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This review covers studies related to groundwater quality and has been arranged by contaminant type. For each contaminant the quantity, fate and transport, remediation measures, and models published over the past year are presented. FLOWA methodology for stochastic management of groundwater flow and quality was presented by Bakr et al (2003) using coupled flow and mass transport equations. Using a multi-objective formulation of the management problem and analysis of its results, it was possible to identify an appropriate remediation scheme. A mathematical model for solute transport, using a laplace transform power series, was used to describe solute transport in a convergent flow field with scale-dependent dispersion (Chen et al, 2003a). The model results showed good agreement with field data. Woods et al (2003) showed that numerical error in groundwater transport models could lead to quantitative and qualitative changes in behavior. The authors confirmed this finding by showing 2190 the Elder problem to be extremely sensitive to the simulation method used. Nonreactive transport at the boarder of various asymmetrical cavities was modeled by Selvadurai (2003). Analytical results were developed for time-and spacedependent distribution of contaminant concentration in porous media, which can also exhibit natural attenuation.A block-effective macrodispersion model was used to simulate transport in heterogeneous aquifers (Rubin et al, 2003). The closed-form analytical results were attained very quickly. Das and Nassehi (2003) modeled contaminant mobility in the subsurface domains with multiple free/porous interfaces. The authors attempted to remove the limitations of previous mathematical models by imposing multiple pervious boundaries. The effects local-scale heterogeneity and non-linear, kinetically limited sorption phenomena on contaminant transport in porous media was discussed by Johnson et al (2003a). The results indicated that local-scale physical heterogeneity controlled the non-ideal transport behavior of trichloroethene and non-ideal sorption was of secondary importance. The flow behavior of liquid carbon tetrachloride in unsaturated heterogeneous porous media was studied by Oostrom et al (2003). The results indicate that nonspreading behavior of NAPLs should be implemented in simulators to account for the formation of residual saturations. A dependence of DNALP behavior on saturation history was demonstrated by Gerhard and Kueper (2003) using laboratory scale testing. Laboratory and numerical modeling investigations of flow and transport near a seepage face boundary was conducted by Simpson et al (2003a). The 2191 authors concluded that the use of the Dupuit approximations might introduce error into the analysis of localized solute transport near the seepage face.Anderson applied an approximation that replaced the leaky boundary with an equivalent layer that had a one-dimensional resistance to flow. The solution compared favorably with the commonly utilized Dupuit approximation.A model for unsaturated flow...

This review covers literature related to groundwater quality and has been arranged by contaminant type. For each contaminant, quantity, fate and transport, remediation measures and models published during 2004 are presented. CHLORINATED ORGANICSSources, Quantities, and Transport. One hundred percent of 413 shallowdomestic supply wells in the United States were found to contain measurable levels of halogenated VOCs (Shapiro, et al., 2004). Atmospheric deposition, spills, leaking landfills, and leaking underground storage tanks were important sources of contamination. The results of a laboratory scale numerical investigation of interfacial mass transfer of volatile chlorinated hydrocarbons during soil vapor extraction were presented by Hoeg et al. (2004). The model allowed for separation of equilibrium and non-equilibrium domains and demonstrated that sorption, volatility, and diffusivity are all important in determining the gas phase concentrations of volatile halogenated organic compounds.Remediation. A novel method for using n-butanol to achieve density conversion of chlorinated DNAPLs followed by surfactant flushing was presented by Ramsburg et al. (2004). This density modified displacement technique was concluded to have great promise as an effective source zone remediation technology. Taylor et al. (2004a) determined that ethanol addition enhanced the micellular solubilization and enhanced the recovery of tetrachloroethene NAPL.Ethanol increased the PCE solubilization capacity of the surfactant (Tween 80) and decreased the density of PCE from 1.002 to 0.986 g/cm super (3).Abiotic natural attenuation of carbon tetrachloride via surface-mediated dehalogenation by Fe (II) on goethite was discussed by Elsner et al. (2004).Increasing pH and the presence of hydrogen radical donors such as natural organic matter both enhanced the formation of the toxic daughter product chloroform. Four samples of two commercially available iron brands were used as substrate for iron permeable reactive barriers for remediation of perchloroethylene, trichloroethylene, cis-dichloroethylene (cDCE), and vinyl chloride. Differences in kinetics and carbon isotope fractionation for cDCE and vinyl chloride may be related to competing hydrogenolysis and beta-elimination reactions during reductive dechlorination on the iron surface. Gusamo et al.(2004) studied iron reactive barriers in columns using 1, 2 dichloroethane, 1, 1, 2trichloroethane, and tetrachloroethene contaminated groundwater. It was concluded that reductive dechlorination with metallic iron can have different results; depending on contaminant type and that the potential for more toxic byproduct formation exists. A batch-test study of 1, 1, 1-trichloroethane 2464 dechlorination by zero-valent iron was conducted by Lookman et al. (2004) which demonstrated that the TCA could be fully removed within hours. Chloroethane, which resists reductive dehalogenation by zero-valent iron did not accumulate in these experiments and was believed to have hydrolyzed of have been degraded by Dehal...

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