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  • 1
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    Arctic springtime observations of volatile organic compounds during the OASIS-2009 campaign (2016)
    Wiley
    Details
    Publication Date: 2016-08-11
    Description: Gas-phase volatile organic compounds (VOCs) were measured at three vertical levels between 0.6 m and 5.4 m in the Arctic boundary layer in Barrow, Alaska for the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS)-2009 field campaign during March - April 2009. C 4 -C 8 nonmethane hydrocarbons (NMHCs) and oxygenated VOCs (OVOCs), including alcohols, aldehydes and ketones, were quantified multiple times per hour, day and night during the campaign using in situ fast gas chromatography-mass spectrometry. Three canister samples were also collected daily and subsequently analyzed for C 2 -C 5 NMHCs. The NMHCs and aldehydes demonstrated an overall decrease in mixing ratios during the experiment whereas acetone and 2-butanone showed increases. Calculations of time-integrated concentrations of Br atoms, ∫[Br] dt , yielded values as high as (1.34 ± 0.27) × 10 14  cm -3 s during the longest observed ozone depletion event (ODE) of the campaign, and were correlated with the steady state Br calculated at the site during this time. Both chlorine and bromine chemistry contributed to the large perturbations on the production and losses of VOCs. Notably, acetaldehyde, propanal and butanal mixing ratios dropped below the detection limit of the instrument (3 parts per trillion by volume (pptv) for acetaldehyde and propanal, 2 pptv for butanal) during several ODEs due to Br chemistry. Chemical flux calculations of OVOC production and loss are consistent with localized high Cl-atom concentrations either regionally or within a very shallow surface layer, while the deeper Arctic boundary layer provides a continuous source of precursor alkanes to maintain the OVOC mixing ratios.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Chemistry – turbulence interactions and mesoscale variability influence the cleansing efficiency of the atmosphere (2015)
    Wiley
    Details
    Publication Date: 2015-11-26
    Description: The hydroxyl radical (OH) is the most important oxidant in the atmosphere and the primary sink for isoprene, the dominant volatile organic compound (VOC) emitted by vegetation. Recent research on the atmospheric oxidation capacity in isoprene dominated environments has suggested missing radical sources leading to significant overestimation of the lifetime of isoprene. Here we report, for the first time, a comprehensive experimental budget of isoprene in the planetary boundary layer based on airborne flux measurements along with in-situ OH observations in the Southeast and Central US. Our findings show that surface heterogeneity of isoprene emissions lead to a physical separation of isoprene and OH resulting in an effective slowdown in the chemistry. Depending on surface heterogeneity, the intensity of segregation (I s ) could locally slow down isoprene chemistry up to 30%. The effect of segregated reactants in the planetary boundary layer (PBL) on average has an influence on modelled OH radicals that is comparable to that of recently proposed radical recycling mechanisms.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    High levels of molecular chlorine in the Arctic atmosphere (2014)
    Springer Nature
    Details
    Publication Date: 2014-01-31
    Description: Nature Geoscience 7, 91 (2014). doi:10.1038/ngeo2046 Authors: Jin Liao, L. Gregory Huey, Zhen Liu, David J. Tanner, Chris A. Cantrell, John J. Orlando, Frank M. Flocke, Paul B. Shepson, Andrew J. Weinheimer, Samuel R. Hall, Kirk Ullmann, Harry J. Beine, Yuhang Wang, Ellery D. Ingall, Chelsea R. Stephens, Rebecca S. Hornbrook, Eric C. Apel, Daniel Riemer, Alan Fried, Roy L. Mauldin, James N. Smith, Ralf M. Staebler, J. Andrew Neuman & John B. Nowak Chlorine radicals can function as a strong atmospheric oxidant, particularly in polar regions, where levels of hydroxyl radicals are low. In the atmosphere, chlorine radicals expedite the degradation of methane and tropospheric ozone, and the oxidation of mercury to more toxic forms. Here we present direct measurements of molecular chlorine levels in the Arctic marine boundary layer in Barrow, Alaska, collected in the spring of 