Tribromoacetic Acid Research Articles

The influence of trihaloacetic acids on the hydrogen sorption properties of palladium nanoparticles-modified AB5 alloy in aprotic ionic liquid: Towards ionic liquid-based electrolytes for hydride batteries

Binary mixtures of acetic acid/trihaloacetic acids with aprotic ionic liquid – 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MS]) are used as electrolytes for hydrogen electrosorption measurements. Preliminary studies are performed with palladium limited volume electrode to determine optimum concentration of the acid additives for hydrogen capacity and physicochemical properties of the electrolytes. The results obtained for trichloro- and tribromoacetic acid indicate that their decarboxylation occurs after mixing with [EMIM][MS] and dissolution of palladium is observed in contact with the decomposed electrolyte. Research on hydrogen capacity of palladium nanoparticles-modified AB5-type alloy is performed in mixtures of acetic acid and trifluoroacetic acid of optimum concentration. The best electrochemical performance is demonstrated by 2 M acetic acid/[EMIM][MS] mixture. The determined value of specific capacity of the investigated hydrogen absorbing material reaches 230 mAh g−1 and is close to that previously obtained from aqueous solutions of acids or bases.

Enhanced deep dehalogenation of brominated DBPs on vitamin B12 composite electrodes by the synergistic effect of UV irradiation: Accelerated formation of Co-Br bonds and enhanced mediation by atomic H*

Complete dehalogenation of halogenated organic pollutants has attracted increasing attention, and electrocatalytic reduction processes are considered prospective technologies due to their high selectivity for carbon-halogen bonds. In this study, a vitamin B12 (VB12) composite electrode was prepared and applied to remove the refractory tribromoacetic acid (TBAA). The reduction process dominated by the VB12 composite electrode showed a degradation efficiency of 55.2 % for 200 μg/L TBAA within 60 min. Interestingly, UV irradiation considerably increased the efficiency of TBAA for dehalogenation on the VB12 composite electrode. The photoelectrochemical co-catalytic system of a VB12 composite electrode coupled with UV (LP UV 254 nm) could remove 92.2 % of TBAA in 20 min with a rate constant 12 times higher than the VB12-only electrolysis system. The in situ Raman characterization and cyclic voltammetry tests confirmed that the accelerated formation of Co-Br bonds and the enhanced atomic H* mediated ability were responsible for improving debromination efficiency. The degradation of TBAA mainly underwent chemical reactions of debromination and mineralization. Acetic acid, formic acid, formaldehyde, and Br- were the major transformation products of TBAA. Acidic conditions favoured TBAA removal in the UV synergistic VB12 electrolytic system, and excellent cycling stability of debromination was obtained in complex aqueous environments (actual bodies of water containing various inorganic and organic matter). This research provides an efficient dehalogenation technology for halogenated micropollutants and novel perspectives on the scientific design of photoelectrochemical dehalogenation processes.

Improvement in radiation sensitivity of poly(methyl methacrylate) film dosimeters doped with Black100 via addition of sensitizers

We fabricated poly(methyl methacrylate) (PMMA) films containing Black100 and trichloroacetic acid (TCA), tribromoacetic acid (TBA), or bis(t-butylsulfonyl) diazomethane, a photoacid generator (BTDPAG), as sensitizers and measured their absorption spectra before and after X-ray irradiation. The films containing TCA, TBA, and BTDPAG exhibited absorption peaks attributed to the oxidized form of Black100. In a previous study, radiochromism due to the oxidation of Black100 was not observed in PMMA films containing only Black100. These results indicate that Black100 underwent oxidation by radicals or acids generated from the sensitizers by X-ray irradiation. The sensitivities of the PMMA films containing Black100 and the sensitizers were 4.5–6.4 times higher than those of the films without sensitizers in the dose range of 0.1–1 kGy. Although this is the comparison of sensitivities at different tube voltages and dose rates, by adding sensitizers, the sensitivity of the PMMA films, which are compatible with three-dimensional (3D) printing, was about one-third that of the widely recognized 3D radiochromic dosimeter, PRESAGE.

