Pollution Assessment and Spatial Distribution of Heavy Metals in the Farmland Soils of Taiyuan City

【Objective】 Heavy metal pollution is an important source of soil pollution. At present, the research mainly focuses on the urban area and the sewage irrigation area soil, but the heavy metal pollution and the spatial distribution of the whole farmland soil in Taiyuan have not been reported. The objective of present study was to describe the present situation, pollution sources and spatial distributions of heavy metals in the farmland soil of Taiyuan city. This work will be helpful for pollution control and agricultural production. 【Method】 The concentrations of Cr, Cd, Pb, Hg and As in the 214 farmland soils of Taiyuan city were determined. The pollution level of soil heavy metal elements was evaluated using single factor index method and nemerow comprehensive index method. The spatial distribution map of heavy metals was drew using ArcGIS 10.3 and the correlation analysis was done by SPSS 16.0 to reveal the pollution sources of heavy metals in soils. 【Result】 ①The concentrations distribution of heavy metals in farmland soils was quite different. The average content of Cr, Cd, As, Hg and Pb in soil was 68.38, 0.121, 8.59, 0.08 and 24.23 mg/kg, respectively. These contents were significantly higher than the corresponding background values of soil in Taiyuan, although they did not exceed the environmental quality standard of the green food producing area. ②The Single Pollution Index was shown as Hg(2.36)>Pb(1.76)>Cd(1.57)>Cr(1.19)>As(1.12). The contaminations of Hg, Pb and Cd mainly originated from industrial production, sewage irrigation, coal burning, application of pesticide and chemical fertilizer and transportation. On the other hand, the pollution of As and Cr were mainly associated with soil parent material and agricultural activities. ③The Nemerow index of Taiyuan farmland soil was 2.14, indicating the moderate pollution. The Nemerow index of farmland soil was 4.17 in Jinyuan district, 2.98 in Xiaodian district, 2.13 in Jiancaoping district, 2.07 in Qingxu county, 1.71 in Yangqu county, 1.67 in Loufan county and 1.57 in Gujiao county. The spatial distribution map of heavy metals and pollution status could be visualized, showing moderately and severely polluted in the suburb soils of Taiyuan city(especially in Jinyuan and Xiaodian districts), and slightly polluted in the countries far from Taiyuan city. 【Conclution】 We conclude that the farmland soils of Taiyuan city were moderately polluted, and Hg and Pb were the main contaminants. The more serious heavy metal pollution was located in the suburbs of Taiyuan city (i.e., Jinyuan, Xiaodian, Jiancaoping and Qingxu). We recommend that it is necessary to strengthen monitoring Hg and Pb in soils in these heavily polluted areas to ensure the soil health and agriculture sustainability.