在线表征萘二次有机气溶胶硝基多环芳烃

On-line characterization of nitrated polycyclic aromatic hydrocarbons in naphthalene secondary organic aerosol

硝基多环芳烃(NPAHs)广泛存在于大气气溶胶中,是棕色碳的重要组成部分.萘和其他多环芳烃是NPAHs的重要前体物.为研究NO_(2)对NPAHs形成的影响,本文利用气溶胶激光飞行时间质谱仪(ALTOFMS)在线测定不同NO_(2)浓度下萘光氧化形成的二次有机气溶胶(SOA)的NPAHs组分.实验结果表明,NO_(2)对NPAHs的产生和萘SOA的形成有促进作用.通过ALTOFMS在线检测、模糊C均值(FCM)聚类分析,结合离线电喷雾电离质谱验证,测得萘酚和羰基化合物是不存在NO_(2)时萘SOA粒子主要成分,而通过OH-萘加合物和萘酚硝化产生的硝基萘、二硝基萘、硝基萘酚和二硝基萘酚及其衍生物是NO_(2)存在时萘SOA粒子的主要组分.这为城市大气高浓度NOx背景下,研究NPAHs的化学组分和形成机理提供了实验依据.

Nitrated Polycyclic aromatic hydrocarbons(NPAHs)widely exist in atmospheric aerosol particles and are important components of brown carbon.Naphthalene and other polycyclic aromatic hydrocarbons(PAHs)are vital precursors of NPAHs.To explore the effect of NO_(2)on formation of NPAHs,the NPAHs components in secondary organic aerosol(SOA)formed from the photooxidation of naphthalene with different concentrations of NO_(2)were on-line measured using aerosol laser time-of-flight mass spectrometer(ALTOFMS)in this study.Experimental results demonstrated that NO_(2)had promotion effect on the generation of NPAHs and formation of SOA.Using ALTOFMS on-line detection,followed by Fuzzy C-means(FCM)algorithm cluster analysis,and combined with off-line electrospray ionization mass spectrometer verification,it was determined that naphthols and carboxyls were the main components of naphthalene SOA particles without NO_(2),and nitro-naphthalene,dinitro-naphthalene,nitro-naphthol,dinitro-naphthol and their derivatives via the nitration of OH-naphthalene adduct and naphthol products of naphthalene were identified as the major constituents of SOA with NO_(2).These provided the experimental basis for exploring the chemical components and formation mechanism of NPAHs under the background of high NOx concentration in urban atmosphere.