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Dense non-aqueous-phase liquids (DNAPLs) represent one of the most hazardous contaminants of groundwater, posing health risks to humans. Radon is generally used to trace DNAPLs; however, external factors, such as rainfall or stream water, can influence its efficacy. To overcome these limitations, this study pioneered the integration of radon and microbial community structures to explore DNAPL tracing and natural attenuation in the context of seasonal variations for human health risk assessments. The results showed that a radon tracer can estimate DNAPL saturation in the source zone, especially during the dry season when radon deficiency predominates. However, samples exhibited mixing effects during the wet season because of local precipitation. Moreover, bioremediation and low health risks were observed in the plume boundary zone, indicating that microbial dechlorination was a predominant factor determining these risks. The abnormal patterns of radon observed during the wet season can be elucidated by examining microbiological communities. Consequently, a combined approach employing radon and microbial analysis is advocated for the boundary zone, albeit with a less intensive management strategy, compared with that for the source zone. This novel coupling method offers a theoretical and practical foundation for managing DNAPL-contaminated groundwater. [Display omitted] • Seasonal variations affected DNAPL characteristics in groundwater. • DNAPL tracing can be simplified using radon in dry season. • Microbial data can explain the abnormal change patterns of radon in wet season. • Bioremediation and low health risk vales were observed in plume boundary zone. • Less intensive management was needed in plume boundary zone after wet season. [ABSTRACT FROM AUTHOR]

The search for stable, high-performance, and low-cost photocatalysts has received considerable interest. In this work, mesoporous LaVO 4 nanoparticles were synthesized for the first time by applying the soft template, and g-C 3 N 4 nanosheets were fabricated using a hard template to design mesoporous LaVO 4 /g-C 3 N 4 heterostructures. The synthesized photocatalysts were assessed by the mineralization of trichloroethylene (TCE) in aqueous media during visible illumination. TEM and XRD measurements verified the existence of porous g-C 3 N 4 with a high distribution of the monoclinic phase LaVO 4 NPs (5 nm). The photocatalytic performance of the LaVO 4 /g-C 3 N 4 heterojunction was much better than that of either LaVO 4 or g-C 3 N 4. 3%LaVO 4 /g-C 3 N 4 exhibited the maximum photocatalytic ability, about 99% during a 3 h illumination at a degradation rate of 6.50 μmolL−1 min−1, which were ∼3.89- and ∼4.67-fold greater than parent LaVO 4 and g-C 3 N 4 , respectively. The first-order kinetics calculations revealed that the 3% LaVO 4 /g-C 3 N 4 heterostructure offered the highest rate constant of 0.0113 min−1, which estimated ∼8.7 and 4.9 folds larger than LaVO 4 (0.0023 min−1) and g-C 3 N 4 (0.0015 min−1), respectively. The importance of the LaVO 4 /g-C 3 N 4 with superb photocatalytic efficiency was demonstrated based on the photoluminescence spectra, transient photocurrent curves, and UV–visible absorption spectra. The obtained LaVO 4 /g-C 3 N 4 photocatalyst exhibited excellent regeneration and recyclability over five consecutive runs. The coupling of LaVO 4 and g-C 3 N 4 with matching alignment potentials and the synergetic effect were thought to be the most interesting processes to promote photocatalytic efficiency. The obtained LaVO 4 /g-C 3 N 4 heterojunction possesses excellent photocatalytic efficiency and is a favorable candidate for potential applications in wastewater remediation using solar energy. [ABSTRACT FROM AUTHOR]

Remedial actions for groundwater contamination such as containment, in-situ remediation, and pump-and-treat have been developed. This study investigates the hydraulic containment of Trichloroethylene (TCE) contaminated groundwater by using pulsed pump-and-treat technology. The hypothetical research site assumed the operation of pulsed pump-and-treat to manage groundwater contaminated with 0.1 mg/L of TCE. at the pump-and-treat facility. Numerical models, employing MODFLOW and MT3DMS for groundwater flow and contamination simulations, were used for case studies to evaluate the performance and risks of pump-and-treat operation strategies. Evaluation criteria included capture width, removal efficiency, and contaminant leakage. Health risks from TCE leakage were assessed using a vapor intrusion risk assessment tool in adjacent areas. In the facility-scale case study, the capture width of the pump-and-treat was controlled by pumping/injection well operations, including schedules and rates. Pumping/injection well configurations impacted facility efficiencies. Pulsed operation led to TCE leakage downstream. Site-scale case studies simulated contaminant transport through pump-and-treat considering various operation stages (continuous; pulsed), as well as various reactions of TCE in subsurface environment (non-reactive; sorption; sorption and biodegradation). Assuming non-reactive tracer, TCE in groundwater was effectively blocked during continuous operation stage but released downstream in the following pulsed operation stage. Considering chemical reactions, the influences of the pump-and-treat operation followed similar trends of the non-reactive tracer but occurred at delayed times. Groundwater contamination levels were reduced through biodegradation. Cancer and non-cancer risks could occur at points of exposure (POEs) where the contamination levels approached or fell below TCE groundwater standards. [Display omitted] • Containment of PCE contaminated groundwater by pump-and-treat. • Vapor intrusion risk assessment using numerical simulation of groundwater contamination. • Possibility of partial release of contaminated groundwater caused by pulse operation. • Health risks via vapor intrusion at even screening level of contaminated groundwater. [ABSTRACT FROM AUTHOR]

Bioremediation is a sustainable, cost-effective, and eco-friendly way to remediate pollutants. However, the effectiveness of bioremediation is constrained by the underground environmental conditions, resulting in poor natural attenuation of organic pollution and degradation by functional microorganisms. In this study, a dechlorinating bacteria (DB) was enriched from contaminated soil and used to degrade trichloroethylene (TCE) in wastewater. The adaptation and degradation mechanisms of DB to TCE were investigated by degradation product analysis and metagenomic sequencing. The degradation of TCE by DB is pH and additional carbon source dependent. The highest TCE removal amount (1.86 × 10−7 mmol/CFU) was achieved at pH=8, 1% DB inoculum volume, and 400 mg/L sodium acetate concentration. Moreover, DB has a high acid resistance and a removal capacity of 1.18×10−7 mmol/CFU for TCE at pH =2. None of the co-occurring pollutants Cr (VI) and toluene had a significant effect on the ability of DB to degrade TCE in wastewater (maintained at 1.13–1.22×10−7 mmol/CFU). DB dechlorinated TCE mainly through the action of extracellular enzymes (contributed 91% of the total removal ability). DB playing a major role in degradation is Paraclostridium. Significant differences in alpha diversity indices were revealed in the reaction systems after 15 days of exposure to TCE (p < 0.01). The degradation of TCE by DB is mainly accomplished through the defense system, energy synthesis, electron supply and biodegradation. Metagenomic sequencing demonstrated that DB achieved adaptation and degradation of TCE through gene-regulated biological processes such as xenobiotic biodegradation and metabolism, carbohydrate metabolism, biosynthesis of other secondary metabolites, amino acid metabolism, membrane transport, and signal transduction. This study reveals for the first time the biodegradation efficiency and biotransformation process of DB under TCE stress. [Display omitted] • A TCE dechlorinating bacteria was successfully extracted from oil-contaminated soil. • Dechlorinating bacteria degrades TCE mainly through the extracellular enzymes. • The degradation ability of dechlorinating bacteria was 1.86 × 10−7 mmol/CFU. • Dechlorinating bacteria playing a major role in degradation is Paraclostridium. [ABSTRACT FROM AUTHOR]

• An efficient ITO-free transparent electrode based on diamond-like carbon is developed for low cost solar cells. • A DLC/Ag/DLC multilayer structure was successfully developed by combining PLD and RF sputtering techniques. • A new hybrid approach based on both FDTD and PSO techniques is proposed to optimize the TCE perormances. • The optimized DLC/Ag/DLC tri-layered TCE exhibits superior FoM of 55.2 × 10−3 Ω−1. In this paper, a novel Diamond-Like Carbon (DLC)-based structure is proposed as an alternative material for transparent electrode applications. In this context, DLC/Ag/DLC multilayer structure was successfully fabricated by combining pulsed laser deposition (PLD) and RF magnetron sputtering techniques. DLC films were deposited at room temperature via PLD on a quartz substrate and their optical constants were extracted using ellipsometry technique. A new hybrid approach based on FDTD method supported by particle swarm optimization (PSO) technique was introduced to find out the best geometry and appropriate intermediate ultrathin metal film of the DLC/Metal/DLC multilayer structure, promoting wider opportunities to overcome the transparency-conductivity trade-off. The optimized design is then prepared by successively depositing DLC films and sputtering ultra-thin Ag layer. Characterizations showcased that the elaborated DLC/Ag/DLC tri-layered structure offers a high Haacke FoM of 55.2 × 10−3 Ω−1, emphasizing the ability of the presented systematic investigation for providing promising pathways to reach enhanced light management and reduced resistive losses. Therefore, the elaborated DLC/Ag/DLC multilayer structure opens up new perspectives towards realizing high-performance transparent electrodes based on free-critical raw materials (CRM) , which are strongly desirable for optoelectronics and low cost thin film photovoltaic applications. [ABSTRACT FROM AUTHOR]

