Fluorine in the Atmosphere
Résumé
Scientific evidence, accumulated over more than two decades of study by the international research community, has shown that human-produced halocarbons are responsible for the observed depletions of the ozone layer. Fluorine-containing chlorofluorocarbons (CFCs) and halons are sufficiently long-lived so as to reach the stratosphere where they are photodissociated to release chlorine, bromine, and fluorine atoms. Although chlorine and bromine have been proven to be main responsible for the destruction of the ozone layer in the polar regions, fluorine by itself does not contribute to ozone depletion. Fluorine atoms released from the photodissociation of fluorine-bearing sources are quickly sequestered into carbonyl compounds and subsequently into the ultimate hydrogen fluoride, which is very stable in the stratosphere. The primary interest in monitoring inorganic fluorine (defined as Fy) in the atmosphere is as a surrogate of the amounts of its precursors, mainly the CFCs and hydrochlorofluorocarbons, involved in ozone depletion by chlorine. Fluorinated halocarbons and other gases such as perfluorocarbons or sulfur hexafluoride (SF6) are also extremely potent greenhouse gases for which the current trends must be monitored and future scenarios of growth must be evaluated.
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