title: Transport of Fecal Indicators from Beach Sand to the Surf Zone by Recirculating Seawater: Laboratory Experiments and Numerical Modeling.
abstract: Recirculating seawater is an important component of submarine groundwater discharge, yet its role in transporting microbial contaminants from beach sand to coastal water is unknown. This study investigated the extent to which recirculating seawater carries fecal indicators, Enterococcus and bird-associated Catellicoccus, through the beach subsurface. Laboratory experiments and numerical modeling were performed to characterize the transport of fecal indicators suspended in seawater through medium-grained beach sand under transient and saturated flow conditions. Enterococcus was measured both by culture (cENT) and DNA assay (tENT), and Catellicoccus (CAT) by DNA assay. There were differences between transport of tENT and CAT compared to cENT through laboratory columns containing beach sands. Under transient flow conditions, first-order attachment rate coefficients (katt) of DNA markers were greater (∼10 h-1) than kattof cENT (∼1 h-1), although under saturated conditions kattvalues were similar (∼1 h-1). First-order detachment rate coefficients, kdet, of DNA markers were greater (∼1 h-1) than kdetof cENT (∼0.1h-1) under both types of flow conditions. Incorporating the rate coefficients into field-scale subsurface transport simulations showed that, in this sand type, the contribution of recirculating seawater to surf zone contamination is likely to be minimal unless bird feces are deposited close to the land-sea interface.
authors: Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305-4020, United States.
authors: Kendra I
authors: KI
authors: Brown
authors: Department of Civil and Environmental Engineering, Stanford University , Stanford, California 94305-4020, United States.
authors: Alexandria B
authors: AB
authors: Boehm
mesh_terms: D001493:Bathing Beaches; D016983:Enterococcus; D004784:Environmental Monitoring; D005243:Feces; D060587:Groundwater; D012623:Seawater; D014871:Water Microbiology