Hygroscopicity of Internally Mixed Ammonium Sulfate and Secondary Organic Aerosol Particles Formed at Low and High Relative Humidity
Hygroscopicity of Internally Mixed Ammonium Sulfate and Secondary Organic Aerosol Particles Formed at Low and High Relative Humidity
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低相对湿度和高相对湿度下形成的内部混合硫酸铵和二次有机气溶胶颗粒的吸湿性
DOI：
10.1039/d1ea00069a
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Asa-Awuku, Akua
中科院分区：
文献类型：
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作者：
Razafindrambinina, Patricia N;Malek, Kotiba A;Dawson, Joseph Nelson;DiMonte, Kristin;Raymond, Timothy M;Dutcher, Dabrina D;Freedman, Miriam A;Asa-Awuku, Akua
悬浮在大气中的挥发性有机物（例如α-蒎烯和β-石竹烯）经历老化过程以及化学和光氧化反应，产生二次有机气溶胶（SOA），这可以影响气溶胶颗粒的间接效应和辐射预算。水蒸气和硫酸铵（大气中普遍存在的物质）的存在及其对 SOA 吸湿性和 CCN 活性的影响尚未得到很好的表征。本研究采用空腔衰荡光谱（CRD）、加湿串联微分迁移率分析（HTDMA）和云凝结核计数（CCNC）三种吸水率测量方法来研究暗臭氧解形成的α-蒎烯和β-石竹烯SOA的吸湿性。我们观察了在 70% RH 和硫酸铵种子存在和不存在水蒸气的情况下 SOA 吸水量的变化。测得的吸湿性由单一吸湿性参数（κ）表示。在所有实验条件和所有初始浓度下，观察到倍半萜 SOA 都是不溶性、疏水性和非吸湿性的，因为 β-石竹烯 SOA 表现出非吸湿性，其值实际上为 0。相反，单萜 SOA 吸水量对二次气溶胶形成过程中室内相对湿度的增加敏感。尽管初始前体浓度存在差异，干种子和湿种子单萜 SOA 显示出类似的增加趋势。我们得出结论，SOA 的粘度、溶解度和疏水性的差异可能是导致低相对湿度和高相对湿度条件下形成的 SOA 吸湿性变化的主要因素。
Volatile organic matter suspended in the atmosphere such as α-pinene and β-caryophyllene undergoes aging processes and chemical, and photo-oxidation reactions to create secondary organic aerosols (SOAs), which can influence the indirect effect of aerosol particles and the radiative budget. The presence and impact of water vapor and ammonium sulfate (ubiquitous species in the atmosphere) on the hygroscopicity and CCN activity of SOA have not been well characterized. In this research, three water-uptake measurement methods, cavity ring-down spectroscopy (CRD), humidified tandem differential mobility analysis (HTDMA), and cloud condensation nuclei counting (CCNC), were employed to study the hygroscopicity of α-pinene and β-caryophyllene SOAs formed by dark ozonolysis. We observed the changes in water uptake of SOAs in the absence and presence of water vapor at ∼70% RH and ammonium sulfate seeds. Measured hygroscopicity was represented by a single hygroscopicity parameter (κ). Sesquiterpene SOA was observed to be insoluble, hydrophobic, and non-hygroscopic under all experimental conditions and at all initial concentrations, as β-caryophyllene SOA exhibited non-hygroscopic properties with values that were effectively 0. Conversely, monoterpene SOA water uptake is sensitive to increasing RH in the chamber during secondary aerosol formation. Dry and wet seeded monoterpene SOA showed a similar trend of increase despite variability in initial precursor concentrations. We conclude that differences in the viscosity, solubility and hydrophobicity of SOAs may be the primary factor that leads to changes in SOA hygroscopicity formed under low and high relative humidity conditions.