<p>This thesis deals with the atmospheric distribution of the cosmogenic isotopes <sup>7</sup>Be (half-life 53 days) and <sup>10</sup>Be (half-life 1.51 million years) as well as the anthropogenic isotope <sup>137</sup>Cs (half-life 30 years) in aerosols and precipitation. Samples covering continuous or selected parts of the period 1972-2005 in Sweden and Europe are evaluated with respect to production, air mass transport and fallout processes. Such information is valuable in assessing the potential of these isotopes as indicators of air mass mixing and solar modulation factors that affect climate change. The results of <sup>7</sup>Be and <sup>10</sup>Be show seasonal variability and an 11-year cyclic pattern which is anti-correlated with the solar activity. Variations in seasonal trends of <sup>7</sup>Be and <sup>137</sup>Cs in aerosols during the post- and pre-Chernobyl period reflect tropospheric influence from <sup>137</sup>Cs-heavily contaminated regions. A clear latitude dependence is observed in our beryllium isotope data where highest fallout is found in mid-latitudes compared to high and low latitude regions in the Northern hemisphere. This pattern reflects the general air mass circulation in the troposphere. However, stratospheric air mass influence was also identified in mainly single events and through tropopause folding during spring-summer seasons. The ratio of <sup>10</sup>Be/<sup>7</sup>Be is used to estimate effects of air mass transport on production signal. The results show ratios between 1 and 3, much higher than the theoretically predicted value (0.6) in the atmosphere, which suggests contribution from <sup>7</sup>Be-depleted (old) air masses. The relationship between monthly <sup>7</sup>Be atmospheric activity and Total Fractional Cloud Cover (TFCC), collected from satellite imagery, over Sweden for the years (1991-2000) indicates a negative seasonal correlation. This observation can be related to depletion of aerosol from the atmosphere due to trapping in clouds. </p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-7965 |
| Date | January 2007 |
| Creators | Kulan, Abdulhadi |
| Publisher | Uppsala University, Department of Earth Sciences, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 321 |
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