Electrokinetics is being applied in combination with common insituremediation technologies, e.g. permeable reactive barriers, bioremediation and in-situ chemical oxidation, to overcome experienced limitations in remediation of chlorinated ethenes in low-permeable subsurface soils. The purpose of this review is to evaluate state-of-theart for identification of major knowledge gaps to obtain robust and successful field-implementations. Some of the major knowledge gaps include the behavior and influence of induced transient changes in soil systems, transport velocities of chlorinated ethenes, and significance of site-specific parameters on transport velocities, e.g. heterogeneous soils and hydrogeochemistry. Furthermore, the various ways of reporting voltage distribution and transport rates complicate the comparison of transport velocities across studies. It was found, that for the combined EK-techniques, it is important to control the pH and redox changes caused by electrolysis for steady transport, uniform distribution of the electric field etc. Specifically for electrokinetically enhanced bioremediation, delivery of lactate and biodegrading bacteria is of the same order of magnitude. This review shows that enhancement of remediation technologies can be achieved by electrokinetics, but major knowledge gaps must be examined to mature EK as robust methods for successful remediation of chlorinated ethene contaminated sites. • EK-combined techniques overcome transport limitations experienced in low-permeable soils. • EK velocity of PCE and TCE is of comparable size to supplied reactants. • In EK-BIO, transport velocity of lactate and biodegrading bacteria are in the same order of magnitude. • General knowledge on the dependency of EK transport velocity on soil type is lacking. • Identified knowledge gaps must be filled in for robust and successful field-implementations. [ABSTRACT FROM AUTHOR]

Trichloroethene (TCE) exposure is associated with the development of various autoimmune diseases (ADs), including autoimmune hepatitis (AIH) and systemic lupus erythematosus (SLE), potentially through the generation of excessive reactive oxygen and nitrogen species (RONS; oxidative stress). However, the mechanisms by which oxidative stress contributes to these TCE-mediated ADs are not fully understood, and are the focus of current investigation. Female MRL+/+ mice were treated with TCE along with or without antioxidant N-acetylcysteine (NAC) for 6 weeks (TCE, 10 mmol/kg, i. p., every 4th day; NAC, 250 mg/kg/day via drinking water). TCE-treated mice had elevated antinuclear antibodies (ANA) and 4-hydroxynonenal (HNE)-specific circulating immune complexes, suggesting the association of TCE-induced oxidative stress with autoimmune response. In addition, TCE exposure led to prominent lobular inflammation with sinusoid dilation, increased sinusoidal cellularity and increased staining for proliferating cell nuclear antigen (PCNA), confirming inflammatory and hepatocellular cell proliferation. Importantly, TCE exposure resulted in the activation of hepatic inflammasome (NLRP3 and caspase-1) and up-regulation of pro-inflammatory cytokine IL-1β, and these changes were attenuated by NAC supplementation. TCE treatment also led to dysregulation of hepatic immune response as evident from markedly increased hepatic lymphocyte infiltration (especially B cells) and imbalance between Tregs (decreased) and Th17 cells (increased). Interestingly, TCE-mediated dysregulation of various hepatic and splenic immune cells was also effectively attenuated by NAC. Taken together, our findings provide evidence for TCE-mediated inflammasome activation, infiltration of various immune cells, and skewed balance of Treg and Th17 cells in the liver. The attenuation of TCE-mediated hepatic inflammasome activation and immune responses by NAC further supports a critical role of oxidative stress in TCE-mediated inflammation and autoimmunity. These novel findings could help in designing therapeutic strategies for such ADs. • TCE exposure led to oxidative stress and hepatic inflammasome NLRP3 activation. • TCE induced hepatic CD8+ T cells, NK cells, dendritic cells, and B cell activation. • TCE exposure was associated with skewed Treg/Th17 ratio in the liver. • NAC attenuated TCE-induced inflammasome activation and autoimmune response. [ABSTRACT FROM AUTHOR]

There have been many studies on TCE degradation by synthesized nanoscale zero-valent iron (nZVIB) and commercial nanoscale zero-valent iron (nZVIH), but the effect of anaerobic corrosion on the dechlorination pathways and speciation distribution of chlorine is still unclear. Compared with nZVIH, nZVIB has a faster degradation rate of TCE and formation rate of Cl−(aq) (k SA, TCE = 3.67 ± 0.85 × 10−4 & 2.17 ± 0.13 × 10−4 L·h−1·m−2 and k obs, Cl − = 0.344 ± 0.027 & 0.166 ± 0.010 μM·h−1 for nZVIB & nZVIH, respectively). Based on the characterization of XRD, XPS and TEM during the anaerobic corrosion, the corrosion of nZVIB was dramatic under the dissolution-reprecipitation mechanism; but that of nZVIH was moderate and inward by maintaining the core-shell structure and shaping slightly rough and lumpy surface. Due to the different corrosion products (FeOOH for nZVIB and Fe 3 O 4 /γ-Fe 2 O 3 for nZVIH) and the catalysis of boron on the nZVIB surface, the preferential dechlorination pathway of TCE was not identical by hydrogenolysis (nZVIB) vs. reductive β-elimination (nZVIH). Meanwhile, the dechlorination pathway of nZVIH was similar to that of ZVI and the reductive pathway to acetylene bypassed the formation of more toxic VC. This study shows that the high reactivity of nZVIB results in rapid corrosion with the side effect of enhanced adsorption of VC while nZVIH has a stable core-shell structure and less sorbed chlorine, which provides a new sight to access the ecological risk of nZVI due to the overlooked effect of non-identical corrosion. Image 1 • Rapid corrosion of nZVIB with higher reactivity gains more adsorbed chlorine. • nZVIH with stable core-shell structure slowly corroded and sorbed less chlorine. • For nZVIB, TCE → cis -DCE → VC → ethylene via hydrogenolysis mainly. [ABSTRACT FROM AUTHOR]

Solvent stabilizer 1,4-dioxane, an emerging recalcitrant groundwater contaminant, was commonly added to chlorinated solvents such as trichloroethene (TCE), and the impact of co-disposal on contaminant transport processes remains uncertain. A series of batch equilibrium experiments was conducted with variations of 1,4-dioxane and TCE composition to evaluate aqueous dissolution of the two components and their sorption to aquifer sediments. The solubility of TCE increased with increasing amounts of 1,4-dioxane, indicating that 1,4-dioxane acts as a cosolvent causing solubility enhancement of co-contaminants. The solubilization results compared favorably with predictions using the log-linear cosolvency model. Equilibrium sorption coefficients (K d and K f) were also measured for different 1,4-dioxane and TCE compositions, and the findings indicate that both contaminants adsorb to aquifer sediments and TCE K d values increased with increasing organic matter content. However, the K d for TCE decreased with increases in 1,4-dioxane concentration, which was attributed to cosolvency impacts on TCE solubility. These findings further advance our understanding of the mass-transfer processes controlling groundwater plumes containing 1,4-dioxane, and also have implications for the remediation of 1,4-dioxane contamination. Image 10485 • Cosolvency impacts of 1,4-dioxane co-disposal with chlorinated solvent TCE. • 1,4-Dioxane increases the TCE solubility and decreases sorption. • Solubility enhancement was predicted using log-linear cosolvency model. 1,4-Dioxane (cosolvent) increased the solubility of TCE and decreases sorption, and log-linear cosolvency model predicted solubility enhancement. [ABSTRACT FROM AUTHOR]

A trichloroethene (TCE)-dechlorinating community (CANAS) maintained in a completely mixed flow reactor was established from a semi-batch enrichment culture (ANAS) and was monitored for 400 days at a low solids retention time (SRT) under electron acceptor limitation. Around 85% of TCE supplied to CANAS (0.13 mmol d−1) was converted to ethene at a rate of 0.1 mmol d−1, with detection of low production rates of vinyl chloride (6.8 × 10−3 mmol d−1) and cis -dichloroethene (2.3 × 10−3 mmol d−1). Two distinct Dehalococcoides mccartyi strains (ANAS1 and ANAS2) were stably maintained at 6.2 ± 2.8 × 108 cells mL−1 and 5.8 ± 1.2 × 108 cells mL−1, respectively. Electron balance analysis showed 107% electron recovery, in which 6.1% were involved in dechlorination. 16 S rRNA amplicon sequencing revealed a structural regime shift between ANAS and CANAS while maintaining robust TCE dechlorination due to similar relative abundances of D. mccartyi and functional redundancy among each functional guild supporting D. mccartyi activity. D. mccartyi transcriptomic analysis identified the genes encoding for ribosomal RNA and the reductive dehalogenases tceA and vcrA as the most expressed genes in CANAS, while hup and vhu were the most critical hydrogenases utilized by D. mccartyi in the community. Image 1 • Reductive dechlorination of TCE to ethene by a steady-state chemostat culture. • Shift of microbial community from batch-fed to continuous exposure to low TCE. • Community functional robustness ensures stable TCE-to-ethene reduction. • Reductive dehalogenases tceA and vcrA show the highest functional gene expression. • Selection of bio-marker genes for monitoring of TCE-contaminated groundwater plumes. [ABSTRACT FROM AUTHOR]

