Bioavailability of pollutants to soil organisms via the soil solution

The hypothesis that the availability of pesticides to organisms in soil is determined solely by their concentration in the pore water was tested. The potato cyst nematode Globodera rostochiensis was exposed to the pesticides chlorpyrifos and pentachlorophenol mixed into two arable soils and one artificial soil. The nematode was also exposed to the pesticides in saline solution and in pore water isolated from these soils. Mixed in soil, chlorpyrifos was a 1000 times, and pentachlorophenol more than 100 times less toxic than if dissolved in solution. Sorption of these pesticides to dissolved organic matter in pore water decreased their toxicity only slightly. The concentrations in the soil solution, in equilibrium with soil at the soil LC 50 content, were similar to the LC 50 values determined in saline or soil solution. The use of non-adsorbing aqueous media is proposed for the toxicity testing of chemicals in the hazard assessment of soil pollution.