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Iodinated disinfection by-products (I-DBPs) exhibited potential health risk owing to the high toxicity. Our recent study demonstrated that I-DBPs from Laminaria japonica (Haidai), the commonly edible seaweed, upon simulated household cooking condition were several hundred times more than the concentration of drinking water. Here, the characterization of Haidai and its leachate tandem with the formation, identification and toxicity of I-DBPs from the cooking of Haidai were systemically investigated. The dominant organic matter in Haidai leachate were polysaccharides, while the highest iodine specie was iodide (∼90% of total iodine). Several unknown I-DBPs generated from the cooking of Haidai were tentatively proposed, of which 3,5-diiodo-4-hydroxybenzaldehyde was dominant specie. Following a simulated household cooking with real chloraminated tap water, the presence of Haidai sharply increased aggregate iodinated trihalomethanes, iodinated haloacetic acids, and total organic iodine concentrations to 97.4 ± 7.6 µg/L,16.4 ± 2.1 µg/L, and 0.53 ± 0.06 mg/L, respectively. Moreover, the acute toxicity of Haidai soup to Vibrio qinghaiensis sp.-Q67 was around 7.3 times higher than that of tap water in terms of EC50. These results demonstrated that the yield of I-DBPs from the cooking of Haidai and other seaweed should be carefully considered.

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In this study, we demonstrate that Fe(III)-doped g-C3N4 can efficiently activate peracetic acid (PAA) to degrade electron-rich pollutants (e.g., sulfamethoxazole, SMX) over a wide pH range (3-7). Almost ∼100% high-valent iron-oxo species (Fe(V)) was generated and acted as the dominant reactive species responsible for the micropollutants oxidation based on the analysis result of quenching experiments, 18O isotope-labeling examination and methyl phenyl sulfoxide (PMSO) probe method. Electrochemical testing (e.g., amperometric i-t and linear sweep voltammetry (LSV)) and density functional theory (DFT) calculations illustrated that the main active site Fe atom and PAA underwent electron transfer to form Fe(V) for attacking SMX. Linear free energy relationship (LFER) between the pseudo-first-order rates of different substituted phenols (SPs) and the Hammett constant σ+ depicted the electrophilic oxidation properties. The selective oxidation of Fe(V) endows the established system remarkable anti-interference capacity against water matrices, while the Fe(V) lead to the formation of iodinated disinfection by-products (I-DBPs) in the presence of I-. Fe(III)-doped g-C3N4/PAA system showed excellent degradation efficiency of aquaculture antibiotics. This study enriches the knowledge and research of high-valent iron-oxo species and provides a novel perspective for the activation of PAA via heterogeneous iron-based catalysts and practical environmental applications.

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Iodinated disinfection by-products (I-DBPs) have attracted extensive interests because of their higher cytotoxicity and genotoxicity than their chlorinated and brominated analogues. Our recent studies have firstly demonstrated that cooking with seaweed salt could enhance the formation of I-DBPs with several tens of µg/L level. Here, I-DBP formation and mitigation from the reaction of disinfectant with Laminaria japonica (Haidai), an edible seaweed with highest iodine content, upon simulated household cooking process was systematically investigated. The total iodine content in Haidai ranged from 4.6 mg-I/g-Haidai to 10.0 mg-I/g-Haidai, and more than 90% of iodine is soluble iodide. During simulated cooking, the presence of disinfectant simultaneously decreased iodide by 15.0-32.8% to 2.7-5.8 mg/L and increased total organic iodine by 1.3-10.9 times to 0.5-1.8 mg/L in Haidai soup, proving I-DBP formation. The concentrations of iodinated trihalomethanes and haloacetic acids were at the levels of several hundreds of µg/L and several µg/L, respectively, which are 2-3 orders and 1-2 orders of magnitude more than those in drinking water. Effects of key factors including disinfectant specie, disinfectant dose, temperature and time on I-DBP formation were also ascertained, and temperature and disinfectant specie played a decisive role in the formation and speciation of I-DBPs. In order to avoid the potential health risk from the exposure of I-DBPs in Haidai soup, it is prerequisite to soak and wash dry Haidai sample over 30.0 min before cooking, which could effectively remove major soluble iodide. In general, this study provided the new insight into I-DBP formation from daily household cooking with Haidai and the corresponding enlightenment for inhabitants to eat Haidai in daily life.

