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Divers, Marion Teresa (2014) SOURCES AND DYNAMICS OF REACTIVE NITROGEN TO AN URBAN WATERSHED. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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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 watersheds receive and export reactive nitrogen (Nr) from a myriad of sources, including sewage, vehicular emissions, stationary source emissions, and lawn fertilizers, whereas forested systems receive Nr from atmospheric deposition and in-situ soil microbial communities. These sources are likely concentrated in urban areas, with the result that urban watersheds can contribute significant amounts of Nr to downstream waterways. Excess nitrogen contributes to downstream eutrophication of water bodies, as seen in large bays and estuaries such as the Chesapeake Bay and Gulf of Mexico. The excess Nr loadings from urban areas will likely increase in the future, as fossil fuel emissions are expected to rise and infrastructure such as sewer networks are expected to degrade over time. Identifying, quantifying, and understanding Nr in urban ecosystems is essential to success in efforts to manage and mitigate as future urban growth is realized.

Stable isotope analysis of nitrogen and oxygen in nitrate is an effective method of providing information about Nr sources and reactions in many ecosystems. Nitrate-nitrogen is persistent in the environment, easily transported via hydrological pathways, and has detrimental ecological effects. This work presents a comprehensive analysis of the sources and fluxes of nitrate to Nine Mile Run, an urban stream in Pittsburgh PA. Inverse modeling methods are used to estimate the extent of sewage leaking from the impaired pipe system and indicate DIN contributions from sewage range from 6 to 14 kg ha-1yr-1. Further, this work reveals that rates of DIN retention in NMR are 84%, on the high end of rates observed in other suburban/urban watersheds. Dual-isotope analysis of nitrate in water samples demonstrates during stormflows that proportionally, atmospheric deposition contributes 22% of nitrate to streamwater, and sewage contributes the remainder. Triple oxygen isotope analysis is used to unequivocally quantify the contributions of atmospheric deposition on streamwater nitrate in urban streams, with flux calculations using this technique indicating higher ADN export than observed through dual-nitrate isotope analysis.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Divers, Marion
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairElliott, Emilyeelliott@pitt.eduEELLIOTT
Committee MemberBain, Danieldbain@pitt.eduDBAIN
Committee MemberVanBriesen,
Committee MemberCapo, Rosemaryrcapo@pitt.eduRCAPO
Committee MemberAnderson, Thomastaco@pitt.eduTACO
Date: 28 January 2014
Date Type: Publication
Defense Date: 21 November 2013
Approval Date: 28 January 2014
Submission Date: 5 December 2013
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Number of Pages: 176
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Geology and Planetary Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Urban Watershed; Nitrogen; Dual-nitrate isotopes; Mass-independent Oxygen Isotopes; Reactive Nitrogen; Urban Nutrient Surces
Date Deposited: 28 Jan 2014 19:25
Last Modified: 28 Jan 2019 06:15


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