Naphthalene Research Articles

DC Electric Fields Promote Biodegradation of Waterborne Naphthalene in Biofilter Systems.

Biofiltration is a simple and low-cost method for the cleanup of contaminated water. However, the reduced availability of dissolved chemicals to surface-attached degrader bacteria may limit its efficient use at certain hydraulic loadings. When a direct current (DC) electric field is applied to an immersed packed bed, it invokes electrokinetic processes, such as electroosmotic water flow (EOF). EOF is a surface-charge-induced plug-flow-shaped movement of pore fluids. It acts at a nanometer distance above surfaces and allows the change of microscale pressure-driven flow profiles and, hence, the availability of dissolved contaminants to microbial degraders. In laboratory percolation columns, we assessed the effects of a weak DC electric field (E = 0.5 V·cm-1) on the biodegradation of waterborne naphthalene (NAH) by surface-attached Pseudomonas fluorescens LP6a. To vary NAH bioavailability, we used different NAH concentrations (C0 = 2.7, 5.1, or 7.8 × 10-5 mol·L-1) and Darcy velocities typical for biofiltration ( = 0.2-1.2 × 10-4 m·s-1). In DC-free controls, we observed higher specific degradation rates (qc) at higher NAH concentrations. The qc depended on , suggesting bioavailability restrictions depending on the hydraulic residence times. DC fields consistently increased qc and resulted in linearly increasing benefits up to 55% with rising hydraulic loadings relative to controls. We explain these biodegradation benefits by EOF-altered microscale flow profiles allowing for better NAH provision to bacteria attached to the collectors even though the EOF was calculated to be 100-800 times smaller than bulk water flow. Our data suggest that electrokinetic approaches may give rise to future technical applications that allow regulating biodegradation, for example, in response to fluctuating hydraulic loadings.

Photocatalytic Polyaromatic hydrocarbons (PAH) utilizing magnetic CrFe2O4 nanoparticle: Green synthesis, characterization, ab initio studies, electronic, magnetic features and water treatment application

Polyaromatic hydrocarbons (PAHs) are priority pollutants due to their mutagenicity, persistence, and proven carcinogenicity. Consequently, we investigated the photooxidative degradation of prototypical toxic PAHs, namely anthracene (ANTH) and phenanthrene (PHEN), and naphthalene (NAPH) utilizing magnetic CrFe2O4 nanoparticles under visible light LED irradiation. The prepared nanoparticles, characterized by P-XRD, IR, and SEM, reveal a cubic (FCC) structure and an average particle size of 25.6 nm. On Ab initio study we employed spin polarized first-principle calculations using the Full-Potential Linearized Augmented Plane-Wave (FLAPW) method with GGA-mBJ potentials implemented in the Wien2k package to investigate the properties of CrFe2O4 spinel compound; the calculations reveal that CrFe2O4 adopts a cubic crystal structure with space group 227 (Fd-3 m), and exhibits semiconductor characteristics in both spin channels, featuring indirect band gaps of 1.12 eV (spin-up) and 0.43 eV (spin-down) at the Γ-L and K-Γ points, respectively. Furthermore, the material demonstrates ferromagnetic behavior, with a spin magnetic moment of 20 µB per unit cell. Optical spectra analysis concurs with band structure calculations, suggesting the suitability of this material for photovoltaic applications. The CrFe2O4 magnetic nanoparticles were synthesized through an eco-friendly approach using Boswellia carteri resin as a natural surfactant in an aqueous medium. Our synthesized materials exhibited excellent photocatalytic performance, leading to a rapid exponential decay of ANTH and PHEN over 3 h under visible LED light. The effect of different radical scavengers revealed the role of the percentage of active species OH, h+, and ˙O2− in the oxidation of selected PAHs. At neutral pH, the photo-degradation of PAHs (200 g L−1) by CrFe2O4 (10 mg) followed first-order kinetics and the Langmuir model (R2: 0.99). Exceptional degradation efficiencies were achieved, with ANTH exhibiting a removal efficiency of 99 %, PHEN of 90 %, and NAPH of 86 %. These results show the effectiveness of the synthesized materials as benign and environmentally friendly magnetic nanoparticles for removing carcinogenic PAHs, offering a sustainable, green, and reusable (n = 7) catalytic system to address this environmental challenge.

