During chlorine disinfection process, reactions between the disinfectant and 17β-estradiol (E2) lead to the formation of halogenated disinfection byproducts (DBPs) which can be a risk to both ecosystem and human health. The degradation and transformation products of E2 in sodium hypochlorite (NaClO) disinfection processes of different water samples were investigated. The reaction kinetics research showed that the degradation rates of E2 were considerably dependent on the initial pH value and the types of water samples. In fresh water, synthetic marine aquaculture water and seawater, the reaction rate constant was 0.133 min−1, 2.067 min−1 and 2.592 min−1, respectively. The reasons for the above phenomena may be due to the different concentrations of bromide ions (Br−) in these three water samples which could promote the reaction between NaClO and E2. Furthermore, Br− could also cause the formation of brominated DBPs (Br-DBPs). The main DBPs, reaction centers and conceivable reaction pathways were explored. Seven halogenated DBPs have been observed including three chlorinated DBPs (Cl-DBPs) and four Br-DBPs. The active sites of E2 were found to be the pentabasic cyclic ring and the ortho position of the phenol moiety as well as C9-C10 position. The identified Cl/Br-DBPs were also confirmed in actual marine aquaculture water from a shrimp pond. The comparison of bio-concentration factors (BCF) values based on calculation of EPI-suite showed that the toxicities of the Br-DBPs were stronger than that of their chloride analogues. The absorbable organic halogens (AOX) analysis also suggested that the DBPs produced in the marine aquaculture water were more toxic than that in the fresh water system.

How to evaluate the ecological risk of transgenic technology is a focus of scientists because of the safety concerns raised by genetically modified (GM) organisms. Nevertheless, most studies are based on individual chemicals and always analyze the GM organism as a type of toxicant. In this study, we changed the approach and used GM organisms as the test objects with normal chemical exposure. Three types of chemicals (two substituted phenols, 4-chlorophenol and 4-nitrophenol; two ionic liquids, 1-butylpyridinium chloride and 1-butylpyridinium bromide; two pesticides, dichlorvos and glyphosate) were used to construct a six-component mixture system. The lethality to wild-type (N2) and sod-3::GFP (SOD-3) Caenorhabditis elegans was determined when they were exposed to the same mixture system after 12 and 24 h. The results showed that the pEC50 values of all of the single chemicals on SOD-3 were greater than those on N2 at 24 h. The toxicities of the single chemicals and nine mixture rays on the two strains increased with time. Notably, we discovered a significant difference between the two strains; time-dependent synergism occurred in mixtures on N2, but time-dependent antagonism occurred in mixtures on SOD-3. Finally, the strength of the synergism or antagonism turned to additive action on the two strains as the exposure time increased. These findings illustrated that the GM factor of the nematode influenced the mixture toxicological interaction at some exposure times. Compared with N2, SOD-3 were more sensitive to stress or toxic reactions. Therefore, the influence of the GM factor on mixture toxicological interactions in environmental risk assessment must be considered.

Polyhalogenated carbazoles (PHCs) are a class of emerging organic contaminants that have received increasing concern due to their widespread distribution and dioxin-like toxicity. Although previous studies have suggested possible natural sources of PHCs in the environment, the formation pathways are poorly understood. Here we explored the production of PHCs from halogenation of carbazole in the presence of Br⁻ and/or Cl⁻ under the catalysis of chloroperoxidase (CPO) isolated from the marine fungus Caldariomyces fumago. Overall, a total of 25 congeners including mono-to tetra-substituted chlorinated, brominated, and mixed halogenated carbazoles (with substitution patterns of –BrCl, –BrCl2, –BrCl3, –Br2Cl, –Br2Cl2, and –Br3Cl) were produced from the reactions under various conditions. The PHC product profiles were apparently dependent on the halide concentrations. In the CPO-mediated chlorination of carbazole, 3-mono- and 3,6-dichlorocarbazoles predominated in the formation products. In addition to the less abundant mixed halogenated carbazoles (-Br2Cl), 1,3,6-tri- and 1,3,6,8-tetrabromocarbazoles were the dominant products in reactions containing both Br⁻ and Cl⁻. The CPO-catalyzed halogenation of carbazole could take place in pH 3–7, but the formation products were pH dependent. Results of this study suggest that CPO-catalyzed halogenation of carbazole may play an important role in the natural formation of PHCs.

