Cadmium accumulation in soils for different land uses in Beijing
北京市不同土地利用类型的土壤镉含量特征

Information on the environmental effects of different land uses is lacking, especially in Beijing, a city with a rapidly increasing rate of development. Such information is important for the understanding of the sustainable development and regional agricultural plans. In this study, through the investigation of 6 types of land use in Beijing, including vegetable field, paddy field, orchard, greenbelt, cornfield, and natural soil, Cd concentrations of 595 soil samples were obtained. Compared with background concentration, the accumulation of Cd in the vegetable field, paddy field, and orchard was significant. ANOVA analysis indicated that land use greatly affected the accumulation of Cd in the soils, especially in the cornfield, vegetable field, and orchard land-use types. The mean Cd concentration in the vegetable field was the highest, while samples from greenbelt and cornfield had the lowest mean concentrations. In addition, Cd concentrations of cornfield samples, which comprised the majority of samples under investigation, were low. Factors such as atmospheric deposition, which controls the large-scale distribution of Cd, might not have an obvious effect. Using a baseline concentration as background, the ratio of soil samples above this limit in orchard, greenbelt, and vegetable field were 9.5%, 7.7%, and 4.6%, respectively, while the overall ratio for the study was 3.2%. According to this investigation, some anthropogenic factors such as industrial activities, traffic, and landfill waste, played quite important roles in the accumulation of soil sample Cd. The soil environment around the landfill, therefore, should be considered seriously. In the Shijingshan, Mentougou and Fengtai districts, the ratios of soil samples above baseline were much higher than those in other districts, and therefore reasonable planning of land use in these areas should be considered. According to the mean concentrations of Cd in the soil, the order of the 6 land-use types, from the highest to the lowest Cd concentration, was vegetable field > paddy field > orchard > natural soil > cornfield > greenbelt.