Optimization of a ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry method for monitoring haloacetic acids as chlorinated disinfection by-products in the fresh-cut industry

Haloacetic acids (HAAs) are one of the most important chlorinated disinfection by-products generated during water disinfection in the fresh-cut industry, and they can remain in the product, resulting in a consumer health risk. In this study, ultra-high-pressure liquid chromatography-tandem multiple reaction monitoring mass spectrometry (UHPLC-MRM) analysis used for drinking water was optimized and applied for the quantification of nine HAAs (HAA9) in fresh-cut lettuce and process water samples, with the complex matrix interferences for separation, and quantification problems. The method showed good selectivity, specificity and linearity, satisfactory values for trueness (recoveries of 80–116 %), precision (<22 %), and uncertainty (<55 %). Quantification limits varied from 1 to 5 µg L−1 or µg kg−1. The matrix effect for tribromoacetic, bromochloroacetic and chlorodibromoacetic acid was corrected by matrix-matched calibration and standard addition. After storage at -20 °C, only monobromoacetic acid was the HAA which loss happened after 7 days. The application of the methodology in lettuce and process water samples from the industry was successfully implemented. Therefore, this method could be employed for the quality control and regulatory analysis of HAAs in fresh products and process water from the fruit and vegetable industry.

Risks of obstructive genitourinary birth defects in relation to trihalomethane and haloacetic acid exposures: expanding disinfection byproduct mixtures analyses using relative potency factors.

Some disinfection byproducts (DBPs) are teratogens based on toxicological evidence. Conventional use of predominant DBPs as proxies for complex mixtures may result in decreased ability to detect associations in epidemiological studies. We assessed risks of obstructive genitourinary birth defects (OGDs) in relation to 12 DBP mixtures and 13 individual component DBPs. We designed a nested registry-based case-control study (210 OGD cases; 2100 controls) in Massachusetts towns with complete quarterly 1999-2004 data on four trihalomethanes (THMs) and five haloacetic acids (HAAs). We estimated temporally-weighted average DBP exposures for the first trimester of pregnancy. We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) for OGD in relation to individual DBPs, unweighted mixtures, and weighted mixtures based on THM/HAA relative potency factors (RPF) from animal toxicology data for full-litter resorption, eye defects, and neural tube defects. We detected elevated aORs for OGDs for the highest of bromodichloromethane (aOR = 1.75; 95% CI: 1.15-2.65), dibromochloromethane (aOR = 1.71; 95% CI: 1.15-2.54), bromodichloroacetic acid (aOR = 1.56; 95%CI: 0.97-2.51), chlorodibromoacetic acid (aOR = 1.97, 95% CI: 1.23-3.15), and tribromoacetic acid (aOR = 1.90; 95%CI: 1.20-3.03). Across unweighted mixture sums, the highest aORs were for the sum of three brominated THMs (aOR = 1.74; 95% CI: 1.15-2.64), the sum of six brominated HAAs (aOR = 1.43; 95% CI: 0.89-2.31), and the sum of nine brominated DBPs (aOR = 1.80; 95% CI: 1.05-3.10). Comparing eight RPF-weighted to unweighted mixtures, the largest aOR differences were for two HAA metrics, which both were higher with RPF weighting; other metrics had reduced or minimally changed ORs in RPF-weighted models.

Potential and mechanism of disinfection by-products removal in drinking water by bubbling corona discharge

