Objective To examine the effect of biochar combining with micro-fertilizer on soil available heavy metal content.
Method Indoor simulation experiment was conducted. Pennisetum hydridum biochar, coffee grounds biochar, peanut shell biochar and micro-fertilizer (iron fertilizer, manganese fertilizer and silicon fertilizer) were added to the vegetable garden soils polluted by heavy metals, and the contents of available Cu, Pb, Zn, Cd and Ni were determined on the 14th and 28th days.
Result The available heavy metal contents in soils added with biochar or micro-fertilizer were lower than that of the control group. In single passivator treatments, P. hydridum biochar and silicon fertilizer had better heavy metal immobilization effects. In the blended passivator treatments, P. hydridum biochar combining with iron fertilizer had better Cu, Pb and Cd immobilization effects, the contents of available Cu, Pb, and Cd decreased by 32.94%, 31.26% and 21.21% respectively on the 14th day. The content of available Zn decreased by 6.82%, and the immobilization effect on Ni was not obvious. When coffee grounds biochar was added with iron fertilizer, the contents of available Ni and Zn decreased by 22.64% and 10.35% respectively on the 14th day. The immobilization effects were remarkable. On the 28th day, peanut shell biochar combining with iron fertilizer showed the best immobilization effect on Cu, the content of available Cu decreased by 49.06%. Coffee grounds biochar combining with silicon fertilizer had the best immobilization effect on Ni and Zn, the contents of available Ni and Zn decreased by 23.73% and 9.72% respectively.
Conclusion The reduction effects of biochar combining with micro-fertilizer on available heavy metal content in soil are better than that of single biochar or micro-fertilizer. P. hydridum biochar combining with iron fertilizer can be used to immobilize combined heavy metal pollution of Cu, Pb, Zn and Cd in soil.
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