On the Regional and Seasonal Ozone Depletion Potential of Chlorinated Very Short-Lived Substances

Chloroform (CHCl₃), dichloromethane (CH₂Cl₂), perchloroethylene (C₂Cl₄), and 1,2-dichloroethane (C₂H₄Cl₂) are chlorinated Very Short-Lived Substances (Cl-VSLS) with a range of commercial/industrial applications. Recent studies highlight the increasing influence of Cl-VSLS on the stratospheric chlorine budget and therefore their possible role in ozone depletion. Here we evaluate the ozone depletion potential (ODP) of these Cl-VSLS using a three-dimensional chemical transport model and investigate sensitivity to emission location/season. The seasonal dependence of the ODPs is small, but ODPs vary by a factor of 2-3 depending on the continent of emission: 0.0143-0.0264 (CHCl₃), 0.0097-0.0208 (CH₂Cl₂), 0.0057-0.0198 (C₂Cl₄), and 0.0029-0.0119 (C₂H₄Cl₂). Asian emissions produce the largest ODPs owing to proximity to the tropics and efficient troposphere-to-stratosphere transport of air originating from industrialized East Asia. The Cl-VSLS ODPs are generally small, but the upper ends of the CHCl₃ and CH₂Cl₂ ranges are comparable to the mean ODP of methyl chloride (0.02), a longer-lived ozone-depleting substance.