香溪河流域人类活动净磷输入量及其影响因素

为了阐明三峡库区第一大支流香溪河流域人类活动对磷输入的影响程度，收集流域所涉及的2001~2019年的乡镇统计数据，运用改进的人类活动净磷输入（NAPI）模型，分析了该流域NAPI的发展趋势.结果表明：在时间尺度上，香溪河流域2001~2019年的NAPI整体呈下降趋势；在空间尺度上，NAPI呈现东北部高于西南部的趋势，影响香溪河流域NAPI的主要乡镇为黄粮镇、峡口镇和昭君镇，占香溪河流域NAPI的63.8%；河流磷输出占NAPI的百分比为10.7%~79.5%；从NAPI结构上看，影响香溪河流域NAPI主要的影响因素为磷肥施入量，占香溪河流域NAPI的46%~68%，次要影响因素为食物磷和磷化工及磷矿开采导致磷素释放量，分别占香溪河流域NAPI的14%~32%和16%~24%；从NAPI影响因素上看，NAPI与人口密度和耕地面积占比均呈极显著正相关（P<0.001），而在小流域研究尺度上，NAPI与河流磷输出的相关性不显著（P>0.05），不具有直接的响应关系.因此，香溪河流域磷素管理应优先考虑重点区域（黄粮镇、峡口镇和昭君镇），控制化肥施用量，并提高工厂污染物排放标准.

Net phosphorus input from human activities and its influencing factors in Xiangxi River Watershed

Anthropogenic phosphorus pollutants have become a major driving factor for water eutrophication. In order to investigate the impact of human activities on the phosphorus input into the Xiangxi River Watershed, i.e., the first tributary in the Three Gorges Reservoir Area, statistical data at a township-level were collected from 2001 to 2019, and other related parameters were obtained from relevant literature. The Net Anthropogenic Phosphorus Inputs (NAPI) of the watershed were simulated and their spatio-temporal characteristics were analyzed. The results showed a declining trend for the NAPI of the Xiangxi River Watershed, and a distribution pattern of being higher in the northeast and lower in the southwest. Huangliang, Xiakou, and Zhaojun townships had the highest NAPI inputs into the Xiangxi River Watershed, accounting for 63.8% of the total. The percentage of NAPI removed from the Watershed by the Xiangxi river ranged between 10.7% and 79.5%. A detailed analysis demonstrated that phosphate fertilizer contributed most of the NAPI into the Xiangxi River Watershed, accounting for 46%~68% of the total. The second and third most important input sources were phosphorus pollutants from food waste and from the chemical industry, accounting for 14%~32% and 16%~24%, respectively. Furthermore, there was a significant positive correlation between NAPI and population density as well as between NAPI and the proportion of the total land area that was under cultivation (P<0.001). There was no significant correlation between NAPI and river phosphorus output (P>0.05) suggesting that there was no direct response. These results suggest that, when managing phosphorus in the Xiangxi River Watershed priority should be given to key township areas (Huangliang, Xiakou and Zhaojun), to controlling the application of chemical fertilizer, and to improving the emission standards for pollutants from factories.