, M; Mosqueda, F; Hurtado, S; Mantero, J; Manjón, G; Periañez, R; Vaca, F; García-Tenorio, R

    2009-12-15

    The Huelva Estuary in Huelva, Spain, has been one of the most studied environmental compartments in the past years from the point of view of naturally occurring radioactive material (NORM) releases. It has been historically affected by waste releases, enriched in radionuclides from the U-decay series, from factories located in the area devoted to the production of phosphoric acid and phosphate fertilizers. Nevertheless, changes in national regulations forced a new waste management practice in 1998, prohibiting releases of phosphogypsum into the rivers. The input of natural radionuclides from phosphate factories to rivers was drastically reduced. Because of this there was a unique opportunity for the study of the response of a contaminated environmental compartment, specifically an estuary affected by tidal influences, after the cessation of the contaminant releases to, in this case, the Huelva Estuary (henceforth referred to as the Estuary). To investigate the environmental response to this new discharge regime, the specific activities of radionuclides 226Ra and 210Pb in water and sediment samples collected in four campaigns (from 1999 to 2005) were determined and compared with pre-1998 values. From this study it is possible to infer the most effective mechanisms of decontamination for the Estuary. Decontamination rates of 210Pb and 226Ra in the sediments and water have been calculated using exponential fittings and corresponding half-lives have been deduced from them. The cleaning half-life in the whole area of the Estuary is about 6 and 3.5 years for 226Ra and 210Pb respectively. The observed trend clearly shows that contamination of the Estuary by natural radionuclides is now decreasing and radioactive levels in waters and sediments are approaching the natural background references. This work attempts to evaluate whether it can be expected that the decontamination of the enhanced levels of natural radioactivity in the Estuary can be performed via natural

  14. Concentration distribution of contaminant transport in wetland flows

    NASA Astrophysics Data System (ADS)

    Wu, Zi; Fu, Xudong; Wang, Guangqian

    2015-06-01

    Study on contaminant transport in wetland flows is of fundamental importance. Recent investigation on scalar transport in laminar tube flows (Wu and Chen, 2014. J. Fluid Mech., 740: 196-213.) indicates that the vertical concentration difference in wetland flows may be remarkable for a very long time, which cannot be captured by the extensively applied one-dimensional Taylor dispersion model. To understand detailed information for the vertical distribution of contaminant in wetland flows, for the first time, the present paper deduces an analytical solution for the multi-dimensional concentration distribution by the method of mean concentration expansion. The solution is verified by both our analytical and numerical results. Representing the effects of vegetation in wetlands, the unique dimensionless parameter α can cause the longitudinal contraction of the contaminant cloud and the change of the shape of the concentration contours. By these complicated effects, it is shown unexpectedly that the maximum vertical concentration difference remains nearly unaffected, although its longitudinal position may change. Thus the slow-decaying transient effect (Wu and Chen, 2014. J. Hydrol., 519: 1974-1984.) is shown also apply to the process of contaminant transport in wetland flows.

  15. THE IMPACT OF GROUND WATER-SURFACE WATER INTERACTIONS ON CONTAMINANT TRANSPORT AT CONTAMINATED SITES

    EPA Science Inventory

    The purpose of this document is to provide an overview of the dynamics of chemical processes that govern contaminant transport and speciation during water exchange across the GW/SW transition zone. A conceptual model of the GW/SW transition zone is defined to serve as a starting...

  16. Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels

    SciTech Connect

    Miller, Julianne J.; Mizell, Steve A.; Nikolich, George; Campbell, Scott A.

    2012-02-01

    The U.S. Department of Energy (DOE) National Nuclear Security Administration (NNSA), Nevada Site Office (NSO), Environmental Restoration Soils Activity has authorized the Desert Research Institute (DRI) to conduct field assessments of potential sediment transport of contaminated soil from Corrective Action Unit (CAU) 550, Area 8 Smoky Contamination Area (CA), during precipitation runoff events. CAU 550 includes Corrective Action Sites (CASs) 08-23-03, 08-23-04, 08-23-06, and 08-23-07; these CASs are associated with tests designated Ceres, Smoky, Oberon, and Titania, respectively.

  17. Identification of Transport Parameters and Pollution Sources for a Physically Based Groundwater Contaminant Transport Model: A Comparison of Algorithms

    NASA Astrophysics Data System (ADS)

    Yin, Y.; Sykes, J. F.

    2006-12-01

    , multi-start PEST performs best in terms of the final best objective function values with equal number of function evaluations. The actual elapsed computer time for multi-start PEST was far less than that for the two heuristic algorithms. For the two heuristic algorithms, up to 500 function evaluations were required. For multi-start PEST, convergence was obtained in approximately 100 function evaluations. Multi-start PEST also was employed to identify contaminant transport and source parameters under different scenarios including spatially and temporally varying recharge and averaged recharge. The estimated transverse dispersivity coefficients were demonstrated to be strongly affected by the recharge averaging. The work clearly demonstrates the utility and feasibility of parameter optimization for large problems.

  18. IMPACT OF REDOX DISEQUILIBRIA ON CONTAMINANT TRANSPORT AND REMEDIATION IN SUBSURFACE SYSTEMS

    EPA Science Inventory

    Partitioning to mineral surfaces exerts significant control on inorganic contaminant transport in subsurface systems. Remedial technologies for in-situ treatment of subsurface contamination are frequently designed to optimize the efficiency of contaminant partitioning to solid s...

  19. Simulation of contaminated sediment transport in White Oak Creek basin

    SciTech Connect

    Bao, Y.; Clapp, R.B.; Brenkert, A.L.; Moore, T.D.; Fontaine, T.A.

    1995-12-31

    This paper presents a systematic approach to management of the contaminated sediments in the White Oak Creek watershed at Oak Ridge National Laboratory near Oak Ridge, Tennessee. The primary contaminant of concern is radioactive cesium-137 ({sup 137}Cs), which binds to soil and sediment particles. The key components in the approach include an intensive sampling and monitoring system for flood events; modeling of hydrological processes, sediment transport, and contaminant flux movement; and a decision framework with a detailed human health risk analysis. Emphasis is placed on modeling of watershed rainfall-runoff and contaminated sediment transport during flooding periods using the Hydrologic Simulation Program- Fortran (HSPF) model. Because a large number of parameters are required in HSPF modeling, the major effort in the modeling process is the calibration of model parameters to make simulation results and measured values agree as closely as possible. An optimization model incorporating the concepts of an expert system was developed to improve calibration results and efficiency. Over a five-year simulation period, the simulated flows match the observed values well. Simulated total amount of sediment loads at various locations during storms match with the observed values within a factor of 1.5. Simulated annual releases of {sup 137}Cs off-site locations match the data within a factor of 2 for the five-year period. The comprehensive modeling approach can provide a valuable tool for decision makers to quantitatively analyze sediment erosion, deposition, and transport; exposure risk related to radionuclides in contaminated sediment; and various management strategies.

  20. Prediction methodology for contaminant transport from rangeland watersheds

    SciTech Connect

    Devaurs, M.A.; Springer, E.P.; Lane, L.J.; Langhorst, G.J.

    1988-01-01

    Weather on arid and semiarid lands can be extremely variable. Runoff is generally emphermeral, and high intensity, short-duration rainfall events are the major stimulus for runoff events. Transport of sediment and associated contaminants occurs with these infrequent events. Incorporation of variability in weather into any prediction technology is essential to provide accurate representations of climate-induced uncertainty in predictions of hydrologic response. The objective of this study is to investigate a method for including short-term climatic variations in analyses for contaminant transport from rangeland watersheds in arid/semiarid regions. Short term is defined here as a twenty to fifty time frame and it is assumed that lone term climatic fluctuations are not observed during this time. Also, most weather records are available for this time period; predictions of greater length are extrapolations of existing records unless corroborative data for longer term trends are collected. Predictions are being made with condensable uncertainty in the weather inputs even if the models for water, sediment, and contaminant transport are perfectly unknown. This study will incorporate uncertainty in weather inputs into the prediction process and address the ramifications of this uncertainty. Uncertainty introduced by improper model or parameter specification is only briefly addressed.

  1. Modeling of contaminant transport in underground coal gasification

    SciTech Connect

    Lanhe Yang; Xing Zhang

    2009-01-15

    In order to study and discuss the impact of contaminants produced from underground coal gasification on groundwater, a coupled seepage-thermodynamics-transport model for underground gasification was developed on the basis of mass and energy conservation and pollutant-transport mechanisms, the mathematical model was solved by the upstream weighted multisell balance method, and the model was calibrated and verified against the experimental site data. The experiment showed that because of the effects of temperature on the surrounding rock of the gasification panel the measured pore-water-pressure was higher than the simulated one; except for in the high temperature zone where the simulation errors of temperature, pore water pressure, and contaminant concentration were relatively high, the simulation values of the overall gasification panel were well fitted with the measured values. As the gasification experiment progressed, the influence range of temperature field expanded, the gradient of groundwater pressure decreased, and the migration velocity of pollutant increased. Eleven months and twenty months after the test, the differences between maximum and minimum water pressure were 2.4 and 1.8 MPa, respectively, and the migration velocities of contaminants were 0.24-0.38 m/d and 0.27-0.46 m/d, respectively. It was concluded that the numerical simulation of the transport process for pollutants from underground coal gasification was valid. 42 refs., 13 figs., 1 tab.

  2. Isotopic Studies of Contaminant Transport at the Hanford Site, Washington.

    SciTech Connect

    Christensen, John N.; Conrad, Mark E.; DePaolo, Donald J.; Dresel, P. Evan

    2007-11-01

    Processes of fluid flow and chemical transport through the vadose zone can be characterized through the isotopic systematics of natural soils, minerals, pore fluids and groundwater. In this contribution, we first review our research using measured isotopic variations, due both to natural and site related processes, of the elements H, O, N, Sr and U, to study the interconnection between vadose zone and groundwater contamination at the Hanford Site in south-central Washington. We follow this brief review with a presentation of new data pertaining to vadose zone and groundwater contamination in the WMA T-TX-TY vicinity. Uranium (U) isotopic data for the C3832 core (WMA TX) indicates the involvement of processed natural U fuel, and links the observed U contamination to the nearby single shelled tank TX-104. The data also precludes contamination from an early 1970’s TX-107 leak. In the case of the C4104 core (WMA T), the U isotopic data indicates a mixture of processed natural and enriched U fuels consistent with the major leak from T-106 in 1973. Uranium and Strontium isotopic data for the cores also provides direct evidence for chemical interaction between high-pH waste fluid and sediment. Isotopic data for groundwater nitrate contamination in the vicinity of WMA-T strongly suggests high-level tank waste (most likely from T-106) as the source of very high 99Tc concentrations recently observed at the NE corner of WMAT.

  3. Geochemical factors affecting radionuclide transport through near and far fields at a Low-Level Waste Disposal Site

    SciTech Connect

    Kaplan, D.I.; Seme, R.J.; Piepkho, M.G.

    1995-03-01

    The concentration of low-level waste (LLW) contaminants in groundwater is determined by the amount of contaminant present in the solid waste, rate of release from the waste and surrounding barriers, and a number of geochemical processes including adsorption, desorption, diffusion, precipitation, and dissolution. To accurately predict radionuclide transport through the subsurface, it is essential that the important geochemical processes affecting radionuclide transport be identified and, perhaps more importantly, accurately quantified and described in a mathematically defensible manner.

  4. Development of versatile molecular transport model for modeling spacecraft contamination

    NASA Astrophysics Data System (ADS)

    Chang, Chien W.; Kannenberg, Keith; Chidester, Michael H.

    2010-08-01

    This paper describes a MATLAB-based molecular transport model developed for modeling contamination of spacecraft and optical instruments in space. The model adopts the Gebhart inverse-matrix theory for thermal radiation to analyze mass (molecular) transfer due to direct and reflected flux processes by balancing the mass fluxes instead of heat fluxes among surfaces with prescribed boundary conditions (contamination sticking fractions). The model can easily input view factor results from current thermal tools as well as measured outgassing data from ASTM E 1559 tests or vacuum bake-outs of flight components. Application examples of a geosynchronous satellite and an optical telescope are given to demonstrate versatile applications of the developed model.

  5. Attenuation of Selected Emerging Contaminants During River Transport

    NASA Astrophysics Data System (ADS)

    Reinhard, M.; Gross, B.; Hadeler, A.

    2002-12-01

    The ubiquitous occurrence of emerging (non-regulated) contaminants in the aquatic environment is of concern because some of these chemicals are biologically active at low concentrations and a potential threat to wildlife and human health.. Emerging contaminants include a diverse range of chemicals, including pharmaceuticals, natural and synthetic hormones and industrial surfactants, such as alkylphenol ethoxylates (APEO) and their metabolites. To address the ecotoxicological impact of these chemicals, it is necessary to know their sources, removal efficiencies during wastewater treatment, and their behavior in the environment. In this study, the fate of selected emerging contaminants in the Santa Ana River (SAR) in Southern California was investigated. The SAR originates in the San Bernardino Mountains and flows 80 miles into the Pacific Ocean. The SAR flow stems mainly from storm runoff, wastewater treatment effluents and several other minor sources. During the dry season, SAR flow is dominated by effluent from public wastewater treatment plants. Input into the SAR was studied by analyzing samples from four major treatment plants that employ different tertiary treatment processes. To assess the fate during river water transport and during wetland treatment, samples from six sites along the river were analyzed. Effluent samples were analyzed every two months, river water every four months. River samples were taken considering the flow velocity, which is approximately 1 mile per hour. The analytical method involves solid-phase extraction using C-18 cartridges and extraction of three fractions. Samples were analyzed with and without further derivatization using GC/MS and GC/MS/MS. Results indicate significant contaminant removal during river transport, presumably by photochemical oxidation. Within a distance of nine miles, pharmaceuticals, plasticizers, flame retardants, APEOs and metabolites were attenuated with removal rates ranging from 76% for a flame retardant

  6. Modeling solute/contaminant transport in heterogeneous aquifers.

    PubMed

    Kocabas, Ibrahim; Bulbul, Mahmut

    2015-03-01

    A fissured aquifer may be considered as a dense network of fissures separated by low permeability matrix blocks. A conceptual modeling of such a system consists of an infinite number of parallel fractures separated by constant width matrix slabs. While the fissures are assumed to be main flow conduits, the fluid in the porous matrix blocks are considered to be virtually immobile. The mathematical model of the transport of a solute and/or contaminant which assumes a purely convective flow in fissures and diffusion into the matrix blocks consists of two coupled differential equations. An analytical solution of this model for the case of solute entering into the system at a constant concentration has been presented by Skopp and Warrick in Soil Sci Soc Am Proc 38:545-550, 1974. Note however, Skopp and Warrick (Soil Sci Soc Am Proc 38:545-550, 1974) have not considered the additional processes of adsorption and radioactive decay. Unfortunately, their solution had computational limitations as it involved numerical integration of a quite complex expression. Therefore, one had to turn to employing numerical Laplace transform inverters to compute the solutions. This work presents simple real space analytical solutions for the contaminant transport model described above including the adsorption and radioactive decay. The real space solutions have been developed using the method of double Laplace transform and binomial series approximation. An accurate approximate solution has also been presented which converges to the exact solution only after computing three terms in the series full solution. The developed model has been used for 1) assessment of the efficiency of numerical Laplace transform algorithms and 2) investigation of the degree and scale of contamination, and 3) designing remediation schemes for the already contaminated aquifers.

  7. Mobile sediment in an urbanizing karst aquifer: Implications for contaminant transport

    USGS Publications Warehouse

    Mahler, B.J.; Lynch, L.; Bennett, P.C.

    2000-01-01

    Here we investigate geochemical characteristics of sediment in different compartments of a karst aquifer and demonstrate that mobile sediments in a karst aquifer can exhibit a wide range of properties affecting their contaminant transport potential. Sediment samples were collected from surface streams, sinkholes, caves, wells, and springs of a karst aquifer (the Barton Springs portion of the Edwards (Balcones Fault Zone) Aquifer, Central Texas) and their mineralogy, grain-size distribution, organic carbon content, and specific surface area analyzed. Statistical analysis of the sediments separated the sampling sites into three distinct groups: (1) streambeds, sinkholes, and small springs; (2) wells; and (3) caves. Sediments from the primary discharge spring were a mix of these three groups. High organic carbon content and increased potential to transport contaminants; the volume of these sediments is likely to increase with continued urbanization of the watershed.

  8. Transport of contaminants in the planetary boundary layer

    NASA Technical Reports Server (NTRS)

    Lee, I. Y.; Swan, P. R.

    1978-01-01

    A planetary boundary layer model is described and used to simulate PBL phenomena including cloud formation and pollution transport in the San Francisco Bay Area. The effect of events in the PBL on air pollution is considered, and governing equations for the average momentum, potential temperature, water vapor mixing ratio, and air contaminants are presented. These equations are derived by integrating the basic equations vertically through the mixed layer. Characteristics of the day selected for simulation are reported, and the results suggest that the diurnally cyclic features of the mesoscale motion, including clouds and air pollution, can be simulated in a readily interpretable way with the model.

  9. Dust resuspension as a contaminant source and transport pathway

    SciTech Connect

    Loosmore, G.A,; Hunt, J.R.

    1999-07-01

    Numerous environmental contaminants sorb to dust particles or exist as particles, including metals, hydrophobic organic compounds, asbestos, pollens, and microbial pathogens. Wind resuspension of dust and other particulate matter provides a dust source for the atmosphere and a contaminant transport pathway. Not only do these materials pose a risk to human health, but also, resuspended dust particles are believed to play a role in global climate change and chemical reactions in the atmosphere. The conditions under which contaminated sites are vulnerable to wind resuspension are not generally known, as the basic physics of the problem are poorly understood. Field data show tremendous variability. Conventional dust flux models assume that dust resuspension occurs only for high winds and then only temporarily, with a transient dust flux occurring only when the bed is first exposed to the high wind. The surface is then assumed to stabilize such that no further dust moves until the surface is disturbed or a higher wind occurs. Recent wind tunnel experiments demonstrate that surfaces yield continuous steady dust fluxes under steady wind conditions well beyond the initial high transient flux, even when no erosion is visible and the velocity is below the predicted threshold velocity for movement. This average steady-state dust flux increases with average wind speed. Ongoing work is investigating the influence of air relative humidity on these processes. Contaminant resuspension models capture trends only and fail to predict sporadic high flux events that may control doses. Successful modeling of contaminant resuspension will depend on development of better dust flux predictions. Risk analyses require better predictive modeling, necessitating a deeper understanding of the underlying phenomena.

  10. Reactive Transport Modeling of Vadose Zone Contamination: Feedback between Reactions and Gas-Phase Transport

    NASA Astrophysics Data System (ADS)

    Molins, S.; Mayer, K.

    2007-05-01

    The unsaturated zone acts as a buffer zone for contaminants on their way to the water table but can also attenuate the emission of contaminants leaving the subsurface environment through the gas phase. A reactive transport model that includes multicomponent gas transport has been developed to investigate the processes that contribute to the generation and attenuation of contaminants in the unsaturated zone. In particular, the model is suitable to study the feedback processes between advective-diffusive gas transport and geochemical reactions. The model is also able to estimate diffusive and advective contributions to gas transport in multicomponent systems. Two model applications are presented that investigate gas transport and reactions in mine tailings and at a site with organic contamination. In mine tailings, atmospheric oxygen transported into the sediment column is consumed in the oxidation of sulfide minerals. Gas volume loss caused by the consumption of atmospheric oxygen drives advective fluxes. In the absence of carbonate minerals, the advective component accounts for 16 % of the net oxygen flux into the column, while, in a carbonate-rich system, advection accounts for 10 % of the net oxygen flux. Dissolution of carbonate minerals has a moderating effect on advective gas transport since carbon dioxide can partially compensate for the depletion of oxygen. At an oil spill site, volatilization and degradation of organic contaminants cause advective and diffusive fluxes of organic vapors away from the source zone. At early stages, volatilization dominates and oxidation of these organic vapors attenuates the emission of contaminants to the atmosphere. The contribution of advection to organic vapor fluxes is significant initially but decreases with time. At later stages, the oil source becomes depleted of its most volatile fraction, and anaerobic degradation of aromatic compounds and heavier n-alkanes results in the production of methane. Up to 15 % of methane

  11. Impact of Temporally Variable and Uniform Pumping Regimes on Contaminant Transport in Heterogeneous Aquifers

    NASA Astrophysics Data System (ADS)

    Libera, A.; de Barros, F.; Guadagnini, A.

    2015-12-01

    We study and compare the effect of temporally variable and uniform pumping regimes on key features of contaminant transport in a randomly heterogeneous aquifer. Pumping wells are used for groundwater supply in the context of urban, agricultural, and industrial activities. Groundwater management agencies typically schedule groundwater extraction through a predefined sequence of pumping periods to balance benefits to anthropogenic activities and environmental needs. The impact of the spatial variability of aquifer hydraulic properties, such as hydraulic conductivity, on contaminant transport and associated solute residence times are widely studied. Only a limited number of studies address the way a given pumping schedule affects contaminant plume behavior in heterogeneous aquifers. In this context, the feedback between a transient pumping regime and contaminant breakthrough curves is largely unexplored. Our goal is to investigate the way diverse groundwater extraction strategies affect the history of solute concentration recovered at the well while accounting for the natural variability of the geological system, in the presence of incomplete information on hydraulic conductivity distribution. Considering the joint effects of spatially heterogeneous hydraulic conductivity and temporally varying well pumping rates, this work offers a realistic evaluation of groundwater contamination risk. The latter is here considered in the context of human health and is quantified in terms of the probability that harm will result from exposure to a contaminant found in groundwater. Two scenarios are considered: a pumping well that extracts a given amount of water operating (a) at a constant pumping rate and (b) under transient conditions. The analysis is performed within a numerical Monte Carlo framework. We probe the impact of diverse geostatistical structures to describe aquifer heterogeneity on solute breakthrough curves and the statistics of target environmental performance

  12. Subsurface Flow and Contaminant Transport Documentation and User's Guide

    SciTech Connect

    Aleman, S.E.

    1999-07-28

    This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media. The code is designed specifically to handle complex multi-layer and/or heterogeneous aquifer systems in an efficient manner and accommodates a wide range of boundary conditions. Additionally, 1-D and 2-D (in Cartesian coordinates) problems are handled in FACT by simply limiting the number of elements in a particular direction(s) to one. The governing equations in FACT are formulated only in Cartesian coordinates.

  13. Contaminant transport in dual-porosity media with dissolved organic matter and bacteria present as mobile colloids.

    PubMed

    Kim, Song-Bae; Corapcioglu, M Yavuz

    2002-12-01

    In riverbank filtration, contaminant transport is affected by colloidal particles such as dissolved organic matter (DOM) and bacterial particles. In addition, the subsurface heterogeneity influences the behavior of contaminant transport in riverbank filtration. A mathematical model is developed to describe the contaminant transport in dual-porosity media in the presence of DOM and bacteria as mobile colloids. In the model development, a porous medium is divided into the mobile and immobile regions to consider the presence of ineffective micropores in physically heterogeneous riverbanks. We assume that the contaminant transport in the mobile region is controlled by the advection and dispersion while the contaminant transport in the immobile region occurs due to the molecular diffusion. The contaminant transfer between the mobile and immobile regions takes place by diffusive mass transfer. The mobile region is conceptualized as a four-phase system: two mobile colloidal phases, an aqueous phase, and a solid matrix. The complete set of governing equations is solved numerically with a fully implicit finite difference method. The model results show that in riverbank filtration, the contaminant can migrate further than expected due to the presence of DOM and bacteria. In addition, the contaminant mobility increases further in the presence of the immobile region in aquifers. A sensitivity analysis shows that in dual-porosity media, earlier breakthrough of the contaminant takes place as the volumetric fraction of the mobile region decreases. It is also demonstrated that as the contaminant mass transfer rate coefficient between the mobile and immobile regions increases, the contaminant concentration gradient between the two regions reverses at earlier pore volumes. The contaminant mass transfer coefficient between the mobile and immobile regions mainly controls the tailing effect of the contaminant breakthrough. The contaminant breakthrough curves are sensitive to changes in

  14. Contaminant transport in dual-porosity media with dissolved organic matter and bacteria present as mobile colloids.

    PubMed

    Kim, Song-Bae; Corapcioglu, M Yavuz

    2002-12-01

    In riverbank filtration, contaminant transport is affected by colloidal particles such as dissolved organic matter (DOM) and bacterial particles. In addition, the subsurface heterogeneity influences the behavior of contaminant transport in riverbank filtration. A mathematical model is developed to describe the contaminant transport in dual-porosity media in the presence of DOM and bacteria as mobile colloids. In the model development, a porous medium is divided into the mobile and immobile regions to consider the presence of ineffective micropores in physically heterogeneous riverbanks. We assume that the contaminant transport in the mobile region is controlled by the advection and dispersion while the contaminant transport in the immobile region occurs due to the molecular diffusion. The contaminant transfer between the mobile and immobile regions takes place by diffusive mass transfer. The mobile region is conceptualized as a four-phase system: two mobile colloidal phases, an aqueous phase, and a solid matrix. The complete set of governing equations is solved numerically with a fully implicit finite difference method. The model results show that in riverbank filtration, the contaminant can migrate further than expected due to the presence of DOM and bacteria. In addition, the contaminant mobility increases further in the presence of the immobile region in aquifers. A sensitivity analysis shows that in dual-porosity media, earlier breakthrough of the contaminant takes place as the volumetric fraction of the mobile region decreases. It is also demonstrated that as the contaminant mass transfer rate coefficient between the mobile and immobile regions increases, the contaminant concentration gradient between the two regions reverses at earlier pore volumes. The contaminant mass transfer coefficient between the mobile and immobile regions mainly controls the tailing effect of the contaminant breakthrough. The contaminant breakthrough curves are sensitive to changes in

  15. Wintertime Factors Affecting Contaminant Distribution in a Swine Farrowing Room

    PubMed Central

    Reeve, Kelsie A.; Peters, Thomas M.; Anthony, T. Renée

    2016-01-01

    An estimated 200,000 to 500,000 U.S. workers in concentrated animal feeding operations (CAFOs) are at risk of adverse respiratory outcomes from exposures to indoor contaminants. In the wintertime, general ventilation is minimized in the Midwest due to high heating costs required to maintain indoor temperatures optimal for animal production. Pit fans typically operate to exhaust under-floor manure pits, but little other fresh air intake exists. Many operators believe that these systems are sufficient to reduce contaminant concentrations within the building during winter. Investigating whether these pit fans provide sufficient protection against classic CAFO contaminants during minimal wintertime ventilation was warranted. Direct-reading instruments were used to measure and record concentrations of multiple contaminants using both fixed-area and mobile contaminant mapping in a farrowing room during a Midwest winter. With the exception of CO, concentrations were significantly (p < 0.001) higher with the pit fan off compared with those with the pit fan on. Additional analyses identified that significant changes (p < 0.001) in mean room concentrations of respirable dust (decreased, 77% with pit fan off and 87% with pit fan on) and CO2 (increased, 24%) over the 5-hr study periods and that multiple fixed-area monitors rather than the much-used, single center-of-room monitor provided a more conservative (e.g., protective) assessment of room concentrations. While concentrations did not exceed occupational exposure limits from OSHA or ACGIH for individual contaminants, recommended agricultural health limits from exposure-response studies suggested in the literature were exceeded for respirable dust, CO2, and NH3, indicating a need to consider personal exposures and control options to reduce contaminant concentrations in farrowing rooms. Pit fans reduced NH3 and H2S concentrations, but these fans may not be sufficient to control dust and eliminate the need for secondary

  16. Wintertime factors affecting contaminant distribution in a swine farrowing room.

    PubMed

    Reeve, Kelsie A; Peters, Thomas M; Anthony, T Renée

    2013-01-01

    An estimated 200,000 to 500,000 U.S. workers in concentrated animal feeding operations (CAFOs) are at risk of adverse respiratory outcomes from exposures to indoor contaminants. In the wintertime, general ventilation is minimized in the Midwest due to high heating costs required to maintain indoor temperatures optimal for animal production. Pit fans typically operate to exhaust under-floor manure pits, but little other fresh air intake exists. Many operators believe that these systems are sufficient to reduce contaminant concentrations within the building during winter. Investigating whether these pit fans provide sufficient protection against classic CAFO contaminants during minimal wintertime ventilation was warranted. Direct-reading instruments were used to measure and record concentrations of multiple contaminants using both fixed-area and mobile contaminant mapping in a farrowing room during a Midwest winter. With the exception of CO, concentrations were significantly (p<0.001) higher with the pit fan off compared with those with the pit fan on. Additional analyses identified that significant changes (p<0.001) in mean room concentrations of respirable dust (decreased, 77% with pit fan off and 87% with pit fan on) and CO2 (increased, 24%) over the 5-hr study periods and that multiple fixed-area monitors rather than the much-used, single center-of-room monitor provided a more conservative (e.g., protective) assessment of room concentrations. While concentrations did not exceed occupational exposure limits from OSHA or ACGIH for individual contaminants, recommended agricultural health limits from exposure-response studies suggested in the literature were exceeded for respirable dust, CO2, and NH3, indicating a need to consider personal exposures and control options to reduce contaminant concentrations in farrowing rooms. Pit fans reduced NH3 and H2S concentrations, but these fans may not be sufficient to control dust and eliminate the need for secondary exposure

  17. Resolution of contamination problems affecting laser surface certification inspection

    NASA Astrophysics Data System (ADS)

    Jackson, L. C.

    1982-03-01

    Contamination from particulate and organic residues which interfered, with the laser surface certification (LSC) inspection of some parts was found to come from three sources: particulate and organic residues from polishing compounds; organic films from cleaning solvents; and particles and organic residues transferred from plastic fixtures used to process these parts. The manufacturing cleaning process was not effective in removing all polishing compound residues, and an extensive cleaning procedure was developed using two solvents in a multicycle ultrasonic/vapor degreasing procedure. Parts were then subjected to gas plasma cleaning which removed the organic films left by the solvent cleaning. Plastic and rubber materials were evaluated for their contamination transfer characteristics; a fluorocarbon elastomer was the least contaminating. Inspection data established the efficacy of the cleaning procedure. After design relaxation, a single stage ultrasonic vapor degreasing process was used to achieve product acceptance.

  18. Factors affecting contamination of blood samples for ethanol determinations.

    PubMed

    Winek, C L; Eastly, T

    1977-01-01

    Contamination of blood samples collected for alcohol analysis from swabbing with an ethanolic antiseptic is minimal (less than 0.6 mg/100 ml or 0.0006 percent ethanol) when routine clinical technique is followed. When technicians were told to be deliberately sloppy, considerable contamination (89 mg/100 ml or 0.09 percent ethanol) occurred. The incidence and extent of contamination from banked blood intended for transfusions are minimal. Two percent of the 1,450 samples analyzed contained alcohol. The average blood alcohol concentration was 26 mg/100 ml or 0.03 percent ethanol. One microliter of rubbing alcohol per milliliter of whole blood, or one-tenth of a drop of rubbing alcohol per milliliter of whole blood, increases the BAC 56.5 mg/100 ml (0.06 percent ethanol) and 67.5 mg/100 ml (0.07 percent ethanol), respectively.

  19. Coliform contamination of a coastal embayment: Sources and transport pathways

    USGS Publications Warehouse

    Weiskel, P.K.; Howes, B.L.; Heufelder, G.R.

    1996-01-01

    Fecal bacterial contamination of nearshore waters has direct economic impacts to coastal communities through the loss of shellfisheries and restrictions of recreational uses. We conducted seasonal measurements of fecal coliform (FC) sources and transport pathways contributing to FC contamination of Buttermilk Bay, a shallow embayment adjacent to Buzzards Bay, MA. Typical of most coastal embayments, there were no direct sewage discharges (i.e., outfalls), and fecal bacteria from human, domestic animal, and wildlife pools entered open waters primarily through direct deposition or after transport through surface waters or groundwaters. Direct fecal coliform inputs to bay waters occurred primarily in winter (December-March) from waterfowl, ~33 x 1012 FC yr-1 or ~67% of the total annual loading. Effects of waterfowl inputs on bay FC densities were mitigated by their seasonality, wide distribution across the bay surface, and the apparent limited dispersal from fecal pellets. On-site disposal of sewage by septic systems was the single largest FC source in the watershed-embayment system, 460 x 1012 FC yr-1, but due to attenuation during subsurface transport only a minute fraction, < 0.006 x 1012 FC yr-1, reached bay waters (<0.01% of annual input to bay). Instead, surface water flows, via storm drains and natural streams under both wet- and dry-weather conditions, contributed the major terrestrial input, 12 x 1012 FC yr-1 (24% of annual input), all from animal sources. Since most of the surface water FC inputs were associated with periodic, short-duration rain events with discharge concentrated in nearshore zones, wet-weather flows were found to have a disproportionately high impact on nearshore FC levels. Elution of FC from shoreline deposits of decaying vegetation (wrack) comprised an additional coliform source. Both laboratory and field experiments suggest significant elution of bacteria from wrack, ~3 x 1012 FC yr-1 on a bay-wide basis (6% of annual input), primarily

  20. Dynamic modeling of contaminant transport with surface runoff and sediment

    SciTech Connect

    Ashraf, M.S.

    1992-01-01

    Non-point source pollution in surface runoff due to agricultural activities presents one of the principal problems in the U.S. Solution to the problem of delivering pollutants is crucial to a non-point abatement program. Mathematical models can serve as tools to relate hydrologic conditions and soil properties to the processes of pollutant transport, and can be used to evaluate the effectiveness of best management practices in reducing non-point source pollutant load in surface waters. In this study, a dynamic model component is developed to simulate transport of non-point source pollutants, mostly agricultural chemicals, with surface runoff and sediment in agricultural watersheds. Algorithms are developed to route chemicals and infiltrating water through different soil increments assuming complete mixing until time of ponding or initiation of runoff. Once runoff starts, the runoff interacts with a mixing soil layer in a non-uniform fashion and exchange of chemicals takes place between runoff and the mixing soil layer. When runoff storage builds up, it is assumed that a relatively stagnant depth of runoff interacts with the mixing soil layer. This stagnant depth is obtained by applying boundary layer theory. Mass balance equations are used to route chemicals associated with runoff and sediment along the slope lengths for overland and channel flow. Model algorithms are coupled with the hydrologic and sediment transport model RUNOFF to simulate transport of contaminants with surface runoff and sediments in agricultural watersheds. The model performance is evaluated with data ranging from controlled laboratory experiments to watershed scale. The concept of non-uniform mixing is tested with a laboratory data set found in the literature. A total of fifteen runs are made, five for each of the chemicals, nitrate, phosphate, and cyanazine. The model results show good agreements with the observed yields of runoff, sediment, orthophosphate, and ammonium.

  1. A Linear Systems Approach to Segmented Watershed Contaminant Transport

    NASA Astrophysics Data System (ADS)

    Carleton, J. N.

    2013-12-01

    The U.S. Environmental Protection Agency (USEPA) employs simulation models to estimate concentrations of pesticide residues in surface waters for risk assessment. These models have historically been used to simulate runoff loadings from homogeneous landscapes to isolated, well-mixed lentic systems that generically represent vulnerable waters. Recent efforts to refine this approach in terms of realism and geographic specificity have focused on enhancing the level of detail of the landscape representation, rather than that of receiving water hydrology. Linear systems theory and transfer function based approaches have been applied by various investigators to the representation of contaminant leaching through soils, and to surface water hydrology (e.g., unit hydrographs), but rarely to contaminant transport either within surface waters, or through multi-compartment systems such as stream networks. This poster describes a straightforward approach to simulating watersheds as segmented into collections of linked water bodies. The approach employs convolution integrals, impulse response functions, and the Discrete Fourier Transform to propagate concentration time series from upstream to downstream locations. Given knowledge only of estimated mean stream residence times, with appropriately-scaled segmentations of catchments, realistic representations of concentration dynamics are shown to be achievable. These representations are based upon high-frequency atrazine monitoring data sets collected over common time periods from upstream and downstream locations within the same small watersheds. Simulated concentrations are shown to match measured concentrations well in both the temporal and spectral domains without the need for calibration, and despite inherent simplifying assumptions such as steady flow. The approach may have utility for enhancing surface water hydrologic representation in contaminant modeling used for regulatory purposes.

  2. Resolution of contamination problems affecting Laser-Surface-Certification inspection

    SciTech Connect

    Jackson, L.C.

    1982-03-01

    Contamination from particulate and organic residues has interfered with the Laser Surface Certification (LSC) inspection of some parts, subsequently preventing their certification to the Ernest Orlando Lawrence Livermore National Laboratory (LLNL) product specification. Contamination was found to come from three sources: particulate and organic residues from polishing compounds; organic films from cleaning solvents; and particles and organic residues transferred from plastic fixtures used to process these parts. The manufacturing cleaning process was not effective in removing all polishing compound residues, and an extensive cleaning procedure was developed using two solvents in a multicycle ultrasonic/vapor degreasing procedure. Parts were then subjected to gas plasma cleaning which removed the organic films left by the solvent cleaning. Plastic and rubber materials were evaluated for their contamination transfer characteristics; a fluorocarbon elastomer was the least contaminating. Inspection data established the efficacy of the cleaning procedure. After design relaxation, Bendix Kansas City was able to rely on a single-stage ultrasonic vapor degreasing process to achieve product acceptance.

  3. Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

    SciTech Connect

    James Saiers; Joseph Ryan

    2006-07-02

    Radionuclides, metals, and dense non-aqueous phase liquids have contaminated about six billion cubic meters of soil at Department of Energy (DOE) sites. The subsurface transport of many of these contaminants is facilitated by colloids (i.e., microscopic, waterborne particles). The first step in the transport of contaminants from their sources to off-site surface water and groundwater is migration through the vadose zone. Developing our understanding of the migration of colloids and colloid-associated contaminants through the vadose zone is critical to assessing and controlling the release of contaminants from DOE sites. In this study, we examined the mobilization, transport, and filtration (retention) of mineral colloids and colloidassociated radionuclides within unsaturated porous media. This investigation involved laboratory column experiments designed to identify properties that affect colloid mobilization and retention and pore-scale visualization experiments designed to elucidate mechanisms that govern these colloid-mass transfer processes. The experiments on colloid mobilization and retention were supplemented with experiments on radionuclide transport through porous media and on radionuclide adsorption to mineral colloids. Observations from all of these experiments – the column and visualization experiments with colloids and the experiments with radionuclides – were used to guide the development of mathematical models appropriate for describing colloids and colloid-facilitated radionuclide transport through the vadose zone.

  4. Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

    SciTech Connect

    James Saiers

    2006-06-28

    Radionuclides, metals, and dense non-aqueous phase liquids have contaminated about six billion cubic meters of soil at Department of Energy (DOE) sites. The subsurface transport of many of these contaminants is facilitated by colloids (i.e., microscopic, waterborne particles). The first step in the transport of contaminants from their sources to off-site surface water and groundwater is migration through the vadose zone. Developing our understanding of the migration of colloids and colloid-associated contaminants through the vadose zone is critical to assessing and controlling the release of contaminants from DOE sites. In this study, we examined the mobilization, transport, and filtration (retention) of mineral colloids and colloid-associated radionuclides within unsaturated porous media. This investigation involved laboratory column experiments designed to identify properties that affect colloid mobilization and retention and pore-scale visualization experiments designed to elucidate mechanisms that govern these colloid-mass transfer processes. The experiments on colloid mobilization and retention were supplemented with experiments on radionuclide transport through porous media and on radionuclide adsorption to mineral colloids. Observations from all of these experiments – the column and visualization experiments with colloids and the experiments with radionuclides – were used to guide the development of mathematical models appropriate for describing colloids and colloid-facilitated radionuclide transport through the vadose zone.

  5. Monitoring and modeling contaminated sediment transport in the White Oak Creek watershed

    SciTech Connect

    Fontaine, T.A.

    1991-11-01

    Over the past 47 years, operations and waste disposal activities at Oak Ridge National Laboratory have resulted in the contamination of the White Oak Creek drainage system. The containments presenting the highest risk to human health and the environment are particle reactive and are associated with the soils and sediments in White Oak Creek. During floods, the erosion of these sediments results in the transport of contaminants out of the catchment into the Clinch River. A long-term strategy is required to monitor the movement of contaminated sediments and to predict the transport of these sediments that could occur during major floods. A monitoring program will provide the information required to (1) evaluate the existing off-site transport of contaminated sediments, (2) evaluate the need for short-term control measures, (3) set priorities for remediation of contaminated areas in White Oak Creek (4) verify the success of completed remedial actions intended to control the movement of contaminated sediments, and (5) develop a computer model to simulate the transport of contaminated sediments in White Oak Creek. A contaminant-transport model will be developed to (1) evaluate the potential for the off-site transport of contaminated sediments during major floods, (2) develop long term control measures and remediation solutions, (3) predict the impact of future land-use changes in White Oak Creek on the transport of contaminated sediment. This report contains a plan for the monitoring and modeling activities required to accomplish these objectives.

  6. Hydrophobic organic contaminant transport property heterogeneity in the Borden Aquifer

    NASA Astrophysics Data System (ADS)

    Allen-King, Richelle M.; Kalinovich, Indra; Dominic, David F.; Wang, Guohui; Polmanteer, Reid; Divine, Dana

    2015-03-01

    We determined that the spatial heterogeneity in aquifer properties governing the reactive transport of volatile organic contaminants is defined by the arrangement of lithofacies. We measured permeability (k) and perchloroethene sorption distribution coefficient (Kd) for lithofacies that we delineated for samples from the Canadian Forces Base Borden Aquifer. We compiled existing data and collected 57 new cores to characterize a 30 m section of the aquifer near the test location of Mackay et al. (1986). The k and Kd were measured for samples taken at six elevations from all cores to create a data set consisting of nearly 400 colocated measurements. Through analysis of variance (corrected for multiple comparisons), we determined that the 12 originally mapped lithofacies could be grouped into five relatively distinct chemohydrofacies that capture the variability of both transport properties. The mean of ln k by lithofacies was related to the grain size and the variance was relatively consistent. In contrast, both the mean and variance of ln Kd were greater for more poorly sorted lithofacies, which were also typically more coarse-grained. Half of the aquifer sorption capacity occurred in the three highest-sorbing lithofacies but comprised only 20% of its volume. The model of the aquifer that emerged is that of discontinuous scour-fill deposits of medium sand, generally characterized by greater Kd and k, within laterally extensive fine-grained to very fine-grained sands of lower Kd and k. Our findings demonstrate the importance of considering source rock composition, transport, and deposition processes when constructing conceptual models of chemohydrofacies.

  7. Isotopic Tracers for Biogeochemical Processes and Contaminant Transport: Hanford, Washington

    SciTech Connect

    Donald J. DePaolo; John N. Christensen; Mark E. Conrad; and P. Evan Dresel

    2007-04-19

    Our goal is to use isotopic measurements to understand how contaminants are introduced to and stored in the vadose zone, and what processes control migration from the vadose zone to groundwater and then to surface water. We have been using the Hanford Site in south-central Washington as our field laboratory, and our investigations are often stimulated by observations made as part of the groundwater monitoring program and vadose zone characterization activities. Understanding the transport of contaminants at Hanford is difficult due to the presence of multiple potential sources within small areas, the long history of activities, the range of disposal methods, and the continuing evolution of the hydrological system. Observations often do not conform to simple models, and cannot be adequately understood with standard characterization approaches, even though the characterization activities are quite extensive. One of our objectives is to test the value of adding isotopic techniques to the characterization program, which has the immediate potential benefit of addressing specific remediation issues, but more importantly, it allows us to study fundamental processes at the scale and in the medium where they need to be understood. Here we focus on two recent studies at the waste management area (WMA) T-TX-TY, which relate to the sources and transport histories of vadose zone and groundwater contamination and contaminant fluid-sediment interaction. The WMA-T and WMA-TX-TY tank farms are located within the 200 West Area in the central portion of the Hanford Site (Fig. 2). They present a complicated picture of mixed groundwater plumes of nitrate, {sup 99}Tc, Cr{sup 6+}, carbon tetrachloride, etc. and multiple potential vadose zone sources such as tank leaks and disposal cribs (Fig. 3). To access potential vadose zone sources, we analyzed samples from cores C3832 near tank TX-104 and from C4104 near tank T-106. Tank T-106 was involved in a major event in 1973 in which 435,000 L

  8. Contaminant transport in a three-zone wetland: Dispersion and ecological degradation

    NASA Astrophysics Data System (ADS)

    Luo, Jing; Huai, Wenxin; Wang, Ping

    2016-03-01

    To further understand the fate of contaminant transport in real waterways interacting with riparian buffers and adjacent aquatic vegetation, solute dispersion is analytically explored for three-zone wetland flows with usually high Péclet number in this paper. Ecological effects are also taken into account. Environmental dispersion is addressed independently via an exponential transformation of the basic formulation of mass transfer in the context of porous media flow. After rigorously generalizing Taylor's classical analysis, asymptotic analysis was used instead of the method of concentration moment or multi-scale analysis to simplify the examination. The mean concentration expansion base in Gill's method is adopted to model concentration deviations produced in the lateral-average operation. With a previously derived velocity profile, environmental dispersivity is obtained, effectively illustrating the effects of critical dimensionless parameters. Analytical expressions for evolution of the lateral mean concentration and critical length of the contaminant cloud are determined by combining the effects of both hydraulic dispersion and ecological degradation. An application example is provided to illustrate the evolution of contaminant cloud in terms of the critical length and duration with concentration greater than a given environmental standard level. Results show that for three-zone wetlands, the duration is clearly increased while the region affected by the contaminant cloud is slightly smaller than that for two-zone wetland flows.

  9. EVALUATION OF THE STATE-OF-THE-ART CONTAMINATED SEDIMENT TRANSPORT AND FATE MODELING SYSTEM

    EPA Science Inventory

    Modeling approaches for evaluating the transport and fate of sediment and associated contaminants are briefly reviewed. The main emphasis is on: 1) the application of EFDC (Environmental Fluid Dynamics Code), the state-of-the-art contaminated sediment transport and fate public do...

  10. Transport and Degradation of Semivolatile Hydrocarbons in a Petroleum-Contaminated Aquifer, Bemidji, Minnesota

    USGS Publications Warehouse

    Furlong, E.T.; Koleis, J.C.; Aiken, G.R.

    1997-01-01

    Polycyclic aromatic hydrocarbons (PAH) were used as probes to identify the processes controlling the transport and fate of aqueous semivolatile hydrocarbons (SVHCs) in a petroleum-contaminated aquifer near Bemidji, Minnesota. PAH and other SVHCs were isolated from ground water by field solid-phase extraction and analyzed using gas chromatography/mass spectrometry. Close to the oil body, aqueous aliphatic hydrocarbon compositions are substantially different from the parent oil, suggesting microbial alteration prior to or during dissolution. Aqueous PAH concentrations are elevated above oil-water equilibrium concentrations directly beneath the oil and decrease dramatically at distances ranging from the 25 to 65 m downgradient from the leading edge of the oil body. Variations in downgradient distributions of naphthalene, fluorene and phenanthrene, coupled with their biodegradation, partitioning and volatility characteristics, suggest that the PAH are useful probes for distinguishing between the biogeochemical processes affecting SVHC transport and persistence in ground water.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    PubMed

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

    2013-03-01

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

  13. Mineral-Water Interface Processes Affecting Uranium Fate in Contaminated Sediments

    NASA Astrophysics Data System (ADS)

    Catalano, J. G.

    2011-12-01

    Widespread uranium contamination of soil, sediments, and groundwater systems has resulted from mining activities, nuclear weapon production, and energy generation. The fate and transport of uranium in such systems is strongly affected by geochemical processes occurring at mineral-water interfaces. I will present a summary of the mineral-water interface processes found to affect uranium fate in example contaminated sediments at the U.S. Department of Energy's Hanford sites and in related model systems. Processes occurring under oxic conditions will be the primary focus of this talk as under these conditions uranium is most mobile and thus presents the greatest hazard. Three dominant solid-phase uranium species are observed in contaminated soil and sediments at the Hanford site: uranyl silicates, uranyl phosphates, and uranyl adsorbed to clays and iron oxides. In deep sediments, uranyl silicates are found in microfractures in feldspar grains, likely because slow diffusion in such fractures maintains a high silicate activity. Such silicates are also found in waste-impacted shallow sediments and soil; waste fluids or evaporative processes may have generated the silicate activity needed to produce such phases. Uranyl phosphates are less abundant, occurring primarily in shallow sediments exposed to P-bearing waste fluids. However, remediation approaches under consideration may produce substantial quantities of uranyl phosphates in the future. Adsorbed uranyl is dispersed throughout contaminated soils and shallow sediments and likely has the greatest potential for remobilization. Analogue studies show that precipitation of uranyl phosphates is rapid when such phases are supersaturated and that both homogeneous and heterogeneous nucleation may occur. Specific adsorption of uranyl to minerals is strongly affected by the presence of complexation anions. Carbonate suppresses uranyl adsorption but also forms uranyl-carbonate ternary surface complexes. At conditions below

  14. Contaminant transport model validation: The Oak Ridge Reservation

    SciTech Connect

    Lee, R.R.; Ketelle, R.H.

    1988-09-01

    In the complex geologic setting on the Oak Ridge Reservation, hydraulic conductivity is anisotropic and flow is strongly influenced by an extensive and largely discontinuous fracture network. Difficulties in describing and modeling the aquifer system prompted a study to obtain aquifer property data to be used in a groundwater flow model validation experiment. Characterization studies included the performance of an extensive suite of aquifer test within a 600-square-meter area to obtain aquifer property values to describe the flow field in detail. Following aquifer test, a groundwater tracer test was performed under ambient conditions to verify the aquifer analysis. Tracer migration data in the near-field were used in model calibration to predict tracer arrival time and concentration in the far-field. Despite the extensive aquifer testing, initial modeling inaccurately predicted tracer migration direction. Initial tracer migration rates were consistent with those predicted by the model; however, changing environmental conditions resulted in an unanticipated decay in tracer movement. Evaluation of the predictive accuracy of groundwater flow and contaminant transport models on the Oak Ridge Reservation depends on defining the resolution required, followed by field testing and model grid definition at compatible scales. The use of tracer tests, both as a characterization method and to verify model results, provides the highest level of resolution of groundwater flow characteristics. 3 refs., 4 figs.

  15. Modeling uranium transport in acidic contaminated groundwater with base addition

    SciTech Connect

    Zhang, Fan; Luo, Wensui; Parker, Jack C.; Brooks, Scott C; Watson, David B; Jardine, Philip; Gu, Baohua

    2011-01-01

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  16. Modeling uranium transport in acidic contaminated groundwater with base addition.

    PubMed

    Zhang, Fan; Luo, Wensui; Parker, Jack C; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

    2011-06-15

    This study investigates reactive transport modeling in a column of uranium(VI)-contaminated sediments with base additions in the circulating influent. The groundwater and sediment exhibit oxic conditions with low pH, high concentrations of NO(3)(-), SO(4)(2-), U and various metal cations. Preliminary batch experiments indicate that additions of strong base induce rapid immobilization of U for this material. In the column experiment that is the focus of the present study, effluent groundwater was titrated with NaOH solution in an inflow reservoir before reinjection to gradually increase the solution pH in the column. An equilibrium hydrolysis, precipitation and ion exchange reaction model developed through simulation of the preliminary batch titration experiments predicted faster reduction of aqueous Al than observed in the column experiment. The model was therefore modified to consider reaction kinetics for the precipitation and dissolution processes which are the major mechanism for Al immobilization. The combined kinetic and equilibrium reaction model adequately described variations in pH, aqueous concentrations of metal cations (Al, Ca, Mg, Sr, Mn, Ni, Co), sulfate and U(VI). The experimental and modeling results indicate that U(VI) can be effectively sequestered with controlled base addition due to sorption by slowly precipitated Al with pH-dependent surface charge. The model may prove useful to predict field-scale U(VI) sequestration and remediation effectiveness.

  17. Nitrogen Transport from Atmospheric Deposition and Contaminated Groundwater to Surface Waters on a Watershed Scale.

    NASA Astrophysics Data System (ADS)

    Showers, W. J.; Demaster, D.

    2005-12-01

    Increasing nitrate contamination of surface water and groundwater is a problem in regions of intensive agriculture and near urban wastewater treatment facilities that land-apply biosolids. The 15N composition of groundwater nitrate has been used to assess potential sources of nitrogen contamination. But because of transformations of nitrogen within the hydrological system, contaminant source tracing with nitrogen isotopes has been complicated. We have used multiple isotope tracers of nitrate (15N, 17O, 18O) to distinguish between different N contamination sources, areas of extensive denitrification, and areas of atmospheric N deposition on the NC coastal plain and piedmont. Areas of extensive denitrification are often associated with hydric soils. The distribution of hydric soils on field and watershed scales correlates with surface and ground water quality degradation. The distribution of hydric soils may thus be an important element in prediction of environmental impacts of agriculture. Transport of atmospheric nitrogen into surface waters as indicated by the 17O of nitrate is event driven. Most surface waters in our study area have low concentrations of nitrate 17O, indicating that the importance of atmospheric N has been overestimated in riverine N flux from watersheds. However, when the atmospheric N flux is integrated over a discharge event, atmospheric N can approach 25 % of the total N riverine flux in urban areas. More work needs to be completed with multiple isotopic tracers and GIS analysis on watershed scales. Using a GIS / isotope approach, areas where the isotopic signature has been affected by denitrification can be predicted, and remediation efforts can be focused on potential areas of N contamination where extensive denitrification is unlikely to occur.

  18. Critical contaminant/critical pathway analysis - surface water transport for nonradioactive contaminants

    SciTech Connect

    Chen, Kuo-Fu

    1996-11-01

    The health risks for an individual exposed to contaminants released from SRS outfalls from 1989 to 1995 were estimated. The exposure pathways studied are ingestion of drinking water, ingestion of contaminated fish and dermal contact with contaminants in water while swimming. The estimated incremental risks for an individual developing cancer vary from 3.E-06 to 1.0E-05. The estimated total exposure chronic noncancer hazard indices vary from 6.E-02 to 1.E-01. The critical contaminants were ranked based on their cancer risks and chronic noncarcinogenic hazard quotients. For cancer risks, the critical contaminants released from SRS outfalls are arsenic, tetrachloroethylene, and benzene. For chronic noncarcinogenic risks, the critical contaminants released from srs outfalls are cadmium, arsenic, silver, chromium, mercury, selenium, nitrate, manganese, zinc, nickel, uranium, barium, copper, tetrachloroethylene, cyanide, and phenol. The critical pathways in decreasing risk order are ingestion of contaminated fish, ingestion of drinking water and dermal contact with contaminants in water while swimming.

  19. Wind-induced contaminant transport in near-surface soils with application to radon entry into buildings

    SciTech Connect

    Riley, W J

    1996-05-01

    Indoor air exposures to gaseous contaminants originating in soil can cause large human health risks. To predict and control these exposures, the mechanisms that affect vapor transport in near-surface soils need to be understood. In particular, radon exposure is a concern since average indoor radon concentrations lead to much higher risks than are generally accepted for exposure to other environmental contaminants. This dissertation examines an important component of the indoor radon problem: the impacts of wind on soil-gas and radon transport and entry into buildings. The research includes experimental and modeling studies of wind`s interactions with a building`s superstructure and the resulting soil-gas and radon flows in the surrounding soil. In addition to exploring the effects of steady winds, a novel modeling technique is developed to examine the impacts of fluctuating winds on soil-gas and radon transport.

  20. Comparison of some parallel Krylov solvers for large scale groundwater contaminant transport simulations

    SciTech Connect

    Mahinthakumar, G.; Saied, F.; Valocchi, A.J.

    1997-03-01

    Some popular iterative solvers for non-symmetric systems arising from the finite-element discretization of three-dimensional groundwater contaminant transport problem are implemented and compared on distributed memory parallel platforms. This paper attempts to determine which solvers are most suitable for the contaminant transport problem under varied conditions for large scale simulations on distributed parallel platforms. The original parallel implementation was targeted for the 1024 node Intel paragon platform using explicit message passing with the NX library. This code was then ported to SGI Power Challenge Array, Convex Exemplar, and Origin 2000 machines using an MPI implementation. The performance of these solvers is studied for increasing problem size, roughness of the coefficients, and selected problem scenarios. These conditions affect the properties of the matrix and hence the difficulty level of the solution process. Performance is analyzed in terms of convergence behavior, overall time, parallel efficiency, and scalability. The solvers that are presented are BiCGSTAB, GMRES, ORTHOMIN, and CGS. A simple diagonal preconditioner is used in this parallel implementation for all the methods. The results indicate that all methods are comparable in performance with BiCGSTAB slightly outperforming the other methods for most problems. The authors achieved very good scalability in all the methods up to 1024 processors of the Intel Paragon XPS/150. They demonstrate scalability by solving 100 time steps of a 40 million element problem in about 5 minutes using either BiCGSTAB or GMRES.

  1. Advances in Understanding Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface

    NASA Astrophysics Data System (ADS)

    Karapanagioti, H. K.; Werner, D.; Werth, C.

    2012-04-01

    The results of a call for a special issue that is now in press by the Journal of Contaminant Hydrology will be presented. This special issue is edited by the authors and is entitled "Sorption and Transport Processes Affecting the Fate of Environmental Pollutants in the Subsurface". A short abstract of each paper will be presented along with the most interesting results. Nine papers were accepted. Pollutants studied include: biocolloids, metals (arsenic, chromium, nickel), organic compounds such as hydrocarbons, chlorinated hydrocarbons, micropollutants (PAHs, PCBs), pesticides (glyphosate, 2,4-D). Findings presented in the papers include a modified batch reactor system to study equilibrium-reactive transport problems of metals. Column studies along with theoretical approximations evaluate the combined effects of grain size and pore water velocity on the transport in water saturated porous media of three biocolloids. A polluted sediment remediation method is evaluated considering site-specific conditions through monitoring results and modelling. A field study points to glogging and also sorption as mechanisms affecting the effectiveness of sub-surface flow constructed wetlands. A new isotherm model combining modified traditionally used isotherms is proposed that can be used to simulate pH-dependent metal adsorption. Linear free energy relationships (LFERs) demonstrate ability to predict slight isotope shifts into the groundwater due to sorption. Possible modifications that improve the reliability of kinetic models and parameter values during the evaluation of experiments that assess the sorption of pesticides on soils are tested. Challenges in selecting groundwater pollutant fate and transport models that account for the effect of grain-scale sorption rate limitations are evaluated based on experimental results and are discussed based on the Damköhler number. Finally, a thorough review paper presents the impact of mineral micropores on the transport and fate of

  2. PREDICTING SUBSURFACE CONTAMINANT TRANSPORT AND TRANSFORMATION: CONSIDERATIONS FOR MODEL SELECTION AND FIELD VALIDATION

    EPA Science Inventory

    Predicting subsurface contaminant transport and transformation requires mathematical models based on a variety of physical, chemical, and biological processes. The mathematical model is an attempt to quantitatively describe observed processes in order to permit systematic forecas...

  3. Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers

    SciTech Connect

    DALE, R.N.

    2000-05-01

    Long Length Contaminated Equipment Removal System Receiver Trailer and Transport Trailer require a configuration management plan for design, requirements and operations baseline documents. This report serves as the plan for the Trailers.

  4. Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers

    SciTech Connect

    DALE, R.N.

    2000-12-18

    Long Length Contaminated Equipment Removal System Receiver Trailers and Transport Trailers require identification and control for the design, requirements and operations baseline documents. This plan serves as those controls for the subject trailers.

  5. Computational modeling of 137Cs contaminant transfer associated with sediment transport in Abukuma River.

    PubMed

    Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I

    2015-01-01

    A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers. PMID:24909793

  6. Computational modeling of 137Cs contaminant transfer associated with sediment transport in Abukuma River.

    PubMed

    Iwasaki, T; Nabi, M; Shimizu, Y; Kimura, I

    2015-01-01

    A numerical model capable of simulating the transfer of (137)Cs in rivers associated with transport of fine sediment is presented. The accident at Fukushima Dai-ichi Nuclear Power Plant (FDNPP) released radionuclides into the atmosphere, and after fallout several radionuclides in them, such as radiocesium ((134)Cs, (137)Cs) and radioiodine ((131)I) were adsorbed on surface soil particles around FDNPP and transported by surface water. To understand the transport and deposition of the radioactive contaminant along with surface soil particles and its flux to the ocean, we modeled the transport of the (137)Cs contaminant by computing the water flow and the associated washload and suspended load transport. We have developed a two-dimensional model to simulate the plane flow structure, sediment transport and associated (137)Cs contaminant transport in rivers by combining a shallow water flow model and an advection-diffusion equation for the transport of sediment. The proposed model has been applied to the lower reach of Abukuma River, which is the main river in the highly contaminated area around FDNPP. The numerical results indicate that most (137)Cs supplied from the upstream river reach with washload would directly reach to Pacific Ocean. In contrast, washload-oriented (137)Cs supplied from the upstream river basin has a limited role in the radioactive contamination in the river. The results also suggest that the proposed framework of computational model can be a potential tool for understanding the sediment-oriented (137)Cs behavior in rivers.

  7. Time series analysis of contaminant transport in the subsurface: applications to conservative tracer and engineered nanomaterials.

    PubMed

    Bai, Chunmei; Li, Yusong

    2014-08-01

    Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed. PMID:24987973

  8. Time series analysis of contaminant transport in the subsurface: Applications to conservative tracer and engineered nanomaterials

    NASA Astrophysics Data System (ADS)

    Bai, Chunmei; Li, Yusong

    2014-08-01

    Accurately predicting the transport of contaminants in the field is subject to multiple sources of uncertainty due to the variability of geological settings, the complexity of field measurements, and the scarcity of data. Such uncertainties can be amplified when modeling some emerging contaminants, such as engineered nanomaterials, when a fundamental understanding of their fate and transport is lacking. Typical field work includes collecting concentration at a certain location for an extended period of time, or measuring the movement of plume for an extended period time, which would result in a time series of observation data. This work presents an effort to evaluate the possibility of applying time series analysis, particularly, autoregressive integrated moving average (ARIMA) models, to forecast contaminant transport and distribution in the subsurface environment. ARIMA modeling was first assessed in terms of its capability to forecast tracer transport at two field sites, which had different levels of heterogeneity. After that, this study evaluated the applicability of ARIMA modeling to predict the transport of engineered nanomaterials at field sites, including field measured data of nanoscale zero valent iron and (nZVI) and numerically generated data for the transport of nano-fullerene aggregates (nC60). This proof-of-concept effort demonstrates the possibility of applying ARIMA to predict the contaminant transport in the subsurface environment. Like many other statistical models, ARIMA modeling is only descriptive and not explanatory. The limitation and the challenge associated with applying ARIMA modeling to contaminant transport in the subsurface are also discussed.

  9. Geohydrology and contamination at the Michigan Department of Transportation maintenance garage area, Kalamazoo County, Michigan

    USGS Publications Warehouse

    Lynch, E.A.; Huffman, G.C.

    1996-01-01

    A leaking underground storage tank was removed from the Michigan Department of Transportation maintenance garage area in Kalamazoo County., Mich., in 1985. The tank had been leaking unleaded gasoline. Although a remediation system was operational at the site for several years after the tank was removed, ground-water samples collected from monitoring wells in the area consistently showed high concentrations of benzene, toluene. ethylbenzene, and xylenes--indicators of the presence of gasoline. The U.S. Geological Survey did a study in cooperation with the Michigan Department of Transportation, to define the geology, hydrology, and occurrence of gasoline contamination in the maintenance garage area. The aquifer affected by gasoline contamination is an unconfined glaci'a.l sand and gravel aquifer. The average depth to water in the study area is about 74.7 feet. Water-level fluctuations are small; maximum fluctuation was slightly more than 1 foot during August 1993-August 1994. Hydraulic conductivities based on aquifer-test data collected for the study and estimated by use of the Cooper-Jacob method of solution ranged from 130 to 144 feet per day. Ground water is moving in an east-southeasterly direction at a rate of about I foot per day. Leakage from perforated pipes leading from the underground storage tanks to the pump station was identified as a second source of gasoline contamination to saturated and unsaturated zones. The existence of this previously unknown second source is part of the reason that previous remediation efforts were ineffective. Residual contaminants in the unsaturated zone are expected to continue to move to the water table with recharge, except in a small area covered by asphalt at the land surface. The gasoline plume from the perforated pipe source has merged with that from the leaking underground storage tank, and the combined plume in the saturated zone is estimated to cover an area of 30,000 square feet. The combined plume is in the upper 20

  10. Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media.

    PubMed

    Kanti Sen, Tushar; Khilar, Kartic C

    2006-02-28

    In this review article, the authors present up-to-date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment/plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here the authors first present the compilation on in situ colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role in inorganic and organic contaminants transport in porous media. The important aspects of this article are as follows: (i) it gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviews the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon also depends on various factors such as concentration of colloidal fines, superficial velocity and bead-to-particle size ratio. This plugging-based contaminant transport can be used to develop containment technique in soil and groundwater remediation. (ii) It also presents the importance of critical salt concentration (CSC), critical ionic strength for mixed salt, critical shear stressor critical particle concentration (CPC) on in situ colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) It also reviews another class of colloidal fines called biocolloids and their transport in porous media. Finally, the authors highlight the future research based on their critical review on colloid-associated contaminant transport in saturated porous media. PMID:16324681

  11. Characterization of Contaminant Transport Using Naturally-Occurring U-Series Disequilibria

    SciTech Connect

    TEH-LUNG KU

    2001-06-01

    Study the migration of nuclear waste contaminants in subsurface fractured systems using naturally occurring uranium and thorium-series radionuclides as tracers under in-situ physico-chemical and hydrogeologic conditions. Radioactive disequilibria among members of these decay-series nuclides can provide information on the rates of adsorption-desorption and transport of contaminants as well as on fluid transport and rock dissolution in a natural setting.

  12. Review on subsurface colloids and colloid-associated contaminant transport in saturated porous media.

    PubMed

    Kanti Sen, Tushar; Khilar, Kartic C

    2006-02-28

    In this review article, the authors present up-to-date developments on experimental, modeling and field studies on the role of subsurface colloidal fines on contaminant transport in saturated porous media. It is a complex phenomenon in porous media involving several basic processes such as colloidal fines release, dispersion stabilization, migration and fines entrapment/plugging at the pore constrictions and adsorption at solid/liquid interface. The effects of these basic processes on the contaminant transport have been compiled. Here the authors first present the compilation on in situ colloidal fines sources, release, stabilization of colloidal dispersion and migration which are a function of physical and chemical conditions of subsurface environment and finally their role in inorganic and organic contaminants transport in porous media. The important aspects of this article are as follows: (i) it gives not only complete compilation on colloidal fines-facilitated contaminant transport but also reviews the new role of colloidal fines in contaminant retardation due to plugging of pore constrictions. This plugging phenomenon also depends on various factors such as concentration of colloidal fines, superficial velocity and bead-to-particle size ratio. This plugging-based contaminant transport can be used to develop containment technique in soil and groundwater remediation. (ii) It also presents the importance of critical salt concentration (CSC), critical ionic strength for mixed salt, critical shear stressor critical particle concentration (CPC) on in situ colloidal fines release and migration and consequently their role on contaminant transport in porous media. (iii) It also reviews another class of colloidal fines called biocolloids and their transport in porous media. Finally, the authors highlight the future research based on their critical review on colloid-associated contaminant transport in saturated porous media.

