In Situ Remediation Of Heavy Metal Contaminated Soil By Biochar Combined With Leguminous Crops

In recent years,the degree of soil heavy metal pollution in China is increasing,which seriously threatens people’s health.Limiting the absorption and accumulation of heavy metals in crops and reducing the content of heavy metals in edible parts are the key measures to ensure food and food safety.This paper attempts to study the changes in the absorption,accumulation and transport of cadmium(Cd),lead(Pb)and copper(Cu)in two legumes by combining different types of biochar with crop rotation agronomic measures,aiming at realizing safe crop production and effective control of soil heavy metal pollution.The results of this study are as follows:1.The physical and chemical properties of biochar prepared from three different raw materials(sugarcane,rice husk and bean pulp)were analyzed,and the feasibility of applying biochar to soil for remediation of heavy metal pollution was explored.The results show that the three kinds of biochar are all alkaline,and there are some differences in cation exchange capacity,which can provide a new idea for improving acid soil.Scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)analysis showed that the three kinds of biochar all had abundant pore structure and abundant surface functional groups,which could be used to immobilize heavy metals through surface complexation.These results indicate that the three biochar have the potential to remediation heavy metal contaminated soil.2.The effects of biochar on the growth,Cd and Pb uptake and transport of Vigna radiata L.and Vicia sativa L.under rotation cropping mode were studied by pot experiments with heavy metal contamination,and the tolerance to Cd and Pb toxicity and remediation potential of the two legumes were investigated after biochar was applied.Seven treatments were set in the experiment.The results showed that compared with the control,the three kinds of biochar could increase the biomass of the two crops to different degrees,and reduce the contents of Cd and Pb in different parts,but there was no significant difference in the translocation factor of Cd and Pb.The p H value and total nitrogen content of the rhizosphere soil in the six treatment groups were increased to varying degrees,while the extracted Cd-and Pb-DTPA content in the rhizosphere soil was decreased.At the same time,the biochar of the three raw materials changed the microbial diversity and bacterial community richness of mung bean rhizosphere soil,so the two concentrations of the three kinds of biochar can be used for safe production of crops in pot,and 1%SBC,5% RHBC and 5%BPBC treatment is the most ideal concentration of three kinds of biochar options.3.Based on the results of pot experiment,field experiment was conducted to study the effects of three biochar on the growth of Vigna radiata L.and Vicia sativa L.,as well as on the absorption,accumulation and transport of heavy metals under rotation cropping mode.The results showed that compared with the control,biochar with two concentration gradients of the three raw materials could increase the biomass of the two crops to different degrees,and reduce the contents of Cd and Cu in each part of the two crops,and the two crops did not show the symptoms of heavy metal stress during the phytoremediation process.However,there was no significant difference in Cd and Cu transcolation factor between the three biochar.All the six treatment groups could increase the p H value of the rhizosphere soil,and reduce the available DTPA content of Cd and Cu in the rhizosphere soil.In conclusion,all three kinds of biochar can be used for remediation of heavy metal contaminated soil in the field,and 10t/ha SBC,20t/ha RHBC and 20t/ha BPBC treatment are the most ideal concentration options for the three kinds of biochar.