Microbial function after assisted natural remediation of a trace element polluted soil

Abstract

We studied the effect of different amendments and/or a plant cover on soil microbial properties of a trace element polluted soil. The experiment lasted 30 months and was carried out in containers filled with ca. 150 kg of contaminated soil. The remediation measures consisted of the application of different amendments and/or development of a plant cover (Agroslis stolonifera L.). Seven treatments were established: four with organic amendments (leonardite LEO, litter LIT, municipal waste compost MWC and biosolid compost BC) and one inorganic amendment (sugarbeet lime SL), where agrostis was sown, and two controls without amendment addition (with Agrostis CTRP or without Agrostis CTR). Microbial function was analysed by means of microbial biomass C (MBC), microbial biomass C to total organic C ratio (MBC/TOC), enzyme activities (dehydrogenase, aryl-sulphatase, β-glucosidase, acid-phophatase and protease) and microbial heterotrophic potential (MHP) to MBC ratio (MHP/MBC). The MWC and BC treatments were the most effective in raising MBC, MBC/TOC, dehydrogenase and aryl-sulphatase activities and reducing the MPH/MBC ratio. Whereas β-glucosidase was higher in the amended treatments, acid-phosphatase and protease activities showed no significant differences between the control and the amended treatments. Assisted natural remediation can be a useful and reliable technique to improve soil microbial function in the mid-term. Further monitoring is necessary to evaluate the potential of this technique in long-term experiments.