Pollution Characteristics Of Typical Heavy Metals In Farmland Soil Of Yangtze River Delta And Regulation On Bioavailability

Serious heavy metals pollution in farmland soil is found in serveral areas of China,High levels of heavy metals might affect crop production and quality,as well as may pose high risk to human health and ecosystem safety via food chains.In this thesis,the current state and temporal trends of heavy metals pollution in farmland soil of Yangtze River Delta（YRD）were evaluated through comprehensive field survey and meta-analysis.Regualtion on heavy metals bioavailability by compound amendents of bentonite and biochar was studied through pot and field experiment.The main findings of this thesis are summarized below:（1）Heavy metals occured relative higher concentrations in soils on the provincial borders.Cd showed relatively higher concentration in Fuyang,Lin’an and provincial borders（Jiashan,Banshan,and Taicang）;Cu showed relatively higher concentration in Jianshan.The results showed an increasing trend for Cd(p<0.05;0.0081 mg kg^-1 yr^-1),a decreasing trend for Cu in the past 15 years(p<0.05;-0.80 mg kg^-1 yr^-1).（2）The compound amendments of bentonite and biochar was recoganized an effective amendents could reduce the bioavailability of heavy metals in farmland soil,which in turn inhibited transfer between soil and rice plant.In pot experiment,80%bentonite-20%biochar was the best amendments to reduce the bioavailability of heavy metals.The content of Cd,Pb,and Cr in overground part of rice plant was decreased by 41.64%,42.02%and 35.61%with the amendment at 2%application rate.In field experiment,the bentonite（at 2%application rate）could reduce the content of Cd and Cr in rice grain to 17.29%and 27.39%,the biochar could reduce the content of Pb in rice grain to 84.53%.