中国西南“三江”流域区土壤铊空间分布及健康风险评估

Spatial variation and health risk assessment of thallium in floodplain soil in“Three Rivers”regions of southwest China

通过对中国西南“三江”流域区土壤样品中铊元素含量的分析,并多方法联合应用综合评价研究区土壤铊的污染状况,结果表明,中国西南“三江”流域区浅层土壤铊元素含量范围为0.17~2.65mg/kg,变异系数小,均值为0.80mg/kg,整体略高于中国土壤背景值,而略低于深层土壤铊元素含量,研究区浅/深层土壤铊元素含量特征主要受控于自然地质背景,整体具有“北高南低,西高东低”的趋势.基于中国不同母岩类型区土壤相关元素含量为背景的富集系数(均值1.30)、地累积指数(均值-0.41)、潜在生态风险(均值12.48)及非致癌健康风险评估(危害商小于1)参数均显示研究区土壤铊污染程度整体较低,不存在土壤重金属铊元素的非致癌健康风险,其实质上反映了在自然背景控制下研究区土壤铊的低污染和低健康风险特征.不同土地利用方式区土壤铊含量特征及浅/深层土壤铊元素含量之比反映了研究区存在一定人为污染,且人为铊污染具有“北轻南重,西轻东重”的趋势.综合分析表明,研究区铅锌等矿产的相关矿业活动可能是该区人为铊污染输入的主要来源,人为污染叠加自然地质背景使研究区存在一定低程度污染及潜在健康风险的区域,即独龙江流域南部和怒江流域中南部、澜沧江流域北部和南部、元江流域中南部地区,该区域应引起人们对土壤铊污染的重视.

Based on the analysis of thallium content in floodplain soil samples obtained by the China Geochemical Baselines project in "Three Rivers" regions of southwest China, the pollution status of the thallium in soil of the study area was comprehensively evaluated by multiple methods. Results showed that, the thallium content in top soil of the region was 0.17~2.65 mg/kg with the mean of 0.80 mg/kg and the coefficients of variation was low, which was slightly higher than soil background value of China and slightly lower than that in deep soil. The characteristics of thallium content in the top/deep soil were mainly controlled by the natural geological background, and its overall trend was "north was higher than south, and west was higher than east". Based on the background of related elements of soil in different parent rock areas in China, the parameters of enrichment coefficient, geoaccumulation index, potential ecological risk with the mean 1.30,-0.41 and 12.48, respectively, and non-carcinogenic health risk assessment with hazard quotient less than 1 all showed that the thallium contamination level of soil in the study area was generally low and there was no non-carcinogenic health risk of heavy metal of thallium in the soil, which essentially reflected that there had the characteristics of low pollution and low health risk of thallium pollution in soil of the study area under the control of natural geological background. Meanwhile, there was a certain amount of man-made pollution with a tendency of "north was lighter than south, and west was lighter than east" in the study area, reflected by the distribution characteristics of thallium content of soil in different land use field and the ratio of thallium content in top and deep soil. Comprehensive analysis showed that, the mining activities related to lead and zinc minerals in the study area might be the main source of man-made thallium pollution. Some parts of the study area had a certain degree of pollution and potential health risks due to the superposition of man-made pollution and natural geological background, including the south of Drung river basin, south central Nujiang river basin, the north and south Lancang river basin and south central Yuanjiang river basin, and these areas should attract people’s attention to thallium pollution in soil.