Photodecay of guaiacol is faster in ice, and even more rapid on ice, than in aqueous solution

Hullar, Ted; Bononi, Fernanda; Chen, Zekun; Magadia, Danielle; Palmer, Oliver; Tran, Theo; Rocca, Dario; Andreussi, Oliviero; Donadio, Davide; Anastasio, Cort

doi:10.1039/d0em00242a

Cited by 21 publications

(68 citation statements)

References 60 publications

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“…S5) because of the uncommon spectroscopic feature with emission and excitation wavelengths of 315 and 452 nm, respectively. This feature is possibly attributed to (1) NADH-like (nicotinamide adenine dinucleotide) compounds, which are an indicator for the metabolism of organisms (Pöhlker et al, 2012), or (2) plantderived water-extractable organic matter (Hunt and Ohno, 2007), e.g., corn. This result suggests strong influence from either microbial activity or plant-sourced organics in snow at site 120, which is also consistent with the UV-vis spectrum shape.…”

Section: Bulk Light-absorbing and Fluorescence Propertiesmentioning

confidence: 99%

Measurement report: Molecular composition, optical properties, and radiative effects of water-soluble organic carbon in snowpack samples from northern Xinjiang, China

et al. 2021

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Abstract. Water-soluble organic carbon (WSOC) in the cryosphere has an important impact on the biogeochemistry cycling and snow–ice surface energy balance through changes in the surface albedo. This work reports on the chemical characterization of WSOC in 28 representative snowpack samples collected across a regional area of northern Xinjiang, northwestern China. We employed multimodal analytical chemistry techniques to investigate both bulk and molecular-level composition of WSOC and its optical properties, informing the follow-up radiative forcing (RF) modeling estimates. Based on the geographic differences and proximity of emission sources, the snowpack collection sites were grouped as urban/industrial (U), rural/remote (R), and soil-influenced (S) sites, for which average WSOC total mass loadings were measured as 1968 ± 953 ng g−1 (U), 885 ± 328 ng g−1 (R), and 2082 ± 1438 ng g−1 (S), respectively. The S sites showed the higher mass absorption coefficients at 365 nm (MAC365) of 0.94 ± 0.31 m2 g−1 compared to those of U and R sites (0.39 ± 0.11 m2 g−1 and 0.38 ± 0.12 m2 g−1, respectively). Bulk composition of WSOC in the snowpack samples and its basic source apportionment was inferred from the excitation–emission matrices and the parallel factor analysis featuring relative contributions of one protein-like (PRLIS) and two humic-like (HULIS-1 and HULIS-2) components with ratios specific to each of the S, U, and R sites. Additionally, a sample from site 120 showed unique pollutant concentrations and spectroscopic features remarkably different from all other U, R, and S samples. Molecular-level characterization of WSOC using high-resolution mass spectrometry (HRMS) provided further insights into chemical differences among four types of samples (U, R, S, and 120). Specifically, many reduced-sulfur-containing species with high degrees of unsaturation and aromaticity were uniquely identified in U samples, suggesting an anthropogenic source. Aliphatic/protein-like species showed the highest contribution in R samples, indicating their biogenic origin. The WSOC components from S samples showed high oxygenation and saturation levels. A few unique CHON and CHONS compounds with high unsaturation degree and molecular weight were detected in the 120 sample, which might be anthraquinone derivatives from plant debris. Modeling of the WSOC-induced RF values showed warming effects of 0.04 to 0.59 W m−2 among different groups of sites, which contribute up to 16 % of that caused by black carbon (BC), demonstrating the important influences of WSOC on the snow energy budget.

