The effect of adsorbent textural and functional properties on model naphthenic acid adsorption.

Naphthenic acids, NAs, are a major contaminant of concern and a focus of much research around remediation of oil sand process affected waters, OSPW. Using activated carbon adsorbents are an attractive option given their low cost of fabrication and implementation. A deeper evaluation of the effect NA structural differences have on uptake affinity is warranted. Here we provide an in-depth exploration of NA adsorption including many more model NA species than have been assessed previously with evaluation of adsorption kinetics and isotherms at the relevant alkaline pH of OSPW using several different carbon adsorbents with pH buffering to simulate the behaviour of real OSPW. Uptake for the NA varied considerably regardless of the activated carbon used, ranging from 350 mg/g to near zero highlighting recalcitrant NAs. The equilibrium data was explored to identify structural features of these species and key physiochemical properties that influence adsorption. We found that certain NA will be resistant to adsorption when hydrophobic adsorbents are used. Adsorption isotherm modelling helped explore interactions occurring at the interface between NA and adsorbent surfaces. We identified the importance of NA hydrophobicity for activated carbon uptake. Evidence is also presented that indicates favorable hydrogen bonding between certain NA and surface site hydroxyl groups, demonstrating the importance of adsorbent surface functionality for NA uptake. This research highlights the challenges associated with removing NAs from OSPW through adsorption and also identifies how adsorbent surface chemistry modification can be used to increase the removal efficiency of recalcitrant NA species.

Assessing Receptor Activation in 2D and 3D Cultured Hepatocytes: Responses to a Single Compound and a Complex Mixture.

Responding to global standards and legislative updates in Canada, including Bill S-5 (2023), toxicity testing is shifting towards more ethical, in vitro methods. Traditional two-dimensional (2D) monolayer cell cultures, limited in replicating the complex in vivo environment, have prompted the development of more relevant three-dimensional (3D) spheroidal hepatocyte cultures. This study introduces the first 3D spheroid model for McA-RH7777 cells, assessing xenobiotic receptor activation, cellular signaling, and toxicity against dexamethasone and naphthenic acid (NA)-fraction components; NAFCs. Our findings reveal that 3D McA-RH7777 spheroids demonstrate enhanced sensitivity and more uniform dose-response patterns in gene expression related to xenobiotic metabolism (AhR and PPAR) for both single compounds and complex mixtures. Specifically, 3D cultures showed significant gene expression changes upon dexamethasone exposure and exhibited varying degrees of sensitivity and resistance to the apoptotic effects induced by NAFCs, in comparison to 2D cultures. The optimization of 3D culture conditions enhances the model's physiological relevance and enables the identification of genomic signatures under varied exposures. This study highlights the potential of 3D spheroid cultures in providing a more accurate representation of the liver's microenvironment and advancing our understanding of cellular mechanisms in toxicity testing.

Photocatalytic treatment of diverse contaminants of potential concern in oil sands process-affected water.

Oil sands process-affected water (OSPW), generated by surface mining in Canada's oil sands, require treatment of environmentally persistent dissolved organic compounds before release to the watershed. Conventional chemical and mechanical treatments have not proved suitable for treating the large quantities of stored OSPW, and the biological recalcitrance of some dissolved organics may not be adequately addressed by conventional passive treatment systems. Previous work has evaluated photocatalytic treatment as a passive advanced oxidation process (P-AOP) for OSPW remediation. This work expands upon this prior research to further characterize the effects of water chemistry on the treatment rate and detoxification threshold. Under artificial sunlight, buoyant photocatalysts (BPCs) detoxified all OSPW samples within 1 week of treatment time with simultaneous treatment of polycyclic aromatic hydrocarbons, naphthenic acid fraction components (NAFCs), and un-ionized ammonia. Overall, these results further demonstrate passive photocatalysis as an effective method for treatment of OSPW contaminants of potential concern (COPCs).

