Combination of electrochemical advanced oxidation and biotreatment for wastewater treatment and soil remediation.

The global concern surrounding the advancement of methods for treating wastewater and polluted soil has markedly increased over time. While electrochemical advanced oxidation processes (EAOPs) and biotreatments are commonly employed technologies for remediating wastewater and polluted soil, their widespread adoption is hindered by their limitations, which include high costs associated with EAOPs and prolonged remediation time of biotreatments. In the review, we provided an overview of EAOP technology and biotreatment, emphasizing the critical aspects involved in building a combined system. This review systematically evaluates recent research that combines EAOPs with bioremediation for treating wastewater or contaminated soil as pretreatment or post-treatment process. Research findings suggest that the combined treatment method represents a promising and competitive technology that can overcome some of the limitations of individual treatments. Additionally, we discussed the potential applications of this technology in varying levels of wastewater and soil pollution, as well as the underlying combination mechanisms.

Hybrid and enhanced electrokinetic system for soil remediation from heavy metals and organic matter.

The electrokinetic (EK) process has been proposed for soil decontamination from heavy metals and organic matter. The advantages of the EK process include the low operating energy, suitability for fine-grained soil decontamination, and no need for excavation. During the last three decades, enhanced and hybrid EK systems were developed and tested for improving the efficiency of contaminants removal from soils. Chemically enhanced-EK processes exhibited excellent efficiency in removing contaminants by controlling the soil pH or the chemical reaction of contaminants. EK hybrid systems were tested to overcome environmental hurdles or technical drawbacks of decontamination technologies. Hybridization of the EK process with phytoremediation, bioremediation, or reactive filter media (RFM) improved the remediation process performance by capturing contaminants or facilitating biological agents' movement in the soil. Also, EK process coupling with solar energy was proposed to treat off-grid contaminated soils or reduce the EK energy requirements. This study reviews recent advancements in the enhancement and hybrid EK systems for soil remediation and the type of contaminants targeted by the process. The study also covered the impact of operating parameters, imperfect pollution separation, and differences in the physicochemical characteristics and microstructure of soil/sediment on the EK performance. Finally, a comparison between various remediation processes was presented to highlight the pros and cons of these technologies.

Enhanced efficiency and stability in the degradation of triazophosphorus pesticides by Al6Si2O13/WO2.72 nanocomposites through synergistic action of S-scheme heterojunction and oxygen vacancies.

The environmental contamination caused by organophosphorus pesticides (for example, triazophos) is an escalating concern. To mitigate this issue, this study introduces a novel Al6Si2O13/WO2.72 (ASO/WO) nanocomposite photocatalyst, which markedly enhances the photocatalytic degradation of triazophos. The optimized nanocomposite material with a 60.0 % ASO loading (60-ASO/WO) achieves a degradation rate of 86.3 % for triazophos within 140.0 min, marginally exceeding 60-ASO/WO3 (72.6 %) and significantly outperforming individual ASO (65.0 %), WO (59.5 %), and WO3 (56.2 %). This catalyst retains 88.9 % of its activity after five cycles, showcasing exceptional efficiency and stability. Additionally, its electrochemical surface area (ECSA, 310.0 cm2), total organic carbon (TOC, removal rate of 73.7 %), photocurrent, and electrochemical impedance are all optimal. X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and theoretical calculations elucidate the critical role of oxygen vacancies and the S-scheme heterojunction in augmenting charge separation and photocatalytic performance, corroborating the synergistic effect of oxygen defects and the S-scheme. While individual factors can enhance photocatalytic activity, their combination results in a more pronounced effect. Liquid chromatography-mass spectrometry (LCMS) identifies the principal degradation intermediates, including 1-phenyl-3-hydroxy-1, 2, 4-triazole, diethyl thiophosphate, and 3, 5, 6-trichloro-2-pyridinol, underscoring the material's potential in environmental remediation.

Research progress on the environmental risk assessment and remediation technologies of heavy metal pollution in agricultural soil.

