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DOI	10.5194/acp-22-1989-2022
	The number fraction of iron-containing particles affects OH, HO2 and H2O2 budgets in the atmospheric aqueous phase
	Khaled, Amina; Zhang, Minghui; Ervens, Barbara
发表日期	2022
ISSN	1680-7316
EISSN	1680-7324
起始页码	1989
结束页码	2009
卷号	22 期号:3 页码:21
英文摘要	Reactive oxygen species (ROS), such as OH, HO2 and H2O2, affect the oxidation capacity of the atmosphere and cause adverse health effects of particulate matter. The role of transition metal ions (TMIs) in impacting the ROS concentrations and conversions in the atmospheric aqueous phase has been recognized for a long time. Model studies usually assume that the total TMI mass as measured in bulk aerosol or cloud water samples is distributed equally across all particles or droplets. This assumption is contrary to single-particle measurements that have shown that only a small number fraction of particles contain iron and other TMIs (F-N,F-Fe < 100 %), which implies that also not all cloud droplets contain TMIs. In the current study, we apply a box model with an explicit multiphase chemical mechanism to simulate ROS formation and cycling in aqueous aerosol particles and cloud droplets. Model simulations are performed for the range of 1 % <= F-N,F-Fe <= 100 % for constant pH values of 3, 4.5 and 6 and constant total iron mass concentration (10 or 50 ng per cubic meter of air). Model results are compared for two sets of simulations with F(N,F)e<100 % (FeN<100) and 100 % (FeBulk). We find the largest differences between model results in OH and HO2 / O-2(-) concentrations at pH = 6. Under these conditions, HO2 is subsaturated in the aqueous phase because of its high effective Henry's law constant and the fast chemical loss reactions of the O-2(-) radical anion. As the main reduction process of Fe(III) is its reaction with HO2 / O-2(-), we show that the HO2 subsaturation leads to Fe(II) / Fe(total) ratios for F-N,F-Fe<100 % that are lower by a factor of <= 2 as compared to bulk model approaches. This trend is largely independent of the total iron concentration, as both chemical source and sink rates of HO2 / O-2(-) scale with the iron concentration. We compare model-derived reactive uptake parameters gamma OH and gamma HO2 for the full range of F-N,F-Fe. While gamma OH is not affected by the iron distribution, the calculated gamma HO2 values range from 0.0004 to 0.03 for F-N,F-Fe=1 % and 100 %, respectively. Implications of these findings are discussed for the application of lab-derived gamma HO2 in models to present reactive HO2 uptake on aerosols. We conclude that the iron distribution (F-N,F-Fe) should be taken into account to estimate the ROS concentrations and oxidation potential of particulate matter that might be overestimated by bulk sampling and model approaches. Our study suggests that the number concentration of iron-containing particles FN,Fe may be more important than the total iron mass concentration in determining ROS budgets and uptake rates in cloud and aerosol water.
学科领域	Environmental Sciences; Meteorology & Atmospheric Sciences
语种	英语
WOS研究方向	Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences
WOS记录号	WOS:000758215300001
来源期刊	ATMOSPHERIC CHEMISTRY AND PHYSICS
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/273689
作者单位	Centre National de la Recherche Scientifique (CNRS); Universite Clermont Auvergne (UCA)
推荐引用方式 GB/T 7714	Khaled, Amina,Zhang, Minghui,Ervens, Barbara. The number fraction of iron-containing particles affects OH, HO2 and H2O2 budgets in the atmospheric aqueous phase[J],2022,22(3):21.
APA	Khaled, Amina,Zhang, Minghui,&Ervens, Barbara.(2022).The number fraction of iron-containing particles affects OH, HO2 and H2O2 budgets in the atmospheric aqueous phase.ATMOSPHERIC CHEMISTRY AND PHYSICS,22(3),21.
MLA	Khaled, Amina,et al."The number fraction of iron-containing particles affects OH, HO2 and H2O2 budgets in the atmospheric aqueous phase".ATMOSPHERIC CHEMISTRY AND PHYSICS 22.3(2022):21.