Effects Of Fe-Mn Modified Biochar On Cd And As Speciation And Accumulation In Rice

The problem of soil pollution by single cadmium and cadmium-arsenic complex in southern China has become increasingly prominent.It has become a research hotspot in recent years to control the Cd and Cd-As combined pollution in farmland soil and ensure the quality and safety of rice.Heavy metals Cd and As exhibit opposite physicochemical behaviors in soils such as adsorption,solubility,and absorption and enrichment by rice.Common single contr ol measures,such as low Cd/As accumulation of rice varieties,application of passivation agents and so on,can not simultaneously inhibit the absorption and accumulation of Cd and As in rice.In this study,iron-manganese modified biochar was prepared by iron-manganese modification two kinds of biochar.A typical pollution of paddy field Cd in Hunan Province and Cd-As contaminated paddy soil around the mining area were studied through outdoor rice pot experiment.By applying coconut shell charcoal?CSB?,rice husk charcoal?RHB?and its two iron-manganese modified biochar?FM-CSB/FM-RHB?combined with Cd low-accumulation rice varieties to medium-sized Cd single-acid rice fields and severe The bioavailability of Cd and As in the soil around the As-Cd complex contaminated mining area and the cumulative effects of various parts of rice and their application value were discussed.The main findings are as follows:?1?After modification by iron and manganese,the pH of CSB and RHB increased;the number of oxygen-containing functional groups and the aromaticity of the two biochars were both increased;XDR results showed that the surface crystal of FM-CSBFM-RHB was MnFe₂O_4.?2?Application of CSB,RHB and its iron-manganese modified materials to Cd single-contaminated acid paddy soil can increase soil pH,reduce soil Eh,and convert strong soluble acid-soluble Cd to other stable forms of Cd.Coconut shell charcoal,rice husk charcoal and its iron-manganese modified materials can reduce the accumulation of Cd in rice and increase rice yield.When the applied amount was 1%,the effect of lowering the Cd by the FM-CSB treatment is better.Under the conditions of this experiment,the Cd content in brown rice can be lower than the national food safety limit.by planting cadmium low-accumulation rice varieties ZhongJia Zhao 17 and LuYou 9803 in moderately Cd-contaminated paddy soil.?3?Compared with CK,each treatment can increase the soil pH of Cd-As complex contaminated paddy field and reduce soil Eh,and the effect of applying 1%FM-CSB was most significant.Compared with CK,each treatment can increase the residual Cd content in the soil,reduce the acid soluble content of soil,and reduce the Cd content in all parts of rice.The application of 1%FM-CSB was the best to treat cadmium.Under each treatment,the ability of Fe plaques to adsorb As in rice root surface is significantly greater than the ability to adsorb Cd.Compared with CK,the application of FM-CSB,RHB,FM-RHB treatment can increase the content of soil O-As and reduce the As content in all parts of rice,and the application of 1%FM-RHB treatment was the best,while applying CSB increases the As content in rice.