Solvent extraction for separating micellar-solubilized contaminants and anionic surfactants

Decontamination of contaminant-laden surfactant solutions is critical to successful implementation of surfactant-enhanced aquifer remediation (SEAR). Solvent extraction was studied for removing micellar-solubilized contaminants having low equivalent alkyl carbon numbers (EACNs) from surfactant solutions. Factors influencing the solvent extraction of micellar-solubilized contaminant were studied, including surfactant concentration, solution salinity, solvent solubilization, and solvent/solution volumetric ratio. A model was developed to quantify the impacts of these factors on contaminant removal. The good agreement between experimental results and model predictions corroborates assumptions made in the model development. From these results, it is concluded that extracting solvents must have much higher EACNs than that of the contaminant to reduce the micellar solubilization of the solvents, which can significantly reduce contaminant removal efficiency. However, the highest EACN solvent is not necessarily the best one for contaminant removal due to other constraints (e.g., molecular weight and viscosity). Increasing the total surfactant concentration or salinity of an anionic surfactant solution increases its contaminant solubilization capacity but reduces the contaminant removal efficiency by solvent extraction. Continuous column extraction operated at a low column surface loading rate allowed contaminant partitioning to approach equilibrium conditions, and multistage column extraction was able to improve the contaminant removal efficiency while minimizing solvent requirement.     

Solid-solution partitioning of organic matter in soils as influenced by an increase in pH or Ca concentration

Organic matter is an important component of soil with regard to the binding of contaminants. Hence, the partitioning of organic matter influences the partitioning of soil contaminants. The partitioning of organic matter is, among other factors, influenced by the ionic composition and ionic strength of the soil solution. This study focuses on the behavior of organic matter after a change in the ionic composition of the soil solution, particularly in Ca concentration and pH. Different amounts of Ca(NO3)2 and NaOH were added to soil suspensions. The dissolved organic carbon (DOC) concentration increased with increasing pH (addition of NaOH), whereas an increase in Ca (addition of Ca(NO3)2) had the opposite effect. A stronger increase in DOC was observed if a single dose of NaOH was added, compared to a gradual addition of the same amount of NaOH. Cation binding by organic matter in the supernatant was calculated using the NICA-Donnan model. The log DOC concentration appeared to be correlated to the Donnan potential, calculated under the assumption that all DOC equals humic acid. This correlation was found for all eight neutral to acidic soils used in this study, although the slopes and elevations of the regression lines varied. The slope varied by a factor of 2 and the elevation appeared to be strongly influenced by the DOC concentration in the untreated soils, which is related to the total organic matter in the soil. Finally, we predicted the Donnan potential on the basis of an extraction of untreated soil with 0.03 M NaNO3, and the total additions of Ca(NO3)2 and NaOH. Comparison of these predictions with speciation calculations in solution showed a good correlation, indicating that a combination of one batch experiment and the presented calculation procedure can provide good estimations of DOC concentrations after addition of chemicals.     

Exposure-effect model for calculating copper effect concentrations in sediments with varying copper binding properties: a synthesis

An exposure-effects model is described for calculating copper effect concentrations for benthic organisms in sediments with varying copper-binding properties. It is based on a bioenergetic-based kinetic model that describes the rate of assimilation of copper by benthic organisms from dissolved and particulate phases. During acute exposures, the total copper assimilated by the organisms was used as a measure of the organisms' exposure to bioavailable copper, and toxicity occurs when the copper exposure exceeds a threshold value. Exposure-effects models were developed for nine benthic organisms and were used to predict the effect of sediment-water partitioning (Kd) and copper assimilation from ingested solids on toxic effects and how these factors will influence derived sediment quality guideline (SQG) concentrations. Species sensitivity distributions were used to calculate SQG concentrations for copper for sediments of varying copper binding properties. The modeling indicated that "single value" SQG concentrations would be ineffective for predicting the toxicity of metals in sediment. It is proposed that, for all contaminants (not just metals), a better approach would be to have SQG concentrations, or ranges, that are applied to different sediment types. SQGs should account for contaminant exposure from both water-filtration and particulate-ingestion exposure routes, as can be achieved by models of sediment-water contaminant partitioning (Kd) and the contaminant assimilation efficiency (AE) of ingested particles. The study indicates that improved mechanistic models of contaminant exposure, as influenced by both organism physiology and sediment properties, are needed to predict toxic effects in sediments.     

