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.

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.

Use of life cycle assessments to evaluate the environmental footprint of contaminated sediment remediation.

Ecological and human risks often drive the selection of remedial alternatives for contaminated sediments. Traditional human and ecological risk assessment (HERA) includes assessing risk for benthic organisms and aquatic fauna associated with exposure to contaminated sediments before and after remediation as well as risk for human exposure but does not consider the environmental footprint associated with implementing remedial alternatives. Assessment of environmental effects over the whole life cycle (i.e., Life Cycle Assessment, LCA) could complement HERA and help in selecting the most appropriate sediment management alternative. Even though LCA has been developed and applied in multiple environmental management cases, applications to contaminated sediments and marine ecosystems are in general less frequent. This paper implements LCA methodology for the case of the polychlorinated dibenzo-p-dioxins and -furans (PCDD/F)-contaminated Grenland fjord in Norway. LCA was applied to investigate the environmental footprint of different active and passive thin-layer capping alternatives as compared to natural recovery. The results showed that capping was preferable to natural recovery when analysis is limited to effects related to the site contamination. Incorporation of impacts related to the use of resources and energy during the implementation of a thin layer cap increase the environmental footprint by over 1 order of magnitude, making capping inferior to the natural recovery alternative. Use of biomass-derived activated carbon, where carbon dioxide is sequestered during the production process, reduces the overall environmental impact to that of natural recovery. The results from this study show that LCA may be a valuable tool for assessing the environmental footprint of sediment remediation projects and for sustainable sediment management.

In situ measurement of PCB pore water concentration profiles in activated carbon-amended sediment using passive samplers.

Vertical pore water profiles of in situ PCBs were determined in a contaminated mudflat in San Francisco Bay, CA, 30 months after treatment using an activated carbon amendment in the upper layer of the sediment. Pore water concentrations were derived from concentrations of PCBs measured in two passive samplers; polyethylene (PE, 51 µm thick) and polyoxymethylene (POM, 17 µm thick) at different sediment depths. To calculate pore water concentrations from PCB contents in the passive samplers, an equilibrium approach and a first-order uptake model were applied, using five performance reference compounds to estimate pore water sampling rates. Vertical pore water profiles showed good agreement among the measurement and calculation methods with variations within a factor of 2, which seems reasonable for in situ measurements. The close agreements of pore water estimates for the two sampler materials (PE and POM) and the two methods used to translate uptake in samplers to pore water concentrations demonstrate the robustness and suitability of the passive sampling approach. The application of passive samplers in the sediment presents a promising method for site monitoring and remedial treatment evaluation of sorbent amendment or capping techniques that result in changes of pore water concentrations in the sediment subsurface.

Remediation of contaminated marine sediment using thin-layer capping with activated carbon--a field experiment in Trondheim harbor, Norway.

In situ amendment of contaminated sediments using activated carbon (AC) is a recent remediation technique, where the strong sorption of contaminants to added AC reduces their release from sediments and uptake into organisms. The current study describes a marine underwater field pilot study in Trondheim harbor, Norway, in which powdered AC alone or in combination with sand or clay was tested as a thin-layer capping material for polycyclic aromatic hydrocarbon (PAH)-contaminated sediment. Several novel elements were included, such as measuring PAH fluxes, no active mixing of AC into the sediment, and the testing of new manners of placing a thin AC cap on sediment, such as AC+clay and AC+sand combinations. Innovative chemical and biological monitoring methods were deployed to test capping effectiveness. In situ sediment-to-water PAH fluxes were measured using recently developed benthic flux chambers. Compared to the reference field, AC capping reduced fluxes by a factor of 2-10. Pore water PAH concentration profiles were measured in situ using a new passive sampler technique, and yielded a reduction factor of 2-3 compared to the reference field. The benthic macrofauna composition and biodiversity were affected by the AC amendments, AC + clay having a lower impact on the benthic taxa than AC-only or AC + sand. In addition, AC + clay gave the highest AC recoveries (60% vs 30% for AC-only and AC + sand) and strongest reductions in sediment-to-water PAH fluxes and porewater concentrations. Thus, application of an AC-clay mixture is recommended as the optimal choice of the currently tested thin-layer capping methods for PAHs, and more research on optimizing its implementation is needed.

