Factors that modulate properties of primary marine aerosol generated from ambient seawater on ships at sea

TitleFactors that modulate properties of primary marine aerosol generated from ambient seawater on ships at sea
Publication TypeJournal Article
Year of Publication2017
AuthorsKeene W.C, Long M.S, Reid J.S, Frossard AA, Kieber D.J, Maben J.R, Russell LM, Kinsey J.D, Quinn P.K, Bates T.S
JournalJournal of Geophysical Research-Atmospheres
Volume122
Pagination11961-11990
Date Published2017/11
Type of ArticleArticle
ISBN Number2169-897X
Accession NumberWOS:000417195500029
Keywordsboundary-layer; breaking waves; bursting bubbles; chemical-composition; cloud condensation nuclei; dissolved organic-carbon; optical depth; radiative properties; side-scan sonar; spray aerosol
Abstract

Model primary marine aerosol (mPMA) was produced by bubbling clean air through flowing natural seawater in a high-capacity generator deployed on ships in the eastern North Pacific and western North Atlantic Oceans. Physicochemical properties of seawater and mPMA were quantified to characterize factors that modulated production. Differences in surfactant organic matter (OM) and associated properties including surface tension sustained plumes with smaller bubble sizes, slower rise velocities, larger void fractions, and older surface ages in biologically productive relative to oligotrophic seawater. Production efficiencies for mPMA number (PEnum) and mass (PEmass) per unit air detrained from biologically productive seawater during daytime were greater and mass median diameters smaller than those in the same seawater at night and in oligotrophic seawater during day and night. PEmass decreased with increasing air detrainment rate suggesting that surface bubble rafts suppressed emission of jet droplets and associated mPMA mass. Relative to bubbles emitted at 60 cm depth, PEnum for bubbles emitted from 100 cm depth was approximately 2 times greater. mPMA OM enrichment factors (EFs) and mass fractions based on a coarse frit, fine frits, and a seawater jet exhibited similar size-dependent variability over a wide range in chlorophyll a concentrations. Results indicate that the physical production of PMA number and mass from the ocean surface varies systematically as interrelated functions of seawater type and, in biologically productive waters, time of day; bubble injection rate, depth, size, and surface age; and physical characteristics of the air-water interface whereas size-resolved OM EFs and mass fractions are relatively invariant.

DOI10.1002/2017jd026872
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