Two kinds of passive monitors - ExposMeter Hydrophobic Devices (EHD, based on SPMD technology) and ExposMeter Metal Devices (EMDs, based on DGT technology), were used to detect chemicals transported from the dumping area. The devices were easy to install, they require no battery or other electricity supply, and they provide both 21-day time-weighted average values of the concentrations of individual dissolved chemical compounds and indications of the integrated toxicity of pollutants in the sampled water. Since they monitor dissolved concentrations, EHDs have advantages over devices that measure particles in the water (turbidity) as indicators of spreading pollution, since they can detect specific compounds and provide information on mixtures/fingerprints of pollutants. During the sampling no metabolism or other sort of degradation of the chemicals occurs and the sampling is not generally affected by pollution levels or water conditions. Provided appropriate sampling locations are selected and the subsequent chemical analysis is reliable, EHDs can also indicate likely pollution sources and serve as efficient tools for risk assessment.

Results from the analysis of EHD extracts with performance reference compounds allow time-weighted average concentrations (TWAs) of pollutants in the sampled water throughout the deployment time to be calculated. EHDs are usually deployed for 3-4 weeks. Longer deployment times can lead to the equilibrium sampling of some compounds by the samplers, and hence should be avoided since, according to theory can only be calculated for compounds for which uptake is still in the kinetic phase at the end of the sampling period. We have combined two deployments following one after each other which gave us the knowledge about TWA concentrations of the investigated compounds in the sampled waters spanning the period from October 30 until December 12, 2006.

In addition to sampling in the vicinity of the dumping area (near Malmokalven), we also sampled water close to the area (Bjorvika) in which the excavated sediment is being extracted, to obtain "fingerprints" of the pollutants to facilitate tracting of the orgin of the water pollution. Since public concern has been expressed about the possible effects of the dumping in the vicinities of Hovedoya and Akers bugge, samples were collected at these sites during the sampling campaign to assess whether or not there was valid cause for sampling points were chosen at various depths, the lowest 3m from the bottom of the fjord; monitors were deployed at sites with bottom water flows; sampling points were selected that would provide information on possible gradients of pollutants spreading from the dumping area; monitors were placed near the sediment excavation area to obtain a pollution fingerprint the scope for obtaining information on the influence of other possible sources of pollution were also considered when deployment locations were selected.