Effects of pentachlorophenol on soil organisms and decomposition in forest soil.
To find a more reliable basis for ecotoxicological risk assessment, two microcosm experiments, one in the laboratory and another in the field (lysimeters), were performed using pentachlorophenol (PCP) as a model contaminant. PCP was applied at three (0, 50 and 500 µg/g dry soil in the laboratory experiment) or at two (0 and 50 µg/g in lysimeters) concentrations in raw humus forest soil and its effects on soil organisms and decomposition processes were monitored. Soil fauna was manipulated at two levels in the laboratory experiment: simple and diverse communities. Results showed that PCP was strongly adsorbed onto the humus. Microbes, nematodes, enchytraeids, and predatory gamasid mites were sensitive to PCP in the laboratory experiment, but no significant faunal effects were observed on C and nutrient mineralization. At the highest PCP concentration, CO2-evolution was lowered and NH4+-N accumulated in the soil. PCP contamination indirectly affected soil pH and water content of the organic soil layer. In the lysimeters, after 15 weeks there were fewer enchytraeids and prostigmatid mites in soil contaminated with PCP, but no changes in N mobilization were observed. After 49 weeks, however, there was less NH4+-N in the contaminated soil, while no differences in faunal composition were found. The results showed that, in comparison with single-species toxicity tests, more ecologically relevant microcosm experiments give important information about the behaviour of the decomposition system under contamination. This information, including also indirect impacts of chemicals, may be useful for the improvement of ecotoxicological risk assessment.