Construction of Whole Cell Bacterial Biosensors as an Alternative Environmental Monitoring Technology to Detect Naphthenic Acids in Oil Sands Process-Affected Water.

After extraction of bitumen from oil sands deposits, the oil sand process-affected water (OSPW) is stored in tailings ponds. Naphthenic acids (NA) in tailings ponds have been identified as the primary contributor to toxicity to aquatic life. As an alternative to other analytical methods, here we identify bacterial genes induced after growth in naphthenic acids and use synthetic biology approaches to construct a panel of candidate biosensors for NA detection in water. The main promoters of interest were the atuAR promoters from a naphthenic acid degradation operon and upstream TetR regulator, the marR operon which includes a MarR regulator and downstream naphthenic acid resistance genes, and a hypothetical gene with a possible role in fatty acid biology. Promoters were printed and cloned as transcriptional lux reporter plasmids that were introduced into a tailings pond-derived Pseudomonas species. All candidate biosensor strains were tested for transcriptional responses to naphthenic acid mixtures and individual compounds. The three priority promoters respond in a dose-dependent manner to simple, acyclic, and complex NA mixtures, and each promoter has unique NA specificities. The limits of NA detection from the various NA mixtures ranged between 1.5 and 15 mg/L. The atuA and marR promoters also detected NA in small volumes of OSPW samples and were induced by extracts of the panel of OSPW samples. While biosensors have been constructed for other hydrocarbons, here we describe a biosensor approach that could be employed in environmental monitoring of naphthenic acids in oil sands mining wastewater.

Attenuation of phenylnaphthenic acids related to oil sands process water using solar activated calcium peroxide: Influence of experimental factors, mechanistic modeling, and toxicity evaluation.

Refractory naphthenic acids (NAs) are among the primary toxic compounds in oil sands process water (OSPW), a matrix with a complex chemical composition that poses challenges to its remediation. This study evaluated the effectiveness of calcium peroxide (CaO2) combined with solar radiation (solar/CaO2) as an advanced water treatment process for degrading model NAs (1,2,3,4-tetrahydronaphthalene-2-carboxylic acid, pentanoic acid, and diphenylacetic acid) in synthetic water (STW) and provide preliminary insights in treating real OSPW. Solar light and CaO2 acted synergistically to degrade target NAs in STW (>67 of synergistic factor) following a pseudo-first-order kinetic (R2 ≥ 0.95), with an optimal CaO2 dosage of 0.1 g L-1. Inorganic ions and dissolved organic matter were found to hinder the degradation of NAs by solar/CaO2 treatment; however, the complete degradation of NAs was reached in 6.7 h of treatment. The main degradation mechanism involved the generation of hydroxyl radicals (•OH), which contributed ∼90% to the apparent degradation rate constant (K), followed by H2O2 (4-5%) and 1O2 (0-5%). The tentative transformation pathways of three NAs were proposed, confirming an open-ring reaction and resulting in short-chain fatty acid ions as final products. Furthermore, a reduction in acute microbial toxicity and genotoxic effect was observed in the treated samples, suggesting that solar/CaO2 treatment exhibits high environmental compatibility. Furthermore, the solar/CaO2 system was successfully applied as a preliminary step for real-world applications to remove natural NAs, fluorophore organic compounds, and inorganic components from OSPW, demonstrating the potential use of this technology in the advanced treatment of oil-tailing-derived NAs.

Naphthenic Acid Corrosion Mitigation: The Role of Niobium in Low-Carbon Steel.

