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- Title
Quantifying the importance of vehicle ammonia emissions in an urban area of northeastern USA utilizing nitrogen isotopes.
- Authors
Walters, Wendell W.; Karod, Madeline; Willcocks, Emma; Baek, Bok H.; Blum, Danielle E.; Hastings, Meredith G.
- Abstract
Atmospheric ammonia (NH 3) is a critical component of our atmosphere that contributes to air quality degradation and reactive nitrogen deposition; however, our knowledge of NH 3 in urban environments remains limited. Year-long ambient NH 3 and related species were measured for concentrations and the nitrogen isotopic compositions (δ15 N) of NH 3 and particulate ammonium (pNH4+) were measured to understand the temporal sources and chemistry of NH 3 in a northeastern US urban environment. We found that urban NH 3 and pNH4+ concentrations were elevated compared to regional rural background monitoring stations, with seasonally significant variations. Local and transported sources of NH x (NH 3+ pNH4+) were identified using polar bivariate and statistical back trajectory analysis, which suggested the importance of vehicles, volatilization, industry, and stationary fuel combustion emissions. Utilizing a uniquely positive δ15 N(NH 3) emission source signature from vehicles, a Bayesian stable isotope mixing model (SIMMR) indicates that vehicles contribute 46.8±3.5% (mean ±1σ) to the annual background level of urban NH x , with a strong seasonal pattern with higher relative contribution during winter (56.4±7.6%) compared to summer (34.1±5.5%). The decrease in the relative importance of vehicle emissions during the summer was suggested to be driven by temperature-dependent NH 3 emissions from volatilization sources, seasonal fuel-combustion emissions related to energy generation, and change in seasonal transport patterns based on wind direction, back trajectory, and NH 3 emission inventory analysis. This work highlights that reducing vehicle NH 3 emissions should be considered to improve wintertime air quality in this region.
- Subjects
NITROGEN isotopes; CARBONACEOUS aerosols; CITIES &; towns; ATMOSPHERIC ammonia; EMISSION inventories; AIR quality; STABLE isotopes
- Publication
Atmospheric Chemistry & Physics, 2022, Vol 22, Issue 20, p13431
- ISSN
1680-7316
- Publication type
Article
- DOI
10.5194/acp-22-13431-2022