Excess nitrogen (N) from anthropogenic sources deteriorates freshwater resources. Actions taken to reduce N inputs to the biosphere often show limited or only delayed effects in receiving surface waters hinting at large legacy N stores built up in the catchments' soils and groundwater. Here, we quantify transport and retention of N in 238 Western European catchments by analyzing a unique data set of long-term N input and output time series. We find that half of the catchments exhibited transport times with an average riverine concentration peak arriving 5 years after application. Longer transport times were evident in catchments with high potential evapotranspiration and low precipitation seasonality. On average the catchments retained 72% (Interquartile Range: 18%) of the N from diffuse sources with retention efficiency being specifically high in catchments with low discharge and thick, unconsolidated aquifers. The estimated transport time scales do not explain the observed N retention, suggesting a dominant role of biogeochemical legacy in the catchments' soils rather than a legacy store in the groundwater. Future water quality management should account for the accumulated biogeochemical N legacy by fostering denitrifying conditions or soil N recycling to avoid long-term leaching and water quality deteriorations for decades to come.

中文翻译：

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西欧流域中硝酸盐的迁移和滞留受水文气候和地下特性的影响

来自人为来源的过量氮 (N) 会恶化淡水资源。为减少对生物圈的氮输入而采取的行动在接收地表水方面往往表现出有限的或只是延迟的影响，这暗示着集水区土壤和地下水中积累了大量遗留的氮。在这里，我们通过分析长期 N 输入和输出时间序列的独特数据集来量化 238 个西欧流域中 N 的传输和保留。我们发现一半的流域表现出运输时间，平均河流浓度峰值在应用后 5 年到达。在具有高潜在蒸散量和低降水季节性的集水区，较长的运输时间很明显。平均而言，流域保留了 72%（四分位距：18%) 来自扩散源的氮，在低排放和厚、松散含水层的集水区中，保留效率特别高。估计的运输时间尺度不能解释观察到的 N 保留，表明生物地球化学遗产在集水区土壤中的主导作用，而不是地下水中的遗留储存。未来的水质管理应通过促进反硝化条件或土壤氮循环来解决累积的生物地球化学氮遗留问题，以避免未来几十年的长期浸出和水质恶化。土壤而不是地下水中的遗留库。未来的水质管理应通过促进反硝化条件或土壤氮循环来解决累积的生物地球化学氮遗留问题，以避免未来几十年的长期浸出和水质恶化。土壤而不是地下水中的遗留库。未来的水质管理应通过促进反硝化条件或土壤氮循环来解决累积的生物地球化学氮遗留问题，以避免未来几十年的长期浸出和水质恶化。