Naphthenic acid corrosion is a well-recognized factor contributing to corrosion in the construction of offshore industry pipelines. To mitigate the corrosive effects, minor quantities of alloying elements are introduced into the steel. This research specifically explores the corrosion effects arising from immersing low-carbon steel, specifically A333 Grade 6, in a naphthenic acid solution. Various weight percentages of niobium were incorporated, and the resulting properties were observed. It was noted that the addition of 2% niobium in low-carbon steel exhibited the least mass loss and a lower corrosion rate after a 12 h immersion in naphthenic acid. Microstructural analysis using scanning electron microscopy (SEM) revealed small white particles, indicating the presence of oil sediment residue, along with corrosion pits. Following the addition of 2% niobium, the occurrence of corrosion pits markedly decreased, and only minor voids were observed. Additionally, the chemical composition analysis using energy-dispersive X-Ray analysis (EDX) showed that the black spot exhibited the highest percentage of carbon, resembling high corrosion attack. Meanwhile, the whitish regions with low carbon content indicated the lowest corrosion attack. The results demonstrated that the addition of 2% niobium yielded optimal properties for justifying corrosion effects. Therefore, low-carbon steel with a 2% niobium addition can be regarded as a superior corrosion-resistant material for offshore platform pipeline applications.

The effect of rhizosphere pH on removal of naphthenic acid fraction compounds from oil sands process-affected water in a willow hydroponic system.

The extraction and processing of bitumen from the oil sands in northern Alberta, Canada generates large volumes of oil sands process-affected water (OSPW). OSPW contains a complex mixture of inorganic and organic compounds, including naphthenic acid fraction compounds (NAFCs) that are of particular concern due to their toxicity to aquatic organisms. Phytoremediation is a cost-effective, scalable approach that has the potential to remove NAFCs from OSPW and reduce OSPW toxicity. Environmental pH influences the chemical form and bioavailability of NAFCs. However, little is known about the influence of pH on the uptake of NAFCs in plant systems. This study sought to elucidate the impact of rhizosphere pH on the uptake of NAFCs using a sandbar willow (Salix interior) hydroponic system. To mimic and maintain the naturally low pH conditions of the root, OSPW solutions in these systems were adjusted to a low pH level (pH 5.0) and their NAFC uptake from solution was compared to that of OSPW at native pH (pH 8.0). Our findings revealed that the lower pH hydroponic systems demonstrated enhanced NAFC removal from solution as determined by LC-MS analysis, where up to 26% of NAFCs were removed from OSPW over 72 h at pH 5.0 compared to 8% removed at pH 8.0. Similarly, analysis of spike-in 13C-labeled NAs demonstrated that the OSPW hydroponic system rapidly removed a relatively labile NA (13C-cyclohexane carboxylic acid) from solution at both pH levels, whereas near complete removal of a recalcitrant NA (13C-1-adamantane carboxylic acid) was observed in pH 5.0 solutions only. These results provide insight into the importance of rhizosphere pH on efficient NAFC uptake by plant root systems. Further research will determine whether OSPW phytoremediation efficiency can be enhanced using field treatment conditions that promote low rhizosphere pH levels.

A multi-step approach: Coupling of biodegradation and UV photocatalytic oxidation TiO2 for the treatment of naphthenic acid fraction compounds in oil sands process-affected water.

Bitumen extraction in Alberta's oil sands region uses large volumes of water, leading to an abundance of oil sands process-affected water (OSPW). OSPW contains naphthenic acid fraction compounds (NAFCs) which have been found to contribute to OSPW toxicity. This study utilized a multistep treatment, coupling biological degradation with UV photocatalytic oxidation, and nutrient addition to boost the native microbial community's degradation capacity. OSPW initially contained 40-42 mg/L NAFCs with a toxicity of 3.8-3.9 TU. Initial biodegradation (Step 1) was used to remove the easily biodegradable NAFCs (11-25% removal), followed by a light or heavy dose of oxidation (Step 2) to breakdown the recalcitrant NAFCs (66-82% removal). Lastly, post-oxidation biodegradation with nutrients (Step 3) removed the residual bioavailable NAFCs (16-31% removal). By the end of the multistep treatment, the final NAFC concentrations and toxicity ranged from 5.3 to 6.8 mg/L and 1.1-1.2 TU. Analysis showed that OPSW was limited in phosphorus (below detection limit), and the addition of nutrients improved the degradation of NAFCs. Two treatments throughout the multistep treatment never received nutrients and showed minimal NAFC degradation post-oxidation. The native microbial community survived the stress from UV photocatalytic oxidation as seen by the post-oxidation NAFC biodegradation. Microbial community diversity was reduced considerably following oxidation, but increased with nutrient addition. The microbial community consisted predominately of Proteobacteria (Gammaproteobacteria and Alphaproteobacteria), and the composition shifted depending on the level of oxidation received. Possible NAFC-degrading microbes identified after a light oxidation dose included Pseudomonas, Acinetobacter and Xanthomonadales, while Xanthobacteracea and Rhodococcus were the dominant microbes after heavy oxidation. This experiment confirms that the microbial community is capable of degrading NAFCs and withstanding oxidative stress, and that degradation is further enhanced with the addition of nutrients.

