Photoconversion of Chlorinated Saline Wastewater DBPs in Receiving

Nov 30, 2016 - The photoconversion-induced variations in the toxicity were evaluated using the embryos of a marine polychaete. Halophenolic DBPs were ...
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Photoconversion of Chlorinated Saline Wastewater DBPs in Receiving Seawater is Overall a Detoxification Process Jiaqi Liu, Xiangru Zhang,* and Yu Li Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China S Supporting Information *

ABSTRACT: Chlorine disinfection of wastewater effluents rich in bromide and iodide ions results in the formation of relatively toxic bromo- and iododisinfection byproducts (DBPs), especially highly toxic bromophenolic and iodophenolic DBPs, which could harm the marine ecosystem when they are discharged into receiving seawater along with the wastewater effluents. In this study, we investigated the conversion of three individual halophenolic DBPs (5-bromosalicylic acid, 2,5-dibromohydroquinone, and 2,4,6-triiodophenol) and two chlorinated saline wastewater DBP mixtures in seawater. The conversion products were analyzed with ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry, and the conversion of overall halo-DBPs in the wastewater DBP mixtures was monitored by measuring total organic halogen. The photoconversioninduced variations in the toxicity were evaluated using the embryos of a marine polychaete. Halophenolic DBPs were found to undergo photoconversion in seawater. The conversion was triggered by photonucleophilic substitution: bromophenolic and iodophenolic DBPs were converted to their chlorophenolic or hydroxyphenolic analogues, via substituting the bromine and iodine atoms with chloride or hydroxide ions in seawater; chlorophenolic DBPs were converted to their hydroxyphenolic analogues, via substituting the chlorine atoms with hydroxide ions in seawater. The hydroxyphenolic analogues thus formed further decomposed and finally cleaved to aliphatic compounds. The photoconversion of chlorinated saline wastewater DBPs in receiving seawater was overall a dehalogenation and detoxification process.

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INTRODUCTION To ease freshwater shortage, Hong Kong and some Pacific island regions use seawater for toilet flushing.1,2 This means having separate domestic water supply systems for potable water and nonpotable water. The practice introduces inorganic salts, including chloride, bromide and iodide ions, into domestic wastewaters. In Hong Kong’s saline wastewater effluents, the salinity is 12−18 psu, and the chloride, bromide and iodide concentrations fall in the ranges of 7200−10 200 mg/L, 20−31 mg/L, and 30−60 μg/L, respectively.2,3 Before their discharge into receiving seawater, saline wastewater effluents are disinfected. Chlorine is a commonly used disinfectant for water disinfection, thanks to its broadspectrum germicidal potency and relatively low cost, but it unintentionally generates disinfection byproducts (DBPs).4−11 Chlorination of water rich in bromide and iodide leads to the formation of bromo- and iodo-DBPs, 11−17 which are substantially more toxic than their chloro-analogues.8,18−20 Recently, by using a precursor ion scan (PIS) approach with ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry (UPLC/ESI-tqMS), our group has identified and confirmed several groups of halophenolic DBPs in chlorinated saline wastewater effluents, including halosalicylic acids, dihalohydroxybenzaldehydes, © XXXX American Chemical Society

halophenols (including mono-, di-, and tri-halophenols), dihalonitrophenols, halohydroquinones, and halotrihydroxybenzenesulfonic acids.20−22 These halophenolic DBPs were generally tens to thousands of times more toxic than the regulated trihalomethanes and haloacetic acids to the marine alga Tetraselmis marina and the marine polychaete Platynereis dumerilii, which sit at the bottom of the marine trophic pyramid.19,20 5-Bromosalicylic acid was the first halophenolic DBP identified in chlorinated saline wastewater.21 2,5Dibromohydroquinone was the most toxic halophenolic DBP to the marine polychaete; 2,4,6-triiodophenol was the most toxic to the marine alga and the second most toxic halophenolic DBP to the marine polychaete.19,20 Because chlorinated wastewater effluents are continuously discharged into the marine water (the ultimate receiving water body), marine species may be persistently exposed to bromophenolic and iodophenolic DBPs, as well as chlorophenolic ones, albeit at low levels. These halophenolic DBPs could have long-term adverse effects on marine organisms.2 Received: Revised: Accepted: Published: A

August 21, 2016 November 30, 2016 November 30, 2016 November 30, 2016 DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology

with a digital photometer (DT-1010B, Shenzhen Golden Octopus, China), with the results shown in SI Figure S2. The average intensity was 6134 lx, and the standard deviation was 231 lx. In the chamber, the temperature was maintained at 22 °C. During each test, repositioning was conducted for all quartz flasks every 2 h to eliminate locational illumination difference. Besides, the volume of each test solution was measured every day and adjusted to the initial volume with ultrapure water to compensate for any evaporated water. Conversion of 5-Bromosalicylic Acid in Seawater. Besides photoconversion, 5-bromosalicylic acid may also undergo biodegradation in seawater. Accordingly, biodegradation was also tested in addition to photoconversion. A 1400 mL 5-bromosalicylic acid solution was prepared by dissolving the standard compound in freshly collected seawater (unfiltered and unautoclaved) at 1 mg/L. The pH of seawater stayed the same after the addition of 5-bromosalicylic acid. The solution was divided into 32 aliquots (40 mL each) and placed in 100 mL quartz flasks. Sixteen aliquots were continuously exposed to simulated sunlight in the test chamber, and the rest were kept in darkness. Another 700 mL of 1 mg/L 5-bromosalicylic acid solution was prepared by dissolving the standard compound in the seawater, which was filtered, autoclaved, and poisoned with 0.37% (v/v) formaldehyde prior to use. Formaldehyde effectively prevents the growth of microorganisms, and 0.37% formaldehyde does not absorb much UV.29 The solution was divided into 16 aliquots (40 mL each), and each aliquot was placed in a 100 mL quartz flask and continuously exposed to simulated sunlight. Each group of samples were either kept in darkness or exposed to light for eight different exposure times (0.025−44 h). After a specific exposure time, two solutions (as duplicates) in each group were pretreated and then analyzed by Waters UPLC/ESI-tqMS (SI). The analyses included concentration measurement and ESI-tqMS full scan. For a halogenated conversion product detected in full scan, UPLC/ESI-tqMS multiple reaction monitoring (MRM) and product ion scans were conducted, and its structure was proposed based on the intensity ratio of selected MRM mass transition, the retention time in the MRM scan, and the fragment ions in product ion scans conducted at the corresponding retention time. For a nonhalogenated conversion product detected in full scan, selected ion recording and product ion scans were conducted. For a tentatively proposed product, the corresponding standard compound was purchased to confirm the proposed structure. As will be shown in the Results and Discussion section, conversion of 5-bromosalicylic acid in seawater was mainly caused by photoconversion, with biodegradation playing only a minor role. Accordingly, in the following tests, we focused on the photoconversion only. Photoconversion of 2,5-Dibromohydroquinone in Seawater. Twenty 40 mL 2,5-dibromohydroquinone seawater solutions at 5 mg/L were prepared in 100 mL quartz flasks. The pH of seawater stayed the same after the addition of 2,5dibromohydroquinone. Then the 20 solutions were divided evenly into 10 groups and exposed to simulated sunlight for a series of exposure times (0.025−166 h). After a given exposure time, two aliquots (as duplicates) were pretreated and analyzed using ESI-tqMS PISs of m/z 79/81 (for selectively detecting bromine-containing compounds), and PISs of m/z 35/37 (for selectively detecting chlorine-containing compounds) (SI). For a halogenated conversion product detected, UPLC/ESI-tqMS MRM scan and product ion scans were conducted to determine its structure. Furthermore, to investigate the photoconversion-