Abstract Thermal proteome profiling (TPP) is increasingly applied in eukaryotes to investigate protein-ligand binding through protein melting curve shifts induced by the presence of a ligand. In anaerobic bacteria, identification of protein-substrate interactions is a major challenge. We applied TPP to Sulfurospirillum multivorans , which is able to use trichloroethene as electron acceptor for growth, to investigate the interaction of its tetrachloroethene reductive dehalogenase PceA with trichloroethene. Several modifications in the protocol (e.g., incubation under anaerobic conditions; increasing the temperature range up to 97 °C) extended the protein detection range and allowed the investigation of oxygen-sensitive proteins. Enzymatic reductive dehalogenation was prevented by omitting the electron donor during incubations. This enabled detecting the interaction of PceA with trichloroethene and confirmed that trichloroethene is a substrate of this enzyme. Interestingly, a putative response regulator showed a similar trend, which is the first biochemical hint for its proposed role in trichloroethene respiration. We proved that our TPP approach facilitates the identification of protein-substrate interactions of strictly anaerobic reductive dehalogenases and probably their regulators. This strategy can be used to identify yet unknown substrate specificities and possible signal-sensing proteins, and therefore has the potential to elucidate one of the unresolved fields in research on organohalide-respiring bacteria. Significance The assessment of enzyme-substrate or protein-ligand interactions in organohalide-respiring bacteria is a fundamental challenge. Thermal proteome profiling (TPP) allows elucidating proteome-wide thermal stability changes relying on the sensitivity of modern mass spectrometry. This gives access to the identification of interactions not detectable with other methods. In this TPP study, we demonstrate the interactions of a chlorinated substrate with a reductive dehalogenase and potentially with a response regulator, thereby supporting the response regulator's function in organohalide respiration. The strategy might also be applied to identify yet unknown substrates of other enzymes in bacteria which are difficult to investigate or for which only low amounts of biomass are available. The assessment of enzyme-substrate interactions, which might enable conclusions about enzyme specificities, represents a new application for TPP. Graphical abstract Unlabelled Image Highlights • Thermal proteome profiling (TPP) was modified for analyzing bacterial oxygen-sensitive enzymes. • Protein-trichloroethene interactions in organohalide-respiring Sulfurospirillum multivorans were identified. • Interaction of the tetrachloroethene reductive dehalogenase with trichloroethene was confirmed. • A first hint for the interaction of a response regulator and a chlorinated ethene was provided. [ABSTRACT FROM AUTHOR]

Abstract A sequential chem-bio hybrid process was developed using a novel biochar supported carboxymethyl cellulose-stabilized nanoscale iron sulfide (CMC-FeS@biochar) as a chemical remover and Corynebacterium variabile HRJ4 as a biological agent for trichloroethylene (TCE) degradation. Compared with CMC-FeS, FeS@biochar600, bare FeS and biochar600, the CMC-FeS@biochar600 composite displayed better physiochemical properties (smaller hydrodynamic diameter and higher stability) and demonstrated excellent removal capacity for TCE from aqueous phase. A facultative bacterial strain, Corynebacterium variabile HRJ4, growing well in the presence of CMC-FeS@biochar (added up to 0.25 g L−1), further enhanced TCE removal after chemical treatment. The dechlorination pathway proposed based on the gas chromatography–mass spectrometry (GC-MS) analysis revealed that TCE was dechlorinated to cis -1,2-dichloroethene (cis -DCE) and acetylene via hydrogenolysis and β -elimination, respectively within 12 h by CMC-FeS@biochar. Addition of HRJ4 strain into the reaction system effectively enhanced the degradation of the residual TCE, cis -DCE and acetylene to ethylene. Acetylene was the main product in chemical process, whereas ethylene was the main product in biological process as strain HRJ4 could reduce acetylene to ethylene effectively. The results of this study signify the potential application of CMC-FeS@biochar600/HRJ4 chem-bio hybrid system for complete degradation of TCE in the anaerobic environment. Graphical abstract Image 1 Highlights • CMC-FeS@biochar was synthesized combining the advantages of biochar, CMC, and FeS. • CMC-FeS@biochar had higher TCE removal ability. • Corynebacterium variabile HRJ4 displayed potential for TCE transformation. • Chem-bio hybrid process can completely dechlorinate TCE to ethylene. [ABSTRACT FROM AUTHOR]

S/mZVI is a promising material for groundwater remediation due to its excellent properties. However, the reactivity and electron selectivity toward target contaminant are critical. Thus, this study investigated the effect of complex groundwater chemistries (Milli-Q water, fresh groundwater and saline groundwater) on the reactivity of S/mZVI toward trichloroethylene (TCE), dechlorination pathway, hydrogen evolution kinetic, electron efficiency and aging behaviors. Results showed that sulfidation appreciably increased the reactivity and electron selectivity. The major degradation product of TCE dechlorination by S/mZVI was acetylene, which was consistent with TCE dechlorination by β-elimination. Moreover, reductive β-elimination was still the dominant dechlorination pathway for the application of S/mZVI in three groundwater conditions. However, the rates and the quantities of major products from TCE degradation varied significantly. S/mZVI in saline groundwater can maintain the reactivity towardTCE due to the protection of Fe0 by Fe 3 O 4 deposited on the surface. Thus, the higher TCE removal efficiency and less hydrogen accumulation resulted in the greatest electron efficiency (4.3–79.2%). Overall, S/mZVI was more effective for the application in saline groundwater. This study proved insight into the comprehensive evaluation and implications for the application of S/mZVI based technologies in saline contaminated groundwater. [Display omitted] • TCE dechlorination by S/mZVI and mZVI was investigated and compared in three media • TCE dechlorination by S/mZVI was mainly via β-elimination • Passive films with diverse structures and patterns were formed in three media • The highest electron efficiency (4.3–79.2%) was obtained in saline groundwater • S/mZVI-IRZ was more effective for the application in saline groundwater [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Simultaneous participation of nickel and acidic active sites in TCE HDC reaction. • 1,1-DCE and 1,2-DCE as intermediate products. • Acid sites decrease → higher dispersion of nickel(0) sites → catalytic activity improvement. Abstract This work was aimed to investigate the catalytic properties of nickel loaded zeolites Y and ZSM-5 as the catalysts in hydrodechlorination of trichloroethylene (TCE HDC) in the aqueous phase. Both acidic forms of the zeolites and Ni loaded zeolites were thoroughly characterized with respect to their structural (XRD), textural (low-temperature nitrogen sorption, STEM) and acidic/redox properties (IR, XPS, EPR spectroscopies). The studies showed the significant impact of acidic properties of the zeolitic support used as well as the framework geometry and the pore distribution within zeolite grains on the catalytic behaviour of zeolitic materials in the removal of TCE. IR studies of hydrodechlorination of trichloroethylene clearly showed the concurrent participation of both nickel and acid active sites in TCE HDC reaction. The activity of the Ni loaded catalysts increased when reducing the number of acid sites in zeolite catalysts, the centres responsible for carbonaceous deposits formation and finally leading to the catalysts deactivation. Nickel in the form of small (∼ 1–8 nm) and uniformly dispersed nanoparticles was found to be very active in the purification of water from TCE in batch conditions. [ABSTRACT FROM AUTHOR]

Abstract As the South Korean coastline features an abundance of islands, an efficient coastal ferry industry is vital to maritime transportation in the area. However, ferry disasters can have a severe effect on the operational efficiency of the industry. Thus, the objective of this study is to garner insights into the operational efficiency of the South Korean coastal ferry industry before and after the sinking of MV Sewol off the coast of South Korea. Data envelopment analysis (DEA)-window analysis and slacks-based measure (SBM)-DEA were applied to analyze time-series data from 2007 to 2016. The results illustrate that the total efficiency of the industry according to Regional Offices of Oceans and Fisheries (ROOFs) in each province of South Korea decreased. In particular, the operational efficiency of coastal ferries in Incheon, Jeju, Mokpo, and Pohang decreased considerably, and Busan was the most inefficient in 2016. These findings can enable ferry companies and government authorities to understand the impact of ferry disasters on the operational efficiency of coastal ferries and assist in developing appropriate strategies to improve the performance of the South Korean coastal ferry industry. [ABSTRACT FROM AUTHOR]

