A gap in emission inventories of urban volatile organic compound (VOC) sources, which contribute to regional ozone and aerosol burdens, has increased as transportation emissions in the United States ...and Europe have declined rapidly. A detailed mass balance demonstrates that the use of volatile chemical products (VCPs)-including pesticides, coatings, printing inks, adhesives, cleaning agents, and personal care products-now constitutes half of fossil fuel VOC emissions in industrialized cities. The high fraction of VCP emissions is consistent with observed urban outdoor and indoor air measurements. We show that human exposure to carbonaceous aerosols of fossil origin is transitioning away from transportation-related sources and toward VCPs. Existing U.S. regulations on VCPs emphasize mitigating ozone and air toxics, but they currently exempt many chemicals that lead to secondary organic aerosols.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Emissions of methane (CH4) from oil and natural gas (O&G) operations in the most densely drilled area of the Denver‐Julesburg Basin in Weld County located in northeastern Colorado are estimated for 2 ...days in May 2012 using aircraft‐based CH4 observations and planetary boundary layer height and ground‐based wind profile measurements. Total top‐down CH4 emission estimates are 25.8 ± 8.4 and 26.2 ± 10.7 t CH4/h for the 29 and 31 May flights, respectively. Using inventory data, we estimate the total emissions of CH4 from non‐O&G gas‐related sources at 7.1 ± 1.7 and 6.3 ± 1.0 t CH4/h for these 2 days. The difference in emissions is attributed to O&G sources in the study region, and their total emission is on average 19.3 ± 6.9 t/h, close to 3 times higher than an hourly emission estimate based on Environmental Protection Agency's Greenhouse Gas Reporting Program data for 2012. We derive top‐down emissions estimates for propane, n‐butane, i‐pentane, n‐pentane, and benzene from our total top‐down CH4 emission estimate and the relative hydrocarbon abundances in aircraft‐based discrete air samples. Emissions for these five nonmethane hydrocarbons alone total 25.4 ± 8.2 t/h. Assuming that these emissions are solely originating from O&G‐related activities in the study region, our results show that the state inventory for total volatile organic compounds emitted by O&G activities is at least a factor of 2 too low for May 2012. Our top‐down emission estimate of benzene emissions from O&G operations is 173 ± 64 kg/h, or 7 times larger than in the state inventory.
Key Points
Emissions from an oil and gas basin are estimated using airborne measurements
Inventories underestimate hydrocarbon emissions by a factor of 2 or more
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Long‐term atmospheric NOx/CO enhancement ratios in megacities provide evaluations of emission inventories. A fuel‐based emission inventory approach that diverges from conventional bottom‐up inventory ...methods explains 1970–2015 trends in NOx/CO enhancement ratios in Los Angeles. Combining this comparison with similar measurements in other U.S. cities demonstrates that motor vehicle emissions controls were largely responsible for U.S. urban NOx/CO trends in the past half century. Differing NOx/CO enhancement ratio trends in U.S. and European cities over the past 25 years highlights alternative strategies for mitigating transportation emissions, reflecting Europe's increased use of light‐duty diesel vehicles and correspondingly slower decreases in NOx emissions compared to the U.S. A global inventory widely used by global chemistry models fails to capture these long‐term trends and regional differences in U.S. and Europe megacity NOx/CO enhancement ratios, possibly contributing to these models' inability to accurately reproduce observed long‐term changes in tropospheric ozone.
Key Points
Measured NOx/CO enhancement ratio trends are compared to inventory emissions ratio trends in megacities
Chemistry‐climate modeling inventory fails to capture NOx/CO emission ratio trends and regional differences
Observations demonstrate divergent paths in motor vehicle emission control strategies in the U.S. versus Europe
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Several different inventories of global and regional anthropogenic and biomass burning emissions are assessed for the 1980–2010 period. The species considered in this study are carbon monoxide, ...nitrogen oxides, sulfur dioxide and black carbon. The inventories considered include the ACCMIP historical emissions developed in support of the simulations for the IPCC AR5 assessment. Emissions for 2005 and 2010 from the Representative Concentration Pathways (RCPs) are also included. Large discrepancies between the global and regional emissions are identified, which shows that there is still no consensus on the best estimates for surface emissions of atmospheric compounds. At the global scale, anthropogenic emissions of CO, NO
x
and SO
2
show the best agreement for most years, although agreement does not necessarily mean that uncertainty is low. The agreement is low for BC emissions, particularly in the period prior to 2000. The best consensus is for NO
x
emissions for all periods and all regions, except for China, where emissions in 1980 and 1990 need to be better defined. Emissions of CO need better quantification in the USA and India for all periods; in Central Europe, the evolution of emissions during the past two decades needs to be better determined. The agreement between the different SO
