STRONTIUM CONTENT AND Na/Ca RATIO IN RECENT MOLLUSK SHELLS AS SALINITY INDICATORS IN FLUVIAL WATER SYSTEMS

Abstract

Mollusk shells of C. (Corbicula) fluminalis (MULLER) and Unio tigridis (BOURGUIGNAT) were collected from 14 sites along the Euphrates River from Kerabla to Nassirriyah. The shells were analysed for their Sr, Ca and Na contents and examined by XRD for mineral composition.The results were compared to the water main constituents of cations and anions as well as the total dissolved salts (TDS) reported in water samples collected from the same sites and in the same year. The results show that Sr and Na concentrations as well as Na/ Ca ratio are directly correlated with the TDS of the water and also with the water content of dissolved Na+, Ca2+, SO42- and Cl-.The nature of Sr and Na presence in these aragonite shells is believed to be in substitution for Ca in the aragonite structure. The Sr and Na contents of the Recent shells in the present study is much higher than that reported in ancient limestones. Strontium and sodium may be expelled and remobilized when aragonite alters to calcite during diagenesis.