广州市城区大气中HCFC-22的变化特征及其与常规大气污染物的比较

利用低温预浓缩-GC/MSD研究了广州市大气中痕量的一氯二氟甲烷(HCFC-22),并且将其变化特征与SO2、NO2和可吸入颗粒物(PM10)等一般空气污染物进行了比较.结果表明,广州市大气中HCFC-22的年平均浓度值是一些全球本底站观测值的3倍左右,表明广州存在较强的HCFC-22排放源,可能与HCFC-22作为制冷剂在城区较大量使用有关.广州市HCFC-22呈现出夏秋季高、冬春季低的特征,这主要与HCFC-22排放的季节性差异有关.而广州市大气一般空气污染物SO2、NOx、PM10和CO的浓度水平则与HCFC-22相反,呈现夏秋季低、冬春季高的特征,主要受扩散条件与季风影响.HCFC-22日变化幅度在夏季远大于冬季,变化规律整体与SO2、NOx和PM10大致相似,夏季呈双峰特征,冬季则呈单峰特征,但与常规污染物不同的是,夏季HCFC-22在17:00～20:00家用空调使用高峰期呈现异常高值.

Variation of atmospheric HCFC-22 in comparison with criteria air pollutants in urban Guangzhou

Atmospheric HCFC-22 in urban Guangzhou was analyzed by the cryogenic pre-concentration-GC-MSD method, and its variation characteristics were compared to those of criteria air pollutants like SO2, NOx, PM10 and CO. The detected annual mean level of HCFC-22 was about 3 times of those in the global background observatories, implying strong local emission sources of HCFC-22 used as cooling agents in urban Guangzhou. The levels of HCFC-22 were much higher in summer and autumn than in winter and spring, mainly due to the seasonality of its emission. The levels of SO2, NOx, PM10 and CO, on the contrary, were higher in spring and winter than in autumn and summer, mainly due to the difference in dispersion conditions and monsoons in the region. HCFC-22 showed much larger diurnal variation in summer than in winter, but shared similar diurnal pattern, which was bimodal in summer and one-peaked in winter, as SO2, NO2 and PM10. One distinct HCFC-22 diurnal pattern was that it had unusually high levels in peak running hours of domestic air-conditioners (17:00- 20:00) during summer days.