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Different groups of disinfection by-products (DBPs) were studied through the degradation of iopamidol by the sequential oxidation process of ozone-low pressure ultraviolet light (O3-LPUV) followed by chlorination. This paper investigates the attenuation of iopamidol under this sequential treatment and the effect of chlorine contact time (30 min versus 3 days) to control the formation potential of DBPs: trihalomethanes (THMs), haloacetonitriles (HANs) and haloacetamides (HAMs). Thirty target DBPs among the 9 iodinated-DBPs (I-DBPs), were monitored throughout the sequential treatment. Results showed that O3-LPUV removed up to 99% of iopamidol, while ozone and LPUV alone removed only 90% and 76% respectively. After chlorine addition, O3-LPUV yielded 56% lower I-DBPs than LPUV. Increasing chlorine contact time resulted in higher concentrations of all DBP groups (THMs, HANs, and HAMs), with the exception of I-DBPs. One new iodinated-haloacetamide, namely chloroiodoacetamide (CIACM) and one iodoacetonitrile (IACN) were detected. These results suggest the iodine incorporated in iopamidol may be a precursor for iodinated-nitrogenous-DBPs, which are currently not well studied.

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Iodinated disinfection by-products (I-DBPs) have recently emerged as part of the pool of DBPs of public health concern. Due to limitations in measuring individual I-DBPs in a water sample, the surrogate measure of total organic iodine (TOI) is often used to account for the sum of all I-DBPs. In this study, TOI and total iodine (TI) are quantified in raw and treated waters in treatment trains at three sites in the Northeast United States. The occurrence, magnitude, and seasonality of these species was investigated within each sampling train and across the different sites. A regression model was developed to explore how TOI occurrence varies with routinely measured physical and chemical parameters in a water sample. The TOI and TI concentration at the three sites ranged from below the method detection limit to 18 µg/L and from 3 and 18.9 µg/L, respectively. There was substantial inter-monthly variability in TOI without a clear seasonal signal, and the concentration of TOI did not increase upon treatment. The results of the multivariate regression model showed that dissolved organic carbon (DOC), specific UV254 absorbance (SUVA), combined chlorine residual (TCl2), and pH were all significantly related to TOI concentration to varying degrees. A Tobit model was fit to show TOI predictions against observed (measured) TOI values. The model could explain approximately 46% of the variance of TOI concentrations in the treated waters.

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Iopamidol (IPM) is a potential source of toxic iodinated byproducts (I-DBPs) during water disinfection. In this work, we determined the kinetics and mechanism of degradation of IPM by a combination of ozone (O3) and peroxymonosulfate (PMS, HSO5-), and assessed its effect on the formation of iodinated trihalomethanes (I-THMs) during chlorination treatment. The degradation of IPM was accelerated by the O3/PMS process, and the hydroxyl (HO•) and sulfate (SO4•-) radicals were major contributors to the degradation. Using identification of the second order reaction rate between SO4•- and IPM (kSO4•-, IPM = 1.6 × 109 M-1 s-1), the contribution of HO• to the degradation was determined to be 78.3%. The degradation of IPM was facilitated by pH > 7, and natural organic matter (NOM) and alkalinity had limited effects on the degradation of IPM in the O3/PMS process. The transformation products of IPM were determined and inferred by QTOF-MS/MS, and the degradation pathways were elucidated. These include amide hydrolysis, amino oxidation, hydrogen abstraction, deiodination, and hydroxyl radical addition. Interestingly, oxidation of IPM by O3/PMS also decreased its potential for formation of I-THMs. After oxidation of IPM, the I-THMs formed from 5-µΜ IPM decreased from 14.7 µg L-1 to 3.3 µg L-1 during chlorination. Although the presence of NOM provided the precursor of I-THMs during chlorination of IPM, the O3/PMS process decreased I-THMs formation by 71%, because oxidation of released iodide into iodate effectively inhibited I-THMs formation. This study provides a new approach for the accelerated degradation of IPM and control of the formation of I-DBPs.

