Sorbent Amendment Research Articles

The Impact of Sorbent Amendments for Mercury Remediation on the Viability of Soil Microorganisms

Mercury (Hg) remediation across contaminated environments in the United States is an ongoing project. As part of the Hg cleanup strategy at East Fork Poplar Creek (EFPC), located in Oak Ridge, TN, the deployment of sorbents is considered. However, the impact of sorbents on soil microorganisms is poorly understood. In this study, we investigated the effect of sorbents on soil microorganism viability and biofilm formation to assess soil health during sorbent application for Hg remediation. We specifically investigated the effect of two engineered sorbents, Organoclay PM-199 and Organoclay MRM (which are manufactured from clay minerals formulated for various remediation applications), on two gram-negative organisms (Serratia marcescens and Burkholderia thailandensis) isolated from the Hg-contaminated EFPC bank soil. Pure cultures of S. marcescens or B. thailandensis were amended with 5% (w/v) and 25% (w/v) PM-199 and MRM, respectively, for 9 days. The samples were harvested, and bacterial cell viability was determined using a BacLight staining kit. Results showed that the growth of sorbent-amended S. marcescens was inhibited in contrast to that of unamended control. Furthermore, biochemical assays were used to analyze bacterial biofilm formation and integral biofilm components. Our results suggest that biofilm formation by sorbent-amended S. marcescens was negatively affected. In contrast, B. thailandensis amended with low concentrations of MRM showed enhanced growth and notable differences in biofilm morphology. These results suggest that the use of organoclay PM-199 and MRM at higher concentrations in field studies may hinder the growth of specific soil microorganisms.

Assessment of activated carbon as a sorbent amendment for immobilizing perfluoroalkyl acids for surface sediment remediation

The detection of elevated levels of perfluoroalkyl acids (PFAAs) in sediments has become a significant concern, urgently requiring management and remediation efforts. In this study, we investigated the effectiveness of industrially cost-effective activated carbon (AC) in remediating PFAA-contaminated sediments at different disturbance intensities and explored the sorption capacity of AC under broad environmentally relevant conditions and in response to environmental variations. AC exhibited high sorption effectiveness for PFAAs (excluding perfluorobutanoic acid < 40 %) across different pH, ionic strengths (IS), and dissolved organic matter (DOM). However, the increase in pH or reduction in IS might reactivate partially immobilized PFAAs. DOM outcompeted longer-chain PFAAs for sorption sites, resulting in their reactivation on AC, while it showed a stronger sorption than a competitive effect on shorter-chain PFAAs. The 192-day remediation experiment showed that AC significantly deactivated mobile PFAAs and decreased PFAA release by 45.5 %–99.2 % and 61.0 %–98.8 % under weak and intense disturbances, respectively, when compared with untreated sediment. Although intense disturbance led to an increase in PFAA release, the PFAA levels in the water column of the AC group after intense disturbance were comparable or even lower than those before intense disturbance, primarily owing to the secondary sorption of suspended AC. These findings are crucial for the appropriate and safe use of AC for PFAA sequestration, the management of PFAA-contaminated sediments, and the development of effective sediment remediation strategies.

Evaluation of sorbent amendments used with stormwater management practices to remove contaminants: Impacts of rainfall intensity and antecedent dry periods

