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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 329 (1987), S. 144-146 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Samples of total atmospheric participate matter were obtained from the filter archives of a number of institutes in eastern North America, and also from our own sampling. Measurement locations are shown in Fig. 1. All were from high-volume samplers operated at ~1.13m3min~1 over periods of one to ...
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] It has been found in recent years that the Arctic atmosphere is highly polluted during winter because of strong transport from Eurasia to the pole, weak pollutant removal by precipitation and inefficient uptake at the cold, relatively inert Earth's surface5. This pollution has been present since at ...
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Two questions must be addressed if gas-phase Br chemistry is identified as the origin of the O3 depletion. The first is the source of the high levels of filterable Br (f-Br, the sum of Br on particles and gaseous species such as HBr efficiently collected by Whatman 41 cellulose ...
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  • 4
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Methyl chloride (CH3Cl), the most abundant halocarbon in the atmosphere, has received much attention as a natural source of chlorine atoms in the stratosphere. The annual global flux of CH3 Cl has been estimated to be around 3.5 Tg on the grounds that this ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 394 (1998), S. 331-332 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Arctic ecosystem is showing increasing evidence of contamination by persistent, toxic substances, including metals such as mercury, that accumulate in organisms. In January 1995, we began continuous surface-level measurements of total gaseous mercury in the air at Alert, Northwest ...
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  • 6
    ISSN: 1573-0662
    Keywords: Atmospheric aerosols ; baseline air chemistry ; precipitation chemistry ; SO2 oxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Selected applications of baseline aerosol, SO2 and deposition chemistry observations in Canada are reviewed to illustrate how new insight can be gained into features of the atmospheric pathway of trace substances such as sources, transformation and removal. A strong annual variation in Arctic aerosol concentration is a manifestation of particle residence times that are much longer in winter than in summer. Differences in the variation of SO4 = and V concentrations in the Arctic winter are due to SO2 oxidation. The mean rate of oxidation between November and April ranges from 0.04 to 0.25%/h and is a minimum in December, January and February. Br measured on filters in the Arctic peaks in concentration later (March and April) than anthropogenic particulate matter suggesting photochemical production. Acidity in Arctic aerosol and in glacial ice are correlated. The relationship yields a best estimate of acidity in the absence of anthropogenic influences of 5.8 μmole/l. Coincident air and precipitation measurements of sulphur oxides indicate that on average in eastern Canada 60% of SO4 = in rain originates from SO2 oxidation in the storm. Trends in Arctic ice core acidity and SO2 emissions in Europe are similar, that is, little variation in the first half of the century and a marked increase since the mid 1950's. This is consistent with meteorological and chemical evidence linking Arctic air pollution with Eurasian sources.
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  • 7
    ISSN: 1573-0662
    Keywords: Lower troposphere ; aerosols ; Arctic ; air pollution ; principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Six years of observations (1980 to 1986) of the composition of lower tropospheric aerosols at Alert on northern Ellesmere Island in the Canadian high Arctic yield insight into the seasonal variation of Arctic air pollutants as well as of substances of natural origin. A principal component analysis of 138 observations of 21 aerosol constituents (major ions, metals, nonmetallic trace elements) for the most polluted period of December to April identified not only a soil, sea salt and anthropogenic aerosol component, but also one associated with photochemical reactions in the atmosphere that occur at polar sunrise. Depending on the source of their gaseous precursors, elements in the photochemical component can be natural or anthropogenic in origin. For instance, SO4 2-, existing mostly as H2SO4, originates probably from both anthropogenic and natural sources while Br− is likely of marine origin. In contrast, SO4 2- in the anthropogenic component has the stoichiometry of NH4HSO4. In the winter months, over 90% of Arctic SO4 2- is in the anthropogenic and photochemical components. In winter, a substantial portion (11 to 35%) of Na+ is associated with the anthropogenic aerosol component suggesting either that marine aerosols have been physically or chemically modified by interactions with air pollution or that there are anthropogenic sources of Na+. The aerosol soil component is controlled by both local and distant dust sources. During a year, it has two peaks at Alert, one in April/May coinciding with the Asian dust storm season and one in September. There is a marked difference in the seasonal variation of particulate Br− and iodine concentrations in the air. Both have a peak in April/May associated with polar sunrise and, hence, photochemical reactions in the atmosphere. However, iodine also peaks in early fall. This may be a product of biogenic iodine emissions to the atmosphere during secondary blooms in northern oceans in late summer.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 21 (1995), S. 97-114 
    ISSN: 1573-0662
    Keywords: Sulphur dioxide ; oxidation ; clouds ; riming ; freezing potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Experiments have been performed to investigate whether the process of freezing during riming in clouds may induce oxidation of dissolved SO2 to SO 4 2− . The experiments were conducted in a cold room at varying temperatures between −6 and −15 °C. Solutions containing dissolved SO2 and NH4OH in various proportions, in the range of concentrations between 3×10−5 and 10−3 M, were sprayed. Rime was collected on a rotating cylinder and analyzed. Absorption of oxygen from laboratory air was prevented, except in the spray, to avoid spurious oxidation. Blank experiments were made at +3 to +6 °C. The results indicate clearly that, as the dominant cation becomes NH 4 + rather than H+, substantial oxidation of S(IV) occurs during riming. This is consistent with redox reactions taking place as a result of charge separation at the ice-water interface during freezing.
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  • 9
    ISSN: 1573-0662
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During April 1986, as part of an international arctic air chemistry study (AGASP-2), ground level observations of aerosol trace elements, oxides of sulphur and nitrogen and particle number size distribution were made at Alert Canada (82.5N, 62.3W). Pollution haze was evident as indicated by daily aerosol number (size 〉 0.15 μm diameter) and SO4 = concentrations in the range 125 – 260 cm−3 and 1.6 – 4.5 μg m−3, respectively. Haze and associated acidic gases tended to increase throughout the period. SO2 and peroxyacetylnitrate (PAN) mixing ratios were in the range 140 – 480 and 370 – 590 ppt(v), respectively. About 88% of the total end-product nitrogen was in the form of PAN. In air dried to 2% relative humidity by warming to room temperature, the aerosol mass size distribution had a major mode at 0.3 μm diameter and a minor one at 2.5 μm. Aerosol mass below 1.5 μm was well correlated with SO4 =, K+ and PAN. There was a steady increase in the oxidized fraction of total airborne sulphur and nitrogen oxide throughout April as the sun rose above the horizon and remained above. The mean oxidation rate of SO2 between Eurasia and Alert was estimated as 0.25 – 0.5% h−1. The molar ratio of total nitrogen oxide to total sulphur oxide in the arctic atmosphere (0.67±0.17) was comparable to that in European emissions. A remarkably strong inverse correlation of filterable Br and O3 led to the conclusion that O3 destruction and filterable Br production below the Arctic surface radiation inversion is associated with tropospheric photochemical reactions involving naturally occurring gaseous bromine compounds.
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