Microcalorimetry as a tool to detect changes in soil microbial biomass

Abstract

High levels of heavy metals such as Cu, Zn and Pb have been found in soils to which composted municipal waste have been added over long periods of time. The impact of heavy metals on the endogenous microbial community was studied by measuring total microbial biomass and biomass activity in soils which contained either low or high heavy metal concentrations. Methods used were fumigation‐incubation, ATP extraction and microcalorimetry. The total amount of microbial biomass was not correlated with the total extractable amounts of heavy metals (extraction with aqua regia) nor with the NH4OAc‐EDTA extractable amounts. Neither the apparent growth rate constants of glucose‐amended soils, as estimated by microcalorimetry, nor the ATP contents were correlated with the amounts of heavy metals present. In contrast, the ratio of the heat evolved 2 hours after glucose addition to the ATP content increased with increasing concentrations of heavy metals. This ratio is a parameter which is inversely proportional to the e...