Study On Heavy Metal And Metalloid F And As Pollution In Soil In Chengdu Plain

98 soil samples of 0-20cm topsoil and 20-40cm bottom-soil were taken from Chengdu Plain by sample survey. The contents of the main contamination elements and the spatiotemporal changes were discussed. The GB15618-1995 'Criterion of Environmental Quality in Soil' was used to evaluate pollution degree in order to know the state of soil contamination .The Geoaccumulation Index was used to evaluate pollution degree for showing the degree of human being influence on the contents of the main contaminatio n elements. The geostatistical method and GIS were used to forecast the contents of the main contamination elements, the trend of which were mapped and the distributions of the main elements and the mobility of the main contamination elements in soils were discussed. Relation between the contents of the main contamination elements and the physical-chemical characters of the soils were discussed too. The results showed:The content of Cd was changed greatly and changeable with time. From northeast to southwest the content of Cd took on a degressive trend, the content of Cd was under 0.33mg/kg in most areas. 15.12% of the soil samples went beyond grade 2 of 'Criterion of Environmental Quality in Soil', 45.35% of the soil samples ran over grade 1. 43.02% of the whole samples was polluted by extrinsic Cd in different degree. The contamination grades were between 1 and 2, the leading grade (account for 38.4% of the total soil samples) was grade 1. Cd was mobile in some soil profiles. The content of Cd closely related to the contamination sources and the physical and chemical characters of soils such as bulk density, physical clay, clay, medium silt, sand, degree of aggregation, total porosity, pH, CEC and cultivated system. In different soil type, the content of Cd was different.The content of Cu was greatly changed but the changes with areas and time were little. The content of Cu was under 30.4-33.8mg/kg in most areas. Cu was mostly 玞cumulated in 0-20cm topsoil. 5 soil samples went beyond grade 2 of 'Criterion of Environmental Quality in Soil'. 26 soil samples ran over grade 1, which accounted for 30.23 %of the total soil samples. 88.37% of soil samples was not influenced by extrinsic Cu. Only 10 soil samples were influenced lightly. Contamination sources could effect the content of Cu and the pesticide and fertilizer could work on the content of Cu in soils. The content of Cu was closed to traffic. The content of organic matter, coarse silt and K, N in soil could effect the content of Cu too.The content of Pb was greatly changed and changeable in different areas. With time going, the content of Pb increased. The content of Pb was high in few areas, the content of Pb was from 62mg/kg to 89mg/kg in some areas, and the content of Pb was under 62mg/kg in most areas. Pb was mostly accumulated in 0-20cm topsoil, and was mobile in some soil profiles, Only 1 soil sample went beyond grade 2 of Criterion of Environmental Quality in Soil', 77.9% of the soil samples ran over grade 1. Only 23.3% of soil samples was not polluted. Among the polluted soil samples, the leading grades were grade 1 and 2. The former had 32 soil samples (accounted for 37.21% of the total soil samples), the latter had 31 soil samples (accounted for 36.05% of the total soil samples). Few samples approached or reached intense contamination degree. The content of Pb was tightly contacted with the pollution sources, traffic and the physical and chemical characters of soils. Great difference existed in different soil type, the content of Pb could be effected by cultivated system and the distribution of rivers.The content of Cr was highly changed and increased with time, the changes in different areas werequite evidence. Cr was mostly accumulated in topsoil. The content of Cr was high in few areas, and the content of Cr was from 94mg/kg to 125mg/kg and under 94mg/kg in most areas. Only 1 soil sample went beyond grade 2 of'Criterion of Environmental Quality in Soil', but 50% of soil samples ran over grade 1. 73.26% of soil samples was not influenced by ex...