Chemistry in the atmosphere

Atmospheric chemistry in the Arctic has been the subject of studies for many years, in part because of the observation of Arctic haze decades ago. This haze is composed of particles with significant amounts of sulfate, about half of which is due to long-range transport from other regions, particularly Eurasia during the winter (e.g., Barrie and Bottenheim, 1991 Polissar et al., 1998a, 1998b). 

To summarize, then, we require a mechanism which (1) describes reaction rate phenomena accurately over a specified range of concentrations, (2) is a parsimonious representation of the actual atmospheric chemistry, in the interest of minimizing computation time, and (3) can be written for a general hydrocarbon species, with the inclusion of variable stoichiometric coefflcients to permit simulation of the behavior of the complex hydrocarbon mixture that actually exists in the atmosphere. Thus, we seek a mechanism which incorporates a balance between accuracy of prediction and ease of computation. 

McElroy M. B. (1989) Smdies of polar ice insights for atmospheric chemistry. In The Environmental Record in Glaciers and Ice Sheets (eds. H. Oeschgers and Langway, Jr.). Wiley, New York, pp. 363—377. 

Yang, D.L. Lin, M.C. The reactions of the CN radical with molecules relevant to combustion and atmospheric chemistry. In The Chemical Dynamics and Kinetics of Small Radicals — Advanced Series in Physical Chemistry - Vol. 6. Liu, K. Wagner, A., Eds. World Scientific, Singapore, 1998, 164-213. 

F.R. Rocha, J.A.F. da SUva, C.L. do Lago, A. Fornaro and I.GR. Gutz, Wet deposition and related atmospheric chemistry in the Sao Paulo metropolis, Brazil Part 1. Major inorganic ions in rainwater... 

A distinctly larger formation enthalpy, AH 298 = 12 3 (50 12 kJ/mol), was reported in a compilation [7] without the source of that value being clear and repeated in a review [8, 9] on kinetic data for atmospheric chemistry. In the last version [9], however, the enthalpy for... 

The 0( P) atoms react with O2 to reform O3 by reaction (5.21) which again may lead back to OH formation, via photolysis reaction (5.52) which regenerates 0( D). In an unpolluted atmosphere the main sink reaction for OH is reaction with CH4. It is this reaction which forms the backdrop to atmospheric chemistry in the troposphere. The sequence is complicated Scheme 5.1 is the model suggested by Crutzen [10], and it illustrates the most likely oxidation route for most hydrocarbons emitted into the atmosphere. 

The Third Rosenblith Lecturer at the Massachusetts Institute of Technology Atmospheric Chemistry in the 21st Century (14 March, 2000)... 

Cmtzen, P.J., 2002 Atmospheric Chemistry in the Anthropocene , in Steffen, W. Jager, J. Carson, D.J. Bradshaw. C. (Eds.) Challenges of a Changing Earth. Proceedings of the Global Change Open Science Conference, Amsterdam, The Netherlands, 10-13 July 2001 (Springer) 45 8. 

Because of the expanded scale and need to describe additional physical and chemical processes, the development of acid deposition and regional oxidant models has lagged behind that of urban-scale photochemical models. An additional step up in scale and complexity, the development of analytical models of pollutant dynamics in the stratosphere is also behind that of ground-level oxidant models, in part because of the central role of heterogeneous chemistry in the stratospheric ozone depletion problem. In general, atmospheric Hquid-phase chemistry and especially heterogeneous chemistry are less well understood than gas-phase reactions such as those that dorninate the formation of ozone in urban areas. Development of three-dimensional models that treat both the dynamics and chemistry of the stratosphere in detail is an ongoing research problem. 

Computer simulation techniques offer the ability to study the potential energy surfaces of chemical reactions to a high degree of quantitative accuracy [4]. Theoretical studies of chemical reactions in the gas phase are a major field and can provide detailed insights into a variety of processes of fundamental interest in atmospheric and combustion chemistry. In the past decade theoretical methods were extended to the study of reaction processes in mesoscopic systems such as enzymatic reactions in solution, albeit to a more approximate level than the most accurate gas-phase studies. 