Controlling heavy metal pollution in agricultural soil has been a significant challenge. These heavy metals seriously threaten the surrounding ecological environment and human health. The effective assessment and remediation of heavy metals in agricultural soils are crucial. These two aspects support each other, forming a close and complete decision-making chain. Therefore, this review systematically summarizes the distribution characteristics of soil heavy metal pollution, the correlation between soil and crop heavy metal contents, the presence pattern and migration and transformation mode of heavy metals in the soil-crop system. The advantages and disadvantages of the risk evaluation tools and models of heavy metal pollution in farmland are further outlined, which provides important guidance for an in-depth understanding of the characteristics of heavy metal pollution in farmland soils and the assessment of the environmental risk. Soil remediation strategies involve multiple physical, chemical, biological and even combined technologies, and this paper compares the potential and effect of the above current remediation technologies in heavy metal polluted farmland soils. Finally, the main problems and possible research directions of future heavy metal risk assessment and remediation technologies in agricultural soils are prospected. This review provides new ideas for effective assessment and selection of remediation technologies based on the characterization of soil heavy metals.

Plant-substrate biochar properties critical for mediating reductive debromination of 1,2-dibromoethane.

Dibromoethane is a widespread, persistent organic pollutant. Biochars are known mediators of reductive dehalogenation by layered FeII-FeIII hydroxides (green rust), which can reduce 1,2-dibromoethane to innocuous bromide and ethylene. However, the critical characteristics that determine mediator functionality are lesser known. Fifteen biochar substrates were pyrolyzed at 600 °C and 800 °C, characterized by elemental analysis, X-ray photo spectrometry C and N surface speciation, X-ray powder diffraction, specific surface area analysis, and tested for mediation of reductive debromination of 1,2-dibromoethane by a green rust reductant under anoxic conditions. A statistical analysis was performed to determine the biochar properties, critical for debromination kinetics and total debromination extent. It was shown that selected plant based biochars can mediate debromination of 1,2-dibromoethane, that the highest first order rate constant was 0.082/hr, and the highest debromination extent was 27% in reactivity experiments with 0.1 µmol (20 µmol/L) 1,2-dibromoethane, ≈ 22 mmol/L FeIIGR, and 0.12 g/L soybean meal biochar (7 days). Contents of Ni, Zn, N, and P, and the relative contribution of quinone surface functional groups were significantly (p < 0.05) positively correlated with 1,2-dibromoethane debromination, while adsorption, specific surface area, and the relative contribution of pyridinic N oxide surface groups were significantly negatively correlated with debromination.

Remediation mechanism of high concentrations of multiple heavy metals in contaminated soil by Sedum alfredii and native microorganisms.

Pollution accident of nonferrous metallurgy industry often lead to serious heavy metal pollution of the surrounding soil. Phytoremediation of contaminated soil is an environmental and sustainable technology, and soil native microorganisms in the process of phytoremediation also participate in the remediation of heavy metals. However, the effects of high concentrations of multiple heavy metals (HCMHMs) on plants and native soil microorganisms remain uncertain. Thus, further clarification of the mechanism of phytoremediation of HCMHMs soil by plants and native soil microorganisms is required. Using the plant Sedum alfredii (S. alfredii) to restore HCMHM-contaminated soil, we further explored the mechanism of S. alfredii and native soil microorganisms in the remediation of HCMHM soils. The results showed that (i) S. alfredii can promote heavy metals from non-rhizosphere soil to rhizosphere soil, which is conducive to the effect of plants on heavy metals. In addition, it can also enrich the absorbed heavy metals in its roots and leaves; (ii) native soil bacteria can increase the abundance of signal molecule-synthesizing enzymes, such as trpE, trpG, bjaI, rpfF, ACSL, and yidC, and promote the expression of the pathway that converts serine to cysteine, then synthesize substances to chelate heavy metals. In addition, we speculated that genes such as K19703, K07891, K09711, K19703, K07891, and K09711 in native bacteria may be involved in the stabilization or absorption of heavy metals. The results provide scientific basis for S. alfredii to remediate heavy metals contaminated soils, and confirm the potential of phytoremediation of HCMHM contaminated soil.

