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Identifier

000292798

Title

Μη μεθανικοί Yδρογονάνθρακες στην Aτμόσφαιρα της Ανατολικής Μεσογείου: Παράγοντες που Eπηρεάζουν τα Eπίπεδα τους και Συμμετοχή στη Οξειδωτική Ικανότητα της Ατμόσφαιρας

Alternative Title

Non Methane hydrocarbons above the Eastern Mediterranean. Factors controlling their levels and contribution to the oxidative capacity of the atmosphere

Author

Λιακάκου, Ελένη

Thesis advisor

Μιχαλόπουλος, Νίκος

Abstract

The present work focuses on the study of light non methane hydrocarbons (NMHCs) in the Eastern Mediterranean. In the frame of this work a gas chromatograph equipped with flame ionization detector and a preconcentration unit was applied at a natural marine site from September 2003 to February 2006. NMHCs depicts a distinct seasonal cycle characterized by winter maximum and summer minimum due to photochemistry. Isoprene is an exception to this seasonal pattern as it presents a summer maximum which is due to photosynthetic induced production. Photochemistry also controls the diurnal variability of NMHCs as most of the species present a mid-day minimum. Isoprene is again an exception, as maximum occurs during mid-day due to enhanced photosynthetic production. Apart chemistry hydrocarbons level (especially the long-lived compounds >1 day ) is also determined by meteorology, namely air masses origin and wind speed. On the other hand due its extremely short lifetime (35min<τ<3.5h), isoprene levels are mainly explained by local production. An oceanic source with emission ranging from 108 - 6x109 molecules cm-2 s-1 has been estimated for isoprene from this data-set. Taking into account NMHCs seasonal and diurnal cycles, daytime annual mean atmospheric Cl atoms and OH radicals levels are estimated to be 2.7x103 atoms/cm3 and 3.5x106 molecules/cm3 respectively. As it concerns the OH radical level, the above estimation converges with box model simulations of 3.8x106 molecules/cm3. Finally, NMHCs and especially isoprene is affecting the oxidation capacity of the atmosphere. According to chemical box model calculations, during daytime the isoprene observed under marine conditions is reducing OH radicals by up to 26%, and 13%, depressing NO3 levels up to 25% during night time, whereas, it can increase the sum of peroxy radicals up to 300-400%.

Language

Greek

Subject

Diurnal variation

Eastern Mediterranean

Isoprene

Marine source

Meteorology - photochemistry influence

Non methane hydrocarbons

Oxidation capacity of the atmosphere

Seasonal variation

Ανατολική Μεσόγειος