Unexpected nascent atmospheric emissions of three ozone-depleting hydrochlorofluorocarbons

Global and regional atmospheric measurements and modeling can play key roles in discovering and quantifying unexpected nascent emissions of environmentally important substances. We focus here on three hydrochlorofluorocarbons (HCFCs) that are restricted by the Montreal Protocol because of their roles in stratospheric ozone depletion. Based on measurements of archived air samples and on in situ measurements at stations of the Advanced Global Atmospheric Gases Experiment (AGAGE) network, we report global abundances, trends, and regional enhancements for HCFC-132b (CH2ClCCIF2), which is newly discovered in the atmosphere, and updated results for HCFC-133a (CH2ClCF3) and HCFC-31 (CH2ClF). No purposeful end-use is known for any of these compounds. We find that HCFC-132b appeared in the atmosphere 20 y ago and that its global emissions increased to 1.1 Gg.y(-1) by 2019. Regional top-down emission estimates for East Asia, based on high-frequency measurements for 2016-2019, account for similar to 95% of the global HCFC-132b emissions and for similar to 80% of the global HCFC-133a emissions of 2.3 Gg.y(-1) during this period. Global emissions of HCFC-31 for the same period are 0.71 Gg.y(-1). Small European emissions of HCFC-132b and HCFC-133a, found in southeastern France, ceased in early 2017 when a fluorocarbon production facility in that area closed. Although unreported emissive end-uses cannot be ruled out, all three compounds are most likely emitted as intermediate by-products in chemical production pathways. Identification of harmful emissions to the atmosphere at an early stage can guide the effective development of global and regional environmental policy.

Automated summary

Global and regional atmospheric measurements and modeling are crucial in identifying and quantifying unexpected emissions of environmentally important substances. This study focuses on newly discovered HCFC-132b and updates on HCFC-133a and HCFC-31, showing global emissions trends and regional enhancements. Emissions of these compounds are most likely as intermediate by-products in chemical production pathways, with East Asia being a significant contributor to global emissions.