HYDROLOGIC TRACER EFFECTS ON SOIL MICROBIAL ACTIVITIES

While much research has shown that the commonly used hydrologic tracers Br-, Cl-, and pentafluorobenzoic acid (PFBA) are not affected by soil microbial processes, much less work has gone into analysis of the effects of these tracers on microbial activity. In this study, we analyzed the effects of Br-, Cl-, and PFBA at 100 mg kg-1 concentration on soil respiration, denitrification, N mineralization, and nitrification in a forest soil under laboratory conditions. Chloride and Br- inhibited all activities other than denitrification and PFBA stimulated respiration and denitrification. Mechanisms for the observed effects may be related to the effects of these anion tracers on soil solution cation activities and microbial membrane processes. The results suggest that effects on microbial activities should be considered when tracers are used in studies of the fate and transport of pollutants that are affected by microbial processes.