Common analytical errors in the radiodating of recent sediments

Four possible sources of analytical error in the measurement of unsupported 210Pb and/or nuclear fallout radionuclide (such as 137Cs) profiles in sediment core are (1) Freezing the entire sediment core prior to precise sectioning; (2) Sectioning the sediment core at room temperature or lower; (3) Determining 210Pb via its 5.01-day half-life beta emitting daughter 210Bi; (4) Determining 210Pb via the 138-day alpha-emitting granddaughter 210Pb. Simple procedural modifications can substantially improve the quality of analytical data that are subsequently used to develop intricate mathematical models to aid the interpretation of observed radionuclide profiles. These modifications include (1) Always store subsamples for sufficiently long periods of time to ensure equilibrium between 210Po and unsupported 210Pb; (2) Always use 208Po as yield monitor and assay autoplated sources on an alpha-particle counter since the alpha particle energies of 208Po and 210Po are separable only on a spectrometer using a detector; (3) Never use any glassware for radiochemical work involved polonium since several polonium compounds are known to absorb onto glass surfaces. Quartz is perhaps the best choice though Teflon or similar materials are also suitable for most situations. Avoid heating above 120 C during HCl leaching and above 90 C during plating since PoCl4 is highly volatile