O-Anisidines (OAs) are extensively used as an intermediate for chemical reactions to produce various triphenylmethane and azo dyes, and also in manufacturing numerous pigments. They are found to be highly toxic and have carcinogenic properties, so it is imperative to treat OA solutions before disposal. In this study a promising approach to degrade OA solutions has been carried out using Fenton’s reagent. Oxidation trials were conducted for 24 hours and various parameters – OA removal, pH, effect of H2O2 and Fe2+, and COD removal – were analysed to understand the oxidative degradation of OA. For varying initial OA concentrations, the OA and COD removal efficiencies of 72 to 85% and 62 to 74%, respectively, were obtained at pH = 3, and at different optimum H2O2 and Fe2+ doses. Lower initial concentrations of OA showed better removal efficiencies. The reaction time was estimated to 360 minutes after which there was negligible degradation occurs.

Immobilizing of zero-valent iron in mono- and bi-metallic systems on the bentonite clay surface as new nanocatalyst were synthesized and used to degrade model acidic dyes from aqueous media. The Fourier-transform infrared spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and Brunauer-Emmett-Teller analysis were used to characterize the synthesized nanocomposites, which demonstrated successful loading of nanoscale Fe-Cu bi-metallic onto bentonite support. Different variables controlling the congo red, methyl orange and methyl red dyes degradation using zero-valent iron based bimetallic nanoparticle on the bentonite clay surface as new nanocatalyst were concurrently optimized through an experimental design. Basic evaluations proved the nanocatalyst quantity, medium pH, initial dye concentration, and contact time as the most important variables influencing the degradation phenomenon and hence a response surface methodology based on the central composite design was conducted to determine the relations between the variables and the degradation efficiencies. The statistical factors (e.g. R2 and F-value) of the derived models were considered. Using response surface plots obtained through the models, the effects of the variables on the degradation efficiencies for each dye were assessed. Also, the Nelder-Mead non-linear optimizations were performed and the optimal degradation efficiencies at a 95% confidence level were determined which were found to comply with the respective experimental response values.

A microbially facilitated approach was developed to degrade 2, 2′, 4, 4′-tetrabrominated diphenyl ether (BDE-47). This approach consisted of biological production of Fe(II) and H₂O₂ by the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 during the repetitive anoxic/oxic cycles and abiotic production of hydroxyl radical (HO●) with the biologically produced Fe(II) and H₂O₂ via Fenton reaction. Under the condition tested, BDE-47 did not inhibit the growth of S. oneidensis MR-1. Water soluble Fe(III)-citrate and the solid minerals ferrihydrite [Fe(III)₂O₃•0.5H₂O] and goethite [Fe(III)OOH] were tested in this study. Under anoxic condition, the amounts of Fe(II) produced by S. oneidensis MR-1 varied among the Fe(III)s tested, which decreased in the order of Fe(III)-citrate > ferrihydrite > goethite. Under subsequent oxic condition, H₂O₂ was produced via O₂ reduction by S. oneidensis MR-1. The amounts of H₂O₂ detected also varied, which decreased in the order of the reactions with Fe(III)-citrate > goethite > ferrihydrite. S. oneidensis MR-1 maintained its ability to produce Fe(II) and H₂O₂ for up to seven anoxic/oxic cycles. At each end of anoxic/oxic cycle, HO● was detected. The amount of HO● produced decreased in the order of the reactions with ferrihydrite > goethite > Fe(III)-citrate, which was opposite to that of H₂O₂ detected. Compared to the controls without HO●, the amounts of BDE-47 in the reactions with HO● decreased. The more HO● in the reaction, the less amount of BDE-47 detected. Furthermore, no BDE-47 degradation was observed when HO● was scavenged or ferrihydrite was either omitted or replaced by nitrate. Finally, identification of degradation products, such as hydroxylated BDE-47 and trisBDE, dibromophenol and monobromophenol, suggested that OH-addition and Br-substitution by HO● were the main mechanisms for degrading BDE-47. Collectively, all these results demonstrated for the first time that the Fenton reaction driven by S. oneidensis MR-1 degraded BDE-47 effectively.

Mycotoxins are high toxic, widely distributed contaminants in foodstuff. In this study, a aflatoxin B1 (AFB1) degrading strain S. acidoaminiphila CW117 was screened, and its detoxification characteristics were investigated. Substrate AFB1 at 45 μg/L was degraded by CW117 within 24 h; meanwhile, 4.1 mg/L AFB1 was almost degraded within 48 h. After 24 h degradation, the biotoxicity of the detoxified culture was eliminated. Strain CW117 efficient degradation to AFB1 (especially to low AFB1 concentrations) suggested its potential significance to detoxification development on food and feedstuff. The active degradation components present in the cell-free supernatant. The degradation ratio increased constantly with increasing incubation temperature raised (0–90 °C) and was even stable at 90 °C. Degradation was optimal at pH 6–7, and was only partially inhibited by metal-chelators (EDTA and EGTA), proteinase K, and a protein denaturant (sodium dodecyl sulfate, SDS). The recombinant laccase rLC1 (0.5 mg/mL) from CW117 degraded 29.3% of AFB1 within 24 h; however, the cell-free supernatant degraded 76.7% of the toxin in same time, with much lower protein content. The results indicated the CW117 degrades AFB1 via a combination of enzymes and micro-molecule oxides.

