沱江流域总氮面源污染负荷时空演变

根据四川省沱江流域水环境受总氮（TN）面源严重污染的现状，采用排污系数法估算2007~2017年该流域来自各面源污染源的TN污染负荷，并利用空间重心统计法和空间分析技术揭示沱江流域TN污染负荷时空分布特征及转移趋势，以期为相关部门精准防控和预警沱江流域面源污染提供理论依据.结果表明，2007~2017年畜禽养殖污染源对整个流域的TN污染负荷贡献率每年均在45%以上，是TN面源污染的主要污染源.农村生活和农村生活垃圾污染源的贡献率呈逐年减少趋势，农田固废和农田径流污染源的贡献率则呈增加趋势.TN总污染负荷总体呈下降趋势，2010年污染负荷最大，达到5.7×10⁴ t，2017年最小，为4.69×10⁴ t.污染负荷在空间上的异质性变化及降雨径流的不均匀分布驱使畜禽养殖、农田固废类和农田径流污染源的TN污染负荷重心由西北向东南方向移动，流域东南部是畜禽养殖、农田固废类和农田径流TN污染的重点防控区域.东南部各区县的农业人口大量向城市人口转化，进而驱动农村生活和农村生活垃圾污染源的TN污染负荷重心由东南向西北方向转移，其转移范围高达66.35 km²，由此确定的最小边界圆是污染源污染负荷变化的重点识别区域，沱江流域西北部则是农村生活和农村生活垃圾TN污染的重点防控区域.本研究拓展了环境科学领域对流域污染负荷时空演变的探究方法，对于改善水环境质量，促进流域经济可持续发展具有重要意义.

Temporal and Spatial Evolution of Non-point Source Pollution Load of Total Nitrogen in Tuojiang River Basin

Currently, the aquatic environment of the Tuojiang River basin in Sichuan Province is severely polluted by non-point sources of total nitrogen (TN). This study adopts the pollution discharge coefficient method to estimate the TN pollution load of non-point sources in this watershed during 2007-2017. The temporal and spatial distribution and transfer trends of the TN pollution load in the Tuojiang River basin were examined, based on center-of-gravity statistical and spatial analysis technology. This study aimed to provide an accurate theoretical basis for the prevention and early identification of non-point source pollution in the Tuojiang River basin. The results indicate that livestock breeding was the main non-point source of TN pollution and contributed more than 45% to the TN pollution load during 2007-2017. The contribution rate of rural life and domestic waste decreased continually during the study period, whereas that of farmland solid waste and farmland runoff exhibited an increasing trend. The total pollution load of TN exhibited a decreasing trend during 2007-2017. The maximum and minimum TN pollution loads occurred in 2010 and 2017 with values of 5.7×10⁴ t and 4.69×10⁴ t, respectively. Spatial heterogeneity of the pollution load, together with the uneven distribution of rainfall runoff, caused a shift from northwest to southeast in the pollution-load centers of gravity for livestock and poultry breeding, farmland solid waste, and farmland runoff. Southeast of the watershed is the key area for prevention and control of these pollution sources. A shift in the centers of gravity for rural living and household waste pollution, from southeast to northwest, was attributed to agricultural populations transforming to urban populations in the southeastern counties. The maximum transfer range was 66.35 km², and this minimum boundary circle is the key identification area of pollution source pollution load change. Northwest of Tuojiang River basin is the key area in which TN pollution from rural living and rural household waste can be prevented. This research expands the methods for exploring the temporal and spatial evolution of pollution load in the Tuojiang River basin, which is of great significance for improving the aquatic environment and promoting sustainable development of the basin economy.