Spatial Distribution and Sources of Heavy Metals in Soil of Dongguan City, Pearl River Delta Economic Zone, Guangdong Province, China

摘要

Dongguan City, located in the Pearl River Delta economic zone, is famous for its rapid developing township-enterprises in the past 30 years. A total of 759 soil samples have been collected in the city, and metal elements (As, Cu, Cd, Cr, Hg, Ni, Pb, Zn, Mn, Co, Si, Fe and Al) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropic activities on the soil environmental quality and to identify the spatial distribution of trace elements and possible sources of trace elements. Results indicate that the mean contents of heavy metals in soil were significantly lower than the threshold of the second grade of Soil Environment Quality Standard in China (GB15618-1995) and the soil environmental quality in this area is comparatively good. But in comparison with local soil background content of elements, the elements As, Cd, Hg, Zn, Cu and Pb have accumulated remarkably here, especially, the contents of As, Cu, Hg and Cd in the small part samples existed in the west plain and central area are partly higher than the national second grade quality standard, should be slightly contaminated to some degree. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that As, Cr, Cu, Ni, Si, Al and Fe are grouped in factor F1, Pb, Zn and Co in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as “industrial and traffic pollution sources”. The source of the third factor is mainly controlled by long-term anthropic activities, as a consequence of agricultural activities, fossil fuel consumption, and atmospheric deposition.