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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. SO F emissions, at a rate of 0.26 (+/-0.10) Gg yr-1 . Furthermore, we estimate that emissions of SO F from California are equal to 5.5-12% of global SO2F2 emissions -- a large contribution from a single state. 

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 SO₂F₂has a relatively long atmospheric lifetime and a high global warming potential. The U.S. is thought to contribute substantially to global SO₂F₂emissions, but there is a paucity of information on how emissions of SO₂F₂are distributed across the U.S., and there is currently no inventory of SO₂F₂emissions for the U.S. or individual states. Here we provide an atmospheric measurement-based estimate of U.S. SO₂F₂emissions using high-precision SO₂F₂measurements from the NOAA Global Greenhouse Gas Reference Network (GGGRN) and a geostatistical inverse model. We find that California has the largest SO₂F₂emissions 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 SO₂F₂emissions are detected by our analysis of GGGRN data. We find that California emits 60-85% of U.S. SO₂F₂emissions, at a rate of 0.26 ( ± 0.10) Gg yr⁻¹. We estimate that emissions of SO₂F₂from California are equal to 5.5–12% of global SO₂F₂emissions. 

The mean abundance of sulfuryl fluoride (SO2F2) in the global atmosphere has been increasing since at least the 1970s, with ambient air mole fractions exceeding 2.5 parts per trillion (ppt) today. SO2F2 is a synthetic pesticide and a potent greenhouse gas (GHG) used for fumigation - predominantly of wooden structures, and increasingly for agricultural and commodity products as well. Worldwide use of SO2F2 has surged since the use of methyl bromide (CH3Br) for fumigation was largely phased out under the Montreal Protocol. Recent atmospheric measurements and modeling work from the Advanced Global Atmospheric Gases Experiment (AGAGE) indicates that global emissions of SO2F2 have reached a historic high in recent years at roughly 3.0 Gg SO2F2 yr-1. However, under the current UNFCCC emissions reporting guidelines, countries are not required to report their emissions of SO2F2, and thus SO2F2 is not included in most national GHG emissions inventories, leading to a scarcity of information on the global distribution and magnitude of SO2F2 emissions. In the U.S., California is the only state that keeps a public record of statewide SO2F2 use, despite the gas being used for termite fumigation in other warm-climate coastal states such as Florida. To fill this information gap, we use flask-sample measurements of SO2F2 from the NOAA Global Greenhouse Gas Reference Network (GGGRN) and a geostatistical inverse model (GIM) to provide a measurement-based top-down constraint on the magnitude and spatial distribution of SO2F2 emissions across the continental U.S. We find that California emits the vast majority (>90%) of U.S. SO2F2 emissions, with the largest emissions coming from the California South Coast (Los Angeles, Orange, and San Diego Counties), and the second largest from the San Francisco Bay Area. Outside of California, SO2F2 emissions are rarely detected by the NOAA GGGRN. However, despite California's oversized contribution to U.S. SO2F2 emissions, a significantly large fraction (>50%) of the 3.0 Gg yr-1 global emissions budget is still emitted elsewhere. We will present insights gained from the NOAA GGGRN measurements and our inverse modeling work, including a case study on California's SO2F2 emissions and reconciliation with California state SO2F2 usage records. 

Abstract. We apply airborne measurements across three seasons(summer, winter and spring 2017–2018) in a multi-inversion framework toquantify methane emissions from the US Corn Belt and Upper Midwest, a keyagricultural and wetland source region. Combing our seasonal results withprior fall values we find that wetlands are the largest regional methanesource (32 %, 20 [16–23] Gg/d), while livestock (enteric/manure; 25 %,15 [14–17] Gg/d) are the largest anthropogenic source. Naturalgas/petroleum, waste/landfills, and coal mines collectively make up theremainder. Optimized fluxes improve model agreement with independentdatasets within and beyond the study timeframe. Inversions reveal coherentand seasonally dependent spatial errors in the WetCHARTs ensemble meanwetland emissions, with an underestimate for the Prairie Pothole region butan overestimate for Great Lakes coastal wetlands. Wetland extent andemission temperature dependence have the largest influence on predictionaccuracy; better representation of coupled soil temperature–hydrologyeffects is therefore needed. Our optimized regional livestock emissionsagree well with the Gridded EPA estimates during spring (to within 7 %) butare ∼ 25 % higher during summer and winter. Spatial analysisfurther shows good top-down and bottom-up agreement for beef facilities (withmainly enteric emissions) but larger (∼ 30 %) seasonaldiscrepancies for dairies and hog farms (with > 40 % manureemissions). Findings thus support bottom-up enteric emission estimates butsuggest errors for manure; we propose that the latter reflects inadequatetreatment of management factors including field application. Overall, ourresults confirm the importance of intensive animal agriculture for regionalmethane emissions, implying substantial mitigation opportunities throughimproved management. 

Abstract Carbon monoxide (CO) is an ozone precursor, oxidant sink, and widely used pollution tracer. The importance of anthropogenic versus other CO sources in the US is uncertain. Here, we interpret extensive airborne measurements with an atmospheric model to constrain US fossil and nonfossil CO sources. Measurements reveal a low bias in the simulated CO background and a 30% overestimate of US fossil CO emissions in the 2016 National Emissions Inventory. After optimization we apply the model for source partitioning. During summer, regional fossil sources account for just 9%–16% of the sampled boundary layer CO, and 32%–38% of the North American enhancement—complicating use of CO as a fossil fuel tracer. The remainder predominantly reflects biogenic hydrocarbon oxidation plus fires. Fossil sources account for less domain‐wide spatial variability at this time than nonfossil and background contributions. The regional fossil contribution rises in other seasons, and drives ambient variability downwind of urban areas.