Soil Solution Assessment of the Soil Availability of Xenobiotics

Abstract

Soil solution displacement provides a means whereby xenobiotic availability in the soil environment can be evaluated rapidly and effectively. The displacement and analysis of soil solution provides (a) refined measurements of the bioavailability of soil active xenobiotics, (b) static measurements of phase partitioning of xenobiotics under conditions which closely mimic soil moisture regimes in field environments, and (c) dynamic measurements of xenobiotic availability as a function of residence time in the soil. The biological availability (efficacy/toxicity) and the geochemical availability (environmental fate) of biologically active molecules are both a function of the xenobiotic intensity in soil solution. Quasi-thermodynamic expression of xenobiotic effective concentration (that is, chemical activity) and solid-liquid distribution in soils is possible based on knowledge of xenobiotic pKa and mole weight, and measurement of soil solution xenobiotic intensity, pH, and ionic strength. Dynamic measures based on soil solution displacement with time offer a means to assess time domain influences on xenobiotic availability. Soil solution displacement and analysis has been employed successfully for refined assessments of leachability, phytotoxicity, and sorptivity of xenobiotics and offers a useful adjunct to more traditional whole soil extractions for determination of xenobiotic fate and behavior in soil.