Zerovalent iron (Fe0, ZVI) has drawn great interest as an inexpensive and effective material to promote the degradation of environmental contaminants. A focus of ZVI research is to increase degradation kinetics and overcome passivation for long-term remediation. Halide ions promote corrosion, which can increase and sustain ZVI reactivity. Adding chloride or bromide salts with Fe0 (1% w/v) greatly enhanced TNT, RDX, and HMX degradation rates in aqueous solution. Adding Cl or Br salts after 24 h also restored ZVI reactivity, resulting in complete degradation within 8 h. These observations may be attributed to removal of the passivating oxide layer and pitting corrosion of the iron. While the relative increase in degradation rate by Cl- and Br- was similar, TNT degraded faster than RDX and HMX. HMX was most difficult to remove using ZVI alone but ZVI remained effective after five HMX reseeding cycles when Br- was present in solution. The addition of halide ions promotes the degradation of high explosives by zerovalent iron.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the authors due to the results of a detailed investigation of the data quality conducted by the Central Analytical Laboratory (CAL) after relocation to the University of Wisconsin (UW) – Wisconsin State Laboratory of Hygiene. Using a subset of the 30 samples with the highest bromide ion (Br-) concentrations, the CAL at UW found 6 samples that could not be verified or were incorrect. Because the extent of the incorrect data is unknown, the NADP Executive Committee voted unanimously in May 2019 to discontinue public access to these data, and they decided to sequester all Br- data prior to June 2018. These issues were not obvious to the authors when the paper was written.The authors apologize for the inconvenience caused.

Aim of this study was to determine by Ion Chromatography ions (Na+, Ca++, Mg++, NH4+, Cl−, Br−, SO42−, NO3−, PO43−) in honeys (honeydew and floral nectar honeys) from different Italian Regions and from countries of the Western Balkan area. The compositional data were processed by multivariate analysis (PCA and HCA). Arboreal honeydew honeys from the Western Balkans had higher concentrations (from two to three times) of some environmental pollutants (Br−, SO42− and PO43− contents), due to industrial and agricultural activities, than those from Italian regions. The cationic profiles were very similar in both groups. Multivariate analysis indicated a clear difference between nectar honeys and arboreal/honeydew honeys (recognition of the botanical origin). These findings point to the potential of ionic constituents of honey as indicators of environmental pollution, botanical origin and authenticity.

N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4′-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O₃) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br⁻), bicarbonate ion (HCO₃⁻), sulfate ion (SO₄²⁻), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O₃ and ∙OH compared to that by O₃ alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br⁻ no matter with or without tBA. The presence of SO₄²⁻ and HCO₃⁻ ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7–8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O₃ however were significantly less pronounced over that by the joint roles of O₃ and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O₃ and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.

The catalytic effect of Cu(II) on the formation of disinfection by-products (DBPs) and chlorine degradation during chlorination of humic acid (HA) solutions was comparatively investigated under different experimental conditions. The experimental results showed that the total organic halogen (TOX) and trihalomethane (THM) formation increased with increasing Cu(II) concentration during chlorination, while haloacetic acids (HAAs) increased insignificantly. Accelerated chlorine decay and increased TOX and HAA formation were observed at high pH in the presence of 1.0 mg/L Cu(II) compared with that observed at low pH but THM formation decrease. Furthermore, the Cu(II) effect catalyzed the formation of brominated DBPs as it did for chlorine analogues in the presence of bromide ion. The microcalorimetry analysis demonstrated that more DBPs were formed in the Cu(II)-catalyzed chlorination, in which second-order rate constants obtained from reaction of HA with chlorine under given experimental conditions were 0.00256 M⁻¹ s⁻¹ (without Cu(II)) and 0.00865 M⁻¹ s⁻¹ (with Cu(II)), respectively. To discriminately examine the role of Cu(II) in greater detail, nine model compounds, which approximately represent the chemical structural units of HA, were individually oxidized by chlorine. It was demonstrated that carboxylic acids significantly enhanced the formation of TOX, THMs, and HAAs in the presence of Cu(II). Based on the previously published information and our experimental results, the possible pathway for Cu(II)-catalyzed TOX, THM, and HAA formation from chlorination of carboxylic acids were tentatively proposed.

Two types of hydrogels with different functional groups, trimethylamine on quaternary ammonium and dimethylethoxyamine on quaternary ammonium, were synthesized. Type 1 and type 2 hydrogels were characterized with Fourier transform infrared, X-ray photoelectron spectroscopy and zeta potential analysis. The anion selectivity of these two hydrogels was investigated. The surface charges of the type 2 hydrogel were lower than those of type 1, probably because of the presence of the hydroxyl group in the ethoxy group. The Cr(VI) removal capacity of type 2 hydrogel was, therefore, less than that of type 1 hydrogel, although their adsorption rates were similar. The anion selectivity of the hydrogels was found to have a similar order: Cr(VI) > sulphate > bromide > As(V). Under the co-presence of Cr(VI) and sulphate conditions, type 2 hydrogel shows a higher selectivity towards Cr(VI). The higher hydrophobicity was caused by the presence of the ethoxy group on the quaternary ammonium in type 2 hydrogel and thus increased in selectivity towards monovalent ions (i.e. HCrO 4 − ). In addition, the hydrogels have a high reusability. Compared with type 1 hydrogel, type 2 hydrogel has an advantage for applications in Cr(VI) removal and recovery processes.