Red sky at night: Long-wavelength photochemistry in the atmosphere

D. J. Donaldson (1) , C. George (2, 3) , Veronica Vaida (4)

1 University of Toronto
2 IRCELYON - Institut de recherches sur la catalyse et l'environnement de Lyon
3 CARE - IRCELYON-Catalytic and Atmospheric Reactivity for the Environment
4 University of Colorado [Boulder]

Chemical reactions occurring in the atmosphere exert a key influence on air quality at the local and regional scales. On a global scale they have a strong affect on climate, through formation and removal of greenhouse gases, as well as driving cloud formation. Earth’s atmosphere is composed roughly 99% of two gases: molecular nitrogen (N2; ∼78%)and molecular oxygen(O2; ∼21%), with variable and highly local amounts of water vapor (H2O [v] ; up to afew percent), as well as various trace gas species (such as CO2,presentlyataconcentrationofalittlelessthan0.04%). On Earth, “atmospheric chemistry” involves chemical species present only in trace amounts, and is almost exclusively oxidative. Because O2 is not particularly reactive toward closed shell compounds (those without free electrons), chemistry is initiated by the formation of reactive free radicals, which are then oxidized via the addition of molecular oxygen. Since this addition reaction itself generates free radicals, it is but one such reaction in a sequence, which together comprise an oxidizing chain reaction system in the atmosphere. There is a multitude of organic species in the atmosphere, the most abundant of which is methane(CH4), which are all eventually oxidized to CO2 and H2O, either by gas or aerosol phase processes.

Domaines: Autre

D. J. Donaldson, C. George, Veronica Vaida. Red sky at night: Long-wavelength photochemistry in the atmosphere. Environmental Science and Technology, 2010, 44 (14), pp.5321-5326. ⟨10.1021/es903680v⟩. ⟨hal-00512074⟩