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In this study, the degradation kinetics of iopamidol (IPM) by three different UV-based oxidation processes including UV/hydrogen peroxide (H2O2), UV/persulfate (PDS) and UV/chlorine (NaClO) were examined and the potential formation of iodinated disinfection byproducts (I-DBPs) in these processes followed by sequential chlorination was comparatively investigated. Increasing pH led to the decrease of IPM degradation rate in UV/NaClO, while it showed negligible impact in UV/PDS and UV/H2O2. Common background constituents such as chloride ions (Cl-), carbonate (HCO3-) and natural organic matter (NOM) inhibited IPM degradation in UV/H2O2 and UV/PDS, while IPM degradation in UV/NaClO was only suppressed by NOM but not Cl- and HCO3-. The differences in transformation products of IPM treated by hydroxyl radical (HO*), sulfate radical (SO4*-), as well as Cl2*- and ClO* generated in these processes, respectively, were also analyzed. The results suggested that hydroxyl radical (HO*) preferred to form hydroxylated derivatives. Sulfate radical (SO4*-) preferred to oxidize amino group of IPM to nitro group, while Cl2*- and ClO* favored the generation of chlorine-containing products. Moreover, specific I-DBPs (i.e., iodoform (IF) and monoiodacetic acid (MIAA)) were detected in the three processes followed by chlorination. The addition of NOM had little effect on IF formation of three processes, while MIAA formation decreased in all processes except UV/H2O2. Given that the formation of I-DBPs in UV/NaClO was less than those formed in the other two processes, UV/NaClO seems to be a more promising strategy for effectively removing IPM with alleviation of I-DBPs in treated water effluents.

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Haloacetamides (HAMs), an emerging class of disinfection by-products, have received increasing attention due to their elevated cyto- and genotoxicity. However, only limited information is available regarding the iodinated analogues. This study investigated the formation and speciation of iodinated haloacetamides (I-HAMs) and their chlorinated/brominated analogues during the chloramination of bromide and/or iodide-containing waters and a model compound solution over various time periods. The rapid formation of diiodoacetamide (DIAM) was observed during chloramination of three simulated samples, whereas brominated (Br-HAMs) and chlorinated haloacetamides (Cl-HAMs) increased slowly with increasing reaction time. To further understand the differences in the formation of HAMs containing different halogens, experiments with the model compound asparagine in the presence/absence of iodide were conducted. Moreover, iodine utilisation factors and iodine incorporation factors were observed to increase significantly faster and were substantially higher than those of bromine. This implied that, compared with bromide, iodide has substantially greater potential to be transformed to the corresponding HAMs during chloramination, similar to that of other classes of DBPs. That is, I-HAMs formed faster than the other species investigated, including Cl-HAMs and Br-HAMs, in the early reaction stages (0-3 h). The effect of the bromide/iodide ratio (i.e., constant iodide, increasing bromide) on I-HAM formation was also examined. With increasing bromide/iodide ratio, the formation of Br-HAMs increased and dichloroacetamide decreased, but the formation of DIAM was largely unchanged. This was consistent with the constant level of iodide in spite of the increasing bromide. Chlorine and ammonia are applied separately during chloramination in water treatment, so the effect of pre-chlorination (before adding ammonia) on the formation and speciation of I-HAMs during in situ chloramination was also evaluated. Effective mitigation of DIAM formation with in situ chloramination was achieved, and the efficiency improved with increasing pre-chlorination time, where iodide was oxidised to iodate. The HAM-associated cytotoxicity was calculated to determine the change in toxicity at different reaction times, bromide/iodide ratios, and pre-chlorination times. A similar trend as the formation of I-HAMs was observed, which increased rapidly in the first 3 h, but decreased somewhat subsequently. When the bromide/iodide ratio and pre-chlorination time was increased, the calculated toxicity of the HAMs increased (due to more formation of Br-HAMs and less Cl-HAMs) and decreased (due to less DIAM formation), respectively.

