北京市大气中CO的浓度变化监测分析

CO是城市大气中一种重要的污染物,在城市和区域的光化学反应中起着重要的作用.用装配氢火焰离子化检测器(FID)的HP5890II气相色谱(GC)方法,以每10min的采样频率,在北京中科院大气物理研究所325m气象环境观测铁塔上(39°9′N,116°4′E),对北京城市大气CO浓度进行了连续监测,时间为2004-01～2004-12.结果显示北京城市大气CO浓度日变化呈双峰型,1d之中出现2个高峰期,早晨07:00～08:00和夜晚22:00～23:00,最高浓度值分别达到13.8mg·m-3,17.1mg·m-3.不同季节CO的日变化存在差异:冬季、秋季的日变化幅度大,而夏季、春季的日变化幅度小.秋季、冬季早晨上班高峰期后CO浓度下降快,春季、夏季上班高峰期后CO浓度下降慢.CO的这种日变化是由地表排放源和气象条件共同决定的.另外,CO存在明显的季节变化,总的表现为浓度最高值出现在冬季12月份(4.0±3.4)mg·m-3,浓度最低值出现在5月份(1.7±0.7)mg·m-3.整个观测期间1a的平均浓度为(2.6±1.9)mg·m-3,采暖期平均浓度为(3.5±2.6)mg·m-3,非采暖期平均浓度为(2.2±1.2)mg·m-3.

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.