A review of functions and mechanisms of clay soil conditioners and catalysts in thermal remediation compared to emerging photo-thermal catalysis.

High temperatures and providing sufficient time for the thermal desorption of persistent organic pollutants (POPs) from contaminated clay soils can lead to intensive energy consumption. Therefore, this article provides a critical review of the potential additives which can improve soil texture and increase the volatility of POPs, and then discusses their enhanced mechanisms for contributing to a green economy. Ca-based additives have been used to reduce plasticity of bentonite clay, absorb water and replenish system heat. In contrast, non-Ca-based additives have been used to decrease the plasticity of kaolin clay. The soil structure and soil plasticity can be changed through cation exchange and flocculation processes. The transition metal oxides and alkali metal oxides can be applied to catalyze and oxidize polycyclic aromatic hydrocarbons, petroleum and emerging contaminants. In this system, reactive oxygen species (•O2- and •OH) are generated from thermal excitation without strong chemical oxidants. Moreover, multiple active ingredients in recycled solid wastes can be controlled to reduce soil plasticity and enhance thermal catalysis. Alternatively, the alkali, nano zero-valent iron and nano-TiN can catalyze hydrodechlorination of POPs under reductive conditions. Especially, photo and photo-thermal catalysis are discussed to accelerate replacement of fossil fuels by renewable energy in thermal remediation.

Multifunctional HxMoO3-y-MoO2/Carbon Composite Particles for Water Remediation.

Solving a scarcity of freshwater resources is an urgent global challenge by a safe and sustainable approach using renewable energy. We demonstrate the multifunctional catalyst of HxMoO3-y-MoO2/carbon composite particles toward highly efficient water remediation. A one-step mechanochemical reaction successfully upgraded the composites from commercially available MoO3-polypropylene (PP) powders without introducing hydrogen gas. The composite particles exhibited broad light absorption in the UV-visible (Vis)-near-infrared (NIR) region (200-2000 nm), with an optical band-gap narrowing to 1.03 eV. The plasmonic properties of HxMoO3-y-MoO2 allowed a fast water evaporation rate (3.29 kg m-2 h-1) with a photothermal conversion efficiency of 88.8%. In addition, the HxMoO3-y-MoO2 heterojunction dominated wide-spectrum activity under Vis and NIR light irradiation, up to 3 orders of magnitude higher than pristine MoO3 in the photocatalytic degradation of azo-dye pollutants. Furthermore, the byproduct carbon with abundant oxygen-containing groups efficiently eliminated water pollutants as a Brønsted acid catalyst and performed exceptional adsorption capacities of heavy metal ions in the dark.

Advancements in microbial-mediated radioactive waste bioremediation: A review.

The global production of radioactive wastes is expected to increase in the coming years as more countries have resorted to adopting nuclear power to decrease their reliance on fossil-fuel-generated energy. Discoveries of remediation methods that can remove radionuclides from radioactive wastes, including those discharged to the environment, are therefore vital to reduce risks-upon-exposure radionuclides posed to humans and wildlife. Among various remediation approaches available, microbe-mediated radionuclide remediation have limited reviews regarding their advances. This review provides an overview of the sources and existing classification of radioactive wastes, followed by a brief introduction to existing radionuclide remediation (physical, chemical, and electrochemical) approaches. Microbe-mediated radionuclide remediation (bacterial, myco-, and phycoremediation) is then extensively discussed. Bacterial remediation involves biological processes like bioreduction, biosorption, and bioprecipitation. Bioreduction involves the reduction of water-soluble, mobile radionuclides to water-insoluble, immobile lower oxidation states by ferric iron-reducing, sulfate-reducing, and certain extremophilic bacteria, and in situ remediation has become possible by adding electron donors to contaminated waters to enrich indigenous iron- and sulfate-reducing bacteria populations. In biosorption, radionuclides are associated with functional groups on the microbial cell surface, followed by getting reduced to immobilized forms or precipitated intracellularly or extracellularly. Myco- and phycoremediation often involve processes like biosorption and bioaccumulation, where the former is influenced by pH and cell concentration. A Strengths, Weaknesses, Opportunities, and Threats (SWOT) analysis on microbial remediation is also performed. It is suggested that two research directions: genetic engineering of radiation-resistant microorganisms and co-application of microbe-mediated remediation with other remediation methods could potentially result in the discovery of in situ or ex situ microbe-involving radioactive waste remediation applications with high practicability. Finally, a comparison between the strengths and weaknesses of each approach is provided.

