The Concentration Characteristics And Source Apportionment Of VOCs In Nanjing Northern Suburb

In this study, concentrations of VOCs were observed at northern suburban area of Nanjing from September2011to August2012by on-line GC-FID instruments. Combined with the data of wind during the same period, the concentration characteristics and reactivity characteristics of VOCs were investigated. Basing on the concentrations of ozone and its precursor (NO, NO2, CO) measured by American EMS system in autumn2011, the effects of ozone precursors on ozone formation were analyzed. Principal component analysis/absolute principal component scores (PCA/APCS) receptor model was applied for source identification of VOCs in four wind direction quadrants (northeast-NE, southeast-SE, southwest-SW and northwest-NW) and in all quadrant, and positive matrix factorization (PMF) receptor model was applied to analyze the source contribution of VOCs in four seasons.Basing on the measured concentration of VOCs, alkanes varied between11.8±6.9and19.6±11.6ppbv, alkenes varied between9.0±4.0and12.4±6.3ppbv, aromatics varied between4.5±2.7and8.7±7.9ppbv. The concentration of ambient VOCs was simultaneously affected by the transport of VOCs, meteorological conditions and photochemical reactions, resulting in no obvious seasonal pattern in this region. The concentrations of VOCs were higher at night than in daytime. The analysis of VOC reactivity showed that alkenes played the most important role in determining ozone formation, accounting for about60%. The monthly variation of propylene-equivalent concentration and ozone formation potential showed that the contribution of VOCs to ozone formation was higher in spring (April and May) and autumn (October and November). Furthermore, it is deduced that the ozone formation was under VOC-sensitive regime in northern Nanjing in autumn through VOCs/NOx ratio.The results show that in autumn and winter the concentration of total VOCs in different quadrants were different. In NE quadrant vehicle related emission (-42%) is the most significant source; Solvent usage and industrial emissions (～55%) is the dominant source in SE quadrant; in NW quadrant the main sources contribute almost the same as～33%. The dominant sources in different quadrants are different, suggesting that in this region the wind directions have great influence on the source contributions of VOCs. In terms of the total VOCs in this region, the dominant sources were vehicle related emissions (-39%) and solvent usage and industrial emissions (-36%).The two significant sources in this region were industrial related emission and vehicle related source in each season. They accounted for27%and28%in autumn,44%and32%in winter,45%and26%in spring,38%and29%in summer. It is found that the vehicle related source contributed almost the same to VOCs in each season as28%-32%, and the contribution of industrial related emission was lager in winter and spring than in summer and autumn.