Comparison of 210Pb and 210Po activity concentrations for sediment dating

Abstract

Records stored in natural archives, such as those for lake sediments, are used in environmental programmes for the assessment of changing erosion rates in a catchment arising from disturbances, and to monitor pollution by heavy metals and other contaminants. Accurate sediment chronologies are important to interpret those practices. One of the most important methods for dating recent sediments is through 210Pb. This radionuclide occurs naturally as one of the 238U decay series. It is widely distributed on Earth owing to its decay from radium in the ground or from radon that emanates to the atmosphere. The 210Pb is deposited as particulates and falls into lakes where it is scavenged from the water column and deposited in the basins. The elevated 210Pb concentrations are measured using the gamma spectrometry technique. However, this technique has a low sensitivity and small values are difficult to detect or require a long measurement time. The determination of 210Po (a decay product of 210Pb) using alpha spectrometry is more sensitive and rapid. The aim of this paper is to compare the activity concentrations of the two radionuclides in lake sediment samples to evaluate the use of 210Po in the dating of sediments with low levels of 210Pb.