Water Resources Research Act Program

Details for Project ID 2011PA154B

Assessing the Influence of Nutrient Sources to Urban Streams Through the use of Triple Nitrate Isotopes

Institute: Pennsylvania
Year Established: 2011 Start Date: 2011-03-01 End Date: 2012-02-29
Total Federal Funds: $20,000 Total Non-Federal Funds: $43,296

Principal Investigators: Emily Elliott

Abstract: Excess nitrate contributes to the overall degraded quality of streams in densely populated, human-engineered regions, compounding existing problems of pollution in urban landscapes. Urban centers, such as Pittsburgh, potentially contribute significant amount of nutrient pollution to large river systems, via concentrated emissions from industry, vehicles, electric generating utilities that burn fossil fuels, and human-produced sewage. In densely populated urban systems, the relative contributions from multiple nitrate sources form a complicated mixture that is difficult to unravel with simple concentration chemistry. In this study, our objective is to further investigate nitrate sources and dynamics in to an urban stream using triple nitrate isotope systematics, coupling traditional, mass-dependent nitrate isotopes (del 15N and del 18O) with a unique tracer of atmospheric deposition (mass-independent delta 17O of nitrate) to evaluate sources and dynamics of nitrate pollution. The proposed research will be the first of its kind to use the mass-independent tracer of atmospheric nitrate to examine the role of atmospheric inputs to urban water quality. The proposed research is focused on analysis of samples collected from Nine Mile Run (NMR), an urban stream in Pittsburgh, Pennsylvania (Figure 1). In 2006 a restoration of NMR was completed at a cost of over $7 million dollars, but streamwater quality monitoring was not part of the restoration. Triple nitrate isotope analyses will be completed on baseflow (sampled bi-weekly from April 2007-2009) and stormflow samples (summer and winter of 2008 and 2010) in order to determine sources of nitrate in streamwater from each sampling location. Utilizing the triple nitrate isotope method on baseflow samples from each site will help us to determine the spatial and seasonal dynamics of nutrient inputs, the relative contribution from different sources in the watershed, as well as source of pollution. Additionally, we will use the triple isotope method to analyze water sampled during high-flow conditions. This will allow us to compare nutrient loads and sources during low and high flow regimes. It is difficult to improve water quality without understanding the relative importance of potential nitrate sources to urban streams. When combined with data from other urban streams, this study will contribute significantly to our understanding of nutrient pollution in urban waterways.