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NOx
About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.
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TL;DR: A recommendation for a nearly complete gas-phase oxidation mechanism of isoprene and its major products is developed, with the aims of providing an accurate representation of the flow of carbon while allowing quantification of the impact ofIsoprene emissions on HO x and NO x free radical concentrations and of the yields of products known to be involved in condensed-phase processes.
Abstract: Isoprene carries approximately half of the flux of non-methane volatile organic carbon emitted to the atmosphere by the biosphere. Accurate representation of its oxidation rate and products is essential for quantifying its influence on the abundance of the hydroxyl radical (OH), nitrogen oxide free radicals (NOx), ozone (O3), and, via the formation of highly oxygenated compounds, aerosol. We present a review of recent laboratory and theoretical studies of the oxidation pathways of isoprene initiated by addition of OH, O3, the nitrate radical (NO3), and the chlorine atom. From this review, a recommendation for a nearly complete gas-phase oxidation mechanism of isoprene and its major products is developed. The mechanism is compiled with the aims of providing an accurate representation of the flow of carbon while allowing quantification of the impact of isoprene emissions on HOx and NOx free radical concentrations and of the yields of products known to be involved in condensed-phase processes. Finally, a sim...
307 citations
TL;DR: In this article, the authors compared coal combustion in air and the mixtures of O2/CO2 mixtures in a 20kW down-firing combustor and found that coal combustion with 30% CO2/70% O2 can produce matching gas temperature profiles.
305 citations
TL;DR: The use of methyl esters (commonly known as biodiesel) instead of conventional diesel fuel reduces emissions such as the overall life cycle of carbon dioxide (CO2), particu... as mentioned in this paper.
Abstract: The demand for energy around the world is increasing, specifically the demand for petroleum-based energy. Appeasing this growing energy demand without irreparably damaging the environment is of primary concern. With rising fuel prices and environmental concerns, alternative fuels could satisfy the need for renewable energy with low environmental impact. Some of the more popular alternative fuels for new vehicles are ethanol, hydrogen, and biodiesel. Although gasoline engines are expected to be replaced by hydrogen-powered fuel cells, compression-ignition engines, the diesel engines, are expected to remain in use for high-power applications because of limitations of hydrogen-storage densities. The viable environmental friendly alternative fuel for compression-ignition engines is methyl esters (commonly known as biodiesel), which is derived from vegetable oils or animal fats. Using biodiesel instead of conventional diesel fuel reduces emissions such as the overall life cycle of carbon dioxide (CO2), particu...
305 citations
304 citations
Harvard University1, University of Wollongong2, Goddard Space Flight Center3, California Institute of Technology4, University of California, Berkeley5, University of New Hampshire6, National Center for Atmospheric Research7, University of Maryland, College Park8, Colorado State University9, National Oceanic and Atmospheric Administration10, University of Colorado Boulder11, New York State Department of Health12, State University of New York System13
TL;DR: The authors used detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.3125° horizontal resolution, to understand the factors controlling surface ozone in the Southeast US.
Abstract: . Ozone pollution in the Southeast US involves complex chemistry driven by emissions of anthropogenic nitrogen oxide radicals (NOx ≡ NO + NO2) and biogenic isoprene. Model estimates of surface ozone concentrations tend to be biased high in the region and this is of concern for designing effective emission control strategies to meet air quality standards. We use detailed chemical observations from the SEAC4RS aircraft campaign in August and September 2013, interpreted with the GEOS-Chem chemical transport model at 0.25° × 0.3125° horizontal resolution, to better understand the factors controlling surface ozone in the Southeast US. We find that the National Emission Inventory (NEI) for NOx from the US Environmental Protection Agency (EPA) is too high. This finding is based on SEAC4RS observations of NOx and its oxidation products, surface network observations of nitrate wet deposition fluxes, and OMI satellite observations of tropospheric NO2 columns. Our results indicate that NEI NOx emissions from mobile and industrial sources must be reduced by 30–60 %, dependent on the assumption of the contribution by soil NOx emissions. Upper-tropospheric NO2 from lightning makes a large contribution to satellite observations of tropospheric NO2 that must be accounted for when using these data to estimate surface NOx emissions. We find that only half of isoprene oxidation proceeds by the high-NOx pathway to produce ozone; this fraction is only moderately sensitive to changes in NOx emissions because isoprene and NOx emissions are spatially segregated. GEOS-Chem with reduced NOx emissions provides an unbiased simulation of ozone observations from the aircraft and reproduces the observed ozone production efficiency in the boundary layer as derived from a regression of ozone and NOx oxidation products. However, the model is still biased high by 6 ± 14 ppb relative to observed surface ozone in the Southeast US. Ozonesondes launched during midday hours show a 7 ppb ozone decrease from 1.5 km to the surface that GEOS-Chem does not capture. This bias may reflect a combination of excessive vertical mixing and net ozone production in the model boundary layer.
303 citations