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

    SciTech Connect

    Truex, Michael J.; Oostrom, Martinus; Tartakovsky, Guzel D.

    2015-09-01

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

  14. Hydrogeological factors affecting the multiple plumes of chlorinated contaminants in an industrial complex, Wonju, Korea

    NASA Astrophysics Data System (ADS)

    Yang, J.; Kaown, D.; Lee, H.; Lee, K.

    2010-12-01

    Apparent plume attenuations of multiple chlorinated contaminants such as TCE, carbon tetrachloride, and its daughter products at an industrial complex, Wonju, Korea were examined through various hydraulic tests and six rounds of groundwater quality analyses. Aquifer media properties and hydrogeologic factors affecting the distribution and attenuation of multiple contaminants were investigated and key attributes were evaluated. The study area has vertically heterogeneous properties from top alluvial layer to crystalline rocks while the weathered fractured layer above intact Jurassic biotite granite acts as the main layer for groundwater flow and aqueous phase multiple contaminants migration. Aerial heterogeneity in surface conditions plays an important role for groundwater recharge because the industrial complex is mostly paved by asphalt and concrete. Due to limited recharge area and concentrated precipitation in summer season, seasonal effects of contaminant plume distribution diminish as the distance increase from the area of recharge. This study analyzed how differently the solute and contaminant concentrations response to the seasonal recharge. For the analyses, the study site was divided into three zones and four transects were established. Groundwater and solute mass balances were estimated by computing groundwater and solute mass flux through transects. The effects of groundwater pumping, groundwater flow and contaminant degradation were examined to simulate the solutes and contaminant concentrations. General tendency of the water quality and contaminant concentration were reproducible with the effects of major components such as groundwater recharge, pumping and estimated degradation rate.

  15. Hydrologic issues in arid, unsaturated systems and implications for contaminant transport

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.; Tyler, Scott W.; Wierenga, Peter J.

    1997-11-01

    Analysis of unsaturated flow and transport in arid regions is important, not only in water resource evaluation but in contaminant transport as well, particularly in siting waste disposal facilities and in remediating contaminated sites. The water fluxes under consideration have a magnitude close to the errors inherent in measuring or in calculating these water fluxes, which makes it difficult to resolve basic issues such as direction and rate of water movement and controls on unsaturated flow. The purpose of this paper is to review these issues on the basis of unsaturated zone studies in arid settings. Because individual techniques for estimating water fluxes in the unsaturated zone have limitations, a variety of physical measurements and environmental tracers should be used to provide multiple, independent lines of evidence to quantify flow and transport in arid regions. The direction and rate of water flow are affected not only by hydraulic head gradients but also by temperature and air pressure gradients. The similarity of water fluxes in a variety of settings in the southwestern United States indicates that vegetative cover may be one of the primary controls on the magnitude of water flow in the unsaturated zone; however, our understanding of the role of plants is limited. Most unsaturated flow in arid systems is focused beneath topographic depressions, and diffuse flow is limited. Thick unsaturated sections and low water fluxes typical of many arid regions result in preservation of paleoclimatic variations in water flux and suggest that deep vadose zones may be out of equilibrium with current climate. Whereas water movement along preferred pathways is common in humid sites, field studies that demonstrate preferential flow are restricted mostly to fractured rocks and root zones in arid regions. Results of field studies of preferential flow in humid sites, generally restricted to the upper 1-2 m because of shallow water tables, cannot be applied readily to thick

  16. Modeling contaminant transport and remediation at an acrylonitrile spill site in Turkey.

    PubMed

    Sengör, S Sevinç; Unlü, Kahraman

    2013-07-01

    The August 1999 earthquake in Turkey damaged three acrylonitrile (AN) storage tanks at a plant producing synthetic fiber by polymerization. A numerical modeling study was carried out to analyze the groundwater flow and contaminant (AN) transport at the spill site. This study presents the application of a numerical groundwater model to determine the hydrogeological parameters of the site, where such data were not available during the field surveys prior to the simulation studies. The two- and three-dimensional transient flow and transport models were first calibrated using the first 266days of observed head and concentration data and then verified using the remaining 540-day observed data set. Off-site migration of the contaminant plume was kept under control within the site boundaries owing to the favorable geology of the site, the characteristics of the local groundwater flow regime and the pumping operations. As expected, the applied pump-and-treat system was effective at high-permeability zones, but not fully effective at low-permeability zones. The results of long-term simulations for unconfined aquifer showed that the size of the plume in the high permeability zone shrank significantly due to the dilution by natural recharge. However, in the low permeability zone, it was not significantly affected. The study showed that accurate and sufficient data regarding the source characteristics, concentration and groundwater level measurements, groundwater pumping rates and their durations at each of the extraction points involved in the pump-and-treat system along with the hydrogeological site characterization are the key parameters for successful flow and transport model calibrations.

  17. Soil and biosolid nano- and macro-colloid properties and contaminant transport behavior

    NASA Astrophysics Data System (ADS)

    Ghezzi, Jessique L.

    Despite indications that they are potential contaminant transport systems and threats to groundwater quality, very little effort has been invested in comparing contaminant transport behavior of natural environmental nanocolloids and their corresponding macrocolloid fractions in the presence of As, Se, Pb, and Cu contaminants. This study involved physico-chemical, mineralogical, stability and contaminant-transport characterizations of nano- (< 100 nm) and macro-colloids (100-2000 nm) fractionated from three Kentucky soils and one biosolid waste. Particle size was investigated with SEM/TEM and dynamic light scattering. Surface reactivity was estimated using CEC and zeta potential. Mineralogical composition was determined by XRD, FTIR, and thermogravimetric analyses. Sorption isotherms assessed affinities for Cu2+, Pb2+, AsO3-, and SeO4 -2 contaminants, while settling kinetics experiments of suspensions at 0, 2 and 10 mg/L contaminants determined stability and transportability potential. Undisturbed 18x30 cm KY Ashton Loam soil monoliths were also used for transport experiments, involving infusion of 50 mg L-1 colloid suspensions spiked with 2 mg L-1 mixed contaminant loads in unsaturated, steady state, unit gradient downward percolation experiments. Overall, nanocolloids exhibited greater stability over corresponding macrocolloids in the presence and absence of contaminants following specific mineralogy trends. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the nanocolloid fractions, in spite of some hindrance by nano-aggregation phenomena. In the transport experiments, nanocolloids eluted significantly higher concentrations of colloids, total, and colloid-bound metals than corresponding macrocolloids. Contaminant elutions varied by colloid type, mineralogy and contaminant, with the following sequences: soil-colloids>bio-colloids, smectitic

  18. Prediction of contaminant fate and transport in potable water systems using H2OFate

    NASA Astrophysics Data System (ADS)

    Devarakonda, Venkat; Manickavasagam, Sivakumar; VanBlaricum, Vicki; Ginsberg, Mark

    2009-05-01

    BlazeTech has recently developed a software called H2OFate to predict the fate and transport of chemical and biological contaminants in water distribution systems. This software includes models for the reactions of these contaminants with residual disinfectant in bulk water and at the pipe wall, and their adhesion/reactions with the pipe walls. This software can be interfaced with sensors through SCADA systems to monitor water distribution networks for contamination events and activate countermeasures, as needed. This paper presents results from parametric calculations carried out using H2OFate for a simulated contaminant release into a sample water distribution network.

  19. The Unpredictable Errors of Micro Tactile Metrology - Factors Affecting Stylus tip Contamination

    NASA Astrophysics Data System (ADS)

    Kinnell, P.; Habeb, R.

    2013-12-01

    In 3D tactile micro-metrology the contamination of probing devices is a major problem that affects the accuracy and repeatability of measured dimensions. Despite a large body of research in the field of micro CMM and micro probe design there is limited research which has been done so far to explain and tackle this problem. In this work, experimental probing on a range of materials using a micro coordinate measuring machine was conducted to investigate the mechanism of stylus tip contamination. In addition the effects of surface finish on the build-up of stylus tip contamination were also studied. The results provide practitioners with guidelines which allow for the likely build-up of stylus tip contamination to be minimized based on sample material type and surface finish.

  20. COLLOID MOBILIZATION AND TRANSPORT IN CONTAMINANT PLUMES: FILED EXPERIMENTS, LABORATORY EXPERIMENTS, AND MODELING

    EPA Science Inventory

    The major hypothesis driving this research, that the transport of colloids in a contaminant plume is limited by the advance of the chemical agent causing colloid mobilization, was tested by (1) examining the dependence of colloid transport and mobilization on chemical perturbatio...

  1. BIODEGRADATION DURING CONTAMINANT TRANSPORT IN POROUS MEDIA: 1. MATHEMATICAL ANALYSIS OF CONTROLLING FACTORS. (R825415)

    EPA Science Inventory

    Abstract

    Interest in coupled biodegradation and transport of organic contaminants has expanded greatly in the past several years. In a system in which biodegradation is coupled with solute transport, the magnitude and rate of biodegradation is influenced not only by pr...

  2. Exact analytical solutions for contaminant transport in rivers 2. Transient storage and decay chain solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Contaminant transport processes in streams, rivers, and other surface water bodies can be analyzed or predicted using the advection-dispersion equation and related transport models. In part 1 of this two-part series we presented a large number of one- and multi-dimensional analytical solutions of t...

  3. FACT (Version 2.0) - Subsurface Flow and Contaminant Transport Documentation and User's Guide

    SciTech Connect

    Aleman, S.E.

    2000-05-05

    This report documents a finite element code designed to model subsurface flow and contaminant transport, named FACT. FACT is a transient three-dimensional, finite element code designed to simulate isothermal groundwater flow, moisture movement, and solute transport in variably saturated and fully saturated subsurface porous media.

  4. Contaminant transport in two central Missouri karst recharge areas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Karst watersheds with significant losing streams represent a particularly vulnerable setting for ground water contamination because of the direct connection to surface water. Because of the existing agricultural land-use and future likelihood of urbanization, two losing stream karst basins were chos...

  5. Tau phosphorylation affects its axonal transport and degradation

    PubMed Central

    Rodríguez-Martín, Teresa; Cuchillo-Ibáñez, Inmaculada; Noble, Wendy; Nyenya, Fanon; Anderton, Brian H.; Hanger, Diane P.

    2013-01-01

    Phosphorylated forms of microtubule-associated protein tau accumulate in neurofibrillary tangles in Alzheimer's disease. To investigate the effects of specific phosphorylated tau residues on its function, wild type or phosphomutant tau was expressed in cells. Elevated tau phosphorylation decreased its microtubule binding and bundling, and increased the number of motile tau particles, without affecting axonal transport kinetics. In contrast, reducing tau phosphorylation enhanced the amount of tau bound to microtubules and inhibited axonal transport of tau. To determine whether differential tau clearance is responsible for the increase in phosphomimic tau, we inhibited autophagy in neurons which resulted in a 3-fold accumulation of phosphomimic tau compared with wild type tau, and endogenous tau was unaffected. In autophagy-deficient mouse embryonic fibroblasts, but not in neurons, proteasomal degradation of phosphomutant tau was also reduced compared with wild type tau. Therefore, autophagic and proteasomal pathways are involved in tau degradation, with autophagy appearing to be the primary route for clearing phosphorylated tau in neurons. Defective autophagy might contribute to the accumulaton of tau in neurodegenerative diseases. PMID:23601672

  6. Processes affecting soil and groundwater contamination by DNAPL in low-permeability media

    SciTech Connect

    McWhorter, D.B.

    1996-08-01

    This paper is one of a set of focus papers intended to document the current knowledge relevant to the contamination and remediation of soils and ground water by dense, nonaqueous phase liquids (DNAPL). The emphasis is on low permeability media such as fractured clay and till and unconsolidated, stratified formations. Basic concepts pertaining to immiscible-fluid mixtures are described and used to discuss such aspects as DNAPL transport, dissolved-phase transport, and equilibrium mass distributions. Several implications for remediation are presented. 27 refs., 8 figs., 4 tabs.

  7. Influencing factors on particle-bound contaminant transport in the Elbe estuary

    NASA Astrophysics Data System (ADS)

    Kleisinger, Carmen; Haase, Holger; Schubert, Birgit

    2016-04-01

    Particulate matter, i.e. suspended particulate matter and sediments in rivers and estuaries, often are contaminated with trace metals and selected organic contaminants and are mainly associated with fine-grained fractions. Transport processes and fate of particles in estuaries are influenced by several factors, e.g. freshwater discharge, tide, flow velocity and dredging activities (Kappenberg et al., 2007). Understanding the transport processes in estuaries may help to achieve the objectives of the Water Framework Directive and the Marine Strategy Framework Directive. The German Federal Institute of Hydrology (BfG) operates for more than 20 years five monitoring sites in the Elbe estuary in order to monitor the development of particle-bound contaminant concentrations over time and to understand their transport mechanisms. Results of the monitoring revealed freshwater discharge as an important influencing factor on the transport of contaminated particulate matter (Ackermann et al., 2007). The bidirectional transport of marine and fluvial water and particulate matter in estuaries results in a turbidity zone where large amounts of particulate matter are temporarily retained and thus in a delayed transport of particulate matter towards the sea. The extent and the location of the turbidity zone as well as the ratio of highly contaminated fluvial and less contaminated marine sediments at a given location are mainly influenced by the freshwater discharge (Kowalewska et al., 2011). Furthermore, at high freshwater discharge conditions the highly contaminated particulate matter from fluvial origin are transported downstream the estuary, whereas at low freshwater discharges, upstream transport of less contaminated marine sediments prevails. Hence, residence times of particulate matter in the estuary are difficult to estimate. Furthermore, sedimentation areas with flow reduced conditions, e.g. wadden areas or branches of the Elbe estuary, may act as sinks for particle bound

  8. Bacillus cereus spores in raw milk: factors affecting the contamination of milk during the grazing period.

    PubMed

    Christiansson, A; Bertilsson, J; Svensson, B

    1999-02-01

    Psychrotrophic Bacillus cereus is a limiting factor for the shelf-life of pasteurized milk, particularly during the grazing season. Potential sources of contamination and factors that might affect the spore content of milk were studied in detail for a group of eight cows during three 2-wk study periods from June to September over 2 yr. The spore content of milk was strongly associated with the degree of contamination of the teats with soil. High water content of soil, low evaporation of water and dirty access alloys were the most important factors correlating with high spore concentrations. The spore content of soil varied from < 50 to 380,000/g, depending on time and sampling site. The milking equipment did not contribute significantly to the contamination. The spore contents in air during milking (< 100 cfu/m3) and in feed (silage, hay, fresh grass, and concentrates) were too low to be of importance for contamination. The spore content in dung was also low. Further support that soil was the major contamination source was found by comparison of genetic fingerprints by random amplified polymorphic DNA polymerase chain reaction of isolates of B. cereus from soil and milk and by teat cleansing experiments, which resulted in reduced contamination levels in milk.

  9. Factors affecting the spatial pattern of nitrate contamination in shallow groundwater.

    PubMed

    Kaown, Dugin; Hyun, Yunjung; Bae, Gwang-Ok; Lee, Kang-Kun

    2007-01-01

    The elevated level of nitrate in groundwater is a serious problem in Korean agricultural areas. To control and manage groundwater quality, the characterization of groundwater contamination and identification of the factors affecting the nitrate concentration of groundwater are significant. The characterization of groundwater contamination at a hydrologically complex agricultural site in Yupori, Chuncheon (Korea) was undertaken by analyzing the hydrochemical data of groundwater within a statistical framework. Multivariate statistical tools such as cluster analyses and Tobit regression were applied to investigate the spatial variation of nitrate contamination and to analyze the factors affecting the NO3-N concentration in a shallow groundwater system. The groundwater groups from the cluster analysis were consistent with the land use pattern of the study area. The clustered group of a gentle-slope area with lower elevations showed higher NO3-N contamination of groundwater than groups on a hillside with higher elevations. Tobit regression results indicated that the agricultural activity in the vegetable fields and barns were the major factors affecting the elevated NO3-N concentration while the land slopes and elevations were negatively correlated with the NO3-N concentration. This shows that topographic characteristics such as land slopes and elevations should be considered to evaluate the land use impact on shallow groundwater quality.

  10. Wastewater contaminant transport and treatment in a nutrient limited ribbed fen

    NASA Astrophysics Data System (ADS)

    McCarter, C. P. R.; Price, J. S.; Branfireun, B. A.

    2015-12-01

    To minimize the discharge of wastewater contaminants from remote northern communities and mining operations, fen peatlands in sub-arctic regions are used for tertiary wastewater treatment to detain, transform, and remove these contaminants. However, there is a limited understanding of contaminant transport and treatment in fen peatlands, particularly in sub-arctic Canada. To better characterize wastewater contaminant transport and treatment in these systems, approximately 44 m3 day-1 of simulated wastewater, concentrated custom-blend fertilizer (NO3-, PO33-, and SO42-) and Cl- diluted with water, was pumped into a small 0.5 ha sub-arctic ribbed fen continuously for 47 days (July 15th -August 31st 2014). Contaminant concentration of 3 similar ribbed fens varied between 0.0-3.0 mg L-1 over the study period (May - September 2014). An exponential increase in transmissivity (2.4 to 16.8 m2 day-1) as the water table rose (~0.16 m) increased the average linear groundwater velocity (0.5 to 3.4 m day-1) and resulted in rapid SO42- (0.8 m day-1) and Cl- (1.9 m day-1) transport. Notwithstanding the rapid transport of Cl-, diffusion into inactive pores still retarded Cl- transport by a factor of 1.8. Contrary to the rapid transport of SO42- and Cl-, the other contaminants were rapidly removed from the pore water (likely through biological uptake or adsorption) and minimal transport was observed (0.29 and 0.04 m day-1 for PO33- and NO3-, respectively). Northern ribbed fens have a large capacity to detain certain wastewater contaminants (e.g., NO3- and PO33-), yet allow rapid transport of others (e.g., SO42- and Cl-). Thus, these peatlands have the potential to significantly decrease wastewater contamination in northern aquatic environment by both biogeochemical and physical processes but careful management of the hydrology is required to prevent the release of mobile contaminants.

  11. From Sequential Extraction to Transport Modeling, Monitored Natural Attenuation as a Remediation Approach for Inorganic Contaminants

    SciTech Connect

    POWELL, KIMBERLYR.

    2004-05-25

    Implementation of monitored natural attenuation (MNA) as a remediation method requires a mechanistic understanding of the natural attenuation processes occurring at a given site. For inorganic contaminants, natural attenuation typically involves a decrease in metal toxicity and/or mobility. These natural processes include dilution, dispersion, sorption (including adsorption, absorption, and precipitation), and redox processes. In order to better quantify these processes in terms of metal availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site. These laboratory scale studies provide mechanistic information regarding the solid phases in the soils associated with natural attenuation of the contaminant metals. This data provides input to be evaluated in the definition of the contaminant source term as well as transport of contaminants for site transport models.

  12. Solute movement through unsaturated fen peat: Lab and greenhouse experiments for transport study of contaminants from Athabasca oil sands tailing pond water

    NASA Astrophysics Data System (ADS)

    Price, J. S.; Rezanezhad, F.; Graf, M.; Rochefort, L.

    2009-12-01

    In the Athabasca oil sands region, wetlands specially peatland dominate the landscape. Processing oil sands produces large volumes of wet material called oil sands tailing water. Discharge of organic liquid contaminants such as Naphthenic Acids (NA) and Sodium (Na) from tailing waters have a toxic effect on plants in this region. One of the greatest barriers to peatland creation will be the elevated amount of toxins (naphthenic acid, metals and salinity) present in the post-mined landscapes. Variability in solute transport properties in the unsaturated zone is of growing concern due to environmental hazards and there are no many scientific challenges in the field of organic liquid contaminants transport through the unsaturated peat soils. The attenuation, degradation and transport of NA and Na in peat are essentially unknown. The ionizable nature of NA and Na along with the complex structure of peat soils poses challenges to characterizing the transport properties of NA and Na in the filed and laboratory. In this experimental research project, we examine the plant responses in 64 greenhouse tubs filled with peat and process-water; and study the transport and attenuation processes of NA and Na through peat in a series of laboratory column experiments. We developed an analytical method for evaluating the transport and adsorption characteristics of NA and Na to derive a clear understanding of the transport, sorption mechanisms and desorption behaviour of NA and Na with temporal evolution of the solute concentration distribution from groundwater to fen plants. The goal of this research project is to investigate how oil sands process-affected waters will affect peatland vegetation, specifically fen vegetation. In particular, we would like to know how contaminants present in oil sand process affected water will be transported through peat and how typical fen vegetation will react to a realistic contamination scenario in a controlled macrocosm environment? Research that

  13. Characterization of contaminant transport by gravity, capillarity and barometric pumping in heterogeneous. 1998 annual progress report

    SciTech Connect

    Carrigan, C.R.; Hudson, G.B.

    1998-06-01

    'The intent of this research program is to obtain an improved understanding of vadose zone transport processes and to develop field and modeling techniques required to characterize contaminant transport in the unsaturated zone at DOE sites. For surface spills and near-surface leaks of chemicals, the vadose zone may well become a long-term source of contamination for the underlying water table. Transport of contaminants can occur in both the liquid and gas phases of the unsaturated zone. This transport occurs naturally as a result of diffusion, buoyancy forces (gravity), capillarity and barometric pressure variations. In some cases transport can be enhanced by anisotropies present in hydrologic regimes. This is particularly true for gas-phase transport which may be subject to vertical pumping resulting from atmospheric pressure changes. For liquid-phase flows, heterogeneity may enhance the downward transport of contaminants to the water table depending on soil properties and the scale of the surface spill or near-surface leak. Characterization techniques based upon the dynamics of transport processes are likely to yield a better understanding of the potential for contaminant transport at a specific site than methods depending solely on hydrologic properties derived from a borehole. Such dynamic-characterization techniques can be useful for evaluating sites where contamination presently exists as well as for providing an objective basis to evaluate the efficacy of proposed as well as implemented clean-up technologies. The real-time monitoring of processes that may occur during clean-up of tank waste and the mobility of contaminants beneath the Hanford storage tanks during sluicing operations is one example of how techniques developed in this effort can be applied to current remediation problems. In the future, such dynamic-characterization methods might also be used as part of the site-characterization process for determining suitable locations of new DOE facilities

  14. [Solute transport modeling application in groundwater organic contaminant source identification].

    PubMed

    Wang, Shu-Fang; Wang, Li-Ya; Wang, Xiao-Hong; Lin, Pei; Liu, Jiu-Rong; Xin, Bao-Dong; He, Guo-Ping

    2012-03-01

    Investigation and numerical simulation, based on RT3D (reactive transport in 3-dimensions)were used to identify the source of tetrachloroethylene (PCE) and trichloroethylene (TCE) in the groundwater of a city in the north of China and reverse the input intensity. Multiple regressions were applied to analyze the influenced factors of input intensity of PCE and TCE using Stepwise function in Matlab. The results indicate that the factories and industries are the source of the PCE and TCE in groundwater. Natural attenuation was identified and the natural attenuation rates are 93.15%, 61.70% and 61.00% for PCE, and 70.05%, 73.66% and 63.66% for TCE in 173 days. The 4 source points identified by the simulation have released 0.910 6 kg PCE and 95.693 8 kg TCE during the simulation period. The regression analysis results indicate that local precipitation and the thickness of vadose zone are the main factors influencing organic solution transporting from surface to groundwater. The PCE and TCE concentration are found to be 0 and 5 mg x kg(-1) from surface to 35 cm in vadose zone. All above results suggest that PCE and TCE in groundwater are from the source in the surface. Natural attenuation occurred when PCE and TCE transporting from the surface to groundwater, and the rest was transported to groundwater through vadose zone. Local precipitation was one of the critical factors influencing the transportation of PCE and TCE to aquifer through sand, pebble and gravel of the Quaternary.

  15. Aquifer reclamation design: the use of contaminant transport simulation combined with nonlinear programing.

    USGS Publications Warehouse

    Gorelick, S.M.; Voss, C.I.; Gill, P.E.; Murray, W.; Saunders, M.A.; Wright, M.H.

    1984-01-01

    A simulation-management methodology is demonstrated for the rehabilitation of aquifers that have been subjected to chemical contamination. Finite element groundwater flow and contaminant transport simulation are combined with nonlinear optimization. The model is capable of determining well locations plus pumping and injection rates for groundwater quality control. Examples demonstrate linear or nonlinear objective functions subject to linear and nonlinear simulation and water management constraints. -from Authors

  16. Analysis of heat transfer and contaminant transport in fume hoods

    SciTech Connect

    Pathanjali, C.; Rahman, M.M.

    1996-12-31

    The paper presents the analysis of three-dimensional flow patterns and the associated heat and mass transfer mechanisms in a fume hood enclosure. The flow enters the hood through the front window opening (positive x-direction) and leaves the cupboard through an opening on the top of the hood (positive z-direction). The flow was assumed to be fully turbulent. The flow pattern for different sash openings were studied. The flow pattern around an object located at the bottom of the hood was studied for different locations of the object. It was found that air entering the hood proceeds directly to the back wall, impinges it and turns upward toward the top wall and exits through the outlet. The flow finds its way around any object forming a recirculating region at its training surface. With an increase in the sash opening, the velocity becomes higher and the fluid traces the path to the outlet more quickly. The volume occupied by recirculating flow decreases with increase in sash opening. Both temperature and concentration were found to be maximum near the source and gradually decreased as the heated air or gaseous contaminant entrained with incoming air. The local concentration decreased with increase in sash opening area. The results will be very useful to design experiments with optimum sash opening providing adequate disposal of contaminants with minimum use of conditioned air inside the room.

  17. Advances in Dynamic Transport of Organic Contaminants in Karst Groundwater Systems

    NASA Astrophysics Data System (ADS)

    Padilla, I. Y.; Vesper, D.; Alshawabkeh, A.; Hellweger, F.

    2011-12-01

    Karst groundwater systems develop in soluble rocks such as limestone, and are characterized by high permeability and well-developed conduit porosity. These systems provide important freshwater resources for human consumption and ecological integrity of streams, wetlands, and coastal zones. The same characteristics that make karst aquifers highly productive make them highly vulnerable to contamination. As a result, karst aquifers serve as an important route for contaminants exposure to humans and wildlife. Transport of organic contaminants in karst ground-water occurs in complex pathways influenced by the flow mechanism predominating in the aquifer: conduit-flow dominated systems tend to convey solutes rapidly through the system to a discharge point without much attenuation; diffuse-flow systems, on the other hand, can cause significant solute retardation and slow movement. These two mechanisms represent end members of a wide spectrum of conditions found in karst areas, and often a combination of conduit- and diffuse-flow mechanisms is encountered, where both flow mechanisms can control the fate and transport of contaminants. This is the case in the carbonate aquifers of northern Puerto Rico. This work addresses advances made on the characterization of fate and transport processes in karst ground-water systems characterized by variable conduit and/or diffusion dominated flow under high- and low-flow conditions. It involves laboratory-scale physical modeling and field-scale sampling and historical analysis of contaminant distribution. Statistical analysis of solute transport in Geo-Hydrobed physical models shows the heterogeneous character of transport dynamics in karstic units, and its variability under different flow regimes. Field-work analysis of chlorinated volatile organic compounds and phthalates indicates a large capacity of the karst systems to store and transmit contaminants. This work is part of the program "Puerto Rico Testsite for Exploring Contamination

  18. The Oak Ridge Field Research Center : Advancing Scientific Understanding of the Transportation, Fate, and Remediation of Subsurface Contamination Sources and Plumes

    SciTech Connect

    David Watson

    2005-04-18

    Historical research, development, and testing of nuclear materials across this country resulted in subsurface contamination that has been identified at over 7,000 discrete sites across the U.S. Department of Energy (DOE) complex. With the end of the Cold War threat, DOE has shifted its emphasis to remediation, decommissioning, and decontamination of the immense volumes of contaminated groundwater, sediments, and structures at its sites. DOE currently is responsible for remediating 1.7 trillion gallons of contaminated groundwater, an amount equal to approximately four times the daily U.S. water consumption, and 40 million cubic meters of contaminated soil, enough to fill approximately 17 professional sports stadiums.* DOE also sponsors research intended to improve or develop remediation technologies, especially for difficult, currently intractable contaminants or conditions. The Oak Ridge FRC is representative of some difficult sites, contaminants, and conditions. Buried wastes in contact with a shallow water table have created huge reservoirs of contamination. Rainfall patterns affect the water table level seasonally and over time. Further, the hydrogeology of the area, with its fractures and karst geology, affects the movement of contaminant plumes. Plumes have migrated long distances and to surface discharge points through ill-defined preferred flowpaths created by the fractures and karst conditions. From the standpoint of technical effectiveness, remediation options are limited, especially for contaminated groundwater. Moreover, current remediation practices for the source areas, such as capping, can affect coupled processes that, in turn, may affect the movement of subsurface contaminants in unknown ways. Research conducted at the FRC or with FRC samples therefore promotes understanding of the processes that influence the transport and fate of subsurface contaminants, the effectiveness and long-term consequences of extant remediation options, and the

  19. Sensitivity analyses of a colloid-facilitated contaminant transport model for unsaturated heterogeneous soil conditions.

    NASA Astrophysics Data System (ADS)

    Périard, Yann; José Gumiere, Silvio; Rousseau, Alain N.; Caron, Jean

    2013-04-01

    Certain contaminants may travel faster through soils when they are sorbed to subsurface colloidal particles. Indeed, subsurface colloids may act as carriers of some contaminants accelerating their translocation through the soil into the water table. This phenomenon is known as colloid-facilitated contaminant transport. It plays a significant role in contaminant transport in soils and has been recognized as a source of groundwater contamination. From a mechanistic point of view, the attachment/detachment of the colloidal particles from the soil matrix or from the air-water interface and the straining process may modify the hydraulic properties of the porous media. Šimůnek et al. (2006) developed a model that can simulate the colloid-facilitated contaminant transport in variably saturated porous media. The model is based on the solution of a modified advection-dispersion equation that accounts for several processes, namely: straining, exclusion and attachement/detachement kinetics of colloids through the soil matrix. The solutions of these governing, partial differential equations are obtained using a standard Galerkin-type, linear finite element scheme, implemented in the HYDRUS-2D/3D software (Šimůnek et al., 2012). Modeling colloid transport through the soil and the interaction of colloids with the soil matrix and other contaminants is complex and requires the characterization of many model parameters. In practice, it is very difficult to assess actual transport parameter values, so they are often calibrated. However, before calibration, one needs to know which parameters have the greatest impact on output variables. This kind of information can be obtained through a sensitivity analysis of the model. The main objective of this work is to perform local and global sensitivity analyses of the colloid-facilitated contaminant transport module of HYDRUS. Sensitivity analysis was performed in two steps: (i) we applied a screening method based on Morris' elementary

  20. Color image analysis of contaminants and bacteria transport in porous media

    SciTech Connect

    Rashidi, M.; Dehmeshid, J.; Dacini, F.; Cole, L.; Dickenson, E.

    1997-07-01

    Transport of contaminants and bacteria in aqueous heterogeneous saturated porous systems have been studies experimentally using a novel fluorescent microscopic imaging (FMI) technique. The approach involves color visualization and quantification of bacterium and contaminant distributions within a transparent porous column. By introducing stained bacteria and an organic dye as a contaminant into the column and illuminating the porous regions with a planar sheet of laser beam, contaminant and bacterial transport processes through the porous medium can be observed and measured microscopically. A computer controlled CCD camera is used to record the fluorescent images as a function of time. These images are recorded by a frame accurate high resolution VCR and are then analyzed using a color image analysis code written in our laboratories. The color images are digitalized this way and simultaneously concentration and velocity distributions of both contaminant and bacterium are evaluated as a function of time and pore characteristics. The approach provides a unique dynamic probe to observe these transport processes microscopically. These results are extremely valuable in in-situ bioremediation problems since microscopic particle-contaminant-bacterium interactions are the key to understanding and optimization of these processes.

  1. Modeling the emission, transport and deposition of contaminated dust from a mine tailing site.

    PubMed

    Stovern, Michael; Betterton, Eric A; Sáez, A Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P; Russell, Mackenzie R; King, Matt

    2014-01-01

    Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

  2. Accounting for Transport Parameter Uncertainty in Geostatistical Groundwater Contaminant Release History Estimation

    NASA Astrophysics Data System (ADS)

    Ostrowski, J.; Shlomi, S.; Michalak, A.

    2007-12-01

    The process of estimating the release history of a contaminant in groundwater relies on coupling a limited number of concentration measurements with a groundwater flow and transport model in an inverse modeling framework. The information provided by available measurements is generally not sufficient to fully characterize the unknown release history; therefore, an accurate assessment of the estimation uncertainty is required. The modeler's level of confidence in the transport parameters, expressed as pdfs, can be incorporated into the inverse model to improve the accuracy of the release estimates. In this work, geostatistical inverse modeling is used in conjunction with Monte Carlo sampling of transport parameters to estimate groundwater contaminant release histories. Concentration non-negativity is enforced using a Gibbs sampling algorithm based on a truncated normal distribution. The method is applied to two one-dimensional test cases: a hypothetical dataset commonly used in validating contaminant source identification methods, and data collected from a tetrachloroethylene and trichloroethylene plume at the Dover Air Force Base in Delaware. The estimated release histories and associated uncertainties are compared to results from a geostatistical inverse model where uncertainty in transport parameters is ignored. Results show that the a posteriori uncertainty associated with the model that accounts for parameter uncertainty is higher, but that this model provides a more realistic representation of the release history based on available data. This modified inverse modeling technique has many applications, including assignment of liability in groundwater contamination cases, characterization of groundwater contamination, and model calibration.

  3. Modeling the emission, transport and deposition of contaminated dust from a mine tailing site

    PubMed Central

    Stovern, Michael; Betterton, Eric A.; Sáez, A. Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P.; Russell, MacKenzie R.; King, Matt

    2014-01-01

    Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations. PMID:24552963

  4. Impact of scaling and body movement on contaminant transport in airliner cabins

    NASA Astrophysics Data System (ADS)

    Mazumdar, Sagnik; Poussou, Stephane B.; Lin, Chao-Hsin; Isukapalli, Sastry S.; Plesniak, Michael W.; Chen, Qingyan

    2011-10-01

    Studies of contaminant transport have been conducted using small-scale models. This investigation used validated Computational Fluid Dynamics (CFD) to examine if a small-scale water model could reveal the same contaminant transport characteristics as a full-scale airliner cabin. But due to similarity problems and the difficulty of scaling the geometry, a perfect scale up from a small water model to an actual air model was found to be impossible. The study also found that the seats and passengers tended to obstruct the lateral transport of the contaminants and confine their spread to the aisle of the cabin. The movement of a crew member or a passenger could carry a contaminant in its wake to as many rows as the crew member or passenger passed. This could be the reason why a SARS infected passenger could infect fellow passengers who were seated seven rows away. To accurately simulate the contaminant transport, the shape of the moving body should be a human-like model.

  5. [Contamination with Sphingomonas paucimobilis: about seven cases isolated in conservation and transport mediums of corneal grafts].

    PubMed

    Bourigault, C; Daniel, L; Jourdain, S; Hardy, E; Heriaud, K; Virmaux, M; Eniafe-Eveillard, B; Lejeune, B

    2007-03-01

    From September to December 2004, contaminations were found in fifteen conservation and transport mediums of corneal grafts at the tissue bank of Brest, including seven by Sphingomonas paucimobilis. The pulsed-field gel electrophoresis made it possible to establish the genotypic profiles of each strain and to compare them. Similarities were found between certain strains of the contaminated mediums and those of the thermostated double boiler of the tissue bank. The link between the contamination and the defrosting of the mediums in the double boiler was thus established. Measures of prevention are currently proposed to defrost the bottles like the use of a dry bath to replace the current one.

  6. Feed gas contaminant control in ion transport membrane systems

    DOEpatents

    Carolan, Michael Francis; Minford, Eric; Waldron, William Emil

    2009-07-07

    Ion transport membrane oxidation system comprising an enclosure having an interior and an interior surface, inlet piping having an internal surface and adapted to introduce a heated feed gas into the interior of the enclosure, and outlet piping adapted to withdraw a product gas from the interior of the enclosure; one or more planar ion transport membrane modules disposed in the interior of the enclosure, each membrane module comprising mixed metal oxide material; and a preheater adapted to heat a feed gas to provide the heated feed gas to the inlet piping, wherein the preheater comprises an interior surface. Any of the interior surfaces of the enclosure, the inlet piping, and the preheater may be lined with a copper-containing metal lining. Alternatively, any of the interior surfaces of the inlet piping and the preheater may be lined with a copper-containing metal lining and the enclosure may comprise copper.

  7. Assessment of post-contamination treatments affecting different bonding stages to dentin

    PubMed Central

    Elkassas, Dina; Arafa, Abla

    2016-01-01

    Objectives: To assess the effect of cleansing treatments following saliva and blood contamination at different bonding stages to dentin. Materials and Methods: Labial surfaces of 168 permanent maxillary central incisors were ground flat exposing superficial dentin. Specimens were divided into: uncontaminated control (A), contamination after etching (B), contamination after adhesive application (C), contamination after adhesive polymerization (D). Groups were further subdivided according to cleansing treatments into: rinsing (B1, C1, D1), re-etching (B2, D3), sodium hypochlorite application (B3), ethyl alcohol application (C2), acetone application (C3), rinsing and rebonding (D2), re-etching and rebonding (D4). Composite microcylinders were bonded to treated substrates and shear loaded micro-shear bond strength (μSBS) until failure and treated surfaces were examined with scanning electron microscope. Debonded surfaces were classified as adhesive, cohesive or mixed failure. The data were analyzed using one-way ANOVA and Tukey's post hoc test. Results: The μSBS values were ranked as follow; Group B: A > B3 > B2 > B1 > B, Group C: A > C3 > C2 > C1 > C, Group D: A > D4 > D1 = D2 ≥ D3. Debonded surfaces showed adhesive failure in Group B while cohesive failure in Groups C and D. Conclusions: Cleansing treatments differ according to bonding step; re-etching then rebonding suggested if etched substrate or polymerized adhesive were contaminated while acetone application decontaminated affected unpolymerized adhesive. PMID:27403048

  8. Factors Affecting Antioxidant Response in Fish from a Long-term Mercury-Contaminated Reservoir.

    PubMed

    Sevcikova, M; Modra, H; Blahova, J; Dobsikova, R; Kalina, J; Zitka, O; Kizek, R; Svobodova, Z

    2015-11-01

    The objective of this work was to evaluate antioxidant defence and oxidative damage in organs (liver, gills, kidney, and brain) of five fish species (Aspius aspius, Esox lucius, Sander lucioperca, Abramis brama, Rutilus rutilus) from the long-term mercury-contaminated Skalka Reservoir in the Czech Republic. Special emphasis was placed on a comprehensive assessment of the factors that may affect the antioxidant response to mercury in fish. Antioxidant enzymes (glutathione reductase, glutathione peroxidase, and glutathione-S-transferase) did not significantly respond to mercury contamination. Levels of the analysed enzymes and oxidative damage to lipids were predominantly determined by a separate organ factor or species factor, or by the combination of both (p < 0.001). Levels of total glutathione and the reduced/oxidized glutathione ratio were influenced by mercury contamination in combination with their specific organ distribution (p < 0.001). Our results suggest that species and type of organ alone or in combination are more important factors than chronic exposure to mercury contamination with respect to effects on antioxidant defence in fish under field conditions. Our findings suggest that the main antioxidant defensive mechanism in fish from the studied long-term mercury contaminated site was the inter-tissue distribution of glutathione.

  9. Factors Affecting Antioxidant Response in Fish from a Long-term Mercury-Contaminated Reservoir.

    PubMed

    Sevcikova, M; Modra, H; Blahova, J; Dobsikova, R; Kalina, J; Zitka, O; Kizek, R; Svobodova, Z

    2015-11-01

    The objective of this work was to evaluate antioxidant defence and oxidative damage in organs (liver, gills, kidney, and brain) of five fish species (Aspius aspius, Esox lucius, Sander lucioperca, Abramis brama, Rutilus rutilus) from the long-term mercury-contaminated Skalka Reservoir in the Czech Republic. Special emphasis was placed on a comprehensive assessment of the factors that may affect the antioxidant response to mercury in fish. Antioxidant enzymes (glutathione reductase, glutathione peroxidase, and glutathione-S-transferase) did not significantly respond to mercury contamination. Levels of the analysed enzymes and oxidative damage to lipids were predominantly determined by a separate organ factor or species factor, or by the combination of both (p < 0.001). Levels of total glutathione and the reduced/oxidized glutathione ratio were influenced by mercury contamination in combination with their specific organ distribution (p < 0.001). Our results suggest that species and type of organ alone or in combination are more important factors than chronic exposure to mercury contamination with respect to effects on antioxidant defence in fish under field conditions. Our findings suggest that the main antioxidant defensive mechanism in fish from the studied long-term mercury contaminated site was the inter-tissue distribution of glutathione. PMID:26276034

  10. Trace contaminant concentration affects mineral transformation and pollutant fate in hydroxide-weathered Hanford sediments.

    PubMed

    Perdrial, Nicolas; Rivera, Nelson; Thompson, Aaron; O'Day, Peggy A; Chorover, Jon

    2011-12-15

    Prior work has shown that when silicaceous sediments are infused with caustic radioactive waste, contaminant fate is tightly coupled to ensuing mineral weathering reactions. However, the effects of local aqueous geochemical conditions on these reactions are poorly studied. Thus, we varied contaminant concentration and pCO(2) during the weathering of previously uncontaminated Hanford sediments over 6 months and 1 year in a solution of caustic waste (pH 13, high ionic strength). Co-contaminants Sr, Cs and I were added at "low" (Cs/Sr: 10(-5)m; I: 10(-7)m) and "high" (Cs/Sr: 10(-3)m; I: 10(-5)m) concentrations, and headspace was held at atmospheric or undetectable (<10ppmv) CO(2) partial pressure. Solid phase characterization revealed the formation of the zeolite chabazite in "high" samples, whereas feldspathoids, sodalite and cancrinite, were formed preferentially in "low" samples. Sr, Cs and I were sequestered in all reacted sediments. Native calcite dissolution in the CO(2)-free treatment drove the formation of strätlingite (Ca(2)Al(2)SiO(7)·8H(2)O) and diminished availability of Si and Al for feldspathoid formation. Results indicate that pCO(2) and contaminant concentrations strongly affect contaminant speciation in waste-weathered sediments, and are therefore likely to impact reaction product stability under any remediation scenario.

  11. Hydrocarbon contamination affects deep-sea benthic oxygen uptake and microbial community composition

    NASA Astrophysics Data System (ADS)

    Main, C. E.; Ruhl, H. A.; Jones, D. O. B.; Yool, A.; Thornton, B.; Mayor, D. J.

    2015-06-01

    Accidental oil well blowouts have the potential to introduce large quantities of hydrocarbons into the deep sea and disperse toxic contaminants to midwater and seafloor areas over ocean-basin scales. Our ability to assess the environmental impacts of these events is currently impaired by our limited understanding of how resident communities are affected. This study examined how two treatment levels of a water accommodated fraction of crude oil affected the oxygen consumption rate of a natural, deep-sea benthic community. We also investigated the resident microbial community's response to hydrocarbon contamination through quantification of phospholipid fatty acids (PLFAs) and their stable carbon isotope (δ13C) values. Sediment community oxygen consumption rates increased significantly in response to increasing levels of contamination in the overlying water of oil-treated microcosms, and bacterial biomass decreased significantly in the presence of oil. Multivariate ordination of PLFA compositional (mol%) data showed that the structure of the microbial community changed in response to hydrocarbon contamination. However, treatment effects on the δ13C values of individual PLFAs were not statistically significant. Our data demonstrate that deep-sea benthic microbes respond to hydrocarbon exposure within 36 h.

  12. Organic contaminant transport and fate in the subsurface: Evolution of knowledge and understanding

    NASA Astrophysics Data System (ADS)

    Essaid, Hedeff I.; Bekins, Barbara A.; Cozzarelli, Isabelle M.

    2015-07-01

    Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.

  13. Organic contaminant transport and fate in the subsurface: evolution of knowledge and understanding

    USGS Publications Warehouse

    Essaid, Hedeff I.; Bekins, Barbara A.; Cozzarelli, Isabelle M.

    2015-01-01

    Toxic organic contaminants may enter the subsurface as slightly soluble and volatile nonaqueous phase liquids (NAPLs) or as dissolved solutes resulting in contaminant plumes emanating from the source zone. A large body of research published in Water Resources Research has been devoted to characterizing and understanding processes controlling the transport and fate of these organic contaminants and the effectiveness of natural attenuation, bioremediation, and other remedial technologies. These contributions include studies of NAPL flow, entrapment, and interphase mass transfer that have advanced from the analysis of simple systems with uniform properties and equilibrium contaminant phase partitioning to complex systems with pore-scale and macroscale heterogeneity and rate-limited interphase mass transfer. Understanding of the fate of dissolved organic plumes has advanced from when biodegradation was thought to require oxygen to recognition of the importance of anaerobic biodegradation, multiple redox zones, microbial enzyme kinetics, and mixing of organic contaminants and electron acceptors at plume fringes. Challenges remain in understanding the impacts of physical, chemical, biological, and hydrogeological heterogeneity, pore-scale interactions, and mixing on the fate of organic contaminants. Further effort is needed to successfully incorporate these processes into field-scale predictions of transport and fate. Regulations have greatly reduced the frequency of new point-source contamination problems; however, remediation at many legacy plumes remains challenging. A number of fields of current relevance are benefiting from research advances from point-source contaminant research. These include geologic carbon sequestration, nonpoint-source contamination, aquifer storage and recovery, the fate of contaminants from oil and gas development, and enhanced bioremediation.

  14. Seismic reflection characteristics of naturally-induced subsidence affecting transportation

    USGS Publications Warehouse

    Miller, R.D.; Xia, J.; Steeples, D.W.

    2009-01-01

    High-resolution seismic reflections have been used effectively to investigate sinkholes formed from the dissolution of a bedded salt unit found throughout most of Central Kansas. Surface subsidence can have devastating effects on transportation structures. Roads, rails, bridges, and pipelines can even be dramatically affected by minor ground instability. Areas susceptible to surface subsidence can put public safety at risk. Subsurface expressions significantly larger than surface depressions are consistently observed on seismic images recorded over sinkholes in Kansas. Until subsidence reaches the ground surface, failure appears to be controlled by compressional forces evidenced by faults with reverse orientation. Once a surface depression forms or dissolution of the salt slows or stops, subsidence structures are consistent with a tensional stress environment with prevalent normal faults. Detecting areas of rapid subsidence potential, prior to surface failure, is the ultimate goal of any geotechnical survey where the ground surface is susceptible to settling. Seismic reflection images have helped correlate active subsidence to dormant paleofeatures, project horizontal growth of active sinkholes based on subsurface structures, and appraise the risk of catastrophic failure. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  15. Investigating the role of gas bubble formation and entrapment in contaminated aquifers: Reactive transport modelling.

    PubMed

    Amos, Richard T; Ulrich Mayer, K

    2006-09-10

    In many natural and contaminated aquifers, geochemical processes result in the production or consumption of dissolved gases. In cases where methanogenesis or denitrification occurs, the production of gases may result in the formation and growth of gas bubbles below the water table. Near the water table, entrapment of atmospheric gases during water table rise may provide a significant source of O(2) to waters otherwise depleted in O(2). Furthermore, the presence of bubbles will affect the hydraulic conductivity of an aquifer, resulting in changes to the groundwater flow regime. The interactions between physical transport, biogeochemical processes, and gas bubble formation, entrapment and release is complex and requires suitable analysis tools. The objective of the present work is the development of a numerical model capable of quantitatively assessing these processes. The multicomponent reactive transport code MIN3P has been enhanced to simulate bubble growth and contraction due to in-situ gas production or consumption, bubble entrapment due to water table rise and subsequent re-equilibration of the bubble with ambient groundwater, and permeability changes due to trapped gas phase saturation. The resulting formulation allows for the investigation of complex geochemical systems where microbially mediated redox reactions both produce and consume gases as well as affect solution chemistry, alkalinity, and pH. The enhanced model has been used to simulate processes in a petroleum hydrocarbon contaminated aquifer where methanogenesis is an important redox process. The simulations are constrained by data from a crude oil spill site near Bemidji, MN. Our results suggest that permeability reduction in the methanogenic zone due to in-situ formation of gas bubbles, and dissolution of entrapped atmospheric bubbles near the water table, both work to attenuate the dissolved gas plume emanating from the source zone. Furthermore, the simulations demonstrate that under the given

  16. Transport of organic contaminants in geomembranes under stress

    SciTech Connect

    Xiao, S. ); Moresoli, C. . Dept. of Chemical Engineering); Burczyk, A. ); Pintauro, P.; De Kee, D. . Dept. of Chemical Engineering)

    1999-07-01

    The transport properties of aqueous solutions of benzene, dichloromethane, and trichloroethylene through extended polyvinyl chloride and high-density polyethylene geomembranes are investigated. It is found that extension enhances the permeation rates of the penetrants through polyvinyl chloride geomembranes, and the opposite effect is found in the case of high-density polyethylene. This difference in response is attributed to the type of structural change, which occurred as a result of the extension. The diffusivities of a mixture of the three organic solvents through the geomembranes are also determined.

  17. Evaluation of Different Modeling Approaches to Simulate Contaminant Transport in a Fractured Limestone Aquifer

    NASA Astrophysics Data System (ADS)

    Mosthaf, K.; Rosenberg, L.; Balbarini, N.; Broholm, M. M.; Bjerg, P. L.; Binning, P. J.

    2014-12-01

    It is important to understand the fate and transport of contaminants in limestone aquifers because they are a major drinking water resource. This is challenging because they are highly heterogeneous; with micro-porous grains, flint inclusions, and being heavily fractured. Several modeling approaches have been developed to describe contaminant transport in fractured media, such as the discrete fracture (with various fracture geometries), equivalent porous media (with and without anisotropy), and dual porosity models. However, these modeling concepts are not well tested for limestone geologies. Given available field data and model purpose, this paper therefore aims to develop, examine and compare modeling approaches for transport of contaminants in fractured limestone aquifers. The model comparison was conducted for a contaminated site in Denmark, where a plume of a dissolved contaminant (PCE) has migrated through a fractured limestone aquifer. Multilevel monitoring wells have been installed at the site and available data includes information on spill history, extent of contamination, geology and hydrogeology. To describe the geology and fracture network, data from borehole logs was combined with an analysis of heterogeneities and fractures from a nearby excavation (analog site). Methods for translating the geological information and fracture mapping into each of the model concepts were examined. Each model was compared with available field data, considering both model fit and measures of model suitability. An analysis of model parameter identifiability and sensitivity is presented. Results show that there is considerable difference between modeling approaches, and that it is important to identify the right one for the actual scale and model purpose. A challenge in the use of field data is the determination of relevant hydraulic properties and interpretation of aqueous and solid phase contaminant concentration sampling data. Traditional water sampling has a bias

  18. Finite element modeling of contaminant transport in soils including the effect of chemical reactions.

    PubMed

    Javadi, A A; Al-Najjar, M M

    2007-05-17

    The movement of chemicals through soils to the groundwater is a major cause of degradation of water resources. In many cases, serious human and stock health implications are associated with this form of pollution. Recent studies have shown that the current models and methods are not able to adequately describe the leaching of nutrients through soils, often underestimating the risk of groundwater contamination by surface-applied chemicals, and overestimating the concentration of resident solutes. Furthermore, the effect of chemical reactions on the fate and transport of contaminants is not included in many of the existing numerical models for contaminant transport. In this paper a numerical model is presented for simulation of the flow of water and air and contaminant transport through unsaturated soils with the main focus being on the effects of chemical reactions. The governing equations of miscible contaminant transport including advection, dispersion-diffusion and adsorption effects together with the effect of chemical reactions are presented. The mathematical framework and the numerical implementation of the model are described in detail. The model is validated by application to a number of test cases from the literature and is then applied to the simulation of a physical model test involving transport of contaminants in a block of soil with particular reference to the effects of chemical reactions. Comparison of the results of the numerical model with the experimental results shows that the model is capable of predicting the effects of chemical reactions with very high accuracy. The importance of consideration of the effects of chemical reactions is highlighted.

  19. THE INTERPLAY BETWEEN GEOCHEMICAL REACTIONS AND ADVECTION-DISPERSION IN CONTAMINANT TRANSPORT AT A URANIUM MILL TAILINGS SITE

    EPA Science Inventory

    It is well known that the fate and transport of contaminants in the subsurface are controlled by complex processes including advection, dispersion-diffusion, and chemical reactions. However, the interplay between the physical transport processes and chemical reactions, and their...

  20. Transport of tritium contamination to the atmosphere in an arid environment

    USGS Publications Warehouse

    Garcia, C. Amanda; Andraski, Brian J.; Johnson, Michael J.; Stonestrom, David A.; Michel, Robert L.; Cooper, C.A.; Wheatcraft, S.W.

    2009-01-01

    Soil–plant–atmosphere interactions strongly influence water movement in desert unsaturated zones, but little is known about how such interactions affect atmospheric release of subsurface water-borne contaminants. This 2-yr study, performed at the U.S. Geological Survey's Amargosa Desert Research Site in southern Nevada, quantified the magnitude and spatiotemporal variability of tritium (3H) transport from the shallow unsaturated zone to the atmosphere adjacent to a low-level radioactive waste (LLRW) facility. Tritium fluxes were calculated as the product of 3H concentrations in water vapor and respective evaporation and transpiration water-vapor fluxes. Quarterly measured 3H concentrations in soil water vapor and in leaf water of the dominant creosote-bush [Larrea tridentata (DC.) Coville] were spatially extrapolated and temporally interpolated to develop daily maps of contamination across the 0.76-km2 study area. Maximum plant and root-zone soil concentrations (4200 and 8700 Bq L−1, respectively) were measured 25 m from the LLRW facility boundary. Continuous evaporation was estimated using a Priestley–Taylor model and transpiration was computed as the difference between measured eddy-covariance evapotranspiration and estimated evaporation. The mean evaporation/transpiration ratio was 3:1. Tritium released from the study area ranged from 0.12 to 12 μg d−1 and totaled 1.5 mg (8.2 × 1010 Bq) over 2 yr. Tritium flux variability was driven spatially by proximity to 3H source areas and temporally by changes in 3H concentrations and in the partitioning between evaporation and transpiration. Evapotranspiration removed and limited penetration of precipitation beneath native vegetation and fostered upward movement and release of 3H from below the root zone.

  1. Occurrence of perchloroethylene in surface water and fish in a river ecosystem affected by groundwater contamination.

    PubMed

    Wittlingerová, Zdena; Macháčková, Jiřina; Petruželková, Anna; Zimová, Magdalena

    2016-03-01

    Long-term monitoring of the content of perchloroethylene (PCE) in a river ecosystem affected by groundwater contamination was performed at a site in the Czech Republic. The quality of surface water was monitored quarterly between 1994 and 2013, and fish were collected from the affected ecosystem to analyse the content of PCE in their tissue in 1998, 2011 and 2012. Concentrations of PCE (9-140 μg/kg) in the tissue of fish collected from the contaminated part of the river were elevated compared to the part of the river unaffected by the contamination (ND to 5 μg/kg PCE). The quality of surface water has improved as a result of groundwater remediation during the evaluated period. Before the remedial action, PCE concentrations ranged from 30 to 95 μg/L (1994-1997). Following commencement of remedial activities in September 1997, a decrease in the content of PCE in the surface water to 7.3 μg/L (1998) and further to 1 μg/L (2011) and 1.1 μg/L (2012) led to a progressive decrease in the average concentration of PCE in the fish muscle tissue from 79 μg/kg (1998) to 24 (2011) and 30 μg/kg (2012), respectively. It was determined that the bioconcentration of PCE does not have a linear dependence because the decrease in contamination in the fish muscle tissue is not directly proportional to the decrease in contamination in the river water. The observed average bioconcentration factors were 24 and 28 for the lower concentrations of PCE and 11 for the higher concentrations of PCE in the river. In terms of age, length and weight of the collected fish, weight had the greatest significance for bioconcentration, followed by the length, with age being evaluated as a less significant factor.

  2. Properties governing the transport of trace organic contaminants through ion-exchange membranes.

    PubMed

    Vanoppen, Marjolein; Bakelants, Annelise F A M; Gaublomme, Dorien; Schoutteten, Klaas V K M; Vanden Bussche, Julie; Vanhaecke, Lynn; Verliefde, Arne R D

    2015-01-01

    Ion exchange membranes could provide a solution to the selective separation of organic and inorganic components in industrial wastewater. The phenomena governing the transport of organics through the IEM however, are not yet fully understood. Therefore, the transport of trace organic contaminants (TOrCs) as a model for a wide variety of organic compounds was studied under different conditions. It was found that in the absence of salt and external potential, the chemical equilibrium is the main driver for TOrC-transport, resulting in the transport of mainly charged TOrCs. When salt is present, the transport of TOrCs is hampered in favor of the NaCl transport, which shows a preferential interaction with the membranes due to its small size, high mobility and concentration. It is hypothesized that electrostatic interactions and electron donor/acceptor interactions are the main drivers for TOrC transport and that transport is mainly diffusion driven. This was confirmed in the experiments with different current densities, where the external potential seemed to have only a minor influence on the transport of TOrCs. It is only when the salt becomes nearly completely depleted that the TOrCs are transported as charge carriers. This shows that it is very difficult to get preferential transport of organic compounds due to the diffusive nature of their transport.

  3. Mineralogical compositions of aquifer matrix as necessary initial conditions in reactive contaminant transport models.

    PubMed

    Zhu, C; Burden, D S

    2001-10-01

    Mineralogical compositions and their spatial distributions are important initial conditions for reactive transport modeling. However, popular Kd-based "reactive" transport models only require contaminant concentrations in the pore fluids as initial conditions, and minerals implicitly represent infinite sources and sinks in these models. That situation results in a general neglect of mineralogical characterization in site investigations. This study uses a coupled multi-component reactive mass transport model to predict the natural attenuation of a ground water plume at a uranium mill tailings site in western USA. Numerous ground water geochemistry data are available at this site, but mineralogical data are sketchy. Even given the well-defined pore fluid chemistry, variations of secondary mineral species and mineral abundances in the aquifer resulted in significantly different modeling outcomes. Results show that the amount of calcite in the aquifer determines the distances of plume migration. The possible presence of jurbanite, an aluminum sulfate phase, can store acidity temporarily but cause more severe contamination on a later date. The surfaces of iron oxyhydroxides can store significant amounts of sulfate and protons and serve as a second source for prolonged contamination. These simulations under field conditions illustrate that mineralogical compositions are an essential requirement for accurate prediction of contaminant fate and transport. PMID:11588823

  4. Exact analytical solutions for contaminant transport in rivers 1. The equilibrium advection-dispersion equation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-w...

  5. Longshore transport modeling of the contaminated sediment in the Fukushima area

    NASA Astrophysics Data System (ADS)

    Kitamura, A.; Machida, M.; Itakura, M.; Yamada, S.

    2015-12-01

    The cesium-contaminated sediment in the Fukushima mountain area is expected to be transported by the river flow to the downstream region, and eventually to the ocean. The contaminated sediment discharged from the river to the ocean settles down to the seabed of the coastal area around the river mouth. Some part of the settled sediment is transported to the offshore region and the contamination of the coastal area is expected to decay gradually. Estimation of the environmental half-life of the contaminated sediment is important for the assessment of the safety of the edible fish in the Fukushima coastal area. Thus we need to calculate the sediment transport in the coastal area induced by various ocean phenomena, such as tidal current, river current, wave and wind-induced current. We have estimated the effect of several kinds of ocean phenomena on the coastal sediment transport, and found that the wind-induced current and the wave-induced suspension are the most dominant phenomena, while contributions from tidal current and the river flow is negligible.

  6. Techniques to better understand complex epikarst hydrogeology and contaminant transport in telogenetic karst settings

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The movement of autogenic recharge through the shallow epikarstic zone in soil-mantled karst aquifers is important in understanding recharge areas and rates, groundwater storage, and contaminant transport processes. The groundwater flow in agricultural karst areas, such as Kentucky’s Pennyroyal Plat...

  7. Grand challenge problems in environmental modeling and remediation: groundwater contaminant transport

    SciTech Connect

    Todd Arbogast; Steve Bryant; Clint N. Dawson; Mary F. Wheeler

    1998-08-31

    This report describes briefly the work of the Center for Subsurface Modeling (CSM) of the University of Texas at Austin (and Rice University prior to September 1995) on the Partnership in Computational Sciences Consortium (PICS) project entitled Grand Challenge Problems in Environmental Modeling and Remediation: Groundwater Contaminant Transport.

  8. Investigation of the pathway of contaminated soil transported to plant surfaces by raindrop splash

    SciTech Connect

    Dreicer, M.; Hakonson, T.E.; Whicker, F.W.; White, G.C.

    1983-10-21

    The environmental transport pathway of soil-borne radioisotopes to vegetation surfaces via raindrop splash was studied. The data show that soil can significantly contribute to the contamination found on plants. Further detailed study is needed to calculate the rate constant for the raindrop splash and retention pathways. 8 references, 1 figure. (ACR)

  9. Evidence for mild sediment Pb contamination affecting leaf-litter decomposition in a lake.

    PubMed

    Oguma, Andrew Y; Klerks, Paul L

    2015-08-01

    Much work has focused on the effects of metal-contaminated sediment on benthic community structure, but effects on ecosystem functions have received far less attention. Decomposition has been widely used as an integrating metric of ecosystem function in lotic systems, but not for lentic ones. We assessed the relationship between low-level sediment lead (Pb) contamination and leaf-litter decomposition in a lentic system. We measured 30-day weight loss in 30 litter-bags that were deployed along a Pb-contamination gradient in a cypress-forested lake. At each deployment site we also quantified macrobenthos abundance, dissolved oxygen, water depth, sediment organic content, sediment silt/clay content, and both total sediment and porewater concentrations of Cd, Cu, Ni, Pb and Zn. Principal components (PC) analysis revealed a negative relationship between Pb concentration and benthic macroinvertebrate abundance, and this covariation dominated the first PC axis (PC1). Subsequent correlation analyses revealed a negative relationship between PC1 and percent leaf-litter loss. Our results indicate that leaf-litter decomposition was related to sediment Pb and benthic macroinvertebrate abundance. They also showed that ecosystem function may be affected even where sediment Pb concentrations are mostly below threshold-effects sediment quality guidelines--a finding with potential implications for sediment risk assessment. Additionally, the litter-bag technique used in this study showed promise as a tool in risk assessments of metal-contaminated sediments in lentic systems.

  10. A Chaotic-Dynamical Conceptual Model to Describe Fluid flow and Contaminant Transport in a Fractured Vadose zone

    SciTech Connect

    Faybishenko, Boris; Doughty, Christine; Stoops, Thomas M.; Wood, thomas R.; Wheatcraft, Stephen W.

    1999-12-31

    (1) To determine if and when dynamical chaos theory can be used to investigate infiltration of fluid and contaminant transport in heterogeneous soils and fractured rocks. (2) To introduce a new approach to the multiscale characterization of flow and transport in fractured basalt vadose zones and to develop physically based conceptual models on a hierarchy of scales. The following activities are indicative of the success in meeting the project s objectives: A series of ponded infiltration tests, including (1) small-scale infiltration tests (ponded area 0.5 m2) conducted at the Hell s Half Acre site near Shelley, Idaho, and (2) intermediate-scale infiltration tests (ponded area 56 m2) conducted at the Box Canyon site near Arco, Idaho. Laboratory investigations and modeling of flow in a fractured basalt core. A series of small-scale dripping experiments in fracture models. Evaluation of chaotic behavior of flow in laboratory and field experiments using methods from nonlinear dynamics; Evaluation of the impact these dynamics may have on contaminant transport through heterogeneous fractured rocks and soils, and how it can be used to guide remediation efforts; Development of a conceptual model and mathematical and numerical algorithms for flow and transport that incorporate (1) the spatial variability of heterogeneous porous and fractured media, and (2) the description of the temporal dynamics of flow and transport, both of which may be chaotic. Development of appropriate experimental field and laboratory techniques needed to detect diagnostic parameters for chaotic behavior of flow. This approach is based on the assumption that spatial heterogeneity and flow phenomena are affected by nonlinear dynamics, and in particular, by chaotic processes. The scientific and practical value of this approach is that we can predict the range within which the parameters of flow and transport change with time in order to design and manage the remediation, even when we can not predict

  11. A cellular automaton simulation of contaminant transport in porous media

    SciTech Connect

    Freed, D.M.; Simonson, S.A.

    1995-12-01

    A simulation tool to investigate radionuclide transport in porous groundwater flow is described. The flow systems of interest are those important in determining the fate of radionuclides emplaced in an underground repository, such as saturated matrix flow, matrix and fracture flow in the unsaturated zone, and viscous fingering in porous fractures. The work discussed here is confined to consideration of saturated flow in porous media carrying a dilute, sorptive species. The simulation technique is based on a special class of cellular automata known as lattice gas automata (LGA) which are capable of predicting hydrodynamic behavior. The original two-dimensional scheme (that of Frisch et. al. known as the FHP model) used particles of unit mass traveling on a triangular lattice with unit velocity and undergoing simple collisions which conserve mass and momentum at each node. These microscopic rules go over to the incompressible Navier-Stokes equations in the macroscopic limit. One of the strengths of this technique is the natural way that heterogeneities, such as boundaries, are accommodated. Complex geometries such as those associated with porous microstructures can be modeled effectively. Several constructions based on the FHP model have been devised, including techniques to eliminate statistical noise, extension to three dimensions, and the addition of surface tension which leads to multiphase flow.

  12. Code System to Solve for Release and Transport of Contaminants through Saturated/Unsaturated Media.

    1996-03-07

    The BLT code solves for release and transport of contaminants from containerized wastes. Each container may have unique properties (i.e., time to failure or localized failure, e.g. pitting) and each waste form may have unique release properties. Release from the waste form is limited by one of four physical or chemical constraints: solubility, diffusion, dissolution, and surface wash-off with partitioning. The release from the waste form acts as a source for transport in the advection/dispersionmore » equation. Transport is modeled in two-dimensions through the groundwater pathway from subsurface disposal.« less

  13. TRANSPORTER POLYMORPHISMS AFFECT NORMAL PHYSIOLOGY, DISEASES, AND PHARMACOTHERAPY

    PubMed Central

    Sissung, Tristan M.; Troutman, Sarah M.; Campbell, Tessa J; Pressler, Heather M.; Sung, Hyeyoung; Bates, Susan E.; Figg, William D.

