A comprehensive investigation and assessment of mercury in intertidal sediment in continental coast of Shanghai.

The aims of this paper were to survey the total Hg levels and distribution character in intertidal sediment in continental coast of Shanghai, and identify the environment factors that might influence the sediment Hg concentrations, and to assess the pollution degree and potential ecological risk of Hg in sediment. Eighty-eight surface sediment samples and 18 sediment cores were collected for Hg contamination analysis. Physicochemical properties including Eh, particle size, content of total organic carbon (TOC), and acid volatile sulfide (AVS) were also measured. Index of geo-accumulation (I geo) and potential ecological risk index were used respectively to assess the pollution levels and the ecological risk of sediment Hg. The average of total Hg concentrations in surface sediments was 107.4 ± 90.9 ng/g with the range from 0 to 465.9 ng/g. Higher Hg concentrations were generally found in surface sediments near sewage outfalls and the mouth of rivers. Total Hg concentrations were significantly correlated with TOC (p < 0.05) both in surface (r = 0.24) and core (r = 0.29) sediments, but not with the other environment factors (Eh, AVS, and particle size). Geo-accumulation index indicated that Hg contamination in intertidal sediments was generally at none to moderate degree, while potential ecological risk index demonstrated that the risk caused by Hg were at moderate to considerable level. Intertidal sediment in continental coast of Shanghai has generally been contaminated by Hg, and it might pose moderate to considerable risk to the local ecosystem. The Hg contamination is related more to the coastal pollution sources and complicated hydrodynamic and sedimentary conditions than the other environment factors studied.

Toxic heavy metal contamination and risk assessment of street dust in small towns of Shanghai suburban area, China.

The aims of this paper were to quantify the heavy metal concentrations in street dust of small towns in Shanghai suburban area compared with those in urban area, and examine their seasonal and spatial variations, and to assess their risks to water environment and local populations. Street dust samples were collected from three small towns and urban area in Shanghai in different seasons. Levels of heavy metals were determined by atomic adsorption spectrophotometer analyzer. The method of potential ecological risk index and the health risk assessment model were used to evaluate the potential risks to water bodies and local residents, respectively. The mean metal concentrations in street dust of small towns were far above soil background values but still lower than those in the urban area. No significant seasonal change was observed except for Cr, Ni, and Zn concentrations. Higher metal concentrations tended to be located in central area of towns and township roads. The integrated metal contamination was high and posed a strong potential ecological risk. Children had greater health risk than adults. The carcinogenic risk probabilities were under the acceptable level. The hazard index values to children were close to the safe level. Street dust from the studied area has been contaminated by heavy metals. The contamination of these elements is related more to the pollution source than seasonal change. The combination of the six metals may threaten the water environment and has non-cancer health risk to children, but not to adults.

Human health risk assessment of lead pollution in atmospheric deposition in Baoshan District, Shanghai.

The lead (Pb) content in atmospheric deposition was determined at 42 sampling sites in Baoshan District of Shanghai, China. Based on exposure and dose-response assessments, the health risk caused by Pb exposure in atmospheric deposition was investigated. The results indicated that Pb was significantly accumulated in atmospheric deposition. The spatial distribution of Pb was mapped by geostatistical analysis, and the results showed that pollution hotspots were present at traffic and industrial zones. Ingestion was the main route of Pb exposure in both adults and children. For children the risk value was above 1, whereas it was below 1 for the adult group. Therefore, children belong to the high-risk group for Pb exposure from atmospheric deposition in the observed area of Shanghai, China.

Monitoring urban expansion and land use/land cover changes of Shanghai metropolitan area during the transitional economy (1979-2009) in China.

This study explored the spatio-temporal dynamics and evolution of land use/cover changes and urban expansion in Shanghai metropolitan area, China, during the transitional economy period (1979-2009) using multi-temporal satellite images and geographic information systems (GIS). A maximum likelihood supervised classification algorithm was employed to extract information from four landsat images, with the post-classification change detection technique and GIS-based spatial analysis methods used to detect land-use and land-cover (LULC) changes. The overall Kappa indices of land use/cover change maps ranged from 0.79 to 0.89. Results indicated that urbanization has accelerated at an unprecedented scale and rate during the study period, leading to a considerable reduction in the area of farmland and green land. Findings further revealed that water bodies and bare land increased, obviously due to large-scale coastal development after 2000. The direction of urban expansion was along a north-south axis from 1979 to 2000, but after 2000 this growth changed to spread from both the existing urban area and along transport routes in all directions. Urban expansion and subsequent LULC changes in Shanghai have largely been driven by policy reform, population growth, and economic development. Rapid urban expansion through clearing of vegetation has led to a wide range of eco-environmental degradation.

[Distribution and ecological risk assessment of polycyclic aromatic hydrocarbons in overlying waters and surface sediments from the Yangtze estuarine and coastal areas].

Polluted levels, temporal and spatial distributions of polycyclic aromatic hydrocarbons (PAHs) were studied in overlying water and surface sediments from nine typical sampling sites in the Yangtze estuarine and coastal areas. The results showed that PAHs concentrations in overlying waters and surface sediments in dry season (1988 ng/L and 1154 ng/g) were both higher than those in flood season (1727 ng/L and 605 ng/g). And phenanthrene (Phe) was dominant among PAH compounds. Temperature was the most important factor that controlled PAHs seasonal variation in overlying waters, while organic carbon and soot carbon influenced PAHs accumulation in surface sediments. Complicated hydrodynamic conditions and pollutant inputs caused by various anthropogenic activities not only affected on PAHs spatial distribution, but also led to complicated sources in the Yangtze estuarine and coastal areas. Ecological risk assessment indicated that PAHs in water-sediment system from the Yangtze estuarine and coastal areas might potentially damage the Yangtze estuary ecosystem to some extent. Some of PAH compounds in overlying waters had exceeded the ecotoxicological assessment standard or EPA National Recommended Water Quality Criteria, and BaP also exceeded the normal concentration of Chinese Environmental Quality Standards for surface water. Some of PAH compounds in surface sediments had exceeded the effects range low (ER-L) levels and ISQV-L values.