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In order to reduce the formation of disinfection by-products (DBPs) during potabilization of water it is necessary to explore the potential of the source water and the applied treatment to generate these chemicals. This is actually more challenging in large drinking water networks that use different source waters to satisfy drinking water demand. In this regard, this work investigated the formation of DBPs in water matrices that are commonly supplied to the city of Barcelona and its metropolitan area. The regulated trihalomethanes and haloacetic acids were the most abundant DBP classes in these waters, followed by haloacetamides and haloacetonitriles or trihalogenated acetaldehydes (THALs). On the contrary, the formation potential of iodo-DBPs was minor. Mixing of drinking water treatment plant finished waters with desalinated water decreased the overall DBP formation potential of the water but resulted in the increased formation of brominated DBPs after long chlorine contact time. The formation of most DBPs was enhanced at high water temperatures (except for Br-THALs) and increasing residence times. Potential cytotoxicity and genotoxicity of the DBP mixtures were mainly attributed to the presence of nitrogen-containing DBPs and HAAs.

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Presence of iodinated X-ray contrast media (ICMs) in source water is of high concern, because of their potential to form highly toxic iodinated disinfection by-products (I-DBPs). This study investigated kinetics, mechanisms and products for oxidation of one ICMs, iopamidol (IPM) by ferrate (Fe(VI)). The obtained apparent second-order rate constants for oxidation of IPM by Fe(VI) ranged from 0.7 M-1 s-1 to 74.6 M-1 s-1 at pH 6.0-10.0, which were highly dependent on pH. It was found that the oxidation of IPM by Fe(VI) led to the formation of highly toxic I-DBPs. Iodoform (IF), iodoacetic acid and triiodoacetic acid formations were observed during the oxidation and IF dominated the formed I-DBPs. The formation of I-DBPs was also governed by pH and the maximum formation of I-DBPs occurred at pH 9.0. Transformation pathways of IPM by Fe(VI) oxidation were speculated to proceed through deiodination, amide hydrolysis and oxidation of amine reactions. The deiodination reaction during the oxidation of IPM by Fe(VI) contributed to the formation of I-DBPs. The formation of I-DBPs during the oxidation of IPM by Fe(VI) was significantly higher than those of iohexol, diatrizoate and iopromide, which was consistent with the lowest molecular orbital energy gap of IPM. Although Fe(VI) is considered as a green oxidant, the formation of highly toxic I-DBPs during the oxidation of IPM should receive great attention.

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Iodinated X-ray contrast media (ICM) is considered as one of iodine sources for formation of toxic iodinated disinfection byproducts (I-DBPs) during disinfection. This study investigated transformation of a typical ICM, iopamidol (IPM) by zero valent iron (ZVI) and the effect of transformation on the formation of I-DBPs during chloramination. It was found that the presence of ZVI could deiodinate IPM into I- and the transformation of IPM exhibited a pseudo-first-order kinetics. Acidic circumstance, SO42-, Cl- and monochloramine could promote the transformation of IPM by ZVI, while SiO32- inhibited the transformation of IPM. Moreover, the transformation of IPM by ZVI changed both the formed species and amounts of I-DBPs during chloramination. During the chloramination of IPM-containing water, CHCl2I and iodoacetic acid were the predominant iodinated trihalomethanes (I-THMs) and iodinated haloacetic acids (I-HAAs), respectively in the absence of ZVI, while CHI3 and triiodoacetic acid became the predominant ones with 1.0 g L-1 ZVI. The addition of 5.0 g L-1 ZVI increased I-DBPs formation amounts by 6.0 folds after 72 h and maximum formation of I-DBPs occurred at pH 5.0. Enhanced I-DBPs formation was also observed with various real water sources. Given that ZVI ubiquitously exists in the unlined cast iron distribution pipes, the deiodination of IPM by ZVI during distribution may increase the formation of I-DBPs, which needs receive enough attention.

