Organic carbon at a remote site of the western Mediterranean Basin: composition, sources and chemistry during the ChArMEx SOP2 field experiment
Vincent Michoud1,2,3, Jean Sciare4,5, Stéphane Sauvage1,2, Sébastien Dusanter1,2,6, Thierry Léonardis1,2, Valérie Gros4, Cerise Kalogridis4, Nora Zannoni4, Anaïs Féron4, Jean-Eudes Petit4,7,a, Vincent Crenn4, Dominique Baisnée4, Roland Sarda-Estève4, Nicolas Bonnaire4, Nicolas Marchand8, H. Langley DeWitt8, Jorge Pey8,b, Aurélie Colomb9, François Gheusi10, Sonke Szidat11, Iasonas Stavroulas5, Agnès Borbon3,c, and Nadine Locoge1,21Mines Douai, SAGE, F-59508, Douai, France 2Université de Lille, 59655, Villeneuve d'Ascq, France 3LISA, UMR-CNRS 7583, Université Paris Est Créteil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), Créteil, France 4LSCE, IPSL, CEA et Université de Versailles, CNRS, Saint-Quentin, France 5The Cyprus Institute, Energy Environment Water Research Center, Nicosia, Cyprus 6School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA 7INERIS, 60550 Verneuil-en-Halatte, France 8Aix Marseille Univ, CNRS, LCE, Marseille, France 9LaMP, UMR-CNRS 6016, Clermont Université, Université Blaise Pascal, Aubière, France 10Laboratoire d'Aérologie, Université de Toulouse, CNRS, Toulouse, France 11Department of Chemistry and Biochemistry & Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland anow at: Air Lorraine, 20 rue Pierre Simon de Laplace, 57070 Metz, France bnow at: the Geological Survey of Spain, 50006 Zaragoza (Spain) cnow at: LaMP, UMR-CNRS 6016, Clermont Université, Université Blaise Pascal, Aubière, France
Received: 26 Oct 2016 – Accepted for review: 15 Jan 2017 – Discussion started: 23 Jan 2017
Abstract. The ChArMEx (Chemistry and Aerosol Mediterranean Experiment) SOP2 (Special Observation Period 2) field campaign took place from 15 July to 05 August 2013 in the western Mediterranean basin, at Ersa a remote site in Cape Corsica. During the campaign more than 80 Volatile Organic Compounds (VOCs), including oxygenated species were measured by different online and offline techniques. At the same time an exhaustive description of the chemical composition of fine aerosols was performed. First we combined a back-trajectory analysis and an estimation of photochemical age to characterize air mass origins and chemical processing times, which confirmed the remote nature of the site. Therefore, low levels of anthropogenic VOCs (typically tens to hundreds of ppt for individual species) and black carbon (0.1–0.9 μg m) were observed while significant levels of biogenic species (peaking at ppb level) were measured. Furthermore, secondary oxygenated VOCs (OVOCs) largely dominated the VOC speciation during the campaign, while Organic Matter (OM) dominated the aerosol chemical composition (55 % of the total mass of non-refractory submicron aerosol on average).
Second, Positive Matrix Factorization (PMF) and Concentration Field (CF) analyses were performed on a database containing 42 VOCs (or grouped VOCs), including OVOCs, to identify co-variation factors of compounds that are representative of primary emissions, or chemical transformation processes. A six-factor solution was found for the PMF analysis, including a primary and secondary biogenic factor, both correlated to temperature and exhibiting a clear diurnal profile. In addition, three anthropogenic factors characterized by compounds of various lifetimes and/or sources have been identified (long-lived, medium-lived and short-lived anthropogenic factors). The anthropogenic nature of these factors was confirmed by the CF analysis which identified potential source areas known for intense anthropogenic emissions (north of Italy and south-east of France). Finally, a factor characterized by OVOCs of both biogenic and anthropogenic origins was found. This factor was well correlated to submicron organic aerosols (OA) measured by an Aerosol Chemical Speciation Monitor (ACSM) highlighting the close link between OVOCs and organic aerosols measured at Cape Corsica mainly associated (96 %) to secondary fraction of OA. The source apportionment of OA measured by ACSM led to a 3-factor solution identified as Hydrogen-like OA (HOA), Semi-Volatile-Oxygenated OA (SV-OOA) and Low-Volatile OOA (LV-OOA) for averaged mass concentration of 0.13, 1.59, and 1.92 μg m−3, respectively.
A combined analysis of gaseous PMF factors with inorganic and organic fractions of aerosols helped distinguishing between anthropogenic/continental and biogenic influences on the aerosol and gas phase compositions.
Michoud, V., Sciare, J., Sauvage, S., Dusanter, S., Léonardis, T., Gros, V., Kalogridis, C., Zannoni, N., Féron, A., Petit, J.-E., Crenn, V., Baisnée, D., Sarda-Estève, R., Bonnaire, N., Marchand, N., DeWitt, H. L., Pey, J., Colomb, A., Gheusi, F., Szidat, S., Stavroulas, I., Borbon, A., and Locoge, N.: Organic carbon at a remote site of the western Mediterranean Basin: composition, sources and chemistry during the ChArMEx SOP2 field experiment, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-955, in review, 2017.