EFFECTIVE MONITORING OF POLLUTION BY TOXIC TRACE-ELEMENTS IN WATERS, SEDIMENT AND BIOTA OF THE DERWENT RIVER ESTUARY, TASMANIA, THROUGH LONG-TERM RETENTION OF ANALYTICAL FACILITIES

This study considers the effectiveness of the monitoring of toxic trac e elements in various media from a polluted river estuary over a perio d of 15 years, using the same analytical techniques, facilities and, i n some cases, the same operators. It shows that reliable comparisons c an be made for monitoring waters, sediment and biota from the Derwent River Estuary between 1975 data and that from 1990. Rigorous studies w ere undertaken before and during 1975 to ensure that reliable data was achieved at that time. Such studies are reviewed and included the eva luation of digestion techniques for a range of heavy metals, specific attention to the reliability of mercury determination in sediments bet ween laboratories, a comparison of direct calibration and standard add ition techniques for metals in seawater, recoveries of an organomercur y compound from fish, and sources of error arising from sample prepara tion of biota for subsequent metal analysis. Comparative results for s tandard reference materials in both 1975 and 1990 show good agreement and are considered reliable except for lead at low concentrations. The long-term retention of the analytical facilities permits a direct com parison of data from 2 monitoring programmes over the space of 15 year s.