Regional atmospheric chemistry

The mechanism of the hydroxyl radical-initiated oxidation of /i-pincnc in the presence of NO has been investigated using a discharge-flow system. Propagation of hydroxyl radicals was observed after the addition of O2 and NO, and the measured concentration profiles were compared with simulations based on both the master chemical mechanism and the regional atmospheric chemistry mechanism for /i-pinene oxidation.228... 

Stockwell WR, Middleton P, Chang JS (1990) The second-generation regional acid deposition model chemical mechanism for regional atmospheric chemistry modelling. J Geophys Res 95 16343-16367... 

Keller, M., D. J. Jacob, S. C. Wofsy, and R. C. Haniss. 1991- Effects of tropical deforestation on global and regional atmospheric chemistry." Climatic Change 19 139-158. 

Geiger, H., I. Barnes, J. Bejan, T. Benter, and M. Spittler The tropospheric degradation of isoprene an updated module for the regional atmospheric chemistry mechanism. Atmospheric Environment, 37 (2003) 1503-1519. 

Optical metiiods, in both bulb and beam expermrents, have been employed to detemiine tlie relative populations of individual internal quantum states of products of chemical reactions. Most connnonly, such methods employ a transition to an excited electronic, rather than vibrational, level of tlie molecule. Molecular electronic transitions occur in the visible and ultraviolet, and detection of emission in these spectral regions can be accomplished much more sensitively than in the infrared, where vibrational transitions occur. In addition to their use in the study of collisional reaction dynamics, laser spectroscopic methods have been widely applied for the measurement of temperature and species concentrations in many different kinds of reaction media, including combustion media [31] and atmospheric chemistry [32]. 

Clean and Polluted Air. In the development of atmospheric chemistry, there has been an historic separation between those studying processes in the natural or unpolluted atmosphere, and those more concerned with air pollution chemistry. As the field has matured, these distinctions have begun to disappear, and with this disappearance has come the realization that few regions of the troposphere are completely unaffected by anthropogenic emissions. An operational definition of clean air could be based upon either the NMHC concentration, or upon the NOjj concentration. 

The presence of ionizing radiation in the upper regions of the earth s atmosphere and the realization that atmospheric chemistry can occur on the surface of ice and dust particles have lead many authors to study on the interaction of LEE with molecular solids of ozone [203], HCl [236], and halogen-containing organic compounds [176,177,195-197,199-202,205,214,217,224-234] in an effort to shed new light on the problem of ozone depletion. In a recent series of experiments, Lu and Madey [297,298] found that the and CG yields... 

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). 

The nitrogen species enter the atmosphere from a variety of natural and anthropogenic sources (7). The largest sources are concentrated in urban and industrialized areas. The levels of the species in the atmosphere vary from hundreds of parts per billion by volume (ppbv, that is, 10 9 mole fraction) in these source regions to below one part per trillion by volume (pptrv, 10"12 mole fraction) in remote areas. Even at the pptrv level, these species can play significant roles in atmospheric chemistry, and measurements of species at the sub-pptrv level can yield useful information concerning atmospheric photochemistry. 

The photodissociation of ozone (2,A,20) in the ultraviolet region is important in atmospheric chemistry, since its main product, 0(1d), reacts further with H2O and N2O to produce OH and NO (2). Recent studies (72-76) have shown that in the Hartley continuum (250-300 nm), 90% of the process is ... 

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