长沙市郊大气CH4浓度变化特征

为研究长江中游地区大气CH4浓度(体积分数)变化特征,2007~2011年,利用内表面硅烷化的苏玛罐采样、GC/FID方法对长沙市郊空气样品中CH4浓度进行测定分析,并结合地面气象要素和后向轨迹,探讨CH4浓度变化特征与源汇的关系.结果表明,观测期间,大气CH4年平均浓度变化范围在2 012×10-9~2 075×10-9之间,季节变化特征为秋季高,春季低,浓度年较差为152×10-9.通过分析地面风和气团传输对长沙市郊大气CH4的影响表明,长沙市郊大气CH4浓度受西北风和偏南风交替控制,贡献率分别为41.1%和20.4%;引起CH4抬升的地面风包括:4个季节中的W-WNW-NW、夏季ESE-SE和冬季S,春夏季节S则导致CH4浓度降低;夏秋季节源自水稻产区的气团、冬春季节源自能源消费量较高地区的气团,对长沙市郊CH4浓度的抬升有显著贡献,南方长距离传输气团有利于CH4扩散和清除.

Distribution of CH4 in the Suburb of Changsha City, China

To study the variation of atmospheric CH₄ concentration in the Yangtze River region, air samples which collected weekly using flasks from the suburb of Changsha City from 2007 to 2011 and the CH₄ concentration was measured by gas chromatography. CH₄ concentrations were analyzed combined with ground meteorological elements and backward trajectories to explore the CH₄ concentration variations with source-sink relationships. The results showed that during the observation period, the annual mean concentration of CH₄ was in the range 2012×10^-9-2075×10^-9 (volume mixing ratio, the same below). The difference between the maximum and minimum monthly mean of CH₄ concentrations was 152×10^-9, with the highest concentration observed in autumn and the lowest in spring. Analysis of the surface wind showed that the concentration of CH₄ was controlled by northwest wind and southerly winds alternately, and the contribution rate was 41.1% and 20.4%, respectively. Surface winds causing CH₄ concentration uplift included W-WNW-NW in all four seasons, ESE-SE in summer and S in winter; while S in spring and summer have resulted in the decrease of CH₄ concentration. Analysis of the air mass transport showed that the concentration of CH₄ in the suburb of Changsha was significantly contributed by air masses from rice-producing areas in summer and high energy consumption areas in winter, and was cleared by air masses of long-distance transport from southern district.