Trace element variations in mussels' shells from continent to sea: The St. Lawrence system, Canada

Rare Earth Elements (REE) and several trace elements abundances in mussel's shells collected along the St. Lawrence River, the Estuary, and the Gulf of St. Lawrence (EGSL) reveal coherent chemical variations, with a sharp contrast between freshwater and seawater bivalves. In freshwater mussel's shells, Rare Earth Elements and Y (REY) patterns are rather flat. Their Mn and Ba concentrations are higher than those of EGSL mussel shells, which are much richer in Sr. Shale-normalized REY abundances in mussel's shells from the EGSL show positive anomalies in La and Y and well-marked negative anomalies in Ce, reflecting those of seawater. Prince Edward Island shells show light REE depletion relative to PAAS, positive La and Y anomalies, and negative Ce anomalies. Our data confirm the lack of detectable Gd pollution in the St. Lawrence River and in the EGSL, as well as Pb pollution at the mouth of the Saguenay Fjord and near Rimouski.