Comparison of soil heavy metal pollution caused by e-waste recycling activities and traditional industrial operations

Environ Sci Pollut Res Comparison of soil heavy metal pollution caused by e-waste recycling activities and traditional industrial operations Kailing He 0 1 2 3 4 Zehang Sun 0 1 2 3 4 Yuanan Hu 0 1 2 3 4 Xiangying Zeng 0 1 2 3 4 Zhiqiang Yu 0 1 2 3 4 Hefa Cheng 0 1 2 3 4 0 University of Chinese Academy of Sciences , Beijing 100049 , China 1 State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences , Guangzhou 510640 , China 2 Responsible editor: Philippe Garrigues 3 MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences, Peking University , Beijing 100871 , China 4 MOE Laboratory of Groundwater Circulation and Evolution, School of Water Resources and Environment, China University of Geosciences (Beijing) , Beijing 100083 , China The traditional industrial operations are well recognized as an important source of heavy metal pollution, while that caused by the e-waste recycling activities, which have sprouted in some developing countries, is often overlooked. This study was carried out to compare the status of soil heavy metal pollution caused by the traditional industrial operations and the e-waste recycling activities in the Pearl River Delta, and assess whether greater attention should be paid to control the pollution arising from e-waste recycling activities. Both the total contents and the chemical fractionation of major heavy metals (As, Cr, Cd, Ni, Pb, Cu, and Zn) in 50 surface soil samples collected from the e-waste recycling areas and 20 soil samples from the traditional industrial zones were determined. The results show that the soils in the e-waste recycling areas were mainly polluted by Cu, Zn, As, and Cd, while Cu, Zn, As, Cd, and Pb were the major heavy metals in the soils from the traditional industrial zones. Statistical analyses consistently show that Cu, Cd, Pb, and Zn in the surface soils from both types of sites were contributed mostly by human activities, while As, Cr, and Ni in the soils were dominated by natural background. No clear distinction was found on the pollution characteristic of heavy metals in the surface soils between the e-waste recycling areas and traditional industrial zones. The potential ecological risk posed by heavy metals in the surface soils from both types of sites, which was dominated by that from Cd, ranged from low to moderate. Given the much shorter development history of e-waste recycling and its largely unregulated nature, significant efforts should be made to crack down on illegal e-waste recycling and strengthen pollution control for related activities. Soil pollution; Heavy metals; E-waste recycling; Traditional industrial operations; Sequential extraction; Potential ecological risk Introduction The quality of soils is closely related to agricultural production, human health, and ecological security (Burges et al. 2015; Chen et al. 2014) . Among all the pollutants in soils, heavy metals are of significant concerns due to their inherent toxicity, bioaccumulation, persistence, and non-degradability (Liu et al. 2013) . Heavy metals are considered as Bcontaminants^ when their occurrences are unwanted, or in forms or concentrations resulting in detrimental effects to human or the ecosystem. Although heavy metals rarely occur at toxic levels naturally, intensive anthropogenic activities can drastically alter the natural biogeochemical cycling and balances of some heavy metals (Alloway 1995). The major anthropogenic sources of heavy metals include industrial point sources, such as mines, foundries, and smelters, as well as diffuse sources, e.g., vehicular emissions and urban and agricultural run-off (Nriagu and Pacyna 1988) . Irrespective of their sources in the soil, accumulation of heavy metals can degrade soil quality, reduce the crop yield and the quality of agricultural products, and thus negatively impacts the health of human, animals, and the ecosystem (Nagajyoti et al. 2010) . The Pearl River Delta (PRD) in Guangdong Province, which is a densely populated region of over 40,000 km2 with a population over 40 million, is a major manufacturing base in China. There used to be few industrial activities in the PRD before the launch of economic reform in the late 1970s (Hu et al. 2013) . Cities, including Dongguan, Zhuhai, and Zhongshan, have been transformed from agricultural lands to major manufacturing hubs over the past three and a half decades. Remarkable heavy metal pollution has resulted from the manufacturing operations and the associated disposal of industrial wastes (Hu et al. 2013) . Along with the rapid industrial and urban development, numerous cases of water, sediment, and soil pollution have occurred in the PRD (Guangdong Environmental Protection Bureau 1996) . Previous studies have documented widespread pollution of surface soils in the PRD (Hu and Cheng 2016; Hu et al. 2013; Qiu et al. 2015, 2016; Wang et al. 2015; Wong et al. 2002; Xiao et (...truncated)