Disinfection by-products (DBPs) with significant teratogenic and carcinogenic properties have become a growing concern among the public. As an efficient and environmentally friendly technology, non-thermal plasma offers potential for removing emerging micro-pollutants. In this study, the degradation performance of bubbling corona discharge was evaluated on 24 halogenated alicyclic and aliphatic DBPs present in drinking water at concentrations ranging from ng/L to μg/L. The degradation of DBPs followed pseudo-first-order kinetics with rate constants (kobs) in the descending order of halonitromethanes (HNMs), halogenated benzoquinones (HBQs), haloacetonitriles, trihalomethanes (THMs), haloketones, halogenated aldehydes, and haloacetic acids (HAAs). THMs, HNMs, and HBQs were effectively removed within 5 min under a discharge power of 28 W. Degradation rates achieved by plasma treatment surpass those of other conventional treatment technologies. The required energy consumption was in the range of 5–30 kW·h/m3/order.Furthermore, the study investigated the effects of discharge power, initial concentration, and economic analysis on the degradation of four selected DBPs as representatives of mono-, di- and multi-carbon-containing DBPs, namely chloroform (TCM) and bromoform (TBM), tribromoacetic acid (TBAA), and 2,3,5,6-tetrachloro-1,4-benzoquinone (TetraC-BQ). Reactive radicals in the plasma system were investigated using electron paramagnetic resonance, optical emission spectroscopy, fluorimetry, and radical scavengers. Hydrated electrons and hydroxyl radicals played an important role in the removal of DBPs. The intermediates generated during the degradation of TCM, TBM, TBAA, and TetraC-BQ were identified, and the possible degradation pathways for mono- and binary C-DBPs and HBQs were deduced. The breakdown of HBQs did not produce secondary contamination with aliphatic DBPs. The carbon in DBPs was primarily converted to formic acid, acetic acid, and oxalic acid, and the halogens were mainly converted to halogen ions. Additionally, luminescent bacteria toxicity testing confirmed that plasma treatment could reduce the acute toxicity of water samples. These findings demonstrate the potential of plasma treatment as a post-treatment device at the household level.

Genotoxicity and endocrine disruption potential of haloacetic acids in human placental and lung cells

Chlorination of water results in the formation of haloacetic acids (HAAs) as major disinfection byproducts (DBPs). Previous studies have reported some HAAs species to act as cytotoxic, genotoxic, and carcinogenic. This work aimed at further exploring the toxicity potential of the most investigated HAAs (chloroacetic (CAA), bromoacetic (BAA), iodoacetic (IAA) acid) and HAAs species with high content of bromine (tribromoacetic acid (TBAA)), and iodine in their structures (chloroiodoacetic (CIAA) and diiodoacetic acid (DIAA)) to human cells. Novel knowledge was generated regarding cytotoxicity, oxidative stress, endocrine disrupting potential, and genotoxicity of these HAAs by using human placental and lung cells as in vitro models, not previously used for DBP assessment. IAA showed the highest cytotoxicity (EC50: 7.5 μM) and ability to generate ROS (up to 3-fold) in placental cells, followed by BAA (EC50: 20–25 μM and 2.1-fold). TBAA, CAA, DIAA, and CIAA showed no significant cytotoxicity (EC50 > 250 μM). All tested HAAs decreased the expression of the steroidogenic gene hsd17b1 up to 40 % in placental cells, and IAA and BAA (0.01–1 μM) slightly inhibited the aromatase activity. HAAs also induced the formation of micronuclei in A549 lung cells after 48 h of exposure. IAA and BAA showed a non-significant increase in micronuclei formation at low concentrations (1 μM), while BAA, CAA, CIAA and TBAA were genotoxic at exposure concentrations above 10 μM (100 μM in the case of DIAA). These results point to genotoxic and endocrine disruption effects associated with HAA exposure at low concentrations (0.01–1 μM), and the usefulness of the selected bioassays to provide fast and sensitive responses to HAA exposure, particularly in terms of genotoxicity and endocrine disruption effects. Further studies are needed to define thresholds that better protect public health.

Toxicity evaluation of chlorinated natural water using Photobacterium phosphoreum: Implications for ballast water management