Abstract The maritime industry has witnessed several accidents worldwide. These disasters have raised the awareness of both researchers and policy makers about the importance of risk assessment and safety in marine transportation and seaport operation. This study aims at clarifying the determinants of maritime risk involved in seaport operation, based on theoretical foundations and empirical findings. From the RBV and SEM estimations, we could identify infrastructure and operational efficiency as important tangible and intangible resources, respectively, to decrease maritime risk and increase traffic volume. TCE was applied to explain theoretically the importance of operational efficiency to consignors, forwarders, and shipping companies in terms of using seaports. From the Institutional Theory, various risks involved in seaport operation could be enhanced where external institutions are uncertain or unstable. [ABSTRACT FROM AUTHOR]

Abstract The objective of this research is to verify gaps in firm performance between the levels of relationships between international freight forwarders and port logistics service providers. To achieve the objective, this research developed the conceptual and operational definitions of the variables through prior research and the questionnaire was sent to the forwarders. The collected data were analyzed by cluster analysis, analysis of variance (ANOVA) and analysis of covariance (ANCOVA). The results are as follows. First, the high level of the inter-corporate collaboration is based on the high level of customer performance. In this regard, the forwarders have the need of operational collaboration with port logistics service providers and as a result, they achieve a high level of customer performance. Second, the high level of the inter-corporate commitment is connected to the high level of firm performance. The forwarders provide shippers with the quality of customer service through commitment with port logistics service providers and this is the cause of firm performance. Third, the high level of the inter-corporate communication is based on a gap in customer performance. The forwarders can achieve the needs of shippers through communication with port logistics service providers and this is connected with a high level of customer performance. [ABSTRACT FROM AUTHOR]

This work is focused on the use of multilayer transparent conductive electrode (TCE) based on ZnO/Ag/ZnO in the fabrication of the organic heterostructures. The ZnO/Ag/ZnO obtained combining sputtering/thermal evaporation/sputtering techniques is featured by a good optical transmittance, a low electrical resistivity and a reduced roughness. All these characteristics recommend it as a viable alternative to indium tin oxide (ITO) for different applications. The organic materials, N,N'−diphenyl−N,N'−bis (1−naphthyl)−1,1´−biphenyl−4,4´−diamine (α-NPD), 5,12-Dihydro-5-12-dimethylquino [2,3-b]acridine-7,14dione (DMQA) and 4,7 diphenyl-1,10-phenanthroline (BPhen) were deposited by vacuum thermal evaporation (VTE) method, the properties of the obtained layers being investigated by FTIR, UV-VIS and PL) spectroscopy. The I-V characteristic (recorded in dark) of the organic heterostructure fabricated on the ZnO/Ag/ZnO electrode shows diode behavior, revealing its potential applications in the organic light emitting devices (OLED). [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Evaluation of photocatalytic oxidation (PCO) degradation of a mixture of three VOCs at ppb level. • Comparison of degradation with single initial compounds and with a mixture. • No significant influence in the degradation rate when compounds are in mixture. • No significant interactions between either VOC or intermediates at ppb level. • Oxygenated intermediated compounds are good indicators in photocatalytic systems performance. Abstract An investigation of the photocatalytic degradation of indoor air model pollutants: toluene, n -decane and trichloroethylene (TCE), as single contaminants and in a mixture is proposed. The degradation of these contaminants was performed in a continuous closed-loop reactor operating in recirculation mode. Degradations were conducted at ppb level concentrations and under humid conditions (RH = 50%) in order to be closer to real applications of photocatalytic oxidation (PCO) systems developed for indoor air quality improvement. Accurate analytical methods were developed to identify and quantify the majority of the potential formed intermediates. Kinetic constants and the time constant of degradation were obtained for the model pollutants. Under these conditions, the degradation of the three VOCs in a mixture did not really show a decrease in the kinetic rates. Toluene and decane degradations were slightly slowed down when they were in a mixture but no significant interference was demonstrated with TCE. The intermediates formed during the PCO of the mixture of VOCs were the same as those identified during single degradation, leading to the hypothesis of few interactions between them. Only the formation and degradation of secondary intermediates, mostly composed of aldehydes, were time delayed. The total VOC concentration may lead to a competitive adsorption that seemed more sensitive for the last formed oxygenated intermediates. This investigation points out the need to always monitor the last formed aldehyde intermediates. Monitoring acetaldehyde and formaldehyde enables an evaluation of the efficiency and a better design of future PCO systems for indoor applications. [ABSTRACT FROM AUTHOR]

Sulfide-modified nanoscale zero-valent iron (S/NZVI) has been considered as an efficient material to degrade trichloroethylene (TCE) in groundwater. However, some critical factors influencing the dechlorination of TCE by S/NZVI have not been investigated clearly. In this study, the effects of Fe/S molar ratio, initial pH, dissolved oxygen and particle aging on TCE dechlorination by S/NZVI (using dithionite as sulfidation reagent) were studied. Besides, the feasibility of reactivation of the aged-NZVI by sulfidation treatment was looked into. The results show that the Fe/S molar ratio and initial pH significantly influenced the TCE dechlorination, and a higher TCE dechlorination was observed at Fe/S molar ratio of ∼60 under alkaline condition. Spectroscopic analyses demonstrate that the enhanced TCE dechlorination was associated with the presence of FeS on the surface of S/NZVI. Dissolved oxygen had little effect on TCE dechlorination by S/NZVI, revealing that the FeS layer could be able to alleviate the surface passivation of NZVI caused by oxidation. Aging of S/NZVI up to 10–20 d only slightly decreased the dechlorination efficiency of TCE. Although an obvious drop in dechorination efficiency was observed for the S/NZVI aged for 30 d, it still exhibited a higher reactivity than the bare NZVI. This indicates that sulfidation of NZVI did prolong its lifetime. Additionally, sulfidation treatment was used to reactivate the aged NZVI, and the results show that the reactivated NZVI even had higher reactivity than the fresh NZVI, suggesting that sulfidation treatment would be a promising method to reactivate the aged NZVI. [ABSTRACT FROM AUTHOR]

The performance of double focusing, sector field mass spectrometry (ICP-SFMS) for determination of analytes, including technology critical elements (TCE), at ultra-trace levels in environmental and clinical matrices was critically evaluated. Different configurations of the ICP-SFMS introduction system as well as various sample preparations, pre-concentration and matrix separation methods were employed and compared. Factors affecting detection capabilities and accuracy of data produced (instrumental sensitivity, contamination risks, purity of reagents, spectral interferences, matrix effects, analyte recovery and losses) were discussed. Optimized matrix-specific methods were applied to a range of reference and control materials (riverine, brackish and seawaters; whole blood, serum and urine) as well as tap water and snow samples collected in the area of Luleå city, northern Sweden; brackish and seawater from the Laptev Sea; venous blood samples with a special emphasis on determination of Au, Ag, Ir, Os, Pd, Pt, Re, Rh, Ru, Sb and Te. Even though these low abundant elements are relatively under-documented, the results produced were compared with published data, where available. [ABSTRACT FROM AUTHOR]

An effective and sensitive method for the analysis of 1,4-dioxane in water has been available since 2008 (EPA 522). This method is increasingly being applied to investigate the distribution of 1,4-dioxane in the aquatic environment. However, there is a need for more information about the possible occurrence of 1,4-dioxane in groundwater in Europe in general, and in Germany in particular, where virtually no data have been collected so far. The possible contamination of groundwater with 1,4-dioxane is of relevance to Germany because up to 70% of Germany's drinking water is obtained from groundwater and about 17% from river bank filtrate, which contains variable proportions of groundwater. The aim of the present study is to investigate selected and representative groundwater sites in Germany that have suspected occurrences of 1,4-dioxane. Five of the sites are well known for their volatile chlorinated hydrocarbon contamination, two sites have representative landfill leachate characteristics, and one site is negatively impacted by a detergent manufacturing plant. The presence of 1,4-dioxane was observed at each of these sites. Measured maximum concentration values ranged from 0.15 μg/L to 152 μg/L. An aquifer containing a trichloroethylene (TCE) plume with 1,4-dioxane as a co-contaminant was investigated in more detail. A perfect match was found between the concentrations of 1,4-dioxane and TCE in the vertical and horizontal distribution profiles. The results indicate the necessity for investigating groundwater contamination by 1,4-dioxane at sites with known 1,1,1-trichloroethane (TCA) and TCE contaminations, in landfill leachates, and at sites of detergent production. [ABSTRACT FROM AUTHOR]