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. In this paper we present the results on uptake of dioxins and furans (PCDD/F) in passive samplers and two sediment-dwelling species exposed in boxcores collected from the test plots during four surveys between 2009 (after cap placement) and 2018. Sediment profile images (SPI) and analyses of dioxins revealed that the thin (1-5 cm) cap layers became buried beneath several centimeters of sediments resuspended from adjacent bottoms and deposited on the test plots after capping. Uptake reduction ratios (R) were calculated as dioxins accumulated in cores collected from capped sediments divided by dioxins accumulated in cores collected from uncapped reference sediments. Cap layers with dredged clay or crushed limestone had only short-term positive effect with R-values increasing to about 1.0 (no effect) 1-4 years after capping. In spite of the recontamination, cap layers with clay and activated carbon had significant long-term effects with R-values slowly increasing from 0.12-0.33 during the first three years to 0.39-0.46 in 2018, showing 54-61% reduced uptake of dioxins (PCDD/F-TE) nine years after capping with AC.

Field measurement of diffusional mass transfer of HOCs at the sediment-water interface.

The sediment to water diffusive flux of PAHs and PCBs was measured under field conditions with a novel infinite-sink benthic flux chamber that deployed semipermeable membrane devices (SPMD) as a sorbing material. Fluxes were measured before and after in situ capping of sediments in Oslo Harbour with clean clay. The fluxes of native pyrene and PCB 52 from uncapped contaminated sediment measured with the flux chamber were 0.3-1.6 microg m(-2) d(-1) and 2-8 ng m(-2) d(-1), respectively. Fluxes from the capped sediment were reduced by 93-97%. The in situ measured fluxes were compared to fluxes independently calculated from freely dissolved concentrations in pore water and overlying water, measured using equilibrium passive samplers, diffusive boundary layer (DBL) thickness, measured by an alabaster dissolution method and literature values of diffusion coefficients. Measured fluxes from the uncapped sediment agreed well with calculated fluxes, the median of the ratio of the measured flux over the calculated flux was 0.9 with an inter quartile range of 0.5-1.6.

The importance of sulphide binding for leaching of heavy metals from contaminated Norwegian marine sediments treated by stabilization/solidification.

Over time, Norwegian fjords and harbour areas have received contaminants from industrial activities and urban run-off, and measures to remediate contaminated marine sediments are therefore needed. Stabilization/solidification (S/S) technology, in which the contaminated marine sediments are mixed with cement and other binding agents, has been shown to be a promising remediation technology. This paper summarizes a study of the environmental effect of stabilization, highlighting the importance of sulphide binding governing the leaching of heavy metals from the S/S of contaminated marine sediments. The study is a part of a research project focusing on developing effective methods for S/S of contaminated seabed sediments for use in new construction areas. Four cementitious binders were tested on sediments from six different locations: Bergen, Gilhus, Grenland, Hammerfest, Sandvika and Trondheim. The sediments differed with respect to properties such as concentration of contaminants, water content, organic content and grain size distribution. Portland cement, Portland cement with fly ash, industry cement, and sulphate resistant cement, were tested as binders. The leaching from the S/S sediments after 28 days of curing was measured by using a standard leaching batch test (EN 12457-2: 2003), with seawater as leaching agent. The eluate was analysed for pH and redox, as well as content of heavy metals and organic contaminants. Available volatile sulphide (AVS) and simultaneously extractable metals (SEM) were also measured in the sediments. This paper focuses on the leaching of lead (Pb) and copper (Cu). A reduced leaching of Pb after stabilization was observed for the mixtures, whereas the leaching of Cu from Hammerfest sediments increased substantially after stabilization for all cementitious additions. Experiments show that Hammerfest samples had lower values of AVS than the other sediments. This was confirmed by the SEM/AVS analysis, highlighting the importance of sulphide binding for mobility of heavy metals in stabilized marine sediments. For practical application of S/S technology to contaminated sediments, it is important to assess the leachability of the stabilized material taking sediment conditions such as AVS content into account. It is however important to be aware that the mobility of contaminants from a S/S sediment is dependent on a combination of contaminant concentrations and hydraulic conductivity (permeability). When devising S/S procedures for environmental projects, in addition to physical strength, the binder should be optimized in relation to leaching and permeability in order to achieve the lowest transport of contaminants through the material.