Differential eco-toxicological responses toward Eisenia fetida exposed to soil contaminated with naphthalene and typical metabolites.

Naphthalene (NAP) was frequently detected in polycyclic aromatic hydrocarbons (PAHs)-contaminated soil, and its residues may pose an eco-toxicological threat to soil organisms. The toxic effects of NAP were closely tied to phenolic and quinone metabolites in biological metabolism. However, the present knowledge concerning the eco-toxicological impacts of NAP metabolites at the animal level is scanty. Here, we assessed the differences in the eco-toxicological responses of Eisenia fetida (E. fetida) in NAP, 1-naphthol (1-NAO) or 1,4-naphthoquinone (1,4-NQ) contaminated soils. NAP, 1-NAO, and 1,4-NQ exposure triggered the onset of oxidative stress as evidenced by the destruction of the antioxidant enzyme system. The lipid peroxidation and DNA oxidative damage levels induced by 1-NAO and 1,4-NQ were higher than those of NAP. The elevation of DNA damage varied considerably depending on differences in oxidative stress and the direct mode of action of NAP or its metabolites with DNA. All three toxicants induced different degrees of physiological damage to the body wall, but only 1, 4-NQ caused the shedding of intestinal epithelial cells. The integrated biomarker response for different exposure times illustrated that the comprehensive toxicity at the animal level was 1,4-NQ > 1-NAO > NAP, and the time-dependent trends of oxidative stress responses induced by the three toxicants were similar. At the initial stage, the antioxidant system of E. fetida responded positively to the provocation, but the ability of E. fetida to resist stimulation decreased with the prolongation of time resulting in provocation oxidative damage. This study would provide new insights into the toxicological effects and biohazard of PAHs on soil animals.

Effects of salinity on naphthalene adsorption and toxicity of polyethylene microparticles on Artemia salina

Plastic pollution in aquatic ecosystems is increasing and plastic particles may adsorb and transport a diverse array of contaminants, thereby increasing their bioavailability to biota. This investigation aimed to evaluate the effects of varying polyethylene microplastics (PE MPs) and naphthalene (NAPH) concentrations on the survival and feeding rates of the model organism, Artemia salina, as well as NAPH adsorption to microplastics at different salinity levels (17, 75, 35.5 and 52.75 g L−1) under selected climate change scenarios. Survival (48 h) and feeding rates (6 h) of A. salina were also monitored, revealing that the presence of higher PE and NAPH concentrations lead to decreased survival rates while also increasing the number and size of microplastic particles in the saline solutions. Higher PE concentrations negatively affected A. salina feeding rates and NAPH concentrations were positively correlated with particle number and size, as well as with NAPH and PE adsorption rates in solution. Our findings demonstrate that the co-occurrence of microplastics and NAPH in aquatic environments can result in detrimental zooplankton survival and feeding rate effects. Furthermore, this interaction may contribute to the accumulation of these contaminants in the environment, highlighting the need to simultaneously monitor and mitigate the presence of microplastics and organic pollutants, like NAPH, in aquatic environments.

Naphthalene and phenanthrene affect differentially two glutathione S-transferases (GSTs) expression, GST activity, and glutathione content in white shrimp P. vannamei

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants ubiquitous in coastal ecosystems. The white shrimp Penaeus vannamei naturally inhabits in coastal areas and is cultivated in farms located nearby the oceans. PAHs can damage shrimp health, endanger natural populations, and lower shrimp aquaculture productivity. However, crustaceans have enzymes capable of metabolizing organic xenobiotics as PAHs and to neutralize reactive oxygen species (ROS) produced during xenobiotics metabolism. An important superfamily of xenobiotic-metabolizing and antioxidant enzymes are glutathione S-transferases (GSTs). In white shrimp, some GSTs are known, but they have been scarcely studied in response to PAHs. In this study we report the molecular cloning and bioinformatic characterization of two novel nucleotide sequences corresponding to cytosolic GSTs belonging the Delta and Theta classes (GSTD and GSTT). Both proteins genes have tissue-specific patterns of expression under normal conditions, that do not necessarily relate to GST activity and glutathione content. The expression of the GSTD and GSTT, GST activity and glutathione content was analyzed in juvenile P. vannamei exposed to two PAHs, naphthalene (NAP) and phenanthrene (PHE) in sub-lethal concentrations for 96 h. GSTD expression was up-regulated by the two PAHs, while GSTT expression was only induced by NAP. In contrast, GST activity towards CDNB was only up-regulated by PHE, suggesting differential effects of PAHs at gene and protein level. On the other hand, lower reduced glutathione content (GSH) caused by PAHs indicates its utilization for detoxification or antioxidant defenses. However, the GSH/GSSG did not change by PAHs treatment, indicating that shrimp can maintain redox balance during short-term sub-lethal exposure to NAP and PHE. Despite the variations in the responses to NAP and PHE, all these results suggest that the GSTD and GSTT genes could be useful biomarkers for PAH exposure in P. vannamei.

