California dominates U.S. emissions of sulfuryl fluoride, a potent greenhouse gas

Abstract:

Sulfuryl fluoride (SO₂F₂) is a potent greenhouse gas whose presence has been steadily rising in the global atmosphere since at least the late 1970’s due to anthropogenic activities. Flask samples from the NOAA global sampling network, collected at observatory stations, tall towers, and aircraft campaigns, and measured via gas chromatography/mass spectrometry (GC-MS), indicate an annual atmospheric growth rate of ~9% per year. Atmospheric mixing ratios measured in the Southern Hemisphere have a 1-2 year lag behind Northern Hemisphere mixing ratios, which suggests that the bulk of global SO₂F₂ emissions occur in the Northern Hemisphere and mix at the interhemispheric exchange timescale. However, not much work has been done thus far to identify SO₂F₂ emission sources and their magnitudes. This study utilizes the NOAA flask sample measurements along with an atmospheric particle dispersion model and an inverse model to provide the first top-down estimate of surface emission fluxes of SO₂F₂ over North America. We find that the vast majority of emissions originate from the State of California, where SO₂F₂ is widely used as a fumigant. SO₂F₂ was not included in the state’s Global Warming Solutions Act of 2006 because its climate warming properties were not known at the time. This work emphasizes the importance of considering SO₂F₂ as part of the state’s emissions reduction goals.