Heavy Metals in Greenhouse Vegetable Soils in Beijing: Accumulation Characteristics of Copper and Cadmium

A survey was conducted to determine the status of copper and cadmium accumulations in greenhouse vegetable soils in Tongzhou of Beijing. Based on the investigated results, the contamination degree of the two heavy metals in the greenhouse vegetable soils was assessed and the main influence factors caused the accumulation of copper and cadmium was analyzed. The results indicated that there was a distinct increase of copper and cadmium concentration in greenhouse vegetable soils. The concentrations of copper and cadmium in part of soil samples exceeded the environmental quality evaluation standard for farmland of greenhouse vegetables production of China. These over-standard soil samples were mainly collected from Lucheng town and Xiji town. The contents of copper and cadmium in greenhouse soil were increased significantly as the cultivated time of the soil added. The content of copper in greenhouse soil varied from 19.8 mg/kg to 39.2 mg/kg when the cultivation time of the greenhouse increased from 1 year to 5 years, nearly increased one times. The content of cadmium in vegetable soils of 20-year age greenhouse was 3.2 times of that in 1-year age greenhouse. Significant correlations were found between the content of copper and cadmium in soil, soil organic carbon content, CEC, and available phosphorus and potassium content in soils. Soil physical and chemical properties should be considerate integrated to reduce the heavy metal contamination in greenhouse soils.