[Accumulation characteristics of arsenic in suburban soils of Beijing]

Various land uses and enormous environmental pressures are characteristics of suburbs. Full understanding of suburban soil pollution is necessary for urban planning and development. In this study, 167 surface soil samples (0-20 cm) located in suburbs of Beijing between the fifth and sixth ring road were collected based on the 3 km x 3 km grids. The purpose of our investigation is to reveal the accumulating characteristics of As in Beijing suburbs. Results showed that arsenic contents in suburban soils of Beijing ranged from 2.89 mg x kg(-1) to 11.38 mg x kg(-1), with mean of 7.11 mg x kg(-1). The means were in the range of the background values reported in late 1990s, but the values of each quantile were lower than the soil background values reported in early 1980s. Factor analysis suggested that As in Beijing suburban soil shared the same group as those elements coming from parent materials such as Co, Mn and Ni. The spatial distribution map using Kriging interpolation showed that As contents in northwestern, eastern and southeastern parts were higher than those in northeastern and southwestern parts. Those plots with contents of the highest 25% were all located near the pollution sources, while most of those with the lowest 25% contents located far from the pollution sources. Comparison of As contents in different land uses showed that human activities had influence on the accumulation of As in soils. Inhabitation areas and agricultural fields had higher As contents than the green lands and vacant lands. Pollution sources significantly affected the accumulation of As in soils of inhabitation areas, green lands and vacant lands. Arsenic contents in soils near factories were significantly higher than those far from factories and traffic corridors. To sum up, the spatial distributions of As contents in soils in Beijing suburban area were generally determined by the distributions of parent materials, while human activities increased the accumulation of As in soils to some degree.