Tadeusz Kuc

Possibilities for Reconstructing Radiocarbon Level Changes During the Late Glacial by Using a Laminated Sequence of Lake

Laminated sediments of Gościąz Lake can be used as an independent source of material for calibrating the radiocarbon time scale. The varve chronology is based on three long cores from the deepest part of the lake, with one additional core from the second deepest part. From pollen and Cladocera spectra and stable isotope and chemical content sequences, we have determined the Allerod(AL)/Younger Dryas(YD) and Younger Dryas/Preboreal(PB) boundaries in the three long cores with relatively good accuracy, and have tentatively defined the AL/YD boundary in the fourth core. The Younger Dryas period contains at least 1520 varves, with 980 varves in fragments well replicated in all four cores. The duration of the Younger Dryas as recorded in sediments of Gościąz Lake corresponds well to the duration derived from 230Th/234U and 14C dates on Barbados corals, but disagrees with estimates from Soppensee, Lake Holzmaar and Swedish varves. Two AMS dates of terrestrial macrofossils from the PB and YD periods seem to fit both the data obtained for Swiss lake sediments and Barbados corals.

Carbon isotopes in atmospheric CO (sub 2) of the Krakow region; a two-year record.

The authors have been measuring concentration of atmospheric CO/sub 2/ and its carbon isotope composition in the Krakow region for about two years. Samples are continuously collected at two-week intervals at ca 20m above ground level, close to the center of the industrialized urban area. Sampled atmospheric CO/sub 2/ is sorbed in a molecular sieve and, after recovery by heating, is converted to benzene. /sup 14/C is measured in a liquid scintillation spectrometer, and delta/sup 13/C of the CO/sub 2/ is determined in a mass spectrometer. The annual record shows winter-summer variation of /sup 14/C, /sup 13/C, and CO/sub 2/ concentration. A long-term trend for the 1983 and 1984 indicates a slight decrease of /sup 14/C activity (122.0 in January 1983; - 1.2% per year), a permanent decrease of delta/sup 13/C/sub PDB/ (09.3 per thousand in January 1983; -0.3 per thousand per year) and an increase of CO/sub 2/ concentration (344 ppm in January 1983; 1.4 ppm per year).

super 14) C traced in Krakow after the Chernobyl accident.

ABSTRACT. Results of the 14C measurements in atmospheric CO2 in the first half of 1986 are presented. CO2 samples were systematically collected in Krakow in two-week cycles and, after conversion to benzene, measured in a liquid scintillation spectrometer. 14C activity and 13C/ 12C ratio are reported as b14C and b13CPDg, respectively. For about three weeks after April 26, 1986 (the Chernobyl accident) an increase of -9% above the normal level for Krakow was observed. A rough estimate of the 14C release to the lower atmosphere during the accident gave a value 900 Ci, which is 1.8 x 105 of the total activity released to the atmosphere.

Gas Counting System for 14C Dating of Small Samples in the Kraków Laboratory

The application of traditional gas or liquid scintillation counting (LSC) is necessary for assessing radionuclide activity in countries without operating accelerator mass spectrometry (AMS) facilities. A simple and relatively inexpensive system of mini gas counters for measurement of radiocarbon in archaeological and environmental samples has been set up recently in the Krakow laboratory (Department of Environmental Physics, University of Mining and Metallurgy). The system is composed of a gas purification and counter filling line, three identical 15-mL copper/quartz counters, active and passive shielding, and an electronic unit with data acquisition. One counter measures 22 mg of carbon as CO (sub 2) with efficiency >95% at a background reduced to 0.044 cpm by a NaJ(T1) guard counter and lead shield. The detection limit (1 sigma ) for a two-week measurement of 48 mL of CO (sub 2) is 0.52 pMC. The corresponding counting error of a 100 pMC environmental sample is 1.3 pMC for 22 mgC (one counter) and 0.75 pMC for 66 mgC (three counters filled with the sample).