Sorption of three PAHs profile groups using eco-friendly and inexpensive hydroxyapatite extracted from camel bone

Hydroxyapatite (HAp) was used in the sorption study for three different polycyclic aromatic hydrocarbons (PAHs) ring structures (Naphthalene (NAP), Anthracene (ANT), and Chrysene). HAp powders were produced from Camelus bone as an eco-friendly and inexpensive source. Three distinct surface areas (66.56, 94.88, and 94.35 m2/g) at three different temperatures (500, 650, and 900 °C), were applied to prepare the HAp500, HAp650, and HAp900 samples after passing CO2 at 700 °C. It was obvious that the surface area of HAp was greatest at 650 °C as compared to 500 °C with a very small variation in uptake between HAP650 and HAP900. Furthermore, for ANT, HAp900 provides the best uptake. In addition, HAp650 is the best since calcining at 650 °C is less expensive than calcining at 900 °C. The effect of shaking time on the sorption of NAP, ANT, and CHR dissolved in n-hexane was carried out using HAp650. The impacts of sorbent amount, concentration, and temperature were studied. The study indicated that the uptake was 66.89, 69.49, and 19.67 mg/g after 120 min of equilibration. It was observed that the uptake of NAP, ANT, and CHR increased as the temperature increased up to 35 °C. A slight increase was obtained from 35–55 °C, indicating that the adsorption occurring on the HAp650 surface is endothermic. The positive values of Δ H demonstrated the endothermic nature of the adsorption process. Furthermore, the positive entropy of adsorption represents the adsorbent material’s affinity for NAP, ANT, and CHR. In addition, several isotherm models were used to deduce an adsorption mechanism. The adsorption system’s R2 values were 0.9615 for NAP, 0.8666 for ANT, and 1.00 for CHR. These values agree well with the Langmuir isotherm.

Impact of aging and ergothioneine pre-treatment on naphthalene toxicity in lung

Aging increases susceptibility to lung disease, but the topic is understudied, especially in relation to environmental exposures with the bulk of rodent studies using young adults. This study aims to define the pulmonary toxicity of naphthalene (NA) and the impacts of a dietary antioxidant, ergothioneine (ET), in the liver and lungs of middle-aged mice. NA causes a well-characterized pattern of conducting airway epithelial injury in the lung in young adult mice, but NA’s toxicity has not been characterized in middle-aged mice, aged 1–1.5 years. ET is a dietary antioxidant that is synthesized by bacteria and fungi. The ET transporter (ETT), SLC22A4, is upregulated in tissues that experience high levels of oxidative stress. In this study, middle-aged male and female C57BL/6 J mice, maintained on an ET-free synthetic diet from conception, were gavaged with 70 mg/kg of ET for five consecutive days. On day 8, the mice were exposed to a single intraperitoneal NA dose of 50, 100, 150, or 200 mg/kg. At 24 hours post NA injection samples were collected and analyzed for ET concentration and reduced (GSH) and oxidized glutathione (GSSG) concentrations. Histopathology, morphometry, and gene expression were examined. Histopathology of mice exposed to 100 mg/kg of NA suggests reduction in toxicity in the terminal airways of both male (p ≤ 0.001) and female (p ≤ 0.05) middle-aged mice by the ET pretreatment. Our findings in this study are the first to document the toxicity of NA in middle-aged mice and show some efficacy of ET in reducing NA toxicity.

