California Dominates U.S. Emissions of Sulfuryl Fluoride, a Synthetic Pesticide and Potent Greenhouse Gas

Sulfuryl fluoride (SO₂F₂) is a synthetic pesticide and a potent greenhouse gas (GHG) that is accumulating in the global atmosphere. SO₂F₂ has been increasingly used for agricultural and structural fumigation worldwide to replace methyl bromide (CH₃Br), which was largely phased out under the Montreal Protocol to protect the ozone layer. Rising emissions of SO₂F₂ are concerning due to its relatively long atmospheric lifetime and high global warming potential (GWP). However, there is a paucity of information on how emissions of SO₂F₂ are distributed across the U.S., and there is currently no inventory of SO₂F₂ emissions for the U.S. or individual states. We provide an atmospheric measurement-based constraint on U.S. SO₂F₂ emissions using high-precision SO₂F₂ measurements from the NOAA Global Greenhouse Gas Reference Network (GGGRN) and a geostatistical inverse model. We find that California has the largest SO₂F₂ emissions among all U.S. states, with the highest emissions from southern coastal California (Los Angeles, Orange, and San Diego counties). Outside of California, only very small and infrequent SO₂F₂ emissions are detected by our analysis of GGGRN data. We find that California emits 60-85\% of U.S. SO₂F₂ emissions, at a rate of 0.26 (+/-0.10) Gg yr^-1. Furthermore, we estimate that emissions of SO₂F₂ from California are equal to 5.5-12% of global SO₂F₂ emissions -- a large contribution from a single state.