Reply to “Comment on ‘Reactivity of Ketyl and Acetyl Radicals from Direct Solar Actinic Photolysis of Aqueous Pyruvic Acid’”

Eugene, Alexis J.; Guzmán, Marcelo I.

doi:10.1021/acs.jpca.7b08273

Cited by 14 publications

(43 citation statements)

References 30 publications

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“…Organic and inorganic molecules can act as chromophores, or light absorbing moieties, that absorb visible and ultraviolet radiation. These compounds, such as conjugated double bonds or carbonyls, lead to the formation of excited state molecules that can undergo homolytic bond cleavage, radical recombination, electron transfer, decomposition, hydrogen abstraction, photosensitization, and proton coupled electron transfer [82,83,93,94,[96][97][98][99][100][101]. The resulting products, which are similar to what is observed with particle-phase accretion chemistry, dehydrate or cyclize during the night to form oligomers or supramacromolecular structures.…”

Section: Aging Of Aerosols In the Atmospherementioning

confidence: 75%

“…As many atmospheric aerosols are comprised of acidic components, these reactions represent a common pathway for the formation of non-volatile species in aerosols [90]. In addition to chemical reactions, sunlight can also facilitate the processing, accretion, and aging chemistry in and on atmospheric particles [82,83,[91][92][93][94][95][96][97]. Noteworthy, when gaseous carboxylic acid partition from air into the particle phase, they exert enhanced acidities to the water interface that are at least larger than 1.7 pH-units than predicted by bulk pK a values [95].…”

Section: Aging Of Aerosols In the Atmospherementioning

confidence: 99%

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An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

Pillar-Little

Guzmán

2018

Environments

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Due to the adverse effect of atmospheric aerosols on public health and their ability to affect climate, extensive research has been undertaken in recent decades to understand their sources and sinks, as well as to study their physical and chemical properties. Atmospheric aerosols are important players in the Earth’s radiative budget, affecting incoming and outgoing solar radiation through absorption and scattering by direct and indirect means. While the cooling properties of pure inorganic aerosols are relatively well understood, the impact of organic aerosols on the radiative budget is unclear. Additionally, organic aerosols are transformed through chemical reactions during atmospheric transport. The resulting complex mixture of organic aerosol has variable physical and chemical properties that contribute further to the uncertainty of these species modifying the radiative budget. Correlations between oxidative processing and increased absorptivity, hygroscopicity, and cloud condensation nuclei activity have been observed, but the mechanisms behind these phenomena have remained unexplored. Herein, we review environmentally relevant heterogeneous mechanisms occurring on interfaces that contribute to the processing of aerosols. Recent laboratory studies exploring processes at the aerosol–air interface are highlighted as capable of generating the complexity observed in the environment. Furthermore, a variety of laboratory methods developed specifically to study these processes under environmentally relevant conditions are introduced. Remarkably, the heterogeneous mechanisms presented might neither be feasible in the gas phase nor in the bulk particle phase of aerosols at the fast rates enabled on interfaces. In conclusion, these surface mechanisms are important to better understand how organic aerosols are transformed in the atmosphere affecting the environment.

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Section: Aging Of Aerosols In the Atmospherementioning

confidence: 75%

Section: Aging Of Aerosols In the Atmospherementioning

confidence: 99%

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

Pillar-Little

Guzmán

2018

Environments

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“…Pyruvic acid (PA, p K a = 2.39) [1] is an abundant component of tropospheric aerosols [2,3,4], and one of the few chromophores capable of undergoing photochemical reactions in water [5,6,7,8,9,10]. It is produced during the atmospheric photooxidative processing of biogenic and anthropogenic emissions [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…The processing of PA in atmospheric waters by sunlight’s photons [7,8,9,23,24,25,26] and by hydroxyl radicals (HO • ), generated from the photolysis of H 2 O 2 [11], have also been reported. Upon excitation of PA, the produced excited state singlet 1 PA * quickly undergoes intersystem crossing (ISC) to produce a reactive triplet 3 PA * .…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Reactant Concentration and Air Flow Rate in the Consumption of Dissolved O2 during the Photochemistry of Aqueous Pyruvic Acid

Eugene

Guzmán

2019

Molecules

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The sunlight photochemistry of the organic chromophore pyruvic acid (PA) in water generates ketyl and acetyl radicals that contribute to the production and processing of atmospheric aerosols. The photochemical mechanism is highly sensitive to dissolved oxygen content, [O2(aq)], among other environmental conditions. Thus, herein we investigate the photolysis (λ ≥ 305 nm) of 10–200 mM PA at pH 1.0 in water covering the relevant range 0 ≤ [O2(aq)] ≤ 1.3 mM. The rapid consumption of dissolved oxygen by the intermediate photolytic radicals is monitored in real time with a dissolved oxygen electrode. In addition, the rate of O2(aq) consumption is studied at air flow rates from 30.0 to 900.0 mL min−1. For the range of [PA]0 covered under air saturated conditions and 30 mL min−1 flow of air in this setup, the estimated half-lives of O2(aq) consumed by the photolytic radicalsfall within the interval from 22 to 3 min. Therefore, the corresponding depths of penetration of O2(g) into water (x = 4.3 and 1.6 µm) are determined, suggesting that accumulation and small coarse mode aqueous particles should not be O2-depleted in the presence of sunlight photons impinging this kind of chromophore. These photochemical results are of major tropospheric relevance for understanding the formation and growth of secondary organic aerosol.

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Formation of highly oxygenated multifunctional compounds from cross-reactions of carbonyl compounds in the atmospheric aqueous phase

Mekić

Liu

Zhou

et al. 2019

Atmospheric Environment

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There is increasing evidence that aqueous-phase atmospheric chemistry is an important source of secondary organic aerosols (SOA), but this chemistry is currently not adequately represented in atmospheric models due to the missing information on most products. The main focus of this study is to provide molecular-level insight into the photosensitized reaction mechanism of pyruvic acid (PA) alone in the atmospheric aqueous phase, and of mixtures of PA with glyoxal (GL), a typical and widely occurring carbonyl compound. With two ultrahigh resolution mass spectrometers, Orbitrap and FT-ICR-MS, a broad and complex spectrum of organic products were unambiguously identified. The detected formation of oligomers illustrates the progression from C 3 to C 20 molecules through direct PA photolysis and irradiation of PA + GL. The performed ab-initio calculations indicate that cross-reactions (i.e., PA + GL) are more likely than self-reactions (i.e., PA alone) in clouds and aerosol deliquescent particles. Hence, this result implies that photosensitizers like PA can initiate the transformation of common organic cloud constituents like GL into oligomers. These oligomeric products that are formed in significant amount could potentially impact optical and cloud-forming properties of aerosols, especially if they partition to the aerosol surface.

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Reply to “Comment on ‘Reactivity of Ketyl and Acetyl Radicals from Direct Solar Actinic Photolysis of Aqueous Pyruvic Acid’”

Cited by 14 publications

References 30 publications

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

The Effects of Reactant Concentration and Air Flow Rate in the Consumption of Dissolved O2 during the Photochemistry of Aqueous Pyruvic Acid

Formation of highly oxygenated multifunctional compounds from cross-reactions of carbonyl compounds in the atmospheric aqueous phase

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