[1] The chemical properties of sea-spray aerosol particles produced by artificially generated bubbles using oceanic waters were investigated during a phytoplankton bloom in the North Atlantic. Spray particles exhibited a progressive increase in the organic matter (OM) content from 3 ± 0.4% up to 77 ± 5% with decreasing particle diameter from 8 to 0.125 mm. Submicron OM was almost entirely water insoluble (WIOM) and consisted of colloids and aggregates exuded by phytoplankton. Our observations indicate that size dependent transfer of sea water organic material to primary marine particles is mainly controlled by the solubility and surface tension properties of marine OM. The pattern of WIOM and sea-salt content in the different size intervals observed in bubble bursting experiments is similar to that measured in atmospheric marine aerosol samples collected during periods of high biological activity. The results point to a WIOM/sea-salt fingerprint associated with submicron primary marine aerosol production in biologically rich waters. Citation: Facchini, M. C., et al.

[1] Volatile organoiodine compounds (VOIs) are the main carrier of iodine from the oceans to the atmosphere. We have identified a novel, sea-surface source of the short-lived VOIs CH 2 I 2 , CHClI 2 and CHI 3 in a series of laboratory experiments. These compounds were formed when seawater, collected during winter in the North Sea, was exposed to ambient levels of ozone. The VOIs are produced from the reaction of marine dissolved organic matter with hypoiodous acid/molecular iodine, which are formed at the sea surface when ozone reacts with dissolved iodide. The same three VOIs were formed when we incubated seawater of different productivity levels with molecular iodine during a cruise in the tropical Atlantic Ocean. We suggest that the presence of dissolved iodide, dissolved organic matter and ozone can lead to the sea-surface production of CH 2 I 2 , CHClI 2 and CHI 3 . As such, this process could provide a ubiquitous source of iodine to the marine atmosphere.

The hydrolysis of (CH 3 ) 2 Sn 2+ was studied potentiometrically, in different aqueous media (sodium and tetramethylammonium chlorides, sodium nitrate, sodium perchlorate, and sodium sulfate), in a wide range of ionic strength, at t ) 25°C. Least squares calculations are consistent with the formation of the species [M(OH)] + , [M(OH) 2 ] 0 , [M(OH) 3 ] -, [M 2 (OH) 2 ] 2+ , and [M 2 (OH) 3 ] + , with M ) (CH 3 ) 2 Sn 2+ . The dependence on ionic strength for different salt solutions was taken into account by using a Debye-Hü ckel type equation. Medium effects were explained by considering the formation of the chloride and sulfate complexes, [(CH 3 ) 2 SnCl] + , [(CH 3 ) 2 SnCl 2 ] 0 , [(CH 3 ) 2 Sn(OH)Cl] 0 , [(CH 3 ) 2 Sn(OH) 2 Cl] -, [(CH 3 ) 2 Sn(SO 4 )] 0 , [(CH 3 ) 2 Sn(SO 4 ) 2 ] 2-, [(CH 3 ) 2 Sn(OH)(SO 4 )] -, and [(CH 3 ) 2 Sn(OH) 2 (SO 4 )] 2-. Thermodynamic hydrolysis constants of (CH 3 ) 2 Sn 2+ and formation constants of the complex species with chloride and sulfate ions are reported.

Abstract. Marine aerosol composition continues to represent a large source of uncertainty in the study of climate and atmospheric chemistry. In addition to their physical size and chemical composition, hygroscopicity plays a significant role, increasing the particles' surface areas and scattering potential. Simultaneous aerosol measurements were performed on board the RRS Discovery and at the Cape Verde atmospheric observatory during the Aerosol Composition and Modelling in the Marine Environment (ACMME) and Reactive Halogens in the Marine Boundary Layer (RHAMBLE) experiments. These included online measurements of number and dry size and bulk collection for offline analysis of aqueous ions. In addition, the measurements on board the Discovery included online measurements of composition using an Aerodyne Aerosol Mass Spectrometer, optical absorption using a Multi Angle Absorption Photometer, ambient humidity size distribution measurements using a humidified differential mobility particle sizer (DMPS) and optical particle counter (OPC) and hygroscopicity measurements with a hygroscopicity tandem differential mobility analyser (HT-DMA).Good agreement between platforms in terms of the sea salt (ss) and non sea salt (nss) modes was found during the period when the Discovery was in close proximity to Cape Verde and showed a composition consistent with remote marine air. As the Discovery approached the African coast, the aerosol showed signs of continental influence such as an increaseCorrespondence to: J. D. Allan (james.allan@manchester.ac.uk) in particle number, optical absorption, enhancement of the nss mode and dust particles. The Cape Verde site was free of this influence during this period. Chloride and bromide showed concentrations with significant deviations from seawater relative to sodium, indicating that atmospheric halogen processing (and/or acid displacement for chloride) had taken place. The time dependent ambient size distribution was synthesised using humidified DMPS and OPC data, corrected to ambient humidity using HTDMA data. Heterogeneous uptake rates of hypoiodous acid (HOI) were also predicted and the nss accumulation mode was found to be the most significant part of the size distribution, which could act as an inert sink for this species. The predicted uptake rates were enhanced by around a factor of 2 during the African influence period due to the addition of both coarse and fine particles.The hygroscopicity of the nss fraction was modelled using the Aerosol Diameter Dependent Equilibrium Model (AD-DEM) using the measured composition and results compared with the HTDMA data. This was the first time such a reconciliation study with this model has been performed with marine data and good agreement was reached within the resolution of the instruments. The effect of hygroscopic growth on HOI uptake was also modelled and ambient uptake rates were found to be approximately doubled compared to equivalent dry particles.