Incorporating porous carbon materials into ionic liquid for high efficiency extraction of polycyclic aromatic hydrocarbons

Ionic liquid is an ideal candidate in the extraction of aromatic compounds. The design and construction of ionic liquids with high extraction efficiency and selectivity towards to the specific aromatics remain crucial question. In this paper, with the aid of orthogonal array experiment, the imidazolium-based ionic liquids with long alkyl chain on the cations were determined to possess high aromatics extraction efficiency. Furthermore, the Lewis acid anion was introduced into the ionic liquid to form 1-dodecyl-3-methylimidazolium ferric chloride ([C12mim][FeCl4]) and performed 62 % and 100 % extractant efficiency of naphthalene (NAP) and anthracene (ANT), respectively. Then the porous carbon materials (P1-1000) derived from hyper-crosslinked porous polymers (HCP) which possessed high BET surface area (1186 m2/g) was dispersed in [C12mim][FeCl4] to form porous ionic liquid. The single extraction efficiency of NAP improved from 62 % to 77 %. The great single extraction efficiency was attributed to the high porosity, additional adsorption sites provided by the Lewis acid anions and the hydrophobic long alkyl chain on the cations. After three times extraction, the concentration of NAP dropped down to 0. The porous ionic liquids also showed good recycle performance. The construction of porous ionic liquids provided an efficient approach for extraction of polycyclic aromatic hydrocarbons from aliphatic hydrocarbon.

Controllable synthesis of naphthalene-derived isotropic pitch with linear molecular structure via Blanc chloromethylation–dechlorination reaction

Isotropic pitches with high softening points were controllably synthesized using naphthalene (NAP) via Blanc chloromethylation–dechlorination. Under mild conditions, chloromethyl was introduced into the NAP ring in the presence of chloromethylation reagent. The chloromethylation products of NAP are mainly composed of 1-chloromethylnaphthalene (1-CMNP) and a small amount of 1,4-dichloromethylnaphthalene (1,4-DCMNP). The results of the thermodynamic and kinetic calculations confirmed that the alpha-hydrogen on the NAP ring was more susceptible to being substituted by chloromethyl during chloromethylation, resulting in the formation of 1-CMNP and 1,4-DCMNP. High-quality isotropic pitches with linear methylene-bridged NAP ring structures, characterized by high purity, a high H/C ratio, 100 % solubility in quinoline, and excellent spinnability, were obtained after thermal dechlorination polymerization. Due to their homogeneous isotropic phase, appropriate viscosity, and outstanding spinnability, the as-synthesized pitches were adopted as precursors to prepare isotropic pitch-based carbon fibers via melt spinning. Additionally, the investigation of the carbonization behavior of the as-synthesized pitches showed that the naphthalene-derived isotropic pitch obtained at a polymerization temperature of 380 °C had a 57 % carbon yield at 800 °C, and its derived semi-cokes displayed an isotropic texture, even when carbonized at 550 °C.

Evaluation of surfactant-aided polycyclic aromatic hydrocarbon biodegradation by molecular docking and molecular dynamic simulation in the marine environment

Marine oil spills directly cause polycyclic aromatic hydrocarbons (PAHs) pollution and affect marine organisms due to their toxic property. Chemical and bio-based dispersants composed of surfactants and solvents are considered effective oil spill-treating agents. Dispersants enhance oil biodegradation in the marine environment by rapidly increasing their solubility in the water column. However, the effect of dispersants, especially surfactants, on PAHs degradation by enzymes produced by microorganisms has not been studied at the molecular level. The role of the cytochrome P450 (CYP) enzyme in converting contaminants into reactive metabolites during the biodegradation process has been evidenced, but the activity in the presence of surfactants is still ambiguous. Thus, this study focused on the evaluation of the impact of chemical and bio-surfactants (i.e., Tween 80 (TWE) and Surfactin (SUC)) on the biodegradation of naphthalene (NAP), chrysene (CHR), and pyrene (PYR), the representative components of PAHs, with CYP enzyme from microalgae Parachlorella kessleri using molecular docking and molecular dynamics (MD) simulation. The molecular docking analysis revealed that PAHs bound to residues at the CYP active site through hydrophobic interactions for biodegradation. The MD simulation showed that the surfactant addition changed the enzyme conformation in the CYP-PAH complexes to provide more interactions between the enzyme and PAHs. This led to an increase in the enzyme's capability to degrade PAHs. Binding free energy (ΔG‌‌Bind) calculations confirmed that surfactant treatment could enhance PAHs degradation by the enzyme. The SUC gave a better result on NAP and PYR biodegradation based on ΔG‌‌Bind, while TWE facilitated the biodegradation of CHR. The research outputs could greatly facilitate evaluating the behaviors of oil spill-treating agents and oil spill response operations in the marine environment.

Siderite with chelator as high-efficiency Fenton reagent to degrade naphthalene via ferrous liberation and carbon dioxide radical anion-mediated iron redox cycle

Siderite (FeCO3) has been verified to be an effective iron material in Fenton-like process, but large dose of FeCO3 and oxidants limits its application. Here, chelators were successfully used to enhance the degradation of naphthalene (NAP). When 1.0 mM of hydrogen peroxide (H2O2) and 1.0 g L−1 of FeCO3 were applied, in the presence of 0.2 mM oxalic acid (OA), 0.1 mM nitrilotriacetic acid (NTA), or 0.1 mM DL-tartaric acid (DL-TA), 99.3 %, 100 %, or 96.7 % of NAP was degraded within 24 h, respectively. The different roles of chelators were confirmed. For OA and DL-TA, due to weak complexation with iron ions, acid effect and generation of carbon dioxide radical anion (CO2−) contributed to high concentration of Fe2+, while for NTA, chelation and CO2− were two major factors. In addition, the excellent potential application of H2O2/FeCO3/chelator was determined because of (1) lower environmental risk of chemicals; (2) strong tolerance to water matrixes; (3) the excellent stability of FeCO3 confirmed by surface characterizations and cyclic experiment, as NAP was completely degraded after the 6th cycle. At last, H2O2/FeCO3/chelator had superiority over other reduced iron minerals due to lower running cost in lab study, better reusability, and environmental friendliness. Therefore, it is expected that H2O2/FeCO3/chelator technique can provide an effective alternative to Fenton-like process in remediation of NAP contaminated sites.

In-situ targeted removal of naphthalene from groundwater by peroxymonosulfate activation using molecularly imprinted activated carbon: Efficacy, mechanism and applicability

Efficient removal of low-concentration refractory polycyclic aromatic hydrocarbons (PAHs) pollutants is crucial for ensuring groundwater safety. In this study, surface molecularly imprinted catalyst (MIP@AC) was developed based on activated carbon (AC) and molecular imprinting technology, and then MIP@AC was introduced into the simulated permeable reaction barrier to evaluate the performance of MIP@AC activated peroxymonosulfate (PMS) in in-situ targeted remediation of naphthalene (NAP) contaminated groundwater. The results showed that the relative adsorption selectivity coefficient and relative degradation selectivity coefficient of the MIP@AC material relative to the non-imprinted material AC was as high as 31.47 and 10.88, respectively; that is, MIP@AC can better resist the interference of competitive pollutants and achieve efficient targeted removal of NAP. Additionally, the reactive oxygen species (ROS) yield was higher in the MIP@AC/PMS system compared to the AC/PMS system. The target pollutant NAP was precisely enriched in the imprinted cavity of the MIP@AC, realizing that ROS production and pollutant degradation occurred simultaneously in the MIP@AC imprinted cavity. Therefore, the spatial confinement effect of the imprinted cavity shortened the mass transfer distance between the ROS and NAP, thereby reducing the loss of ROS due to self-quenching. Besides, Cl- significantly promoted the targeted removal of NAP, while HCO3- had a slight inhibitory effect; humic acid had no effect because of its larger molecular structure, which does not fit into the small imprinted cavities preferred by NAP. Importantly, the MIP@AC/PMS system demonstrated effective anti-complex matrix interference ability and targeted removal performance for NAP under natural groundwater conditions. This study can promote further research on the surface molecularly imprinted catalyst/PMS system as a new strategy for in-situ targeted remediation technology of contaminated groundwater.

Formation of nitrated naphthalene in the sulfate radical oxidation process in the presence of nitrite

Polycyclic aromatic hydrocarbons (PAHs) have become a global environmental concern due to their potential hazardous implication for human health. In this study, we found that sulfate radical (SO4•−) could effectively degrade naphthalene (NAP), a representative PAH in groundwaters, generating 1-naphthol. This intermediate underwent further degradation, yielding ring-opening products including phthalic acid and salicylic acid. However, the presence of nitrite (NO2−), a prevalent ion in subsurface environments, was observed to compete with NAP for SO4•−, thus slowing down the NAP degradation. The reaction between NO2− and SO4•− generated a nitrogen dioxide radical (NO2•). Concurrently, in-situ formed 1-naphthol underwent further oxidization to the 1-naphthoxyl radical by SO4•−. The coupling of 1-naphthoxyl radicals with NO2• gave rise to a series of nitrated NAP, namely 2-nitro-1-naphthol, 4-nitro-1-naphthol, and 2,4-dinitro-1-naphthol. In addition, the in-situ formed phthalic acid and salicylic acid also underwent nitration, generating nitrophenolic products, although this pathway appeared less prominent than the nitration of 1-naphthol. When 10 μΜ NAP was subjected to heat activated peroxydisulfate oxidation in the presence of 10 μΜ NO2−, the total yield of nitrated products reached 0.730 μΜ in 120 min. Overall, the presence of NO2− dramatically altered the behavior of NAP degradation by SO4•− oxidation and contributed to the formation of toxic nitrated products. These findings raise awareness of the potential environmental risks associated with the application of SO4•−-based oxidation processes for the remediation of PAHs-polluted sites in presence of NO2−.

Toxic effects of polycyclic aromatic hydrocarbons on the two-sludge system: Combined functional gene, resistance gene and microbial community assessment

Polycyclic aromatic hydrocarbons (PAHs) were a class of persistent organic matter, and contained PAHs wastewater was discharged into wastewater treatment plants (WWTPs) finally, which could greatly affect their operational efficiency. The toxic effects of PAHs on the two-sludge system were assessed from functional genes, resistance genes, and microbial community. Three types of PAHs including Naphthalene (NAP), Anthracene (ANT), and Phenanthrene (PHE) were individually introduced into three separate two-sludge systems. Results showed that three types of PAHs did not adversely affect on nitrification performance, but exhibited a significant toxic effect on denitrification and phosphorus (PO43--P) removal. The effluent NH4+-N was almost 0 mg/L in all three systems, the highest total nitrogen (TN) removal rate was achieved at 90.88% in the PHE system, whereas the lowest rate was 72.46% in the ANT system. Concurrently, the PO43--P removal rate decreased from 93.10% to 51.22% in the ANT system. Functional genes, such as NORB and NIRS, and resistance genes such as PAH-RHD GNF/R and NAH-F/NH-R, were enriched in the PHE and NAP system, contributing to improved pollutant removal. However, the NIRK and PAH-RHD GPF/R were more abundant in the ANT system, resulting in varied pollutant removal capabilities. The composition of the microbial community was also influenced by PAH exposure with some specific functional bacteria being identified across the different systems. Among the PAHs tested, ANT was found to exert the highest toxicity towards the two-sludge system, surpassing the toxic effects of NAP and PHE. This study highlights the importance of considering PAH toxicity in the context of WWTPs operations and the potential need for tailored strategies to mitigate their impact on biological processes.

Characteristics of polycyclic aromatic hydrocarbons (PAHs) removal by nanofiltration with and without coexisting organics

Polycyclic aromatic hydrocarbons (PAHs) are contaminants of great concern owing to their persistence, toxicity, and bioaccumulation in aquatic environments. In this study, nanofiltration (NF) was used to investigate the removal of naphthalene (NAP) and phenanthrene (PHE) using three membranes of NF270, NF90, and DK. Subsequently, we examined the effects of coexisting organics on PAHs removal. Based on the results, DK was determined to be the optimal membrane for removing PAHs by comparing the membrane flux and pollutant rejection. The membrane flux reached 34.32 L/m2·h, and the NAP and PHE rejections were 92.21% and 97.85%, respectively, at transmembrane pressure (TMP) of 5 bar using DK. Coexisting organics decreased the membrane fluxes of NF270 and DK in the following order: protein > glucose > humic acid. The NAP and PHE rejections were obviously improved using NF270 in the following order: humic acid > protein > glucose. The PHE rejection was slightly improved using DK. A low concentration of organics could reduce the NAP rejection using DK; however, the NAP rejection could be restored at high concentrations of organics, except for humic acid. Coexisting organics could cause severe membrane fouling. The order of the effect of different coexisting organics on membrane fouling was protein > humic acid > glucose. The total investment and operating costs were about 1.47 and 0.187 million dollars, respectively, for treating PAHs solution using DK when the feed flow was 300 m3/d.

