电子废物拆解区典型用地土壤重金属分布特征

以广东清远的电子废物拆解区为研究对象，采集了遗留拆解场地，水稻田，蔬菜地，旱地和林地等5种用地类型土壤，分析了土壤基本理化指标和重金属含量.结果表明，各重金属元素含量高低总体呈现出：拆解场地 > 蔬菜地 > 水稻田 > 旱地 > 林地的趋势.其中，拆解场地的As、Cd、Cu、Hg、Pb和Zn均超过《土壤环境质量标准》（GB 15618–1995）二级标准，超标倍数最高的为Cd、Cu、Pb和Zn.蔬菜地和水稻田也出现不同程度的Cd和Cu超标，但林地与旱地的各元素含量均接近于背景值.在垂向分布上，受拆解活动直接影响的拆解场地中，各重金属含量随深度而显著递减，呈现出明显的表聚特征；而电子废物拆解活动影响较小的林地和旱地变化趋势不明显.冗余分析结果表明，研究区域土壤中重金属的迁移主要受土壤pH值、有机质和总磷的共同影响.各重金属元素的潜在生态危害风险程度处于轻微至极强，其中Cd和Cu的危害指数最高；各用地类型土壤的综合生态风险指数介于93（林地）~4750（拆解场地），平均为1187，属于很强的风险水平.本研究的结果可为政府部门科学开展电子废物拆解综合整治和土地管理提供基础信息.

Distribution pattern of heavy metals in soils with respect to typical land uses in electronic waste recycling region

Heavy metal contaminations in soils caused by improper electronic-waste (e-waste) recycling activities have been attracted wide attentions. However, the studies on the enrichment and migration of heavy metals with respect to land uses were scarce. In the study, Longtang, a town located in Qingyuan City, Guangdong Province was selected as the representative region, and soil samples from five land uses, including abandoned e-waste recycling site (ERS), paddy field (PAF), vegetable field (VEF), dry field (DRF), and forest field (FOF) were collected to analyze the distributions of eight heavy metals and their relations with soil physicochemical properties. The results showed that the mean concentrations of heavy metals in soils associated with land uses were generally ranged in the decreasing order as ERS > VEF > PAF > DRF > FOF. In special, concentrations of As, Cd, Cu, Hg, Pb, and Zn in ERS exceeded the maximum allowable concentrations (CEPA, 1995). Cd, Cu, Pb, and Zn were identified as the major pollutants. Additionally, soils from VEF and PAF were also contaminated by Cd and Cu, which were probably originated from ERS via irrigation. While the concentrations of heavy metals in soils from DRF and FOF were comparable with the corresponding background values of Guangdong Province. On the other hand, the concentrations of heavy metals in soils influenced by e-waste recycling activities (e.g., ERS) were significantly decreased against with vertical depth, however, less variation was observed for FOF and DRF. These above-mentioned distribution patterns might be ascribed to the factors including soil pH value, organic matters content, and total phosphorus content. Furthermore, the potential ecological risk of heavy metals ranged from low to serious degree, in special of Cd and Cu. The ecological risk index in soils with respect to land uses ranged from 93 (in FOF) to 4750 (in ERS), with an average value of 1187, which was classified as higher ecological risk. Accordingly, this study provides fundamental data to strongly support the management of e-waste recycling activities and land uses.