In receiving seawater, halophenolic DBPs could undergo photoconversion. In several studies, haloaliphatic DBPs (including trihalomethanes, halonitromethanes, haloacetic acids, haloacetonitriles, and haloacetamides) in drinking water or swimming pool water were degraded by UV radiation;23−27 chlorophenols, which had been considered merely as environmental pollutants, decomposed in freshwater or estuarine water via photochemical dehalogenation and oxidation,28,29 and haloquinones underwent UV-induced transformation during drinking water treatment.30 However, the photoconversion of other halophenolic DBPs (especially the emerging bromo- and iodo-phenolic ones) in seawater has never been reported. It is unknown if the conversion products of a halophenolic DBP are more or less toxic than the original DBP to organisms in receiving seawater. The objectives of this study were to investigate the photoconversion of individual halophenolic DBPs, including 5-bromosalicylic acid (the first identified halophenolic DBP), 2,5-dibromohydroquinone and 2,4,6-triiodophenol (the two most toxic halophenolic DBPs), and DBP mixtures from two chlorinated saline wastewater effluents (one primary and one secondary) in seawater. The photoconversion-induced variations in the toxicity of 2,5-dibromohydroquinone and the chlorinated saline wastewater DBP mixtures were also evaluated using the marine polychaete P. dumerilii. This polychaete is a cosmopolitan species, extending from the tropics to cold temperate latitudes in both hemispheres.31 The in vivo bioassay using the embryo-larval stages of P. dumerilii is a sensitive metric and has been successfully applied in determining the developmental toxicity of DBPs and chlorinated saline wastewater effluents.2,20,32 The importance of bioanalytical assessment as a complement to the chemical evaluation of water quality has been increasingly recognized in recent years.33,34

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MATERIALS AND METHODS Seawater, Chemicals, and Photoconversion Test Chamber. Seawater was drawn from a submerged intake in Hong Kong, and its pH, salinity, and concentrations of chloride, bromide and iodide were measured to be 8.2, 35 psu, 19 200 mg/L, 64 mg/L, and 32.1 μg/L, respectively. Unless otherwise specified, for DBP photoconversion tests, the seawater was filtered with a 0.45 μm filter, autoclaved at 121 °C, and cooled to room temperature before use. Additionally, for polychaete cultivation and toxicity tests, the seawater was further aerated with an air pump for 15 min. Details of standard compounds used are given in Table S1 of Supporting Information (SI). Other organic solvents and chemicals used, including methyl tert-butyl ether (HPLC grade), acetonitrile (HPLC grade), formaldehyde (35 wt %) and dimethyl sulfoxide, were ordered from Sigma−Aldrich. For photoconversion studies, the quartz flasks (without cover) were ordered from Technical Glass Products Inc., and the fullspectrum simulated sunlight lamps (BlueMax Spectra 5900, with the spectrum shown in SI Figure S1) were ordered from Full Spectrum Solutions. Two sizes of quartz flasks (i.e., 100 and 500 mL) were used in this study, and their dimensions are shown in SI Table S2. The quartz flasks containing test solutions were kept in a chamber with the dimensions of 1180 mm × 485 mm × 615 mm (length × width × height). Eight simulated sunlight lamps were installed at the top of the chamber and spaced evenly apart. The light intensities at different positions at the bottom of the chamber were measured B

DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Furthermore, to investigate the photoconversion-induced variation in the toxicity of the two chlorinated saline wastewater DBP mixtures, an additional series of seawater-diluted effluent samples were prepared and their toxicity to the marine polychaete P. dumerilii during growth and development was tested (SI).

induced variation in the toxicity of 2,5-dibromohydroquinone, an additional series of samples were prepared and their toxicity to the marine polychaete P. dumerilii during growth and development was tested (SI). Photoconversion of 2,4,6-Triiodophenol in Seawater. As will be shown in the Results and Discussion section, 5bromosalicylic acid and 2,5-dibromohydroquinone underwent photonucleophilic substitution in seawater under illumination. To check if iodophenolic DBPs would also undergo photonucleophilic substitution, the photoconversion of 2,4,6triiodophenol in seawater was studied. Two 40 mL 2,4,6triiodophenol seawater solutions at 5 mg/L were prepared in 100 mL quartz flasks. The pH of seawater remained constant after the addition of 2,4,6-triiodophenol. One solution was continuously exposed to simulated sunlight for 44 h, then pretreated and analyzed by ESI-tqMS (SI). The other solution was pretreated and analyzed right after preparation. Photoconversion of Two Chlorinated Saline Wastewater DBP Mixtures in Seawater. Two undisinfected saline wastewater effluents were collected (24 h composite), one from a primary treatment plant and the other from a secondary treatment plant. Wastewater effluent samples were transferred to the laboratory in an ice cooler and stored at 4 °C. Before an experiment, each effluent sample was warmed to room temperature, and filtered with 0.45 μm filters. The characteristics of the two wastewater effluents are shown in SI Table S3. Two liters of each filtered wastewater effluent was disinfected with 6.0 mg/L NaOCl as Cl2 for a 30 min contact time. After chlorination, the chlorine residual in each effluent was measured (following the DPD titration method)35 and dechlorinated with a certain amount of sodium thiosulfate (SI Table S4) for another 30 min. After dechlorination, each effluent was divided into 12 aliquots (150 mL each), and each aliquot was mixed with 150 mL of seawater in a 500 mL quartz flask. The mixing time of the chlorinated wastewater effluent and seawater in each sample was negligible. Then the seawaterdiluted chlorinated wastewater effluent samples were exposed to simulated sunlight for a series of exposure times (0−84 h). After a given exposure time, each sample was subjected to duplicate total organic halogen (TOX) measurements. TOX is a collective parameter for all halo-DBPs in a water sample, and it is differentiated into total organic chlorine (TOCl), total organic bromine (TOBr), and total organic iodine (TOI), which are collective parameters for all chloro-, bromo-, and iodo-DBPs, respectively. TOX has been demonstrated to be a good indicator for the overall toxicity of halo-DBPs in a disinfected water sample.32,36 TOCl, TOBr, and TOI were measured according to Standard Method 5320B and previous studies (SI).35,37−41 Briefly, all chloro-, bromo-, and iodo-DBPs were adsorbed by activated carbon and converted by pyrolysis to chloride, bromide, and iodide, respectively, and then the chloride and bromide were quantified with an ion chromatograph, and the iodide was quantified with UPLC/ESI-tqMS. To further investigate the photoconversion products of polar haloDBPs, 6500 mL of the saline primary or secondary effluent was chlorinated and dechlorinated as aforementioned. Then the effluent was divided into 40 aliquots (150 mL each), and each aliquot was mixed with 150 mL of seawater in a 500 mL quartz flask. The 40 aliquots were divided evenly into four groups and exposed to simulated sunlight for 0, 5, 28, and 84 h. After a given exposure time, the 10 aliquots in each group were combined into a 3000 mL sample, and the sample was subjected to pretreatment and UPLC/ESI-tqMS analyses (SI).

