ECOLOGICAL EFFECTS OF COMBINED ORGANIC OR INORGANIC POLLUTION ON SOILMICROBIAL ACTIVITIES

Combined effects of organic or inorganic pollutants on soil microbial activities were investigated in field plots grown with four types of c overing plants. It was derived from this study that combined effects w ere dependent not only on the type and dose of pollutants, addition of soda lime, plant type and season variation, but also on test paramete rs. When jointly added, higher doses of Cd, Cu, Pb, Zn and As caused s ignificant inhibition. Addition of soda lime could even enhance inhibi tion. Joint effects of phenanthrene, MET (active ingredient: paclobutr azol) and 1,2,4-trichlorobenzene were not significant, and may be cove red by other biotic or abiotic factors. Compared with other two parame ters (respiration and microbial biomass), dehydrogenase activity appea red to be more sensitive for evaluating the toxicity of anthropogenic pollutants in soil. Soil samples collected in summer often had higher microbial activities than those in fall. The microbial activity in soi l decreased with covering vegetation in the order alfalfa > pine > pop lar and maize, albeit some exceptions were observed.