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Iodine containing disinfection by-products (I-DBPs) and haloacetaldehydes (HALs) are emerging disinfection by-product (DBP) classes of concern. The former due to its increased potential toxicity and the latter because it was found to be the third most relevant DBP class in mass in a U.S. nationwide drinking water study. These DBP classes have been scarcely investigated, and this work was performed to further explore their formation in drinking water under chlorination and chloramination scenarios. In order to do this, iodo-trihalomethanes (I-THMs), iodo-haloacetic acids (I-HAAs) and selected HALs (mono-HALs and di-HALs species, including iodoacetaldehyde) were investigated in DBP mixtures generated after chlorination and chloramination of different water matrices containing different levels of bromide and iodide in laboratory controlled reactions. Results confirmed the enhancement of I-DBP formation in the presence of monochloramine. While I-THMs and I-HAAs contributed almost equally to total I-DBP concentrations in chlorinated water, I-THMs contributed the most to total I-DBP levels in the case of chloraminated water. The most abundant and common I-THM species generated were bromochloroiodomethane, dichloroiodomethane, and chlorodiiodomethane. Iodoacetic acid and chloroiodoacetic acid contributed the most to the total I-HAA concentrations measured in the investigated disinfected water. As for the studied HALs, dihalogenated species were the compounds that predominantly formed under both investigated treatments.

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The comprehensive control efficiency for the formation potentials (FPs) of a range of regulated and unregulated halogenated disinfection by-products (DBPs) (including carbonaceous DBPs (C-DBPs), nitrogenous DBPs (N-DBPs), and iodinated DBPs (I-DBPs)) with the multiple drinking water treatment processes, including pre-ozonation, conventional treatment (coagulation-sedimentation, pre-sand filtration), ozone-biological activated carbon (O3-BAC) advanced treatment, and post-sand filtration, was investigated. The potential toxic risks of DBPs by combing their FPs and toxicity values were also evaluated. The results showed that the multiple drinking water treatment processes had superior performance in removing organic/inorganic precursors and reducing the formation of a range of halogenated DBPs. Therein, ozonation significantly removed bromide and iodide, and thus reduced the formation of brominated and iodinated DBPs. The removal of organic carbon and nitrogen precursors by the conventional treatment processes was substantially improved by O3-BAC advanced treatment, and thus prevented the formation of chlorinated C-DBPs and N-DBPs. However, BAC filtration leads to the increased formation of brominated C-DBPs and N-DBPs due to the increase of bromide/DOC and bromide/DON. After the whole multiple treatment processes, the rank order for integrated toxic risk values caused by these halogenated DBPs was haloacetonitriles (HANs)≫haloacetamides (HAMs)>haloacetic acids (HAAs)>trihalomethanes (THMs)>halonitromethanes (HNMs)≫I-DBPs (I-HAMs and I-THMs). I-DBPs failed to cause high integrated toxic risk because of their very low FPs. The significant higher integrated toxic risk value caused by HANs than other halogenated DBPs cannot be ignored.

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Benzophenone-type UV filters are a group of compounds widely used to protect human skin from damage of UV irradiation. Benzophenone-4 (BP-4) was targeted to explore its transformation behaviors during chlorination disinfection treatment in the presence of iodide ions. With the help of ultra performance liquid phase chromatograph and high-resolution quadrupole time-of-flight mass spectrometer, totally fifteen halogenated products were identified, and five out of them were iodinated products. The transformation mechanisms of BP-4 involved electrophilic substitution generating mono- or di-halogenated products, which would be oxidized into esters and further hydrolyzed into phenolic derivatives. The desulfonation and decarboxylation were observed in chlorination system either. Obeying the transformation pathways, five iodinated products formed. The pH conditions of chlorination system determined the reaction types of transformation and corresponding species of products. The more important was that, the acute toxicity had significant increase after chlorination treatment on BP-4, especially in the presence of iodide ions. When the chlorination treatment was performed on ambient water spiked with BP-4 and iodide ions, iodinated by-products could be detected.

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Formation of halogenated disinfection by-products (DBPs) in sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted considerable concerns recently. Previous studies have focused on the formation of chlorinated and brominated DBPs. This research examined the transformation of I- in heat activated PS oxidation process. Phenol was employed as a model compound to mimic the reactivity of dissolved natural organic matter (NOM) toward halogenation. It was found that I- was transformed to free iodine which attacked phenol subsequently leading to iodinated DBPs such as iodoform and iodoacetic acids. Iodophenols were detected as the intermediates during the formation of the iodoform and triiodoacetic acid (TIAA). However, diiodoacetic acid (DIAA) was formed almost concomitantly with iodophenols. In addition, the yield of DIAA was significantly higher than that of TIAA, which is distinct from conventional halogenation process. Both the facts suggest that different pathway might be involved during DIAA formation in SR-AOPs. Temperature and persulfate dose were the key factors governing the transformation process. The iodinated by-products can be further degraded by excessive SO4- and transformed to iodate. This study elucidated the transformation pathway of I- in SR-AOPs, which should be taken into consideration when persulfate was applied in environmental matrices containing iodine.

