县域尺度耕地土壤重金属污染评价中的标准选择研究

为提升区域土壤重金属污染风险评价的科学性与准确性，本研究以太湖沿岸某产粮大县为研究对象，分别基于国家《土壤环境质量/农用地土壤污染风险管控标准（试行）》（GB15618-2018）与地区土壤环境负载容量对研究区耕地土壤中As、Hg、Cr、Cd、Pb五种重金属进行污染风险评价.结果显示，两种评价方式在区域整体评价结果上趋于一致，却在各类土壤重金属污染程度评价上存在一定差异.有别于"一刀切式"的浓度标准评价模式，土壤环境负载容量法通过"双界面"标准进行污染总量控制，可以在一定时空范围内较为准确的反映外源污染累积变化情况.为提升区域耕地土壤重金属污染评价的准确性，建议相关评价在普适性国标的基础上引入土壤环境负载容量评价作为有益补充，继而为县、镇尺度土壤污染责任主体认定与风险控制区划提供参考借鉴.

Criterion selection in assessment of soil heavy metal pollution in farmland on county scale

To improve the scientific validity and accuracy of regional risk assessment of soil heavy metal pollution, a county with high grain yield along Taihu Lake was chosen as a research site to assess the risks of pollution associated with five heavy metals:As, Hg, Cr, Cd, and Pb. Pollution risks were assessed according to two sets of criteria as stipulated by a national regulation (GB15618-2018) and Regional Soil Environment Load Capacity, respectively. Results show that while the two sets of criteria produce converging assessments for the region as a whole, there were considerable differences across different types of heavy metals. In contrast to the "One Size Fits All" model that relied exclusively on concentration criteria, the Soil Environment Load Capacity's approach, which relied on "dual interface" criteria to control the total stock of pollution, could more accurately capture changes in the accumulation of external-source pollution within certain ranges of temporal and spatial dimensions. To improve the accuracy of regional farmland soil heavy metal pollution assessment, it is recommended that Soil Environment Load Capacity assessment be introduced as a valuable complement to assessment based on general national criteria. This would provide a source of reference for determining soil pollution responsible parties and for drawing risk control zones at the county and township levels.