Thorium isotopes as analogues for “particle-reactive” pollutants in coastal marine environments

Experiments using radioactive tracers in microcosms of 150 l and 13 m³ volumes, which are designed to mimic Narragansett Bay, indicate that Th isotopes are good analogues for studying the removal behavior of “particle-reactive” pollutants such as Am, Pb, Po, Hg and Cr(III) in coastal environments. The removal of Th isotopes and Fe has been found to be closely linked in microcosms and Narragansett Bay. In addition, the settling velocities of tracer microspheres in the experimental tanks were found to be faster in spring and summer than expected from Stokes' law and similar to those of²³⁴Th-containing particles in Narragansett Bay [5]. It is concluded that aggregation of particles is important in accelerating the removal of surface-reactive elements during the warm season.