Heavy metal contamination of urban soil in an old industrial city (Shenyang) in Northeast China

The purpose of this study is to investigate the current status of heavy metal soil pollution in one of the cradles of industry in China, the Tiexi Industrial District in the city of Shenyang, Ninety-three soil samples were collected from the top 15 cm of the soil layer and were analyzed for heavy metal concentrations of Pb, Cu, Cr, Zn, Mn, Cd, As and Hg. The data reveal a remarkable variation in heavy metal concentration among the sampled soils; the mean values of all the heavy metal concentrations were higher than the background values, and the mean concentrations of Pb, Cu, Cd and As were as high as 5.75, 5.08, 12.12 and 13.02 times their background values, respectively. The results of principal component analysis (PCA) indicate that Pb, Cu, Zn, Cd, As and Hg are closely associated with the first principal component (PC1), which explained 46.7% of the total variance, while Cr and Mn are mainly distributed with the second component (PC2), which explained 22.5% of the total variance. Geostatistical analyses, including the calculation of semivariogram parameters and model fitting, further confirmed the results of the statistical analysis. In the estimated maps of heavy metals, several hotspots of high metal concentrations were identified; Pb and Cu,showed a very similar spatial pattern, indicating that they were likely from the same source. There is a clear heavy polluted hotspot of Pb, Cu, Zn, Cd and As in the northeast part of the Tiexi Industrial District because of the Shenyang Smelting Plant, which was a backbone enterprise of China's metallurgical industry. There were also hotspots for other heavy metals in other areas. This is mainly the result of the industrial processing that occurred in the study area. All of these data confirm that Pb, Cu, Zn, Cd and As are a result of anthropogenic activities, especially from industrial processes. For Cr and Mn, the concentration patterns indicate low spatial heterogeneity, with low correlation to other metals, indicating that the concentration of Cr and Mn are mainly caused by natural factors such as soil parent materials. Although the city government of Shenyang has placed a high priority on improving the environment in recent years, it will require a long time to completely eliminate pollution in this area. (C) 2012 Elsevier B.V. All rights reserved.