Chlorination of ballast water could produce harmful disinfection by-products (DBPs) and total residual oxidants. The International Maritime Organization calls for toxicity testing of discharged ballast water with fish, crustacea and algae to reduce the risk, but it is difficult to evaluate the toxicity of treated ballast water in a short time. Therefore, the purpose of this study was to analyze the applicability of luminescent bacteria to the assessment of residual toxicity of chlorinated ballast water. The toxicity unit for all treated samples were higher for Photobacterium phosphoreum than for microalgae (Selenastrum capricornutum and Chlorella pyrenoidosa), after adding neutralizer, all samples showed little effect on the luminescent bacteria and microalgae. For the DBPs, except for 2,4,6-Tribromophenol, Photobacterium phosphoreum could produce more sensitive and rapid test results than other species, the results in Photobacterium phosphoreum showed that the toxicity of DBPs in order of: 2,4-Dibromophenol > 2,6-Dibromophenol > 2,4,6-Tribromophenol > Monobromoacetic acid > Dibromoacetic acid > Tribromoacetic acid, and most binary mixtures (aromatic DBPs and aliphatic DBPs) presented synergistic effects based on the CA model. The aromatic DBPs in ballast water deserve more attention. In general, for ballast water management, the use of luminescent bacteria to evaluate the toxicity of treated ballast water and DBPs is desirable, this study could provide beneficial information for enhancing ballast water management.

Enhanced dehalogenation of brominated DBPs by catalyzed electrolysis using Vitamin B12 modified electrodes: Kinetics, mechanisms, and mass balances

Vitamin B12 (VB12) modified electrodes were prepared for the electrocatalytic reductive debromination of tribromoacetic acid (TBAA). Under galvanostatic conditions set as 5 mmol/L VB12 loading, 20 mmol/L Na2SO4 as electrolyte, 10.0 mA/cm2 current density, pH 3, and 298 K, the degradation efficiency of 200 μg/L TBAA at the VB12 modified electrode could reach 99.9 % after 6 h. The debromination of TBAA followed the first-order kinetic model. The masses of carbon and bromine elements were conserved before and after the reaction, together with the qualitative analysis of the degradation products showed the likely degradation pathways as TBAA→dibromoacetic acid (DBAA)→monobromoacetic acid (MBAA)→acetic acid (AA). ESR detection and quenching experiments confirmed the role of atomic H* in TBAA debromination. In-situ Raman spectroscopy showed that the Co-Br bond was strongly enriched to the electrode surface, accelerating the electron transfer. The H2O dissociation performance and transition states searching catalyzed by VB12 were calculated by Density Functional Theory (DFT) and proved that the composite electrode can effectively promote atomic H* generation. Material characterization and electrochemical performance tests showed that the VB12 modified electrode had excellent stability and atomic H* catalytic activity. The electrocatalytic debromination of TBAA at VB12 modified electrodes mainly involves two mechanisms, direct reduction by electron transfer and indirect reduction by the strongly reducing atom H*. The results provide an efficient way to achieve safe removal of brominated DBPs from drinking water after chlorination and before human consumption.

Insights into the oxidation of bisphenol A by peracetic acid enhanced with bromide: The role of free bromine

Peracetic acid (PAA) has received great attention in wastewater treatment as an alternative to free chlorine. However, wastewater constituents such as bromide (Br−) may affect the PAA-based oxidation process. In this study, we reported a detailed kinetic and mechanistic study on bisphenol A (BPA, 20 μM) oxidation by PAA in the presence of Br−. When the concentration of Br− was increased from 20 to 100 μM, the removal rate of BPA was significantly increased, which was attributed to the formation of secondary oxidant hypobromous acid. When BPA was treated with 5 mM PAA in the presence of 100 µM Br− at pH 7.0, ∼26 % of bromide was converted into organic bromine in 24 h. Brominated disinfection byproducts (Br-DBPs) accounted for ∼8.2 % of total organic bromine generated, among them the concentrations of bromoform (CHBr3), dibromoacetic acid (DBAA), and tribromoacetic acid (TBAA), were determined to be 0.94, 0.99, and 0.21 µM, respectively. A total of 23 transformation products were identified by high-resolution mass spectrometry (HRMS) analyses. Three transformation pathways, including CC (C1-C2 and C2-C4) bridge bond cleavage, phenyl ring bromination, and stepwise oxidation were proposed and rationalized by theoretical calculations. In conclusion, the presence of Br− can enhance the degradation efficiency of BPA in the PAA disinfection process; however, the formation of potentially carcinogenic brominated intermediates in Br−-containing wastewaters should be scrutinized.

