The formation of SOA and chemical tracer compounds from the photooxidation of naphthalene and its methyl analogs in the presence and absence of nitrogen oxides
The formation of SOA and chemical tracer compounds from the photooxidation of naphthalene and its methyl analogs in the presence and absence of nitrogen oxides
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DOI：
10.5194/acp-12-8711-2012
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发表时间：
2012-01-01
影响因子：
6.3
通讯作者：
Docherty, K. S.
中科院分区：
文献类型：
--
作者：
Kleindienst, T. E.;Jaoui, M.;Docherty, K. S.
为了研究萘及其甲基类似物，1-甲基萘和2-甲基萘（分别为1- mn和2-MN）的光氧化形成的二次有机气溶胶（SOA），进行了实验室雾霾室实验。实验室烟雾室以流动模式照射，以确保在合理低的反应物浓度和存在或不存在氮氧化物的情况下充分收集气溶胶。邻苯二甲酸和甲基类似物被确定后，BSTFA衍生的气溶胶提取物。对这些化合物进行了检测，以确定它们是否可以作为合理的分子示踪剂，以估计这些前体对环境PM2.5的贡献。还测量了萘、1-MN和2-MN的二次有机气溶胶的气溶胶参数。采用质量分数法来确定可应用于环境气溶胶中邻苯二甲酸浓度的因素，假设主要来源的贡献可以忽略不计。邻苯二甲酸酐的摄取（和水解）进行了测试，发现在有和没有在线剥蚀器的过滤器测量中代表了一个中等的过滤器伪影。本研究提供了机会来检查使用邻苯二甲酸的真实标准与替代标准的差异。虽然基于替代化合物的质量分数略低，但差异在很大程度上不重要。根据邻苯二甲酸标准，在存在和不存在氮氧化物的情况下，分别测定萘的质量分数为0.0199（推荐用于环境样品）和0.0206。根据实验室数据确定的质量分数应用于发现邻苯二甲酸的环境样品，并表示为“萘”，因为发现邻苯二甲酸是在颗粒相中由其他甲基萘产生的。质量分数值应用于2005年加州河滨市SOAR研究和2010年帕萨迪纳市CalNex研究期间采集的样本。在这两项研究中，除了邻苯二甲酸外，还检测到邻苯二甲酸的一种未确定的异构体。实验室实验保留时间和质谱表明，该化合物的主要前体是2-MN。在CalNex研究中，发现2环前体多环芳烃（如萘）的SOC值范围从低于检测限到20 ngC m(-3)，结合实验室质量分数数据表明，由于2环多环芳烃，SOA的上限约为1 μ g m（-3）。在为期一个月的CalNex研究过程中的时间数据表明，在研究期间，邻苯二甲酸的主要来源可能可以忽略不计。然而，考虑到潜在的水解反应或邻苯二甲酸酐（随后水解）被吸收到收集介质上，该值仍然必须被视为上限。
Laboratory smog chamber experiments have been carried out to investigate secondary organic aerosol (SOA) formation from the photooxidation of naphthalene and its methyl analogs, 1- and 2-methylnaphthalene (1-MN and 2-MN, respectively). Laboratory smog chamber irradiations were conducted in a flow mode to ensure adequate collection of the aerosol at reasonably low reactant concentrations and in the presence and absence of nitrogen oxides. Phthalic acid and methyl analogs were identified following BSTFA derivatization of the aerosol extract. These compounds were examined to determine whether they could serve as reasonable molecular tracers to estimate the contributions of these precursors to ambient PM2.5. Measurements were also made to determine aerosol parameters from secondary organic aerosol from naphthalene, 1-MN, and 2-MN.A mass fraction approach was used to establish factors which could be applied to phthalic acid concentrations in ambient aerosols, assuming a negligible contribution from primary sources. Phthalic anhydride uptake (and hydrolysis) was tested and found to represent a moderate filter artifact in filter measurements with and without in-line denuders. This study provided the opportunity to examine differences using authentic standards for phthalic acid compared to surrogate standards. While the mass fraction based on a surrogate compounds was somewhat lower, the differences are largely unimportant. For naphthalene, mass fractions of 0.0199 (recommended for ambient samples) and 0.0206 were determined in the presence and absence of nitrogen oxides, respectively, based on phthalic acid standards.The mass fractions determined from the laboratory data were applied to ambient samples where phthalic acid was found and expressed "as naphthalene" since phthalic acid was found to be produced in the particle phase from other methylnaphthalenes. The mass fraction values were applied to samples taken during the 2005 SOAR Study in Riverside, CA and 2010 CalNex Study in Pasadena. In both studies an undetermined isomer of methylphthalic acid was detected in addition to phthalic acid. Laboratory experiment retention times and mass spectra suggest that the major precursor for this compound is 2-MN. For the CalNex Study, SOC values for the 2-ring precursor PAHs (as naphthalene) were found to range from below the detection limit to 20 ngC m(-3) which with the laboratory mass fraction data suggests an upper limit of approximately 1 mu g m(-3) for SOA due to 2-ring PAHs. Temporal data over the course of the one-month CalNex study suggest that primary sources of phthalic acid were probably negligible during this study period. However, the values must still be considered upper limits given a potential hydrolysis reaction or uptake of phthalic anhydride (subsequently hydrolyzed) onto the collection media.