Title: Seasonal evolutions of ozone (O3) and its nitrogen precursors (NO, NO2) in urban Sfax (Tunisia)

Authors: C. Azri, A. Tlijani, H. Abida, A. Maalej, K. Medhioub

Addresses: Faculte des Sciences de Sfax, Departement des Sciences de la Terre, BP 802, 3018 Sfax, Tunisia. ' Faculte des Sciences de Sfax, Departement des Sciences de la Terre, BP 802, 3018 Sfax, Tunisia. ' Faculte des Sciences de Sfax, Departement des Sciences de la Terre, BP 802, 3018 Sfax, Tunisia. ' Faculte des Sciences de Sfax, Departement de Physique, BP 802, 3018 Sfax, Tunisia. ' Institut Preparatoire aux Etudes d'Ingenieurs de Sfax (IPEIS), BP 805, 3018 Sfax, Tunisia

Abstract: Seasonal evolution of ozone (O3) and its nitrogen precursors (NO, NO2) in downtown Sfax (Tunisia) was monitored. Nitrogen oxides are shown to be closely related to local vehicle sources. Seasonal ozone levels, however, are shown to be dependent on regional meteorological conditions. High ozone levels are due to the effect of anticyclones and stratosphere intrusions (cut-off lows). Low levels are associated with cyclonic conditions of small vertical range of motion. Other than these particular conditions, ozone levels are shown to be relatively higher in fall and winter seasons, characterised by a very steady atmosphere. Overall, the examined meteorological conditions, the ozone concentrations observed in downtown Sfax are characterised by clear day/night cycles, which can be explained by the significant ventilation of the region.

Keywords: ozone levels; nitrogen precursors; traffic sources; mixing layer; cyclones; anticyclones; Tunisia; nitrogen oxides; vehicle emissions; air quality; air pollution.

DOI: 10.1504/IJEP.2008.021132

International Journal of Environment and Pollution, 2008 Vol.35 No.1, pp.71 - 89

Published online: 05 Nov 2008 *

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