2
emissions datasets is rather good for the USA, but better quantification is needed elsewhere, particularly for Central Europe, India and China. The comparisons performed in this study show that the use of RCP8.5 for the extension of the ACCMIP inventory beyond 2000 is reasonable, until more global or regional estimates become available. Concerning biomass burning emissions, most inventories agree within 50–80%, depending on the year and season. The large differences between biomass burning inventories are due to differences in the estimates of burned areas from the different available products, as well as in the amount of biomass burned.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Recent studies suggest overestimates in current U.S. emission inventories of nitrogen oxides (NO x = NO + NO2). Here, we expand a previously developed fuel-based inventory of motor-vehicle emissions ...(FIVE) to the continental U.S. for the year 2013, and evaluate our estimates of mobile source emissions with the U.S. Environmental Protection Agency’s National Emissions Inventory (NEI) interpolated to 2013. We find that mobile source emissions of NO x and carbon monoxide (CO) in the NEI are higher than FIVE by 28% and 90%, respectively. Using a chemical transport model, we model mobile source emissions from FIVE, and find consistent levels of urban NO x and CO as measured during the Southeast Nexus (SENEX) Study in 2013. Lastly, we assess the sensitivity of ozone (O3) over the Eastern U.S. to uncertainties in mobile source NO x emissions and biogenic volatile organic compound (VOC) emissions. The ground-level O3 is sensitive to reductions in mobile source NO x emissions, most notably in the Southeastern U.S. and during O3 exceedance events, under the revised standard proposed in 2015 (>70 ppb, 8 h maximum). This suggests that decreasing mobile source NO x emissions could help in meeting more stringent O3 standards in the future.
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IJS, KILJ, NUK, PNG, UL, UM
We present an updated fuel-based oil and gas (FOG) inventory with estimates of nitrogen oxide (NOx) emissions from oil and natural gas production in the contiguous US (CONUS). We compare the FOG ...inventory with aircraft-derived (“top-down”) emissions for NOx over footprints that account for ∼25% of US oil and natural gas production. Across CONUS, we find that the bottom-up FOG inventory combined with other anthropogenic emissions is on average within ∼10% of top-down aircraft-derived NOx emissions. We also find good agreement in the trends of NOx from drilling- and production-phase activities, as inferred by satellites and in the bottom-up inventory. Leveraging tracer–tracer relationships derived from aircraft observations, methane (CH4) and non-methane volatile organic compound (NMVOC) emissions have been added to the inventory. Our total CONUS emission estimates for 2015 of oil and natural gas are 0.45 ± 0.14 Tg NOx/yr, 15.2 ± 3.0 Tg CH4/yr, and 5.7 ± 1.7 Tg NMVOC/yr. Compared to the US National Emissions Inventory and Greenhouse Gas Inventory, FOG NOx emissions are ∼40% lower, while inferred CH4 and NMVOC emissions are up to a factor of ∼2 higher. This suggests that NMVOC/NOx emissions from oil and gas basins are ∼3 times higher than current estimates and will likely affect how air quality models represent ozone formation downwind of oil and gas fields.
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IJS, KILJ, NUK, PNG, UL, UM
The Safety of Oral Anticoagulants Registry (SOAR) was designed to describe the evaluation and management of patients with oral anticoagulant (OAC)-related major bleeding or bleeding concerns who ...present to the emergency department (ED) with acute illness or injury. Patients in the ED are increasingly taking anticoagulants, which can cause bleeding-related complications as well as impact the acute management of related or unrelated clinical issues that prompt presentation. Modifications of emergency evaluation and management due to anticoagulation have not previously been studied.
This was a multicenter observational in-hospital study of patients who were judged to be experiencing an active OAC effect and had (a) an obvious bleeding event or (b) were deemed at risk for serious bleeding spontaneously, after injury, or during an indicated invasive procedure. Diagnostic testing, therapies employed, and clinical outcomes were collected.
Thirty-one US hospitals contributed data to SOAR. Of 1513 subjects, acute hemorrhage (AH) qualified 78%, while 22% had a bleeding concern (BC). Warfarin was the index OAC in 37.3%, dabigatran in 13.3%, and an anti-Factor Xa in 49.4%. The most common sites of AH were gastrointestinal (51.0%) and intracranial (26.8%). In warfarin-treated patients, the mean (IQR) presenting INR was 3.1 (2.2, 4.8) in AH patients and 3.9 (2.4, 7.2) in BC patients. Three-fifths of SOAR patients were treated with factor repletion or specific reversal agents, and those patients had a longer length of stay. In addition, seven (0.76%) of the treated patients experienced an in-hospital thrombotic complication; two of these seven died on the index admission, both of fatal pulmonary embolism. Vitamin K was used and dosed inconsistently in both warfarin and NOAC cohorts.
