Heterogeneous Hydroxyl Radical Oxidation of Isoprene-Epoxydiol-Derived Methyltetrol Sulfates: Plausible Formation Mechanisms of Previously Unexplained Organosulfates in Ambient Fine Aerosols
Heterogeneous Hydroxyl Radical Oxidation of Isoprene-Epoxydiol-Derived Methyltetrol Sulfates: Plausible Formation Mechanisms of Previously Unexplained Organosulfates in Ambient Fine Aerosols
复制标题
DOI：
10.1021/acs.estlett.0c00276
复制
发表时间：
2020-07-14
影响因子：
10.9
通讯作者：
Surratt, Jason D.
中科院分区：
文献类型：
--
作者：
Chen, Yuzhi;Zhang, Yue;Surratt, Jason D.
甲基四醇硫酸盐是由异戊二烯衍生的环氧二醇的酸驱动的多相化学形成的二次有机气溶胶（SOA）的独特示踪剂。2-甲基四醇硫酸盐非对映异构体（2-MTSs）是大气细颗粒物（PM2.5）中最主要的异构体和单一最丰富的SOA示踪剂，但其大气汇仍然未知。我们通过气相羟基自由基（（OH）-O-中心点）在61 +/-1%的相对湿度下研究了真实2-MTS气溶胶的氧化老化。该非均相反应的有效速率常数被确定为4.9 +/- 0.6 x 10（-13）cm（3）molecules（-1）s（-1），对应于16 +/- 2天的大气寿命（假设（OH）-O-中心点浓度为1.5 x 10（6）molecules cm（-3））。通过亲水相互作用液相色谱连接电喷雾电离高分辨率四极杆飞行时间质谱法（HILIC/ESI-HR-QTOFMS）监测2-MTS的化学变化。提出了在大气PM2.5中检测到的质荷比（m/z）为139的以前未知的OS的合理反应机制（C2H3O5S-），155（C2H3O6S-），169（C3H5O6S-）、171（C3H7O6S-）、185（C3H5O7S-）、199（C4H7O7S-）、211（C5H7O7S-）、213（C5H9O7S-）、227（C5H7O8S-）、229（C5H9O8S-）和231（C5H11O8S-）。2-MTS的异质H-中心点氧化将颗粒硫形态重新分布到更多氧化/官能化的OS中，可能修改含有2-MTS的SOA的气溶胶物理化学性质。
Methyltetrol sulfates are unique tracers for secondary organic aerosols (SOA) formed from acid-driven multiphase chemistry of isoprene-derived epoxydiols. 2-Methyltetrol sulfate diastereomers (2-MTSs) are the dominant isomers and single most-abundant SOA tracers in atmospheric fine particulate matter (PM2.5), but their atmospheric sinks remain unknown. We investigated the oxidative aging of authentic 2-MTS aerosols by gas-phase hydroxyl radicals ((OH)-O-center dot) at a relative humidity of 61 +/- 1%. The effective rate constant for this heterogeneous reaction was determined as 4.9 +/- 0.6 x 10(-13) cm(3) molecules(-1) s(-1), corresponding to an atmospheric lifetime of 16 +/- 2 days (assuming an (OH)-O-center dot concentration of 1.5 x 10(6) molecules cm(-3)). Chemical changes to 2-MTSs were monitored by hydrophilic interaction liquid chromatography interfaced to electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry (HILIC/ESI-HR-QTOFMS). Plausible reaction mechanisms are proposed for previously unknown OSs detected in atmospheric PM2.5 at mass-to-charge ratios (m/z) of 139 (C2H3O5S-), 155 (C2H3O6S-), 169 (C3H5O6S-), 171 (C3H7O6S-), 185 (C3H5O7S-), 199 (C4H7O7S-), 211 (C5H7O7S-), 213 (C5H9O7S-), 227 (C5H7O8S-), 229 (C5H9O8S-), and 231 (C5H11O8S-). Heterogeneous H-center dot oxidation of 2-MTSs redistributes the particulate sulfur speciation into more oxygenated/functionalized OSs, likely modifying the aerosol physicochemical properties of SOA containing 2-MTSs.