APEC前后北京SO2垂直分布特征及其对二次硫酸盐生成的影响  

Vertical distribution of SO_2 and its impact on the formation of secondary sulfate in urban Beijing during 2014 APEC summit

作　　者：陈辰[1,2] 高志球[2,3] 徐惟琦[2] 杜蔚[2] 韩婷婷[2] 王晴晴[2] 王自发[2] 张英杰[2,4] 石立庆[2] 孙业乐[2,3] 

机构地区：[1]南京信息工程大学,应用气象学院,南京210044 [2]中国科学院大气物理研究所,大气边界层物理和大气化学国家重点实验室,北京100029 [3]南京信息工程大学,气候与气象灾害协同创新中心,南京210044 [4]南京信息工程大学,大气物理学院,南京210044

出　　处：《环境科学学报》2016年第6期2131-2141,共11页Acta Scientiae Circumstantiae

基　　金：国家重点基础研究计划(No.2014CB447900);中国科学院战略性先导专项B(No.XDB05020501);环保公益性行业科研专项(No.201409001)~~

摘　　要：SO_2是北京大气中重要的污染气体.为探讨亚太经合组织(APEC)峰会前后北京大气SO_2的垂直分布及其对二次硫酸盐(SO_4^(2-))生成的影响,我们于2014年10月21日至11月30日在地面和北京325 m气象塔260 m高度处同步开展了气体SO_2和亚微米颗粒物中硫酸盐(SO_4^(2-))实时连续在线观测.结果显示,采暖前,北京地面SO_2浓度较低,但高层由于显著受到区域输送的影响浓度较高,两层污染物变化趋势也存在明显差异.采暖后,即APEC后,受本地供暖排放影响,SO_2和SO_4^(2-)浓度显著增加,两层的总体差异也相应减小,变化趋势也更为一致.湿度对SO_2的液相转化起关键作用.我们发现近地面SO_2的转化率(SOR)显著高于260 m,这主要与地面较高的湿度相关.事实上,SOR随着湿度增加而迅速增大,进一步凸显了湿度对SO_2液相氧化的影响.另外,我们也发现SO_2特别是260 m在低湿范围(RH<40%)内随湿度增加而逐渐升高,但在高湿范围(RH>50%)内则呈下降趋势,说明不同湿度范围内的来源或者生成机制可能有所不同.SO_4^(2-)和PM_(2.5)浓度均随着湿度的增加而增加,但不同湿度范围,增加速率不同.通过相关性和和后向轨迹分析表明,区域输送(特别是途经北京西部和南部的气团)和本地燃煤排放分别是采暖前后污染物的主要来源.SO2is an important pollutant in the atmosphere. To investigate the vertical distribution of atmospheric SO2 and its impact on the formation ofsecondary sulfate（ SO4^2-） during 2014 APEC summit,gaseous SO2 and submicron sulfate were measured simultaneously in real-time at the ground level and a height of 260 m on the Beijing 325 meteorological tower from October 21 to November 30,2014. The concentration of SO2 was relatively low at the ground level before heating period due to low emissions from local sources,whereas it was much higher at 260 m owing to the influences of regional transport. As a result,the variations of SO2 and sulfate at the two heights were substantially different. However,the differences between the two heights were smaller showing similar time trends after APEC. The relative humidity（ RH） played an important role in affecting the variations of SO2 and SO4^2-.The higher RH at ground level facilitated the aqueous-phase processing of SO2 to form SO4^2-,leading to higher sulfur oxidation ratio（ SOR） at ground level than 260 m. Indeed,SOR showed a substantial increase with the increase of humidity. In this study,we found that SO2,especially at 260 m,increased with RH at low RH levels（ RH〈40%）,while decreased gradually at high RH levels（ RH〉50%）. These results illustrated different sources and formation mechanisms at different RH levels. Both SO4^2- and PM（2.5） were observed to increase as a function of RH,yet with different increasing rates at different RH levels. The correlation and backward trajectory analysis suggested that regional transport（ especially air masses passing through the south and west of Beijing） and local coal emissions were the main sources before and during heating season,respectively.

关 键 词：APEC 北京 SO2 硫酸盐 湿度 

分 类 号：X511[环境科学与工程—环境工程]