State Water Resources Research Institute Program

Project ID: 2011PA154B
Title: Assessing the Influence of Nutrient Sources to Urban Streams Through the use of Triple Nitrate Isotopes
Project Type: Research
Start Date: 3/01/2011
End Date: 2/29/2012
Congressional District: 14
Focus Categories: Nitrate Contamination, Non Point Pollution, Water Quality
Keywords: nitrate contamination, urban water quality, isotopes
Principal Investigator: Elliott, Emily
Federal Funds: $ 20,000
Non-Federal Matching Funds: $ 43,296
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 (δ15N and δ18O) with a unique tracer of atmospheric deposition (mass-independent δ17O 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.

Progress/Completion Report, 2011, PDF

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