2009 over a six-week period using chemical ionization mass spectrometry. We report high levels of molecular chlorine, of up to 400 pptv. Concentrations peaked in the early morning and late afternoon, and fell to near-zero levels at night. Average daytime molecular chlorine levels were correlated with ozone concentrations, suggesting that sunlight and ozone are required for molecular chlorine formation. Using a time-dependent box model, we estimate that the chlorine radicals produced from the photolysis of molecular chlorine oxidized more methane than hydroxyl radicals, on average, and enhanced the abundance of short-lived peroxy radicals. Elevated hydroperoxyl radical levels, in turn, promoted the formation of hypobromous acid, which catalyses mercury oxidation and the breakdown of tropospheric ozone. We therefore suggest that molecular chlorine exerts a significant effect on the atmospheric chemistry of the Arctic.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 4
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    Nitrous acid (HONO) during polar spring in Barrow, Alaska: A net source of OH radicals? (2011)
    Wiley
    Details
    Publication Date: 2011-12-23
    Description: HONO was measured by a LOPAP instrument (LOng Path Absorption Photometer) for one month during the OASIS spring 2009 campaign in Barrow, Alaska. HONO concentrations between ≤ 0.4 pptv (DL) and ∼500 pptv were measured. The very high concentrations observed on several days were caused by local direct emissions and were highly correlated with the NOx and CO data. When only “clean days” were considered, average HONO concentrations varied between ≤ 0.4 - 10 pptv. Average HONO/NOx and HONO/NOy ratios of ∼6% and ∼1% were observed, respectively, in good agreement with other remote LOPAP measurement data, but lower than measured in most other polar regions by other methods. The strong correlation between sharp peaks of OH and HONO during daytime, which was not observed for any other measured radical precursor, suggested that HONO photolysis was a major source of OH radicals in Barrow. This was supported by calculated net OH radical production by HONO and O3 photolysis for which the contribution of O3 (2%) could be neglected compared to that of HONO (98%). A net extra HONO/OH source necessary to explain elevated HONO levels during daytime of up to 90 pptv/h was determined, which was highly correlated with the actinic flux. Accordingly, a photochemical HONO source is proposed here, in good agreement with recent studies. From the higher correlation of the net HONO source with JNO2 and [NO2] compared to JO(1D) and [NO3−], photosensitized conversion of NO2 on humic acid containing snow surfaces may be a more likely source of HONO in the polar atmosphere of Barrow than nitrate photolysis.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Yersinia YopJ activates casp-1 via casp-8 [Immunology] (2014)
    National Academy of Sciences
    Details
    Publication Date: 2014-05-21
    Description: Toll-like receptor signaling and subsequent activation of NF-κB– and MAPK-dependent genes during infection play an important role in antimicrobial host defense. The YopJ protein of pathogenic Yersinia species inhibits NF-κB and MAPK signaling, resulting in blockade of NF-κB–dependent cytokine production and target cell death. Nevertheless, Yersinia infection induces inflammatory responses...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 6
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    Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources (1998)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1998-10-02
    Description: New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clarke -- Davis -- Kapustin -- Eisele -- Chen -- Paluch I -- Lenschow -- Bandy -- Thornton -- Moore -- Mauldin -- Tanner -- Litchy -- Carroll -- Collins -- Albercook -- New York, N.Y. -- Science. 1998 Oct 2;282(5386):89-92.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉A. D. Clarke, V. N. Kapustin, K. Moore, M. Litchy, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI, USA. D. Davis, F. Eisele, G. Chen, School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atl.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9756483" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Direct observations of atmospheric aerosol nucleation (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-02-23
