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  • 1
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    Evidence of atmospheric nanoparticle formation from emissions of marine microorganisms (2016)
    Wiley
    Details
    Publication Date: 2016-06-03
    Description: Earth, as a whole, can be considered as a living organism emitting gases and particles into its atmosphere, in order to regulate its own temperature. In particular, oceans may respond to climate change by emitting particles that ultimately will influence cloud coverage. At the global scale, a large fraction of the aerosol number concentration is formed by nucleation of gas-phase species, but this process has never been directly observed above oceans. Here we present, using semi-controlled seawater-air enclosures, evidence that nucleation may occur from marine biological emissions in the atmosphere of the open ocean. We identify iodine-containing species as major precursors for new particle clusters formation, while questioning the role of the commonly accepted dimethyl sulfide oxidation products, in forming new particle clusters in the region investigated and within a time scale on the order of an hour. We further show that amines would sustain the new particle formation process by growing the new clusters to larger sizes. Our results suggest that iodine-containing species and amines are correlated to different biological tracers. These observations, if generalized, would call for a substantial change of modeling approaches of the sea-to-air interactions.
    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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  • 2
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    Hydrogen oxide photochemistry in the northern Canadian spring time boundary layer (2011)
    Wiley
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    Publication Date: 2011-11-22
    Description: Measurements of OH and HO2 concentrations were made at the surface of the eastern coast of the Hudson Bay during the COBRA campaign from February 18th to March 8th 2008. Diurnally averaged OH and HO2 concentrations peaked at 1.16 (±1.02) × 106 molecule cm−3 and 1.42 (±0.64) × 108 molecule cm−3 respectively. A box-model, constrained to supporting observations, is used to access the radical budget in this cold, northerly environment. Formaldehyde (HCHO) photolysis is found to be the dominant daytime radical source, providing 74% of the observed HOx. A considerable (〉80% of the total source) surface HCHO source is required to reconcile the model and observed HCHO concentrations. Model simulations also suggest significant roles for the heterogeneous loss of HO2 and for halogen chemistry in the cycling of HO2 to OH. The formation of HO2NO2 is identified as an important radical reservoir, reducing HOx concentrations during the day and enhancing them at night. This impacts both local oxidizing capacity and reduces local ozone production by approximately 30%. The sensitivity of the local chemistry to uncertainties in these processes is explored. The majority of these processes are not currently represented in global chemistry models.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Extensive halogen-mediated ozone destruction over the tropical Atlantic Ocean (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-06-27
    Description: Increasing tropospheric ozone levels over the past 150 years have led to a significant climate perturbation; the prediction of future trends in tropospheric ozone will require a full understanding of both its precursor emissions and its destruction processes. A large proportion of tropospheric ozone loss occurs in the tropical marine boundary layer and is thought to be driven primarily by high ozone photolysis rates in the presence of high concentrations of water vapour. A further reduction in the tropospheric ozone burden through bromine and iodine emitted from open-ocean marine sources has been postulated by numerical models, but thus far has not been verified by observations. Here we report eight months of spectroscopic measurements at the Cape Verde Observatory indicative of the ubiquitous daytime presence of bromine monoxide and iodine monoxide in the tropical marine boundary layer. A year-round data set of co-located in situ surface trace gas measurements made in conjunction with low-level aircraft observations shows that the mean daily observed ozone loss is approximately 50 per cent greater than that simulated by a global chemistry model using a classical photochemistry scheme that excludes halogen chemistry. We perform box model calculations that indicate that the observed halogen concentrations induce the extra ozone loss required for the models to match observations. Our results show that halogen chemistry has a significant and extensive influence on photochemical ozone loss in the tropical Atlantic Ocean boundary layer. The omission of halogen sources and their chemistry in atmospheric models may lead to significant errors in calculations of global ozone budgets, tropospheric oxidizing capacity and methane oxidation rates, both historically and in the future.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Read, Katie A -- Mahajan, Anoop S -- Carpenter, Lucy J -- Evans, Mathew J -- Faria, Bruno V E -- Heard, Dwayne E -- Hopkins, James R -- Lee, James D -- Moller, Sarah J -- Lewis, Alastair C -- Mendes, Luis -- McQuaid, James B -- Oetjen, Hilke -- Saiz-Lopez, Alfonso -- Pilling, Michael J -- Plane, John M C -- England -- Nature. 2008 Jun 26;453(7199):1232-5. doi: 10.1038/nature07035.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18580948" target="_blank"〉PubMed〈/a〉
