Determination of benzene, toluene, ethylbenzene, and xylenes in urban air of Thessaloniki, Greece.

In this study, quasicontinuous measurements of major aromatic volatile organic compounds (VOCs), which include benzene, toluene, ethylbenzene, and xylenes were carried out by means of an automatic gas chromatograph (GC-PID analyzer), in the urban air of Thessaloniki, at a mean level of 27 m above ground, during the years 2003 and 2004. The highest measured concentrations of aromatic hydrocarbons were observed during the winter period of the year. The data indicate that the annual mean benzene concentration levels were around 1 ppb, less than the E.U. annual limit value of 5.0 microg m(-3) (1.44 ppb at STP). The diurnal variation of aromatic hydrocarbons suggests that emissions from motor vehicles are their dominant source, at the commercial center of the city, while meteorological conditions (wind speed and direction) are important variables that control the atmospheric abundance of these pollutants, especially during stagnant weather conditions that favor the development of land-sea breeze circulations. Copyright 2006 Wiley Periodicals, Inc.