Abstract. Nitrogen-containing organic compounds, which may be directly emitted into the atmosphere or which may form via reactions with prevalent reactive nitrogen species (e.g., NH3, NOx, NO3), have important but uncertaineffects on climate and human health. Using gas and liquid chromatographywith soft ionization and high-resolution mass spectrometry, we performed amolecular-level speciation of functionalized organic compounds at a coastal site on the Long Island Sound in summer (during the 2018 Long Island Sound Tropospheric Ozone Study – LISTOS – campaign) and winter. This region often experiences poor air quality due to theemissions of reactive anthropogenic, biogenic, and marine-derived compoundsand their chemical transformation products. We observed a range offunctionalized compounds containing oxygen, nitrogen, and/or sulfur atomsresulting from these direct emissions and chemical transformations,including photochemical and aqueous-phase processing that was more pronounced in summer and winter, respectively. In both summer and winter, nitrogen-containing organic aerosols dominated the observed distribution offunctionalized particle-phase species ionized by our analytical techniques,with 85 % and 68 % of total measured ion abundance containing a nitrogenatom, respectively. Nitrogen-containing particles included reduced nitrogen functional groups (e.g., amines, imines, azoles) and common NOz contributors (e.g., organonitrates). Reduced nitrogen functional groups observed in the particle phase were frequently paired with oxygen-containing groups elsewhere on the molecule, and their prevalence often rivaled that of oxidized nitrogen groups detected by our methods. Supplemental gas-phasemeasurements, collected on adsorptive samplers and analyzed with a novelliquid chromatography-based method, suggest that gas-phase reduced nitrogen compounds are possible contributing precursors to the observed nitrogen-containing particles. Altogether, this work highlights theprevalence of reduced nitrogen-containing compounds in the less-studied northeastern US and potentially in other regions with similar anthropogenic, biogenic, and marine source signatures.
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An investigation into the chemistry of HONO in the marine boundary layer at Tudor Hill Marine Atmospheric Observatory in Bermuda
Abstract. Here we present measurement results of temporal distributions of nitrous acid (HONO) along with several chemical and meteorologicalparameters during the spring and the late summer of 2019 at Tudor Hill Marine Atmospheric Observatory in Bermuda. Large temporal variations inHONO concentration were controlled by several factors including local pollutant emissions, air mass interaction with the island, andlong-range atmospheric transport of HONO precursors. In polluted plumes emitted from local traffic, power plant, and cruise ship emissions,HONO and nitrogen oxides (NOx) existed at substantial levels (up to 278 pptv and 48 ppbv, respectively),and NOx-related reactions played dominant roles in daytime formation of HONO. The lowest concentration of HONO wasobserved in marine air, with median concentrations at ∼ 3 pptv around solar noon and < 1 pptv during thenighttime. Considerably higher levels of HONO were observed during the day in the low-NOx island-influenced air([NO2] < 1 ppbv), with a median HONO concentration of ∼ 17 pptv. HONO mixing ratios exhibiteddistinct diurnal cycles that peaked around solar noon and were lowest before sunrise, indicating the importance of photochemical processes forHONO formation. In clean marine air, NOx-related reactions contribute to ∼ 21 % of the daytime HONOsource, and the photolysis of particulate nitrate (pNO3) can account for the missing source assuming a moderate enhancement factorof 29 relative to gaseous nitric acid photolysis. In low-NOx island-influenced air, the contribution from bothNOx-related reactions and pNO3 photolysis accounts for only ∼ 48 % of the daytime HONOproduction, and the photochemical processes on surfaces of the island, such as the photolysis of nitric acid on the forest canopy, might contributesignificantly to the daytime HONO production. The concentrations of HONO, NOx, and pNO3 were lowerwhen the site was dominated by the aged marine air in the summer and were higher when the site was dominated by North American air in the spring,reflecting the effects of long-range transport on the reactive nitrogen chemistry in background marine environments.
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- NSF-PAR ID:
- 10351475
- Date Published:
- Journal Name:
- Atmospheric Chemistry and Physics
- Volume:
- 22
- Issue:
- 9
- ISSN:
- 1680-7324
- Page Range / eLocation ID:
- 6327 to 6346
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.5194/acp-22-6327-2022
