From the Atmosphere to the Sea: Atmospheric Nitrogen Deposition to Aquatic Ecosystems

Joyce, Emily Elizabeth

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Year:: 2022
Contributor:: Joyce, Emily Elizabeth (creator); Hastings, Meredith (Advisor); Huber, Christian (Reader); Herbert, Timothy (Reader); Russell, James (Reader); Altieri, Katye (Reader); Brown University. Department of Earth, Environmental, and Planetary Sciences (sponsor)
Genre:: theses
Subject:: Atmospheric chemistry and biogeochemistry; Stable isotopes; Nitrogen; Atmospheric deposition; Ocean-atmosphere interaction
Extent:: xxv, 227 p.

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Abstract:: The availability of nutrients in surface waters, including inorganic nitrogen (N) (i.e., nitrate (NO3-), nitrite (NO2-), and ammonium (NH4+)), regulates estuarine and ocean primary production. Yet, an excess amount of N can significantly impact biogeochemical cycles and even degrade water quality. The focus of this work is to better understand the influence that atmospheric N deposition (i.e., wet (precipitation) and dry (gases and particles)) has on these important ecosystems, and the role aquatic ecosystems play in the atmospheric N cycle. Narragansett Bay, the largest estuary in the northeastern U.S., extends through the center of Rhode Island and spans a land-use gradient (from urban–semi-rural). The Bay often experiences poor water quality, which has been attributed to high nutrient N loading. Using precipitation samples, we find that urban N concentrations are higher than nearby rural areas. Additionally, total N wet deposited from the atmosphere onto the Bay is underestimated today by ~2.5×, due to a ~6× increase in NH4+ deposition. Including dry deposition to these measurements increases the total by 30%. The dominant flux of ammonia (NH3) is upward (i.e., out of the Bay) during the Fall season, and we estimate that NH3 emitted from the Bay to the atmosphere makes up to 10% of the local NH3 emission budget. The amount of N entering the Pacific Ocean from the atmosphere has increased since the industrial revolution and is predicted to continue to grow with anthropogenic N emissions. Transport modeling and the co-occurrence of low isotopic compositions of atmospheric NO3- (δ15N-, δ18O-, and Δ17O-NO3-) collected along two open ocean cruises provided evidence for an important influence of a marine-derived N source (i.e., RONO2) on aerosol NO3- formation in the tropics (7.5-47.5% contribution). We estimate that an average δ15N-RONO2 of -27.8±23.3‰. The isotopic composition of aerosol NO3- collected in Northern China displayed strong seasonality, reflecting changes in emission sources, airmass origins, and oxidant chemistry. Lockdown orders were established during sampling due to the novel coronavirus (COVID-19), which provided a unique opportunity to observe the sensitivity of the isotopic composition to fast changes in chemistry and emission sources that occurred during the lockdown.
Notes:: Thesis (Ph. D.)--Brown University, 2022

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Citation

Joyce, Emily Elizabeth, "From the Atmosphere to the Sea: Atmospheric Nitrogen Deposition to Aquatic Ecosystems" (2022). Earth, Environmental and Planetary Sciences Theses and Dissertations. Brown Digital Repository. Brown University Library. https://repository.library.brown.edu/studio/item/bdr:ytp8w8gx/

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Earth, Environmental and Planetary Sciences Theses and Dissertations

Theses and Dissertations for the Earth, Environmental and Planetary Sciences department.
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