Unveiling trends in migration of iron-based nanoparticles in saturated porous media.

Nanoscale zero-valent iron (nZVI) particles are routinely used for environmental remediation, but their transport dynamics in different settings remain unclear, hindering optimization. This study introduces a novel approach to predicting nZVI transport in saturated porous model environment. The method employs advanced long column devices for real-time monitoring via controlled magnetic susceptibility measurements. Numerical modeling with a modified version of the MNMs 2023 software was then used to predict nZVI and its derivatives mobility in field-like conditions, offering insights into the radius of influence (ROI) and shape factor (SF) of their distribution. A standard nZVI precursor was compared with its four major commercial derivatives: nitrided, polyacrylic acid-coated, oxide-passivated, and sulfidated nZVI. All these iron-based nanoparticles exhibited identical particle sizes, morphologies, surface areas, and phase compositions, isolating surface properties, dominated by charge, as the sole variable affecting their mobility. The study revealed optimal transport when the surface charge of nZVI and its derivatives was strongly negative, while rapid aggregation of nZVI derivatives due magnetic attraction reduced their mobility. Modeling predictions based on column scale-up, indicated that detectable concentrations of 20 g L⁻1 were found at distances ranging from 0.4 to 1.1 m from the injection well. Slightly sulfidated nZVI traveled farther than the nZVI precursor and ensured more homogenous particle distribution around the well. Organically modified nZVI migrated the longest distances but showed particle accumulation close to the injection point. The findings suggest that minimal sulfidation combined with organic modification of nZVI surfaces may effectively enhance radial and vertical nZVI distribution in aquifers. Such improvements increase the commercial viability of modified nZVI, reduce their adverse impacts, and boosts their practical applications in real-world scenarios.

Electrokinetic remediation of cadmium-contaminated soil using polarity reversal method: Optimization analysis and mechanism exploration.

Electrokinetic remediation (EKR) has been applied for in-situ removal of Cd from contaminated soil, and the EKR enhanced with polarity reversal has achieved a higher Cd removal efficiency. However, the migration and accumulation mechanisms of Cd in the EKR process have not been investigated. In this paper, the cross-impacts of the voltage gradient, citric acid concentration in the electrolyte, and polarity reversal frequency on the removal efficiency by EKR of Cd and the optimization conditions were investigated. The migration and accumulation mechanisms of Cd were explored by analyzing the changes in electrokinetic process parameters, experimental phenomena, and X-ray diffraction (XRD) analysis. The results showed that the maximum removal efficiency of Cd reached 82.26%. The optimal conditions were determined by fitting the RSM model using the BBD design. In the EKR experiment with polarity reversal, Cd accumulated mainly in the middle part of the soil, attributed to the formation of chemical precipitation focusing area caused by soil pH transition, ion-induced potential gradient well trapping effect (IIPGWTE), or soil compaction induced by water loss. In conclusion, the various parameters have cross-impacts on the EKR of Cd-contaminated soil, and efficient in-situ removal of Cd from the contaminated soil can be achieved by adjusting the parameter conditions.

Ionic and nano calcium to reduce cadmium and arsenic toxicity in plants: Review of mechanisms and potentials.

