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The Endangered Global Atmosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
In addition to acting as a greenhouse gas, methane has significant effects on atmospheric chemistry. It produces atmospheric CO as an intermediate oxidation product and influences concentrations of atmospheric hydroxyl radicals and ozone. In the stratosphere, it produces hydrogen and H2O , but acts to remove ozone-destroying chlorine.
A changing context for civil nuclear power
Published in Chris Anastasi, Who Needs Nuclear Power, 2020
The attributes that made CFCs highly effective in their applications meant that, when released into the atmosphere at ground level, they passed unchanged through the troposphere and into the stratosphere, a stable part of the earth’s atmosphere that contains the ozone layer. It was possible to explain the complex atmospheric chemistry of CFCs in ozone depletion, including the need for polar clouds in the highly stable stratospheric environment above the Antarctic. The subsequent observation of a key, short-lived chemical species in the stratosphere confirmed the hypothesis that CFCs and other man-made chemicals were indeed leading to widespread destruction of the ozone layer above the Antarctic. And the ‘hole’ was getting bigger each year.
Heterogeneous–Homogeneous and Homogeneous–Heterogeneous Processes in Atmospheric Chemistry
Published in Robert Bakhtchadjian, Bimodal Oxidation: Coupling of Heterogeneous and Homogeneous Reactions, 2019
Nearly all studies on the heterogeneous reactions of atmospheric radicals directly or indirectly relate to problems involving the depletion of ozone.11,12 In the 1990s, Calvert revealed the crucial role of aerosol particles (polar stratospheric clouds, PSCs) in the Antarctic's ozone depletion at the end of winters and in extremely cold conditions.10 The results of the investigations of the heterogeneous chemistry on the polar stratospheric clouds were successfully applied in modeling of ozone depletion problems at low stratosphere, which led to important conclusions in atmospheric chemistry.
Bioaerosol field measurements: Challenges and perspectives in outdoor studies
Published in Aerosol Science and Technology, 2020
Tina Šantl-Temkiv, Branko Sikoparija, Teruya Maki, Federico Carotenuto, Pierre Amato, Maosheng Yao, Cindy E. Morris, Russ Schnell, Ruprecht Jaenicke, Christopher Pöhlker, Paul J. DeMott, Thomas C. J. Hill, J. Alex Huffman
Bioaerosols were among the first types of atmospheric aerosols to be identified (Carnelley et al. 1887; De Bary 1887; Pasteur 1862; Ehrenberg 1847). Contemporary outdoor field measurements of bioaerosols are performed within a tremendously widespread set of basic and applied scientific disciplines that foster research toward separate scientific goals and with distinct sets of community-associated terminology and assumptions. For example, areas of scientific research with established application to outdoor bioaerosols very broadly include the following: (i) atmospheric physics, clouds, climate, and hydrological cycle, (ii) atmospheric chemistry, (iii) airborne allergen-containing particles, (iv) airborne human pathogens and national security, (v) airborne livestock and crop pathogens, and (vi) biogeography and biodiversity. The role of outdoor bioaerosol field measurements for each of these areas is discussed in Section 2.
A perspective on the development of gas-phase chemical mechanisms for Eulerian air quality models
Published in Journal of the Air & Waste Management Association, 2020
William R. Stockwell, Emily Saunders, Wendy S. Goliff, Rosa M. Fitzgerald
Global atmospheric chemistry models are becoming increasingly important as sources of boundary conditions for air quality models (Henderson et al. 2014; Saunders 2017). The mechanisms employed in global models require different chemical mechanisms than mechanisms prepared for regional models. Global models require chemical mechanisms that are valid over oceans as well as over land masses. Oceans are significant sources of halogens and reduced sulfur compounds that have complex chemistries (Warneck 2000). However, there are differences in the VOC emissions since anthropogenic emissions are not as prevalent over the ocean although polluted plumes from continental sources can cover significant areas of the oceans (Lelieveld et al. 2001). Global atmospheric chemistry models may include a significant amount of stratospheric chemistry. In this section, we discuss the GEOS-Chem Mechanism, the Model for Ozone and Related chemical Tracers (MOZART) mechanism and the Global Atmospheric Chemistry Mechanism (GACM). GACM is part of the RADM/RACM mechanism series.
Resonance enhanced multiphoton ionisation (REMPI) detection of Cl(2Pj) atom in the photodissociation of halogenated pyrimidines at 235 nm: role of triplet states
Published in Molecular Physics, 2019
Doddipatla Srinivas, Monali Kawade, Hari P. Upadhyaya
Photodissociation of halogen (Cl and Br) containing organic molecules has attracted a lot of experimental and theoretical studies since these compounds produce halogen atoms which play an important role in atmospheric chemistry, particularly in ozone depletion. In general, impulsive atomic eliminations are observed in the dissociation process of these compounds which arise mainly from either a dissociative surface adiabatically or non-adiabatically, after curve crossing. In this context, various photodissociation studies of alkyl halides and aryl halides have been well investigated. However, these kinds of studies are very scarce in literature for halogenated heterocyclic molecules. The most studied heterocyclic compound is pyridine (c-C5H5N), where one of the CH group in benzene is replaced by N. The interesting outcome of our recent work on the photodissociation of halogenated pyridines motivated us to probe the dissociation dynamics of these heterocyclic compounds further. In this context, we have undertaken the present study on the photodissociation of halogenated pyrimidines.