Distribution Of Anthropogenic Input Of Heavy Metals In Arable Land Soil Of Hainan Island

Over accumulation of heavy metals in soil will adversely affect the original ecological balance, alter soil components, structure or function, lower the yield and quality of the agricultural products, and pollute the air and waters as secondary pollution source. Low quality but high increase in chemical fertilizers in Hainan has imposed great threat to product safety and physical health. The study, taking Hainan Island as the study case and applying soil sampling, has analyzed the features of distribution of As, Pb, Cr and Cd in soils and evaluate respectively the background content to provide assessment of ecological risks. It can be concluded that,1. The contents of As, Pb, Cr and Cd is relatively lower in soil of Hainan Island. And the averages are below the critical points provided in the National Soil Quality, except certain samples collected.2. The spatial distributions of four elements varied significantly. In spite of the varying content of heavy metals in parent soils, the spatial distribution of soil As, Pb and Cd has no indication of features of parent soils. The content of Cd in soil derived from pyroclastic and basic igneous are obviously higher than other parent soils.3. There exist differences among the background values. The background concentrations of As and Pb are highest in soil derived from acid metaprophic. The background concentration of Cd is highest in soil derived from pyroclastic and clastic sediments. And the pyroclastic and basic igneous derived soil has highest Cr background concentration.4. The extensive distribution of As, Pb and Cd are the result of local mining, exploration and release of urban pollutions, while the over low distribution of soils is related with inputs of agricultural chemical inputs.5. The pollute levels of As, Pb, Cr and Cd in soil are relatively lower in Hainan, and the Igeo mainly distributed in the range of0to1. The Igeo of these four heavy metals are relatively higher in the soils derived from parent material of matine.6. The As and Cd are primarily exists as residual fraction. Liable fractions of As and Cd mainly related with pedogenesis and weathering processes. Anthropogenically added As and Cd accumulated mainly as WS and EX fractions in soil. The irrigation water was a mainly pathway of contaminants enter soils as highly bioavailable fractions in pollution area. Therefore, measures should be taken to control the anthropogenic emission of heavy metals in this area.