Comparison of hygroscopicity, volatility, and mixing state of submicrometer particles between cruises over the Arctic Ocean and the Pacific Ocean

Abstract

Ship-borne measurements of ambient aerosols were conducted during an 11,937-km cruise over the Arctic Ocean (cruise 1) and the Pacific Ocean (cruise 2). A frequent nucleation event was observed during cruise 1 under marine influence, and the abundant organic matter resulting from the strong biological activity in the ocean could contribute to the formation of new particles and their growth to a detectable size. Concentrations of particle mass and black carbon increased with increasing continental influence from polluted areas. During cruise 1, multiple peaks of hygroscopic growth factor (HGF) of 1.1-1.2, 1.4, and 1.6 were found, and higher amounts of volatile organic species existed in the particles compared to during cruise 2, which is consistent with the greater availability of volatile organic species caused by the strong oceanic biological activity (cruise 1). Internal mixtures of volatile and non-hygroscopic organic species, non-volatile and less-hygroscopic organic species, and non-volatile and hygroscopic nss-sulfate with varying fractions can be assumed to constitute the submicrometer particles. Based on elemental composition and morphology, the submicrometer particles were classified into C-rich mixture, S-rich mixture, C/S-rich mixture, Na-rich mixture, C/P-rich mixture, and mineral-rich mixture. Consistently, the fraction of biological particles (i.e., P-containing particles) increased when the ship travelled along a strongly biologically active area.