农业非点源污染田间模型及其应用

非点源污染的负荷定量化研究是控制、评价和管理非点源污染的基础.农业非点源污染负荷估算包括农田排水估算和排水中的污染物浓度预测2个环节.依据水量平衡原理,农田排水应用DRAINMOD模型估算;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,农田排水中的污染物浓度变化则视作对应于此脉冲输入的响应过程,而污染物在田间的复杂迁移转化过程以逆高斯概率密度函数隐含表达.以此为基础,构建了农田尺度农业非点源污染负荷估算模型.以青铜峡灌区典型试验区为例,对稻田排水沟中硝态氮(NO_3~--N)和总磷(TP)的负荷过程进行了模拟,结果表明,模型估算结果和实测污染物负荷过程非常接近,Nash-Suttcliffe模拟效率系数分别为0.963和0.945,表明该模型具有较高的可靠性.

Establishment and Application of the Estimation Model for Agricultural Non-point Source Pollution in the Field

The quantitative research on pollution loads is the basis of control,evaluation and management of non-point source pollution. The estimation of agricultural non-point source pollution loads includes two steps: evaluation of water discharge and prediction of pollutant concentration in agricultural drain.Water discharge was calculated by DRAINMOD model based on the principle of water balance on farmland. Meanwhile,the synthesis of fertilization and irrigation is used as an impulse input to the farmland, the pollutant concentration changes in agricultural drain is looked as the response process corresponding to the impulse input, the complex migratory and transforming process of pollutant in soil are expressed impliedly by Inverse Gaussian Probability Density Function. Based on the above, the estimation model of agricultural non-point source pollution loads at field scale was constructed. Taking the typical experimentation area of Qingtongxia Irrigation District in Ningxia as an example, the loads of nitrate nitrogen and total phosphorus in paddy-field drain was simulated by this model. The results show that the simulated accorded with measured data approximately and Nash-Suttcliffe coefficient is 0.963 and 0.945 respectively.