Ultraviolet treatment and biodegradation of dibenzothiophene: Identification and toxicity of products

Chemotaxis-mediated degradation of PAHs and heterocyclic PAHs under low-temperature stress by Pseudomonas fluorescens S01: Insights into the mechanisms of biodegradation and cold adaptation

As wellknown persistent contaminants, polycyclic aromatic hydrocarbons (PAHs) and heterocyclic polyaromatic hydrocarbons (Heterocyclic PAHs)'s fates in cryogenic environments are remains uncertain. Herein, strain S01 was identified as Pseudomonas fluorescens, a novel bacterium tolerant to low temperature and capable of degrading PAHs and heterocyclic PAHs. Strain S01 exhibited growth at 5-40 ℃ and degradation rate of mixed PAHs and heterocyclic PAHs reached 52% under low-temperature. Through comprehensive metabolomic, genomic, and transcriptomic analyses, we reconstructed the biodegradation pathway for PAHs and heterocyclic PAHs in S01 while investigating its response to low temperature. Further experiments involving deletion and replacement of methyl-accepting chemotaxis protein (MCP) confirmed its crucial role in enabling strain S01's adaptation to dual stress of low temperature and pollutants. Additionally, our analysis revealed that MCP was upregulated under cold stress which enhanced strain S01's motility capabilities leading to increased biofilm formation. The establishment of biofilm promoted preservation of distinct cellular membrane stability, thereby enhancing energy metabolism. Consequently, this led to heightened efficiency in pollutant degradation and improved cold resistance capabilities. Our findings provide a comprehensive understanding of the environmental fate of both PAHs and heterocyclic PAHs under low-temperature conditions while also shedding light on cold adaptation mechanism employed by strain S01.

Assessing the hydroxyl radical and volatilization roles in aquatic fate estimations of sulfur heterocycles: Dibenzothiophene derivatives

Polycyclic aromatic sulfur heterocycles (PASHs) and their alkyl derivatives can be released into aquatic systems via crude oil spills or runoff from petroleum-treated areas, such as asphalt. Dibenzothiophene (DBT) and its derivatives (C1-DBT, C2-DBT, and C4-DBT) were chosen as model compounds to investigate the relative impact of volatilization and hydroxyl radical degradation on estimates of their overall dissipation after entry into aquatic ecosystems as a function of depth using the exposure analysis modeling system (EXAMS). The hydroxyl radical rate constant (K _· OH ) and Henry's law constant of PASHs were determined in distilled water. The analogue C1-DBT reacted fastest with · OH relative to other PASHs. The C2-DBT and C4-DBT analogues had higher Henry's law constants compared with other derivatives. Steric hindrance by alkyl substituents on the sulfur moiety most strongly impacted measured rate and Henry's law constants between DBT and individual alkyl derivatives. These steric effects do not appear to be considered in the physical property estimation software EPI Suite. Simulated dissipation of PASHs using EXAMS suggests that volatilization is a dominant fate pathway for the higher molecular weight and less polar C2-DBT and C4-DBT at all depths and DBT and C1-DBT at 0.1-m. However, model scenarios suggest that hydroxyl radical degradation may significantly contribute to the degradation of more polar DBT and C1-DBT at 1-m and 2-m depths. Environ Toxicol Chem 2017;36:1998-2004. © 2017 SETAC.

Influence of physical factors on polycyclic aromatic hydrocarbons (PAHs) content in vegetable oils

The aim of this study was to test the hypothesis about physical factors causing a significant decrease of polycyclic aromatic hydrocarbon (PAH) compounds in foodstuffs. For this purpose, extraction of 16 PAHs (prioritised by EPA) from selected foodstuffs (rapeseed oil and sunflower oil) was carried out. The changes in PAH content in oils exposed to selected physical factors (UV radiation, temperature and time) were observed. Oils under study were exposed to two types of UV radiation: direct and indirect (through a glass plate). In both experiments, a reduction of 16 PAHs in oils was recorded but in the latter a PAH reduction was not as high. In another experiment, the temperature of oils was raised to 40, 100 and 200°C. As a result, the content of PAHs has decreased significantly. In both cases, exposure to UV radiation and high temperature resulted in the reduction of PAHs, it was strongly correlated with the duration of experiments. The results showed relatively low contamination of oil with PAHs. Only for rapeseed oil, the level of said contamination was substantially higher than laid down limits.

