Articles | Volume 17, issue 14
Atmos. Chem. Phys., 17, 8837–8865, 2017

Special issue: CHemistry and AeRosols Mediterranean EXperiments (ChArMEx)...

Atmos. Chem. Phys., 17, 8837–8865, 2017

Research article 21 Jul 2017

Research article | 21 Jul 2017

Organic carbon at a remote site of the western Mediterranean Basin: sources and chemistry during the ChArMEx SOP2 field experiment

Vincent Michoud1,2, Jean Sciare3,4, Stéphane Sauvage1, Sébastien Dusanter1,5, Thierry Léonardis1, Valérie Gros3, Cerise Kalogridis3, Nora Zannoni3, Anaïs Féron3, Jean-Eudes Petit3,6,a, Vincent Crenn3, Dominique Baisnée3, Roland Sarda-Estève3, Nicolas Bonnaire3, Nicolas Marchand7, H. Langley DeWitt7, Jorge Pey7,b, Aurélie Colomb8, François Gheusi9, Sonke Szidat10, Iasonas Stavroulas4, Agnès Borbon2,c, and Nadine Locoge1 Vincent Michoud et al.
  • 1IMT Lille Douai, Univ. Lille, SAGE – Département Sciences de l'Atmosphère et Génie de l'Environnement, 59000 Lille, France
  • 2LISA, CNRS UMR7583, Université Paris Est Créteil (UPEC), Université Paris Diderot (UPD), Institut Pierre Simon Laplace (IPSL), Créteil, France
  • 3LSCE, IPSL, CEA et Université de Versailles, CNRS, Saint-Quentin, France
  • 4The Cyprus Institute, Energy, Environment and Water Research Center, Nicosia, Cyprus
  • 5School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA
  • 6INERIS, 60550 Verneuil-en-Halatte, France
  • 7Aix Marseille Univ., CNRS, LCE, Marseille, France
  • 8LaMP, CNRS UMR6016, Clermont Université, Université Blaise Pascal, Aubière, France
  • 9Laboratoire d'Aérologie, Université de Toulouse, CNRS, Toulouse, France
  • 10Department 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, CNRS UMR6016, Clermont Université, Université Blaise Pascal, Aubière, France

Abstract. The ChArMEx (Chemistry and Aerosols Mediterranean Experiments) SOP2 (special observation period 2) field campaign took place from 15 July to 5 August 2013 in the western Mediterranean Basin at Ersa, a remote site in Cape Corse. 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 with an aerosol chemical speciation monitor (ACSM). Low levels of anthropogenic VOCs (typically tens to hundreds of parts per trillion for individual species) and black carbon (0.1–0.9 µg m−3) were observed, while significant levels of biogenic species (peaking at the 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, representing 55 % of the total mass of non-refractory PM1 on average (average of 3.74 ± 1.80 µg m−3), followed by sulfate (27 %, 1.83 ± 1.06 µg m−3), ammonium (13 %, 0.90 ± 0.55 µg m−3) and nitrate (5 %, 0.31 ± 0.18 µg m−3).

Positive matrix factorization (PMF) and concentration field (CF) analyses were performed on a database containing 42 VOCs (or grouped VOCs), including OVOCs, to identify the covariation 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 correlated with temperature and exhibiting a clear diurnal profile. In addition, three anthropogenic factors characterized by compounds with 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 southeast of France). Finally, a factor characterized by OVOCs of both biogenic and anthropogenic origin was found. This factor was well correlated with submicron organic aerosol (OA) measured by an aerosol chemical speciation monitor (ACSM), highlighting the close link between OVOCs and organic aerosols; the latter is mainly associated (96 %) with the secondary OA fraction. The source apportionment of OA measured by ACSM led to a three-factor solution identified as hydrogen-like OA (HOA), semi-volatile oxygenated OA (SV-OOA) and low volatility OOA (LV-OOA) for averaged mass concentrations 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 distinguish between anthropogenic continental and biogenic influences on the aerosol- and gas-phase compositions.

Short summary
The ChArMEx SOP2 field campaign took place from 15 July to 5 August 2013 in the western Mediterranean Basin at Ersa, a remote site in Cape Corse. Exhaustive descriptions of the chemical composition of air masses in gas and aerosol phase were performed. An analysis of these measurements was performed using various source-receptor approaches. This led to the identification of several factors linked to primary sources but also to secondary processes of both biogenic and anthropogenic origin.
Final-revised paper