汉江流域农业面源污染的源解析

农业面源污染是水体污染的重要污染源。为明确汉江流域农业面源污染负荷及其空间分布,运用输出系数法,对2015年汉江流域范围内的13个地市的农业面源污染总氮(TN)、总磷(TP)污染负荷量进行估算,采用等标污染负荷法进行污染评价,再运用GIS软件分析农业面源污染负荷空间分布格局,通过快速聚类法划分汉江流域各地市的农业面源污染类型。结果表明:2015年汉江流域的TN、TP污染负荷量分别为179 127、26 975 t,相应的等标污染负荷量为2.26×10~(11)、1.68×10~(11)m~3;汉江流域农业面源污染TN等标污染负荷贡献率最大的污染源是农田化肥,TP等标污染负荷贡献率最大的污染源是畜禽养殖;TN、TP的等标污染负荷在空间分布上有很强的一致性,但各地市的等标污染负荷仍存在差异,等标污染高负荷区集中在流域中游,TN、TP的等标污染负荷最大值均出现在流域中游的南阳市;基于快速聚类结果确定汉江流域主要有6种污染类型。汉江流域的农业面源氮磷污染物污染负荷和空间分布研究为汉江流域面源污染的防治提供了决策参考。

Source apportionment of agricultural nonpoint source pollution in the Hanjiang River Basin

Agricultural nonpoint source pollution is an important type of water pollution. To clarify the agricultural nonpoint source pollution load and its spatial distribution in the Hanjiang River Basin, the total nitrogen (TN) and total phosphorus (TP) pollution loads from agricultural nonpoint source pollution of 13 cities in the Hanjiang River Basin in 2015 were estimated according to the export coefficient model approach. Pollution evaluation was carried out using an equivalent standard pollution load method. The spatial distribution of the agricultural nonpoint source pollution load was drawn via GIS. The types of agricultural nonpoint source pollution in the cities of the Hanjiang River Basin were divided through rapid clustering. The results demonstrated that the TN and TP loads from agricultural nonpoint source pollution in the Hanjiang River Basin in 2015 were 179 127 and 26 975 t, respectively, and the corresponding equivalent standard pollution loads were 2.26×10¹¹ and 1.68×10¹¹ m³. In the Hanjiang River Basin, the pollution source with the largest contribution rate of TN standard pollution load was farmland fertilizer, and the pollution source with the largest contribution rate of TP standard pollution load was livestock and poultry breeding. There was a strong consistency in the spatial distribution of TN and TP standard pollution loads, but differences existed among the pollution loads of different cities. Equivalent standard pollution high load areas were concentrated in the middle of the river basin, with the highest in the city of Nanyang. Based on the rapid clustering method, the Hanjiang River Basin could be divided into six types of pollution. Study on pollution load and spatial distribution of the TN and TP from agricultural nonpoint sources pollutants provide a decision reference for the prevention and treatment of nonpoint source pollution in the Hanjiang River Basin.