Zero valent iron and amorphous boron-assisted nano calcium peroxide/Fe(III) system for naphthalene degradation: Efficient performance and diverse mechanisms

Nano calcium peroxide (nCP) has attracted attention as an alternative for liquid H2O2-mediated advanced oxidation processes. However, the slow reduction kinetics of Fe(III) still significantly limit its application. Here, zero valent iron (ZVI) and amorphous boron (B) could remarkably promote the Fe(III)/Fe(II) cycle in nCP/Fe(III) system to generate various active species (HO•, O2−•, and 1O2) with HO• acting as the predominant role in naphthalene (NAP) degradation. nCP/Fe(III)/ZVI process could achieve 98.2% NAP degradation and 70.6% TOC removal, compared with 97.5% NAP degradation and 56.3% TOC removal in nCP/Fe(III)/B process. ZVI could donate electrons to Fe(III) to generate Fe(II) and itself could also be corroded to release Fe(II). B was stepwise oxidized (B0 to B(I)/B(II) to B2O3) and continuously supplied electrons to Fe(III) to ensure fast and long-lasting Fe(II) generation. Moreover, B2O3 was dissolved as H3BO3 in aqueous solution, which kept the B surface reactive for the continuous reduction of Fe(III). Although the two co-activators showed different promotion mechanisms in nCP/Fe(III) system, both systems exhibited excellent NAP degradation performance in different experimental conditions and various water matrixes. Overall, this study provided the strategies to overcome the limitation of nCP/Fe(III) system and extended its application potential in contaminants remediation.

Facilitated transport of toluene and naphthalene with humic acid in high- and low-permeability systems: Role of ionic strength and cationic type

The occurrence of colloids on pollutants transport in groundwater has attracted more attention. However, the research on the regulation mechanism of colloids on combined pollutants transport in heterogeneous aquifers is limited. In this study, a series of tank experiments were conducted to systematically investigate the effects of ionic strength, and cation type on humic acid (HA) facilitated transport of toluene (TOL), and naphthalene (NAP) in high- and low-permeability systems. The results showed that HA facilitated pollutants transport in low Na+ solution. In Ca2+ solution, the presence of HA hindered pollutants transport, and the inhibition increased with the increase of ionic strength. Both in Na+ solution and low Ca2+ solution, the influence of heterogeneous structure on pollutant transport played a dominant role, and TOL and NAP had a greater transport potential in the high permeability zone (HPZ) due to the preferential flow. Whereas, deposition of HA aggregates, and electrostatic attractive interaction had negative effects on transport than groundwater flow in high Ca2+ solution. Pollutants were prone to accumulate at the bottom of the HPZ, and the top of the low permeability zone (LPZ). These new findings provide insights into the mechanism of colloids influence on the pollutants transport in heterogenous aquifer.

Geochemical status of non-reclaimed ash dumps subjected to long-term self-overgrowing: Evidence from the Tyumen, Russia

Establishing the geochemical state of ash dumps of solid fuel thermal power plants in the absence of reclamation is extremely important in urban conditions. The current study was performed to assess the level, spatial distribution, soil pollution and risk of potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in soils of abandoned ash dumps from the city of Tyumen, Russia. In general, the soils of as dumps had elevated levels of PTEs and PAHs compared to the crustal abundance and global soil background. A number of metals, namely Sr, Ni, Cu, Cr, Zn, and V, were concentrated in the soils of ash dumps (2–6 times), while As, Co, and Pb slightly exceeded the citywide average (up to 1.5 times). Naphthalene (NAP) was the only representative of the studied PAHs, the concentrations of which in the soils of ash dumps significantly exceeded the median content in urban soils of Tyumen. Elevated levels of NAP are likely a consequence of frequent fires occurring in grassy areas. Spatial patterns of pollutants are mainly controlled by the initial heterogeneity of technogenic substrates, rather than the post-depositional processes including vegetation and soil cover development. Low and moderate pollution and human health risks of PTEs and PAHs were revealed in topsoils of the studied sites. Although elevated levels of pollutants in coal ash dump soils are due to peat combustion, they pose less of an environmental risk than the more common coal ash dumps and are potentially suitable for a wider variety of management practices.