Desorption of hydrophobic compounds from laboratory-spiked sediments measured by Tenax absorbent and matrix solid-phase microextraction

Tenax extraction and matrix solid-phase microextraction (matrix-SPME) were used to study desorption of hydrophobic contaminants (HOC) from sediments. 14C-labeled hexachlorobiphenyl, DDE, permethrin, chlorpyrifos, and phenanthrene were individually spiked into sediments differing in physical characteristics. Sequestration of the HOCs into sediment was observed for all compounds, and desorption was described by rapid, slow, and very slow rates. The freely dissolved HOC concentration in the sediment porewater was estimated by matrix-SPME, and serial sampling was used to ensure equilibrium was achieved among sediment, porewater and matrix-SPME fiber. Differences in partitioning of the HOCs between sediment and porewater for the different sediments were reduced by replacing the HOC concentration in sediment with the rapidly desorbing fraction. The significantly lower porewater concentration determined from matrix-SPME, than predicted from equilibrium partitioning theory (EPT), showed that only a small fraction of sediment HOCs were available for equilibrium and the predictability of EPT can be improved with the consideration of sequestration in sediment. A good correlation was noted between sediment concentration in the rapidly desorbing fraction measured by Tenax extraction, and SPME fiber concentration as determined by matrix-SPME. Thus, the two methods both tracked the readily desorbed contaminant equally well though Tenax extraction measures the accessible pool, and matrix-SPME measures the chemical activity of the HOCs.     

Bioaccessibility of metals in dust from the indoor environment: application of a physiologically based extraction test

A physiologically based extraction test, simulating sequential digestion in the stomach and intestine, has been applied to dust samples collected from various domestic and working settings to define bioaccessible concentrations of metals (Al, Ca, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sn, U, Zn) in the indoor environment. With the exception of Ca, Cd, and Zn in the stomach phase, mean bioaccessibilities (relative to respective total metal concentrations) were less than 50%. For a given metal, bioaccessibility in either phase was variable among samples but, in many cases, displayed an inverse dependence on total concentration. This suggests that, to a good approximation, variations in both metal contamination and accessibility in the indoor environment arise from variable proportions of metal-rich particulates of low digestibility. Compared with accessibility in the stomach, accessibility in the more alkaline, carbonate-rich intestine was either lower (Al, Ca, Cd, Mn, Ni, Sn, Pb, Zn), similar (Co, Cu, Fe) or greater (Cr, U). We attribute these observations to precipitation and/or readsorption in the intestine, stabilization by complexation, or anion-like adsorption of negatively charged, polyatomic species, respectively.     

Assessment of a sequential extraction procedure for perturbed lead-contaminated samples with and without phosphorus amendments

Sequential extraction procedures are used to determine the solid-phase association in which elements of interest exist in soil and sediment matrixes. Foundational work by Tessier et al. (Tessier, A.; Campbell, P. G. C.; Bisson, M. Anal. Chem. 1979, 51, 844-851) has found widespread acceptance and has been employed as an operational definition for metal speciation in solid matrixes. However, a major obstacle confronting sequential extraction procedures is species alteration of extracted metals before, during, and after separation of solids from solution. If this occurs, the results obtained from sequential extraction do not provide an accurate account of metal speciation within the matrix because the metal forms are altered from their field state. Many researchers dismiss this drawback since several sorption and precipitation processes are believed to occur at time scales much longer than any particular extraction step. This assumption may not be valid. The objectives of this study were to investigate the potential formation of pyromorphite (Pb5(PO4)3Cl) during the sequential extraction steps of Pb-spiked samples with and without calcium phosphate amendments and to examine the differences in the operationally defined distribution of Pb in samples with and without the presence of P. The systems that were examined in the absence of phosphate behaved, for the most part, adequately according to the operational definitions of the extraction procedure. However, when the samples were amended with phosphate, results were drastically changed with a significant shift of extractable Pb to the residual phase. This redistribution was due to pyromorphite formation during the extraction procedure as confirmed by X-ray diffraction and X-ray absorption (XAS) spectroscopies. These results indicate that sequential extraction methods may not be suitable for Pb speciation in perturbed environmental systems (i.e., fertilized agricultural soils or amended contaminated soils) and that rigorous interpretation should be avoided, if not supported by methods to definitively prove metal speciation (e.g., XAS).     

