Magnetic evidence for heavy metal pollution of topsoil in Shanghai, China

This study presents the results obtained from magnetic susceptibility and heavy metal （Cu, Zn, Pb, and Cr） concentration measurements of soil profiles collected from arable land and urban parks in Baoshan District, an industrial district of Shanghai, China. The study focuses on the investigation of vertical variations in magnetic susceptibilities and heavy metal concentrations and on correlations between magnetic susceptibilities and heavy metal concentrations in soil profiles. The results demon- strate that magnetic enhancement in the surface layer of the soil profile is associated with increased heavy metal pollution. The enrichment factors （EF） and the Tomlinson Pollution Load Index （PLI-EF） are calculated for estimat- ing the level of heavy metal pollution of soil profiles in the study. The significant positive correlations between heavy metal contents, enrichment factors （EF）, Tomlinson pollution load index （PLI-CF）, modified Tomlinson pollution load index （PLI-EF）, and magnetic susceptibility （X） indicate that much of the heavy metal contamination in the study area is linked to combustion derived particulate emissions. The results confirm that the combined magnetic measurement and heavy metal concentration analysis could provide useful information for soil monitoring in urban environments. However, the use of magnetic technique to locate the heavy metal pollution boundary in the soil profile of this studied area should be confirmed by further geochemical analysis.

Assessment of major ions and heavy metals in groundwater： a case study from Guangzhou and Zhuhai of the Pearl River Delta, China

Anthropogenic activities in the Pearl River Delta （PRD） have caused a deterioration of groundwater quality over the past twenty years as a result of rapid urbanization and industrial development. In this study, the hydrochemical characteristics, quality, and sources of heavy metals in the groundwater of the PRD were investigated. Twenty-five groundwater samples were collected and analyzed for pH, electrical conductivity （EC）, total dissolved solids （TDS）, δ18O,δ~2H, major ions, and heavy metals. The groundwater was slightly acidic and presented TDS values that ranged from 35.5 to 8,779.3 mg.L-1. The concentrations of the major ions followed the order Cl- 〉 HCO3-〉 Na＋ 〉 SO24- 〉 NO3 〉 NH4＋ 〉 Ca2＋ 〉 K＋ 〉 Mg2＋ 〉 Fe2＋/3＋ 〉 Al3＋. Ca-Mg- HCO3 and Na-K-HCO3 were the predominant types of facies, and the chemical composition of the groundwater was primarily controlled by chemical weathering of the basement rocks, by mixing of freshwater and seawater and by anthropogenic activities. The heavy metal pollution index （HPI） indicated that 64% of the samples were in the low category, 16% were in the medium category and 20% were in the high category, providing further evidence that this groundwater is unsuitable for drinking. Lead, arsenic, and manganese were mainly sourced from landfill leachate; cadmium from landfill leachate and agricultural wastes; mercury from the discharge of leaehate associated with mining activities and agricultural wastes; and chromium primarily from industrial wastes. According to the irrigation water quality indicators, the groundwater in the PRD can be used for irrigation in most farmland without strong negative impacts. However, approximately9 million people in the Guangdong Province are at risk due to the consumption of untreated water. Therefore, we suggest that treating the groundwater to achieve safer levels is necessary.