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RESULTS AND DISCUSSION Photoconversion of Individual Halophenolic DBPs in Seawater. Figure 1a shows the ln(concentration) of 5bromosalicylic acid with exposure time under different conditions. In the solution kept in darkness, the concentration remained constant over time, indicating that no conversion occurred during the 44 h in darkness. In the two solutions exposed to light, ln(concentration) exhibited good linearity with exposure time, indicating that photoconversion of 5bromosalicylic acid was a first-order reaction. The reaction rate constant (k) and half-life in each condition were calculated according to the regression equation (SI Table S5). The k value in the solution with formaldehyde (0.110 h−1) was slightly

Figure 1. (a) Conversion of 5-bromosalicylic acid in seawater under different conditions: “darkness”, “light”, and “formaldehyde + light” indicate that the solutions were kept in darkness, exposed to light, and spiked with formaldehyde and exposed to light, respectively. (b) Photoconversion of 5-bromosalicylic acid in seawater with different light exposure times: the five curves illustrate the concentrations of 5bromosalicylic acid, 5-chlorosalicylic acid, and 5-hydroxysalicylic acid, and the ESI-tqMS full scan intensities of tetrahydroxybenzene and 3hydroxy-2,4-hexadienedioic acid. C

DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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seawater stayed at 8.2 throughout the experiment, that is, the concentration of hydroxide ions did not change. Consequently, photonucleophilic hydroxyl substitution was also a pseudo-firstorder reaction. The concentrations of 5-chlorosalicylic acid and 5-hydroxysalicylic acid in each 5-bromosalicylic acid solution exposed to light were measured. These two products formed and then decomposed as reflected in the concentration variations with exposure time (Figure 1b). Because of the higher dissociation energy of the C6H5−OH bond than the C6H5−Cl bond, and the higher stability of 5-hydroxysalicylic acid than 5chlorosalicylic acid, 5-chlorosalicylic acid could also be converted via photonucleophilic hydroxyl substitution to 5hydroxysalicylic acid, which further decomposed. Scheck and Frimmel 44 reported that salicylic acid hydrolyzed (by substituting the carboxyl group with an hydroxyl group) in an alkaline solution under UV irradiation to form 1,2-hydroquinone, which was in equilibrium with 1,2-quinone; then 1,2quinone was cleaved to 2,4-hexadienedioic acid. Similarly in this study, 5-hydroxysalicylic acid was expected to hydrolyze in seawater (pH 8.2) under illumination and generate 1,2,4trihydroxybenzene, which was in equilibrium with 4-hydroxy1,2-quinone; then 4-hydroxy-1,2-quinone was cleaved to 3hydroxy-2,4-hexadienedioic acid, which was confirmed by the detected molecular ion m/z 157 (SI Figure S3). The intensity of 3-hydroxy-2,4-hexadienedioic acid kept increasing until the exposure time of 10 h and then decreased (Figure 1b). It might be further cleaved to lower molecular weight carboxylic acids. Besides, 1,2,4-trihydroxybenzene was also in equilibrium with 2-hydroxy-1,4-quinone. It has been reported that in an aqueous solution, a para-quinone could undergo photoaddition reaction with a water molecule, resulting in one more hydroxyl group substituted on the benzene ring of the quinone.45 Accordingly, 2-hydroxy-1,4-quinone might be converted to 1,2,3,4-, 1,2,4,5-, or 1,2,4,6-tetrahydroxybenzene. This was confirmed by the detected molecular ion corresponding to tetrahydroxybenzene (m/z 141) in SI Figure S3. The intensity of tetrahydroxybenzene kept increasing until the exposure time of 10 h and then became relatively stable (Figure 1b). The photoconversion pathway of 5-bromosalicylic acid in seawater is illustrated in SI Figure S7. Because the toxicity of 5-bromosalicylic acid was relatively low,19,20 the photoconversion-induced variation in its toxicity in seawater was not studied. SI Figures S8 and S9 show the ESI-tqMS PIS spectra of m/z 79 and m/z 35 of the 2,5-dibromohydroquinone seawater solutions with different light exposure times. Eight conversion products were detected (SI Table S6), and their intensity variations with light exposure time are illustrated in Figure 2. The photoconversion pathway of 2,5-dibromohydroquinone in seawater is illustrated in Figure 3. 2,5-Dibromohydroquinone (m/z 265/267) was in equilibrium with 2,5-dibromoquinone (m/z 264/266) in solution, and both decomposed quickly. At the exposure time of 0.025 h, 2-bromo-5-hydroxy-1,4-quinone (m/z 201) was generated via the photonucleophilic hydroxyl substitution of 2,5-dibromoquinone, and its intensity kept increasing until the exposure time of 6.3 h and then decreased. 2,5-Dibromo-3-hydroxy-1,4-quinone (m/z 279/281) (which was in equilibrium with 2,5-dibromo-3-hydroxy-1,4-hydroquinone) was generated via the photoaddition reaction of 2,5-dibromoquinone and water, with the proposed mechanism shown in SI Figure S10a. The mechanism of the photoaddition reaction between a haloquinone and a water molecule in the presence of UV radiation has been reported elsewhere.30 The

lower than that in the solution without formaldehyde (0.121 h−1), indicating that the presence of microorganisms slightly accelerated the conversion. SI Figure S3 shows the ESI-tqMS full scan spectra of the 5bromosalicylic acid solutions with different light exposure times. Two conversion products, 5-chlorosalicylic acid (m/z 171/173) and 5-hydroxysalicylic acid (m/z 153), were detected and confirmed (SI Figures S4−S6). The former was generated via the substitution of the bromine atom in 5-bromosalicylic acid with a chlorine atom and the latter with a hydroxyl group following the mechanism of SN2Ar* photonucleophilic substitution as shown below. Photonucleophilic substitution (with details shown in SI) of aromatic compounds has been widely applied in organic synthesis,42 but it is the first time that this reaction was observed in the photoconversion of halophenolic DBPs in seawater.