    2014-01-01

    Drug transporters mediate the movement of endobiotics and xenobiotics across biological membranes in multiple organs and in most tissues. As such, they are involved in physiology, development of disease, drug pharmacokinetics, and ultimately the clinical response to myriad medications. Genetic variants in transporters cause population-specific differences in drug transport and are responsible for considerable inter-individual variation in physiology and pharmacotherapy. The purpose of this review is to provide a broad overview of how inherited variants in transporters are associated with disease etiology, disease state, and the pharmacological treatment of diseases. Given that there are thousands of published papers related to the interplay between transporter genetics and medicine, this review will provide examples that exemplify the broader focus of the literature. PMID:22284781

  14. Perched-Water Analysis Related to Deep Vadose Zone Contaminant Transport and Impact to Groundwater

    SciTech Connect

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

    2013-11-15

    Perched-water conditions have been observed in the vadose zone above a fine-grained zone that is located just a few meters above the water table beneath the B-complex at the Hanford Site. The perched water, containing elevated concentrations of uranium and technetium-99, is important to consider in evaluating the future flux of contaminated water into the groundwater. A study was conducted to examine the perched-water conditions and quantitatively evaluate 1) factors that control perching behavior, 2) contaminant flux toward groundwater, and, 3) associated groundwater impact. Based on the current vertical transport pathways and large areal extent of the perched system, the evaluation was conducted using a one-dimensional (1-D) analysis. Steady-state scoping calculations showed that the perching-layer hydraulic conductivity is likely to be up to two orders of magnitude less than the base case value obtained from Hanford site literature. Numerical flow and transport simulations provided both steady-state and transient system estimates of water and contaminant behavior and were used to further refine the range of conditions consistent with current observations of perched water height and to provide estimates of future water and contaminant flux to groundwater. With a recharge rate of 6 cm/yr, representative of current disturbed surface conditions, contaminant flux from the perched water occurs over a time interval of tens of years. However, if the recharge rate is 0.35 cm/yr, representative of returning recharge to pre-Hanford Site levels, the contaminant flux into the groundwater is spread over hundreds of years. It was also demonstrated that removal of perched water by pumping would reduce the flux of water (and associated contaminants) to the groundwater, thereby impacting the long-term rate of contaminant movement to the groundwater.

  15. Effect of focused ion beam deposition induced contamination on the transport properties of nano devices.

    PubMed

    Lan, Yann-Wen; Chang, Wen-Hao; Chang, Yuan-Chih; Chang, Chia-Seng; Chen, Chii-Dong

    2015-02-01

    Focused ion beam (FIB) deposition produces unwanted particle contamination beyond the deposition point. This is due to the FIB having a Gaussian distribution. This work investigates the spatial extent of this contamination and its influence on the electrical properties of nano-electronic devices. A correlation study is performed on carbon-nanotube (CNT) devices manufactured using FIB deposition. The devices are observed using transmission electron microscopy (TEM) and these images are correlated with device electrical characteristics. To discover how far Pt-nanoparticle contamination occurs along a CNT after FIB electrical contact deposition careful TEM inspections are performed. The results show FIB deposition efficiently improves electrical contact; however, the practice is accompanied by serious particle contamination near deposition points. These contaminants include metal particles and amorphous elements originating from precursor gases and residual water molecules in the vacuum chamber. Pt-contamination extends for approximately 2 μm from the point of FIB contact deposition. These contaminants cause current fluctuations and alter the transport characteristics of devices. It is recommended that nano-device fabrication occurs at a distance greater than 2 μm from the FIB deposition of an electrical contact.

  16. Retardation of ammonium and potassium transport through a contaminated sand and gravel aquifer: The Role of cation exchange

    USGS Publications Warehouse

    Ceazan, M.L.; Thurman, E.M.; Smith, R.L.

    1989-01-01

    The role of cation exchange in the retardation of ammonium (NH4+) and potassium (K+) transport in a shallow sand and gravel aquifer was evaluated by use of observed distributions of NH4+ and K+ within a plume of sewage-contaminated groundwater, small-scale tracer injection tests, and batch sorption experiments on aquifer material. Both NH4+ and K+ were transported ???2 km in the 4-km-long contaminant plume (retardation factor, Rf = 2.0). Sediments from the NH4+-containing zone of the plume contained significant quantities of KCl-extractable NH4+ (extraction distribution coefficient, Kd,extr = 0.59-0.87 mL/g of dry sediment), and when added to uncontaminated sediments, NH4+ sorption followed a linear isotherm. Small-scale tracer tests demonstrated that NH4+ and K+ were retarded (Rf =3.5) relative to a nonreactive tracer (Br-). Sorption of dissolved NH4+ was accompanied by concomitant release of calcium (Ca2+), magnesium (Mg2+), and sodium (Na+) from aquifer sediments, suggesting involvement of cation exchange. In contrast, nitrate (NO3-) was not retarded and cleanly separated from NH4+ and K+ in the small-scale tracer tests. This study demonstrates that transport of NH4+ and K+ through a sand and gravel aquifer can be markedly affected by cation-exchange processes even at a clay content less than 0.1%.

  17. Transport of microbial tracers in clean and organically contaminated silica sand in laboratory columns compared with their transport in the field.

    PubMed

    Weaver, Louise; Sinton, Lester W; Pang, Liping; Dann, Rod; Close, Murray

    2013-01-15

    Waste disposal on land and the consequent transport of bacterial and viral pathogens in soils and aquifers are of major concern worldwide. Pathogen transport can be enhanced in the presence of organic matter due to occupation of attachment sites in the aquifer materials thus preventing pathogen attachment leading to their faster transport for longer distances. Laboratory column studies were carried out to investigate the effect of organic matter, in the form of dissolved organic carbon (DOC), on the transport of Escherichia coli and MS2 phage in saturated clean silica sand. Transport rates of these microbial tracers were also studied in a contaminated field site. Laboratory column studies showed that low concentrations (0.17 mg L(-1)) of DOC had little effect on E. coli J6-2 removal and slightly reduced the attachment of MS2 phage. After progressive conditioning of the column with DOC (1.7 mg L(-1) and 17 mg L(-1)), neither E. coli J6-2 nor MS2 phage showed any attachment and recovery rates increased dramatically (up to 100%). The results suggest that DOC can affect the transport rates of microbial contaminants. For E. coli J6-2 the predominant effect appeared to be an increase in the secondary energy minimum leading to an increase in E. coli attachment initially. However, after 17 mg L(-1) DOC conditioning of the silica sand no attachment of E. coli was observed as the DOC took up attachment sites in the porous media. MS2 phage appeared to be affected predominantly by out-competition of binding sites in the clean silica sand and a steady reduction in attachment was observed as the DOC conditioning increased. Field study showed a high removal of both E. coli and MS2 phage, although E. coli was removed at a lower rate than MS2 phage. In the field it is likely that a combination of effects are seen as the aquifer material will be heterogeneous in its surface nanoscale properties, demonstrated by the differing removal of E. coli and MS2 phage compared to the

  18. Transport of microbial tracers in clean and organically contaminated silica sand in laboratory columns compared with their transport in the field.

    PubMed

    Weaver, Louise; Sinton, Lester W; Pang, Liping; Dann, Rod; Close, Murray

    2013-01-15

    Waste disposal on land and the consequent transport of bacterial and viral pathogens in soils and aquifers are of major concern worldwide. Pathogen transport can be enhanced in the presence of organic matter due to occupation of attachment sites in the aquifer materials thus preventing pathogen attachment leading to their faster transport for longer distances. Laboratory column studies were carried out to investigate the effect of organic matter, in the form of dissolved organic carbon (DOC), on the transport of Escherichia coli and MS2 phage in saturated clean silica sand. Transport rates of these microbial tracers were also studied in a contaminated field site. Laboratory column studies showed that low concentrations (0.17 mg L(-1)) of DOC had little effect on E. coli J6-2 removal and slightly reduced the attachment of MS2 phage. After progressive conditioning of the column with DOC (1.7 mg L(-1) and 17 mg L(-1)), neither E. coli J6-2 nor MS2 phage showed any attachment and recovery rates increased dramatically (up to 100%). The results suggest that DOC can affect the transport rates of microbial contaminants. For E. coli J6-2 the predominant effect appeared to be an increase in the secondary energy minimum leading to an increase in E. coli attachment initially. However, after 17 mg L(-1) DOC conditioning of the silica sand no attachment of E. coli was observed as the DOC took up attachment sites in the porous media. MS2 phage appeared to be affected predominantly by out-competition of binding sites in the clean silica sand and a steady reduction in attachment was observed as the DOC conditioning increased. Field study showed a high removal of both E. coli and MS2 phage, although E. coli was removed at a lower rate than MS2 phage. In the field it is likely that a combination of effects are seen as the aquifer material will be heterogeneous in its surface nanoscale properties, demonstrated by the differing removal of E. coli and MS2 phage compared to the

  19. Annual loads of organic contaminants in Chesapeake Bay contributed through fluvial transport

    SciTech Connect

    Foster, G.D.; Lippa, K.A.

    1994-12-31

    Organic contaminants in fluvial transport, atmospheric deposition, urban runoff, and shoreline erosion are being quantified and compared in an effort to understand contaminant inputs and mass balances in Chesapeake Bay. Concentrations of nine organonitrogen and organophosphorus (organo-N/P) pesticides, eight organochlorine (OC) pesticides, polychlorinated biphenyls (PCBs), and four polynuclear aromatic hydrocarbons in fluvial transport were determined at the Susquehanna, Potomac, and James River fall lines for the period of March 1992 through February 1993. Together these rivers account for ca. 75% of the freshwater inflow to the bay from fluvial sources. Sampling was conducted monthly during base flow conditions and during all major storm events. Analysis of nanogram and picogram per liter concentrations of the organic contaminants was performed for both the dissolved and particulate phases of the surface water samples. Daily fluvial loads were calculated using an iterative-increment method from concentration and discharge data, and the resulting daily load estimates were summed to provide annual loads. Loads contributed by the three tributaries from March 1992 through February 1993 were 6.9 metric tons for the organo-N/P pesticides, 0.73 metric tons for the OC compounds and PCBs, and 1.2 metric tons for the PAH. Preliminary comparisons show that loads from fluvial transport are generally greater than other sources for most contaminants except PAH, where atmospheric deposition and urban runoff contribute greater loads of some compounds.

  20. Ascaridia galli infection affects pullets differently when feed is contaminated with the Fusarium toxin deoxynivalenol (DON).

    PubMed

    Dänicke, S; Beineke, A; Rautenschlein, Silke; Valenta, Hana; Kersten, Susanne; Gauly, M

    2013-12-01

    The Fusarium mycotoxin deoxynivalenol (DON) is a common contaminant of cereal grains used as animal feed. DON is known for its cytotoxic and anti-proliferative properties and might adversely affect the health of poultry. The prevalence of the intestinal parasitizing roundworm Ascaridia galli is higher in outdoor housing systems and has been associated with maldigestion and malabsorption. It was hypothesized that ingested DON might not only affect the pullet itself but could also act on the nematode parasitizing in the ingesta. To examine these interactions between A. galli infection and DON contamination of feed 4 groups of 9 pullets in each were tested; non-infected groups were fed either an uncontaminated control (CON-) or a Fusarium toxin contaminated and mainly DON-containing diet (FUS-), and the corresponding A. galli inoculated groups were fed accordingly (CON+, FUS+). A. galli infection significantly reduced the jejunal villi height and increased the thickness of the tunica muscularis with the effect being more pronounced when the DON-containing diet was fed (Group FUS+). Only in this group significantly increased weights of jejunal and ileal tissues and of livers were noticed. Moreover, DON was detected in plasma of the pullets at higher frequencies when they were infected suggesting a facilitated absorption of DON. Group FUS+ was characterized by a significantly higher excretion of A. galli eggs and a concomitant lower proportion of pullets with detectable antibodies against a somatic antigen of A. galli while worm burden and worm characteristics were not affected by diet. Other effects of feeding the FUS diet to the infected pullets included an increased mass per length of male worms. In conclusion, infection of pullets with A. galli might increase the susceptibility towards DON as indicated by an increased DON absorption rate and a compromised antibody formation. The effects of DON on fecundity and worm morphology require further examination. PMID

  1. Evaluation of factors affecting stakeholder risk perception of contaminated sediment disposal in Oslo harbor.

    PubMed

    Sparrevik, Magnus; Ellen, Gerald Jan; Duijn, Mike

    2011-01-01

    The management of environmental pollution has changed considerably since the growth of environmental awareness in the late 1960s. The general increased environmental concern and involvement of stakeholders in today's environmental issues may enhance the need to consider risk in a much broader social context rather than just as an estimate of ecological hazard. Risk perception and the constructs and images of risks held by stakeholders and society are important items to address in the management of environmental projects, including the management of contaminated sediments. Here we present a retrospective case study that evaluates factors affecting stakeholder risk perception of contaminated sediment disposal that occurred during a remediation project in Oslo harbor, Norway. The choice to dispose dredged contaminated sediments in a confined aquatic disposal (CAD) site rather than at a land disposal site has received a lot of societal attention, attracted large media coverage, and caused many public discussions. A mixed method approach is used to investigate how risk perceptive affective factors (PAF), socio-demographic aspects, and participatory aspects have influenced the various stakeholders' preferences for the two different disposal options. Risk perceptive factors such as transparency in the decision making process and controllability of the disposal options have been identified as important for risk perception. The results of the study also support the view that there is no sharp distinction in risk perception between experts and other parties and emphasizes the importance of addressing risk perceptive affective factors in similar environmental decision-making processes. Indeed, PAFs such as transparency, openness, and information are fundamental to address in sensitive environmental decisions, such as sediment disposal alternatives, in order to progress to more technical questions such as the controllability and safety.

  2. Ascaridia galli infection affects pullets differently when feed is contaminated with the Fusarium toxin deoxynivalenol (DON).

    PubMed

    Dänicke, S; Beineke, A; Rautenschlein, Silke; Valenta, Hana; Kersten, Susanne; Gauly, M

    2013-12-01

    The Fusarium mycotoxin deoxynivalenol (DON) is a common contaminant of cereal grains used as animal feed. DON is known for its cytotoxic and anti-proliferative properties and might adversely affect the health of poultry. The prevalence of the intestinal parasitizing roundworm Ascaridia galli is higher in outdoor housing systems and has been associated with maldigestion and malabsorption. It was hypothesized that ingested DON might not only affect the pullet itself but could also act on the nematode parasitizing in the ingesta. To examine these interactions between A. galli infection and DON contamination of feed 4 groups of 9 pullets in each were tested; non-infected groups were fed either an uncontaminated control (CON-) or a Fusarium toxin contaminated and mainly DON-containing diet (FUS-), and the corresponding A. galli inoculated groups were fed accordingly (CON+, FUS+). A. galli infection significantly reduced the jejunal villi height and increased the thickness of the tunica muscularis with the effect being more pronounced when the DON-containing diet was fed (Group FUS+). Only in this group significantly increased weights of jejunal and ileal tissues and of livers were noticed. Moreover, DON was detected in plasma of the pullets at higher frequencies when they were infected suggesting a facilitated absorption of DON. Group FUS+ was characterized by a significantly higher excretion of A. galli eggs and a concomitant lower proportion of pullets with detectable antibodies against a somatic antigen of A. galli while worm burden and worm characteristics were not affected by diet. Other effects of feeding the FUS diet to the infected pullets included an increased mass per length of male worms. In conclusion, infection of pullets with A. galli might increase the susceptibility towards DON as indicated by an increased DON absorption rate and a compromised antibody formation. The effects of DON on fecundity and worm morphology require further examination.

  3. Effects of dissolved organic matter on the co-transport of mineral colloids and sorptive contaminants.

    PubMed

    Cheng, Tao; Saiers, James E

    2015-01-01

    Colloid-facilitated transport of contaminants in the vadose zone has important implications to groundwater quality, and has received considerable attention. Natural organic matter (NOM) is ubiquitous in subsurface environments, and its influence on mineral colloids and solute transport has been well documented. However, research on the influence of NOM on colloid-facilitated transport is limited. The objective of this paper is to elucidate the effects of NOM on colloid-facilitated transport of a radioactive contaminant (Cs-137) within partially-saturated sediments. Measurements made with re-packed columns reveal that Cs-137 mobility was low when mineral colloids were absent and was unaffected by the presence of NOM. The addition of mineral colloids to influent increased Cs-137 mobility, and effluent Cs-137 was dominated by the colloid-associated form. When NOM was added to systems that contained mineral colloids and Cs-137, the mobility of Cs-137 further increased. A mathematical model simulating colloid-facilitated transport showed that NOM increases Cs-137 transport by increasing colloid mobility and reducing the rate of Cs-137 adsorption to the porous medium.

  4. Effects of dissolved organic matter on the co-transport of mineral colloids and sorptive contaminants

    NASA Astrophysics Data System (ADS)

    Cheng, Tao; Saiers, James E.

    2015-06-01

    Colloid-facilitated transport of contaminants in the vadose zone has important implications to groundwater quality, and has received considerable attention. Natural organic matter (NOM) is ubiquitous in subsurface environments, and its influence on mineral colloids and solute transport has been well documented. However, research on the influence of NOM on colloid-facilitated transport is limited. The objective of this paper is to elucidate the effects of NOM on colloid-facilitated transport of a radioactive contaminant (Cs-137) within partially-saturated sediments. Measurements made with re-packed columns reveal that Cs-137 mobility was low when mineral colloids were absent and was unaffected by the presence of NOM. The addition of mineral colloids to influent increased Cs-137 mobility, and effluent Cs-137 was dominated by the colloid-associated form. When NOM was added to systems that contained mineral colloids and Cs-137, the mobility of Cs-137 further increased. A mathematical model simulating colloid-facilitated transport showed that NOM increases Cs-137 transport by increasing colloid mobility and reducing the rate of Cs-137 adsorption to the porous medium.

  5. Contaminant loading in remote Arctic lakes affects cellular stress-related proteins expression in feral charr.

    USGS Publications Warehouse

    Wiseman, Steve; Jorgensen, Even H.; Maule, Alec G.; Vijayan, Mathilakath M.

    2011-01-01

    The remote Arctic lakes on Bjornoya Island, Norway, offer a unique opportunity to study possible affect of lifelong contaminant exposure in wild populations of landlocked Arctic charr (Salvelinus alpinus). This is because Lake Ellasjoen has persistent organic pollutant (POP) levels that are significantly greater than in the nearby Lake Oyangen. We examined whether this differential contaminant loading was reflected in the expression of protein markers of exposure and effect in the native fish. We assessed the expressions of cellular stress markers, including cytochrome P4501A (Cyp1A), heat shock protein 70 (hsp70), and glucocorticoid receptor (GR) in feral charr from the two lakes. The average polychlorinated biphenyl (PCB) load in the charr liver from Ellasjoen was approximately 25-fold higher than in individuals from Oyangen. Liver Cyp1A protein expression was significantly higher in individuals from Ellasjoen compared with Oyangen, confirming differential PCB exposure. There was no significant difference in hsp70 protein expression in charr liver between the two lakes. However, brain hsp70 protein expression was significantly elevated in charr from Ellasjoen compared with Oyangen. Also, liver GR protein expression was significantly higher in the Ellasjoen charr compared with Oyangen charr. Taken together, our results suggest changes to cellular stress-related protein expression as a possible adaptation to chronic-contaminant exposure in feral charr in the Norwegian high-Arctic.

  6. Sensitivity analysis of pesticides contaminating groundwater by applying probability and transport methods.

    PubMed

    Zhang, Pengxin; Aagaard, Per; Nadim, Farrokh; Gottschalk, Lars; Haarstad, Ketil

    2009-07-01

    The use of pesticides is a potential threat to local groundwater. Once groundwater is contaminated, it is very difficult to clean. Thus, it is of importance to assess the risk of contaminating local groundwater at an early stage when pesticides are found in soils. This knowledge will also help in remediation strategies. Traditional methods of deterministic analysis cannot explicitly account for the sometimes large uncertainties that exist at this stage in the work, whereas probabilistic analyses are better suited for dealing with these problems. In this paper, we have combined contaminant transport with a 1st-order reliability approach. Pesticide concentrations in soil have been studied to estimate the probability of failure--that is, of pesticides exceeding established critical levels in groundwater. Results indict that failure probability increases rapidly within a certain range of pesticide concentrations in soil for different critical levels. In given aquifer conditions and contaminants, probabilities of contaminants exceeding particular critical levels can easily be obtained according to various water usage scenarios. The distribution of importance factors among variables indicates the contribution their relative weights make to the failure probability. Hence, authorities can easily form sensitivity factors to take action and reduce the risk of contaminating the groundwater.

  7. Impact of mineral micropores on transport and fate of organic contaminants: a review.

    PubMed

    Cheng, Hefa; Hu, Erdan; Hu, Yuanan

    2012-03-15

    Nanometer-scale pores are abundant in porous geological media (soils, sediments, and aquifer materials), and may account for over >90% of total mineral surface areas. Sorption of organic contaminants in mineral micropores (<2 nm) plays a key role in controlling their fate and transport when the porous geological media have very low organic carbon contents (<0.1%). Significant adsorption of hydrophobic organic contaminants could only occur in the hydrophobic micropore spaces because of the strong competition from water. The rate of desorption from micropores is very slow due to hindered diffusion, resulting in distinct two-stage desorption behavior for microporous solids. Size exclusion effect prevents micropore-sorbed contaminants from being accessed by microorganisms and their extracellular enzymes, thus reducing their bioavailability and biodegradation rates. Results from recent studies indicate that sorption in micropores can also inhibit abiotic degradation of reactive contaminants by protecting them in confined spaces with little reactive water, slowing down hydrolysis and other water-mediated transformations. As a result of the inhibitory effect on abiotic and biotic transformations, and the slow desorption due to hindered diffusion, sorption in hydrophobic micropores of porous geological media can cause preservation of anthropogenic organic contaminants in the subsurface and may increase their persistence to the time scale of geological ages under appropriate conditions. From a practical perspective, understanding the role of mineral micropores is important in assessing the long-term ecotoxicological risk of organic contaminants in the subsurface and designing remediation strategies.

  8. Coupled Geochemical and Reactive Transport Modeling of Organic Contaminants in a Pyrite-Rich Aquifer

    NASA Astrophysics Data System (ADS)

    Sarioglu, S. M.; Copty, N. K.

    2004-12-01

    Although pH is recognized as a key factor influencing bacterial activity, existing groundwater transport models generally do not directly account for the effect of pH on the biodegradation of organic compounds. The purpose of this study is to develop a coupled reactive transport and geochemical model that explicitly incorporates the effect of spatial and temporal variations of the pH on the biodegradation of organic contaminants. The model consists of two modules: a transport module and a geochemical module. The transport module uses a Crank-Nicholson finite-difference formulation to solve the groundwater flow and transport equations for the hydrocarbon, dissolved oxygen, microbial mass and all reactive groundwater species influencing the hydrocarbon biodegradation and pH distribution. The geochemical module allows for the simulation of both kinetically defined as well as geochemical equilibrium reactions. The governing non-linear system of equations is solved using an iterative multi-step operator-splitting algorithm. Both modules account for heterogeneity in the definition of the hydrogeological and biochemical parameters. For demonstration, the model is applied to a hypothetical pyrite-rich aquifer contaminated with petroleum hydrocarbons. A commonly used practice for the remediation of aquifers contaminated with petroleum hydrocarbons is the delivery of oxygen for the enhanced aerobic biodegradation of the organic contaminant. However, the presence of pyrite may interfere with the intended purpose of the supplied oxygen, leading to undesirable side effects. Specifically, oxygen readily reacts with the sulfide minerals leading to depletion of oxygen and acidification of the subsurface environment and, subsequently, the inadvertent inhibition of the microbial activity. The developed coupled geochemical and reactive transport model is used to quantify these processes and assess the dominance of the various chemical reactions. Both abiotic and biotic pyrite

  9. Contaminant transport in a two-zone wetland: Dispersion and ecological degradation

    NASA Astrophysics Data System (ADS)

    Chen, Bin

    2013-04-01

    SummaryUnderstanding the fate of contaminant in wetland flows is essential in applications such as ecological risk assessment and environmental hydraulic design. Presented in this paper is an analytical study on the dispersion of contaminant in a two-zone wetland, with the effect of ecological degradation taken into consideration. Environmental dispersion is discussed separately via an exponential transformation for the general formulation of contaminant transport. Taylor's classical analysis for solute dispersion in a long and thin tube flow is rigorously generalized for the dispersion of the lateral mean contaminant concentration in the longitudinal direction. A method of asymptotic analysis is adopted instead of the concentration moment method in order to simplify the process of deduction and the expression of the analytical solution. Gill's method of mean concentration expansion is applied to model the concentration deviation terms produced in an averaging operation. With the velocity profile obtained previously, the enhancement of the environmental dispersivity under long time evolution is determined and shown to be consistent with that obtained by the method of concentration moment. Analytical solutions for the evolution of the contaminant concentration and the influenced region of the contaminant cloud are obtained by combining both the hydraulic and the ecological effects. For typical pollutant as the heavy metal Hg, the evolution of contaminant cloud is illustrated by critical length and duration in an application with concentration beyond some given environmental standard level. Results show that for wetland flows with a two-zone structure, the influenced region is reduced evidently while the duration of the contaminant cloud remains nearly unchanged, compared with that for the single-zone wetland flow.

  10. Kinetically influenced terms for solute transport affected by heterogeneous and homogeneous classical reactions

    USGS Publications Warehouse

    Bahr, J.M.

    1990-01-01

    This paper extends a four-step derivation procedure, previously presented for cases of transport affected by surface reactions, to transport problems involving homogeneous reactions. Derivations for these classes of reactions are used to illustrate the manner in which mathematical differences between reaction classes are reflected in the mathematical derivation procedures required to identify kinetically influenced terms. Simulation results for a case of transport affected by a single solution phase complexation reaction and for a case of transport affected by a precipitation-dissolution reaction are used to demonstrate the nature of departures from equilibrium-controlled transport as well as the use of kinetically influenced terms in determining criteria for the applicability of the local equilibrium assumption. A final derivation for a multireaction problem demonstrates the application of the generalized procedure to a case of transport affected by reactions of several classes. -from Author

  11. A cocktail of contaminants: how mixtures of pesticides at low concentrations affect aquatic communities.

    PubMed

    Relyea, Rick A

    2009-03-01

    The ubiquity of anthropogenic chemicals in nature poses a challenge to understanding how ecological communities are impacted by them. While we are rapidly gaining an understanding of how individual contaminants affect communities, communities are exposed to suites of contaminants yet investigations of the effects of diverse contaminant mixtures in aquatic communities are rare. I examined how a single application of five insecticides (malathion, carbaryl, chlorpyrifos, diazinon, and endosulfan) and five herbicides (glyphosate, atrazine, acetochlor, metolachlor, and 2,4-D) at low concentrations (2-16 p.p.b.) affected aquatic communities composed of zooplankton, phytoplankton, periphyton, and larval amphibians (gray tree frogs, Hyla versicolor, and leopard frogs, Rana pipiens). Using outdoor mesocosms, I examined each pesticide alone, a mix of insecticides, a mix of herbicides, and a mix of all ten pesticides. Individual pesticides had a wide range of direct and indirect effects on all trophic groups. For some taxa (i.e., zooplankton and algae), the impact of pesticide mixtures could largely be predicted from the impacts of individual pesticides; for other taxa (i.e., amphibians) it could not. For amphibians, there was an apparent direct toxic effect of endosulfan that caused 84% mortality of leopard frogs and an indirect effect induced by diazinon that caused 24% mortality of leopard frogs. When pesticides were combined, the mix of herbicides had no negative effects on the survival and metamorphosis of amphibians, but the mix of insecticides and the mix of all ten pesticides eliminated 99% of leopard frogs. Interestingly, these mixtures did not cause mortality in the gray tree frogs and, as a result, the gray tree frogs grew nearly twice as large due to reduced competition with leopard frogs. In short, wetland communities can be dramatically impacted by low concentrations of pesticides (both separate and combined) and these results offer important insights for the

  12. Time Evolution of Activity Concentration of Natural Emitters in a Scenario Affected By Previous Phosphogypsum Contamination

    NASA Astrophysics Data System (ADS)

    Villa, M.; Mantero, J.; Mosqueda, F.; Hurtado, S.; Manjón, G.; Vaca, F.; García-Tenorio, R.

    2008-08-01

    The estuary formed by the confluence of Tinto and Odiel river-mouths is located in the South of Spain, close to Huelva town. This estuary has been deeply studied through the years because it has a double particularity. On one hand, since the beginning of the 1960s, the estuary has been affected by direct and indirect phosphogypsum (pg.) releases from two phosphoric acid and fertilizers factories that are working in the area. On the other hand, the pyrite mining operations upstream the Odiel and Tinto rivers has caused historically the formation of H2SO4, through oxidation of the natural sulphur deposits, the acidification of the waters and the consequent mobilisation of heavy metals from the mining area to the Huelva estuary. As a consequence, enhancement contamination levels in natural emitters from the 238U series were found in the surroundings of the factories in the previous years to 1998. However, in 1998 the management policy of waste releases drastically changed in the area, and direct discharges to Tinto and Odiel River had to be ceased. A thorough study of the affected zone is being carried out. Riverbed sediments and water samples have been analyzed from four different sampling campaigns in the estuary during the years 1999, 2001, 2002 and 2005. Different radioanalytical techniques have been employed to obtain the activity concentrations of U-isotopes, Th-isotopes, 226Ra, 210Pb and 210Po. Furthermore, the results for the rates of de-contamination of the area are presented. This data will be discussed in order to establish the present status of the contamination in the area, and moreover, to predict the time-evolution of the self-cleaning

  13. Time Evolution of Activity Concentration of Natural Emitters in a Scenario Affected By Previous Phosphogypsum Contamination

    SciTech Connect

    Villa, M.; Hurtado, S.; Mantero, J.; Manjon, G.; Garcia-Tenorio, R.; Mosqueda, F.; Vaca, F.

    2008-08-07

    The estuary formed by the confluence of Tinto and Odiel river-mouths is located in the South of Spain, close to Huelva town. This estuary has been deeply studied through the years because it has a double particularity. On one hand, since the beginning of the 1960s, the estuary has been affected by direct and indirect phosphogypsum (pg.) releases from two phosphoric acid and fertilizers factories that are working in the area. On the other hand, the pyrite mining operations upstream the Odiel and Tinto rivers has caused historically the formation of H{sub 2}SO{sub 4}, through oxidation of the natural sulphur deposits, the acidification of the waters and the consequent mobilisation of heavy metals from the mining area to the Huelva estuary. As a consequence, enhancement contamination levels in natural emitters from the {sup 238}U series were found in the surroundings of the factories in the previous years to 1998. However, in 1998 the management policy of waste releases drastically changed in the area, and direct discharges to Tinto and Odiel River had to be ceased.A thorough study of the affected zone is being carried out. Riverbed sediments and water samples have been analyzed from four different sampling campaigns in the estuary during the years 1999, 2001, 2002 and 2005. Different radioanalytical techniques have been employed to obtain the activity concentrations of U-isotopes, Th-isotopes, {sup 226}Ra, {sup 210}Pb and {sup 210}Po. Furthermore, the results for the rates of de-contamination of the area are presented. This data will be discussed in order to establish the present status of the contamination in the area, and moreover, to predict the time-evolution of the self-cleaning.

  14. Chemical factors affecting fission product transport in severe LMFBR accidents

    SciTech Connect

    Wichner, R.P.; Jolley, R.L.; Gat, U.; Rodgers, B.R.

    1984-10-01

    This study was performed as a part of a larger evaluation effort on LMFBR accident, source-term estimation. Purpose was to provide basic chemical information regarding fission product, sodium coolant, and structural material interactions required to perform estimation of fission product transport under LMFBR accident conditions. Emphasis was placed on conditions within the reactor vessel; containment vessel conditions are discussed only briefly.

  15. Solid waste leach characteristics and contaminant-sediment interactions Volume 2: Contaminant transport under unsaturated moisture contents

    SciTech Connect

    Lindenmeier, C.W.; Serne, R.J.; Conca, J.L.

    1995-09-01

    The objectives of this report and subsequent volumes include describing progress on (1) development and optimization of experimental methods to quantify the release of contaminants from solid wastes and their subsequent interactions with unsaturated sediments and (2) the creation of empirical data that become input parameters to performance assessment (PA) analyses for future Hanford Site disposal units and baseline risk assessments for inactive and existing solid waste disposal units. For this report, efforts focused on developing methodologies to evaluate contaminant transport in Trench 8 (W-5 Burial Ground) sediments under unsaturated (vadose zone) conditions. To accomplish this task, a series of flow-through column tests were run using standard saturated column systems, Wierenga unsaturated column systems (both commercial and modified), and the Unsaturated Flow Apparatus (UFA). The reactants investigated were {sup 85}Sr, {sup 236}U, and {sup 238}U as reactive tracers, and tritium as a non-reactive tracer. Results indicate that for moderately unsaturated conditions (volumetric water contents >50 % of saturation), the Wierenga system performed reasonably well such that long water residence times (50-147 h) were achieved, and reasonably good steady-state flow conditions were maintained. The major drawbacks in using this system for reactive tracer work included (1) the inability to achieve reproducible and constant moisture content below 50% of saturation, (2) the four to six month time required to complete a single test, and (3) the propensity for mechanical failure resulting from laboratory power outages during the prolonged testing period.

  16. Packaging, Transportation, and Disposal Logistics for Large Radioactively Contaminated Reactor Decommissioning Components

    SciTech Connect

    Lewis, Mark S.

    2008-01-15

    The packaging, transportation and disposal of large, retired reactor components from operating or decommissioning nuclear plants pose unique challenges from a technical as well as regulatory compliance standpoint. In addition to the routine considerations associated with any radioactive waste disposition activity, such as characterization, ALARA, and manifesting, the technical challenges for large radioactively contaminated components, such as access, segmentation, removal, packaging, rigging, lifting, mode of transportation, conveyance compatibility, and load securing require significant planning and execution. In addition, the current regulatory framework, domestically in Titles 49 and 10 and internationally in TS-R-1, does not lend itself to the transport of these large radioactively contaminated components, such as reactor vessels, steam generators, reactor pressure vessel heads, and pressurizers, without application for a special permit or arrangement. This paper addresses the methods of overcoming the technical and regulatory challenges. The challenges and disposition decisions do differ during decommissioning versus component replacement during an outage at an operating plant. During decommissioning, there is less concern about critical path for restart and more concern about volume reduction and waste minimization. Segmentation on-site is an available option during decommissioning, since labor and equipment will be readily available and decontamination activities are routine. The reactor building removal path is also of less concern and there are more rigging/lifting options available. Radionuclide assessment is necessary for transportation and disposal characterization. Characterization will dictate the packaging methodology, transportation mode, need for intermediate processing, and the disposal location or availability. Characterization will also assist in determining if the large component can be transported in full compliance with the transportation

  17. Reduction of spatial distribution of risk factors for transportation of contaminants released by coal mining activities.

    PubMed

    Karan, Shivesh Kishore; Samadder, Sukha Ranjan

    2016-09-15

    It is reported that water-energy nexus composes two of the biggest development and human health challenges. In the present study we presented a Risk Potential Index (RPI) model which encapsulates Source, Vector (Transport), and Target risks for forecasting surface water contamination. The main aim of the model is to identify critical surface water risk zones for an open cast mining environment, taking Jharia Coalfield, India as the study area. The model also helps in feasible sampling design. Based on spatial analysis various risk zones were successfully delineated. Monthly RPI distribution revealed that the risk of surface water contamination was highest during the monsoon months. Surface water samples were analysed to validate the model. A GIS based alternative management option was proposed to reduce surface water contamination risk and observed 96% and 86% decrease in the spatial distribution of very high risk areas for the months June and July respectively.

  18. Technology assessment of future intercity passenger transporation systems. Volume 2: Identification of issues affecting intercity transportation

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Papers on major issues and trends that affect the future of intercity transportation are presented. Specific areas covered include: political, social, technological, institutional, and economic mechanisms, the workings of which determine how future intercity transporation technologies will evolve and be put into service; the major issues of intercity transportation from the point of view of reform, including candidate transporation technologies; and technical analysis of trends affecting the evolution of intercity transportation technologies.

  19. Composite resin bond strength to caries-affected dentin contaminated with 3 different hemostatic agents.

    PubMed

    Khoroushi, Maryam; Hosseini-Shirazi, Moeen; Farahbod, Foroozan; Keshani, Fatemeh

    2016-01-01

    Bonding of composite resins to sound and caries-affected dentin in cervical areas may necessitate the use of hemostatic agents to control sulcular fluid and hemorrhage. The aim of this in vitro study was to evaluate the bond strengths of a self-etching adhesive system to sound and caries-affected dentin after the use of 3 different hemostatic agents. Composite resin cylinders were bonded to 48 caries-affected and 48 sound dentin surfaces in 8 groups. Groups 1-4 utilized caries-affected dentin: group 1, uncontaminated control; 2, ViscoStat; 3, ViscoStat Clear; and 4, trichloroacetic acid (TCA). Groups 5-8 utilized sound dentin: group 5, uncontaminated control; 6, ViscoStat; 7, ViscoStat Clear; and 8, TCA. The hemostatic agents were applied for 2 minutes and rinsed. After 500 rounds of thermocycling, shear bond strength tests were carried out. Data were analyzed with 1- and 2-way analyses of variance, t test, and post hoc Tukey tests at a significance level of P < 0.05. Bond strength was significantly influenced by dentin type (F = 38.23; P = 0.0001) and hemostatic agent (F = 6.32; P = 0.001). Furthermore, groups 2 and 6 (ViscoStat) showed significantly lower bond strength values than the control groups (groups 1 and 5) in both affected and sound dentin (P = 0.043 and P = 0.009, respectively). Within the limitations of this study, the bond strength of composite resin to caries-affected dentin was significantly reduced compared to that with sound dentin. Among the studied hemostatic agents, ViscoStat resulted in a greater decrease in dentin bond strength. Contamination of both sound and caries-affected dentin with hemostatic agents decreased composite resin bond strength. Of the 3 hemostatic agents used, ViscoStat Clear appeared to have the least detrimental effect on bond strength. PMID:27367640

  20. The feed contaminant deoxynivalenol affects the intestinal barrier permeability through inhibition of protein synthesis.

    PubMed

    Awad, Wageha A; Zentek, Jürgen

    2015-06-01

    Deoxynivalenol (DON) has critical health effects if the contaminated grains consumed by humans or animals. DON can have negative effects on the active transport of glucose and amino acids in the small intestine of chickens. As the underlying mechanisms are not fully elucidated, the present study was performed to delineate more precisely the effects of cycloheximide (protein synthesis inhibitor, CHX) and DON on the intestinal absorption of nutrients. This was to confirm whether DON effects on nutrient absorption are due to an inhibition of protein synthesis. Changes in ion transport and barrier function were assessed by short-circuit current (Isc) and transepithelial ion conductance (Gt) in Ussing chambers. Addition of D-glucose or L-glutamine to the luminal side of the isolated mucosa of the jejunum increased (P < 0.001) the Isc compared with basal conditions in the control tissues. However, the Isc was not increased by the glucose or glutamine addition after pre-incubation of tissues with DON or CHX. Furthermore, both DON and CHX reduced Gt, indicating that the intestinal barrier is compromised and consequently induced a greater impairment of the barrier function. The remarkable similarity between the activity of CHX and DON on nutrient uptake is consistent with their common ability to inhibit protein synthesis. It can be concluded that the decreases in transport activity by CHX was evident in this study using the chicken as experimental model. Similarly, DON has negative effects on the active transport of some nutrients, and these can be explained by its influence on protein synthesis. PMID:24888376

  1. The feed contaminant deoxynivalenol affects the intestinal barrier permeability through inhibition of protein synthesis.

    PubMed

    Awad, Wageha A; Zentek, Jürgen

    2015-06-01

    Deoxynivalenol (DON) has critical health effects if the contaminated grains consumed by humans or animals. DON can have negative effects on the active transport of glucose and amino acids in the small intestine of chickens. As the underlying mechanisms are not fully elucidated, the present study was performed to delineate more precisely the effects of cycloheximide (protein synthesis inhibitor, CHX) and DON on the intestinal absorption of nutrients. This was to confirm whether DON effects on nutrient absorption are due to an inhibition of protein synthesis. Changes in ion transport and barrier function were assessed by short-circuit current (Isc) and transepithelial ion conductance (Gt) in Ussing chambers. Addition of D-glucose or L-glutamine to the luminal side of the isolated mucosa of the jejunum increased (P < 0.001) the Isc compared with basal conditions in the control tissues. However, the Isc was not increased by the glucose or glutamine addition after pre-incubation of tissues with DON or CHX. Furthermore, both DON and CHX reduced Gt, indicating that the intestinal barrier is compromised and consequently induced a greater impairment of the barrier function. The remarkable similarity between the activity of CHX and DON on nutrient uptake is consistent with their common ability to inhibit protein synthesis. It can be concluded that the decreases in transport activity by CHX was evident in this study using the chicken as experimental model. Similarly, DON has negative effects on the active transport of some nutrients, and these can be explained by its influence on protein synthesis.

  2. Removing volatile contaminants from the unsaturated zone by inducing advective air-phase transport

    USGS Publications Warehouse

    Baehr, A.L.; Hoag, G.E.; Marley, M.C.

    1989-01-01

    Organic liquids inadvertently spilled and then distributed in the unsaturated zone can pose a long-term threat to ground water. Many of these substances have significant volatility, and thereby establish a premise for contaminant removal from the unsaturated zone by inducing advective air-phase transport with wells screened in the unsaturated zone. In order to focus attention on the rates of mass transfer from liquid to vapour phases, sand columns were partially saturated with gasoline and vented under steady air-flow conditions. The ability of an equilibrium-based transport model to predict the hydrocarbon vapor flux from the columns implies an efficient rate of local phase transfer for reasonably high air-phase velocities. Thus the success of venting remediations will depend primarily on the ability to induce an air-flow field in a heterogeneous unsaturated zone that will intersect the distributed contaminant. To analyze this aspect of the technique, a mathematical model was developed to predict radially symmetric air flow induced by venting from a single well. This model allows for in-situ determinations of air-phase permeability, which is the fundamental design parameter, and for the analysis of the limitations of a single well design. A successful application of the technique at a site once contaminated by gasoline supports the optimism derived from the experimental and modeliing phases of this study, and illustrates the well construction and field methods used to document the volatile contaminant recovery. ?? 1989.

  3. Coupled effect of flow variability and mass transfer on contaminant transport and attenuation in groundwater

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Vladimir; Fiori, Aldo; Dagan, Gedeon

    2016-04-01

    The driving mechanism of contaminant transport in aquifers is groundwater flow, which is controlled by boundary conditions and heterogeneity of hydraulic properties. In this work we show how hydrodynamics and mass transfer can be combined in a general analytical manner to derive a physically-based (or process-based) residence time distribution for a given integral scale of the hydraulic conductivity; the result can be applied for a broad class of linear mass transfer processes. The derived tracer residence time distribution is a transfer function with parameters to be inferred from combined field and laboratory measurements. It is scalable relative to the correlation length and applicable for an arbitrary statistical distribution of the hydraulic conductivity. Based on the derived residence time distribution, the coefficient of variation and skewness of contaminant residence time are illustrated assuming a log-normal hydraulic conductivity distribution and first-order mass transfer. We show that for a low Damkohler number the coefficient of variation is more strongly influenced by mass transfer than by heterogeneity, whereas skewness is more strongly influenced by heterogeneity. The derived physically-based residence time distribution for solute transport in heterogeneous aquifers is particularly useful for studying natural attenuation of contaminants. We illustrate the relative impacts of high heterogeneity and a generalised (non-Fickian) multi-rate mass transfer on natural attenuation defined as contaminant mass loss from injection to a downstream compliance boundary.

  4. Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

    SciTech Connect

    Chorover, Jon; Perdrial, Nico; Mueller, Karl; Strepka, Caleb; O’Day, Peggy; Rivera, Nelson; Um, Wooyong; Chang, Hyun-Shik; Steefel, Carl; Thompson, Aaron

    2012-11-05

    Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, partial pressure of carbon dioxide, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. In this final report, we provide detailed descriptions of our results from this three-year study, completed in 2012 following a one-year no cost extension.

  5. Testing of a benchscale Reverse Osmosis/Coupled Transport system for treating contaminated groundwater

    SciTech Connect

    Hodgson, K.M.; Lunsford, T.R.; Panjabi, G.

    1994-01-01

    The Reverse Osmosis/Coupled Transport process is a innovative means of removing radionuclides from contaminated groundwater at the Hanford Site. Specifically, groundwater in the 200 West Area of the Hanford Site has been contaminated with uranium, technetium, and nitrate. Investigations are proceeding to determine the most cost effective method to remove these contaminants. The process described in this paper combines three different membrane technologies (reverse osmosis, coupled transport, and nanofiltration to purify the groundwater while extracting and concentrating uranium, technetium, and nitrate into separate solutions. This separation allows for the future use of the radionuclides, if needed, and reduces the amount of waste that will need to be disposed of. This process has the potential to concentrate the contaminants into solutions with volumes in a ratio of 1/10,000 of the feed volume. This compares to traditional volume reductions of 10 to 100 for ion exchange and stand-alone reverse osmosis. The successful demonstration of this technology could result in significant savings in the overall cost of decontaminating the groundwater.

  6. High-Level Waste Tanks Multi-Dimensional Contaminant Transport Model Development Enhancements for 2000

    SciTech Connect

    Collard, L.B.

    2001-09-21

    A suite of multi-dimensional computer models was developed in 1999 (Collard and Flach) to analyze the transport of residual contamination from high-level waste tanks through the subsurface to seeplines. Enhancements in 2000 to those models include investigate the effect of numerical dispersion, develop a solubility-limited case for U and Pu, and develop a plan for a database as part of the Rapid Screening Tool and start to implement that plan.

  7. Characterizing the Transport of a Novel, Engineered Nanoparticle for Use in Remediation of Hydrophobic Contaminants

    NASA Astrophysics Data System (ADS)

    Sanders, J. E.; Miller, G. R.

    2015-12-01

    Magnetic shell crosslinked knedel-like nanoparticles (MSCKs) were originally engineered to aid in the cleanup of oil spills. These polymeric particles are spherical and approximately 70 nm in diameter. MSCKs have a hydrophobic shell and hydrophilic core which encapsulates suspended iron oxide nanoparticles, rendering them magnetic. MSCKs operate like discrete surfactant packets: increasing the mobility and apparent solubility of hydrophobic species, but do so within the confines of discrete particles which can then be recovered by filtration or magnetic removal. MSCKs accomplish this via sequestration of hydrophobic species from through the hydrophilic shell and into the hydrophobic core where hydrocarbon contaminants are entropically stabilized. In batch reactor testing, MSCKs have been shown to sequester crude oil up to ten times their mass (1000 mg of oil per 100 mg of MSCKs). This study examines the transport characteristics and contaminant sequestration capabilities of MSCKs in saturated porous media, in order to establish their potential for use in groundwater remediation. Baseline MSCK transport parameters were determined via one dimensional impulse column experiments. MSCKs were readily transported in saturated sand, with an average recovery rate of 99%. In the presence of 10% clay particles, recovery was reduced to 68%. MSCKs were able to completely sequester an aqueous phase pollutant (8.7 mg/L m-xylene), although it further reduced their recovery rate to 61% in sand and 53% in clay. The presence of a free phase contaminant (5% of pore space occupied by mineral oil) reduced MSCKs recovery in sand to 53%. The MSCKs recovered in the effluent had sequestered the mineral at ratios far below their capability (3-10 mg of oil per 100 mg of MSCKs). Overall, this study indicated that MSCKs show a number of promising attributes for use in remediation. However, further manipulation of their chemical and morphological properties is needed, with the objective of

  8. Safety analysis report for packaging, onsite, long-length contaminated equipment transport system

    SciTech Connect

    McCormick, W.A.

    1997-05-09

    This safety analysis report for packaging describes the components of the long-length contaminated equipment (LLCE) transport system (TS) and provides the analyses, evaluations, and associated operational controls necessary for the safe use of the LLCE TS on the Hanford Site. The LLCE TS will provide a standardized, comprehensive approach for the disposal of approximately 98% of LLCE scheduled to be removed from the 200 Area waste tanks.

  9. Analytical Solution for Multi-Species Contaminant Transport Subject to Sequential First-Order Decay Reactions in Finite Media

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport equations governing the movement of multiple solutes undergoing sequential first-order decay reactions have relevance in analyzing a variety of subsurface contaminant transport problems. In this study, a one-dimensional analytical solution for multi-species transport is obtained for finite...

  10. MODELING MICROBIAL TRANSPORT IN SOIL AND GROUNDWATER: MICROBIOLOGISTS CAN ASSIST IN THE DEVELOPMENT OF MODELS OF CONTAMINANT TRANSPORT

    EPA Science Inventory

    A large body of literature describes the processes affecting the fate of microorganisms in the subsurface environment (i.e., soil and groundwater). The fate of microorganisms depends on two main components: survival and transport. other components must be considered when determin...

  11. The antiepileptic drug phenytoin affects sodium transport in toad epithelium.

    PubMed

    Suwalsky, Mario; Mennickent, Sigrid; Norris, Beryl; Cárdenas, Hernan

    2006-01-01

    The effects of phenytoin on isolated Pleurodema thaul toad skin were investigated. Low (micromolar) concentrations of the antiepileptic agent applied to the outside surface of the toad epithelium increased the electrical parameters (short-circuit current and potential difference) by over 40%, reflecting stimulation of Na(+) transport, whereas higher (millimolar concentrations, outside and inside surface) decreased both electric parameters, the effect being greater at the inside surface (40% and 80% decrease, respectively). The amiloride test showed that the stimulatory effect was accompanied by an increase and the inhibitory effect by a decrease in the sodium electromotive force (ENa). It is concluded that the drug interaction with membrane lipid bilayers might result in a distortion of the lipid-protein interface contributing to disturbance of Na(+) epithelial channel activity. After applying the Na(+)-K(+)-ATPase blocker ouabain and replacing the Na(+) ions in the outer Ringer's solution by choline, it was concluded that both active and passive transport are involved in sodium absorption, although active transport predominates. PMID:16314149

  12. Modeling hydrology and reactive transport in roads: the effect of cracks, the edge, and contaminant properties.

    PubMed

    Apul, Defne S; Gardner, Kevin H; Eighmy, T Taylor

    2007-01-01

    The goal of this research was to provide a tool for regulators to evaluate the groundwater contamination from the use of virgin and secondary materials in road construction. A finite element model, HYDRUS2D, was used to evaluate generic scenarios for secondary material use in base layers. Use of generic model results for particular applications was demonstrated through a steel slag example. The hydrology and reactive transport of contaminants were modeled in a two-dimensional cross section of a road. Model simulations showed that in an intact pavement, lateral velocities from the edge towards the centerline may transport contaminants in the base layer. The dominant transport mechanisms are advection closer to the edge and diffusion closer to the centerline. A shoulder joint in the pavement allows 0.03 to 0.45 m(3)/day of infiltration per meter of joint length as a function of the base and subgrade hydrology and the rain intensity. Scenario simulations showed that salts in the base layer of pavements are depleted by 99% in the first 20 years, whereas the metals may not reach the groundwater in 20 years at any significant concentrations if the pavement is built on adsorbing soils. PMID:17521900

  13. Modeling hydrology and reactive transport in roads: the effect of cracks, the edge, and contaminant properties.

    PubMed

    Apul, Defne S; Gardner, Kevin H; Eighmy, T Taylor

    2007-01-01

    The goal of this research was to provide a tool for regulators to evaluate the groundwater contamination from the use of virgin and secondary materials in road construction. A finite element model, HYDRUS2D, was used to evaluate generic scenarios for secondary material use in base layers. Use of generic model results for particular applications was demonstrated through a steel slag example. The hydrology and reactive transport of contaminants were modeled in a two-dimensional cross section of a road. Model simulations showed that in an intact pavement, lateral velocities from the edge towards the centerline may transport contaminants in the base layer. The dominant transport mechanisms are advection closer to the edge and diffusion closer to the centerline. A shoulder joint in the pavement allows 0.03 to 0.45 m(3)/day of infiltration per meter of joint length as a function of the base and subgrade hydrology and the rain intensity. Scenario simulations showed that salts in the base layer of pavements are depleted by 99% in the first 20 years, whereas the metals may not reach the groundwater in 20 years at any significant concentrations if the pavement is built on adsorbing soils.

  14. Modeling hydrology and reactive transport in roads: The effect of cracks, the edge, and contaminant properties

    SciTech Connect

    Apul, Defne S. Gardner, Kevin H. Eighmy, T. Taylor

    2007-07-01

    The goal of this research was to provide a tool for regulators to evaluate the groundwater contamination from the use of virgin and secondary materials in road construction. A finite element model, HYDRUS2D, was used to evaluate generic scenarios for secondary material use in base layers. Use of generic model results for particular applications was demonstrated through a steel slag example. The hydrology and reactive transport of contaminants were modeled in a two-dimensional cross section of a road. Model simulations showed that in an intact pavement, lateral velocities from the edge towards the centerline may transport contaminants in the base layer. The dominant transport mechanisms are advection closer to the edge and diffusion closer to the centerline. A shoulder joint in the pavement allows 0.03 to 0.45 m{sup 3}/day of infiltration per meter of joint length as a function of the base and subgrade hydrology and the rain intensity. Scenario simulations showed that salts in the base layer of pavements are depleted by 99% in the first 20 years, whereas the metals may not reach the groundwater in 20 years at any significant concentrations if the pavement is built on adsorbing soils.

  15. Processes affecting transport of uranium in a suboxic aquifer

    USGS Publications Warehouse

    Davis, J.A.; Curtis, G.P.; Wilkins, M.J.; Kohler, M.; Fox, P.; Naftz, D.L.; Lloyd, J.R.

    2006-01-01

    At the Naturita site in Colorado, USA, groundwaters were sampled and analyzed for chemical composition and by culture and culture-independent microbiological techniques. In addition, sediments were extracted with a dilute sodium carbonate solution to determine quantities of labile uranium within the sediments. Samples from the upgradient portion of the contaminated aquifer, where very little dissolved Fe(II) is found in the groundwater, have uranium content that is controlled by U(VI) adsorption and few metal-reducing bacteria are observed. In the extreme downgradient portion of the aquifer, where dissolved Fe(II) is observed, uranium content of the sediments includes significant quantities of reduced U(IV) and diverse populations of Fe(III)-reducing bacteria were present in the subsurface with the potential of reducing U(VI) to U(IV). ?? 2006 Elsevier Ltd. All rights reserved.

  16. A semi-analytical solution for simulating contaminant transport subject to chain-decay reactions.

    PubMed

    Sudicky, Edward A; Hwang, Hyoun-Tae; Illman, Walter A; Wu, Yu-Shu; Kool, Jan B; Huyakorn, Peter

    2013-01-01

    We present a set of new, semi-analytical solutions to simulate three-dimensional contaminant transport subject to first-order chain-decay reactions. The aquifer is assumed to be areally semi-infinite, but finite in thickness. The analytical solution can treat the transformation of contaminants into daughter products, leading to decay chains consisting of multiple contaminant species and various reaction pathways. The solution in its current form is capable of accounting for up to seven species and four decay levels. The complex pathways are represented by means of first-order decay and production terms, while branching ratios account for decay stoichiometry. Besides advection, dispersion, bio-chemical or radioactive decay and daughter product formation, the model also accounts for sorption of contaminants on the aquifer solid phase with each species having a different retardation factor. First-type contaminant boundary conditions are utilized at the source (x=0 m) and can be either constant-in-time for each species, or the concentration can be allowed to undergo first-order decay. The solutions are obtained by exponential Fourier, Fourier cosine and Laplace transforms. Limiting forms of the solutions can be obtained in closed form, but we evaluate the general solutions by numerically inverting the analytical solutions in exponential Fourier and Laplace transform spaces. Various cases are generated and the solutions are verified against the HydroGeoSphere numerical model.

  17. Bioassessment of contaminant transport and distribution in aquatic ecosystems by chemical analysis of burrowing mayflies (Hexagenia)

    USGS Publications Warehouse

    Steingraeber, M.T.; Wiener, J.G.

    1995-01-01

    Burrowing mayfly nymphs (Ephemeroptera) inhabit and ingest fine-grained sediments and detritus that may be enriched with metals and persistent organic compounds. The burrowing nymphs can externally adsorb and internally assimilate these contaminants, providing a link for the food chain transfer of potentially toxic substances from sediments to organisms in higher trophic levels. The emergent adults are short-lived and do not feed, thus their gut contents do not contribute greatly to their total contaminant burden. These characteristics make Hexagenia spp. And certain other burrowing mayflies useful for assessing ecosystem contamination. General protocols are presented for the collection, processing and analysis of emergent mayflies to assess the spatial distribution and bioaccumulation of sediment-associated contaminants in aquatic ecosystems. Two essential components of this bioassessment approach are a network of on-site volunteers with the materials and instructions needed to correctly collect and store samples and quality assurance procedures to estimate the accuracy of chemical analyses. The utility of this approach is demonstrated with an example of its application to the Upper Mississippi River (USA). Determination of cadmium, mercury and polychlorinated biphenyl congeners in emergent Hexagenia bilineata from a 1250 km reach of this river revealed (1) several source areas of contaminants and (2) distinct patterns in the bioaccumulation (and apparent sediment-associated transport) of each residue on both small and large spatial scales.

  18. TRANSPORT OF INORGANIC COLLOIDS THROUGH NATURAL AQUIFER MATERIAL: IMPLICATIONS FOR CONTAMINANT TRANSPORT

    EPA Science Inventory

    The stability and transport of radiolabeled Fe2O3 particles were studied using laboratory batch and column techniques. Core material collected from a shallow sand and gravel aquifer was used as the immobile column matrix material. Variables in the study incl...

  19. TREX: spatially distributed model to assess watershed contaminant transport and fate.

    PubMed

    Velleux, Mark L; England, John F; Julien, Pierre Y

    2008-10-01

    Contaminant releases from upland areas can have adverse water quality and stream ecology impacts. TREX (Two-dimensional, Runoff, Erosion, and Export) is a spatially distributed, physically-based model to simulate chemical transport and fate at the watershed scale. TREX combines surface hydrology and sediment transport features from the CASC2D watershed model with chemical transport features from the WASP/IPX series of water quality models. In addition to surface runoff and sediment transport, TREX simulates: (1) chemical erosion, advection, and deposition; (2) chemical partitioning and phase distribution; and (3) chemical infiltration and redistribution. Floodplain interactions for water, sediment, and chemicals are also simulated. To demonstrate the potential for using TREX to simulate chemical transport at the watershed scale, a screening-level application was developed for the California Gulch watershed mine-waste site in Colorado. Runoff, sediment transport, and metals (Cu, Cd, Zn) transport were simulated for a calibration event and a validation event. The model reproduced measured peak flows, and times to peak at the watershed outlet and three internal locations. Simulated flow volumes were within approximately 10% of measured conditions. Model results were also generally within measured ranges of total suspended solid and metal concentrations. TREX is an appropriate tool for investigating multimedia environmental problems that involve water, soils, and chemical interactions in a spatially distributed manner within a watershed. PMID:18649925

  20. Characterization of Uranium Contamination, Transport, and Remediation at Rocky Flats - Across Remediation into Post-Closure

    NASA Astrophysics Data System (ADS)

    Janecky, D. R.; Boylan, J.; Murrell, M. T.

    2009-12-01

    The Rocky Flats Site is a former nuclear weapons production facility approximately 16 miles northwest of Denver, Colorado. Built in 1952 and operated by the Atomic Energy Commission and then Department of Energy, the Site was remediated and closed in 2005, and is currently undergoing long-term surveillance and monitoring by the DOE Office of Legacy Management. Areas of contamination resulted from roughly fifty years of operation. Of greatest interest, surface soils were contaminated with plutonium, americium, and uranium; groundwater was contaminated with chlorinated solvents, uranium, and nitrates; and surface waters, as recipients of runoff and shallow groundwater discharge, have been contaminated by transport from both regimes. A region of economic mineralization that has been referred to as the Colorado Mineral Belt is nearby, and the Schwartzwalder uranium mine is approximately five miles upgradient of the Site. Background uranium concentrations are therefore elevated in many areas. Weapons-related activities included work with enriched and depleted uranium, contributing anthropogenic content to the environment. Using high-resolution isotopic analyses, Site-related contamination can be distinguished from natural uranium in water samples. This has been instrumental in defining remedy components, and long-term monitoring and surveillance strategies. Rocky Flats hydrology interlinks surface waters and shallow groundwater (which is very limited in volume and vertical and horizontal extent). Surface water transport pathways include several streams, constructed ponds, and facility surfaces. Shallow groundwater has no demonstrated connection to deep aquifers, and includes natural preferential pathways resulting primarily from porosity in the Rocky Flats alluvium, weathered bedrock, and discontinuous sandstones. In addition, building footings, drains, trenches, and remedial systems provide pathways for transport at the site. Removal of impermeable surfaces (buildings

  1. Copper phytoavailability and uptake by Elsholtzia splendens from contaminated soil as affected by soil amendments.

    PubMed

    Peng, Hong-Yun; Yang, Xiao-E; Jiang, Li-Ying; He, Zhen-Li

    2005-01-01

    Pot and field experiments were conducted to evaluate bioavailability of Cu in contaminated paddy soil (PS) and phytoremediation potential by Elsholtzia splendens as affected by soil amendments. The results from pot experiment showed that organic manure (M) applied to the PS not only remarkably raised the H2O exchangeable Cu, which were mainly due to the increased exchangeable and organic fractions of Cu in the PS by M, but also stimulated plant growth and Cu accumulation in E. splendens. At M application rate of 5.0%, shoot Cu concentration in the plant increased by four times grown on the PS, so as to the elevated shoot Cu accumulation by three times as compared to the control. In the field trial, soil amendments by M and furnace slag (F), and soil preparations like soil capping (S) and soil discing (D) were performed in the PS. Soil capping and discing considerably declined total Cu in the PS. Application of M solely or together with F enhanced plant growth and increased H2O exchangeable Cu levels in the soil. The increased extractability of Cu in the rhizosphere of E. splendens was noted, which may have mainly attributed to the rhizospheric acidification and chelation by dissolved organic matter (DOM), thus resulting in elevating Cu uptake and accumulation by E. splendens. Amendments with organic manure plus furnace slag (MF) to the PS caused the highest exactable Cu with saturated H2O in the rhizospheric soil of E. splendens after they were grown for 170 days in the PS, thus achieving 1.74 kg Cu ha(-1) removal from the contaminated soil by the whole plant of E. splendens at one season, which is higher than those of the other soil treatments. The results indicated that application of organic manure at a proper rate could enhance Cu bioavailability and increase effectiveness of Cu phytoextraction from the contaminated soil by the metal-tolerant and accumulating plant species (E. splendens). PMID:15792303

  2. Electron donors and co-contaminants affect microbial community composition and activity in perchlorate degradation.

    PubMed

    Guan, Xiangyu; Xie, Yuxuan; Wang, Jinfeng; Wang, Jing; Liu, Fei

    2015-04-01

    Although microbial reduction of perchlorate (ClO4(-)) is a promising and effective method, our knowledge on the changes in microbial communities during ClO4(-) degradation is limited, especially when different electron donors are supplied and/or other contaminants are present. Here, we examined the effects of acetate and hydrogen as electron donors and nitrate and ammonium as co-contaminants on ClO4(-) degradation by anaerobic microcosms using six treatments. The process of degradation was divided into the lag stage (SI) and the accelerated stage (SII). Quantitative PCR was used to quantify four genes: pcrA (encoding perchlorate reductase), cld (encoding chlorite dismutase), nirS (encoding copper and cytochrome cd1 nitrite reductase), and 16S rRNA. While the degradation of ClO4(-) with acetate, nitrate, and ammonia system (PNA) was the fastest with the highest abundance of the four genes, it was the slowest in the autotrophic system (HYP). The pcrA gene accumulated in SI and played a key role in initiating the accelerated degradation of ClO4(-) when its abundance reached a peak. Degradation in SII was primarily maintained by the cld gene. Acetate inhibited the growth of perchlorate-reducing bacteria (PRB), but its effect was weakened by nitrate (NO3(-)), which promoted the growth of PRB in SI, and therefore, accelerated the ClO4(-) degradation rate. In addition, ammonia (NH4(+)), as nitrogen sources, accelerated the growth of PRB. The bacterial communities' structure and diversity were significantly affected by electron donors and co-contaminants. Under heterotrophic conditions, both ammonia and nitrate promoted Azospira as the most dominant genera, a fact that might significantly influence the rate of ClO4(-) natural attenuation by degradation.

  3. Monitoring Potential Transport of Radioactive Contaminants in Shallow Ephemeral Channels: FY 2012

    SciTech Connect

    Miller, Julianne J.; Mizell, Steve A.; McCurdy, Greg; Campbell, Scott A.

    2012-09-01

    The US Department of Energy (DOE) National Nuclear Security Administration (NNSA), Nevada Site Office (NSO), Environmental Management’s Soils Activity has authorized the Desert Research Institute (DRI) to conduct field assessments of potential sediment transport of contaminated soil from Corrective Action Unit (CAU) 550, Smoky Contamination Area (CA), during precipitation runoff events. CAU 550 includes Corrective Action Sites (CASs) 08-23-03, 08-23-04, 08-23-06, and 08-23-07; these CASs are associated with tests designated Ceres, Smoky, Oberon, and Titania, respectively. Field measurements at the T-4 Atmospheric Test Site, CAU 370, suggest that radioactive material may have migrated along a shallow ephemeral drainage that traverses the site (NNSA/NSO, 2009). (It is not entirely clear how contaminated soils got into their present location at the T-4 Site, but flow to the channel has been redirected and the contamination does not appear to be migrating at present.) Although DRI initially looked at the CAU 370 site, given that it could not be confirmed that migration of contamination into the channel was natural, an alternate study site was selected at CAU 550. Aerial surveys in selected portions of the Nevada National Security Site (NNSS) also suggest that radioactivity may be migrating along ephemeral channels in Areas 3, 8, 11, 18, and 25 (Colton, 1999). Figure 1 shows the results of a low-elevation aerial survey (Colton, 1999) in Area 8. The numbered markers in Figure 1 identify ground zero for three safety experiments conducted in 1958 [Oberon (number 1), Ceres (number 2), and Titania (number 4)] and a weapons effects test conducted in 1964, Mudpack (number 3). This survey suggests contaminants may be migrating down the ephemeral channels that traverse CAU 550. Note particularly the lobe of higher concentration extending southeastward at the south end of the high concentration area marked as number 3 in Figure 1. CAU 550 in Area 8 of the NNSS was selected for

  4. Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder.