Cancer Hazard Evaluations for Contemporary Needs: Highlights From New National Toxicology Program Evaluations and Methodological Advancements.

The National Toxicology Program strives to raise awareness of cancer hazards in our environment. Identifying cancer hazards is key to primary prevention, informing public health decision making, and decreasing the global cancer burden. In December 2021, the US congressionally mandated 15th Report on Carcinogens was released, adding 8 new substances to the cumulative report. Chronic infection withHelicobacter pyloriis listed as "known to be a human carcinogen." Antimony trioxide and 6 haloacetic acids found as water disinfection by-products-dichloroacetic acid, dibromoacetic acid, bromochloroacetic acid, tribromoacetic acid, bromodichloroacetic acid, chlorodibromoacetic acid-are listed as "reasonably anticipated to be a human carcinogen." A new dashboard provides interactive visualization and interrogation of the 256 listed substances, their uses, and associated cancers. Also, the National Toxicology Program recently published a Cancer Hazard Assessment Report on exposure scenarios associated with circadian disruption, concluding that persistent night shift work can cause breast cancer and certain lighting conditions may cause cancer.As highlighted in these reports and evaluations, we are evolving our approaches to meet contemporary challenges. These approaches include focusing on real-world exposures and advancing our methods to address challenges in cancer hazard assessments (eg, developing more structured approaches to evaluate mechanistic data and incorporating read-across approaches to assess chemicals lacking adequate human or animal cancer data). To promote public health, we provide information on environmental health disparities and disease prevention. Building on these efforts, we aim to continue our contributions to the war on cancer, declared 50 years ago.

Dissipative Formation of Covalent Basket Cages

AbstractLiving systems use chemical fuels to transiently assemble functional structures. As a step toward constructing abiotic mimics of such structures, we herein describe dissipative formation of covalent basket cage CBC 5 by reversible imine condensation of cup‐shaped aldehyde 2 (i.e., basket) with trivalent aromatic amine 4. This nanosized [4+4] cage (V=5 nm3, Mw=6150 Da) has shape of a truncated tetrahedron with four baskets at its vertices and four aromatic amines forming the faces. Importantly, tris‐aldehyde basket 2 and aliphatic tris‐amine 7 undergo condensation to give small [1+1] cage 6. The imine metathesis of 6 and aromatic tris‐amine 4 into CBC 5 was optimized to bias the equilibrium favouring 6. Addition of tribromoacetic acid (TBA) as a chemical fuel perturbs this equilibrium to result in the transient formation of CBC 5, with subsequent consumption of TBA via decarboxylation driving the system back to the starting state.

Dissipative Formation of Covalent Basket Cages.

Living systems use chemical fuels to transiently assemble functional structures. As a step toward constructing abiotic mimics of such structures, we herein describe dissipative formation of covalent basket cage CBC 5 by reversible imine condensation of cup‐shaped aldehyde 2 (i.e., basket) with trivalent aromatic amine 4. This nanosized [4+4] cage (V=5 nm3, M w=6150 Da) has shape of a truncated tetrahedron with four baskets at its vertices and four aromatic amines forming the faces. Importantly, tris‐aldehyde basket 2 and aliphatic tris‐amine 7 undergo condensation to give small [1+1] cage 6. The imine metathesis of 6 and aromatic tris‐amine 4 into CBC 5 was optimized to bias the equilibrium favouring 6. Addition of tribromoacetic acid (TBA) as a chemical fuel perturbs this equilibrium to result in the transient formation of CBC 5, with subsequent consumption of TBA via decarboxylation driving the system back to the starting state.

