UV-Induced Transformation of Four Halobenzoquinones in Drinking Water

Environmental Science & Technology (Impact Factor: 5.33). 04/2013; 47(9). DOI: 10.1021/es305044k
Source: PubMed


Halobenzoquinones (HBQs) are a group of emerging disinfection byproducts (DBPs) found in treated drinking water. Because the use of UV treatment for disinfection is becoming more widespread, it is important to understand how the HBQs may be removed or changed due to UV irradiation. Water samples containing four HBQs, 2,6-dichloro-1,4-benzoquinones (DCBQ), 2,3,6-trichloro-1,4-benzoquinone (TCBQ), 2,6-dichloro- 3-methyl-1,4-benzoquinone (DCMBQ), and 2,6-dibromo-1,4- benzoquinone (DBBQ) were treated using a modified bench scale collimated beam device, mimicking UV treatment. Water samples before and after UV irradiation were analyzed for the parent compounds and products using a high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) method. As much as 90% of HBQs (0.25 nmol L-1) in both pure water and tap water were transformed to other products after UV254 irradiation at 1000 mJ cm-2. The major products of the four HBQs were identified as 3-hydroxyl-2,6-dichloro-1,4-benzoquinone (OH-DCBQ) from DCBQ, 5-hydroxyl-2,6-dichloro-3-methyl-1,4-benzoquinone (OH-DCMBQ) from DCMBQ, 5-hydroxyl-2,3,6-trichloro-1,4-benzoquinone (OH-TCBQ) from TCBQ and 3-hydroxyl-2,6-dibromo-1,4-benzoquinone (OH-DBBQ) from DBBQ. These four OH-HBQs were further modified to mono-halogenated benzoquinones when the UV dose was higher than 200 mJ cm-2. These results suggested possible pathways of UV-induced transformation of HBQs to other compounds. Under the UV dose commonly used in water treatment plants, it is likely that HBQs are partially converted to other halo-DBPs. The occurrence and toxicity of these mixed DBPs warrant further investigation to understand whether they pose a health risk.

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Available from: Minghuo Wu
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    • "Presence of bromide and DOC in seawater environment plays a significant role in the reactivity of benzophenone-4 during photolysis. Four halobenzoquinones, a class of emerging disinfection byproduct , showed as much as 90% degradation by UV irradiation in both pure and tap water, and several major byproducts were identified (Qian et al., 2013). Keen et al. (2013) studied the photodegradation of diclofenac under UV and found that quantum yield of photolysis was independent of wavelength, and that one of the products of photolysis is a dimer of the parent molecule. "
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    • "Therefore, application of chlorine-based disinfectant (chlorine, monochloramine and chlorine dioxide ) so as to resupply residual disinfection after UV is technically necessary in water treatment process. However, a few literature have reported that UV irradiation may enhance the formation of dichloroacetic acid, trichloroacetic acid, cyanogen chloride (Liu et al., 2006, 2012) and chloropicrin (Shah et al., 2011), or induce transformation of halobenzoquinones (Qian et al., 2013) and N-nitrosodimethylamine (Lee et al., 2007; Soltermann et al., 2013). Nevertheless, there are no reports relating to effects of UV treatment to the formation of I- DBPs and little research has been conducted about UV degradation removal of ICM. "
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