| 摘要: |
| 湟水是黄河上游最大的支流，沙塘川流域是湟水重要且具有代表性的支流。通过建立SWAT非点源污染模型，研究沙塘川流域氮磷非点源污染特征，并识别面源污染发生的关键源区，对湟水流域水污染治理具有重要意义。研究结果表明：沙塘川进入湟水河的非点源总氮污染负荷为236.77 t · a−1，非点源总磷污染负荷为51.02 t · a−1；非点源总氮和总磷负荷均呈现丰水期＞平水期＞枯水期的规律；非点源总氮负荷从沙塘川流域上游至下游逐渐增大，在中上游流域东部负荷明显高于西部；非点源总磷负荷主要集中在沙塘川上游东部地区和下游地区；非点源总氮的关键源区为13、15、16、17和19号子流域，非点源总磷的关键源区为11、12、13和19号子流域，本研究结果可为典型流域非点源污染防控与治理提供科学依据。 |
| 关键词: SWAT 模型 非点源 氮磷污染 关键源区 |
| DOI：10.7515/JEE222001 |
| CSTR：32259.14.JEE222001 |
| 分类号: |
| 基金项目:青海省重大科技专项（2018-SF-A4） |
| 英文基金项目:Major Science and Technology Projects of Qinghai Province (2018-SF-A4) |
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| Characteristics of non-point source nitrogen and phosphorus pollution and identification of key source areas in the Shatangchuan watershed based on SWAT model |
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ZHANG Qian, CHAO Shijun, YANG Xiaoli, LI Fajuan, HU Jian
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Qinghai Research and Design Institute of Environmental Sciences Co. Ltd., Xining 810000, China
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| Abstract: |
| Background, aim, and scope With the improvement of the control level of point source pollution such as urban industrial wastewater and domestic sewage, the seriousness of non-point source pollution has become increasingly prominent. The treatment of non-point source pollution in Qinghai Province lacks scientificity, and the treatment practice has a certain degree of blindness. This is majorly induced by the unclear spatial distribution of the key source areas of non-point source pollution and the pollution load. In this study, Shatangchuan, a tributary of Huangshui, was selected to explore the characteristics and spatial distribution of non-point source nitrogen and phosphorus pollution in the watershed. Key source areas were identified. A set of technical methods suitable for identifying key source areas of non-point source pollution in high-altitude plateau areas were investigated. Materials and methods Based on the watershed delineation module of the SWAT model, river network extraction and sub-watershed delineation were conducted. Firstly, the land use / soil / slope definition module of Arc SWAT was employed to load the land use and soil map, and the corresponding index relationship table was selected for spatial superposition analysis. Secondly, the multi-hydrological response unit division method was adopted to set the land use threshold, soil area threshold, and slope grade. Finally, the applicability of the model was evaluated using the coefficient of determination (R2) and the Nash efficiency coefficient (NS). Results The results demonstrated that the non-point source total nitrogen and total phosphorus pollution loads entering Shatangchuan were 236.77 t·a−1 and 51.02 t·a−1, respectively. The non-point source total nitrogen and total phosphorus load presented the law of high-water period > normal-water period > low-water period. The largest non-point source nitrogen and phosphorus contribution were derived from the planting industry, whose total nitrogen and total phosphorus contributions were 64.42% and 61.95%, respectively. The non-point source total nitrogen load gradually increased from the upper reaches to the lower reaches of the Shatangchuan watershed. The load in the eastern part of the middle and upper reaches was significantly higher than that in the western part. The total phosphorus load of non-point sources is primarily concentrated in the eastern and downstream areas of the upper reaches of Shatangchuan. The critical source areas of non-point source total nitrogen contain sub-catchments 13, 15, 16, 17, and 19; the critical source areas of non-point source total phosphorus consist of sub-catchments 11, 12, 13, and 19. Discussion As suggested by the temporal distribution of non-point nitrogen and phosphorus pollution, the load of total nitrogen is relatively balanced in percentage by month, but there is a significant variation by month for total phosphorus. To be exact, the percentage reaches 0.12%, 13.74% and 85.91% in dry season, level season and flood season, respectively. It is suggested that the more persistent precipitation in flood season has a more significant impact on the load of non-point total phosphorus flowing into rivers. The areas with a high contribution of total nitrogen in the Shatangchuan watershed are mainly distributed in the agricultural land concentration areas where the land use type is dry land. The areas with a low contribution of total nitrogen are majorly distributed in the Nanmenxia Reservoir and the urban areas of Shatangchuan tributaries. The areas as a major contributor to non-point total phosphorus concentrate in the east of upstream Shatangchuan and its downstream section. In these areas, the predominant types of land use include forestry, shrubbery and high-coverage grassland, with livestock breeding as the main source of total phosphorus. Conclusions With the SWAT non-point source pollution model constructed in this study, the non-point source nitrogen and phosphorus pollution load in the Shatangchuan watershed were quantitatively assessed, and a key source area identification system was established based on the analysis of its temporal and spatial distribution characteristics and sources. The identification of the key source areas of non-point source total nitrogen and total phosphorus in the watershed laid a foundation for the subsequent formulation of high-efficiency management and control measures for non-point sources in the watershed. Recommendations and perspectives The results of this study can enlighten the prevention, control, and treatment of non-point source pollution in typical watershed. |
| Key words: SWAT model non-point source nitrogen and phosphorus pollution key source area |
