Evaluation and analysis of heavy metals in cultivated soils in the suburbs of Beijing.

The cultivated soils in Changping, Tongzhou, Shunyi, Haidian and Daxing districts in the suburbs of Beijing were selected with 74 sampling points to assess the accumulation status and potential ecological risk of six heavy metals of As, Cd, Cr, Cu, Hg and Pb. The individual pollution index, synthetical pollution index and potential ecological risk index were calculated with National Soil Heavy Metals Standards (GB15618-1995 Grade Ⅱ) and with the background level of heavy metals in Beijing as the assessment criteria to explore the accumulation degree and the pollution status of soil heavy metals. Results showed that heavy metal concentration in the cultivated soils did not exceed the national standards Grade Ⅱ and could satisfy the safety qualification. Lead, Cu and Cd might have homology, but Cr had not similar source as the others. The six heavy metals in soils showed certain accumulation effects. Cadmium and Hg were in a higher potential risk grade, and especially Hg in Haidian District reached a very high potential risk level. About 17% of the soil samples had potential ecological threat to a certain degree. The high accumulation degree and potential ecological risk grade occurred in relatively developed districts like Haidian, Tongzhou and Changping. Analyses showed that human activities had influenced soil environmental quality in recent years. Therefore, we should take immediate regional monitoring management and related measures in accordance with the principles of territorial administration.