Automated sampling of stormwater runoff in an urban watershed, north-central Texas

Automated samplers were used to collect urban runoff in Pecan Creek, Denton, Texas. Runoff from four storm events was sampled at four stations. Concentrations of some heavy metals (cadmium and arsenic), as well as pesticides (atrazine and diazinon), exceeded maximum contaminant levels for drinking water, but were within ranges typical for urban runoff. Calcium and phosphorous concentrations were high compared to previous studies, which was attributed to soils, building materials, and fertilizer applications in the study area. First flush samples were more concentrated than composite samples for most of the constituents analyzed, but statistically different for only five constituents. Concentrations of four constituents differed significantly among stations, and six differed significantly among storms, due to variations in land use, channel composition, and storm conditions. Overall, the automated samplers were an effective way to sample urban runoff in Pecan Creek.