What controls volatility of sea spray aerosol? Results from laboratory studies using artificial and real seawater samples

Abstract Seawater samples were collected in the Bay of Aarhus, Denmark, from April 9 to June 1, 2015, and laboratory generated sea spray aerosol (SSA) were characterized with regards to volatility, particle size distributions and cloud condensation nuclei (CCN) activity. The volatile fraction of SSA generated in a sea spray tank from real and artificial seawater was determined using a thermodenuder at temperatures up to 400 °C. SSA generated from artificial seawater consisting of a mixture of inorganic salts show a larger volatile fraction than SSA from the real seawater samples. Measurements of different artificial saltwater solutions revealed that the volatile fraction of dried artificial SSA is likely due to evaporation of water in the thermodenuder. Thermal decomposition of hydrates in the thermodenuder, in particular magnesium chloride hydrates can explain the observed behavior. The presented results suggest that the inorganic salt composition may influence and even dominate the volatility of SSA generated from artificial and real seawater samples.