    PubMed

    Mc Mahon, Brenda; Andersen, Sofie B; Madsen, Martin K; Hjordt, Liv V; Hageman, Ida; Dam, Henrik; Svarer, Claus; da Cunha-Bang, Sofi; Baaré, William; Madsen, Jacob; Hasholt, Lis; Holst, Klaus; Frokjaer, Vibe G; Knudsen, Gitte M

    2016-05-01

    Cross-sectional neuroimaging studies in non-depressed individuals have demonstrated an inverse relationship between daylight minutes and cerebral serotonin transporter; this relationship is modified by serotonin-transporter-linked polymorphic region short allele carrier status. We here present data from the first longitudinal investigation of seasonal serotonin transporter fluctuations in both patients with seasonal affective disorder and in healthy individuals. Eighty (11)C-DASB positron emission tomography scans were conducted to quantify cerebral serotonin transporter binding; 23 healthy controls with low seasonality scores and 17 patients diagnosed with seasonal affective disorder were scanned in both summer and winter to investigate differences in cerebral serotonin transporter binding across groups and across seasons. The two groups had similar cerebral serotonin transporter binding in the summer but in their symptomatic phase during winter, patients with seasonal affective disorder had higher serotonin transporter than the healthy control subjects (P = 0.01). Compared to the healthy controls, patients with seasonal affective disorder changed their serotonin transporter significantly less between summer and winter (P < 0.001). Further, the change in serotonin transporter was sex- (P = 0.02) and genotype- (P = 0.04) dependent. In the patients with seasonal affective disorder, the seasonal change in serotonin transporter binding was positively associated with change in depressive symptom severity, as indexed by Hamilton Rating Scale for Depression - Seasonal Affective Disorder version scores (P = 0.01). Our findings suggest that the development of depressive symptoms in winter is associated with a failure to downregulate serotonin transporter levels appropriately during exposure to the environmental stress of winter, especially in individuals with high predisposition to affective disorders.media-1vid110.1093/brain/aww043_video_abstractaww043_video

  5. Seasonal difference in brain serotonin transporter binding predicts symptom severity in patients with seasonal affective disorder.

    PubMed

    Mc Mahon, Brenda; Andersen, Sofie B; Madsen, Martin K; Hjordt, Liv V; Hageman, Ida; Dam, Henrik; Svarer, Claus; da Cunha-Bang, Sofi; Baaré, William; Madsen, Jacob; Hasholt, Lis; Holst, Klaus; Frokjaer, Vibe G; Knudsen, Gitte M

    2016-05-01

    Cross-sectional neuroimaging studies in non-depressed individuals have demonstrated an inverse relationship between daylight minutes and cerebral serotonin transporter; this relationship is modified by serotonin-transporter-linked polymorphic region short allele carrier status. We here present data from the first longitudinal investigation of seasonal serotonin transporter fluctuations in both patients with seasonal affective disorder and in healthy individuals. Eighty (11)C-DASB positron emission tomography scans were conducted to quantify cerebral serotonin transporter binding; 23 healthy controls with low seasonality scores and 17 patients diagnosed with seasonal affective disorder were scanned in both summer and winter to investigate differences in cerebral serotonin transporter binding across groups and across seasons. The two groups had similar cerebral serotonin transporter binding in the summer but in their symptomatic phase during winter, patients with seasonal affective disorder had higher serotonin transporter than the healthy control subjects (P = 0.01). Compared to the healthy controls, patients with seasonal affective disorder changed their serotonin transporter significantly less between summer and winter (P < 0.001). Further, the change in serotonin transporter was sex- (P = 0.02) and genotype- (P = 0.04) dependent. In the patients with seasonal affective disorder, the seasonal change in serotonin transporter binding was positively associated with change in depressive symptom severity, as indexed by Hamilton Rating Scale for Depression - Seasonal Affective Disorder version scores (P = 0.01). Our findings suggest that the development of depressive symptoms in winter is associated with a failure to downregulate serotonin transporter levels appropriately during exposure to the environmental stress of winter, especially in individuals with high predisposition to affective disorders.media-1vid110.1093/brain/aww043_video_abstractaww043_video_abstract.

  6. A Generalized Model for Transport of Contaminants in Soil by Electric Fields

    PubMed Central

    Paz-Garcia, Juan M.; Baek, Kitae; Alshawabkeh, Iyad D.; Alshawabkeh, Akram N.

    2012-01-01

    A generalized model applicable to soils contaminated with multiple species under enhanced boundary conditions during treatment by electric fields is presented. The partial differential equations describing species transport are developed by applying the law of mass conservation to their fluxes. Transport, due to migration, advection and diffusion, of each aqueous component and complex species are combined to produce one partial differential equation hat describes transport of the total analytical concentrations of component species which are the primary dependent variables. This transport couples with geochemical reactions such as aqueous equilibrium, sorption, precipitation and dissolution. The enhanced model is used to simulate electrokinetic cleanup of lead and copper contaminants at an Army Firing Range. Acid enhancement is achieved by the use of adipic acid to neutralize the basic front produced for the cathode electrochemical reaction. The model is able to simulate enhanced application of the process by modifying the boundary conditions. The model showed that kinetics of geochemical reactions, such as metals dissolution/leaching and redox reactions might be significant for realistic prediction of enhanced electrokinetic extraction of metals in real world applications. PMID:22242884

  7. A generalized model for transport of contaminants in soil by electric fields.

    PubMed

    Paz-Garcia, Juan Manuel; Baek, Kitae; Alshawabkeh, Iyad D; Alshawabkeh, Akram N

    2012-01-01

    A generalized model applicable to soils contaminated with multiple species under enhanced boundary conditions during treatment by electric fields is presented. The partial differential equations describing species transport are developed by applying the law of mass conservation to their fluxes. Transport, due to migration, advection and diffusion, of each aqueous component and complex species are combined to produce one partial differential equation that describes transport of the total analytical concentrations of component species which are the primary dependent variables. This transport couples with geochemical reactions such as aqueous equilibrium, sorption, precipitation and dissolution. The enhanced model is used to simulate electrokinetic cleanup of lead and copper contaminants at an Army Firing Range. Acid enhancement is achieved by the use of adipic acid to neutralize the basic front produced for the cathode electrochemical reaction. The model is able to simulate enhanced application of the process by modifying the boundary conditions. The model showed that kinetics of geochemical reactions, such as metals dissolution/leaching and redox reactions, may be significant for realistic prediction of enhanced electrokinetic extraction of metals in real-world applications.

  8. Application of SPARROW modeling to understanding contaminant fate and transport from uplands to streams

    USGS Publications Warehouse

    Ator, Scott; Garcia, Ana Maria.

    2016-01-01

    Understanding spatial variability in contaminant fate and transport is critical to efficient regional water-quality restoration. An approach to capitalize on previously calibrated spatially referenced regression (SPARROW) models to improve the understanding of contaminant fate and transport was developed and applied to the case of nitrogen in the 166,000 km2 Chesapeake Bay watershed. A continuous function of four hydrogeologic, soil, and other landscape properties significant (α = 0.10) to nitrogen transport from uplands to streams was evaluated and compared among each of the more than 80,000 individual catchments (mean area, 2.1 km2) in the watershed. Budgets (including inputs, losses or net change in storage in uplands and stream corridors, and delivery to tidal waters) were also estimated for nitrogen applied to these catchments from selected upland sources. Most (81%) of such inputs are removed, retained, or otherwise processed in uplands rather than transported to surface waters. Combining SPARROW results with previous budget estimates suggests 55% of this processing is attributable to denitrification, 23% to crop or timber harvest, and 6% to volatilization. Remaining upland inputs represent a net annual increase in landscape storage in soils or biomass exceeding 10 kg per hectare in some areas. Such insights are important for planning watershed restoration and for improving future watershed models.

  9. A generalized model for transport of contaminants in soil by electric fields.

    PubMed

    Paz-Garcia, Juan Manuel; Baek, Kitae; Alshawabkeh, Iyad D; Alshawabkeh, Akram N

    2012-01-01

    A generalized model applicable to soils contaminated with multiple species under enhanced boundary conditions during treatment by electric fields is presented. The partial differential equations describing species transport are developed by applying the law of mass conservation to their fluxes. Transport, due to migration, advection and diffusion, of each aqueous component and complex species are combined to produce one partial differential equation that describes transport of the total analytical concentrations of component species which are the primary dependent variables. This transport couples with geochemical reactions such as aqueous equilibrium, sorption, precipitation and dissolution. The enhanced model is used to simulate electrokinetic cleanup of lead and copper contaminants at an Army Firing Range. Acid enhancement is achieved by the use of adipic acid to neutralize the basic front produced for the cathode electrochemical reaction. The model is able to simulate enhanced application of the process by modifying the boundary conditions. The model showed that kinetics of geochemical reactions, such as metals dissolution/leaching and redox reactions, may be significant for realistic prediction of enhanced electrokinetic extraction of metals in real-world applications. PMID:22242884

  10. Modeling of multiphase transport of multicomponent organic contaminants and heat in the subsurface: Numerical model formulation

    NASA Astrophysics Data System (ADS)

    Adenekan, A. E.; Patzek, T. W.; Pruess, K.

    1993-11-01

    A numerical compositional simulator (Multiphase Multicomponent Nonisothermal Organics Transport Simulator (M2NOTS)) has been developed for modeling transient, three-dimensional, nonisothermal, and multiphase transport of multicomponent organic contaminants in the subsurface. The governing equations include (1) advection of all three phases in response to pressure, capillary, and gravity forces; (2) interphase mass transfer that allows every component to partition into each phase present; (3) diffusion; and (4) transport of sensible and latent heat energy. Two other features distinguish M2NOTS from other simulators reported in the groundwater literature: (1) the simulator allows for any number of chemical components and every component is allowed to partition into all fluid phases present, and (2) each phase is allowed to completely disappear from, or appear in, any region of the domain during a simulation. These features are required to model realistic field problems involving transport of mixtures of nonaqueous phase liquid contaminants, and to quantify performance of existing and emerging remediation methods such as vacuum extraction and steam injection.

  11. Lead contamination of an old shooting range affecting the local ecosystem--A case study with a holistic approach.

    PubMed

    Rantalainen, Minna-Liisa; Torkkeli, Minna; Strömmer, Rauni; Setälä, Heikki

    2006-10-01

    The aim of this case study was to uncover the consequences of lead pellet-derived heavy lead contamination at a cast-off shooting range in southern Finland, covering aspects from soil chemistry and biology up to ecosystem level. The observed changes in the soil properties of the most contaminated areas suggest that the contamination may be disturbing processes of decomposition and nutrient mineralisation. Also two functionally important groups of soil organisms, microbes (as analysed using the PLFA analysis) and enchytraeid worms, were negatively affected by the contamination. Furthermore, there was an indication of reduced pine litter production at the contaminated areas. On the other hand, lead contamination appears not to have affected pine growth or soil-dwelling nematodes and microarthropods, and the general outlook of the whole ecosystem is that of a healthy forest. Thus, the boreal forest ecosystem studied as a whole appears to bear strong resistance to contamination, despite negative effects of lead on many of its components. This resistance may result from e.g. low bioavailability of lead, avoidance of the most contaminated soil horizons and microsites by the organisms, and functional redundancy and development of lead-tolerant populations amongst the organisms. The relative importance of these factors and the mechanisms behind them will be investigated in forthcoming studies.

  12. Isotopic Tracing of Thallium Contamination in Soils Affected by Emissions from Coal-Fired Power Plants.

    PubMed

    Vaněk, Aleš; Grösslová, Zuzana; Mihaljevič, Martin; Trubač, Jakub; Ettler, Vojtěch; Teper, Leslaw; Cabala, Jerzy; Rohovec, Jan; Zádorová, Tereza; Penížek, Vít; Pavlů, Lenka; Holubík, Ondřej; Němeček, Karel; Houška, Jakub; Drábek, Ondřej; Ash, Christopher

    2016-09-20

    Here, for the first time, we report the thallium (Tl) isotope record in moderately contaminated soils with contrasting land management (forest and meadow soils), which have been affected by emissions from coal-fired power plants. Our findings clearly demonstrate that Tl of anthropogenic (high-temperature) origin with light isotope composition was deposited onto the studied soils, where heavier Tl (ε(205)Tl ∼ -1) naturally occurs. The results show a positive linear relationship (R(2) = 0.71) between 1/Tl and the isotope record, as determined for all the soils and bedrocks, also indicative of binary Tl mixing between two dominant reservoirs. We also identified significant Tl isotope variations within the products from coal combustion and thermo-desorption experiments with local Tl-rich coal pyrite. Bottom ash exhibited the heaviest Tl isotope composition (ε(205)Tl ∼ 0), followed by fly ash (ε(205)Tl between -2.5 and -2.8) and volatile Tl fractions (ε(205)Tl between -6.2 and -10.3), suggesting partial Tl isotope fractionations. Despite the evident role of soil processes in the isotope redistributions, we demonstrate that Tl contamination can be traced in soils and propose that the isotope data represent a possible tool to aid our understanding of postdepositional Tl dynamics in surface environments for the future.

  13. Food contaminant zearalenone and its metabolites affect cytokine synthesis and intestinal epithelial integrity of porcine cells.

    PubMed

    Marin, Daniela E; Motiu, Monica; Taranu, Ionelia

    2015-06-01

    The intestinal epithelium is the first barrier against food contaminants. Zearalenone (ZEN) is an estrogenic mycotoxin that was identified as a common contaminant of cereal grains and food and feedstuffs. In the present study, we have investigated the in vitro effects of ZEN and some of its metabolites (α-ZOL, β-ZOL) in concentrations of 10-100 µM on a swine epithelial cell line: Intestinal porcine epithelial cells (IPEC-1). We demonstrated that both ZEN metabolites were more toxic for IPEC cells as resulted from the XTT test, while for doses lower than 10 µM, only β-ZOL showed a more pronounced cytotoxicity versus epithelial cells as resulted from neutral red assay. ZEN has no effect on TER values, while α-ZOL significantly decreased the TER values, starting with day 4 of treatment. β-ZOL had a dual effect, firstly it induced a significant increase of TER, and then, starting on day 6, it induced a dramatic decrease of TER values as compared with on day 0. Concerning the cytokine synthesis, our results showed that ZEN has a tendency to increase the synthesis of IL-8 and IL-10. By contrast, α- and β-ZOL decreased the expression of both IL-8 and IL-10, in a dose dependent manner. In conclusion, our results showed that ZEN and its metabolites differently affected porcine intestinal cell viability, transepithelial resistance and cytokine synthesis with important implication for gut health. PMID:26035492

  14. Food Contaminant Zearalenone and Its Metabolites Affect Cytokine Synthesis and Intestinal Epithelial Integrity of Porcine Cells

    PubMed Central

    Marin, Daniela E.; Motiu, Monica; Taranu, Ionelia

    2015-01-01

    The intestinal epithelium is the first barrier against food contaminants. Zearalenone (ZEN) is an estrogenic mycotoxin that was identified as a common contaminant of cereal grains and food and feedstuffs. In the present study, we have investigated the in vitro effects of ZEN and some of its metabolites (α-ZOL, β-ZOL) in concentrations of 10–100 µM on a swine epithelial cell line: Intestinal porcine epithelial cells (IPEC-1). We demonstrated that both ZEN metabolites were more toxic for IPEC cells as resulted from the XTT test, while for doses lower than 10 µM, only β-ZOL showed a more pronounced cytotoxicity versus epithelial cells as resulted from neutral red assay. ZEN has no effect on TER values, while α-ZOL significantly decreased the TER values, starting with day 4 of treatment. β-ZOL had a dual effect, firstly it induced a significant increase of TER, and then, starting on day 6, it induced a dramatic decrease of TER values as compared with on day 0. Concerning the cytokine synthesis, our results showed that ZEN has a tendency to increase the synthesis of IL-8 and IL-10. By contrast, α- and β-ZOL decreased the expression of both IL-8 and IL-10, in a dose dependent manner. In conclusion, our results showed that ZEN and its metabolites differently affected porcine intestinal cell viability, transepithelial resistance and cytokine synthesis with important implication for gut health. PMID:26035492

  15. Food contaminant zearalenone and its metabolites affect cytokine synthesis and intestinal epithelial integrity of porcine cells.

    PubMed

    Marin, Daniela E; Motiu, Monica; Taranu, Ionelia

    2015-05-29

    The intestinal epithelium is the first barrier against food contaminants. Zearalenone (ZEN) is an estrogenic mycotoxin that was identified as a common contaminant of cereal grains and food and feedstuffs. In the present study, we have investigated the in vitro effects of ZEN and some of its metabolites (α-ZOL, β-ZOL) in concentrations of 10-100 µM on a swine epithelial cell line: Intestinal porcine epithelial cells (IPEC-1). We demonstrated that both ZEN metabolites were more toxic for IPEC cells as resulted from the XTT test, while for doses lower than 10 µM, only β-ZOL showed a more pronounced cytotoxicity versus epithelial cells as resulted from neutral red assay. ZEN has no effect on TER values, while α-ZOL significantly decreased the TER values, starting with day 4 of treatment. β-ZOL had a dual effect, firstly it induced a significant increase of TER, and then, starting on day 6, it induced a dramatic decrease of TER values as compared with on day 0. Concerning the cytokine synthesis, our results showed that ZEN has a tendency to increase the synthesis of IL-8 and IL-10. By contrast, α- and β-ZOL decreased the expression of both IL-8 and IL-10, in a dose dependent manner. In conclusion, our results showed that ZEN and its metabolites differently affected porcine intestinal cell viability, transepithelial resistance and cytokine synthesis with important implication for gut health.

  16. Isotopic Tracing of Thallium Contamination in Soils Affected by Emissions from Coal-Fired Power Plants.

    PubMed

    Vaněk, Aleš; Grösslová, Zuzana; Mihaljevič, Martin; Trubač, Jakub; Ettler, Vojtěch; Teper, Leslaw; Cabala, Jerzy; Rohovec, Jan; Zádorová, Tereza; Penížek, Vít; Pavlů, Lenka; Holubík, Ondřej; Němeček, Karel; Houška, Jakub; Drábek, Ondřej; Ash, Christopher

    2016-09-20

    Here, for the first time, we report the thallium (Tl) isotope record in moderately contaminated soils with contrasting land management (forest and meadow soils), which have been affected by emissions from coal-fired power plants. Our findings clearly demonstrate that Tl of anthropogenic (high-temperature) origin with light isotope composition was deposited onto the studied soils, where heavier Tl (ε(205)Tl ∼ -1) naturally occurs. The results show a positive linear relationship (R(2) = 0.71) between 1/Tl and the isotope record, as determined for all the soils and bedrocks, also indicative of binary Tl mixing between two dominant reservoirs. We also identified significant Tl isotope variations within the products from coal combustion and thermo-desorption experiments with local Tl-rich coal pyrite. Bottom ash exhibited the heaviest Tl isotope composition (ε(205)Tl ∼ 0), followed by fly ash (ε(205)Tl between -2.5 and -2.8) and volatile Tl fractions (ε(205)Tl between -6.2 and -10.3), suggesting partial Tl isotope fractionations. Despite the evident role of soil processes in the isotope redistributions, we demonstrate that Tl contamination can be traced in soils and propose that the isotope data represent a possible tool to aid our understanding of postdepositional Tl dynamics in surface environments for the future. PMID:27536872

  17. Moisture content-affected electrokinetic remediation of Cr(VI)-contaminated clay by a hydrocalumite barrier.

    PubMed

    Xu, Yunfeng; Xu, Xiangjian; Hou, Hetian; Zhang, Jia; Zhang, Dayi; Qian, Guangren

    2016-04-01

    An electrokinetic-permeable reaction barrier (EK-PRB) system was introduced in this study with hydrocalumite as the barrier material. The combined system effectively remediated the Cr(VI)-contaminated clay after a 72-h treatment, and the Cr(VI) removal efficiency increased with the initial soil moisture content. Further evidence was found that the changing soil pH value and current density were highly associated with the initial moisture content, showing its important roles in the Cr(VI) removal process. Additionally, the total Cr removal efficiency was much lower than that of Cr(VI) owing to the partial conversion of Cr(VI) to Cr(III) in the electrokinetic remediation process. Under high soil moisture conditions (40%), the removal efficiency of Cr(VI) and total Cr was 96.6 and 67.3%, respectively. Further analysis also revealed the new mineral phase, chromate hydrocalumite, for Cr fixation in the hydrocalumite barrier, which was significantly affected by the initial soil moisture content. Our results showed that the EK-PRB system with a hydrocalumite barrier is highly promising with great potential for the effective remediation of Cr(VI)-contaminated clay and engineering implementation. PMID:26635219

  18. CHROMATOGRAPHIC ALTERATION OF A NONIONIC SURFACTANT MIXTURE DURING TRANSPORT IN DENSE NONAQUEOUS PHASE LIQUID CONTAMINATED SEDIMENT (R826650)

    EPA Science Inventory

    Chromatographic alteration of a nonionic surfactant mixture during transport through DNAPL-contaminated aquifer sediment may occur due to differential loss of oligomers to sediment and to dense nonaqueous phase liquid (DNAPL). These losses may significantly alter the solubilizing...

  19. CONTAMINANT TRANSPORT RESULTING FROM MULTICOMPONENT NONAQUEOUS PHASE LIQUID POOL DISSOLUTION IN THREE-DIMENSIONAL SUBSURFACE FORMATIONS (R823579)

    EPA Science Inventory

    A semi-analytical method for simulating transient contaminant transport originating from the dissolution of multicomponent nonaqueous phase liquid (NAPL) pools in three-dimensional, saturated, homogeneous porous media is presented. Each dissolved component may undergo first-order...

  20. Using Contaminant Transport Modeling to Determine Historical Discharges at the Surface

    NASA Astrophysics Data System (ADS)

    Fogwell, T. W.

    2013-12-01

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

  1. Are reactive transport models reliable tools for reconstructing historical contamination scenarios?

    NASA Astrophysics Data System (ADS)

    Clement, P.

    2009-12-01

    This presentation will be based on a recent project effort that I completed while serving as a member of National Academy of Sciences and Engineering panel. The primary goal of this congressionally-mandated project effort was to review scientific evidence on the association between adverse health effect s and exposure to a contaminated water supply system at the U.S. Marine Corps Base Camp Lejeune (CLJ) in North Carolina. The detailed NRC study report was released in June 2009, and is available at this NRC weblink: http://www.nap.edu/catalog.php?record_id=12618. Multiple water supply systems at this Marine Base were contaminated with harmful chemicals, such as PCE, TCE and other waste products, since the early 50s. In 1982, a routine water quality survey completed at the site indicated the presence of several volatile organic compounds including PCE and TCE. Further investigations revealed that there are several waste disposal facilities located on-site that have discharged TCE and other waste products into groundwater systems. In addition, there was also an off-site dry cleaning facility located close to the Tarawa Terrace in-take well locations that disposed PCE into the subsurface environment. The dry cleaner has been using PCE since 1953 and disposed various forms of PCE-contaminated wastes in a septic tank and in several shallow pits. Therefore, the residents who lived in Tarawa Terrace on-site family housing units had the potential to be exposed to these harmful environmental contaminants through the drinking water source. In late 1980s, the concerns raised by CLJ public lead to an epidemiological study to evaluate the potential associations of utero and infant exposures to the VOCs and childhood cancers and birth defects. The study included births occurring during the period of 1968-1985 to women who were pregnant while they resided at the base. Since there was no monitoring data available for the study period (1968-1982), researchers used reactive transport

  2. Isotopic evolution of groundwater in a telogenetic karst aquifer: A method to study recharge and contaminant transport

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There exists a limited understanding of hydrogeologic flow and contaminant transport within karst aquifers, particularly in the epikarst zone, which are highly susceptible to natural and anthropogenic contamination, such as agricultural runoff, due to the interconnected nature of the surface and sub...

  3. Study of the contaminant transport into granite microfractures using nuclear ion beam techniques.

    PubMed

    Alonso, Ursula; Missana, Tiziana; Patelli, Alessandro; Rigato, Valentino; Rivas, Pedro

    2003-03-01

    Hydrated bentonite is a very plastic material and it is expected to enter in the rock microfractures at the granite/bentonite boundary of a deep geological high-level waste repository. This process is enhanced by the high swelling pressure of the clay. Since bentonite has a very good sorption capability for many radionuclides, the displacement of the clay might lead to a "clay-mediated" contaminant transport into the rock. The aim of this work is to study the contaminant transport into granite microfractures using nuclear ion beam techniques, and to determine to what extent the clay can favour it. To do so, bentonite previously doped with uranium, cesium and europium was put in contact with the surface of granite sheets. Granite sheets contacted with non-doped bentonite and with radionuclide solutions were also prepared as references. This allowed analysing the differences in the diffusion behaviour of the three systems: clay, radionuclides and clay plus radionuclides. A combination of Rutherford backscattering spectrometry (RBS) and other nuclear ion-beam techniques such as particle-induced X-ray emission (PIXE) and microPIXE was used to study the depth and lateral distribution of clay and contaminants inside granite. It was also tried to evaluate not only the diffusion depth and diffusion coefficients but also the different areas of the granite where the diffusants have a preferential access.

  4. Long Length Contaminated Equipment Retrieval System Receiver Trailer and Transport Trailer Operations and Maintenance Manual

    SciTech Connect

    DALE, R.N.

    2000-05-01

    A system to accommodate the removal of long-length contaminated equipment (LLCE) from Hanford underground radioactive waste storage tanks was designed, procured, and demonstrated, via a project activity during the 1990s. The system is the Long Length Contaminated Equipment Removal System (LLCERS). LLCERS will be maintained and operated by Tank Farms Engineering and Operations organizations and other varied projects having a need for the system. The responsibility for the operation and maintenance of the LLCERS Receiver Trailer (RT) and Transport Trailer (TT) resides with the RPP Characterization Project Operations organization. The purpose of this document is to provide vendor supplied operating and maintenance (O & M) information for the RT and TT in a readily retrievable form. This information is provided this way instead of in a vendor information (VI) file to maintain configuration control of the operations baseline as described in RPP-6085, ''Configuration Management Plan for Long Length Contaminated Equipment Receiver and Transport Trailers''. Additional Operations Baseline documents are identified in RPP-6085.

  5. Essays on alternative energy policies affecting the US transportation sector

    NASA Astrophysics Data System (ADS)

    O'Rear, Eric G.

    This dissertation encompasses three essays evaluating the impacts of different policies targeting the greenhouse gas (GHG) emissions, fuel demands, etc. of the transportation sector. Though there are some similarities across the three chapters, each essay stands alone as an independent work. The 2010 US EPA MARKAL model is used in each essay to evaluate policy effects. Essay 1 focuses on the recent increases in Corporate Average Fuel Economy (CAFE) standards, and the implications of a "rebound effect." These increases are compared to a carbon tax generating similar reductions in system-wide emissions. As anticipated, the largest reductions in fuel use by light-duty vehicles (LDV) and emissions are achieved under CAFE. Consideration of the rebound effect does little to distort CAFE benefits. Our work validates many economists' belief that a carbon tax is a more efficient approach. However, because the tax takes advantage of cheaper abatement opportunities in other sectors, reductions in transportation emissions will be much lower than what we observe with CAFE. Essay 2 compares CAFE increases with what some economists suggest would be a much more "efficient" alternative -- a system-wide oil tax internalizing some environmental externalities. Because oil taxes are likely to be implemented in addition to CAFE standards, we consider a combined policy case reflecting this. Our supplementary analysis approximates the appropriate tax rates to produce similar reductions in oil demands as CAFE (CAFE-equivalent tax rates). We discover that taxes result in greater and more cost-effective reductions in system-wide emissions and net oil imports than CAFE. The current fuel tax system is compared to three versions of a national vehicle miles traveled (VMT) tax charged to all LDVs in Essay 3. VMT taxes directly charge motorists for each mile driven and help to correct the problem of eroding tax revenues given the failure of today's fuel taxes to adjust with inflation. Results

  6. Mechanisms affecting the transport and retention of bacteria, bacteriophage and microspheres in laboratory-scale saturated fractures

    NASA Astrophysics Data System (ADS)

    Seggewiss, G.; Dickson, S. E.

    2013-12-01

    Groundwater is becoming an increasingly important water source due to the ever-increasing demands from agricultural, residential and industrial consumers. In search of more secure sources, wells are routinely finished over large vertical depths in bedrock aquifers, creating new hydraulic pathways and thus increasing the risk of cross contamination. Moreover, hydraulic pathways are also being altered and created by increasing water withdrawal rates from these wells. Currently, it is not well understood how biological contaminants are transported through, and retained in, fractured media thereby making risk assessment and land use decisions difficult. Colloid transport within fractured rock is a complex process with several mechanisms affecting transport and retention, including: advection, hydrodynamic dispersion, diffusion, size exclusion, adsorption, and decay. Several researchers have investigated the transport of bacteria, bacteriophage, and microspheres (both carboxylated and plain) to evaluate the effects of surface properties and size on transport and retention. These studies have suggested that transport is highly dependent on the physico-chemical properties of the particle, the fracture, and the carrying fluid. However, these studies contain little detail regarding the specific mechanisms responsible for transport beyond speculating about their existence. Further, little work has been done to compare the transport of these particulate materials through the same fracture, allowing for direct observations based on particulate size and surface properties. This research examines the similarities and differences in transport and retention between four different particles through two different laboratory-scale, saturated fractures. This work is designed to explore the effects of particle size, surface properties, ionic strength of the carrying solution, and aperture field characteristics on transport and retention in single, saturated fractures. The particulates

  7. The antiepileptic drug carbamazepine affects sodium transport in toad epithelium.

    PubMed

    Suwalsky, Mario; Mennickent, Sigrid; Norris, Beryl; Cardenas, Hernán

    2006-09-01

    The present work investigates the effects of the antiepileptic drug carbamazepine (CBZ) on sodium transport in the isolated skin of the toad Pleurodema thaul. A submaximal concentration of the drug (0.2 mM) applied to the outer surface of the epithelium increased the electrical parameters short-circuit current (Isc) and potential difference (PD) by over 28%, whereas only a higher concentration (1 mM) induced over a 45% decrease in these parameters when applied to the inner surface. The amiloride test showed that the outer surface stimulatory effect was accompanied by an increase and the inner surface inhibitory effect by a decrease in the sodium electromotive force (ENa). Exploration of these effects of CBZ on the outer surface showed that 0.2 mM increased net Na+ (22Na) influx by 20% and 0.6 mM CBZ decreased Na+ mucosa-serosa flux by 19%, a result in agreement with the finding that higher concentrations of CBZ applied to the inner surface not only decreased ENa but also sodium conductance (GNa). PMID:16542818

  8. Dynamics of coupled contaminant and microbial transport in heterogeneous porous media. 1997 annual progress report

    SciTech Connect

    Ginn, T.R.; Boone, D.R.; Fletcher, M.M.; Friedrich, D.M.; Murphy, E.M.

    1997-06-01

    'Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project will provide fundamental information on the attachment/detachment dynamics of anaerobic bacteria in heterogeneous porous media under growth and growth-limiting conditions. Experiments will provide information on passive and active attachment/detachment mechanisms used by growing anaerobes capable of reductive dechlorination. Theoretical representations of these attachment/detachment mechanisms will be incorporated into existing groundwater flow and contaminant transport models that incorporate heterogeneity effects and can be used to predict behavior at field scales. These mechanistic-based models will be tested against experimental data provided through controlled laboratory experiments in heterogeneous porous media in large (meter-scale) 2-D flow cells. In addition to a mechanistic-based predictive model, this research will lead to new theories for the transient spatial distribution of microbial populations and contaminant plumes in heterogeneous porous media, improving the capability for designing staged remediation strategies for dealing with mixed contaminants.'

  9. Assessment of Contaminated Brine Fate and Transport in MB139 at WIPP

    SciTech Connect

    Kuhlman, Kristopher L.; Malama, Bwalya

    2014-07-01

    Following the radionuclide release event of February 14, 2014 at the Waste Isolation Pilot Plant (WIPP), actinide contamination has been found on the walls and floor in Panel 7 as a result of a release in Room 7 of Panel 7. It has been proposed to decontaminate Panel 7 at the WIPP by washing contaminated surfaces in the underground with fresh water. A cost-effective cleanup of this contamination would allow for a timely return to waste disposal operations at WIPP. It is expected that the fresh water used to decontaminate Panel 7 will flow as contaminated brine down into the porosity of the materials under the floor – the run-of-mine (ROM) salt above Marker Bed 139 (MB139) and MB139 itself – where its fate will be controlled by the hydraulic and transport properties of MB139. Due to the structural dip of MB139, it is unlikely that this brine would migrate northward towards the Waste-Handling Shaft sump. A few strategically placed shallow small-diameter observation boreholes straddling MB139 would allow for monitoring the flow and fate of this brine after decontamination. Additionally, given that flow through the compacted ROM salt floor and in MB139 would occur under unsaturated (or two-phase) conditions, there is a need to measure the unsaturated flow properties of crushed WIPP salt and salt from the disturbed rock zone (DRZ).

  10. Isotopic Studies of Contaminant Transport at the Hanford Site,WA

    SciTech Connect

    Christensen, J.N.; Conrad, M.E.; DePaolo, D.J.; Dresel, P.E.

    2006-11-01

    Processes of fluid flow and chemical transport through thevadose zone can be characterized through the isotopic systematics ofnatural soils, minerals, pore fluids and groundwater. In thiscontribution, we first review our research using measured isotopicvariations, due both to natural and site related processes, of theelements H, O, N, Sr and U, to study the interconnection between vadosezone and groundwater contamination at the Hanford Site in south-centralWashington. We follow this brief review with a presentation of new datapertaining to vadose zone and groundwater contamination in the WMAT-TX-TY vicinity. Uranium (U) isotopic data for the C3832 core (WMA TX)indicates the involvement of processed natural U fuel, and links theobserved U contamination to the nearby single shelled tank TX-104. Thedata also precludes contamination from an early 1970 s TX-107 leak. Inthe case of the C4104 core (WMA T), the U isotopic data indicates amixture of processed natural and enriched U fuels consistent with themajor leak from T-106 in 1973. Uranium and Strontium isotopic data forthe cores also provides direct evidence for chemical interaction betweenhigh-pH waste fluid and sediment. Isotopic data for groundwater nitratecontamination in the vicinity of WMA-T strongly suggests high-level tankwaste (most likely from T-106) as the source of very high 99Tcconcentrations recently observed at the NE corner of WMAT.

  11. From Sequential Extraction to Transport Modeling: Monitored Natural Attenuation as a Remediation Approach for Inorganic Contaminants

    SciTech Connect

    Crapse, Kimberly P.; Serkiz, Steven M.; Pishko, Adrian L.; Kaplan, Daniel L.; Lee, Cindy M.; Schank, Anja

    2005-08-18

    To quantify metal natural attenuation processes in terms of environmental availability, sequential extraction experiments were carried out on subsurface soil samples impacted by a low pH, high sulfate, metals (Be, Ni, U, As) plume associated with the long-term operation of a coal plant at the Savannah River Site in South Carolina. Despite significant heterogeneity resulting both from natural and anthropogenic factors, sequential extraction results demonstrate that pH is a controlling factor in the prediction of the distribution of metal contaminants within the solid phases in soils at the site as well as the contaminant partitioning between the soil and the soil solution. Results for beryllium, the most mobile metal evaluated, exhibit increasing attenuation along the plume flow path which corresponds to an increasing plume pH. These laboratory- and field-scale studies provide mechanistic information regarding partitioning of metals to soils at the site (one of the major attenuation mechanisms for the metals at the field site). Subsequently, these data have been used in the definition of the contaminant source terms and contaminant transport factors in risk modeling for the site.

  12. Analysis of matrix effects critical to microbial transport in organic waste-affected soils across laboratory and field scales

    NASA Astrophysics Data System (ADS)

    Unc, Adrian; Goss, Michael J.; Cook, Simon; Li, Xunde; Atwill, Edward R.; Harter, Thomas

    2012-06-01

    Organic waste applications to soil (manure, various wastewaters, and biosolids) are among the most significant sources of bacterial contamination in surface and groundwater. Transport of bacteria through the vadose zone depends on flow path geometry and stability and is mitigated by interaction between soil, soil solution, air-water interfaces, and characteristics of microbial surfaces. After initial entry, the transport through soil depends on continued entrainment of bacteria and resuspension of those retained in the porous structure. We evaluated the retention of bacteria-sized artificial microspheres, varying in diameter and surface charge and applied in different suspending solutions, by a range of sieved soils contained in minicolumns, the transport of hydrophobic bacteria-sized microspheres through undisturbed soil columns as affected by waste type under simulated rainfall, and the field-scale transport of Enterococcus spp. to an unconfined sandy aquifer after the application of liquid manure. Microsphere retention reflected microsphere properties. The soil type and suspending solution affected retention of hydrophilic but not hydrophobic particles. Retention was not necessarily facilitated by manure-microsphere-soil interactions but by manure-soil interactions. Undisturbed column studies confirmed the governing role of waste type on vadose-zone microsphere transport. Filtration theory applied as an integrated analysis of transport across length scales showed that effective collision efficiency depended on the distance of travel. It followed a power law behavior with the power coefficient varying from ˜0.4 over short distances to >0.9 over 1 m (i.e., very little filtration for a finite fraction of biocolloids), consistent with reduced influence of soil solution and biocolloid properties at longer travel distances.

  13. Surfactant-enhanced remediation of a trichloroethene-contaminated aquifer. 1. Transport of triton X-100

    USGS Publications Warehouse

    Smith, J.A.; Sahoo, D.; Mclellan, H.M.; Imbrigiotta, T.E.

    1997-01-01

    Transport of a nonionic surfactant (Triton X-100) at aqueous concentrations less than 400 mg/L through a trichloroethene-contaminated sand-and-gravel aquifer at Picatinny Arsenal, NJ, has been studied through a series of laboratory and field experiments. In the laboratory, batch and column experiments were conducted to quantify the rate and amount of Triton X-100 sorption to the aquifer sediments. In the field, a 400 mg/L aqueous Triton X-100 solution was injected into the aquifer at a rate of 26.5 L/min for a 35-d period. The transport of Triton X-100 was monitored by sampling and analysis of groundwater at six locations surrounding the injection well. Equilibrium batch sorption experiments showed that Triton X-100 sorbs strongly and nonlinearly to the field soil with the sharpest inflection point of the isotherm occurring at an equilibrium aqueous Triton X-100 concentration close to critical micelle concentration. Batch, soil column, and field experimental data were analyzed with zero-, one-, and two- dimensional (respectively) transient solute transport models with either equilibrium or rate-limited sorption. These analyses reveal that Triton X- 100 sorption to the aquifer solids is slow relative to advective and dispersive transport and that an equilibrium sorption model cannot simulate accurately the observed soil column and field data. Comparison of kinetic sorption parameters from batch, column, and field transport data indicate that both physical heterogeneities and Triton X-100 mass transfer between water and soil contribute to the kinetic transport effects.Transport of a nonionic surfactant (Triton X-100) at aqueous concentrations less than 400 mg/L through a trichloroethene-contaminated sand-and-gravel aquifer was studied. Equilibrium batch sorption experiments showed that Triton X-100 sorbs strongly and nonlinearly to the field soil with the sharpest inflection point of the isotherm occurring at an equilibrium aqueous Triton X-100 concentration close to

  14. RAFT: A simulator for ReActive Flow and Transport of groundwater contaminants

    SciTech Connect

    Chilakapati, A

    1995-07-01

    This report documents the use of the simulator RAFT for the ReActive flow and Transport of groundwater contaminants. RAFT can be used as a predictive tool in the design and analysis of laboratory and field experiments or it can be used for the estimation of model/process parameters from experiments. RAFT simulates the reactive transport of groundwater contaminants in one, two-, or three-dimensions and it can model user specified source/link configurations and arbitrary injection strategies. A suite of solvers for transport, reactions and regression are employed so that a combination of numerical methods best suited for a problem can be chosen. User specified coupled equilibrium and kinetic reaction systems can be incorporated into RAFT. RAFT is integrated with a symbolic computational language MAPLE, to automate code generation for arbitrary reaction systems. RAFT is expected to be used as a simulator for engineering design for field experiments in groundwater remediation including bioremediation, reactive barriers and redox manipulation. As an integrated tool with both the predictive ability and the ability to analyze experimental data, RAFT can help in the development of remediation technologies, from laboratory to field.

  15. An experimental methodology for monitoring contaminant transport through geotechnical centrifuge models.

    PubMed

    Kumar, P R

    2006-06-01

    In this paper, an attempt has been made to highlight an experimental methodology for monitoring contaminant transport through locally available silty soil and commercially available clay in geotechnical centrifuge models, for different compaction states. Use of multiple depth sensors to determine depth distribution of sodium chloride in the soil column has been detailed. The obtained results have been compared with argentometric method. To validate the centrifuge modelling, modelling of models has been used. The test setup developed can simulate contaminant transport mechanisms through the soil mass, which is approximately 10 m deep, over a period of 600 days. R (e) and P (e) are found to be N times higher in the centrifuge models. These numbers are found to be several orders less than unity. This indicates that laminar flow prevails and the dominating Cl(-) transport mechanism in centrifuge is diffusion. The study also highlights the fact that the geotechnical centrifuge modelling can be used as a viable alternative to field scale experimentation. PMID:16917708

  16. FLAME: A finite element computer code for contaminant transport n variably-saturated media

    SciTech Connect

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

    1992-06-01

    A numerical model was developed for use in performance assessment studies at the INEL. The numerical model referred to as the FLAME computer code, is designed to simulate subsurface contaminant transport in a variably-saturated media. The code can be applied to model two-dimensional contaminant transport in an and site vadose zone or in an unconfined aquifer. In addition, the code has the capability to describe transport processes in a porous media with discrete fractures. This report presents the following: description of the conceptual framework and mathematical theory, derivations of the finite element techniques and algorithms, computational examples that illustrate the capability of the code, and input instructions for the general use of the code. The development of the FLAME computer code is aimed at providing environmental scientists at the INEL with a predictive tool for the subsurface water pathway. This numerical model is expected to be widely used in performance assessments for: (1) the Remedial Investigation/Feasibility Study process and (2) compliance studies required by the US Department of energy Order 5820.2A.

  17. Modeling water chemistry change and contaminant transport in riverbank filtration systems

    NASA Astrophysics Data System (ADS)

    Mustafa, Shaymaa; Bahar, Arifah; Aziz, Zainal Abdul; Suratman, Saim

    2016-06-01

    Riverbank filtration system is river water treatment approach based on natural removal of contaminants due to physical, chemical and biological processes. In this article, an analytical model is developed by using Green's function method to simulate the effects of pumping well and microbial activity that occurs in riverbed sediments on contaminant transport and evolution of water chemistry. The model is tested with data collected previously for RBF site in France. The results are compared with numerical simulation conducted in the literature by using finite difference method. Graphically, it is noticed that both numerical and analytical results have almost the same behavior. Also it is found that the model can simulate the decreasing of one pollutant concentration at the zone where the bacteria starts to consume this pollutant.

  18. High-Level Waste Tanks Multi-Dimensional Contaminant Transport Model Development

    SciTech Connect

    Collard, L.B.

    1999-11-15

    A suite of multi-dimensional computer models was developed to analyze the transport of residual contamination from high-level waste tanks through the subsurface to seeplines. Cases analyzed ranged from all the tanks in the F- and H-tank farms for an overall look; to the Tank 17-20 4-pack to study plume interaction; to individual tanks, such as Tank 17 and 20 for comparison with one-dimensional and modeling. The main purpose of this work was to develop and test the models, so only two relatively conservative contaminants were examined, Tc-99 and I-129. More complex analyses, such as solubility-limited species and radionuclides that head a decay chain were not addressed in this study.

  19. A probabilistic cellular automaton for two dimensional contaminant transport simulation in ground water.

    PubMed

    Palanichamy, Jegathambal; Schüttrumpf, Holger; Palani, Sundarambal

    2008-01-01

    In recent years evolutionary computing algorithms have been proposed to solve many engineering problems. Genetic algorithms, Neural Networks, and Cellular Automata are the branches of evolutionary computing techniques. In this study, it is proposed to simulate the contaminant transport in porous media using a Cellular Automaton. The physical processes and chemical reactions occurring in the ground water system are intricately connected at various scales of space, time, transport coefficients and molecular concentration. The validity of continuous approach for the simulation of chemical systems with low concentration of species and intracellular environments has become subtle. Due to the difference in scales of various processes that occur in the ground water system, the description of the system can be well defined in the intermediate scale called mesoscopic scale, which is in between microscopic and macroscopic description. Mesoscopic models provide the relationship between various parameters and their evolvement in time, thus establishing the contact between modeling at various scales at the interface. In this paper, a Probabilistic Cellular Automaton (PCA) model has been developed based on the transport and reaction probability values. The developed model was verified and validated for one, two dimensional transport systems and also for the simulation of BTEX transport in two dimensional system in ground water.

  20. In-situ Lysimeter Experiments For Validating Predictions of Contaminant Leachate Transport In Unsaturated Soils

    NASA Astrophysics Data System (ADS)

    Buczko, U.; Hopp, L.; Durner, W.; Peiffer, S.

    The German Soil Protection Law (Bundesbodenschutzgesetz - BBodSchG, 1998) pre- scribes - in case of a supposed soil contamination - a prognosis of the quality and quan- tity of the water percolating through the unsaturated (vadose) zone into the groundwa- ter. The methodology to accomplish this percolation water prognosis is not specified neither in the German Soil Protection Law, nor in the German Soil Protection Regula- tion (July 1999). Since direct measurements of contaminant entries at the groundwater surface are in most cases not feasible, indirect methodologies for the percolation im- mission prognosis are needed. The development of such a methodology for soils con- taminated by heavy metals, which should be relatively simple, yet scientifically sound, is the subject of an ongoing research project at the Chair of Hydrology, University of Bayreuth. The focus in this project lies on the redox-sensitive metals As, Cr, Pb, Cu and Cd. The objective of this contribution is to present the scientific approach used in this study and to discuss first results, with a special focus on the transport simula- tion through the unsaturated zone and the in-situ lysimeter experiments. Our approach for the percolation immission prognosis consists of three parts: 1. Estimation of the emission of metals from the contaminated source soil (using elutions, soil saturation extracts, and column experiments). 2. Transport simulations through the unsaturated zone. 3. Validation of the results gained by those first two steps by analysis of percola- tion water extracted in-situ from undisturbed soil by lysimeters which are installed at two different soil depths. First results indicate, that modeling solute transport of redox sensitive metals has to account for the pertinent redox reactions, which those metals are subject to on their passage through the unsaturated zone. Preferential flow phe- nomena and the heterogeneity of the subsurface may be accounted for in a 1D vertical model by

  1. Theory of phase-separate multicomponent contaminant transport in frozen soils

    NASA Astrophysics Data System (ADS)

    Panday, Sorab; Yavuz Corapcioglu, M.

    1994-08-01

    Groundwater is an essential source of water in Arctic regions due to largely frozen surface water resources. Since the development of Alaskan oil fields and the construction of the trans-Alaska pipeline, there have been a large number of accidental oil spillages in the tundra. The physico-, thermo- and ecosystem of the Arctic has unique features requiring special attention due to low temperatures and the presence of ice. Furthermore, a hot oil spill is subjected to large variations of temperature which creates a dominant impact on flow and phase behavior. Modeling studies of phase-separate contaminants for isothermal conditions neglect these crucial factors. A predictive model is developed herein, to simulate the transport and fate of multicomponent petroleum products in Arctic soils and groundwater. The model is based on identification and quantification of the significant physical, thermal, chemical and biological processes, and construction of mathematical representations of these phenomena to describe the transport and fate of petroleum spills in frozen soils. Since a petroleum product consists of many chemically and biologically reactive components, a general compositional-type model is developed to describe multiphase transport of the petroleum products, or any other multicomponent, phase-separate contaminant under non-isothermal conditions. The model incorporates thermodynamic principles to quantify phase partitioning of contaminant components and phase separation. Aerobic biodegradation of hydrocarbon constituents is incorporated into the formulation through Monod-type kinetics. A limit on biodegradation is imposed when oxygen is depleted from the system beyond which the biodegradation rate depends on the flux rate of oxygen.

  2. Lead contamination in tea leaves and non-edaphic factors affecting it.

    PubMed

    Jin, Chong Wei; He, Yun Feng; Zhang, Kai; Zhou, Gen Di; Shi, Jian Liang; Zheng, Shao Jian

    2005-11-01

    Recent tests have detected high lead (Pb) concentrations in some commercial brands of tea leaves and this finding has raised concerns due to the possible health-related problems associated with Pb poisoning. In present research, we investigated the Pb contamination in tea leaves produced in Zhejiang province in China. Pb concentrations in all tea leaves sampled were below 5 mg/kg, the permissible levels given by Chinese Ministry of Agriculture, indicating that Pb contamination in this province is not excessive. We then investigated the non-edaphic factors that may potentially contribute to Pb accumulation in tea leaves. Pb concentration in tea leaves was found to be positively correlated with the industrialization level of a district (R = 0.83, the significant level at P < 0.05), and greater amounts of Pb were washed from the leaves of plants in districts with more industrial activity. This suggests that Pb accumulation in tea leaves could, in part, be attributed to industrial activity through the precipitation of atmospheric Pb. Furthermore greater amounts of Pb were washed from the leaves of plants growing near road than those growing farther away from road. This trend indicates that automobile activity was another likely contributor to Pb accumulation in tea. Pb content of green tea was also affected by the processing of the leaves in the factory. In particular the twisting and water-removal stages caused increases in Pb content in the tea product. This study suggests that non-edaphic factors also contribute to the Pb accumulation in tea. PMID:16219507

  3. Factors affecting metribuzin retention in Algerian soils and assessment of the risks of contamination.

    PubMed

    Oukali-Haouchine, Ouzna; Barriuso, Enrique; Mayata, Yamina; Moussaoui, Khadija M

    2013-05-01

    Metribuzin is a widely used herbicide around the world but it could lead to soil and water contamination. Metribuzin retention on a silty-clay agricultural soil of Algeria was studied in laboratory batch experiments to assess the contamination risk of the groundwater. Factors conditioning the fate of metribuzin were investigated: soil nature, metribuzin formulation, NPK fertilizer, and soil pH. Freundlich sorption isotherms gave the coefficients K F between 1.2 and 4.9 and 1/n a between 0.52 and 0.93. The adsorption is directly dependent on organic and clay soil contents. Formulated metribuzin (Metriphar) reduces the adsorption (K F = 1.25) compared to pure metribuzin (K F = 2.81). The addition of an NPK fertilizer decreases the soil pH (6.67 for the soil without fertilizer and 5.86 for 2 % of fertilizer) and increases metribuzin adsorption (K F is 4.83 for 2 % of fertilizer). The pH effect on the adsorption is corroborated in experiments changing the soil pH between 5 (K F is 4.17) and 8 (K F is 1.57) under controlled conditions. Desorption isotherms show a hysteresis and only 30 to 40 % of the initially adsorbed metribuzin is released. The estimated GUS index is ≥ 2.8 for a DT50 ≥ 30 days. K F values and the hysteresis show that metribuzin is little but strongly retained on the soil. Formulated metribuzin and addition of fertilizer affect the retention. However, the GUS index indicates a high mobility and a significant risk of leaching. The most appropriate risk management measure would be an important increase in organic matter content of the soil by addition of organic amendments.

  4. INEEL Subregional Conceptual Model Report Volume 2: Summary of Existing Knowledge of Geochemical Influences on the Fate and Transport of Contaminants in the Subsurface at the INEEL

    SciTech Connect

    Paul L. Wichlacz; Robert C. Starr; Brennon Orr

    2003-09-01

    This document summarizes previous descriptions of geochemical system conceptual models for the vadose zone and groundwater zone (aquifer) beneath the Idaho National Engineering and Environmental Laboratory (INEEL). The primary focus is on groundwater because contaminants derived from wastes disposed at INEEL are present in groundwater, groundwater provides a pathway for potential migration to receptors, and because geochemical characteristics in and processes in the aquifer can substantially affect the movement, attenuation, and toxicity of contaminants. The secondary emphasis is perched water bodies in the vadose zone. Perched water eventually reaches the regional groundwater system, and thus processes that affect contaminants in the perched water bodies are important relative to the migration of contaminants into groundwater. Similarly, processes that affect solutes during transport from nearsurface disposal facilities downward through the vadose zone to the aquifer are relevant. Sediments in the vadose zone can affect both water and solute transport by restricting the downward migration of water sufficiently that a perched water body forms, and by retarding solute migration via ion exchange. Geochemical conceptual models have been prepared by a variety of researchers for different purposes. They have been published in documents prepared by INEEL contractors, the United States Geological Survey (USGS), academic researchers, and others. The documents themselves are INEEL and USGS reports, and articles in technical journals. The documents reviewed were selected from citation lists generated by searching the INEEL Technical Library, the INEEL Environmental Restoration Optical Imaging System, and the ISI Web of Science databases. The citation lists were generated using the keywords ground water, groundwater, chemistry, geochemistry, contaminant, INEL, INEEL, and Idaho. In addition, a list of USGS documents that pertain to the INEEL was obtained and manually searched

  5. Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores.

    PubMed

    Chekli, L; Brunetti, G; Marzouk, E R; Maoz-Shen, A; Smith, E; Naidu, R; Shon, H K; Lombi, E; Donner, E

    2016-09-01

    The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to n

  6. Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores.

    PubMed

    Chekli, L; Brunetti, G; Marzouk, E R; Maoz-Shen, A; Smith, E; Naidu, R; Shon, H K; Lombi, E; Donner, E

    2016-09-01

    The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to n

  7. Understanding how hydrodynamics affects particle transport in saturated fractures using modelling and experimental results

    NASA Astrophysics Data System (ADS)

    Cianflone, S.; Lakhian, V.; Dickson, S. E.

    2013-12-01

    Approximately 35% of Canadians and Americans utilize groundwater for drinking water and as such, it is essential to understand the mechanisms which may jeopardize this resource. Porous media aquifers typically provide significant removal of particulate contaminants (eg. viruses, bacteria); however, fractures in fractured rock aquifers and aquitards often provide pathways for particles to move in greater numbers and speed than in porous media. Thus, understanding flow and transport in fractures is important for the preservation and use of groundwater sources. Models based on coupling flow and transport equations can be used in understanding transport in fractures. Both experiments and simulations have shown that there are inconsistencies in current transport, attachment and detachment theory, particularly when particle size is varied. The assumption that hydrodynamic effects do not significantly affect transport of particles is likely untrue. As well, it has been shown that preferential flow paths occur in fractures, but the effects of path specific properties such as fracture geometry have yet to be thoroughly explored. It has been observed that eddies caused by local changes in geometry exist in fractures in the environment and models have demonstrated that such eddies will retard the flow of particles. In this work, two 2D fractures were randomly generated with a mean aperture of approximately 2mm. Finite element software, COMSOL Multiphysics, generated flow fields through the fractures by numerically solving the steady-state Navier-Stokes equation for varied flow rates. Eddies were observed in one of the fractures at both low (~1 m/day) and high (>100 m/day) velocities. A program was written using random walk particle tracking to simulate transport. Theories of attachment, detachment and matrix flow are not included in this model in order to isolate hydrodynamic forces. In combination with the modelling procedure, the two fractures were inscribed into pieces of

  8. Symmetry reductions of a nonlinear convection-dispersion model arising in contaminant transport theory

    NASA Astrophysics Data System (ADS)

    Ntsime, Basetsana P.; Moitsheki, Raseelo J.

    2016-06-01

    In this paper we consider a nonlinear convection-dispersion equation arising in contaminant transport. The water flow velocity is considered to be spatially-dependent and dispersion coefficient depends on concentration. A direct group classification resulted in a number of cases for which the governing equation admits Lie point symmetries. In each case the one dimensional optimal system of subalgebras is constructed. Reductions are performed. The reduced ordinary differential equations (ODEs) are nonlinear and difficult to solve exactly. On the other hand we consider the steady state problem and applied the method of canonical coordinates to determine exact solutions.

  9. Effect of Saltstone Vault Roof Configuration on the Rate of Contaminant Transport

    SciTech Connect

    Hsu, R.H.; Yu, A.D.; Lam, Poh-Sang

    1994-12-28

    At the Savannah River Site, low-level radioactive decontaminated salt solution is mixed with slag, flyash, and cement to form a grout-like material called ``Saltstone``. The Saltstone is poured into concrete vaults constructed at the Saltstone Disposal Facility (SDF). The impact of SDF on groundwater has been studied in a radiological performance assessment (PA). Sophisticated groundwater models were used to predict the groundwater flow and contaminant transport problems. The modeling effort was divided into two parts: the unsaturated-zone model and the saturated zone model. One of the major performance objectives is to show that the impacted groundwater will be in compliance with the Safe Drinking Water Act.

  10. Processes affecting the transport of nitrogen in groundwater and factors related to slope position

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nitrate (NO3-) pollution of water resources has been a major problem for years, causing contaminated water supplies, harmful effects on human health, and widespread eutrophication of fresh water resources. The main objectives of this study were to: 1) understand the processes affecting NO3- transpor...

  11. Simulation of Groundwater Contaminant Transport at a Decommissioned Landfill Site—A Case Study, Tainan City, Taiwan

    PubMed Central

    Chen, Chao-Shi; Tu, Chia-Huei; Chen, Shih-Jen; Chen, Cheng-Chung

    2016-01-01

    Contaminant transport in subsurface water is the major pathway for contamination spread from contaminated sites to groundwater supplies, to remediate a contaminated site. The aim of this paper was to set up the groundwater contaminant transport model for the Wang-Tien landfill site, in southwestern Taiwan, which exhibits high contamination of soil and groundwater and therefore represents a potential threat for the adjacent Hsu-Hsian Creek. Groundwater Modeling System software, which is the most sophisticated groundwater modeling tool available today, was used to numerically model groundwater flow and contaminant transport. In the simulation, the total mass of pollutants in the aquifer increased by an average of 72% (65% for ammonium nitrogen and 79% for chloride) after 10 years. The simulation produced a plume of contaminated groundwater that extends 80 m in length and 20 m in depth northeastward from the landfill site. Although the results show that the concentrations of ammonium nitrogen and chlorides in most parts are low, they are 3.84 and 467 mg/L, respectively, in the adjacent Hsu-Hsian Creek. PMID:27153078

  12. Development of one-dimensional computational fluid dynamics code 'GFLOW' for groundwater flow and contaminant transport analysis

    SciTech Connect

    Rahatgaonkar, P. S.; Datta, D.; Malhotra, P. K.; Ghadge, S. G.

    2012-07-01

    Prediction of groundwater movement and contaminant transport in soil is an important problem in many branches of science and engineering. This includes groundwater hydrology, environmental engineering, soil science, agricultural engineering and also nuclear engineering. Specifically, in nuclear engineering it is applicable in the design of spent fuel storage pools and waste management sites in the nuclear power plants. Ground water modeling involves the simulation of flow and contaminant transport by groundwater flow. In the context of contaminated soil and groundwater system, numerical simulations are typically used to demonstrate compliance with regulatory standard. A one-dimensional Computational Fluid Dynamics code GFLOW had been developed based on the Finite Difference Method for simulating groundwater flow and contaminant transport through saturated and unsaturated soil. The code is validated with the analytical model and the benchmarking cases available in the literature. (authors)

  13. COLLOID MOBILIZATION AND TRANSPORT IN CONTAMINANT PLUMES: FIELD EXPERIMENTS, LABORATORY EXPERIMENTS, AND MODELING (EPA/600/S-99/001)

    EPA Science Inventory

    The major hypothesis driving this research, that the transport of colloids in a contaminant plume is limited by the advance of the chemical agent causing colloid mobilization, was tested by (1) examining the dependence of colloid transport and mobilization on chemical perturbatio...

  14. Surfactant-enhanced remediation of a trichloroethene-contaminated aquifer. 2. Transport of TCE

    USGS Publications Warehouse

    Sahoo, D.; Smith, J.A.; Imbrigiotta, T.E.; Mclellan, H.M.

    1998-01-01

    Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added for a 36-day period (days 36-71 from the start of clean water injection). The effect of Triton X-100 on the desorption and transport of TCE in the field was examined by observing the concentrations of these two solutes in four monitoring wells 3-9 m from the injection wells. These data show a small but discernible increase in the TCE concentration in two of the wells corresponding approximately to the time when surfactant reaches the wells; in the other two monitoring wells, the increase in TCE concentration is negligible. A solute transport model that assumes local sorption equilibrium and used a laboratory-derived distribution coefficient could not adequately describe TCE desorption and transport observed in the aquifer. Two model formulations that accounted for rate-limited sorption - two-site and multisite models - fit the data well. TCE concentrations after surfactant injection were underpredicted by the models unless mass transfer rate was increased to account for the effect of surfactant on the rate of TCE desorption. The concentration data from the two wells and the model analysis suggest that the rate of TCE desorption is increased (by approximately 30%) as a result of Triton X-100 injection.Field studies were conducted under an induced gradient in a trichloroethene (TCE)-contaminated aquifer at Picatinny Arsenal, NJ, to study (a) the rate-limited desorption of TCE from aquifer sediments to water and (b) the effect of a surfactant (Triton X-100) on the desorption and transport of TCE. Clean water was injected into the contaminated aquifer for 206 day. Triton X-100 was added

  15. Particle-Based Direct Numerical Simulation of Contaminant Transport and Deposition in Porous Flow

    SciTech Connect

    Ray A. Berry; Richard C. Martineau; Thomas R. Wood

    2004-02-01

    This work describes an approach to porous flow modeling in which the "micro-length scale to macro-length scale" physical descriptions are addressed as Lagrangian, pore-level flow and transport. The flow features of the physical domain are solved by direct numerical simulation (DNS) with a grid-free, hybrid smoothed particle hydrodynamics (SPH) numerical method (Berry, 2002) based on a local Riemann solution. In addition to being able to handle the large deformation, fluid–fluid and fluid–solid interactions within the contorted geometries of intra- and inter-pore-scale modeling, this Riemann–SPH method should be able to simulate other complexities, such as multiple fluid phases and chemical, particulate, and microbial transport with volumetric and surface reactions. A simple model is presented for the transfer of a contaminant from a carrier fluid to solid surfaces and is demonstrated for flow in a simulated porous media

  16. Assessing of Conceptual Models for Subsurface Reactive Transport of Inorganic Contaminants

    NASA Astrophysics Data System (ADS)

    Davis, James A.; Yabusaki, Steven B.; Steefel, Carl I.; Zachara, John M.; Curtis, Gary P.; Redden, George D.; Criscenti, Louise J.; Honeyman, Bruce D.

    2004-11-01

    In many subsurface situations where human health and environmental quality are at risk (e.g., contaminant hydrogeology, petroleum extraction, carbon sequestration, etc.), scientists and engineers are being asked by federal agency decision-makers to predict the fate of chemical species under conditions where both reactions and transport are processes of first-order importance. In 2002, a working group (WG) was formed by representatives of the U.S. Geological Survey, Environmental Protection Agency, Department of Energy, Nuclear Regulatory Commission, Department of Agriculture, and Army Engineer Research and Development Center to assess the role of reactive transport modeling (RTM) in addressing these situations. Specifically, the goals of the WG are to (1) evaluate the state of the art in conceptual model development and parameterization for RTM, as applied to soil, vadose zone, and groundwater systems, and (2) prioritize research directions that would enhance the practical utility of RTM.

  17. Role of transportation in the persuasion process: cognitive and affective responses to antidrug narratives.

    PubMed

    Banerjee, Smita C; Greene, Kathryn

    2012-01-01

    This study examined transportation effects of first- and third-person narratives as well as the role of transportation in the persuasion process. In particular, the authors evaluated the role of transportation in affecting cognitive and affective responses. Last, they addressed the relation between (a) cognitive and affective responses and (b) antidrug expectancies. Participants were 500 undergraduate students at a large northern university in the United Kingdom who were randomly assigned to 1 of 2 conditions: first- or third-person narratives on cocaine use. The results demonstrated that there was no difference between first- and third-person narratives in terms of transportation. However, overall, greater transportation was associated with more favorable cognitive responses, and more favorable cognitive response was associated with stronger anticocaine expectancies. In terms of affective responses, results indicated the mediating role of sadness and contentment in the association between transportation and anticocaine expectancies. In particular, increased transportation was associated with greater sadness and lower contentment. Lower sadness and contentment were associated with stronger anticocaine expectancies. Important theoretical and empirical implications are discussed.

  18. Colloid facilitated transport of strongly sorbing contaminants in natural porous media: mathematical modeling and laboratory column experiments.

    PubMed

    Grolimund, Daniel; Borkovec, Michal

    2005-09-01

    Mobile colloidal particles may act as carriers of strongly sorbing contaminants in subsurface materials. Such colloid-facilitated transport can be induced by changes in salinity, similar to freshwater intrusion to a contaminated aquifer saturated with saltwater, or groundwater penetration into a contaminated site saturated with a dumpsite leachate. This process is studied for noncalcareous soil material with laboratory column experiments with sodium and calcium as major cations and with lead as a strongly sorbing model contaminant. The measured breakthrough curves of these elements were described with a mathematical transport model, which invokes release and deposition kinetics of the colloids, together with adsorption and desorption of the relevant ions to the solid matrix as well as to the suspended colloids. In particular, the specific coupling between colloid and solute transport is considered. The crux of a successful description of such colloidal transport processes is to capture the inhibition of the particle release by adsorbed divalent ions properly and explicitly to considerthe dependence of colloid release on the solution chemistry and the chemical conditions at the solid-liquid interface. Experiments and modeling address colloid-facilitated transport of lead out of a contaminated zone and through a noncontaminated zone, including effects of flow velocity and length of the noncontaminated zone. We finally show that colloid-facilitated transport can be suppressed by the injection of a suitably chosen solution of a calcium salt.

  19. Modeling aeolian transport in response to succession, disturbance and future climate: Dynamic long-term risk assessment for contaminant redistribution

    USGS Publications Warehouse

    Breshears, D.D.; Kirchner, T.B.; Whicker, J.J.; Field, J.P.; Allen, C.D.

    2012-01-01

    Aeolian sediment transport is a fundamental process redistributing sediment, nutrients, and contaminants in dryland ecosystems. Over time frames of centuries or longer, horizontal sediment fluxes and associated rates of contaminant transport are likely to be influenced by succession, disturbances, and changes in climate, yet models of horizontal sediment transport that account for these fundamental factors are lacking, precluding in large part accurate assessment of human health risks associated with persistent soil-bound contaminants. We present a simple model based on empirical measurements of horizontal sediment transport (predominantly saltation) to predict potential contaminant transport rates for recently disturbed sites such as a landfill cover. Omnidirectional transport is estimated within vegetation that changes using a simple Markov model that simulates successional trajectory and considers three types of short-term disturbances (surface fire, crown fire, and drought-induced plant mortality) under current and projected climates. The model results highlight that movement of contaminated soil is sensitive to vegetation dynamics and increases substantially (e.g., > fivefold) when disturbance and/or future climate are considered. The time-dependent responses in horizontal sediment fluxes and associated contaminant fluxes were sensitive to variability in the timing of disturbance, with longer intervals between disturbance allowing woody plants to become dominant and crown fire and drought abruptly reducing woody plant cover. Our results, which have direct implications for contaminant transport and landfill management in the specific context of our assessment, also have general relevance because they highlight the need to more fully account for vegetation dynamics, disturbance, and changing climate in aeolian process studies. ?? 2011.

