Reconstructing seawater column 90Sr based upon 210Pb/226Ra disequilibrium dating of mollusk shells

The shells of marine and fresh water mollusks can serve as effective archives in retrieving information on natural and anthropogenic environmental changes. The advantage of using bivalves is that they integrate water chemistry changes into their shells during their life span. Retrospective study of environmental changes and pollutants using bivalve shells requires precise determination of the time of incorporation into the abiotic environmental matrix (here after age) of the specimen. For the first time, a set of archived bivalve samples (for which date of the death/collection is known) has been analyzed to establish the ages of mollusk shells using the 210 Pb– 226 Ra disequilibrium method. In addition, Sr and 90 Sr were analysed. The ages obtained using the 210 Pb/ 226 Ra disequilibrium dating method agrees well with the calendar years calculated from the date of death/collection. The ages obtained can be utilized to reconstruct the 90 Sr levels in the water column at sites where the mollusk shells were collected.