Advances in Instrumental Analysis of Brominated Flame Retardants: Current Status and Future Perspectives

This review aims to highlight the recent advances and methodological improvements in instrumental techniques applied for the analysis of different brominated flame retardants (BFRs). The literature search strategy was based on the recent analytical reviews published on BFRs. The main selection criteria involved the successful development and application of analytical methods for determination of the target compounds in various environmental matrices. Different factors affecting chromatographic separation and mass spectrometric detection of brominated analytes were evaluated and discussed. Techniques using advanced instrumentation to achieve outstanding results in quantification of different BFRs and their metabolites/degradation products were highlighted. Finally, research gaps in the field of BFR analysis were identified and recommendations for future research were proposed.

The effect of salinity, redox mediators and temperature on anaerobic biodegradation of petroleum hydrocarbons in microbial fuel cells

Microbial fuel cells (MFCs) need to be robust if they are to be applied in the field for bioremediation. This study investigated the effect of temperature (20-50°C), salinity (0.5-2.5% (w/v) as sodium chloride), the use of redox mediators (riboflavin and anthraquinone-2-sulphonate, AQS) and prolonged fed-batch operation (60 days) on biodegradation of a petroleum hydrocarbon mix (i.e. phenanthrene and benzene) in MFCs. The performance criteria were degradation efficiency, % COD removal and electrochemical performance. Good electrochemical and degradation performance were maintained up to a salinity of 1.5% (w/v) but deteriorated by 35-fold and 4-fold respectively as salinity was raised to 2.5%w/v. Degradation rates and maximum power density were both improved by approximately 2-fold at 40°C compared to MFC performance at 30°C but decreased sharply by 4-fold when operating temperature was raised to 50°C. The optimum reactor performance obtained at 40°C was 1.15 mW/m(2) maximum power density, 89.1% COD removal and a degradation efficiency of 97.10%; at moderately saline (1% w/v) conditions the maximum power density was 1.06 mW/m(2), 79.1% COD removal and 91.6% degradation efficiency. This work suggests the possible application of MFC technology in the effective treatment of petroleum hydrocarbons contaminated site and refinery effluents.

Sequential chemical-biological processes for the treatment of industrial wastewaters: review of recent progresses and critical assessment

When direct wastewater biological treatment is unfeasible, a cost- and resource-efficient alternative to direct chemical treatment consists of combining biological treatment with a chemical pre-treatment aiming to convert the hazardous pollutants into more biodegradable compounds. Whereas the principles and advantages of sequential treatment have been demonstrated for a broad range of pollutants and process configurations, recent progresses (2011-present) in the field provide the basis for refining assessment of feasibility, costs, and environmental impacts. This paper thus reviews recent real wastewater demonstrations at pilot and full scale as well as new process configurations. It also discusses new insights on the potential impacts of microbial community dynamics on process feasibility, design and operation. Finally, it sheds light on a critical issue that has not yet been properly addressed in the field: integration requires complex and tailored optimization and, of paramount importance to full-scale application, is sensitive to uncertainty and variability in the inputs used for process design and operation. Future research is therefore critically needed to improve process control and better assess the real potential of sequential chemical-biological processes for industrial wastewater treatment.

Products of polycyclic aromatic sulfur heterocycles in oil spill photodegradation

Photo-oxidation is a potentially significant process in the degradation of crude oil spilled in the environment. The polycyclic aromatic sulfur heterocycles (PASHs) in an Egyptian crude oil (0.8 % sulfur) were photo-oxidized as a film on the surface of water in the presence of anthraquinone as photosensitizer under simulated solar irradiation. The polar photoproducts were characterized using negative ion electrospray ionization with time of flight mass spectrometry and, after trimethylsilylation, gas chromatography with mass spectrometry. The photoproducts identified revealed the presence of a large variety of sulfonic acids, aliphatic and aromatic acids, and alcohols. The data also give new information on the substituents of the aromatic compounds in the unexposed oil and indicate the presence of cyclohexyl substituted aromatic compounds.