三峡库区非点源污染氮磷负荷时空变化及其来源解析

三峡库区是我国重要水源保护区，也是长江流域经济迅速发展区域之一.非点源污染是库区水环境恶化的主要原因，因此研究库区非点源污染状况对于区域的生态安全以及可持续发展具有重要意义.研究采用改进输出系数模型，估算库区1990~2015年的非点源氮磷污染负荷总量，分析非点源氮磷污染的时空变化特征，并通过计算各污染源的贡献率确定主要污染来源.结果表明，氮磷污染负荷量在空间上均呈现库区腹地高，库尾次之，库首最低的分布特征；氮磷污染负荷总量在时间上均呈现先增加后降低的趋势，在2000年达到最高值，2015年降到最低值；各污染源对氮磷污染负荷量的贡献率按从大到小依此为：土地利用、农村生活以及畜禽养殖；其中，旱地这种土地利用类型是非点源氮磷污染的主要来源.

Spatiotemporal Change and Source Apportionment of Non-point Source Nitrogen and Phosphorus Pollution Loads in the Three Gorges Reservoir Area

The Three Gorges Reservoir area (TGRA) is a critical water source protection area in China and one of the regions with rapid economic development in the Yangtze River basin. Non-point source pollution is the leading cause of the deterioration of the water environment in the TGRA; therefore, studying the non-point source pollution status in the TGRA is of great significance to the regional ecological security and sustainable development. The improved export coefficient model was used to estimate the total non-point source nitrogen and phosphorus pollution loads in the TGRA from 1990 to 2015, the spatial and temporal characteristics of the non-point source nitrogen and phosphorus pollution were analyzed, and the primary sources of pollution were determined by calculating the contribution rate of each pollution source. The results concluded that the nitrogen and phosphorus pollution loads were highest in the hinterland of the reservoir, followed by the end of the reservoir, with the lowest in the head of the reservoir, showing significant spatial heterogeneity in the TGRA. The total loads of nitrogen and phosphorus pollution increased firstly and then decreased, which reached the highest value in 2000 and the lowest value in 2015. The contribution rate of each pollution source to the nitrogen and phosphorus pollution loads, from highest to lowest, were land use, rural life, livestock, and poultry farming. Among them, the land use type of dry land was the predominant source of non-point source nitrogen and phosphorus pollution.