El-Sayed Marwa M H, Hennigan Christopher J
Department of Civil Engineering, Embry-Riddle Aeronautical University, Daytona Beach, FL, USA.
Department of Chemical, Biochemical and Environmental Engineering, University of Maryland, Baltimore County, Baltimore, MD, USA.
Environ Sci Process Impacts. 2023 Feb 22;25(2):241-253. doi: 10.1039/d2em00115b.
Aqueous multi-phase processes are significant contributors to organic aerosol (OA) mass in the atmosphere. This study characterizes the formation of water-soluble organic matter during the winter in the eastern United States through simultaneous measurements of water-soluble organic carbon in the gas and particle phases (WSOC and WSOC, respectively). The formation of secondary WSOC occurred primarily through two pathways: (1) absorptive partitioning of oxygenated organics to the bulk OA and (2) aqueous phase processes. WSOC formation through the former pathway was evident through the relationship between the fraction of total WSOC in the particle phase () and the total OA concentration. Conversely, evidence for nighttime aqueous WSOC formation was based upon the strong enhancement in with increasing relative humidity, indicating the uptake of WSOC to aerosol liquid water (ALW). The -RH relationship was only observed for temperatures between 0-10 °C, suggesting conditions for aqueous multi-phase processes were enhanced during these times. Temperature exhibited an inverse relationship with ALW and a proportional relationship with aerosol potassium. ALW and biomass burning precursors were both abundant in the 0-10 °C temperature range, facilitating aqueous WSOC formation. To assess the impact of particle drying on the WSOC concentrations, the particle measurements alternated between ambient and dried channels. No change was observed in the concentration of particles before and after drying, indicating that the WSOC formed through the uptake of WSOC into OA and ALW remained in the condensed phase upon particle drying at all temperature ranges. This work contributes to our understanding of sources, pathways, and factors affecting aqueous aerosol formation in the winter.
水相多相过程是大气中有机气溶胶（OA）质量的重要贡献因素。本研究通过同时测量气相和颗粒相中的水溶性有机碳（分别为WSOCg和WSOCp），对美国东部冬季水溶性有机物的形成进行了表征。二次WSOC的形成主要通过两条途径：（1）氧化有机物向总OA的吸收分配，以及（2）水相过程。通过颗粒相中总WSOC的分数（）与总OA浓度之间的关系，可以明显看出通过前一种途径形成的WSOC。相反，夜间水相WSOC形成的证据基于随着相对湿度增加而强烈增强，表明WSOC被气溶胶液态水（ALW）吸收。仅在0-10°C的温度范围内观察到 -RH关系，这表明在此期间水相多相过程的条件增强。温度与ALW呈反比关系，与气溶胶钾呈正比关系。在0-10°C的温度范围内，ALW和生物质燃烧前体都很丰富，这有利于水相WSOC的形成。为了评估颗粒干燥对WSOC浓度的影响，颗粒测量在环境通道和干燥通道之间交替进行。干燥前后颗粒浓度没有变化，这表明通过WSOC吸收到OA和ALW中形成的WSOC在所有温度范围内颗粒干燥后仍保留在凝聚相中。这项工作有助于我们理解冬季影响水生气溶胶形成的来源、途径和因素。