Exposure to trichloroethylene (TCE) is linked to formation of congenital heart defects in humans and animals. Prior interactome analysis identified the transcription factor, Hepatocyte Nuclear Factor 4 alpha (HNF4a), as a potential target of TCE exposure. As a role for HNF4a is unknown in the heart, we examined developing avian hearts for HNF4a expression and for sensitivity to TCE and the HNF4a agonist, Benfluorex. In vitro analysis using a HNF4a reporter construct showed both TCE and HFN4a to be antagonists of HNF4a-mediated transcription at the concentrations tested. HNF4a mRNA is expressed transiently in the embryonic heart during valve formation and cardiac development. Embryos were examined for altered gene expression in the presence of TCE or Benfluorex. TCE altered expression of selected mRNAs including HNF4a, TRAF6 and CYP2C45. There was a transition between inhibition and induction of marker gene expression in embryos as TCE concentration increased. Benfluorex was largely inhibitory to selected markers. Echocardiography of exposed embryos showed reduced cardiac function with both TCE and Benfluorex. Cardiac contraction was reduced by 29% and 23%, respectively at 10 ppb. The effects of TCE and Benfluorex on autocrine regulation of HNF4a, selected markers and cardiac function argue for a functional interaction of TCE and HNF4a. Further, the dose-sensitive shift between inhibition and induction of marker expression may explain the nonmonotonic-like dose response observed with TCE exposure in the heart. [ABSTRACT FROM AUTHOR]

Trichloroethylene (TCE) degradation in sand columns has been investigated to evaluate the potential of chelates-enhanced Fenton-like reaction with magnetite as iron source for in situ treatment of TCE-contaminated groundwater. The results showed that successful degradation of TCE in sand columns was obtained by nitrilotriacetic acid (NTA)-assisted Fenton-like reaction of magnetite. Addition of ethylenediaminedisuccinic acid (EDDS) resulted in an inhibitory effect on TCE degradation in sand columns. Similar to EDDS, addition of ethylenediaminetetraacetic acid (EDTA) also led to an inhibition of TCE degradation in sand column with small content of magnetite (0.5 w.t.%), but enhanced TCE degradation in sand column with high content of magnetite (7.0 w.t.%). Additionally, the presence of NTA, EDDS and EDTA greatly decreased H 2 O 2 uptake in sand columns due to the competition between chelates and H 2 O 2 for surface sites on magnetite (and sand). Furthermore, the presented results show that magnetite in sand columns remained stable in a long period operation of 230 days without significant loss of performance in terms of TCE degradation and H 2 O 2 uptake. Moreover, it was found that TCE was degraded mainly to formic acid and chloride ion, and the formation of chlorinated organic intermediates was minimal by this process. [ABSTRACT FROM AUTHOR]

An in situ field demonstration was performed in fractured rock impacted with trichloroethene (TCE) and cis -1,2-dichloroethene (DCE) to assess the impacts of contaminant rebound after removing dissolved contaminants within hydraulically conductive fractures. Using a bedrock well pair spaced 2.4 m apart, TCE and DCE were first flushed with water to create a decrease in dissolved contaminant concentrations. While hydraulically isolating the well pair from upgradient contaminant impacts, contaminant rebound then was observed between the well pair over 151 days. The magnitude, but not trend, of TCE rebound was reasonably described by a matrix back-diffusion screening model that employed an effective diffusion coefficient and first-order abiotic TCE dechlorination rate constant that was based on bench-scale testing. Furthermore, a shift in the TCE:DCE ratio and carbon isotopic enrichment was observed during the rebound, suggesting that both biotic and abiotic dechlorination were occurring within the rock matrix. The isotopic data and back-diffusion model together served as a convincing argument that matrix back-diffusion was the mechanism responsible for the observed contaminant rebound. Results of this field demonstration highlight the importance and applicability of rock matrix parameters determined at the bench-scale, and suggest that carbon isotopic enrichment can be used as a line of evidence for abiotic dechlorination within rock matrices. [ABSTRACT FROM AUTHOR]

Diffusion is regarded as the dominant transport mechanism into and out of low permeable subsurface lenses and layers in the subsurface. But, some reports of mass storage in such zones are higher than what might be attributable to diffusion, based on estimated diffusion coefficients. Despite the importance of diffusion to efforts to estimate the quantity of residual contamination in the subsurface, relatively few studies present measured diffusion coefficients of organic solutes in saturated low permeability soils. This study reports the diffusion coefficients of a trichloroethylene (TCE), and an anionic surfactant, Aerosol OT (AOT), in water-saturated silt and a silt-montmorillonite (25:75) mixture, obtained using steady-state experiments. The relative diffusivity ranged from 0.11 to 0.17 for all three compounds for the silt and the silt-clay mixture that was allowed to expand. In the case in which the swelling was constrained, the relative diffusivity was about 0.07. In addition, the relative diffusivity of 13 C-labeled TCE through a water saturated silt-clay mixture that had contacted a field dense non-aqueous phase liquid (DNAPL) for 18 months was measured and equaled 0.001. These experimental results were compared with the estimates generated using common correlations, and it was found that, in all cases, the measured diffusion coefficients were significantly lower than the estimated. Thus, the discrepancy between mass accumulations observed in the field and the mass storage that can attributable to diffusion may be greater than previously believed. [ABSTRACT FROM AUTHOR]

Laboratory batch experiments were performed to assess the impacts of temperature and mineralogy on the abiotic dechlorination of tetrachloroethene (PCE) or trichloroethene (TCE) due to the presence of ferrous minerals in natural aquifer clayey soils under anaerobic conditions. A combination of x-ray diffraction (XRD), magnetic susceptibility, and ferrous mineral content were used to characterize each of the 3 natural soils tested in this study, and dechlorination at temperatures ranging from 20 to 55 °C were examined. Results showed that abiotic dechlorination occurred in all 3 soils examined, yielding reduced gas abiotic dechlorination products acetylene, butane, ethene, and/or propane. Bulk first-order dechlorination rate constants (k bulk ), scaled to the soil:water ratio expected for in situ conditions, ranged from 2.0 × 10 − 5 day − 1 at 20 °C, to 32 × 10 − 5 day − 1 at 55 °C in the soil with the greatest ferrous mineral content. For the generation of acetylene and ethene from PCE, the reaction was well described by Arrhenius kinetics, with an activation energy of 91 kJ/mol. For the generation of coupling products butane and propane, the Arrhenius equation did not provide a satisfactory description of the data, likely owing to the complex reaction mechanisms associated with these products and/or diffusional mass transfer processes associated with the ferrous minerals likely responsible for these coupling reactions. Although the data set was too limited to determine a definitive correlation, the two soils with elevated ferrous mineral contents had elevated abiotic dechlorination rate constants, while the one soil with a low ferrous mineral content had a relatively low abiotic dechlorination rate constant. Overall, results suggest intrinsic abiotic dechlorination rates may be an important long-term natural attenuation component in site conceptual models for clays that have the appropriate iron mineralogy. [ABSTRACT FROM AUTHOR]

cis -1,2-Dichloroethene ( cis -DCE) and trichloroethene (TCE) are persistent, toxic and mobile pollutants in groundwater systems. They are both conducive to reductive dehalogenation and to oxidation by permanganate. In this study, the potential of dual element (C, Cl) compound specific isotope analyses (CSIA) for distinguishing between chemical oxidation and anaerobic reductive dechlorination of cis -DCE and TCE was investigated. Well-controlled cis -DCE degradation batch tests gave similar carbon isotope enrichment factors ε C (‰), but starkly contrasting dual element isotope slopes Δ δ 13 C/Δ δ 37 Cl for permanganate oxidation (ε C = − 26‰ ± 6‰, Δ δ 13 C/Δ δ 37 Cl ≈ − 125 ± 47) compared to reductive dechlorination (ε C = − 18‰ ± 4‰, Δ δ 13 C/Δ δ 37 Cl ≈ 4.5 ± 3.4). The difference can be tracked down to distinctly different chlorine isotope fractionation: an inverse isotope effect during chemical oxidation (ε Cl = + 0.2‰ ± 0.1‰) compared to a large normal isotope effect in reductive dechlorination (ε Cl = − 3.3‰ ± 0.9‰) ( p ≪ 0.05). A similar trend was observed for TCE. The dual isotope approach was evaluated in the field before and up to 443 days after a pilot scale permanganate injection in the subsurface. Our study indicates, for the first time, the potential of the dual element isotope approach for distinguishing cis -DCE (and TCE) concentration drops caused by dilution, oxidation by permanganate and reductive dechlorination both at laboratory and field scale. [ABSTRACT FROM AUTHOR]

