Concentration-discharge (C-Q) relationships have been widely used to assess the hydrochemical processes that control solute fluxes from streams. Here, using a large regional dataset we assessed long-term C-Q relationships for total phosphorus (TP), soluble reactive phosphorus (SRP), total Kjeldahl nitrogen (TKN), and nitrate (NO₃) for 63 streams in Ontario, Canada, to better understand seasonal regional behavior of nutrients. We used C-Q plots, Kruskal-Wallis tests, and breakpoint analysis to characterize overall regional nutrient C-Q relationships and assess seasonal effects, anthropogenic impacts, and differences between “rising” and “falling” hydrograph limbs to gain an understanding of the dominant processes controlling overall C-Q relationships. We found that all nutrient concentrations were higher on average in catchments with greater levels of anthropogenic disturbance (agricultural and urban land use). TP, SRP, and TKN showed similar C-Q dynamics, with nearly flat or gently sloping C-Q relationships up to a discharge threshold after which C-Q slopes substantially increased during the rising limb. These thresholds were seasonally variable, with summer and winter thresholds occurring at lower flows compared with autumn and greater variability during snowmelt. These patterns suggest that seasonal strategies to reduce high flows, such as creating riparian wetlands or reservoirs, in conjunction with reducing related nutrient transport during high flows would be the most effective way to mitigate elevated in-stream concentrations and event export. Elevated rising limb concentrations suggest that nutrients accumulate in upland parts of the catchment during drier periods and that these are released during rain events. NO₃ C-Q patterns tended to be different from the other nutrients and were further complicated by anthropogenic land use, with greater reductions on the falling limb in more disturbed catchments during certain seasons. There were few significant NO₃ hydrograph limb differences, indicating that there was likely to be no dominant hysteretic pattern across our study region due to variability in hysteresis from catchment to catchment. This suggests that this nutrient may be difficult to successfully manage at the regional scale.

中文翻译：

---

从更大的区域数据集导出的浓度-流量关系作为流域管理的工具

浓度-排放 (CQ) 关系已广泛用于评估控制流中溶质通量的水化学过程。_{在这里，我们使用大型区域数据集评估了总磷 (TP)、可溶性活性磷 (SRP)、总凯氏氮 (TKN) 和硝酸盐 (NO 3} ) 的长期 CQ 关系) 用于加拿大安大略省的 63 条溪流，以更好地了解养分的季节性区域行为。我们使用 CQ 图、Kruskal-Wallis 检验和断点分析来表征整体区域养分 CQ 关系，并评估季节性影响、人为影响以及“上升”和“下降”水文图肢之间的差异，以了解控制整体的主要过程CQ 关系。我们发现，在人为干扰（农业和城市土地利用）水平较高的流域，所有养分浓度平均较高。TP、SRP 和 TKN 表现出相似的 CQ 动态，在达到放电阈值后 CQ 斜率在上升肢体期间显着增加，其 CQ 关系几乎平坦或平缓倾斜。这些阈值随季节变化，与秋季相比，夏季和冬季阈值发生在较低的流量和融雪期间较大的变化。这些模式表明，减少高流量的季节性策略，例如创建河岸湿地或水库，以及在高流量期间减少相关的养分运输，将是缓解河内浓度升高和事件输出的最有效方法。肢体浓度升高表明，在干旱时期，营养物质会在集水区的高地部分积累，而这些营养物质会在降雨事件中释放出来。不 与在高流量期间减少相关的养分运输相结合，将是减轻河内浓度升高和事件输出的最有效方法。肢体浓度升高表明，在干旱时期，营养物质会在集水区的高地部分积累，而这些营养物质会在降雨事件中释放出来。不 与在高流量期间减少相关的养分运输相结合，将是减轻河内浓度升高和事件输出的最有效方法。肢体浓度升高表明，在干旱时期，营养物质会在集水区的高地部分积累，而这些营养物质会在降雨事件中释放出来。不₃ CQ 模式往往与其他养分不同，并且由于人为土地利用而进一步复杂化，在某些季节，在更受干扰的流域中，落肢的减少幅度更大。几乎没有显着的 NO ₃水文曲线肢体差异，表明由于流域之间滞后的可变性，在我们的研究区域内可能没有显着的滞后模式。这表明这种营养素可能难以在区域范围内成功管理。