Thallium speciation in the Great Lakes

An ion-exchange separation technique followed by analysis with atomic absorption spectroscopy was used to study the chemical forms and distribution of thallium in Lakes Michigan, Huron, and Erie. The dominant thallium form found in water samples analyzed was the oxidized TI(III) which comprised 68 +/- 6% of the total dissolved thallium, contrary to thermodynamic prediction that TI(I) is favored in natural waters. A significant proportion of TI(III) may be in colloidal form. No definite spatial (horizontal or vertical) pattern was found in the distribution of total dissolved thallium in the water columns of Lakes Michigan, Huron, and Erie. An overall decline of thallium concentration from Lake Michigan to Lake Erie was observed which may be related to rapid scavenging removal from the water column.