中国水利

为揭示砂页岩山区小流域洪水驱动下污染物的输移特征与滞后机制，本研究监测了赤水河支流七里坎小流域2025年汛期洪水事件，系统分析了氨氮(NH⁺_4-N)、总磷(TP)和总悬浮固体(TSS)的浓度变化及输出通量和滞后模式，并结合冗余分析识别了污染物的关键控制因子及输移路径差异。结果表明：NH⁺_4-N与TP的事件最大/最小浓度比值范围分别为1.3～3.0和1.3～3.8，而TSS比值达12.7～871.0，反映出颗粒物对洪水过程响应更为敏感。输移路径上，NH⁺_4-N部分来源于壤中流及地下水补给，浓度峰多滞后于流量峰；TP以颗粒态形式存在，受地表侵蚀作用驱动显著，浓度峰出现较早；TSS则主要受远坡及沟道等慢响应源区控制，浓度峰滞后现象最为普遍。控制因子识别表明，NH⁺_4-N浓度主要受降雨强度影响，TSS浓度与前期土壤含水量关联密切，其输出通量由事件历时主导。滞后特征方面，NH⁺_4-N和TP的滞后指数(HI)与降雨强度呈正相关，而TSS的HI及冲刷指数(FI)则与洪峰流量及前期条件呈正相关。研究结果可为砂页岩山区小流域污染防控与水环境管理提供科学依据。

To reveal the transport characteristics and hysteresis mechanisms of pollutants driven by floods in a sandstone-shale mountainous catchment, this study monitored flood events during the 2025 wet season in the Qilikan Catchment, a tributary of the Chishui River. The variations in concentration, export fluxes, and hysteresis patterns of ammonia nitrogen(NH₄~+-N), total phosphorus(TP), and total suspended solids(TSS) were systematically analyzed, and redundancy analysis was employed to identify the key controlling factors for pollutants and the differences in their transport pathways. The results show that the event-based maximum/minimum concentration ratios for NH₄~+-N and TP range from 1.3 to 3.0 and 1.3 to 3.8, respectively, while that for TSS ranges from 12.7 to 871.0, reflecting that particulate matter is more sensitive to flood processes. Regarding transport pathways, NH₄~+-N originates partly from interflow and groundwater recharge, with its concentration peaks generally exhibiting hysteresis relative to the flow peaks. TP, primarily in particulate form, is significantly driven by surface erosion, with its concentration peaks appearing relatively early. TSS is mainly controlled by slow-response source areas such as distant hillslopes and gullies, exhibiting the most prevalent hysteresis in sediment concentration peaks. The identification of controlling factors reveals that NH₄~+-N concentration is mainly influenced by rainfall intensity, while TSS concentration is closely related to antecedent soil moisture, and its export flux is dominated by event duration. In terms of hysteresis characteristics, the hysteresis index(HI) of NH₄~+-N and TP is positively correlated with rainfall intensity, whereas the HI and flushing index(FI) of TSS are positively correlated with peak flow and antecedent conditions. The research results can provide scientific evidence for pollution control and water environment management in sandstoneshale mountainous catchments.