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Groundwater Contamination (groundwater + contamination)
Selected AbstractsMeasurement of Henry's law constant for methyl tert -butyl ether using solid-phase microextractionENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Britta G. Bierwagen Abstract Increasing groundwater contamination with methyl tert -butyl ether (MTBE) requires more efficient remediation technologies. Accurate measurement of MTBE's air,water partitioning coefficient (Henry's law constant, H) is important for the design and optimization of removal efficiency for many treatment systems as well as for predicting its fate and transport. Previously published data for MTBE appear to have some unusual nonlinearity at lower temperatures (15,30°C), and a wide range of values exists for dimensionless H at 25°C, from 0.0216 to 0.1226 in the published literature. We measured H for MTBE using headspace solid-phase microextraction (SPME) and a static method that considers equilibrium partitioning in a closed system, for temperatures between 15 and 40°C. To validate our methods, we measured H for benzene, toluene, and trichloroethylene and compared our results to previously published values, with excellent agreement. The Arrhenius plot for MTBE indicates that ln(HMBTE) = 6.85,2,900 T,1, with T in K. At 25°C, HMBTE = 0.0555 ± 0.0122. [source] Analysis of Soil Vapor Extraction Data to Evaluate Mass-Transfer Constraints and Estimate Source-Zone Mass FluxGROUND WATER MONITORING & REMEDIATION, Issue 3 2010Mark L. Brusseau Methods are developed to use data collected during cyclic operation of soil vapor extraction (SVE) systems to help characterize the magnitudes and time scales of mass flux associated with vadose zone contaminant sources. Operational data collected at the Department of Energy's Hanford site are used to illustrate the use of such data. An analysis was conducted of carbon tetrachloride vapor concentrations collected during and between SVE operations. The objective of the analysis was to evaluate changes in concentrations measured during periods of operation and nonoperation of SVE, with a focus on quantifying temporal dynamics of the vadose zone contaminant mass flux, and associated source strength. Three mass flux terms, representing mass flux during the initial period of an SVE cycle, during the asymptotic period of a cycle, and during the rebound period, were calculated and compared. It was shown that it is possible to use the data to estimate time frames for effective operation of an SVE system if a sufficient set of historical cyclic operational data exists. This information could then be used to help evaluate changes in SVE operations, including system closure. The mass flux data would also be useful for risk assessments of the impact of vadose zone sources on groundwater contamination or vapor intrusion. [source] Simultaneous analyses and applications of multiple fluorobenzoate and halide tracers in hydrologic studiesHYDROLOGICAL PROCESSES, Issue 14 2005Qinhong Hu Abstract An analytical method that employs ion chromatography has been developed to exploit the use of fluorobenzoic acids (FBAs) and halides more fully as hydrologic tracers. In a single run, this reliable, sensitive, and robust method can simultaneously separate and quantify halides (fluoride, chloride, bromide, and iodide) and up to seven FBAs from other common groundwater constituents (e.g. nitrate and sulphate). The usefulness of this analytical method is demonstrated in both field and laboratory tracer experiments. The field study examines the hydrologic response of fractures and the matrix to different flow rates and the contribution of matrix diffusion in chemical transport. Laboratory tracer experiments with eight geologic media from across the USA,mostly from Department of Energy facilities where groundwater contamination is prevalent and where subsurface characterization employing tracers has been ongoing or is in need,reveal several insights about tracer transport behaviour: (1) bromide and FBAs are not always transported conservatively; (2) the delayed transport of these anionic tracers is likely related to geologic media characteristics, such as organic matter, pH, iron oxide content, and clay mineralogy; (3) use of iodine as a hydrologic tracer should take into account the different sorption behaviours of iodide and iodate and the possible conversion of iodine's initial chemical form; (4) the transport behaviour of potential FBA and halide tracers under relevant geochemical conditions should be evaluated before beginning ambitious, large-scale field tracer experiments. Copyright © 2005 John Wiley & Sons, Ltd. [source] Effect of gas evolution on mixing and conversion in a flow-through electrochemical reactorAICHE JOURNAL, Issue 9 2009Matthew A. Petersen Abstract Flow-through electrolytic reactors (FTER) emplaced below the subsurface may be used to control the migration of groundwater contamination away from source zones. During prior studies with FTERs, water electrolysis and associated gas generation have occurred concurrently with contaminant degradation. Gas evolution-induced mixing within the electrode assembly has the potential to impact system performance. A mathematical model of the system was developed to capture the impact of mixing on transport processes in the system. Corresponding transient and steady-state tracer experiments using ferricyanide as a model contaminant were conducted to quantify mixing-dependent parameters and verify modeling results. Over a range of relevant groundwater flowrates, Peclet numbers were between 0.1 and 10, indicating that mixing was a important process under low-flow conditions. Comparison of experiments and model calculations demonstrated that incorporating gas evolution into the model was necessary for accurate performance prediction. