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Isotopic evidence that alkyl nitrates are important to aerosol nitrate formation in the Equatorial Pacific
  • Emily Elizabeth Joyce,
  • Sawyer Balint,
  • Meredith G. Hastings
Emily Elizabeth Joyce
Brown University

Corresponding Author:[email protected]

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Sawyer Balint
Brown University
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Meredith G. Hastings
Brown University
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Abstract

Concentrations and the stable isotopic composition of bulk aerosol nitrate (NO3-) were quantified from two fall GEOTRACES cruises: 1) Alaska–Tahiti (GP15; n=22) and 2) Peru–Tahiti (GP16; n=17) to explore the hypothesis that marine emissions influence aerosol NO3- in the Equatorial Pacific. The δ15N-NO3- ranged from -14.5–0.5‰, with lowest values far from the coast and primarily reflecting a shift in sources. The δ18O- and Δ17O-NO3- were both high (65.2–85.4‰ and 21.4–30.7‰, respectively) and decreased away from continental regions, reflecting a shift in the oxidants that influence the formation of NO3-. Transport modeling and co-occurrence of low δ15N, δ18O and Δ17O provided evidence for an important influence of alkyl nitrates (RONO2) on aerosol NO3- formation. Based on the Δ17O, we quantified that the contribution of RONO2 to aerosol NO3- can be as high as 48% (range 15–48%). We were also able to estimate an average δ15N-RONO2 of -22.9 ± 19.1‰.