近15年三峡库区典型流域农业非点源污染时空特征分析以澎溪河流域为例

目的 揭示三峡库区北岸最大支流澎溪河流域非点源污染时空特征，能够明确农业非点源污染的来源、总量等动态变化及风险等级分布规律，为三峡库区的农业非点源污染分区防控决策提供切实科学建议。方法 文章运用改进输出系数模型、污染风险指数及冷热点分析，采用高程、土地利用/覆被类型、降雨等多元数据，对2000—2015年流域内农村生活源、畜禽养殖源、土地利用源的总氮、总磷排放量进行估算。结果 （1）澎溪河流域农业非点源污染氮磷排放量呈现先减少再缓慢增长的趋势，其总氮、总磷排放均值分别为5 919.89 t和499.06 t，年均排放强度分别为12.53 kg/hm²、1.06 kg/hm²；（2）土地利用源对氮磷污染的贡献占较大比重，年均占比分别为60.05%、74.67%；（3）不同子流域总氮、总磷污染年际变化空间表现特征均为南河（1 560.59 t、139.44 t）>澎溪河干流（1 181.51 t、95.70 t）、桃溪河（1 179.56 t、106.27 t）>普里河（1 000.32 t、76.48 t）、东河（997.91 t、79.22 t），南河子流域是氮磷污染的重点防控子流域；（4）流域内氮磷污染重点控制乡镇应为多年污染等级较高的镇安、高桥、金峰、铁峰、黄石、后山及2015年的热点及次热点区域铁桥、南雅、临江、南门镇。结论 澎溪河流域氮磷污染明显向中部和南部即澎溪河干流处汇集，流域中部水系污染程度普遍高于北部山区，因此可对中部、南部乡镇重点防控。

SPATIAL AND TEMPORAL CHARACTERISTICS OF NON-POINT SOURCE POLLUTION IN THE TYPICAL WATERSHED OF THE THREE GORGES RESERVOIR AREA: A CASE STUDY OF THE PENGXI RIVER BASIN

This research aims to reveal the temporal and spatial characteristics of non-point source pollution in the Pengxi River Basin, the largest tributary of the Three Gorges Reservoir area, and clarify the dynamic changes in the source and total amount of agricultural non-point source pollution and the distribution of risk levels, so as to provide practical scientific advice for prevention and control decision-making. Based on the multivariate data, such as elevation, land use/cover type, rainfall and so on, and using improved output coefficient model, pollution risk index and cold and hot spot analysis, it estimated the total nitrogen and total phosphorus emissions from rural living sources, livestock and poultry breeding sources, and land use sources in the basin from 2000 to 2015. The results were indicated as follow. The agricultural non-point source pollution nitrogen and phosphorus emissions in the Pengxi River Basin showed a trend of first reduction and then a slow increase. The average TN and TP emissions were 5,919.89 t and 499.06 t, respectively, and the average annual emission intensities were 12.53 and 1.06 kg/hm². (2) The contribution of land use sources to Nitrogen and Phosphorus pollution accounted for a large proportion, with an average annual proportion of 60.05% and 74.67% respectively. (3) The spatial performance characteristics of the interannual variation of TN and TP pollution in different sub-basins were Nanhe (1 560.59 t, 139.44 t)> Pengxi River (1 181.51 t, 95.70 t), Taoxi River (1 179.56 t, 106.27 t)> Puli River (1 000.32 t, 76.48 t), Donghe (997.91 t, 79.22 t), and the Nanhe sub-basin was a key sub-basin for the prevention and control of nitrogen and phosphorus pollution. (4) The key towns and towns under the control of Nitrogen and Phosphorus pollution in the basin should be Zhen''an, Gaoqiao, Jinfeng, Tiefeng, Huangshi, Houshan, which had high pollution levels for many years, and the hot and sub-hot spots in 2015, namely, Tieqiao, Nanya, Linjiang and Nan Gate town. It concludes that Nitrogen and Phosphorus pollution in the Pengxi River Basin obviously collects in the central and southern parts of the Pengxi River, and the pollution degree of the water system in the middle of the basin is generally higher than that in the northern mountainous areas, therefore, key prevention and control of towns and towns in the central and southern parts can be achieved.