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Volume 18, issue 19 | Copyright

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

Atmos. Chem. Phys., 18, 14297-14325, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 09 Oct 2018

Research article | 09 Oct 2018

Driving parameters of biogenic volatile organic compounds and consequences on new particle formation observed at an eastern Mediterranean background site

Cécile Debevec1, Stéphane Sauvage1, Valérie Gros2, Karine Sellegri3, Jean Sciare4,2, Michael Pikridas4, Iasonas Stavroulas4, Thierry Leonardis1, Vincent Gaudion1, Laurence Depelchin1, Isabelle Fronval1, Roland Sarda-Esteve2, Dominique Baisnée2, Bernard Bonsang2, Chrysanthos Savvides5, Mihalis Vrekoussis4,6, and Nadine Locoge1 Cécile Debevec et al.
  • 1IMT Lille Douai, Univ. Lille, SAGE – Département Sciences de l'Atmosphère et Génie de l'Environnement, Lille, France
  • 2Equipe CAE, Laboratoire des Sciences du Climat et de l'Environnement (LSCE), Unité Mixte CEA-CNRS-UVSQ, Gif-sur-Yvette, France
  • 3Laboratoire de Météorologie Physique (LaMP), CNRS UMR 6016, Université Blaise Pascal, Aubière, France
  • 4Energy, Environment and Water Research Centre, the Cyprus Institute (CyI), Nicosia, Cyprus
  • 5Department of Labour Inspection (DLI), Ministry of Labour, Welfare and Social Insurance, Nicosia, Cyprus
  • 6Institute of Environmental Physics (IUP), University of Bremen, Bremen, Germany

Abstract. As a part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) and Cyprus Aerosols and Gas Precursors (ENVI-Med CyAr) programs, this study aims primarily to provide an improved understanding of the sources and the fate of volatile organic compounds (VOCs) in the eastern Mediterranean. More than 60 VOCs, including biogenic species (isoprene and eight monoterpenes) and oxygenated VOCs, were measured during a 1-month intensive field campaign performed in March 2015 at the Cyprus Atmospheric Observatory (CAO), a regional background site in Cyprus. VOC measurements were conducted using complementary online and offline techniques. Biogenic VOCs (BVOCs) were principally imputed to local sources and characterized by compound-specific daily cycles such as diurnal maximum for isoprene and nocturnal maximum for α- and β-pinenes, in connection with the variability of emission sources. The simultaneous study of pinene and isoprene temporal evolution and meteorological parameters has shown that BVOC emissions were mainly controlled by ambient temperature, precipitation and relative humidity. It was found that isoprene daytime emissions at CAO depended on temperature and solar radiation changes, whereas nocturnal BVOC concentrations (e.g., from oak and pine forests) were more prone to the relative humidity and temperature changes. Significant changes in monoterpene mixing ratios occurred during and after rainfall. The second part of the study focused on new particle formation (NPF) events at CAO. BVOCs are known to potentially play a role in the growth as well as in the early stages of formation of new atmospheric particles. Based on observations of the particle size distribution performed with a differential mobility particle sizer (DMPS) and the total number concentrations of particles larger than 1nm diameter measured by particle size magnifier (PSM), NPF events were found on 14 out of 20 days of the field campaign. For all possible proxy parameters (meteorological parameters, calculated H2SO4 and measured gaseous compounds) having a role in NPF, we present daily variations of different classes during nucleation event and non-event days. NPF can occur at various condensational sink (CS) values and both under polluted and clean atmospheric conditions. High H2SO4 concentrations coupled with high BVOC concentrations seemed to be one of the most favorable conditions to observe NPF at CAO in March 2015. NPF event days were characterized by either (1) a predominant anthropogenic influence (high concentrations of anthropogenic source tracers observed), (2) a predominant biogenic influence (high BVOC concentrations coupled with low anthropogenic tracer concentrations), (3) a mixed influence (high BVOC concentrations coupled with high anthropogenic tracer concentrations) and (4) a marine influence (both low BVOC and anthropogenic tracer concentrations). More pronounced NPF events were identified during mixed anthropogenic–biogenic conditions compared to the pure anthropogenic or biogenic ones, for the same levels of precursors. Analysis of a specific NPF period of the mixed influence type highlighted that BVOC interactions with anthropogenic compounds enhanced nucleation formation and growth of newly formed particles. During this period, the nucleation-mode particles may be formed by the combination of high H2SO4 and isoprene amounts, under favorable meteorological conditions (high temperature and solar radiation and low relative humidity) along with low CS. During the daytime, growth of the newly formed particles, not only sulfate but also oxygen-like organic aerosol (OOA) mass contributions, increased in the particle phase. High BVOC concentrations were observed during the night following NPF events, accompanied by an increase in CS and in semi-volatile OOA contributions, suggesting further BVOC contribution to aerosol nighttime growth by condensing onto pre-existing aerosols.

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This work focuses on the study of the sources and fates of BVOCs and new particle formation (NPF) events in the eastern Mediterranean. NPF events were found on 14 out of 20 days of the campaign. NPF occurred at various condensational sinks and both under polluted and clean atmospheric conditions. Analysis of specific NPF periods of the mixed influence type highlighted that BVOC interactions with anthropogenic compounds enhanced nucleation formation and growth of new particles.
This work focuses on the study of the sources and fates of BVOCs and new particle formation...