南京北郊VOCs对臭氧和二次有机气溶胶潜在贡献的研究

2013年3月1日~2014年2月28日采用GC5000在线气相色谱仪对南京北郊大气环境中的挥发性有机物(VOCs)进行了为期一年的连续监测,分析了VOCs的组成特征及季节、日变化规律,并结合PMF受体模型,采用最大增量反应活性(MIR)系数及气溶胶生成系数(FAC)分析了VOCs及其各来源的O3和SOA生成潜势.结果显示,南京北郊大气环境中TVOCs小时平均体积分数为45.63×10-9,TVOCs及各组分浓度呈现秋冬季高、夏季低的季节变化特征和双峰结构的日变化规律.SOA总生成量约为2.07μg/m3,芳香烃对其贡献率最大,占95.93%,其中的苯系物是生成SOA的优势物种;烯烃对OFP的贡献最大,接近65%;烷烃虽为VOCs的优势组分,却并非OFP和SOA的主要贡献者.不同季节VOCs的受体模型解析结果显示,工业排放和汽车尾气是南京北郊最主要的VOCs来源.富含苯系物的VOCs来源对SOA的贡献最大,对OFP贡献最大的则为富含乙、丙烯及异戊二烯的VOCs来源;春、秋、冬三季汽车尾气及工业排放(包括石化工业)二源对大气中的VOCs浓度、SOA的贡献及OFP的贡献影响最为显著,而夏季溶剂使用及植物源对SOA及OFP的贡献不容忽视.

Potential contribution of secondary organic aerosols and ozone of VOCs in the Northern Suburb of Nanjing

A continuous observation campaign was carried out with the GC5000 volatile organics online monitoring system from March 1, 2013 to February 28, 2014 in the northern suburb of Nanjing, characteristics of their composition, seasonal variation and diurnal variation were analyzed, PMF, the maximum incremental reactivity coefficient (MIR)and the fractional aerosol coefficients (FAC)were used to estimate the potential formation of secondary organic aerosols (SOA) and O3 from VOCs and their sources. The results showed that the hourly average mixing ratio of the TVOCs was 45.63×10-9. There was an obvious seasonal cycle of VOCs, with the maximum in winter and autumn and minimum in summer. Diurnal variation of VOCs mixing ratios showed a very clear bimodal structure. The SOA concentration values obtained by the VOCs were 2.07μg/m3, as the largest contributor, aromatic hydrocarbons accounted for 95.93% and BTEX are the dominant species. Alkenes contributed the largest parts of the ozone formation potential (OFP), closing to 65%. Although alkanes were the most abundant components of VOCs, it is not the main contributor of OFP and SOA. The results from different seasons of receptor model showed that vehicle emissions and industrial emissions were main sources of VOCs in the northern suburb of Nanjing. The sources which contain rich BTEX contributed the largest parts of SOA. Moreover, the sources which contain rich ethylene, propylene and isoprene are the largest contributor of OFP. Vehicle emissions and industrial emissions (including the petrochemical industry) were the main contributor to the concentrations of VOCs, SOA and OFP in spring, autumn and winter. As the influential sources to SOA and OFP, solvent source and plant source should not be overlooked in summer.