Preprints
https://doi.org/10.5194/acp-2021-365
https://doi.org/10.5194/acp-2021-365

  18 May 2021

18 May 2021

Review status: this preprint is currently under review for the journal ACP.

Urban aerosol chemistry at a land-water transition site during summer – Part 1: Impact of agricultural and industrial ammonia emissions

Nicholas Balasus1, Michael A. Battaglia1, Katherine Ball1, Vanessa Caicedo2, Ruben Delgado2, Annmarie G. Carlton3, and Christopher J. Hennigan1 Nicholas Balasus et al.
  • 1Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland, Baltimore County, Baltimore, MD, 21250
  • 2Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Baltimore, MD, 21250
  • 3Department of Chemistry, University of California, Irvine, CA 92697, USA

Abstract. This study characterizes the impact of the Chesapeake Bay and associated meteorological phenomena on aerosol chemistry during the second Ozone Water-Land Environmental Transition Study (OWLETS-2) field campaign during summer 2018. Measurements of inorganic PM2.5 composition, gas-phase ammonia (NH3), and an array of meteorological parameters were undertaken at Hart-Miller Island (HMI), a land-water transition site just east of downtown Baltimore on the Chesapeake Bay. The observations at HMI were characterized by abnormally high NH3 concentrations (maximum of 19.3 μg m-3, average of 3.83 μg m-3), which were more than a factor of three higher than NH3 levels measured at the closest Atmospheric Ammonia Network (AMoN) site (approximately 45 km away). While sulfate concentrations at HMI agreed quite well with those measured at a regulatory monitoring station 45 km away, aerosol ammonium and nitrate concentrations were significantly higher, due to the ammonia-rich conditions that resulted from the elevated NH3. The high NH3 concentrations were largely due to regional agricultural emissions, including dairy farms in southeastern Pennsylvania and poultry operations in the Delmarva Peninsula (Delaware-Maryland-Virginia). Reduced NH3 deposition during transport over the Chesapeake Bay likely contributed to enhanced concentrations at HMI compared to the more inland AMoN site. Several peak NH3 events were recorded, including the maximum NH3 observed during OWLETS-2, that appear to originate from a cluster of industrial sources near downtown Baltimore. Such events were all associated with nighttime emissions and advection to HMI under low 15 wind speeds (< 1 m s-1) and stable atmospheric conditions. Our results demonstrate the importance of industrial sources, including several that are not represented in the emissions inventory, on urban air quality. Together with our companion paper, which examines aerosol liquid water and pH during OWLETS-2, we highlight unique processes affecting urban air quality of coastal cities that are distinct from continental locations.

Nicholas Balasus et al.

Status: open (until 13 Jul 2021)

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Nicholas Balasus et al.

Nicholas Balasus et al.

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Short summary
Measurements of aerosol and gas composition were carried out at a land-water transition site near Baltimore, MD. Gas-phase ammonia concentrations were highly elevated compared to measurements at a nearby inland site. Our analysis reveals that NH3 was from both industrial and agricultural sources. This had a pronounced effect on aerosol chemical composition at the site, most notably contributing to episodic spikes of aerosol nitrate.
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