Passivation remediation of weak alkaline cadmium contaminated soil with biochar and sepiolite
The effects of biochar combined with sepiolite on Cd availability,occurrence and soil quality in weakly alkaline soil and Cd uptake and accumulation in maize were studied through field experiments.The results showed that the composite material has a rough surface and fibrous structure,which combines the mineral crystal composition of sepiolite and biochar.Different passivation treatments decreased the availability of Cd in soil,the content of available Cd in soil decreased from 0.38 mg·kg-1 to 0.25 mg·kg-1 after addition of 0.2％biochar+0.2％sepiolite,and the occurrence form of Cd changed from exchangeable and carbonate-bound states with higher activity to more stable residue state.The application of biochar and sepiolite with different mixture ratio significantly decreased the Cd content in each part of corn.Compared with the control,the Cd content in the three corn grains decreased by 37.14％～40.55％(Liyu 16),59.46％～68.78％(Zhengdan 958)and 40.94％～47.84％(Sanbei 218),respectively.Compared with the control treatment,the addition of passivation material significantly increased soil soluble organic carbon content,soil urease,alkaline phosphatase and catalase activities.Among them,0.2％biochar+0.2％sepiolite treatment has the best effect on soil urease and alkaline phosphatase activity,0.2％biochar+0.5％sepiolite treatment has the best effect on soil catalase activity.Considering comprehensively,the application of 0.2％biochar+0.2％sepiolite composite material has high application potential in the remediation of weakly alkaline Cd contaminated soil,the safe production of corn and the improvement of soil environmental quality.
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