Zhang Zhenyu, Huang Jinliang, Chen Shengyue, Sun Changyang
School of Geographical Sciences, Fujian Normal University, Fuzhou, 350007, China; Fujian Key Laboratory of Coastal Pollution Prevention and Control, Xiamen University, 361102, Xiamen, China.
Fujian Key Laboratory of Coastal Pollution Prevention and Control, Xiamen University, 361102, Xiamen, China.
J Environ Manage. 2024 Jun;360:121104. doi: 10.1016/j.jenvman.2024.121104. Epub 2024 May 11.
Excess nitrogen (N) discharged into streams and rivers degrades freshwater quality and threatens ecosystems worldwide. Land use patterns may influence riverine N export, yet the effect of location on N export and removal is not fully understood. We proposed a hybrid model to analyze N export and removal within the watersheds. The proposed model is satisfied for the riverine N modelling. The KGE and R are 0.75 and 0.72 in the calibration period which are 0.76 and 0.61 in the validation period. Human-impacted land use may modify the N yield in the watershed, and the net N export from built-up to the in-stream system was highest in the urbanized sub-watersheds (0.81), followed by the agricultural sub-watersheds (0.88), and forested sub-watersheds (0.96). Agricultural activities make a large contribution to the N exports in the watersheds, and the mean N input from the agricultural land use to in-stream were 2069-4353 kg km yr. Besides, the excess inputs of N by overapplication of fertilizer and manure during the agricultural activities may increase legacy N in soil and groundwater. Biological processes for the riverine N removal may be controlled by the available substrate in the freshwater system, and temperature sensitivity of denitrification is highest in the flood seasons, especially for the human-impacted sub-watersheds. The riverine biological processes may be limited by other competitions. Our model results provide evidence that quantity and location of specific land use may control biogeochemistry within watersheds. We demonstrate the need to understand nutrient export and removal within watersheds by improving the representation of spatial patterns in existing watershed models, and we consider this study to be a new effort for the spatially explicit modeling to support land-use based N management in watersheds.
排放到溪流和河流中的过量氮（N）会降低淡水质量，并威胁全球生态系统。土地利用模式可能会影响河流氮输出，然而位置对氮输出和去除的影响尚未完全了解。我们提出了一种混合模型来分析流域内的氮输出和去除情况。所提出的模型适用于河流氮建模。在校准期内，KGE和R分别为0.75和0.72，在验证期内分别为0.76和0.61。受人类影响的土地利用可能会改变流域内的氮产量，从建成区到河流系统的净氮输出在城市化子流域中最高（0.81），其次是农业子流域（0.88）和森林子流域（0.96）。农业活动对流域内的氮输出贡献很大，从农业土地利用到河流的平均氮输入为2069 - 4353 kg km yr。此外，农业活动期间过量施用化肥和粪肥导致的氮过量输入可能会增加土壤和地下水中的残留氮。河流氮去除的生物过程可能受淡水系统中可用底物的控制，反硝化作用的温度敏感性在洪水季节最高，尤其是在受人类影响的子流域。河流生物过程可能受到其他竞争的限制。我们的模型结果表明，特定土地利用的数量和位置可能控制流域内的生物地球化学过程。我们证明了需要通过改进现有流域模型中的空间模式表示来了解流域内的养分输出和去除情况，并且我们认为这项研究是在空间明确建模方面的一项新努力，以支持基于土地利用的流域氮管理。
