New insights into submarine tailing disposal for a reduced environmental footprint: Lessons learnt from Norwegian fjords.

Submarine tailing disposal (STD) in fjords from land-based mines is common practice in Norway and takes place in other regions worldwide. We synthesize the results of a multidisciplinary programme on environmental impacts of STDs in Norwegian fjords, providing new knowledge that can be applied to assess and mitigate impact of tailing disposal globally, both for submarine and deep-sea activities. Detailed geological seafloor mapping provided data on natural sedimentation to monitor depositional processes on the seafloor.

Long-term response of marine benthic fauna to thin-layer capping with powdered activated carbon in the Grenland fjords, Norway.

The Grenland fjords in Norway have a long history of contamination by large emissions of dioxins and mercury. As a possible sediment remediation method in situ, thin-layer capping with powdered activated carbon (AC) mixed with clay was applied at two test sites at 30 m and 95 m depth in the Grenland fjords. This study presents long-term effects of the AC treatment on the benthic community structure, i.

Impaired benthic macrofauna function 4 years after sediment capping with activated carbon in the Grenland fjords, Norway.

The sediments in the Grenland fjords in southern Norway are heavily contaminated by large emissions of dioxins and mercury from historic industrial activities. As a possible in situ remediation option, thin-layer sediment surface capping with powdered activated carbon (AC) mixed with clay was applied at two large test sites (10,000 and 40,000 m) at 30-m and 95-m depths, respectively, in 2009. This paper describes the long-term biological effects of the AC treatment on marine benthic communities up to 4 years after treatment.

Long-term effects of thin layer capping in the Grenland fjords, Norway: Reduced uptake of dioxins in passive samplers and sediment-dwelling organisms.

The Grenlandfjords in South East Norway are severely contaminated with dioxins from a magnesium smelter operated between 1950 and 2001. In 2009, the proposal of thin-layer capping as a potential mitigation method to reduce spreading of dioxins from the fjord sediments, resulted in the set-up of a large-scale field experiment in two fjord areas at 30 and 100 m depth. After capping, several investigations have been carried out to determine effects on benthic communities and bioavailability of dioxins.

Benthic community status and mobilization of Ni, Cu and Co at abandoned sea deposits for mine tailings in SW Norway.

During 1960-94 tailings from an ilmenite mine in southwest Norway were placed in sea deposits in a sheltered fjord and a more exposed coastal basin. In 2015 both deposit sites were sampled to assess the state of metal contamination and macrobenthic communities 20-30 years after deposition was ended. The results showed that nickel and copper still exceeded environmental quality standards in sediment and pore water from the 0-1 cm layer, and fluxes of nickel, copper and cobalt to the overlying water was high compared to adjacent reference stations.

Effects of submarine mine tailings on macrobenthic community structure and ecosystem processes.

A mesocosm experiment with intact benthic communities was conducted to evaluate the effects of mine tailings on benthic community structure and biogeochemical processes. Two types of tailings were supplied from process plants using flotation and flocculation chemicals, while a third type was absent of added chemicals. All tailings impacted the sediment community at thin layers, and through more mechanisms than merely hypersedimentation.

The influence of permanently submerged macrophytes on sediment mercury distribution, mobility and methylation potential in a brackish Norwegian fjord.

Macrophytes are shown to affect the microbial activity in different aqueous environments, with an altering of the sediment cycling of mercury (Hg) as a potential effect. Here, we investigated how a meadow with permanently submerged macrophytes in a contaminated brackish fjord in southern Norway influenced the conditions for sulfate reducing microbial activity, the methyl-Hg (MeHg) production and the availability of MeHg. Historically discharged Hg from a chlor-alkali plant (60-80tons, 1947-1987) was evident through high Hg concentrations (491mgTot-Hgkg, 268μgMeHgkg) in intermediate sediment depths (10-20cm) outside of the meadow, with reduced concentrations within the meadow.

In vivo bioaccumulation of contaminants from historically polluted sediments - relation to bioavailability estimates.

Many contaminants are recalcitrant against degradation. Therefore, when primary sources have been discontinued, contaminated sediments often function as important secondary pollution sources. Since the management and potential remediation of contaminated marine sediments may be very costly, it is important that the environmental risks of contaminants present in these sediments and benefits of remediation are evaluated as accurately as possible.

Measuring nonpolar organic contaminant partitioning in three Norwegian sediments using polyethylene passive samplers.

Freely dissolved pore water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), penta- and hexachlorobenzene (PeCB and HCB), octachlorostyrene (OCS), p,p'-DDE and p,p'-DDD were measured in bottom sediments from three sites in Norway. Sediments were from Aker Brygge, site of a former shipyard in the inner part of Oslofjord, Frierfjord in the Grenlandsfjord area, impacted during the 50 year-long activity of a magnesium smelter plant, and from Kristiansand harbour, site with high industrial activity. Low density polyethylene (LDPE) membrane samplers were exposed to these sediments in laboratory incubation under constant and low-level agitation for periods of 1, 2, 6, 13, 23 and 50 days.

Effects of increased sea water concentrations of CO2 on growth of the bivalve Mytilus edulis L.

It has been proposed that emission of anthropogenic carbon dioxide to the atmosphere will lead to increased concentrations of CO(2) in sea water corresponding to a decrease of pH of several tenths of pH units. An experiment was performed to test the effects of increased sea water concentrations of CO(2) on shell growth of the blue mussel Mytilus edulis. The experiment was performed in aquaria continuously flushed with sea water spiked with CO(2) to provide five different levels of pH between 6.