Offline analysis of the chemical composition and hygroscopicity of sub-micrometer aerosol at an Asian outflow receptor site and comparison with online measurements
Offline analysis of the chemical composition and hygroscopicity of sub-micrometer aerosol at an Asian outflow receptor site and comparison with online measurements
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DOI：
10.5194/acp-2021-704
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发表时间：
2021-10
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通讯作者：
Yange Deng;Hiroaki Fujinari;Hikari Yai;Kojiro Shimada;Y. Miyazaki;E. Tachibana;D. Deshmukh;K. Kawam
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文献类型：
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作者：
Yange Deng;Hiroaki Fujinari;Hikari Yai;Kojiro Shimada;Y. Miyazaki;E. Tachibana;D. Deshmukh;K. Kawam
抽象。对大气气溶胶吸湿性的基于过滤器的离线分析与成分分析相结合，提供了与在线分析所获得的信息互补的信息。然而，它的应用本身和比较在线分析仍然有限的日期。在这项研究中，2015年秋季，在东亚外流的受体冲绳岛，每天将亚微米气溶胶颗粒物（PM0.95，50%截止直径：0.95 μm）收集到石英纤维过滤器上。通过离线使用气溶胶质谱仪和吸湿性串联微分迁移率分析仪，表征了PM 0. 95和PM 0. 95本身的水溶性物质（WSM）的化学组成及其各自的吸湿性。此后，将结果与在线分析结果进行比较。硫酸盐占WSM质量的60%，其次是水溶性有机物（WSOM，20%）和铵（13%）。WSOM占提取的有机物（EOM）质量的大部分（93%），并且WSOM和EOM的原子O：C比（O：C）很高（平均值±标准差分别为0.84 ± 0.08和0.79 ± 0.08），这两者都表明所观察到的气溶胶的高度老化特征。大多数样品的吸湿增长曲线显示出明显的滞后现象。在85%RH下，计算的WSM（κWSM）、WSOM、EOM和PM 0.95（κ PM 0.95）的吸湿性参数κ分别为0.50 ± 0.03、0.22 ± 0.12、0.20 ± 0.11和0.47 ± 0.03。使用热力学E-AIM模型的分析表明，平均而言，无机盐和WSOM分别贡献了κWSM（或κPM0.95）的88%和12%。离线和在线分析之间的高度相似性被发现与颗粒吸湿性（有机物的质量分数和O：C，和中和度），以及气溶胶吸湿性的化学成分。作为控制κWSM变化的可能因素，评估了WSOM丰度和无机盐中和的影响。在高RH（70- 90%）下，WSM和PM0.95的吸湿性受到有机组分存在的显著影响;在低RH（20- 50%）下，中和度可能很重要。这项研究不仅表征了东亚外流受体站点的气溶胶吸湿性，而且还表明离线吸湿性分析是一种适当的方法，至少对于所研究类型的气溶胶。结果鼓励进一步应用到其他环境和更深入的吸湿性分析，特别是有机馏分。
Abstract. Filter-based offline analysis of atmospheric aerosol hygroscopicity coupled to composition analysis provides information complementary to that obtained from online analysis. However, its application itself and comparison to online analysis have remained limited to date. In this study, daily submicrometer aerosol particles (PM0.95, 50 % cutoff diameter: 0.95 μm) were collected onto quartz fiber filters in Okinawa Island, a receptor of East Asian outflow, in the autumn of 2015. The chemical composition of water-soluble matter (WSM) in PM0.95 and PM0.95 itself, and their respective hygroscopicities were characterized through the offline use of an aerosol mass spectrometer and a hygroscopicity tandem differential mobility analyzer. Thereafter, results were compared with those obtained from online analyses. Sulfate dominated the WSM mass (60 %), followed by water-soluble organic matter (WSOM, 20 %) and ammonium (13 %). WSOM accounted for most (93 %) of the mass of extracted organic matter (EOM) and the atomic O to C ratios (O : C) of WSOM and EOM were high (mean ± standard deviation were, respectively, 0.84 ± 0.08 and 0.79 ± 0.08), both of which indicate highly aged characteristics of the observed aerosol. The hygroscopic growth curves showed clear hysteresis for most samples. At 85 % RH, the calculated hygroscopicity parameter κ of the WSM (κWSM), WSOM, EOM, and PM0.95 (κPM0.95) were, respectively, 0.50 ± 0.03, 0.22 ± 0.12, 0.20 ± 0.11, and 0.47 ± 0.03. An analysis using the thermodynamic E-AIM model shows, on average, that inorganic salts and WSOM respectively contributed 88 % and 12 % of the κWSM (or κPM0.95). High similarities were found between offline and online analysis for chemical compositions that are related to particle hygroscopicity (the mass fractions and O : C of organics, and the degree of neutralization), and also for aerosol hygroscopicity. As possible factors governing the variation of κWSM, the influences of WSOM abundance and the neutralization of inorganic salts were assessed. At high RH (70–90 %), the hygroscopicity of WSM and PM0.95 was affected considerably by the presence of organic components; at low RH (20–50 %), the degree of neutralization could be important. This study not only characterized aerosol hygroscopicity at the receptor site of East Asian outflow, but also shows that the offline hygroscopicity analysis is an appropriate method, at least for aerosols of the studied type. The results encourage further applications to other environments and to more in-depth hygroscopicity analysis, in particular for organic fractions.