    Description: Atmospheric nucleation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2-nanometer (nm) size range, in which direct size-segregated observations have not been possible until very recently. Here, we present detailed observations of atmospheric nanoparticles and clusters down to 1-nm mobility diameter. We identified three separate size regimes below 2-nm diameter that build up a physically, chemically, and dynamically consistent framework on atmospheric nucleation--more specifically, aerosol formation via neutral pathways. Our findings emphasize the important role of organic compounds in atmospheric aerosol formation, subsequent aerosol growth, radiative forcing and associated feedbacks between biogenic emissions, clouds, and climate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kulmala, Markku -- Kontkanen, Jenni -- Junninen, Heikki -- Lehtipalo, Katrianne -- Manninen, Hanna E -- Nieminen, Tuomo -- Petaja, Tuukka -- Sipila, Mikko -- Schobesberger, Siegfried -- Rantala, Pekka -- Franchin, Alessandro -- Jokinen, Tuija -- Jarvinen, Emma -- Aijala, Mikko -- Kangasluoma, Juha -- Hakala, Jani -- Aalto, Pasi P -- Paasonen, Pauli -- Mikkila, Jyri -- Vanhanen, Joonas -- Aalto, Juho -- Hakola, Hannele -- Makkonen, Ulla -- Ruuskanen, Taina -- Mauldin, Roy L 3rd -- Duplissy, Jonathan -- Vehkamaki, Hanna -- Back, Jaana -- Kortelainen, Aki -- Riipinen, Ilona -- Kurten, Theo -- Johnston, Murray V -- Smith, James N -- Ehn, Mikael -- Mentel, Thomas F -- Lehtinen, Kari E J -- Laaksonen, Ari -- Kerminen, Veli-Matti -- Worsnop, Douglas R -- New York, N.Y. -- Science. 2013 Feb 22;339(6122):943-6. doi: 10.1126/science.1227385.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics, University of Helsinki, Finland. markku.kulmala@helsinki.fi〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23430652" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 8
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    Rapid cycling of reactive nitrogen in the marine boundary layer (2016)
    Springer Nature
    In: Nature
    Details
    Publication Date: 2016-04-28
    Description: Rapid cycling of reactive nitrogen in the marine boundary layer Nature 532, 7600 (2016). doi:10.1038/nature17195 Authors: Chunxiang Ye, Xianliang Zhou, Dennis Pu, Jochen Stutz, James Festa, Max Spolaor, Catalina Tsai, Christopher Cantrell, Roy L. Mauldin, Teresa Campos, Andrew Weinheimer, Rebecca S. Hornbrook, Eric C. Apel, Alex Guenther, Lisa Kaser, Bin Yuan, Thomas Karl, Julie Haggerty, Samuel Hall, Kirk Ullmann, James N. Smith, John Ortega & Christoph Knote Nitrogen oxides are essential for the formation of secondary atmospheric aerosols and of atmospheric oxidants such as ozone and the hydroxyl radical, which controls the self-cleansing capacity of the atmosphere. Nitric acid, a major oxidation product of nitrogen oxides, has traditionally been considered to be a permanent sink of nitrogen oxides. However, model studies predict higher ratios of nitric acid to nitrogen oxides in the troposphere than are observed. A ‘renoxification’ process that recycles nitric acid into nitrogen oxides has been proposed to reconcile observations with model studies, but the mechanisms responsible for this process remain uncertain. Here we present data from an aircraft measurement campaign over the North Atlantic Ocean and find evidence for rapid recycling of nitric acid to nitrous acid and nitrogen oxides in the clean marine boundary layer via particulate nitrate photolysis. Laboratory experiments further demonstrate the photolysis of particulate nitrate collected on filters at a rate more than two orders of magnitude greater than that of gaseous nitric acid, with nitrous acid as the main product. Box model calculations based on the Master Chemical Mechanism suggest that particulate nitrate photolysis mainly sustains the observed levels of nitrous acid and nitrogen oxides at midday under typical marine boundary layer conditions. Given that oceans account for more than 70 per cent of Earth’s surface, we propose that particulate nitrate photolysis could be a substantial tropospheric nitrogen oxide source. Recycling of nitrogen oxides in remote oceanic regions with minimal direct nitrogen oxide emissions could increase the formation of tropospheric oxidants and secondary atmospheric aerosols on a global scale.