For a comprehensive evaluation of the suitability and efficiency of soil amendments in bioretention systems, it is crucial to investigate the capability of amendments for simultaneously serving three important functions under intermittent and variable flow conditions: removing a wide range of contaminants, supporting plant health, and maintaining media infiltration rate. However, most studies have not considered these important factors and conditions simultaneously, which may overestimate or underestimate the bioretention performance. In this study, a long-term vegetated column study was conducted to investigate the ability of various sorbent amendments– coconut coir fiber (CCF), blast furnace slag (BFS), and waste tire crumb rubber (WTCR) –for removal of metals, nutrients, and polycyclic aromatic hydrocarbons (PAHs) from stormwater. The experiments were performed under intermittent flow conditions considering different runoff intensities and antecedent dry periods (ADP). The long-term effect of bioretention usage on plant health and media infiltration rate was also investigated.All amended and unamended columns were able to remove >99 % of influent metals, except Cu, over the 7-month experiment period with different rain intensities and dry periods; modest effluent Cu concentrations occurred with higher rainfall. The performance of different media for removing PAHs such as naphthalene and acenaphthylene varied with the rain intensity. The BFS-amended media had high phosphate removal capacity (>90 %) under tested conditions. In all columns, nitrate removal was notably affected by changes in stormwater intensity and ADP, with high nitrate removal during heavy rainfall. Over the entire experiment, all media had good infiltration rate within the locally acceptable range (1–25 cm/h). The high iron and aluminum contents of BFS adversely affected the plant health in BFS-amended media. Overall, this study identifies the opportunities and challenges associated with the usage of bioretention amendments, and improves awareness among bioretention designers to consider seasonal effect on the performance of bioretention systems.

The effects of soil properties and sorbent amendments on immobilization of perfluorooctane sulfonate (PFOS) in contrasting soils: Experimental and numerical study

Per- and polyfluoroalkyl substances (PFAS), a class of manmade organo-fluorine chemicals, are a serious challenge to water supplies. In this study, the effects of physicochemical properties of Florida topsoil and Ringold formation Hanford site sediment as well as the influence of immobilizers on the sorption behavior of PFOS were tested. Activated charcoal (AC) and food waste compost amendments were added to the soil and sediment at 0.1 and 3 wt% concentration, respectively. The PFOS adsorption fits best to pseudo second-order kinetic and Freundlich isotherm models. PFOS uptake was greater in Florida topsoil compared to Hanford site sediment, indicating that organic matter played a key role in the retention of PFOS. The food waste compost amendment at 3 wt% had no impact on PFOS uptake. However, AC amendment at 0.1 wt% enhanced PFOS sorption in Florida topsoil by 80% and Hanford site sediment by 99% through increasing the soil/water partitioning coefficients (kd value). A one-dimensional model was used to simulate the influence of AC in Florida topsoil on the leaching of PFOS to the groundwater by the percolation of rainwater over time. The results demonstrated the addition of 0.1 wt% AC, to the soil dramatically inhibits or delays the leaching of PFOS for up to one year under certain conditions to below the guideline for maximum concentration level (0.02 ng/L). The amendment could control PFOS release for more than 10 years by increasing the kd value by 10 times.

Bioretention soil capacity for removing nutrients, metals, and polycyclic aromatic hydrocarbons; roles of co-contaminants, pH, salinity and dissolved organic carbon

Conventional bioretention soil media (BSM: e.g., loamy sand) is employed in infiltration-based stormwater management practices, but concerns exist on its limited sorption capacity. However, limited quantitative data is available, particularly considering the wide range of contaminants and water quality conditions that occur in stormwater. This study utilized batch tests to investigate the capability of conventional BSM for simultaneous removal of three nutrients (ammonium, nitrate, and phosphate), six metals (Cd, Cr, Cu, Ni, Pb and Zn), and four polycyclic aromatic hydrocarbons (PAHs: naphthalene, acenaphthylene, phenanthrene, and pyrene) from synthetic stormwater. Moreover, the effects of co-contaminants and different stormwater chemistry parameters (pH, salinity, and dissolved organic carbon (DOC)) on BSM sorption capacity were investigated. BSM was not effective for nutrients removal; however, it had good removal efficiency for metals such as Cu, Pb, and Cr which are less soluble at neutral pH values compared to metals such as Ni, Cd and Zn. Moreover, BSM was effective for removing PAHs with higher hydrophobicity such as pyrene and phenanthrene. Metals sorption capacity of BSM was greater at higher pH, lower salinity and DOC; however, the sorption capacity of BSM for PAHs was not sensitive to stormwater chemistry parameters. However, competitive sorption had a notable effect on low molecular weight PAHs, Cd, and Ni. This study provides a quantitative evaluation of the BSM performance and compares the sorption capacity to potential sorptive amendments used in stormwater management. While select sorbent amendments out-performed the BSM, this was not universal and was contaminant specific; careful consideration of water quality enhancement goals and solution chemistry are required in selecting a sorbent. Overall, this study identifies the possible limitations in BSM compositions and factors that may adversely affect BSM sorption capacity, and finally describes options to enhance BSM performance and recommendations for future research.

