[Measurement and study on the atmospheric trace BTEX in Beijing].

Atmospheric trace BTEX in Beijing was observed by a gas chromatography/mass spectrometry in the latest 4 years. The diurnal, lunar and annual concentration variations of these pollutants were reported. In winter and spring, the diurnal profiles exhibited two peak values corresponding to the daily rush hours 08:00-10:00 am and 17:00 pm; in autumn, there was the third peak value in the night at 22:00; the highest concentration of BTEX in summer appeared in the midday and totally three daily maxima were in the sampled day. In the lunar variation of the BTEX from 2000 to 2002, the average concentration was about (44.1 +/- 24.5) nmol/mol (C unit), and the seasonal maximum value appeared in summer. The trend of BTEX was decreased greatly from 1999 to 2002.