Research On Safe Cultivation Of Wheat In Acidic Cadmium-contaminated Soil And Field Screening Of Phytoremediation Resource

Cadmium（Cd）pollution in farmland soil leads to excessive Cd in agricultural products such as wheat,which is harmful to human health,it is urgent to carry out safe utilization and remediation of contaminated farmland.Among them,when planting food crops in light and moderate contaminated soil,it is necessary to ensure that the heavy metal content of agricultural products does not exceed the standard through safe utilization technologies such as soil conditioners and leaf blockers;For heavily polluted soil,planting edible agricultural products is usually prohibited,and purification and remediation measures such as soil heavy metal removal are needed first.In this article the Cd-contaminated farmland in Jiangsu province was taken as the object,43 pairs of soil-wheat samples were randomly collected from farmland,and the relationship between Cd content and soil properties was analyzed,iron,manganese and their composite modified rice husk biochar were developed as soil Cd passivator,and Zn SO₄·7H₂O solution and Na₂Se O₃ solution were used as foliar inhibitors,through pot and field experiments on Cd contaminated soil,the Cd reduction effect and mechanism of modified biochar,foliar spraying of Zn and Se and their combination were studied to ensure the quality of agricultural products.In addition,the Cd content characteristics of various organs of 19 wild plants were analyzed by field investigation and sampling of polluted farmland,so as to screen out the practical Cd high enrichment plant resources and evaluate their remediation ability.The results show that:（1）Cd in farmland soil and wheat around historical pollution sources exceeded the standard seriously,there was a significant positive correlation between Cd content in wheat grain and Cd content in soil,multiple regression analysis showed that Cd content in wheat grains could be predicted to a certain extent by soil Cd content and p H,Fe,Mn,Zn and S had positive effects on reducing Cd content in grains.（2）Rice husk biochar（BC）and its iron（FBC）,manganese（MBC）and composite（FMBC）were alkaline after modification,the average pore size of modified biochar increased,The application of biochar can increase soil p H and reduce the content of available Cd（DTPA-Cd）in soil,thus reducing the absorption and accumulation of Cd by wheat.MBC and FMBC had better effects on reducing Cd content in endosperm,and the maximum Cd reduction rates were 26.03%and 21.67%,respectively.（3）Spraying Zinc and Selenium elements can reduce the content of Cd in wheat bran and endosperm,and the content of Zinc and Selenium elements in wheat bran and endosperm is increased,which can achieve the effect of supplementing Zinc and enriching Selenium and increasing yield.Field experiments showed that spraying Zinc and Selenium elements made the Cd content of wheat grains meet the food safety limit standard.（4）The combination of iron-manganese composite modified rice husk biochar（FMBC）and foliar spraying of zinc and selenium can reduce the Cd bio-concentration factors of wheat bran and endosperm,and effectively reduce the Cd content of wheat grains,the combination of 1%FMBC and spraying Se has the best Cd reduction effect.（5）The 19 plants collected in the field of contaminated farmland can adapt to the soil Cd concentration that is higher than the risk control value of agricultural land pollution,among them,the Cd bio-concentration factors and Cd transfer factors of the above-ground parts of Ammannia baccifera L.,Lactuca indica L.,Avena fatua L.,Phytolacca acinosa Roxb.,Cucumis melo var.agrestis Naudin and Bidens pilosa L.,were exceeded unity,which had the characteristics of heavy metal cadmium hyperaccumulator;Based on the plant Cd bio-concentration and transfer factors,taking into account biomass,Ammannia baccifera L.（discovered first time）,Rumex dentatus L.,Cyperus iria L.and Lactuca indica L.had high potential for phytoremediation of cadmium pollution in farmland.