Occurrence, speciation, source and geochemical cycle of arsenic.

Based on comprehensive review of related literature,content and distribution of As in the surface water,groundwater,soil,sediments,lithosphere and atmosphere were summarized,geochemical cycle of As in the earth surface layer was reviewed,species and transform of As in water and soil/sediment solid phases were discussed.As in soil and sediments usually associates with iron,aluminum and manganese(hydro) oxides,clays and mineral oxyanions such as sulfates,phosphates and carbonates,which play an important role in controlling the distribution and mobility of arsenic.Quantitative evaluation of As sources including metal smelting,fossil-fuel combustion and arsenic chemicals were conducted as well.