关键词: 镉, 黑土, 棕壤, 吸附反应, 热力学, 化学动力学

Abstract: Five urban area were classified by the land use vector data and natural zoning map of China during 1990～2000. The first grade urban area included East Liaoning and East Shandong mountain and upland, North China plain, Middle Shandong mountain and upland, Huaihe basin and middle and lower reaches of Yangtze River, Guangdong, Guangxi and Fujian mountain plain, and North China mountain upland. The urban landuse percentage of these area and the speed of urban expansion were higher. The urban expansion in these area amounted to 71.47% of the total expansion of China, and the loss of cultivated land was 69.88% of the total,among which, North China was 24.54%, and Huaihe basin and middle, lower reaches of Yangtze River was 20.15%. The major source of urban land was derived from cultivated land and the percentage was 78.96%. Agreat amount of cultivated land will be lost by urban expansion,which will threaten the grain safety in China.

Key words: Cadmium, Phaeozem, Burozem, Adsorption reaction, Thermodynamics, Chemical kinetics