MICROBIAL BIOMASS, ACTIVITY, AND ORGANIC-MATTER ACCUMULATION IN SOILSCONTAMINATED WITH HEAVY-METALS

Chemical characteristics and some parameters related to biological com ponents were determined in 16 soils from a fairly homogeneous area in the north of Italy, contaminated with different levels of heavy metals . Correlation analysis of the parameters studied showed close positive relationships among the metals and with the organic C content in the soils studied. Negative relationships were observed among the heavy me tals, soil respiration, and the ratio between evolved CO2-C and microb ial biomass C per unit time (specific respiratory activity). This was ascribed to an adverse heavy metal effect on the soil microflora, whic h appeared to increase the accumulation of organic matter as the heavy metal content increased, probably because the biomass was less effect ive in mineralising soil organic matter under these conditions.