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  • 1
    Electronic Resource
    Electronic Resource
    The marine source of C2-C6 aliphatic hydrocarbons (1988)
    Springer
    Journal of atmospheric chemistry 6 (1988), S. 3-20 
    Details
    ISSN: 1573-0662
    Keywords: Nonmethane hydrocarbons ; sea-air exchanges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract C2-C6 Nonmethane hydrocarbon (NMHC) concentrations in the atmospheric boundary layer and in surface seawater were simultaneously measured during an oceanographic cruise in the intertropical Indian Ocean. NMHC were found to be mainly C2-C4 alkenes and C2-C3 alkanes. Their concentrations ranged from 1 to 30×10−9 l/l in the seawater and 0.1 to 15 ppbv in the atmosphere. Seawater appeared to be a source because the C2-C6 NMHC were supersaturated with respect to the atmosphere by 2 or 3 orders of magnitude. After a selection of the pure marine atmospheric samples, performed with the help of stable and radioactive continental tracers, we found an identical composition in NMHC of surface air and seawater. This observation enabled us to establish that the gas transfer between sea and air occurred according to nonsteady state processes, and that the fluxes cannot be deduced only from atmospheric measurements. An order of magnitude value of the oceanic source for the different NMHC is however derived from the comparison of their sea water concentrations to that of propane and an independent evluation of the marine source of this last compound.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048328
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  • 2
    Electronic Resource
    Electronic Resource
    TROPOZ II: Global distributions and budgets of methane and light hydrocarbons (1996)
    Springer
    Journal of atmospheric chemistry 25 (1996), S. 115-148 
    Details
    ISSN: 1573-0662
    Keywords: NMHC budget ; tropospheric distributions ; methane budget ; TROPOZ II experiment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract One hundred atmospheric samples were collected aboard the French Caravelle research aircraft, during the TROPOZ II experiment (January 1991). Tropospheric meridional distributions versus height were then derived from 70° N to 60° S and between 0.25 km and 11 km for methane, acetylene, ethane and propane. Areas of significant emissions were identified over northern latitudes with, for acetylene, maximum mixing ratios in the north (1.896 ppbv) more than 70 times higher than in background southern latitudes (0.025 ppbv). The influence of emissions from biomass burning was also obvious in the tropical boundary layer. Significant dynamic phenomena led to high mixing ratio zones above 8 or 10 km even for the most reactive hydrocarbons. For the first time, simultaneous assessment of global tropospheric contents of several light hydrocarbons was carried out. Using TROPOZ II data (January 1991) and STRATOZ III data (June 1984) collected by Rudolph (1988) during similar aircraft flights in 1988, the following tropospheric loads (in Tg-compound) were estimated, in January 1991 and June 1984, respectively: 1.1 and 0.4 for acetylene, 5.0 and 3.9 for ethane, 3.6 and 1.4 for propane and 3545 for methane in January only. According to our results, 40 to 65% of acetylene and alkanes are oxidized in the tropics. In addition, by computing the annual tropospheric sink of acetylene and alkanes, an evaluation of their annual global fluxes was performed. The figures are, in Tg-compound y-1 with an uncertainty of 80% to an order of magnitude, based on January and June data, respectively: 10 and 6.6 for acetylene, 16.3 and 17.6 for ethane and 52.3 and 26.5 for propane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053788
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  • 3
    Electronic Resource
    Electronic Resource
    NMHC in the marine atmosphere: Preliminary results of monitoring at Amsterdam Island (1990)
    Springer
    Journal of atmospheric chemistry 11 (1990), S. 169-178 
    Details
    ISSN: 1573-0662
    Keywords: Nonmethane hydrocarbons ; tropospheric chemistry ; background pollution ; air-sea exchanges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Between January 1984 and May 1987, C2 to C5 NMHC concentrations, and Radon-222 activities were measured at Amsterdam Island in the Indian Ocean. A large variability of about one order of magnitude was observed in the NMHC concentrations. Most of the samples were collected under marine influence. Using ethene as a reference compound for marine emissions, it appears that the NMHC/ethene composition of the air and its variability directly reflect the composition of dissolved gases in surface seawater. Only the ethane/ethene ratio presents a significant deviation from this typical composition and this can be attributed to a continental component. At sea level, the reation frequency of OH radicals with the NMHC is similar to that of methane and carbon monoxide. Thus, the contribution of marine NMHC should be taken into account in the modelling of oxidants in remote atmospheres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00053673
