Organosulfates in Nascent and Aged Sea Spray Aerosols

DILINI KIRINDIGODA GAMAGE, Elias Hasenecz, Glorianne Dorcé, Kathryn Mayer, Jon Sauer, Christopher Lee, Kimberly Prather, Elizabeth Stone, University of Iowa

     Abstract Number: 141
     Working Group: Aerosols, Clouds and Climate

Abstract
Organosulfates are components of secondary organic aerosols that contain a distinctive sulfate ester functional group (R-O-SO₃^-). Organosulfates in the marine environment can arise from both primary and secondary sources. Liquid chromatography coupled to high resolution and tandem mass spectrometry (MS/MS) with negative mode electrospray ionization was used to determine the composition and abundance of organosulfates in PM_2.5 nascent and aged sea spray aerosol (SSA) collected during the Sea Spray Chemistry and Particle Evolution (SeaSCAPE) study. Nascent SSA was generated from natural seawater via breaking waves generated in 30 m glass wave channel. Aged SSA was generated by oxidizing the wave channel headspace, including nascent SSA, in an oxidative flow reactor (OFR), and it includes both heterogeneously oxidized SSA and secondary marine aerosol formed by the oxidation of volatile organic compounds. Anthropogenic anionic surfactants including ethylhexyl sulfate (C₈H₁₇SO₄^-; 209.0848), dodecyl sulfate (C₁₂H₂₅SO₄^-; 265.1474), tridecyl sulfate (C₁₃H₂₇SO4^-; 279.1630), and myristyl sulfate (C₁₄H₂₉SO₄^- ; 293.1787) contributed the most to the bisulfate (HSO₄^-; 97) product ion as determined by precursor-ion MS/MS. These alkyl sulfates likely entered the ocean by runoff and were enriched during SSA production due to their high surface activity. Secondary organosulfates derived from isoprene, monoterpene, fatty acids, and other sources were identified in nascent and aged SSA. Isoprene derived organosulfates (e.g., 2-methyltetrol sulfate, C₅H₁₁SO₇^–; m/z 215) were greatly enhanced in the sampling channel where marine volatile organic compounds were oxidized. The presence of the precursor ion signal at m/z 294, which corresponds to monoterpene-derived organosulfates with a nitroxy functional group (C₁₀H₁₆NSO₇^-) in nascent and aged SSA, indicates NO₃-initiated oxidation of monoterpenes in the presence of acidified sulfate in the marine environment. Findings from this study provide molecular insight into the composition of sea spray aerosol and reveal likely primary and secondary sources of organosulfates and their formation pathways in the marine environment.