Comparison of Pollutant Concentrations from Weekly Discrete Versus Daily Composite Samples for Residential Dry-Weather Runoff.

摘要

As urbanization has increased, so has degradation of urban streams. Urban water quality monitoring has focused on storm runoff sampling, but in arid climates, dry-weather runoff is a significant contributor of pollutants to aquatic systems. Through limited sampling protocols the majority of dry-weather runoff studies only sample a small window of the entire dry season. For this study constituent concentrations were compared using two sampling protocols. The first protocol repeatedly collected samples on the same day of the week at the same time of day and the second protocol collected samples during two week-long intensive sampling events consisting of sample collection every hour for 24 hours for seven consecutive days. The comparison was performed to determine if sampling at the same time of the week was representative of the entire week. For nitrate, total phosphorous, fipronil, permethrin, and total organic carbon, sampling at the same time was not representative of the entire week; however, there is variation between sites and constituents. For those constituent loads not represented by sampling consistently at the same time of the week, load adjustment coefficients (kla) were determined, using a ratio of treatment means, and employed to adjust dry season load estimates. Future work should include determining if kla values can be used at similar sites excluded from the study or for similar constituents from the current sampling sites.