Joint inversions of HCFC-22 and HFC-23 for partitioning emission sources of HCFC-22 in eastern China (2010-2024)

Abstract: Emissions verification of controlled substances, such as HFC-23 and HCFC-22, is needed to ensure compliance with the Montreal Protocol and its amendments, and greenhouse gas emission reduction goals. Atmospheric trace gas measurements are often used to infer surface emissions through inverse modelling. HFC-23 emissions are thought to predominantly arise as a byproduct of HCFC-22 production (which is used as a refrigerant and as a feedstock). Recent observation-inferred HFC-23 emissions for eastern China were found to be substantially higher than 2020-2022 emissions reported for the whole of China, the world’s largest HCFC-22 producer. The cause of this large discrepancy remains unexplained. However, constraining HCFC-22 emissions from production vs. usage/end-of-life could add constraints on the cause of the HFC-23 emissions discrepancy and improve our understanding of how emissions of these two species are interlinked.

Here, we developed an inverse method for partitioning production and usage/end-of-life HCFC-22 emissions by using HFC-23 as a tracer for HCFC-22 production emissions – linked through an adjustable HCFC-22-HFC-23 emissions ratio factor. We will present inversion results for 2010 to 2023 for eastern China for HFC-23 and HCFC-22 using two different inverse frameworks in our model, ARTEMIS (Atmospheric Regional Trace gas Emissions Modeling Inverse System), with atmospheric HFC-23 and HCFC-22 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network. We will show how using a multi-species inverse method changes the observation-inferred HFC-23 and HCFC-22 emission magnitudes and spatial distributions for eastern China compared to when a single-species inverse method is used. An advantage of the multi-species approach is that it will impose additional constraints on the partitioning of HCFC-22 emission sources and on our understanding of the HCFC-22 production and HFC-23 emissions relationship.