Stability of Capped Dredged Sediments in a Confined Disposal Facility at Malmøykalven,Oslofjord, SE Norway

Conventional sediment capping is a widely used technique where clean sediments are placed over contaminated sediments to reduce the migration of contaminants to the environment. A concern of the method is initial contaminant transport through the cap during the consolidation of the underlying disposed sediments. The current study was conducted to investigate the efficiency of the cap placed over the Malmøykalven confined disposal facility (CDF). The thickness of the soft disposed sediments reached 6 m in maximum, and was subject to extensive consolidation when the cap was placed. Vertical profiles of trace metals (Cd, Cu, Hg, Pb, Zn) and the structure of the cap layer were studied in six gravity cores. The cap material was clearly distinguishable in the sediment cores, both visually and chemically. The results provided evidence that consolidation-induced pore water advection was able to transport fine particles (<63 µm) and organic material into the cap layer. Metal transport in the particulate phase was suggested to be the main transport process into the cap layer. The study shows the importance of an appropriate cap layer design to prevent any particle transport and to minimize the effects of consolidation-induced advective transport.     

Chemical criteria for marine eutrophication with special reference to the Oslofjord,Norway

Results of a chemical and geochemical study of the Oslofjord system are presented to explore the possibility of qualitatively identifying a eutrophication gradient. Nutrient concentration and dissolved oxygen may indicate such a gradient in areas of similar hydrographies. Uncertainties due to minor differences in hydrography may be resolved by considering sedimentary organic carbon, C:N ratios and the accumulation of mineralisation products in the sediment pore water. The reliability of the sedimentary organic matter and the pore water composition as gradient indicators can be impaired by input of terrestrial organics, dispersal of mineralisation products by the benthic fauna or the apparent high levels of organic carbon and pore water nutrients in the absence of the benthic fauna under anoxic conditions.     

Aspects of the general biology of Sars' eelpout, Lycenchelys sarsi (Collett, 1871) (Pisces, Zoarcidae), in Oslofjorden, Norway

Biological data on the sizes, age, growth and aspects of the reproduction of Sars' eelpout Lycenchelys sarsi were obtained during a study of the Oslojord fish fauna in 1981. Lycenchelys sarsi is a relatively small zoarcid that occurs on soft sediment. Spawning in the Oslofjord occurs between April and possibly as late as August. This species is typical for zoarcids in that it has a relatively low fecundity (20-40 eggs per female) and the eggs are relatively large (yolked oocytes up to 5.4 mm diameter). Sexual maturity is reached when the fish are approximately 11 cm in total length, corresponding to an age of 3-5 years. The maximum ages of L. sarsi found in the Oslofjord were 6+ years. In general, males reach a larger size than females.