Levels and patterns of fecal indicator bacteria in stormwater runoff from homogenous land use sites and urban watersheds

摘要

Routine stormwater monitoring programs focus on quantification of average fecal indicatornbacteria (FIB) concentration at the terminal watershed discharge point. While important for permitncompliance, such monitoring provides little insight into relative bacteria levels from different landnuse types or the mechanisms that influence FIB concentrations. The goal of this study was tonquantify the relative levels and flux patterns of Escherichia coli, enterococci, and total coliformsnfrom representative land use (LU) types. Bacteria concentrations were measured over thenentire storm duration from 8 different LU types over 13 storm events in 5 southern Californianwatersheds during the 2000–2005 storm seasons. In addition, runoff samples were collected fromn8 bottom of the watershed mass emission (ME) sites. Intra-storm and intra-season patterns wereninvestigated in order to identify mechanisms that influence patterns of FIB concentrations.nMean FIB event mean concentrations (EMCs) at LU sites ranged from 103 to 105 MPN/100 ml.nRecreational (horse stables) LU sites contributed significantly higher storm EMCs than other LUntypes. Early season storms repeatedly produced higher EMCs than comparably sized late seasonnstorms. For most storms sampled, the highest bacterial concentrations occurred during the earlynphases of stormwater runoff with peak concentrations usually preceding peak flow.