Introduction to the Special Series, "Incorporating Nature-based Solutions into the Built Environment".

Incorporating nature-based solutions (NBSs) into the built environment supports the ongoing sustainability challenge as emphasized in the United Nations' Sustainable Development Goals (SDGs) and has particular relevance for SDG Goal #11 (Sustainable cities and communities), which seeks greater efficiencies in urban planning and management practices that address aging infrastructure and ongoing air, water, and soil pollution. The short communications and research articles in this special series exemplify many of these aspects, highlighting the application of NBSs and showcasing the latest environmental research and policy solutions to support this. Nature-based solutions in the built environment aim to promote the understanding of the transdisciplinary nature of NBSs and enhance the global awareness of the value of NBSs by providing a diversity of solutions to illustrate the positive economic, social, and environmental benefits of NBSs in the built environment. Integr Environ Assess Manag 2022;18:39-41. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

From landfills to landscapes-Nature-based solutions for water management taking into account legacy contamination.

Nature-based solutions (NBS) can be used in combination with the reopening of piped rivers to support area development. In certain cases, piped rivers can run through disused landfills. This presents a complicating factor because landfills provide the possibility for river water to be contaminated by waste. In Skien municipality, close to Oslo, Norway, NBS are being considered as part of a potential reopening of the Kjørbekk stream. A 4-km stretch of the stream is contained in an aging pipe infrastructure that is buried under two disused landfills. The pipe infrastructure does not have the physical capacity to cope with an increase in precipitation brought about by current climate change, and in certain areas, the pipe has started to leak. This means that surface water runoff that cannot be accommodated by the pipe, as well as water that leaks from the pipe, can become contaminated by the waste in the disused landfill. Furthermore, the water can be transported with the stream course to the final recipient, taking the contamination with it. Reopening the stream and providing new water pathways can alleviate these problems, but it must be carried out so that contamination is not allowed to spread. This case study reveals how certain NBS that focus on reducing the amount of water in contact with pollutants, reducing the amount of particle spreading, remediating contaminated water, and remediating contaminated soil could be implemented at the site and function as a catalyst for an incremental city development. Integr Environ Assess Manag 2022;18:99-107. © 2021 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Vertical profiles of sedimentary polycyclic aromatic hydrocarbons and black carbon in the Gulf of Gdansk (Poland) and Oslofjord/Drammensfjord (Norway), and their relation to regional energy transitions.

The analysis of undisturbed sediment cores is a powerful tool for understanding spatial and temporal impacts of anthropogenic emissions from the energy and transport sectors at a regional scale. The spatial and vertical distribution of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) were determined in 12 cores of recent (up to 20cm long) sediments from the Gulf of Gdansk in Poland, and Oslofjord/Drammensfjord in Norway. The Σ12PAHs levels in individual sediment layers varied from 250 to 4500ng/g d.w. in the Gulf of Gdansk, and from 210 to 4580ng/g d.w. in the Norwegian fjords. Analysis of PAH ratios indicates that PAHs in both studied areas originated mainly from pyrogenic sources. The BC concentrations in sediments were up to 0.9% and were generally higher in the Gulf of Gdansk (mean - 0.39%) than in Oslofjord/Drammensfjord (mean - 0.19%). The deposition history of anthropogenic emissions over the last 100years was reconstructed based on the analysis of dated and well-laminated sediment cores from two stations from the Gulf of Gdansk and two stations from the Norwegian fjords. The evolution in energy structure was especially evident in the Oslofjord, where transition from fossil fuel combustion to hydropower after 1960 coincided with a sharp decrease in sedimentary PAHs. Despite significant changes in the economic development in Poland, temporal patterns in PAH concentrations/profiles in the Gulf of Gdansk were not as obvious. The historical PAH trends in the Gulf of Gdansk may be related to the overwhelming PAH inputs from domestic combustion of solid fuels (coal, wood) for heating purposes. The implementation of legislation and other activities addressed to restrict the use of solid fuels in residential heating should reduce PAH emissions.

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.

Anthropogenic impact on marine ecosystem health: A comparative multi-proxy investigation of recent sediments in coastal waters.

Hazardous substances entering the sea, and ultimately deposited in bottom sediments, pose a growing threat to marine ecosystems. The present study characterized two coastal areas exposed to significant anthropogenic impact - Gulf of Gdansk (Poland), and Oslofjord/Drammensfjord (Norway) - by conducting a multi-proxy investigation of recent sediments, and comparing the results in light of different available thresholds for selected contaminants. Sediment samples were analyzed for benzo(a)pyrene (B(a)P) and other polycyclic aromatic hydrocarbons (PAHs), nonylphenols (NPs), organotin compounds (OTs), toxic metals (Cd, Hg, Pb), as well as mutagenic, genotoxic and endocrine-disrupting activities (in CALUX bioassays). In general, a declining trend in the deposition of contaminants was observed. Sediments from both basins were not highly contaminated with PAHs, NPs and metals, while OT levels may still give rise to concern in the Norwegian fjords. The results suggest that the contamination of sediments depends also on water/sediment conditions in a given region.

Advancing the Use of Passive Sampling in Risk Assessment and Management of Sediments Contaminated with Hydrophobic Organic Chemicals: Results of an International Ex Situ Passive Sampling Interlaboratory Comparison.

This work presents the results of an international interlaboratory comparison on ex situ passive sampling in sediments. The main objectives were to map the state of the science in passively sampling sediments, identify sources of variability, provide recommendations and practical guidance for standardized passive sampling, and advance the use of passive sampling in regulatory decision making by increasing confidence in the use of the technique. The study was performed by a consortium of 11 laboratories and included experiments with 14 passive sampling formats on 3 sediments for 25 target chemicals (PAHs and PCBs). The resulting overall interlaboratory variability was large (a factor of ∼10), but standardization of methods halved this variability. The remaining variability was primarily due to factors not related to passive sampling itself, i.e., sediment heterogeneity and analytical chemistry. Excluding the latter source of variability, by performing all analyses in one laboratory, showed that passive sampling results can have a high precision and a very low intermethod variability (

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.

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.

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.

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.

Sorption of organic compounds to fresh and field-aged activated carbons in soils and sediments.

Activated carbon (AC) amendment to polluted sediment or soil is an emerging in situ treatment technique that reduces freely dissolved porewater concentrations and subsequently reduces the ecological and human health risk of hydrophobic organic compounds (HOCs). An important question is the capacity of the amended AC after prolonged exposure in the field. To address this issue, sorption of freshly spiked and native HOCs to AC aged under natural field conditions and fresh AC amendments was compared for one soil and two sediments. After 12-32 months of field aging, all AC amendments demonstrated effectiveness for reducing pore water concentrations of both native (30-95%) and spiked (10-90%) HOCs compared to unamended sediment or soil. Values of K(AC) for field-aged AC were lower than freshly added AC for spiked HOCs up to a factor of 10, while the effect was less for native HOCs. The different behavior in sorbing native HOCs compared to freshly spiked HOCs was attributed to differences in the sorption kinetics and degree of competition for sorption sites between the contaminants and pore-clogging natural organic matter. The implications of these findings are that amended AC can still be effective in sorbing additional HOCs some years following amendment in the field. Thus, a certain level of long-term sustainability of this remediation approach is observed, but conclusions for decade-long periods cannot be drawn solely based on the present study.

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.

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.

Influence of historical industrial epochs on pore water and partitioning profiles of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in Oslo Harbor, Norway, sediment cores.

Contaminant levels in urban harbor sediments vary with contaminant emission levels, sedimentation rates, and sediment resuspension processes such as propeller wash. Levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) are decreasing in many urban harbors, as heavily contaminated sediments that accumulated during past decades are being buried by less-contaminated sediments. However, PAHs and PCBs remain a concern in areas where burial is slow or resuspension processes re-expose heavily contaminated older layers. Chronostratigraphic sediment core studies typically characterize contaminant level histories by using total sediment concentrations, C(sed) , and do not determine the freely dissolved porewater concentrations, C(pw) , which provide a better measure of bioavailability. Here both C(sed) and C(pw) profiles were established for PAHs and PCBs in dated sediment cores from diverse areas of Oslo Harbor, Norway. Sediment-porewater partitioning profiles were established alongside profiles of various sorbing carbonaceous phases, including total organic carbon (TOC), black carbon, and diverse carbonaceous geosorbents identified by petrographic analysis. Stratigraphic trends in carbonaceous phases and C(sed) could be associated with different industrial epochs: hydropower (post-1960, approximately), manufactured gas (∼1925-1960), coal (∼1910-1925), and early industry (∼1860-1910). Partitioning was highly variable and correlated best with the TOC. Hydropower-epoch sediments exhibit decreasing C(sed) with time and a relatively strong sorption capacity compared with the manufactured-gas epoch. Sediments from the manufactured-gas epoch exhibit substantial PAH and metal contamination, large amounts of coke and char, and a low sorption capacity. Reexposure of sediments of this epoch increases risks to local benthic species. Implications on natural recovery as a sediment management strategy are discussed.

Use of multicriteria involvement processes to enhance transparency and stakeholder participation at Bergen Harbor, Norway.

Use of participatory stakeholder engagement processes could be important to reduce the risk of potential conflicts in managing contaminated sites. Most stakeholder engagement techniques are qualitative in nature and require experienced facilitators. This study proposes a multicriteria involvement process to enhance transparency and stakeholder participation and applies it to a contaminated sediment management case study for Bergen Harbor, Norway. The suggested multicriteria involvement process builds on the quantitative principles of multicriteria decision analysis and also incorporates group interaction and learning through qualitative participatory methods. Three different advisory groups consisting of local residents, local stakeholders, and nonresident sediment experts were invited to participate in a stakeholder engagement process to provide consensual comparative advice on sediment remediation alternatives. In order for stakeholders or residents to be able to embrace a complex decision such as selection of remediation alternatives, the involvement process with lateral learning, combined with multicriteria decision analysis providing structure, robustness and transparent documentation was preferable. In addition, a multicriteria involvement process resulted in consistent ranking of remediation alternatives across residents, stakeholder, and experts, relative to individual intuitive ranking without the multicriteria involvement process.

Assessment of field-related influences on polychlorinated biphenyl exposures and sorbent amendment using polychaete bioassays and passive sampler measurements.

Field-related influences on polychlorinated biphenyl (PCB) exposure were evaluated by employing caged deposit-feeders, Neanthes arenaceodentata, along with polyoxymethylene (POM) samplers using parallel in situ and ex situ bioassays with homogenized untreated or activated carbon (AC) amended sediment. The AC amendment achieved a remedial efficiency in reducing bioaccumulation by 90% in the laboratory and by 44% in the field transplants. In situ measurements showed that PCB uptake by POM samplers was greater for POM placed in the surface sediment compared with the underlying AC amendment, suggesting that tidal exchange of surrounding material with similar PCB availability as untreated sediment was redeposited in the cages. Polychlorinated biphenyls bioaccumulation with caged polychaetes from untreated sediment was half as large under field conditions compared with laboratory conditions. A biodynamic model was used to confirm and quantify the different processes that could have influenced these results. Three factors appeared most influential in the bioassays: AC amendment significantly reduces bioavailability under laboratory and field conditions; sediment deposition within test cages in the field partially masks the remedial benefit of underlying AC-amended sediment; and deposit-feeders exhibit less PCB uptake from untreated sediment when feeding is reduced. Ex situ and in situ experiments inevitably show some differences that are associated with measurement methods and effects of the environment. Parallel ex situ and in situ bioassays, passive sampler measurements, and quantifying important processes with a model can tease apart these field influences.

Bioaccumulation of native polycyclic aromatic hydrocarbons from sediment by a polychaete and a gastropod: freely dissolved concentrations and activated carbon amendment.