How Important is Bioturbation for Sediment-to-Water Flux of Polycyclic Aromatic Hydrocarbons in the Baltic Sea?

In the present study a recently developed benthic flow-through chamber was used to assess the sediment-to-water flux of polycyclic aromatic hydrocarbons (PAHs) at 4 sites on the Swedish Baltic Sea coast. The flow-through chamber allows for assessment of the potential effect of bioturbation on the sediment-to-water flux of hydrophobic organic contaminants. The sediments at the 4 investigated sites have both varying contamination degree and densities of bioturbating organisms. The flux of individual PAHs measured with the flow-through chamber ranged between 21 and 510, 11 and 370, 3 and 9700, and 62 and 2300 ng m-2 d-1 for the 4 sites. To assess the potential effect of bioturbation on the sediment-to-water flux, 3 flow-through and closed chambers were deployed in parallel at each site. The activity of benthic organisms is attenuated or halted because of depletion of oxygen in closed benthic chambers. Therefore, the discrepancy in flux measured with the 2 different chamber designs was used as an indication of a possible effect of bioturbation. A potential effect of bioturbation on the sediment-to-water flux by a factor of 3 to 55 was observed at sites with a high density of bioturbating organisms (e.g., Marenzelleria spp., Monoporeia affinis, and Macoma balthica of approximately 860-1200 individuals m-2 ) but not at the site with much lower organism density (<200 individuals m-2 ). One site had a high organism density and a low potential effect of bioturbation, which we hypothesize to be caused by the dominance of oligochaetes/polychaetes at this site because worms (Marenzelleria spp.) reach deeper into the sediment than native crustaceans and mollusks. Environ Toxicol Chem 2019;38:1803-1810. © 2019 SETAC.

Monitoring wastewater discharge from the oil and gas industry using passive sampling and Danio rerio bioassay as complimentary tools.

Produced water (PW) represents the largest volume waste stream in oil and gas production operations from most offshore platforms. PW is difficult to monitor as releases are rapidly diluted and concentrations can reach trace levels. The use of passive samplers can over come this. Here polyethylene (PE) was calibrated for a diverse range of PW pollutants. Zebrafish were exposed to dilutions of PW and passive sampler extracts in order to investigate the relationship between freely dissolved chemical concentrations and acute toxic effects. The raw PW had an LC50 of 13% (percentage of PW in the standardized zebrafish medium). Observed non-viable deformations to embryos (at 5 hpf) included heart and yolk edema, head, spine and tail deformations. The dose-response relationship of lethal effects showed that if 0.0041 g of PE is exposed to this PW, then extracted, 50% of exposed D. rerio will suffer lethal effects. The sum of tested freely dissolved concentrations that led to 50% lethal effects (mortality and non-viable deformations) was 2.32 × 10-4 mg/L for PW and 7.92 × 10-2 mg/L for PE. This implies that exposure to raw PW was more toxic than exposure to PE extracts. This toxicity was attributed both to the presence of contaminants as well as PW salinity. Passive samplers are able to detect very low freely dissolved pollutant concentrations which is important for assessing the spatial dilution of PW releases. Bioassays provide complimentary information as they account for all toxic compounds including those that are not taken up by passive samplers.

Diffusion of PAH and PCB from contaminated sediments with and without mineral capping; measurement and modelling.

A novel laboratory microcosm test was developed to measure the diffusion of native PAHs and PCBs from sediments in the presence and absence of a capping layer. Diffusive flux of 15 PAHs and 7 PCBs from uncapped sediment from Oslo harbour was 3.8+/-0.9 microg m(-2)d(-1) and 0.010+/-0.003 microg m(-2)d(-1), respectively. The flux from sediments capped with 1cm mineral cap (crushed limestone or crushed gneiss (0-2mm)), observed during the first 410 d, was 3.5-7.3% of the flux from uncapped sediments. By measuring freely dissolved pore water concentrations of 10 PAHs the flux in the microcosm was modelled with steady state and transient diffusion models. The measured flux from uncapped sediment was 27-290% of modelled steady state flux. Good agreement was also found between the measured flux of pyrene from capped sediment and the flux modelled with the transient model when fitting only with the distribution coefficients for pyrene between the cap material and water (Kd_pyr). Fitted Kd_pyr, (210 and 23 l kg(-1) for limestone and gneiss, respectively) was in the same order of magnitude as K(d) calculated from organic carbon content in the cap materials (68 and 14 l kg(-1) respectively). Calculation of the efficiency of a hypothetical cap with 10 cm diffusion path shows that the increased diffusion path length alone can yield a flux reduction >99% through a strong increase in the stagnant diffusive boundary layer from <1 to 100mm.