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Section: Bulk Light-absorbing and Fluorescence Propertiesmentioning

confidence: 99%

Measurement report: Molecular composition, optical properties, and radiative effects of water-soluble organic carbon in snowpack samples from northern Xinjiang, China

et al. 2021

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“…However, measurements in different solute locations, e.g., in solution, in LLRs, and at the air-ice interface, found that photon fluxes varied by less than a factor of 1.5 (McFall and Anastasio 2016). In addition, in our recent work with guaiacol we normalized photodecay rate constants by photon flux but still saw large differences in rate constants between solution, in ice, and at the air-ice interface (Hullar et al 2020). Thus local photon flux differences do not appear to a major factor in observed reaction rate enhancements in/on ice.…”

Section: Introductionmentioning

confidence: 83%

“…Harmine has also been reported to photodegrade faster at the air-ice interface . Most recently, we found that guaiacol photodegradation was somewhat faster in LLRs, and considerably faster at the-air ice interface, than in aqueous solution (Hullar et al 2020).…”

Section: Introductionmentioning

confidence: 91%

“…Finally, an increased quantum yield at the air-ice interface could explain a faster reaction rate, due to a greater fraction of absorbed photons resulting in loss of the chemical. Some studies suggest LLRs and solution represent similar reaction environments (Chu and Anastasio 2003, Chu and Anastasio 2005, Chu and Anastasio 2007, Ram and Anastasio 2009, while others have found higher quantum yields at the air-ice interface (Hullar et al 2020, Zhu et al 2010.…”

Section: Introductionmentioning

confidence: 99%

“…Our recent work with guaiacol (Hullar et al 2020) found that changes in the quantum yield were the dominant contributor to reaction rate differences between aqueous solution, LLRs, and…”

Section: Introductionmentioning

confidence: 99%

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Enhanced photodegradation of dimethoxybenzene isomers in/on ice compared to in aqueous solution

Hullar

Tran

Chen

et al. 2021

Preprint

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Abstract. Photochemical reactions of contaminants in snow and ice can be important sources and sinks for various organic and inorganic compounds. Snow contaminants can be found in the bulk ice matrix, in internal liquid-like regions (LLRs), or in quasi-liquid layers (QLLs) at the air-ice interface, where they can readily exchange with the firn air. Some studies have reported that direct photochemical reactions occur faster in LLRs and QLLs than in aqueous solution, while others have found similar rates. Here, we measure the photodegradation rate constants of the three dimethoxybenzene isomers under varying experimental conditions, including in aqueous solution, in LLRs, and at the air-ice interface of nature-identical snow. Relative to aqueous solution, we find modest photodegradation enhancements (3- and 6-fold) in LLRs for two of the isomers, and larger enhancements (15- to 30-fold) at the air-ice interface for all three isomers. We use computational modeling to assess the impact of light absorbance changes on photodegradation rate enhancements at the interface. We find small (2–5 nm) bathochromic (red) absorbance shifts at the interface relative to in solution, which increases light absorption, but this factor only accounts for less than 50 % of the measured rate constant enhancements. The major factor responsible for photodegradation rate enhancements at the air-ice interface appears to be more efficient photodecay: estimated dimethoxybenzene quantum yields are 6- to 24-fold larger at the interface compared to in aqueous solution and account for the majority (51–96 %) of the observed enhancements. Using a hypothetical model compound with an assumed Gaussian-shaped absorbance peak, we find that a shift in the peak to higher or lower wavelengths can have a minor to substantial impact on photodecay rate constants, depending on the original location of the peak and the magnitude of the shift. Changes in other peak properties at the air-ice interface, such as peak width and height (i.e., molar absorptivity) can also impact rates of light absorption and direct photodecay.

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Photodegradation of norfloxacin in ice: Role of the fluorine substituent

Dong

Zhang

et al. 2022

Chemosphere

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Photodecay of guaiacol is faster in ice, and even more rapid on ice, than in aqueous solution

Abstract: Guaiacol photodegradation rate constants in solution, liquid-like regions in ice (frozen solutions), and at the air–ice interface (vapor-deposited to snow).

Cited by 21 publications

References 60 publications

Measurement report: Molecular composition, optical properties, and radiative effects of water-soluble organic carbon in snowpack samples from northern Xinjiang, China

Measurement report: Molecular composition, optical properties, and radiative effects of water-soluble organic carbon in snowpack samples from northern Xinjiang, China

Enhanced photodegradation of dimethoxybenzene isomers in/on ice compared to in aqueous solution

Photodegradation of norfloxacin in ice: Role of the fluorine substituent

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