The bacteria toxicity of nanoscale zero-valent iron (nZVI) can be changed during its application in water treatment but the toxicity mechanism is still not well understood, particularly under anaerobic conditions. Here, the toxicity of nZVI and its aging products towards Escherichia coli (E. coli) and the mechanisms of extracellular and intracellular reactive oxygen species (ROS) damage were deeply probed in the presence and absence of oxygen in ultrapure water. Under aerobic conditions, the ROS damage primarily caused by the generation of extracellular free •OH can be a major contributor to the toxicity of nZVI to E. coli. By contrast, in anaerobic nZVI treatment system, the intracellular •OH can be quenched by benzoic acid which is a cell permeable quencher and the electron spin resonance (ESR) signals of 5,5-dimethy-1-pyrroline (DMPO)- •OH were evidently observed in system with the addition of F⁻ which could desorb the surface •OH into solution. It indicated that the intracellular •OH adsorbed on the particle surface can also play an indispensable role in inactivating cells under anaerobic conditions. Moreover, nZVI can steeply decline the membrane potential, causing severe membrane disruption and therefore resulting in the stronger toxicity in anaerobic conditions. Furthermore, the chemical composition transformation of nZVI and generation of benign iron corrosion products (e.g., Fe₃O₄, γ-Fe₂O₃, γ-FeOOH) are mainly responsible for the reduced toxicity with the increasing aging time. These results provide insights into the extracellular and intracellular ROS damage occurred in aerobic and anaerobic nZVI treatment systems, offering more perspective to the risk assessment of nZVI application.

A new bacterium, Rhodococcus sp. S2-17, which could completely degrade an emerging organic pollutant, benzophenone-3 (BP-3), was isolated from contaminated sediment through an enrichment procedure, and its BP-3 catabolic pathway and genes were identified through metabolic intermediate and transcriptomic analyses and biochemical and genetic studies. Metabolic intermediate analysis suggested that strain S2-17 may degrade BP-3 using a catabolic pathway progressing via the intermediates BP-1, 2,4,5-trihydroxy-benzophenone, 3-hydroxy-4-benzoyl-2,4-hexadienedioic acid, 4-benzoyl-3-oxoadipic acid, 3-oxoadipic acid, and benzoic acid. A putative BP-3 catabolic gene cluster including cytochrome P450, flavin-dependent oxidoreductase, hydroxyquinol 1,2-dioxygenase, maleylacetate reductase, and α/β hydrolase genes was identified through genomic and transcriptomic analyses. Genes encoding the cytochrome P450 complex that demethylates BP-3 to BP-1 were functionally verified through protein expression, and the functions of the other genes were also verified through knockout mutant construction and intermediate analysis. This study suggested that strain S2-17 might have acquired the ability to catabolize BP-3 by recruiting the cytochrome P450 complex and α/β hydrolase, which hydrolyzes 4-benzoyl-3-oxoadipic acid to benzoic acid and 3-oxoadipic acid, genes, providing insights into the recruitment of genes of for the catabolism of emerging organic pollutants.

Despite high production and usage of parabens and bisphenols, little is known about their spatiotemporal distribution in the marine environment. In this study, we determined the concentrations of several parabens and their metabolites as well as bisphenol analogues in sediment collected from coastal areas of northern China. All sediment samples, including surface sediment and sediment cores, contained at least one of the parabens analyzed, and the total concentrations of parabens (ΣPBs; sum of six parabens) ranged from 1.37 to 24.2 ng/g dw (geometric mean: 3.30–6.09 g/g dw), which was comparable to or slightly higher than those found for the total concentrations of five detectable bisphenols (ΣBPAs; geometric mean: 2.18–4.61 ng/g dw). 4-hydroxybenzoic acid, a common metabolite of parabens, was found in all samples at concentrations in the range of 6.85–437 ng/g dw, which was one order of magnitude lower than those found for benzoic acid. Methyl-, ethyl-, and propyl-parabens were the predominant paraben analogues, collectively accounting for >88% of ΣPBs. Bisphenol A and bisphenol F were the two major bisphenols, collectively accounting for >86% of ΣBPAs. We also examined vertical profiles in concentrations of target analytes in sediment cores. The sediment core from the Shandong Peninsula showed a gradual increase in the concentrations of several parent and metabolic parabens as well as bisphenols during the past decade. Relatively higher concentrations of parabens and bisphenols were found in sediment cores collected from industrialized areas. Significant positive correlations were found among the concentrations of parabens in sediment, which suggested the existence of similar sources for these compounds. Overall, our findings suggest that the Bohai Sea coast is moderately contaminated with parabens and bisphenols in comparison to other coastal areas in China or elsewhere.

