Environmental and Water Studies, Department of Civil and Environmental Engineering, Stanford University, Stanford, California 94305, United States.
Environ Sci Technol. 2012 Jun 5;46(11):5988-96. doi: 10.1021/es300408z. Epub 2012 May 9.
This study explores the transport of enterococci (ENT) from naturally contaminated beach sands to the groundwater table via infiltrating seawater using field, laboratory, and modeling experiments. ENT were readily mobilized and transported through the unsaturated zone during infiltration events in both the field and laboratory column experiments. Detachment mechanisms were investigated using a modified version of HYDRUS-1D. Three models for detachment kinetics were tested. Detachment kinetics that are first order with respect to the rate of change in the water content and attached surface bacterial concentrations were found to provide a best fit between predicted and observed data. From these experimental and model results we conclude that detachment mechanisms associated with the rapid increases in pore water content such as air-water interface scouring and thin film expansion are likely drivers of ENT mobilization in the investigated system. These findings suggest that through-beach transport of ENT may be an important pathway through which ENT from beach sands are transported to beach groundwater where they may be discharged to coastal waters via submarine groundwater discharge.
本研究通过野外、实验室和模型实验，探索了肠球菌（ENT）通过渗透海水从受自然污染的海滩砂向地下水位运移的过程。在野外和实验室柱实验中，ENT 在渗透过程中很容易通过非饱和带迁移和运移。使用 HYDRUS-1D 的修改版本研究了分离机制。测试了三种分离动力学模型。发现与水含量和附着表面细菌浓度变化率呈一阶关系的分离动力学模型最能拟合预测数据和观测数据。根据这些实验和模型结果，我们得出结论，与孔隙水含量快速增加相关的分离机制，如气-水界面冲刷和薄膜扩展，可能是研究系统中 ENT 迁移的驱动因素。这些发现表明，通过海滩的 ENT 迁移可能是一种重要途径，通过这种途径，来自海滩砂的 ENT 被运移到海滩地下水，然后通过海底地下水排放到沿海水域。