Role of weathered coal tar pitch in the partitioning of polycyclic aromatic hydrocarbons in manufactured gas plant site sediments

Polycyclic aromatic hydrocarbons (PAHs) in manufactured gas plant (MGP) site sediments are often associated with carbonaceous particles that reduce contaminant bioavailability. Although black carbon inclusive partitioning models have been proposed to describe elevated PAH partitioning behavior, questions remain on the true loading and association of PAHs in different particle types in industrially impacted sediments. In the studied MGP sediments, the light density organic particles (coal, coke, wood, and coal tar pitch) comprised 10-20% of the total mass and 70-95% of the PAHs. The remainder of the PAHs in sediment was associated with the heavy density particles (i.e., sand, silt, and clays). Among the different particle types, coal tar pitch (quantified by a quinoline extraction method) contributed the most to the bulk sediment PAH concentration. Aqueous partition coefficients for PAHs measured using a weathered pitch sample from the field were generally an order of magnitude higher than reported for natural organic matter partitioning, and match well with theoretical predictions based on a coal tar-water partitioning model. A pitch-partitioning inclusive model is proposed that gives better estimates of the measured site-specific PAH aqueous equilibrium values than standard estimation based on natural organic matter partitioning only. Thus, for MGP impacted sediments containing weathered pitch particles, the partitioning behavior may be dominated by the sorption characteristics of pitch and not by natural organic matter or black carbon.     

A chemical extraction method for mimicking bioavailability of polycyclic aromatic hydrocarbons to wheat grown in soils containing various amounts of organic matter

In this study, we have evaluated the extent to which organic matter contents in soils influence the accumulation of PAHs by the roots of wheat plants and have developed a rapid chemical method for determining the bioavailability of PAH. Four polycyclic aromatic hydrocarbons (PAHs), naphthalene, acenaphthylene, fluorene, and phenanthrene, were added to natural soil samples with different amounts of organic matterfor pot experiments to evaluate apparent bioavailability of PAHs to wheat roots (Triticum aestivum L.). The extractabilities of PAHs in the soil were tested by a sequential extraction scheme using accelerated solvent extraction with water, n-hexane, and a mixture of dichloromethane and acetone as solvents. The water or n-hexane-extractable PAHs were positively correlated to dissolved organic matter (DOM) and negatively correlated to total organic matter (TOM), indicating mobilization and immobilization effects of DOM and TOM on soil PAHs, respectively. The apparent accumulation of PAHs by wheat roots was also positively and negatively correlated to DOM and TOM, respectively. As a result, there are positive correlations between the amounts of PAHs extracted by water or n-hexane and the quantities accumulated in plant roots, suggesting the feasibility of using water- or n-hexanes-extractable fractions as indicators of PAH availability to plants.     

Modeling the transport of metals with rate-limited EDTA-promoted extraction and dissolution during EDTA-flushing of copper-contaminated soils

EDTA-flushing of artificially contaminated soils enhanced Cu extraction but also induced mineral dissolution simultaneously. The mobilization and transport of these metal-EDTA complexes was investigated with column experiments. A quantitative transport model was proposed for simulating the experimental breakthrough curves of Cu, Fe, Al, and Ca. The rate-limited EDTA-promoted extraction and dissolution could be described by respective second-order kinetic terms, which were necessary for explaining the time-dependent depletion of extractable metals (sorbed and indigenous) in soils with continuous EDTA-flushing. Simultaneous simulation of extraction of sorbed Cu and dissolution of soil Fe, Al, and Ca is more conceptually accurate than individual modeling of each metal because the latter approach tends to overestimate the concentration of free EDTA during transport and thus underestimate the rate coefficients of EDTA-promoted dissolution. The fitted rate coefficients of Cu were about an order of magnitude larger than those of Fe and Al; these values probably reflect Cu extraction from weakly sorbed fractions and Fe and Al dissolution from amorphous oxides. The apparent retardation of Fe, Al, and Ca transport had to be taken into account by empirical determination, which was attributed to the metal lability in soils and thermodynamics of surface complexation.     

