title: Intra-storm variability in microbial partitioning and microbial loading rates.
abstract: Association with particles in the water column can have a significant impact on microbial fate and transport. This study analyzed multiple stormwater samples taken throughout the duration of three separate storms (at two different sites) to evaluate the fraction of microbes partitioning to denser "settleable" particles and to examine how partitioning behavior varied over the course of a storm. Intra-storm sampling also allowed for estimates of microbial loading rates (both total and particle-associated) and cumulative storm-induced microbial load. Five different indicator organisms were examined, with the fraction of microbes associated with settleable particles assessed via a calibrated centrifugation method. Partitioning behavior varied across microorganism type, with an average of 40% of fecal coliforms, Escherichia coli, and enterococci associating with settleable particles, compared to approximately 65% of Clostridium perfringens spores and only 13% of total coliphage. Partitioning remained fairly constant for each type of organism throughout storm events. Nonetheless, higher concentrations of both settleable particles and microbes entering the water column soon after the onset of a storm led to higher loading rates of settleable microbes in the storm's earliest stages, a trend that could have important implications for the design of stormwater management structures (e.g., detention basins). Estimates of cumulative storm-induced microbial loading suggested that one day's worth of storm loading can be the equivalent of months, or even years, of dry-weather loading.
authors.affiliation: Department of Environmental Sciences and Engineering, School of Public Health, Rosenau Hall-CB #7431, University of North Carolina, Chapel Hill, NC 27599-7431, USA. krometis@email.unc.edu
authors.forename: Leigh-Anne H
authors.initials: LA
authors.lastname: Krometis
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Characklis
authors.forename: Otto D
authors.initials: OD
authors.lastname: Simmons
authors.forename: Mackenzie J
authors.initials: MJ
authors.lastname: Dilts
authors.forename: Christina A
authors.initials: CA
authors.lastname: Likirdopulos
authors.forename: Mark D
authors.initials: MD
authors.lastname: Sobsey
mesh_terms: D003016:Clostridium perfringens / Q000302:isolation & purification; D003090:Coliphages / Q000302:isolation & purification; D015169:Colony Count, Microbial; D004323:Drainage, Sanitary; D004755:Enterobacteriaceae / Q000302:isolation & purification; D016983:Enterococcus / Q000302:isolation & purification; D004784:Environmental Monitoring / Q000379:methods*; D009657:North Carolina; D010316:Particle Size; D011891:Rain / Q000382:microbiology*; D045483:Rivers / Q000382:microbiology*; D013997:Time Factors; D014872:Water Movements; D014873:Water Pollutants
chemical_list: D014873:Water Pollutants