Photochemical Degradation of Iron Citrate in Anoxic Viscous Films Enhanced by Redox Cascades DOI Creative Commons
Ashmi Mishra, Kevin Kilchhofer,

Lucia Iezzi

et al.

ACS Earth and Space Chemistry, Journal Year: 2025, Volume and Issue: 9(3), P. 689 - 698

Published: Feb. 25, 2025

Iron contained in atmospheric aerosol particles can form complexes with organic ligands and initiate photochemical reactions that alter the composition physicochemical properties of particles. Depending on temperature humidity, exist different phase states, which affects reactant diffusivity chemical reaction rates. We performed coated-wall flow-tube experiments using citric acid films doped iron as proxies for secondary aerosols. quantified CO2 production under UV irradiation a function time relative humidity (RH) observed pronounced decrease decreasing RH. The kinetic multilayer model surface bulk chemistry (KM-SUB) Monte Carlo-based global optimization method were applied to all measured data determine underlying effects mass transport reactions. analysis revealed after an initial rapid reaction, photooxidation becomes limited by reoxidation FeII. Under dry conditions (RH < 65%), FeII is kinetically supply O2, slow diffusion viscous matrix leads anoxia interior film. At high > 85%), limitations cease, resulting full O2 saturation, oxidants. Reactive oxygen species play key role thus perpetuating chemistry. A single molecule triggers redox cascade from HO2, H2O2, OH, leading ≈3 cycles FeII/FeIII pair. Our parameters provide new insights constraints interplay microphysical aging mixed organic–inorganic particles, may influence their air quality, climate, public health.

Language: Английский

Photochemical Degradation of Iron Citrate in Anoxic Viscous Films Enhanced by Redox Cascades DOI Creative Commons
Ashmi Mishra, Kevin Kilchhofer,

Lucia Iezzi

et al.

ACS Earth and Space Chemistry, Journal Year: 2025, Volume and Issue: 9(3), P. 689 - 698

Published: Feb. 25, 2025

Iron contained in atmospheric aerosol particles can form complexes with organic ligands and initiate photochemical reactions that alter the composition physicochemical properties of particles. Depending on temperature humidity, exist different phase states, which affects reactant diffusivity chemical reaction rates. We performed coated-wall flow-tube experiments using citric acid films doped iron as proxies for secondary aerosols. quantified CO2 production under UV irradiation a function time relative humidity (RH) observed pronounced decrease decreasing RH. The kinetic multilayer model surface bulk chemistry (KM-SUB) Monte Carlo-based global optimization method were applied to all measured data determine underlying effects mass transport reactions. analysis revealed after an initial rapid reaction, photooxidation becomes limited by reoxidation FeII. Under dry conditions (RH < 65%), FeII is kinetically supply O2, slow diffusion viscous matrix leads anoxia interior film. At high > 85%), limitations cease, resulting full O2 saturation, oxidants. Reactive oxygen species play key role thus perpetuating chemistry. A single molecule triggers redox cascade from HO2, H2O2, OH, leading ≈3 cycles FeII/FeIII pair. Our parameters provide new insights constraints interplay microphysical aging mixed organic–inorganic particles, may influence their air quality, climate, public health.

Language: Английский

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