Rate constants for the reaction of Cl atoms with O3 at temperatures from 298 to 184 K

Using the standard, low pressure, discharge-flow technique, with resonance fluorescence in the vacuum ultraviolet to observe Cl atoms, rate constants have been determined for the reaction of Cl atoms with O$_3$ at temperatures down to 184 K. The measured rate constants for 298-184 K fit the Arrhenius expression: k(T) = (3.6 $\pm$ 0.7) $\times$ 10$^{-11}$ exp(( - 310 $\pm$ 50 K) / T) cm$^3$ molecule$^{-1}$ s$^{-1}$. The results extend the data on this key atmospheric reaction to slightly lower temperatures. The data are in fairly good agreement with those currently in the literature but suggest that the rate constant approximately 15% lower than that given by currently recommended rate expressions at the lowest temperatures found in the stratosphere

Statin use after acute myocardial infarction by patient complexity: Are the rates right?

Reprinted with permission of the publisher.Background: Guidelines suggest statin use after acute myocardial infarction (AMI) should be close to universal in patients without safety concerns yet rates are much lower than recommended, decline with patient complexity, and display substantial geographic variation. Trial exclusions have resulted in little evidence to guide statin prescribing for complex patients. Objective: Assess the benefits and risks associated with higher rates of statin use after AMI by baseline patient complexity. Research Design: Sample includes Medicare fee-for-service patients with AMIs in 2008-2009. Instrumental variable estimators using variation in local area prescribing patterns by statin-intensity as instruments were used to assess the association of higher statin prescribing rates by statin-intensity on 1-year survival, adverse events, and cost by patient complexity. Results: Providers appear to have individualized statin use across patients based on potential risks. Higher statin rates for non-complex AMI patients were associated with increased survival rates with little added adverse event risk. Higher statin rates for complex AMI patients were associated with tradeoffs between higher survival rates and higher rates of adverse events. Conclusions: Higher rates of statin use for non-complex AMI patients are associated with outcome rate changes similar to existing evidence. For the complex patients in our study, who were least represented in existing trials, higher statin-use rates were associated with survival gains and higher adverse event risks not previously documented. Policy interventions promoting higher statin-use rates for complex patients may need to be re-evaluated taking careful consideration of these tradeoffs.This project was supported by an Agency for Healthcare Research and Quality grant (1R21HS019574-01) under the American Recovery and Reinvestment Act of 2009

Offering weight management support to pregnant women with high body mass index: A qualitative study with midwives

Objective: The prevalence of pregnant women with high body mass index is increasing worldwide. High body mass index is associated with health risks for mother and baby and supporting healthy gestational weight gain is important. Midwives play an important role in supporting women to engage in behaviours such as healthy eating and physical activity. The aim of this study was to explore how midwives’ support pregnant women with high body mass index to establish a healthy lifestyle with emphasis on nutrition and physical activity in order to minimise gestational weight gain. Methods: Semi-structured interviews were conducted with 16 midwives working in antenatal health care in Sweden. Interviews were conducted shortly after new guidelines on care for pregnant women with high body mass index had been introduced. The interviews were recorded, transcribed and analysed by thematic analysis. Results: Three main themes were identified; use a conscious approach, invite to participate and have a long-term health perspective. Midwives built a relationship with a woman through identifying her concerns and circumstances, before sensitively discussing weight. Some midwives used Motivational Interviewing to help women identify their own resources. To reach long-term health benefits, midwives set achievable goals with the women. Conclusion: These study findings provide practical examples of how midwives can support women with weight management during pregnancy. Through being sensitive when developing a relationship, midwives enabled the women to identify their own resources and achievable goals. Support after the baby is born is needed subsequently to help women maintain their healthy behaviour changes

Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley

Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. It is essential to understand the emissions and air quality impacts of these relatively understudied sources, especially for oil/gas operations in light of increasing US production. Ground site measurements in Bakersfield and regional aircraft measurements of reactive gas-phase organic compounds and methane were part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions, and provide average source profiles. To examine the spatial distribution of emissions in the San Joaquin Valley, we developed a statistical modeling method using ground-based data and the FLEXPART-WRF transport and meteorological model. We present evidence for large sources of paraffinic hydrocarbons from petroleum operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes, most of which have limited previous in situ measurements or characterization in petroleum operation emissions. Observed dairy emissions were dominated by ethanol, methanol, acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The petroleum operations source profile was developed using the composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil. The observed source profile is consistent with fugitive emissions of condensate during storage or processing of associated gas following extraction and methane separation. Aircraft observations of concentration hotspots near oil wells and dairies are consistent with the statistical source footprint determined via our FLEXPART-WRF-based modeling method and ground-based data. We quantitatively compared our observations at Bakersfield to the California Air Resources Board emission inventory and find consistency for relative emission rates of reactive organic gases between the aforementioned sources and motor vehicles in the region. We estimate that petroleum and dairy operations each comprised 22% of anthropogenic non-methane organic carbon at Bakersfield and were each responsible for 8-13% of potential precursors to ozone. Yet, their direct impacts as potential secondary organic aerosol (SOA) precursors were estimated to be minor for the source profiles observed in the San Joaquin Valley