Tungsten sulfide highly boosted Fe(III)/peroxymonosulfate system for rapid degradation of cyclohexanecarboxylic acid: Performance, mechanisms, and applications.

In this study, the Fe(III)/WS2/peroxymonosulfate (PMS) system was found to remove up to 97% of cyclohexanecarboxylic acid (CHA) within 10 min. CHA is a model compound for naphthenic acids (NAs), which are prevalent in petroleum industrial wastewater. The addition of WS2 effectively activated the Fe(III)/PMS system, significantly enhancing its ability to produce reactive oxidative species (ROS) for the oxidation of CHA. Further experimental results and characterization analyses demonstrated that the metallic element W(IV) in WS2 could provide electrons for the direct reduction of Fe(III) to Fe(II), thus rapidly activating PMS and initiating a chain redox process to produce ROS (SO4•-, •OH, and 1O2). Repeated tests and practical exploratory experiments indicated that WS2 exhibited excellent catalytic performance, reusability and anti-interference capacity, achieving efficient degradation of commercial NAs mixtures. Therefore, applying WS2 to catalyze the Fe(III)/PMS system can overcome speed limitations and facilitate simple, economical engineering applications.

Environmentally relevant concentrations of naphthenic acids initiate intestinal injury and gut microbiota dysbiosis in marine medaka (Oryzias melastigma).

Naphthenic acids (NAs) are important pollutants in marine crude oils and have obvious toxic effects on marine organisms. However, the effects of NAs on the intestine are largely unknown. Thus, we evaluated the effects of NAs exposure in the intestines of marine medaka. Fish were experimentally exposed to NAs (0.5 mg/L, 5 mg/L, and 10 mg/L) for 96 h and monitored for changes in intestinal histology, markers of oxidative stress, and intestinal microbiome responses. Significant mucosal damage, inflammation, and oxidative stress were observed in the intestines of marine medaka after exposure to NAs. In addition, significant changes in the gut microbiota were observed. Specifically, the relative abundance of Proteobacteria decreased, while that of Verrucomicrobiota increased in the high-concentration exposure group. In addition, nutrient synthesis and metabolism in the gut were affected. The results of this study contribute to a better understanding of the ecological risk of different concentrations of NAs to marine organisms. CAPSULE ABSTRACT: Changes in the gut microbial community of marine medaka (Oryzias melastigma) caused by naphthenic acids in the marine environment were investigated through the assessment of gut inflammatory factors and comprehensive analysis using 16S rDNA high-throughput sequencing. The results indicated the induction of intestinal inflammation and changes in the structural composition of the intestinal flora.

Comprehensive characterization of organics in oil sands process water in constructed mesocosms utilizing multiple analytical methods.