  20. Modeling aeolian transport in response to succession, disturbance and future climate: Dynamic long-term risk assessment for contaminant redistribution

    NASA Astrophysics Data System (ADS)

    Breshears, David D.; Kirchner, Thomas B.; Whicker, Jeffrey J.; Field, Jason P.; Allen, Craig D.

    2012-01-01

    Aeolian sediment transport is a fundamental process redistributing sediment, nutrients, and contaminants in dryland ecosystems. Over time frames of centuries or longer, horizontal sediment fluxes and associated rates of contaminant transport are likely to be influenced by succession, disturbances, and changes in climate, yet models of horizontal sediment transport that account for these fundamental factors are lacking, precluding in large part accurate assessment of human health risks associated with persistent soil-bound contaminants. We present a simple model based on empirical measurements of horizontal sediment transport (predominantly saltation) to predict potential contaminant transport rates for recently disturbed sites such as a landfill cover. Omnidirectional transport is estimated within vegetation that changes using a simple Markov model that simulates successional trajectory and considers three types of short-term disturbances (surface fire, crown fire, and drought-induced plant mortality) under current and projected climates. The model results highlight that movement of contaminated soil is sensitive to vegetation dynamics and increases substantially (e.g., > fivefold) when disturbance and/or future climate are considered. The time-dependent responses in horizontal sediment fluxes and associated contaminant fluxes were sensitive to variability in the timing of disturbance, with longer intervals between disturbance allowing woody plants to become dominant and crown fire and drought abruptly reducing woody plant cover. Our results, which have direct implications for contaminant transport and landfill management in the specific context of our assessment, also have general relevance because they highlight the need to more fully account for vegetation dynamics, disturbance, and changing climate in aeolian process studies.

  1. Coupling Between Flow and Precipitation in Heterogeneous Subsurface Environments and Effects On Contaminant Fate and Transport

    SciTech Connect

    Tartakovsky, Alexandre M.; Redden, George D.; Yoshiko Fujita; Scheibe, Tim; Smith, Robert; Reddy, Michael; Kelly, Shelly

    2006-06-01

    Reactive mixing fronts can occur at large scales, e.g. when chemical amendments are injected in wells, or at small scales (pore-scales) when reactive intermediates are being generated in situ at grain boundaries, cell surfaces and adjacent to biofilms. The product of the reactions such as mineral precipitates, biofilms or filtered colloids modifies permeability leading to the complex coupling between flow and reactions and precipitation. The objectives are to determine how precipitates are distributed within large and small scale mixing fronts, how permeability and flow is modified by precipitation, how the mobility of a representative contaminant, strontium, is affected by the precipitation of carbonates, and how subsequent dissolution of the carbonates result in mobilization of Sr and increased flow. The desired outcomes of the project are to help develop methods leading to sequestration of metal contaminants, and to determine how macroscopic field-scale modeling can be applied to predict the outcome of remediation activities.

  2. Spatial and temporal features of density-dependent contaminant transport: Experimental investigation and numerical modeling

    NASA Astrophysics Data System (ADS)

    Zoia, Andrea; Latrille, Christelle; Beccantini, Alberto; Cartadale, Alain

    2009-10-01

    We investigate the spatial and temporal features of variable-density contaminant plumes migration in porous materials. Our analysis is supported by novel experimental results concerning concentration profiles inside a vertical column setup that has been conceived at CEA to this aim. The experimental method relies on X-ray spectrometry, which allows determining solute profiles as a function of time at several positions along the column. The salient outcomes of the measurements are elucidated, with focus on miscible fluids in homogeneous saturated media. The role of the injected solution molarity is evidenced. As molarity increases, the solutes plume transport progressively deviates from the usual Fickian behavior, and pollutants distribution becomes skewed in the direction dictated by gravity. By resorting to a finite elements approach, we numerically solve the nonlinear equations that rule the pollutants migration: a good agreement is found between the simulated profiles and the experimental data. At high molarity, a strong dependence on initial conditions is found. Finally, we qualitatively explore the (unstable) interfacial dynamics between the dense contaminant plume and the lighter resident fluid that saturates the column, and detail its evolution for finite-duration contaminant injections.

  3. Spatial and temporal features of density-dependent contaminant transport: experimental investigation and numerical modeling.

    PubMed

    Zoia, Andrea; Latrille, Christelle; Beccantini, Alberto; Cartadale, Alain

    2009-10-13

    We investigate the spatial and temporal features of variable-density contaminant plumes migration in porous materials. Our analysis is supported by novel experimental results concerning concentration profiles inside a vertical column setup that has been conceived at CEA to this aim. The experimental method relies on X-ray spectrometry, which allows determining solute profiles as a function of time at several positions along the column. The salient outcomes of the measurements are elucidated, with focus on miscible fluids in homogeneous saturated media. The role of the injected solution molarity is evidenced. As molarity increases, the solutes plume transport progressively deviates from the usual Fickian behavior, and pollutants distribution becomes skewed in the direction dictated by gravity. By resorting to a finite elements approach, we numerically solve the nonlinear equations that rule the pollutants migration: a good agreement is found between the simulated profiles and the experimental data. At high molarity, a strong dependence on initial conditions is found. Finally, we qualitatively explore the (unstable) interfacial dynamics between the dense contaminant plume and the lighter resident fluid that saturates the column, and detail its evolution for finite-duration contaminant injections.

  4. A Review of Removable Surface Contamination on Radioactive Materials Transportation Containers

    SciTech Connect

    Kennedy, Jr, W. E.; Watson, E. C.; Murphy, D. W.; Harrer, B. J.; Harty, R.; Aldrich, J. M.

    1981-05-01

    This report contains the results of a study sponsored by the U.S. Nuclear Regulatory Commission (NRC) of removable surface contamination on radioactive materials transportation containers. The purpose of the study is to provide information to the NRC during their review of existing regulations. Data was obtained from both industry and literature on three major topics: 1) radiation doses, 2) economic costs, and 3) contamination frequencies. Containers for four categories of radioactive materials are considered including radiopharmaceuticals, industrial sources, nuclear fuel cycle materials, and low-level radioactive waste. Assumptions made in this study use current information to obtain realistic yet conservative estimates of radiation dose and economic costs. Collective and individual radiation doses are presented for each container category on a per container basis. Total doses, to workers and the public, are also presented for spent fuel cask and low-level waste drum decontamination. Estimates of the additional economic costs incurred by lowering current limits by factors of 10 and 100 are presented. Current contamination levels for each category of container are estimated from the data collected. The information contained in this report is designed to be useful to the NRC in preparing their recommendations for new regulations.

  5. Dynamics of coupled contaminant and microbial transport in heterogeneous porous media. 1998 annual progress report

    SciTech Connect

    Ginn, T.R.; Cushman, J.H.; Murphy, E.M.; Fletcher, M.

    1998-06-01

    'Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in-situ bioremediation efforts. This interdisciplinary research project will provide fundamental information on the attachment/detachment dynamics of anaerobic bacteria in heterogeneous porous media under growth and growth-limiting conditions. Experiments will provide information on passive and active attachment/detachment mechanisms used by growing anaerobes capable of reductive dechlorination. Theoretical representations of these attachment/detachment mechanisms will be incorporated into existing flow and transport models that incorporate heterogeneity effects and can be used to predict behavior at field scales. These mechanistic-based models will be tested against experimental data provided through controlled laboratory experiments in heterogeneous porous media in large (meter-scale) 2-D flow cells. In addition to a mechanistic-based predictive model, this research will lead to new theories for the transient spatial distribution of microbial populations and contaminant plumes in heterogeneous porous media, improving the capability for designing staged remediation strategies for dealing with mixed contaminants.'

  6. A reactive transport model for mercury fate in contaminated soil--sensitivity analysis.

    PubMed

    Leterme, Bertrand; Jacques, Diederik

    2015-11-01

    We present a sensitivity analysis of a reactive transport model of mercury (Hg) fate in contaminated soil systems. The one-dimensional model, presented in Leterme et al. (2014), couples water flow in variably saturated conditions with Hg physico-chemical reactions. The sensitivity of Hg leaching and volatilisation to parameter uncertainty is examined using the elementary effect method. A test case is built using a hypothetical 1-m depth sandy soil and a 50-year time series of daily precipitation and evapotranspiration. Hg anthropogenic contamination is simulated in the topsoil by separately considering three different sources: cinnabar, non-aqueous phase liquid and aqueous mercuric chloride. The model sensitivity to a set of 13 input parameters is assessed, using three different model outputs (volatilized Hg, leached Hg, Hg still present in the contaminated soil horizon). Results show that dissolved organic matter (DOM) concentration in soil solution and the binding constant to DOM thiol groups are critical parameters, as well as parameters related to Hg sorption to humic and fulvic acids in solid organic matter. Initial Hg concentration is also identified as a sensitive parameter. The sensitivity analysis also brings out non-monotonic model behaviour for certain parameters.

  7. Contaminant transport in groundwater in the presence of colloids and bacteria: model development and verification.

    PubMed

    Bekhit, Hesham M; El-Kordy, Mohamed A; Hassan, Ahmed E

    2009-09-01

    Colloids and bacteria (microorganisms) naturally exist in groundwater aquifers and can significantly impact contaminant migration rates. A conceptual model is first developed to account for the different physiochemical and biological processes, reaction kinetics, and different transport mechanisms of the combined system (contaminant-colloids-bacteria). All three constituents are assumed to be reactive with the reactions taking place between each constituent and the porous medium and also among the different constituents. A general linear kinetic reaction model is assumed for all reactive processes considered. The mathematical model is represented by fourteen coupled partial differential equations describing mass balance and reaction processes. Two of these equations describe colloid movement and reactions with the porous medium, four equations describe bacterial movement and reactions with colloids and the porous medium, and the remaining eight equations describe contaminant movement and its reactions with bacteria, colloids, and the porous medium. The mass balance equations are numerically solved for two-dimensional groundwater systems using a third-order, total variance-diminishing scheme (TVD) for the advection terms. Due to the complex coupling of the equations, they are solved iteratively each time step until a convergence criterion is met. The model is tested against experimental data and the results are favorable.

  8. Inverse Reactive Transport Simulator (Inverts): An Inverse Model for Contaminant Transport with Nonlinear Adsorption and Source Terms

    SciTech Connect

    McGrail, B. Peter

    2001-10-31

    A numerically based simulator was developed to assist in the interpretation of complex laboratory experiments examining transport processes of chemical and biological contaminants subject to nonlinear adsorption and/or source terms. The inversion is performed with any of three nonlinear regression methods, Marquardt-Levenberg, conjugate gradient, or quasi-Newton. The governing equations for the problem are solved by the method of finite-differences including any combination of three boundary conditions: (1) Dirichlet, (2) Neumann, and (3) Cauchy. The dispersive terms in the transport equations were solved using the second-order accurate in time and space Crank-Nicolson scheme, while the advective terms were handled using a third-order in time and space, total variation diminishing (TVD) scheme that damps spurious oscillations around sharp concentration fronts. The numerical algorithms were implemented in the computer code INVERTS, which runs on any standard personal computer. Apart from a comprehensive set of test problems, INVERTS was also used to model the elution of a nonradioactive tracer, {sup 185}Re, in a pressurized unsaturated flow (PUF) experiment with a simulated waste glass for low-activity waste immobilization. Interpretation of the elution profile was best described with a nonlinear kinetic model for adsorption.

  9. Characterization on the rhizoremediation of petroleum contaminated soil as affected by different influencing factors

    NASA Astrophysics Data System (ADS)

    Tang, J.; Wang, R.; Niu, X.; Wang, M.; Zhou, Q.

    2010-06-01

    In this paper, pilot experiments were conducted to analyze the effect of different environmental factors on the rhizoremediation of petroleum contaminated soil. Different plant species (cotton, ryegrass, tall fescue, and alfalfa), addition of fertilizer, different concentration of TPH in soil, bioaugmentation with effective microbial agent (EMA) and PGPR, and remediation time were tested as influencing factors during bioremediation process of Total Petroleum Hydrocarbon (TPH). The result shows that the remediation process can be enhanced by different plants species with the following order: tall fescue > ryegrass > alfalfa > cotton. The degradation rate of TPH increased with increased fertilizer addition and moderate level of 20 g/m2 urea is best for both plant growth and TPH remediation. High TPH content is toxic to plant growth and inhibits the degradation of petroleum hydrocarbon with 5% TPH content showing the best degradation result in soil planted with ryegrass. Bioaugmentation with different bacteria and plant growth promoting rhizobacteria (PGPR) showed the following results for TPH degradation: cotton + EMA + PGPR > cotton + EMA > cotton + PGPR > cotton > control. Rapid degradation of TPH was found at the initial period of remediation caused by the activity of microorganisms, continuous increase was found from 30-90 d period and slow increase was found from 90 to 150 d. The result suggests that rhizoremediation can be enhanced with the proper control of different influencing factors that affect both plant growth and microbial activity in the rhizosphere environment.

  10. Relationship between Microtubule Network Structure and Intracellular Transport in Cultured Endothelial Cells Affected by Shear Stress

    NASA Astrophysics Data System (ADS)

    Kudo, Susumu; Ikezawa, Kenji; Ikeda, Mariko; Tanishita, Kazuo

    Endothelial cells (ECs) that line the inner surface of blood vessels are barriers to the transport of various substances into or from vessel walls, and are continuously exposed to shear stress induced by blood flow in vivo. Shear stress affects the cytoskeleton (e.g., microtubules, microfilaments, intermediate filaments), and affects the transport of macromolecules. Here, the relationship between the microtubule network structure and this transport process for albumin uptake within cultured aortic endothelial cells affected by shear stress was studied. Based on fluorescent images of albumin uptake obtained by using confocal laser scanning microscopy (CLSM), both the microtubule network and albumin uptake in ECs were disrupted by colchicine and were affected by shear stress loading.

  11. Transport of Aquatic Contaminant and Assessment of Radioecological Exposure with Spatial and Temporal Effects

    NASA Astrophysics Data System (ADS)

    Feng, Ying

    1995-01-01

    A comprehensive study of the radioecological exposure assessment for a contaminated aquatic ecosystem has been performed in this dissertation. The primary objectives of this research were to advance the understanding of radiation exposure in nature and to increase current capabilities for estimating aquatic radiation exposure with the consideration of spatial and temporal effect in nature. This was accomplished through the development of a two-dimensional aquatic exposure assessment framework and by applying the framework to the contaminated Chernobyl cooling lake (pond). This framework integrated spatial and temporal heterogeneity effects of contaminant concentration, abundance and distribution of ecosystem populations, spatial- and temporal-dependent (or density-dependent) radionuclide ingestion, and alternative food web structures. The exposure model was built on the population level to allow for the integration of density dependent population regulation into the exposure assessment. Plankton population dynamics have been integrated into the hydrodynamic-transport model to determine plankton biomass density changes and distributions. The distribution of contaminant in water was also calculated using a hydrodynamic-transport model. The significance of adding spatial and temporal effects, spatial and temporal related ecological functions, and hydrodynamics in the exposure assessment was illustrated through a series of case studies. The results suggested that the spatial and temporal heterogeneity effects of radioactive environments were substantial. Among the ecological functions considered, the food web structure was the most important contributor to the variations of fish exposure. The results obtained using a multiple prey food web structure differed by a factor of 20 from the equilibrium concentration, and by a factor of 2.5 from the concentration obtained using a single-prey food web. Impacts of changes in abundance and distribution of biomass on contaminant

  12. Investigating the Impact of Pore Scale Microenvironments on Contaminant Biogeochemical Reactive Transport

    NASA Astrophysics Data System (ADS)

    Wilkins, M. J.; Pearce, C.; Zhang, C.; Heald, S.; Fredrickson, J. K.; Zachara, J. M.

    2011-12-01

    Microenvironments and transition zones dominate the subsurface biogeochemical cycling of key contaminants, with strong effects resulting from the coupling of chemical reactions, physical transport and microbiological processes. Understanding the impact of pore-scale environments (e.g. spatial heterogeneity, chemical gradients, and redox potential) is essential for modeling contaminant fate and transport in the subsurface. The driver for biogeochemical processes at the pore scale changes from macroscopic advection to microscale diffusion, and this has a significant effect on the retention of soluble, highly mobile contaminants such as U(VI). Here, etched-silicon microfluidic models with defined chemistry, mineralogy, microbiology, and flow regimes are used for the incremental development of complex microenvironments that approach real-world systems. We demonstrate the colonization of such pore spaces by an anaerobic Fe(III)-reducing bacterium, the enzymatic reduction of a bioavailable Fe(III) phase within this environment, and the subsequent effects of both oxidized and reduced Fe phases on uranium biogeochemistry under flow conditions using both X-ray Microprobe (XMP) and X-ray Absorption Spectroscopy (XAS). Precipitated Fe(III) phases within the microfluidic model were most effectively reduced in the presence of an electron shuttle (e.g. AQDS), with Fe(II) ions adsorbing onto mineral precipitates and surfaces. In the absence of Fe, U(VI) was effectively reduced by the microbial population to insoluble U(IV), which was precipitated in discrete regions associated within biomass. In the presence of both oxidized and reduced Fe phases however, differing effects were observed with regards to U behavior; oxidized U(VI) was frequently adsorbed to poorly crystalline Fe(III), and reduced U(IV) associated with more reduced regions of the microscale flow cell. In the future, the flexibility in the design of the microfluidic models, in combination with advanced

  13. Simulation of phosphate transport in sewage-contaminated groundwater, Cape Cod, Massachusetts

    USGS Publications Warehouse

    Stollenwerk, K.G.

    1996-01-01

    Sewage-contaminated groundwater currently discharges to Ashumet Pond, located on Cape Cod, Massachusetts Phosphate concentrations as high as 60 ??mol l-1 have been measured in groundwater entering Ashumet Pond, and there is concern that the rate of eutrophication could increase. Phosphate in the sewage plume is sorbed by aquifer sediment; the amount is a function of phosphate concentration and pH. A nonelectrostatic surface-complexation model coupled with a one-dimensional solute-transport code was used to simulate sorption and desorption of phosphate in laboratory column experiments. The model simulated sorption of phosphate reasonably well, although the slow rate of approach to complete breakthrough indicated a nonequilibrium process that was not accounted for in the solute-transport model The rate of phosphate desorption in the column experiments was relatively slow Phosphate could still be measured in effluent after 160 pore volumes of uncontaminated groundwater had been flushed through the columns. Desorption was partly a function of the slowly decreasing pH in the columns and could be modeled quantitatively. Disposal of sewage at this site is scheduled to stop in 1995; however, a large reservoir of sorbed phosphate exists on aquifer sediment upgradient from Ashumet Pond. Computer simulations predict that desorption of phosphate could result in contamination of Ashumet Pond for decades.

  14. Disgust as a Unique Affective Predictor of Mental Contamination Following Sexual Trauma

    PubMed Central

    Badour, Christal L.; Ojserkis, Rachel; McKay, Dean; Feldner, Matthew T.

    2014-01-01

    Mental contamination has been described as an internal experience of dirtiness that can arise and persist in the absence of contact with observable physical contaminants. Recent research has examined mental contamination specifically related to unwanted physical contact and sexual trauma. This study evaluated the degree to which disgust propensity and both self-focused and perpetrator-focused peritraumatic disgust were associated with mental contamination in a sample of women who experienced sexual trauma (n = 72). Results showed that peritraumatic self-focused disgust, but not peritraumatic perpetrator-focused disgust or fear, was significantly associated with mental contamination. Additionally, disgust propensity contributed significantly to the incremental validity of the model. These findings support the nascent literature showing that disgust plays a significant role in mental contamination, particularly following sexual trauma. Future research directions, and clinical/theoretical implications of these results are discussed. PMID:25129888

  15. Flood-related contamination in catchments affected by historical metal mining: an unexpected and emerging hazard of climate change.

    PubMed

    Foulds, S A; Brewer, P A; Macklin, M G; Haresign, W; Betson, R E; Rassner, S M E

    2014-04-01

    Floods in catchments affected by historical metal mining result in the remobilisation of large quantities of contaminated sediment from floodplain soils and old mine workings. This poses a significant threat to agricultural production and is preventing many European river catchments achieving a 'good chemical and ecological status', as demanded by the Water Framework Directive. Analysis of overbank sediment following widespread flooding in west Wales in June 2012 showed that flood sediments were contaminated above guideline pollution thresholds, in some samples by a factor of 82. Most significantly, silage produced from flood affected fields was found to contain up to 1900 mg kg(-1) of sediment associated Pb, which caused cattle poisoning and mortality. As a consequence of climate related increases in flooding this problem is likely to continue and intensify. Management of contaminated catchments requires a geomorphological approach to understand the spatial and temporal cycling of metals through the fluvial system.

  16. Flood-related contamination in catchments affected by historical metal mining: an unexpected and emerging hazard of climate change.

    PubMed

    Foulds, S A; Brewer, P A; Macklin, M G; Haresign, W; Betson, R E; Rassner, S M E

    2014-04-01

    Floods in catchments affected by historical metal mining result in the remobilisation of large quantities of contaminated sediment from floodplain soils and old mine workings. This poses a significant threat to agricultural production and is preventing many European river catchments achieving a 'good chemical and ecological status', as demanded by the Water Framework Directive. Analysis of overbank sediment following widespread flooding in west Wales in June 2012 showed that flood sediments were contaminated above guideline pollution thresholds, in some samples by a factor of 82. Most significantly, silage produced from flood affected fields was found to contain up to 1900 mg kg(-1) of sediment associated Pb, which caused cattle poisoning and mortality. As a consequence of climate related increases in flooding this problem is likely to continue and intensify. Management of contaminated catchments requires a geomorphological approach to understand the spatial and temporal cycling of metals through the fluvial system. PMID:24463253

  17. Distribution and transport of sediment-bound metal contaminants in the rio grande de tarcoles, costa rica (Central America)

    USGS Publications Warehouse

    Fuller, C.C.; Davis, J.A.; Cain, D.J.; Lamothe, P.J.; Fries Fernandez, T.L.G.; Vargas, J.A.; Murillo, M.M.

    1990-01-01

    A reconnaissance survey of the extent of metal contamination in the Rio Grande de Tarcoles river system of Costa Rica indicated high levels of chromium (Cr) in the fine-grain bed sediments (83 times Cr background or 3000->5000 ??g/g). In the main channel of the river downstream of the San Jose urban area, Cr contamination in sediments was 4-6 times background and remained relatively constant over 50 km to the mouth of the river. Sediment from a mangrove swamp at the river mouth had Cr levels 2-3 times above background. Similar patterns of dilution were observed for lead (Pb) and zinc (Zn) sediment contamination, although the contamination levels were lower. The high affinity of Cr towards particulate phases, probably as Cr(III), allows the use of Cr contamination levels for delineating regions of deposition of fine-grained sediments and dilution of particle associated contaminants during transport and deposition.A reconnaissance survey of the extent of metal contamination in the Rio Grande de Tarcoles river system of Costa Rica indicated high levels of chromium (Cr) in the fine-grain bed sediments (83 times Cr background or 3000->5000 ??g/g). In the main channel of the river downstream of the San Jose urban area, Cr contamination in sediments was 4-6 times background and remained relatively constant over 50 km to the mouth of the river. Sediments from a mangrove swamp at the river mouth had Cr levels 2-3 times above background. Similar patterns of dilution were observed for lead (Pb) and zinc (Zn) sediment contamination, although the contamination levels were lower. The high affinity of Cr towards particulate phases, probably as Cr(III), allows the use of Cr contamination levels for delineating regions of deposition of fine-grained sediments and dilution of particle associated contaminants during transport and deposition.

  18. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    PubMed

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  19. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating

    NASA Astrophysics Data System (ADS)

    Munholland, Jonah L.; Mumford, Kevin G.; Kueper, Bernard H.

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water.

  20. Factors affecting gas migration and contaminant redistribution in heterogeneous porous media subject to electrical resistance heating.

    PubMed

    Munholland, Jonah L; Mumford, Kevin G; Kueper, Bernard H

    2016-01-01

    A series of intermediate-scale laboratory experiments were completed in a two-dimensional flow cell to investigate gas production and migration during the application of electrical resistance heating (ERH) for the removal of dense non-aqueous phase liquids (DNAPLs). Experiments consisted of heating water in homogeneous silica sand and heating 270 mL of trichloroethene (TCE) and chloroform (CF) DNAPL pools in heterogeneous silica sands, both under flowing groundwater conditions. Spatial and temporal distributions of temperature were measured using thermocouples and observations of gas production and migration were collected using front-face image capture throughout the experiments. Post-treatment soil samples were collected and analyzed to assess DNAPL removal. Results of experiments performed in homogeneous sand subject to different groundwater flow rates showed that high groundwater velocities can limit subsurface heating rates. In the DNAPL pool experiments, temperatures increased to achieve DNAPL-water co-boiling, creating estimated gas volumes of 131 and 114 L that originated from the TCE and CF pools, respectively. Produced gas migrated vertically, entered a coarse sand lens and subsequently migrated laterally beneath an overlying capillary barrier to outside the heated treatment zone where 31-56% of the original DNAPL condensed back into a DNAPL phase. These findings demonstrate that layered heterogeneity can potentially facilitate the transport of contaminants outside the treatment zone by mobilization and condensation of gas phases during ERH applications. This underscores the need for vapor phase recovery and/or control mechanisms below the water table during application of ERH in heterogeneous porous media during the co-boiling stage, which occurs prior to reaching the boiling point of water. PMID:26638038

  1. Response of barley plants to Fe deficiency and Cd contamination as affected by S starvation.

    PubMed

    Astolfi, S; Zuchi, S; Neumann, G; Cesco, S; Sanità di Toppi, L; Pinton, R

    2012-02-01

    Both Fe deficiency and Cd exposure induce rapid changes in the S nutritional requirement of plants. The aim of this work was to characterize the strategies adopted by plants to cope with both Fe deficiency (release of phytosiderophores) and Cd contamination [production of glutathione (GSH) and phytochelatins] when grown under conditions of limited S supply. Experiments were performed in hydroponics, using barley plants grown under S sufficiency (1.2 mM sulphate) and S deficiency (0 mM sulphate), with or without Fe(III)-EDTA at 0.08 mM for 11 d and subsequently exposed to 0.05 mM Cd for 24 h or 72 h. In S-sufficient plants, Fe deficiency enhanced both root and shoot Cd concentrations and increased GSH and phytochelatin levels. In S-deficient plants, Fe starvation caused a slight increase in Cd concentration, but this change was accompanied neither by an increase in GSH nor by an accumulation of phytochelatins. Release of phytosiderophores, only detectable in Fe-deficient plants, was strongly decreased by S deficiency and further reduced after Cd treatment. In roots Cd exposure increased the expression of the high affinity sulphate transporter gene (HvST1) regardless of the S supply, and the expression of the Fe deficiency-responsive genes, HvYS1 and HvIDS2, irrespective of Fe supply. In conclusion, adequate S availability is necessary to cope with Fe deficiency and Cd toxicity in barley plants. Moreover, it appears that in Fe-deficient plants grown in the presence of Cd with limited S supply, sulphur may be preferentially employed in the pathway for biosynthesis of phytosiderophores, rather than for phytochelatin production.

  2. The relationships of salmonellae from infected broiler flocks, transport crates or processing plants to contamination of eviscerated carcases.

    PubMed Central

    Rigby, C E; Pettit, J R; Bentley, A H; Spencer, J L; Salomons, M O; Lior, H

    1982-01-01

    Three flocks raised for broiler or roaster performance tests were studied to determine the incidence and sources of salmonellae during the growing period, transport and processing and to relate these to contamination of processed carcasses. Day old chicks in two of the tests, (tests IV and V), were treated with a culture of intestinal anaerobes derived from mature chickens. The incidence of salmonellae during the growing period was too low to permit any conclusions about the efficacy of this culture in preventing Salmonella infection, but it had no adverse effect on flock performance. Carcasses from all three flocks were contaminated with salmonellae. Although the test IV flock was raised free of salmonellae, 46% of the carcasses tested from this flock were contaminated. The apparent source was the transport crates, 99% of which yielded salmonellae before the flock was loaded. In test V, 92% of the carcasses tested yielded salmonellae. The apparent sources were: flock infection (apparently originating from the parent flock), contaminated crates, spread during transport, and plant contamination. The flock of test VI was infected with Salmonella albany, and 54% of the carcasses tested were contaminated with this serovar. Carcasses of chicks infected early in life were more likely to be contaminated than those of chickens which contacted salmonellae later in the growing period. PMID:7127193

  3. Experimental investigation of airborne contaminant transport by a human wake moving in a ventilated aircraft cabin

    NASA Astrophysics Data System (ADS)

    Poussou, Stephane B.

    The air ventilation system in jetliners provides a comfortable and healthy environment for passengers. Unfortunately, the increase in global air traffic has amplified the risks presented by infectious aerosols or noxious material released during flight. Inside the cabin, air typically flows continuously from overhead outlets into sidewall exhausts in a circular pattern that minimizes secondary flow between adjacent seat rows. However, disturbances frequently introduced by individuals walking along an aisle may alter air distribution, and contribute to spreading of contaminants. Numerical simulation of these convoluted transient flow phenomena is difficult and complex, and experimental assessment of contaminant distribution in real cabins often impractical. A fundamental experimental study was undertaken to examine the transport phenomena, to validate computations and to improve air monitoring systems. A finite moving body was modeled in a 10:1 scale simplified aircraft cabin equipped with ventilation, at a Reynolds number (based on body diameter) of the order of 10,000. An experimental facility was designed and constructed to permit measurements of the ventilation and wake velocity fields using particle image velocimetry (PIV). Contaminant migration was imaged using the planar laser induced fluorescence (PLIF) technique. The effect of ventilation was estimated by comparison with a companion baseline study. Results indicate that the evolution of a downwash predominant behind finite bodies of small aspect ratio is profoundly perturbed by the ventilation flow. The reorganization of vortical structures in the near-wake leads to a shorter longitudinal recirculation region. Furthermore, mixing in the wake is modified and contaminant is observed to convect to higher vertical locations corresponding to seated passenger breathing level.

  4. Current conceptual model of groundwater flow and contaminant transport at Sandia National Laboratories/New Mexico Technical Area V.

    SciTech Connect

    Orr, Brennon R.; Dettmers, Dana L.

    2004-04-01

    The New Mexico Environment Department (NMED) requires a Corrective Measures Evaluation to evaluate potential remedial alternatives for contaminants of concern (COCs) in groundwater at Sandia National Laboratories New Mexico (SNUNM) Technical Area (TA)-V. These COCs consist of trichloroethene, tetrachloroethene, and nitrate. This document presents the current conceptual model of groundwater flow and transport at TA-V that will provide the basis for a technically defensible evaluation. Characterization is defined by nine requirement areas that were identified in the NMED Compliance Order on Consent. These characterization requirement areas consist of geohydrologic characteristics that control the subsurface distribution and transport of contaminants. This conceptual model document summarizes the regional geohydrologic setting of SNUNM TA-V. The document also presents a summary of site-specific geohydrologic data and integrates these data into the current conceptual model of flow and contaminant transport. This summary includes characterization of the local geologic framework; characterization of hydrologic conditions at TA-V, including recharge, hydraulics of vadose-zone and aquifer flow, and the aquifer field of flow as it pertains to downgradient receptors. The summary also discusses characterization of contaminant transport in the subsurface, including discussion about source term inventory, release, and contaminant distribution and transport in the vadose zone and aquifer.

  5. Reductive dissolution and reactive solute transport in a sewage-contaminated glacial outwash aquifer

    USGS Publications Warehouse

    Lee, R.W.; Bennett, P.C.

    1998-01-01

    Contamination of shallow ground water by sewage effluent typically contains reduced chemical species that consume dissolved oxygen, developing either a low oxygen geochemical environment or an anaerobic geochemical environment. Based on the load of reduced chemical species discharged to shallow ground water and the amounts of reactants in the aquifer matrix, it should be possible to determine chemical processes in the aquifer and compare observed results to predicted ones. At the Otis Air Base research site (Cape Cod, Massachusetts) where sewage effluent has infiltrated the shallow aquifer since 1936, bacterially mediated processes such as nitrification, denitrification, manganese reduction, and iron reduction have been observed in the contaminant plume. In specific areas of the plume, dissolved manganese and iron have increased significantly where local geochemical conditions are favorable for reduction and transport of these constituents from the aquifer matrix. Dissolved manganese and iron concentrations ranged from 0.02 to 7.3 mg/L, and 0.001 to 13.0 mg/L, respectively, for 21 samples collected from 1988 to 1989. Reduction of manganese and iron is linked to microbial oxidation of sewage carbon, producing bicarbonate and the dissolved metal ions as by-products. Calculated production and flux of CO2 through the unsaturated zone from manganese reduction in the aquifer was 0.035 g/m2/d (12% of measured CO2 flux during winter). Manganese is limited in the aquifer, however. A one-dimensional, reaction-coupled transport model developed for the mildly reducing conditions in the sewage plume nearest the source beds showed that reduction, transport, and removal of manganese from the aquifer sediments should result in iron reduction where manganese has been depleted.

  6. Biochar pyrolyzed at two temperatures affects Escherichia coli transport through a sandy soil.

    PubMed

    Bolster, Carl H; Abit, Sergio M

    2012-01-01

    The incorporation of biochar into soils has been proposed as a means to sequester carbon from the atmosphere. An added environmental benefit is that biochar has also been shown to increase soil retention of nutrients, heavy metals, and pesticides. The goal of this study was to evaluate whether biochar amendments affect the transport of Escherichia coli through a water-saturated soil. We looked at the transport of three E. coli isolates through 10-cm columns packed with a fine sandy soil amended with 2 or 10% (w/w) poultry litter biochar pyrolyzed at 350 or 700°C. For all three isolates, mixing the high-temperature biochar at a rate of 2% into the soil had no impact on transport behavior. When added at a rate of 10%, a reduction of five orders of magnitude in the amount of E. coli transported through the soil was observed for two of the isolates, and a 60% reduction was observed for the third isolate. Mixing the low-temperature biochar into the soil resulted in enhanced transport through the soil for two of the isolates, whereas no significant differences in transport behavior were observed between the low-temperature and high-temperature biochar amendments for one isolate. Our results show that the addition of biochar can affect the retention and transport behavior of E. coli and that biochar application rate, biochar pyrolysis temperature, and bacterial surface characteristics were important factors determining the transport of E. coli through our test soil. PMID:22218181

  7. Biodegradation during contaminant transport in porous media: 4. Impact of microbial lag and bacterial cell growth

    NASA Astrophysics Data System (ADS)

    Sandrin, Susannah K.; Jordan, Fiona L.; Maier, Raina M.; Brusseau, Mark L.

    2001-08-01

    Miscible-displacement experiments were conducted to examine the impact of microbial lag and bacterial cell growth on the transport of salicylate, a model hydrocarbon compound. The impacts of these processes were examined separately, as well as jointly, to determine their relative effects on biodegradation dynamics. For each experiment, a column was packed with porous medium that was first inoculated with bacteria that contained the NAH plasmid encoding genes for the degradation of naphthalene and salicylate, and then subjected to a step input of salicylate solution. The transport behavior of salicylate was non-steady for all cases examined, and was clearly influenced by a delay (lag) in the onset of biodegradation. This microbial lag, which was consistent with the results of batch experiments, is attributed to the induction and synthesis of the enzymes required for biodegradation of salicylate. The effect of microbial lag on salicylate transport was eliminated by exposing the column to two successive pulses of salicylate, thereby allowing the cells to acclimate to the carbon source during the first pulse. Elimination of microbial lag effects allowed the impact of bacterial growth on salicylate transport to be quantified, which was accomplished by determining a cell mass balance. Conversely, the impact of microbial lag was further investigated by performing a similar double-pulse experiment under no-growth conditions. Significant cell elution was observed and quantified for all conditions/systems. The results of these experiments allowed us to differentiate the effects associated with microbial lag and growth, two coupled processes whose impacts on the biodegradation and transport of contaminants can be difficult to distinguish.

  8. Metal contaminated biochar and wood ash negatively affect plant growth and soil quality after land application.

    PubMed

    Jones, D L; Quilliam, R S

    2014-07-15

    Pyrolysis or combustion of waste wood can provide a renewable source of energy and produce byproducts which can be recycled back to land. To be sustainable requires that these byproducts pose minimal threat to the environment or human health. Frequently, reclaimed waste wood is contaminated by preservative-treated timber containing high levels of heavy metals. We investigated the effect of feedstock contamination from copper-preservative treated wood on the behaviour of pyrolysis-derived biochar and combustion-derived ash in plant-soil systems. Biochar and wood ash were applied to soil at typical agronomic rates. The presence of preservative treated timber in the feedstock increased available soil Cu; however, critical Cu guidance limits were only exceeded at high rates of feedstock contamination. Negative effects on plant growth and soil quality were only seen at high levels of biochar contamination (>50% derived from preservative-treated wood). Negative effects of wood ash contamination were apparent at lower levels of contamination (>10% derived from preservative treated wood). Complete removal of preservative treated timber from wood recycling facilities is notoriously difficult and low levels of contamination are commonplace. We conclude that low levels of contamination from Cu-treated wood should pose minimal environmental risk to biochar and ash destined for land application. PMID:24915641

  9. Pulse exposure of cultured rat neurons to aluminum-maltol affected the axonal transport system.

    PubMed

    Kashiwagi, Y; Nakamura, Y; Miyamae, Y; Hashimoto, R; Takeda, M

    1998-08-01

    Although chronic aluminum neurotoxicity has been well established, the mechanism of the toxicity has not been elucidated yet. In order to simplify the study of the aluminum neurotoxicity, we employed the pulse exposure of cultured rat cortical neurons to 250 microM aluminum-maltol for 1 h at the early stage (6 h after plating), which resulted in abnormal distribution of neurofilament L (NFL) and fast axonal transported proteins, whereas the axonal transport of tubulin, actin, and clathrin were not impaired. Otherwise, the pulse exposure of neurons at the late stage (4 days after plating) to the same concentration of aluminum-maltol did not affect the cell morphology and the distribution of NFL. The pulse exposure of cultured neurons to aluminum-maltol at the early stage might affect the axonal transport system of NFL and fast axonal transported proteins. PMID:9756345

  10. Analysis of Contaminant Transport through the Vadose and Saturated Zones for Source Screening

    NASA Astrophysics Data System (ADS)

    Bedekar, V.; Neville, C. J.; Tonkin, M. J.

    2010-12-01

    At complex sites there may be many potential source areas. Screening level analyses are useful to identify which of the source areas should be the focus of detailed investigation and analysis. A screening tool has been developed to evaluate the threat posed by waste sites on groundwater quality. This tool implements analytical solutions to simulate contaminant transport through the vadose and saturated zones and predict time-varying concentrations at potential groundwater receptors. The screening tool is developed within a user friendly, Microsoft ExcelTM based interface; however, care has been taken to implement rigorous solutions. The screening tool considers the following mechanisms: (a) Partitioning of soil contamination in to an equivalent dissolved concentration. For a time-invariant source, the solution is generalized from [3] for sorption and decay. For a time-varying source, the solution represents a special, degenerate, case of a solution implemented in ATRANS [2]; (b) One-dimensional (1D) transport of the dissolved contamination through the vadose zone considering 1D dispersion, equilibrium sorption, and first order transformation reactions. Steady state infiltration and moisture content are assumed; (c) Blending (mixing) of ambient water quality in the saturated zone with the contaminated water leaching from the vadose zone; and (d) Three-dimensional (3D) transport through the saturated zone using the formulation provided in [2], considering advection, dispersion, sorption, and first-order transformation reactions. The solution is derived using integral transform methods, following approaches adopted in [1] and [4]. Independent verification showed that the analytical techniques implemented in this study generate solutions that closely approximate those obtained using sophisticated numerical approaches, with a systematic over-estimate of the likely impact to groundwater that (predictably) stems from the use of a 1D approximation in the vadose zone. As a

  11. The Role of Natural Organic Matter and Mineral Colloids in the Transport of Contaminants through Heterogeneous Vadose-Zone Environments

    SciTech Connect

    James Saiers, Yale University; Joseph Ryan, University of Colorado

    2009-01-31

    Our research was guided by a key objective of the Environmental Management Science Program (EMSP), which is to improve conceptual and predictive models for contaminant movement in complex vadose zone environments. In this report, increases in the understanding of colloidcontaminant interactions, colloid mobilization, and colloid deposition within unsaturated soils are cited as requisite needs for predicting contaminant fate and distribution in the vadose zone. We addressed these needs by pursuing three key goals: 1. Identify the mechanisms that govern OM and mineral-colloid reaction and transport in heterogeneous, unsaturated porous media; 2. Quantify the role of OM and mineral colloids in scavenging and facilitating the transport of contaminants of concern to DOE; and 3. Develop and test a mathematical model suitable for simulating the movement of OM- and colloid-associated contaminants through heterogeneous, unsaturated porous media.

  12. Final Project Report: Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

    SciTech Connect

    Jon Chorover, University of Arizona; Peggy O'€™Day, University of California, Merced; Karl Mueller, Penn State University; Wooyong Um, Pacific Northwest National Laboratory; Carl Steefel, Lawrence Berkeley National Laboratory

    2012-10-01

    Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided detailed characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, PCO2, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions.

  13. Evaluation of microbial transport during aerobic bioaugmentation of an RDX-contaminated aquifer.

    PubMed

    Crocker, Fiona H; Indest, Karl J; Jung, Carina M; Hancock, Dawn E; Fuller, Mark E; Hatzinger, Paul B; Vainberg, Simon; Istok, Jonathan D; Wilson, Edward; Michalsen, Mandy M

    2015-11-01

    In situ bioaugmentation with aerobic hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading bacteria is being considered for treatment of explosives-contaminated groundwater at Umatilla Chemical Depot, Oregon (UMCD). Two forced-gradient bacterial transport tests of site groundwater containing chloride or bromide tracer and either a mixed culture of Gordonia sp. KTR9 (xplA (+)Km(R)), Rhodococcus jostii RHA1 (pGKT2 transconjugant; xplA (+)Km(R)) and Pseudomonas fluorescens I-C (xenB (+)), or a single culture of Gordonia sp. KTR9 (xplA (+); i.e. wild-type) were conducted at UMCD. Groundwater monitoring evaluated cell viability and migration in the injection well and downgradient monitoring wells. Enhanced degradation of RDX was not evaluated in these demonstrations. Quantitative PCR analysis of xplA, the kanamycin resistance gene (aph), and xenB indicated that the mixed culture was transported at least 3 m within 2 h of injection. During a subsequent field injection of bioaugmented groundwater, strain KTR9 (wild-type) migrated up to 23-m downgradient of the injection well within 3 days. Thus, the three RDX-degrading strains were effectively introduced and transported within the UMCD aquifer. This demonstration represents an innovative application of bioaugmentation to potentially enhance RDX biodegradation in aerobic aquifers. PMID:26438043

  14. Evaluation of microbial transport during aerobic bioaugmentation of an RDX-contaminated aquifer.

    PubMed

    Crocker, Fiona H; Indest, Karl J; Jung, Carina M; Hancock, Dawn E; Fuller, Mark E; Hatzinger, Paul B; Vainberg, Simon; Istok, Jonathan D; Wilson, Edward; Michalsen, Mandy M

    2015-11-01

    In situ bioaugmentation with aerobic hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading bacteria is being considered for treatment of explosives-contaminated groundwater at Umatilla Chemical Depot, Oregon (UMCD). Two forced-gradient bacterial transport tests of site groundwater containing chloride or bromide tracer and either a mixed culture of Gordonia sp. KTR9 (xplA (+)Km(R)), Rhodococcus jostii RHA1 (pGKT2 transconjugant; xplA (+)Km(R)) and Pseudomonas fluorescens I-C (xenB (+)), or a single culture of Gordonia sp. KTR9 (xplA (+); i.e. wild-type) were conducted at UMCD. Groundwater monitoring evaluated cell viability and migration in the injection well and downgradient monitoring wells. Enhanced degradation of RDX was not evaluated in these demonstrations. Quantitative PCR analysis of xplA, the kanamycin resistance gene (aph), and xenB indicated that the mixed culture was transported at least 3 m within 2 h of injection. During a subsequent field injection of bioaugmented groundwater, strain KTR9 (wild-type) migrated up to 23-m downgradient of the injection well within 3 days. Thus, the three RDX-degrading strains were effectively introduced and transported within the UMCD aquifer. This demonstration represents an innovative application of bioaugmentation to potentially enhance RDX biodegradation in aerobic aquifers.

  15. Toward a better understanding of the complex geochemical processes governing subsurface contaminant transport

    SciTech Connect

    Puls, R.W.

    1991-07-01

    Identification and understanding of the chemical, physical, and biological processes controlling subsurface contaminant migration is essential for making accurate predictions on the fate and transport of these constituents. Remediation assessment requires these predictions where pollution from municipal and industrial activities has occurred, and for the responsible siting of waste isolation and storage facilities. Geochemical processes include ion-exchange, precipitation, organic partitioning, chemisorption, aqueous complexation, and colloidal stability and transport. Current approaches to quantify the effect of these processes on transport in a ground water system primarily involve laboratory techniques. These include the use of closed static systems (batch experiments) and dynamic systems (column experiments) where a larger segment of the aquifer is investigated by analyzing the breakthrough profiles of reactive and non-reactive species. The latter approach may be more representative of in situ conditions than the former, however, when compared to large-scale field experiments both are still constrained by: differences in scale, alteration of media during sample collection and use, and spatial variability. More field reactivity studies are needed to complement established laboratory approaches for the determination of retardation factors, scaling factors for laboratory versus field data, corroboration or confirmation of batch and column results, and for validation of sampling techniques.

  16. Facilities, breed and experience affect ease of sheep handling: the livestock transporter's perspective.

    PubMed

    Burnard, C L; Pitchford, W S; Hocking Edwards, J E; Hazel, S J

    2015-08-01

    An understanding of the perceived importance of a variety of factors affecting the ease of handling of sheep and the interactions between these factors is valuable in improving profitability and welfare of the livestock. Many factors may contribute to animal behaviour during handling, and traditionally these factors have been assessed in isolation under experimental conditions. A human social component to this phenomenon also exists. The aim of this study was to gain a deeper understanding of the importance of a variety of factors affecting ease of handling, and the interactions between these from the perspective of the livestock transporter. Qualitative interviews were used to investigate the factors affecting sheep behaviour during handling. Interview transcripts underwent thematic analysis. Livestock transporters discussed the effects of attitudes and behaviours towards sheep, helpers, facilities, distractions, environment, dogs and a variety of sheep factors including breed, preparation, experience and sex on sheep behaviour during handling. Transporters demonstrated care and empathy and stated that patience and experience were key factors determining how a person might deal with difficult sheep. Livestock transporters strongly believed facilities (ramps and yards) had the greatest impact, followed by sheep experience (naivety of the sheep to handling and transport) and breed. Transporters also discussed the effects of distractions, time of day, weather, dogs, other people, sheep preparation, body condition and sheep sex on ease of handling. The concept of individual sheep temperament was indirectly expressed.

  17. Facilities, breed and experience affect ease of sheep handling: the livestock transporter's perspective.

    PubMed

    Burnard, C L; Pitchford, W S; Hocking Edwards, J E; Hazel, S J

    2015-08-01

    An understanding of the perceived importance of a variety of factors affecting the ease of handling of sheep and the interactions between these factors is valuable in improving profitability and welfare of the livestock. Many factors may contribute to animal behaviour during handling, and traditionally these factors have been assessed in isolation under experimental conditions. A human social component to this phenomenon also exists. The aim of this study was to gain a deeper understanding of the importance of a variety of factors affecting ease of handling, and the interactions between these from the perspective of the livestock transporter. Qualitative interviews were used to investigate the factors affecting sheep behaviour during handling. Interview transcripts underwent thematic analysis. Livestock transporters discussed the effects of attitudes and behaviours towards sheep, helpers, facilities, distractions, environment, dogs and a variety of sheep factors including breed, preparation, experience and sex on sheep behaviour during handling. Transporters demonstrated care and empathy and stated that patience and experience were key factors determining how a person might deal with difficult sheep. Livestock transporters strongly believed facilities (ramps and yards) had the greatest impact, followed by sheep experience (naivety of the sheep to handling and transport) and breed. Transporters also discussed the effects of distractions, time of day, weather, dogs, other people, sheep preparation, body condition and sheep sex on ease of handling. The concept of individual sheep temperament was indirectly expressed. PMID:25874817

  18. Coupling of hydrologic transport and chemical reactions in a stream affected by acid mine drainage

    USGS Publications Warehouse

    Kimball, B.A.; Broshears, R.E.; Bencala, K.E.; McKnight, Diane M.

    1994-01-01

    Experiments in St. Kevin Gulch, an acid mine drainage stream, examined the coupling of hydrologic transport to chemical reactions affecting metal concentrations. Injection of LiCl as a conservative tracer was used to determine discharge and residence time along a 1497-m reach. Transport of metals downstream from inflows of acidic, metal-rich water was evaluated based on synoptic samples of metal concentrations and the hydrologic characteristics of the stream. Transport of SO4 and Mn was generally conservative, but in the subreaches most affected by acidic inflows, transport was reactive. Both 0.1-??m filtered and particulate Fe were reactive over most of the stream reach. Filtered Al partitioned to the particulate phase in response to high instream concentrations. Simulations that accounted for the removal of SO4, Mn, Fe, and Al with first-order reactions reproduced the steady-state profiles. The calculated rate constants for net removal used in the simulations embody several processes that occur on a stream-reach scale. The comparison between rates of hydrologie transport and chemical reactions indicates that reactions are only important over short distances in the stream near the acidic inflows, where reactions occur on a comparable time scale with hydrologic transport and thus affect metal concentrations.

  19. Modeling and testing of reactive contaminant transport in drinking water pipes: Chlorine response and implications for online contaminant detection

    EPA Science Inventory

    Reactive contaminants introduced to chlorinated drinking water can cause water quality change directly related to their reactivity and other physiochemical properties. This general principle is further developed and utilized in a proposed real-time event adaptive detection, iden...

  20. Understanding contaminant transport to model and quantify bioremediation in the microbial filters project

    SciTech Connect

    Ude, Kristin

    1996-05-01

    The efficacy of in situ bioremediation remains difficult to quantitatively demonstrate. One aim of the microbial filters project is to evaluate the in situ bioremediation of chlorinated ethenes such as trichloroethylene (TCE). To meet this need, a downhole treatability tool was developed to enable us to assess field biodegradation applications. A tracer lab experiment run in a column of the downhole treatability tool combined with tracer data analyzed from a microbial filters field test were used to understand the flow of water through porous media in the lab and in the field. A spreadsheet template was written to evaluate the contaminant transport equations and predict breakthrough curves of the tracer and TCE. The resulting tracer curve correlated well with experimental data and will lay the foundation for experiments performed with bacteria to assess the extent of bioremediation.

  1. Vadose Zone Contaminant Fate and Transport Analysis for the 216-B-26 Trench

    SciTech Connect

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

    2004-10-14

    The BC Cribs and Trenches, part of the 200 TW 1 OU waste sites, received about 30 Mgal of scavenged tank waste, with possibly the largest inventory of 99Tc ever disposed to the soil at Hanford and site remediation is being accelerated. The purpose of this work was to develop a conceptual model for contaminant fate and transport at the 216-B-26 Trench site to support identification and development and evaluation of remediation alternatives. Large concentrations of 99Tc high above the water table implicated stratigraphy in the control of the downward migration. The current conceptual model accounts for small-scale stratigraphy; site-specific changes soil properties; tilted layers; and lateral spreading. It assumes the layers are spatially continuous causing water and solutes to move laterally across the boundary if conditions permit. Water influx at the surface is assumed to be steady. Model parameters were generated with pedotransfer functions; these were coupled high resolution neutron moisture logs that provided information on the underlying heterogeneity on a scale of 3 inches. Two approaches were used to evaluate the impact of remedial options on transport. In the first, a 1-D convolution solution to the convective-dispersive equation was used, assuming steady flow. This model was used to predict future movement of the existing plume using the mean and depth dependent moisture content. In the second approach, the STOMP model was used to first predict the current plume distribution followed by its future migration. Redistribution of the 99Tc plume was simulated for the no-action alternative and on-site capping. Hypothetical caps limiting recharge to 1.0, 0.5, and 0.1 mm yr-1 were considered and assumed not to degrade in the long term. Results show that arrival time of the MCLs, the peak arrival time, and the arrival time of the center of mass increased with decreasing recharge rate. The 1-D convolution model is easy to apply and can easily accommodate initial

  2. Prediction of contaminant retention and transport in soils using kinetic multireaction models.

    PubMed Central

    Selim, H M

    1989-01-01

    Mathematical models that describe the retention reactions of contaminants in the soil system are presented. Single and multireaction-type models for simultaneous retention and transport in the soil profile are discussed. Single retention models are classified into two types: equilibrium and kinetic models. Emphasis is given to the nonlinearity and kinetic behavior of solute retention processes in soils. Two-site models that include the equilibrium-kinetic types as well as the fully kinetic type are also examined. A multireaction-type model is also presented, which includes reversible and irreversible retention processes of the equilibrium and kinetic types. Advantages of the multireaction approach over the single or two-site models are discussed. The predictive capability of the two-site model and the multireaction model for their description of experimental results for phosphorus and two heavy metals (Cd and Cr) are examined. PMID:2695326

  3. Source identification of hydrocarbon contaminants and their transportation over the Zonguldak shelf, Turkish Black Sea

    NASA Astrophysics Data System (ADS)

    Unlu, S.; Alpar, B.

    2009-04-01

    Under great anthropogenic pressure due to the substantial freshwater input from the surrounding industrial and agricultural areas, especially central and middle-Eastern Europe, the Black Sea basin is ranked among the most ecologically threatened water bodies of the world. Oil levels are unacceptable in many coastal areas perilously close to polluted harbors and many river mouths; the places presenting the highest levels of bio-diversity and having a high socio-economic importance due to human use of coastal resources. There are about sixty sources of pollution which resulted in "hot spots" having disastrous impacts on sensitive marine and coastal areas and needing immediate priorities for action. Beyond such land-based sources, trans-boundary pollution sources from Black Sea riparian countries, heavy maritime traffic, particularly involving petroleum transports and fishing boats, and the improper disposal of ballast and bilge waters and solid waste are also important marine sources of pollution. Found in fossil fuels such as Polycyclic Aromatic Hydrocarbons are generated by incomplete combustion of organic matter. In order to estimate their distribution in sediment and their sources, they were monitored from the bottom samples offshore the Zonguldak industry region, one of the most polluted spots in the Turkish Black Sea. There the budget of pollutants via rivers is not precisely known due to an evident lack of data on chemical and granulometric composition of the river runoff and their fluxes. Therefore the marine sediments, essential components of marine ecosystems, are very important in our estimating the degree of the damage given to the ecosystem by such inputs. Realization of the sources and transport of these contaminants will be a critical tool for future management of the Zonguldak industry region and its watershed. The sea bottom in study area is composed of mainly sand and silt mixtures with small amount of clay. Geochemical analyses have shown that oil

  4. Multiple-tracer tests for contaminant transport process identification in saturated municipal solid waste

    SciTech Connect

    Woodman, N.D. Rees-White, T.C.; Stringfellow, A.M.; Beaven, R.P.; Hudson, A.P.

    2015-04-15

    Highlights: • Multiple tracers were applied to saturated MSW to test dual-porosity properties. • Lithium demonstrated to be non-conservative as a tracer. • 260 mm diameter column too small to test transport properties of MSW. • The classical advection-dispersion mode was rejected due to high dispersivity. • Characteristic diffusion times did not vary with the tracer. - Abstract: Two column tests were performed in conditions emulating vertical flow beneath the leachate table in a biologically active landfill to determine dominant transport mechanisms occurring in landfills. An improved understanding of contaminant transport process in wastes is required for developing better predictions about potential length of the long term aftercare of landfills, currently measured in timescales of centuries. Three tracers (lithium, bromide and deuterium) were used. Lithium did not behave conservatively. Given that lithium has been used extensively for tracing in landfill wastes, the tracer itself and the findings of previous tests which assume that it has behaved conservatively may need revisiting. The smaller column test could not be fitted with continuum models, probably because the volume of waste was below a representative elemental volume. Modelling compared advection-dispersion (AD), dual porosity (DP) and hybrid AD–DP models. Of these models, the DP model was found to be the most suitable. Although there is good evidence to suggest that diffusion is an important transport mechanism, the breakthrough curves of the different tracers did not differ from each other as would be predicted based on the free-water diffusion coefficients. This suggested that solute diffusion in wastes requires further study.

  5. The role of colloids in the transport of contaminants at the Rocky Mountain Arsenal, Denver, CO

    SciTech Connect

    Honeyman, B.D.; Mackay, D.M.

    1993-12-31

    A forced-gradient, pilot-study of ground contaminant transport in an existing plume was conducted at the Rocky Mountain Arsenal in November 1991. Plume contaminants included halogenated VOCs, aromatic hydrocarbons, organchlorine pesticides and other more polar organic compounds. The pilot system consisted of an injection well screened over the entire saturated zone, an extraction well located 30 feet away and granulated activated carbon canisters for the treatment of extracted water. Treated water was spiked with bromide prior to reinjection. A series of observation wells was established between the injection and extraction wells. Organic analysis of extracted colloidal material (10K daltons - 0.1{mu}m) showed the colloids to be with substantional amounts of a number of the target analytes including atrazine (100{mu}g/g colloids), dde (3200{mu}g/g) and DDT (400{mu}g/g). In addition, colloidal material was found to be mobile, although slightly retarded (R{sub f} = 1.5 - 2.0) relativeomide tracer.

  6. The effects of a perturbed source on contaminant transport near the Weldon Spring quarry

    SciTech Connect

    Tomasko, D.

    1989-03-01

    The effects of a perturbed contamination source at the Weldon Spring quarry in St. Charles County, Missouri, on downstream solute concentrations were investigated using one-dimensional analytical solutions to an advection-dispersion equation developed for both constant-strength and multiple-stepped source functions. A sensitivity study using parameter base-case values and ranges consistent with the geologic conceptualization of the quarry area indicates that the parameters having the greatest effect on predicted concentrations are the distance from the quarry to the point of interest, the average linear groundwater velocity, the contaminant retardation coefficient, and the amplitude and duration of the source perturbation caused by response action activities. Use of base-case parameter value and realistic values for the amplitude and duration of the source perturbation produced a small effect on solute concentrations near the western extremity of the nearby municipal well field, as well as small uncertainties in the predicted results for the assumed model. The effect of simplifying assumptions made in deriving the analytic solution is unknown: use of a multidimensional flow and transport model and additional field work are needed to validate the model. 13 refs., 18 figs.

  7. Mass transfer model of nanoparticle-facilitated contaminant transport in saturated porous media.

    PubMed

    Johari, Wan Lutfi Wan; Diamessis, Peter J; Lion, Leonard W

    2010-02-01

    A one-dimensional model has been evaluated for transport of hydrophobic contaminants, such as polycyclic aromatic hydrocarbon (PAH) compounds, facilitated by synthetic amphiphilic polyurethane (APU) nanoparticles in porous media. APU particles synthesized from poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains have been shown to enhance the desorption rate and mobility of phenanthrene (PHEN) in soil. A reversible process governed by attachment and detachment rates was considered to describe the PMUA binding in soil in addition to PMUA transport through advection and dispersion. Ultimately, an irreversible second-order PMUA attachment rate in which the fractional soil saturation capacity with PMUA was a rate control was found to be adequate to describe the retention of PMUA particles. A gamma-distributed site model (GS) was used to describe the spectrum of physical/chemical constraints for PHEN transfer from solid to aqueous phases. Instantaneous equilibrium was assumed for PMUA-PHEN interactions. The coupled model for PMUA and PHEN behavior successfully described the enhanced elution profile of PHEN by PMUA. Sensitivity analysis was performed to analyze the significance of model parameters on model predictions. The adjustable parameter alpha in the gamma-distribution shapes the contaminant desorption distribution profile as well as elution and breakthrough curves. Model simulations show the use of PMUA can be also expected to improve the release rate of PHEN in soils with higher organic carbon content. The percentage removal of PHEN mass over time is shown to be influenced by the concentration of PMUA added and this information can be used to optimize cost and time require to accomplish a desired remediation goal. PMID:19406449

  8. Mass transfer model of nanoparticle-facilitated contaminant transport in saturated porous media.

    PubMed

    Johari, Wan Lutfi Wan; Diamessis, Peter J; Lion, Leonard W

    2010-02-01

    A one-dimensional model has been evaluated for transport of hydrophobic contaminants, such as polycyclic aromatic hydrocarbon (PAH) compounds, facilitated by synthetic amphiphilic polyurethane (APU) nanoparticles in porous media. APU particles synthesized from poly(ethylene glycol)-modified urethane acrylate (PMUA) precursor chains have been shown to enhance the desorption rate and mobility of phenanthrene (PHEN) in soil. A reversible process governed by attachment and detachment rates was considered to describe the PMUA binding in soil in addition to PMUA transport through advection and dispersion. Ultimately, an irreversible second-order PMUA attachment rate in which the fractional soil saturation capacity with PMUA was a rate control was found to be adequate to describe the retention of PMUA particles. A gamma-distributed site model (GS) was used to describe the spectrum of physical/chemical constraints for PHEN transfer from solid to aqueous phases. Instantaneous equilibrium was assumed for PMUA-PHEN interactions. The coupled model for PMUA and PHEN behavior successfully described the enhanced elution profile of PHEN by PMUA. Sensitivity analysis was performed to analyze the significance of model parameters on model predictions. The adjustable parameter alpha in the gamma-distribution shapes the contaminant desorption distribution profile as well as elution and breakthrough curves. Model simulations show the use of PMUA can be also expected to improve the release rate of PHEN in soils with higher organic carbon content. The percentage removal of PHEN mass over time is shown to be influenced by the concentration of PMUA added and this information can be used to optimize cost and time require to accomplish a desired remediation goal.

  9. Equivalent Porous Media (EPM) Simulation of Groundwater Hydraulics and Contaminant Transport in Karst Aquifers

    PubMed Central

    Ghasemizadeh, Reza; Yu, Xue; Butscher, Christoph; Hellweger, Ferdi; Padilla, Ingrid; Alshawabkeh, Akram

    2015-01-01

    Karst aquifers have a high degree of heterogeneity and anisotropy in their geologic and hydrogeologic properties which makes predicting their behavior difficult. This paper evaluates the application of the Equivalent Porous Media (EPM) approach to simulate groundwater hydraulics and contaminant transport in karst aquifers using an example from the North Coast limestone aquifer system in Puerto Rico. The goal is to evaluate if the EPM approach, which approximates the karst features with a conceptualized, equivalent continuous medium, is feasible for an actual project, based on available data and the study scale and purpose. Existing National Oceanic Atmospheric Administration (NOAA) data and previous hydrogeological U. S. Geological Survey (USGS) studies were used to define the model input parameters. Hydraulic conductivity and specific yield were estimated using measured groundwater heads over the study area and further calibrated against continuous water level data of three USGS observation wells. The water-table fluctuation results indicate that the model can practically reflect the steady-state groundwater hydraulics (normalized RMSE of 12.4%) and long-term variability (normalized RMSE of 3.0%) at regional and intermediate scales and can be applied to predict future water table behavior under different hydrogeological conditions. The application of the EPM approach to simulate transport is limited because it does not directly consider possible irregular conduit flow pathways. However, the results from the present study suggest that the EPM approach is capable to reproduce the spreading of a TCE plume at intermediate scales with sufficient accuracy (normalized RMSE of 8.45%) for groundwater resources management and the planning of contamination mitigation strategies. PMID:26422202

  10. Equivalent Porous Media (EPM) Simulation of Groundwater Hydraulics and Contaminant Transport in Karst Aquifers.

    PubMed

    Ghasemizadeh, Reza; Yu, Xue; Butscher, Christoph; Hellweger, Ferdi; Padilla, Ingrid; Alshawabkeh, Akram

    2015-01-01

    Karst aquifers have a high degree of heterogeneity and anisotropy in their geologic and hydrogeologic properties which makes predicting their behavior difficult. This paper evaluates the application of the Equivalent Porous Media (EPM) approach to simulate groundwater hydraulics and contaminant transport in karst aquifers using an example from the North Coast limestone aquifer system in Puerto Rico. The goal is to evaluate if the EPM approach, which approximates the karst features with a conceptualized, equivalent continuous medium, is feasible for an actual project, based on available data and the study scale and purpose. Existing National Oceanic Atmospheric Administration (NOAA) data and previous hydrogeological U. S. Geological Survey (USGS) studies were used to define the model input parameters. Hydraulic conductivity and specific yield were estimated using measured groundwater heads over the study area and further calibrated against continuous water level data of three USGS observation wells. The water-table fluctuation results indicate that the model can practically reflect the steady-state groundwater hydraulics (normalized RMSE of 12.4%) and long-term variability (normalized RMSE of 3.0%) at regional and intermediate scales and can be applied to predict future water table behavior under different hydrogeological conditions. The application of the EPM approach to simulate transport is limited because it does not directly consider possible irregular conduit flow pathways. However, the results from the present study suggest that the EPM approach is capable to reproduce the spreading of a TCE plume at intermediate scales with sufficient accuracy (normalized RMSE of 8.45%) for groundwater resources management and the planning of contamination mitigation strategies.

  11. Growth rate and nutrient limitation affect the transport of Rhodococcus sp. strain DN22 through sand.

    PubMed

    Priestley, James T; Coleman, Nicholas V; Duxbury, Trevor

    2006-12-01

    Rhodococcus strain DN22 grows on the nitramine explosive RDX as a sole nitrogen source, and is potentially useful for bioremediation of explosives-contaminated soil. In order for strain DN22 to be effectively applied in situ, inoculum cells must reach zones of RDX contamination via passive transport, a process that is difficult to predict at field-scale. We examined the effect of growth conditions on the transport of DN22 cells through sand columns, using chemostat-grown cultures. Strain DN22 formed smaller coccoid cells at low dilution rate (0.02 h(-1)) and larger rods at high dilution rate (0.1 h(-1)). Under all nutrient limitation conditions studied, smaller cells grown at low dilution rate were retained more strongly by sand columns than larger cells grown at high dilution rate. At a dilution rate of 0.05, cells from nitrate-limited cultures were retained more strongly than cells from RDX-limited or succinate-limited cultures. Breakthrough concentrations (C/C (0)) from sand columns ranged from 0.04 (nitrate-limited, D=0.02 h(-1)) to 0.98 (succinate-limited, D=0.1 h(-1)). The observed strong effect of culture conditions on transport of DN22 cells emphasizes the importance of physiology studies in guiding the development of bioremediation technologies.

