设施农田土壤重金属污染评价及分区阈值研究

设施农田高强度的耕作模式使土壤重金属累积日益加重，因地制宜地确定其土壤重金属目标值与筛选值对设施农田可持续生产意义重大。本文以石家庄、衡水与唐山为研究区，基于土壤重金属污染风险和生态风险评价，用熵权法得出综合风险等级并确定重金属污染分区阈值。结果表明土壤Cd、Cu、Zn污染最严重，高风险区占比达40.57%。研究区设施农田土壤Cd、Cu、Pb、Zn全量与有效态的目标值分别为0.12、40.17、19.23、116.03 mg·kg^-1与0.02、4.19、0.59、8.80 mg·kg^-1；筛选值分别为0.40、90.27、38.33、170.68 mg·kg^-1与0.11、11.77、1.55、14.24 mg·kg^-1。基于综合评价结果反推分区阈值的方法简单便捷，重金属全量与有效态的目标值及筛选值的确定为研究区设施农田重金属污染的预防提供了多方位的指导。

Assessment and partition threshold for heavy metals pollution in soil of facility farmland

Intensive cultivation patterns of facility farmlands increase the accumulation of heavy metals in soils. The determination of locally-adapted target and screening values of soil heavy metals is important for the sustainable production of facility farmland. Using the soil samples from facility farmlands in Shijiazhuang, Hengshui, and Tangshan, the entropy weight method was adopted to comprehensively evaluate the risk level of heavy metals pollution based on the pollution risk and ecological risk assessment of soil heavy metals. Then, the partition threshold of facility soil heavy metals pollution was determined. The results showed that Cd, Cu, and Zn posed the highest risks in facility farmland soil, with high-risk areas accounting for 40.57% of the land. The target values of the total and available states of Cd, Cu, Pb, and Zn in facility farmland soil in the study area were 0.12, 40.17, 19.23, and 116.03 mg·kg^-1 and 0.02, 4.19, 0.59, and 8.80 mg·kg^-1, respectively; the screening values were 0.40, 90.27, 38.33, and 170.68 mg·kg^-1 and 0.11, 11.77, 1.55, and 14.24 mg·kg^-1, respectively. The method established in this study to estimate the partition threshold based on comprehensive evaluation results is simple and convenient. Moreover, the determination of target values and screening values of the total and available state of heavy metals can provide multidirectional guidance for the prevention of heavy metals pollution in facility farmland.