Distribution and source analysis of heavy metals in farmland soils along Danjiangkou reservoir area
Danjiangkou Reservoir is a water source for the middle route of the South-to-North Water Diversion Project.The distribution characteristics of heavy metals in the soil along the reservoir directly affect the water quality safety of the reservoir.To study the pollution characteristics and sources of heavy metals in farmland soils along the Danjiangkou Reservoir,eight heavy metals,including As,Cd,Cu,Pb,Hg,Ni,Zn,and Cr,were measured.Geological accumulation index and enrichment factor were used to evaluate the soil pollution status,while correlation analysis and principal component analysis were applied to develop traceability.The results showed that none of the eight heavy metals in the study area(except for the total As concentration in two samples)exceeded the risk screening value of"Soil Environmental Quality-risk control standard for soil contamination of Agricultural Land"(GB 15618-2018),while Hg was the most enriched,with both 4%of the sampling sites in the moderate enrichment state(1<Igeo≤2)and heavy enrichment status(2<Igeo≤3).The non-polluted to slightly polluted areas of As,Cd,Cu,Pb,Hg,Ni,Zn,and Cr in farmland soil in the whole reservoir area were all more than 92%,the moderately polluted areas of As,Cd,Hg,and Cr were 4%,4%,6%,and 4%,respectively,and only 2%of the area of Hg was heavily polluted.Spatially,the distribution of the eight heavy metals varied significantly,and the farmland soil in the reservoir area showed a slight enrichment trend.Source analysis showed that As,Cu,Ni,and Zn were mainly affected by a mixture of living pollution sources and industrial pollution,Pb was mainly from transportation sources,Cd was mainly from agricultural pollution sources,Hg was polluted by atmospheric deposition sources,and Cr was mainly imported from natural sources of soil-forming matrices.Their contribution rates were 44.655%,15.376%,13.093%,11.178%,and 8.386%,respectively.
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