Application of an in situ passive sampling technique for assessment of contaminants in the Antarctic environment

• Main Author: Larner, BL
• Format: Thesis
• Language: English
• Published: 2006
• Subjects: Trace elements; Waste disposal sites; Antarctic; Casey Station; The Antarctic; Antarc*
• Online Access: https://eprints.utas.edu.au/20644/; https://eprints.utas.edu.au/20644/1/whole_LarnerBronwynLesley2006_thesis.pdf; https://eprints.utas.edu.au/20644/2/whole_LarnerBronwynLesley2006Vol2_thesis.pdf

This study investigates the use ofthe in situ passive sampling technique of diffusive gradients in thin films (DGT) to measure trace metal contaminants in overlying water and sediment porewater adjacent to a waste disposal site at the year-round Australian Antarctic research base, Casey Station. Marine sediment in a bay adjacent to the waste disposal site has been previously identified as having elevated levels oftrace metals, in particular Cd, Pb, Sn, Cu and Zn. Further development of the DGT technique was investigated with the application and testing of a new paper-based DGT sampler. These samplers were more cheaper, robust and easier to assemble than the original gel-based model, and were less affectedby pH and ionic strength. The paper-based DGT samplers had a lower than expected uptake of metals compared to the gel-based samplers in a field trial, so these samplers were not considered for Antarctic field work. Calibration of the gel-based DGT samplers using the "DGT uptake method" at a temperature suitable for Antarctic deployments resulted in diffusion coefficients 93-114% of the literature values, indicating that the technique is suitable for use in Antarctic waters. Deployment of DGT water samplers in Antarctic waters adjacent to the waste disposal site and in pristine waters resulted in only Cd, Fe and Ni being measured, with other metals being less than detection limits. The annual summer melt draining through the tip did not appear to affect the concentrations of these metals in the water. The use of Empore reconcentration disks resulted in the quantification of all metals analysed, except Cr, and the comparison of results between Empore and DGT supports previous findings that metals in the marine environment are associated with colloidal or particulate material. The use of DGT sediment probes demonstrated elevated levels of Sn, Pb, Fe and As in the sediment porewater, consistent with direct porewater measurements which showed elevated levels of Sn, Pb, Mn and Fe compared to pristine locations. Comparison of DGT sediment probe results to direct porewater measurements showed that Sn and Fe were resupplied to the porewater from the solid phase. Further sediment characterisation work was undertaken to investigate why some of the metals (such as Cd, Cu and Zn) were present in low concnetraions in the porewater. Very high levels of acid volatile sulfides, up to 1600 pg g\(^{-1}\), were detected in sediment adjacent to-the waste disposal site. The high concentration of reactive sulfides in the sediment appears to be the main controlling factor of metal availability in the porewater.