Predicting bioavailability of sediment-associated organic contaminants for Diporeia spp. and oligochaetes

Biota-sediment accumulation factors (BSAF) were calculated for Diporeia spp. and oligochaete worms exposed to polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) from field-collected sediment. These data were compared to the contaminant fraction extracted from sediment with Tenax resin using a 24 h extraction. A previous laboratory study suggested a linear relationship between log BSAF and the contaminant fraction rapidly desorbed from sediment. However, the BSAF data in our study did not fit this relationship. Better predictive regressions for both PCBs and PAHs were found when the log of the lipid-normalized organism contaminant concentrations were plotted against the log of the Tenax-extracted organic carbon-normalized sediment contaminant concentration. Regression lines for the two species had the same slope, but the Diporeia intercept was 2.3 times larger. When adjusted for a 6 h Tenax extraction, based on a regression between 6 and 24 h Tenax extractions, data from this study and two other studies that included multiple oligochaete species fit a single predictive regression. The exception included some PAHs that fell below the regression line. Thus, a single relationship generally predicted bioaccumulation across sediments, compound classes, oligochaete species, and among laboratories.     

Improved extraction of oil from chickpea under ultrasound in a dynamic system

In this work, ultrasound-assisted dynamic extraction (UADE) is proposed. The dynamic approach allows go-and-backward circulation of solvent through the sample subjected to the action of ultrasound. The extraction efficiency of hexane, isopropanol, a hexane–isopropanol mixture as well as the comparison between static extraction and flow-through extraction with or without ultrasound were evaluated. The effects of ultrasonic power, extraction temperature, time and extractant flow rate on the yield of oil from chickpea were also investigated. Results showed that solvent type significantly influenced extraction efficiency, the combination of hexane and isopropanol obtained the highest oil yield. Dynamic system and ultrasonication dramatically enhanced the extraction of oil. Moreover, results indicated that 20 min was sufficient for UADE with lower cost to obtain higher extraction yields (10.45% and 2.06% higher) than those by 4 h conventional solvent extraction (CSE) and 30 min ultrasound-assisted extraction (UAE) for oil. Gas chromatography analysis of chickpea oil indicated that the oil was enriched with polyunsaturated fatty acids and few changes in fatty acid composition occurred in ultrasonicated oil.     

三相分离技术在食品原料中营养组分提取的应用进展

近年来,在生物分离技术领域人们越来越追求绿色、高效、经济、可扩展的分离方法。三相分离法作为一种新型的非色谱生物分离技术,受到研究人员的广泛关注。随着三相分离技术的不断发展,各种类型的三相分离体系层出不穷,即以叔丁醇为提取剂的传统三相分离体系和以碳酸二甲酯、离子液体、低共熔溶剂为提取剂的其他三相分离体系。此外三相分离法对于成分的提取范围也越来越广泛,不仅涉及油脂、蛋白质、酶、多糖和脂溶性色素等化合物的提取,还可满足多种组分的同时分离,实现对原料样品的高值化利用。因此本文主要综述不同类型的三相分离体系、机制并对目前三相分离法在提取组分中的应用进行归纳,以期为更好地利用三相分离法提取食品组分提供科学的理论参考。     

Use of polymer mats in series for sequential reactive barrier remediation of ammonium-contaminated groundwater: field evaluation

A pilot-scale field trial was undertaken to evaluate the potential of in situ polymer mats (installed in series) as permeable reactive barriers within a treatment wall remediation system to induce sequential bioremediation of ammonium-contaminated groundwater. The treatment wall consisted of 10 m wide impermeable wings on either side of a 0.75 m wide permeable reactive zone flow-through box. Two polymer mats were positioned in the flow-through box. The upgradient polymer mat within the flow-through box was used to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/nitrate as the groundwater moved past. The downgradient polymer mat delivered ethanol to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. The field trial was carried out at a near-shore location. Initially the flow-through box was left open; however, this resulted in substantial groundwater mixing, which inhibited sequential remediation. Once the flow-through box was in-filled with gravel, groundwater mixing was reduced, achieving a greater than 90% reduction in total N. Estimated first-order half-lives for nitrification and denitrification rates were 1.2 and 0.4 d, respectively. Field nitrification half-lives were approximately an order of magnitude greater than rates determined in large-scale columns using soil and groundwater from the site, while denitrification half-lives were similar. The results of this pilot-scale field trial indicate that sequential bioremediation of ammonium-contaminated groundwater at field scale is feasible using in situ polymer mats as permeable reactive barriers, although hydraulic conditions can be complex in such barrier systems.     

