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Ozone chemiluminescent detection of olefins: Potential applications for real-time measurements of natural hydrocarbon emissions

Description: A chemiluminescence analyzer has been constructed that takes advantage of the temperature dependence of the ozone-hydrocarbon reaction. When operated at a temperature of 170 C, the analyzer functions as a total nonmethane hydrocarbon analyzer with sensitivities 10--1,000 times better than a conventional FID. However, with operation at varying temperatures, the chemiluminescent signal reflects the differences in rates of reaction of the hydrocarbons with ozone. Preliminary studies at room temperature indicated that the relative rates of reaction of isoprene, {alpha}-pinene, {beta}-pinene, and limonene with ozone correlated with the observed chemiluminescence signal. When hydrocarbons are grouped in classes of similar structure, their rates of reaction with electrophilic atmospheric oxidants (e.g., OH, O{sub 3}, NO{sub 3}) can be correlated with each other. By varying the temperature of the reaction chamber, the chemiluminescence analyzer can be tuned to more reactive classes of hydrocarbons. Therefore, the chemiluminescence analyzer has the ability to determine atmospheric hydrocarbon concentrations as a function of class and will also provide a measure of the atmospheric reactivity of the hydrocarbons.
Date: October 1, 1997
Creator: Marley, N.A.; Gaffney, J.S. & Cunningham, M.M.
Partner: UNT Libraries Government Documents Department

Residence times of fine tropospheric aerosols as determined by {sup 210}Pb progeny.

Description: Fine tropospheric aerosols can play important roles in the radiative balance of the atmosphere. The fine aerosols can act directly to cool the atmosphere by scattering incoming solar radiation, as well as indirectly by serving as cloud condensation nuclei. Fine aerosols, particularly carbonaceous soots, can also warm the atmosphere by absorbing incoming solar radiation. In addition, aerosols smaller than 2.5 {micro}m have recently been implicated in the health effects of air pollution. Aerosol-active radioisotopes are ideal tracers for the study of atmospheric transport processes. The source terms of these radioisotopes are relatively well known, and they are removed from the atmosphere only by radioactive decay or by wet or dry deposition of the host aerosol. The progeny of the primordial radionuclide {sup 238}U are of particular importance to atmospheric studies. Uranium-238 is common throughout Earth's crust and decays to the inert gas {sup 222}Rn, which escapes into the atmosphere. Radon-222 decays by the series of alpha and beta emissions shown in Figure 1 to the long-lived {sup 210}Pb. Once formed, {sup 210}Pb becomes attached to aerosol particles with average attachment times of 40 s to 3 min.
Date: October 5, 1999
Creator: Marley, N. A.; Gaffney, J. S.; Drayton, P. J.; Cunningham, M. M.; Mielcarek, C.; Ravelo, R. et al.
Partner: UNT Libraries Government Documents Department

Phoenix, Arizona, revisited : indications of aerosol effects on O{sub 3}, NO{sub 2}, UV-B, and NO{sub 3}.

Description: Fine particulate matter and tropospheric ozone levels are of concern because of their potential for health impacts, as well as their radiative effects. Both ozone and PM-2.5 standards are being exceeded in many urban and regional areas where transport and background levels can appreciably affect observed concentrations. Anthropogenic nitrogen oxides and other primary pollutant species can interact with natural organics to form secondary aerosol products via synthesis of nitric acid and its subsequent reaction with ammonia to yield ammonium nitrate. In addition, natural organics and lower-reactivity organic compounds, particularly aromatic species and monoterpenes, can generate secondary organic aerosols, both of which contribute to the formation of PM-2.5. Long-range transport and chemical transformation of hydrocarbons and NO{sub x} via both photochemical reactions and nighttime chemistry can generate significant regional levels of ozone (O{sub 3}) and other oxidants, such as peroxyacyl nitrates.
Date: September 30, 1999
Creator: Gaffney, J. S.; Marley, N. A.; Drayton, P. J.; Cunningham, M. M.; Baird, J. C.; Dintaman, J. et al.
Partner: UNT Libraries Government Documents Department