洪水过程下的砂页岩山区小流域污染物-水文响应规律OA

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 sandstone-shale mountainous catchments.