Disinfection byproducts in chlorinated or brominated swimming pools and spas: Role of brominated DBPs and association with mutagenicity

Although the health benefits of swimming are well-documented, health effects such as asthma and bladder cancer are linked to disinfection by-products (DBPs) in pool water. DBPs are formed from the reaction of disinfectants such as chlorine (Cl) or bromine (Br) with organics in the water. Our previous study (Daiber et al., Environ. Sci. Technol. 50, 6652; 2016) found correlations between the concentrations of classes of DBPs and the mutagenic potencies of waters from chlorinated or brominated swimming pools and spas. We extended this study by identifying significantly different concentrations of 21 individual DBPs in brominated or chlorinated pool and spa waters as well as identifying which DBPs and additional DBP classes were most associated with the mutagenicity of these waters. Using data from our previous study, we found that among 21 DBPs analyzed in 21 pool and spa waters, the concentration of bromoacetic acid was significantly higher in Br-waters versus Cl-waters, whereas the concentration of trichloroacetic acid was significantly higher in Cl-waters. Five Br-DBPs (tribromomethane, dibromochloroacetic acid, dibromoacetonitrile, bromoacetic acid, and tribromoacetic acid) had significantly higher concentrations in Br-spa versus Cl-spa waters. Cl-pools had significantly higher concentrations of Cl-DBPs (trichloroacetaldehyde, trichloromethane, dichloroacetic acid, and chloroacetic acid), whereas Br-pools had significantly higher concentrations of Br-DBPs (tribromomethane, dibromoacetic acid, dibromoacetonitrile, and tribromoacetic acid). The concentrations of the sum of all 4 trihalomethanes, all 11 Br-DBPs, and all 5 nitrogen-containing DBPs were each significantly higher in brominated than in chlorinated pools and spas. The 8 Br-DBPs were the only DBPs whose individual concentrations were significantly correlated with the mutagenic potencies of the pool and spa waters. These results, along with those from our earlier study, highlight the importance of Br-DBPs in the mutagenicity of these recreational waters.

Determination of Haloacetic Acids, Disinfection Byproducts, in Tap Water with Reversed-Phase Ultra-Performance Liquid Chromatography-High Resolution Mass Spectrometry

To establish a method for quantitative analysis of haloacetic acids (HAAs), disinfection byproducts, in tap water with reversed-phase ultra-performance liquid chromatography-quadrupole-orbitrap high resolution mass spectrometry. Tap water samples were collected and 0.70 g/L ascorbic acid was added to eliminate residual chlorine. Then, the water samples were directly injected into the instrument for analysis after filtration. After separation on a pentafluorobenzene (PFP) column with an inner diameter of 1.0 mm at a higher linear velocity and a lower volume flow rate compared with those of a narrow-bore column, nine HAAs, namely, monochloroacetic acid (MCAA), monobromoacetic acid (MBAA), dichloroacetic acid (DCAA), bromochloroacetic acid (BCAA), dibromoacetic acid (DBAA), trichloroacetic acid (TCAA), bromodichloroacetic acid（BDCAA), chlorodibromoacetic acid (CDBAA) and tribromoacetic acid (TBAA), were examined by negative electrospray ionization and full MS/dd-MS 2 acquisition mode. In order to adjust for the matrix effect, matrix matching calibration curves were used to quantitate the nine HAAs. Good linearity was obtained for each of the nine HAAs within their respective linear ranges. The detection limits and quantification limits of the method were 0.020-1.0 μg/L and 0.060-3.0 μg/L. The recoveries were 69.8%-119%. The proposed method showed strengths in separation speed and qualitative accuracy. It did not require for complicated pretreatment procedures and can meet the need of tap water sample analysis.

Degradation of bisphenol A by UV/persulfate process in the presence of bromide: Role of reactive bromine