Long-range pollution transport during the MILAGRO-2006 campaign: a case study of a major Mexico City outflow event using free-floating altitude-controlled balloons

One of the major objectives of the Megacities Initiative: Local And Global Research Observations (MILAGRO-2006) campaign was to investigate the long-range transport of polluted Mexico City Metropolitan Area (MCMA) outflow and determine its downwind impacts on air quality and climate. Six research aircraft, including the National Center for Atmospheric Research (NCAR) C-130, made extensive chemical, aerosol, and radiation measurements above MCMA and more than 1000 km downwind in order to characterize the evolution of the outflow as it aged and dispersed over the Mesa Alta, Sierra Madre Oriental, Coastal Plain, and Gulf of Mexico. As part of this effort, free-floating Controlled-Meteorological (CMET) balloons, commanded to change altitude via satellite, made repeated profile measurements of winds and state variables within the advecting outflow. In this paper, we present an analysis of the data from two CMET balloons that were launched near Mexico City on the afternoon of 18 March 2006 and floated downwind with the MCMA pollution for nearly 30 h. The repeating profile measurements show the evolving structure of the outflow in considerable detail: its stability and stratification, interaction with other air masses, mixing episodes, and dispersion into the regional background. Air parcel trajectories, computed directly from the balloon wind profiles, show three transport pathways on 18–19 March: (a) high-altitude advection of the top of the MCMA mixed layer, (b) mid-level outflow over the Sierra Madre Oriental followed by decoupling and isolated transport over the Gulf of Mexico, and (c) low-level outflow with entrainment into a cleaner northwesterly jet above the Coastal Plain. The C-130 aircraft intercepted the balloon-based trajectories three times on 19 March, once along each of these pathways; in all three cases, peaks in urban tracer concentrations and LIDAR backscatter are consistent with MCMA pollution. In comparison with the transport models used in the campaign, the balloon-based trajectories appear to shear the outflow far more uniformly and decouple it from the surface, thus forming a thin but expansive polluted layer over the Gulf of Mexico that is well aligned with the aircraft observations. These results provide critical context for the extensive aircraft measurements made during the 18–19 March MCMA outflow event and may have broader implications for modelling and understanding long-range transport

Mapping carbon monoxide pollution from space down to city scales with daily global coverage

On 13 October 2017, the European Space Agency (ESA) successfully launched the Sentinel-5 Precursor satellite with the Tropospheric Monitoring Instrument (TROPOMI) as its single payload. TROPOMI is the first of ESA's atmospheric composition Sentinel missions, which will provide complete long-term records of atmospheric trace gases for the coming 30 years as a contribution to the European Union's Earth Observing program Copernicus. One of TROPOMI's primary products is atmospheric carbon monoxide (CO). It is observed with daily global coverage and a high spatial resolution of 7×7&thinsp;km2. The moderate atmospheric resistance time and the low background concentration leads to localized pollution hotspots of CO and allows the tracking of the atmospheric transport of pollution on regional to global scales. In this contribution, we demonstrate the groundbreaking performance of the TROPOMI CO product, sensing CO enhancements above cities and industrial areas and tracking, with daily coverage, the atmospheric transport of pollution from biomass burning regions. The CO data product is validated with two months of Fourier-transform spectroscopy (FTS) measurements at nine ground-based stations operated by the Total Carbon Column Observing Network (TCCON). We found a good agreement between both datasets with a mean bias of 6&thinsp;ppb (average of individual station biases) for both clear-sky and cloudy TROPOMI CO retrievals. Together with the corresponding standard deviation of the individual station biases of 3.8&thinsp;ppb for clear-sky and 4.0&thinsp;ppb for cloudy sky, it indicates that the CO data product is already well within the mission requirement.</p

Contribution of isoprene-derived organosulfates to free tropospheric aerosol mass

Recent laboratory studies have demonstrated that isoprene oxidation products can partition to atmospheric aerosols by reacting with condensed phase sulfuric acid, forming low-volatility organosulfate compounds. We have identified organosulfate compounds in free tropospheric aerosols by single particle mass spectrometry during several airborne field campaigns. One of these organosulfates is identified as the sulfate ester of IEPOX, a second generation oxidation product of isoprene. The patterns of IEPOX sulfate ester in ambient data generally followed the aerosol acidity and NOx dependence established by laboratory studies. Detection of the IEPOX sulfate ester was most sensitive using reduced ionization laser power, when it was observed in up to 80% of particles in the tropical free troposphere. Based on laboratory mass calibrations, IEPOX added > 0.4% to tropospheric aerosol mass in the remote tropics and up to 20% in regions downwind of isoprene sources. In the southeastern United States, when acidic aerosol was exposed to fresh isoprene emissions, accumulation of IEPOX increased aerosol mass by up to 3%. The IEPOX sulfate ester is therefore one of the most abundant single organic compounds measured in atmospheric aerosol. Our data show that acidity-dependent IEPOX uptake is a mechanism by which anthropogenic SO2 and marine dimethyl sulfide emissions generate secondary biogenic aerosol mass throughout the troposphere