Nitrogen (N) pollution is the major type of non-point pollution in watersheds. The nitrogen transport process is significantly controlled by the watershed hydrological connectivity under different rainfall conditions. Changes in hydrological connectivity were controlled by extreme rainfall events, resulting in a more uncertain response mechanism for dynamic nitrogen transport. In this study, four typical rainfall events were selected based on long-term positional monitoring of a small watershed using high-frequency sampling (long duration rainfall events E1, E2; short duration rainfall events E3, E4). Characterizing spatial and temporal changes in hydrological connectivity under different types of rainfall events. Revealing how hydrological connectivity shape the nitrogen dynamic processes. The results showed that the hydrological functional connectivity was better for long duration rainfall events than for short duration rainfall events as influenced by rainfall events (E1, E2: 4.58, 5.5; E3, E4: 5.25, 5.18). The difference in hydrological connectivity not only made the average and peak nitrogen concentration load under the long duration rainfall events higher than that under the short duration rainfall events. It also resulted in different nitrogen source composition, with soil nitrogen (SN) and manure & sewage (M&S) being the main sources under long duration rainfall events (SN: 28.3%, 25.5%; M&S: 41%, 53%), whereas M&S dominated under short duration rainfall events (37%, 67%). The antecedent precipitation index (API) also constrained the timing of onset of hydrological functional connectivity, in addition to rainfall events influencing watershed hydrological connectivity. The landscape characteristics of the watershed also affected the spatial and temporal characteristics of hydrological connectivity, which shaped the nitrogen source-sink transition relationship in the watershed. Based on the differences in the response of nitrogen transport characteristics to hydrological connectivity under different rainfall events. Considering hydrological connectivity dimensions and intervention can help to achieve precise management of nitrogen in the watershed.

中文翻译：

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流域水文功能连通性塑造的氮动力输运过程


氮 （N） 污染是流域的主要面源污染类型。在不同降雨条件下，氮素传输过程受到流域水文连通性的显著控制。水文连通性的变化受到极端降雨事件的控制，导致动态氮运输的响应机制更加不确定。在本研究中，基于使用高频采样对小流域的长期位置监测，选择了四种典型的降雨事件（长持续时间降雨事件 E1、E2;短持续时间降雨事件 E3、E4）。表征不同类型降雨事件下水文连通性的空间和时间变化。揭示水文连通性如何塑造氮动力学过程。结果表明，受降雨事件影响，长时降雨事件的水文功能连通性优于短时降雨事件（E1，E2：4.58,5.5;E3、E4：5.25、5.18）。水文连通性的差异不仅使长时降雨事件下的平均氮浓度负荷和峰值氮浓度负荷高于短时降雨事件下的平均氮浓度负荷和峰值氮浓度负荷。这也导致了氮源组成的不同，土壤氮（SN）和肥料和污水（M&S）是长时间降雨事件下的主要来源（SN： 28.3%， 25.5%;M&S：41%，53%），而 M&S 在短期降雨事件中占主导地位（37%，67%）。除了影响流域水文连通性的降雨事件外，前行降水指数 （API） 还限制了水文功能连通性的开始时间。 流域的景观特征还影响了水文连通性的时空特征，从而塑造了流域氮源-汇过渡关系。基于不同降雨事件下氮运特征对水文连通性响应的差异。考虑水文连通性维度和干预有助于实现流域氮的精确管理。