Bromide (Br−), a ubiquitous species in natural water, is capable of reacting with sulfate radical (SO4∙−) and hydroxyl radical (∙OH) to form secondary reactive bromine species (RBS). The reaction routes can influence the degradation mechanisms and performance of these radicals for removal of target pollutants and may also form harmful bromine-containing disinfection by-products (Br-DBPs) during subsequent chlorination. In the present research, the UV-activated persulfate (PS) degradation of bisphenol A (BPA) was systematically examined in the presence of Br−. Results indicated that the presence of Br−enhanced the BPA degradation and both UV/PS and UV/PS/Br− processes followed the pseudo-first-order kinetics. At 0–0.8 mM Br−, 0.2 mM Br− exerted the best enhanced effect on BPA degradation, while RBS functioned as the major contributor in the presence of 0.05–0.5 mM Br−. Solution pH (6.0–8.0) barely affected the BPA degradation in the UV/PS system, but the introduction of Br− augmented the pH dependence. In the UV/PS/Br−system, the reaction rate constant of BPA increased/decreased with increasing PS/HA dosage, and was affected slightly in the presence of bicarbonate and chloride. According to the quantum chemical calculation, the second-order rate constants of BPA with ∙OH, SO4∙−, Br∙ and Br2∙− were calculated as 7.65 × 1010, 1.67 × 109, 1.77 × 108 and 2.83 × 102 M−1 s−1, respectively. Additionally, three degradation pathways of BPA were proposed based on DFT calculation and HPLC/MS analysis, and the formed bromine-containing products exhibited higher toxicity than BPA. Br-DBPs, particularly tribromomethane and tribromoacetic acid, generated from UV/PS/Br−pre-oxidation during BPA chlorination significantly increased the toxicity of total DBPs.

Effects of seawater intrusion on the formation of disinfection byproducts in drinking water

Seawater contains high levels of halides, which can increase the concentrations of bromide and iodide ions in coastal groundwater and surface water sources. Intrusion of seawater alters the chemistry of fresh water leading to the formation of additional brominated and iodinated disinfection byproducts (DBPs), many of which are cyto- and genotoxic to the mammalian cells, and have cancer risks to humans. In this study, effects of seawater intrusion on the formation of trihalomethanes (THMs), and haloacetic acids (HAAs) were investigated by spiking groundwater using 0.0–2.0% seawater (by volume) and liquid chlorine as disinfectant. The concentrations of bromide and iodide ions in groundwater (0.0% seawater) were 42.5 and non-detected (ND) μg/L respectively, which were increased up to 1100 and 2.1 μg/L respectively, following mixing with 2.0% seawater. The regulated THMs (THM4) were increased from 30.4 to 106.3 μg/L while iodinated THMs (I-THMs) were increased from 0.13 to 1.6 μg/L respectively due possibly to molecular substitution and additional pathways of THMs formation. Bromoform was increased from 0.5 to 94.3 μg/L while iodoform was increased from ND to 1.02 μg/L. HAAs were increased from 27.9 to 72.9 μg/L where tribromoacetic acid was increased from 2.0 to 43.7 μg/L. In 0.0% seawater, bromine incorporation factor (BIF) for THM4 and HAAs were 0.077 and 0.050 respectively, which were increased to 0.942 and 0.38 at 2% seawater respectively. For dihalogenated HAAs (X2AA) and trihalogenated HAAs (X3AA), BIF in 0.0% seawater were 0.098 and 0.14 respectively, which were increased to 0.863 and 0.924 for 2.0% seawater respectively. Mixing of 2.0 seawater increased the toxicity of THM4, HAAs and I-THMs by 4.2, 5.9 and 201.8 folds, respectively indicating the importance of reducing seawater intrusion into the freshwater sources. Further, alteration of water sources and/or adaptation of advanced treatment can assist in lowering the risks.

Nickel dual-atom catalysts for the selective electrocatalytic debromination of tribromoacetic acid as a green chemistry process

Electrocatalytic dehalogenation provides a promising strategy to degrade refractory tribromoacetic acid (TBAA) pollutant into nontoxic acetic acid (AA) and bromide ions. Herein, a novel atomic nickel anchored nitrogenated carbon (Ni1-N-C) featured of Ni-Ni dual-atom catalysts (DACs) was first reported for the electrochemical debromination of TBAA. At the potential of −0.86 V vs. SCE, nearly 100% of TBAA (10 mg/L) was reduced to AA by Ni1-N-C within 3 h with a high selectivity (88%), surpassing Pd nanoparticles (NPs), Ni NPs and Ag NPs. Moreover, Ni1-N-C exhibited outstanding cycling performance during the long-term test. It is found that TBAA debromination followed a stepwise pathway via a direct mechanism and accorded with a pseudo-first-order kinetics. Density functional theory calculations reveal that Ni-Ni DACs was responsible for the efficient and selective debromination of TBAA to AA owing to the optimized adsorption and desorption for reaction intermediates as compared to Ni single-atom catalysts (Ni-N3 and Ni-N4). This work presents new perspectives to rationally design novel and efficient atomic catalysts for the electrochemical dehalogenation.

