Environment, chemistry troposphere

Existence of the PSS was predicted theoretically by Leighton (61), and experimental studies of this relationship date back almost 20 years. These experiments have been accomplished in smog chambers (62), polluted urban air (63,64,65), rural environments (66), and in the free troposphere (67). The goal of these experiments has been to verify that our understanding of NOjj chemistry is fundamentally correct, and to ver the role of H02 and R02 in ozone formation. Studies in polluted air seem to confirm the dominance... 

Atkinson R (1990) Gas-phase troposphere chemistry of organic compounds a review. Atmos Environ 24A 1-41. 

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) ... 

There has been a great deal of research activity on the effects of subsonic aircraft in the upper troposphere, with respect to impacts both on the chemistry and on the radiation balance through effects on clouds and 03 (e.g., see April 15, May 1, and May 15, 1998, issues of Geophysical Research Letters and the July 27, 1998, issue of Atmospheric Environment). Aircraft emit a variety of pollutants, including NOx, S02, and particles whose concentrations have provided exhaust signatures in some studies (e.g., Schlager et al., 1997 Hofmann et al., 1998). 

Sequential Oxidation Products from Tropospheric Isoprene Chemistry MACR and MPAN at a NOt-Rich Forest Environment in the Southeastern United States, J. Geophys. Res., 103, 22463-22471 (1998). 

Nouaime, G S. B. Bertman, C. Seaver, D. Elyea, H. Huang, P. B. Shepson, T. K. Starn, D. D. Riemer, R. G. Zika, and K. Olszyna, Sequential Oxidation Products from Tropospheric Isoprene Chemistry MACR and MPAN at a NO,-Rich Forest Environment in the Southeastern United States, J. Geophys. Res., 103, 22463-22471 (1998). 

Hayman, G. D., M. E. Jenkin, T. P. Murrells, and C. E. Johnson, Tropospheric Degradation Chemistry of HCFC-123 (CF,CHCI2) —A Proposed Replacement Chlorofluorocarbon, Atmos. Environ., 28, 421-437 (1994). 

R. Atkinson. Gas-phase tropospheric chemistry of organic-compounds — a review, Atmos. Environ. Part A - Gen. Top., 24 1 1 (1990). 

Stimulated by Levy s paper my attention turned towards tropospheric chemistry. First presented at the 1972 International Ozone Symposium in Davos, Switzerland, I proposed that in situ chemical processes could produce or destroy ozone in quantities larger than the estimated downward flux of ozone from the stratosphere to the troposphere (15, 16). Destruction of ozone occurs via reactions R5, R6 and R7 + R8. Ozone production takes place in environments containing sufficient NOx, via... 

Atkinson, R. and Arey, J. (2003) Gas-phase tropospheric chemistry of biogenic volatile organic compounds a review. Atmospheric Environment, 37 (Suppl. 2), S197-219. 

Singh H.B. and Jacob D.J. (2000). Future directions Satellite observations of tropospheric chemistry. Atmospheric Environment, 34, 4399-4401. 

Calvert, J. G. Stockwell, W. R. Acid generation in the troposphere by gas-phase chemistry. Environ. Sci. Technol. 1983, 17, 428A-442A. 

Although only 10% of atmospheric ozone resides in the troposphere (0-15 km altitude) it has a profound impact on tropospheric chemistry. Ozone concentrations in the troposphere vary from typically 20-40 ppb for a remote pristine site to 100-200 ppb in a highly polluted urban environment. Ozone is a reactive molecule, which readily adds to carbon-carbon double bonds [8]. Reaction with ozone provides an important removal mechanism for many unsaturated reactive organic compounds. 

Lighteoot PD, Cox RA, Crowley JN, Des-TRiAu M, Hayman GD, Jenkin me, Moorgat GK, Zabel E (1992) Organic Per-oxy Radicals, Kinetics, Spectroscopy and Tropospheric Chemistry, Atmos. Environ. 

The tropospheric sulfur chemistry is different. Unlike the nitrogen and carbon chemistry, where combustion is an insignificant source, the combustion source of SO2 appears to be very important. While OH reactions can be shown to convert sulfides to SO2, it is not clear that normal atmospheric chemistry is important in the next step—the conversion of S02 to H2SO, which is then removed from the atmosphere by rainout. It has also been suggested that a large amount of SO2 is removed directly by rainout. Unfortunately we have the fewest data, both kinetic and atmospheric, on sulfur compounds. Most of the kinetic data we do have are at high temperatures, and most of the atmospheric data are for polluted environments. 

It is quite ambitious for a scientist to describe a natural phenomenon in terms of a specific reaction. The situation in the atmospheric environment is however more complicated as a variety of reactions are occurring simultaneously and a certain species may take part in different reactions affecting the relative equilibria. Most data are coming from laboratory work and experimental conditions are definitely different from the ones observed in the troposphere. As an example the mechanism of oxidation of sulphur dioxide, in gas phase is usually reported occur to a large extent through free radicals. If the presence of humidity and of particulated matter is considered, specifically in the lower part of the troposphere, definitely also heterogeneous reactions play a very important role. I feel that experiments carried on in the atmosphere yield more consistent results to elucidate the chemistry of the atmospheric environment. 

Jacob D. J. (2000) Heterogeneous chemistry and tropospheric ozone. Atmos. Environ. 34, 2131-2159. 

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