Uncertainties of aging after the injection of microscale zero valent iron (mZVI) into subsurface hinder the widespread application of this technology into in-situ groundwater remediation. As TCE removal by mZVI is usually accompanied by mZVI anaerobic reaction with water, this study investigated the hydrogen evolution kinetics, TCE removal performance, and electron efficiency (EE) of mZVI particles under single and combined effects of organic geochemical constituents (humic acid (HA)), inorganic constituents (hardness (Ca 2+ ) and alkalinity (HCO 3 − )) in groundwater. The results showed that both H 2 generation and TCE removal were enhanced in the presence of HA (5–20 mg L −1 as DOC), and significant delay of aging precipitates formation was supported by SEM-EDS, XRD and XPS depth-profiling characterization. With increasing Ca 2+ -HCO 3 − concentrations (0.4–2 mM), the mZVI corrosion were inhibited for the formation of a thin compact passive film on mZVI surface. Furthermore, in co-presence of organic and inorganic constituents, the negatively-impacted iron corrosion kinetics suggested that promotional effects of organic constituents were dwarfed by the inhibitory effects of inorganic constituents. In addition, the EE values in different systems ranged among 1.31–7.40%, and decreased significantly with time. Hence, these findings provide insight into aging mechanism and performance prediction of mZVI under different groundwater geochemical conditions. [ABSTRACT FROM AUTHOR]

Historical heavy use of chlorinated solvents in conjunction with improper disposal practices and accidental releases has resulted in widespread contamination of soils and groundwater in North America and worldwide. As a result, remediation of chlorinated solvents is required at many sites. For source zone treatment, common remediation strategies include in-situ chemical oxidation (ISCO) using potassium or sodium permanganate, and the enhancement of biodegradation by primary substrate addition. It is well known that these remediation methods tend to generate gas (carbon dioxide (CO 2 ) in the case of ISCO using permanganate, CO 2 and methane (CH 4 ) in the case of bioremediation). Vigorous gas generation in the presence of chlorinated solvents, which are categorized as volatile organic contaminants (VOCs), may cause gas exsolution, ebullition and stripping of the contaminants from the treatment zone. This process may lead to unintentional ‘compartment transfer’, whereby VOCs are transported away from the contaminated zone into overlying clean sediments and into the vadose zone. To this extent, benchtop column experiments were conducted to quantify the effect of gas generation during remediation of the common chlorinated solvent trichloroethylene (TCE/C 2 Cl 3 H). Both ISCO and enhanced bioremediation were considered as treatment methods. Results show that gas exsolution and ebullition occurs for both remediation technologies. Facilitated by ebullition, TCE was transported from the source zone into overlying clean groundwater and was subsequently released into the column headspace. For the case of enhanced bioremediation, the intermediate degradation product vinyl chloride (VC) was also stripped from the treatment zone. The concentrations measured in the headspace of the columns (TCE ∼ 300 ppm in the ISCO column, TCE ∼ 500 ppm and VC ∼ 1380 ppm in the bioremediation column) indicate that substantial transfer of VOCs to the vadose zone is possible. These findings provide direct evidence for the unintended spreading of contaminants as a result of remediation efforts, which can, under some circumstances, result in enhanced risks for soil vapour intrusion. [ABSTRACT FROM AUTHOR]

1,4-dioxane is an emerging contaminant that was used as a corrosion inhibitor with chlorinated solvents. Metal-activated persulfate can degrade dioxane but reaction kinetics have typically been characterized by a rapid decrease during the first 30 min followed by either a slower decrease or no further change (i.e., plateau). Our objective was to identify the factors responsible for this plateau and then determine if slow-release formulations of sodium persulfate and Fe 0 could provide a more sustainable degradation treatment. We accomplished this by conducting batch experiments where Fe 0 -activated persulfate was used to treat dioxane. Treatment variables included the timing at which the dioxane was added to the Fe 0 -persulfate reaction (T = 0 and 30 min) and including various products of the Fe 0 -persulfate reaction at T = 0 min (Fe 2+ , Fe 3+ , and SO 4 2− ). Results showed that when dioxane was spiked into the reaction at 30 min, no degradation occurred; this is in stark contrast to the 60% decrease observed when added at T = 0 min. Adding Fe 2+ at the onset (T = 0 min) also severely halted the reaction and caused a plateau. This indicates that excess ferrous iron produced from the Fe 0 -persulfate reaction scavenges sulfate radicals and prevents further dioxane degradation. By limiting the release of Fe 0 in a slow-release wax formulation, degradation plateaus were avoided and 100% removal of dioxane observed. By using 14 C-labeled dioxane, we show that ∼40% of the dioxane carbon is mineralized within 6 d. These data support the use of slow-release persulfate and zerovalent iron to treat dioxane-contaminated water. [ABSTRACT FROM AUTHOR]

BTEX (benzene, toluene, ethylbenzene, ortho -, meta -, and para -xylenes), methyl tert -butyl ether (MTBE), cis -1,2-dichloroethylene ( cis -DCE), and trichloroethylene (TCE) are among the major soil and groundwater contaminants frequently co-existing, as a result of their widespread uses. Pseudomonas plecoglossicida was immobilized on waste scrap tyre to remove these contaminants mixture from synthetic contaminated water. The microbial activity was enhanced in the immobilized system, shown by the higher colony forming units (CFUs) (40%), while BTEX were used as growth substrates. The adsorption capacity of tyres toward contaminants reached a maximum within one day, with BTEX (76.3%) and TCE (64.3%) showing the highest sorption removal capacities, followed by cis -DCE (30.0%) and MTBE (11.0%). The adsorption data fitted the Freundlich isotherm with a good linear correlation (0.989–0.999) for the initial contaminants concentration range applied (25–125 mg/L). The monoaromatic hydrocarbons were almost completely removed in the immobilized system and the favourable removal efficiencies of 78% and 90% were obtained for cis -DCE and TCE, respectively. The hybrid (biological, immobilization/physical, sorption) system was further evaluated with the contaminants spiked intermittently for the stable performance. The addition of mineral salt medium further enhanced the bioremoval of contaminants by stimulating the microbial growth to some extent. [ABSTRACT FROM AUTHOR]

We enriched a trichloroethene (TCE)-dechlorinating consortium from a perchlorate-reducing bacterial culture (PRB) with a very low initial abundance of Dehalococcoides by feeding the culture lactate and TCE; named the novel culture perchlorate-reducing dechlorinating bacteria (PRTB). Short batch tests showed that the PRTB consortium reduced up to 0.45 mmol/L of TCE to non-toxic ethene in eight days after two additions of TCE and simultaneously reduced up to 0.15 mmol/L of ClO 4 − to Cl − . TCE reduction by PRTB was sensitive to oxygen: 0.2 mg/L of oxygen delayed reduction of TCE to ethene from 5 to 15 days, while ⩾0.5 mg/L of oxygen significantly inhibited TCE reduction, causing vinyl chloride accumulation. After the consortium was enriched twice with TCE, the Dhc gene (reflecting the abundance of Dehalococcoides ) increased from 1.14 × 10 4 to 3.25 × 10 8 copies/mL. The original PRB culture was dominated by Proteobacteria (78.4%), but the enriched PRTB culture was dominated by Chloroflexi (57.7%). The relative abundance of Dehalococcoides increased from 0.02% to 57.4%. Other presumptive dechlorinators Desulfuromonas and Geobacter were enriched as well. Possible acetogens ( Spirochaetes ) and putative fermenters ( Bacteroidetes and Desulfovibrio ) were also present in the culture, providing Dehalococcoides with acetate as the carbon source, hydrogen gas as the electron donor, and Vitamin B 12 as a growth factor. [ABSTRACT FROM AUTHOR]

A small-scale flow-through limestone column was used to evaluate the effect of common coexisting organic and inorganic compounds on the electrochemical dechlorination of trichloroethylene (TCE) in karst media. Iron anode was used to produce ferrous ions and promote reducing conditions in the column. The reduction of TCE under 90 mA current, 1 mL min −1 flow rate, and 1 mg L −1 initial TCE concentration, was inhibited in the presence of humic acids due to competition for direct electron transfer and/or reaction with atomic hydrogen produced at the cathode surface by water electrolysis. Similarly, presence of 10 mg L −1 chromate decreased TCE reduction rate to 53%. The hexavalent chromium was completely reduced to trivalent chromium due to the ferrous species produced from iron anode. Presence of 5 mg L −1 selenate decreased the removal of TCE by 10%. Chromium and selenate complexation with dissolved iron results in formation of aggregates, which cover the electrodes surface and reduce TCE dechlorination rate. Presence of 40 mg L −1 nitrates caused reductive transformation of TCE up to 80%. Therefore, TCE removal is influenced by the presence of other contaminants that are present as a mixture in groundwater in the following order: humic acid, chromate, selenate, and nitrate. [ABSTRACT FROM AUTHOR]

