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首页> 外文期刊>Canadian Journal of Fisheries and Aquatic Sciences >Long-term declines in phosphorus export from forested catchments in south-central Ontario
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Long-term declines in phosphorus export from forested catchments in south-central Ontario

机译：安大略省中南部森林集水区磷出口的长期下降

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摘要

Total phosphorus (TP) levels in many Canadian Shield lakes in central Ontario have declined over recent decades, despite increases in human activity in most watersheds. To investigate the contribution of changes in catchment export to long-term declines in lake TP, we examined temporal and spatial patterns in TP concentrations and export (1980-1981 to 2001-2002) across 11 subcatchments that drain into three lakes in which average ice-free TP levels have declined by approximately 35%. Annual stream export of TP decreased significantly by 30%-89% in eight of the I I subcatchments, and decreases in export were driven by declines in TP concentration, not changes in stream flow. Annual average TP concentrations varied fivefold among adjacent subcatchments, and temporal patterns in annual average TP concentrations were poorly correlated. Seasonal patterns of TP concentration were most similar among streams in the spring (March-April-May), and TP export in the spring declined significantly in 10 of the 11 subcatchments. Because spring melt is the principal hydrologic event in these seasonally snow-covered basins, decreases in TP export during the spring were primarily responsible for declines observed in annual export. The drivers of changes in TP over time are unclear at this point but are the focus of current research.
机译：尽管大多数流域的人类活动有所增加，但安大略省中部许多加拿大盾构湖中的总磷（TP）水平在近几十年来有所下降。为了调查集水区出口变化对湖泊TP长期下降的贡献，我们研究了11个流域的TP浓度和出口（1980-1981年至2001-2002年）的时空格局，这些区域汇入了三个湖泊，平均冰游离TP水平下降了约35％。在I I子汇水区中的八个流域，TP的年溪流出口量显着下降了30％-89％，而出口量的下降是由TP浓度的下降而不是溪流的变化驱动的。年平均TP浓度在相邻子集水区之间变化五倍，并且年平均TP浓度的时间模式相关性很差。春季（三月至四月至五月）溪流中总磷浓度的季节性模式最为相似，而在11个小流域中，春季总磷出口量显着下降。由于春季融化是这些季节性积雪盆地的主要水文事件，因此春季TP出口量的减少是造成年出口量下降的主要原因。 TP随时间变化的驱动因素目前尚不清楚，但这是当前研究的重点。

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