Insights into unexpected photoisomerization from photooxidation of tribromoacetic acid in aqueous environment using ultrafast spectroscopy

Haloacetic acids are carcinogenic disinfection by-products (DPBs) and their photo-decomposition pathways, especially for those containing bromine and iodine, are not fully understood. In this study, femtosecond transient absorption (fs-TA) spectroscopy experiments were introduced for the first time to investigate the photochemistry of tribromoacetic acid. The fs-TA experiments showed that a photoisomerization intermediate species HOOCCBr2−Br (iso-TBAA) was formed within several picoseconds after the excitation of TBAA. The absorption wavelength of the iso-TBAA was supported by time-dependent density calculations. With the Second-order Møller-Plesset perturbation theory, the structures and thermodynamics of the OH-insertion reactions of iso-TBAA were elucidated when water molecules were involved in the reaction complex. The calculations also revealed that the isomer species were able to react with water with its reaction dynamics dramatically catalyzed by the hydrogen bonding network. The proposed water catalyzed OH-insertion/HBr elimination mechanism predicted three major photoproducts, namely, HBr, CO and CO2, which was consistent with the photolysis experiments with firstly reported CO formation rate and mass conversion yield as 0.096 min-1 and 0.75 ± 0.1 respectively. The spectroscopic technique, numerical tool and disclosed mechanisms provided insights on photodecomposition and subsequent reactions of polyhalo-DPBs contain heavy atom(s) (e.g., Br, I) with water, aliphatic alcohols or other nucleophiles.

Concentration Addition, Independent Action, and Quantitative Structure-Activity Relationships for Chemical Mixture Toxicities of the Disinfection By products of Haloacetic Acids on the Green Alga Raphidocelis subcapitata.

The potential toxicity of haloacetic acids (HAAs), common disinfection by products (DBPs), has been widely studied; but their combined effects on freshwater green algae remain poorly understood. The present study was conducted to investigate the toxicological interactions of HAA mixtures in the green alga Raphidocelis subcapitata and predict the DBP mixture toxicities based on concentration addition, independent action, and quantitative structure-activity relationship (QSAR) models. The acute toxicities of 6 HAAs (iodoacetic acid [IAA], bromoacetic acid [BAA], chloroacetic acid [CAA], dichloroacetic acid [DCAA], trichloroacetic acid [TCAA], and tribromoacetic acid [TBAA]) and their 68 binary mixtures to the green algae were analyzed in 96-well microplates. Results reveal that the rank order of the toxicity of individual HAAs is CAA > IAA ≈ BAA > TCAA > DCAA > TBAA. With concentration addition as the reference additive model, the mixture effects are synergetic in 47.1% and antagonistic in 25%, whereas the additive effects are only observed in 27.9% of the experiments. The main components that induce synergism are DCAA, IAA, and BAA; and CAA is the main component that causes antagonism. Prediction by concentration addition and independent action indicates that the 2 models fail to accurately predict 72% mixture toxicity at an effective concentration level of 50%. Modeling the mixtures by QSAR was established by statistically analyzing descriptors for the determination of the relationship between their chemical structures and the negative logarithm of the 50% effective concentration. The additive mixture toxicities are accurately predicted by the QSAR model based on 2 parameters, the octanol-water partition coefficient and the acid dissociation constant (pKa ). The toxicities of synergetic mixtures can be interpreted with the total energy (ET ) and pKa of the mixtures. Dipole moment and ET are the quantum descriptors that influence the antagonistic mixture toxicity. Therefore, in silico modeling may be a useful tool in predicting disinfection by-product mixture toxicities. Environ Toxicol Chem 2021;40:1431-1442. © 2021 SETAC.