Online and offline mass spectrometric study of the impact of oxidation and ageing on glyoxal chemistry and uptake onto ammonium sulfate aerosols.
Online and offline mass spectrometric study of the impact of oxidation and ageing on glyoxal chemistry and uptake onto ammonium sulfate aerosols.
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DOI：
10.1039/c3fd00051f
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发表时间：
2013-12
影响因子：
3.4
通讯作者：
J. Hamilton;M. Baeza_Romero;E. Finessi;R. Andrew;Rickard;R. Healy;S. Peppe;T. J. Adams;S. M
中科院分区：
文献类型：
--
作者：
J. Hamilton;M. Baeza_Romero;E. Finessi;R. Andrew;Rickard;R. Healy;S. Peppe;T. J. Adams;S. M
最近的实验室和模型研究表明，气溶胶对乙二醛 (GLY) 等低分子量 α-二羰基化合物的反应性吸收是二次有机气溶胶 (SOA) 的潜在重要来源。然而，之前的研究对于 GLY 的吸收程度、所涉及的机制以及影响颗粒形成的物理化学因素存在分歧。在本研究中，研究了实验室散装溶液和气溶胶颗粒中 GLY 与硫酸铵 (AS) 的化学反应。首次将单粒子技术气溶胶飞行时间质谱 (ATOFMS) 与离线（ESI-MS 和 LC-MS2）质谱技术结合使用，研究由 OH 水溶液光氧化和溶液在黑暗中老化引起的 GLY 和 AS 本体溶液组成的变化。在这些实验室研究中获得的质谱离子被用作在室外欧洲光反应器 (EUPHORE) 的黑暗和自然照射条件下进行的一系列实验中 AS 种子颗粒中 GLY 吸收和化学的示踪剂。 ATOFMS 未检测到形成的乙二醛低聚物，这可能是由于激光波长吸收效率低。然而，GLY 与氨反应形成的有机氮化合物的存在得到证实，导致气溶胶的吸收效率增加，这增加了 ATOFMS 成功电离的颗粒数量。先前在实验室水溶液中鉴定出的许多吸光有机氮物质，包括 1H-咪唑、1H-咪唑-2-甲醛、2,2'-双咪唑和乙二醛取代的 2,2'-双咪唑，也在室内气溶胶中鉴定出，并在大气相关时间尺度上形成。另一种化合物（预计为 1,2,5-恶二唑）在腔室打开时具有较高的形成速率，预计通过光激活途径形成，涉及氨自由基氧化为羟胺，随后与乙二醛反应形成中间体乙二肟。
Recent laboratory and modelling studies have shown that reactive uptake of low molecular weight alpha-dicarbonyls such as glyoxal (GLY) by aerosols is a potentially significant source of secondary organic aerosol (SOA). However, previous studies disagree in the magnitude of the uptake of GLY, the mechanism involved and the physicochemical factors affecting particle formation. In this study, the chemistry of GLY with ammonium sulfate (AS) in both bulk laboratory solutions and in aerosol particles is investigated. For the first time, Aerosol Time of Flight Mass Spectrometry (ATOFMS), a single particle technique, is used together with offline (ESI-MS and LC-MS2) mass spectrometric techniques to investigate the change in composition of bulk solutions of GLY and AS resulting from aqueous photooxidation by OH and from ageing of the solutions in the dark. The mass spectral ions obtained in these laboratory studies were used as tracers of GLY uptake and chemistry in AS seed particles in a series of experiments carried out under dark and natural irradiated conditions at the outdoor European Photo-reactor (EUPHORE). Glyoxal oligomers formed were not detected by the ATOFMS, perhaps due to inefficient absorption at the laser wavelength. However, the presence of organic nitrogen compounds, formed by reaction of GLY with ammonia was confirmed, resulting in an increase in the absorption efficiency of the aerosol, and this increased the number of particles successfully ionised by the ATOFMS. A number of light absorbing organic nitrogen species, including 1H-imidazole, 1H-imidazole-2-carboxaldehyde, 2,2'-bis-imidazole and a glyoxal substituted 2,2'-bisimidazole, previously identified in aqueous laboratory solutions, were also identified in chamber aerosol and formed on atmospherically relevant timescales. An additional compound, predicted to be 1,2,5-oxadiazole, had an enhanced formation rate when the chamber was open and is predicted to be formed via a light activated pathway involving radical oxidation of ammonia to hydroxylamine, followed by subsequent reaction with glyoxal to form an intermediate glyoxime.