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.

Diversity change of microbial communities responding to zinc and arsenic pollution in a river of northeastern China

Pollution discharge disturbs the natural functions of water systems. The environmental microbial com-munity composition and diversity are sensitive key indicators to the impact of water pol utant on the microbial ecology system over time. It is meaningful to develop a way to identify the microbial diversity related to heavy metal effects in evaluating river pol ution. Water and sediment samples were col ected from eight sections along the Tiaozi River where wastewater and sewage were discharged from Siping City in northeastern China. The main pollutants contents and microbial communities were analyzed. As the primary metal pol utants, zinc （Zn） and arsenic （As） were recorded at the maximum concentrations of 420 and 5.72 μg/L in the water, and 1704 and 1.92 mg/kg in the sediment, re-spectively. These pollutants posed a threat to the microbial community diversity as only a few species of bacteria and eukaryotes with strong resistance were detected through denaturing gradient gel electrophoresis （DGGE）. Acineto-bacter johnsoni , Clostridium cel ulovorans, and Trichococcus pasteuri were the dominant bacteria in the severely pol uted areas. The massive reproduction of Limnodrilus hoffmeisteri almost depleted the dissolved oxygen （DO） and resulted in the decline of the aerobic bacteria. It was noted that the pollution reduced the microbial diversity but the L. hoffmeisteri mass increased as the dominant community, which led to the overconsuming of DO and anaerobic stinking water bodies. Water quality, concentrations of heavy metals, and the spatial distribution of microbial popula-tions have obvious consistencies, which mean that the heavy metals in the river pose a serious stress on the microorganisms.

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.