Summertime OH reactivity from a receptor coastal site in
the Mediterranean basin
Nora Zannoni1, Valerie Gros1, Roland Sarda Esteve1, Cerise Kalogridis1,2, Vincent Michoud3,4,5, Sebastien Dusanter3,4,6, Stephane Sauvage3,4, Nadine Locoge3,4, Aurelie Colomb7, and Bernard Bonsang11SCE, Laboratorie Scientifique du Climat et de l’Environnement, CNRS-CEA-UVSQ, 91191 Gif sur Yvette, France 2Institute of Nuclear Technology and Radiation Protection, National Centre of Scientific Research "Demokritos", 15310 Ag. Paraskevi, Attiki, Greece 3Mines Douai, Département Sciences de l’Atmosphère et Génie de l’Environnement (SAGE), 59508 Douai, France 4Universite de Lille, F-59000 Lille, France 5Laboratoire Interuniversitaire des Systèmes Atmosphériques (LISA), 61 avenue du Général de Gaulle, 94010 Créteil, France 6School of Public and Environmental Affairs, Indiana University, Bloomington, IN, USA 7LAMP, Campus universitaire des Cezeaux, 4 Avenue Blaise Pascal, 63178 Aubiere, France
Received: 28 Jul 2016 – Accepted for review: 19 Sep 2016 – Discussion started: 04 Oct 2016
Abstract. Total OH reactivity, the total loss frequency of the hydroxyl radical in ambient air, provides the total loading of reactive gases in air. We measured the total OH reactivity for the first time during summertime at a coastal receptor site located in the western Mediterranean basin. Measurements were performed at a temporary field site located in the northern cape of Corsica (France), during summer 2013 for the project CARBOSOR (CARBOn within continental pollution plumes: SOurces and Reactivity) -ChArMeX (Chemistry-Aerosols Mediterranean Experiment). Here, we compare the measured total OH reactivity with the OH reactivity inferred from the measured reactive gases. The difference between these two parameters is termed missing OH reactivity, i.e., the fraction of OH reactivity not explained by the measured compounds. The total OH reactivity at the site varied between the instrumental LoD (limit of detection = 3 s−1) to a maximum of 17 ± 6 s−1 (35 % uncertainty) and was 5 ± 4 s−1 (1σ standard deviation) on average. It varied with air temperature exhibiting a diurnal profile comparable to the one of the biogenic volatile organic compounds measured at the site. We observed a fraction of missing OH reactivity during two distinct periods (on average 56 %), associated respectively to transported aged air masses and low-wind speed conditions at the site. We suggest that oxygenated molecules, mostly formed from reactions of biogenic gases precursors, were the major contributors to the missing OH reactivity.
Zannoni, N., Gros, V., Sarda Esteve, R., Kalogridis, C., Michoud, V., Dusanter, S., Sauvage, S., Locoge, N., Colomb, A., and Bonsang, B.: Summertime OH reactivity from a receptor coastal site in
the Mediterranean basin, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-684, in review, 2016.