Photochemistry of iron-containing secondary organic aerosol is impacted by relative humidity during formation

IF 8.5 1区地球科学 Q1 METEOROLOGY & ATMOSPHERIC SCIENCES

npj Climate and Atmospheric Science Pub Date : 2025-07-01 DOI:10.1038/s41612-025-01109-6

Natasha M. Garner, Fabian Mahrt, Jens Top, Virginia Tadei, Kevin Kilchhofer, Satoshi Takahama, Imad El Haddad, David M. Bell, Markus Ammann, Peter A. Alpert

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Abstract

Secondary organic aerosol (SOA) comprises most of the submicron atmospheric particle mass, and often becomes internally mixed with other particles. When SOA mixes with transition metal (e.g., iron) containing particles, metal-organic complexes can form, enabling photochemical reactions that change aerosol physicochemical properties. We studied the photochemistry of α-pinene SOA formed on iron-containing ammonium sulfate seed particles at varying relative humidities (RH). Chemical composition and photochemical reduction of particles were analyzed by X-ray spectromicroscopy and infrared spectroscopy. SOA formed at low vs. high RH had different chemical functionality, including abundant carboxylic acids and alcohols. Following photolysis, carboxylic acids and unsubstituted alkanes decreased, and alcohols increased, consistent with decarboxylation reactions. Iron in SOA formed at high RH was readily photochemically reduced, but iron in SOA formed at low RH was not. Overall, RH conditions at SOA formation affect not only chemical composition but also iron-complex formation and hence photochemical processing of aerosols.

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含铁二次有机气溶胶在形成过程中受相对湿度的影响

二次有机气溶胶（SOA）包含大部分亚微米大气粒子质量，并且经常在内部与其他粒子混合。当SOA与含过渡金属（如铁）的颗粒混合时，可以形成金属-有机配合物，从而实现改变气溶胶物理化学性质的光化学反应。研究了不同相对湿度（RH）条件下含铁硫酸铵种子颗粒上α-蒎烯SOA的光化学性质。用x射线光谱显微镜和红外光谱分析了颗粒的化学成分和光化学还原。在低相对湿度和高相对湿度下形成的SOA具有不同的化学功能，包括丰富的羧酸和醇。光解后，羧酸和未取代烷烃减少，醇增加，与脱羧反应一致。在高相对湿度下形成的SOA中的铁易于光化学还原，而在低相对湿度下形成的SOA中的铁则不易光化学还原。总的来说，SOA形成的RH条件不仅影响化学成分，还影响铁络合物的形成，从而影响气溶胶的光化学处理。

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来源期刊

npj Climate and Atmospheric Science Earth and Planetary Sciences-Atmospheric Science

CiteScore

8.80

自引率

3.30%

发文量

审稿时长

21 weeks

期刊介绍： npj Climate and Atmospheric Science is an open-access journal encompassing the relevant physical, chemical, and biological aspects of atmospheric and climate science. The journal places particular emphasis on regional studies that unveil new insights into specific localities, including examinations of local atmospheric composition, such as aerosols. The range of topics covered by the journal includes climate dynamics, climate variability, weather and climate prediction, climate change, ocean dynamics, weather extremes, air pollution, atmospheric chemistry (including aerosols), the hydrological cycle, and atmosphere–ocean and atmosphere–land interactions. The journal welcomes studies employing a diverse array of methods, including numerical and statistical modeling, the development and application of in situ observational techniques, remote sensing, and the development or evaluation of new reanalyses.