Pb isotopes in mussels as tracers of metal sources and water movements in a lagoon (Thau Basin, S. France)

Metal concentrations (Cu, Zn, Cd, Pb) and lead isotopic compositions have b een determined in mussel's fleshes from the Thau lagoon (S. France). Mussel spat from sea was introduced at different locations in the lagoon in June 1995, and subsequently sampled in October 1995, and January, May, and July 1996. Each location was chosen for its particular environment: (1) an indus trial harbour at sea, (2) water treatment plant effluents. (3) nearby city with no seawater entries. and (4) the middle of the lagoon. A reference poi nt was also kept at sea. Variations in heavy metal concentrations generally correlate with weight of the animals, but some could be linked to particul ar local and temporal events such as outflows or tourist activity. The Pb i sotopic compositions of the soft parts allow: (1) to identify the predomina nt sources of Pb and their seasonal variations; (2) to estimate their respe ctive impact; and (3) to present a dynamic vision of the water movements in the lagoon comparing with climatic observations (wind), and their mixing w ith seawater entries. The possible use of isotopic tools in understanding t he capture and the storage of metal in different organs in the mussels is a lso discussed. (C) 2001 Elsevier Science B.V. All rights reserved.