Effect of different washing solutions on soil enzyme activity and microbial community in agricultural soil severely contaminated with cadmium

Soil enzyme activities and microbial communities have a good response to the remediation effect of heavy metal-contaminated soils. To evaluate the effect of three commonly used washing agents, ferric chloride (FC), ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-tetra-methylenephosphonic acid (EDTMP) on soil enzyme activities and microbial community in cadmium (Cd)-contaminated agricultural soil were collected from farmland near a non-ferrous metal smelter. The soil enzyme activities, microbial community, chemical forms of Cd and some physicochemical properties of the soil washed with different washing solutions were determined. The results showed that the three washing solutions had moderate removal efficiencies for Cd in the tested soil and the breakdown product of EDTMP has a certain stabilizing effect on Cd. The geometric mean and the integrated total enzyme activity index showed that soil washing with FC and EDTA was more beneficial to the restoration of biochemical functions than that with EDTMP. After soil washing, the Chao1 index of bacteria increased, and the microbial community structure changed. Pearson correlation analysis and redundancy analysis (RDA) indicated that the three washing solutions affected soil enzyme activities and microbial community by altering soil nutrient, total Cd concentration and Cd fractions in soils.