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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  • 9
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    A new atmospherically relevant oxidant of sulphur dioxide (2012)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2012-08-10
    Description: Atmospheric oxidation is a key phenomenon that connects atmospheric chemistry with globally challenging environmental issues, such as climate change, stratospheric ozone loss, acidification of soils and water, and health effects of air quality. Ozone, the hydroxyl radical and the nitrate radical are generally considered to be the dominant oxidants that initiate the removal of trace gases, including pollutants, from the atmosphere. Here we present atmospheric observations from a boreal forest region in Finland, supported by laboratory experiments and theoretical considerations, that allow us to identify another compound, probably a stabilized Criegee intermediate (a carbonyl oxide with two free-radical sites) or its derivative, which has a significant capacity to oxidize sulphur dioxide and potentially other trace gases. This compound probably enhances the reactivity of the atmosphere, particularly with regard to the production of sulphuric acid, and consequently atmospheric aerosol formation. Our findings suggest that this new atmospherically relevant oxidation route is important relative to oxidation by the hydroxyl radical, at least at moderate concentrations of that radical. We also find that the oxidation chemistry of this compound seems to be tightly linked to the presence of alkenes of biogenic origin.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mauldin, R L 3rd -- Berndt, T -- Sipila, M -- Paasonen, P -- Petaja, T -- Kim, S -- Kurten, T -- Stratmann, F -- Kerminen, V-M -- Kulmala, M -- England -- Nature. 2012 Aug 9;488(7410):193-6. doi: 10.1038/nature11278.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉University of Helsinki, Department of Physics, FI-00014 Helsinki, Finland. roy.mauldin@helsinki.fi〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22874964" target="_blank"〉PubMed〈/a〉
    Keywords: Alkenes/metabolism ; Atmosphere/*chemistry ; Finland ; Free Radicals/chemistry ; Hydroxyl Radical/chemistry ; Oxidants/*chemistry/metabolism ; Ozone/chemistry ; Sulfur Dioxide/analysis/*chemistry ; Terpenes/chemistry/metabolism ; Trees/metabolism ; Volatile Organic Compounds/analysis/chemistry/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 10
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    The role of sulfuric acid in atmospheric nucleation (2010)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2010-03-06
    Description: Nucleation is a fundamental step in atmospheric new-particle formation. However, laboratory experiments on nucleation have systematically failed to demonstrate sulfuric acid particle formation rates as high as those necessary to account for ambient atmospheric concentrations, and the role of sulfuric acid in atmospheric nucleation has remained a mystery. Here, we report measurements of new particles (with diameters of approximately 1.5 nanometers) observed immediately after their formation at atmospherically relevant sulfuric acid concentrations. Furthermore, we show that correlations between measured nucleation rates and sulfuric acid concentrations suggest that freshly formed particles contain one to two sulfuric acid molecules, a number consistent with assumptions that are based on atmospheric observations. Incorporation of these findings into global models should improve the understanding of the impact of secondary particle formation on climate.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sipila, Mikko -- Berndt, Torsten -- Petaja, Tuukka -- Brus, David -- Vanhanen, Joonas -- Stratmann, Frank -- Patokoski, Johanna -- Mauldin, Roy L 3rd -- Hyvarinen, Antti-Pekka -- Lihavainen, Heikki -- Kulmala, Markku -- New York, N.Y. -- Science. 2010 Mar 5;327(5970):1243-6. doi: 10.1126/science.1180315.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Leibniz-Institut fur Tropospharenforschung e.V., Leipzig 04318, Germany. mikko.sipila@helsinki.fi〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20203046" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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