When exposed to sunlight (more precisely UV radiation), 5bromosalicylic acid became excited. Because the bromine atom is at the para-position to the hydroxyl group (an electron donating group) and at the meta-position of the carboxyl group (an electron withdrawing group), it is ready to be substituted. An excited 5-bromosalicylic acid molecule combined with either a chloride ion or a hydroxide ion (acting as a nucleophile) in seawater, yielding an unstable δ-complex 5,5bromochlorosalicylic acid or 5,5-bromohydroxysalicylic acid, respectively. In 5,5-bromochlorosalicylic acid, either the bromine atom or the chlorine atom would leave the molecule, and in 5,5-bromohydroxysalicylic acid, either the bromine atom or the hydroxyl group would leave the molecule. The dissociation energies of C6H5−OH, C6H5−Cl and C6H5−Br bonds are 463.6, 399.6, and 336.4 kJ/mol, respectively.43 Accordingly, in both δ-complexes, the bromine atom left in the form of a bromide ion, and 5-chlorosalicylic acid and 5hydroxysalicylic acid were generated. The standard Gibbs free energies of formation (ΔGf°) of 5-bromosalicylic acid, 5chlorosalicylic acid and 5-hydroxysalicylic acid were calculated with the software Chem3D Ultra 8.0 (CambridgeSoft), and the results showed that 5-chlorosalicylic acid (ΔGf° = −399.62 kJ/ mol) and 5-hydroxysalicylic acid (ΔGf° = −532.68 kJ/mol) were more stable than 5-bromosalicylic acid (ΔGf° = −373.37 kJ/mol). This confirms that the conversion from 5bromosalicylic acid to 5-chlorosalicylic acid or 5-hydroxysalicylic acid is thermodynamically favorable. Besides, the formation of a δ-complex (5,5-bromochlorosalicylic acid or 5,5-bromohydroxysalicylic acid) would be the rate-determining step of the whole substitution reaction, and the reaction rate was related to the concentrations of excited 5-bromosalicylic acid molecules, chloride ions and hydroxide ions. The concentration of chloride in seawater (19200 mg/L) was significantly higher than that of 5-bromosalicylic acid (1 mg/L initially), and thus photonucleophilic chlorine substitution was a pseudo-first-order reaction. Due to the alkalinity, the pH of D

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exposure time of 0.6 h, 2,5-dibromo-3-hydroxy-1,4-quinone began converting to 2-bromo-5-chloro-3-hydroxy-1,4-quinone (or its isomer) (m/z 235/237) via photonucleophilic chlorine substitution, and also to 2,5-dibromo-3,6-dihydroxy-1,4-hydroquinone (m/z 297/299) via photoaddition reaction with water (SI Figure S10b). Meanwhile, 2-bromo-5-chloro-3,6-dihydroxy1,4-hydroquinone (m/z 253/255) was generated from the photonucleophilic chlorine substitution of 2,5-dibromo-3,6dihydroxy-1,4-hydroquinone, or the photoaddition reaction of 2-bromo-5-chloro-3-hydroxy-1,4-quinone with water (SI Figure S10c). The intensities of 2-bromo-5-chloro-3-hydroxy-1,4quinone, 2,5-dibromo-3,6-dihydroxy-1,4-hydroquinone, and 2bromo-5-chloro-3,6-dihydroxy-1,4-hydroquinone kept increasing until the exposure time of 6.3 h and then decreased. At the exposure time of 3 h, 2,5-dibromo-3,6-dihydroxy-1,4-hydroquinone began converting to bromopentahydroxybenzene (m/ z 235) via photonucleophilic hydroxyl substitution. Its intensity kept increasing until the exposure time of 11.5 h and then quickly decreased. 2-Bromo-5-chloro-3,6-dihydroxy-1,4-hydroquinone and bromopentahydroxybenzene contain more than three hydroxyl groups substituted on the benzene ring, and were consequently unstable and readily cleaved to small aliphatic compounds.28,44,45 Besides, at the exposure time of 3 h, bromomaleic acid (m/z 193) was detected and confirmed with the standard compound (SI Figure S11). This compound was generated from 2-bromo-5-hydroxy-1,4-quinone (m/z 201) via two steps (Figure 3). In the first step, a photoaddition reaction occurred between 2-bromo-5-hydroxy-1,4-quinone and water to generate 2-bromo-5,6-dihydroxy-1,4-hydroquinone (SI Figure S10d), which was in equilibrium with 2-bromo-5,6dihydroxy-1,4-quinone. In the second step, 2-bromo-5,6dihydroxy-1,4-quinone was cleaved to bromomaleic acid. The photochemical cleavages of 2,3-dihydroxy-1,4-quinone to maleic acid, and 2,3-dichloro-5,6-dihydroxy-1,4-quinone to

Figure 2. Intensity variations of 2,5-dibromohydroquinone and its photoconversion products with exposure time. For 2,5-dibromo-3,6dihydroxy-1,4-hydroquinone (m/z 297/299), the adducts with 2H2O (m/z 333/335), and H2O+H2CO3 (m/z 377/379) were detected by ESI-tqMS PIS of m/z 79, and the intensity of 2,5-dibromo-3,6dihydroxy-1,4-hydroquinone was calculated as the summation of the intensities of both adducts. For bromopentahydroxybenzene (m/z 235), the adduct with 2H2O (m/z 271) was detected by ESI-tqMS PIS of m/z 79. For 2-bromo-5-chloro-3,6-dihydroxy-1,4-hydroquinone (m/z 253/255), the adduct with H2O+H2CO3 (m/z 333/335) was detected by ESI-tqMS PIS of m/z 35. 2-Bromo-5-chloro-3-hydroxy1,4-quinone might have another isomer 2-bromo-5-chloro-6-hydroxy1,4-quinone.

intensity of 2,5-dibromo-3-hydroxy-1,4-quinone kept increasing until the exposure time of 3 h and decreased afterward. At the

Figure 3. Proposed photoconversion pathway of 2,5-dibromohydroquinone in seawater. Bromomaleic acid was a confirmed product, and the other structures marked with m/z values indicate that the corresponding ions or ion clusters were detected by ESI-tqMS PIS of m/z 79 or m/z 35. For 2,5dibromo-3,6-dihydroxy-1,4-hydroquinone (m/z 297/299), the adducts with 2H2O (m/z 333/335), and H2O+H2CO3 (m/z 377/379) were detected by ESI-tqMS PIS of m/z 79. For bromopentahydroxybenzene (m/z 235), the adduct with 2H2O (m/z 271) was detected by ESI-tqMS PIS of m/z 79. For 2-bromo-5-chloro-3,6-dihydroxy-1,4-hydroquinone (m/z 253/255), the adduct with H2O+H2CO3 (m/z 333/335) was detected by ESItqMS PIS of m/z 35. The structures marked with asterisks may have other isomers. E

DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

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Environmental Science & Technology dichloromaleic acid have been demonstrated elsewhere.28,44 The intensity of bromomaleic acid kept increasing until the exposure time of 42 h and decreased afterward. At the exposure time of 166 h, bromomaleic acid was the only polar halogenated compound detected in the solution (SI Figures S8j and S9j). Figure 4 displays the percentages of normal development of the marine polychaete P. dumerilii in the 2,5-dibromohydro-

The photoconversion mechanisms of 5-bromosalicylic acid and 2,5-dibromohydroquinone in seawater exhibited three common phenomena. First, photonucleophilic chlorine and hydroxyl substitutions occurred. Second, quinone compounds (as intermediates) formed. Third, (halo)quinone intermediates further decomposed and finally cleaved to aliphatic products. Unlike para-quinone, ortho-quinone is unstable and readily cleaved to aliphatic dicarboxylic acids.47 In seawater, due to the occurrence of photonucleophilic hydroxyl substitution, each halophenolic DBP may be converted to its hydroxyphenolic analogue, a (halo)hydroquinone. This (halo)hydroquinone is in equilibrium with a (halo)quinone. The (halo)quinone will then decompose following the mechanism described above. It needs mentioning that the dissociation energy of the C6H5−I bond is 272.0 kJ/mol, which is lower than those of the C6H5−Cl (399.6 kJ/mol) and C6H5−OH (463.6 kJ/mol) bonds.43 Thus, photonucleophilic chlorine and hydroxyl substitutions could occur in iodophenolic DBPs. SI Figure S12 shows the PIS spectra of m/z 126.9 of 2,4,6-triiodophenol seawater solutions without and with exposure to light. After 44 h exposure to light, two photonucleophilic chlorine substituted products (chlorodiiodophenol and dichloroiodophenol), and one photonucleophilic hydroxyl substituted product (diiodohydroquinone) were generated, confirming that iodophenolic DBPs did undergo photonucleophilic chlorine and hydroxyl substitutions under illumination. Photoconversion and Detoxification of Chlorinated Saline Wastewater DBP Mixtures in Seawater. Figure 5 shows the TOCl, TOBr and TOI concentrations in seawaterdiluted chlorinated saline primary and secondary effluents with different light exposure times. Notably, both effluents contained dissolved organic carbon (DOM) and the secondary effluent contained nitrate (SI Table S3). DOM and nitrate might induced indirect effects on the photoconversion of haloDBPs.48,49 At the beginning of the light exposure, the TOCl, TOBr, and TOI concentrations were 36.8, 20.8, 2.0 μg/L as Cl in the seawater-diluted chlorinated primary effluent, and 88.1, 125.8, 1.2 μg/L as Cl in the seawater-diluted chlorinated secondary effluent, respectively. These results were comparable with the concentrations reported in previous studies.21,22 In the seawater-diluted chlorinated saline primary effluent, the concentrations of TOBr and TOI and the ratios of TOBr/ TOX and TOI/TOX decreased with exposure time. The TOCl concentration remained stable during the first 5 h of light exposure and then decreased, but at a lower rate than the decreases in the TOBr and TOI concentrations. Consequently, the TOCl/TOX ratio showed a rising trend with exposure time, confirming the conversion of bromophenolic and iodophenolic DBPs to their chlorophenolic analogues via photonucleophilic substitution with chloride ions in seawater. The TOX concentration (the summation of TOCl, TOBr and TOI concentrations as Cl) kept decreasing until the exposure time of 70 h. TOX includes halophenolic and haloaliphatic DBPs. In seawater (pH 8.2), halophenolic DBPs were converted to their hydroxyphenolic analogues via photonucleophilic substitution with hydroxide ions. Haloaliphatic DBPs have been reported to hydrolyze in alkaline conditions.50 The TOI, TOBr, and TOCl concentrations did not change significantly from the exposure time of 70 to 84 h, indicating that some relatively persistent halo-organic DBPs might have formed in the effluent. In the seawater-diluted chlorinated saline secondary effluent, the variations in TOCl, TOBr, and TOI concentrations, and the variations in TOCl/TOX, TOBr/TOX, and TOI/TOX ratios

Figure 4. Percentages of normal development of the marine polychaete P. dumerilii in the “2,5-dibromohydroquinone” solutions with different light exposure times. The x-axis indicates the concentration of 2,5-dibromohydroquinone in the concentrated test sample prior to photoconversion.

quinone solutions with different light exposure times. It needs pointing out that each concentration in the figure is the concentration of 2,5-dibromohydroquinone in the concentrated test sample prior to photoconversion. A higher percentage of normal development indicates a lower toxicity. For each curve, a regression analysis was conducted using the software SigmaPlot 12 (Systat Software Inc., San Jose, CA), and the EC50 value was obtained as in a previous study.20 A higher EC50 value also indicates a lower toxicity. According to the EC50 values (SI Table S7), the toxicity of “2,5-dibromohydroquinone”, or the overall toxicity of “2,5-dibromohydroquinone and its conversion products” to be exact, quickly decreased with exposure time. Photonucleophilic chlorine substitution triggered the conversion from a bromophenolic photoconversion product of 2,5-dibromohydroquinone to its chlorophenolic analogue, and consequently reduced the toxicity. This is because chlorophenolic DBPs were substantially less toxic than their bromo-analogues.8,18−20 Besides, photoaddition reaction with water led to an increasing number of hydroxyl groups substituted on the benzene ring, and reduced the log Kow of a halophenolic product. Because log Kow is positively related to toxicity,19,20 we conclude that the toxicity of the product was reduced. Wang et al.46 measured the cytotoxicity of four halobenzoquinones and the corresponding halohydroxyl-benzoquinones and also found that the addition of one hydroxyl group to the halobenzoquinones was partially a detoxifying process. At the exposure time of 166 h, the percentage of normal development in the “2,5-dibromohydroquinone” solution with the concentration up to 300 μM was close to that in the control sample. This was because the remaining conversion product, bromomaleic acid, is an aliphatic DBP with low toxicity.19 F

