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The purpose of the present study was to conduct a comprehensive field-scale investigation to evaluate the effectiveness of the in situ cosolvent flushing technique for enhanced remediation of aquifers contaminated with residual NAPLs. Limitations or difficulties related to larger-scale applications were 2673

Experimental data on air−water partitioning of organic contaminants at temperatures above 40 °C is extremely scarce. We present Henry's law constants for trichloroethylene (TCE) in water between 10 and 95 °C determined using a modification of the Equilibrium Partitioning in Closed System (EPICS) procedure and calculated from vapor pressure and measured aqueous solubility data obtained by a column generator technique. The Henry's law constant for TCE increases by a factor of 20 between 10 and 95 °C, which is a dramatic change in volatility. Our results and a critical review of the thermodynamic equations suggest that the heat (enthalpy) of dissolution decreases with temperature and that Henry's law constants cannot be extrapolated to higher temperatures from the existing literature data. Heat of dissolution may be approximated by a linear function of temperature, leading to a simple equation for Henry's law constant ln k H = A − B/T + C ln T that fits the majority of the previously published experimental data. This equation is more precise than previously published equations, is valid for temperatures approaching 100 °C, and will assist in more accurate interpretation of Henry's law constant data for other chemicals of environmental concern.

Macromolecules in the pore fluid influence the mobility of hydrophobic compounds through soils. This study evaluated the significance of macromolecules in facilitating chemical transport under laboratory conditions. Partition coefficients between 14C-labeled hexachlorobenzene and three macromolecules [dextran, humic acid, and groundwater dissolved organic carbon (DOC)] were determined in a three-phase (water-macromolecule-soil) system. There were significant differences between the macro-molecu1e:water partition coefficients, which ranged from 1 X lo3 to 1 X 106. Soikwater partitioning for humic acid was demonstrated by using column breakthrough curves where the breakthrough curve for humic acid was retarded behind 3H20. Breakthrough curves for dextran and groundwater DOC demonstrated apparent size exclusion, as these compounds eluted from the soil column before the 3H20. The impact of the dextran was demonstrated under dynamic conditions by use of hexachlorobenzene, anthracene, and pyrene with and without macromolecules in replicated, biologically inhibited (sodium azide), saturated soil columns. The results may help explain the mechanism by which hydrophobic pollutants appear in deep groundwater aquifers.