Understanding how engineered nanoparticles (ENPs) interact with natural organic acids is important to ecological risk assessment of ENPs, but this interaction remains poorly studied. Here, we investigate the dispersion stability, ion release, and toxicity of yttrium oxide nanoparticles (nY2O3) suspensions after exposure to two low molecular weight natural organic acids (LOAs), namely benzoic acid and gallic acid. We find that in the presence of LOAs the nY2O3 suspensions become more stable with surface zeta potential more positive or negative, accompanied by small agglomerated size. LOA interaction with nY2O3 is shown to promote the release of dissolved yttrium from the nanoparticles, depending on the concentrations of LOAs. Toxic effects of the nY2O3 suspensions incubated with LOAs on Scenedesmus obliquus as a function of their mixture levels show three types of signs: stimulation, inhibition, and alleviation. The mechanism of the effects of LOAs on the nY2O3 toxicity may be mainly associated with the degree of agglomeration, particle-induced oxidative stress, and dissolved yttrium. Our results stressed the importance of LOA impacts on the fate and toxicity of ENPs in the aquatic environment.

Phthalate ester (PAE) pollution is an increasing problem globally. Paracoccus kondratievae BJQ0001 was isolated from the fermentation starter of Baijiu and showed an efficient degradation capability toward PAEs. To our poor knowledge, this is the first report of a P. kondratievae strain capable of degrading PAEs. The first complete genome sequence of P. kondratievae was presented without gaps, and composed of two circular chromosomes and one plasmid. The species simultaneously degraded di-methyl phthalate (DMP), di-ethyl phthalate (DEP), di-butyl phthalate (DBP), di-isobutyl phthalate (DIBP) and di-(2-ethylhexyl) phthalate (DEHP), with DMP and DEP as the preferred substrates. The half-life (t₁/₂) of DMP was only 6.34 h with an initial concentration of 200 mg/L. Combined with gene annotation and metabolic intermediate analysis, a metabolic pathway was proposed for the species. Benzoic acid, the intermediate of anaerobic PAE metabolism, was identified in the aerobic degradation process. Two key enzymes for alkyl ester bond hydrolysis were obtained, and belonged to families IV and VI of hydrolases, respectively. These results will promote the investigation of PAE degradation by P. kondratievae, and provide useful information for improving the quality control of food and environmental PAE treatment.

This work evaluates the degradation of benzoic acid, a tracer from biomass burning, by different oxidation agents (Fe (III); H₂O₂; sunlight; and combinations of the previous ones) in model solutions and in real atmospheric waters. The extent of reactions was assessed by Ultraviolet–Visible and molecular fluorescence spectroscopies. The oxidation of benzoic acid occurred with the chemical oxidants Fe (III), H₂O₂, Fe (III) and H₂O₂ simultaneously in the presence of sunlight, and with Fe (III) and H₂O₂ simultaneously in the absence of light. The decrease of the pH value from neutral to acid for atmospheric waters generally increased the extent of oxidation. Sunlight was an important oxidation agent, and its combination with chemical oxidants increased the oxidation rate of benzoic acid, possibly due to the photogeneration of hydroxyl radicals. The results also suggested the occurrence of direct and indirect photolysis of benzoic acid in atmospheric waters. Moreover, the oxidation of benzoic acid produced new and more complex chromophoric compounds, which were then degraded. In addition, the nocturnal period is not sufficient for the full degradation of benzoic acid and of the intermediates formed by Fenton-like oxidation. The diurnal period may be enough for their full degradation through photo-Fenton-like oxidation, but this depends on the composition of the atmospheric waters, namely of the chromophoric content. Thus, this study highlights that benzoic acid from biomass burning, and its derivatives, may persist in atmospheric waters for periods of longer than one day, becoming available for other reactions, and may also affect the terrestrial and aquatic ecosystems through the wet depositions.

