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

Chloroform (CHCl ₃ ), dichloromethane (CH ₂ Cl ₂ ), perchloroethylene (C ₂ Cl ₄ ), and 1,2-dichloroethane (C ₂ H ₄ Cl ₂ ) 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 (CHCl ₃ ), 0.0097–0.0208 (CH ₂ Cl ₂ ), 0.0057–0.0198 (C ₂ Cl ₄ ), and 0.0029–0.0119 (C ₂ H ₄ Cl ₂ ). 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 CHCl ₃ and CH ₂ Cl ranges are comparable to the mean ODP of methyl chloride (0.02), a longer-lived ozone-depleting substance.