Fingerprinting the sources of suspended sediment delivery to a large municipal drinking water reservoir: Falls Lake, Neuse River, North Carolina, USA
Fingerprinting the sources of suspended sediment delivery to a large municipal drinking water reservoir: Falls Lake, Neuse River, North Carolina, USA
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DOI：
10.1007/s11368-013-0758-3
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发表时间：
2013-09
影响因子：
3.6
通讯作者：
M. Voli;K. Wegmann;D. Bohnenstiehl;E. Leithold;C. Osburn;V. Polyakov
中科院分区：
文献类型：
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作者：
M. Voli;K. Wegmann;D. Bohnenstiehl;E. Leithold;C. Osburn;V. Polyakov
目的：我们采用地球化学指纹方法来估计从进入瀑布湖的支流收集的悬浮沉积物的来源，瀑布湖是美国北卡罗来纳州纽瑟河上一个50公里的饮用水水库。该湖的许多主要支流都在北卡罗来纳州303(d)名单上，因为河流受到损害，2008年，该湖被列入该名单，因为浑浊度很高，可能来自支流。材料与方法采用时间积分采样器采集了四条河流的悬浮物。此外，从河岸、森林、牧场、建筑工地、泥土和铺砌的道路以及支流盆地内的道路切割处收集了代表潜在来源的复合沉积物样本。用放射性碳测年和磁化率测定确定了河岸冲积沉积物的来源。对沉积物样品进行了55种元素和两种放射性核素的浓度分析，以确定能够区分潜在沉积物来源的示踪剂。通过蒙特卡罗模拟，在混合模型中参数化了地球化学示踪剂数据，确定了相对沉积物来源的贡献。结果和讨论放射性碳和磁化率测量证实了“遗留”沉积物在Ellerbe和New Light Creek山谷底部的存在。混合模型结果表明，在New Light Creek， Ellerbe Creek（58%）和Little Lick Creek（33%）中，河岸侵蚀是悬浮泥沙荷载的最大贡献者（62%），在Lick Creek中是第二大贡献者（27%），仅次于建筑工地（43%）。我们发现，在四个集水区中有三个集水区，河岸侵蚀是悬浮泥沙负荷的最大非点源，因此是福尔斯湖浊度的重要来源。遗留沉积物的存在似乎与埃勒贝河和新光河的河岸侵蚀增加的贡献相吻合。活跃的建筑工地和木材采伐也是悬浮沉积物的重要来源。减缓水质的努力需要考虑欧洲人定居后河谷底部沉积物的河岸侵蚀对非点源的贡献。
PurposeWe employ a geochemical-fingerprinting approach to estimate the source of suspended sediments collected from tributaries entering Falls Lake, a 50-km2drinking water reservoir on the Neuse River, North Carolina, USA. Many of the major tributaries to the lake are on North Carolina’s 303(d) list for impaired streams, and in 2008, the lake was added to that list because of high values of turbidity, likely sourced from tributary streams.Materials and methodsSuspended sediments were collected from four streams with a time-integrated sampler during high-flow events. In addition, composite sediment samples representing potential sources were collected from stream banks, forests, pastures, construction sites, dirt and paved roads, and road cuts within tributary basins. Radiocarbon dating and magnetic susceptibility measurements were used to determine the origin of stream bank alluvial deposits. Sediment samples were analyzed for the concentrations of 55 elements and two radionuclides in order to identify tracers capable of distinguishing between potential sediment sources. The relative sediment source contributions were determined by applying a Monte Carlo simulation that parameterized the geochemical tracer data in a mixing model.Results and discussionRadiocarbon and magnetic susceptibility measurements confirmed the presence of “legacy” sediment in the Ellerbe and New Light Creek valley bottoms. Mixing model results demonstrate that stream bank erosion is the largest contributor to the suspended sediment load in New Light Creek (62%), Ellerbe Creek (58%), and Little Lick Creek (33%), and is the second largest contributor in Lick Creek (27%) behind construction sites (43%).ConclusionsWe find that stream bank erosion is the largest nonpoint source contributor to the suspended sediment load in three of the four catchments and is therefore a significant source of turbidity in Falls Lake. The presence of legacy sediment appears to coincide with increased contributions from stream bank erosion in Ellerbe and New Light creeks. Active construction sites and timber harvesting were also significant sources of suspended sediment. Water quality mitigation efforts need to consider nonpoint-source contributions from stream bank erosion of valley bottom sediments aggraded after European settlement.