Use of natural sorbents for accelerated bioremediation of grey forest soil contaminated with crude oil

Due to the extensive oil extraction and transportation that occurs in oil-producing countries, many lands remain contaminated because of accidental leakages. Despite its low cost and environmentally safe nature, bioremediation technology is not always successful, mainly because of the soil toxicity to the degrading microbial populations and plants. Here we report a three-year microfield experiment on the influence of natural sorbents of mineral (zeolite, kaolinite, vermiculite, diatomite), organic (peat), carbonaceous (biochar) origin, and a mixed sorbent ACD (composed of granular activated carbon and diatomite) on the bioremediation of grey forest soil contaminated with weathered crude oil (40.1 g total petroleum hydrocarbons (TPH) kg−1). Optimal doses of the sorbents significantly accelerated bioremediation of petroleum-contaminated soil through bioaugmentation followed by phytoremediation. The main reason for the influence of the sorbent amendments relied upon the creation of optimal conditions for the activation of hydrocarbon-utilizing bacteria and plant growth due to the reduction of soil toxicity, as well as maintaining an optimal pH and water-air regime in the soil. That happened because of reducing the soil hydrophobicity, increasing porosity and water holding capacity. The content of the TPH in the best samples (2% biochar or ACD) reduced to their local permissible concentration accepted for remediated soils in the Russian Federation (≤5 g kg−1) after two warm seasons compared to that after three warm seasons in the other samples. Although some sorbents decelerated biodegradation of highly condensed polycyclic aromatic hydrocarbons (PAHs, including benzo(a)pyrene) in the soil, the overall risk from the residual contaminants present in the remediated soil and plants was minimized. The final total content of the main PAHs in the sorbent-amended soils did not exceed the maximal permissible levels that are accepted in most EU countries (1000–40,000 μg kg−1), and they did not accumulate in the aboveground phytomass of grasses in dangerous concentrations.

Comparing biochar and hydrochar for reducing the risk of organic contaminants in polluted river sediments used for growing energy crops

In Europe alone, >200 million m3 of river sediments are dredged each year, part of which are contaminated to such an extent that they have to be landfilled. This study compares the use of biochar and hydrochar for the remediation of sediment contaminated with pentachlorobenzene, hexachlorobenzene, lindane, trifluralin, alachlor, simazine, and atrazine with the motivation to make sediments contaminated by such priority substances usable as arable land for growing energy crops. Biochar and hydrochar originating from Miscanthus giganteus and Beta vulgaris shreds were compared for their potential to reduce contaminant associated risk in sediments. Specifically, by investigating the effects of sorbent amendment rate (1, 5, and 10 %) and incubation time (14, 30, and 180 d) on contaminant bioaccessibility, toxicity to the bacteria Vibrio fischeri, as well as toxicity and plant uptake in Zea mays. Biochar reduced contaminant bioaccessibility up to five times more than hydrochar. The bioaccessibility of contaminants decreased up to sevenfold with increasing incubation time, indicating that the performance of carbonaceous sorbents may be underestimated in short-term lab experiments. Biochar reduced contaminants toxicity to Vibrio fischeri, whereas hydrochar was itself toxic to the bacteria. Toxicity to Zea mays was determined by contaminant bioaccessibility but also sorbent feedstock with cellulose rich Beta vulgaris based sorbents exhibiting toxic effects. The plant uptake of all contaminants decreased after sorbent amendment.