Many groundwater aquifers around the world are contaminated with trichloroethene (TCE), which can be harmful to human and ecosystem health. Permeable Reactive Barriers (PRB) are commonly used to remediate TCE-contaminated groundwaters especially when a point source is ill defined. Using biosolids from wastewater treatment plants as a PRB filling material can provide a source of carbon and nutrients for dechlorinating bacterial activity. However, under the anaerobic conditions of the PRB, methanogenesis can also occur which can adversely affect reductive dechlorination. We conducted bench scale experiments to evaluate the effect of biosolids on TCE reductive dechlorination and found that methanogenesis was significantly higher in the reactors amended with biosolids, but that reductive dechlorination did not decrease. Furthermore, the microbial communities in the biosolid-enhanced reactors were more abundant with obligate dechlorinators, such as Dehalobacter and Dehalogenimonas , than the reactors amended only with the dechlorinating culture. The biosolids enhanced the presence and abundance of methanogens and acetogens, which had a positive effect on maintaining an efficient dechlorinating microbial community and provided the necessary enzymes, cofactors, and electron donors. These results indicate that waste materials such as biosolids can be turned into a valuable resource for bioremediation of TCE and likely other contaminants. [Display omitted] • Application of alternative organic amendments for bioremediation of groundwater. • Sustainable and beneficial application of biosolids derived biomass. • Biologically active filling material for bioremediation of contaminated groundwater. • Biosolids derived amendment enhanced the presence and abundance of methanogens and acetogens. • Efficient maintenance of active dechlorinating microbial community with biosolids. [ABSTRACT FROM AUTHOR]

Atomic hydrogen (H*) has long been thought to play an important role in the dechlorination of trichloroethylene (TCE) by carbon-supported zero-valent iron (ZVI), which offers an alternative pathway for TCE dechlorination. Herein, we demonstrate that the reductive dechlorination of TCE by sulfidated microscale ZVI (S-mZVI) can be further enhanced by promoting the formation of H* through the introduction of reduced graphene oxide (rGO). The completely degradation of 10 mg/L TCE can be achieved by S-mZVI/rGO within 24 h, which was 3.3 times faster than that of S-mZVI. The change in the distribution of TCE degradation products over time suggests that the introduction of rGO leads to a change in the dechlorination pathway. The percentage of ethane in the final products of TCE degradation by S-mZVI/rGO was 34.3 %, while that of S-mZVI was only 21.9 %. The electrochemical tests confirmed the occurrence of hydrogen spillover in the S-mZVI/rGO composite, which promoted the reductive dechlorination of TCE by H*. Although the S-mZVI/rGO composite had stronger hydrogen evolution propensity than S-mZVI, the S-mZVI/rGO composite still exhibited higher electron utilization efficiency than S-mZVI thanks to the increased utilization of hydrogen. [Display omitted] • The dechlorination of TCE by S-mZVI/rGO was 3.3 time faster than that of S-mZVI. • S-mZVI/rGO exhibited higher electron utilization efficiency than S-mZVI. • The introduction of rGO induced hydrogen spillover effect. • S-mZVI/rGO exhibited enhanced atomic hydrogen generation. [ABSTRACT FROM AUTHOR]

In this study, iron was deposited to titanium dioxide nanotube arrays (TNAs) by impregnation method to enhance its photocatalytic ability. The as-synthesized iron-modified TNAs (Fe-TNAs) was employed in a photoelectrochemical (PEC) system to degrade trichloroethylene (TCE). Results of AFE-SEM analysis showed that the iron nanoparticles (NPs) were successfully attached evenly to the nozzle of Fe-TNAs. Results of XRD analysis confirmed the findings of EDS and XPS, indicating the success of iron modification. The absorption wavelength of Fe-TNAs-27 mL red-shifts to 543 nm which corresponds to the band gap of 2.54 eV after iron modification. Mott–Schottky analysis yielded a donor density of 7.21 × 1020 and 2.30 × 1020/cm3 for TNAs and Fe-TNAs-27 mL, respectively. The photo-generated electrons had a lifetime (τ el) of 21.49 and 39.19 ms for TNAs and Fe-TNAs-27 mL, respectively, illustrating the reduce of recombination of photo-generated electron-hole pairs. process. PEC methods performed the most effective way to degrade TCE with a rate constant of 0.079 min−1 in Fe-TNAs PEC system. Mechanism of Fe-TNAs PEC system was proposed in detail. [Display omitted] • Fe-TNAs was synthesized successfully via impregnation deposition method. • Electron lifetime of TNAs was enhanced after iron modification. • TCE degradation was significantly enhanced by PEC system. • Mechanism of TCE degradation via Fe-TNAs in PEC system was investigated. [ABSTRACT FROM AUTHOR]

This work evaluated the interaction of perchlorate and trichloroethene (TCE), two common co-contaminants in groundwater, during bioreduction in serum bottles containing synthetic mineral salts media and microbial consortia. TCE at concentrations up to 0.3 mM did not significantly affect perchlorate reduction; however, perchlorate concentrations higher than 0.1 mM made the reduction of TCE significantly slower. Perchlorate primarily inhibited the reduction of vinyl chloride (VC, a daughter product of TCE) to ethene. Mechanistic analysis showed that the inhibition was mainly because perchlorate reduction is thermodynamically more favorable than reduction of TCE and its daughter products and not because of toxicity due to accumulation of dissolved oxygen produced during perchlorate reduction. As the initial perchlorate concentration increased from 0 to 600 mg/L in a set of serum bottles, the relative abundance of Rhodocyclaceae (a putatively perchlorate-reducing genus) increased from 6.3 to 80.6%, while the relative abundance of Dehalococcoides , the only known genus that is able to reduce TCE all the way to ethene, significantly decreased. Similarly, the relative abundance of Proteobacteria (a phylum to which most known perchlorate-reducing bacteria belong) increased from 22% to almost 80%. [ABSTRACT FROM AUTHOR]

Few studies have evaluated how rainfall recharges affect biological dechlorination of trichloroethene (TCE). In this study, a sequence of three well-to-well tests (Phases I, II, and III) were performed for 100 d to investigate the variation of biological dechlorination of TCE at a highly recharged and TCE-contaminated aquifer. Test solutions containing different nutrients were delivered into the aquifer through a nitrogen gas spray. In Phase I, where only formate was supplied, the degradation of TCE to cis-dichloroethene (cis-DCE) was negligible. However, when sulfate as well as formate was introduced during Phase II, the reductive dechlorination of TCE occurred. During Phase III, fumarate was also provided as an alternative electron donor. High cis-DCE production rates were observed with complete degradation of formate and sulfate at 65th day monitoring, the end of dry period in Phase III. Since then, there were heavy rainfalls that accounted for approximately 36% of total annual precipitation in this area. Although oxygenated rain was rapidly infiltrated into the bioactive zone, the consumption of formate and sulfate were not significantly affected, with the DO as low as <0.2 mg/L. Nonetheless, the dechlorination activity of TCE was decreased as evidenced by 70% reduction in the cis-DCE production rate compared to that before the heavy rainfall. In 10 d after heavy rainfall ceased, the dechlorination activity was partially recovered (approximately 60%), while sulfate and formate consumptions were fully recovered. These results suggest that the dechlorination activity of TCE at the tested aquifer was sustained even in the presence of heavy rainfall recharges. This was probably due to the growth of the dechlorinating microbes on solid surfaces by forming biofilms. [ABSTRACT FROM PUBLISHER]

Contamination of groundwater with the gasoline additive methyl tert -butyl ether (MTBE) is often accompanied by the coexistence of chlorinated aliphatic contaminants such as trichloroethylene (TCE). This study reports for the first time an indigenous Paracoccus sp. using MTBE as a sole carbon source while cometabolizing TCE from the mixture. The culture was originally enriched and isolated from the sludge sample at a regional wastewater treatment plant in Macau Special Administrative Region (SAR), China. Waste silica gel was used as a matrix for the microbial immobilization. The effects of different concentrations of MTBE and TCE on the removal efficiencies were investigated, together with their interactions during the bioremoval process, as well as the effects of pH and temperature on MTBE and TCE removal rates. The adsorption kinetics of contaminants on silica gel was also evaluated and the adsorption capacities of MTBE (50 mg l −1 ) and TCE (50 mg l −1 ) were 0.42 mg g −1 and 0.65 mg g −1 , respectively. In the immobilized system, TCE (20 mg l −1 ) was removed to non-detectable level while the highest removal efficiency for MTBE (40 mg l −1 ) was 70.2 ± 3.1%. [ABSTRACT FROM AUTHOR]

