不同农地利用方式土壤砷、汞累积特征分析及评价研究

Accumulation and Evaluation of Arsenic and Mercury in Soils under Different Land Use

为了解成都平原土壤砷、汞的污染状况,揭示不同农地利用方式对土壤砷、汞含量的积累特征,本文以都江堰为研究区域,采集了不同农地利用下73个土壤样点,测定样品中砷、汞含量。结果表明,样点土壤砷平均含量为7.24mg/kg,不同农地利用方式下砷含量从高到低依次为:果园>水田>菜地>旱地;土壤汞平均含量为0.29 mg/kg,不同农业利用方式汞含量由高到低依次为:果园>菜地>旱地>水田。土壤砷、汞含量与川西平原背景值比较均出现了累积趋势,其中以果园的累积问题最突出,其砷、汞含量分别为8.61mg/kg、0.33mg/kg,分别高出川西平原背景值10.5%、83.3%;与土壤环境质量标准比较,4类农地利用方式中砷、汞均未超过规定的二级标准。地质累积指数和潜在生态风险指数研究表明,研究区农地砷、汞尚属轻微污染,从单元素角度分析汞潜在生态风险高于砷。

In order to explore the heavy metal concentrations and the characteristic of accumulation in different types of agricultural lands in Dujiangyan City, 73 sampling points in topsoil （0-20 cm）were collected for testing the content of arsenic and mercury. The results showed that the average contents of arsenic and mercury were 7.24 mg/kg and 0.29 mg/kg respectively. In comparison with different agricultural lands, the highest concentration for arsenic and mercury appeared in the fruit field with the average content of 8.61 mg/kg for arsenic, 1.105 times higher than background, and the content of mercury was 0.33 mg/kg, which is 1.833 times higher than background. The content of arsenic in different soils ranked in this order： fruit field〉paddy field〉 vegetable field 〉dry farm, while soil mercury content from high to low in turn for： fruit field〉 vegetable field 〉dry farm〉paddy field. Though accumulation of arsenic and mercury in soils occurred in different agricultural lands, reference Quality Standard of Soil Environmental the content of arsenic and mercury did not exceed the permitted. Through Geo-accumulation index method and ecological risk index method to evaluate the pollution status of different heavy metals separately, we found that the potential pollution risk of mercury was higher than arsenic, while both of mercury and arsenic were at a slight ecological pollution level in the samplings region.