[Modeling the Cd accumulation in agricultural soil irrigated with reclaimed water]

Recent years, soil pollution of heavy metal has affected human life seriously, especially in farmland. Heavy metal pollution in farmland is mainly caused by irrigation, fertilizing and atmospheric fallout. As the character of heavy metal input in farmland is chronic and low dosage, application of model would be more suitable than routine methods to illustrate the dynamic changes of heavy metals in soil. In this paper, we use the model of STEM-profile to analyze and predict Cd pollution in farmland in Tongzhou, Beijing, based on the data from field survey. The results showed that: the concentration of Cd in this land would exceed the national soil environment standard after 100 years under current situations, reaching 0.866 mg x kg(-1) in plow layer. Studies of the influence of the amount and the form of inputs and the amount of irrigation water on the distribution of Cd in soil showed that irrigated with reclaimed water or fertilized with organic manure could lead to accumulation of Cd in the soil, while groundwater irrigation with inorganic fertilization would not cause accumulation of Cd in soil. When Cd inputs changed from mineral to organic form, the concentration of Cd in plow layer would be 0.943 mg x kg(-1) after 100 year. When the amount of irrigation water increased from 0.8 ET to 1.5 ET and to 2.0 ET, the plow layer Cd content would be 0.952, 0.784 and 0.638 mg x kg(-1) respectively.