Risk assessments of heavy metals in typical greenhouse soils

Contents of copper(Cu), chromium(Cr), lead(Pb), zinc(Zn)and cadmium(Cd)in greenhouse soils were measured by using a flame atomic absorption spectrophotometer. The soil samples were collected in Shouguang, Shandong Province. The environmental quality of greenhouse soils was assessed by applying the single pollutant index method and the Nemerow comprehensive index method based on the environmental quality evaluation standards of farmland for greenhouse vegetables production. The results indicated that Cu, Cr and Pb accumulations in greenhouse topsoils(0-20 cm)were the largest and higher than those of open field topsoils. Soil Zn and Cd contents were the highest at the depths of 20-40 cm and 40-60 cm in greenhouse soils, respectively. There were significant differences of soil Zn content between greenhouse and open field soils at depths of 0-20 cm and 60-80 cm, while those of Cd contents were at depths of 0-20 cm, 40-60 cm, 60-80 cm and 80-100 cm. The maximum values of heavy metal contents of greenhouse soils occured when greenhouses were cultivated for 2 to 4 years. According to the risk evaluation results of the heavy metals in greenhouse soils, there was Cd contamination in greenhouse topsoils in Shouguang, Shandong Province.