北京市面源入河污染物负荷测算方法体系研究

选择北京市城乡接合部南沙河流域为典型区,采用传统面源方法中的输出系数法和EcoHat-NPS模型方法分别计算典型区的面源污染入河负荷量及入河污染浓度,利用一维水质模型实现入河点源和面源污染分离,计算各入河口基于实测的面源浓度推算值,并对输出系数法和EcoHat-NPS模型2种方法测算结果的精度进行对比分析。结果表明:1)输出系数法计算精度一般,EcoHat-NPS模型模拟方法计算精度和稳定性良好,COD、NH₃-N、TP、TN的平均模拟精度R2为0.83、0.94、0.94、0.82,NH₃-N、TP模拟效果较好,COD、TN次之;2)输出系数法计算得到COD、NH₃-N、TN、TP入河量依次为1110.9,70.9,391.8,5.02 t/a;EcoHat-NPS模型方法则依次为1403.34,78,388.2,7.3 t/a;3)EcoHat-NPS模型方法可识别主要的面源污染区域,计算时间尺度灵活,更适用于北京市面源污染测算,在数据进一步精细化后,可推广用于全市面源入河污染物的测算。

STUDY ON CALCULATION METHOD SYSTEM OF POLLUTANT LOAD FROM NON-POINT SOURCE INTO RIVERS IN BEIJING

In this study, the Nansha River Basin in the urban-rural fringe of Beijing was selected, and the inflow concentration of non-point source pollution in the typical area was calculated with traditional export coefficient method and the EcoHat-NPS model method, respectively. The point source and non-point source pollution were separated by using one-dimensional water quality model, and the calculated value of non-point source concentration in each estuary was calculated based on the measured non-point source concentration. The accuracy of the calculation results of the two methods was compared and analyzed. The results showed that:1) there was a plain calculation accuracy in the export coefficient method and a good calculation accuracy in the EcoHat-NPS model simulation method. The average simulation accuracy R2 of the four pollutants (COD, NH₃-N, TP, TN) was 0.83, 0.94, 0.94, 0.82, respectively. The simulation effect of NH₃-N and TP was better, followed by COD and TN; 2) the inflow COD, NH₃-N, TN and TP calculated by export coefficient method was 1110.9, 70.9, 391.8, 5.02 t/a, respectively; while that of the EcoHat-NPS model method was 1403.34, 78, 388.2, 7.3 t/a, respectively; 3) Ecohat-NPS model with the flexible calculation time scale could identify the main non-point source pollution areas, which was more suitable for the estimation of non-point source pollution in Beijing. After the further data refining, it could be extended to the whole city's rivers for the estimation of non-point source pollution in Beijing.