A novel approach to sorbent-based remediation of soil impacted by organic micropollutants and heavy metals using granular biochar amendment and magnetic separation

Soil remediation by sorbent amendment is a popular method to immobilize contaminants but it is limited by the fact that the sorbent cannot be retrieved from the soil, posing as a threat to its quality, due to the gradual leaching of the sorbed contaminants. To address this challenge, this work proposes the use of granular-sized, magnetically retrievable sorbents for soil remediation. Specifically, granular biochar, that offers favorable sorption sites for both organic and inorganic contaminants, was used to treat contaminated soil samples. It is demonstrated that sorbent size plays a crucial role in its separation from the soil matrix by magnetic field. Granular magnetic biochar (gMBC) of 1–2 mm was found to be the most suitable sorbent size because it does not assimilate into the soil matrix and can be quantitatively retrieved both from wet and dry soil by means of magnetism, yielding a sorbent-free matrix. In this manner, the soil is relieved from both the hazardous contaminants and the contaminant-laden sorbent. Using gMBC, the remediation of contaminated soil from both organic micropollutants and heavy metals was optimized accomplishing remediation efficiencies from 40% to 90% for organic compounds and 30–65% for heavy metals through sorption and chemical transformation of the contaminants. The results of the study show that granular magnetic sorbents can be an effective and practical solution to the remediation of soils by facilitating their retrieval directly from the solid matrix which is not possible with micro/nanoparticle sorbents.

The Effects of Soil Properties and Sorbent Amendments on Immobilization of Perfluorooctane Sulfonate (Pfos) in Contrasting Soils: Experimental and Numerical Study

The Effects of Soil Properties and Sorbent Amendments on Immobilization of Perfluorooctane Sulfonate (Pfos) in Contrasting Soils: Experimental and Numerical Study

Application of Sorbent Amendments in Pfas Immobilization in Two Contrasting Soils

Application of Sorbent Amendments in Pfas Immobilization in Two Contrasting Soils

Sediment Remediation with New Composite Sorbent Amendments to Sequester Phosphorus, Organic Contaminants, and Metals.

This study tested two sediment amendments with active sorbents: injection of aluminum (Al) into sediments and thin-layer capping with Polonite (calcium–silicate), with and without the addition of activated carbon (AC), for their simultaneous sequestration of sediment phosphorus (P), hydrophobic organic contaminants (HOCs), and metals. Sediment cores were collected from a eutrophic and polluted brackish water bay in Sweden and incubated in the laboratory to measure sediment-to-water contaminant release and effects on biogeochemical processes. We used diffusive gradients in thin-film passive samplers for metals and semi-permeable membrane devices for the HOC polychlorinated biphenyls and polycyclic aromatic hydrocarbons. Al injection into anoxic sediments completely stopped the release of P and reduced the release of cadmium (Cd, −97%) and zinc (Zn, −95%) but increased the sediment fluxes of PAH (+49%), compared to the untreated sediment. Polonite mixed with AC reduced the release of P (−70%), Cd (−67%), and Zn (−89%) but increased methane (CH4) release. Adding AC to the Al or Polonite reduced the release of HOCs by 40% in both treatments. These results not only demonstrate the potential of innovative remediation techniques using composite sorbent amendments but also highlight the need to assess possible ecological side effects on, for example, sedimentary microbial processes.

Interaction of Soil Microbes with Organoclays and their Impact on the Immobilization of Hg under Aerobic Conditions

Immobilization of mercury (Hg) leaching from bank soils of East Fork Poplar Creek (EFPC) is considered part of remediation strategies to mitigate the amount of Hg entering the creek. Different approaches are currently being evaluated, such as utilizing engineered sorbents to immobilize Hg species in EFPC bank soils. However, the influence of environmental microbes on the immobilization of Hg by sorbents is unknown. Organocation-modified phyllosilicate clay minerals (organoclays) are widely used as sorbents for the immobilization of contaminants. This study evaluates the interactions of Serratia marcescens and Burkholderia thailandensis with the sorbent Organoclay PM-199 and their impact on the immobilization of Hg under aerobic conditions. We evaluated the competitive binding of Hg between sorbents and selected microorganisms in a series of pure culture studies using bacterial strains identified in EFPC bank soil samples. Our results suggest that Hg sorption by Organoclay PM-199 is not significantly impacted by common soil bacteria present in EFPC, specifically Serratia marcescens and Burkholderia thailandensis, which are known to form biofilms. These findings suggest that sorbent amendments are an effective strategy for the remediation of Hg contamination in natural ecosystems.

