Important Source of Marine Secondary Organic Aerosol from Biogenic Amines MARIA CRISTINA FACCHINI,* ,† STEFANO DECESARI, † MATTEO RINALDI, † CLAUDIO CARBONE, † EMANUELA FINESSI, † MIHAELA MIRCEA, † SANDRO FUZZI, † FABIO MORETTI, ‡ EMILIO TAGLIAVINI, ‡ DARIUS CEBURNIS, § AND COLIN D. O’DOWD § Institute of Atmospheric Sciences and Climate, National Research Council, Bologna, I-40129, Italy, Department of Chemistry, University of Bologna, Bologna, I-40126, Italy, Centro Interdipartimentale di Ricerca per le Scienze Ambientali, University of Bologna, Ravenna, I-48100 Italy, and School of Physics and Centre for Climate and Air Pollution Studies, Environmental Change Institute, National University of Ireland, Galway, Ireland Received July 3, 2008. Revised manuscript received September 28, 2008. Accepted September 30, 2008. Relevant concentrations of dimethyl- and diethylammonium salts (DMA + and DEA + ) were measured in submicrometer marine aerosol collected over the North Atlantic during periods of high biological activity (HBA) in clean air masses (median concentration (minimum-maximum) ) 26 (6-56) ng m -3 ). Much lower concentrations were measured during periods of low biological activity (LBA): 1 ( <0.4-20) ng m -3 and when polluted air masses were advected to the sampling site: 2 ( <0.2-24) ng m -3 . DMA + and DEA + are the most abundant organic species, second only to MSA, detected in fine marine particles representing on average 11% of the secondary organic aerosol (SOA) fraction and a dominant part (35% on average) of the water- soluble organic nitrogen (WSON). Several observations support the hypothesis that DMA + and DEA + have a biogenic oceanic source and are produced through the reaction of gaseous amines with sulfuric acid or acidic sulfates. Moreover, the water-soluble fraction of nascent marine aerosol particles produced by bubble-bursting experiments carried out in parallel to ambient aerosol sampling over the open ocean showed WSON, DMA + , and DEA + concentrations always below the detection limit, thus excluding an important primary sea spray source. Introduction The natural marine aerosol is of paramount importance at the global scale and influences the Earth’s radiative budget, biogeochemical cycles, and impacts on marine ecosystems (1). In clean marine environments the concentration of primary and secondary aerosol components is driven by the seasonality of oceanic biological productivity (2-4). Primary aerosols are produced by sea spray, while the mechanisms responsible for secondary organic aerosol (SOA) formation in the marine atmosphere, although considered very im- portant, are not fully clarified (1). Identified SOA components include methanesulfonic acid (MSA) and dicarboxylic acids (5, 6). Recently, oxidation of isoprene produced by phy- toplankton has been proposed as an additional source of SOA in the marine atmosphere (3). Nonetheless, the observed high concentrations of oxidized organic matter in marine aerosol remain unexplained, suggesting that other formation mechanisms and alternative SOA components should be considered. In spite of the considerable interest in the biogeochemical cycle of nitrogen in marine ecosystems and the crucial role of the atmosphere in redistributing nitrogen species, research on organic nitrogen in the marine atmosphere has received only limited attention (7-9). Several observations have shown that water-soluble organic nitrogen (WSON), a major com- ponent of submicrometer aerosol, is mainly formed by gas- to-particle conversion in the atmosphere (7, 8), even though oxidation of reduced organic nitrogen species of biogenic origin produced by mechanical processes (as sea spray or soil mobilization) has also been considered as a potentially important WSON source (7, 10). Moreover, the biogenic versus anthropogenic contribution to aerosol WSON is still not quantified (7, 10, 11). Amines and amino acids are known to be an important fraction of WSON in different environments, clean and polluted (9, 12, 13). Several studies hypothesized that amines and amino acids detected in marine particles are produced by bubble bursting at the air-sea interface (12-14). These reduced nitrogen species can subsequently be transformed by photo-oxidation and degradation processes into oxidized organic nitrogen species (14). In contrast, several field experiments carried out in conti- nental polluted and forested environments have shown the potential role of aliphatic amines in SOA formation (15-17). Laboratory studies (15, 18) and thermodynamic calculation on new particle formation (11) strongly support this hypothesis. Formation of more oxidized particulate organic nitrogen species from different amine oxidation pathways has also been explored in several chamber experiments (15, 16, 19). This paper investigates the origin and processes potentially responsible for the relevant concentration of alkylammonium salts detected in the accumulation mode marine aerosol and assesses the importance of such species as biogenic com- ponents of marine SOA along with their contribution to the marine aerosol organic nitrogen budget. For this purpose we adopted an integrated approach based on field and chamber experiments in which primary and secondary organic components of marine aerosol have been resolved. Experimental Section Sampling Strategy. Aerosol samples discussed in this study were collected during the experiments carried out in 2006 within the EU Project MAP (Marine Aerosol Production, http://macehead.nuigalway.ie/map) and during a chamber experiment performed within the BIOFLUX campaign held in September 2003 (20). Intermittent sampling of ambient aerosol was carried out over 1 year within MAP at the Mace Head Research Station in Ireland (MH). Aerosol particles were sampled differentiating clean and polluted air masses by means of an automated sampling system (2, 4). Due to the long sampling time required to collect sufficient material * Corresponding author: phone: +390516399563; fax: +3901639- 9647; e-mail: mc.facchini@isac.cnr.it. † National Research Council. ‡ University of Bologna. § National University of Ireland. Environ. Sci. Technol. 2008, 42, 9116–9121 9116 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 42, NO. 24, 2008 10.1021/es8018385 CCC: $40.75  2008 American Chemical Society Published on Web 11/07/2008