The contribution of urban runoff to organic contaminant levels in harbour sediments near two Norwegian cities.

The main aim of the present study was to compare the quality of particle emissions (urban runoff and settling particles in rivers and harbours) to the quality of top-layer bed sediments, for two Norwegian harbours (Oslo and Drammen). A sub-aim was to investigate whether non-industrial urban runoff contributed to the organotin load of sediments, apart from leaching from ship hulls. Time-integrated samples of stormwater runoff were obtained in an innovative manner, by sampling man-holes in the stormwater system. Settling particles were sampled with sediment traps. The study focused on PAHs, PCBs and organotin compounds. Contaminant levels were generally a factor of 2-10 (PAHs) and 3-30 (TBT) lower in emitted riverine and runoff particles than in top-layer bed sediments, except for PCBs in Oslo harbour (only 20-30% lower). Significant levels of tributyltin (TBT; median 140mug/kg) were shown in runoff particles, showing that TBT can also be emitted via urban sources, since the sampled man-holes were not in areas where dry-docking activities take place. Possible land-based TBT sources include long-lasting house paint and use of TBT as PVC stabilizer and timber preservative. Since there are ongoing emissions into the two studied harbour areas, it is concluded that the addition of an actively sorbing capping material such as activated carbon might be the best remediation alternative.

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-1, 268µgMeHgkg-1) in intermediate sediment depths (10-20cm) outside of the meadow, with reduced concentrations within the meadow. Natural recovery of the fjord was revealed by lower sediment surface concentrations (1.9-15.5mgTot-Hgkg-1, 1.3-3.2µgMeHgkg-1). Within the meadow, vertical gradients of sediment hydrogen sulfide (H2S) Eh and pH suggested microbial sulfate reduction in 2-5cm depths, coinciding with peak values of relative MeHg levels (0.5% MeHg). We assume that MeHg production rates was stimulated by the supply and availability of organic carbon, microbial activity and a sulfide oxidizing agent (e.g. O2) within the rhizosphere. Following this, % MeHg in sediment (0-5cm) within the meadow was approximately 10× higher compared to outside the meadow. Further, enhanced availability of MeHg within the meadow was demonstrated by significantly higher fluxes (p<0.01) from sediment to overlying water (0.1-0.6ngm-2d-1) compared to sediment without macrophytes (0.02-0.2ngm-2d-1). Considering the productivity and species richness typical for such habitats, submerged macrophyte meadows located within legacy Hg contaminated sediment sites may constitute important entry points for MeHg into food webs.

Experimental determination of efficiency of capping materials during consolidation of metal-contaminated dredged material.

Capping has received considerable attention as a method to reduce contaminant transport from contaminated sediments and sub-aqueous disposed dredged materials. Consolidation of dredged material after capping can result in a substantial advection of pore water, into or through the capping layer. The effect of two different capping materials (crushed limestone and gneiss) on the transport of heavy metals and phosphorus during consolidation was studied with a novel experimental design. Capped dredged material was placed in a consolidation cell and pore water expelled during the consolidation was collected for chemical analysis. To support interpretation of the results from this test, interactions between the capping material and the dredged material were also studied in batch tests. The study revealed large differences in the capping efficiency (CE) between the two materials. Both materials were efficient caps for Fe and P (CE>99% with 2cm cap), while limestone also was efficient for Mn (CE>92% with 2cm cap). Contrary to what was expected, capping of dredged material with crushed gneiss increased the release of Ca, Mn, Co, Ni, Cd, and Cu, resulting in negative CE. The batch tests showed that leaching from the crushed gneiss was the source of the observed release of metals. The results also show that the high concentrations of heavy metals in the dredged material were immobilised, probably by sulphides. Protection against re-suspension and oxidation will therefore in many cases be the most important effect of the cap.

