基于气团72h后向轨迹输送特征,结合数值统计方法,对北京上甸子站2010~2014年瓶采样样品大气CH4进行污染/非污染数据筛分.结果表明约42%的数据筛分为污染数据,剩余数据则被认为是未受局地源汇污染、混合较为均匀的本底数据.基于这些本底数据对上甸子站大气 CH4本底浓度变化特征进行研究,结果表明:观测期间上甸子站大气 CH4本底浓度从1884.0×10-9(2010年)增长到1916.4×10-9(2014年),年均增长率为8.5 ×10-9/a.其季节变化特征与北半球平均状况类似,冬春季高、夏秋季低,高值出现在1~2月,低值出现在6~7月,季节振幅达32.8×10-9,主要与·OH 自由基浓度季节变化有关.此外,CH4本底浓度年均值及平均季节变化月均值均高于同纬度带海洋边界层水平及全球大气本底站瓦里关站.%Based on transport characteristics of air mass 72h back trajectories and statistical data filtered method, measurement data of atmospheric CH4 obtained at Shangdianzi (SDZ) regional background station in Beijing during 2010 and 2014 were analyzed for non-pollution and pollution events. About 42% of the complete data set was filtered as pollution data, and the remainders not polluted by local emission sources were flagged as "representative background data". Variations of background CH4 concentrations at SDZ station can be obtained based on the "representative background data". The annual mean background CH4 concentrations varied from 1884.0×10 2014 observed at SDZ, with the averaged growth rate of 8.5 ×10-9-9 in 2010 to 1916.4×10-9 in/a. Background atmospheric CH4presented obvious seasonal fluctuations, the higher and lower levels of seasonal CH4 cycle appeared in Jan-Feb and Jun-Jul, respectively,-9 with the peak-to-peak amplitude of 32.8×10. The seasonal variations of atmospheric CH4 might be owing to the variations of OH concentration in atmosphere. Furthermore, the annual and "detrended" monthly CH4 background concentrations observed at SDZ were higher than those of MBL at the same latitude and WLG global baseline station.
展开▼
