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  • 1
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    Variabilities in ozone at a semi-urban site in the Indo-Gangetic Plain region: Association with the meteorology and regional processes (2012)
    Wiley
    Details
    Publication Date: 2012-10-19
    Description: The Indo-Gangetic Plain (IGP) region is one of the most densely populated regions in the World, but ground-based observations of air pollutants are highly limited in this region. Here, surface ozone observations made during March 2009–June 2011 at a semi-urban site (Pantnagar; 29.0°N, 79.5°E, 231 m amsl) in the IGP region are presented. Ozone mixing ratios show a daytime photochemical buildup with ozone levels sometimes as high as 100 ppbv. Seasonal variation in 24-h average ozone shows a distinct spring maximum (39.3 ± 18.9 ppbv in May) while daytime (1130–1630 h) average ozone shows an additional peak during autumn (48.7 ± 13.8 ppbv in November). The daytime, but not daily average, observed ozone seasonality is in agreement with the space-borne observations of OMI tropospheric column NO2, TES CO (681 hPa), surface ozone observations at a nearby high altitude site (Nainital) in the central Himalayas and to an extent with results from a global chemistry transport model (MATCH-MPIC). It is suggested that spring and autumn ozone maximum are mainly due to photochemistry, involving local pollutants and small-scale dynamical processes. Biomass burning activity over the northern Indian region could act as an additional source of ozone precursors during spring. The seasonal ozone photochemical buildup is estimated to be 32–41 ppbv during spring and autumn and 9–14 ppbv during August–September. A correlation analysis between ozone levels at Pantnagar and Nainital along with the mixing depth data suggests that emissions and photochemical processes in the IGP region influence the air quality of pristine Himalayan region, particularly during midday hours of spring. The evening rate of change (8.5 ppbv hr−1) is higher than the morning rate of change, which is dissimilar to those at other urban or rural sites. Ozone seasonality over the IGP region is different than that over southern India. Results from the MATCH-MPIC model capture observed ozone seasonality but overestimate ozone levels. Model simulated daytime ratios of H2O2/HNO3 are higher and suggesting that this region is in a NOx-limited regime. A chemical box model (NACR Master Mechanism) is used to further corroborate this using a set of sensitivity simulations, and to estimate the integrated net ozone production in a day (72.9 ppbv) at this site.
    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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    Hydroxyl radical buffered by isoprene oxidation over tropical forests (2012)
    Springer Nature
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    Publication Date: 2012-02-29
    Description: Hydroxyl radical buffered by isoprene oxidation over tropical forests Nature Geoscience 5, 190 (2012). doi:10.1038/ngeo1405 Authors: D. Taraborrelli, M. G. Lawrence, J. N. Crowley, T. J. Dillon, S. Gromov, C. B. M. Groß, L. Vereecken & J. Lelieveld The hydroxyl radical is a key oxidant in the Earth’s atmosphere. This short-lived highly reactive molecule plays an important role in the degradation of volatile organic compounds, leading to the production of ozone and the formation and growth of aerosol particles. In this way, hydroxyl radicals influence air quality and regional climate. Measurements over tropical forests suggest that hydroxyl radicals are recycled following reaction with the volatile organic compound isoprene, but the chemistry underpinning this observation is uncertain. Here, we propose a detailed chemical mechanism for the oxidation of isoprene by hydroxyl radicals. The photo-oxidation of unsaturated hydroperoxy-aldehydes—a product of isoprene oxidation—is a central part of the mechanism; their photolysis initiates a hydroxyl radical production cascade that is limited by the reaction of hydroperoxy-aldehydes with the hydroxyl radical itself. We incorporate this mechanism into a global atmospheric chemistry model and find that measurements of hydroxyl radical concentrations over a pristine region of the Amazon, and in moderately polluted conditions, are captured well. On the basis of this agreement, we suggest that isoprene oxidation can buffer hydroxyl radical concentrations, by serving as both a sink and source for these radicals.
