LEAFS DETERMINATION AND CONCENTRATION OF METALS IN GREAT-LAKES ECOSYSTEM

A Laser-Excited Atomic Fluorescence Spectrometric (LEAFS) method for T l determination has been extended to investigate the direct determinat ion (without preconcentration nor acid digestion) of total Pb, for whi ch the method validation was successfully achieved by using a standard reference material as well as many spike recoveries of digested and u ndigested unfiltered water samples. The method was applied to study to tal and dissolved Pb in many water columns collected from different st ations in Lake Ontario. Dissolved Pb was found to be about twice as mu ch as dissolved Tl, and total Pb about seven times higher than total T l. Seventy five percent of Pb is in particulate form versus 11% for Tl . Also, a simple cold dissolution procedure using HNO3 and HF (not a h ot acid digestion) is proposed to ''liquefy'' sediments in a form suit able for LEAFS analysis and was used to analyze a sediment core, where pore water samples were also collected. The interaction dynamics of T l within the natural environment of a water/pore water/sediment system from Lake Erie was assessed. The calculations of fluxes suggest a str ong similarity between Tl and Cd geochemical transport. The paper also presents for the first time a genuine sediment pore water profile of Tl concentration, which ranged from sub- to 40 ng/l and which was dire ctly determined by LEAFS.