    Keywords: Africa, Western ; Atlantic Ocean ; Atmosphere/*chemistry ; Eukaryota/metabolism ; Geography ; Halogens/*chemistry ; Marine Biology ; Methane/chemistry ; Ozone/analysis/*chemistry/radiation effects ; Seasons ; Seawater/*chemistry/microbiology ; Temperature ; *Tropical Climate
    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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  • 4
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    Boundary layer halogens in coastal Antarctica (2007)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2007-07-21
    Description: Halogens influence the oxidizing capacity of Earth's troposphere, and iodine oxides form ultrafine aerosols, which may have an impact on climate. We report year-round measurements of boundary layer iodine oxide and bromine oxide at the near-coastal site of Halley Station, Antarctica. Surprisingly, both species are present throughout the sunlit period and exhibit similar seasonal cycles and concentrations. The springtime peak of iodine oxide (20 parts per trillion) is the highest concentration recorded anywhere in the atmosphere. These levels of halogens cause substantial ozone depletion, as well as the rapid oxidation of dimethyl sulfide and mercury in the Antarctic boundary layer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Saiz-Lopez, Alfonso -- Mahajan, Anoop S -- Salmon, Rhian A -- Bauguitte, Stephane J-B -- Jones, Anna E -- Roscoe, Howard K -- Plane, John M C -- New York, N.Y. -- Science. 2007 Jul 20;317(5836):348-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17641195" 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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  • 5
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    On the Variability of Ozone in the Equatorial Eastern Pacific Boundary Layer (2016)
    Wiley
    Details
    Publication Date: 2016-09-06
    Description: Observations of surface ozone (O 3 ) mixing ratios carried out during two ground-based field campaigns in the Galápagos Islands are reported. The first campaign, PIQUERO (Primera Investigación sobre la Química, Evolución y Reparto de Ozono) was carried out from September 2000 to July 2002. The second study, CHARLEX (Climate and HAlogen Reactivity tropicaL EXperiment), was conducted from September 2010 to March 2012. These measurements complement the SHADOZ ozonesonde observations made with weekly to monthly frequency at Galápagos. In this work, the daily, intraseasonal, seasonal and interannual variability of O 3 in the marine boundary layer are described and compared to those observed in other tropical locations. The O 3 diurnal cycle shows two regimes: i) photochemical destruction followed by nighttime recovery in the cold season (July to November), and ii) daytime advection and photochemical loss followed by nighttime depositional loss associated to windless conditions in the warm season (February to April). Wavelet spectral analysis of the intraseasonal variability of O 3 reveals components with periods characteristic of Tropical Instability Waves. The O 3 seasonal variation in Galápagos is typical of the Southern Hemisphere, with a maximum in August and a minimum in February-March. Comparison with other measurements in remote tropical ocean locations shows that the change of the surface O 3 seasonal cycle across the Equator is explained by the position of the Inter-Tropical Convergence Zone and the O 3 levels upwind.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Cancer-associated mutation and beyond: The emerging biology of isocitrate dehydrogenases in human disease (2019)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2019
    Description: 〈p〉Isocitrate dehydrogenases (IDHs) are critical metabolic enzymes that catalyze the oxidative decarboxylation of isocitrate to α-ketoglutarate (αKG), NAD(P)H, and CO〈sub〉2〈/sub〉. IDHs epigenetically control gene expression through effects on αKG-dependent dioxygenases, maintain redox balance and promote anaplerosis by providing cells with NADPH and precursor substrates for macromolecular synthesis, and regulate respiration and energy production through generation of NADH. Cancer-associated mutations in 〈i〉IDH1〈/i〉 and 〈i〉IDH2〈/i〉 represent one of the most comprehensively studied mechanisms of IDH pathogenic effect. Mutant enzymes produce (〈i〉R〈/i〉)-2-hydroxyglutarate, which in turn inhibits αKG-dependent dioxygenase function, resulting in a global hypermethylation phenotype, increased tumor cell multipotency, and malignancy. Recent studies identified wild-type IDHs as critical regulators of normal organ physiology and, when transcriptionally induced or down-regulated, as contributing to cancer and neurodegeneration, respectively. We describe how mutant and wild-type enzymes contribute on molecular levels to disease pathogenesis, and discuss efforts to pharmacologically target IDH-controlled metabolic rewiring.〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Electric field (1980)
    Institute of Physics
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    Publication Date: 1980-03-01
    Print ISSN: 0031-9120
    Electronic ISSN: 1361-6552
    Topics: Physics
    Published by Institute of Physics
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  • 8
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    On the vertical distribution of boundary layer halogens over coastal Antarctica: implications for O3, HOx, NOx and the Hg lifetime (2007)