The 2011 EPA trichloroethylene (TCE) IRIS assessment, used developmental cardiac defects from a controversial drinking water study in rats (Johnson et al. [51]), along with several other studies/endpoints to derive reference values. An updated literature search of TCE-related developmental cardiac defects was conducted. Study quality, strengths, and limitations were assessed. A putative adverse outcome pathway (AOP) construct was developed to explore key events for the most commonly observed cardiac dysmorphologies, particularly those involved with epithelial-mesenchymal transition (EMT) of endothelial origin (EndMT); several candidate pathways were identified. A hypothesis-driven weight-of-evidence analysis of epidemiological, toxicological, in vitro, in ovo, and mechanistic/AOP data concluded that TCE has the potential to cause cardiac defects in humans when exposure occurs at sufficient doses during a sensitive window of fetal development. The study by Johnson et al. [51] was reaffirmed as suitable for hazard characterization and reference value derivation, though acknowledging study limitations and uncertainties. [ABSTRACT FROM AUTHOR]

In 2009, we identified a TCE plume at an abandoned landfill that was located in a low permeable silty-clay aquifer. To treat the TCE, we manufactured slow-release potassium permanganate cylinders (oxidant candles) that had diameters of either 5.1 or 7.6 cm and were 91.4 cm long. In 2010, we compared two methods of candle installation by inserting equal masses of the oxidant candles (7.6-cm vs 5.1-cm dia). The 5.1-cm dia candles were inserted with direct-push rods while the 7.6-cm candles were housed in screens and lowered into 10 permanent wells. Since installation, the 7.6-cm oxidant candles have been refurbished approximately once per year by gently scraping off surface oxides. In 2012, we reported initial results; in this paper, we provide a 5-yr performance review since installation. Temporal sampling shows oxidant candles placed in wells have steadily reduced migrating TCE concentrations. Moreover, these candles still maintain an inner core of oxidant that has yet to contribute to the dissolution front and should provide several more years of service. Oxidant candles inserted by direct-push have stopped reducing TCE concentrations because a MnO 2 scale developed on the outside of the candles. To counteract oxide scaling, we fabricated a second generation of oxidant candles that contain sodium hexametaphosphate. Laboratory experiments (batch and flow-through) show that these second-generation permanganate candles have better release characteristics and are less prone to oxide scaling. This improvement should reduce the need to perform maintenance on candles placed in wells and provide greater longevity for candles inserted by direct-push. [ABSTRACT FROM AUTHOR]

In this study, the feasibility of degrading trichloroethylene (TCE)-contaminated water (initial TCE concentration of approximately 45 mg/L) was evaluated via persulfate oxidation activated by red mud. The study indicates that red mud is able to activate the persulfate oxidation mechanism producing sulfate radicals () to oxidize TCE. There is a higher TCE removal (92%) with the addition of 2 g/L red mud after 5 h of oxidation reaction vs. non red mud system (42% TCE removal). A maximum TCE removal efficiency is obtained at neutrality condition. The TCE degradation rate reached 95% at lower temperature with the oxidation of hydrogen peroxide and sodium persulfate, respectively. This result reveals that the ability of activated persulfate () to generate sulfate radicals () is limited by thermal. In addition, a favorable TCE degradation rate is acquired for Fenton-like oxidation reaction with hydrogen peroxide and sodium persulfate as oxidant. [ABSTRACT FROM PUBLISHER]

Palladium-catalytic hydrodechlorination of trichloroethylene (TCE) by cathodic H 2 produced from water electrolysis has been tested. For a field in-well application, the flow rate is generally high. In this study, the performance of Pd-catalytic hydrodechlorination of TCE using cathodic H 2 is evaluated under high flow rate (1 L min −1 ) in a circulated column system, as expected to occur in practice. An iron anode supports reduction conditions and it is used to enhance TCE hydrodechlorination. However, the precipitation occurs and high flow rate was evaluated to minimize its adverse effects on the process (electrode coverage, clogging, etc.). Under the conditions of 1 L min −1 flow, 500 mA current, and 5 mg L −1 initial TCE concentration, removal efficacy using iron anodes (96%) is significantly higher than by mixed metal oxide (MMO) anodes (66%). Two types of cathodes (MMO and copper foam) in the presence of Pd/Al 2 O 3 catalyst under various currents (250, 125, and 62 mA) were used to evaluate the effect of cathode materials on TCE removal efficacy. The similar removal efficiencies were achieved for both cathodes, but more precipitation generated with copper foam cathode (based on the experiments done by authors). In addition to the well-known parameters such as current density, electrode materials, and initial TCE concentration, the high velocities of groundwater flow can have important implications, practically in relation to the flush out of precipitates. For potential field application, a cost-effective and sustainable in situ electrochemical process using a solar panel as power supply is being evaluated. [ABSTRACT FROM AUTHOR]

Nanoscale zero-valent iron particles (nZVI) are already applied for in-situ dechlorination of halogenated organic contaminants in the field. We performed batch experiments whereby trichloroethene (TCE) was dehalogenated by nZVI under different environmental conditions that are relevant in practice. The tested conditions include different ionic strengths, addition of polyelectrolytes (carboxymethylcellulose and ligninsulphonate), lowered temperature, dissolved oxygen and different particle contents. Particle properties were determined by Mössbauer spectroscopy, XRD, TEM, SEM, AAS and laser obscuration time measurements. TCE dehalogenation and H 2 evolution were decelerated by reduced ionic strength, addition of polyelectrolytes, temperature reduction, the presence of dissolved oxygen and reduced particle content. The partitioning of released electrons between reactions with the contaminant vs. with water (selectivity) was low, independent of the tested conditions. Basically out of hundred electrons that were released via nZVI oxidation only 3.1 ± 1.4 were used for TCE dehalogenation. Even lower selectivities were observed at TCE concentrations below 3.5 mg l − 1 , hence particle modifications and/or combination of nZVI with other remediation technologies seem to be necessary to reach target concentrations for remediation. Our results suggest that selectivity is particle intrinsic and not as much condition dependent, hence particle synthesis and potential particle modifications of nZVI particles may be more important for optimization of the pollutant degradation rate, than tested environmental conditions. [ABSTRACT FROM AUTHOR]

This work systematically compared the potential of a conventional fungal biofilter (BF) and a fungal biotrickling filter (BTF) for the abatement of a mixture of hydrophobic volatile organic compounds (VOCs). Candida subhashii was herein used for the first time, to the best of the author's knowledge, to remove n -hexane, trichloroethylene, toluene and α-pinene under aerobic conditions. C. subhashii immobilized on polyurethane foam supported steady state removal efficiencies of n -hexane, trichloroethylene, toluene and α-pinene of 25.4 ± 0.9%, 20.5 ± 1.0%, 19.6 ± 1.5% and 25.6 ± 2.8% in the BF, and 35.7 ± 0.9%, 24.0 ± 1.6%, 44.0 ± 1.7% and 26.2 ± 1.8% in the BTF, respectively, at relatively short gas residence times (30 s). The ability of C. subhashii to biodegrade n -hexane, TCE, toluene and α-pinene was confirmed in a batch test conducted in serum bottles, where a biodegradation pattern (toluene ≈ n -hexane > α-pinene > trichloroethylene) comparable to that recorded in the BF and BTF was recorded. [Display omitted] • A fungal BF and BTF treating hydrophobic VOCs were systematically compared. • subhashii supported an effective removal of VOCs at short EBRT of 30 s. • Fungal BTF supported a slightly higher VOC abatement performance than fungal BF. • The ability of C. subhashii to remove VOCs was also confirmed in batch assays. • A consistent biodegradation pattern was recorded: toluene ≈ n-hexane>α-pinene > TCE. [ABSTRACT FROM AUTHOR]

Summary This paper investigates the role of spatial and temporal averaging of recharge upon the calibration of trichloroethylene (TCE) contaminant transport parameters for a transient, three-dimensional, variably saturated, physically based, field-scale groundwater flow system in Toms River, New Jersey. Coarse vertical discretizations of unsaturated groundwater systems are prone to numerical difficulties requiring, in some cases, the linearization of the van Genuchten or Brooks Corey equations. A flux-based method for calculating relative permeability was developed and shown to improve numerical stability. To reduce the computational burden of calibration, the simulation time of the transport models was reduced by 95% by decoupling the transport model from the flow model. Multi-start PEST was used to calibrate four models with recharge specified as: constant, spatially varying, temporally varying, and both spatially and temporally varying. For the transient flow model with spatially and temporally varying recharge, the estimated transverse dispersivity coefficients were estimated to be significantly less than those calculated from simulations with spatial and/or temporal averaging of recharge. The calibrated TCE retardation value of 1.58 is within 5% of the laboratory determined value of 1.65. Furthermore, the calibrated TCE retardation values are not as sensitive to the spatial and/or temporal averaging of recharge as compared to transverse dispersivity. [ABSTRACT FROM AUTHOR]