三峡库区(重庆段)菜地土壤重金属污染特征、潜在生态风险评估及源解析

为探究三峡库区菜地土壤重金属的污染特征、潜在生态风险和污染物的来源，于2021年10月采集了库区（重庆段）14个蔬菜种植区（县）菜地的表层土壤样品，分析了样本中7种重金属元素（As、Cd、Cr、Cu、Ni、Pb和Zn）的含量，分别利用单因子指数法、内梅罗综合污染指数法和潜在生态风险评价法对土壤重金属的富集状况和潜在风险进行了评估，并分析了蔬菜种植年限和栽培方式（露天和大棚）对土壤重金属累积的影响.结果表明，库区菜地土壤中重金属的含量高于重庆市三峡库区土壤背景值，但均低于《农用地土壤污染风险管控标准（试行）》（GB 15618-2018）规定的土壤污染风险管制值；单因子污染评价结果表明，区域土壤Pb、Zn、Cu和Cd处于轻微污染水平；内梅罗综合污染指数法表明，研究区处于轻度污染水平，主要污染因子为Cd和Ni，有91.4%的土壤样品存在不同程度的污染（P_N>1），其中9.19%的样品处于重度污染；潜在生态风险评估结果指出，研究区以轻度生态风险为主，Cd中度生态风险的土壤样本数占比为9.77%，存在一定的生态风险.聚类分析结果显示Cd-Cu-Pb-Zn和As-Cr-Ni分别具有相同的污染源.菜地土壤中重金属含量随着种植年限的增加均呈上升趋势；总体上大棚土壤中重金属含量均高于露天菜地土壤.

Pollution Characteristics and Source Apportionment of Heavy Metals in Vegetable Field in the Three Gorges Reservoir Area (Chongqing Section)

To explore the pollution characteristics, ecological risks, and sources of heavy metals, soil surface samples of vegetable fields in 14 typical districts of the Three Gorges Reservoir area (Chongqing section) were collected in October 2021. The contents of seven types of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were analyzed. Based on the single-factor pollution index, the Nemerow integrated pollution index and potential ecological risk coefficient of heavy metals were evaluated. Additionally, the effects of different planting years and methods (open-field and greenhouse planting) on soil heavy metal accumulation were analyzed. The results indicated that the mean concentrations of heavy metals in vegetable soils in the area were lower than the national risk screening values for soil contamination of agricultural land (GB 15618-2018) but higher than their background values in Chongqing. According to the single-factor pollution index method, Pb, Zn, Cu, and Cd showed negligible slight hazards. The Nemerow pollution index showed that the study area was at a slight hazard level, and the main factors were Ni and Cd. Heavy metal pollution was found in 91.4% of the soil samples (P_N>1) with different degrees, and 9.19% of them were severely polluted. The potential ecological risk coefficient showed that the vegetable lands were polluted slightly, and 9.77% of soil samples polluted by Cd were at moderate ecological risk. According to cluster analysis, the sources of Cd-Cu-Pb-Zn and As-Cr-Ni were similar. The content of heavy metals in the open field and greenhouse showed an increasing trend with the increase in planting years, and the content of heavy metals in greenhouse soil were generally higher than that in open field soil.