Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian, 116024, China.
Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian, 116024, China; State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, 116024, China.
Environ Pollut. 2021 Jun 15;279:116885. doi: 10.1016/j.envpol.2021.116885. Epub 2021 Mar 10.
It is still a great challenge to address nutrient pollution issues caused by various point sources and non-point sources on the watershed scale. Source contribution analysis based on watershed modeling can help watershed managers identify major pollution sources, propose effective management plans and make smart decisions. This study demonstrated a technical procedure for addressing watershed-scale water pollution problems in an agriculture-dominated watershed, using the Dengsha River Watershed (DRW) in Dalian, China as an example. The SWAT model was improved by considering the constraints of soil nutrient concentration, i.e., nitrogen (N) and phosphorus (P), when modeling the nutrient uptake by a typical crop, corn. Then the modified SWAT model was used to quantify the contributions of all known pollution sources to the N and P pollution in the DRW. The results showed that crop production and trans-administrative wastewater discharge were the two dominant sources of nutrient pollution. This study further examined the responses of nutrient loss and crop yield to different fertilizer application schemes. The results showed that N fertilizer was the limiting factor for crop yield and that excessive levels of P were stored in the agricultural soils of the DRW. An N fertilizer application rate of approximately 40% of the current rate was suggested to balance water quality and environmental protection with crop production. The long-term impact of legacy P was investigated with a 100-year future simulation that showed the crop growth could maintain for 12 years even after P fertilization ceased. Our study highlights the need to consider source attribution, fertilizer application and legacy P impacts in agriculture-dominated watersheds. The analysis framework used in this study can provide a scientifically sound procedure for formulating adaptive and sustainable nutrient management strategies in other study areas.
解决流域尺度上各种点源和非点源引起的养分污染问题仍然是一个巨大的挑战。基于流域模型的污染源贡献分析可以帮助流域管理者识别主要污染源，提出有效的管理计划并做出明智的决策。本研究以中国大连登沙河流域（DRW）为例，展示了一种用于解决以农业为主的流域尺度水污染问题的技术流程。通过考虑土壤养分浓度（即氮（N）和磷（P））的限制，改进了 SWAT 模型，以模拟典型作物玉米对养分的吸收。然后，使用改进后的 SWAT 模型量化了所有已知污染源对 DRW 中 N 和 P 污染的贡献。结果表明，作物生产和跨行政污水排放是养分污染的两个主要来源。本研究进一步研究了养分流失和作物产量对不同施肥方案的响应。结果表明，氮肥是作物产量的限制因素，过量的 P 储存在 DRW 的农业土壤中。建议将氮肥施用量减少到当前用量的约 40%，以平衡水质保护与作物生产。通过 100 年未来模拟研究了遗留 P 的长期影响，结果表明即使停止 P 施肥，作物生长仍可维持 12 年。本研究强调需要考虑农业为主的流域中的源归因、施肥和遗留 P 的影响。本研究中使用的分析框架可以为其他研究区域制定适应性和可持续的养分管理策略提供科学合理的程序。
