By-products as amendment to improve biochemical properties of trace element contaminated soils: Effects in time

Abstract

Temporal dynamic of several microbiological properties in two trace element polluted soils with different pH (soil A pH 4 and soil B pH 7) under the influence of various by-products during a 40-week-period was studied. The experiment was carried out in microcosms under controlled conditions. For each soil four treatments were established: biosolid compost (BC), fresh “alperujo” (AL), sugarbeet lime (SL), and a control (C) without by-product addition. Soil was sampled eight times during the experiment. The microbiological properties studied were: microbial biomass C (MBC), dehydrogenase, arylsulphatase and protease enzyme activities. Different fractions of organic C were also evaluated. In acid soil increases in pH caused by the addition of the alkaline by-products (SL and BC) decreased trace element availability and slight improved biochemical status during the first weeks of incubation. Although the reduction of trace element availability was not as effective as in the case of alkaline amendments, AL produced higher increase of WSC that stimulated biological activity. In neutral soil, with low trace element availability, the addition of by-products did not cause any change. Nonetheless, in this soil microbial biomass and activities were generally higher in by-product treated soil compared to control. Remediation practices had a positive and significant effect on enhance microbial activity in the contaminated soil.