Carbon mass balance model to investigate biochar and activated carbon amendment effects on the biodegradation of stable-isotope labeled toluene in gravelly sand

Fully stable isotope-labeled toluene was used as a model volatile petroleum hydrocarbon (VPH) to investigate the mineralization of VPHs and soil organic matter (SOM) by soil microorganisms in the presence and absence of 2%%(w/w) wood-chip biochar or bitumen-derived activated carbon. Biodegradation of 13C7 -toluene was monitored in batch microcosms for 19 days by measuring headspace CO2 and toluene concentrations. A numerical carbon mass balance model was developed to interpret the experimental observations. Increased 44CO2 and 45CO2 headspace concentrations following 13C7 -toluene addition as compared to live and abiotic controls indicated a stimulation of microbial activity. By fitting a maximum specific growth rate (μmax) of 0.6 h −1 (in line with published rates), it was possible to match model predictions of 45CO2 and 44CO2 concentrations with the experimentally determined data. Half-saturation constants (Ks) of 4.06 × 103 mgL −1, 7.76 × 102 mgL −1 and 1.83 × 102 mgL −1 were predicted for soil, soil & BC and soil & AC respectively, much higher than previously reported values. Differences in the half-saturation constant suggests that sorbent amendment affects the microbial ecology, by making microorganisms which can utilize substrates at lower concentrations more competitive. Consequently, amending soils with 2% BC or AC changed the biokinetics of VPH degradation by rendering VPHs less bioavailable, but did not appear to have any detrimental effects on VPH degradation and may serve as a sustainable, cost-effective approach for enhancing the natural attenuation of VPHs in soil on the long term.

Synthesis and evaluation of Fe3O4-impregnated activated carbon for dioxin removal

Polychlorinated dibenzo-p-dioxins and -furans (PCDD/PCDFs) are highly toxic organic pollutants in soils and sediments which persist over timescales that extend from decades to centuries. There is a growing need to develop effective technologies for remediating PCDD/Fs-contaminated soils and sediments to protect human and ecosystem health. The use of sorbent amendments to sequester PCDD/Fs has emerged as one promising technology. A synthesis method is described here to create a magnetic activated carbon composite (AC-Fe3O4) for dioxin removal and sampling that could be recovered from soils using magnetic separation. Six AC-Fe3O4 composites were evaluated (five granular ACs (GACs) and one fine-textured powder AC(PAC)) for their magnetization and ability to sequester dibenzo-p-dioxin (DD). Both GAC/PAC and GAC/PAC-Fe3O4 composites effectively removed DD from aqueous solution. The sorption affinity of DD for GAC-Fe3O4 was slightly reduced compared to GAC alone, which is attributed to the blocking of sorption sites. The magnetization of a GAC-Fe3O4 composite reached 5.38 emu/g based on SQUID results, allowing the adsorbent to be easily separated from aqueous solution using an external magnetic field. Similarly, a fine-textured PAC-Fe3O4 composite was synthesized with a magnetization of 9.3 emu/g.

Evaluation of fly ash, apatite and rice straw derived-biochar in varying combinations for in situ remediation of soils contaminated with multiple heavy metals

