Mediterranean nascent sea spray organic aerosol and relationships with seawater biogeochemistry

The organic mass fraction from sea spray aerosol (SSA) is currently a subject of intense research. The majority of this research is dedicated to measurements in ambient air, although recently a small number of studies have additionally focused on nascent sea spray aerosol. This work presents measurements collected during a five-week cruise in May and June 2017 in the central and western Mediterranean Sea, an oligotrophic marine region with low phytoplankton biomass. Surface seawater was continuously pumped into a bubble bursting apparatus to generate nascent sea spray aerosol. Size distributions were measured with a differential mobility particle sizer (DMPS). Chemical characterization of the submicron aerosol was performed with a time of flight aerosol chemical speciation monitor (ToF-ACSM) operating with a 15-minute time resolution, and with filter-based chemical analysis on a daily basis. Using a positive matrix factorization analysis, the ToF-ACSM non-refractory organic matter (OMNR) was separated into four different organic aerosols types which were identified as primary OA (POANR), oxidized OA (OOANR), a methanesulfonic acid type OA (MSA-OANR) and a mixed OA (MOANR). In parallel, surface seawater biogeochemical properties were monitored providing information on phytoplankton cell abundance and seawater particulate organic carbon (one-hour time resolution), and seawater surface microlayer (SML) dissolved organic carbon (DOC) (on a daily basis). Statistically robust correlations (for n > 500) were found between MOANR and nano phytoplankton cell abundance, as well as between POANR, OOANR, and particulate organic carbon (POC). Filter-based analysis of the submicron SSA showed that the non-refractory organic mass represented only 13 ± 3 % of the total organic mass, which represents 22 ± 6 % of the total sea spray mass. Parameterizations of the contributions of different types of organics to the submicron nascent sea spray aerosol are proposed as a function of the seawater biogeochemical properties for use in models.

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Freney Evelyn, Sellegri Karine, Nicosia Alessia, Trueblood Jonathan T, Rinaldi Matteo, Williams Leah R, Prévôt André SH, Thyssen Melilotus, Gregori Gerald, Haëntjens Nils, Dinasquet Julie, Obernosterer Ingrid, Van Wambeke France, Engel Anja, Zancker Birthe, Desboeufs Karine, Asmi Eija, Timmonen Hilka, Guieu Cécile (2021). Mediterranean nascent sea spray organic aerosol and relationships with seawater biogeochemistry. Atmospheric Chemistry And Physics. 21 (13). 10625-10641. https://doi.org/10.5194/acp-21-10625-2021, https://archimer.ifremer.fr/doc/00688/80017/

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