Cai Chonggui. Radium in the soil exhibits the same level of radioactivity as uranium from which it was originally derived, because of a natural phenomenon called secular equilibrium. It is based on the assumption that a 'perfect' core will exhibit a linear decrease in log [excess Po activity] vs. The sediment samples must remain totally undisturbed during sampling to obtain the best possible dating. Earth and Planetary Science Letters, Cores which are rich in organics tend to have higher Po activities in their surface sediments, and as a consequence, generally yield better data because the excess Po is much higher than the background Po In the water phase Pb is adsorbed to particulate matter and together they are deposited in the sediment.
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We believe that proper use of Pb dating data may provide helpful information on our understanding of sediment records and recent environmental changes.
In case 3where the deepest core sections appear to be above background level, the excess Po activity cannot be calculated because there is no estimate of the background level of Po We welcome suggested improvements to any of our articles. Lake Sediments and Environmental History. Advertisement Hide. Wan Guojiang. Journal of Asian Earth Sciences, 20 8: