Morten Schaanning

Capping Efficiency of Various Carbonaceous and Mineral Materials for In Situ Remediation of Polychlorinated Dibenzo-p-dioxin and Dibenzofuran Contaminated Marine Sediments : Sediment-to-Water Fluxes and Bioaccumulation in Boxcosm Tests

The efficiency of thin-layer capping in reducing sediment-to-water fluxes and bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans, hexachlorobenzene, and octachlorostyrene was investigated in a boxcosm experiment. The influence of cap thickness (0.5-5 cm) and different cap materials was tested using a three-factor experimental design. The cap materials consisted of a passive material (coarse or fine limestone or a marine clay) and an active material (activated carbon (AC) or kraft lignin) to sequester the contaminants. The cap thickness and the type of active material were significant factors, whereas no statistically significant effects of the type of passive material were observed. Sediment-to-water fluxes and bioaccumulation by the two test species, the surface-dwelling Nassarius nitidus and the deep-burrowing Nereis spp., decreased with increased cap thickness and with addition of active material. Activated carbon was more efficient than lignin, and a ~90% reduction of fluxes and bioaccumulation was achieved with 3 cm caps with 3.3% AC. Small increases in fluxes with increased survival of Nereis spp. indicated that bioturbation by Nereis spp. affected the fluxes.

Submarine and deep-sea mine tailing placements: a review of current practices, environmental issues, natural analogs and knowledge gaps in Norway and internationally

The mining sector is growing in parallel with societal demands for minerals. One of the most important environmental issues and economic burdens of industrial mining on land is the safe storage of the vast amounts of waste produced. Traditionally, tailings have been stored in land dams, but the lack of land availability, potential risk of dam failure and topography in coastal areas in certain countries results in increasing disposal of tailings into marine systems. This review describes the different submarine tailing disposal methods used in the world in general and in Norway in particular, their impact on the environment (e.g. hyper-sedimentation, toxicity, processes related to changes in grain shape and size, turbidity), current legislation and need for future research. Understanding these impacts on the habitat and biota is essential to assess potential ecosystem changes and to develop best available techniques and robust management plans.

A soft-bottom sublittoral mesocosm by the Oslofjord: Description, performance and examples of application

Abstract Controlled experiments and detailed studies of behaviour in the subtidal require diving, submersible vessels or instruments placed in situ. These methods often limit experimental design. Furthermore, experiments with toxic chemicals in the field may not be possible due to lack of dosage control, environmental consequences, and public welfare. Such problems can be overcome by the use of mesocosms. In this paper a soft-bottom mesocosm in the Oslofjord, Norway is described. The mesocosm consists of two indoor basins each with a surface area of 100 m2 and a maximum water depth of 1.7 m. Each basin is divided into three compartments. Soft-bottom sediment sections were collected in the field by a modified USNEL box-corer (0.25 m2). The sediment was transferred to boxes and brought into the mesocosm. The water level in the mesocosm can be lowered so that the sediment surfaces are easily accessible for sampling, manipulation, inspection, or measurements requiring equipment or techniques not compatible wi...

Interactions between eutrophication and contaminants. II. Mobilization and bioaccumulation of Hg and Cd from marine sediments

Abstract The availability of labile organic matter and oxygen from the bottom water are primary factors most likely to affect the accumulation of contaminants in benthic invertebrates. To test this hypothesis, a two-factor microcosm experiment was designed. Three species of sediment-dwelling organisms were kept in sediments spiked with 203 Hg and 109 Cd. Blue mussels were kept downstream in separate vessels. Different treatments were obtained by combination of two levels of organic carbon (enriched, not enriched) with two levels of oxygen (7–9 mg l −1 and 2–3 mg l −1 ) in the water flowing through the aquaria. After an experimental period of three months, gamma emission from the two isotopes were counted in samples of sediments, porewater and biota. The results showed initial retention of a labile fraction of Cd in the carbon-enriched sediments. Hg was retained to the same extent in all treatments and no significant loss from the sediment was observed during the experimental period. In the porewater, Hg was not detectable whereas the concentration of Cd was consistent with the levels predicted from low sulphide ion activities recorded on Ag|Ag 2 S electrodes and the solubility of CdS (s) . Two-way ANOVA analyses revealed significant effects of carbon enrichment on bioaccumulation of both Cd and Hg. Significant effects of oxygen level and oxygen-organic interactions were found for the bioaccumulation of Cd only.