ABSTRACT In -situ sorbent amendment is a relatively low-cost, low-impact approach for remediation of soil contaminated with heavy metals (HMs), and thus is considered a way to be favored in developing countries. In this study, materials of non-hazardous, alkaline agronomic and industrial by-products were used as sorbents to explore their capacity of in situ immobilization of multiple HMs in mining-impacted arable soil. These sorbents included fly ash (FA), biochar (BC) and apatite (AP) and they were implemented with varying ratios of combinations. Results of soil microcosm tests showed that after incubation for 90 days, concentrations of Pb, Zn, and Cd in their exchangeable forms determined by a sequential extraction method significantly decreased in amended soils, as opposed to the unamended control. Of the five sets of amendments, the composite of FA, BC, and AP resulted in the maximum reduction (up to 80%) in the mobility of Pb, Zn, and Cd in soils. The mechanisms underlying the immobilization of HMs in amended soils might involve processes of surface precipitation, ion exchange and complexation, in which the physicochemical properties of sorbent materials played an important role. The immobilization efficacy of sorbent amendments on HMs in soil was further supported by pot experiments in which significant inhibition of HM accumulation in the belowground and aboveground tissues of maize was observed after 50-day cultivation in amended soils as compared with control soil. Together, these results suggest that the application of cost-saving and environmentally friendly materials derived from wastes as sorbents to remediate soils contaminated with multiple HMs is promising for developing countries like Vietnam.

Functionalized Biochar/Clay Composites for Reducing the Bioavailable Fraction of Arsenic and Cadmium in River Sediment.

Biochar has frequently been used for the treatment of heavy metal pollution in water and soil; its effect on contaminated sediments requires further research. To improve the ability of biochar to immobilize heavy metals in sediment, we prepared a functionalized biochar/attapulgite composite by pyrolysis of the clay attapulgite and zinc chloride-pretreated rice straw biomass. Compared with the original biochar, the biochar/attapulgite composite had a large increase in specific surface area, pore volume, oxygen-containing functional groups, and cation exchange capacity. Biochar effectively improved the dispersibility of attapulgite as a matrix. The results showed that the biochar/attapulgite composite effectively reduced the bioavailable fraction of arsenic (As) and cadmium (Cd) in river sediment, which was a great improvement compared with the raw biochar. After the sediment was treated with different biochar/attapulgite composites, the concentrations of As and Cd in the overlying water and the porewater, and the content of acid-extractable and toxicity characteristic leaching procedure (TCLP)-extractable As and Cd in the solid phase of the sediment decreased significantly. Both zinc chloride activation and attapulgite improved As and Cd immobilization in sediment when we used the biochar/attapulgite composite. The results suggest that biochar/attapulgite composite can be used as an efficient in situ sorbent amendment to improve the heavy metal immobilization ability of the sediment. Environ Toxicol Chem 2019;38:2337-2347. © 2019 SETAC.

Effect of corn straw biochar application to sediments on the adsorption of 17α-ethinyl estradiol and perfluorooctane sulfonate at sediment-water interface

The immobilization of organic contaminants in sediment-water systems is of growing concern. Using biochar as sorbent amendment to reduce the mobility of pollutants in the sediment-water interface is becoming increasingly popular as a low-cost and environmentally friendly option. In this study, we mixed sediment from the Weishan Lake with biochar (0%, 2%, and 5% (w/w)) derived from corn straw to investigate the adsorption of perfluorooctane sulfonate (PFOS) and 17α-ethinyl estradiol (EE2). Biochar addition significantly improved the adsorption rates and capacities of EE2 and PFOS on sediments by the factors 1.7–3.5; the organic carbon concentration in the sediment was the main factor influencing this process. The sorption of EE2 and PFOS to sediment was near-linear (Freundlich exponent 1/n of 0.799–0.805), but non-linear for biochar (0.430–0.476) and sediment+biochar (0.370–0.421). The mobility of PFOS in the water-sediment system after biochar addition was significantly reduced, with a considerable increase (about three times) in the sediment-water distribution coefficient Kd. Compared to EE2, PFOS is anionic compound and contains hydrophobic C–F chains and hydrophilic S–O groups, making it more susceptible pH influences and resulting in interactions with–OH, –C=O, Si–O–Si, –O–Si, and –Al–O–Al groups via hydrogen bonding, ligand exchange, and surface complexation. We suggest that biochar amendment at ～5% is a viable approach to immobilize EE2 and PFOS at the sediment-water interface.

Evaluation of the effectiveness of in situ stabilization in the field aged arsenic-contaminated soil: Chemical extractability and biological response.

