 |
| Titel |
Radioisotopes in sedimentary study of the Black Sea and Caspian Sea |
| VerfasserIn |
Gennady Laptev, Oleg V. Voitsekhovych |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250082189
|
|
|
|
|
|
| Zusammenfassung |
| Natural archives, such as lake or marine sediment, are widely used in erosion/sedimentation,
water quality, climate change and eutrophication study alongside with the retrospective
reanalysis of contaminants fluxes (trace metals, organic pollutants or radionuclides). In order
to "read" information stored in sediment sequences a chronostatigraphic method have been
developed and used since 1950s which is based upon variation of activity of 210Pb over the
sediment profile, natural radioisotope of Uranium decay series with half-life 22 years, and
hence valid for the last 100–150 years of recent sedimentation history. The 210Pb chronology
is prone to be validated by other time-markers, such as artificial radionuclides globally
dispersed after the nuclear weapons tests of 1960s or major accidents on NPP (the Chernobyl
accident of 1986 or latest on the Fukushima Daiichi in 2011). In the last decade an intensive
study using sediment cores collected from shelf and deep-sea areas in the Black Sea
and the Caspian Sea have been undertaken within the framework of a number of
international research projects organized by IAEA and UNOPS-GEF and devoted to
environmental problems of this enclosed, and therefore sensitive to environmental impact,
marine systems. Elaborative analysis of the experimental data and sediment age
calculation have been done by application of CRS and CIC dating models to unsupported
210Pb activity over the sediment profile. Measured in sediment 137Cs and 241Am
clearly showed well resolved Bomb test and Chernobyl fallout peaks and were used
as markers in order to corroborate radiometrically determined age of sediment.
Geochronological reconstruction of the fallout radionuclides inventory, fluxes and
accumulation rate in the sediment of the Black Sea and Caspian Sea by application
of combined radiometric dating technique proved to be very consistent with the
historical data of atmospheric fallout observations of that artificial radionuclides
recorded worldwide since nuclear era onset in early 1950s. Another finding of the
initially radioactivity related to project was suitability of unmixed sediment cores
recovered from the deep anoxic floor and continental slope of the Black Sea to be
used for proxy reconstruction of the late Holocene climate variability in the region.
This well preserved sediment are characteristic in finely laminated coccolith ooze
(Unit I – approximate age 2000 years) overlaying above rich in organic matter
sapropels of Unit II. Variations in accumulation rates of biogenic carbonate sediment
fraction of Unit I were found to be satisfactory correlate with changes in winter
SST anomaly calibrated in recent radiometricaly dated topmost sediment. Further
development and rectification of the proposed interdisciplinary method is in progress. |
|
|
|
|
|
|