This study aims to provide a thorough characterization of dissolved organics in oil sands process water (OSPW) in field-based aquatic mesocosms at both molecular and bulk measurement levels using multiple analytical methods. In a 3-year outdoor mesocosm experiment, the analysis of naphthenic acid (NA) species was conducted using ultra-performance liquid chromatography time-of-flight mass spectrometry (UPLC-TOFMS). The results revealed the removal of both total NAs (38% and 35%) and classical NAs (O2-NAs, 58% and 49%) in undiluted and half-diluted OSPW, respectively. The increased ratios of oxidized NAs (O3-O6 NAs) to classical NAs suggested a transformation trend. The results also indicated that O2-NAs with higher carbon number and lower double bond equivalent (DBE) were more easily degraded in the mesocosm systems. Biomimetic extraction using solid-phase microextraction (BE-SPME) measurement displayed 26% (undiluted OSPW) and 30% (half-diluted OSPW) decrease in total bioavailable organics over 3 years. Naphthenic acids fraction compounds (NAFCs) obtained by liquid-liquid extraction (LLE) were also determined using Fourier transform infrared spectroscopy (FTIR). Reduction in acute toxicity for undiluted (43%) and half-diluted (26%) OSPW was observed over 3 years, which are well correlated with the decreases of NAs and BE-SPME concentrations. Moreover, BE-SPME values were found to be linearly correlated with total NAs concentrations (r = 0.96) and NAFCs (r = 0.96). Additionally, the linear relationships of individual O2-O6 NA species and BE-SPME concentrations unveiled the changes in the relative abundances of O2-O6 NA species in total bioavailable organics over time in the mesocosms. The present study has provided comprehensive insights by integrating various analytical methods, contributing valuable information for assessing the effectiveness of aquatic mesocosm systems in studying the temporal changes of organics in OSPW.

A model naphthenic acid decouples oxidative phosphorylation through selective inhibition of mitochondrial complex activity.

The naphthenic acid fraction compound (NAFC), 3,5-dimethyladamantane-1-acetic acid, was tested for its ability to uncouple mitochondrial oxidative phosphorylation. Mitochondria isolated from rainbow trout (Oncorhynchus mykiss) liver were exposed to 3,5-dimethyladamantane-1-acetic acid in state 3 and 4 respiration, and mitochondrial membrane potential were quantified. Electron transport chain (ETC) protein complexes were isolated using pharmacological agents and inhibitors, and their activities measured. The NAFC compound completely inhibited states 3 and 4 respiration with an IC50 of 0.77 and 1.01 mM, respectively. The NAFC compound partially uncoupled mitochondrial membrane potential in state 3 and 4 respiration with an IC50 of 2.19 and 1.73 mM, respectively. The NAFC impaired the activities of ETC protein complexes with a 9.5-fold range in sensitivity. The relative inhibitory effect of the ETC protein complexes to NAFC was CIV≥CI>CIII>CII. The impairment of mitochondrial oxidative phosphorylation by adamantane 3,5-dimethyladamantane-1-acetic acid is mediated via its inhibition of ETC protein complexes.

Microstructure-dependent CO2-responsive microemulsions for deep-cleaning of oil-contaminated soils.

CO2-responsive microemulsion (ME) is considered a promising candidate for deep-cleaning and oil recovery from oil-contaminated soils. Understanding the responsive nature of different microstructures (i.e., oil-in-water (O/W), bicontinuous (B.C.) and water-in-oil (W/O)) is essential for unlocking the potential and mechanisms of CO2-responsive emulsions in complex multiphase systems and providing comprehensive guidance for remediation of oil-contaminated soils. Herein, the responsiveness of microstructures of ME to CO2 trigger was investigated using experimental designs and coarse-grained molecular dynamic simulations. MEs were formed for the first time by a weakly associated pseudo-Gemini surfactant of indigenous organic acids (naphthenic acids, NAs are a class of natural surface-active molecules in crude oil) and tetraethylenepentamine (TEPA) through fine tuning of co-solvent of dodecyl benzene sulfonic acid (DBSA) and butanol. The O/W ME exhibited an optimal CO2-responsive character due to easier proton migration in the continuous aqueous phase and more pronounced dependence of configuration on deprotonated NA ions. Conversely, the ME with W/O microstructure exhibited a weak to none responsive characteristic, most likely attributed to its high viscosity and strong oil-NA interactions. The O/W ME also showed superior cleaning efficiency and oil recovery from oil-contaminated soils. The results from this study provide insights for the design of CO2-responsive MEs with desired performance and guidance for choosing the favorable operating conditions in various industrial applications, such as oily solid waste treatment, enhanced oil recovery (EOR), and pipeline transportation. The insights from this work allow more efficient and tailored design of switchable MEs for manufacturing advanced responsive materials in various industrial sectors and formulation of household products.

