The cooperative application of oyster shell and biochar efficiently enhanced in-situ remediation of cadmium contaminated soil around intensive industry

Abstract. Biochar has been widely used for the in-situ remediation in the cadmium (Cd) contaminated soil, while the high-cost of biochar limited its application in farmland. In this study, we firstly investigated the possibility of cooperative application of oyster shell and biochar to enhance Cd immobilization efficiency and reduce the cost in field experiments under rice-oilseed rape rotation. Treatments were comprised of: rice planting without amendments (R-PA0); followed with 15000 kg/ha biochar (R-PA1); followed with 15000 kg/ha oyster shell (R-PA2); followed with 7500 kg/ha biochar and 7500 kg/ha oyster shell (R-PA3); rice-oilseed rape rotation without amendments (RT-PA0); rotation with 15000 kg/ha biochar (RT-PA1); rotation with 15000 kg/ha oyster shell (RT-PA2); rotation with 7500 kg/ha biochar and 7500 kg/ha oyster shell (RT-PA3). Results revealed that HOAc-extractable Cd was significantly decreased by 38.46 % in R-PA2. Cd contents in brown rice and oilseed were reduced by 29.67 % in R-PA3 and 19.74 % in RT-PA3 compared with control. Meanwhile, Hazard Quotient of brown rice and oilseed significantly decreased in RT-PA3. The Olsen-P in R-PA3 and RT-PA3 was markedly increased by 187.46 % and 184.73 %, respectively. In addition, activities of urease, catalase, and β-galactosidase in RT-PA3 were significantly increased by 268.88 %, 30.44 % and 245.28 %, respectively. Furthermore, the jiont application of biochar with oyster shell significantly decreased the cost of soil remediation at least 9600 RMB/ha. These results demonstrated that the joint utilization of biochar with oyster shell might be an economical and effective pathway to achieve in-situ remediation of Cd contaminated farmland.