Uncertainty analysis of the use of a retailer fidelity card scheme in the assessment of food additive intake

The feasibility of using a retailer fidelity card scheme to estimate food additive intake was investigated in an earlier study. Fidelity card survey information was combined with information provided by the retailer on levels of the food colour Sunset Yellow (E110) in the foods to estimate a daily exposure to the additive in the Swiss population. As with any dietary exposure method the fidelity card scheme is subject to uncertainties and in this paper the impact of uncertainties associated with input variables including the amounts of food purchased, the levels of E110 in food, the proportion of food purchased at the retailer, the rate of fidelity card usage, the proportion of foods consumed outside of the home and bodyweights and with systematic uncertainties was assessed using a qualitative, deterministic and probabilistic approach. An analysis of the sensitivity of the results to each of the probabilistic inputs was also undertaken. The analysis identified the key factors responsible for uncertainty within the model and demonstrated how the application of some simple probabilistic approaches can be used quantitatively to assess uncertainty.     

Sequential electrolytic oxidation and reduction of aqueous phase energetic compounds

Contamination of soils and groundwater with energetic compounds has been documented at many former ammunition manufacturing plants and ranges. Recent research at Colorado State University (CSU) has demonstrated the potential utility of electrolytic degradation of organic compounds using an electrolytic permeable reactive barrier (e-barrier). In principle, an electrolytic approach to degrade aqueous energetic compounds such as hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) or 2,4,6-trinitrotoluene (TNT) can overcome limitations of management strategies that involve solely oxidation or reduction, through sequential oxidation-reduction or reduction-oxidation. The objective of this proof-of-concept research was to evaluate transformation of aqueous phase RDX and TNT in flow-through electrolytic reactors. Laboratory experiments were conducted using six identical column reactors containing porous media and expanded titanium-mixed-metal-oxide electrodes. Three columns tested TNT transformation and three tested RDXtransformation. Electrode sequence was varied between columns and one column for each contaminant acted as a no-voltage control. Over 97% of TNT and 93% of RDX was transformed in the reactors under sequential oxidation-reduction. Significant accumulation of known degradation intermediates was not observed under sequential oxidation-reduction. Removal of approximately 90% of TNT and 40% of RDX was observed under sequential reduction-oxidation. Power requirements on the order of 3 W/m2 were measured during the experiment. This suggests that an in-situ electrolytic approach may be cost-practical for managing groundwater contaminated with explosive compounds.     

Column extraction of heavy metals from soils using the biodegradable chelating agent EDDS

A possible remediation strategy for metal polluted soils is washing with chelants. Here, we compare the efficiency of batch and column extraction of Cu, Zn, and Pb from three soils using the biodegradable chelant EDDS. A total of 53-80% of Cu was extracted in batch and 18-26% in column extraction. For Zn, the extractability was 16-50% in batch and 20-64% in columns and for Pb 25-52 and 18-91%, respectively. Column leaching was therefore equally or better suited for Zn and Pb removal. The longer extraction time in the column resulted in more formations of Fe(III)EDDS by slow dissolution of iron oxides. Zn was uniformly washed from the column, while Cu and Pb were extracted in the top layers and deposited in the bottom layers, presumably by biodegradation of the metal-EDDS complexes and slow dissolution of iron oxides. Between 18 and 42% of the applied EDDS was lost through biodegradation after 7 weeks. In short time experiments, only 6% of EDDS was degraded. Using EDDS concentrations in excess of available heavy metals caused pronounced leaching of organic matter and clogging of the column. Our results prove that heap leaching using EDDS is a promising approach to reduce the heavy metal content of polluted soils.     