Biodegradation in oil sands process-affected water: A comprehensive laboratory analysis of the in situ biodegradation of dissolved organic acids.

Oil sands process-affected water (OSPW) is a by-product of the extraction of bitumen, and volumes of OSPW have accumulated across the Alberta oil sands region due to the governments zero-discharge policy. Some dissolved organics in OSPW, including toxic naphthenic acids (NAs), can be biodegraded in oxic conditions, thereby reducing the toxicity of OSPW. While there has been much focus on degradation of NAs, the biodegradation of other dissolved organic chemicals by endogenous organisms remains understudied. Here, using the HPLC-ultrahigh resolution Orbitrap mass spectrometry, we examined the microbial biodegradation of dissolved organic acids in OSPW. Non-targeted analysis enabled the estimation of biodegradation rates for unique heteroatomic chemical classes detected in negative ion mode. The microcosm experiments were conducted with and without nutrient supplementation, and the changes in the microbial community over time were investigated. Without added nutrients, internal standard-adjusted intensities of all organics, including NAs, were largely unchanged. The addition of nutrients increased the biodegradation rate of O2- and SO2- chemical classes. While anoxic biodegradation can occur in tailings ponds and end pit lakes, microbial community analyses confirmed that the presence of oxygen stimulated biodegradation of the OSPW samples studied. We detected several aerobic hydrocarbon-degrading microbes (e.g., Pseudomonas and Brevundimonas), and microbes capable of degrading sulfur-containing hydrocarbons (e.g., Microbacterium). Microbial community diversity decreased over time with nutrient addition. Overall, the results from this study indicate that toxic dissolved organics beyond NAs can be biodegraded by endogenous organisms in OSPW, but reaffirms that biological treatment strategies require careful consideration of how nutrients and dissolved oxygen may impact efficacy.

Sample preparation, analytical characterization, monitoring, risk assessment and treatment of naphthenic acids in industrial wastewater and surrounding water impacted by unconventional petroleum production.

Industrial extraction of unconventional petroleum results in notable volumes of oil sands process water (OSPW), containing elevated concentrations of naphthenic acids (NAs). The presence of NAs represents an intricate amalgamation of dissolved organic constituents, thereby presenting a notable hurdle for the domain of environmental analytical chemistry. There is growing concern about monitoring the potential seepage of OSPW NAs into nearby groundwater and river water. This review summarizes recent studies on sample preparation, characterization, monitoring, risk assessment, and treatment of NAs in industrial wastewater and surrounding water. Sample preparation approaches, such as liquid-liquid extraction, solid phase microextraction, and solid phase extraction, are crucial in isolating chemical standards, performing molecular level analysis, assessing aquatic toxicity, monitoring, and treating OSPW. Instrument techniques for NAs analysis were reviewed to cover different injection modes, ionization sources, and mass analyzers. Recent studies of transfer and transformation of NAs provide insights to differentiate between anthropogenic and natural bitumen-derived sources of NAs. In addition, related risk assessment and treatment studies were also present for elucidation of environmental implication and reclamation strategies. The synthesis of the current state of scientific knowledge presented in this review targets government regulators, academic researchers, and industrial scientists with interests spanning analytical chemistry, toxicology, and wastewater management.

