Long-term effect of E-waste dismantling activities on the heavy metals pollution in paddy soils of southeastern China.

The heavy metal pollution in soils has attracted a growing concern from environmental researchers worldwide. Heavy metals derived from E-waste dismantling process now is one of the main pollution sources. Wenling city is one of the large E-waste dismantling sites as well as a commercial grain production area in China. In this study, the Cd, Cu, Ni, Pb and Zn concentrations of paddy soils were determined to reveal the temporal trends over the past decade based on the samples collected from 2006 a (96) and 2016 a (167), respectively. From 2006 a to 2016 a, the averages values of Cd, Cu, Ni and Zn concentrations in soils increased by 0.11, 11.81, 1.01 and 6.82 mg kg-1, respectively. The average concentration of Pb in soils decreased by 14.06 mg kg-1. All of the five heavy metals shared the similar spatial distribution patterns with high-concentration values located in northwestern part of the study area. The results of principal component analysis (PCA) revealed that the E-waste was the main source of pollution for Cd, Cu, Pb and Zn in soils. The spatial patterns revealed by local Moran' I indicated that the northwestern part were identified as priority areas for soil heavy metal remediation. During the last decade, a continuing increase trend of the concentrations of heavy metals in soils was found, however, the other parts of the study area had an obvious decrease trend of heavy metals in soils under the implementation of environmental protection policies. Therefore, sustainable remediation measures and E-waste dismantling management are necessary to reduce heavy metal concentrations in specific areas of Wenling.