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首页> 外文期刊>Environmental Science & Technology >Oxidation of Gas-Phase SO_2 on the Surfaces of Acidic Microdroplets: Implications for Sulfate and Sulfate Radical Anion Formation in the Atmospheric Liquid Phase
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Oxidation of Gas-Phase SO_2 on the Surfaces of Acidic Microdroplets: Implications for Sulfate and Sulfate Radical Anion Formation in the Atmospheric Liquid Phase

机译：酸性微滴表面上气相SO_2的氧化：对大气液相中硫酸根和硫酸根自由基形成的影响

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摘要

The oxidation of SO_2(g) on the interfacial layers of microdroplet surfaces was investigated using a spray-chamber reactor coupled to an electrospray ionization mass spectrometer. Four major ions, HSO_3~-, SO_3~(·-), SO_4~(·-) and HSO_4~-, were observed as the SO_2(g)/N_2(g) gas-mixture was passed through a suspended microdroplet flow, where the residence time in the dynamic reaction zone was limited to a few hundred microseconds. The relatively high signal intensities of SO_3~(·-), SO_4~(·-), and HSO_4~- compared to those of HSO_3~- as observed at pH ＜ 3 without addition of oxidants other than oxygen suggests an efficient oxidation pathway via sulfite and sulfate radical anions on droplets possibly via the direct interfacial electron transfer from HSO_3~- to O_2. The concentrations of HSO_3~- in the aqueous aerosol as a function of pH were controlled by the deprotonation of hydrated sulfur dioxide, SO_2·H_2O, which is also affected by the pH dependent uptake coefficient. When H_2O_2(g) was introduced into the spray chamber simultaneously with SO_2(g), HSO_3~- is rapidly oxidized to form bisulfite in the pH range of 3 to 5. Conversion to sulfate was less at pH ＜ 3 due to relatively low HSO_3~- concentration caused by the fast interfacial reactions. The rapid oxidation of SO_2(g) on the acidic microdroplets was estimated as 1.5 × 10~6 [S(Ⅳ)] (M s~(-1)) at pH ＜ 3. In the presence of acidic aerosols, this oxidation rate is approximately 2 orders of magnitude higher than the rate of oxidation with H_2O_2(g) at a typical atmospheric H_2O_2(g) concentration of 1 ppb. This finding highlights the relative importance of the acidic surfaces for SO_2 oxidation in the atmosphere. Surface chemical reactions on aquated aerosol surfaces, as observed in this study, are overlooked in most atmospheric chemistry models. These reaction pathways may contribute to the rapid production of sulfate aerosols that is often observed in regions impacted by acidic haze aerosol such as Beijing and other megacities around the world.
机译：使用与电喷雾电离质谱仪耦合的喷雾室反应器研究了微滴表面界面层上SO_2（g）的氧化。当SO_2（g）/ N_2（g）气体混合物通过悬浮微滴流时，观察到四个主要离子HSO_3〜-，SO_3〜（·-），SO_4〜（·-）和HSO_4〜-。其中在动态反应区的停留时间限制在几百微秒。在pH ＜3时观察到的SO_3〜（·-），SO_4〜（·-）和HSO_4〜-相对于HSO_3〜-的信号强度相对较高，而没有添加除氧气以外的氧化剂，表明通过液滴上的亚硫酸根和硫酸根自由基可能通过HSO_3〜-到O_2的直接界面电子转移而形成。水合气溶胶中HSO_3〜-的浓度随pH的变化是通过水合二氧化硫SO_2·H_2O的去质子化来控制的，这也受pH依赖的吸收系数的影响。当H_2O_2（g）与SO_2（g）同时引入喷雾室时，HSO_3〜-在3至5的pH范围内迅速氧化形成亚硫酸氢盐。由于HSO_3相对较低，在pH ＜3时向硫酸盐的转化较少。 〜-浓度由快速的界面反应引起。在pH ＜3时，酸性微滴上SO_2（g）的快速氧化估计为1.5×10〜6 [S（Ⅳ）]（M s〜（-1））。在酸性气溶胶存在下，该氧化速率在典型的大气H_2O_2（g）浓度为1 ppb时，H_2O_2（g）的氧化速率比H_2O_2（g）的氧化速率高约2个数量级。这一发现突显了酸性表面对于大气中SO_2氧化的相对重要性。正如本研究中所观察到的那样，水化气溶胶表面的表面化学反应在大多数大气化学模型中都被忽略了。这些反应途径可能有助于硫酸盐雾剂的快速产生，而硫酸盐雾剂通常在受酸性雾霾气雾影响的地区（例如北京和世界其他大城市）中观察到。

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  • 来源
    《Environmental Science & Technology》 |2015年第23期|13768-13776|共9页
  • 作者

    Hui-Ming Hung; Michael R. Hoffmann;

  • 作者单位

    Department of Atmospheric Sciences, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617 Taiwan;

    Linde Center for Global Environmental Science, California Institute of Technology Linde-Robinson Laboratory, Pasadena, California 91125, United States;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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  • 正文语种 eng
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