Effects of Different Remediation Measures on Physicochemical Properties and Enzyme Activities of Paddy Soil Polluted by Cadmium

Purpose To evaluate the passivation and remediation effects of different remediation measures on cadmium (Cd) contaminated paddy fields and their impacts on soil environmental quality.

Methods Using field greenhouse in-situ passivation remediation experiments, the effects of four remediation measures, including soil acidity regulation (AR), iron fertilizer application (IFe), functional composite microbial fertilizer (MF1), and commercial composite microbial fertilizer (MF2), on the cadmium uptake of rice, soil physicochemical properties, microbial biomass carbon , and enzyme activities were analyzed.

Results 1) Different remediation measures could significantly reduce the cadmium content in rice (with a decrease of more than 26.01%); and compared with the control group, the soil available cadmium content of AR and IFe treatments decreased by 25.13% and 15.99%, respectively. 2) AR treatment had a significant effect on the physicochemical properties of soil, which could significantly increase soil pH, organic carbon content, and total phosphorus content. In addition, all remediation treatments could reduce soil ammonium nitrogen and nitrate nitrogen contents. 3) Compared with the control group, only AR treatment significantly reduced microbial biomass carbon, while AR, IFe, and MF2 treatments significantly decreased β-glucosidase and nitrate reductase activities; and IFe treatment significantly decreased acid phosphatase activity, while MF1 treatment significantly enhanced the activities of polyphenol oxidase and nitrate reductase.

Conclusion Different cadmium pollution remediation measures have differentiated effects on soil environment, among which, functional composite microbial fertilizer is the most environmentally friendly.