Care of anticoagulated patients in the acute care setting is inconsistent, reflecting the diversity of presentation. As the prevalence of OAC use increases with the aging of the US population, further study and targeted educational efforts are needed to drive more evidence-based care of these patients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
While the formation pathways and thermodynamic properties of inorganic species (e.g., sulphate) in atmospheric aerosols are well understood, many more uncertainties exist about organics. In the ...present study we present oxidation pathways of organic gas phase species that lead to low volatility organic compounds (C2‐C6 dicarboxylic acids, pyruvic acid) in both the aqueous and gas phases. This mechanism is implemented in a cloud parcel model initialized with pure (NH4)2SO4 particles in 10 discrete sizes. Under clean continental conditions a few cloud processing cycles produce a total organic mass addition of ∼150 ng m−3. Individual resuspended aerosol size classes contain significant organic fractions, sometimes higher than 50%. These are likely upper bound estimates of organic mass production. In a polluted, i.e., SO2‐rich scenario, about 400 ng m−3 organic material is produced after about eight cloud cycles. Since the initial conditions in this latter case favor significant production of sulphate, the organic fraction of the aerosol mass after cloud processing represents a much lower percentage of the total aerosol mass. Oxalic, glutaric, adipic, and pyruvic acids are the main contributors to the organic fraction in both cases. In agreement with observations, the oxalate fraction in processed particles exceeds the fractions of other dicarboxylic acids since it represents an end product in the oxidation of several organic gas phase species. The study suggests that cloud processing may act as a significant source of small dicarboxylic acids, some fraction of which can be retained in the aerosol phase upon drop evaporation.
We quantify methane (CH4) emissions in California's San Joaquin Valley (SJV) by using 4 days of aircraft measurements from a field campaign during May–June 2010 together with a Bayesian inversion ...method and a mass balance approach. For the inversion estimates, we use the FLEXible PARTicle dispersion model (FLEXPART) to establish the source‐receptor relationship between sampled atmospheric concentrations and surface fluxes. Our prior CH4 emission estimates are from the California Greenhouse Gas Emissions Measurements (CALGEM) inventory. We use three meteorological configurations to drive FLEXPART and subsequently construct three inversions to analyze the final optimized estimates and their uncertainty (one standard deviation). We conduct May and June inversions independently and derive similar total CH4 emission estimates for the SJV: 135 ± 28 Mg/h in May and 135 ± 19 Mg/h in June. The inversion result is 1.7 times higher than the prior estimate from CALGEM. We also use an independent mass balance approach to estimate CH4 emissions in the northern SJV for one flight when meteorological conditions allowed. The mass balance estimate provides a confirmation of our inversion results, and these two independent estimates of the total CH4 emissions in the SJV are consistent with previous studies. In this study, we provide optimized CH4 emissions estimates at 0.1° horizontal resolution. Using independent spatial information on major CH4 sources, we estimate that livestock contribute 75–77% and oil/gas production contributes 15–18% of the total CH4 emissions in the SJV. Livestock explain most of the discrepancies between the prior and the optimized emissions from our inversion.
Key Points
Estimate of methane emissions in the San Joaquin Valley using inverse modeling and a mass balance approach
Methane emissions are estimated to be greater than the bottom‐up inventory by a factor of 1.7
Livestock largely account for differences between the optimized and prior methane emission estimates
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Methane (CH4) is the primary component of natural gas and has a larger global warming potential than CO2. Recent top‐down studies based on observations showed CH4 emissions in California's South ...Coast Air Basin (SoCAB) were greater than those expected from population‐apportioned bottom‐up state inventories. In this study, we quantify CH4 emissions with an advanced mesoscale inverse modeling system at a resolution of 8 km × 8 km, using aircraft measurements in the SoCAB during the 2010 Nexus of Air Quality and Climate Change campaign to constrain the inversion. To simulate atmospheric transport, we use the FLEXible PARTicle‐Weather Research and Forecasting (FLEXPART‐WRF) Lagrangian particle dispersion model driven by three configurations of the Weather Research and Forecasting (WRF) mesoscale model. We determine surface fluxes of CH4 using a Bayesian least squares method in a four‐dimensional inversion. Simulated CH4 concentrations with the posterior emission inventory achieve much better correlations with the measurements (R2 = 0.7) than using the prior inventory (U.S. Environmental Protection Agency's National Emission Inventory 2005, R2 = 0.5). The emission estimates for CH4 in the posterior, 46.3 ± 9.2 Mg CH4/h, are consistent with published observation‐based estimates. Changes in the spatial distribution of CH4 emissions in the SoCAB between the prior and posterior inventories are discussed. Missing or underestimated emissions from dairies, the oil/gas system, and landfills in the SoCAB seem to explain the differences between the prior and posterior inventories. We estimate that dairies contributed 5.9 ± 1.7 Mg CH4/h and the two sectors of oil and gas industries (production and downstream) and landfills together contributed 39.6 ± 8.1 Mg CH4/h in the SoCAB.
Key Points
A mesoscale inversion ensemble is used to estimate CH4 emissions in the LA basin
Emission estimates are consistent with published observation‐based estimates
Oil and gas industries explain the differences between posterior and prior inventories
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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