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This study investigated systematically the factors influencing the formation of iodinated disinfection by-products (I-DBPs) during chloramination of I--containing waters, including reaction time, NH2Cl dose, I- concentration, pH, natural organic matter (NOM) concentration, Br-/I- molar ratio, and water matrix. Among the I-DBPs detected, iodoform (CHI3), iodoacetic acid (IAA), diiodoacetic acid (DIAA), triiodoacetic acid (TIAA), and diiodoacetamide (DIAcAm) were the major species produced from reactions between reactive iodine species (HOI/I2) and NOM. A kinetic model involving the reactions of NH2Cl auto-decomposition, iodine species transformation and NOM consumption was developed, which could well describe NH2Cl decay and HOI/I2 evolution. Higher concentrations of CHI3, IAA, DIAA, TIAA, and DIAcAm were observed in chloramination than in chlorination, whereas IO3- was only formed significantly in chlorination. Maximum formation of I-DBPs occurred at pH 8.0, but acidic conditions favored the formation of iodinated haloacetic acids and DIAcAm. Increasing Br-/I- molar ratio from 1 to 10 did not increase the total amount of I-DBPs, but produced more bromine-substituting species. In addition, chloramination of 18 model compounds indicated that low-SUVA254 (specific ultraviolet absorbance at 254nm) NOM generally favored the formation of I-DBPs compared to high-SUVA254 NOM. Finally, potential pathways for I-DBPs formation from chloramination of NOM were proposed.

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A concise, rapid, and sensitive method is developed to measure organically-bound iodine in water. Total organic iodine (TOI) is used as an integrative surrogate that reflects the amount of iodinated organics in a water sample and is quantified using a refined method that builds on previous adsorption and detection approaches. The proposed method combines adsorption, combustion, and trapping of combustion products, with an offline inductively coupled plasma/mass spectrometer (ICP-MS) for iodide detection. During method development, three analytical variables (factors) were varied across two levels each in order to optimize the method for iodine recovery: 1) the sample pH prior to adsorption on the granular activated carbon (GAC); 2) the amount of base addition to the trap solution; and 3) composition of the ICP-MS wash solution. These factors were tested with solutions of eight iodinated model organic compounds, two iodinated inorganic compounds, and field water samples using a full factorial experimental design. An analysis of variance (ANOVA) and related statistical methods were deployed to identify the best combination of conditions (i.e., treatment) that results in the most complete recovery of iodine from the model compounds and the highest rejection of inorganic iodine. The chosen treatment for TOI measurement incorporates a sample pH of less than 1 prior to adsorption onto the GAC, a solution of 2% (v/v) tetramethyl ammonium hydroxide (TMAH) for trapping of combustion products, and a TMAH wash solution of 0.1% (v/v) for the ICP-MS.

