Pb content in the soil-crop system in the Dongting Lake region, Hunan, China, and its influence factors

The authors studied the influence of organic matter,pH values,P and N in soils on Pb migration in the soil-crop system as well the influence of compound pollution of Cd and Pb on the concentration of Pb and Ca in rice in the Dongting Lake region,Hunan.The results of correlation analysis indicates that:the content of ion-exchangeable Pb in soils decreases somewhat with increasing organic matter,but the content of organic bound-state Pb,which can be absorbed by plants,increases through conversion,and thus the capacity of absorption of Pb in soils by rice increases;when the soils are neutral-subalkaline,the bioactivity of Pb in soils and Pb concentration factor(CF) in rice are both lower than those in acid soils;when nitrogenous and phosphate fertilizers are applied to the soils,the ion exchangeable Pb in soils can be reduced and so can the capacity of absorption of Pb by rice.Therefore organic matter,pH values,P and N in soils are important factors influencing the Pb content in rice and Pb bioactivity in soils.The study of compound pollution of Cd and Pb shows that the presence of Pb in soils may promote the absorption of Cd by rice,whereas the presence of Cd inhibits the absorption of Pb by rice.