Land-Use-Based Sources of Pollutants in Urban Storm Water

Urban storm water is recognized as a major source of pollution to many of the nation's waterways. However, little is known about the mechanisms and processes that influence pollutant loadings from specific land-use types. The goals of this study were (1) to examine event mean concentrations (EMC) and fluxes of TSS, metals, PAHs, and bacteria associated with storm water runoff from representative land-uses and (2) to investigate within storm and within season patterns in order to identify mechanisms that influence constituent loading. Pollutant concentrations and flow were measured over the entire storm duration from eight different land-use types over 11 storm events in five southern California watersheds during the 2000/01 through 2004/05 storm seasons. Mean TSS EMCs were significantly higher at the recreational site compared to all other land-use types. For trace metals, Cu, Pb, and Zn, values were significantly higher at industrial sites than at other land-use types. Despite some apparent differences between land-uses there were no significant differences in PAH concentration among land-use types, rather PAHs from all land use sites had clear signatures of pyrogenic (combustion by-product) derived PAHs. Recreational land-use sites contributed significantly higher levels of both E. Coli and Enterococcus, compared to other land-use types. For all constituents, the greatest concentrations occurred during the rising limb of the storm hydrograph. Concentrations stayed high for relatively short periods and decreased back to base levels within one to two hours. Results of this study can be used to calibrate watershed models that may be used for contaminant load allocations. Similarly, these data sets can assist storm water engineers in the design of more effective monitoring programs and better performing treatment practices (i.e. BMPs) that address specific rainfall/runoff conditions.