Evaluating the role of sediment-bacteria interactions on Escherichia coli concentrations at beaches in southern Lake Michigan
Evaluating the role of sediment-bacteria interactions on Escherichia coli concentrations at beaches in southern Lake Michigan
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评估沉积物-细菌相互作用对密歇根湖南部海滩大肠杆菌浓度的作用
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发表时间：
2013
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通讯作者：
R. Whitman
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作者：
P. Thupaki;M. Phanikumar;D. Schwab;M. B. Nevers;R. Whitman
2013 年 3 月 11 日收到； 2013 年 9 月 30 日修订； 2013 年 11 月 20 日接受； 2013 年 12 月 20 日发表。 [1] 细菌与水柱中悬浮沉积物的关联使近岸水质的评估和预测变得复杂。我们使用三维 EC 命运和传输模型（有或没有明确描述沉积物 - 细菌相互作用）研究了沉积物细菌相互作用对密歇根湖南部海滩大肠杆菌 (EC) 水平的影响。我们使用嵌套网格数值模型来模拟流体动力学，并使用半参数波浪模型来计算波高和净底部剪应力。使用线性分配系数对水柱中细菌的附着-脱离动力学进行建模。数值模型根据 2008 年夏季收集的数据进行了测试，其中包括三个海滩的 EC 测量以及针对海流和波浪的多个 ADCP 部署。我们的结果表明，解释沉积物与细菌相互作用的模型明显更好地描述了观察到的数据，并且沉积物直接和间接与细菌相互作用，影响其命运和运输。这一改进源于该模型能够描述我们采样点的多个短持续时间、低强度的再悬浮事件。在模拟期间注意到主要的再悬浮事件，但事件期间的采样频率不足以解析峰的细节。使用线性等温线模型来模拟水柱中细菌的附着-脱离动力学，我们发现附着在水柱中悬浮沉积物颗粒上的细菌分数在近海位置在垂直方向上变化很大，但在靠近海岸的地方几乎恒定。
Received 11 March 2013; revised 30 September 2013; accepted 20 November 2013; published 20 December 2013. [1] Association of bacteria with suspended sediment in the water column complicates the assessment and prediction of nearshore water quality. We examine the impact of sedimentbacteria interactions on Escherichia coli (EC) levels at beaches in southern Lake Michigan using three-dimensional EC fate and transport models with and without explicit descriptions of sediment-bacteria interactions. We simulate hydrodynamics using a nested-grid numerical model and use a semiparametric wave model to compute wave heights and net bottom shear stress. The attachment-detachment dynamics of bacteria in the water column are modeled using a linear partition coefficient. The numerical models were tested against data, collected in summer 2008, which included measurements of EC at three beaches and multiple ADCP deployments for currents and waves. Our results indicate that the model that accounts for sediment-bacteria interactions describes the observed data significantly better and that sediment, directly and indirectly, interacts with bacteria to influence their fate and transport. The improvement results from the model’s ability to describe the multiple short-duration, low-intensity resuspension events at our sampling sites. A major resuspension event was noted during the simulation period but the sampling frequency during the event was inadequate to resolve the details of the peak. Using the linear isotherm model to simulate attachment-detachment dynamics of bacteria in the water column, we found that the fraction of bacteria attached to suspended sediment particles in the water column is highly variable in the vertical at offshore locations but nearly constant closer to the shore.