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 3
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    Hydroxyl radical buffered by isoprene oxidation over tropical forests (2012)
    Springer Nature
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    Publication Date: 2012-03-31
    Description: Hydroxyl radical buffered by isoprene oxidation over tropical forests Nature Geoscience 5, 300 (2012). doi:10.1038/ngeo1433 Authors: D. Taraborrelli, M. G. Lawrence, J. N. Crowley, T. J. Dillon, S. Gromov, C. B. M. Groß, L. Vereecken & J. Lelieveld
    Print ISSN: 1752-0894
    Electronic ISSN: 1752-0908
    Topics: Geosciences
    Published by Springer Nature
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  • 4
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    Urban emission hot spots as sources for remote aerosol deposition (2012)
    Wiley
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    Publication Date: 2012-01-14
    Description: Large point sources such as major population centers (MPCs) emit pollutants which can be deposited nearby or transported over long distances before deposition. We have used tracer simulations of aerosols emitted from MPCs worldwide to assess the fractions which are deposited at various distances away from their source location. Considering only source location, prevailing meteorology, and the aerosol size and solubility, we show that fine aerosol particles have a high potential to pollute remote regions. About half of the emitted mass of aerosol tracers with an ambient diameter ≤1.0 μm is typically deposited in regions more than 1000 km away from the source. Furthermore, using the Köppen-Geiger climate classification to categorize the sources into various climate classes we find substantial differences in the deposition potential between these classes. Tracers originating in arid regions show the largest remote deposition potentials, with values more than doubled compared to the smallest potentials from tracers in tropical regions. Seasonal changes in atmospheric conditions lead to variations in the remote deposition potentials. On average the remote deposition potentials in summer correspond to about 70–80% of the values in winter, with a large spread among the climate classes. For tracers from tropical regions the summer remote deposition values are only about 31% of the winter values, while they are about 95% for tracers from arid regions.
    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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  • 5
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    The Indian Ocean experiment: widespread air pollution from South and Southeast Asia (2001)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2001-02-13
    Description: The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6 degrees S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lelieveld, J -- Crutzen, P J -- Ramanathan, V -- Andreae, M O -- Brenninkmeijer, C M -- Campos, T -- Cass, G R -- Dickerson, R R -- Fischer, H -- de Gouw, J A -- Hansel, A -- Jefferson, A -- Kley, D -- de Laat, A T -- Lal, S -- Lawrence, M G -- Lobert, J M -- Mayol-Bracero, O L -- Mitra, A P -- Novakov, T -- Oltmans, S J -- Prather, K A -- Reiner, T -- Rodhe, H -- Scheeren, H A -- Sikka, D -- Williams, J -- New York, N.Y. -- Science. 2001 Feb 9;291(5506):1031-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institute for Chemistry, Post Office Box 3060, D-55020 Mainz, Germany. lelieveld@mpch-mainz.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11161214" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols ; Agriculture ; *Air Pollution ; Asia ; Asia, Southeastern ; Atmosphere ; Biomass ; Carbon ; Carbon Monoxide ; Coal Ash ; Fossil Fuels ; Industrial Waste ; Nitrogen Oxides ; Oceans and Seas ; Ozone ; Particulate Matter ; Seasons
    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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  • 6
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    Global air pollution crossroads over the Mediterranean (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-10-26
    Description: The Mediterranean Intensive Oxidant Study, performed in the summer of 2001, uncovered air pollution layers from the surface to an altitude of 15 kilometers. In the boundary layer, air pollution standards are exceeded throughout the region, caused by West and East European pollution from the north. Aerosol particles also reduce solar radiation penetration to the surface, which can suppress precipitation. In the middle troposphere, Asian and to a lesser extent North American pollution is transported from the west. Additional Asian pollution from the east, transported from the monsoon in the upper troposphere, crosses the Mediterranean tropopause, which pollutes the lower stratosphere at middle latitudes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lelieveld, J -- Berresheim, H -- Borrmann, S -- Crutzen, P J -- Dentener, F J -- Fischer, H -- Feichter, J -- Flatau, P J -- Heland, J -- Holzinger, R -- Korrmann, R -- Lawrence, M G -- Levin, Z -- Markowicz, K M -- Mihalopoulos, N -- Minikin, A -- Ramanathan, V -- De Reus, M -- Roelofs, G J -- Scheeren, H A -- Sciare, J -- Schlager, H -- Schultz, M -- Siegmund, P -- Steil, B -- Stephanou, E G -- Stier, P -- Traub, M -- Warneke, C -- Williams, J -- Ziereis, H -- New York, N.Y. -- Science. 2002 Oct 25;298(5594):794-9.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Chemistry, Post Office Box 3060, 55020 Mainz, Germany. lelieveld@mpch-mainz.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12399583" target="_blank"〉PubMed〈/a〉
    Keywords: Aerosols ; *Air Pollutants ; *Air Pollution ; Asia ; Atmosphere ; *Carbon Monoxide ; Climate ; Europe ; Mediterranean Region ; North America ; Ozone ; Weather
    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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    Side effects of oceanic iron fertilization (2002)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2002-09-24
