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.

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.

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.

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.

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.

This study investigated the formation of volatile carbonaceous disinfection by-products (DBPs) and nitrogenous DBPs from chlorination of oxytetracycline. Six DBPs were identified including chloroform (CF), 1,1-dichloroacetone, 1,1,1-trichloroacetone (TCP), dichloroacetonitrile (DCAN), trichloroacetonitrile, and trichloronitromethane. DBP yields varied with different reaction conditions, including chlorine concentration, reacting time, pH, and bromide concentration. The highest DBP yields were found at Cl₂/C mass ratio and reaction time of 5 and 3 days, respectively. The solution pH had significant influence on CF, DCAN, and 1,1,1-TCP formation. The concentration of CF increased with the increase of pH, while DCAN and 1,1,1-TCP yields were high at acidic pH and decreased greatly under alkaline conditions. In the presence of bromide, the DBP composition shifted to multiple bromide compounds, including bromodichloromethane, dibromochloromethane, bromoform, bromochloroacetonitrile, and dibromoacetonitrile.

The toxicities of three synthetic surfactants to the marine macroalga, Ulva lactuca, have been examined by monitoring chlorophyll a fluorescence quenching. The anionic surfactant, sodium dodecyl sulphate (SDS), exerted no measurable toxicity over the concentration range 0–10 mg L−1, while presence of the non-ionic surfactant, Triton X-100 (TX), elicited a small reduction in photochemical efficiency that was independent of concentration. The cationic surfactant, hexadecyltrimethylammonium bromide (HDTMA), incurred a dose-dependent response to ∼3 mg L−1 (EC50 = 2.4 mg L−1), but a reduction in toxicity thereafter. Presence of TX had little effect on the toxicity of HDTMA but an equimolar concentration of SDS directly offset the impact of HDTMA on photochemical efficiency. Relative toxicities of the surfactants are attributed to differences in affinity for the algal surface and tendencies to disrupt cell membranes and interact with intracellular macromolecules. Non-linear dose responses and antagonistic effects are attributed to non-specific interactions between molecules of the same surfactant and electrostatic interactions between molecules of different amphiphilic character.

The objective of this study is to develop a method for using the single-well natural gradient drift test (SWNGDT) in the field to assess in situ aerobic cometabolism of trichloroethylene (TCE) and to analyze microbial community changes. The SWNGDT was performed in a monitoring well installed in a TCE-contaminated aquifer in Wonju, South Korea. The natural gradient drift biostimulation test (NGDBT) and surrogate test (NGDST) were performed by injecting dissolved solutes (bromide (a tracer), toluene (a growth substrate), ethylene (a nontoxic surrogate substrate to probe for TCE transformation activity), dissolved oxygen (DO, an electron acceptor), and nitrate (nutrient)) into the aquifer. Push–pull blocking tests (PPBT) were also performed to examine whether the monooxygenase of toluene oxidizers is involved in the degradation of toluene and the transformation of ethylene. Through the NGDBT, NGDST, and PPBT, we confirmed that the addition of toluene and oxygen in these field tests stimulated indigenous toluene utilizers to cometabolize aerobically TCE, with the following results: (1) the observed simultaneous utilization of toluene and DO; (2) the transformation of ethylene to ethylene oxide and propylene to propylene oxide; and (3) the transformation of TCE. Furthermore, the results of restriction fragment length polymorphism suggested that the microbial community shifts and the microbes capable of transforming TCE are stimulated by injecting the growth substrate, toluene.