Contamination of agricultural soils with heavy metal(loid)s like arsenic (As) and cadmium (Cd) is an ever increasing concern for crop production, quality, and global food security. Numerous in-situ and ex-situ remediation approaches have been developed to reduce As and Cd contamination in soils. However, field-scale applications of conventional remediation techniques are limited due to the associated environmental risks, low efficacy, and large capital investments. Recently, calcium (Ca) and Ca-based nano-formulations have emerged as promising solutions with the large potential to mitigate As and Cd toxicity in soil for plants. This review provides comprehensive insights into the phytotoxic effects of As and Cd stress/toxicity and discusses the applications of Ca-based ionic and nano-agrochemicals to alleviate As and Cd toxicity in important crops such as rice, wheat, maize, and barley. Further, various molecular and physiological mechanisms induced by ionic and nano Ca to mitigate As and Cd stress/toxicity in plants are discussed. This review also critically analyzes the efficiency of these emerging Ca-based approaches, both ionic and nano-formulations, in mitigating As and Cd toxicity in comparison to conventional remediation techniques. Additionally, future perspectives and ecological concerns of the remediation approaches encompassing ionic and nano Ca have been discussed. Overall, the review provides an updated and in-depth knowledge for developing sustainable and effective strategies to address the challenges posed by As and Cd contamination in agricultural crops.

Investigating the Effect of UV Irradiation and TiO2 Addition on Heavy Metal Adsorption by Inverse Vulcanized Sulfur Polymers.

Organomercury contamination in wastewater is a longstanding global concern, prompting the establishment of the Mi-namata Convention in 2013, following the tragic Minamata Bay incident in Japan. Despite numerous proposed solutions, the development of an affordable and convenient adsorbent remains a challenge. Sulfur, being one of the most abundant elements globally, has shown promise in mercury adsorption in previous research. This study delves into the influence of light exposure on the process of mercury adsorption. Our findings reveal that exposure to UV-A wavelengths (315 nm - 400 nm), in combination with the addition of titanium dioxide (TiO2), enhances the adsorption capacity of a sulfur-rich polymer. The maximum observed adsorption capacity reached 47 mg/g under these conditions. Notably, the presence of TiO2 and UV exposure did not significantly impact the adsorption of inorganic mercury and gold.

Microbial strategies for lead remediation in agricultural soils and wastewater: mechanisms, applications, and future directions.

High lead (Pb) levels in agricultural soil and wastewater threaten ecosystems and organism health. Microbial remediation is a cost-effective, efficient, and eco-friendly alternative to traditional physical or chemical methods for Pb remediation. Previous research indicates that micro-organisms employ various strategies to combat Pb pollution, including biosorption, bioprecipitation, biomineralization, and bioaccumulation. This study delves into recent advancements in Pb-remediation techniques utilizing bacteria, fungi, and microalgae, elucidating their detoxification pathways and the factors that influence Pb removal through specific case studies. It investigates how bacteria immobilize Pb by generating nanoparticles that convert dissolved lead (Pb-II) into less harmful forms to mitigate its adverse impacts. Furthermore, the current review explores the molecular-level mechanisms and genetic engineering techniques through which microbes develop resistance to Pb. We outline the challenges and potential avenues for research in microbial remediation of Pb-polluted habitats, exploring the interplay between Pb and micro-organisms and their potential in Pb removal.

Effects of cognitive training under hypoxia on cognitive proficiency and neuroplasticity in remitted patients with mood disorders and healthy individuals: ALTIBRAIN study protocol for a randomized controlled trial.