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108, 1.24 × 108, 0.93 × 108, and 0.72 × 108, respectively, and the TII values in the PIS spectra of m/z 35 were 5.47 × 107, 5.58 × 107, 4.94 × 107, and 4.69 × 107, respectively. These variation trends were consistent with those of TOI and TOCl concentrations. SI Figures S16 and S17 display the ESI-tqMS PIS spectra of m/z 79 and m/z 35 of the seawater-diluted chlorinated saline secondary effluent samples with different exposure times, respectively. Several DBPs were detected at the beginning of the exposure, and five halophenolic DBPs, namely 5bromosalicylic acid, 5-chlorosalicylic acid, 2,4,6-tribromophenol (m/z 327/329/331/333), 2,6-dibromo-4-nitrophenol (m/z 294/296/298), and 2,6-dichloro-4-nitrophenol (m/z 206/ 208/210), and one nonhalogenated DBP, namely 5-hydroxysalicylic acid, were confirmed with standard compounds (SI Figures S18−23). Photonucleophilic substitution of the confirmed halophenolic DBPs and bromonitrophenol (m/z 216/218, a proposed DBP) was observed (SI Figures S18−20 and S24−26). The TII in the PIS spectrum of m/z 79 is approximately proportional to the total amount of polar bromo-DBPs in a water sample,36 and in this study it was defined as the summation of ion intensities from m/z 100 to 500. At the exposure times of 0, 5, 28, and 84 h, the TII values in the PIS spectra of m/z 79 were 4.24 × 108, 3.36 × 108, 3.17 × 108, and 2.51 × 108, respectively, the TII values in the PIS spectra of m/z 35 were 2.70 × 107, 3.04 × 107, 2.89 × 107, and 2.73 × 107, respectively. These variation trends were consistent with those of TOBr and TOCl concentrations. To evaluate the variations in the toxicity of chlorinated saline wastewater DBP mixtures with light exposure time, a series of seawater-diluted chlorinated saline primary or secondary effluent samples with different exposure times (0−84 h, as in the TOX measurements) were prepared and concentrated, and their toxicity to the marine polychaete P. dumerilii during growth and development was tested. The primary effluent sample was concentrated by 10 times and the secondary effluent sample by 30 times (relative to the original water sample) (SI). Figure 6a shows the developmental toxicity variation of the DBP mixture of the seawater-diluted chlorinated saline primary effluent sample with exposure time. The percentage of normal development kept increasing until the exposure time of 56 h, indicating that the toxicity of the DBP mixture was decreasing. After 56 h of light exposure, the percentage of normal development stayed almost constant, but it was still lower than that in the control sample. This might have been caused by certain persistent toxic DBPs in the effluent. Figure 6b shows the developmental toxicity variation of the DBP mixture of the seawater-diluted chlorinated saline secondary effluent sample. The percentage of normal development kept increasing during the 84 h of light exposure, and the increase was faster than that in the primary effluent. Therefore, the photoconversion of halo-DBPs from both chlorinated saline wastewater effluents in receiving seawater was overall a detoxification process. It needs to be mentioned that the photoconversion of halophenolic DBPs in a natural marine environment depends on the actual intensity of sunlight, the penetration of sunlight (especially UV) in seawater, and other physical and biological conditions of the water body. Solar elevation angle is positively related to the solar intensity on horizontal surface. SI Tables S8−S10 summarized the solar elevations and intensities on horizontal surface in Hong Kong at different times on three representative days, including June 3, 2016 (a summer day, the

Figure 5. TOCl, TOBr, and TOI concentrations and TOCl/TOX, TOBr/TOX, and TOI/TOX ratios in seawater-diluted chlorinated saline wastewater effluent samples with different light exposure times: (a) chlorinated saline primary effluent; (b) chlorinated saline secondary effluent.

were similar to those in the seawater-diluted chlorinated primary effluent, except that the TOI concentration was below the detection limit after 56 h of light exposure, and the TOBr and TOCl concentrations decreased from the exposure time of 56−84 h. SI Figures S13 and S14 display the ESI-tqMS PIS spectra of m/z 126.9 and m/z 35 of the seawater-diluted chlorinated saline primary effluent samples with different light exposure times, respectively. Halotrihydroxybenzenesulfonic acids, a group of newly identified DBPs by Gong and Zhang,22 were detected at the beginning of the exposure, including chloro-, iodo-, dichloro-, chloroiodo-, bromoiodo-, and diiodo-trihydroxybenzenesulfonic acids. Via photonucleophilic substitution with chloride ions in seawater, iodotrihydroxybenzenesulfonic acid was converted to chlorotrihydroxybenzenesulfonic acid; bromoiodo- and diiodo-trihydroxybenzenesulfonic acids converted first to chloroiodotrihydroxybenzenesulfonic acid and further to dichlorotrihydroxybenzenesulfonic acid (SI Figure S15). The total ion intensity (TII) in the PIS spectrum of m/z 126.9 (or m/z 35) is approximately proportional to the total amount of polar iodo-DBPs (or chloro-DBPs) in a water sample.22,36 In this study, the parameter was defined as the summation of ion intensities from m/z 150 to 500 in the PIS spectrum of m/z 126.9 (or from m/z 50 to 400 in the PIS spectrum of m/z 35). At the exposure times of 0, 5, 28, and 84 h, the TII values in the PIS spectra of m/z 126.9 were 1.70 × G

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photoconversion of 5-bromosalicylic acid could only occur with a surface light intensity ≥61 340 lx. Accordingly, on June 3, 2016 and March 20, 2016, the half-life of 5-bromosalicylic acid should be 5.7 h, if the effluent was discharged around 9:00 and 9:30, respectively. Whereas, on December 22, 2015, since the 3 h period with enough light intensity was shorter than 5.7 h, the photoconversion of 5-bromosalicylic acid could not be continued until the next day, that is, 21 h later, leading to a half-life of 26.7 h. Hong Kong is a tropical region receiving relatively high solar radiation. In regions with higher latitude receiving lower solar radiation, photoconversion of halophenolic DBPs might be weakened. The results of this study showed that the photoconversion of 2,5-dibromohydroquinone (the most toxic halophenolic DBP) and chlorinated saline wastewater DBP mixtures was overall a dehalogenation and detoxification process, indicating that the emerging bromophenolic and iodophenolic DBPs in chlorinated saline wastewater effluents might not be too severe a threat to the organisms in receiving seawater. Of note was that some halo-DBPs in the chlorinated saline wastewater effluents might be persistent in receiving seawater, and further studies are needed to identify them and control their formation.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.est.6b04232. Additional details, Tables S1−S10 and Figures S1−S26 (PDF)

Figure 6. Percentages of normal development of the marine polychaete P. dumerilii in seawater-diluted chlorinated saline wastewater effluent samples with different light exposure times: (a) chlorinated saline primary effluent; (b) chlorinated saline secondary effluent.

