LONG-TERM BEHAVIOR AND DEGRADATION KINETICS OF TRIBUTYLTIN IN A MARINA SEDIMENT

One-meter sediment cores sampled in a marina have been submitted to ex tensive characterization and organotin speciation. Geochemical homogen eity has been demonstrated. Butyltin species are present at all depths with a predominance of TBT or MBT in the upper or lower layers, respe ctively. Seasonal variations of butyltin compounds have been identifie d and together with a knowledge of local conditions we estimate the se diment layers represent 14 years of deposition. A first order multi-st ep kinetic model of the sequential degradation of TBT in, successively , DBT, MBT and Sn (IV) is proposed. The half-life of TBT was estimated (on a 14-year period) to be 2.1 years and those of DBT and MBT (on a 5-year period) 1.9 and 1.1 years, respectively.