Environmental Radioactivity Research Centre
210Pb Dating Facility
The ERRC has carried out 210Pb dating of lake and marine sediments and peat bog cores for a wide range of academic research institutes studying environmental records stored in these natural archives. Sediments are analysed for 210Pb, 226Ra, 137Cs and 241Am by gamma spectrometry in the Liverpool University Environmental Radioactivity Laboratory. 210Pb dates are calculated using the CRS and CIC models. Chronostratigraphic dates (e.g. 1963 from nuclear weapons test fallout and 1986 from Chernobyl fallout) are determined from the 137Cs and 241Am records.
Submission of samples
The radiometric analyses are carried out on dried sediment samples from a representative set of depths spanning the 210Pb record. The number of analyses required depends on the complexity of the record but is normally between 15-18. Samples should preferably be between 1-2 gDW, though samples as small as 0.5 gDW are acceptable.
In order to carry out 210Pb calculations it is necessary to have access to the dry bulk density data for the core, or equivalently, the water content data. This should be submitted, preferably in the form of a spreadsheet, along with the samples.
This will normally be ~3 months. 226Ra (supported 210Pb) is measured by gamma emissions from the short-lived daughter 214Pb. Samples first need to be packed and stored in sealed containers for ~25 days to enable 214Pb to come into radioactive equilibrium with 226Ra. Since sedimentation rates can vary from as little as 5 cm to over 50 cm per 100 years, an initial batch of around 6-8 samples are selected for analysis order to determine the nature and extent of the record. The results are used to select further samples for analysis to fill in detail (including the precise depths of any chronostratigraphic features).
A report is provided containing the results of the radiometric analyses, an assessment of those results, and a best chronology based on an assessment of all the data carried out using the methods described in Appleby (2001)
210Pb dating horizon
Although the 210Pb dating horizon can be as much as 130 years (~6 210Pb half-lives) it may be less at sites with low 210Pb concentrations.
Appleby PG, Chronostratigraphic techniques in recent sediments, in Tracking Environmental Change Using Lake Sediments Volume 1: Basin Analysis, Coring, and Chronological Techniques, (eds W M Last & J P Smol), Kluwer Academic, 2001, pp171-203.