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Identifier

000287070

Title

Συνεισφορά των νιτρικών ριζών στην οξειδωτική ικανότητα της ατμόσφαιρας της Ανατολικής Μεσογείου

Alternative Title

The contribution of nitrate radicals to the oxidizing capacity of the eastern Mediterranean atmosphere

Author

Βρεκούσης, Μιχάλης

Thesis advisor

Κανακίδου, Μαρία

Abstract

Free radicals are known to play an important role in atmospheric chemistry. It has been found that in most cases two radicals, the hydroxyl (OH) radical during daytime and the nitrate (NO3) during nighttime, by reacting with an important number of Volatile Organic Compounds (VOC) regulate the oxidation capacity of the atmosphere. However, measurements of OH and NO₃ have been proven difficult due to the high reactivity and the low concentration of these radicals. Consequently the relative contribution of these two radicals to the oxidation capacity of the atmosphere is still an open question. Simultaneous measurements of both radicals have been performed, for the first time to our knowledge, in a marine location in the southern Europe during the MINOS campaign (28 July - 18 August 2001). Nitrate radical was measured using the Differential Optical Absorption Spectroscopy (DOAS) operating with a light path totaling 10.4 km. Hydroxyl radical was measured by Chemical Ionization Mass-Spectrometer. OH radical ranges from less than 105 molecules.cm during night up to 2.910-3.7 moleculescm with a mean value of 5.610 molecules.-3.6.cm. NO-33 radical ranges from less than 310 moleculescm.7.-3 up to 90.110 molecules.7.cm-3 (on 12th of August) with an average value of 11.3.10 molecules7.cm. -3 The observed NO3 mixing ratios are presented in details. Their correlation with meteorological data obtained at the Finokalia station is investigated. The relative contribution of NO3 to the degradation process of dimethylsulfide (DMS), which is a very important marine biological source of Sulphur, is also presented. The current study was supported by an arithmetic box model which was firstly evaluated for its consistency with the experimental data. Afterwards it has been used to calculate parameters such as the OH radicals, a key species with a major contribution to the oxidizing capacity of the atmosphere, which is difficult to be monitored continiously.

Language

Greek

Subject

Homogeneous and heterogeneous chemistry

Nitrate radicals

Nitrogen cycle

Oxidizing capacity

Ετερογενής χημεία

Κύκλος αζώτου

Νιτρικές ρίζες

Ομογενής χημεία

Οξειδωτική ικανότητα