School for Environment and Sustainability, University of Michigan, 440 Church St., Ann Arbor, Michigan 48109, United States.
Great Lakes Environmental Research Laboratory, National Oceanic and Atmospheric Administration, 4840 S. State Rd., Ann Arbor, Michigan 48108, United States.
Environ Sci Technol. 2020 May 5;54(9):5550-5559. doi: 10.1021/acs.est.0c00383. Epub 2020 Apr 22.
The United States and Canada called for a 40% load reduction of total phosphorus from 2008 levels entering the western and central basins of Lake Erie to achieve a 6000 MTA target and help reduce its central basin hypoxia. The Detroit River is a significant source of total phosphorus to Lake Erie; it in turn has been reported to receive up to 58% of its load from Lake Huron when accounting for resuspended sediment loads previously unmonitored at the lake outlet. Key open questions are where does this additional load originate, what drives its variability, and how often does it occur. We used a hydrodynamic model, satellite images of resuspension events and ice cover, wave hindcasts, and continuous turbidity measurements at the outlet of Lake Huron to determine where in Lake Huron the undetected load originates and what drives its variability. We show that the additional sediment load, and likely phosphorus, is from wave-induced Lake Huron sediment resuspension, primarily within 30 km of the southeastern shore. When the flow is from southwest or down the center of the lake, the resuspended sediment is not detected at Canada's sampling station at the head of the St. Clair River.
美国和加拿大呼吁将进入伊利湖西部和中部流域的总磷负荷从 2008 年水平减少 40%，以实现 6000 MTA 的目标，并帮助减少其中心盆地缺氧。底特律河是伊利湖中总磷的重要来源；据报道，当考虑到以前在湖出口处未监测到的再悬浮泥沙负荷时，它反过来接收了来自休伦湖的高达 58%的负荷。关键的开放性问题是，这种额外的负荷来自何处，是什么驱动了它的可变性，以及它多久发生一次。我们使用水动力模型、再悬浮事件和冰盖的卫星图像、波浪回溯以及休伦湖出口处的连续浊度测量来确定休伦湖中未检测到的负荷来自何处以及是什么驱动了它的可变性。我们表明，额外的泥沙负荷，可能还有磷，是由休伦湖波浪引起的泥沙再悬浮产生的，主要来自东南岸 30 公里范围内。当水流来自西南或湖中心时，加拿大在圣克莱尔河源头的采样站无法检测到再悬浮的泥沙。
