Regional risk assessment of trace elements in farmland soils associated with improper e-waste recycling activities in Southern China

Trace elements contamination in soils caused by improper electrical waste (e-waste) recycling activities has attracted a lot of attention, and soaring levels of trace elements in e-waste recycling sites and the adjacent farmlands were well-recognized. However, the knowledge of pollution degree, ecological risk of trace elements in a whole e-waste recycling region was still limited. In this study, soil samples collection was conducted in a typical e-waste recycling region (approximately 30 km2), and the concentrations of eight trace elements (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were analyzed. Moreover, pollution index, enrichment factor, potential ecological risk, hazard quotient, and hazard index were calculated and used to assess the risk of the ecosystem and human health. The results showed that the mean concentrations of Cd, Cu, and Hg were significantly higher than their standard values of China; the excess portion was 90.2% for Cu, 87.4% for Cd, and 47.6% for Hg, indicating the regional contamination of these metals. The values of enrichment factors further demonstrated that Cd, Cu, and Hg were the most significantly enriched metals in the study area, which might be associated with e-waste activities. On the other hand, the concentrations of Cr and Ni were comparable with their background values, suggesting that they were mainly affected by soil parent materials. Health risk assessment indicated that the carcinogenic risk for the local habitants was unacceptable. Results of this study suggest that soil remediation strategies in e-waste recycling region should not only focus on the sites where e-waste recycling facilities located (i.e. hot spots), but consideration should also be given to control regional risk in farmlands.