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  • 1
    Monograph available for loan
    Monograph available for loan
    Call number: MOP S 12153
    Type of Medium: Monograph available for loan
    Pages: S. 73-79
    Location: MOP - must be ordered
    Branch Library: GFZ Library
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  • 2
    ISSN: 1573-0662
    Keywords: Arctic pollution ; Hydrocarbons ; Halocarbons ; Global model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract A 2-D meridional model for the chemistry and transport in the troposphere is used to study the seasonal variation of the concentration of organic gases like C2H2, C2H6, C3H8, C6H6, C7H8. CHCl3 and C2Cl4 at high latitudes. The anthropogenic sources for these species were estimated, and the temporal and latitudinal distribution of OH and O3 was calculated using a complex photochemical reaction system. There is fair agreement between the calculated annual variation and the measured concentrations for C2H2, C2H6, C3H8, C7H8 and C2Cl4 at Spitsbergen during July 1982 and March/April 1983, with a distinct late winter maximum and summer minimum. For CHCl3, the direct anthropogenic source is minor compared to indirect anthropogenic or natural sources. For benzene, emission in car exhaust is important, but other anthropogenic sources are required for the calculations to agree with the measurements. Measured C2H4 and C3H6 concentrations are much higher than the calculated ones based on anthropogenic emissions, and show opposite seasonal trends. This indicates biogenic sources for these compounds. A buildup of PAN (≈300 pptv) is calculated at high latitudes during winter. This makes it the dominant source for NOx as the temperature increases in the spring. NOx is found to be a limiting factor for O3 production at high latitudes during spring.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-0662
    Keywords: Nonmethane hydrocarbons ; seasonal variation ; photochemical oxidants ; Europe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Two years of individual nonmethane hydrocarbon (NMHC) measurements at a rural site close to the south coast of Norway show that there was a distinct annual cycle with a late winter maximum and late summer minimum in the slowly reacting NMHCs acetylene, ethane, propane and i- and n-butane. The average January—March concentrations were a factor 2–4 higher than the July-September concentrations. Also ethene, propene and the pentanes show a similar annual cycle, but the individual scatter in the measurements in particular of propene, is large. The highest concentrations of NMHC were found in winter for easterly transport on a regional scale (out to 1500 km from the site), and for southeasterly transport in the summer.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-0662
    Keywords: tropospheric ozone ; Arctic ; hydrocarbons ; halogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-0662
    Keywords: convection ; free troposphere ; ozone ; oxides of nitrogen ; three-dimensional model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The fluxes of ozone and NOx out of the atmospheric boundary layer (ABL) over Europe are calculated in a mesoscale chemical transport model (MCT) and compared with the net chemical production or destruction of ozone and the emissions of precursors within the ABL for two 10 days' periods which had quite different synoptic situations and levels of photochemical activity (1–10 July 1991 (JUL91) and 26 October–4 November 1994 (ON94)). Over the European continent, about 8% of the NOx emissions were brought from the ABL to the free troposphere as NOx, while about 15% of the NOx emissions were brought to the free troposphere as NOy–NOx, i.e. as PAN or HNO3. The convection dominates over the synoptic scale vertical advection as a transport mechanism both for NOx and NOy out of the boundary layer in the summertime high pressure situation (JUL91), while in the fall situation (ON94) the convective part was calculated to be the smallest. NOx was almost completely transformed to NOy–NOx or removed within the ABL. Also for NOy the major part of the atmospheric cycle is confined to the ABL both for JUL91 and ON94. The vertical transport time out of the ABL is of the order of 100h both for the total model domain and over the European continent. The net convective exchange of ozone from the ABL is not a dominant process for the amount of ozone in the ABL averaged over 10 days and the whole domain, but convection reduces the maximum ozone concentration in episodes significantly. The ozone producing efficiency of NOx is calculated to increase with height to typically 15–20 in the upper half of the troposphere from around 5 in the ABL, but in the middle free troposphere the concentration of NOx is often too low to cause net chemical formation of ozone there.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-0662
    Keywords: Peroxyacetylnitrate ; long-range transport ; model ; measurements
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Model calculations and field measurements have shown that when air masses accumulate emissions of hydrocarbons and nitrogen oxides from sources in continental Europe and then move towards Scandinavia without any synoptic scale break-up of the atmospheric boundary layer (e.g. frontal passages), elevated PAN concentrations in southern Norway or Sweden in the range 1–5 ppb may be caused by long-range transport. The model calculations showed that over sea, the persistence of PAN was comparable to that of ozone in an ageing air mass when the temperatures were fairly low (5–10°C). At higher temperatures the thermal decomposition of PAN made the compound less persistent than ozone. Over land, the situation may be different since the ground removal is typically three times more efficient for ozone than for PAN. According to the model, the concentration of PAN did not change very much when an ageing air mass was exposed to moderate emissions of hydrocarbons, nitrogen oxides, or both. The concentration of PAN decreased less than the concentration of ozone when an ageing air mass was exposed to high emissions of nitrogen oxides.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-0662
    Keywords: surface ozone ; seasonal cycles ; NOx
