Abstract Livestock-derived phosphorus (P) loading values are largely based on studies performed in small experimental fields, leading to uncertainties when applying the results at larger scale. This five-year study estimated annual loads of P, nitrogen (N), dissolved organic carbon (DOC) and total suspended solids (TSS) in a small 3.2 km2 agricultural and forested catchment by monitoring water quality and discharge in four ditches reflecting different land uses. The monitored catchment has intensive livestock production, with proportions of grassland, cereal and forest area typical for east-central Finland. Typically, spring runoff started in early April under snow cover and peaked during snowmelt. There was great variation in the amount and pattern of discharge between years. Mean annual total P (TP) load (± SD) from an agricultural sub-catchment was 1.0 ± 0.37 kg ha−1. Mean TP load from a forested (PS) sub-catchment was 0.4 ± 0.17 kg ha−1 when a point source of pollution (PS) was included and 0.06 kg ha-1 when it was excluded. The point source of pollution contributed 12 % of the TP load from the whole 3.2 km2 catchment. The proportion of dissolved reactive P (DRP) to TP load varied between 34 % and 67 % in the study period (largest for the forested (PS) sub-catchment and smallest for the whole catchment). Observed erosion rates were very low when measured as TSS, with the highest (115 ± 103 kg ha−1) and lowest (3.4 ± 2.3 kg ha−1) mean annual erosion rate in the agricultural and forested (PS) sub-catchments, respectively. In the agricultural sub-catchment, the relationship between TP and DOC tended to be stronger than that between TP and TSS. Mean annual total N load from the agricultural sub-catchment was 19.0 ± 7.2 kg ha−1 and from the whole catchment 10 ± 2.7 kg ha−1, while mean annual DOC load was 45 ± 13 kg ha-1 and 92 ± 28 kg ha−1, respectively. These results are important in developing, implementing and targeting mitigation measures to control agricultural nutrient losses to surface waters.

中文翻译：

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芬兰中东部一个小型农业和森林集水区磷、氮、溶解有机碳和土壤的流失

摘要 牲畜衍生的磷 (P) 负荷值主要基于在小型试验田中进行的研究，导致在更大规模应用结果时存在不确定性。这项为期五年的研究通过监测反映不同土地的四个沟渠的水质和排放量，估计了一个 3.2 平方公里的农业和森林集水区的年磷、氮 (N)、溶解有机碳 (DOC) 和总悬浮固体 (TSS) 负荷使用。受监测的集水区畜牧业生产集约化，草地、谷物和森林面积占芬兰中东部的典型比例。通常，春季径流开始于 4 月初在积雪覆盖下并在融雪期间达到顶峰。不同年份的排放量和方式差异很大。来自农业子流域的平均年总磷 (TP) 负荷 (± SD) 为 1.0 ± 0.37 kg ha-1。当包括点污染源 (PS) 时，森林 (PS) 子流域的平均 TP 负荷为 0.4 ± 0.17 kg ha-1，排除点污染源时为 0.06 kg ha-1。点污染源贡献了整个 3.2 平方公里流域的 TP 负荷的 12%。在研究期间，溶解活性磷 (DRP) 与 TP 负荷的比例在 34% 和 67% 之间变化（森林（PS）子流域最大，整个流域最小）。当以 TSS 测量时，观测到的侵蚀率非常低，农业和森林 (PS) 子流域中最高 (115 ± 103 kg ha-1) 和最低 (3.4 ± 2.3 kg ha-1) 平均年侵蚀率，分别。在农业子流域，TP 和 DOC 之间的关系趋于强于 TP 和 TSS 之间的关系。来自农业子流域的平均年总氮负荷为 19.0 ± 7.2 kg ha-1 和来自整个流域的 10 ± 2.7 kg ha-1，而年均 DOC 负荷为 45 ± 13 kg ha-1 和 92 ± 28 kg ha-1，分别。这些结果对于制定、实施和确定缓解措施以控制农业养分向地表水的流失非常重要。