RESPONSE OF SOIL AUTOTROPHIC NITRIFICATION AND SOIL RESPIRATION TO CHEMICAL POLLUTION IN LONG-TERM EXPERIMENTS

The influence of anthracene oil and dicyandiamide on the activity of s oil microorganisms has been investigated. Soils amended with the test substances were incubated for 29 days under defined laboratory conditi ons. Changes in the activities of autotrophic nitrifiers and respiring organisms were determined by regular sampling of soil samples from th e same test set using a short-term assay. Due to the sensitivity of au totrophic nitrifiers their activity can be used as indicator for the p otential toxicity of the test chemical on soil microorganisms. Dependi ng on the quantity and quality of the pollutants; i.) no effect; ii.) toxicity after a lag phase of > 3 days; iii.) inhibition and reestabli shment of the initial activity, and iv.) total inhibition during the i ncubation time of 29 days were observed, Measurements of microbial res piraton provide information about the bioavailability and degradabilit y of the test chemicals. Anthracene oil serves as carbon source, where as dicyandiamide is not metabolized. The combined measurement of autot rophic nitrification and microbial respiration allows a comprehensive assessment of the influence of chemicals on the soil microflora.