Natural radioactivity in environmental studies

Full text: The use natural radioactivity in environmental studies has proven a very powerful tool to determine the dynamics of both natural and antrophogenic processes in our environment. The use of 14C in archeology and past climate studies has led to many scientific discoveries (i.e. shroud of Turin and Utze 'the ice-man' from Austria). The use of the 238U-decay series is of at least equal value to studies in archeology and past climates. Some of the Isotopes studied supplement 14C (which is limited to 40,000 years) up to 350,000 years and others can be utilized to date very young sediments, which can't be dated by 14C. The so-called 210Pb dating method has been used over the past 3 decades to date recent sediment. The method uses the disequilibrium in the 238U decay chain, caused by the escape of the intermediate daughter 222Rn (a noble gas) from the earth's crust. In the atmosphere the 222Rn decays via short-lived daughter isotopes to 210Pb. This 210Pb with a very convenient half-life of 22,3 years decays to stable 206Pb. By measuring the surface activity of a sediment core and subsequent samples at regular intervals one can establish a chronology for the sediment core. By studying the trace metals in these cores, one could deduce a contamination history for the region. Examples of studies supported by AINSE and ANSTO will be given