C2–C8 NMHCs over the Eastern Mediterranean: Seasonal variation and impact on regional oxidation chemistry |
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| Authors: | E Liakakou B Bonsang J Williams N Kalivitis M Kanakidou N Mihalopoulos |
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| Institution: | aEnvironmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, P.O. Box 2208, Voutes, 71003 Heraklion, Greece;bLaboratoire des Sciences du Climat et de l'Environnement, CNRS/CEA, Orme des Merisiers, 91190 Gif-sur-Yvette, France;cMax Planck Institute for Chemistry, Atmospheric Chemistry Department, Joh. Joachim-Becher-Weg 27, P.O. Box 3060, D-55020 Mainz, Germany |
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| Abstract: | More than 2500 measurements of C2–C8 non-methane hydrocarbons (NMHCs) have been conducted at Finokalia sampling station on the island of Crete over a thirty-month period (September 2003–February 2006), to investigate the factors controlling NMHC levels and estimate their role in the oxidizing capacity of the Eastern Mediterranean atmosphere. Atmospheric concentrations of NMHCs range from below the detection limit (5 pptv) to a few ppbv and present a hydroxyl radical (OH) driven seasonal pattern with lower values during summer. The diel variability was also influenced by the reaction of the NMHC with the OH radical, exhibiting a nighttime maximum and a midday or early afternoon minimum. Long-lived compounds demonstrate higher concentrations under the influence of the northern sector (European continent), indicating that besides chemistry, transport significantly contributes to NMHCs levels in the area. Based on the observed NMHCs diurnal cycles, mean OH radical levels of 3.5 × 106 molecules cm−3 have been derived for May–October period. |
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| Keywords: | NMHCs Seasonal variability Diel variability Oxidation capacity Mediterranean |
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