Smoked and Fermented Bushmeat (Mpunam) Products: Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) Resulting From Processing.

The polycyclic aromatic hydrocarbons (PAHs) congener concentrations and risk upon human exposure to smoked bushmeat products were analyzed. GC/MS MRM and QuEChERS methods were used for the analysis. This work has become necessary due to the need for more information concerning the quantitative determination of these compounds and their health risk assessment. The 16 PAH congeners identified were acenaphthylene (ACA), naphthalene (NAP), acenaphthene (ACE), fluorene (FLU), anthracene (ANT), phenanthrene (PHE), fluoranthene (FLT), pyrene (PYR), benzo[b]fluoranthene (BBF), benzo[k]fluoranthene (BKF), benzo[a]anthracene (BAA), chrysene (CHR), indeno(1,2,3-cd)pyrene (IND), dibenzo(a,h)anthracene (DAA), benzo(g,h,i)pyrene (BGP), and benzo[a]pyrene (BAP). At the 5% and 95% daily intake levels, BAP was at 3.34 and 17.39 μg/kg(bw)/day, ΣPAH4 was at 25.11 and 109.15 μg/kg(bw)/day, and ΣPAH8 was at 55.76 and 236.68 μg/kg(bw)/day, respectively. BAP, ΣPAH4, and ΣPAH8 concentration exceeded the European Union limits, as BAP concentration was as low as 6.09 μg/kg and as high as 34.19. The exposure values were significantly high. Specifically, the margin of exposure for BAP was as low as 2.09 × 10-2; for ΣPAH4, it was 1.36 × 10--2; and for ΣPAH8, it was 1.95 × 10-2 all at the 95% level. These figures are substantially lower than the benchmark of 10,000, indicating a higher ILTCR. Furthermore, the ILTCR ranged from a minimum of 47.77 to a maximum of 248.53 at the 5% and 95% levels, respectively. This study makes smoked bushmeat a public health concern because the higher figures obtained indicate higher carcinogenicity upon consumption.

SOURCES OF POLYCYCLIC AROMATIC HYDROCARBONS IN LANDSCAPE COMPONENTS IN THE ZONE AFFECTED BY THE GORLOVO ANTHRACITE DEPOSIT

The content and composition of 19 priority polycyclic aromatic hydrocarbons (PAH) in the rocks and soils of dumps, mushrooms growing on them (Verpa bohemica and Suillus luteus), as well as infiltrated and thawed snow waters on the territory of the Gorlovo anthracite deposit were evaluated. It is shown that the main source of PAH in the components of technogenic and adjacent natural landscapes of the deposit are fine coal particles and products of their transformation of non-pyrogenic nature. The flux of PAH into the components of the environment occurs due to: 1) dust fallout near the road along which the extracted coal is transported; 2) transformation of anthracite inclusions in the upper horizons of coal-bearing soils of dumps; 3) migration of transformation products with infiltrated waters. A distinctive feature of the composition of PAH in the samples of the studied objects is the predominance of light PAH (LPAH) in rocks and coals and heavy PAH (HPAH) in infiltrated and thawed snow waters. The composition of the polyarenes of rocks is dominated by PHE (phenanthrene) > FLT (fluoranthene) > NAP (naphthalene), waters - FLT > PYR (pyrene) > CHR (chrysene). The composition of PAH of soils depends on the presence of coal inclusions. For carbonaceous soils, the predominant polyarenes are FLT > PYR > PHE = CHR. With depth in soils, the composition of PAHs changes and becomes close to the composition of soil-forming rocks. Mushrooms have a selective ability to absorb PAH. Regardless of the presence of coal in the soils on which the mushrooms grow, the predominant compounds are FLT for V. bohemica and PHE for S. luteus. Based on the results of the analysis of the principal components, as well as the correlation of the priority PAH indices with their total content and the content of carcinogenic polyarenes, it has been found that the most representative ratios for assessing the impact of technogenic sources associated with anthracite extraction and transportation are PHE/(PHE + CHR) and ΣLPAH/ΣHPAH.