南京北郊秋季VOCs及其光化学特征观测研究

Characteristics of VOCs and Their Photochemical Reactivity in Autumn in Nanjing Northern Suburb

采用GC5000挥发性有机物在线监测系统和EMS系统,于2011年11月在南京北郊开展了为期一个月的连续观测,分别测量了大气中56种VOCs组分和反应性气体(NOx、CO和O3).结果表明,南京北郊的VOCs小时平均体积分数大约在48.17×10-9,日变化呈明显双峰型特征,受机动车影响比较显著,极小值出现在下午16:00,白天与O3浓度曲线呈负相关;VOCs的平均OH消耗速率常数约为3.26×10-12cm3.(molecule.s)-1,最大增量反应活性约为3.26 mol·mol-1;烯烃对OH消耗速率(LOH)和臭氧生成潜势(OFP)贡献率最大,芳香烃次之,而烷烃在大气中含量最为丰富,却并不是LOH和OFP主要贡献者;VOCs关键活性组分是乙烯、丙烯、1-丁烯、间,对-二甲苯及异戊二烯等物质;臭氧生成过程处于VOCs控制区.

A continuous observation campaign was carried out with the GC5000 volatile organics online monitoring system and the EMS system for one month in November 2011 in the northern suburb of Nanjing, and 56 VOC components and reactive gases （NOx, CO and O3） were measured. The results showed that the VOC hourly averaged volume fraction in Nanjing northern suburb was about 48.17×10-9, and the minimum value of VOCs occurred at 16：00. The diurnal variation showed a bimodal characteristic, indicating the significant impact of motor vehicle emission. The VOC concentration and O3 concentration exhibited negative correlation in the day-time. The average OH consumption rate of VOCs was approximately 3.26×10-12 cm3·（molecule·s）-1, and the largest incremental reactivity was about 3.26 mol·mol-1; Alkenes contributed the largest parts of the OH consumption rate （LOH） and the ozone formation potential （OFP）, followed by aromatics. Although alkanes were the most abundant components of VOCs in the atmosphere, it is not the main contributor of LOH and OFP.The key active components in VOCs were ethylene, propylene, 1-butene, m,p-xylene and isoprene, etc. The dominant factor of ozone formation was VOCs in this observation.