Acidification alters the functionality of metal polluted soils

Abstract

Acidification can alter soil ecosystem functioning, thus jeopardizing the provision of valuable ecosystem services. Moreover, soil acidification can be accompanied by other soil threats, such as, for instance, metal pollution. The aim of this work was to assess to what extent acidification affects the functionality of metal polluted soils. To this aim, the pH of two soils (a highly metal polluted and a moderately metal polluted soil) was lowered by adding elemental sulphur at different doses, resulting in the following pH gradient in both soils: 7.5, 7.0, 6.5, 6.0, 5.5, 5.0, 4.5, 4.0 and 3.5. A variety of microbial indicators of soil health were measured in the treated soils: enzyme activities, substrate-induced respiration, microbial biomass carbon, bacterial and fungal abundances by qPCR, and bacterial and fungal richness by DGGE. Metal (Cd, Cu, Pb, Zn) bioavailability increased at decreasing pH values. The values of enzyme activities were strongly affected by acidification in both soils, followed by the values of soluble organic carbon in the highly polluted soil and bioavailable metal concentrations in the moderately polluted soil. These results improve our understanding of the role of microorganisms in the biogeochemical cycles of metal polluted acidic soils.