ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-6-3337-2006 The composition of nucleation and Aitken modes particles during coastal nucleation events: evidence for marine secondary organic contribution Vaattovaara P. 1 Huttunen P. E. 2 Yoon Y. J. 4 5 Joutsensaari J. 2 Lehtinen K. E. J. 3 O’Dowd C. D. 4 Laaksonen A. 1 University of Kuopio, Department of Physics, P.O. Box 1627, FI-70211 Kuopio, Finland University of Kuopio, Department of Environmental Sciences, P.O. Box 1627, FI-70211 Kuopio, Finland University of Kuopio and Finnish Meteorological Institute, Department of Physics, P.O. Box 1627, FI-70211 Kuopio, Finland Department of Experimental Physics and Environmental Change Institute, National University of Ireland, Galway, Ireland now at: Korea Polar Research Institute, Ansan P.O. Box 29, Seoul 425-600, Republic of Korea 21 04 2006 6 2 3337 3379 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/6/3337/2006/acpd-6-3337-2006.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/6/3337/2006/acpd-6-3337-2006.pdf

Newly-formed nanometer-sized particles have been observed at coastal and marine environments worldwide. Interestingly, organic species have so far not been detected in those newly-formed nucleation mode particles. In this study, we applied the UFO-TDMA (ultrafine organic tandem differential mobility analyzer) method to study the possible existence of an organic fraction in recently formed coastal nucleation mode particles (d<20 nm) at the Mace Head research station. Furthermore, effects of those nucleation events to potential CCN (cloud condensation nuclei) were studied. The coastal events were typical for the Mace Head region and they occurred at low tide conditions during efficient solar radiation and high biological activity (HBA, i.e. a high mass concentration of chlorophyll a of the ocean) in spring 2002. Additionally, a PHA-UCPC (pulse height analyzer ultrafine condensation particle counter) technique was used to study the composition of newly-formed particles formed in low tide conditions during a lower biological activity (LBA, i.e. a lower mass concentration of chlorophyll a of the ocean) in October 2002. The overall results of the UFO-TDMA and the PHA-UCPC measurements indicate that those coastally/marinely formed nucleation mode particles include a remarkable fraction of secondary organic products, beside iodine oxides, which are likely to be responsible for the nucleation. During clean marine air mass conditions, the origin of those secondary organic oxidation compounds can be related to marine/coastal biota and thus a major fraction of the organics may originate from biosynthetic production of alkenes such as isoprene and their oxidation by iodine, hydroxyl radical, and ozone. During modified marine conditions, also anthropogenic secondary organic compounds may contribute to the nucleation mode organic mass, in addition to biogenic secondary organic compounds. Thus, the UFO-TDMA results suggest that the secondary organic compounds may, in addition to being significant contributors to the nucleation mode processes, accelerate the growth of freshly nucleated particles and increase their survival probability to CCN and even larger radiatively active particle sizes. The results give new insights to the coastal/marine particle formation, growth, and properties. The marine biota driven secondary organic contributions to coastal/marine particle formation and composition can be anticipated in other species specific biologically active oceans and fresh-waters areas around the world and thus, they may be significant also to the global radiative bugdet, atmosphere-biosphere feedbacks, and climate change.