[Measurement on the atmospheric CO concentration in Beijing]

Carbon monoxide is considered as a criteria pollutant in urban areas, and plays an important role in photochemistry of regional and urban environments. Continuous measurement of CO at the meteorological observation tower in IAP-CAS (39 degrees 9'N, 116 degrees 4'E) from January to December 2004 was carried out in Beijing, using HP5890II gas chromatography (GC) with flame ionization detector(FID), at measurement frequency of 10 minutes. The diurnal variations of the atmospheric CO concentration at the urban area in Beijing show a very clear cycle with two peaks, one appears about 07:00 to approximately 08:00 in the morning and the other is at 22:00 to approximately 23:00 in the evening, with the maximum of 13.8mg x m(-3), 17.1 mg x m(-3), respectively. However, diurnal variations in four seasons are not very same. The variation range is bigger in winter and autumn seasons than that in summer and spring seasons. The concentration in fall and winter seasons dropped more quickly than that in spring and summer seasons after 07:00 to approximately 08:00. CO concentration diurnal variations are believed to be due to the combination results of surface emission sources and meteorological factors. The results indicate that there is an obviously seasonal cycle of CO concentration, with the maximum in Dec (4.0 +/- 3.4)mg x m(-3) and minimum in May (1.7 +/- 0.7)mg x m(-3). The average concentration of CO during the whole year is (2.6 +/- 1.9) mg x m(-3). The average concentration of CO during the heating period is (3.5 +/- 2.6)mg x m(-3), and (2.2 +/- 1.2) mg x m(-3) during the period without heating.