Estimation of experimental conditions to maximize mussels shell capability in trace metals accumulation.

The evaluation of mussels shell capability of concentrate heavy metals was performed by means of a set of laboratory experiments conducted with mussels collected in unpolluted sites exposed to sub-lethal concentrations of a known toxic metal. Multiple cycles of accumulation and depuration were carried out all along the experimental period; the constant monitoring of experimental conditions and periodical metal determination in shell and tissue samples allowed the individuation of the accumulation and depuration patterns in both Bivalves materials in the selected species. Alternative exposure to contaminated and clean seawater respectively was performed in order to record the different metal concentration trends in shell and soft tissues. In fact it is demonstrated that once the metal is incorporate in the crystalline calcium carbonate lattice, his loss from the shell during mussels lifetime can be considered of no concern; in the other hand it is known that soft tissues are able to release contaminants in response to changed environmental conditions. The aim was to establish a set of experimental conditions able to optimize metal accumulation in mussel hard parts and to calculate the specific MATC (Maximum Acceptable Toxic Concentration) value. So it was possible to settle physical, chemical and physiological parameters in order to maximize the shell metal content and set the basis for implementation of bioinertization strategies exploiting mussels metabolic activity and detoxification mechanisms.