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lawrence, Mark G -- New York, N.Y. -- Science. 2002 Sep 20;297(5589):1993.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12243191" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; Carbon Dioxide/metabolism ; Climate ; *Ecosystem ; Fertilizers ; Hydrocarbons, Halogenated/metabolism ; *Iron ; Oceans and Seas ; Phytoplankton/*physiology ; *Seawater ; Sulfides/metabolism ; Temperature
    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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    Atmospheric oxidation capacity sustained by a tropical forest (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-04-11
    Description: Terrestrial vegetation, especially tropical rain forest, releases vast quantities of volatile organic compounds (VOCs) to the atmosphere, which are removed by oxidation reactions and deposition of reaction products. The oxidation is mainly initiated by hydroxyl radicals (OH), primarily formed through the photodissociation of ozone. Previously it was thought that, in unpolluted air, biogenic VOCs deplete OH and reduce the atmospheric oxidation capacity. Conversely, in polluted air VOC oxidation leads to noxious oxidant build-up by the catalytic action of nitrogen oxides (NO(x) = NO + NO2). Here we report aircraft measurements of atmospheric trace gases performed over the pristine Amazon forest. Our data reveal unexpectedly high OH concentrations. We propose that natural VOC oxidation, notably of isoprene, recycles OH efficiently in low-NO(x) air through reactions of organic peroxy radicals. Computations with an atmospheric chemistry model and the results of laboratory experiments suggest that an OH recycling efficiency of 40-80 per cent in isoprene oxidation may be able to explain the high OH levels we observed in the field. Although further laboratory studies are necessary to explore the chemical mechanism responsible for OH recycling in more detail, our results demonstrate that the biosphere maintains a remarkable balance with the atmospheric environment.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lelieveld, J -- Butler, T M -- Crowley, J N -- Dillon, T J -- Fischer, H -- Ganzeveld, L -- Harder, H -- Lawrence, M G -- Martinez, M -- Taraborrelli, D -- Williams, J -- England -- Nature. 2008 Apr 10;452(7188):737-40. doi: 10.1038/nature06870.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Chemistry, 27 Becherweg, 55128 Mainz, Germany. lelieveld@mpch-mainz.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18401407" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atlantic Ocean ; Atmosphere/*chemistry ; Butadienes/metabolism ; French Guiana ; Guyana ; Hemiterpenes/metabolism ; Hydroxyl Radical/metabolism ; Nitric Oxide/metabolism ; Oxidation-Reduction ; Ozone/analysis ; Pentanes/metabolism ; Suriname ; Trees/*metabolism ; *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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  • 9
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    Megacity emissions and lifetimes of nitrogen oxides probed from space (2011)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2011-09-24
    Description: Megacities are immense sources of air pollutants, with large impacts on air quality and climate. However, emission inventories in many of them still are highly uncertain, particularly in developing countries. Satellite observations allow top-down estimates of emissions to be made for nitrogen oxides (NO(x) = NO + NO(2)), but require poorly quantified a priori information on the NO(x) lifetime. We present a method for the simultaneous determination of megacity NO(x) emissions and lifetimes from satellite measurements by analyzing the downwind patterns of NO(2) separately for different wind conditions. Daytime lifetimes are ~4 hours at low and mid-latitudes, but ~8 hours in wintertime for Moscow. The derived NO(x) emissions are generally in good agreement with existing emission inventories, but are higher by a factor of 3 for the Saudi Arabian capital Riyadh.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beirle, Steffen -- Boersma, K Folkert -- Platt, Ulrich -- Lawrence, Mark G -- Wagner, Thomas -- New York, N.Y. -- Science. 2011 Sep 23;333(6050):1737-9. doi: 10.1126/science.1207824.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max-Planck-Institut fur Chemie, Joh.-Joachim-Becherweg 27, 55128 Mainz, Germany. steffen.beirle@mpic.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21940891" 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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  • 10
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    The extended loops of ribosomal proteins uL4 and uL22 of Escherichia coli contribute to ribosome assembly and protein translation (2016)
    Oxford University Press
    Details
    Publication Date: 2016-07-09
    Description: Nearly half of ribosomal proteins are composed of a domain on the ribosome surface and a loop or extension that penetrates into the organelle's RNA core. Our previous work showed that ribosomes lacking the loops of ribosomal proteins uL4 or uL22 are still capable of entering polysomes. However, in those experiments we could not address the formation of mutant ribosomes, because we used strains that also expressed wild-type uL4 and uL22. Here, we have focused on ribosome assembly and function in strains in which loop deletion mutant genes are the only sources of uL4 or uL22 protein. The uL4 and uL22 loop deletions have different effects, but both mutations result in accumulation of immature particles that do not accumulate in detectable amounts in wild-type strains. Thus, our results suggest that deleting the loops creates kinetic barriers in the normal assembly pathway, possibly resulting in assembly via alternate pathway(s). Furthermore, deletion of the uL4 loop results in cold-sensitive ribosome assembly and function. Finally, ribosomes carrying either of the loop-deleted proteins responded normally to the secM translation pausing peptide, but the uL4 mutant responded very inefficiently to the cmlA crb pause peptide.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
    Published by Oxford University Press
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