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Large amount of iodinated contrast media (ICM) are found in natural waters (up to µg.L(-)(1) levels) due to their worldwide use in medical imaging and their poor removal by conventional wastewater treatment. Synthetic water samples containing different ICM and natural organic matter (NOM) extracts were subjected to UV254 irradiation followed by the addition of chlorine (HOCl) or chloramine (NH2Cl) to simulate final disinfection. In this study, two new quantum yields were determined for diatrizoic acid (0.071 mol.Einstein(-1)) and iotalamic acid (0.038 mol.Einstein(-1)) while values for iopromide (IOP) (0.039 mol.Einstein(-1)), iopamidol (0.034 mol.Einstein(-1)) and iohexol (0.041 mol.Einstein(-1)) were consistent with published data. The photodegradation of IOP led to an increasing release of iodide with increasing UV doses. Iodide is oxidized to hypoiodous acid (HOI) either by HOCl or NH2Cl. In presence of NOM, the addition of oxidant increased the formation of iodinated disinfection by-products (I-DBPs). On one hand, when the concentration of HOCl was increased, the formation of I-DBPs decreased since HOI was converted to iodate. On the other hand, when NH2Cl was used the formation of I-DBPs was constant for all concentration since HOI reacted only with NOM to form I-DBPs. Increasing the NOM concentration has two effects, it decreased the photodegradation of IOP by screening effect but it increased the number of reactive sites available for reaction with HOI. For experiments carried out with HOCl, increasing the NOM concentration led to a lower formation of I-DBPs since less IOP are photodegraded and iodate are formed. For NH2Cl the lower photodegradation of IOP is compensated by the higher amount of NOM reactive sites, therefore, I-DBPs concentrations were constant for all NOM concentrations. 7 different NOM extracts were tested and almost no differences in IOP degradation and I-DBPs formation was observed. Similar behaviour was observed for the 5 ICM tested. Both oxidant poorly degraded the ICM and a higher formation of I-DBPs was observed for the chloramination experiments compared to the chlorination experiment. Results from toxicity testing showed that the photodegradation products of IOP are toxic and confirmed that the formation of I-DBPs leads to higher toxicity. Therefore, for the experiment with HOCl where iodate are formed the toxicity was lower than for the experiments with NH2Cl where a high formation of I-DBPs was observed.

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The use of persulfate oxidation processes is receiving increasing interest for the removal of aquatic contaminants. However, it is unknown whether its application in the presence of iodide has the potential to directly form iodinated DBPs. This study investigated formation of six chlorinated, brominated and iodinated di-haloacetamides (DHAcAms) during persulfate oxidation in the presence of bromide and iodide. Formation of the same DHAcAms during chlorination was monitored for comparison. Persulfate oxidation of natural water formed diiodoacetamide (DIAcAm), and heat-activated persulfate, at 45 °C and 55 °C, generated bromoiodoacetamide (BIAcAm) and dibromoacetamide (DBAcAm), besides DIAcAm. At an ambient iodide concentration of 0.3 µM, total DHAcAms increased slightly from 0.43 to 0.57 nM as the water temperature increased from 4 °C to 35 °C, respectively (only DIAcAm detected), then significantly increased to 1.6 nM at 55 °C (DIAcAm, BIAcAm and DBAcAm detected). Equivalent total DHAcAm concentrations in the presence of 3.0 µM iodide were 0.5, 0.91 and 2.1 nM, respectively. Total DHAcAms formed during chlorination, predominantly dichloroacetamide (DCAcAm) and bromochloroacetamide (BCAcAm), were always significantly higher than that during persulfate oxidation. However, an integrated risk assessment showed the toxicity resulting from the DHAcAms was higher during persulfate oxidation than chlorination. An increase in water temperature from 25 °C to 55 °C significantly increased the integrated toxic risk values for both persulfate oxidation and chlorination. Use of persulfate oxidation should be weighed against the formation of high-toxicity iodinated HAcAms in waters with high ambient iodide concentrations.

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Recent developments in gas chromatography (GC)-mass spectrometry (MS) have opened up the possibility to use the high resolution-accurate mass (HRAM) Orbitrap mass analyzer to further characterize the volatile and semivolatile fractions of environmental samples. This work describes the utilization of GC Orbitrap MS technology to characterize iodine-containing disinfection by-products (iodo-DBPs) in chlorinated and chloraminated DBP mixture concentrates. These DBP mixtures were generated in lab-scale disinfection reactions using Llobregat river water and solutions containing Nordic Lake natural organic matter (NOM). The DBPs generated were concentrated using XAD resins, and extracts obtained were analyzed in full scan mode with the GC Orbitrap MS. Integration of high resolution accurate mass information and fragment rationalization allowed the characterization of up to 11 different iodo-DBPs in the water extracts analyzed, including one new iodo-DBP reported for the first time. Overall, formation of iodo-DBPs was enhanced during chloramination reactions. As expected, NOM characteristics and iodide and bromide content of the tested waters affected the amount and type of iodo-DBPs generated.

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