Microbial degradation of naphthenic acids using constructed wetland treatment systems: metabolic and genomic insights for improved bioremediation of process-affected water.

Naphthenic acids (NAs) are a complex mixture of organic compounds released during bitumen extraction from mined oil sands that are important contaminants of oil sands process-affected water (OSPW). NAs can be toxic to aquatic organisms and, therefore, are a main target compound for OSPW. The ability of microorganisms to degrade NAs can be exploited for bioremediation of OSPW using constructed wetland treatment systems (CWTS), which represent a possible low energy and low-cost option for scalable in situ NA removal. Recent advances in genomics and analytical chemistry have provided insights into a better understanding of the metabolic pathways and genes involved in NA degradation. Here, we discuss the ecology of microbial NA degradation with a focus on CWTS and summarize the current knowledge related to the metabolic pathways and genes used by microorganisms to degrade NAs. Evidence to date suggests that NAs are mostly degraded aerobically through ring cleavage via the beta-oxidation pathway, which can be combined with other steps such as aromatization, alpha-oxidation, omega-oxidation, or activation as coenzyme A (CoA) thioesters. Anaerobic NA degradation has also been reported via the production of benzoyl-CoA as an intermediate and/or through the involvement of methanogens or nitrate, sulfate, and iron reducers. Furthermore, we discuss how genomic, statistical, and modeling tools can assist in the development of improved bioremediation practices.

Efficient removal of naphthenic acids from real petroleum wastewater by natural pyrite activated persulfate system.

The petroleum wastewater (PWW) contains a diverse range of recalcitrant organic contaminants. Of particular concern is the removal of naphthenic acids (NAs) due to the high toxicity and persistence. Persulfate (PS) based oxidation processes have shown promising in treating refractory wastewater, while the high costs of prepared catalysts limited their widespread implementation. This study aims to develop a cost-effective natural pyrite activated PS system for PWW treatment. The removal of NAs by pyrite/PS system was initially investigated. More than 90% of cyclohexanoic acid (CHA), a model NA, was removed in pyrite/PS system (2.0 g/L pyrite, 4.0 mM PS) at initial pH of 3-11. Scavenging experiments revealed that Fe(II) on pyrite surface was the reactive site for PS activation to generate reactive species, including sulfate radical (SO4·-), Fe(IV) and hydroxyl radical (·OH) for CHA degradation. Reactions of Fe(III) with S helped restore Fe(II) and enhance PS activation, resulting in the sustained catalytic activity of pyrites over five cycles. Cl-, SO42- and NO3- below 10 mM had minimal impact on CHA degradation in pyrite/PS system. However, over 1 mM of HCO3- inhibited 80% of CHA removal due to the buffer effect to maintain the high solution pH. Removing HCO3- from real PWW restored the removal of CHA and of total organic carbon (TOC) to over 90% and 71.3% in pyrite/PS system, respectively. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) results indicated that O2‒6 species including NAs were primarily eliminated through mineralization and oxygen addition. Besides, O3-5S, NO3-5S and N3O2‒4 species were the most susceptible to oxidation in PWW, resulting in the increase of the oxidation level (i.e., O/Cwa) from 0.41 to 0.56 after treatment. This study provides valuable insights into the treatment of NAs in real PWW, and potential application of natural minerals in the treatment of industrial wastewater.

Utilization of Fe-Ethylenediamine-N,N'-Disuccinic Acid Complex for Electrochemical Co-Catalytic Activation of Peroxymonosulfate under Neutral Initial pH Conditions.

