电子废弃物拆解区周边农田土壤重金属污染评价及成因解析

摘要

Investigating soil environmental problems, such as the contamination status and the ecological risk of heavy metals (HMs) caused by dismantling, dumping and diffusion of waste electrical and electronic equipments (WEEEs), is crucial to scientific classification management and reasonable utilization of farm soils around recycling sites. In a typical WEEEs recycling site in Taizhou city, Zhejiang province (one of the three major WEEEs recycling bases in China), 12 soil samples from dismantling, dumping and neighboring farmland sites were randomly collected. The contents and the contamination indices of soil HMs were analyzed and calculated, and the ecological risk assessment and the genesis analysis of soil HMs were also carried out. For the investigated area, the contamination degrees of Cd, Cu, Pb, and Zn were all high (based on the single factor pollution index calculated by the average value of all detected samples), while the contamination degrees of Cr and Ni were moderate and low, respectively. However, the potential ecological risk levels of Cd, Pb, and Cu varied from very high to moderate, while the risk levels of Ni, Cr, and Zn were consistently low. Specifically, the dismantling and dumping sites were highly polluted as indicated by the HM pollution indices peaked at 164.2 and 152.9, respectively. The potential ecological risk indices peaked at 2685 and 6914, respectively, suggested high ecological hazard degree in both dismantling and dumping sites. In addition, the HM pollution levels for 57.14% of the farmland soils varied from moderate to high, and the ecological hazard levels for 28.57% of the farmland soils were moderate. The principal component analysis and correlation analysis suggested that there were two major diffusion ways of HMs in this study area. The primary way was the atmospheric deposition of dust and fly ash caused by WEEEs dismantling and incineration, respectively. The second one was the rainfall erosion, leaching infiltration and surface runoff of WEEEs tailings. Overall, the soils in this investigated area were widely polluted by HMs (firstly due to Cd, Pb, and Cu, and then Zn, Cr, and Ni), and the diffusion pathway was mainly air transportation, supplemented by rainfall transportation.%深入了解电子废弃物拆解、倾倒及扩散引发的土壤环境问题,有助于根据土壤重金属污染程度及其潜在生态风险实现拆解区周边农田土壤的分类分级管理和科学合理利用.在浙江台州(国内电子废弃物三大拆解基地之一)某典型电子废弃物拆解区的拆解点、倾倒点及周边农田随机采集12个土壤样本,测定了土壤重金属(Cd、Cu、Cr、Ni、Pb、Zn)质量分数与污染指数,并开展了生态风险评估与成因推测研究.从研究区土壤重金属单项污染指数(以所有样点的平均值计)来看,Cd、Cu、Pb、Zn为重度污染,Cr与Ni分别为中度与轻微污染,其中Cd、Pb与Cu分别具有极强、强和中等生态危害,而Ni、Cr、Zn具有轻微生态危害.从具体样点来看,电子废弃物拆解点和倾倒点土壤重金属污染指数最高分别达164.2和152.9(均为重度污染),其潜在生态风险指数最高分别达2685和6914(均为很强生态危害);57.14%的农田样点土壤重金属已达中度至重度污染水平,28.57%的农田样点土壤重金属生态危害达中等级别.主成分分析与相关性分析结果显示,研究区土壤重金属污染存在两条主要扩散途经,首要的是电子废弃物拆解产生的粉尘与焚烧产生的飞灰随大气沉降而产生的污染,次要的是拆解点与废渣倾倒点经雨水冲刷、淋溶下渗、地表径流所造成的污染.结果表明,研究区土壤重金属污染较为普遍,且以Cd、Pb、Cu为主,Zn、Cr、Ni次之;电子废弃物拆解与处置过程中重金属的扩散途径以空气传输为主、雨水迁移为辅.