Interactions between eutrophication and contaminants. III. Mobilization and bioaccumulation of benzo(a)pyrene from marine sediments

Abstract A major environmental issue is to understand how eutrophication processes, such as organic enrichment and hypoxia may act on the distribution patterns and bioavailability of contaminants to benthic organisms. An experiment with sediment organic C content (control vs enriched with concentrated phytoplankton) and oxygen level (normoxia vs 2–3 mg O 2 l −1 ) as fixed factors, and 14 C-B(a)P in benthic organisms and sediment as dependent variable, was conducted for 93 days. Three species of sediment-dwelling organisms with different feeding strategies ( Amphiura filiformis, Nereis diversicolor and Abra alba ) were chosen. Blue mussels ( Mytilus edulis ), kept in separate aquaria, were exposed to the outflowing water of the microcosms. Concentration of 14 C-B(a)P in the sediment surface at the end of the experiment was significantly higher in the organically enriched sediments than in the control sediments. Accumulation of 14 C-B(a)P in A. filiformis and N. diversicolor was also higher in the presence of organic enrichment. Concentrations of 14 C-B(a)P in M. edulis placed downstream of aquaria treated with organic matter were also higher, indicating a higher leaching of bioavailable 14 C-B(a)P from the enriched sediments. Hypoxia had no significant effect on the sediment distribution and bioaccumulation of 14 C-B(a)P, and there was no significant interaction between hypoxia and organic enrichment. Our results support the concept of selective feeding on labile organic matter as a major exposure route of organic contaminants in benthic organisms.

Large-scale field study on thin-layer capping of marine PCDD/F-contaminated sediments in Grenlandfjords, Norway: physicochemical effects.

A large-scale field experiment on in situ thin-layer capping was carried out in the polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) contaminated Grenlandsfjords, Norway. The main focus of the trial was to test the effectiveness of active caps (targeted thickness of 2.5 cm) consisting of powdered activated carbon (AC) mixed into locally dredged clean clay. Nonactive caps (targed thickness of 5 cm) consisting of clay without AC as well as crushed limestone were also tested. Fields with areas of 10,000 to 40,000 m(2) were established at 30 to 100 m water depth. Auxiliary shaken laboratory batch experiments showed that 2% of the applied powdered AC substantially reduced PCDD/F porewater concentrations, by >90% for tetra-, penta- and hexa-clorinated congeners to 60-70% for octachlorinated ones. In-situ AC profiles revealed that the AC was mixed into the sediment to 3 to 5 cm depth in 20 months. Only around 25% of the AC was found inside the pilot fields. Sediment-to-water PCDD/F fluxes measured by in situ diffusion chambers were significantly lower at the capped fields than at reference fields in the same fjord, reductions being largest for the limestone (50-90%) followed by clay (50-70%), and the AC + clay (60%). Also reductions in overlying aqueous PCDD/F concentrations measured by passive samplers were significant in most cases (20-40% reduction), probably because of the large size of the trial fields. The AC was less effective in the field than in the laboratory, probably due to prolonged sediment-to-AC mass transfer times for PCDD/Fs and field factors such as integrity of the cap, new deposition of contaminated sediment particles, and bioturbation. The present field data indicate that slightly thicker layers of limestone and dredged clay can show as good physicochemical effectiveness as thin caps of AC mixed with clay, at least for PCDD/Fs during the first two years after cap placement.

Interactions between eutrophication and contaminants. I. Principles, experimental design and synthesis

