210Pb, 226Ra and 32Si in Pavin lake (Massif Central,France) |
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| Institution: | 1. Dipartimento di Scienze della Terra, Sapienza University of Rome, Italy;2. Consiglio delle Nazionale Ricerche, IGAG, Rome, Italy;3. CERTEMA, Multidisciplinary technology laboratory, Cinigiano, Grosseto, Italy;4. INGV, Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy;1. Assistant Professor, School of Natural Resource Sciences, North Dakota State University, Fargo, ND 58102, USA;2. Regents Professor, Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA;3. Assistant Professor, Biology Program, Ambrose University College, Calgary, AB T3H 0L5, USA;4. Professor and Director, Department of Zoology, Southern Illinois University Carbondale, Carbondale, IL 62901, USA |
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| Abstract: | Measurements of cosmogenic 32Si and the U-decay series' nuclides 210Pb and 226Ra in waters and sediments of lake Pavin are reported. Both 210Pb and 226Ra are enriched in the anoxic deep waters compared to the oxic surface waters, respectively by a factor of 4 and 10, whereas 32Si is depleted by a factor of2. Redox conditions in the lake appear to have no marked effect on the 32Si. Using a steady-state box model it is shown that the deep-water 32Si concentration is controlled by the underground lacustrine springs. The residence times of 210Pb, 32Si and 226Ra are1,10 and80 a, respectively. In the case of 32Si, where more data are available, the assessed inventory data from the overhead atmospheric fallout and that measured in the sediments agree very well as expected. The 210Pb- and 32Si-based deposition rates during the past100 a ranged from 0.8 to 1.9 mm a?1, earlier these were a factor of3–5 faster. The geochemistry of 32Si and 210Pb in lake Pavin in many ways resembles that in the ocean, only the time scales of the processes involved are faster. |
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