Toolset for assessment of natural recovery from legacy contaminated sediment: Case study of Pallanza Bay, Lake Maggiore, Italy.

The aim of this study was to develop a toolset that can be used by site managers to assess and monitor natural attenuation processes in sediments contaminated with legacy hydrophobic organic contaminants. The toolset is composed of sediment traps to measure quality and deposition rate of incoming sediment under different hydrodynamic conditions, sediment cores to show trends in sediment bed concentrations over time, and passive samplers attached to a porewater probe frame to assess the mobility of buried contaminants and possible contaminant flux from sediment. These three tools were used together for the first time to assess the mobility of dichlorodiphenyltrichloroethane (DDT) contaminants in sediment in Pallanza Bay, Lake Maggiore, Italy. Depositing sediment and sediment cores were consistent in showing that DDT-contaminated sediment is undergoing burial by cleaner sediment. Elevated DDT concentrations from historical contamination seemed to be effectively buried and immobilized by ongoing deposition by cleaner sediment, because the positive flux from the elevated DDT concentration in the sediment porewater should not advance towards the sediment surface. The monitoring toolset introduced in this study enabled us to more effectively assess ongoing natural attenuation processes and provide more risk relevant data than traditional methods used in monitored natural recovery projects, such as bulk sediment concentrations from sediment cores. Our field assessment results suggest that incoming sediment from the Toce River have reduced DDT concentrations in the sediment compared to historic levels, and will continue to do so in locations where higher DDT concentrations are found within the bioactive layer.

Monitoring chemical and biological recovery at a confined aquatic disposal site, Oslofjord, Norway.

The recovery of the confined aquatic disposal (CAD) facility located at Malmøykalven in Oslofjord, Norway, has been assessed using an array of field measurement techniques. These methods were used prior to the disposal of dredged sediments as well as during 3 annual postdisposal monitoring campaigns. Traditional sampling to assess chemical recovery indicates that an immediate reduction in total sediment concentrations and surface sediments can be characterized as having good quality. Deposition of new material indicates that the quality of depositing material at the CAD is stabile and representative of the natural background quality in the area. Continued deposition of this material will improve the long-term chemical recovery of the CAD. A positive biological recovery of the benthic community has been observed and is expected to continue along a typical benthic succession pattern. To supplement traditional sampling, passive samplers were deployed at the CAD. Results suggest that the flux and concentrations of polycyclic aromatic hydrocarbon 16 and polychlorinated biphenyl 7 released from the CAD will continue to decrease over time. The combined results from these multiple lines of evidence indicate that the CAD and capping layer function as predicted 3 yr after the construction was completed. There is not only an improvement in the efficacy of the CAD itself but also a general improvement of the area, compared with the situation prior to disposal. Environ Toxicol Chem 2017;36:2552-2559. © 2017 SETAC.

In situ benthic flow-through chambers to determine sediment-to-water fluxes of legacy hydrophobic organic contaminants.

Contaminated sediment can release hydrophobic organic contaminants (HOCs) and thereby act as a secondary source of primarily legacy hazardous substances to the water column. There is therefore a need for assessments of the release of HOCs from contaminated sediment for prioritization of management actions. In situ assessment of HOC sediment-to-water flux is currently done with (closed) benthic flux chambers, which have a sampling time exceeding one month. During this time, the water inside the chamber is depleted of oxygen and the effect of bioturbation on the sediment-to-water release of HOCs is largely ignored. Here we present a novel benthic flux chamber, which measures sediment-to-water flux of legacy HOCs within days, and includes the effect of bioturbation since ambient oxygen levels inside the chamber are maintained by continuous pumping of water through the chamber. This chamber design allows for sediment-to-water flux measurements under more natural conditions. The chamber design was tested in a contaminated Baltic Sea bay. Measured fluxes were 62-2300 ng m-2 d-1 for individual polycyclic aromatic hydrocarbons (PAHs), and 5.5-150 ng m-2 d-1 for polychlorinated biphenyls (PCBs). These fluxes were 3-23 times (PAHs) and 12-74 times (PCBs) higher than fluxes measured with closed benthic chambers deployed in parallel at the same location. We hypothesize that the observed difference in HOC flux between the two chamber designs are partly an effect of bioturbation. This hypothesized effect of bioturbation was in accordance with literature data from experimental studies.