Microplastic pollution is a major global environmental problem in both aquatic and terrestrial environments. Pesticides are frequently applied to agricultural soil to reduce the effects of pests on crops, but may also affect the degradation of plastics. In this study, we generated microplastics from polyethylene (PE) film and biodegradable poly(butylene adipate-co-terephthalate) (PBAT) film and determined (1) the effect of prothioconazole on degradation of the microplastics, and (2) the adsorption and release characteristics of heavy metals (Cr, Cu, As, Pb, Ba, and Sn) by the microplastics during degradation process. Changes of surface functional groups and morphologies were measured by FTIR and SEM, while metal concentrations were determined by ICPMS. Prothioconazole was found to promote plastic degradation. PBAT degraded faster and adsorbed more heavy metals from the soil than PE. Whether the microplastics adsorb or release heavy metals depended on the metal and their concentrations. Prothioconazole inhibited the adsorption of Cr, As, Pb and Ba by microplastics, promoted the adsorption of Cu, and had no significant effect for Sn. These results can help to assess the ecological risk of microplastic pollution from plastic mulch when combined with heavy metals.

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been banned around the world. However, DDT is still frequently detected in natural environments, particularly in aquaculture and harbor sediments. In this study, 15 surface sediment samples were collected from a typical tropical bay (Zhanjiang Bay) in the South China Sea, and the levels of DDT and its metabolites in sediment and porewater samples were investigated. The results showed that concentrations of DDXs (i.e., DDT and its metabolites) in bulk sediments were 1.58–51.0 ng g⁻¹ (mean, 11.5 ng g⁻¹). DDTs (DDT and its primary metabolites, dichlorodiphenyldichloroethane (DDD) and dichlorodiphenyldichloroethylene (DDE)) were the most prominent, accounting for 73.2%–98.3% (86.1% ± 12.8%) of the DDXs. Additionally, high-order metabolites (i.e., 1-chloro-2,2-bis(4′-chlorophenyl)ethylene (p,p′-DDMU), 2,2-bis(p-chlorophenyl)ethylene (p,p′-DDNU), 2,2-bis(p-chlorophenyl)ethanol (p,p′-DDOH), 2,2-bis(p-chlorophenyl)methane (p,p′-DDM), and 4,4′-dichlorobenzophenone (p,p′-DBP)) were also detected in most of the sediment and porewater samples, with DDMU and DBP being predominant. The DDTs concentration differed among the sampling sites, with relatively high DDTs concentrations in the samples from the aquaculture zone and an area near the shipping channel and the Haibin shipyard. The DDD/DDE ratios indicated a reductive dichlorination of DDT to DDD under anaerobic conditions at most of the sampling sites of Zhanjiang Bay. The possible DDT degradation pathway in the surface sediments of Zhanjiang Bay was p,p′-DDT/p,p′-DDD(p,p′-DDE)/p,p′-DDMU/p,p′-DDNU/ … /p,p′-DBP. The DDXs in the sediments of Zhanjiang Bay were mainly introduced via mixed sources of industrial DDT and dicofol, including fresh input and historical residue. The concentrations of DDXs in porewater samples varied from 66.3 to 250 ng L⁻¹, exhibiting a distribution similar to that in the accompanying sediments. However, the content of high-order metabolites was relatively lower in porewater than in sediment, indicating that high-order degradation mainly occurs in particles. Overall, this study helps in understanding the distribution, source, and degradation of DDT in a typical tropical bay.

