排水沟渠水-底泥-植物协同作用下非点源溶质氮运移模拟研究

沟渠系统"过程拦截"是现阶段农业非点源污染控制和管理的重要手段。针对当前农田排水沟渠水体-底泥-植物系统内各介质间非点源溶质迁移转化机制不清的现状,在简要分析农田排水沟渠水-底泥-植物复合生态结构及其各组分功能特征的基础上,以沟渠中水体为中心,解析了非点源溶质氮在沟渠系统单一介质以及不同介质间的迁移转化过程;考虑到排水沟渠中水体和污染物均以沿沟渠方向线性迁移为主,应用水流连续方程和非保守性污染物迁移扩散方程,构建了农田排水及其中非点源污染物在排水沟渠中的一维迁移模型,并结合试验沟渠具体情况进行了适度简化;通过内业可控性监测试验,同时提出了沟渠系统水-底泥-植物不同介质对水体中非点源污染物衰减程度影响的量化计算方法;将所建模型与计算参数应用于野外试验沟渠,以氨态氮和硝酸盐氮为例进行模拟,结果表明模拟结果与实测值结合较好,其中氨态氮模拟效率系数为0.87,硝态氮模拟效率系数0.93,表明所建模型及模拟手段符合试验沟渠实际情况,具有较好的适用性。

Simulation of non-point source solute nitrogen transport in drainage ditches under water-sediment-aquatic plant synergy

Along highlighted water environmental issues and gradual evolution of point source pollution (PSP) such as industrial waste,agricultural non-point source pollution (AGNSP) due to non-scientific applications of fertilizers and pesticides has had an increasing attention in recent years. On the basis of strengthening field "source control",making the best use of agricultural drainage ditch/pond system (interception process) is critical for agriculture non-point source pollution control and management. Drainage ditches have compound ecosystem structures,which are consisted of water-sediment-plant synergy. Migration and transformation of non-point source solute is important in the study of interception,control and management of agricultural non-point source pollution in drainage ditches. However,non-point source solute transformation processes in each medium in water-sediment-plant system of farmland drainage ditch have remained largely unclear. Based on the analysis of ecological structure and drainage ditch characteristics,this paper described the transformation of non-point source soluble nitrogen in water-sediment-plant system of farmland drainage ditch. In combination with the characteristics of farmland drainage ditch water pollution migration,a model of agricultural water pollution migration in drainage ditch system was constructed. The model was based on continuity equation for flow and pollutants migration. It was used to test,monitor and advance a quantitative method of calculation of the effect of different water-sediment-plant media on attenuation degree of non-point source pollutant in water body. Using Qingshui drainage ditch in the People''s Victory Canal Irrigation District in Henan Province as a case study,the model was used to calculate the parameters of a field experimental ditch loaded with ammonia nitrogen and nitrate nitrogen pollutants. The results showed that the simulated and measured values fitted well. The simulation efficiency coefficient of ammonia nitrogen was 0.87 and that of nitrate nitrogen was 0.93. The results demonstrated that the model was available and effective for the simulation of drain pollution in ditches in agricultural farmlands.