BACKGROUND: Cognitive impairment is prevalent across neuropsychiatric disorders but there is a lack of treatment strategies with robust, enduring effects. Emerging evidence indicates that altitude-like hypoxia cognition training may induce long-lasting neuroplasticity and improve cognition. We will investigate whether repeated cognition training under normobaric hypoxia can improve cognitive functions in healthy individuals and patients with affective disorders and the neurobiological underpinnings of such effects. METHODS: In sub-study 1, 120 healthy participants are randomized to one of four treatment arms in a double-blind manner, allowing for examination of separate and combined effects of three-week repeated moderate hypoxia and cognitive training, respectively. In sub-study 2, 60 remitted patients with major depressive disorder or bipolar disorder are randomized to hypoxia with cognition training or treatment as usual. Assessments of cognition, psychosocial functioning, and quality of life are performed at baseline, end-of-treatment, and at 1-month follow-up. Functional magnetic resonance imaging (fMRI) scans are conducted at baseline and 1-month follow-up, and [11C]UCB-J positron emission tomography (PET) scans are performed at end-of-treatment to quantify the synaptic vesicle glycoprotein 2A (SV2A). The primary outcome is a cognitive composite score of attention, verbal memory, and executive functions. Statistical power of ≥ 80% is reached to detect a clinically relevant between-group difference with minimum n = 26 per treatment arm. Behavioral data are analyzed with an intention-to-treat approach using mixed models. fMRI data is analyzed with the FMRIB Software Library, while PET data is quantified using the simplified reference tissue model (SRTM) with centrum semiovale as reference region. DISCUSSION: The results will provide novel insights into whether repeated hypoxia cognition training increases cognition and brain plasticity, which can aid future treatment development strategies. TRIAL REGISTRATION: ClinicalTrials.gov, NCT06121206 . Registered on 31 October 2023.

The stigma of underperformance in assessment and remediation.

The stigma of underperformance is widely acknowledged but seldom explored. 'Failure to fail' is a perennial problem in health professions education, and learner remediation continues to tax supervisors. In this study, we draw on Goffman's seminal work on stigma to explore supervisors' accounts of judging performance and managing remediation in specialty anesthesia training in Australia and New Zealand. In doing so, we focus on what Goffman calls a "stigma theory" to explain the supervisors' reported practices. We performed a secondary analysis of nineteen interviews originally gathered using purposive sampling to explore how assessment decisions were made. We conducted a theory-informed thematic analysis of the supervisors' accounts to identify signifiers of stigma and underlying structures and beliefs. From both deductive and inductive analysis, we developed themes that demonstrate how the stigma of underperformance influences and is induced by supervisors' reticence to discuss underperformance, their desire to conceal remediation, and their differential treatment of trainees. We also found that accounts of trainees 'lacking insight' resembled stigma-induced stereotyping. We argue from our data that our cultural expectations of perfectionism propagate a stigma that undermines our efforts to remediate underperformance and that our remediation practices inadvertently induce stigma. We suggest that a multifaceted approach using both individual and collective action is necessary to change both culture and practice and encourage the normalisation of remediation.

Synergistic effect between biochar and nitrate fertilizer facilitated arsenic immobilization in an anaerobic contaminated paddy soil.

Nitrate nitrogen fertilizer was usually used to mitigate arsenic (As) release and mobilization in the anaerobic contaminated paddy soil. However, the effect of the interplay between nitrate fertilizer and biochar on As availability as well as the involved mechanism were poorly understood. Herein, the effects and mechanisms of biochar, nitrate fertilizer, and biochar-based nitrate fertilizer on the availability of As in the contaminated paddy soil were investigated via a microcosm incubation experiment. Results indicated that the application of biochar-based nitrate fertilizer significantly lessened the available As concentration in the contaminated paddy soil from 3.01 ± 0.03 (control group) to 2.24 ± 0.08 mg kg-1, which presented an immobilization efficiency of 26.6 % better than those of individual biochar (13.5 %) and nitrate fertilizer (17.6 %), exhibiting a synergistic effect. Moreover, the biochar-based nitrate fertilizer also facilitated the transformation of more toxic arsenite in the contaminated soil to less toxic arsenate. Further, biochar-based nitrate fertilizer increased soil redox potential (Eh), dissolved organic carbon, organic matter, and nitrate yet decreased soil pH and ammonium, which changed the microbial community in the soil, enhancing the relative abundance of Bacillus, Arthrobacter, and Paenibacillus. These functional microorganisms drove the coupled transformation between nitrate denitrification and Fe(II) or As(III) oxidation, favoring As immobilization in the anaerobic paddy soil. Additionally, the co-application of biochar offset the negative effect of single nitrate fertilizer on microbial community diversity. Overall, biochar-based nitrate fertilizer could be a promising candidate for the effective immobilization of As in the anaerobic paddy soil. The current research can provide a valuable reference to the remediation of As-contaminated paddy soil and the production of safe rice.

