Seasonal and diurnal variations of BTEX compounds in the semi-urban environment of Orleans, France.

Atmospheric concentrations of BTEX (benzene, toluene, ethylbenzene and xylene) were measured at a semi-urban site in Orleans, France, from October 2010 to August 2011. Air samples were collected by multi-bed adsorbent tubes. The BTEX concentrations were determined by thermal desorption-gas chromatography-mass spectrometry detector (TD-GC-MSD) technique. The average concentrations of the total measured BTEX during spring, summer, autumn and winter were 724.2, 337.4, 682.3, 823.0ppt, respectively. Maximal values for their diurnal variations usually happened during rush hours in the morning and late afternoon, and the minimal values in the daytime usually happened in around noontime. The diurnal variation of BTEX in four seasons and the correlations between BTEX and NO indicated that vehicular exhaust might be the primary source of BTEX. Benzene was found in relatively high levels and the B/T ratio was significant high in spring, indicating an irregular emission source of benzene other than traffic-related emissions.