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 soil microorganisms has been investigated. Soils amended with the test substances were incubated for 29 days under defined laboratory conditions. Changes in the activities of autotrophic nitrifiers and respiring organisms were determined by regular sampling of soil samples from the same test set using a short-term assay. Due to the sensitivity of autotrophic nitrifiers their activity can be used as indicator for the potential toxicity of the test chemical on soil microorganisms. Depending on the quantity and quality of the pollutants; i.) no effect; ii.) toxicity after a lag phase of > 3 days; iii.) inhibition and reestablishment of the initial activity, and iv.) total inhibition during the incubation time of 29 days were observed, Measurements of microbial respiraton provide information about the bioavailability and degradability of the test chemicals. Anthracene oil serves as carbon source, whereas dicyandiamide is not metabolized. The combined measurement of autotrophic nitrification and microbial respiration allows a comprehensive assessment of the influence of chemicals on the soil microflora.