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Aging induced changes in ice nucleation activity of combustion aerosol as determined by near edge X-ray absorption fine structure (NEXAFS) spectroscopy.
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2020-04-29 , DOI: 10.1039/c9em00525k Fabian Mahrt 1 , Peter A Alpert , Jing Dou , Philippe Grönquist , Pablo Corral Arroyo , Markus Ammann , Ulrike Lohmann , Zamin A Kanji
Environmental Science: Processes & Impacts ( IF 4.3 ) Pub Date : 2020-04-29 , DOI: 10.1039/c9em00525k Fabian Mahrt 1 , Peter A Alpert , Jing Dou , Philippe Grönquist , Pablo Corral Arroyo , Markus Ammann , Ulrike Lohmann , Zamin A Kanji
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Fresh soot particles are generally hydrophobic, however, particle hydrophilicity can be increased through atmospheric aging processes. At present little is known on how particle chemical composition and hydrophilicity change upon atmospheric aging and associated uncertainties governing the ice cloud formation potential of soot. Here we sampled two propane flame soots referred to as brown and black soot, characterized as organic carbon rich and poor, respectively. We investigated how the ice nucleation activity of these particles changed through aging in water and aqueous acidic solutions, using a continuous flow diffusion chamber operated at cirrus cloud temperatures (T ≤ 233 K). Single aggregates of both unaged and aged soot were chemically characterized by scanning transmission X-ray microscopy and near edge X-ray absorption fine structure (STXM/NEXAFS) measurements. Particle wettability was determined through water sorption measurements. Unaged black and brown soot particles exhibited significantly different ice nucleation activities. Our experiments revealed significantly enhanced ice nucleation activity of the aged soot particles compared to the fresh samples, lowering the required relative humidities at which ice formation can take place at T = 218 K by up to 15% with respect to water (ΔRHi ≈ 25%). We observed an enhanced water uptake capacity for the aged compared to the unaged samples, which was more pronounced for the black soot. From these measurements we concluded that there is a change in ice nucleation mechanism when aging brown soot. Comparison of the NEXAFS spectra of unaged soot samples revealed a unique spectral feature around 287.5 eV in the case of black soot that was absent for the brown soot, indicative of carbon with hydroxyl functionalities. Comparison of the NEXAFS spectra of unaged and aged soot particles indicates changes in organic functional groups, and the aged spectra were found to be largely similar across soot types, with the exception of the water aged brown soot. Overall, we conclude that atmospheric aging is important to representatively assess the ice cloud formation activity of soot particles.
中文翻译：
通过近边缘X射线吸收精细结构（NEXAFS）光谱确定，老化引起的燃烧气溶胶的冰成核活性变化。
新鲜的烟灰颗粒通常是疏水的，但是，可以通过大气老化过程来增加颗粒的亲水性。目前，关于大气老化时颗粒化学成分和亲水性如何变化以及控制烟尘冰云形成潜力的相关不确定性知之甚少。在这里，我们采样了两种丙烷火焰烟灰，分别称为棕色和黑色烟灰，分别表征为富有机碳和贫碳。我们使用在卷云温度（T≤233 K）下运行的连续流动扩散室，研究了这些颗粒的冰成核活性如何在水和酸性水溶液中老化后发生变化。通过扫描透射X射线显微镜和近边缘X射线吸收精细结构（STXM / NEXAFS）测量对未老化和老化烟灰的单一聚集体进行化学表征。通过吸水率测定来确定颗粒的润湿性。未老化的黑色和棕色烟灰颗粒表现出明显不同的冰核活性。我们的实验表明，与新鲜样品相比，老化烟灰颗粒的冰成核活性显着增强，相对于水，可降低所需的相对湿度，使在T = 218 K时可形成冰的相对湿度降低15％（ΔRHi≈25％）。 ）。与未老化的样品相比，我们观察到老化后的吸水能力增强了，对于黑烟尘更明显。从这些测量结果可以得出结论，当老化棕色烟灰时，冰成核机制发生了变化。未老化烟灰样品的NEXAFS光谱的比较显示，在黑烟灰的情况下，黑烟灰没有288.7 eV左右的独特光谱特征，表明碳具有羟基官能度。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。在黑色烟灰的情况下为5 eV，对于棕色烟灰则没有，表明碳具有羟基官能团。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。在黑色烟灰的情况下为5 eV，对于棕色烟灰则没有，表明碳具有羟基官能团。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。
更新日期：2020-03-18
中文翻译：
通过近边缘X射线吸收精细结构（NEXAFS）光谱确定，老化引起的燃烧气溶胶的冰成核活性变化。
新鲜的烟灰颗粒通常是疏水的，但是，可以通过大气老化过程来增加颗粒的亲水性。目前，关于大气老化时颗粒化学成分和亲水性如何变化以及控制烟尘冰云形成潜力的相关不确定性知之甚少。在这里，我们采样了两种丙烷火焰烟灰，分别称为棕色和黑色烟灰，分别表征为富有机碳和贫碳。我们使用在卷云温度（T≤233 K）下运行的连续流动扩散室，研究了这些颗粒的冰成核活性如何在水和酸性水溶液中老化后发生变化。通过扫描透射X射线显微镜和近边缘X射线吸收精细结构（STXM / NEXAFS）测量对未老化和老化烟灰的单一聚集体进行化学表征。通过吸水率测定来确定颗粒的润湿性。未老化的黑色和棕色烟灰颗粒表现出明显不同的冰核活性。我们的实验表明，与新鲜样品相比，老化烟灰颗粒的冰成核活性显着增强，相对于水，可降低所需的相对湿度，使在T = 218 K时可形成冰的相对湿度降低15％（ΔRHi≈25％）。 ）。与未老化的样品相比，我们观察到老化后的吸水能力增强了，对于黑烟尘更明显。从这些测量结果可以得出结论，当老化棕色烟灰时，冰成核机制发生了变化。未老化烟灰样品的NEXAFS光谱的比较显示，在黑烟灰的情况下，黑烟灰没有288.7 eV左右的独特光谱特征，表明碳具有羟基官能度。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。在黑色烟灰的情况下为5 eV，对于棕色烟灰则没有，表明碳具有羟基官能团。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。在黑色烟灰的情况下为5 eV，对于棕色烟灰则没有，表明碳具有羟基官能团。比较未老化和老化的烟灰颗粒的NEXAFS光谱表明有机官能团的变化，除水老化的棕色烟灰之外，老化的光谱在各种烟灰类型上都非常相似。总的来说，我们得出结论，大气老化对于代表性地评估烟灰颗粒的冰云形成活动很重要。
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