奎河污灌区土壤重金属As变化系统动力学分析

污灌污染是一个亟待解决的土壤环境问题,研究污灌区土壤重金属污染状况及其动态对于土壤重金属污染修复具有现实意义。该文以奎河污灌区为例,通过文献资料搜集和现场监测获取相关数据,采用单因子污染指数法和内梅罗综合污染指数法评价了污灌区重金属污染状况,结果表明土壤As轻度污染,水田样点超标率达89.93%,旱地样点超标率达82.39%,水田综合污染指数为1.39,旱地综合污染指数为1.19。以As为例,采用系统动力学方法分析了As含量的变化。结果表明在当前种植制度下,土壤As的消除是一个漫长的过程,需要到2016年土壤As质量分数才会降低到30mg/kg以下,2024年后才会低于25mg/kg,达到当地土壤As背景值更需要到2073年。清除作物秸秆和根系对于消除土壤As污染有益,尤其是远期效果明显,而表层土壤的流失对于土壤As的清除作用显著。

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.