The aim of the study was to determine centimeter-scale spatial variation in mineralization potential in diffusely polluted soil. To this end we employed a 96-well microplate method to measure the mineralization of ¹⁴C-labeled organic compounds in deep-well microplates and thereby compile mineralization curves for 348 soil samples of 0.2-cm³. Centimeter-scale spatial variation in organic matter and the mineralization of glucose, benzoic acid, and PAHs (phenanthrene and pyrene) was determined for urban road-side soil sampled as arrays (7×11cm) of 96 subsamples. The spatial variation in mineralization was visualized by means of 2-D contour maps and quantified by means of semivariograms. The geostatistical analysis showed that the easily degradable compounds (glucose and benzoic acid) exhibited little spatial variation in mineralization potential, whereas the mineralization was highly heterogeneous for the PAH compounds that require specialized degraders. The spatial heterogeneity should be taken into account when estimating natural attenuation rates.

Petroleum-industry wastewater (PI-WW) is a potential source of water that can be reused in areas suffering from water stress. This water contains various fractions that need to be removed before reuse, such as light hydrocarbons, heavy metals and conditioning chemicals. Constructed wetlands (CWs) can remove these fractions, but the range of PI-WW salinities that can be treated in CWs and the influence of an increasing salinity on the CW removal efficiency for abovementioned fractions is unknown. Therefore, the impact of an increasing salinity on the removal of conditioning chemicals benzotriazole, aromatic hydrocarbon benzoic acid, and heavy metal zinc in lab-scale unplanted and Phragmites australis and Typha latifolia planted vertical-flow CWs was tested in the present study. P. australis was less sensitive than T. latifolia to increasing salinities and survived with a NaCl concentration of 12 g/L. The decay of T. latifolia was accompanied by a decrease in the removal efficiency for benzotriazole and benzoic acid, indicating that living vegetation enhanced the removal of these chemicals. Increased salinities resulted in the leaching of zinc from the planted CWs, probably as a result of active plant defence mechanisms against salt shocks that solubilized zinc. Plant growth also resulted in substantial evapotranspiration, leading to an increased salinity of the CW treated effluent. A too high salinity limits the reuse of the CW treated water. Therefore, CW treatment should be followed by desalination technologies to obtain salinities suitable for reuse. In this technology train, CWs enhance the efficiency of physicochemical desalination technologies by removing organics that induce membrane fouling. Hence, P. australis planted CWs are a suitable option for the treatment of water with a salinity below 12 g/L before further treatment or direct reuse in water scarce areas worldwide, where CWs may also boost the local biodiversity. [Figure not available: see fulltext.]

Rhizoctonia zeae SOL3 fungus was isolated from contaminated soil based on its ability to decolorize remazol brilliant blue R in solid medium. This fungus has been used to degrade pyrene a four-ring polycyclic aromatic hydrocarbon. R. zeae SOL3 could biodegrade pyrene as a sole source of carbon and energy. Different parameters were investigated to study their effect on the biodegradation rate. The highest biodegradation rate reached at 28 °C, non-agitated culture, 20 g/L glucose, 24 g/L NaCl, and 20 mg/L pyrene. The metabolites of pyrene were detected by thin layer chromatography (TLC) and confirmed by gas chromatography–mass spectrometry (GC-MS), which were identified as benzoic acid, 4-hydroxybenzoic acid and botanic acid.

The photocatalytic degradation effectiveness of six selected typical phytotoxic substances (ferulic, benzoic, gallic, salicylic, tannic, and acetic acid) by two levels of 10 nm TiO₂ (11 and 22 g/m²) immobilized on tiles under 254 nm of UV light irradiation was investigated. The results showed that the immobilized nano-TiO₂ significantly degraded all phytotoxic substances dissolved in distilled water, and the cumulative degradation rates of ferulic, benzoic, gallic, salicylic, tannic, and acetic acid reached 22.2, 33.6, 48.2, 56.9, 57.5, and 76.0 % after 6 h of treatment, respectively. Furthermore, the cumulative degradation rates of six phytotoxic substances by immobilized nano-TiO₂ were different remarkably, i.e., salicylic acid > benzoic acid, gallic acid > ferulic acid, acetic acid > tannic acid. The maximal photocatalytic degradation efficiencies of all phytotoxic substances appeared at the first 2 h in the three experiments. During the 6-h treatment period, the photocatalytic degradation efficiency of all phytotoxic substances decreased gradually. There was no significant difference in the photocatalytic degradation of benzoic acid and ferulic acid between the two levels of immobilized nano-TiO₂ treatments, whereas a significant difference was found in the photocatalytic degradation of salicylic acid, gallic acid, tannic acid, and acetic acid. In a word, nano-TiO₂ photocatalysis is an effective method to degrade phytotoxic substances. And the photocatalytic degradation effectiveness of six typical phytotoxic substances may be related to their structures.