Freeze–thaw processes and intense rainfall: the one-two punch for high sediment and nutrient loads from mid-Atlantic watersheds
Freeze–thaw processes and intense rainfall: the one-two punch for high sediment and nutrient loads from mid-Atlantic watersheds
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DOI：
10.1007/s10533-017-0417-7
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发表时间：
2018-12
期刊：
影响因子：
4
通讯作者：
S. Inamdar;Erin L. Johnson;R. Rowland;D. Warner;R. Walter;D. Merritts
中科院分区：
文献类型：
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作者：
S. Inamdar;Erin L. Johnson;R. Rowland;D. Warner;R. Walter;D. Merritts
由于个别极端气候事件或多种水文和气象条件的组合，流域可能会出现大量径流、沉积物和养分输出。利用高频水文、沉积物和浊度数据，我们发现，冬季（2月）强暴雨之后的冻融事件可以从美国大西洋中部流域输出非常高浓度和负载的悬浮沉积物和颗粒有机碳（POC）和氮（PN）。在我们的12公顷和79公顷森林流域，2月份降雨径流事件中悬浮沉积物（bbb50 000 mg L−1）、POC （> 250 mg L−1）和PN （> 15 mg L−1）的峰值浓度是有记录以来最高的，通量与热带风暴测量的通量相当。在美国地质勘测局监测的较大流域，浑浊度值（bb0 ~ 400 FNU）也观察到类似的响应。大部分沉积物和颗粒营养物可能来自河岸沉积物和/或河道储存的侵蚀。目前，这些来源对非点源污染的贡献存在相当大的不确定性，特别是在具有大量遗留沉积物的流域。未来的气候预估表明，风暴事件会加剧，冬季气温的变异性也会增加。冻融循环加上冬季降雨事件可能会增加河岸沉积物的侵蚀和运移，对水质和下游水生生态系统的健康产生不利影响。
Large runoff, sediment, and nutrient exports from watersheds could occur due to individual extreme climate events or a combination of multiple hydrologic and meteorological conditions. Using high-frequency hydrologic, sediment, and turbidity data we show that freeze–thaw episodes followed by intense winter (February) rainstorms can export very high concentrations and loads of suspended sediment and particulate organic carbon (POC) and nitrogen (PN) from mid-Atlantic watersheds in the US. Peak suspended sediment (> 5000 mg L−1), POC (> 250 mg L−1) and PN (> 15 mg L−1) concentrations at our 12 and 79 ha forested watersheds for the February rainfall-runoff events were highest on record and the fluxes were comparable to those measured for tropical storms. Similar responses were observed for turbidity values (> 400 FNU) at larger USGS-monitored watersheds. Much of the sediments and particulate nutrients likely originated from erosion of stream bank sediments and/or channel storage. Currently, there is considerable uncertainty about the contribution of these sources to nonpoint source pollution, particularly, in watersheds with large legacy sediment deposits. Future climate projections indicate increased intensification of storm events and increased variability of winter temperatures. Freeze–thaw cycles coupled with winter rain events could increase erosion and transport of streambank sediments with detrimental consequences for water quality and health of downstream aquatic ecosystems.