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several years of continuous measurements of surfaceozone at Norwegian monitoring sites are studied in aclimatological way. The monitoring sites are at rurallocations extending from 58°N, a few hundredkilometers from the European continent and into theArctic at 79°N. The ozone observations are sorted intoclasses of integrated NOx emissions along 96 h backtrajectories. The average seasonal cycles of ozone areestimated for each class separately. The differencesindicate the change from the background air due toanthropogenic emissions. The average seasonal cycle ofozone in the cleanest air masses showed a maximum inspring and a minimum during summer and autumn at allsites, but the spring maximum was more pronounced atthe southernmost locations. Polluted air masses showedan ozone deficit during winter and a surplus duringsummer. The deviation from the background was clearlylinked to the integrated NOx emission along thetrajectories. In summer the calculations indicate thatthe number of ozone molecules formed per NOx moleculedrops with increasing emissions. The average seasonalcycle of ozone at Birkenes for different transportsectors indicate that the most pronounced ozoneformation takes place in air masses from E-Europe/Russia.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-0662
    Keywords: volatile hydrocarbons ; observations and computer modelling ; tropospheric concentrations ; long range transport ; emission validation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Observations and model calculations of the concentration of hydrocarbonsat five Scandinavian rural sites during March–June 1993are reported.Decreasing concentrations from March to June are observedat all sites. The highest concentrations of hydrocarbons were found in air massescoming in from the southwest to southeast, indicating that long rangetransport fromcontinental Europe and the U.K. is important in pollution episodes. An episode of elevated concentrations of hydrocarbons observed at three of the sites in the middle of Marchis described and discussed in relation to the synoptic situation and thepresenceof other chemical compounds (NO2, PAN, total nitrate andozone).A Lagrangian numerical model is used to calculate the concentrations of theindividual hydrocarbons at the fivesites and comparison with observations is made.The calculated concentrations for nonmethane hydrocarbons with quite longchemicallifetimes agree well with the observations.For the sum of observed and calculated hydrocarbons the correlationcoefficientsare in the range of 0.65–0.88 for the five sitesand the ratio between calculated and measured concentrations was0.72–0.97, indicating thatthe European VOC emission inventory is quite well estimated.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-0662
    Keywords: total nitrate ; total ammonium ; ozone ; filter pack ; denuder ; numerical modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Observations of the concentration of several nitrogen containing compounds at five rural Scandinavian sites during March–June 1993 are reported. Total nitrate (NO 3 - + HNO3) and total ammonium (NH 4 + + NH3) were measured by denuder and filter pack. In general the methods agree well. At all sites the particulate fraction dominated, with the largest fraction of NO 3 - and the lowest of NH 4 + at the sites which were closest to the emission sources. The fraction of NO 3 - of total nitrate increased with increasing NO2 concentrations, indicating that the nighttime conversion of NO2 to NO 3 - is an important route of formation for NO 3 - . A positive correlation was found between HNO3 and O3 in June at all sites, while no correlation was found early in the spring. Model calculations were made with a lagrangian boundary layer photooxidant model for the whole period, and compared to the measured concentrations. The calculated ratio between mean observed and modelled daily maximum concentrations of ozone over the measurement period were within +/−10% at all sites. The models ability to describe the daily ozone maximum concentration was satisfactory with an average deviation of 19–22% from the observed concentrations. HNO3 was underestimated by over 50% at all sites except the one closest to the emission sources. The correlation between modelled and observed concentrations was generally best for the sites with shortest transport distance from the sources of emission.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A model strategy that can be used for the study of global distributions of chlorinated hydrocarbons in the environment is presented. In this first approach the number of compartments and processes are kept on a minimum level by only considering the atmosphere, ocean and soil. Important processes are simulated or replaced by simple parameterizations, while processes believed to be less important are temporally omitted. The transport in the atmosphere is simulated by a simple two-dimensional zonally averaged model with a rather coarse resolution of 6 equally spaced latitude zones and 4 vertical layers. The soil is included in the model by dividing the continents into the same latitude zones as the atmosphere, and the land area in each zone into an uncultivated part and a cultivated part where pesticides may be incorporated. A model for tracer transport in the ocean which combines the features of the box and box-diffusion models has been modified for use in this study. Material is exchanged between the compartments by the processes believed to be most important in the real environment. The model is tested by simulating the life cycle of the α and γ isomers of hexachlorocyclohexane in the environment. The emissions of the two isomers are estimated from the total world consumption of HCH, and it is assumed that a fraction of 50% is lost to the atmosphere for long range transport during application or during the first days therefore. Comparison with observations indicates that in spite of the many assumptions and uncertain parameters the model is able to reproduce the atmospheric and oceanic concentration levels of εHCH. The HCH simulation indicates that the presented model strategy is usable when the aim is to increase the understanding of chlorinated hydrocarbons in the global environment. For the prediction of concentration levels in specific areas on the other hand, the present model strategy does not apply. The resolution of the model is too coarse and the simplifications are too extensive for such estimates to be valid.
    Type of Medium: Electronic Resource
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