The half-life of 32Si: a new estimate based on varved lake sediments

Cosmic ray produced 32Si has found several applications as a tracer in aqueous geochemical processes. These applications require precise knowledge of the half-life of 32Si. The reported values show a wide range that varies from 101±18 to 330±40 years, thus leaving the question of the half-life of 32Si still wide open. In this study, we have determined the half-life of 32Si to be 178±10 years by measuring the decrease of its activity with depth in an accurately dated varved sediment core from the Kassjon lake, North Sweden. This result reinforces the use of 32Si as a geochronometer to study earth surface processes that have occurred during the last millennium.