Monitoring alkylphenols in water using the polar organic chemical integrative sampler (POCIS): Determining sampling rates via the extraction of PES membranes and Oasis beads.

Polar organic chemical integrative samplers (POCIS) have previously been used to monitor alkylphenol (AP) contamination in water and produced water. However, only the sorbent receiving phase of the POCIS (Oasis beads) is traditionally analyzed, thus limiting the use of POCIS for monitoring a range of APs with varying hydrophobicity. Here a "pharmaceutical" POCIS was calibrated in the laboratory using a static renewal setup for APs (from 2-ethylphenol to 4-n-nonylphenol) with varying hydrophobicity (log Kow between 2.47 and 5.76). The POCIS sampler was calibrated over its 28 day integrative regime and sampling rates (Rs) were determined. Uptake was shown to be a function of AP hydrophobicity where compounds with log Kow < 4 were preferentially accumulated in Oasis beads, and compounds with log Kow > 5 were preferentially accumulated in the PES membranes. A lag phase (over a 24 h period) before uptake in to the PES membranes occurred was evident. This work demonstrates that the analysis of both POCIS phases is vital in order to correctly determine environmentally relevant concentrations owing to the fact that for APs with log Kow ≤ 4 uptake, to the PES membranes and the Oasis beads, involves different processes compared to APs with log Kow ≥ 4. The extraction of both the POCIS matrices is thus recommended in order to assess the concentration of hydrophobic APs (log Kow ≥ 4), as well as hydrophilic APs, most effectively.

A large-scale field trial of thin-layer capping of PCDD/F-contaminated sediments: Sediment-to-water fluxes up to 5 years post-amendment.

The longer-term effect (3-5 y) of thin-layer capping on in situ sediment-to-surface water fluxes was monitored in a large-scale field experiment in the polychlorinated dibenzodioxin and dibenzofuran (PCDD/F) contaminated Grenlandfjords, Norway (4 trial plots of 10,000 to 40,000 m(2) at 30 to 100 m water depth). Active caps (designed thickness 2.5 cm) were established in 2 fjords, consisting of dredged clean clay amended with powdered activated carbon (PAC) from anthracite. These active caps were compared to 2 nonactive caps in one of the fjords (designed thickness 5 cm) consisting of either clay only (i.e., without PAC) or crushed limestone. Sediment-to-water PCDD/F fluxes were measured in situ using diffusion chambers. An earlier study showed that during the first 2 years after thin-layer capping, flux reductions relative to noncapped reference fields were more extensive at the fields capped with nonactive caps (70%-90%) than at the ones with PAC-containing caps (50%-60%). However, the present work shows that between 3 and 5 years after thin-layer capping, this trend was reversed and cap effectiveness in reducing fluxes was increasing to 80% to 90% for the PAC caps, whereas cap effectiveness of the nonactive caps decreased to 20% to 60%. The increasing effectiveness over time of PAC-containing "active" caps is explained by a combination of slow sediment-to-PAC mass transfer of PCDD/Fs and bioturbation by benthic organisms. The decreasing effectiveness of "nonactive" limestone and clay caps is explained by deposition of contaminated particles on top of the caps. The present field data indicate that the capping efficiency of thin active caps (i.e., enriched with PAC) can improve over time as a result of slow diffusive PCDD/F transfer from sediment to PAC particles and better mixing of the PAC by bioturbation.

The role of passive sampling in monitoring the environmental impacts of produced water discharges from the Norwegian oil and gas industry.

Stringent and periodic iteration of regulations related to the monitoring of chemical releases from the offshore oil and gas industry requires the use of ever changing, rapidly developing and technologically advancing techniques. Passive samplers play an important role in water column monitoring of produced water (PW) discharge to seawater under Norwegian regulation, where they are used to; i) measure aqueous concentrations of pollutants, ii) quantify the exposure of caged organisms and investigate PW dispersal, and iii) validate dispersal models. This article summarises current Norwegian water column monitoring practice and identifies research and methodological gaps for the use of passive samplers in monitoring. The main gaps are; i) the range of passive samplers used should be extended, ii) differences observed in absolute concentrations accumulated by passive samplers and organisms should be understood, and iii) the link between PW discharge concentrations and observed acute and sub-lethal ecotoxicological end points in organisms should be investigated.