System dynamics analysis on soil heavy metal As in sewage irrigation area of Kuihe River

Abstract: The sewage irrigation has a soil environmental problem which urgent to be solved. Studying the condition and the trend of soil heavy metal pollution in sewage irrigation area has practical significance to the remedy of heavy metals soil pollution. A case of Kuihe River sewage irrigation was studied, and the relevant data through the collection of literature data and field monitoring were obtained. By both the single factor index method and Nemerow multi-factor index method, the pollution indices were calculated for assessing pollution extent. The results showed that the soil was mild contamination of As. The As content of 89.93% paddy field samples and 82.39% upland soil samples exceed the state soil environment quality standard grade two, paddy field comprehensive pollution index was 1.39 and upland soil was 1.19. The results showed that in the current planting system, it would take a long time to eliminate the As in the soil. The As content would be reduced to less than 30 mg/kg in 2016, 25mg/kg in 2024, and achieve the local soil background of As in 2073. It is benefit to eliminate the As in the soil by clearing the crop straws and roots, especially the long-term results. The loss of surface soils also work remarkable to eliminate the As in the farmland soil. The study provides a reference for analyzing the changes of As content by system dynamics approach.