  12. Characterization of Anomalous Contaminant Transport via Push-Pull Tracer Tests

    NASA Astrophysics Data System (ADS)

    Hansen, S. K.; Vesselinov, V. V.; Berkowitz, B.

    2015-12-01

    Push-pull (single-well-injection-withdrawal) tracer tests are widely used as an economical means of characterizing field-scale solute transport properties such as sorption and dispersion. Typically, these are analyzed by means of analytic solutions that assume transport obeys the radial advection-dispersion equation. We revisit this approach as: (1) Recognition of the ubiquity of anomalous transport and its impact on contaminant remediation necessitates the use of new methods to characterize it, and (2) Improved computational power and numerical methods have rendered reliance on analytical solutions obsolete. Here, we present a technique for characterizing diffusion-driven anomalous transport (i.e., anomalous transport driven by a "trapping" process whose trapping and release statistics are independent of the groundwater flow velocity). Examples include diffusion into low permeability zones, kinetic sorption, and matrix diffusion. Using field observations, we simultaneously calibrate an exponential probability distribution for time spent on a single sojourn in the mobile domain and a truncated power law probability distribution for time spent on a single sojourn in the immobile domain via a stochastic global optimization technique. The calibrated distributions, being independent of the flow regime, are applicable to the same domain under any flow conditions, including linear flow. In the context of the continuous time random walk (CTRW), one may simply define a transition to represent a single trap-and-release cycle, and directly compute the spatiotemporal transition distribution that defines the CTRW from the two calibrated distributions and the local seepage velocity (so that existing CTRW transport theory applies). A test of our methodology against a push-pull test from the MADE site demonstrated fitting performance comparable to that of a 3-D MODFLOW/MT3DMS model with a variety of hydraulic conductivity zones and explicit treatment of mobile-immobile mass

  13. Modeling contaminant transport in a three-phase groundwater system with the Freundlich-type retardation factor.

    PubMed

    Kim, M; Kim, S B

    2007-02-01

    Colloid-facilitated contaminant transport was simulated in this study for the three-phase groundwater system where one or more sorption processes can be described with nonlinear sorption isotherm (Freundlich isotherm). A concise form of contaminant transport equation was derived from the mass balance equation of the contaminant. The developed model was numerically solved by the finite difference method along with the Picard iteration. The simulation results were used to quantitatively analyze the previously reported column data showing nonlinear sorption behavior. The analysis led to the following observations: (i) increases of the distribution coefficient of contaminant between the aqueous and solid phases (K(S)c) and the one between the dissolved natural organic matters and solid phase ( K(S)OM) generate less facilitation (i.e., late arrival of contaminant breakthrough curves (BTCs), and the distribution coefficient of contaminant between the aqueous and the solid phases (K(OM)c) gives the opposite result; (ii) the increase of the Freundlich constant for the sorption isotherm between the aqueous and the solid phases (N(S)c) yields the late arrival of BTC, and the other two Freundlich constants produce the opposite results; (iii) the Freundlich constants generally yield a sharper front as the BTC arrives at later pore volumes, while the distribution coefficients generally yield a more spread of the BTC as it arrives at later volumes. This modeling study shows that transport modeling provides a more efficient analyzing tool than the retardation factor alone concerning the colloid-facilitated contaminant transport with nonlinear sorption processes.

  14. Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

    NASA Astrophysics Data System (ADS)

    Frohne, T.; Rinklebe, J.; Langer, U.; Du Laing, G.; Mothes, S.; Wennrich, R.

    2012-01-01

    An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg Hg kg-1 and >30 mg Hg kg-1). The experiment was conducted under stepwise variation from reducing (approximately -350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0, cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (ln(DOC/Hgt) ratio) (R2 = 0.39, p<0.0001, n= 63) whereas the relation between ln(MeHg/Hgt ratio and lnDOC is weaker (R2 = 0.09; p<0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas EH and pH values, as well as concentration of dissolved Fe3+/Fe2+ and Cl- seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

  15. Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils

    NASA Astrophysics Data System (ADS)

    Frohne, T.; Rinklebe, J.; Langer, U.; Du Laing, G.; Mothes, S.; Wennrich, R.

    2011-09-01

    An automated biogeochemical microcosm system allowing controlled variation of redox potential (EH) in soil suspensions was used to assess the effect of various factors on the mobility of mercury (Hg) as well as on the methylation of Hg in two contaminated floodplain soils with different Hg concentrations (approximately 5 mg kg-1 Hg and >30 mg kg-1 Hg). The experiment was conducted under stepwise variation from reducing (approximately -350 mV at pH 5) to oxidizing conditions (approximately 600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10me16:0, cy17:0, 10me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered to promote Hg methylation. The products of the methylation process are lipophilic, highly toxic methyl mercury species such as the monomethyl mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt) ratio is assumed to reflect the net production of monomethyl mercury normalized to total dissolved Hg (Hgt) concentration. This ratio increases with rising dissolved organic carbon (DOC) to Hgt ratio (lnDOC/lnHgt ratio) (R2 = 0.39, p < 0.0001, n = 63) whereas the relation between ln(MeHg/Hgt) ratio and lnDOC is weaker (R2 = 0.09; p < 0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a more important factor for the Hg net methylation than DOC alone in the current study. Redox variations seem to affect the biogeochemical behavior of dissolved inorganic Hg species and MeHg indirectly through related changes in DOC, sulfur cycle, and microbial community structure whereas E,H and pH values, as well as concentration of dissolved Fe,3+/Fe2+ and Cl- seem to play subordinate roles in Hg mobilization and methylation under our experimental conditions.

  16. Sediment storage and severity of contamination in a shallow reservoir affected by historical lead and zinc mining

    USGS Publications Warehouse

    Juracek, K.E.

    2008-01-01

    A combination of sediment-thickness measurement and bottom-sediment coring was used to investigate sediment storage and severity of contamination in Empire Lake (Kansas), a shallow reservoir affected by historical Pb and Zn mining. Cd, Pb, and Zn concentrations in the contaminated bottom sediment typically exceeded baseline concentrations by at least an order of magnitude. Moreover, the concentrations of Cd, Pb, and Zn typically far exceeded probable-effects guidelines, which represent the concentrations above which toxic biological effects usually or frequently occur. Despite a pre-1954 decrease in sediment concentrations likely related to the end of major mining activity upstream by about 1920, concentrations have remained relatively stable and persistently greater than the probable-effects guidelines for at least the last 50 years. Cesium-137 evidence from sediment cores indicated that most of the bottom sediment in the reservoir was deposited prior to 1954. Thus, the ability of the reservoir to store the contaminated sediment has declined over time. Because of the limited storage capacity, Empire Lake likely is a net source of contaminated sediment during high-inflow periods. The contaminated sediment that passes through, or originates from, Empire Lake will be deposited in downstream environments likely as far as Grand Lake O' the Cherokees (Oklahoma). ?? 2007 Springer-Verlag.

  17. Contaminant transport in soil with depth-dependent reaction coefficients and time-dependent boundary conditions.

    PubMed

    Gao, Guangyao; Fu, Bojie; Zhan, Hongbin; Ma, Ying

    2013-05-01

    Predicting the fate and movement of contaminant in soils and groundwater is essential to assess and reduce the risk of soil contamination and groundwater pollution. Reaction processes of contaminant often decreased monotonously with depth. Time-dependent input sources usually occurred at the inlet of natural or human-made system such as radioactive waste disposal site. This study presented a one-dimensional convection-dispersion equation (CDE) for contaminant transport in soils with depth-dependent reaction coefficients and time-dependent inlet boundary conditions, and derived its analytical solution. The adsorption coefficient and degradation rate were represented as sigmoidal functions of soil depth. Solute breakthrough curves (BTCs) and concentration profiles obtained from CDE with depth-dependent and constant reaction coefficients were compared, and a constant effective reaction coefficient, which was calculated by arithmetically averaging the depth-dependent reaction coefficient, was proposed to reflect the lumped depth-dependent reaction effect. With the effective adsorption coefficient and degradation rate, CDE could produce similar BTCs and concentration profiles as those from CDE with depth-dependent reactions in soils with moderate chemical heterogeneity. In contrast, the predicted concentrations of CDE with fitted reaction coefficients at a certain depth departed significantly from those of CDE with depth-dependent reactions. Parametric analysis was performed to illustrate the effects of sinusoidally and exponentially decaying input functions on solute BTCs. The BTCs and concentration profiles obtained from the solutions for finite and semi-infinite domain were compared to investigate the effects of effluent boundary condition. The finite solution produced higher concentrations at the increasing limb of the BTCs and possessed a higher peak concentration than the semi-infinite solution which had a slightly long tail. Furthermore, the finite solution gave

  18. Contaminant transport in soil with depth-dependent reaction coefficients and time-dependent boundary conditions.

    PubMed

    Gao, Guangyao; Fu, Bojie; Zhan, Hongbin; Ma, Ying

    2013-05-01

    Predicting the fate and movement of contaminant in soils and groundwater is essential to assess and reduce the risk of soil contamination and groundwater pollution. Reaction processes of contaminant often decreased monotonously with depth. Time-dependent input sources usually occurred at the inlet of natural or human-made system such as radioactive waste disposal site. This study presented a one-dimensional convection-dispersion equation (CDE) for contaminant transport in soils with depth-dependent reaction coefficients and time-dependent inlet boundary conditions, and derived its analytical solution. The adsorption coefficient and degradation rate were represented as sigmoidal functions of soil depth. Solute breakthrough curves (BTCs) and concentration profiles obtained from CDE with depth-dependent and constant reaction coefficients were compared, and a constant effective reaction coefficient, which was calculated by arithmetically averaging the depth-dependent reaction coefficient, was proposed to reflect the lumped depth-dependent reaction effect. With the effective adsorption coefficient and degradation rate, CDE could produce similar BTCs and concentration profiles as those from CDE with depth-dependent reactions in soils with moderate chemical heterogeneity. In contrast, the predicted concentrations of CDE with fitted reaction coefficients at a certain depth departed significantly from those of CDE with depth-dependent reactions. Parametric analysis was performed to illustrate the effects of sinusoidally and exponentially decaying input functions on solute BTCs. The BTCs and concentration profiles obtained from the solutions for finite and semi-infinite domain were compared to investigate the effects of effluent boundary condition. The finite solution produced higher concentrations at the increasing limb of the BTCs and possessed a higher peak concentration than the semi-infinite solution which had a slightly long tail. Furthermore, the finite solution gave

  19. Oocyte aging-induced Neuronatin (NNAT) hypermethylation affects oocyte quality by impairing glucose transport in porcine

    PubMed Central

    Gao, Ying-Ying; Chen, Li; Wang, Tao; Nie, Zheng-Wen; Zhang, Xia; Miao, Yi-Liang

    2016-01-01

    DNA methylation plays important roles in regulating many physiological behaviors; however, few studies were focused on the changes of DNA methylation during oocyte aging. Early studies showed that some imprinted genes’ DNA methylation had been changed in aged mouse oocytes. In this study, we used porcine oocytes to test the hypothesis that oocyte aging would alter DNA methylation pattern of genes and disturb their expression in age oocytes, which affected the developmental potential of oocytes. We compared several different types of genes and found that the expression and DNA methylation of Neuronatin (NNAT) were disturbed in aged oocytes significantly. Additional experiments demonstrated that glucose transport was impaired in aged oocytes and injection of NNAT antibody into fresh oocytes led to the same effects on glucose transport. These results suggest that the expression of NNAT was declined by elevating DNA methylation, which affected oocyte quality by decreasing the ability of glucose transport in aged oocytes. PMID:27782163

  20. Geologic, hydrologic, and geochemical interpretations of mineral deposits as analogs for understanding transport of environmental contaminants

    USGS Publications Warehouse

    Wanty, R.B.; Berger, B.R.

    2006-01-01

    Base- and precious-metal mineral deposits comprise anomalous concentrations of metals and associated elements, which may be useful subjects for study as analogs for migration of environmental contaminants. In the geologic past, hydrothermal mineral deposits formed at the intersection of favorable geologic, hydrologic and geochemical gradients. In the present, weathering of these sulfide-rich deposits occurs as a result of the interplay between rates of oxygen supply versus rates of ground or surface-water flow. Transport and spatial dispersion of elements from a mineral deposit occurs as a function of competing rates of water flow versus rates of attenuation mechanisms such as adsorption, dilution, or (co)precipitation. In this paper we present several case studies from mineralized and altered sedimentary and crystalline aquifers in the western United States to illustrate the geologic control of ground-water flow and solute transport, and to demonstrate how this combined approach leads to a more complete understanding of the systems under study as well as facilitating some capability to predict major flow directions in aquifers.

  1. Transport of Organic Contaminants Mobilized from Coal through Sandstone Overlying a Geological Carbon Sequestration Reservoir

    SciTech Connect

    Zhong, Lirong; Cantrell, Kirk J.; Bacon, Diana H.; Shewell, Jesse L.

    2014-02-01

    Column experiments were conducted using a wetted sandstone rock installed in a tri-axial core holder to study the flow and transport of organic compounds mobilized by scCO2 under simulated geologic carbon storage (GCS) conditions. The sandstone rock was collected from a formation overlying a deep saline reservoir at a GCS demonstration site. Rock core effluent pressures were set at 0, 500, or 1000 psig and the core temperature was set at 20 or 50°C to simulate the transport to different subsurface depths. The concentrations of the organic compounds in the column effluent and their distribution within the sandstone core were monitored. Results indicate that the mobility though the core sample was much higher for BTEX compounds than for naphthalene. Retention of organic compounds from the vapor phase to the core appeared to be primarily controlled by partitioning from the vapor phase to the aqueous phase. Adsorption to the surfaces of the wetted sandstone was also significant for naphthalene. Reduced temperature and elevated pressure resulted in greater partitioning of the mobilized organic contaminants into the water phase.

  2. Integration of field measurements and reactive transport modelling to evaluate contaminant transport at a sulfide mine tailings impoundment

    NASA Astrophysics Data System (ADS)

    Brookfield, A. E.; Blowes, D. W.; Mayer, K. U.

    2006-11-01

    Over a decade of field observations including geochemical, mineralogical and hydrological information are available on the generation of acid mine drainage from the Pistol Dam region of the P-area of Inco's tailings impoundment in Copper Cliff, Ontario. This work focuses on the integration and quantitative assessment of this data set using reactive transport modeling. The results of the reactive transport simulations are in general agreement with the field observations; however, exact agreement between the field and simulated results was not the objective of this study, and was not attained. Many factors contribute to the discrepancies between the field observations and simulation results including geochemical and hydrogeological complexities and necessary model simplifications. For example, fluctuating water levels observed at the site were averaged and described using a steady state flow system. In addition, the lack of representative thermodynamic and rate expression data contributed to the discrepancies between observations and simulation results, thus further research into the applicability of laboratory-derived thermodynamic and rate expression data to field conditions could minimize these discrepancies. Despite the discrepancies between the field observations and simulated results, integrating field observations with numerical modelling of the P-area tailings impoundment allowed for a more complete understanding of what affects the complex geochemical reactions.

  3. Integration of field measurements and reactive transport modelling to evaluate contaminant transport at a sulfide mine tailings impoundment.

    PubMed

    Brookfield, A E; Blowes, D W; Mayer, K U

    2006-11-20

    Over a decade of field observations including geochemical, mineralogical and hydrological information are available on the generation of acid mine drainage from the Pistol Dam region of the P-area of Inco's tailings impoundment in Copper Cliff, Ontario. This work focuses on the integration and quantitative assessment of this data set using reactive transport modeling. The results of the reactive transport simulations are in general agreement with the field observations; however, exact agreement between the field and simulated results was not the objective of this study, and was not attained. Many factors contribute to the discrepancies between the field observations and simulation results including geochemical and hydrogeological complexities and necessary model simplifications. For example, fluctuating water levels observed at the site were averaged and described using a steady state flow system. In addition, the lack of representative thermodynamic and rate expression data contributed to the discrepancies between observations and simulation results, thus further research into the applicability of laboratory-derived thermodynamic and rate expression data to field conditions could minimize these discrepancies. Despite the discrepancies between the field observations and simulated results, integrating field observations with numerical modelling of the P-area tailings impoundment allowed for a more complete understanding of what affects the complex geochemical reactions. PMID:16844261

  4. Importance and Use of Plants in Evaluating Water Flow and Contaminant Transport in Arid Environments

    NASA Astrophysics Data System (ADS)

    Andraski, B. J.; Sandstrom, M. W.; Michel, R. L.; Radyk, J. C.; Stonestrom, D. A.; Johnson, M. J.; Mayers, C. J.

    2002-12-01

    Improved understanding of soil-plant-atmosphere interactions is critical to water-resource and waste management decisions. Multiple-year field studies of soil-water movement at the Amargosa Desert Research Site (ADRS; http://nevada.usgs.gov/adrs/) near Beatty, Nevada identified plants as the primary control on the near-surface water balance and showed that the boundary conditions imposed by plant activity in the uppermost soil layer results in episodic, deep drying well below the root zone during periods of below-average precipitation. The results help to explain the evidence for negligible recharge and upward flow that has been inferred from environmental-tracer and soil-physics based studies of undisturbed, arid sites. The findings have contributed to the development of new conceptual models that incorporate the influence of desert vegetation in analyses of paleo- to present-day water fluxes in deep unsaturated zones. Studies at the ADRS are also using plants to investigate the transport of contaminants away from a closed low-level radioactive waste disposal area. Soil-gas sampling results indicated that tritium has moved as much as 300 m from the disposal area, and that transport primarily occurs in the gas phase with preferential transport through coarse-textured sediment layers. The need for an efficient means of gathering plume-scale data led to the development of a method that uses plant water to identify the presence and distribution of tritium. The method entails field sampling and solar distillation of foliage to collect plant water, followed by laboratory filtration and adsorption of scintillation-interfering constituents on a graphite-based, solid-phase-extraction (SPE) column. The method was evaluated using an evergreen shrub (creosote bush; Larrea tridentata (DC.) Cov.). Tritium concentrations in plant water determined with the distillation-SPE method did not differ significantly from those determined with the standard (and more laborious) toluene

  5. A mixture of environmental organic contaminants in lake sediments affects hatching from Daphnia resting eggs.

    PubMed

    Möst, Markus; Chiaia-Hernandez, Aurea C; Frey, Martin P; Hollender, Juliane; Spaak, Piet

    2015-02-01

    Despite the relevance of resting eggs for ecology and evolution of many aquatic organisms and their exposure to contaminants accumulating in sediments, ecotoxicological studies using resting eggs are vastly underrepresented. The authors established a method to perform exposure assays with resting eggs produced by the Daphnia longispina species complex, key species in large lake ecosystems. A mixture of organic contaminants previously detected in sediments of Lake Greifensee was selected to test the potential effect of organic contaminants present in sediments on the hatching process. Resting eggs were exposed to a mix of 10 chemicals, which included corrosion inhibitors, biocides, pesticides, and personal care products, for a period of 15 d. Using an automated counting software, the authors found a significant increase in hatching success in the exposed resting eggs compared with controls. Such an effect has not yet been reported from ecotoxicological assays with resting eggs. Possible mechanistic explanations as well as the potential implications on the ecology and evolution of aquatic species that rely on a resting egg banks are discussed. Observed increased mortality and developmental abnormalities for hatchlings in the exposure treatments can be explained by toxic contaminant concentrations. The results of the present study highlight the need for additional studies assessing the effects of organic contaminants on resting egg banks and aquatic ecosystems.

  6. Connexin-deficiency affects expression levels of glial glutamate transporters within the cerebrum.

    PubMed

    Unger, Tina; Bette, Stefanie; Zhang, Jiong; Theis, Martin; Engele, Jürgen

    2012-01-01

    The glial glutamate transporter subtypes, GLT-1/EAAT-2 and GLAST/EAAT-1 clear the bulk of extracellular glutamate and are severely dysregulated in various acute and chronic brain diseases. Despite the previous identification of several extracellular factors modulating glial glutamate transporter expression, our knowledge of the regulatory network controlling glial glutamate transport in health and disease still remains incomplete. In studies with cultured cortical astrocytes, we previously obtained evidence that glial glutamate transporter expression is also affected by gap junctions/connexins. To assess whether gap junctions would likewise control the in vivo expression of glial glutamate transporters, we have now assessed their expression levels in brains of conditional Cx43 knockout mice, total Cx30 knockouts, as well as Cx43/Cx30 double knockouts. We found that either knocking out Cx30, Cx43, or both increases GLT-1/EAAT-2 protein levels in the cerebral cortex to a similar extent. By contrast, GLAST/EAAT-1 protein levels maximally increased in cerebral cortices of Cx30/Cx43 double knockouts, implying that gap junctions differentially affect the expression of GLT-1/EAAT-2 and GLAST/EAAT-1. Quantitative PCR analysis further revealed that increases in glial glutamate transporter expression are brought about by transcriptional and translational/posttranslational processes. Moreover, GLT-1/EAAT-2- and GLAST/EAAT-1 protein levels remained unchanged in the hippocampi of Cx43/Cx30 double knockouts when compared to Cx43fl/fl controls, indicating brain region-specific effects of gap junctions on glial glutamate transport. Since astrocytic gap junction coupling is affected in various forms of brain injuries, our findings point to gap junctions/connexins as important regulators of glial glutamate turnover in the diseased cerebral cortex.

  7. DIRECT COMPARISON OF KINETIC AND LOCAL EQUILIBRIUM FORMULATIONS FOR SOLUTE TRANSPORT AFFECTED BY SURFACE REACTIONS.

    USGS Publications Warehouse

    Bahr, Jean M.; Rubin, Jacob

    1987-01-01

    Modeling transport of reacting solutes in porous media often requires a choice between models based on the local equilibrium assumption (LEA) and models involving reaction kinetics. Direct comparison of the mathematical formulations for these two types of transport models can aid in this choice. For cases of transport affected by surface reaction, such a comparison is made possible by a new derivation procedure. This procedure yields a kinetics-based formulation that is the sum of the LEA formulation and one or more kinetically influenced terms. The dimensionless form of the new kinetics-based formulation facilitates identification of critical parameter groupings which control the approach to transport behavior consistent with LEA model predictions. Results of numerical experiments demonstrate that criteria for LEA applicability can be expressed conveniently in terms of these parameter groupings. The derivation procedure is demonstrated for examples of surface reactions including first-order reversible sorption, Langmuir-type kinetics and binary, homovalent ion exchange.

  8. Implications for Ecosystem Services of Watershed Processes that affect the Transport and Transformations of Mercury in an Adirondack Stream Basin

    NASA Astrophysics Data System (ADS)

    Burns, D. A.; Riva-Murray, K.; Bradley, P. M.

    2012-12-01

    Mercury (Hg) is a potent neurotoxin that can affect the health of humans and wildlife through the ingestion of methyl Hg. Mercury contamination of ecosystems originates from human activities such as mining, coal burning and other industrial emissions, and the use of Hg-containing products. Natural sources such as volcanic and geothermal emissions and the weathering of Hg-bearing minerals also contribute to Hg contamination, but are believed to be minor sources in most ecosystems. Various ecosystem disturbances including fires, forest harvesting, and the submergence of land by impoundment may also contribute to Hg ecosystem contamination by mobilizing stores that have previously originated from the sources described above. Mercury from a mix of regional and global emissions sources is transported in the atmosphere to remote landscapes that are distant from local emissions sources. The Adirondacks of New York State is a forested, mountainous region characterized by abundant lakes and streams, and is distant from local emissions sources. Recreational fishing, wildlife viewing, hiking, and hunting are valued ecosystem services in this region. Here, we report on the relevance to ecosystem services of findings based on five years of Hg data collection of stream water, groundwater, invertebrates, and fish in the upper Hudson River basin in the central part of the Adirondack region. The New York State Dept. of Health has issued fish consumption advisories for the entire Adirondacks based on elevated levels previously measured in lakes and rivers of this region. Our work seeks improved understanding and models of the landscape sources and watershed processes that control the transformation of Hg to its methyl form (MeHg), the transport of MeHg to streams, and bioaccumulation of MeHg in aquatic food webs. Mean annual atmospheric Hg deposition was 6.3 μg/m2/yr during 2007-09, compared to mean annual filtered total Hg stream yields of 1.66 μg/m2/yr and filtered MeHg stream

  9. Mutations in the white gene of Drosophila melanogaster affecting ABC transporters that determine eye colouration.

    PubMed

    Mackenzie, S M; Brooker, M R; Gill, T R; Cox, G B; Howells, A J; Ewart, G D

    1999-07-15

    The white, brown and scarlet genes of Drosophila melanogaster encode proteins which transport guanine or tryptophan (precursors of the red and brown eye colour pigments) and belong to the ABC transporter superfamily. Current models envisage that the white and brown gene products interact to form a guanine specific transporter, while white and scarlet gene products interact to form a tryptophan transporter. In this study, we report the nucleotide sequence of the coding regions of five white alleles isolated from flies with partially pigmented eyes. In all cases, single amino acid changes were identified, highlighting residues with roles in structure and/or function of the transporters. Mutations in w(cf) (G589E) and w(sat) (F590G) occur at the extracellular end of predicted transmembrane helix 5 and correlate with a major decrease in red pigments in the eyes, while brown pigments are near wild-type levels. Therefore, those residues have a more significant role in the guanine transporter than the tryptophan transporter. Mutations identified in w(crr) (H298N) and w(101) (G243S) affect amino acids which are highly conserved among the ABC transporter superfamily within the nucleotide binding domain. Both cause substantial and similar decreases of red and brown pigments indicating that both tryptophan and guanine transport are impaired. The mutation identified in w(Et87) alters an amino acid within an intracellular loop between transmembrane helices 2 and 3 of the predicted structure. Red and brown pigments are reduced to very low levels by this mutation indicating this loop region is important for the function of both guanine and tryptophan transporters. PMID:10407069

  10. Groundwater contamination: identification of source signal by time-reverse mass transport computation and filtering

    NASA Astrophysics Data System (ADS)

    Koussis, A. S.; Mazi, K.; Lykoudis, S.; Argyriou, A.

    2003-04-01

    Source signal identification is a forensic task, within regulatory and legal activities. Estimation of the contaminant's release history by reverse-solution (stepping back in time) of the mass transport equation, partialC/partialt + u partialC/partialx = D partial^2C/ partialx^2, is an ill-posed problem (its solution is non-unique and unstable). For this reason we propose the recovery of the source signal from measured concentration profile data through a numerical technique that is based on the premise of advection-dominated transport. We derive an explicit numerical scheme by discretising the pure advection equation, partialC/ partialt + u partial C/partialx = 0, such that it also models gradient-transport by matching numerical diffusion (leading truncation error term) to physical dispersion. The match is achieved by appropriate choice of the scheme’s spatial weighting coefficient q as function of the grid Peclet number P = u Δx/D: θ = 0.5 - P-1. This is a novel and efficient direct solution approach for the signal identification problem at hand that can accommodate space-variable transport parameters as well. First, we perform numerical experiments to define proper grids (in terms of Courant {bf C} = uΔt/Δx and grid Peclet P numbers) for control of spurious oscillations (instability). We then assess recovery of source signals, from perfect as well as from error-seeded field data, considering field data resulting from single- and double-peaked source signals. With perfect data, the scheme recovers source signals with very good accuracy. With imperfect data, however, additional data conditioning is required for control of signal noise. Alternating reverse profile computation with Savitzky-Golay low-pass filtering allows the recovery of well-timed and smooth source signals that satisfy mass conservation very well. Current research focuses on: a) optimising the performance of Savitzky-Golay filters, through selection of appropriate parameters (order of least

  11. In Brief: Some decline in contaminants affecting U.S. coastal waters

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2008-05-01

    A new report indicates that environmental laws enacted in the 1970s are having a positive effect on reducing overall contaminant levels in U.S. coastal waters. However, there are continuing concerns with elevated levels of metals and organic contaminants found near urban and industrial areas of the coasts, according to the 12 May report issued by the U.S. National Oceanic and Atmospheric Administration (NOAA). ``Pesticides such as DDT [dichlorodiphenyltrichloroethane] and industrial chemicals such as PCBs [polychlorinated biphenyls] show significant decreasing trends around the nation, but similar trends were not found for trace metals,'' said Gunnar Lauenstein, manager of the NOAA Mussel Watch program, the nation's longest continuous national contaminant-monitoring program in U.S. coastal waters.

  12. Understanding Contaminant Transport Pathways at Rocky Flats - A Basis for the Remediation Strategy

    SciTech Connect

    Paton, Ian

    2008-01-15

    The Rocky Flats Environmental Technology Site (RFETS) is a Department of Energy facility located approximately 16 miles northwest of Denver, Colorado. Processing and fabrication of nuclear weapons components occurred at Rocky Flats from 1952 through 1989. Operations at the Site included the use of several radionuclides, including plutonium-239/240 (Pu), americium-241 (Am), and various uranium (U) isotopes, as well as several types of chlorinated solvents. The historic operations resulted in legacy contamination, including contaminated facilities, process waste lines, buried wastes and surface soil contamination. Decontamination and removal of buildings at the site was completed in late 2005, culminating more than ten years of active environmental remediation work. The Corrective Action Decision/Record of Decision was subsequently approved in 2006, signifying regulatory approval and closure of the site. The use of RFETS as a National Wildlife Refuge is scheduled to be in full operation by 2012. To develop a plan for remediating different types of radionuclide contaminants present in the RFETS environment required understanding the different environmental transport pathways for the various actinides. Developing this understanding was the primary objective of the Actinide Migration Evaluation (AME) project. Findings from the AME studies were used in the development of RFETS remediation strategies. The AME project focused on issues of actinide behavior and mobility in surface water, groundwater, air, soil and biota at RFETS. For the purposes of the AME studies, actinide elements addressed included Pu, Am, and U. The AME program, funded by DOE, brought together personnel with a broad range of relevant expertise in technical investigations. The AME advisory panel identified research investigations and approaches that could be used to solve issues related to actinide migration at the Site. An initial step of the AME was to develop a conceptual model to provide a

  13. REPORT ON THE HOMELAND SECURITY WORKSHOP ON TRANSPORT AND DISPOSAL OF WASTES FROM FACILITIES CONTAMINATED WITH CHEMICAL AND BIOLOGICAL AGENTS

    EPA Science Inventory

    This report summarizes discussions from the "Homeland Security Workshop on Transport and Disposal of Wastes From Facilities Contaminated With Chemical or Biological Agents." The workshop was held on May 28-30, 2003, in Cincinnati, Ohio, and its objectives were to:

    .Documen...

  14. Reconstruction of (131)I radioactive contamination in Ukraine caused by the Chernobyl accident using atmospheric transport modelling.

    PubMed

    Talerko, Nikolai

    2005-01-01

    The evaluation of (131)I air and ground contamination field formation in the territory of Ukraine was made using the model of atmospheric transport LEDI (Lagrangian-Eulerian DIffusion model). The (131)I atmospheric transport over the territory of Ukraine was simulated during the first 12 days after the accident (from 26 April to 7 May 1986) using real aerological information and rain measurement network data. The airborne (131)I concentration and ground deposition fields were calculated as the database for subsequent thyroid dose reconstruction for inhabitants of radioactive contaminated regions. The small-scale deposition field variability is assessed using data of (137)Cs detailed measurements in the territory of Ukraine. The obtained results are compared with available data of radioiodine daily deposition measurements made at the network of meteorological stations in Ukraine and data of the assessments of (131)I soil contamination obtained from the (129)I measurements. PMID:16024139

  15. Coupling Sorption to Soil Weathering During Reactive Transport: Impacts of Mineral Transformation and Sorbate Aging on Contaminant Speciation and Mobility

    SciTech Connect

    Chorover, Jon; Mueller, Karl T.; O'Day, Peggy; Serne, R. Jeff; Um, Wooyong; Steefel, Carl

    2006-06-01

    Our work is aimed at developing a predictive-mechanistic understanding of the coupling between mineral weathering from caustic waste release and contaminant (Cs, Sr, I) fate and transport in waste-impacted sediments across space, time and geochemical gradients that encompass the process-level heterogeneity observed at the Hanford DOE site. Our specific objectives are: (1) to assess the molecular-scale mechanisms responsible for time-dependent sequestration of contaminants (Cs, Sr and I) during penetration of waste-induced weathering fronts through sedimentary media; (2) to determine the rate and extent of contaminant release from the sorbed state; (3) to develop a reactive transport model based on molecular mechanisms and macroscopic flow experiments (from (1) and (2)) that accurately simulates adsorption, aging, and desorption at the bench-scale, and that can be applied to--and validated at--field sites such as Hanford.

  16. Decreased vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT) function in knockout mice affects aging of dopaminergic systems

    PubMed Central

    Hall, F. S.; Itokawa, K.; Schmitt, A.; Moessner, R.; Sora, I.; Lesch, K. P.; Uhl, G. R.

    2013-01-01

    Dopamine (DA) is accumulated and compartmentalized by the dopamine transporter (DAT; SLC3A6) and the vesicular monoamine transporter 2 (VMAT2; SLC18A2). These transporters work at the plasma and vesicular membranes of dopaminergic neurons, respectively, and thus regulate levels of DA in neuronal compartments that include the extravesicular cytoplasmic compartment. DA in this compartment has been hypothesized to contribute to oxidative damage that can reduce the function of dopaminergic neurons in aging brains and may contribute to reductions in dopaminergic neurochemical markers, locomotor behavior and responses to dopaminergic drugs that are found in aged animals. The studies reported here examined aged mice with heterozygous deletions of VMAT2 or of DAT, which each reduce transporter expression to about 50% of levels found in wild-type (WT) mice. Aged mice displayed reduced locomotor responses under a variety of circumstances, including in response to locomotor stimulants, as well as changes in monoamine levels and metabolites in a regionally dependent manner. Several effects of aging were more pronounced in heterozygous VMAT2 knockout (KO) mice, including aging induced reductions in locomotion and reduced locomotor responses to cocaine. By contrast, some effects of aging were reduced or not observed in heterozygous DAT KO mice. These findings support the idea that altered DAT and VMAT2 expression affect age-related changes in dopaminergic function. These effects are most likely mediated by alterations in DA compartmentalization, and might be hypothesized to be more exacerbated by other factors that affect the metabolism of cytosolic DA. PMID:23978383

  17. Simulations of groundwater flow, transport, and age in Albuquerque, New Mexico, for a study of transport of anthropogenic and natural contaminants (TANC) to public-supply wells

    USGS Publications Warehouse

    Heywood, Charles E.

    2013-01-01

    Vulnerability to contamination from manmade and natural sources can be characterized by the groundwater-age distribution measured in a supply well and the associated implications for the source depths of the withdrawn water. Coupled groundwater flow and transport models were developed to simulate the transport of the geochemical age-tracers carbon-14, tritium, and three chlorofluorocarbon species to public-supply wells in Albuquerque, New Mexico. A separate, regional-scale simulation of transport of carbon-14 that used the flow-field computed by a previously documented regional groundwater flow model was calibrated and used to specify the initial concentrations of carbon-14 in the local-scale transport model. Observations of the concentrations of each of the five chemical species, in addition to water-level observations and measurements of intra-borehole flow within a public-supply well, were used to calibrate parameters of the local-scale groundwater flow and transport models. The calibrated groundwater flow model simulates the mixing of “young” groundwater, which entered the groundwater flow system after 1950 as recharge at the water table, with older resident groundwater that is more likely associated with natural contaminants. Complexity of the aquifer system in the zone of transport between the water table and public-supply well screens was simulated with a geostatistically generated stratigraphic realization based upon observed lithologic transitions at borehole control locations. Because effective porosity was simulated as spatially uniform, the simulated age tracers are more efficiently transported through the portions of the simulated aquifer with relatively higher simulated hydraulic conductivity. Non-pumping groundwater wells with long screens that connect aquifer intervals having different hydraulic heads can provide alternate pathways for contaminant transport that are faster than the advective transport through the aquifer material. Simulation of

  18. Nitrate and ammonia contaminations in drinking water and the affecting factors in Hailun, northeast China.

    PubMed

    Zhao, Xinfeng; Chen, Liding; Zhang, Haiping

    2013-03-01

    Drinking water samples (N = 228) from domestic tube wells (DTWs) and seven samples from public water supply wells (PWSWs) were collected and tested in Hailun, northeast China. The percentage of samples with nitrate and ammonia concentrations above the maximum acceptable concentration of nitrate, 10 mg N/L, and the maximum ensure concentration of ammonia, 1.5 mg/L, for the DTWs were significantly higher than for the PWSWs. Of the DTWs, an important observation was that the occurrence of groundwater nitrate contamination was directly related to well tube material with different joint pathways. Nitrate in seamless-tube wells was lower statistically significantly than those in multiple-section-tube wells (p < .001). Furthermore, well depth and hydrogeological setting might have some impacts on nitrogen contamination and the major sources of inorganic nitrogen contamination may be nitrogenous chemical fertilizer. Therefore, PWSWs built for all families are the best way to ensure the drinking water safety in villages. For DTWs it is necessary to use seamless tubes and to dig deep enough according to the depth of groundwater level. Improving the efficiency of chemical fertilizer use would also reduce the risk of groundwater contamination.

  19. MICROBIAL PROCESSES AFFECTING MONITORED NATURAL ATTENUATION OF CONTAMINANTS IN THE SUBSURFACE

    EPA Science Inventory

    Among the alternatives considered for the remediation of soil and ground water at hazardous wastes sites are the use of natural processes to reduce or remove the contaminants of concern. Under favorable conditions, the use of natural attenuation can result in significant cost sa...

  20. Phase I Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 97: Yucca Flat/Climax Mine, Nevada Test Site, Nye County, Nevada, Revision 0

    SciTech Connect

    John McCord

    2007-09-01

    This report documents transport data and data analyses for Yucca Flat/Climax Mine CAU 97. The purpose of the data compilation and related analyses is to provide the primary reference to support parameterization of the Yucca Flat/Climax Mine CAU transport model. Specific task objectives were as follows: • Identify and compile currently available transport parameter data and supporting information that may be relevant to the Yucca Flat/Climax Mine CAU. • Assess the level of quality of the data and associated documentation. • Analyze the data to derive expected values and estimates of the associated uncertainty and variability. The scope of this document includes the compilation and assessment of data and information relevant to transport parameters for the Yucca Flat/Climax Mine CAU subsurface within the context of unclassified source-term contamination. Data types of interest include mineralogy, aqueous chemistry, matrix and effective porosity, dispersivity, matrix diffusion, matrix and fracture sorption, and colloid-facilitated transport parameters.

  1. Formation, Transport, Aggregation and Coarsening of Biogenic Metal-Sulfide Nanoparticles in Contaminated Near-Surface Aqueous Environments

    NASA Astrophysics Data System (ADS)

    Moreau, J. W.; Webb, R. I.; Banfield, J. F.

    2002-12-01

    The form of biogenic metal-sulfides produced by sulfate-reducing bacteria (SRB) found in many contaminated natural environments can control the fate of toxic metals in groundwater and sediments. SRB activity in microbial consortia affects the rate of sulfide precipitation and thus the potential for bioremediation. We have studied SRB populations and biogenic ZnS in a natural biofilm formed on degraded wood in a flooded mine in Upper Mississippi Valley-type ore deposits. We have also characterized microbial populations and associated mineralization in a natural wetland contaminated with acid mine drainage. Fluorescent in-situ hybridization (FISH) studies of biofilm samples were conducted using newly designed rRNA probes. Results show the abundant distribution of SRB from groups Desulfobacteraceae and Desulfobulbaceae. Scanning electron microscopy (SEM) and optical microscopy on cryofixed freeze-fractured or ultramicrotomed biofilm reveals the association of cells with ~~1 μm m spherical aggregates of ZnS nanoparticles. The spheres are concentrated in contiguous areas with textures similar to fossilized wood. High-resolution transmission electron microscopy (HRTEM) images show that most nanoparticles found in the biofilm are sequestered into the spheres and exhibit sphalerite, wurtzite, or hybrid structures. The smallest particles (<2 nm), however, are commonly associated with residual organic material between or away from the spheres, and rarely exhibit periodic structure. We infer that ZnS nanoparticles form homogenously in solution and are transported to localized sites to aggregate and coarsen. The spheres contain concentric bands of low particle density and voids 1-2 nm wide spaced 10s of nm's apart. We interpret these bands to reflect episodic ZnS precipitation due to increased SRB activity; adhesion and aggregation of the nanoparticles seems to have occurred at relatively controlled rates to form the nearly symmetrical spheres. The formation of

  2. Transport of tritium contamination to the atmosphere in an arid environment

    USGS Publications Warehouse

    Garcia, C.A.; Andraski, B.J.; Stonestrom, D.A.; Cooper, C.A.; Johnson, M.J.; Michel, R.L.; Wheatcraft, S.W.

    2009-01-01

    Soil-plant-atmosphere interactions strongly infl uence water movement in desert unsaturated zones, but litile is known about how such interactions aff ect atmospheric release of subsurface water-borne contaminants. This 2-yr study, performed at the U.S. Geological Survey's Amargosa Desert Research Site in southern Nevada, quantifi ed the magnitude and spatiotemporal variability of tritium (3H) transport from the shallow unsaturated zone to the atmosphere adjacent to a low-level radioactive waste (LLRW) facility. Tritium fl uxes were calculated as the product of 3H concentrations in water vapor and respective evaporation and transpiration water-vapor fl uxes. Quarterly measured 3H concentrations in soil water vapor and in leaf water of the dominant creosote-bush [Larrea tridentata (DC.) Coville] were spatially extrapolated and temporally interpolated to develop daily maps of contamination across the 0.76-km2 study area. Maximum plant and root-zone soil concentrations (4200 and 8700 Bq L-1, respectively) were measured 25 m from the LLRW facility boundary. Continuous evaporation was estimated using a Priestley-Taylor model and transpiration was computed as the diff erence between measured eddy-covariance evapotranspiration and estimated evaporation. The mean evaporation/transpiration ratio was 3:1. Tritium released from the study area ranged from 0.12 to 12 ??g d-1 and totaled 1.5 mg (8.2 ?? 1010 Bq) over 2 yr. Tritium fl ux variability was driven spatially by proximity to 3H source areas and temporally by changes in 3H concentrations and in the partitioning between evaporation and transpiration. Evapotranspiration removed and limited penetration of precipitation beneath native vegetation and fostered upward movement and release of 3H from below the root zone. ?? Soil Science Society of America.

  3. Bacillus cereus spores during housing of dairy cows: factors affecting contamination of raw milk.

    PubMed

    Magnusson, M; Christiansson, A; Svensson, B

    2007-06-01

    The contamination of raw milk with Bacillus cereus spores was studied during the indoor confinement of dairy cattle. The occurrence of spores in fresh and used bedding material, air samples, feed, feces, and the rinse water from milking equipment was compared with the spore level in bulk tank milk on 2 farms, one of which had 2 different housing systems. A less extensive study was carried out on an additional 5 farms. High spore concentrations of >100 spores/L in the raw milk were found on 4 of the farms. The number of spores found in the feed, feces, and air was too small to be of importance for milk contamination. Elevated spore contents in the rinse water from the milking equipment (up to 322 spores/L) were observed and large numbers of spores were found in the used bedding material, especially in free stalls with >5 cm deep sawdust beds. At most, 87,000 spores/g were found in used sawdust bedding. A positive correlation was found between the spore content in used bedding material and milk (r = 0.72). Comparison of the genetic fingerprints obtained by the random amplified polymorphic DNA PCR of isolates of B. cereus from the different sources indicated that used bedding material was the major source of contamination. A separate feeding experiment in which cows were experimentally fed B. cereus spores showed a positive relationship between the number of spores in the feed and feces and in the feces and milk (r = 0.78). The results showed that contaminated feed could be a significant source of spore contamination of raw milk if the number of spores excreted in the feces exceeded 100,000/g.

  4. Characterizing multiple timescales of stream and storage zone interaction that affect solute fate and transport in streams

    USGS Publications Warehouse

    Choi, J.; Harvey, J.W.; Conklin, M.H.

    2000-01-01

    The fate of contaminants in streams and rivers is affected by exchange and biogeochemical transformation in slowly moving or stagnant flow zones that interact with rapid flow in the main channel. In a typical stream, there are multiple types of slowly moving flow zones in which exchange and transformation occur, such as stagnant or recirculating surface water as well as subsurface hyporheic zones. However, most investigators use transport models with just a single storage zone in their modeling studies, which assumes that the effects of multiple storage zones can be lumped together. Our study addressed the following question: Can a single-storage zone model reliably characterize the effects of physical retention and biogeochemical reactions in multiple storage zones? We extended an existing stream transport model with a single storage zone to include a second storage zone. With the extended model we generated 500 data sets representing transport of nonreactive and reactive solutes in stream systems that have two different types of storage zones with variable hydrologic conditions. The one storage zone model was tested by optimizing the lumped storage parameters to achieve a best fit for each of the generated data sets. Multiple storage processes were categorized as possessing I, additive; II, competitive; or III, dominant storage zone characteristics. The classification was based on the goodness of fit of generated data sets, the degree of similarity in mean retention time of the two storage zones, and the relative distributions of exchange flux and storage capacity between the two storage zones. For most cases (> 90%) the one storage zone model described either the effect of the sum of multiple storage processes (category I) or the dominant storage process (category III). Failure of the one storage zone model occurred mainly for category II, that is, when one of the storage zones had a much longer mean retention time (t(s) ratio > 5.0) and when the dominance of

  5. Canyon Disposal Initiative - Numerical Modeling of Contaminant Transport from Grouted Residual Waste in the 221-U Facility (U Plant)

    SciTech Connect

    Rockhold, Mark L.; White, Mark D.; Freeman, Eugene J.

    2004-10-12

    This letter report documents initial numerical analyses conducted by PNNL to provide support for a feasibility study on decommissioning of the canyon buildings at Hanford. The 221-U facility is the first of the major canyon buildings to be decommissioned. The specific objective of this modeling effort was to provide estimates of potential rates of migration of residual contaminants out of the 221-U facility during the first 40 years after decommissioning. If minimal contaminant migration is predicted to occur from the facility during this time period, then the structure may be deemed to provide a level of groundwater protection that is essentially equivalent to the liner and leachate collection systems that are required at conventional landfills. The STOMP code was used to simulate transport of selected radionuclides out of a canyon building, representative of the 221-U facility after decommissioning, for a period of 40 years. Simulation results indicate that none of the selected radionuclides that were modeled migrated beyond the concrete structure of the facility during the 40-year period of interest. Jacques (2001) identified other potential contaminants in the 221-U facility that were not modeled, however, including kerosene, phenol, and various metals. Modeling of these contaminants was beyond the scope of this preliminary effort due to increased complexity. Simulation results indicate that contaminant release from the canyon buildings will be diffusion controlled at early times. Advection is expected to become much more important at later times, after contaminants have diffused out of the facility and into the surrounding soil environment. After contaminants have diffused out of the facility, surface infiltration covers will become very important for mitigating further transport of contaminants in the underlying vadose zone and groundwater.

  6. Psychostimulants affect dopamine transmission through both dopamine transporter-dependent and independent mechanisms

    PubMed Central

    dela Peña, Ike; Gevorkiana, Ruzanna; Shi, Wei-Xing

    2015-01-01

    The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs. PMID:26209364

  7. Psychostimulants affect dopamine transmission through both dopamine transporter-dependent and independent mechanisms.

    PubMed

    dela Peña, Ike; Gevorkiana, Ruzanna; Shi, Wei-Xing

    2015-10-01

    The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs. PMID:26209364

  8. Spatial and temporal distribution of contaminated, effluent-affected sediment on the Palos Verdes margin, southern California

    USGS Publications Warehouse

    Lee, H.J.; Sherwood, C.R.; Drake, D.E.; Edwards, B.D.; Wong, F.; Hamer, M.

    2002-01-01

    A sedimentary deposit on the continental margin near the Palos Verdes Peninsula, California is comprised of sewage effluent and geologic materials and is contaminated with metals, pesticides (including DDT and associated compounds), and PCBs. The deposit was mapped with subbottom acoustic profilers, and sediment cores were analyzed for geochemical and physical properties to determine the volume of the deposit and the distribution and mass of contaminants. Mapping showed that the deposit ranges up to 60-cm thick, has a total volume exceeding 9 million m3, and covers over 40 km2. Virtually the entire effluent-affected deposit is contaminated with DDT and PCBs. Nearly half of the area of the deposit lies on the continental slope, but 70-75% of the volume of the deposit and total mass of DDT reside on the continental shelf. Analysis of data collected biennially since 1981 by the Sanitation Districts of Los Angeles County show that the mass of DDT has apparently decreased at some stations but has remained essentially constant at others. Temporal changes m mass per unit area of DDT are not statistically significant (at the 90% confidence level) at the most contaminated locations over a 16-yr period. The results of this mapping effort were used as a basis for modeling efforts described elsewhere in this issue. ?? 2002 Elsevier Science Ltd. All rights reserved.

  9. Characterization of Contaminant Transport by Gravity, Capillarity and Barometric Pumping in Heterogeneous Vadose Zones

    SciTech Connect

    Carrigan, C R; Martins, S A; Ramirez, A L; Daily, W D; Hudson, G B; Ralsont, D; Ekwurzel, B

    2001-02-27

    in the vadose zone. From the VZO at the LLNL site and from 3-D diagnostic simulations of our very first tracer-spiked plume infiltration event, we produced a much better understanding of the implications of soil heterogeneity for unsaturated zone contaminant transport at DOE sites. Even though the LLNL VZO site is considered to be hydrologically ''tight'' owing to the low permeability of the clays and silts that dominate the soil formations there, we find that saturation increases resulting from a near-surface ''leak'' reach the water table across the 20-meter-thick vadose zone in only tens of hours. This rapid transport at the site cannot be accurately simulated by layered models that derive their hydrologic properties from borehole-soil samples. In the LLNL vadose zone, layered infiltration models clearly underpredict of the rate of contaminant infiltration to the water table. Chemical transport simulations based on layered models of the Hanford vadose zone also appear to drastically underpredict contaminant migration. Furthermore, only simulations assuming a heterogeneous regime ''threaded'' by extremely high-permeability pathways can explain the rapid increase in saturation observed with ERT near the water table. Three-dimensional predictive models of a hypothetical tritiated water leak that are based on the above mentioned VZO infiltration-experiment diagnostic models were run. Tritiated water is an excellent conservative tracer and the infiltration simulations predict, in very good agreement with VZO experiments, that a continuous hypothetical tritium release (2-3 liters/rein) would be expected to reach the water table at significant concentrations within days. The numerical model suggests that this arrival time is determined by the amount of time required, infiltrating liquid at a given rate, to flush one pore volume in the soil between the infiltration point and the water table. Another infiltration event monitored by ERT demonstrated that infiltration could

  10. Modeling the Influence of Variable Tributary Inflow on Circulation and Contaminant Transport in a Water Supply Reservoir

    NASA Astrophysics Data System (ADS)

    Nguyen, L. H.; Wildman, R.

    2012-12-01

    This study characterizes quantitatively the flow and mixing regimes of a water supply reservoir, while also conducting numerical tracer experiments on different operation scenarios. We investigate the effects of weather events on water quality via storm water inflows. Our study site the Kensico Reservoir, New York, the penultimate reservoir of New York City's water supply, is never filtered and thus dependent on stringent watershed protection. This reservoir must meet federal drinking water standards under changing conditions such as increased suburban, commercial, and highway developments that are much higher than the rest of the watershed. Impacts from these sources on water quality are magnified by minor tributary flows subject to contaminants from development projects as other tributaries providing >99% of water to this reservoir are exceedingly clean due to management practices upstream. These threats, coupled with possible changes in the frequency/intensity of weather events due to climate change, increase the potential for contaminants to enter the reservoir and drinking water intakes. This situation provides us with the unique ability to study the effects of weather events on water quality via insignificant storm water inflows, without influence from the major tributaries due to their pristine water quality characteristics. The concentration of contaminants at the drinking water intake depends partially on transport from their point of entry in the reservoir. Thus, it is crucial to understand water circulation in this reservoir and to estimate residence times and water ages at different locations and under different hydrologic scenarios. We described water age, residence time, thermal structure, and flow dynamics of tributary plumes in Kensico Reservoir during a 22-year simulation period using a two-dimensional hydrodynamic and water quality model (CE-QUAL-W2). Our estimates of water age can reach a maximum of ~300 days in deep-reservoir-cells, with

  11. Osmium isotopes demonstrate distal transport of contaminated sediments in Chesapeake Bay

    USGS Publications Warehouse

    Helz, G.R.; Adelson, J.M.; Miller, C.V.; Cornwell, J.C.; Hill, J.M.; Horan, M.; Walker, R.J.

    2000-01-01

    Because the isotopic composition of anthropogenic Os is normally distinctive in comparison to continental crust and is precisely measurable, this platinum-group element is attractive as a tracer of transport pathways for contaminated sediments in estuaries. Evidence herein and elsewhere suggest that biomedical research institutions are the chief source of anthropogenic Os. In the Chesapeake Bay region, uncontaminated sediments bear a crustal 187Os/188Os signature of 0.73 ?? 0.10. Slightly higher 187Os/188Os ratios occur in Re-rich Coastal Plain deposits due to post- Miocene 187Re decay. The upper Susquehanna Basin yields sediments also with higher 187Os/188Os. Beginning in the late 1970s, this signal was overprinted by a low 187Os/188Os (anthropogenic) source in the lower Susquehanna Basin. In the vicinity of Baltimore, which is a major center of heavy industry as well as biomedical research, anthropogenic Os has been found only in sediments impacted by the principal wastewater treatment plant. Surprisingly, a mid-Bay site distant from anthropogenic sources contains the strongest anthropogenic Os signal in the data set, having received anthropogenic Os sporadically since the mid-20th Century. Transport of particles to this site overrode the northward flowing bottom currents. Finding anthropogenic Os at this site cautions that other particle-borne substances, including hazardous ones, could be dispersed broadly in this estuary.Because the isotopic composition of anthropogenic Os is normally distinctive in comparison to continental crust and is precisely measurable, this platinum-group element is attractive as a tracer of transport pathways for contaminated sediments in estuaries. Evidence herein and elsewhere suggest that biomedical research institutions are the chief source of anthropogenic Os. In the Chesapeake Bay region, uncontaminated sediments bear a crustal 187Os/188Os signature of 0.73 ?? 0.10. Slightly higher 187Os/188Os ratios occur in Re-rich Coastal

  12. Probabilities of adverse weather affecting transport in Europe: climatology and scenarios up to the 2050s

    NASA Astrophysics Data System (ADS)

    Vajda, A.; Tuomenvirta, H.; Jokinen, P.; Luomaranta, A.; Makkonen, L.; Tikanmäki, M.; Groenemeijer, P.; Saarikivi, P.; Michaelides, S.; Papadakis, M.; Tymvios, F.; Athanasatos, S.

    2012-04-01

    This paper provides the first comprehensive climatology of the adverse and extreme weather events affecting the European transport system by estimating the frequency (or probability) of phenomena for the present climate (1971-2000) and an overview of the projected changes in some of these extremes in the future climate until the 2050s. The research was carried out within the framework of the EWENT Project that addresses the European Union (EU) policies and strategies related to climate change, with a particular focus on extreme weather impacts on the EU transportation system. This project is funded by the Seventh Framework Programme (Transports, call ID FPT7-TPT-2008-RTD-1). The analyzed phenomena are wind, snow, blizzards, heavy precipitation, cold spells and heat waves. In addition, reduced visibility conditions determined by fog and dust events, small-scale phenomena affecting the transport system, such as thunderstorms, lightning, large hail and tornadoes and events damaging infrastructure of the transport system, have been considered. Frequency and probability analysis of past and present ex¬tremes were performed using observational and atmospheric reanalysis data. Future changes in the probability of severe events were assessed based on six regional climate model simulations produced in the FP6 ENSEMBLES project (http://www.ensembles-eu.org/). To facilitate the assessment of impacts and consequences of extreme phenomena on a continental level, the WP2 Deliverable introduces a regionalization of the European extreme phenomena, defining the climate zones with similarities in extreme phenomena. The projected changes as well as large natural variability in weather extremes on the transportation network will have impacts of both signs. The decline of extreme cold and snowfall over most of the continent implies a positive impact on road, rail, inland water and air transportation, e.g., by reducing snow removal. However, even with a general decreasing trend in

  13. Eww she sneezed! Contamination context affects children's food preferences and consumption.

    PubMed

    DeJesus, Jasmine M; Shutts, Kristin; Kinzler, Katherine D

    2015-04-01

    Does contextual information about disgust influence children's food consumption and subjective experience of taste? Three- to eight-year-old children (N = 60) were presented with two identical foods, yet children were led to believe that one food had been contaminated by sneezing and licking, while the other was clean. When given the opportunity to eat the foods, 5- to 8-year-old children consumed more clean food and rated the clean food's taste more positively; younger children did not distinguish between the foods. The relation between contamination and subjective taste held even among children who ate both foods and had direct evidence that they were identical. These data indicate that children's consumption behavior and food preferences are influenced by information external to foods themselves. PMID:25558024

  14. Phase II Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Unit 98: Frenchman Flat, Nye County, Nevada, Rev. No.: 0

    SciTech Connect

    DeNovio, Nicole M.; Bryant, Nathan; King, Chrissi B.; Bhark, Eric; Drellack, Sigmund L.; Pickens, John F.; Farnham, Irene; Brooks, Keely M.; Reimus, Paul; Aly, Alaa

    2005-04-01

    This report documents pertinent transport data and data analyses as part of the Phase II Corrective Action Investigation (CAI) for Frenchman Flat (FF) Corrective Action Unit (CAU) 98. The purpose of this data compilation and related analyses is to provide the primary reference to support parameterization of the Phase II FF CAU transport model.

  15. Multidisciplinary Studies of the Fate and Transport of Contaminants in Ground Water at the U.S. Geological Survey Cape Cod Toxic Substances Hydrology Program Research Site, Massachusetts

    NASA Astrophysics Data System (ADS)

    Leblanc, D. R.; Smith, R. L.; Kent, D. B.; Barber, L. B.; Harvey, R. W.

    2008-12-01

    The U.S. Geological Survey conducts multidisciplinary research on the physical, chemical, and microbiological processes affecting ground-water contaminants of global concern at its Cape Cod Toxic Substances Hydrology Program site in Massachusetts, USA. The work centers on a 6-kilometer-long plume of treated wastewater in a glacial sand and gravel aquifer. The plume is characterized by distinct geochemical zones caused by the biodegradation of organic materials in treated wastewater that was disposed to the aquifer by rapid infiltration during the period 1936-95. A core group of hydrogeologists, geochemists, microbiologists, and geophysicists has been involved in the research effort for more than two decades. The effort has been enhanced by stable funding, a readily accessible site, a relatively simple hydrologic setting, and logistical support from an adjacent military base. The research team uses a three-part approach to plan and conduct research at the site. First, detailed spatial and temporal monitoring of the plume since the late 1970s provides field evidence of important contaminant-transport processes and provides the basis for multidisciplinary, process-oriented studies. Second, ground-water tracer experiments are conducted in various geochemical zones in the plume to study factors that control the rate and extent of contaminant transport. Several arrays of multilevel sampling devices, including an array with more than 15,000 individual sampling points, are used to conduct these experiments. Plume-scale (kilometers) and tracer-test-scale (1- 100 meters) studies are complemented by laboratory experiments and mathematical modeling of flow and reactive transport. Third, results are applied to the treated-wastewater plume, other contaminant plumes at the military base, and other sites nationally to evaluate the applicability of the findings and to point toward further research. Examples of findings to date include that (1) macrodispersivity can be related to

  16. EVALUATION OF BIOAEROSOL COMPONENTS, GENERATION FACTORS, AND AIRBORNE TRANSPORT ASSOCIATED WITH LIME TREATMENT OF CONTAMINATED SEDIMENT

    EPA Science Inventory

    Lime treatment has been used in contaminated sediment management activities for many purposes such as dewatering, improvement of physical properties, and reducing contaminant mobility. Exothermic volatilization of volatile organic compounds from lime-treated sediment is well kno...

  17. Physiologically-based toxicokinetic models help identifying the key factors affecting contaminant uptake during flood events.

    PubMed

    Brinkmann, Markus; Eichbaum, Kathrin; Kammann, Ulrike; Hudjetz, Sebastian; Cofalla, Catrina; Buchinger, Sebastian; Reifferscheid, Georg; Schüttrumpf, Holger; Preuss, Thomas; Hollert, Henner

    2014-07-01

    As a consequence of global climate change, we will be likely facing an increasing frequency and intensity of flood events. Thus, the ecotoxicological relevance of sediment re-suspension is of growing concern. It is vital to understand contaminant uptake from suspended sediments and relate it to effects in aquatic biota. Here we report on a computational study that utilizes a physiologically based toxicokinetic model to predict uptake, metabolism and excretion of sediment-borne pyrene in rainbow trout (Oncorhynchus mykiss). To this end, data from two experimental studies were compared with the model predictions: (a) batch re-suspension experiments with constant concentration of suspended particulate matter at two different temperatures (12 and 24°C), and (b) simulated flood events in an annular flume. The model predicted both the final concentrations and the kinetics of 1-hydroxypyrene secretion into the gall bladder of exposed rainbow trout well. We were able to show that exhaustive exercise during exposure in simulated flood events can lead to increased levels of biliary metabolites and identified cardiac output and effective respiratory volume as the two most important factors for contaminant uptake. The results of our study clearly demonstrate the relevance and the necessity to investigate uptake of contaminants from suspended sediments under realistic exposure scenarios.

  18. Modern contaminants affecting microscopic residue analysis on stone tools: A word of caution.

    PubMed

    Pedergnana, A; Asryan, L; Fernández-Marchena, J L; Ollé, A

    2016-07-01

    Residue analysis is a method frequently used to infer the function of stone tools and it is very often applied in combination with use-wear analysis. Beyond its undeniable potential, the method itself has several intrinsic constraints. Apart from the exceptional circumstances necessary for residues to survive, the correct identification of the residue type is a very debatable topic. Before attempting to recognise ancient residues, a proper method should allow analysts to identify possible modern contaminants and exclude them from the final interpretation. Therefore, analysts should not underestimate the presence of modern contaminants and might learn how to discriminate the background noise due to handling. The main aim of this research is to provide some methodological improvements to residue analysis through the characterisation of some modern residues often present on the surface of stone tools (e.g. skin flakes, modelling clay). This characterisation was done by using both optical light microscopy (OLM) and scanning electron microscopy (SEM). Finally, a special care in the post-excavation treatment of stone tools is claimed in order to avoid major contamination of the samples. PMID:27113340

  19. Physiologically-based toxicokinetic models help identifying the key factors affecting contaminant uptake during flood events.

    PubMed

    Brinkmann, Markus; Eichbaum, Kathrin; Kammann, Ulrike; Hudjetz, Sebastian; Cofalla, Catrina; Buchinger, Sebastian; Reifferscheid, Georg; Schüttrumpf, Holger; Preuss, Thomas; Hollert, Henner

    2014-07-01

    As a consequence of global climate change, we will be likely facing an increasing frequency and intensity of flood events. Thus, the ecotoxicological relevance of sediment re-suspension is of growing concern. It is vital to understand contaminant uptake from suspended sediments and relate it to effects in aquatic biota. Here we report on a computational study that utilizes a physiologically based toxicokinetic model to predict uptake, metabolism and excretion of sediment-borne pyrene in rainbow trout (Oncorhynchus mykiss). To this end, data from two experimental studies were compared with the model predictions: (a) batch re-suspension experiments with constant concentration of suspended particulate matter at two different temperatures (12 and 24°C), and (b) simulated flood events in an annular flume. The model predicted both the final concentrations and the kinetics of 1-hydroxypyrene secretion into the gall bladder of exposed rainbow trout well. We were able to show that exhaustive exercise during exposure in simulated flood events can lead to increased levels of biliary metabolites and identified cardiac output and effective respiratory volume as the two most important factors for contaminant uptake. The results of our study clearly demonstrate the relevance and the necessity to investigate uptake of contaminants from suspended sediments under realistic exposure scenarios. PMID:24727214

  20. Application methods affect phosphorus-induced lead immobilization from a contaminated soil.

    PubMed

    Yoon, Joon Ki; Cao, Xinde; Ma, Lena Q

    2007-01-01

    Phosphate rock (PR) and phosphoric acid (PA) are an effective combination of P sources for immobilizing Pb in contaminated soils. This column experiment examined the effectiveness of different application methods on Pb immobilization in a contaminated soil. Phosphate was applied at a P/Pb molar ratio of 4 with half as PR and half PA. While PR was mixed with the soil or placed as a layer, aqueous PA was applied from the top of the column as one or two applications. After 4 wk of incubation, total and soluble Pb and P, TCLP-Pb (toxicity characteristic leaching procedure) and PBET-Pb (physiologically-based extraction test) in the P-treated soil were determined. Phosphate addition effectively reduced leachable Pb to below the EPA drinking water standard of 15 microg L(-1) in all treatments. Mixing both PA and PR with the soil was the most effective method in Pb immobilization, reducing TCLP-Pb by up to 95% and PBET-Pb by 25 to 42%. Application of PR as a layer in the soil column was the most effective in reducing Pb migration (by 73-79%) and minimizing soil acidification and P entrophication, potential drawbacks of PA. Applying PA in two applications was less effective than one application. Mixing PR and PA with the soil plus placing PR as a layer can be employed for effective remediation of Pb-contaminated soils, reducing Pb leachability, bioavailability, and mobility while minimizing soil acidification and P entrophication.

  1. Modern contaminants affecting microscopic residue analysis on stone tools: A word of caution.

    PubMed

    Pedergnana, A; Asryan, L; Fernández-Marchena, J L; Ollé, A

    2016-07-01

    Residue analysis is a method frequently used to infer the function of stone tools and it is very often applied in combination with use-wear analysis. Beyond its undeniable potential, the method itself has several intrinsic constraints. Apart from the exceptional circumstances necessary for residues to survive, the correct identification of the residue type is a very debatable topic. Before attempting to recognise ancient residues, a proper method should allow analysts to identify possible modern contaminants and exclude them from the final interpretation. Therefore, analysts should not underestimate the presence of modern contaminants and might learn how to discriminate the background noise due to handling. The main aim of this research is to provide some methodological improvements to residue analysis through the characterisation of some modern residues often present on the surface of stone tools (e.g. skin flakes, modelling clay). This characterisation was done by using both optical light microscopy (OLM) and scanning electron microscopy (SEM). Finally, a special care in the post-excavation treatment of stone tools is claimed in order to avoid major contamination of the samples.

  2. Transport and transformations of chlorinated-solvent contamination in a saprolite and fractured rock aquifer near a former wastewater-treatment plant, Greenville, South Carolina

    USGS Publications Warehouse

    Vroblesky, D.A.; Bradley, P.M.; Lane, J.W.; Robertson, J.F.

