Introductory lecture: atmospheric chemistry in the Anthropocene

Finlayson-Pitts, Barbara J.

doi:10.1039/c7fd00161d

Cited by 20 publications

(15 citation statements)

References 580 publications

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“…Nitrous acid is generated in the gas phase, with indications that it results from the decomposition of the -NO 2 containing CI. This acid absorbs strongly in the actinic region that reaches Earth's surface, and, through its photolysis, it is a major source of the OH radical that drives the chemistry of the atmosphere (17,65). While the NPM−O 3 reaction is not expected to be a significant source of HONO relative to other known outdoor and indoor sources on a global basis (66,67), it may play a role locally where NPM is used, and its production in this reaction is certainly of mechanistic interest.…”

Section: Resultsmentioning

confidence: 99%

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram

Wang

Ezell

Lakey

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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The neonicotinoid nitenpyram (NPM) is a multifunctional nitroenamine [(R1N)(R2N)C=CHNO2] pesticide. As a nitroalkene, it is structurally similar to other emerging contaminants such as the pharmaceuticals ranitidine and nizatidine. Because ozone is a common atmospheric oxidant, such compounds may be oxidized on contact with air to form new products that have different toxicity compared to the parent compounds. Here we show that oxidation of thin solid films of NPM by gas-phase ozone produces unexpected products, the majority of which do not contain oxygen, despite the highly oxidizing reactant. A further surprising finding is the formation of gas-phase nitrous acid (HONO), a species known to be a major photolytic source of the highly reactive hydroxyl radical in air. The results of application of a kinetic multilayer model show that reaction was not restricted to the surface layers but, at sufficiently high ozone concentrations, occurred throughout the film. The rate constant derived for the O3−NPM reaction is 1 × 10−18cm3⋅s−1, and the diffusion coefficient of ozone in the thin film is 9 × 10−10cm2⋅s−1. These findings highlight the unique chemistry of multifunctional nitroenamines and demonstrate that known chemical mechanisms for individual moieties in such compounds cannot be extrapolated from simple alkenes. This is critical for guiding assessments of the environmental fates and impacts of pesticides and pharmaceuticals, and for providing guidance in designing better future alternatives.

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Section: Resultsmentioning

confidence: 99%

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram

Wang

Ezell

Lakey

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…On the other hand, experiments in thin water films containing nitrate, chlorine, and bromine salts have shown that the photolysis of NO 3 – occurs much faster at interfaces than in the bulk, ,,− with J values ranging between 1.2 × 10 –3 and 3 × 10 –6 s –1 , depending on the features of the interface. ,,, A potential explanation for this enhancement is associated with the solvation of nitrate anion. In bulk water, nitrate is surrounded by a solvent cage that facilitates both the recombination of the NO 2 and OH radicals produced by reaction and their deactivation by collision with solvent molecules, thus decreasing the photolysis quantum yield. ,,, MD simulations have shown that when halide anions (especially bromide) are present, nitrate ions are dragged closer to the interface so that the water solvent cage surrounding them is reduced, , arguably making the escape of NO 2 to the gas phase easier. ,,− Nevertheless, despite the large amount of work done on nitrate photochemistry, open issues remain that are not yet completely understood. For instance, it was recently shown that an important part of nitric acid remains undissociated at the air–water interface, ,− and the relevance of the corresponding photochemistry is still undetermined.…”

Section: Photochemistry Of Oh Precursorsmentioning

confidence: 99%

“…On one hand, field observations have shown that the photolysis of HNO3 adsorbed on the forest canopy surface is an important source of HONO. 82 On the other hand, experiments in thin water films containing nitrate, chlorine, and bromine salts have shown that the photolysis of NO " % occurs much faster at interfaces than in the bulk, 63,81,[90][91][92][93][94] with J values ranging between 1.2 × 10 −3 s −1 and 3 × 10 −6 s −1 depending on the features of the interface. 63,83,95,96 A potential explanation for this enhancement is associated with the solvation of nitrate anion.…”

Section: Reactive Nitrogen Species (Rns)mentioning

confidence: 99%

Photoinduced Oxidation Reactions at the Air–Water Interface

et al. 2020

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Chemistry on water is a fascinating area of research. The surface of water and the interfaces between water and air or hydrophobic media represent asymmetric environments with unique properties that lead to unexpected solvation effects on chemical and photochemical processes. Indeed, the features of interfacial reactions differ, often drastically, from those of bulk-phase reactions. In this Perspective, we focus on photoinduced oxidation reactions, which have attracted enormous interest in recent years because of their implications in many areas of chemistry, including atmospheric and environmental chemistry, biology, electrochemistry, and solar energy conversion. We have chosen a few representative examples of photoinduced oxidation reactions to focus on in this Perspective. Although most of these examples are taken from the field of atmospheric chemistry, they were selected because of their broad relevance to other areas. First, we outline a series of processes whose photochemistry generates hydroxyl radicals. These OH precursors include reactive oxygen species, reactive nitrogen species, and sulfur dioxide. Second, we discuss processes involving the photooxidation of organic species, either directly or via photosensitization. The photochemistry of pyruvic acid and fatty acid, two examples that demonstrate the complexity and versatility of this kind of chemistry, is described. Finally, we discuss the physicochemical factors that can be invoked to explain the kinetics and thermodynamics of photoinduced oxidation reactions at aqueous interfaces and analyze a number of challenges that need to be addressed in future studies.

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“…The setup utilized a flow-through reactor to provide the reactive uptake coefficient of ozone on catechol films [61] under variable humidity conditions, and elucidated the formation of quinones as well as biphenyl and terphenyl rings [61]. Present and future laboratory, chamber, and field studies to examine the product mixtures resulting from these mechanisms are being inspired [152][153][154][155][156][157][158][159][160][161][162][163] by this work, to gather information for inclusion in the next generation of computational models to predict the effects of aerosols on climate.…”

Section: Outcomes Learned From Recent Interfacial Studiesmentioning

confidence: 99%

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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Introductory lecture: atmospheric chemistry in the Anthropocene

Cited by 20 publications

References 580 publications

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram

Unexpected formation of oxygen-free products and nitrous acid from the ozonolysis of the neonicotinoid nitenpyram

Photoinduced Oxidation Reactions at the Air–Water Interface

An Overview of Dynamic Heterogeneous Oxidations in the Troposphere

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