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AUTHOR INFORMATION

Corresponding Author

sun directed at Hong Kong’s latitude, 22°17′ N), March 20, 2016 (a spring day, the sun directed at the equator), and December 22, 2015 (a winter day, the sun directed at the Tropic of Capricorn, 23°26′ S). Besides, the penetration of sunlight decreases with water depth mainly due to absorption by chromophoric dissolved organic matter. Tedetti and Sempere51 reported that the 10% UV irradiance depths (at which 10% of surface UV radiation remains) of UVB (280−315 nm) and UVA (315−400 nm) in different coastal waters were in the ranges of 0.09−6.7 m and 0.33−22 m, respectively. The discharging point of a wastewater effluent (containing emerging halophenolic DBPs) is usually below the seawater surface. Once discharged, an effluent plume (whose shape depends on the diffusion and convection of the effluent in seawater) will form. With a density lower than the seawater density, the wastewater effluent has a tendency to move upward to the seawater surface, where UV radiation will trigger the photoconversion of halophenolic DBPs. Estimation of the half-life of a halophenolic DBP via photoconversion in a natural marine environment, though challenging, was exemplified with 5-bromosalicylic acid. The half-life of 5-bromosalicylic acid was measured to be 5.7 h in this study (SI Table S5). It is assumed that the discharging point of a wastewater effluent is within the 10% UV irradiance depth of receiving seawater, and 5-bromosalicylic acid is evenly distributed within such a depth. The average light intensity used in this study was 6134 lx. To keep the same UV intensity at the 10% UV irradiance depth, the solar intensity on seawater surface should be 61340 lx. In the three representative days, the periods with solar intensities higher than 61340 lx were 7.0 h (9:00−16:00), 6.0 h (9:30−15:30), and 3.0 h (11:00−14:00), respectively. For conservative estimation, it is assumed that

*Phone: +852 2358 8479; fax: +852 2358 1534; e-mail: [email protected]. ORCID

Xiangru Zhang: 0000-0001-6382-0119 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This study was financially supported by the Research Grants Council of Hong Kong, China (projects 622913 and DAG11EG02S) and the Environment & Conservation Fund and Woo Wheelock Green Fund (no. ECWW15EG07). We thank Adriaan Dorresteijn for providing parental polychaete P. dumerilii; Jing Li, Yi Ouyang, Yulan Ouyang, Yan Hang Ho and Shueng Yu Sin for preparing and pretreating the samples; and Dave Ho for maintaining the TOX analyzer on a daily basis.

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REFERENCES

(1) Mirti, A. V.; Davies, S. Drinking Water Quality in the Pacific Island Countries: Situation Analysis and Needs Assessment; SOPAC Joint Contribution Report 181; Applied Geoscience and Technology Division, Secretariat of the Pacific Community: Suva, Fiji Islands, 2005. (2) Yang, M.; Liu, J.; Zhang, X.; Richardson, S. D. Comparative toxicity of chlorinated saline and freshwater wastewater effluents to marine organisms. Environ. Sci. Technol. 2015, 49 (24), 14475−14483. (3) Gong, T.; Zhang, X. Determination of iodide, iodate and organoiodine in waters with a new total organic iodine measurement approach. Water Res. 2013, 47 (17), 6660−6669. (4) Krasner, S. W.; Westerhoff, P.; Chen, B.; Rittmann, B. E.; Amy, G. Occurrence of disinfection byproducts in United States wastewater

H

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Environmental Science & Technology treatment plant effluents. Environ. Sci. Technol. 2009, 43 (21), 8320− 8325. (5) Hua, G.; Reckhow, D. A. Comparison of disinfection byproduct formation from chlorine and alternative disinfectants. Water Res. 2007, 41 (8), 1667−1678. (6) Tang, H. L.; Chen, Y. C.; Regan, J. M.; Xie, Y. F. Disinfection byproduct formation potentials in wastewater effluents and their reductions in a wastewater treatment plant. J. Environ. Monit. 2012, 14 (6), 1515−1522. (7) Agus, E.; Voutchkov, N.; Sedlak, D. L. Disinfection by-products and their potential impact on the quality of water produced by desalination systems: A literature review. Desalination 2009, 237 (1), 214−237. (8) Richardson, S. D.; Plewa, M. J.; Wagner, E. D.; Schoeny, R.; DeMarini, D. M. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutat. Res., Rev. Mutat. Res. 2007, 636 (1−3), 178−242. (9) Song, H.; Addison, J. W.; Hu, J.; Karanfil, T. Halonitromethanes formation in wastewater treatment plant effluents. Chemosphere 2010, 79 (2), 174−179. (10) Gonsior, M.; Schmitt-Kopplin, P.; Stavklint, H.; Richardson, S. D.; Hertkorn, N.; Bastviken, D. Changes in dissolved organic matter during the treatment processes of a drinking water plant in Sweden and formation of previously unknown disinfection byproducts. Environ. Sci. Technol. 2014, 48 (21), 12714−12722. (11) Yang, M.; Zhang, X. Current trends in the analysis and identification of emerging disinfection byproducts. Trends Environ. Anal. Chem. 2016, 10, 24−34. (12) Jones, D. B.; Saglam, A.; Song, H.; Karanfil, T. The impact of bromide/iodide concentration and ratio on iodinated trihalomethane formation and speciation. Water Res. 2012, 46 (1), 11−20. (13) Richardson, S. D.; Thruston, A. D., Jr; Rav-Acha, C.; Groisman, L.; Popilevsky, I.; Juraev, O.; Glezer, V.; McKague, A. B.; Plewa, M. J.; Wagner, E. D. Tribromopyrrole, brominated acids, and other disinfection byproducts produced by disinfection of drinking water rich in bromide. Environ. Sci. Technol. 2003, 37 (17), 3782−3793. (14) Bichsel, Y.; von Gunten, U. Formation of iodo-trihalomethanes during disinfection and oxidation of iodide-containing waters. Environ. Sci. Technol. 2000, 34 (13), 2784−2791. (15) Roccaro, P.; Korshin, G. V.; Cook, D.; Chow, C. W. K.; Drikas, M. Effects of pH on the speciation coefficients in models of bromide influence on the formation of trihalomethanes and haloacetic acids. Water Res. 2014, 62, 117−126. (16) Roccaro, P.; Chang, H. S.; Vagliasindi, F. G. A.; Korshin, G. V. Modeling bromide effects on yields and speciation of dihaloacetonitriles formed in chlorinated drinking water. Water Res. 2013, 47, 5995−6006. (17) Bond, T.; Huang, J.; Graham, N. J. D.; Templeton, M. R. Examining the interrelationship between DOC, bromide and chlorine dose on DBP formation in drinking waterA case study. Sci. Total Environ. 2014, 470, 469−479. (18) Pals, J.; Attene-Ramos, M. S.; Xia, M.; Wagner, E. D.; Plewa, M. J. Human cell toxicogenomic analysis linking reactive oxygen species to the toxicity of monohaloacetic acid drinking water disinfection byproducts. Environ. Sci. Technol. 2013, 47 (21), 12514−12523. (19) Liu, J.; Zhang, X. Comparative toxicity of new halophenolic DBPs in chlorinated saline wastewater effluents against a marine alga: Halophenolic DBPs are generally more toxic than haloaliphatic ones. Water Res. 2014, 65, 64−72. (20) Yang, M.; Zhang, X. Comparative developmental toxicity of new aromatic halogenated DBPs in a chlorinated saline sewage effluent to the marine polychaete Platynereis dumerilii. Environ. Sci. Technol. 2013, 47 (19), 10868−10876. (21) Ding, G.; Zhang, X.; Yang, M.; Pan, Y. Formation of new brominated disinfection byproducts during chlorination of saline sewage effluents. Water Res. 2013, 47 (8), 2710−2718.