    1997-01-01

    The transport and fate of chlorinated-ethene contamination was investigated in a fractured-rock aquifer downgradient from a wastewater-treatment plant at a gas-turbine manufacturing facility inGreenville, South Carolina. A vapor-diffusion- sampler technique, developed for this investigation, located fracture zones that discharged contaminated ground water to surface water. The distribution ofchlorinated compounds and sulfate, comparison of borehole geophysical data, driller's logs, and the aquifer response to pumpage allowed subsurface contaminant-transport pathways to be delineated.The probable contaminant-transport pathway from the former aeration lagoon was southward. The probable pathway of contaminant transport from the former sludge lagoon was southward to and beneath Little Rocky Creek. South of the creek, the major pathway of contaminant transport appeared to be at a depth of approximately 80 to 107 feet below land surface. The contaminant-transport pathway from the former industrial lagoon was not readily discernible from existing data. A laboratory investigation, as well as examination of ground- water-chemistry data collected during this investigation and concentrations of chlorinated compounds collected during previous investigations,indicates that higher chlorinated compounds are being degraded to lower-chlorinated compounds in the contaminated aquifer. The approaches used in this investigation, as well as the findings, havepotential application to other fractured-rock aquifers contaminated by chlorinated ethenes.

  3. Coupling Sorption to Soil Weathering During Reactive Transport: Impacts of Mineral Transformation and Sorbent Aging on Contaminant Speciation and Mobility

    SciTech Connect

    Chorover, J.; Mueller, K. T.; O'Day, P. A.; Serne, R. J.; Steefel, C. I.

    2009-10-30

    This project aimed for a predictive-mechanistic understanding of the coupling between mineral weathering and contaminant (Cs, Sr, I) transport/fate in caustic waste-impacted sediments. Based on our prior studies of model clay mineral systems, we postulated that contaminant uptake to Hanford sediments would reflect concurrent adsorption and co-precipitation effects. Our specific objectives were: (1) to assess the molecular-scale mechanisms responsible for time-dependent sequestration of contaminants (Cs, Sr and I) during penetration of waste-induced weathering fronts; (2) to determine the rate and extent of contaminant release from the sorbed state; (3) to develop a reactive transport model based on molecular mechanisms and macroscopic flow experiments [(1) and (2)] that simulates adsorption, aging, and desorption dynamics. Progress toward achieving each of these objectives is discussed below. We observed unique molecular mechanisms for sequestration of Sr, Cs and I during native silicate weathering in caustic waste. Product solids, which included poorly crystalline aluminosilicates and well-crystallized zeolites and feldspathoids, accumulate contaminant species during crystal growth.

  4. Flow and contaminant transport in an airliner cabin induced by a moving body: Model experiments and CFD predictions

    NASA Astrophysics Data System (ADS)

    Poussou, Stephane B.; Mazumdar, Sagnik; Plesniak, Michael W.; Sojka, Paul E.; Chen, Qingyan

    2010-08-01

    The effects of a moving human body on flow and contaminant transport inside an aircraft cabin were investigated. Experiments were performed in a one-tenth scale, water-based model. The flow field and contaminant transport were measured using the Particle Image Velocimetry (PIV) and Planar Laser-Induced Fluorescence (PLIF) techniques, respectively. Measurements were obtained with (ventilation case) and without (baseline case) the cabin environmental control system (ECS). The PIV measurements show strong intermittency in the instantaneous near-wake flow. A symmetric downwash flow was observed along the vertical centerline of the moving body in the baseline case. The evolution of this flow pattern is profoundly perturbed by the flow from the ECS. Furthermore, a contaminant originating from the moving body is observed to convect to higher vertical locations in the presence of ventilation. These experimental data were used to validate a Computational Fluid Dynamic (CFD) model. The CFD model can effectively capture the characteristic flow features and contaminant transport observed in the small-scale model.

  5. Colloidal-facilitated transport of inorganic contaminants in ground water: part 1, sampling considerations

    USGS Publications Warehouse

    Puls, Robert W.; Eychaner, James H.; Powell, Robert M.

    1996-01-01

    Investigations at Pinal Creek, Arizona, evaluated routine sampling procedures for determination of aqueous inorganic geochemistry and assessment of contaminant transport by colloidal mobility. Sampling variables included pump type and flow rate, collection under air or nitrogen, and filter pore diameter. During well purging and sample collection, suspended particle size and number as well as dissolved oxygen, temperature, specific conductance, pH, and redox potential were monitored. Laboratory analyses of both unfiltered samples and the filtrates were performed by inductively coupled argon plasma, atomic absorption with graphite furnace, and ion chromatography. Scanning electron microscopy with Energy Dispersive X-ray was also used for analysis of filter particulates. Suspended particle counts consistently required approximately twice as long as the other field-monitored indicators to stabilize. High-flow-rate pumps entrained normally nonmobile particles. Difference in elemental concentrations using different filter-pore sizes were generally not large with only two wells having differences greater than 10 percent in most wells. Similar differences (>10%) were observed for some wells when samples were collected under nitrogen rather than in air. Fe2+/Fe3+ ratios for air-collected samples were smaller than for samples collected under a nitrogen atmosphere, reflecting sampling-induced oxidation.

  6. Experimental Model of Contaminant Transport by a Moving Wake Inside an Aircraft Cabin

    NASA Astrophysics Data System (ADS)

    Poussou, Stephane; Sojka, Paul; Plesniak, Michael

    2008-11-01

    The air cabin environment in jetliners is designed to provide comfortable and healthy conditions for passengers. The air ventilation system produces a recirculating pattern designed to minimize secondary flow between seat rows. However, disturbances are frequently introduced by individuals walking along the aisle and may significantly modify air distribution and quality. Spreading of infectious aerosols or biochemical agents presents potential health hazards. A fundamental study has been undertaken to understand the unsteady transport phenomena, to validate numerical simulations and to improve air monitoring systems. A finite moving body is modeled experimentally in a 10:1 scale simplified aircraft cabin equipped with ventilation, at a Reynolds number (based on body height) of the order of 10,000. Measurements of the ventilation and wake velocity fields are obtained using PIV and PLIF. Results indicate that the evolution of the typical downwash behind the body is profoundly perturbed by the ventilation flow. Furthermore, the interaction between wake and ventilation flow significantly alters scalar contaminant migration.

  7. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    SciTech Connect

    Cushman, J.H.

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media.

  8. Dynamics of Coupled Contaminant and Microbial Transport in Heterogeneous Porous Media: Purdue Component

    SciTech Connect

    Cushman, J.H.; Madilyn Fletcher

    2000-06-01

    Dynamic microbial attachment/detachment occurs in subsurface systems in response to changing environmental conditions caused by contaminant movement and degradation. Understanding the environmental conditions and mechanisms by which anaerobic bacteria partition between aqueous and solid phases is a critical requirement for designing and evaluating in situ bioremediation efforts. This interdisciplinary research project, of which we report only the Purdue contribution, provides fundamental information on the attachment/detachment dynamics of bacteria in heterogeneous porous media. Fundamental results from the Purdue collaboration are: (a) development of a matched-index method for obtaining 3-D Lagrangian trajectories of microbial sized particles transporting within porous media or microflow cells, (b) application of advanced numerical methods to optimally design a microflow cell for studying anaerobic bacterial attachment/detachment phenomena, (c) development of two types of models for simulating bacterial movement and attachment/detachment in microflow cells and natural porous media, (d) application of stochastic analysis to upscale pore scale microbial attachment/detachment models to natural heterogeneous porous media, and (e) evaluation of the role nonlocality plays in microbial dynamics in heterogeneous porous media

  9. Reactive transport of metal contaminants in alluvium - Model comparison and column simulation

    USGS Publications Warehouse

    Brown, J.G.; Bassett, R.L.; Glynn, P.D.

    2000-01-01

    A comparative assessment of two reactive-transport models, PHREEQC and HYDROGEOCHEM (HGC), was done to determine the suitability of each for simulating the movement of acidic contamination in alluvium. For simulations that accounted for aqueous complexation, precipitation and dissolution, the breakthrough and rinseout curves generated by each model were similar. The differences in simulated equilibrium concentrations between models were minor and were related to (1) different units in model output, (2) different activity coefficients, and (3) ionic-strength calculations. When adsorption processes were added to the models, the rinseout pH simulated by PHREEQC using the diffuse double-layer adsorption model rose to a pH of 6 after pore volume 15, about 1 pore volume later than the pH simulated by HGC using the constant-capacitance model. In PHREEQC simulation of a laboratory column experiment, the inability of the model to match measured outflow concentrations of selected constituents was related to the evident lack of local geochemical equilibrium in the column. The difference in timing and size of measured and simulated breakthrough of selected constituents indicated that the redox and adsorption reactions in the column occurred slowly when compared with the modeled reactions. MINTEQA2 and PHREEQC simulations of the column experiment indicated that the number of surface sites that took part in adsorption reactions was less than that estimated from the measured concentration of Fe hydroxide in the alluvium.

  10. Ammonium transport and reaction in contaminated groundwater: Application of isotope tracers and isotope fractionation studies

    USGS Publications Warehouse

    Böhlke, J.K.; Smith, R.L.; Miller, D.N.

    2006-01-01

    Ammonium (NH4+) is a major constituent of many contaminated groundwaters, but its movement through aquifers is complex and poorly documented. In this study, processes affecting NH4+ movement in a treated wastewater plume were studied by a combination of techniques including large-scale monitoring of NH4+ distribution; isotopic analyses of coexisting aqueous NH4+, NO3-, N2, and sorbed NH 4+; and in situ natural gradient 15NH 4+ tracer tests with numerical simulations of 15NH4+, 15NO3-, and 15N2 breakthrough data. Combined results indicate that the main mass of NH4+ was moving downgradient at a rate about 0.25 times the groundwater velocity. Retardation factors and groundwater ages indicate that much of the NH4+ in the plume was recharged early in the history of the wastewater disposal. NO3- and excess N2 gas, which were related to each other by denitrification near the plume source, were moving downgradient more rapidly and were largely unrelated to coexisting NH 4+. The ??15N data indicate areas of the plume affected by nitrification (substantial isotope fractionation) and sorption (no isotope fractionation). There was no conclusive evidence for NH 4+-consuming reactions (nitrification or anammox) in the anoxic core of the plume. Nitrification occurred along the upper boundary of the plume but was limited by a low rate of transverse dispersive mixing of wastewater NH4+ and O2 from overlying uncontaminated groundwater. Without induced vertical mixing or displacement of plume water with oxic groundwater from upgradient sources, the main mass of NH4+ could reach a discharge area without substantial reaction long after the more mobile wastewater constituents are gone. Multiple approaches including in situ isotopic tracers and fractionation studies provided critical information about processes affecting NH4+ movement and N speciation.

  11. Soil water repellency affects production and transport of CO2 and CH4 in soil

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2016-04-01

    Soil moisture is known to be vital in controlling both the production and transport of C gases in soil. Water availability regulates the decomposition rates of soil organic matter by the microorganisms, while the proportion of water/air filled pores controls the transport of gases within the soil and at the soil-atmosphere interface. Many experimental studies and process models looking at soil C gas fluxes assume that soil water is uniformly distributed and soil is easily wettable. Most soils, however, exhibit some degree of soil water repellency (i.e. hydrophobicity) and do not wet spontaneously when dry or moderately moist. They have restricted infiltration and conductivity of water, which also results in extremely heterogeneous soil water distribution. This is a world-wide occurring phenomenon which is particularly common under permanent vegetation e.g. forest, grass and shrub vegetation. This study investigates the effect of soil water repellency on microbial respiration, CO2 transport within the soil and C gas fluxes between the soil and the atmosphere. The results from the field monitoring and laboratory experiments show that soil water repellency results in non-uniform water distribution in the soil which affects the CO2 and CH4 gas fluxes. The main conclusion from the study is that water repellency not only affects the water relations in the soil, but has also a great impact on greenhouse gas production and transport and therefore should be included as an important parameter during the sites monitoring and modelling of gas fluxes.

  12. Widespread listeriosis outbreak attributable to pasteurized cheese, which led to extensive cross-contamination affecting cheese retailers, Quebec, Canada, 2008.

    PubMed

    Gaulin, Colette; Ramsay, Danielle; Bekal, Sadjia

    2012-01-01

    A major Listeria monocytogenes outbreak occurred in the province of Quebec, Canada, in 2008, involving a strain of L. monocytogenes (LM P93) characterized by pulsed-field gel electrophoresis (PFGE) and associated with the consumption of pasteurized milk cheese. This report describes the results of the ensuing investigation. All individuals affected with LM P93 across the province were interviewed with a standardized questionnaire. Microbiological and environmental investigations were conducted by the Quebec's Food Inspection Branch of Ministère de l'Agriculture, des Pêcheries et de l'Alimentation du Québec among retailers and cheese plants involved in the outbreak. Between 8 June and 31 December 2008, 38 confirmed cases of LM P93 were reported to public health authorities, including 16 maternal-neonatal cases (14 pregnant women, and two babies born to asymptomatic mothers). The traceback of many brands of cheese that tested positive for LM P93 collected from retailers identified two cheese plants contaminated by L. monocytogenes strains on 3 and 4 September. PFGE profiles became available for both plants on 8 September, and confirmed that a single plant was associated with the outbreak. Products from these two plants were distributed to more than 300 retailers in the province, leading to extensive cross-contamination of retail stock. L. monocytogenes is ubiquitous, and contamination can occur subsequent to heat treatment, which usually precedes cheese production. Contaminated soft-textured cheese is particularly prone to bacterial growth. Ongoing regulatory and industry efforts are needed to decrease the presence of Listeria in foods, including pasteurized products. Retailers should be instructed about the risk of cross-contamination, even with soft pasteurized cheese and apply methods to avoid it.

  13. Interacting Physical and Biological Processes Affecting Nutrient Transport Through Human Dominated Landscapes

    NASA Astrophysics Data System (ADS)

    Finlay, J. C.

    2015-12-01

    Human activities increasingly dominate biogeochemical cycles of limiting nutrients on Earth. Urban and agricultural landscapes represent the largest sources of excess nutrients that drive water quality degradation. The physical structure of both urban and agricultural watersheds has been extensively modified, and these changes have large impacts on water and nutrient transport. Despite strong physical controls over nutrient transport in human dominated landscapes, biological processes play important roles in determining the fates of both nitrogen and phosphorus. This talk uses examples from research in urban and agricultural watersheds in the Midwestern USA to illustrate interactions of physical and biological controls over nutrient cycles that have shifted nitrogen (N) and phosphorus (P) sources and cycling in unexpected ways in response to management changes. In urban watersheds, efforts to improve water quality have been hindered by legacy sources of phosphorus added to storm water through transport to drainage systems by vegetation. Similarly, reductions in field erosion in agricultural watersheds have not led to major reductions in phosphorus transport, because of continued release of biological sources of P. Where management of phosphorus has been most effective in reducing eutrophication of lakes, decreases in N removal processes have led to long term increases in N concentration and transport. Together, these examples show important roles for biological processes affecting nutrient movement in highly modified landscapes. Consideration of the downstream physical and biological responses of management changes are thus critical toward identification of actions that will most effectively reduce excess nutrients watersheds and coastal zones.

  14. Contaminant Transport Parameters for the Groundwater Flow and Contaminant Transport Model of Corrective Action Units 101 and 102: Central and Western Pahute Mesa, Nye County, Nevada, Revision 0

    SciTech Connect

    Drici, Warda

    2003-08-01

    This report documents the analysis of the available transport parameter data conducted in support of the development of a Corrective Action Unit (CAU) groundwater flow model for Central and Western Pahute Mesa: CAUs 101 and 102.

  15. Arsenic contamination: a potential hazard to the affected areas of West Bengal, India.

    PubMed

    Rahaman, Sefaur; Sinha, A C; Pati, R; Mukhopadhyay, D

    2013-02-01

    Arsenic contamination in groundwater is becoming more and more a worldwide problem. Nearing 50 million of people are at health risk from arsenic contamination at Ganga-Meghna-Bramhaputra basin. The experimental results of the five blocks under Malda district of West Bengal, India, showed that the arsenic concentration in groundwater (0.41-1.01 mg/l) was higher than the permissible limit for drinking water (0.01 mg/l) (WHO) and FAO (Food and Agriculture Organization) permissible limit for irrigation water (0.10 mg/l). The soil arsenic level (13.12 mg/kg) crossed the global average (10.0 mg/kg), but within the maximum acceptable limit for agricultural soil (20.0 mg/kg) recommended by the European Union. The total arsenic concentration on food crops varied from 0.000 to 1.464 mg/kg of dry weight. The highest mean arsenic concentration was found in potato (0.456 mg/kg), followed by rice grain (0.429 mg/kg). The total mean arsenic content (milligrams per kg dry weight) in cereals ranged from 0.121 to 0.429 mg/kg, in pulses and oilseeds ranged from 0.076 to 0.168 mg/kg, in tuber crops ranged from 0.243 to 0.456 mg/kg, in spices ranged from 0.031 to 0.175 mg/kg, in fruits ranged from 0.021 to 0.145 mg/kg and in vegetables ranged from 0.032 to 0.411 mg/kg, respectively. Hence, arsenic accumulation in cereals, pulses, oilseed, vegetables, spices, cole crop and fruits crop might not be safe in future without any sustainable mitigation strategies to avert the potential arsenic toxicity on the human health in the contaminated areas.

  16. Arsenic contamination: a potential hazard to the affected areas of West Bengal, India.

    PubMed

    Rahaman, Sefaur; Sinha, A C; Pati, R; Mukhopadhyay, D

    2013-02-01

    Arsenic contamination in groundwater is becoming more and more a worldwide problem. Nearing 50 million of people are at health risk from arsenic contamination at Ganga-Meghna-Bramhaputra basin. The experimental results of the five blocks under Malda district of West Bengal, India, showed that the arsenic concentration in groundwater (0.41-1.01 mg/l) was higher than the permissible limit for drinking water (0.01 mg/l) (WHO) and FAO (Food and Agriculture Organization) permissible limit for irrigation water (0.10 mg/l). The soil arsenic level (13.12 mg/kg) crossed the global average (10.0 mg/kg), but within the maximum acceptable limit for agricultural soil (20.0 mg/kg) recommended by the European Union. The total arsenic concentration on food crops varied from 0.000 to 1.464 mg/kg of dry weight. The highest mean arsenic concentration was found in potato (0.456 mg/kg), followed by rice grain (0.429 mg/kg). The total mean arsenic content (milligrams per kg dry weight) in cereals ranged from 0.121 to 0.429 mg/kg, in pulses and oilseeds ranged from 0.076 to 0.168 mg/kg, in tuber crops ranged from 0.243 to 0.456 mg/kg, in spices ranged from 0.031 to 0.175 mg/kg, in fruits ranged from 0.021 to 0.145 mg/kg and in vegetables ranged from 0.032 to 0.411 mg/kg, respectively. Hence, arsenic accumulation in cereals, pulses, oilseed, vegetables, spices, cole crop and fruits crop might not be safe in future without any sustainable mitigation strategies to avert the potential arsenic toxicity on the human health in the contaminated areas. PMID:22618763

  17. Quantitative Analysis of Major Factors Affecting Black Carbon Transport and Concentrations in the Unique Atmospheric Structures of Urban Environment

    NASA Astrophysics Data System (ADS)

    Liang, Marissa Shuang

    combined contribution from both traffic and atmospheric circulation accounted for observed spatiotemporal variability in PM2.5 concentrations. Based on these experimental and quantitative analyses, a three-dimensional model is proposed for contaminant's transport in highly urbanized Cincinnati region. Furthermore this dissertation explored implications on roadside pollutant evaluation, and on the risk analysis of future fuel substitution using biodiesel. The Gaussian-type models are poor in determining the effective emission factor particularly under nocturnal thermal inversion for which the effective emission factor is a function of lapse rate in the morning. The Gaussian models are applicable in daytime after the breakdown of thermal inversion. Lastly, among three types of fuels examined, the proposed butanol-added biodiesel-diesel blend (D80B15Bu5) yielded a good compromise between black carbon and NOx emissions while maintaining proper combustion properties. It is also found that the emission contained less black carbon and had higher organic carbon (OC) and elemental (EC) ratio than tested petroleum diesel. As demonstrated in other parts of this study, the OC-enriched emission will likely affect the black carbon occurrence and PM concentrations in the urban environments. Overall, it is suggested that urban formation and biofuel usage define the environmental impacts of black carbon, and are the focus for climate change mitigation and adaptation.

  18. Long-term transport behavior of psychoactive compounds in sewage-affected groundwater

    NASA Astrophysics Data System (ADS)

    Nham, Hang Thuy Thi; Greskowiak, Janek; Hamann, Enrico; Meffe, Raffaella; Hass, Ulrike; Massmann, Gudrun

    2016-09-01

    The present study provides a model-based characterization of the long-term transport behavior of five psychoactive compounds (meprobamate, pyrithyldione, primidone, phenobarbital and phenylethylmalonamide) introduced into groundwater via sewage irrigation in Berlin, Germany. Compounds are still present in the groundwater despite the sewage farm closure in the year 1980. Due to the limited information on (i) compound concentrations in the source water and (ii) substance properties, a total of 180 cross-sectional model realizations for each compound were carried out, covering a large range of possible parameter combinations. Results were compared with the present-day contamination patterns in the aquifer and the most likely scenarios were identified based on a number of model performance criteria. The simulation results show that (i) compounds are highly persistent under the present field conditions, and (ii) sorption is insignificant. Thus, back-diffusion from low permeability zones appears as the main reason for the compound retardation.

  19. Influence of surface water/groundwater interactions on stream and wetland water quality: analytical solutions for coupled contaminant transport equations

    NASA Astrophysics Data System (ADS)

    Melek Kazezyilmaz-Alhan, Cevza

    2014-05-01

    Wetlands are located in transitional zones between uplands and downstream flooded systems and surface water/groundwater interactions are frequently observed especially in riparian wetlands where the water level fluctuates frequently during the rainy season. Moreover, surface water/groundwater interactions also influence the characteristics of contaminant transport in pools and riffles, and in meandering type of streams. Therefore, it is important to investigate and solve these processes accurately to improve the prediction of downstream water quality. Although there are many experimental and numerical studies available in the literature which discuss and model the surface water/ground water interactions in streams and wetlands, very few analytical solutions have been conducted. Analytical solutions are helpful tools for verification of numerical solutions and they provide fast and accurate results for practical problems. Furthermore, they provide an understanding to the influence of each parameter in hydrological and contaminant transport models for streams and wetlands. In order to contribute to the research in understanding the behavior of water quality in streams and wetlands, analytical solutions are developed for the coupled contaminant transport equations of several transient storage and wetland models. Among these models are the wetland model WETland Solute TrANsport Dynamics (WETSAND) developed by Kazezyilmaz-Alhan et al. (2007), the transient storage models developed by Bencala and Walters (1983), and Kazezyilmaz-Alhan and Medina (2006). WETSAND is a general comprehensive wetland model, which has both surface flow and solute transport components. In this wetland model, water quality components are solved by advection-dispersion-reaction equations which incorporate surface water/groundwater interactions by including the incoming/outgoing mass due to the groundwater recharge/discharge. The transient storage model developed by Bencala and Walters (1983

  20. Monitoring Fish Contaminant Responses to Abatement Actions: Factors that Affect Recovery

    NASA Astrophysics Data System (ADS)

    Southworth, George R.; Peterson, Mark J.; Roy, W. Kelly; Mathews, Teresa J.

    2011-06-01

    Monitoring of contaminant accumulation in fish has been conducted in East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee since 1985. Bioaccumulation trends are examined over a twenty year period coinciding with major pollution abatement actions by a Department of Energy facility at the stream's headwaters. Although EFPC is enriched in many contaminants relative to other local streams, only polychlorinated biphenyls (PCBs) and mercury (Hg) were found to accumulate in the edible portions of fish to levels of human health concern. Mercury concentrations in redbreast sunfish were found to vary with season of collection, sex and size of individual fish. Over the course of the monitoring, waterborne Hg concentrations were reduced >80%; however, this did not translate into a comparable decrease in Hg bioaccumulation at most sites. Mercury bioaccumulation in fish did respond to decreased inputs in the industrialized headwater reach, but paradoxically increased in the lowermost reach of EFPC. As a result, the downstream pattern of Hg concentration in fish changed from one resembling dilution of a headwater point source in the 1980s to a uniform distribution in the 2000s. The reason for this remains unknown, but is hypothesized to involve changes in the chemical form and reactivity of waterborne Hg associated with the removal of residual chlorine and the addition of suspended particulates to the streamflow. PCB concentrations in fish varied greatly from year-to-year, but always exhibited a pronounced downstream decrease, and appeared to respond to management practices that limited episodic inputs from legacy sources within the facility.

  1. Monitoring Fish Contaminant Responses to Abatement Actions: Factors that Affect Recovery

    SciTech Connect

    Southworth, George R; Peterson, Mark J; Roy, W Kelly; Mathews, Teresa J

    2011-01-01

    Monitoring of contaminant accumulation in fish has been conducted in East Fork Poplar Creek (EFPC) in Oak Ridge, Tennessee since 1985. Bioaccumulation trends are examined over a twenty year period coinciding with major pollution abatement actions by a Department of Energy facility at the stream s headwaters. Although EFPC is enriched in many contaminants relative to other local streams, only polychlorinated biphenyls (PCBs) and mercury (Hg) were found to accumulate in the edible portions of fish to levels of human health concern. Mercury concentrations in redbreast sunfish were found to vary with season of collection, sex and size of individual fish. Over the course of the monitoring, waterborne Hg concentrations were reduced[80%; however, this did not translate into a comparable decrease in Hg bioaccumulation at most sites. Mercury bioaccumulation in fish did respond to decreased inputs in the industrialized headwater reach, but paradoxically increased in the lowermost reach of EFPC. As a result, the downstream pattern of Hg concentration in fish changed from one resembling dilution of a headwater point source in the 1980s to a uniform distribution in the 2000s. The reason for this remains unknown, but is hypothesized to involve changes in the chemical form and reactivity of waterborne Hg associated with the removal of residual chlorine and the addition of suspended particulates to the streamflow. PCB concentrations in fish varied greatly from year-to-year, but always exhibited a pronounced downstream decrease, and appeared to respond to management practices that limited episodic inputs from legacy sources within the facility.

  2. Growth and aggregation behavior of representative phytoplankton as affected by the environmental contaminant di-n-butyl phthalate

    SciTech Connect

    Acey, R.; Healy, P.; Unger, T.F.; Ford, C.E.; Hudson, R.A.

    1987-07-01

    The authors' continuing efforts to characterize the molecular basis for the development-stage-dependent phthalate ester toxicity in the brine shrimp, Artemia, led them to consider a number of microorganisms as foraging species for Artemia. The sensitivity of these microorganisms to phthalate esters was surprising and suggests that the nature and distribution of fresh water phytoplankton may already have been significantly altered by phthalates. The purpose of our experiments was to demonstrate the extent to which present levels of oceanic contamination by phthalates may be approaching those necessary to affect the distribution and survival of phytoplankton in the biosphere.

  3. Methane transport and emissions from soil as affected by water table and vascular plants

    PubMed Central

    2013-01-01

    Background The important greenhouse gas (GHG) methane is produced naturally in anaerobic wetland soils. By affecting the production, oxidation and transport of methane to the atmosphere, plants have a major influence upon the quantities emitted by wetlands. Different species and functional plant groups have been shown to affect these processes differently, but our knowledge about how these effects are influenced by abiotic factors such as water regime and temperature remains limited. Here we present a mesocosm experiment comparing eight plant species for their effects on internal transport and overall emissions of methane under contrasting hydrological conditions. To quantify how much methane was transported internally through plants (the chimney effect), we blocked diffusion from the soil surface with an agar seal. Results We found that graminoids caused higher methane emissions than forbs, although the emissions from mesocosms with different species were either lower than or comparable to those from control mesocosms with no plant (i.e. bare soil). Species with a relatively greater root volume and a larger biomass exhibited a larger chimney effect, though overall methane emissions were negatively related to plant biomass. Emissions were also reduced by lowering the water table. Conclusions We conclude that plant species (and functional groups) vary in the degree to which they transport methane to the atmosphere. However, a plant with a high capacity to transport methane does not necessarily emit more methane, as it may also cause more rhizosphere oxidation of methane. A shift in plant species composition from graminoids to forbs and/or from low to high productive species may lead to reduction of methane emissions. PMID:24010540

  4. Contamination, Transport, and Exposure Mapping and Assessment of Karst Groundwater Systems in Northern Puerto Rico Using GIS

    NASA Astrophysics Data System (ADS)

    Howard, J.; Schifman, L. A.; Irrizary, C.; Torres, P.; Padilla, I. Y.

    2011-12-01

    Ground waters from karst aquifer systems are one of the most important sources of freshwater worldwide and are highly vulnerable to both natural and anthropogenic contamination. Contaminants released into karst groundwater systems move through complex pathways from their sources to discharge areas of potential exposure. Points of exposure can include wells, springs, and surface waters that serve as drinking water sources. In Puerto Rico, the North Coast Limestone Aquifer System, which extends 90 miles across the north coast with an area of nearly 700 sq. miles, provides more than 50% of the potable water demand for industrial and drinking purposes. Historical reports from the 1980s revealed that volatile organic compounds, phthalates, and metals were close to or exceeded maximum contaminant levels. Exposure to such contaminants has been reported to cause reproductive and developmental issues, such as preterm birth. Since there is minimal understanding of the extent of contamination it is important to identify areas of potential concern. Preliminary analysis of 20 groundwater/springs and 20 tap water sites within the North Coast suggest that contamination is still a major concern. In addition, mixed effects models analyses suggest that >60% of pre-term birth rates may be explained by the presence of sites contaminated with volatile organic compounds, phthalates, and metals within the North Coast region. This presentation will focus primarily on how GIS was used as a tool for developing sampling strategies for collecting groundwater and tap water sources within the North Coast Limestone Aquifer System of Puerto Rico. In addition, the linkage of contamination, transport, and exposure to volatile organic compounds and phthalates will be addressed.

  5. Contamination of soil, medicinal, and fodder plants with lead and cadmium present in mine-affected areas, Northern Pakistan.

    PubMed

    Nawab, Javed; Khan, Sardar; Shah, Mohammad Tahir; Qamar, Zahir; Din, Islamud; Mahmood, Qaisar; Gul, Nayab; Huang, Qing

    2015-09-01

    This study aimed to investigate the lead (Pb) and cadmium (Cd) concentrations in the soil and plants (medicinal and fodder) grown in chromite mining-affected areas, Northern Pakistan. Soil and plant samples were collected and analyzed for Pb and Cd concentrations using atomic absorption spectrometer. Soil pollution load indices (PLIs) were greater than 2 for both Cd and Pb, indicating high level of contamination in the study area. Furthermore, Cd concentrations in the soil surrounding the mining sites exceeded the maximum allowable limit (MAL) (0.6 mg kg(-1)), while the concentrations of Pb were lower than the MAL (350 mg kg(-1)) set by State Environmental Protection Administration (SEPA) for agriculture soil. The concentrations of Cd and Pb were significantly higher (P < 0.001) in the soil of the mining-contaminated sites as compared to the reference site, which can be attributed to the dispersion of toxic heavy metals, present in the bed rocks and waste of the mines. The concentrations of Pb and Cd in majority of medicinal and fodder plant species grown in surrounding areas of mines were higher than their MALs set by World Health Organization/Food Agriculture Organization (WHO/FAO) for herbal (10 and 0.3 mg kg(-1), respectively) and edible (0.3 and 0.2 mg kg(-1), respectively) plants. The high concentrations of Cd and Pb may cause contamination of the food chain and health risk.

  6. Pore-scale experimental study of multiphase flow relevant to CO2 sequestration and biogeochemical reactive transport relevant to contaminant fate in the subsurface

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Oostrom, M.; Liu, C.

    2012-12-01

    Pore-scale micromodel experiments are being conducted at EMSL PNNL to gain better understanding of i) fundamental interfacial processes that control multiphase flow relevant to CO2 sequestration, and ii) biogeochemical reactive transport that affect the fate of contaminants in the subsurface. During the main drainage process, unstable capillary and viscous fingering mechanisms were observed in a nearly homogeneous micromodel and a dual-permeability micromodel that affect supercritical CO2 (scCO2, 9 MPa, 41 degree C) displacement of water from the pore space. During primary imbibition, water flooding of a micromodel partially saturated with scCO2 resulted in preferential dissolution of scCO2 (i.e., dissolution fingering). Micromodel experiments were also performed to investigate kinetics of reductive dissolution of hematite coating on grain surfaces when coupled with pore diffusion. Results showed hematite reduction rate in micropores where transport is dominated by diffusion is 1 to 2 orders of magnitude lower than macropores where transport is controlled by advection.

  7. Xenobiotic-contaminated diets affect hepatic lipid metabolism: Implications for liver steatosis in Sparus aurata juveniles.

    PubMed

    Maradonna, F; Nozzi, V; Santangeli, S; Traversi, I; Gallo, P; Fattore, E; Mita, D G; Mandich, A; Carnevali, O

    2015-10-01

    The metabolic effects induced by feed contaminated with a lower or a higher concentration of -nonylpnenol (NP), 4-tert-octylphenol (t-OP) or bisphenol A (BPA), three environmental endocrine disruptors, were assessed in juvenile sea bream liver. Histological analysis demonstrated that all these three xenobiotics induced hepatic lipid accumulation and steatosis. These findings prompted analysis of the expression of the major molecules involved in lipid metabolism: peroxisome proliferator activated receptors (which is encoded by ppars), fatty acid synthase (encoded by fas), lipoprotein lipase (encoded by lpl) and hormone-sensitive lipase (encoded by hsl). The enzymes encoded by ppars and fas are in fact responsible for lipid accumulation, whereas lpl- and hsl- encoded proteins play a pivotal role in fat mobilization. The three xenobiotics modulated ppar mRNA expression: pparα mRNA expression was induced by the higher dose of each contaminant; pparβ mRNA expression was upregulated by the lower doses and in BPA2 fish ppary mRNA overexpression was induced by all pollutants. These data agreed with the lipid accumulation profiles documented by histology. Fas mRNA levels were modulated by the two NP doses and the higher BPA concentration. Lpl mRNA was significantly upregulated in all experimental groups except for BPA1 fish while hsl mRNA was significantly downregulated in all groups except for t-OP2 and BPA1 fish. The plasma concentrations of cortisol, the primary stress biomarker, were correlated with the levels of pepck mRNA level. This gene encodes phosphoenolpyruvate carboxykinase which is one of the key enzymes of gluconeogenesis. Pepck mRNA was significantly overexpressed in fish exposed to NP2 and both t-OP doses. Finally, the genes encoding cyclooxygenase 2 (cox2) and 5-lipoxygenase (5 lox), the products of which are involved in the inflammatory response, transcriptions were significantly upregulated in NP and BPA fish, whereas they were unchanged in t

  8. Xenobiotic-contaminated diets affect hepatic lipid metabolism: Implications for liver steatosis in Sparus aurata juveniles.

    PubMed

    Maradonna, F; Nozzi, V; Santangeli, S; Traversi, I; Gallo, P; Fattore, E; Mita, D G; Mandich, A; Carnevali, O

    2015-10-01

    The metabolic effects induced by feed contaminated with a lower or a higher concentration of -nonylpnenol (NP), 4-tert-octylphenol (t-OP) or bisphenol A (BPA), three environmental endocrine disruptors, were assessed in juvenile sea bream liver. Histological analysis demonstrated that all these three xenobiotics induced hepatic lipid accumulation and steatosis. These findings prompted analysis of the expression of the major molecules involved in lipid metabolism: peroxisome proliferator activated receptors (which is encoded by ppars), fatty acid synthase (encoded by fas), lipoprotein lipase (encoded by lpl) and hormone-sensitive lipase (encoded by hsl). The enzymes encoded by ppars and fas are in fact responsible for lipid accumulation, whereas lpl- and hsl- encoded proteins play a pivotal role in fat mobilization. The three xenobiotics modulated ppar mRNA expression: pparα mRNA expression was induced by the higher dose of each contaminant; pparβ mRNA expression was upregulated by the lower doses and in BPA2 fish ppary mRNA overexpression was induced by all pollutants. These data agreed with the lipid accumulation profiles documented by histology. Fas mRNA levels were modulated by the two NP doses and the higher BPA concentration. Lpl mRNA was significantly upregulated in all experimental groups except for BPA1 fish while hsl mRNA was significantly downregulated in all groups except for t-OP2 and BPA1 fish. The plasma concentrations of cortisol, the primary stress biomarker, were correlated with the levels of pepck mRNA level. This gene encodes phosphoenolpyruvate carboxykinase which is one of the key enzymes of gluconeogenesis. Pepck mRNA was significantly overexpressed in fish exposed to NP2 and both t-OP doses. Finally, the genes encoding cyclooxygenase 2 (cox2) and 5-lipoxygenase (5 lox), the products of which are involved in the inflammatory response, transcriptions were significantly upregulated in NP and BPA fish, whereas they were unchanged in t

  9. Zero-tension lysimeters: An improved design to monitor colloid-facilitated contaminant transport in the vadose zone

    SciTech Connect

    Thompson, M.L.; Scharf, R.L.; Shang, C.

    1995-04-24

    There is increasing evidence that mobile colloids facilitate the long-distance transport of contaminants. The mobility of fine particles and macromolecules has been linked to the movement of actinides, organic contaminants, and heavy metals through soil. Direct evidence for colloid mobility includes the presence of humic materials in deep aquifers as well as coatings of accumulated clay, organic matter, or sesquioxides on particle or aggregate surfaces in subsoil horizons of many soils. The potential for colloid-facilitated transport of contaminants from hazardous-waste sites requires adequate monitoring before, during, and after in-situ remediation treatments. Zero-tension lysimeters (ZTLs) are especially appropriate for sampling water as it moves through saturated soil, although some unsaturated flow events may be sampled as well. Because no ceramic barrier or fiberglass wick is involved to maintain tension on the water (as is the case with other lysimeters), particles suspended in the water as well as dissolved species may be sampled with ZTLs. In this report, a ZTL design is proposed that is more suitable for monitoring colloid-facilitated contaminant migration. The improved design consists of a cylinder made of polycarbonate or polytetrafluoroethylene (PTFE) that is placed below undisturbed soil material. In many soils, a hydraulically powered tube may be used to extract an undisturbed core of soil before placement of the lysimeter. In those cases, the design has significant advantages over conventional designs with respect to simplicity and speed of installation. Therefore, it will allow colloid-facilitated transport of contaminants to be monitored at more locations at a given site.

  10. The Effect of Microbial Activity on Flow and Transport of an Organic Contaminant in Naturally Fractured Chalk Cores

    NASA Astrophysics Data System (ADS)

    Arnon, S.; Adar, E.; Ronen, Z.; Yakirevich, A.; Nativ, R.

    2001-12-01

    Low-permeability rock formations, such as chalk, are being selected as hydrogeological barriers for waste disposal sites and industrial areas throughout the world. Many sites constructed on chalk formations have failed due to existing fractures. Subsurface natural or enhanced microbial activity is the main biological process that causes transformation of organic contaminants in groundwater. However, this beneficial activity may result in physical, chemical, geological and biological changes affecting the hydrological properties of the fractured domain. Whereas these effects have been extensively investigated in porous media, they are less familiar in fractured formations, the topic of this work. A set of experiments was designed to quantify 2-D flow distribution along a single fracture and to assess the effect of biodegradation on its hydraulic properties. The experiments were carried out using 20-cm diameter and 30-50-cm long chalk cores, each intersected by a single natural fracture. Flow across the fracture was defined through both direct measurements of the out flux under various (controlled) hydraulic gradients, and through 2-D multi-tracer tests. The 2-D-distribution of flow in the fracture was investigated by injecting four non-reactive tracers (fluorobenzoic acids), each along a different section of the fracture inlet. Similarly, the outflux was sampled from four vertically aligned segments at the fracture outlet. Tracer breakthrough curves, mixing ratios and fluxes were evaluated for quantitative assessment of the 2-D flow distribution within the fracture. Results from the flow experiments suggested deviation from a linear relationship between the flux and the hydraulic gradient for Reynolds numbers exceeding 8, probably due to the increase of inertial forces. In addition, although flow out of the fracture was evenly distributed along the fracture width, different mixing ratios of tracers in neighboring sections were observed probably due to hydrodynamic

  11. Mercury Contamination in an Indicator Fish Species from Andean Amazonian Rivers Affected by Petroleum Extraction.

    PubMed

    Webb, Jena; Coomes, Oliver T; Mainville, Nicolas; Mergler, Donna

    2015-09-01

    Elevated mercury (Hg) concentrations in fish from Amazonia have been associated with gold-mining, hydroelectric dams and deforestation but few studies consider the role of petroleum extraction. Hg levels were determined in fish samples collected in three river basins in Ecuador and Peru with contrasting petroleum exploitation and land-use characteristics. The non-migratory, piscivorous species, Hoplias malabaricus, was used as a bioindicator. The rate of Hg increase with body weight for this species was significantly higher on the Corrientes River, near the site of a recent oil spill, than on the other two rivers. In the absence of substantial deforestation and other anthropogenic sources in the Corrientes River basin, this finding suggests that oil contamination in Andean Amazonia may have a significant impact on Hg levels in fish. PMID:26205230

  12. Mercury Contamination in an Indicator Fish Species from Andean Amazonian Rivers Affected by Petroleum Extraction.

    PubMed

    Webb, Jena; Coomes, Oliver T; Mainville, Nicolas; Mergler, Donna

    2015-09-01

    Elevated mercury (Hg) concentrations in fish from Amazonia have been associated with gold-mining, hydroelectric dams and deforestation but few studies consider the role of petroleum extraction. Hg levels were determined in fish samples collected in three river basins in Ecuador and Peru with contrasting petroleum exploitation and land-use characteristics. The non-migratory, piscivorous species, Hoplias malabaricus, was used as a bioindicator. The rate of Hg increase with body weight for this species was significantly higher on the Corrientes River, near the site of a recent oil spill, than on the other two rivers. In the absence of substantial deforestation and other anthropogenic sources in the Corrientes River basin, this finding suggests that oil contamination in Andean Amazonia may have a significant impact on Hg levels in fish.

  13. Factors affecting microbial 2,4,6-trinitrotoluene mineralization in contaminated soil

    USGS Publications Warehouse

    Bradley, P.M.; Chapelle, F.H.

    1995-01-01

    The influence of selected environmental factors on microbial TNT mineralization in soils collected from a TNT-contaminated site at Weldon Spring, MO, was examined using uniformly ring-labeled [14C]TNT. Microbial TNT mineralization was significantly inhibited by the addition of cellobiose and syringate. This response suggests that the indigenous microorganisms are capable of metabolizing TNT but preferentially utilize less recalcitrant substrates when available. The observed inhibition of TNT mineralization by TNT concentrations higher than 100 ??mol/kg of soil and by dry soil conditions suggests that toxic inhibition of microbial activity at high TNT concentrations and the periodic drying of these soils have contributed to the long-term persistence of TNT at Weldon Spring. In comparison to aerobic microcosms, mineralization was inhibited in anaerobic microcosms and in microcosms with a headspace of air amended with oxygen, suggesting that a mosaic of aerobic and anaerobic conditions may optimize TNT degradation at this site.

  14. [Factors affecting benzene diffusion from contaminated soils to the atmosphere and flux characteristics].

    PubMed

    Du, Ping; Wang, Shi-Jie; Zhao, Huan-Huan; Wu, Bin; Han, Chun-Mei; Fang, Ji-Dun; Li, Hui-Ying; Hosomi, Masaaki; Li, Fa-Sheng

    2013-12-01

    The influencing factors of benzene diffusion fluxes from sand and black soil to atmosphere were investigated using a flux chamber (30.0 cm x 17.5 cm x 29.0 cm). In this study, the benzene diffusion fluxes were estimated by measuring the benzene concentrations both in the headspace of the chamber and in the soils of different layers. The results indicated that the soil water content played an important role in benzene diffusion fluxes. The diffusion flux showed positive correlation with the initial benzene concentration and the benzene dissolution concentration for both soil types. The changes of air flow rate from 300 to 900 mL x min(-1) and temperature from 20 degrees C to 40 degrees C resulted in increases of the benzene diffusion flux. Our study of benzene diffusion fluxes from contaminated soils will be beneficial for the predicting model, and emergency management and precautions.

  15. Alternative Methods for Assessing Contaminant Transport from the Vadose Zone to Indoor Air

    NASA Astrophysics Data System (ADS)

    Baylor, K. J.; Lee, A.; Reddy, P.; Plate, M.

    2010-12-01

    Vapor intrusion, which is the transport of contaminant vapors from groundwater and the vadose zone to indoor air, has emerged as a significant human health risk near hazardous waste sites. Volatile organic compounds (VOCs) such as trichloroethylene (TCE) and tetrachloroethylene (PCE) can volatilize from groundwater and from residual sources in the vadose zone and enter homes and commercial buildings through cracks in the slab, plumbing conduits, or other preferential pathways. Assessment of the vapor intrusion pathway typically requires collection of groundwater, soil gas, and indoor air samples, a process which can be expensive and time-consuming. We evaluated three alternative vapor intrusion assessment methods, including 1) use of radon as a surrogate for vapor intrusion, 2) use of pressure differential measurements between indoor/outdoor and indoor/subslab to assess the potential for vapor intrusion, and 3) use of passive, longer-duration sorbent methods to measure indoor air VOC concentrations. The primary test site, located approximately 30 miles south of San Francisco, was selected due to the presence of TCE (10 - 300 ug/L) in shallow groundwater (5 to 10 feet bgs). At this test site, we found that radon was not a suitable surrogate to asses vapor intrusion and that pressure differential measurements are challenging to implement and equipment-intensive. More significantly, we found that the passive, longer-duration sorbent methods are easy to deploy and compared well quantitatively with standard indoor air sampling methods. The sorbent technique is less than half the cost of typical indoor air methods, and also provides a longer duration sample, typically 3 to 14 days rather than 8 to 24 hours for standard methods. The passive sorbent methods can be a reliable, cost-effective, and easy way to sample for TCE, PCE and other VOCs as part of a vapor intrusion investigation.

  16. Health risk assessment from contaminated foodstuffs: a field study in chromite mining-affected areas northern Pakistan.

    PubMed

    Nawab, Javed; Li, Gang; Khan, Sardar; Sher, Hassan; Aamir, Muhammad; Shamshad, Isha; Khan, Anwarzeb; Khan, Muhammad Amjad

    2016-06-01

    This study aimed to investigate the potential health risk associated with toxic metals in contaminated foodstuffs (fruits, vegetables, and cereals) collected from various agriculture fields present in chromite mining-affected areas of mafic and ultramafic terrains (northern Pakistan). The concentrations of Cr, Ni, Zn, Cd, and Pb were quantified in both soil and food samples. The soil samples were highly contaminated with Cr (320 mg/kg), Ni (108 mg/kg), and Cd (2.55 mg/kg), which exceeded their respective safe limits set by FAO/WHO. Heavy metal concentrations in soil were found in the order of Cr>Ni>Pb>Zn>Cd and showed significantly (p < 0.001) higher concentrations as compared to reference soil. The integrated pollution load index (PLI) value was observed greater than three indicating high level of contamination in the study area. The concentrations of Cr (1.80-6.99 mg/kg) and Cd (0.21-0.90 mg/kg) in foodstuffs exceeded their safe limits, while Zn, Pb, and Ni concentrations were observed within their safe limits. In all foodstuffs, the selected heavy metal concentrations were accumulated significantly (p < 0.001) higher as compared to the reference, while some heavy metals were observed higher but not significant like Zn in pear, persimmon, white mulberry, and date-plum; Cd in pear, fig and white mulberry; and Pb in walnut, fig, and pumpkin. The health risk assessment revealed no potential risk for both adults and children for the majority of heavy metals, except Cd, which showed health risk index (HRI) >1 for children and can pose potential health threats for local inhabitants. Graphical Abstract Heavy metals released from chromite mining lead to soil and foodstuff contamination and human health risk.

  17. Health risk assessment from contaminated foodstuffs: a field study in chromite mining-affected areas northern Pakistan.

    PubMed

    Nawab, Javed; Li, Gang; Khan, Sardar; Sher, Hassan; Aamir, Muhammad; Shamshad, Isha; Khan, Anwarzeb; Khan, Muhammad Amjad

    2016-06-01

    This study aimed to investigate the potential health risk associated with toxic metals in contaminated foodstuffs (fruits, vegetables, and cereals) collected from various agriculture fields present in chromite mining-affected areas of mafic and ultramafic terrains (northern Pakistan). The concentrations of Cr, Ni, Zn, Cd, and Pb were quantified in both soil and food samples. The soil samples were highly contaminated with Cr (320 mg/kg), Ni (108 mg/kg), and Cd (2.55 mg/kg), which exceeded their respective safe limits set by FAO/WHO. Heavy metal concentrations in soil were found in the order of Cr>Ni>Pb>Zn>Cd and showed significantly (p < 0.001) higher concentrations as compared to reference soil. The integrated pollution load index (PLI) value was observed greater than three indicating high level of contamination in the study area. The concentrations of Cr (1.80-6.99 mg/kg) and Cd (0.21-0.90 mg/kg) in foodstuffs exceeded their safe limits, while Zn, Pb, and Ni concentrations were observed within their safe limits. In all foodstuffs, the selected heavy metal concentrations were accumulated significantly (p < 0.001) higher as compared to the reference, while some heavy metals were observed higher but not significant like Zn in pear, persimmon, white mulberry, and date-plum; Cd in pear, fig and white mulberry; and Pb in walnut, fig, and pumpkin. The health risk assessment revealed no potential risk for both adults and children for the majority of heavy metals, except Cd, which showed health risk index (HRI) >1 for children and can pose potential health threats for local inhabitants. Graphical Abstract Heavy metals released from chromite mining lead to soil and foodstuff contamination and human health risk. PMID:26971962

  18. Arbuscular mycorrhiza affects nickel translocation and expression of ABC transporter and metallothionein genes in Festuca arundinacea.

    PubMed

    Shabani, Leila; Sabzalian, Mohammad R; Mostafavi pour, Sodabeh

    2016-01-01

    Mycorrhizal fungi are key microorganisms for enhancing phytoremediation of soils contaminated with heavy metals. In this study, the effects of the arbuscular mycorrhizal fungus (AMF) Funneliformis mosseae (=Glomus mosseae) on physiological and molecular mechanisms involved in the nickel (Ni) tolerance of tall fescue (Festuca arundinacea = Schedonorus arundinaceus) were investigated. Nickel addition had a pronounced negative effect on tall fescue growth and photosynthetic pigment contents, as well as on AMF colonization. Phosphorus content increased markedly in mycorrhizal plants (M) compared to non-inoculated (NM) ones. However, no significant difference was observed in root carbohydrate content between AMF-inoculated and non-inoculated plants. For both M and NM plants, Ni concentrations in shoots and roots increased according to the addition of the metal into soil, but inoculation with F. mosseae led to significantly lower Ni translocation from roots to the aboveground parts compared to non-inoculated plants. ABC transporter and metallothionein transcripts accumulated to considerably higher levels in tall fescue plants colonized by F. mosseae than in the corresponding non-mycorrhizal plants. These results highlight the importance of mycorrhizal colonization in alleviating Ni-induced stress by reducing Ni transport from roots to shoots of tall fescue plants.

  19. Development of RWHet to Simulate Contaminant Transport in Fractured Porous Media

    SciTech Connect

    Zhang, Yong; LaBolle, Eric; Reeves, Donald M; Russell, Charles

    2012-07-01

    Accurate simulation of matrix diffusion in regional-scale dual-porosity and dual-permeability media is a critical issue for the DOE Underground Test Area (UGTA) program, given the prevalence of fractured geologic media on the Nevada National Security Site (NNSS). Contaminant transport through regional-scale fractured media is typically quantified by particle-tracking based Lagrangian solvers through the inclusion of dual-domain mass transfer algorithms that probabilistically determine particle transfer between fractures and unfractured matrix blocks. UGTA applications include a wide variety of fracture aperture and spacing, effective diffusion coefficients ranging four orders of magnitude, and extreme end member retardation values. This report incorporates the current dual-domain mass transfer algorithms into the well-known particle tracking code RWHet [LaBolle, 2006], and then tests and evaluates the updated code. We also develop and test a direct numerical simulation (DNS) approach to replace the classical transfer probability method in characterizing particle dynamics across the fracture/matrix interface. The final goal of this work is to implement the algorithm identified as most efficient and effective into RWHet, so that an accurate and computationally efficient software suite can be built for dual-porosity/dual-permeability applications. RWHet is a mature Lagrangian transport simulator with a substantial user-base that has undergone significant development and model validation. In this report, we also substantially tested the capability of RWHet in simulating passive and reactive tracer transport through regional-scale, heterogeneous media. Four dual-domain mass transfer methodologies were considered in this work. We first developed the empirical transfer probability approach proposed by Liu et al. [2000], and coded it into RWHet. The particle transfer probability from one continuum to the other is proportional to the ratio of the mass entering the other

  20. STRUCTURE AND FUNCTION OF SUBSURFACE MICROBIAL COMMUNITIES AFFECTING RADIONUCLIDE TRANSPORT AND BIOIMMOBILIZATION

    SciTech Connect

    Joel E. Kostka; Lee Kerkhof; Kuk-Jeong Chin; Martin Keller; Joseph W. Stucki

    2011-06-15

    The objectives of this project were to: (1) isolate and characterize novel anaerobic prokaryotes from subsurface environments exposed to high levels of mixed contaminants (U(VI), nitrate, sulfate), (2) elucidate the diversity and distribution of metabolically active metal- and nitrate-reducing prokaryotes in subsurface sediments, and (3) determine the biotic and abiotic mechanisms linking electron transport processes (nitrate, Fe(III), and sulfate reduction) to radionuclide reduction and immobilization. Mechanisms of electron transport and U(VI) transformation were examined under near in situ conditions in sediment microcosms and in field investigations at the Oak Ridge Field Research Center (ORFRC), in Oak Ridge, Tennessee, where the subsurface is exposed to mixed contamination predominated by uranium and nitrate. A total of 20 publications (16 published or 'in press' and 4 in review), 10 invited talks, and 43 contributed seminars/ meeting presentations were completed during the past four years of the project. PI Kostka served on one proposal review panel each year for the U.S. DOE Office of Science during the four year project period. The PI leveraged funds from the state of Florida to purchase new instrumentation that aided the project. Support was also leveraged by the PI from the Joint Genome Institute in the form of two successful proposals for genome sequencing. Draft genomes are now available for two novel species isolated during our studies and 5 more genomes are in the pipeline. We effectively addressed each of the three project objectives and research highlights are provided. Task I - Isolation and characterization of novel anaerobes: (1) A wide range of pure cultures of metal-reducing bacteria, sulfate-reducing bacteria, and denitrifying bacteria (32 strains) were isolated from subsurface sediments of the Oak Ridge Field Research Center (ORFRC), where the subsurface is exposed to mixed contamination of uranium and nitrate. These isolates which are new

  1. The assessment of heat transport circuit: Contamination at Candu 600 reactor

    SciTech Connect

    Barariu, G.; Bican, M.; Dogaru, D.

    1994-12-31

    The radioactive contamination of inner surfaces of the PHT circuit in normal operation is being produced by deposits from the coolant (D{sub 2}O) of activated and fission products. In order to determine the modifications of circuit contamination that can arise by changing the standard operation parameters, preliminary calculations have been effected taking into account the determinative physico-chemical parameters.

  2. Factors affecting xylene-contaminated air removal by the ornamental plant Zamioculcas zamiifolia.

    PubMed

    Sriprapat, Wararat; Boraphech, Phattara; Thiravetyan, Paitip

    2014-02-01

    Fifteen plant species-Alternanthera bettzickiana, Drimiopsis botryoides, Aloe vera, Chlorophytum comosum, Aglaonema commutatum, Cordyline fruticosa, Philodendron martianum, Sansevieria hyacinthoides, Aglaonema rotundum, Fittonia albivenis, Muehlenbeckia platyclada, Tradescantia spathacea, Guzmania lingulata, Zamioculcas zamiifolia, and Cyperus alternifolius-were evaluated for the removal efficiency of xylene from contaminated air. Among the test plants, Z. zamiifolia showed the highest xylene removal efficiency. Xylene was toxic to Z. zamiifolia with an LC50 of 3,464 ppm. Higher concentrations of xylene exhibited damage symptoms, including leaf tips turning yellow, holonecrosis, and hydrosis. TEM images showed that a low concentration of xylene vapors caused minor changes in the chloroplast, while a high concentration caused swollen chloroplasts and damage. The effect of photosynthetic types on xylene removal efficiency suggests that a mixture of Z. zamiifolia, S. hyacinthoides, and A. commutatum which represent facultative CAM, CAM, and C3 plants, is the most suitable system for xylene removal. Therefore, for maximum improvement in removing xylene volatile compounds under various conditions, multiple species are needed. The effect of a plant's total leaf area on xylene removal indicates that at lower concentrations of xylene, a small leaf area might be as efficient as a large leaf area.

  3. Contaminating levels of zinc found in commonly-used labware and buffers affect glycine receptor currents

    PubMed Central

    Cornelison, Garrett L.; Mihic, S. John

    2013-01-01

    Zinc is an allosteric modulator of glycine receptor function, enhancing the effects of glycine at nM to low μM concentrations, and inhibiting its effects at higher concentrations. Because of zinc’s high potency at the glycine receptor, there exists a possibility that effects attributed solely to exogenously-applied glycine in fact contain an undetected contribution of zinc acting as an allosteric modulator. We found that glycine solutions made up in standard buffers and using deionized distilled water produced effects that could be decreased by the zinc chelator tricine. This phenomenon was observed in three different vials tested and persisted even if vials were extensively washed, suggesting the zinc was probably present in the buffer constituents. In addition, polystyrene, but not glass, pipets bore a contaminant that enhanced glycine receptor function and that could also be antagonized by tricine. Our findings suggest that without checking for this effect using a chelator such as tricine, one cannot assume that responses elicited by glycine applied alone are not necessarily also partially due to some level of allosteric modulation by zinc. PMID:24177173

  4. Contaminating levels of zinc found in commonly-used labware and buffers affect glycine receptor currents.

    PubMed

    Cornelison, Garrett L; Mihic, S John

    2014-01-01

    Zinc is an allosteric modulator of glycine receptor function, enhancing the effects of glycine at nM to low μM concentrations, and inhibiting its effects at higher concentrations. Because of zinc's high potency at the glycine receptor, there exists a possibility that effects attributed solely to exogenously-applied glycine in fact contain an undetected contribution of zinc acting as an allosteric modulator. We found that glycine solutions made up in standard buffers and using deionized distilled water produced effects that could be decreased by the zinc chelator tricine. This phenomenon was observed in three different vials tested and persisted even if vials were extensively washed, suggesting the zinc was probably present in the buffer constituents. In addition, polystyrene, but not glass, pipets bore a contaminant that enhanced glycine receptor function and that could also be antagonized by tricine. Our findings suggest that without checking for this effect using a chelator such as tricine, one cannot assume that responses elicited by glycine applied alone are not necessarily also partially due to some level of allosteric modulation by zinc.

  5. Factors affecting xylene-contaminated air removal by the ornamental plant Zamioculcas zamiifolia.

    PubMed

    Sriprapat, Wararat; Boraphech, Phattara; Thiravetyan, Paitip

    2014-02-01

    Fifteen plant species-Alternanthera bettzickiana, Drimiopsis botryoides, Aloe vera, Chlorophytum comosum, Aglaonema commutatum, Cordyline fruticosa, Philodendron martianum, Sansevieria hyacinthoides, Aglaonema rotundum, Fittonia albivenis, Muehlenbeckia platyclada, Tradescantia spathacea, Guzmania lingulata, Zamioculcas zamiifolia, and Cyperus alternifolius-were evaluated for the removal efficiency of xylene from contaminated air. Among the test plants, Z. zamiifolia showed the highest xylene removal efficiency. Xylene was toxic to Z. zamiifolia with an LC50 of 3,464 ppm. Higher concentrations of xylene exhibited damage symptoms, including leaf tips turning yellow, holonecrosis, and hydrosis. TEM images showed that a low concentration of xylene vapors caused minor changes in the chloroplast, while a high concentration caused swollen chloroplasts and damage. The effect of photosynthetic types on xylene removal efficiency suggests that a mixture of Z. zamiifolia, S. hyacinthoides, and A. commutatum which represent facultative CAM, CAM, and C3 plants, is the most suitable system for xylene removal. Therefore, for maximum improvement in removing xylene volatile compounds under various conditions, multiple species are needed. The effect of a plant's total leaf area on xylene removal indicates that at lower concentrations of xylene, a small leaf area might be as efficient as a large leaf area. PMID:24091527

  6. Epoxyeicosatrienoic Acids Affect Electrolyte Transport in Renal Tubular Epithelial Cells: Dependence on Cyclooxygenase and Cell Polarity

    PubMed Central

    Nüsing, Rolf M.; Schweer, Horst; Fleming, Ingrid; Zeldin, Darryl C.; Wegmann, Markus

    2007-01-01

    We investigated the effects of epoxyeicosatrienoic acids (EETs) on ion transport in the polarized renal distal tubular cell line, MDCK C7. Of the four EET regioisomers (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) studied, only apical, but not basolateral, application of 5,6-EET increased short circuit current (Isc) with kinetics similar to those of arachidonic acid. The ion transport was blocked by preincubation with the cyclooxygenase inhibitor indomethacin or with the chloride channel blocker NPPB. Further, both a Cl−-free bath solution and the Ca2+ antagonist verapamil blocked 5,6-EET-induced ion transport. Although the presence of the PGE2 receptors EP2, EP3, and EP4 was demonstrated, apically added PGE2 was ineffective and basolaterally added PGE2 caused a different kinetics in ion transport compared to 5,6-EET. Moreover, PGE2 sythesis in MDCK C7 cells was unaffected by 5,6-EET treatment. GC/MS/MS analysis of cell supernatants revealed the presence of the biologically inactive 5,6-dihydroxy-PGE1 in 5,6-EET-treated cells, but not in control cells. Indomethacin suppressed the formation of 5,6-dihydroxy-PGE1. 5,6-epoxy-PGE1 the precursor of 5,6-dihydroxy-PGE1, caused a similar ion transport as 5,6-EET. Cytochrome P450 enzymes homolog to human CYP2C8, CYP2C9, and CYP2J2 protein were detected immunologically in the MDCK C7 cells. Our findings suggest that 5,6-EET affects Cl-transport in renal distal tubular cells independent of PGE2 but by a mechanism, dependent on its conversion to 5,6-epoxy-PGE1 by cyclooxygenase. We suggest a role for this P450 epoxygenase product in the regulation of electrolyte transport, especially as a saluretic compound acting from the luminal side of tubular cells in the mammalian kidney. PMID:17494091

  7. Long-term environmental and health implications of morphological change and sediment transport with respect to contaminants

    NASA Astrophysics Data System (ADS)

    Sneddon, Christopher; Copplestone, David; Tyler, Andrew; Hunter, Peter; Smith, Nick

    2014-05-01

    The EPSRC-funded Adaptation and Resilience of Coastal Energy Supply (ARCoES) project encompasses four research strands, involving 14 institutions and six PhD studentships. ARCoES aims to determine the threats posed to future energy generation and the distribution network by flooding and erosion, changing patterns of coastal sedimentation, water temperature and the distribution of plants and animals in the coastal zone. Whilst this research has direct benefits for the operation of coastal power stations, ARCoES aims to have a wider stakeholder engagement through assessing how the resilience of coastal communities may be altered by five hundred years of coastal evolution. Coastal evolution will have substantial implications for the energy sector of the North West of England as former waste storage sites are eroded and remobilised within the intertidal environment. The current intertidal environmental stores of radioactivity will also experience reworking as ocean chemistry changes and saltmarsh chronologies are reworked in response to rising sea levels. There is a duel requirement to understand mass sediment movement along the North West coast of England as understanding the sediment transport dynamics is key to modelling long term coastal change and understanding how the environmental store of radioactivity will be reworked. The University of Stirling is researching the long-term environmental and health implications of remobilisation and transport of contaminated sediments around the UK coastline. Using a synergy of hyperspectral and topographic information the mobilisation of sediment bound contaminants within the coastal environment will be investigated. Potential hazards posed by contaminants are determined by a set of environmental impact test criteria which evaluate the bio-accessibility and ionising dose of contaminants. These test criteria will be used to comment on the likely environmental impact of modelled sediment transport and anticipated changes in

  8. A whole cell bioreporter approach to assess transport and bioavailability of organic contaminants in water unsaturated systems.

    PubMed

    Schamfuß, Susan; Neu, Thomas R; Harms, Hauke; Wick, Lukas Y

    2014-01-01

    Bioavailability of contaminants is a prerequisite for their effective biodegradation in soil. The average bulk concentration of a contaminant, however, is not an appropriate measure for its availability; bioavailability rather depends on the dynamic interplay of potential mass transfer (flux) of a compound to a microbial cell and the capacity of the latter to degrade the compound. In water-unsaturated parts of the soil, mycelia have been shown to overcome bioavailability limitations by actively transporting and mobilizing organic compounds over the range of centimeters. Whereas the extent of mycelia-based transport can be quantified easily by chemical means, verification of the contaminant-bioavailability to bacterial cells requires a biological method. Addressing this constraint, we chose the PAH fluorene (FLU) as a model compound and developed a water unsaturated model microcosm linking a spatially separated FLU point source and the FLU degrading bioreporter bacterium Burkholderia sartisoli RP037-mChe by a mycelial network of Pythium ultimum. Since the bioreporter expresses eGFP in response of the PAH flux to the cell, bacterial FLU exposure and degradation could be monitored directly in the microcosms via confocal laser scanning microscopy (CLSM). CLSM and image analyses revealed a significant increase of the eGFP expression in the presence of P. ultimum compared to controls without mycelia or FLU thus indicating FLU bioavailability to bacteria after mycelia-mediated transport. CLSM results were supported by chemical analyses in identical microcosms. The developed microcosm proved suitable to investigate contaminant bioavailability and to concomitantly visualize the involved bacteria-mycelial interactions. PMID:25590867

  9. Fish bioturbation of cadmium-contaminated sediments: Factors affecting Cd availability to Daphnia magna

    SciTech Connect

    Wall, S.B.; La Point, T.W.; Isely, J.J.

    1996-03-01

    Benthic fish bioturbation of contaminated sediments is thought to enhance exposure and, potentially, bioaccumulation into planktonic organisms. Exposures were conducted with cadmium-spiked sediment, 1.0 mg/kg nominal concentrations, and koi carp (Cyprinus carpio). Daphnia magna were placed in aquaria with and without fish for 6 d and Cd bioaccumulation was measured every 48 h. Koi carp bioturbation increased mean total suspended solids (TSS) in two trials from 0.001 mg/L to 44.4 mg/L and 19.2 mg/L to 762.4 mg/L. Mean aqueous Cd concentrations increased from1.4 {micro}g/L to 2.8 {micro}g/L, and from 1.6 {micro}g/L to 13.2 {micro}g/L. Cadmium binding capacity increased from 28.9 {micro}g/L to 169.8 {micro}g/L in with-fish treatments when compared to controls. However, Daphnia magna body burdens did not increase. Mean Cd residues of daphnids exposed with fish, 9.2 {micro}g/g, were not statistically different from without-fish exposures, 8.0 {micro}g/g. Body burdens slightly decreased in the first trial after the with-fish treatment, 9.4 {micro}g/g to 8.3 {micro}g/g. Fish size was partially correlated with TSS and aqueous Cd concentrations and TSS positively correlated with binding capacity. Because increased TSS in the with-fish treatment resulted in increased binding capacity, it is probable that cadmium bioavailability decreased. Although koi carp were capable of remobilizing Cd from sediment, Cd bioaccumulation into Daphnia magna was not significant.

