Department of Chemical Engineering and Materials Science, Henry Samueli School of Engineering, University of California, Irvine, California 92697, United States.
Environ Sci Technol. 2010 Dec 1;44(23):8804-13. doi: 10.1021/es101732m. Epub 2010 Oct 15.
Nearshore waters in bays, harbors, and estuaries are frequently contaminated with human pathogens and fecal indicator bacteria. Tracking down and mitigating this contamination is complicated by the many point and nonpoint sources of fecal pollution that can degrade water quality along the shore. From a survey of the published literature, we propose a conceptual and mathematical framework, the "beach boundary layer model", for understanding and quantifying the relative impact of beach-side and bay-side sources of fecal pollution on nearshore water quality. In the model, bacterial concentration in ankle depth water C(ankle) [bacteria L(-3)] depends on the flux m'' [bacteria L(-2) T(-1)] of fecal bacteria from beach-side sources (bather shedding, bird and dog feces, tidal washing of sediments, decaying vegetation, runoff from small drains, and shallow groundwater discharge), a cross-shore mass transfer velocity k [L T(-1)] that accounts for the physics of nearshore transport and mixing, and a background concentration C(bay) [bacteria L(-3)] attributable to bay-side sources of pollution that impact water quality over large regions (sewage outfalls, creeks and rivers): C(ankle) = m''/k + C(bay). We demonstrate the utility of the model for identifying risk factors and pollution sources likely to impact shoreline water quality, and evaluate the model's underlying assumptions using computational fluid dynamic simulations of flow, turbulence, and mass transport in a trapezoidal channel.
近岸水域的港湾、港口和河口经常受到人类病原体和粪便指示菌的污染。由于粪便污染的许多点源和非点源都可能沿岸边降低水质,因此追踪和减轻这种污染是很复杂的。从已发表文献的调查中,我们提出了一个概念和数学框架,即“海滩边界层模型”,用于理解和量化海滩和海湾两侧粪便污染源对近岸水质的相对影响。在该模型中,脚踝深度水中的细菌浓度 C(ankle)[细菌 L(-3)]取决于来自海滩源(游泳者脱落、鸟类和狗的粪便、潮汐冲刷沉积物、腐烂的植被、小排水沟的径流和浅层地下水排放)的粪便细菌通量 m''[细菌 L(-2) T(-1)]、考虑近岸输运和混合物理过程的横向质量传递速度 k [L T(-1)],以及归因于海湾源污染的背景浓度 C(bay)[细菌 L(-3)],这些污染会对大面积地区的水质产生影响(污水排放口、小溪和河流):C(ankle) = m''/k + C(bay)。我们展示了该模型用于识别可能影响海岸线水质的风险因素和污染源的实用性,并使用梯形通道中的流动、湍流和物质输运的计算流体动力学模拟来评估模型的基本假设。