SOIL HEAVY-METAL CONCENTRATIONS, MICROBIAL BIOMASS AND ENZYME-ACTIVITIES IN A CONTAMINATED GRASSLAND ECOSYSTEM

Soil enzyme activities and microbial biomass were measured in a grassl and ecosystem with a wide range of heavy metal concentrations ranging from 7.2 to 48.1 mmol kg(-1) (As, Cd, Cr, Cu, Ni, Pb and Zn) in portio ns of the U.S. Army's Aberdeen Proving Ground, Maryland, U.S.A. Total and fluorescein diacetate active (FDA) fungal biomass, FDA-active bact erial biomass, substrate-induced respiration (SIR), the activity of N- acetylglucosaminidase, beta-glucosidase, endocellulase, and acid and a lkaline phosphatases were also measured. Most measures of microbial bi omass were lower in polluted soils. Significant reductions (10- to 50- fold) in the activities of all enzymes closely paralleled the increase in heavy metal concentrations. These results demonstrate that heavy m etal contamination of soil has adversely affected the abundance and ac tivity of microorganisms involved in organic matter decomposition and nutrient cycling in this site. (C) 1997 Elsevier Science Ltd.