  10. Probing Contaminant Transport to and from Clay Surfaces in Organic Solvents and Water Using Solution Calorimetry.

    PubMed

    Pourmohammadbagher, Amin; Shaw, John M

    2015-09-15

    Clays, in tailings, are a significant ongoing environmental concern in the mining and oilsands production industries, and clay rehabilitation following contamination poses challenges episodically. Understanding the fundamentals of clay behavior can lead to better environmental impact mitigation strategies. Systematic calorimetric measurements are shown to provide a framework for parsing the synergistic and antagonistic impacts of trace (i.e., parts per million level) components on the surface compositions of clays. The enthalpy of solution of as-received and "contaminated" clays, in as-received and "contaminated" organic solvents and water, at 60 °C and atmospheric pressure, provides important illustrative examples. Clay contamination included pre-saturation of clays with water and organic liquids. Solvent contamination included the addition of trace water to organic solvents and trace organic liquids to water. Enthalpy of solution outcomes are interpreted using a quantitative mass and energy balance modeling framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Underlying surface energies are shown to dominate the energetics of the solvent-clay interaction, and organic liquids as solvents or as trace contaminants are shown to displace water from as-received clay surfaces. This approach can be readily extended to include pH, salts, or other effects and is expected to provide mechanistic and quantitative insights underlying the stability of clays in tailings ponds and the behaviors of clays in diverse industrial and natural environments.

  11. Probing Contaminant Transport to and from Clay Surfaces in Organic Solvents and Water Using Solution Calorimetry.

    PubMed

    Pourmohammadbagher, Amin; Shaw, John M

    2015-09-15

    Clays, in tailings, are a significant ongoing environmental concern in the mining and oilsands production industries, and clay rehabilitation following contamination poses challenges episodically. Understanding the fundamentals of clay behavior can lead to better environmental impact mitigation strategies. Systematic calorimetric measurements are shown to provide a framework for parsing the synergistic and antagonistic impacts of trace (i.e., parts per million level) components on the surface compositions of clays. The enthalpy of solution of as-received and "contaminated" clays, in as-received and "contaminated" organic solvents and water, at 60 °C and atmospheric pressure, provides important illustrative examples. Clay contamination included pre-saturation of clays with water and organic liquids. Solvent contamination included the addition of trace water to organic solvents and trace organic liquids to water. Enthalpy of solution outcomes are interpreted using a quantitative mass and energy balance modeling framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Underlying surface energies are shown to dominate the energetics of the solvent-clay interaction, and organic liquids as solvents or as trace contaminants are shown to displace water from as-received clay surfaces. This approach can be readily extended to include pH, salts, or other effects and is expected to provide mechanistic and quantitative insights underlying the stability of clays in tailings ponds and the behaviors of clays in diverse industrial and natural environments. PMID:26296102

  12. A Two-Dimensional Model for the Analysis of Contaminant Transport in a Fractured Porous Medium.

    1991-03-05

    CHAINT-MC is a two-dimensional finite element model applicable to the transport of a dissolved radionuclide in a fractured porous medium along with radioactive chain decay and subsequent transport of the dissolved daughters.

  13. Defective copper transport in the copt5 mutant affects cadmium tolerance.

    PubMed

    Carrió-Seguí, Angela; Garcia-Molina, Antoni; Sanz, Amparo; Peñarrubia, Lola

    2015-03-01

    Cadmium toxicity interferes with essential metal homeostasis, which is a problem for both plant nutrition and the consumption of healthy food by humans. Copper uptake is performed by the members of the Arabidopsis high affinity copper transporter (COPT) family. One of the members, COPT5, is involved in copper recycling from the vacuole toward the cytosolic compartment. We show herein that copt5 mutants are more sensitive to cadmium stress than wild-type plants, as indicated by reduced growth. Exacerbated cadmium toxicity in copt5 mutants is due specifically to altered copper traffic through the COPT5 transporter. Three different processes which have been shown to affect cadmium tolerance are altered in copt5 mutants. First, ethylene biosynthesis diminishes under copper deficiency and, in the presence of cadmium, ethylene production diminishes further. Copper deficiency responses are also attenuated under cadmium treatment. Remarkably, while copt5 roots present higher oxidative stress toxicity symptoms than controls, aerial copt5 parts display lower oxidative stress, as seen by reduced cadmium delivery to shoots. Taken together, these results demonstrate that copper transport plays a key role in cadmium resistance, and suggest that oxidative stress triggers an NADPH oxidase-mediated signaling pathway, which contributes to cadmium translocation and basal plant resistance. The slightly lower cadmium levels that reach aerial parts in the copt5 mutants, irrespective of the copper content in the media, suggest a new biotechnological approach to minimize toxic cadmium entry into food chains.

  14. Transport and transformation of pharmaceuticals and other contaminants of emerging concern from wastewater discharge through surface water to drinking water intake and treatment

    EPA Science Inventory

    The ubiquitous presence of pharmaceuticals, hormones, and other contaminants of emerging concern (CECs) in surface-water resources have necessitated research that better elucidates pathways of transport and transformation for these compounds from their discharged wastewater, thro...

  15. Interaction of environmental contaminants with zebrafish organic anion transporting polypeptide, Oatp1d1 (Slco1d1)

    SciTech Connect

    Popovic, Marta; Zaja, Roko; Fent, Karl; Smital, Tvrtko

    2014-10-01

    Polyspecific transporters from the organic anion transporting polypeptide (OATP/Oatp) superfamily mediate the uptake of a wide range of compounds. In zebrafish, Oatp1d1 transports conjugated steroid hormones and cortisol. It is predominantly expressed in the liver, brain and testes. In this study we have characterized the transport of xenobiotics by the zebrafish Oatp1d1 transporter. We developed a novel assay for assessing Oatp1d1 interactors using the fluorescent probe Lucifer yellow and transient transfection in HEK293 cells. Our data showed that numerous environmental contaminants interact with zebrafish Oatp1d1. Oatp1d1 mediated the transport of diclofenac with very high affinity, followed by high affinity towards perfluorooctanesulfonic acid (PFOS), nonylphenol, gemfibrozil and 17α-ethinylestradiol; moderate affinity towards carbaryl, diazinon and caffeine; and low affinity towards metolachlor. Importantly, many environmental chemicals acted as strong inhibitors of Oatp1d1. A strong inhibition of Oatp1d1 transport activity was found by perfluorooctanoic acid (PFOA), chlorpyrifos-methyl, estrone (E1) and 17β-estradiol (E2), followed by moderate to low inhibition by diethyl phthalate, bisphenol A, 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4 tetrahydronapthalene and clofibrate. In this study we identified Oatp1d1 as a first Solute Carrier (SLC) transporter involved in the transport of a wide range of xenobiotics in fish. Considering that Oatps in zebrafish have not been characterized before, our work on zebrafish Oatp1d1 offers important new insights on the understanding of uptake processes of environmental contaminants, and contributes to the better characterization of zebrafish as a model species. - Highlights: • We optimized a novel assay for determination of Oatp1d1 interactors • Oatp1d1 is the first SLC characterized fish xenobiotic transporter • PFOS, nonylphenol, diclofenac, EE2, caffeine are high affinity Oatp1d1substrates • PFOA, chlorpyrifos

  16. The DOE Vadose Zone Science and Technology Roadmap: A National Program to Address Characeterization, Monitoring and Simulation of Subsurface Contaminant Fate and Transport

    SciTech Connect

    Kowall, Stephen Jacob

    2001-02-01

    The vadose zone comprises the region lying between the earth’s surface and the top of the regional seasonal aquifer. Until recently contamination in the vadose zone was believed to remain relatively immobile. Thus, little attention was paid to understanding the nature of the vadose zone or the potential pathways for contaminants to migrate through it to the water table or other accessible environments. However, recent discoveries of contaminants migrating considerable distances through the vadose zone at several Department of Energy (DOE) sites have changed many assumptions both about the nature and function of the vadose zone and the importance we place on understanding this region. As a result of several vadose zone surprises, DOE Environmental Management (EM) tasked the Idaho National Engineering and Environmental Laboratory (INEEL) to lead the development of a vadose zone science and technology roadmap. The roadmap is focused on identifying research spanning the next 25 years necessary to be able to better predict the fate and transport of contaminants in the vadose zone. This in turn will provide the basis for reducing scientific uncertainty in environmental remediation and, especially, vadose zone related long-term stewardship decisions across the DOE complex. Vadose zone issues are now recognized as a national problem affecting other federal agencies as well as state and municipal sites with similar problems. Over the next few decades, dramatic and fundamental advances in computing, communication, electronics and micro-engineered systems will transform our understanding of many aspects of the scientific and technical challenges we face today. The roadmap will serve to develop a common perspective on possible future science and technology needs in an effort to help make better R&D investment decisions.

  17. Elevated CO2 affects secondary metabolites in Robinia pseudoacacia L. seedlings in Cd- and Pb-contaminated soils.

    PubMed

    Jia, Xia; Zhao, Yonghua; Liu, Tuo; Huang, Shuping

    2016-10-01

    Secondary metabolites play important roles in plant interactions with the environment. The co-occurrence of heavy metal contamination of soils and rising atmospheric CO2 has important effects on plant. It is important to explore the ways in which production of plant secondary metabolites is affected by heavy metals under elevated atmospheric CO2. We examined the effects of elevated CO2 on secondary metabolite contents in Robinia pseudoacacia seedlings grown in Cd- and lead (Pb)-contaminated soils. The increase in secondary metabolites was greater under Cd + Pb exposure than under exposure to individual metals regardless of elevated CO2 with the exception of condensed tannins in leaves and total alkaloids in stems. Except for phenolic compounds and condensed tannins, elevated CO2 was associated with increased secondary metabolite contents in leaves and stems of plants exposed to Cd, Pb, and Cd + Pb compared to plants exposed to ambient CO2 + metals. Changes in saponins in leaves and alkaloids in stems were greater than changes in the other secondary metabolites. Significant interactive effects of CO2, Cd, and Pb on secondary metabolites were observed. Saponins in leaves and alkaloids in stems were more sensitive than other secondary metabolites to elevated CO2 + Cd + Pb. Elevated CO2 could modulate plant protection and defense mechanisms in R. pseudoacacia seedlings exposed to heavy metals by altering the production of secondary metabolites. The increased Cd and Pb uptake under elevated CO2 suggested that R. pseudoacacia may be used in the phytoremediation of heavy metal-contaminated soils under global environmental scenarios.

  18. Elevated CO2 affects secondary metabolites in Robinia pseudoacacia L. seedlings in Cd- and Pb-contaminated soils.

    PubMed

    Jia, Xia; Zhao, Yonghua; Liu, Tuo; Huang, Shuping

    2016-10-01

    Secondary metabolites play important roles in plant interactions with the environment. The co-occurrence of heavy metal contamination of soils and rising atmospheric CO2 has important effects on plant. It is important to explore the ways in which production of plant secondary metabolites is affected by heavy metals under elevated atmospheric CO2. We examined the effects of elevated CO2 on secondary metabolite contents in Robinia pseudoacacia seedlings grown in Cd- and lead (Pb)-contaminated soils. The increase in secondary metabolites was greater under Cd + Pb exposure than under exposure to individual metals regardless of elevated CO2 with the exception of condensed tannins in leaves and total alkaloids in stems. Except for phenolic compounds and condensed tannins, elevated CO2 was associated with increased secondary metabolite contents in leaves and stems of plants exposed to Cd, Pb, and Cd + Pb compared to plants exposed to ambient CO2 + metals. Changes in saponins in leaves and alkaloids in stems were greater than changes in the other secondary metabolites. Significant interactive effects of CO2, Cd, and Pb on secondary metabolites were observed. Saponins in leaves and alkaloids in stems were more sensitive than other secondary metabolites to elevated CO2 + Cd + Pb. Elevated CO2 could modulate plant protection and defense mechanisms in R. pseudoacacia seedlings exposed to heavy metals by altering the production of secondary metabolites. The increased Cd and Pb uptake under elevated CO2 suggested that R. pseudoacacia may be used in the phytoremediation of heavy metal-contaminated soils under global environmental scenarios. PMID:27376859

  19. Distribution of heavy metals in vegetation surrounding the Blackstone River, USA: considerations regarding sediment contamination and long term metals transport in freshwater riverine ecosystems.

    PubMed

    Ozdilek, Hasan Goksel; Mathisen, Paul P; Pellegrino, Don

    2007-04-01

    River was affected by the river morphology and flow characteristics (including velocity, flow rate and depth of flow, which can govern the potential for plant submergence, as well as the dynamics of flow and transport in the soil near the river). The analyses help to provide an improved understanding of metals transport and potential significance of metals contamination in a terrestrial ecosystem that is located adjacent to a river.

  20. Multiphase transport simulation and venting experiments to identify NAPL source in vadose zone at a site contaminated with chlorinated solvents

    NASA Astrophysics Data System (ADS)

    Joun, W.; Lee, K.

    2013-12-01

    In many countries, groundwater is threatened by contamination from Non-Aqueous Phase Liquids such as chlorinated solvents (e.g. TCE). Existing as a residual or trapped source in the unsaturated zone, NAPLs remain in a continuous contamination source to groundwater even after groundwater itself was remediated because the residual NAPL source could be dissolved into the groundwater intermittently. In this study, 1-D and 2-D experiments were conducted. For 1-D experiment, a column (1 m) packed with well-sorted sand was used for developing the hydraulic properties in VOC transport. In 2-D experiment, hydraulic and contaminant properties in unsaturated condition were investigated including gas-phase concentration of a volatile organic compound (trichloroethylene, TCE) originated from residual or trapped NAPLs with different distances between an extraction well and source point, with different extraction rates and with different extraction intervals. While extracting air from the sand-tank (50 x 30 x 5 cm), temperature, humidity and pressure data were compiled with logging sensors. One and two-dimensional STOMP (Subsurface Transport Over Multiple Phases) simulator were used to simulate the experimental conditions. The experimental and simulation results can be used to estimate distances from extraction wells to source locations of residual NAPLs.

  1. Influences of Flow Transients and Porous Medium Heterogeneity on Colloid-Associated Contaminant Transport in the Vadose Zone

    SciTech Connect

    Saiers, James; Ryan, Joseph

    2005-06-01

    Our research is guided by an EMSP objective to improve conceptual and predictive models of contaminant movement in vadose-zone environments. As described in the report National Roadmap for Vadose-Zone Science and Technology [DOE, 2001], soil-water colloids are capable of adsorbing contaminants, such as radionuclides and metals, and facilitating their migration through the vadose zone and towards groundwater reservoirs. Our research centers on advancing understanding of this phenomenon. In particular, we are combining mathematical modeling with laboratory experimentation at pore and column scales to (1) elucidate the effects of porewater-flow transients on colloid mobilization in unsaturated porous media; (2) explore the sensitivity of colloid deposition rates to changes in porewater chemistry and colloid mineralogy; (3) develop mathematical models appropriate for simulating colloid mobilization, transport, and deposition under both steady-flow and transient-flow conditions; (4) identify mechanisms that govern mineral-colloid mobilization and deposition in unsaturated porous media; (5) quantify the effects of mineral-grain geometry and surface roughness on colloid-filtration rates; and (6) evaluate the influences of colloids on the transport of strontium and cesium (i.e., DOE-contaminants-of-concern) through soils and sediments.

  2. Contaminant transport in a municipal drinking water supply: a steady-state approach to estimate rate and uncertainty.

    PubMed

    Bergvall, Martin; Grip, Harald; Sjöström, Jan; Laudon, Hjalmar

    2007-09-01

    Contaminant transport is generally considered to be a key factor when assessing and classifying the environmental risk of polluted areas. In the study presented here, a steady-state approach was applied to obtain estimates of the transit time and concentration of the pesticide metabolite BAM (2,6-dichlorobenzoamide) at a site where it is contaminating a municipal drinking water supply. A Monte Carlo simulation technique was used to quantify the uncertainty of the results and to evaluate the sensitivity of the used parameters. The adopted approach yielded an estimated median transit time of 10 y for the BAM transport from the polluted site to the water supply. Soil organic carbon content in the unsaturated zone and the hydraulic conductivity in the saturated zone explained 44% and 23% of the uncertainty in the transit time estimate, respectively. The sensitivity analysis showed that the dilution factor due to regional groundwater flow and the soil organic carbon content at the polluted site explained 53% and 31% of the uncertainty of concentration estimates, respectively. In conclusion, the adopted steady-state approach can be used to obtain reliable first estimates of transit time and concentration, but to improve concentration predictions of degrading contaminants, a dynamic model is probably required.

  3. Fuel-mix, fuel efficiency, and transport demand affect prospects for biofuels in northern Europe.

    PubMed

    Bright, Ryan M; Strømman, Anders Hammer

    2010-04-01

    Rising greenhouse gas (GHG) emissions in the road transport sector represents a difficult mitigation challenge due to a multitude of intricate factors, namely the dependency on liquid energy carriers and infrastructure lock-in. For this reason, low-carbon renewable energy carriers, particularly second generation biofuels, are often seen as a prominent candidate for realizing reduced emissions and lowered oil dependency over the medium- and long-term horizons. However, the overarching question is whether advanced biofuels can be an environmentally effective mitigation strategy in the face of increasing consumption and resource constraints. Here we develop both biofuel production and road transport consumption scenarios for northern Europe-a region with a vast surplus of forest bioenergy resources-to assess the potential role that forest-based biofuels may play over the medium- and long-term time horizons using an environmentally extended, multiregion input-output model. Through scenarios, we explore how evolving vehicle technologies and consumption patterns will affect the mitigation opportunities afforded by any future supply of forest biofuels. We find that in a scenario involving ambitious biofuel targets, the size of the GHG mitigation wedge attributed to the market supply of biofuels is severely reduced under business-as-usual growth in consumption in the road transport sector. Our results indicate that climate policies targeting the road transport sector which give high emphases to reducing demand (volume), accelerating the deployment of more fuel-efficient vehicles, and promoting altered consumption patterns (structure) can be significantly more effective than those with single emphasis on expanded biofuel supply. PMID:20163088

  4. Fuel-mix, fuel efficiency, and transport demand affect prospects for biofuels in northern Europe.

    PubMed

    Bright, Ryan M; Strømman, Anders Hammer

    2010-04-01

    Rising greenhouse gas (GHG) emissions in the road transport sector represents a difficult mitigation challenge due to a multitude of intricate factors, namely the dependency on liquid energy carriers and infrastructure lock-in. For this reason, low-carbon renewable energy carriers, particularly second generation biofuels, are often seen as a prominent candidate for realizing reduced emissions and lowered oil dependency over the medium- and long-term horizons. However, the overarching question is whether advanced biofuels can be an environmentally effective mitigation strategy in the face of increasing consumption and resource constraints. Here we develop both biofuel production and road transport consumption scenarios for northern Europe-a region with a vast surplus of forest bioenergy resources-to assess the potential role that forest-based biofuels may play over the medium- and long-term time horizons using an environmentally extended, multiregion input-output model. Through scenarios, we explore how evolving vehicle technologies and consumption patterns will affect the mitigation opportunities afforded by any future supply of forest biofuels. We find that in a scenario involving ambitious biofuel targets, the size of the GHG mitigation wedge attributed to the market supply of biofuels is severely reduced under business-as-usual growth in consumption in the road transport sector. Our results indicate that climate policies targeting the road transport sector which give high emphases to reducing demand (volume), accelerating the deployment of more fuel-efficient vehicles, and promoting altered consumption patterns (structure) can be significantly more effective than those with single emphasis on expanded biofuel supply.

  5. Transport behaviour and natural attenuation of organic contaminants at spill sites.

    PubMed

    Schirmer, Mario; Butler, Barbara J

    2004-12-15

    Organic contaminants pose a significant threat to groundwater resources. These contaminants are often released as non-aqueous phase liquids (NAPLs) during spills of, for example, gasoline, crude oil, creosote, coal tar or chlorinated solvents. Once released, the liquids seep downward and dissolve into the groundwater. In many cases, the impacted groundwater contains a mixture of contaminants, either due to the complexity of the NAPL (e.g., gasoline) or due to co-disposal/co-spillage (e.g., landfill leachates). Many organic contaminants are hazardous to human health and the environment and therefore threaten our potable water resources and natural ecosystems. Active remediation of contaminated groundwater is often very expensive so that cost-effective alternatives have to be found. If natural attenuation is intended to be used as a means of achieving specific remedial objectives at a contaminated site, it will require a sound understanding of the ongoing processes as well as careful control and monitoring ("monitored natural attenuation" (MNA)). Therefore, a major goal of remediation research today is to develop methods to predict the mass fate of multiple organic compounds in heterogeneous aquifers under natural conditions.

  6. The effect of a zero-concentration sink on contaminant transport and remedial-action designs for the Weldon Spring quarry, Weldon Spring, Missouri

    SciTech Connect

    Tomasko, D.

    1990-04-01

    One-dimensional analytical expressions are developed to simulate two processes in a homogeneous porous medium: contaminant transport through a porous medium that has a zero-concentration sink located at a finite distance from a step-function source; and contaminant transport through a porous medium that has an initial steady-state distribution corresponding to a constant strength source and zero-concentration sink separated by a finite distance. The governing equations are cast in dimensionless form, making use of the flow system's Peclet number. Evaluation of the analytical expressions is accomplished by numerical inversion of Laplace-space concentrations using either a full Fourier series approach with acceleration, or the Stehfest algorithm. The analytical expressions are used to evaluate possible contaminant conditions at the Weldon Spring quarry near Weldon Spring, Missouri. The following results have been found: contaminant concentrations should be at or near steady-state conditions; the spatial distribution of contaminants should be a function of the flow system's Peclet number; contaminant concentrations near the Femme Osage Slough should approach zero; contaminant concentrations near the quarry during dewatering and bulk-waste removal should monotonically decrease with time; and the spatial distribution of contaminants during remedial activities should be relatively flat, especially near the dewatering pumps. Future work will entail evaluating existing radionuclide or chemical concentration data to determine the applicability of the proposed contaminant transport model and to improve the hydrogeological conceptualization of the quarry area and vicinity. 20 refs., 27 figs.

  7. Processes affecting the fate of monoaromatic hydrocarbons in an aquifer contaminated by crude oil

    USGS Publications Warehouse

    Eganhouse, R.P.; Dorsey, T.F.; Phinney, C.S.; Westcott, A.M.

    1996-01-01

    Crude oil spilled from a subsurface pipeline in north-central Minnesota has dissolved in the groundwater, resulting in the formation of a plume of aliphatic, aromatic, and alicyclic hydrocarbons. Comparison of paired oil and groundwater samples collected along the central axis of the residual oil body shows that the trailing edge of the oil is depleted in the more soluble aromatic hydrocarbons (e.g., benzene, toluene, etc.) when compared with the leading edge. At the same time, concentrations of monoaromatic hydrocarbons in groundwater beneath the oil increase as the water moves toward the leading edge of the oil. Immediately downgradient from the leading edge of the oil body, certain aromatic hydrocarbons (e.g., benzene) are found at concentrations near those expected of a system at equilibrium, and the concentrations exhibit little variation over time (???8-20%). Other compounds (e.g., toluene) appear to be undersaturated, and their concentrations show considerably more temporal variation (???20-130%). The former are persistent within the anoxic zone downgradient from the oil, whereas concentrations of the latter decrease rapidly. Together, these observations suggest that the volatile hydrocarbon composition of the anoxic groundwater near the oil body is controlled by a balance between dissolution and removal rates with only the most persistent compounds reaching saturation. Examination of the distributions of homologous series and isomeric assemblages of alkylbenzenes reveals that microbial degradation is the dominant process controlling the fate of these compounds once groundwater moves away from the oil. For all but the most persistent compounds, the distal boundary of the plume at the water table extends no more than 10-15 m down-gradient from the oxic/anoxic transition zone. Thus, transport of the monoaromatic hydrocarbons is limited by redox conditions that are tightly coupled to biological degradation processes.

  8. Contamination of an arctic terrestrial food web with marine-derived persistent organic pollutants transported by breeding seabirds.

    PubMed

    Choy, Emily S; Kimpe, Linda E; Mallory, Mark L; Smol, John P; Blais, Jules M

    2010-11-01

    At Cape Vera, Devon Island (Nunavut, Canada), a colony of northern fulmars (Fulmarus glacialis) concentrates and releases contaminants through their guano to the environment. We determined whether persistent organic pollutants (POPs) from seabirds were transferred to coastal food webs. Snow buntings (Plectrophenax nivalis) were the most contaminated species, with ∑PCB and ∑DDT (mean: 168, 106 ng/g ww) concentrations surpassing environmental guidelines for protecting wildlife. When examined collectively, PCB congeners and DDT in jewel lichen (Xanthoria elegans) were lower in samples taken farther from the seabird colony, and increased with increasing δ(15)N values. However, only concentrations of p'p-DDE:∑DDT and PCB-95 were significantly correlated inversely with distance from the seabird cliffs. Linkages between marine-derived POPs and their concentrations in terrestrial mammals were less clear. Our study provides novel contaminant data for these species and supports biovector transport as a source of organic contaminants to certain components of the terrestrial food web.

  9. Coupling Between Flow and Precipitation In Heterogeneous Subsurface Environments and Effects on Contaminant Fate and Transport (Project no. 99272)

    SciTech Connect

    Redden, G.D.; Fujita, Y.; Scheibe, T.D.; Tartakovsky, A.M.; Smith, R.W.; Reddy, M.M.; Kelly, S.D.

    2006-04-05

    This project is aimed at understanding how contaminant transport in heterogeneous porous media is impacted by precipitation and dissolution events through chemical interactions with precipitates and as a consequence of coupling between precipitation and flow. We hypothesize that precipitation/coprecipitation, encapsulation, isolation from flow and alteration of reactive surfaces will contribute to altering contaminant mobility during precipitation events, and that predicting the release of contaminants during precipitate dissolution requires an understanding of how precipitates are distributed and how contaminants are released from the different compartments over time. Using calcium carbonate as a model system, physical experiments and modeling at the pore-scale and continuum-scale will be used to improve the conceptual approach to predicting the impact of flow-precipitation coupling on solute migration. Column and 2-dimensional intermediate-scale experiments with constructed physical and chemical heterogeneities will be used to investigate the movement of fluids and reactive solutes during different types of mixing events that lead to calcium carbonate supersaturation and precipitation. Smoothed particle hydrodynamic modeling will be used to simulate pore-scale mixing and precipitation in heterogeneous porous media and estimate continuum-scale parameters. Continuum-scale modeling will be used to test conceptual models and associated effective parameters that simulate the macroscopic behavior of the experimental domains.

  10. The importance of evaluating the physicochemical and toxicological properties of a contaminant for remediating environments affected by chemical incidents.

    PubMed

    Wyke, S; Peña-Fernández, A; Brooke, N; Duarte-Davidson, R

    2014-11-01

    In the event of a major chemical incident or accident, appropriate tools and technical guidance need to be available to ensure that a robust approach can be adopted for developing a remediation strategy. Remediation and restoration strategies implemented in the aftermath of a chemical incident are a particular concern for public health. As a result an innovative methodology has been developed to help design an effective recovery strategy in the aftermath of a chemical incident that has been developed; the UK Recovery Handbook for Chemical Incidents (UKRHCI). The handbook consists of a six-step decision framework and the use of decision trees specifically designed for three different environments: food production systems, inhabited areas and water environments. It also provides a compendium of evidence-based recovery options (techniques or methods for remediation) that should be selected in relation to their efficacy for removing contaminants from the environment. Selection of effective recovery options in this decision framework involves evaluating the physicochemical and toxicological properties of the chemical(s) involved. Thus, the chemical handbook includes a series of tables with relevant physicochemical and toxicological properties that should be assessed in function of the environment affected. It is essential that the physicochemical properties of a chemical are evaluated and interpreted correctly during the development of a remedial plan in the aftermath of a chemical incident to ensure an effective remedial response. This paper presents a general overview of the key physicochemical and toxicological properties of chemicals that should be evaluated when developing a recovery strategy. Information on how physicochemical properties have impacted on previous remedial responses reported in the literature is also discussed and a number of challenges for remediation are highlighted to include the need to develop novel approaches to remediate sites contaminated

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

    SciTech Connect

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

    2008-05-12

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

  12. Variations in heavy metal contamination of stream water and groundwater affected by an abandoned lead-zinc mine in Korea.

    PubMed

    Lee, Jin-Yong; Choi, Jung-Chan; Lee, Kang-Kun

    2005-09-01

    This study evaluated variations in heavy metal contamination of stream waters and groundwaters affected by an abandoned lead-zinc mine, where a rockfill dam for water storage will be built 11 km downstream. For these purposes, a total of 10 rounds of stream and groundwater samplings and subsequent chemical analyses were performed during 2002-2003. Results of an exploratory investigation of stream waters in 2000 indicated substantial contamination with heavy metals including zinc (Zn), iron (Fe) and arsenic (As) for at least 6 km downstream from the mine. Stream waters near the mine showed metal contamination as high as arsenic (As) 8,923 microg L(-1), copper (Cu) 616 microg L(-1), cadmium (Cd) 223 microg L(-1) and lead (Pb) 10,590 microg L(-1), which greatly exceeded the Korean stream water guidelines. Remediation focused on the mine tailing piles largely improved the stream water qualities. However, there have still been quality problems for the waters containing relatively high concentrations of As (6-174 microg L(-1)), Cd (1-46 microg L(-1)) and Pb (2-26 microg L(-1)). Rainfall infiltration into the mine tailing piles resulted in an increase of heavy metals in the stream waters due to direct discharge of waste effluent, while dilution of the contaminated stream waters improved the water quality due to mixing with metal free rain waters. Levels of As, Cu and chromium (Cr) largely decreased after heavy rain but that of Pb was rather elevated. The stream waters were characterized by high concentrations of calcium (Ca) and sulfate (SO(4)), which were derived from dissolution and leaching of carbonate and sulfide minerals. It was observed that the proportions of Ca and SO(4) increased while those of bicarbonate (HCO(3)) and sodium and potassium (Na+K) decreased after a light rainfall event. Most interestingly, the reverse was generally detected for the groundwaters. The zinc, being the metal mined, was the most dominant heavy metal in the groundwaters (1758

  13. Variations in heavy metal contamination of stream water and groundwater affected by an abandoned lead-zinc mine in Korea.

    PubMed

    Lee, Jin-Yong; Choi, Jung-Chan; Lee, Kang-Kun

    2005-09-01

    This study evaluated variations in heavy metal contamination of stream waters and groundwaters affected by an abandoned lead-zinc mine, where a rockfill dam for water storage will be built 11 km downstream. For these purposes, a total of 10 rounds of stream and groundwater samplings and subsequent chemical analyses were performed during 2002-2003. Results of an exploratory investigation of stream waters in 2000 indicated substantial contamination with heavy metals including zinc (Zn), iron (Fe) and arsenic (As) for at least 6 km downstream from the mine. Stream waters near the mine showed metal contamination as high as arsenic (As) 8,923 microg L(-1), copper (Cu) 616 microg L(-1), cadmium (Cd) 223 microg L(-1) and lead (Pb) 10,590 microg L(-1), which greatly exceeded the Korean stream water guidelines. Remediation focused on the mine tailing piles largely improved the stream water qualities. However, there have still been quality problems for the waters containing relatively high concentrations of As (6-174 microg L(-1)), Cd (1-46 microg L(-1)) and Pb (2-26 microg L(-1)). Rainfall infiltration into the mine tailing piles resulted in an increase of heavy metals in the stream waters due to direct discharge of waste effluent, while dilution of the contaminated stream waters improved the water quality due to mixing with metal free rain waters. Levels of As, Cu and chromium (Cr) largely decreased after heavy rain but that of Pb was rather elevated. The stream waters were characterized by high concentrations of calcium (Ca) and sulfate (SO(4)), which were derived from dissolution and leaching of carbonate and sulfide minerals. It was observed that the proportions of Ca and SO(4) increased while those of bicarbonate (HCO(3)) and sodium and potassium (Na+K) decreased after a light rainfall event. Most interestingly, the reverse was generally detected for the groundwaters. The zinc, being the metal mined, was the most dominant heavy metal in the groundwaters (1758

  14. Long-term contamination in a recovered area affected by a mining spill.

    PubMed

    Martín Peinado, F J; Romero-Freire, A; García Fernández, I; Sierra Aragón, M; Ortiz-Bernad, I; Simón Torres, M

    2015-05-01

    Soil pollution from the spill of Aznalcóllar mine (S Spain) was monitored by analysing polluted soils in 1998, 1999, and 2004. Following the methodology used in previous studies, in 2013 we conducted a new sampling and analysis of the soils affected by the spill and the data were compared with those of 2004. The results confirm that the pH tended to rise and concentration of pollutants tended to diminish over time. In 2013, the total concentration of pollutants was within the normal range for uncontaminated soils and close to the background concentration of the soils prior to the spill; while the soluble concentration of pollutants was clearly below the toxic level. These results indicate that remediation measures implemented have been effective. However, the removal of tailings (first remediation measure applied) was deficient and in many places the tailings were mixed with the soil. The high concentration of sulphides and metal(loid)s in the tailings gave rise to spots with very acidic and highly polluted soils devoid of vegetation. In 2013, fifteen years after the spill, these spots of bare soils remain a major source of pollution from which pollutants are scattered through the solid and liquid phases of runoff water, requiring action to immobilize pollutants and encourage the restoration of vegetation on these soils. In this type of pollution in a Mediterranean environment, the complete removal of tailings is more important than the speed at which they are removed.

  15. Municipal sludge metal contamination of old-field ecosystems: Do liming and tilling affect remediation

    SciTech Connect

    Benninger-Truax, M.; Taylor, D.H. . Dept. of Zoology)

    1993-10-01

    Mechanisms of ecosystem recovery following 11 years of sewage sludge disposal were addressed by examining the effects of tilling and/or liming on soil chemistry and the heavy metal (Cd, Cu, Pb, and Zn) concentrations in soil, earthworms, vegetation, spiders, and crickets. In 1989 and 1990, subplots in each of three former 0.1-ha, long-term treatments (sludge, fertilizer, and control) were either unmanipulated or manipulated via tilling and/or liming. Liming significantly increased the pH of soil from the long-term sludge and fertilizer plots, and the combination of tilling and liming affected the heavy metal concentrations in earthworms, as lower concentrations of Cd, Cu, Pb, and Zn were found in earthworms collected from subplots that had been both tilled and limed. However, most observed significant differences in heavy metal concentrations reflected the long-term treatments, as heavy metal concentrations tended to be greater in the soil and biota collected from sludge-treated plots. Thus, heavy metals remained in the soil in forms available to the biota, regardless of the cessation of sludge application or subplot manipulations (liming and/or tilling) for two years following cessation of sludge application.

  16. Inhibition of ABC transport proteins by oil sands process affected water.

    PubMed

    Alharbi, Hattan A; Saunders, David M V; Al-Mousa, Ahmed; Alcorn, Jane; Pereira, Alberto S; Martin, Jonathan W; Giesy, John P; Wiseman, Steve B

    2016-01-01

    The ATP-binding cassette (ABC) superfamily of transporter proteins is important for detoxification of xenobiotics. For example, ABC transporters from the multidrug-resistance protein (MRP) subfamily are important for excretion of polycyclic aromatic hydrocarbons (PAHs) and their metabolites. Effects of chemicals in the water soluble organic fraction of relatively fresh oil sands process affected water (OSPW) from Base Mine Lake (BML-OSPW) and aged OSPW from Pond 9 (P9-OSPW) on the activity of MRP transporters were investigated in vivo by use of Japanese medaka at the fry stage of development. Activities of MRPs were monitored by use of the lipophilic dye calcein, which is transported from cells by ABC proteins, including MRPs. To begin to identify chemicals that might inhibit activity of MRPs, BML-OSPW and P9-OSPW were fractionated into acidic, basic, and neutral fractions by use of mixed-mode sorbents. Chemical compositions of fractions were determined by use of ultrahigh resolution orbitrap mass spectrometry in ESI(+) and ESI(-) mode. Greater amounts of calcein were retained in fry exposed to BML-OSPW at concentration equivalents greater than 1× (i.e., full strength). The neutral and basic fractions of BML-OSPW, but not the acidic fraction, caused greater retention of calcein. Exposure to P9-OSPW did not affect the amount of calcein in fry. Neutral and basic fractions of BML-OSPW contained relatively greater amounts of several oxygen-, sulfur, and nitrogen-containing chemical species that might inhibit MRPs, such as O(+), SO(+), and NO(+) chemical species, although secondary fractionation will be required to conclusively identify the most potent inhibitors. Naphthenic acids (O2(-)), which were dominant in the acidic fraction, did not appear to be the cause of the inhibition. This is the first study to demonstrate that chemicals in the water soluble organic fraction of OSPW inhibit activity of this important class of proteins. However, aging of OSPW attenuates

  17. Inhibition of ABC transport proteins by oil sands process affected water.

    PubMed

    Alharbi, Hattan A; Saunders, David M V; Al-Mousa, Ahmed; Alcorn, Jane; Pereira, Alberto S; Martin, Jonathan W; Giesy, John P; Wiseman, Steve B

    2016-01-01

    The ATP-binding cassette (ABC) superfamily of transporter proteins is important for detoxification of xenobiotics. For example, ABC transporters from the multidrug-resistance protein (MRP) subfamily are important for excretion of polycyclic aromatic hydrocarbons (PAHs) and their metabolites. Effects of chemicals in the water soluble organic fraction of relatively fresh oil sands process affected water (OSPW) from Base Mine Lake (BML-OSPW) and aged OSPW from Pond 9 (P9-OSPW) on the activity of MRP transporters were investigated in vivo by use of Japanese medaka at the fry stage of development. Activities of MRPs were monitored by use of the lipophilic dye calcein, which is transported from cells by ABC proteins, including MRPs. To begin to identify chemicals that might inhibit activity of MRPs, BML-OSPW and P9-OSPW were fractionated into acidic, basic, and neutral fractions by use of mixed-mode sorbents. Chemical compositions of fractions were determined by use of ultrahigh resolution orbitrap mass spectrometry in ESI(+) and ESI(-) mode. Greater amounts of calcein were retained in fry exposed to BML-OSPW at concentration equivalents greater than 1× (i.e., full strength). The neutral and basic fractions of BML-OSPW, but not the acidic fraction, caused greater retention of calcein. Exposure to P9-OSPW did not affect the amount of calcein in fry. Neutral and basic fractions of BML-OSPW contained relatively greater amounts of several oxygen-, sulfur, and nitrogen-containing chemical species that might inhibit MRPs, such as O(+), SO(+), and NO(+) chemical species, although secondary fractionation will be required to conclusively identify the most potent inhibitors. Naphthenic acids (O2(-)), which were dominant in the acidic fraction, did not appear to be the cause of the inhibition. This is the first study to demonstrate that chemicals in the water soluble organic fraction of OSPW inhibit activity of this important class of proteins. However, aging of OSPW attenuates

  18. Modeling Three-Dimensional Groundwater Flow and Advective Contaminant Transport at a Heterogeneous Mountainous Site in Support of Remediation Strategy

    SciTech Connect

    Zhou, Quanlin; Birkholzer, Jens T.; Javandel, Iraj; Jordan, Preston D.

    2004-01-14

    A calibrated groundwater flow model for a contaminated site can provide substantial information for assessing and improving hydraulic measures implemented for remediation. A three-dimensional transient groundwater flow model was developed for a contaminated mountainous site, at which interim corrective measures were initiated to limit further spreading of contaminants. This flow model accounts for complex geologic units that vary considerably in thickness, slope, and hydrogeologic properties, as well as large seasonal fluctuations of the groundwater table and flow rates. Other significant factors are local recharge from leaking underground storm drains and recharge from steep uphill areas. The zonation method was employed to account for the clustering of high and low hydraulic conductivities measured in a geologic unit. A composite model was used to represent the bulk effect of thin layers of relatively high hydraulic conductivity found within bedrock of otherwise low conductivity. The inverse simulator ITOUGH2 was used to calibrate the model for the distribution of rock properties. The model was initially calibrated using data collected between 1994 and 1996. To check the validity of the model, it was subsequently applied to predicting groundwater level fluctuation and groundwater flux between 1996 and 1998. Comparison of simulated and measured data demonstrated that the model is capable of predicting the complex flow reasonably well. Advective transport was approximated using pathways of particles originating from source areas of the plumes. The advective transport approximation was in good agreement with the trend of contaminant plumes observed over the years. The validated model was then refined to focus on a subsection of the large system. The refined model was subsequently used to assess the efficiency of hydraulic measures implemented for remediation.

  19. Ammonia gas transport and reactions in unsaturated sediments: implications for use as an amendment to immobilize inorganic contaminants.

    PubMed

    Zhong, L; Szecsody, J E; Truex, M J; Williams, M D; Liu, Y

    2015-05-30

    Use of gas-phase amendments for in situ remediation of inorganic contaminants in unsaturated sediments of the vadose zone may be advantageous, but there has been limited development and testing of gas remediation technologies. Treatment with ammonia gas has a potential for use in treating inorganic contaminants (such as uranium) because it induces a high pore-water pH, causing mineral dissolution and subsequent formation of stable precipitates that decrease the mobility of some contaminants. For field application of this treatment, further knowledge of ammonia transport in porous media and the geochemical reactions induced by ammonia treatment is needed. Laboratory studies were conducted to support calculations needed for field treatment design, to quantify advective and diffusive ammonia transport in unsaturated sediments, to evaluate inter-phase (gas/sediment/pore water) reactions, and to study reaction-induced pore-water chemistry changes as a function of ammonia delivery conditions, such as flow rate, gas concentration, and water content. Uranium-contaminated sediment was treated with ammonia gas to demonstrate U immobilization. Ammonia gas quickly partitions into sediment pore water and increases the pH up to 13.2. Injected ammonia gas advection front movement can be reasonably predicted by gas flow rate and equilibrium partitioning. The ammonia gas diffusion rate is a function of the water content in the sediment. Sodium, aluminum, and silica pore-water concentrations increase upon exposure to ammonia and then decline as aluminosilicates precipitate when the pH declines due to buffering. Up to 85% of the water-leachable U was immobilized by ammonia treatment.

  20. Speciation, distribution, and transport of mercury in contaminated soils from Descoberto, Minas Gerais, Brazil.

    PubMed

    Durão Júnior, Walter Alves; Palmieri, Helena Eugênia Leonhardt; Trindade, Mauro Campos; de Aquino Branco, Otávio Eurico; Filho, Carlos Alberto Carvalho; Fleming, Peter Marschall; da Silva, José Bento Borba; Windmöller, Cláudia Carvalhinho

    2009-05-01

    This work describes an investigation of mercury contamination in an abandoned gold mining site in the rural area of Descoberto, Minas Gerais, Brazil, whose inhabitants have reported "silver balls" present in the soil. Different granulometric fractions of soil samples and sedimented material from rainwater retention tanks in this area were analyzed for total mercury, organic matter, and mercury speciation by thermodesorption/atomic absorption spectrometry. The results showed mercury concentrations in the soils in the range of (0.0371-161) mg kg(-1), and the occurrence of Hg(0) oxidation. Some samples had concentrations as high as 90 mg kg(-1) with the majority as Hg(2+), which is important information in order to understand the biogeochemical behavior of mercury in contaminated sites and to apply the appropriate remediation technology. The retention boxes and tank samples showed that fine particles with high mercury content (3.3-90) mg kg(-1) are leached from the contaminated area, which reveals the need for efficient control of this material to prevent the contamination of stream waters. This study is an example that may be useful for other contaminated sites.

  1. Fractal stream chemistry and its implications for contaminant transport in catchments

    PubMed

    Kirchner; Feng; Neal

    2000-02-01

    The time it takes for rainfall to travel through a catchment and reach the stream is a fundamental hydraulic parameter that controls the retention of soluble contaminants and thus the downstream consequences of pollution episodes. Catchments with short flushing times will deliver brief, intense contaminant pulses to downstream waters, whereas catchments with longer flushing times will deliver less intense but more sustained contaminant fluxes. Here we analyse detailed time series of chloride, a natural tracer, in both rainfall and runoff from headwater catchments at Plynlimon, Wales. We show that, although the chloride concentrations in rainfall have a white noise spectrum, the chloride concentrations in streamflow exhibit fractal 1/f scaling over three orders of magnitude. The fractal fluctuations in tracer concentrations indicate that these catchments do not have characteristic flushing times. Instead, their travel times follow an approximate power-law distribution implying that they will retain a long chemical memory of past inputs. Contaminants will initially be flushed rapidly, but then low-level contamination will be delivered to streams for a surprisingly long time.

  2. Parameters describing nonequilibrium transport of polycyclic aromatic hydrocarbons through contaminated soil columns: estimability analysis, correlation, and optimization.

    PubMed

    Ngo, Viet V; Michel, Julien; Gujisaite, Valérie; Latifi, Abderrazak; Simonnot, Marie-Odile

    2014-03-01

    The soil and groundwater at former industrial sites polluted by polycyclic aromatic hydrocarbons (PAHs) produce a very challenging environmental issue. The description of PAH transport by means of mathematical models is therefore needed for risk assessment and remediation strategies at these sites. Due to the complexity of release kinetics and transport behavior of the PAHs in the aged contaminated soils, their transport is usually evaluated at the laboratory scale. Transport parameters are then estimated from the experimental data via the inverse method. To better assess the uncertainty of optimized parameters, an estimability method was applied to firstly investigate the information content of experimental data and the possible correlations among parameters in the two-site sorption model. These works were based on the concentrations of three PAHs, Acenaphthene (ACE), Fluoranthene (FLA) and Pyrene (PYR), in the leaching solutions of the experiments under saturated and unsaturated flow conditions. The estimability results showed that the experiment under unsaturated flow conditions contained more information content for estimating four transport parameters than under the saturated one. In addition, whatever the experimental conditions for all three PAHs the fraction of sites with instantaneous sorption, f, was highly correlated with the adsorption distribution coefficient, Kd. The very strong correlation between the two parameters f and Kd suggests that they should not be simultaneously calibrated. Transport parameters were optimized using HYDRUS-1D software with different scenarios based on the estimability analysis results. The optimization results were not always reliable, especially in the case of the experiment under saturated flow conditions because of its low information content. In addition, the estimation of transport parameters became very uncertain if two parameters f and Kd were optimized simultaneously. The findings of the current work can suggest some

  3. Fate and transport of linear alkylbenzenesulfonate in a sewage- contaminated aquifer: A comparison of natural-gradient pulsed tracer tests

    USGS Publications Warehouse

    Krueger, C.J.; Barber, L.B.; Metge, D.W.; Field, J.A.

    1998-01-01

    Two natural-gradient tracer tests were conducted to determine the transport and biodegradation behavior of linear alkylbenzenesulfonate (LAS) surfactant under in situ conditions in a sewage-contaminated aquifer. The tests were conducted in two biogeochemically distinct zones of the aquifer: (1) an aerobic uncontaminated zone (oxic zone) and (2) a moderately aerobic, sewage-contaminated zone (transition zone). Chromatographic separation of the surfactant mixture was observed in both zones and attributed to the retardation of the longer alkyl chain homologues during transport. No significant loss of IAS mass was observed for the oxic zone while 20% of the LAS mass injected into the transition zone was removed due to biodegradation. Biodegradation preferentially removed the longer alkyl chain homologues and the external isomers (i.e., 2- and 3-phenyl). The removal of LAS mass coincided with a decrease in dissolved oxygen concentrations, the appearance of LAS metabolites, and an increase in the number of free-living bacteria with a concomitant change in bacteria morphology. The formation of LAS metabolites accounted for 86% of the LAS mass removed in the transition zone. Over the duration of the test, sorption and biodegradation enriched the LAS mixture in the more water-soluble and biologically resistant components.Two natural-gradient tracer tests were conducted to determine the transport and biodegradation behavior of linear alkylbenzenesulfonate (LAS) surfactant under in situ conditions in a sewage-contaminated aquifer. The tests were conducted in two biogeochemically distinct zones of the aquifer: (1) an aerobic uncontaminated zone (oxic zone) and (2) a moderately aerobic, sewage-contaminated zone (transition zone). Chromatographic separation of the surfactant mixture was observed in both zones and attributed to the retardation of the longer alkyl chain homologues during transport. No significant loss of LAS mass was observed for the oxic zone while 20% of the LAS

  4. Factors influencing aquatic-to-terrestrial contaminant transport to terrestrial arthropod consumers in a multiuse river system.

    PubMed

    Alberts, Jeremy M; Sullivan, S Mažeika P

    2016-06-01

    Emerging aquatic insects are important vectors of contaminant transfer from aquatic to terrestrial food webs. However, the environmental factors that regulate contaminant body burdens in nearshore terrestrial consumers remain largely unexplored. We investigated the relative influences of riparian landscape composition (i.e., land use and nearshore vegetation structure) and contaminant flux via the emergent aquatic insect subsidy on selenium (Se) and mercury (Hg) body burdens of riparian ants (Formica subsericea) and spiders of the family Tetragnathidae along 11 river reaches spanning an urban-rural land-use gradient in Ohio, USA. Model-selection results indicated that fine-scale land cover (e.g., riparian zone width, shrub cover) in the riparian zone was positively associated with reach-wide body burdens of Se and Hg in both riparian F. subsericea and tetragnathid spiders (i.e., total magnitude of Hg and Se concentrations in ant and spider populations, respectively, for each reach). River distance downstream of Columbus, Ohio - where study reaches were impounded and flow through a large urban center - was also implicated as an important factor. Although stable-isotope analysis suggested that emergent aquatic insects were likely vectors of Se and Hg to tetragnathid spiders (but not to F. subsericea), emergent insect contaminant flux did not emerge as a significant predictor for either reach-wide body burdens of spider Hg or Se. Improved understanding of the pathways and influences that control aquatic-to-terrestrial contaminant transport will be critical for effective risk management and remediation. PMID:26874875

  5. Event-based stormwater quality and quantity loadings from elevated urban infrastructure affected by transportation.

    PubMed

    Sansalone, John J; Hird, Jonathan P; Cartledge, Frank K; Tittlebaum, Marty E

    2005-01-01

    Urban-rainfall runoff affected by transportation is a complex matrix of a very wide gradation of particulate matter (< 1 to > 10 000 microm) and dissolved inorganic and organic constituents. Particulate matter transported by rainfall runoff can be a significant vector for many reactive particulate-bound constituents, particularly metal elements. The water quality and hydrology of nine events from a representative elevated section of Interstate 10 (I-10) (eastbound average daily traffic load of 70 400 vehicles) in Baton Rouge, Louisiana, were characterized and compared with respect to the passage of each hydrograph. Residence time on the paved concrete surface was less than 30 minutes for all events. Results indicate that event-mean concentrations (EMCs) of particulate matter as total-suspended solids (TSS) (138 to 561 mg/L) and chemical-oxygen demand (COD) (128 to 1440 mg/L) were greater than those found in untreated municipal wastewater from the same service area. Particulate-matter dissolution and COD partitioned as a function of pH, pavement residence time, and organic content. In general, delivery of mass for aggregate indices, such as particulate matter (measured as TSS) and COD mass, were driven by the hydrology of the event, while concentrations of aggregate-constituent measurements, such as total-dissolved solids (TDS), illustrated an exponential-type decline during the rising limb of the hydrograph. Despite the short residence times, wide solids gradation, partitioning, and complexity of the rainfall-runoff chemistry, conductivity and dissolved solids were strongly correlated. Characterization of the transport and loads of constituents in urban-rainfall runoff, as a function of hydrology, is a necessary first step when considering treatability, structural or nonstructural controls, and mass trading for discharges from paved infrastructure. PMID:16121503

  6. Lactate kinetics of rainbow trout during graded exercise: do catheters affect the cost of transport?

    PubMed

    Teulier, Loïc; Omlin, Teye; Weber, Jean-Michel

    2013-12-15

    Changes in lactate kinetics as a function of exercise intensity have never been measured in an ectotherm. Continuous infusion of a tracer is necessary to quantify rates of lactate appearance (Ra) and disposal (Rd), but it requires double catheterization, which could interfere with swimming. Using rainbow trout, our goals were to: (1) determine the potential effects of catheters and blood sampling on metabolic rate (O2), total cost of transport (TCOT), net cost of transport (NCOT) and critical swimming speed (Ucrit), and (2) monitor changes in lactate fluxes during prolonged, steady-state swimming or graded swimming from rest to Ucrit. This athletic species maintains high baseline lactate fluxes of 24 μmol kg(-1) min(-1) that are only increased at intensities >2.4 body lengths (BL) s(-1) or 85% Ucrit. As the fish reaches Ucrit, Ra is more strongly stimulated (+67% to 40.4 μmol kg(-1) min(-1)) than Rd (+41% to 34.7 μmol kg(-1) min(-1)), causing a fourfold increase in blood lactate concentration. Without this stimulation of Rd during intense swimming, lactate accumulation would double. By contrast, steady-state exercise at 1.7 BL s(-1) increases lactate fluxes to ~30 μmol kg(-1) min(-1), with a trivial mismatch between Ra and Rd that only affects blood concentration minimally. Results also show that the catheterizations and blood sampling needed to measure metabolite kinetics in exercising fish have no significant impact on O2 or TCOT. However, these experimental procedures affect locomotion energetics by increasing NCOT at high speeds and by decreasing Ucrit.

  7. Aquaporin-9 and urea transporter-A gene deletions affect urea transmembrane passage in murine hepatocytes.

    PubMed

    Jelen, Sabina; Gena, Patrizia; Lebeck, Janne; Rojek, Aleksandra; Praetorius, Jeppe; Frøkiaer, Jørgen; Fenton, Robert A; Nielsen, Søren; Calamita, Giuseppe; Rützler, Michael

    2012-12-01

    In mammals, the majority of nitrogen from protein degradation is disposed of as urea. Several studies have partly characterized expression of urea transporters (UTs) in hepatocytes, where urea is produced. Nevertheless, the contribution of these proteins to hepatocyte urea permeability (P(urea)) and their role in liver physiology remains unknown. The purpose of this study was to biophysically examine hepatocyte urea transport. We hypothesized that the water, glycerol, and urea channel aquaporin-9 (AQP9) is involved in hepatocyte urea release. Stopped-flow light-scattering measurements determined that the urea channel inhibitors phloretin and dimethylurea reduced urea permeability of hepatocyte basolateral membranes by 70 and 40%, respectively. In basolateral membranes isolated from AQP9(-/-) and UT-A1/3(-/-) single-knockout and AQP9(-/-):UT-A1/3(-/-) double-knockout mice, P(urea) was decreased by 30, 40, and 76%, respectively, compared with AQP9(+/-):UT-A1/3(+/-) mice. However, expression analysis by RT-PCR did not identify known UT-A transcripts in liver. High-protein diet followed by 24-h fasting affected the concentrations of urea and ammonium ions in AQP9(-/-) mouse liver and plasma without generating an apparent tissue-to-plasma urea gradient. We conclude that AQP9 and unidentified UT-A urea channels constitute primary but redundant urea facilitators in murine hepatocytes.

  8. Exploring Factors Affecting Emergency Medical Services Staffs' Decision about Transporting Medical Patients to Medical Facilities

    PubMed Central

    Seyedin, Hesam; Jamshidi-Orak, Roohangiz

    2014-01-01

    Transfer of patients in medical emergency situations is one of the most important missions of emergency medical service (EMS) staffs. So this study was performed to explore affecting factors in EMS staffs' decision during transporting of patients in medical situations to medical facilities. The participants in this qualitative study consisted of 18 EMS staffs working in prehospital care facilities in Tehran, Iran. Data were gathered through semistructured interviews. The data were analyzed using a content analysis approach. The data analysis revealed the following theme: “degree of perceived risk in EMS staffs and their patients.” This theme consisted of two main categories: (1) patient's condition' and (2) the context of the EMS mission'. The patent's condition category emerged from “physical health statuses,” “socioeconomic statuses,” and “cultural background” subcategories. The context of the EMS mission also emerged from two subcategories of “characteristics of the mission” and EMS staffs characteristics'. EMS system managers can consider adequate technical, informational, financial, educational, and emotional supports to facilitate the decision making of their staffs. Also, development of an effective and user-friendly checklist and scoring system was recommended for quick and easy recognition of patients' needs for transportation in a prehospital situation. PMID:24891953

  9. Factors affecting pesticide occurrence and transport in a large Midwestern river basin

    USGS Publications Warehouse

    Crawford, Charles G.

    2001-01-01

    Several factors affect the occurrence and transport of pesticides in surface waters of the 29,400 km2 White River Basin in Indiana. A relationship was found between pesticide use and the average annual concentration of that pesticide in the White River, although this relationship varies for different classes of pesticides. About one percent of the mass applied of each of the commonly used agricultural herbicides was transported from the basin via the White River. Peak pesticide concentrations were typically highest in late spring or early summer and were associated with periods of runoff following application. Concentrations of diazinon were higher in an urban basin than in two agricultural basins, corresponding to the common use of this insecticide on lawns and gardens in urban areas. Concentrations of atrazine, a corn herbicide widely used in the White River Basin, were higher in an agricultural basin with permeable, well-drained soils, than in an agricultural basin with less permeable, more poorly drained soils. Although use of butylate and cyanazine was comparable in the White River Basin between 1992 and 1994, concentrations in the White River of butylate, which is incorporated into soil, were substantially less than for cyanazine, which is typically applied to the soil surface.

  10. New HYDRUS Modules for Simulating Preferential Flow, Colloid-Facilitated Contaminant Transport, and Various Biogeochemical Processes in Soils

    NASA Astrophysics Data System (ADS)

    Simunek, J.; Sejna, M.; Jacques, D.; Langergraber, G.; Bradford, S. A.; van Genuchten, M. Th.

    2012-04-01

    We have dramatically expanded the capabilities of the HYDRUS (2D/3D) software package by developing new modules to account for processes not available in the standard HYDRUS version. These new modules include the DualPerm, C-Hitch, HP2/3, Wetland, and Unsatchem modules. The dual-permeability modeling approach of Gerke and van Genuchten [1993] simulating preferential flow and transport is implemented into the DualPerm module. Colloid transport and colloid-facilitated solute transport, the latter often observed for many contaminants, such as heavy metals, radionuclides, pharmaceuticals, pesticides, and explosives [Šimůnek et al., 2006] are implemented into the C-Hitch module. HP2 and HP3 are the two and three-dimensional alternatives of the HP1 module, currently available with HYDRUS-1D [Jacques and Šimůnek, 2005], that couple HYDRUS flow and transport routines with the generic geochemical model PHREEQC of Parkhurst and Appelo [1999]. The Wetland module includes two alternative approaches (CW2D of Langergraber and Šimůnek [2005] and CWM1 of Langergraber et al. [2009]) for modeling aerobic, anaerobic, and anoxic biogeochemical processes in natural and constructed wetlands. Finally, the Unsatchem module simulates the transport and reactions of major ions in a soil profile. Brief descriptions and an application of each module will be presented. Except for HP3, all modules simulate flow and transport processes in two-dimensional transport domains. All modules are fully supported by the HYDRUS graphical user interface. Further development of these modules, as well as of several other new modules (such as Overland), is still envisioned. Continued feedback from the research community is encouraged.

  11. Disposal Unit Source Term by One-Dimensional, Transient, Finite-Difference, Subsurface Release and Transport of Contaminants.

    1995-07-07

    DUST solves for release and transport of contaminants from containerized wastes. Each container may have unique properties (i.e., time to failure or localized failure, e.g., pitting) and each waste form may have unique release properties. Release from the waste form is limited by one of four physical or chemical restraints: solubility, diffusion, dissolution, and surface wash-off with partitioning. The release from the waste form acts as a source for transport in the advection/dispersion equation. Transportmore » is modeled in one-dimension through the groundwater pathway from subsurface disposal. RNUCL.DAT, database of half-lives, solubility limits, and atomic mass for selected radionuclides, is included in this package.« less

  12. NUMERICAL MODELING OF CONTAMINANT TRANSPORT IN FRACTURED POROUS MEDIA USING MIXED FINITE ELEMENT AND FINITE VOLUME METHODS

    SciTech Connect

    Taylor, G.; Dong, C.; Sun, S.

    2010-03-18

    A mathematical model for contaminant species passing through fractured porous media is presented. In the numerical model, we combine two locally conservative methods, i.e. mixed finite element (MFE) and the finite volume methods. Adaptive triangle mesh is used for effective treatment of the fractures. A hybrid MFE method is employed to provide an accurate approximation of velocities field for both the fractures and matrix which are crucial to the convection part of the transport equation. The finite volume method and the standard MFE method are used to approximate the convection and dispersion terms respectively. The model is used to investigate the interaction of adsorption with transport and to extract information on effective adsorption distribution coefficients. Numerical examples in different fractured media illustrate the robustness and efficiency of the proposed numerical model.

  13. Metal contamination of soils and crops affected by the Chenzhou lead/zinc mine spill (Hunan, China).

    PubMed

    Liu, Hongyu; Probst, Anne; Liao, Bohan

    2005-03-01

    , and rice and capsicum had high Cd concentration in the edible parts. However, the toxic element concentrations in maize, sorghum, Adzuki bean, soybean and mung bean remained lower than the threshold levels. The bio-accumulation factors (BAFs) of crops were in the order: Cd>Zn>Cu>Pb>As. BAF was typically lower in the edible seeds or fruits than in stems and leaves. The accumulation effect strongly depends on the crop's physiological properties, the mobility, of the metals, and the availability of metals in soils but not entirely on the total element concentrations in the soils. Even so, the estimated daily intake amount of Cu, Zn, Cd, and Pb from the crops grown in the affected three sites and arsenic at SZY and GYB exceeded the RDA (Recommended dietary allowance) levels. Subsequently, the crops grown in Chenzhou Pb/Zn mine waste affected area might have a hazardous effect on the consumer's health. This area still needs effective measures to cure the As, Cd, Pb, Zn and Cu contamination. PMID:15740766

  14. A large-scale model for simulating the fate & transport of organic contaminants in river basins.

    PubMed

    Lindim, C; van Gils, J; Cousins, I T

    2016-02-01

    We present STREAM-EU (Spatially and Temporally Resolved Exposure Assessment Model for EUropean basins), a novel dynamic mass balance model for predicting the environmental fate of organic contaminants in river basins. STREAM-EU goes beyond the current state-of-the-science in that it can simulate spatially and temporally-resolved contaminant concentrations in all relevant environmental media (surface water, groundwater, snow, soil and sediments) at the river basin scale. The model can currently be applied to multiple organic contaminants in any river basin in Europe, but the model framework is adaptable to any river basin in any continent. We simulate the environmental fate of perfluoroctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in the Danube River basin and compare model predictions to recent monitoring data. The model predicts PFOS and PFOA concentrations that agree well with measured concentrations for large stretches of the river. Disagreements between the model predictions and measurements in some river sections are shown to be useful indicators of unknown contamination sources to the river basin.

  15. NUTRIENT TRANSPORT DURING BIOREMEDIATION OF CONTAMINATED BEACHES: EVALUATION WITH LITHIUM AS A CONSERVATIVE TRACER

    EPA Science Inventory

    Bioremediation of oil-contaminated beaches typically involves fertilization with nutrients that are thought to limit the growth rate of hydrocarbon-degrading bacteria. Much of the available technology involves application of fertilizers that release nutrients in a water-soluble ...

  16. THE TRANSPORT AND FATE OF ETHANOL AND BTEX IN GROUNDWATER CONTAMINATED BY GASOHOL. (R821114)

    EPA Science Inventory

    Ethanol is used a component in all gasoline in Brazil, and its use could increase significantly in the U.S. to meet the requirements of the Clean Air Act Amendments. Recent problems with ground water contamination by methyl tert-butyl ether (MTBE) have made policymakers more c...

  17. Role of benthic communities in organic contaminant transport and fate. 2: Bioaccumulation and biotransformation

    SciTech Connect

    Dickhut, R.M.; Schaffner, L.C.; Lay, P.W.; Mitra, S. |

    1994-12-31

    Numerous macrobenthic organisms from lower Chesapeake Bay have been observed to rapidly accumulate and transform a series of organic contaminants (OCs). Bioaccumulation and biotransformation vary both within and among major taxa, and with the OC physical-chemical properties. Bioaccumulation of OCs is rapid for various organisms regardless of feeding behavior indicating that uptake of contaminants from the dissolved phase may be important. Comparison of OC and metabolite body burdens to those in the corresponding sediment indicate three types of behavior for OC fluxes through the organisms over 56 days of exposure to contaminated sediments: steady state between contaminant uptake and elimination, faster uptake than elimination corresponding to bioaccumulation, and rapid loss relative to uptake, with decreasing bioaccumulation factors with time. OC loss mechanisms from operationally defined detectable pools in benthic biota may include: elimination of parent compound or metabolites, and binding of reactive metabolites to cellular structures. OC metabolite production and loss rates in benthic macrofauna from Chesapeake Bay are currently under investigation. Bioaccumulation and transformation of OCs by benthic organisms are of importance in determining their effects, including trophic transfer of organic pollutants, on aquatic ecosystems.

  18. Study of contaminant transport at an open-tipping waste disposal site.

    PubMed

    Ashraf, Muhammad Aqeel; Yusoff, Ismail; Yusof, Mohamad; Alias, Yatimah

    2013-07-01

    Field and laboratory studies were conducted to estimate concentration of potential contaminants from landfill in the underlying groundwater, leachate, and surface water. Samples collected in the vicinity of the landfill were analyzed for physiochemical parameters, organic contaminants, and toxic heavy metals. Water quality results obtained were compared from published data and reports. The results indicate serious groundwater and surface water contamination in and around the waste disposal site. Analysis of the organic samples revealed that the site contains polychlorinated biphenyls and other organo-chlorine chemicals, principally chloro-benzenes. Although the amount of PCB concentration discovered was not extreme, their presence indicates a potentially serious environmental threat. Elevated concentrations of lead, copper, nickel, manganese, cadmium, and cobalt at the downgradient indicate that the contamination plume migrated further from the site, and the distribution of metals and metals containing wastes in the site is nonhomogeneous. These results clearly indicate that materials are poorly contained and are at risk of entering the environment. Therefore, full characterization of the dump contents and the integrity of the site are necessary to evaluate the scope of the problem and to identify suitable remediation options.

  19. Factors Affecting Occurrence and Distribution of Selected Contaminants in Ground Water From Selected Areas in the Piedm