水口山水稻土与菜地土中砷的有效性

Availability of arsenic in paddy and vegetable soils in Shuikoushan mining area of Hunan Province,South-central China

对湖南省水口山矿冶周边土壤进行采样分析,以土壤砷总量与有效态砷含量以及土壤基本理化性质(pH、有机质含量、土壤粘粒含量)为参数,研究各参数在两种土地利用类型(菜地土和水稻土)间的差异以及有效态砷与土壤理化性质之间的关系。结果表明,水口山水稻土与菜地土平均砷含量分别达72.01和30.71mg.kg-1,接近或已超过国家土壤环境质量二级标准;两种土地利用类型的土壤基本理化性质差异显著,水稻土粘粒含量、有机质含量显著高于菜地土,pH则显著低于菜地土,水稻土存在明显的酸化现象;不同土地利用类型显著影响土壤有效砷含量,尽管菜地土土壤砷总量大大低于水稻土,两者的有效态砷含量水平却基本相当;除总砷外,水稻土有效砷含量还与土壤有机质含量显著正相关,菜地土有效砷含量与土壤pH值显著正相关。水口山菜地土砷污染的危害程度高于水稻土,应采取必要的修复措施或调整土地利用方式以降低砷的健康风险。

Soil samples were collected from the surrounding areas of Shuikoushan mining area in Hunan Province of South-central China to determine the soil total and available arsenic contents and the soil physical and chemical properties （pH value, organic matter content, and clay content）, with the differences of the test parameters in two agricultural soils （vegetable soil and paddy soil） and the relationships between the soil available arsenic content and the soil physical and chemical properties analyzed. The average content of the arsenic in paddy soil and vegetable soil was 72.01 and 30.71 mg·kg^-1, respectively, being close to or exceeding the National Soil Environmental Quality Standard Ⅱ. There existed significant differences in the soil physical and chemical properties between the two agricultural soils, with the higher contents of clay and organic matter but lower pH value in paddy soil than those in vegetable soil, and the paddy soil being obviously acidified. The total arsenic content in vegetable soil was far higher than that in paddy soil, but the available arsenic content of the two soils had less difference. Except for total arsenic, the available arsenic content in paddy soil was significantly positively correlated with organic matter content, and that in vegetable soil was significantly positively correlated with pH value. In the Shuikoushan mining area, vegetable soil had a higher risk of arsenic pollution than paddy soil, and thus, necessary remediation strategies or adjustment of land use pattern should be adopted to reduce the health risk of soil arsenic contamination.