Rosenzweig Bernice R, Moon Hee Sun, Smith James A, Baeck Mary Lynn, Jaffe Peter R
Department of Civil and Environmental Engineering, Princeton University, Princeton, New Jersey, USA.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Sep;43(11):1223-33. doi: 10.1080/10934520802225190.
Urban streams play a significant role in the transport of dissolved inorganic nitrogen (DIN) from uplands to sensitive coastal receiving waters. In this study, we investigate the timing of DIN export through monitoring conducted during several storm events of different magnitude and with different antecedent conditions in an urban catchment. Our monitoring was conducted at a first-order stream site in a highly urban catchment in the northeastern United States during four rainstorms. Nitrate made up the dominant portion of the DIN load during all four events and the response of nitrate and ammonia were very different. Discharge, rather than concentration, was the most important factor in determining nitrate export with hot moments of nitrate export coinciding with peaks in flow. However, the highest nitrogen concentrations were observed after the streamflow peak during all of the events. During extreme rainstorms, this delayed response may constitute an important secondary hot-moment of nitrate export. These results may be significant for the development of nitrogen management plans for urban watersheds, especially since many water quality improvement BMPs (best management practices) are being designed to treat the first-flush of stormwater and would miss much of the DIN load.
