Characterization of Reactive Nitrogen Transport in Pittsburgh's Three Rivers During Dry-and Wet-Weather Conditions
Abstract
While it is well-established that human activity has greatly altered the global nitrogen (N) cycle and excess nitrate in aquatic systems is a key factor in the formation of algal blooms and dead zones, the relative contribution of N-inputs from different sources remains uncertain in many cases. 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 N-rich wastewater and stormwater runoff during rain events. Here we estimate the N loads entering the Ohio River from the Allegheny and Monongahela Rivers under dry and wet weather conditions and the sources of nitrate to these rivers under different conditions.
To characterize total N export into the Ohio River, we 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 and nutrient concentrations. This high-resolution spatial data, along with dual nitrate isotopes, are utilized to assess river conditions and whether CSO location influences water quality and reactive N concentrations. Using available N concentration data from the Three Rivers, we use simple regression models to estimate total N loads entering the Ohio River. Through comparing N loads under dry- and wet-weather conditions, we evaluate the influence of urban infrastructure on water quality in the Pittsburgh region.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMGC23H1304C
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCESDE: 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGE