Chung, Angela
(2019)
Assessing Spatial and Temporal Variability of Reactive Nitrogen in an Urban Fluvial System.
Master's Thesis, University of Pittsburgh.
(Unpublished)
Abstract
It is well-established that human activity has greatly altered the global nitrogen (N) cycle whereupon excess nitrate in aquatic systems is a key factor in the formation of algal blooms and dead zones. While agricultural watersheds are the major contributors of nitrogen to the Mississippi River, the contributions from urban watersheds are less clear. In particular, our understanding of N budgets and dynamics in watersheds dominated by urban and suburban land use remains limited. Pittsburgh’s “Three Rivers” describes the confluence of the Allegheny and the Monongahela Rivers that form the Ohio River. N loads from Pittsburgh area surface waters are of interest given the presence of combined sewage overflows (CSO) that discharge wastewater and stormwater runoff during rain events. To effectively remediate excess nitrogen delivery to aquatic environments (e.g. Gulf of Mexico), we must have a more refined understanding of N loads from urban systems.
In this study we estimate the N loads exporting from the Ohio River Basin in Pennsylvania using the USGS program LOADEST. Available N concentration and discharge data from 3 USGS gage stations on the rivers were used in the regression-based model. To characterize the spatial variation of different water quality parameters, we also conducted longitudinal sampling along the Three Rivers to collect grab samples under dry weather conditions, as well as after a rain storm during a combined sewage overflow event. Water samples were analyzed for reactive N species and nitrate isotopic composition. Additionally, during field sampling continuous measurement of nitrate (SUNA), dissolved oxygen, turbidity, pH, water temperature, and specific conductivity (YSI EXO2 Sonde) were used to evaluate high-resolution spatial patterns in water quality. This high-resolution spatial data, along with dual nitrate isotopes, are utilized to assess river conditions, explore the influence of urban infrastructure on water quality, and determine the sources of nitrate in Pittsburgh’s Three Rivers. This study’s dual nitrate isotope values all fall within the range of isotope ratios that are characteristic of nitrate of human and animal waste. The nitrogen load estimates signify additional nitrogen inputs in the Pittsburgh region.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
19 June 2019 |
| Date Type: |
Publication |
| Defense Date: |
5 April 2019 |
| Approval Date: |
19 June 2019 |
| Submission Date: |
10 April 2019 |
| Access Restriction: |
5 year -- Restrict access to University of Pittsburgh for a period of 5 years. |
| Number of Pages: |
99 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Geology and Environmental Science |
| Degree: |
MS - Master of Science |
| Thesis Type: |
Master's Thesis |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
Nitrogen, flux, isotopes |
| Date Deposited: |
19 Jun 2019 19:56 |
| Last Modified: |
19 Jun 2019 19:56 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/36445 |
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