大冶市农田土壤中镉的空间分布特征及污染评价

矿山开采和冶炼是造成土壤重金属Cd污染的主要原因，了解典型区域土壤中Cd的空间分布特征及其污染现状，可为区域土壤污染防治与安全利用提供重要信息。本研究针对湖北省大冶市所有农田采集92个表层土壤样品和3个土壤剖面，利用GIS方法对土壤重金属Cd空间分布特征及污染状况进行了研究。结果表明大冶市土壤中Cd的含量范围为0.6 ~ 4.6 mg/kg，平均值为1.41 mg/kg，Cd迁移深度可达 40 cm。区域内土壤Cd污染范围较广，空间变异较大，还地桥镇、罗桥街办、陈贵镇等地农田土壤Cd含量较高。地积累指数评价结果显示大冶市大部分农田土壤为轻度、中度污染程度，在合理调整种植结构等方式下仍可保障农田安全利用。

Spatial Distribution and Assessment of Cadmium Pollution in Farmland Soils, Daye City

Heavy metal contaminated soils were primarily caused by mining and smelting activities. Exploring the spatial distribution and the pollution level of typical heavy metal in soil is of great significance in regional environmental management, pollution control and ecological protection. In this study, the typical heavy metal of Cd was studied for the farmland soils in Daye city, Hubei Province, and totally 92 top-soil samples and three typical soil profiles were collected and determined. The results showed that Cd concentration of farmland soil ranged from 0.6 to 4.6 mg/kg. The GIS analysis of Cd concentration showed its spatial distribution varied significantly due to the effects of pollution sources. The soil quality was assessed based on the geo-accumulation index and single factor index, and the heavily Cd polluted sites were in the vicinity of mining and smelting plants. The analysis results from different soil profiles indicated that the Cd content in the top 20 cm of soil was much higher than that in the deeper soil layers because of the enrichment of exogenous heavy metal. Cd concentration of soil profiles decreased with increasing soil depth until it is incline to the background value, while its vertical transport was influenced by the land use characteristics of paddy field or abandoned land.