The effectiveness of in situ stabilization in the long-term As-contaminated soil was assessed. In situ stabilization of As was conducted through a Fe-based sorbent amendment. Chemical extractability of As was first determined by solubility/bioavailability research consortium extraction method and any change in human health risk through oral ingestion was characterized. Also, nonspecifically bound As in soil was determined by five-step sequential extraction. The results indicate that such extractable fractions of As decreased, and consequently risk through oral ingestion decreased probably due to hematite transformed from both the goethite in the original soil and the Fe-based sorbent, which was identified through the X-ray absorption spectroscopy. In ecotoxicity test with Hordeum vulgare, root and shoot elongation and germination rate decreased which was contrary to the chemical extraction data. Such increase in As toxicity is because of increased exchangeable Ca2+ concentration causing As accumulation in the membrane surface of H. vulgare. Also, adsorption of phosphorus onto the Fe-based sorbent decreased available phosphorus concentration causing phosphorus deficiency for growth. Our results demonstrate that the effectiveness of in situ stabilization should be evaluated by means of both chemical extractability and biological response, as chemical analysis alone may not be sufficient to assess the ecotoxicity.

State of the art and future challenges for polycyclic aromatic hydrocarbons is sediments: sources, fate, bioavailability and remediation techniques

Polycyclic aromatic hydrocarbons (PAHs) are amongst the most abundant contaminants found in the aquatic environment. Due to their toxicity and carcinogenicity, their sources, fate, behaviour, and cleanup techniques have been widely investigated in the last several decades. When entering the sediment-water system, PAH fate is determined by particular PAH and sediment physico-chemical properties. Most of the PAHs will be associated with fine-grained, organic-rich, sediment material. This makes sediment an ultimate sink for these pollutants. This association results in sediment contamination, and in this manner, sediments represent a permanent source of water pollution from which benthic organisms may accumulate toxic compounds, predominantly in lipid-rich tissues. A tendency for biomagnification can result in critical body burdens in higher trophic species. In recent years, researchers have developed numerous methods for measuring bioavailable fractions (chemical methods, non-exhaustive extraction, and biomimetic methods), as valuable tools in a risk-based approach for remediation or management of contaminated sites. Contaminated sediments pose challenging cleanup and management problems, as conventional environmental dredging techniques are invasive, expensive, and sometimes ineffective or hard to apply to large and diverse sediment sites. Recent studies have shown that a combination of strategies including in situ approaches is likely to provide the most effective long-term solution for dealing with contaminated sediments. Such in situ approaches include, but are not limited to: bioaugmentation, biostimulation, phytoremediation, electrokinetic remediation, surfactant addition and application of different sorbent amendments (carbon-rich such as activated carbon and biochar) that can reduce exposure and limit the redistribution of contaminants in the environment.

Activated carbons of varying pore structure eliminate the bioavailability of 2,3,7,8-tetrachlorodibenzo-p-dioxin to a mammalian (mouse) model

The use of activated carbon (AC) as an in situ sorbent amendment to sequester polychlorinated-dibenzo-p-dioxins and furans (PCDD/Fs) present in contaminated soils and sediments has recently gained attention as a novel remedial approach. This remedy could be implemented at much lower cost while minimizing habitat destruction as compared to traditional remediation technologies that rely on dredging/excavation and landfilling. Several prior studies have demonstrated the ability of AC amendments to reduce pore water concentrations and hence bioaccumulation of PCDD/Fs in invertebrate species. However, our recent study was the first to show that AC had the ability to sequester 2,3,7,8‑tetrachlorodibenzo‑p‑dioxin (TCDD) in a form that eliminated bioavailability to a mammalian (mouse) model. Here we show that three commercially available ACs, representing a wide range of pore size distributions, were equally effective in eliminating the bioavailability of TCDD based upon two sensitive bioassays, hepatic induction of cyp1A1 mRNA and immunoglobulin M antibody-forming cell response. These results provide direct evidence that a wide range of structurally diverse commercially available ACs may be suitable for use as in situ sorbent amendments to provide a cost-effective remedy for PCDD/F contaminated soils and sediments. Potentially, adaption of this technology would minimize habitat destruction and be protective of ecosystem and human health.