Fate of Treated and Weathered Hydrocarbons in Soil—Long-Term Changes

Abstract

Information about the loss and mobility of anthropogenic chemicals in soils over long periods of time—years to decades—was evaluated, with the purpose of providing a perspective on the extent to which such chemicals remain sequestered over time. Such information is needed to help ensure that decisions made to leave concentrations of chemicals in soil—based on short-term chemical availability data—are environmentally sound and protective. The information evaluated was obtained from field studies that considered changes in chemical concentrations over extended periods of time. The chemicals evaluated were petroleum hydrocarbons, polynuclear aromatic hydrocarbons (PAH), and pentachlorophenol (PCP). The sites considered were those where decisions had been made to let such organic chemicals remain in the soil after some degree of treatment or weathering. The evaluation indicated that only a few long-term studies provide adequate data to identify what happens to weathered or treated hydrocarbons, PCP, and PAH that are allowed to remain at a site. However, for the examples evaluated, the initial chemical mobility was low and there were no indications that the residual hydrocarbons, PCP, or PAH became more mobile over time. In addition, the data indicated that there was continued slow degradation over time. The results suggest that the current measures of chemical release and mobility, even though they may measure only short-term effects, may be reasonable indicators of the long-term effects.