    Copernicus
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    Publication Date: 2007-07-02
    Description: A one-dimensional chemical transport model has been developed to investigate the vertical gradients of bromine and iodine compounds in the Antarctic coastal boundary layer. The model has been applied to interpret recent year-round observations of iodine and bromine monoxides (IO and BrO) at Halley Station, Antarctica. The model requires an equivalent I atom flux of ~109 molecule cm−2 s−1 from the snowpack in order to account for the measured IO levels, which are up to 20 ppt during spring. Using the current knowledge of gas-phase iodine chemistry, the model predicts significant gradients in the vertical distribution of iodine species. However, recent ground-based and satellite observations of IO imply that the radical is well-mixed in the boundary layer, indicating a longer than expected atmospheric lifetime for the radical. This can be modelled by including photolysis of the higher iodine oxides (I2O2, I2O3, I2O4 and I2O5), and rapid recycling of HOI and INO3 through sea-salt aerosol. The model also predicts significant concentrations (up to 25 ppt) of I2O5 in the lowest 10 m of the boundary layer, which could lead to the formation of ultrafine iodine oxide aerosols. Heterogeneous chemistry involving sea-salt aerosol is also necessary to account for the vertical profile of BrO. Iodine chemistry causes a large increase (typically more than 3-fold) in the rate of O3 depletion in the BL, compared with bromine chemistry alone. Rapid entrainment of O3 from the free troposphere is required to account for the observation that on occasion there is little O3 depletion at the surface in the presence of high concentrations of IO and BrO. The halogens also cause significant changes to the vertical profiles of HO and HO2 and the NO2/NO ratio. The average Hg0 lifetime against oxidation is also predicted to be about 10 h during springtime. Overall, our results show that halogens profoundly influence the oxidizing capacity of the Antarctic troposphere.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Iodine-mediated coastal particle formation: an overview of the Reactive Halogens in the Marine Boundary Layer (RHaMBLe) Roscoff coastal study (2009)
    Copernicus
    Details
    Publication Date: 2009-12-10
    Description: This paper presents a summary of the measurements that were made during the heavily-instrumented Reactive Halogens in the Marine Boundary Layer (RHaMBLe) coastal study in Roscoff on the North West coast of France. It was clearly demonstrated that iodine-mediated coastal particle formation occurs, driven by daytime low tide emission of molecular iodine, I2, by macroalgal species fully or partially exposed by the receding waterline. Ultrafine particle concentrations strongly correlate with the rapidly recycled reactive iodine species, IO, produced at high concentrations following photolysis of I2. The heterogeneous macroalgal I2 sources lead to variable relative concentrations of iodine species observed by path-integrated and in situ measurement techniques. Apparent particle emission fluxes were associated with an enhanced apparent depositional flux of ozone, consistent with both a direct O3 deposition to macroalgae and involvement of O3 in iodine photochemistry and subsequent particle formation below the measurement height. The magnitude of the particle formation events was observed to be greatest at the lowest tides with higher concentrations of ultrafine particles growing to much larger sizes, probably by the condensation of anthropogenically-formed condensable material. At such sizes the particles should be able to act as cloud condensation nuclei at reasonable atmospheric supersaturations.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Concurrent observations of atomic iodine, molecular iodine and ultrafine particles in a coastal environment (2010)
    Copernicus
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    Publication Date: 2010-11-10
    Description: Simultaneous measurements of atomic iodine (I), molecular iodine (I2) and ultrafine particles were made at O Grove, Galicia (42.50° N, 8.87° W), on the northwest coast of Spain. The observations show a strong tidal signature, and indicate that the most probable sources of reactive iodine species are the exposed macroalgae during low tide. For the first time, I2 and I were concurrently measured revealing a high average I2/I ratio of ~32, which is higher than previously inferred by modelling studies. A 1-dimensional photochemical model is employed to simulate the observations showing that the high I2/I ratio can be reproduced in the presence of fast vertical mixing close to the surface, or using an extra chemical loss for I atoms with an unknown species. There is a lack of strong correlation between the I2/I and ultrafine particles, indicating that although they both have macroalgal sources, these were not at the same location. The model simulations also suggest that the source of the observed ultrafine particles is likely not very close to the measurement site, in order for the particles to form and grow, but the source for I and I2 must be local. Finally, the effect of NOx levels on iodine oxides, and the conditions under which iodine particle bursts will be suppressed, are explored.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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