ATMOSPHERIC CHEMISTRY OF TOXIC CONTAMINANTS .4. SATURATED HALOGENATED ALIPHATICS - METHYL-BROMIDE, EPICHLORHYDRIN, PHOSGENE

Mechanisms are outlined for the reactions that contribute to in-situ formation and atmospheric removal of the saturated halogenated allphatic contaminants methyl bromide, epichlorhydrin, and phosgene. In-situ formation is important only for phosgene and involves the reaction of OH with chloroethenes and other chlorinated hydrocarbons. A ranking of these phosgene precursors is given using data for precursor ambient concentrations and chemical reactivity. The three toxic compounds studied are long-lived in the atmosphere, where removal of phosgene and methyl bromide by chemical reactions is negligibly slow. Epichlorhydrin is removed slowly by reaction with OH, leading to formaldehyde, chloroacetaldehyde, and the chlorinated peroxyacyl nitrate CH2ClC(O)OONO2.