The properties of water near ionic salt surfaces are of interest not only for the understanding of the mechanism of dissolution processes but also for the understanding of the chemistry in the atmosphere next to oceans [205]. Experiments in UHV [205-208] indicate that the water-covered NaCl surface is quite stable at low temperatures. An early simulation study by Anastasiou et al. [209] focused on the arrangements and orientations of water molecules in contact with a rigid NaCl crystal. Ohtaki and coworkers investigated the dissolution of very small cubic crystals of NaF, KF, CsF, LiCl, NaCl, and KCl [210] and the nucleation [211] of NaCl and CsF in a... 

Nitrogen forms several oxides, with oxidation numbers ranging from - -l to +5. All nitrogen oxides are acidic oxides and some are the acid anhydrides of the nitrogen oxoacids (Table 15.2). In atmospheric chemistry, where the oxides play an important two-edged role in both maintaining and polluting the atmosphere, the) are referred to collectively as NO (read nox ). 

Essentially, all reactions that require the formation of a chemical bond with an activation energy of around 100 kJ mol-1 are frozen out at the surface of Titan but are considerably faster in the stratosphere, although still rather slow compared with the rates of reaction at 298 K. Chemistry in the atmosphere of Titan will proceed slowly for neutral reactions but faster for ion-molecule reactions and radical-neutral reactions, both of which have low activation barriers. The Arrhenius equation provides the temperature dependence of rates of reactions but we also need to consider the effect of cold temperatures on thermodynamics and in particular equilibrium. 

One early controversy with regard to NO chemistry revolved around what was termed prompt NO. Prompt NO was postulated to form in the flame zone by mechanisms other than those thought to hold exclusively for NO formation from atmospheric nitrogen in the high-temperature zone of the flame or post-flame zone. Although the amount of prompt NO formed is quite... 

In principle, mass spectrometry is not suitable to differentiate enantiomers. However, mass spectrometry is able to distinguish between diastereomers and has been applied to stereochemical problems in different areas of chemistry. In the field of chiral cluster chemistry, mass spectrometry, sometimes in combination with chiral chromatography, has been extensively applied to studies of proton- and metal-bound clusters, self-recognition processes, cyclodextrin and crown ethers inclusion complexes, carbohydrate complexes, and others. Several excellent reviews on this topic are nowadays available. A survey of the most relevant examples will be given in this section. Most of the studies was based on ion abundance analysis, often coupled with MIKE and CID ion fragmentation on MS " and FT-ICR mass spectrometric instruments, using Cl, MALDI, FAB, and ESI, and atmospheric pressure ionization (API) methods. 

ROLE OF HYDROTHERMAL CHEMISTRY IN THE CRUSTAL-OCEAN-ATMOSPHERE FACTORY... 

Filby. W. G., The participation of free radicals in atmospheric chemistry, in Chemical Kinetics of Small Organic Molecules IV Reactions in Special Systems (Alfassi, Z. B, ed.). CRC Press, Boca Raton, Florida, 1988. 

Most chemical reactions occur in solutions. This is because a substance dissolved in a solvent, the solute, will be in its smallest state of subdivision, existing as individual molecules or ions that will increase their ability to react with other molecules or ions. Most chemistry in the body takes place in solution in the absence of the solution, much of the chemistry of life would not take place. You are familiar with solutions that are liquid, like iced tea and sea water, but solutions can also be gases, like the atmosphere, or solids, like a gold ring, which is a mixture of silver dissolved in gold. 

The chemistry of the troposphere (the layer of the atmosphere closest to earth s surface) overlaps with low-temperature combustion, as one would expect for an oxidative environment. Consequently, the concerns of atmospheric chemistry overlap with those of combustion chemistry. Monks recently published a tutorial review of radical chemistry in the troposphere. Atkinson and Arey have compiled a thorough database of atmospheric degradation reactions of volatile organic compounds (VOCs), while Atkinson et al. have generated a database of reactions for several reactive species with atmospheric implications. Also, Sandler et al. have contributed to the Jet Propulsion Laboratory s extensive database of chemical kinetic and photochemical data. These reviews address reactions with atmospheric implications in far greater detail than is possible for the scope of this review. For our purposes, we can extend the low-temperature combustion reactions [Equations (4) and (5)], whereby peroxy radicals would have the capacity to react with prevalent atmospheric radicals, such as HO2, NO, NO2, and NO3 (the latter three of which are collectively known as NOy) ... 

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