Formation of highly oxygenated low-volatility products from cresol oxidation
Formation of highly oxygenated low-volatility products from cresol oxidation
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DOI：
10.5194/acp-17-3453-2017
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发表时间：
2016-10
影响因子：
6.3
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中科院分区：
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抽象的。甲苯的羟基自由基（OH）氧化产生保环产物：甲酚和苯甲醛，以及开环产物：双环中间体化合物和环氧化物。在这里，在实验室室实验中鉴定了甲酚和苯甲醛的第一代和新一代 OH 氧化产物。对于苯甲醛，鉴定出第一代保环产物，但未检测到新一代产物。对于甲酚，低挥发性（饱和质量浓度，C* ∼ 3.5 × 104 − 7.7 × 10−3 µg m−3），鉴定出第一代和后来的环保留产物。随后 OH 加成到邻甲酚的芳环上，生成羟基、二羟基和三羟基甲基苯醌以及二羟基、三羟基、四羟基和五羟基甲苯等化合物。 These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real-time mass spectrometry (DART-MS).我们的数据表明，从二羟基甲苯生产三羟基甲苯的产率很高。虽然由于无法获得可靠的标准而无法报告确切的产率，但我们发现从二羟基甲苯到三羟基甲苯的产率约为 0.7（等于报道的从邻甲酚得到二羟基甲苯的产率；Olariu 等，2002）与低 NO 条件下邻甲酚氧化的实验结果一致。这些结果表明，尽管甲酚途径仅占甲苯氧化产物的~20%，但由于低挥发性产物的形成，它是很大一部分（~20-40%）甲苯二次有机气溶胶（SOA）的来源。
Abstract. Hydroxyl radical (OH) oxidation of toluene produces ring-retaining products: cresol and benzaldehyde, and ring-opening products: bicyclic intermediate compounds and epoxides. Here, first- and later-generation OH oxidation products from cresol and benzaldehyde are identified in laboratory chamber experiments. For benzaldehyde, first-generation ring-retaining products are identified, but later-generation products are not detected. For cresol, low-volatility (saturation mass concentration, C* ∼ 3.5 × 104 − 7.7 × 10−3 µg m−3), first- and later-generation ring-retaining products are identified. Subsequent OH addition to the aromatic ring of o-cresol leads to compounds such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones and dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes. These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real-time mass spectrometry (DART-MS). Our data suggest that the yield of trihydroxy toluene from dihydroxy toluene is substantial. While an exact yield cannot be reported as authentic standards are unavailable, we find that a yield for trihydroxy toluene from dihydroxy toluene of ∼ 0.7 (equal to the reported yield of dihydroxy toluene from o-cresol; Olariu et al., 2002) is consistent with experimental results for o-cresol oxidation under low-NO conditions. These results suggest that even though the cresol pathway accounts for only ∼ 20 % of the oxidation products of toluene, it is the source of a significant fraction (∼ 20–40 %) of toluene secondary organic aerosol (SOA) due to the formation of low-volatility products.