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Leaching of heavy metals and nutrients from calcareous sandy-loam soil receiving municipal solid sewage sludgeJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2010Mohsen Jalali Abstract Leaching column experiments were conducted to determine the degree of mobility of heavy metals (HMs) and nutrients after the addition of municipal solid sewage sludge (MSS) in a sandy-loam soil. Treatments were (1) soil application of low metal content MSS, (2) soil application of metal-enriched municipal solid sewage sludge (EMSS), and (3) control. The MSS application represented a dose of 200 Mg dry weight (dw) ha,1. Soil columns were incubated at room temperature for 15 d and were irrigated daily with distilled water to make a total of 557,mm. Leachates were collected and analyzed for HMs and nutrients. The Ni and Pb added to soil via MSS and EMSS were found to be leached through the 20,cm columns of calcareous sandy soil although Ni and Pb concentrations in the percolate were small relative to the total amounts of metals applied. Losses of K+ from the EMSS, MSS, and control were 92.5, 82.0, and 52.5,kg ha,1, respectively. Losses of Mg2+ were in the range from 104.4 (control treatment) to 295.2,kg ha,1 (EMSS), while the loss of Ca2+ was in the range from 265.0 (control treatment) to 568.2,kg ha,1 (EMSS). The results showed that the amounts of P leached from EMSS (3.02,kg ha,1) and MSS (2.97,kg,1 ha,1) were significantly larger than those from the control treatment (1.54,kg ha,1). The geochemical code Visual MINTEQ was used to calculate saturation indices. Leaching of P in different treatments was controlled by rate-limited dissolution of hydroxyapatite, ,-tri-Ca phosphate, and octa-Ca phosphate. The results indicate that application of MSS to a sandy soil, at the loading rate used in this study, may pose a risk in terms of groundwater contamination with Ni, Pb, and the studied nutrients. [source] Heavy-metal displacement in chelate-treated soil with sludge during phytoremediationJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2006Stanley Liphadzi Abstract Heavy metals (HMs) in domestic sewage sludge, applied to land, contaminate soils. Phytoremediation is the use of plants to clean-up toxic HMs from soil. Chelating agents are added to soil to solubilize the metals for enhanced uptake. Yet no studies report the displacement of HMs in soil with sludge following solubilization with chelates. The objective of this work was to determine the uptake or leaching of HMs due to a chelate added to a soil from a sludge farm that had received sludge for 25 y. The soil was placed in long columns (105,cm long; , 39,cm) in a greenhouse. Columns either had a plant (hybrid poplar; Populus deltoides Marsh. × P. nigra L.) or no plant. After the poplar seedlings had grown for 144 d, the tetrasodium salt of the chelating agent EDTA was irrigated onto the surface of the soil at a rate of 1 g per,kg of soil. Drainage water, soil, and plants were analyzed for three toxic HMs (Cd, Ni, Pb) and four essential HMs (Cu, Fe, Mn, Zn). At harvest, extractable and total concentrations of each HM in the soil with EDTA were similar to those in soil without EDTA. The chelate did not affect the concentrations of HMs in the roots or leaves. With or without plants, EDTA mobilized all seven HMs and increased their concentrations in drainage water. Lower concentrations of Cd, Cu, Fe, Ni, and Zn in leachate from columns with EDTA and plants compared to columns with EDTA and no plants showed that poplars can reduce groundwater contamination by intercepting these HMs in the soil. But the poplar plants did not reduce Pb and Mn in the leachate from columns with EDTA. Concentrations of Cd and Pb in the leachate mobilized by EDTA remained above drinking-water standards with or without plants. The results showed that a chelate (EDTA) should not be added to a soil at a sludge farm to enhance phytoremediation. The chelate mobilized HMs that leached to drainage water and contaminated it. [source] Cryogenic extinguishment of liquid pool firesPROCESS SAFETY PROGRESS, Issue 1 2010Yiannis Levendis Abstract Results on fire extinguishment using direct application of liquid nitrogen are presented in this article. This technique targets challenging fires, such as burning hazardous chemicals or fuels, in which cases prompt suppression or extinguishment is paramount to prevent explosions, avoid release of toxic fumes and avert environmental catastrophes. Liquid nitrogen is a rather environmentally benign extinguishing agent that does not cause property damage or groundwater contamination. Application of this cryogen onto a hot pyrolyzing/burning surface induces abrupt vaporization, spread and expansion. The pyrolyzing gases are inerted, the surface is cooled and hence its pyrolysis rate is reduced, air is separated from the fuel, and the fire extinguishes. To demonstrate this