北京市CFCs和CCl_4的浓度水平与变化趋势

采用预浓缩-GC/MS方法对2009年4—8月北京市大气中CFC-11,CFC-12,CFC-113,CFC-114和CCl45种主要消耗臭氧层物质进行了监测.结果表明:观测期内北京市大气中φ(CFC-11),φ(CFC-12)和φ(CCl4)的平均值高于全球本底站观测值,而φ(CFC-113)和φ(CFC-114)与全球本底水平相当,其原因是这5种物质在我国的排放水平差异所致,其中CFC-11,CFC-12和CCl4仍存在一定量的排放.不同季节的日变化分析表明,4月5种物质的体积分数日变化趋势平缓,而8月观测日内基本呈现出夜间物质的体积分数高于白天的特征.8月φ(CFC-11),φ(CFC-12)和φ(CCl4)的平均值比4月高,这可能是由于8月的温度较高,致使这3种物质现有排放源的排放量增加.

Concentrations and Trends of CFCs and CCl[STHZ]4[STBZ] in the Atmosphere of Beijing

The atmospheric concentrations of CFC-11, CFC-12, CFC-113, CFC-114 and CCl₄ in Beijing were measured using the cryogenic preconcentration-GC/MS method from April to August 2009. The results showed that the mean concentrations of CFC-11, CFC-12 and CCl₄ over the sampling period in Beijing were higher than those obtained in global background stations, while the levels of CFC-113 and CFC-114 in Beijing were close to those in global background stations. This was mainly because the former three substances are still being released in considerable amounts in China, while the latter two were neither banked nor emitted at large scale. Diurnal variations of these substances in April were small, but in August the night concentrations of these substances were significantly higher. The mean levels of CFC-11, CFC-12 and CCl₄ were lower in April than in August, when the higher temperatures caused greater emissions of the substances.