Showing papers by "Thomas C. Voice published in 1999"

Sorption and bioavailability of carbon tetrachloride in a low organic content sandy soil

Abstract: Two sets of parallel columns were packed with a low-organic-content aquifer soil contaminated with carbon tetrachloride (CT) and flushed with water under bioactive and abiotic saturated conditions Both effluent and soil concentrations (by sacrificing columns) were monitored for CT Desorption of CT from the aquifer material could be described by a two-site nonequilibrium model The columns were found to operate far from desorption equilibrium conditions Inoculation with Pseudomonas sp strain KC resulted in rapid transformation of CT in the liquid phase, but no evidence of solid-phase degradation was found Mathematical modeling of desorption and biodegradation as sequential and independent processes appears to be justified for this soil/contaminant combination

Effect of Water Saturation on Retardation of Ground-Water Contaminants

Abstract: This study is the first to report the effect of water saturation on the retardation of nonionic organic compounds under dynamic conditions. Three nonaggregated sandy soil samples, that varied in their organic carbon content but had similar grain size distributions, were utilized. Two nonionic organic compounds were used: (1) dimethylphthalate, which served as a nonvolatile compound; and (2) benzene, which was volatile. Results showed that retardation coefficients for unsaturated soils are higher than those determined when the soil is saturated. The extent of deviation in retardation between the saturated and unsaturated soils generally increased as the degree of water saturation was reduced. No functional relationship between the extent of deviation in the retardation coefficient and the amount of organic carbon on the soil was found. When normalized to the saturated solid-to-water ratio, retardation coefficients for dimethylphthalate determined at different degrees of saturation were similar, leading to the conclusion that the distribution coefficient did not increase as the media was desaturated. Volatilization did not significantly affect the retardation of benzene under the employed range of saturation. Theoretical analysis showed that the impact would be significant for volatile compounds with higher Henry`s coefficients and in aquifers with low organic matter content. Diffusivemore » transport in the air phase had a significant impact on the spreading of benzene. Previously developed empirical relations reasonably predicted this impact.« less

Impact of dissolved organic matter on the desorption and mineralization rates of naphthalene

Abstract: The persistence of organic contaminants in plant-soil systems will be largely determined by the basic processes controlling bioavailability: desorption and biodegradation. Both processes can be affected by the presence of and variations in dissolved organic matter (DOM). To evaluate potential effects of DOM in surface soil remediation systems, the kinetics of naphthalene desorption from soil and mineralization in soil solution in the presence of DOM were studied in completely mixed batch reactors (CMBRs). Three different DOM solutions were studied. These were obtained from water extraction of two different soils (muck-highly organic and alfalfa field-agricultural) and a third prepared by reconstituting a fulvic acid reference standard purchased commercially. Neither the desorption rate nor equilibrium partitioning of naphthalene was affected by the presence of varying DOM solutions. The effect on mineralization was evaluated based on an evaluation of a first-order rate constant produced by nonlinear regre...