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  • 4
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    NMHC in the marine atmosphere: Preliminary results of monitoring at Amsterdam Island (1990)
    Springer
    Details
    Publication Date: 1990-01-01
    Print ISSN: 0167-7764
    Electronic ISSN: 1573-0662
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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  • 5
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    The marine source of C2-C6 aliphatic hydrocarbons (1988)
    Springer
    Details
    Publication Date: 1988-01-01
    Print ISSN: 0167-7764
    Electronic ISSN: 1573-0662
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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  • 6
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    TROPOZ II: Global distributions and budgets of methane and light hydrocarbons (1996)
    Springer
    Details
    Publication Date: 1996-10-01
    Print ISSN: 0167-7764
    Electronic ISSN: 1573-0662
    Topics: Chemistry and Pharmacology , Geosciences
    Published by Springer
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  • 7
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    Assessment of the MODIS Collections C005 and C004 aerosol optical depth products over the Mediterranean basin (2008)
    Copernicus
    Details
    Publication Date: 2008-09-09
    Description: The second generation Collection 005 (C005) MODIS operational algorithm for retrieval of aerosol properties was evaluated and validated for the greater Mediterranean basin (29.5° N–46.5° N and 10.5° W–38.5° E), a region with an atmosphere under siege by air pollution and diminishing water resources that are exacerbated by high aerosol loads and climatic change. The present study aims to quantify the differences between the C005 and the previous (C004) MODIS collections, and re-assess the results of previous studies that have been performed for the region using MODIS C004 aerosol optical depth (AOD) products. Daily data of AOD from EOS-Terra covering the 6-year period 2000–2006 were taken from both C005 and C004 Level-3 datasets, and were inter-compared and validated against ground-based measurements from 29 AERONET stations. The C005 data were found to significantly better agree with the AERONET data than those of C004. The correlation coefficient between MODIS and AERONET was found to increase from 0.66 to 0.76 and the slope of linear regression MODIS/AERONET from 0.79 to 0.85. The MODIS C005 data still overestimate/underestimate the AERONET AOD values smaller/larger than 0.25, but to a much smaller extent than C004 data. The better agreement of C005 with AERONET data arises from the generally lower C005 values, with regional mean AOD values equal to 0.27 and 0.22 for C004 and C005, respectively. This decrease, however, is not uniform over the region and involves a significant decrease over land and a small increase over the ocean for AOD values greater than 0.1 (opposite changes were found under aerosol-clean conditions). Both data sets indicate a decrease in the regional mean AOD over the period 2000–2006, equal to 20% based on C005 and 17% based on C004 datasets, though the intra-annual and inter-annual variation did not change significantly, thus indicating a systematic correction to C004 values.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    The influence of natural and anthropogenic secondary sources on the glyoxal global distribution (2008)
    Copernicus
    Details
    Publication Date: 2008-01-31
    Description: Glyoxal, the smallest dicarbonyl, which has recently been observed from space, is expected to provide indications on VOC oxidation and secondary aerosol formation in the troposphere. Glyoxal is known to be mostly of natural origin and is produced during biogenic VOC oxidation. However, a number of anthropogenically emitted hydrocarbons, like acetylene and aromatics, have been positively identified as glyoxal precursors. The present study investigates the contribution of pollution emissions to the glyoxal levels by taking into account only the secondary chemical formation of glyoxal from precursors emitted from biogenic, anthropogenic and biomass burning sources. For this purpose, a global 3-dimensional chemistry transport model of the troposphere (TM4) able to simulate the gas phase chemistry coupled with all major aerosol components is