Solid-phase extraction for replacing dichloromethane partitioning in pesticide multiresidue analysis

 The Deutsche Forschungsgemeinschaft S 19 method is widely used for pesticide multiresidue analysis in crops. It includes a liquid-liquid partition step with dichloromethane, which is undesirable for toxicological and ecological reasons. Therefore, this step was replaced by a solid-phase extraction (SPE) of the diluted acetone extract with a mixture of RP-18-PolarPlus and cyano material, which was afterwards eluted with ethyl acetate. Using this novel approach for extraction, concentration and clean-up, the recovery rates from fruits and vegetables fortified with 0.12–0.48 mg/kg of 31 pesticides with different chemical structures and polarities averaged 80% in most cases, except for some extremely polar compounds. The variation coefficients observed were near 5%. Compared to the partitioning step used hitherto, even higher recoveries were obtained by SPE for non-polar and medium-polar pesticides. In addition, the gas chromatograms often showed fewer interfering peaks from plant coextractives. Received: 20 July 1998     

A contaminant trap as a tool for isolating and measuring the desorption resistant fraction of soil pollutants

Bioremediation of contaminated soils often leaves a desorption-resistant pollutant fraction behind in the soil, which in the present study was isolated with a combination of diffusive carrier and infinite diffusive sink. Such a diffusive sink was made by casting a composite of silicone and activated carbon into the bottom of a large glass. Field-contaminated soil samples were then suspended in a cyclodextrin solution and incubated in such glasses for the continuous trapping of PAH molecules during their release from the soil matrix. The PAH concentrations remaining in the soil were determined by exhaustive extraction and compared with a biodegradation experiment. The concentration decline in the first soil was faster in the contaminant trap than in the biodegradation experiment, but the halting of the biodegradation process before reaching the legal threshold level was well indicated by the contaminant trap. The PAH concentrations in the second soil hardly decreased in the traps at all, in good agreement with the biodegradation experiment. The PAHs in this soil appeared to be "stuck" by strong sorption. The contaminant trap proved to be a practical approach to the isolation and quantification of the desorption-resistant PAH fraction.     

Evaluation of DNA extraction methods for PCR detection of fungal and bacterial contamination in cocoa extracts

Direct and sensitive PCR detection of contaminant microflora in cocoa extracts is affected by the quality of the template DNA. This study compares the efficacy of five different commercial DNA extraction methods, selective enrichment broths and use of glycolitic enzymes to obtain quality DNA for PCR detection of both fungi and bacteria in artificially inoculated cocoa extract samples. PCR-based methods were applied to detect contaminant microflora in cocoa extracts using as model organisms: Aspergillus nidulans, Bacillus subtilis, Escherichia coli and Salmonella enterica. The quality of the extracted DNA was assessed in terms of PCR inhibitor content with results indicating that the HighPure PCR template (Roche) kit was the best methodology under the conditions assayed. PCR protocols using this commercial kit and a combination of glycolitic enzymes and enrichment procedures gave a detection limit of 100 conidia/g and 100 cfu/g for filamentous fungi and bacteria, respectively. The selected extraction and PCR procedures were also tested to assess their suitability for detecting filamentous fungi and bacteria on an industrial scale. They were sensitive enough to detect fungal and bacterial contaminants within the legally required limits. The results obtained with the molecular approach were in agreement with those of standard microbiological tests but require a considerably shorter analysis time. Thus, the molecular approach provides a sensitive and rapid alternative to check for microbial contamination in cocoa extracts.     

Field-scale evaluation of the passive flux meter for simultaneous measurement of groundwater and contaminant fluxes

A new method, passive flux meter (PFM), has been developed and field-tested for simultaneously measuring contaminant and groundwater fluxes in the saturated zone at hazardous waste sites. The PFM approach uses a sorptive permeable medium placed in either a borehole or monitoring well to intercept contaminated groundwater and release "resident" tracers. The sorbent pack is placed in a groundwater flow field for a specified exposure time and then recovered for extraction and analysis. By quantifying the mass fraction of resident tracers lost and the mass of contaminant sorbed, groundwater and contaminant fluxes are calculated. Here, we assessed the performance of PFMs at the Canadian Forces Base Borden field site in Ontario, Canada. Two field tests were conducted under imposed groundwater flow fields: (1) radial flow to a well and (2) linear flow in a test channel confined by sheet pile walls on three sides. Both tests demonstrate that the local fluxes measured by PFM and averaged overthe screen interval were within 15% of imposed groundwaterflow and within 30% of measured contaminant mass flux. Patterns in depth variations in groundwater and contaminant fluxes, determined by the PFM approach, allow for site characterization at a higher spatial resolution. These results support the PMF method as a potential innovative alternative for measuring groundwater and contaminant fluxes in screened wells.