The present paper describes a study on the bioaccumulation of native polycyclic aromatic hydrocarbons (PAHs) from three harbors in Norway using the polychaete Nereis diversicolor and the gastropod Hinia reticulata. First, biota-sediment accumulation factors (BSAFs) were measured in laboratory bioassays using the original sediments. Median BSAFs were 0.004 to 0.01 kg organic carbon/kg lipid (10 PAHs and 6 organism-sediment combinations), which was a factor of 89 to 240 below the theoretical BSAF based on total sediment contents (which is approximately one). However, if BSAFs were calculated on the basis of measured freely dissolved PAH concentrations in the pore water (measured with polyoxymethylene passive samplers), it appeared that these BSAFfree values agreed well with the measured BSAFs, within a factor of 1.7 to 4.3 (median values for 10 PAHs and six organism-sediment combinations). This means that for bioaccumulation, freely dissolved pore-water concentrations appear to be a much better measure than total sediment contents. Second, we tested the effect of 2% (of sediment dry wt) activated carbon (AC) amendments on BSAE The BSAFs were significantly reduced by a factor of six to seven for N. diversicolor in two sediments (i.e., two of six organism-sediment combinations), whereas no significant reduction was observed for H. reticulata. This implies that either site-specific evaluations of AC amendment are necessary, using several site-relevant benthic organisms, or that the physiology of H. reticulata caused artifactually high BSAF values in the presence of AC.

How quality and quantity of organic matter affect polycyclic aromatic hydrocarbon desorption from Norwegian harbor sediments.

The desorption behavior of phenanthrene, pyrene, and benzo[a]pyrene was investigated for three Norwegian harbor sediments and their respective particle size fractions using the Tenax desorption method. Rate constants for rapidly, slowly, and very slowly desorbing fractions were on the order of 10(-1), 10(-2) to 10(-4), and 10(-4) to 10(-6)/h, respectively. Relatively small amounts were present in the rapidly desorbing fractions (F(rapid): < 6% for phenanthrene, 3-19% for pyrene, and 1-12% for benzo[a]pyrene). With the exception of benzo[a]pyrene, these F(rapid) values were generally lower than median F(rapid) values obtained from more than 100 literature values for native polycyclic aromatic hydrocarbons (PAHs) (22% for phenanthrene, 29% for pyrene, and 8% for benzo[a]pyrene). To understand which parameters influence PAH desorption, relations between desorption behavior and the sediment characteristics were investigated. A significant positive correlation was found between the extent of slow and very slow desorption and the ratios of black carbon to total organic carbon, as well as the temperature at which 50 and 90%, respectively, of the organic matter was oxidized, as obtained from oxidation-only Rock Eval analysis. Thus, black carbon-bound PAHs probably desorb slowly and very slowly. Furthermore, significant positive correlations between desorption behavior and the average particle size were observed, which could be explained by retarded intraparticle diffusion.

Strong sorption of native PAHs to pyrogenic and unburned carbonaceous geosorbents in sediments.

It has recently been shown that the presence of carbonaceous geosorbents (CG, including black carbon (BC), unburned coal, and kerogen) can cause strong sorption of polycyclic aromatic hydrocarbons (PAHs) in sediments. We studied sorption of native PAHs in four Norwegian harbor sediments of which high fractions (21-56%) of the total organic carbon (TOC) consisted of CG carbon (CGC), as shown by organic petrography. PAH sorption coefficients were 1-2 orders of magnitude above predictions based on amorphous organic carbon partitioning alone. In recent studies, such strong sorption was attributed solely to BC sorption under the implicit assumption that sorption is linear for coal and kerogen. The most important result of the present study is that total sorption is better explained by considering all three nonlinearly sorbing CGC materials than by only considering BC. In addition, it was evaluated whether activated carbon (AC) amendments could be effective in reducing the freely dissolved pore-water concentrations (CW) and thus the environmental risks of the PAHs in such strongly sorbing sediments. The results indicated that an addition of 2 weight % AC reduced the Cw by factors of 21-153 for the four sediments (average values for all PAHs). Itwas shown that phenanthrene sorption to AC was, on average, reduced by a factor of 6 in sediment-AC mixtures compared to pure AC.