滇池宝象河流域氮磷流失空间格局解析

Spatial Pattern Analysis of Nitrogen and Phosphorus Losses in Baoxiang River Watershed of Dianchi Lake

有效控制氮磷流失量是水质持续改善的关键因素,定量解析流域氮磷流失量对于氮磷污染精准控制至关重要.宝象河作为滇池流域最主要的入湖河流之一,对滇池水质的影响极为重要.该研究基于第二次全国污染源普查数据,建立了宝象河流域高分辨率的氮磷排放清单,通过构建宝象河LODEST模型估算流域氮磷非点源污染入河系数,并对宝象河流域的氮磷流失量及其空间格局进行解析.结果表明:①2018年宝象河流域TN和TP的排放量分别为1456.92、191.16 t,流域内种植业非点源是最大的污染源,其次是城镇生活点源和未收集点源.②2018年宝象河干海子断面TN和TP的径流通量分别为270.49和11.19 t,非点源入河系数分别为0.297和0.048.③2018年宝象河流域TN和TP流失量分别为432.28和18.57 t,氮磷流失空间格局呈显著的空间异质性,流域内TN和TP流失强度总体呈外高内低的分布,农业污染为主的子流域氮磷流失最为严重.该研究提出的氮磷流失量估算方法较好地揭示了流域氮磷流失空间分布规律,论证了降雨和地形的不均匀性是造成流域氮磷流失量呈显著空间异质性的重要因素.研究成果可为滇池流域入湖污染负荷控制与削减工程提供重要的科学依据,同时能够为宝象河流域水环境的精准控污和精细管理提供有效的决策支撑.

Effective control of nitrogen and phosphorus losses is the key factor for sustained improvement of water quality.Therefore,quantitative analysis of nitrogen and phosphorus losses in the basin is very important for precise control of nitrogen and phosphorus pollution.As the second largest inflow river of Dianchi Lake,the Baoxiang River has a very important impact on the water quality of Dianchi Lake.Based on the data of the second national pollution source survey,a high-resolution inventory of nitrogen and phosphorus discharges in the Baoxiang River Watershed was established,the loss rates of N and P non-point source pollution loads were calculated by LOADEST,and the amount of nitrogen and phosphorus losses and their spatial pattern were analyzed.The results showed that:(1)In 2018,the TN and TP discharges in the Baoxiang River Watershed were 1456.92 t and 191.16 t,respectively.The contribution of non-point sources of planting industry was the largest,followed by urban living point sources and non-collected point sources.(2)The annual fluxes of TN and TP of the Baoxiang River Watershed were 270.49 t and 11.19 t,respectively.The loss rates of TN and TP non-point source pollution loads were 0.297 and 0.048,respectively.(3)The annual TN and TP losses in the Baoxiang River Watershed were 432.28 t and 18.57 t,respectively.Spatial heterogeneities of TN and TP losses were obvious.The spatial pattern of TN and TP losses presented overall distribution of high on the outside and low on the inside,and the TN and TP losses in sub-basins dominated by agricultural pollution were the most serious.The results showed that the spatial distribution of nitrogen and phosphorus losses was better revealed by the method proposed in this study,and it was demonstrated that the heterogeneity of rainfall and terrain were important factors that causes the significant spatial heterogeneity of nitrogen and phosphorus losses.The research results can provide an important scientific basis for the pollution load control and reduction project in the Dianchi Lake Basin,and provide effective decision support for precise pollution control and fine management of the water environment in the Baoxiang River Watershed.