used. The model results are compared with satellite observations of glyoxal columns over hot spot areas. According to TM4 model results, the anthropogenic contribution to the glyoxal columns is found to reach 70% in the industrialized areas of the northern hemisphere and up to 20% in the tropics. It is on average three times larger than the secondary production of glyoxal from biomass burning sources. The chemical production of glyoxal is calculated to equal about 56 Tg y−1 with 70% produced from biogenic hydrocarbons oxidation, 17% from acetylene, 11% from aromatic chemistry, and 2% from ethene and propene. Glyoxal is destroyed by reactions mainly with OH radicals (22%) and by photolysis (65%), but it is also removed from the atmosphere through wet (11%) and dry deposition (6%). Secondary organic aerosol potential formation through glyoxal losses on/in aerosols and clouds was neglected here due to the significant uncertainties associated with the underlying chemistry. The global annual mean glyoxal burden and lifetime in the model domain are estimated at 0.02 Tg and 3 h, respectively.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    Critical assessment of the current state of scientific knowledge, terminology, and research needs concerning the role of organic aerosols in the atmosphere, climate, and global change (2006)
    Copernicus
    Details
    Publication Date: 2006-06-09
    Description: In spite of impressive advances in recent years, our present understanding of organic aerosol (OA) composition, physical and chemical properties, sources and transformation characteristics is still rather limited, and their environmental effects remain highly uncertain. This paper discusses and prioritizes issues related to organic aerosols and their effects on atmospheric processes and climate, providing a basis for future activities in the field. Four main topical areas are addressed: i) sources of OA; ii) formation transformation and removal of OA; iii) physical, chemical and mixing state of OA; iv) atmospheric modelling of OA. Key questions and research priorities regarding these four areas are synthesized in this paper, and outstanding issues for future research are presented for each topical area. In addition, an effort is made to formulate a basic set of consistent and universally applicable terms and definitions for coherent description of atmospheric OA across different scales and disciplines.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Global modelling of secondary organic aerosol in the troposphere: a sensitivity analysis (2003)
    Copernicus
    Details
    Publication Date: 2003-10-31
    Description: A global 3-dimensional chemistry/transport model able to describe O3, NOx, Volatile Organic Compounds (VOC), sulphur and NH3 chemistry has been extended to simulate the temporal and spatial distribution of primary and secondary carbonaceous aerosols in the troposphere focusing on Secondary Organic Aerosol (SOA) formation. A number of global simulations have been performed to determine a possible range of annual global SOA production and investigate uncertainties associated with the model results. The studied uncertainties in the SOA budget have been evaluated to be in decreasing importance: the potentially irreversible sticking of the semi-volatile compounds on aerosols, the enthalpy of vaporization of these compounds, the partitioning of SOA on non-carbonaceous aerosols, the conversion of aerosols from hydrophobic to hydrophilic, the emissions of primary carbonaceous aerosols, the chemical fate of the first generation products and finally the activity coefficient of the condensable species. The large uncertainties associated with the emissions of VOC and the adopted simplification of chemistry have not been investigated in this study. Although not all sources of uncertainties have been investigated, according to our calculations, the above factors within the experimental range of variations could result to an overall uncertainty of about a factor of 20 in the global SOA budget. The global annual SOA production from biogenic VOC might range from 2.5 to 44.5 Tg of organic matter per year, whereas that from anthropogenic VOC ranges from 0.05 to 2.62 Tg of organic matter per year. These estimates can be considered as a lower limit, since partitioning on coarse particles like nitrate, dust or sea-salt, together with the partitioning and the dissociation of the semi-volatile products in aerosol water has been neglected. Comparison of model results to observations, where available, shows a better agreement for the upper budget estimates than for the lower ones.
    Print ISSN: 1680-7316
    Electronic ISSN: 1680-7324
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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