Boehm Alexandria B, Keymer Daniel P, Shellenbarger Gregory G
Department of Civil and Environmental Engineering, Environmental and Water Studies, Stanford University, Stanford, CA 94305-4020, USA.
Water Res. 2005 Sep;39(15):3565-78. doi: 10.1016/j.watres.2005.06.026.
An analytical model of enterococci (ENT) concentrations in the surf zone of a long sandy beach is constructed considering the physical processes of dilution by rip currents and alongshore littoral drift, and the biological processes of inactivation and mortality by grazing. The solution is used to construct an expression for the length of shoreline adversely impacted by ENT from a point source. Two non-dimensional parameters are developed whose magnitude can be used to ascertain whether dilution, inactivation, or grazing is the dominant sink for ENT in the surf zone. The model is applied to beaches in southern California, USA. Model input parameters related to physical processes and inactivation are compiled from the literature. Laboratory experiments are conducted to determine grazing mortality rates of ENT (6.5 x 10(-6) s(-1)). Results indicate that at the field sites, between 1000 and 5000 m of shoreline are typically impacted by a continuous point source of ENT. Dilution is the primary cause of decline in ENT concentrations within the surf zone, with inactivation secondary and grazing tertiary. Results recommend strategic positioning of point sources and timing of effluent releases to take advantage of high dilution conditions. Our estimates for grazing mortality rates are within the same order of magnitude as some published inactivation rates, thus we cannot rule out the possibility that grazing is an important sink for ENT, especially in low dilution environments like enclosed bays.
构建了一个长沙滩冲浪区肠球菌（ENT）浓度的分析模型，该模型考虑了离岸流稀释和沿岸沿岸漂移的物理过程，以及捕食导致的失活和死亡的生物过程。该解决方案用于构建一个表达式，以确定点源对ENT产生不利影响的海岸线长度。开发了两个无量纲参数，其大小可用于确定稀释、失活或捕食是否是冲浪区ENT的主要汇。该模型应用于美国南加州的海滩。与物理过程和失活相关的模型输入参数来自文献。进行了实验室实验以确定ENT的捕食死亡率（6.5×10⁻⁶ s⁻¹）。结果表明，在现场，1000至5000米的海岸线通常受到ENT连续点源的影响。稀释是冲浪区内ENT浓度下降的主要原因，失活次之，捕食第三。结果建议合理定位点源和废水排放时间，以利用高稀释条件。我们对捕食死亡率的估计与一些已发表的失活率处于同一数量级，因此我们不能排除捕食是ENT重要汇的可能性，特别是在封闭海湾等低稀释环境中。
