The physical and chemical characteristics of marine organic aerosols: a review

Abstract. Knowledge of the physical characteristics and chemical composition of marine organic aerosols is needed for the quantification of their effects on solar radiation transfer and cloud processes. Global emission estimates of marine organic aerosol are in a range of 2 to 70 Tg yr−1 and occur over regions most susceptible to aerosol perturbations. This review examines research pertinent to the chemical composition, size distribution, mixing state, emission mechanism, and climatic impact of marine primary organic aerosols associated with sea spray. Numerous measurements have shown that both the ambient mass concentration of marine organic aerosol and size-resolved organic mass fraction of sea spray aerosol are related to surface ocean biological activity. Recent studies have also indicated that fine mode (smaller than 200 nm in diameter) marine organic aerosols can have a size distribution independent from sea-salt, while coarse mode aerosols (larger than 1000 nm in diameter) are more likely to be internally-mixed with sea-salt. Climate studies have found that marine organic aerosols can cause large local increases in the cloud condensation nuclei concentration, with the potential to have a non-negligible influence on the anthropogenic aerosol indirect forcing. Despite these signs of climate-relevance for marine organic aerosols, the source strength, chemical composition, mixing state, hygroscopicity, cloud droplet activation potential, atmospheric aging, and removal of marine organic aerosols remain poorly quantified. Additional laboratory, field, and modeling studies focused on the chemistry, size distribution, and mixing state of sea spray aerosols are needed to better understand and quantify their importance.