Polycyclic aromatic hydrocarbons (PAHs) are prone to post-emission transformation and degradation to yield transformed PAH products (TPPs) that are potentially more hazardous than parent PAHs. This review provides a comprehensive evaluation of the potential environmental processes of PAHs such as sorption, volatilisation, photo- and bio-transformation and degradation on road surfaces, a significant accumulation point of PAHs. The review primarily evaluates key influential factors, toxicity implications, PAHs and TPPs fate and viable options for mitigating environmental and human health impacts. Photolysis was identified as the most significant transformation and degradation process due to the light absorption capacity of most PAHs. Climate conditions, physicochemical properties of road dust (sorbent), PAHs and TPPs and the existence of heavy metals such as Fe (III) are notable underlying factors for photolysis. Available data points to the predominance of carbonyl TPPs than other products such as nitro and hydroxyl TPPs with decreasing concentration trend of 9-fluorenone > 9,10-anthraquinone > benzo[a]fluorenone on road surfaces. The review recommends conducting future investigations targeting the influential factors pertaining to the fate of road deposited PAHs and TPPs. Furthermore, development of cost and time effective modern analytical methods is needed to quantify PAHs and TPPs present in minute quantities of samples. The review also identified that the unavailability of toxicity equivalency factors (TEF) for the most critical TPPs can be addressed using quantitative structure-activity relationship (QSAR) models and bioassays simultaneously. The content of this review is significant to the future work of researchers across various fields including analytical and environmental chemistry, stormwater pollution and toxicology.

Recently it was demonstrated that mealworm (Tenebrio molitor) larvae consume and biodegrade polystyrene. Thus, in this study a breeding investigation with various types of polystyrene was performed to follow the changes in the gut microbiome diversity. Polystyrene used for packaging purposes (PSp) and expanded polystyrene (EPS) were perceived as more favorable and attacked more frequently by mealworms compared to raw polystyrene (PS) and material commercially available for parcels (PSp). Although our studies showed that larvae could bite and chew selected materials, they are not able to degrade and use them for consumption purposes. In a next-generation sequencing experiment, among all samples, seven classes, Gammaproteobacteria, Bacilli, Clostridia, Acidobacteria, Actinobacteria, Alphaproteobacteria and Flavobacteria, were indicated as the most abundant, whereas the predominant genera were Enterobacter, Lactococcus and Enterococcus. Additionally, we isolated three bacteria strains able to use diverse types of bioplastic as a sole carbon source. The strains with biodegradable activity against bioplastic were identified as species of the genera Klebsiella, Pseudomonas and Serratia. The presence of a bacterial strain able to degrade bioplastic may suggest a potential niche for further investigations.

17β-estradiol (E2) often coexists with tetracyclines (TCs) in wastewater lagoons at intensive breeding farms, threatening the quality of surrounding water bodies. Microbial degradation is vital in E2 removal, but it is unclear how TCs affect E2 biodegradation. This primary study investigated the mechanisms of E2 degradation by Novosphingobium sp. ES2-1 in the presence of TCs and assessed the removal efficiency of E2 by strain ES2-1 in natural waters containing TCs. E2 biodegradation was unaffected at TCs concentrations below 0.1 mg L⁻¹ yet significantly inhibited at TCs above 10 mg L⁻¹. As elevation of TCs, E2 biodegradation rate constant decreased, and the biodegradation kinetics equation gradually deviated from the pseudo-first-order dynamics model. Importantly, the presence of TCs, especially at high-level concentrations, significantly hindered E2 ring-opening process but promoted the condensation of some phenolic ring-opening products with NH₃, thereby increasing the abundance of pyridine derivatives, which were difficult to decompose over time. Additionally, strain ES2-1 could remove 52.1–100% of nature estrogens in TCs-contaminated natural waters within 7 d. Results revealed the mechanisms of TCs in E2 biodegradation and the performance of a functional strain in estrogen removal in realistic TCs-contaminated aqueous solution.

Solutions of technical polychlorinated naphthalene (PCN) Halowax formulations (Halowax 1014 and Halowax 1051) diluted with Milli-Q water and sealed in the Pyrex glass tubes and quartz tubes were subjected to artificial solar and natural solar irradiation under different time intervals and field conditions. In particular, the results of several field irradiation experiments have shown increased PCN photodegradation as altitude increases above sea level. Irradiation in artificial solar conditions caused a substantial change in the PCN congener profiles of Halowax 1014 and Halowax 1051 test solutions. Interestingly, in long-term experiments, the relative abundance of congeners that contribute to dioxin-like activity, i.e. the compounds such as 1,2,3,5,7- and 1,2,4,6,7-PentaCN (PeCNs #52/60), 1,2,3,4,6,7- and 1,2,3,5,6,7-HexaCN (HxCNs #66/67), and 1,2,3,4,5,6,7-HeptaCN (HpCN #73), temporally increased substantially. In the field photodegradation experiments, the PCNs #52/60 and #66/67 were formed, while a relative persistence of PCN #73 was evident. Highest chlorinated octachloronaphthalene (OcCN #75), exposed to strong UV radiation at high altitude, was much less stable than lower molecular mass PCNs. Photodegradation of the technical PCN formulations produced also an unidentified aromatic compound. We conclude, that photodegradation of PCNs, which are considered as a widespread anthropogenic pollutants, is not restricted to any specific environmental condition. It can also be observed at low altitudes.