Pb-210 dating sediments Is it advisable to do Pb-210 sediment core dating in a harbour that was dredged 10 years ago?

Pb-210 dating sediments

Using Pb alone cannot do this it can only suggest a problem. Local changes of current conditions may also cause changes of the chronology of the layers.

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Assuming you want a much longer time line than that, then you need a portion of the harbor that has not been dredged and does not experience erosion or much reworking of the sediment after deposition. If you intend to determine only pollutants there is no problem, you can determine what happened in these last 10 years, but dating with Pb it is not possible, perhaps you can measure Be-7 in the cores to obtain only very recent ages. The rate of diffusion between sites in the crystal lattice increases with P and, theoretically, rapid diffusion should be expected at high P in geological bodies in the absence of melts and solutions.

This isotope was released in huge quantities in connection with the atmospheric nuclear explosions in and later by the Tjernobyl accident in I take it that you are concerned by the dating sediments of information due to the loss of anthrpogenic sediments before 10 years ago due to sediment dredging and spill to the land, or indeed to other parts of your estuary, thus contaminanting any signal with older sediments.

Subsequently, they are cut into slices of approximately 1 cm and dried, whereupon the content of dry matter and possibly the loss on ignition are determined.

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Depending on the core, calculated ages greater than years should be treated with caution because counting errors and small variations in the background Po can cause large changes in the age kent dating free. But anyway you need to know some more about the stratigraphy of the investigated area in order to choose the best sites to sample and to be aware about their significance in the context you are delaing with. If the concentration of substances at different depths is compared with the corresponding ages, the accumulation rates of these substances at different times may be determined from the sediment accumulation rate.

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 Here are the instructions how to enable JavaScript in your web browser.

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The sediment samples must remain totally undisturbed during sampling to obtain the best possible dating. The grand daughter of Pb is Po. In addition, the results of the sensitivity analysis are reported. This gas produces Pb by decay in the atmosphere. The excess Po is assumed to be from direct atmospheric deposition of Pb plus the import of Pb from the watershed. Return to the Flett Research Home Page. Can you help by adding an answer? The possible importance of solid phase reactions in geologic process.

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Reads 45 Followers 17 Answers The separation procedure consists of the following general steps. Under a Creative Commons license. Usually, to find not altered zones or the dating sediments of strata dredged, and so on, we perform on the study area a seismic survey at hight resolution.

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You can then measure the expected tptal inventory to match the local inventory taken fro global surveys e. In the water phase Pb is adsorbed to particulate matter and together they are deposited in the sediment.

Constant Sedimentation Rate model for the isotopic method.

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