technique, experiments were conducted with pool fires of ethanol, propanol, and diesel fuel. To examine the underlying principles, analysis of the results was conducted based on simplified calculations. Sufficient quantities of the cryogen extinguished the fires nearly instantaneously. Half-liter quantities were sufficient to extinguish 1 m2 pool fires. The method of dispensing and distributing the cryogen on the pool fires proved to be of considerable importance. The existence of wind, which disturbed the flame, was not found to prevent extinguishment. © 2009 American Institute of Chemical Engineers Process Saf Prog 2010 [source] The Impact of Environmental Contamination on Condo Prices: A Hybrid Repeat-Sale/Hedonic ApproachREAL ESTATE ECONOMICS, Issue 1 2006Bradford Case We extend the literature on the impact of externalities using an approach based on a hybrid of hedonic and repeat-sales methods. The externality in question is groundwater contamination in Scottsdale, Arizona. The use of condominium sales allows us to assume that major physical characteristics remain unchanged, but location parameters may be altered by urban growth and development as well as contamination. We find an economically significant discount for properties located in the contaminated area. Interestingly, it does not appear until several years after the contamination becomes publicly known, and it seems to have disappeared before the end of the study period. [source] An evaluation of permeable reactive barrier projects in CaliforniaREMEDIATION, Issue 1 2009John P. Muegge Permeable reactive barriers made of zero-valent iron (ZVI PRBs) have become a prominent remediation technology in addressing groundwater contamination by chlorinated solvents. Many ZVI PRBs have been installed across the United States, some as research projects, some at the pilot scale, and many at full scale. As a passive and in situ remediation technology, ZVI PRBs have many attractive features and advantages over other approaches to groundwater remediation. Ten ZVI PRBs installed in California were evaluated for their performance. Of those ten, three are discussed in greater detail to illustrate the complexities that arise when quantifying the performance of ZVI PRBs, and to provide comment on the national debate concerning the downgradient effects of source-zone removal or treatment on plumes of contaminated groundwater. © 2009 Wiley Periodicals, Inc. [source] Addressing soil gas vapor intrusion using sustainable building solutionsREMEDIATION, Issue 4 2009Ellen Moyer Soil gas vapor intrusion (VI) emerged in the 1990s as one of the most important problems in the investigation and cleanup of thousands of sites across the United States. A common practice for sites where VI has been determined to be a significant pathway is to implement interim building engineering controls to mitigate exposure of building occupants to VI while the source of contamination in underlying soil and groundwater is assessed and remediated. Engineering controls may include passive barriers, passive or active venting, subslab depressurization, building pressurization, and sealing the building envelope. Another recent trend is the emphasis on "green" building practices, which coincidentally incorporate some of these same engineering controls, as well as other measures such as increased ventilation and building commissioning for energy conservation and indoor air quality. These green building practices can also be used as components of VI solutions. This article evaluates the sustainability of engineering controls in solving VI problems, both in terms of long-term effectiveness and "green" attributes. Long-term effectiveness is inferred from extensive experience using similar engineering controls to mitigate intrusion of radon, moisture, mold, and methane into structures. Studies are needed to confirm that engineering controls to prevent VI can have similar long-term effectiveness. This article demonstrates that using engineering controls to prevent VI is "green" in accelerating redevelopment of contaminated sites, improving indoor air quality, and minimizing material use, energy consumption, greenhouse gas emissions, and waste generation. It is anticipated that engineering controls can be used successfully as sustainable solutions to VI problems at some sites, such as those deemed technically impracticable to clean up, where remediation of underlying soil or groundwater contamination will not be completed in the foreseeable future. Furthermore, green buildings to be developed in areas of potential soil or groundwater contamination may be designed to incorporate engineering controls to prevent VI. © 2009 Wiley Periodicals, Inc. [source] Use of mixed technologies to remediate chlorinated DNAPL at a Brownfields siteREMEDIATION, Issue 3 2008David Robinson A former chlorofluorocarbon manufacturing facility in northern New Jersey was purchased for redevelopment as a warehousing/distribution center as part of the New Jersey Department of Environmental Protection's Brownfields redevelopment initiative. Soil and groundwater at the site were impacted with dense nonaqueous-phase liquids (chlorinated organic compounds) and light nonaqueous-phase liquids (petroleum hydrocarbons). The initial remedial strategy (excavation and offsite disposal) developed by prior site owners would have been cost-prohibitive to the new site owners and made redevelopment infeasible. Mixed remedial technologies were employed to reduce the cost of remediation while meeting regulatory contaminant levels that are protective of human health and the environment. The most heavily impacted soils (containing greater than 95 percent of the contaminant mass) were excavated and treated onsite by the addition of calcium oxide and lime kiln dust coupled with physical mixing. Treated soils were reused onsite as part of the redevelopment. Residual soil and groundwater contamination was treated via in situ injections of emulsified oil to enhance anaerobic biodegradation, and emulsified oil/zero-valent iron to chemically reduce residual contaminants. Engineering (cap) and administrative (deed restriction) controls were used as part of the final remedy. The remedial strategy presented in this article resulted in a cost reduction of 50 percent of the initial remedial cost estimate. © 2008 Wiley Periodicals, Inc. [source] Remedial options for chlorinated volatile organics in a partially anaerobic aquiferREMEDIATION, Issue 4 2004Xiujin Qiu A laboratory study was conducted for the selection of appropriate remedial technologies for a partially anaerobic aquifer contaminated with chlorinated volatile organics (VOCs). Evaluation of in situ bioremediation demonstrated that the addition of electron donors to anaerobic microcosms enhanced biological reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA) with half-lives of 20, 22, and 41 days, respectively. Nearly complete reductions of PCE, TCE, 1,1,1-TCA, and the derivative cis-dichloroethene were accompanied by a corresponding increase in chloride concentrations. Accumulation of vinyl chloride, ethene, and ethane was not observed; however, elevated levels of 14CO2 (from 14C-TCE spiked) were recovered, indicating the occurrence of anaerobic oxidation. In contrast, very little degradation of 1,2-dichloropropane (1,2-DCP) and 1,1-dichlorethane (1,1-DCA) was observed in the anaerobic microcosms, but nutrient addition enhanced their degradation in the aerobic biotic microcosms. The aerobic degradation half-lives for 1,2-DCP and 1,1-DCA were 63 and 56 days, respectively. Evaluation of in situ chemical oxidation (ISCO) demonstrated that chelate-modified Fenton's reagent was effective in degrading aqueous-phase PCE, TCE, 1,1,1-TCA, 1,2-DCP, etc.; however, this approach had minimal effects on solid-phase contaminants. The observed oxidant demand was 16 g-H2O2/L-groundwater. The oxidation reaction rates were not highly sensitive to the molar ratio of H2O2:Fe2+:citrate. A ratio of 60:1:1 resulted in slightly faster removal of chemicals of concern (COCs) than those of 12:1:1 and 300:1:1. This treatment resulted in increases in dissolved metals (Ca, Cr, Mg, K, and Mn) and a minor increase of vinyl chloride. Treatment with zero-valent iron (ZVI) resulted in complete dechlorination of PCE, and TCE to ethene and ethane. ZVI treatment reduced 1,1,1-TCA only to 1,1-DCA and chloroethane (CA) but had little effect on reducing the levels of 1,2-DCP, 1,1-DCA, and CA. The longevity test showed that one gram of 325-mesh iron powder was exhausted in reaction with > 22 mL of groundwater. The short life of ZVI may be a barrier to implementation. The ZVI surface reaction rates (ksa) were 1.2 × 10,2 Lm,2h,1, 2 × 10,3 Lm,2h,1, and 1.2 × 10,3 Lm,2h,1 for 1,1,1-TCA, TCE, and PCE, respectively. Based upon the results of this study, in situ bioremediation appeared to be more suitable than ISCO and ZVI for effectively treating the groundwater contamination at the site. © 2004 Wiley Periodicals, Inc. [source] Using wind to power a groundwater circulation well,preliminary resultsREMEDIATION, Issue 4 2004Andrew Curtis Elmore In areas of the country where the U.S. Department of Energy has classified the available wind resources as Class 3 or greater, the use of wind turbines to provide power to relatively small remediation systems such as groundwater circulation wells may be technically and economically feasible. Groundwater circulation wells are a good candidate technology to couple with renewable energy, because the remediation system removes contamination from the subject aquifer with no net loss of the groundwater resource, while the wind turbine does not create potentially harmful air emissions. Wind data collected in the vicinity of the former Nebraska Ordnance Plant Superfund site were used to select a wind turbine system to provide a portion of the energy necessary to power a groundwater circulation well located in an area of high trichloroethylene groundwater contamination. Because utility power was already installed at the remediation system, a 10 kW grid inter-tie wind turbine system supplements the utility system without requiring batteries for energy storage. The historical data from the site indicate that the quantity of energy purchased correlates poorly with the quantity of groundwater treated. Preliminary data from the wind turbine system indicate that the wind turbine provides more energy than the remediation system treatment components and the well submersible pump require on a monthly average. The preliminary results indicate that the coupling of wind turbines and groundwater circulation wells may be an attractive alternative in terms of the system operation time, cost savings, and contaminant mass removal. © 2004 Wiley Periodicals, Inc. [source] | ||||||||||||||||