Vertical Distribution of Heavy Metals in Soil of Facility Vegetable Fields from Beijing Suburbs, China

The vertical distribution of cadmium (Cd), chromium (Cr), copper (Cu), zinc (Zn), arsenic (As) and lead (Pb) in the soils of the facility vegetable fields from Beijing suburbs were studied. With increasing depth in the soil profile (0~100 cm), the concentrations of heavy metals decreased, except As. By comparison with those of the control (open vegetable fields), the concentrations of Cd, Cr, Cu, Zn and Pb in the soil profile (0~20 cm) of the facility vegetable fields increased 21.8%, 11.3%, 29.4%, 27.6% and 5.8%, respectively, but Cd, Cr, Cu, Zn, Pb and As concentrations in the soil profile (80~100 cm) increased by 12.5%、6.7%、1.4%、1.5%、17.3% and 1.3%, respectively. Besides, the contents of Zn, Cr, Cd, Cu and Pb in the soil profile (0~20 cm) of facility vegetable fields, had significant positive correlations with planting years, with the accumulation rates of Cd, Cr, Zn, Cu and Pb being 4.584, 0.933 8, 0.013 3, 1.243, 0.641 7 mg·kg-1·a-1, respectively. Meanwhile, the test six heavy metals contents were significantly positively correlated with the contents of soil organic matter and total nitrogen, and the Zn, Cr, Cd, Cu and Pb contents were significantly correlated with the content of soil total phosphorus, applying organic fertilizer and chemical fertilizer could induce the heavy metals accumulation in the soils of facility vegetable fields to some extent