Isotopic Evidence That Alkyl Nitrates Are Important to Aerosol Nitrate Formation in the Equatorial Pacific

Concentrations and the stable isotopic composition of bulk aerosol nitrate (NO3?) were quantified from two GEOTRACES cruises: (a) Alaska–Tahiti (GP15; n = 22) (b) Peru–Tahiti (GP16; 17) to explore hypothesis that a marine source influences NO3? in equatorial Pacific. The ?15N-NO3? ranged ?14.5‰–0.5‰, with lowest values furthest coast, primarily reflecting shift sources. ?18O- ?17O-NO3? both relatively high (65.2‰–85.4‰ 21.4‰–30.7‰, respectively) decreased away continental regions, oxidants influence formation NO3?. Transport modeling co-occurrence low ?15N, ?18O ?17O provided evidence for an important marine-derived alkyl nitrates (RONO2) on formation. Based ?17O, we contribution RONO2 can be as 47.5% (range 7.5%–47.5%). We also estimate average ?15N-RONO2 ?27.8‰ ± 23.3‰.