DGT - a new assessment tool for toxic metals in Norwegian aquaculture

The passive sampling technique DGT (Diffusive Gradients in Thin films) developed by Davison and Zhang at Aquatic Chemistry, Environmental Science Department, Lancaster University, UK, is a major breakthrough in sampling of labile ("bioavailable") metal sp ecies in water. Diffusional uptake of metals during the deployment time makes a quantification of the average concentration of labile metal species possible. The sampler performs well for heavy metals such as Pb, Cd, Cu, Zn, Co and Ni. Laboratory experiments also suggest that AI, Fe, and several other trivalent metals can be determined using DGT. The objective of this projeet is to use gained experience on the DGT technique adapted to metal toxicity problems in Norwegian aquaculture. The focus will be on the water types normally used (fresh water, brackish water and seawater), metals most frequently causing problems (At, Fe, Mn, Co, Zn) and other metals of env ironmental interest (Pb, Cd, Cr, Ni, Co Hg etc.). Other techniques for speciation analysis (SPE, DET/in situ dialysis, equilibrium modelling) will be employed parallel to the DGT investigations. The results will be compared to biomarkers of metal exposure such as analysis of gill tissue and blood plasma parameters. The work will consist of laboratory tests and field studies in aquaculture plants with documented water quality problems.