Progress in Microbial Activity and Chemical Properties of a Trace Element Polluted Soil Under Assisted Natural Remediation

Abstract

In this work, we studied the temporal dynamics of several microbiological properties in a trace element polluted soil under the influence of various amendments and/or a plant cover during a 30 month-period. The experiment was carried out in containers filled with ca. 150 kg of contaminated soil. Seven treatments were established: four organic (leonardite LEO, litter LIT, municipal waste compost MWC and biosolid compost BC) and one inorganic (sugarbeet lime SL), where the grass Agrostis stolonifera L. was sown, and two control treatments (with plant CTRP or without plant CTR). Soil was sampled four times during the experimental period. The microbiological properties studied were: microbial biomass C, microbial biomass C/total organic C, dehydrogenase, aryl-sulphatase, β-glucosidase, acid-phosphatase and protease enzyme activities. Dynamics of microbiological properties differed between treatments being results not only affected by soil pH or trace element concentrations, but also by changes derived from the different treatments in organic matter quality and quantity, as well as nutrient content in soil. While microbial biomass C, dehydrogenase, aryl-sulphatase and protease activities were highly correlated with soil pH and soluble trace element contents, changes in β-glucosidase activity were mainly influenced by water soluble C concentrations. It was also observed that enzymatic activities generally decreased over time after no more amendment additions occurred. Nonetheless, during the experiment microbial biomass and activities were generally higher in all treatments compared to the untreated control and thus remediation practices had a positive and significant effect on trace element stabilization and microbial activity in the contaminated soil.