The ethylenediamine-N,N'-disuccinic acid (EDDS) was utilized to form Fe-EDDS complex to activate peroxymonosulfate (PMS) in the electrochemical (EC) co-catalytic system for effective oxidation of naphthenic acids (NAs) under neutral pH conditions. 1-adamantanecarboxylic acid (ACA) was used as a model compound to represent NAs, which are persistent pollutants that are abundantly present in oil and gas field wastewater. The ACA degradation rate was significantly enhanced in the EC/PMS/Fe(III)-EDDS system (96.6%) compared to that of the EC/PMS/Fe(III) system (65.4%). The addition of EDDS led to the formation of a stable complex of Fe-EDDS under neutral pH conditions, which effectively promoted the redox cycle of Fe(III)-EDDS/Fe(II)-EDDS to activate PMS to generate oxidative species for ACA degradation. The results of quenching and chemical probe experiments, as well as electron paramagnetic resonance (EPR) analysis, identified significant contributions of •OH, 1O2, and SO4•- in the removal of ACA. The ACA degradation pathways were revealed based on the results of high resolution mass spectrometry analysis and calculation of the Fukui index. The presence of anions, such as NO3-, Cl-, and HCO3-, as well as humic acids, induced nonsignificant influence on the ACA degradation, indicating the robustness of the current system for applications in authentic scenarios. Overall results indicated the EC/PMS/Fe(III)-EDDS system is a promising strategy for the practical treatment of NAs in oil and gas field wastewater.

Evaluating the attenuation of naphthenic acids in constructed wetland mesocosms planted with Carex aquatilis.

Surface oil sands mining and extraction in northern Alberta's Athabasca oil sands region produce large volumes of oil sands process-affected water (OSPW). OSPW is a complex mixture containing major contaminant classes including trace metals, polycyclic aromatic hydrocarbons, and naphthenic acid fraction compounds (NAFCs). Naphthenic acids (NAs) are the primary organic toxicants in OSPW, and reducing their concentrations is a priority for oil sands companies. Previous evidence has shown that constructed wetland treatment systems (CWTSs) are capable of reducing the concentration of NAs and the toxicity of OSPW through bioremediation. In this study, we constructed greenhouse mesocosms with OSPW or lab process water (LPW) (i.e., water designed to mimic OSPW minus the NAFC content) with three treatments: (1) OSPW planted with Carex aquatilis; (2) OSPW, no plants; and (3) LPW, no plants. The OSPW-C. aquatilis treatment saw a significant reduction in NAFC concentrations in comparison to OSPW, no plant treatments, but both changed the distribution of the NAFCs in similar ways. Upon completion of the study, treatments with OSPW saw fewer high-molecular-weight NAs and an increase in the abundance of O3- and O4-containing formulae. Results from this study provide invaluable information on how constructed wetlands can be used in future remediation of OSPW in a way that previous studies were unable to achieve due to uncontrollable environmental factors in field experiments and the active, high-energy processes used in CWTSs pilot studies.

Assessment of the effect of short-term weathering on the molecular-level chemical composition of crude oils in contact with aquatic environments.

Multiple studies have focused on the effect of long-term weathering processes on oils after spill events, without considering the chemical compositional changes occurring shortly after the release of oil into the environment. Therefore, the present study provides a broad chemical characterization for understanding of the changes occurring in the chemical compositions of intermediate (°API = 27.0) and heavy (°API = 20.9) oils from the Sergipe-Alagoas basin submitted to two simulated situations, one under marine conditions and the other in a riverine environment. Samples of the oils were collected during the first 72 h of contact with the simulated environments, followed by evaluation of their chemical compositions. SARA fractionation was used to isolate the resins, which were characterized at the molecular level by UHRMS. The evaporation process was highlighted, with the GC-FID chromatographic profiles showing the disappearance of compounds from n-C10 until n-C16, as well as changes in the weathering indexes and pristane + n-C17/phytane + n-C18 ratios for the crude oils submitted to the riverine conditions. Analysis of the resins fraction showed that basic polar compounds underwent little or no alterations during the early stages of weathering. The marine environment was shown to be much less oxidative than the riverine environment. For both environments, a feature highlighted was an increase of acidic oxygenated compounds with the increase of weathering, especially for the crude oil with °API = 27.0.