基于“源”、“汇”过程的农业非点源污染模型构建及应用

根据农业非点源污染产移特点, 将农业非点源污染模型分为田间产污的“源”模块以及模拟污染物在排水沟渠中运移的“汇”模块, 其中“源”模块又包括农田灌溉(降水)排水子模块及农田灌溉(降水)排水中污染物浓度计算子模块。应用DRAINMOD模型模拟田间尺度的灌溉(降水)排水, 同时将农田的施肥和灌溉过程“合成”作为田间污染物浓度的脉冲输入, 以逆高斯分布作为综合作用函数, 建立农田尺度的灌溉排水污染物浓度估算模型, 二者结合构成农业非点源污染田间产污模块; 应用一维水动力学基本方程和非保守性污染物迁移方程, 建立农业非点源污染物沟渠“汇”模块。并以黄河上游青铜峡灌区为例进行了示例应用, 依据典型田块以及排水沟渠农业非点源污染监测试验资料, 结合灌区作物种植结构, 计算了2008年5~9月青铜峡灌区输出污染负荷, 结果为盐分470 099 t、总磷98.17 t、总氮3 593 t、硝态氮2 122 t、氨态氮426 t。通过示例验证, 表明所建模型具有较好的模拟效果, 可进一步推广应用。

Establishment and application of source/sink-based agricultural non-point source pollution model

Improving control standards of point (PSP) and non-point (NSP) source pollutions are recent highlights of water and environmental issues. Agricultural non-point source pollution (AGNSP) problems caused especially by heavy use of chemical fertilizers and pesticides are prominent in this regard. Quantitative research on pollution loads is the basis of control standard, evaluation and management of AGNSP. Using AGNSP and unit-load characteristics, an AGNSP model was developed that uses source/sinks modules determine the complex migration routes of pollutants. The source module was further divided into farmland irrigation drainage and farmland contaminant concentration estimation sub-modules. The sink module was also divided into farmland drainage and pollutant migration/transformation sub-modules. By integrating the modules, a complete AGNSP load model was therefore established. The integrated AGNSP model was tested in the Qingtongxia Irrigation District (QID) in upstream reaches of the Yellow River. The 2008 crop pattern was used in the developed AGNSP model to simulate AGNSP load and output in QID. Based on the simulation results, salinity, total phosphorus, total nitrogen, nitrate nitrogen and ammonia nitrogen in QID were 470 099 t, 98.17 t, 3 593 t, 2 122 t and 426 t, respectively. The application of the established AGNSP model indicated that the model presented preferable simulated results, and was practicable in the similar studies.