袁河流域土地利用方式对河流水体碳、氮、磷的影响

为探明土地利用方式对袁河水体碳、氮、磷浓度的影响，于2018年8月（丰水期）和2019年1月（枯水期）在袁河干流和支流38个采样点采集水样并测定碳、氮、磷（DOC、NO₃--N、NH₄+-N和TP）浓度.将流域划分为子流域和沿河岸不同距离（100、200、300、400、500、1 000和2 000 m）缓冲区，结合Pearson相关性分析、冗余分析（redundancy analysis，RDA）和回归分析等方法，量化不同尺度土地利用方式对干支流碳、氮、磷浓度的影响.结果表明:①建设用地、农田、水域是袁河水体碳、氮、磷浓度的主要影响因素，其中建设用地对NH₄+-N、DOC和TP浓度影响最大，水域、农田分别对NO₃--N、DOC浓度影响较大.②土地利用方式对干流碳、氮、磷浓度变化的解释量大于支流，丰、枯水期对干流碳、氮、磷浓度变化的解释量分别为47.2%、36.7%，对支流的解释量分别为23.2%、26.4%.③土地利用方式对干流DOC浓度变化的解释量在丰水期低于对TP、NH₄+-N和NO₃--N浓度变化的解释量，在枯水期高于对TP、NH₄+-N和NO₃--N浓度变化的解释量；土地利用方式对支流DOC浓度变化的解释量在丰、枯水期均高于对TP、NH₄+-N和NO₃--N浓度变化的解释量.④缓冲区尺度土地利用方式对河流碳、氮、磷浓度的影响大于子流域尺度，且干流缓冲区大于支流缓冲区.随缓冲区尺度增加，土地利用方式对水体碳、氮、磷浓度变化的解释能力在干流丰水期和支流枯水期均先增后降，在干流枯水期和支流丰水期的解释能力逐渐增强.研究显示，加强缓冲区土地利用方式的管理，特别是对干流建设用地点源污染和支流农田面源污染的控制，是袁河水环境管理的关键. 

Influence of Land Use on Carbon,Nitrogen and Phosphorus in Water of Yuan River Basin

In order to reveal the impacts of land use patterns on carbon, nitrogen and phosphorus concentrations in the Yuan River, we collected water samples at 38 sampling points from the mainstream and tributaries in August 2018 (wet season) and January 2019 (dry season), and analyzed carbon, nitrogen and phosphorus (DOC, NO₃--N, NH₄+-N and TP). The watershed was divided into two spatial scales: sub-basin and buffer zones along the river bank (at distances of 100, 200, 300, 400, 1000 and 2000 m). Pearson correlation analysis, redundancy analysis (RDA) and other methods were used to quantify the impacts of land use patterns on the concentrations of carbon, nitrogen and phosphorus in the mainstream and tributaries. The result showed that: (1) Construction land, farmland, and water area were the main variables influencing the concentrations of carbon, nitrogen and phosphorus. Construction land had the greatest influence on NH₄+-N, DOC and TP, while water area and farmland had greater influence on NO₃--N and DOC. (2) The land use patterns explained more variations in carbon, nitrogen and phosphorus concentrations in the mainstream than tributaries. For the mainstream, the explained variations were 47.2% in the wet season and 36.7% in the dry season; for tributaries, the percentages were 23.2% and 26.4%, respectively. (3) In the mainstream, the land use patterns explained more variations in TP, NH₄+-N and NO₃--N concentrations than DOC in wet season, and more variations in DOC than TP, NH₄+-N and NO₃--N in dry season. In tributaries, the land use patterns explained more variations in DOC than TP, NH₄+-N and NO₃--N both in wet and dry season. (4) The impacts of land use patterns on the concentrations of carbon, nitrogen and phosphorus were higher in buffer zone than in sub-basin, and higher in mainstream buffer zone than in tributary buffer zone. With the increase of buffer distance, the variations in carbon, nitrogen and phosphorus concentrations explained by the land use patterns increased first and then decreased in wet season of mainstream and dry season of tributaries, and increased continuously in dry season of mainstream and wet season of tributaries. The research shows that the key to protecting the water quality of the Yuan River is to strengthen the management of the land use patterns of the buffer zone, especially the control of the point source pollution from the construction land in the mainstream and the non-point source pollution from the farmland in tributaries.