Levels of arsenic and heavy metals in the rural soils of Beijing and their changes over the last two decades (1985-2008).

Heavy metal levels in the rural soils are associated with the quality of agricultural products. In this study, soil samples were collected from the rural soils of Beijing; distribution of As, Co, Cr, Cu, Hg, Mn, Ni, Pb, V, Zn and their changes over the last two decades have been investigated. The results indicated that the concentrations of Co, Cr, Mn, Ni, and V were primarily controlled by the parent materials of soils, while concentrations of Hg, As, Cu, Pb, and Zn were affected by anthropogenic activities. Hg concentration in the surface soils was 2-3 times the subsurface soils; slight accumulations of As, Cu, Pb, and Zn in the top soils were also observed. The bioavailable fractions of heavy metals including exchangeable and carbonate-bounded fraction were lower than 10% except for Cr, Mn and Zn. In general, the concentrations of heavy metals in the rural soils of Beijing met environmental quality standard (grade II) for soils of China. Although some elements such as Hg and As have increased significantly in several sample sites, the average concentrations of all heavy metals had no significant change over the past 20 years due to effective environmental protection for many years in Beijing. 2010 Elsevier B.V. All rights reserved.