(22) Gong, T.; Zhang, X. Detection, identification and formation of new iodinated disinfection byproducts in chlorinated saline wastewater effluents. Water Res. 2015, 68, 77−86. (23) Fang, J.; Ling, L.; Shang, C. Kinetics and mechanisms of pHdependent degradation of halonitromethanes by UV photolysis. Water Res. 2013, 47 (3), 1257−1266. (24) Xiao, Y.; Fan, R.; Zhang, L.; Yue, J.; Webster, R. D.; Lim, T. T. Photodegradation of iodinated trihalomethanes in aqueous solution by UV 254 irradiation. Water Res. 2014, 49, 275−285. (25) Hansen, K. M. S.; Zortea, R.; Piketty, A.; Vega, S. R.; Andersen, H. R. Photolytic removal of DBPs by medium pressure UV in swimming pool water. Sci. Total Environ. 2013, 443, 850−856. (26) Chen, B.; Lee, W.; Westerhoff, P. K.; Krasner, S. W.; Herckese, P. Solar photolysis kinetics of disinfection byproducts. Water Res. 2010, 44 (11), 3401−3409. (27) Abusallout, I.; Hua, G. Photolytic dehalogenation of disinfection byproducts in water by natural sunlight irradiation. Chemosphere 2016, 159, 184−192. (28) Wong, A. S.; Crosby, D. G. Photodecomposition of pentachlorophenol in water. J. Agric. Food Chem. 1981, 29 (1), 125−130. (29) Hwang, H. M.; Hodson, R. E.; Lee, R. F. Degradation of phenol and chlorophenols by sunlight and microbes in estuarine water. Environ. Sci. Technol. 1986, 20 (10), 1002−1007. (30) Qian, Y.; Wang, W.; Boyd, J. M.; Wu, M.; Hrudey, S. E.; Li, X.-F. UV-induced transformation of four halobenzoquinones in drinking water. Environ. Sci. Technol. 2013, 47 (9), 4426−4433. (31) Jha, A. N.; Hutchinson, T. H.; Mackay, J. M.; Elliott, B. M.; Dixon, D. R. Development of an in vivo genotoxicity assay using the marine worm Platynereis dumerilii (Polychaeta: Nereidae). Mutat. Res. 1996, 359 (2), 141−150. (32) Gong, T.; Zhang, X.; Li, Y.; Xian, Q. Formation and toxicity of halogenated disinfection byproducts resulting from linear alkylbenzene sulfonates. Chemosphere 2016, 149, 70−75. (33) Escher, B. I.; Allinson, M.; Altenburger, R.; et al. Benchmarking organic micropollutants in wastewater, recycled water and drinking water with in vitro bioassays. Environ. Sci. Technol. 2014, 48, 1940− 1956. (34) Jia, A.; Escher, B. I.; Leusch, F. D. L.; Tang, J. Y. M.; Prochazka, E.; Dong, B.; Snyder, E. M.; Snyder, S. A. In vitro bioassays to evaluate complex chemical mixtures in recycled water. Water Res. 2015, 80, 1− 11. (35) APHA; AWWA; WEF. Standard Methods for the Examination of Water and Wastewater, 22nd ed.; Washington, DC, 2012. (36) Liu, J.; Zhang, X.; Li, Y. Effect of boiling on halogenated DBPs and their developmental toxicity in real tap water. In Recent Advances in Disinfection By-Products; Karanfil, T., Mitch, W. A., Westerhoff, P., Xie, Y., Eds.; American Chemical Society: Washington, DC, 2015; pp 45− 60. (37) Hua, G.; Reckhow, D. A. Determination of TOCl, TOBr and TOI in drinking water by pyrolysis and off-line ion chromatography. Anal. Bioanal. Chem. 2006, 384 (2), 495−504. (38) Kristiana, I.; Gallard, H.; Joll, C.; Croué, J. P. The formation of halogen-specific TOX from chlorination and chloramination of natural organic matter isolates. Water Res. 2009, 43 (17), 4177−4186. (39) Liu, J.; Zhang, X. Effect of quenching time and quenching agent dose on total organic halogen measurement. Int. J. Environ. Anal. Chem. 2013, 93 (11), 1146−1158. (40) Li, Y.; Zhang, X.; Shang, C. Effect of reductive property of activated carbon on total organic halogen analysis. Environ. Sci. Technol. 2010, 44 (6), 2105−2111. (41) Pan, Y.; Zhang, X. Total organic iodine measurement: A new approach with UPLC/ESI-MS for off-line iodide separation/detection. Water Res. 2013, 47 (1), 163−172. (42) Cornelisse, J. Photochemical aromatic substitution. In CRC Handbook of Organic Photochemistry and Photobiology; Horspol, W. M., Song, P. S., Eds.; CRC Press, Boca Raton: New York, 1995; pp 1250− 1262. I

DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX

Article

Environmental Science & Technology (43) Luo, Y.-R.; Kerr, J. A. Bond dissociation energies. In CRC Handbook of Chemistry and Physics; CRC Press, Boca Raton: New York, 2012. (44) Scheck, C. K.; Frimmel, F. H. Degradation of phenol and salicylic acid by ultraviolet radiation/hydrogen peroxide/oxygen. Water Res. 1995, 29 (10), 2346−2352. (45) Gillner, M.; Moore, G. S.; Cederberg, H.; Gustafsson, K. Environmental health criteria 157: Hydroquinone International Program on Chemical Safety 1994. (46) Wang, W.; Qian, Y.; Li, J.; Moe, B.; Huang, R.; Zhang, H.; Hrudey, S. E.; Li, X.-F. Analytical and toxicity characterization of halohydroxylbenzoquinones as stable halobenzoquinone disinfection byproducts in treated water. Anal. Chem. 2014, 86 (10), 4982−4988. (47) Monks, T. J.; Hanzlik, R. P.; Cohen, G. M.; Ross, D.; Graham, D. C. Quinone chemistry and toxicity. Toxicol. Appl. Pharmacol. 1992, 112 (1), 2−16. (48) Jacobs, L. E.; Weavers, L. K.; Chin, Y. P. Direct and indirect photolysis of polycyclic aromatic hydrocarbons in nitrate-rich surface waters. Environ. Toxicol. Chem. 2008, 27 (8), 1643−1648. (49) Chin, Y. P.; Miller, P. L.; Zeng, L.; Cawley, K.; Weavers, L. K. Photosensitized degradation of bisphenol A by dissolved organic matter. Environ. Sci. Technol. 2004, 38 (22), 5888−5894. (50) Hua, G. H.; Reckhow, D. A. Effect of alkaline pH on the stability of halogenated DBPs. J. Am. Water Works Assoc. 2012, 104, E107− E119. (51) Tedetti, M.; Sempere, R. Penetration of ultraviolet radiation in the marine environment. A Review. Photochem. Photobiol. 2006, 82 (2), 389−397.

J

DOI: 10.1021/acs.est.6b04232 Environ. Sci. Technol. XXXX, XXX, XXX−XXX