Abstract In marine environments influenced by human activities, the sea-bed is a major recipient of both contaminants and organic matter. Deposition and recycling of contaminants from bottom sediments may be affected by the eutrophication status of the area. Contaminants and eutrophication factors may also interact to affect bioaccumulation as well as the growth, health and reproduction of benthic organisms. Consequently, from an environmental management point of view, these interactions should be considered when decisions are made about input of contaminants and organic matter to the aquatic environment. In order to elucidate interaction patterns between eutrophication and contaminants, radio-labelled contaminants were applied in a large scale experiment performed at Marine Research Station Solbergstrand, situated by the Oslofjord, Norway. The continous flow through experiment was performed in glass aquaria containing three sediment-dwelling species ( Abra alba, Nereis diversicolor and Amphiura filiformis ) placed in marine clay sediments. Blue mussels ( Mytilus edulis ) were kept in separate downstream aquaria and exposed to the out-flowing water from the sediment aquaria. In 12 contaminated aquaria the sediment was spiked with 203 Hg (0.23 mg Hg kg −1 dry sediment), 109 Cd (5 mg Cd kg −1 ) and 14 C-benzo[ a ]pyrene (1 mg BaP kg −1 ). In 12 organically enriched aquaria, phytoplankton (2 mg C kg −1 dry sediment) was initially mixed into the sediment and two months later another batch corresponding to 20 g C m −2 was added to the aquaria. Finally, the concentration of oxygen was continuously lowered from 7–9 mg O 2 l −1 in 12 well-oxygenated aquaria to 2.4–3.5 mg O 2 l −1 in 12 low-oxic aquaria by purging the source water with nitrogen. Allowing three replicate aquaria for each treatment, all combinations of the two levels (high/low) of the three factors (contaminants, oxygen availability and carbon load) could be tested in a factorial design using 24 aquaria. Sulphide ion activies were continuously recorded by Ag|AgS electrodes in the sediments and overlying water, and redox potentials were measured by Pt-electrodes inserted in the sediment. There were only minor changes in redox and sulphide potentials during the experimental period. Also, mortalities of the test species were negligible in all aquaria. After an experimental period of three months, the concentration of contaminants was quantified in sediments, porewater and biota using beta/gamma emission from the isotopes. Effects of the treatments on sediment-dwelling invertebrates were assessed using growth ( Nereis, Abra and Amphiura ), arm regeneration ( Amphiura ) and biomarker responses. In this paper (paper I) the principles and hypotheses for studying interactions between organic loading and contaminants are outlined as well as the experimental design. The results from the experiment are presented in three separate papers (papers II–IV) elsewhere in this volume. A short synthesis is presented in this paper, comparing the conclusions from the individual studies.

Assessment of the direct effects of biogenic and petrogenic activated carbon on benthic organisms.

Activated carbon (AC) has long been associated with the capacity to effectively remove organic substances from aquatic and sediment matrices; however, its use in remediation purposes has drawn some concern due to possible impacts on benthic communities. Within the inner Oslofjord, the use of AC has been well documented for reducing the risks associated with dioxins or dioxin-like compounds from contaminated areas. However, benthic surveys performed on areas treated with AC have revealed that the abundance of organisms inhabiting these areas can be reduced significantly in the subsequent years following treatment. The reason for the reduction in the benthic communities is currently unknown, and therefore, an integrated approach to assess the effects of 2 different forms of AC (biogenic and petrogenic) on benthic organisms has been performed. A battery of 3 different benthic organisms with different feeding and life-cycle processes has been used encompassing sediment surface feeders, sediment ingestors, and sediment reworkers. Results of the tests indicated that although AC is not acutely toxic at concentrations up to 1000 mg/L, there may be physical effects of the substance on benthic dwelling organisms at environmentally relevant concentrations of AC at remediated sites.

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. The objective of this study was to evaluate the bioavailability of common organochlorine contaminants and polycyclic aromatic hydrocarbons (PAHs) in selected polluted sediments from Norway by simple generic sorption models (free energy relationships), as well as by pore water concentration measurements. Furthermore, the aim was to predict bioaccumulation from these bioavailability estimates for comparison with in vivo bioaccumulation assessments using ragworm (Nereis virens) and netted dogwhelk (Hinia reticulata). Predicted biota-to-sediment accumulation factors (BSAFs) derived from pore water concentration estimates were in better agreement with the bioaccumulation observed in the test organisms, than the generic BSAFs expected based on linear sorption models. The results therefore support that site-specific evaluations of bioaccumulation provide useful information for more accurate risk assessments. A need for increased knowledge of the specific characteristics of benthic organisms, which may influence the exposure, uptake and elimination of contaminants, is however emphasized.

Denitrification in the water column of an intermittently anoxic fjord

Denitrification was studied in the water column in the Bunnefjord, inner part of the Oslofjord in southern Norway, using a 15N-technique (the isotope pairing method). The fjord is 150 m deep and during our surveys in September–December 1998 hydrogen sulphide was present in the deep water below 80 m. No significant denitrification was found in water samples from the surface layer (4 m depth), but high rates were observed within a deep density gradient between 62 and 78 m depth. Oxygen concentration within this layer was low (<21 mmol m−3), and the concentration of NO3 decreased from ca. 15 mmolċm−3 at 62 m depth to not detectable below 78 m. Pronounced peaks of NO2 up to 4.4 mmol m−3 were observed at 70–78 m depth. The maximum denitrification rate of 1.5 mmol N m−3 d−1 was observed at 70 m depth. Integrated for the whole layer, the denitrification rate was 13 mmol N m−2 d−1. A significant linear correlation was found between the denitrification rate and the ambient nitrate concentration which indicated that the rate was primarily controlled by the availability of nitrate in the O2-poor water. Compared to rates reported for coastal water, denitrification in the water column in the Bunnefjord was high and the process appears to be a major sink of bioavailable nitrogen in the fjord.