Bioremediation of cadmium-dichlorophen co-contaminated soil by spent Lentinus edodes substrate and its effects on microbial activity and biochemical properties of soil

Abstract

Soil contamination resulting from industrial and agricultural activities has caused high concerns in recent years. Compared with single pollutant, co-contaminants of heavy metal and organic pollutant in soil are quite complicated. The overall objective of this study was to evaluate the potential of spent Lentinus edodes substrate (SLS) as an organic amendment for bioremediation of cadmium (Cd) and dichlorophen (DCP) co-contaminated soil. Pot experiments were conducted to investigate the effect of SLS on the distribution of Cd and dissipation of DCP. The microbial counts and soil respiration rate were determined. The ligninolytic enzymes (manganese peroxidase and laccase) and soil enzymes (dehydrogenase, urease, and acid phosphatase) were analyzed. Variations of Cd fractions in soil were determined following the modified BCR sequential extraction procedure. DCP in soil was detected on a gas chromatography–mass spectrometry (Agilent 6890N GC–MS). Results showed that the addition of SLS or sterilized SLS (SSLS) could facilitate soil biological properties including microbial counts, respiration intensity, and soil enzyme activities compared to control soil. The HOAc extractable Cd decreased by 10.94–17.09 and 9.63–12.02 % in SLS and SSLS amended soil, respectively. As for the dissipation of DCP, the SSLS amended soil recorded 82.4–92.8 % while the SLS amended soil recorded 85.0–96.9 % compared to the non-amended soil (68.3–84.1 %). The presence of available residual nutrients in the substrate could promote the growth of indigenous microbes, which could contribute to the dissipation of DCP. This study investigated the potential of SLS on the bioremediation of sites co-contaminated with Cd and DCP. The SLS-facilitated removal of soil DCP was due to SLS-promoted soil biological properties including the microbial numbers and soil respiration as well as the ligninolytic enzymes. The addition of SSLS and SLS resulted in a decrease of Cd extractability in soil, and significantly facilitated the activities of dehydrogenase, urease, and acid phosphatase. The results demonstrated the potential of SLS in ex situ bioremediation of soil co-contaminated with Cd and DCP, providing an attractive reusing option of this organic waste.