Phytoextraction of Cadmium from Contaminated Soil Assisted By Microbial Biopolymers

Heavy metal contaminated soils remain as a challenging and essential task for environmental engineering. Phytoremediation (plant-based remediation) is effective for the mitigation of large area surface soil contamination, but needs long time and the efficiency is not high. Chemical agents could increase heavy metal bioavailability in soil and bring greater accumulation in plants, but also pose risks to soil, plant growth and ground water environment. In this study, microbial biopolymers, mainly composed of protein and polysaccharide, were obtained from non-induced, copper-induced and cadmium-induced activated sludge culture, and named as ASBP, ASBPCu and ASBPCd, respectively. The influence of microbial biopolymers on phytoextraction of cadmium in contaminated soil was investigated. Microbial biopolymers, compared to other agents, were found to be more effective in improving the phytoextraction of cadmium from soil. In ASBP, ASBPCu and ASBPCd, the cadmium content in plants was found to be 1.52, 1.63 and 1.33 μg (1.9, 2.0 and 1.6 times of the control), respectively. It was also found that in the presence of microbial biopolymers ASBP, ASBPCu and ASBPCd, 10.9%, 26.2% and 13.7% of exchangeable cadmium fraction was extracted from c to plant or liquid, higher than the control test (4.3%). Microbial biopolymers were more effective in improving cadmium accumulation in plants than other chemical agents. Owing to the benign nature, ease of production, and cadmium binding feasibility, microbial biopolymers may find utility as a new environmentally safe extracting agent for improving phytoextraction of cadmium from contaminated soil.