近年来珠三角地区大气中痕量氟氯烃(CFCs)的浓度水平与变化特征

用预浓缩-GC/MS方法研究了珠江三角洲大气中的CCl3F、CFC-12、CFC-113和CFC-114等4种痕量氟氯烷烃气体。结果表明,2005年珠江三角洲背景点鼎湖山大气中CFC-12和CFC-11的年平均浓度高于全球本底站,说明珠三角地区还存在一定CFC-11和CFC-12的排放源;CFC-113浓度水平则与全球本底站点浓度接近,且CFC-113和CFC-114在广州城区与鼎湖山差别不显著,表明区内其排放源强度应很小。观测日内广州和鼎湖山大气中四种CFCs的日变化幅度均较小,无明显的昼夜变化规律。广州市CFCs总体呈夏秋高、冬春低的特征,与城区致冷设备高温季节使用频率较大有关;鼎湖山则呈冬春高、夏秋低的特征,主要受扩散作用和季风的影响。初步分析显示,从1997年到2005年,CFC-11、CFC-12和CFC-114浓度总体呈现先上升后缓慢降低的趋势,而CFC-113的浓度一直逐年下降。

RECENT LEVELS AND TRENDS OF TRACE CHLOROFLUOROCARBONS (CFCs) IN THE PEARL RIVER DELTA REGION

Ambient chlorofluorocarbons(CFCs),including CFC-11,CFC-12,CFC-113 and CFC-114,were measured in the Pearl River Delta(PRD) region by the cryogenic pre-concentration-GC/MS method.The annual mean levels of CFC-12 and CFC-11 in the Dinghu Mountain,a regional background site in PRD,were higher than those in global background stations,indicating that there were emission sources of CFC-12 and CFC-11 in PRD.Levels of CFC-113 are approximate to those in global background stations,also the levels in urban areas of Guangzhou were almost close to those in the Dinghu Mountain for both CFC-113 and CFC-114,implying negligible emission of CFC-113 and CFC-114 in PRD.Diurnal variations are of small scale for the four CFCs both in Guangzhou and Dinghu Mountain without obvious patterns.CFCs in Guangzhou are higher in summer and autumn when air conditioning systems with CFCs as refrigerants are frequently used due to higher air temperature.The mean levels of CFCs in the Dinghu Mountain,however,are lower in summer and autumn than in winter and spring.The reason is that there are no emission sources in Dinghu and the levels there are mainly controlled and influenced by diffusion conditions and monsoons in PRD.Preliminary estimation shows that in PRD the atmospheric levels of CFC-12,CFC-11 and CFC-114 reached peak values around 2001 and decreased slowly afterwards,whereas the levels of CFC-113 monotonously decreased during 1997-2005.