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Abstract Sulfuryl fluoride (SO2F2) is a synthetic pesticide and a potent greenhouse gas that is accumulating in the global atmosphere. Rising emissions are a concern since SO2F2 has a relatively long atmospheric lifetime and a high global warming potential. The U.S. is thought to contribute substantially to global SO2F2 emissions, but 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. Here we provide an atmospheric measurement-based estimate of 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. We estimate that emissions of SO2F2 from California are equal to 5.5–12% of global SO2F2 emissions.

We present measurements of CO mole fraction and CO stable isotopes (δ13CO and δC18O) in air during the winters of 2013–14 and 2014–15 at tall tower sampling sites in and around Indianapolis, USA. A tower located upwind of the city was used to quantitatively remove the background CO signal, allowing for the first unambiguous isotopic characterization of the urban CO source and yielding 13CO of –27.7 ± 0.5‰ VPDB and C18O of 17.7 ± 1.1‰ VSMOW for this source. We use the tower isotope measurements, results from a limited traffic study, as well as atmospheric reaction rates to examine contributions from different sources to the Indianapolis CO budget. Our results are consistent with earlier findings that traffic emissions are the dominant source, suggesting a contribution of 96% or more to the overall Indianapolis wintertime CO emissions. Our results are also consistent with the hypothesis that emissions from a small fraction of vehicles without functional catalytic systems dominate the Indianapolis CO budget.