AbstractThe diffusion gradient technique in thin films (DGT) technique has over severalyears proven to be effective in measuring trace elements. It is an advantageoustechnique as it is a relatively simple method of studying the speciation of many trace elements in natural waters, whilst allowing in situ pre-concentration of the analyte and eliminating matrix effects.
The labile fraction of copper obtained via DGT was compared to dissolved and total copper concentrations in Cullen Bay Marina seawater, and partitioning of copper between particulate, colloidal/organically complexed and labile phases was determined. Particulate copper was found to the 30-40% of total copper. Colloidal and organically complexed copper was 53% of dissolved copper and labile copper was 47%. These values indicated overlap between colloidal and organically complexed copper and DGT-labile copper resulting in lower colloidal/organically complexed copper than that generally reported in literature.
All fractions measured in Cullen Bay, total (9.5tg/L). dissolved (6.4ig/L). DGT (3.0jtg/L) and ASV (4.2ig/L) were higher than the ANZECC 2000 guideline for 95% species protection (I .4j.tg/L). Dissolved. DGT and ASV concentrations were also slightly higher in surface waters, which correlates to the lower DOC, TOC, TSS and turbidity values observed here.
Sediment-water interactions were quite substantial in Cullen Bay Marina resulting in dissolved copper concentrations of up to 22µg/L at 10-15cm above the sediment surface. However DGT copper concentrations were lower at this depth than in the water column possibly due to high concentrations of organically complexed copper.
Sediment copper concentrations were observed to be highest in surface sediments with copper in the 0-5cm section exceeding the effect-high guideline limit. Zinc was also highly concentrated at this depth generally exceeding the effect low-guideline and the effect high guideline at 0-1cm depth of one sediment core. Lead was also observed to exceed the effect-low guideline in Cullen Bay Marina sediment. The bioavailable concentrations of these and other metals were also high and simultaneously extracted metal concentrations [SEM] greatly exceeded acid volatile sulfide concentrations [AyS], resulting in very low AVS/SEM ratios and indicating the potential for toxicity. However, porewater dissolved and DGT copper concentrations were very low, dissolved copper ranging from (0.22-0.75jig/L) possibly indicating the presence of insoluble covellite (CuS). Alternatively copper may be immobilised by adsorption to iron oxides or organic material, since TOC is very high in Cullen Bay Marina sediment (over 3% in surface sediment).
|Date of Award||Nov 2001|
|Supervisor||David Parry (Supervisor) & Niels Munksgaard (Supervisor)|