Ethical Approach to the Abusive/Disruptive Physician.

Abusive, intimidating, and disruptive behavior is unprofessional and antithetical to the provision of medical care within a culture of safety. These behaviors affect all members of the health-care team, including trainees, and have shown to result in adverse patient outcomes. When events occur, rapid intervention utilizing structured processes as required by The Joint Commission and consistent with the AMA Code of Medical Ethics needs to be implemented to protect all involved. These processes must allow for an anonymous reporting system, impartial evaluation, and graded response to these behaviors. Unfortunately, anonymity in reporting may result in the weaponization of the system.

Effects of Biochar on Arsenic-Contaminated Soil: Chemical Fractionation, Vegetation Growth, and Oral Bioaccessibility.

Contamination by arsenic (As) is a pressing environmental and public health issue requiring urgent remediation strategies. One cost-effective and eco-friendly method involves adding stabilizing agents to soils to reduce As mobility. However, remediation projects must also address potential ecotoxicological effects. These effects may include harmful impacts on both aquatic and terrestrial organisms, including plants, disruption of ecosystem balance, and the potential bioaccumulation of toxic substances in the food chain. Biochar from organic fraction of municipal solid waste (OFMSW) shows promise for As-contaminated soil remediation. Pot experiments were conducted with soil contaminated with As (100 mg kg-1) and amended with biochar produced at three different temperatures (300, 500, and 700 °C) and addition rates (1 and 5%, w/w). Chemical fractionation showed higher As concentration in a less accessible fraction (F4). Biochar amendments did not significantly differ from the control in As immobilization, but enhanced maize (Zea mays) growth and reduced As uptake, with the most promising results seen with 1% of biochar produced at 700 °C. The bioaccumulation factor (BCF) and translocation factor (TF) were both lower than 1, indicating a low absorption of As and minimal translocation from the root to the shoot. The bioaccessible percentage was higher in the samples treated with biochar compared to the control. According to the results, biochar showed no satisfactory potential for As immobilization and its approach of pretreatment/modification should be tested regarding possible improvements in the immobilization performance of As. Since most contaminations involve multiple contaminants simultaneously, it is essential to test the interactions between arsenic and other pollutants to understand the effects of biochar in such complex scenarios, which will be explored in future studies. Graphical abstract.

Bioaccumulation in fish (Cyprinodon variegatus) during rejuvenations of a thin active cap over field-aged PCB contaminated sediment: The effect of clean versus contaminated ongoing influx.

Repeated addition of activated carbon (AC) via the water column was applied to rejuvenate sorption capacity of thin AC-amended sand caps placed over polychlorinated biphenyl- (PCB) contaminated marine bed sediment receiving ongoing input of sediment (contaminated or clean) in mesocosms. Bioaccumulation of PCBs in sheepshead minnows (Cyprinodon variegatus) from bed sediment was reduced by repeated application of rejuvenating AC when the ongoing input was contaminated. However, when the input sediment was clean, the novel AC addition increased fish uptake of bedded PCBs in the first 60-days of the 90-day experiments. The 79 % increase of bedded PCB bioaccumulation in fish, for clean versus contaminated inputs, was statistically significant (p < 0.05) in experiments where the rejuvenating AC was applied. Equilibrium concentrations in low-density polyethylene (LDPE) passive samplers did not fully explain bioaccumulation. Field implications of this research include setting appropriate temporal expectations of this novel remediation strategy regarding the primary desired effect (i.e., PCB bioavailability reductions).