Reactive uptake of ozone to azo dyes in a coated-wall flow tube

Al-Mashala, Habeeb H; Boone, Alison M; Schnitzler, Elijah G.

doi:10.1039/d1em00478f

Cited by 2 publications

(2 citation statements)

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“…Since the mass of the films does not change upon irradiation, as described above, these changes in reactive uptake are due to changes in film composition, not film thickness. Based on recent observations of depletion near the surface in various multiphase reactions, , the rapid approach toward steady-state uptake indicates that the mixing between the bulk and near-surface layers is much slower after UV irradiation, attributed to greater viscosity. Our observation of slower diffusion after UV irradiation is consistent with direct measurements of increased viscosity for secondary organic aerosol after UV irradiation .…”

Section: Resultsmentioning

confidence: 99%

“…Reactive uptake of ozone to the thin films was measured using a coated-wall flow-tube, which was slightly modified from the setup described previously. 40 Ozone was generated using a Hg lamp (UVP, SOG-2) and measured using a UV absorption analyzer (Ecotech, Serinus 10) to be stable at 100 ppb, initially. Relative humidity (RH) was set to 0%, monitored by a temperature and RH probe (Vaisala, HMP75).…”

Section: ■ Introductionmentioning

confidence: 99%

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Ultraviolet Irradiation Can Increase the Light Absorption and Viscosity of Primary Brown Carbon from Biomass Burning

Al-Mashala,

Betz,

Calvert

et al. 2023

ACS Earth Space Chem.

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The light absorption of brown carbon (BrC) constituents of biomass burning organic aerosol (BBOA) changes in the atmosphere, in part due to multiphase oxidation. For example, ozonolysis leads to the whitening of primary BrC constituents. Irradiation can also change the properties of BrC. Here, we investigate the interplay between irradiation and multiphase processing by measuring the reactive uptake of ozone to thin films of BBOA before and after exposure to UV radiation in a photoreactor. Thin films were prepared from the lower volatility fraction of BBOA from eastern red cedar, a species associated with wildfires and prescribed fires in the southern Great Plains, United States. Irradiation increased the mass absorption coefficient of the BrC at near-UV and visible wavelengths. It also significantly decreased the reactive uptake of ozone, which was attributed to increased viscosity of the BBOA material. These changes in absorptivity and viscosity are consistent with results of mass spectrometry and volatility tandem differential mobility analysis, which show that high-molecular-weight species constitute a greater fraction of the total mass after irradiation. Our results may have significant implications on the warming effect of BrC, since UV irradiation here both darkens this BBOA material and makes it more resistant to multiphase processing and whitening by ozone under the conditions investigated.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%