Journal of Japan Society on Water Environment

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Halobenzoquinones (HBQs) are one of the groups of disinfection byproducts newly detected in drinking water. In this study, a method of analyzing 2,6-dichloro-1,4-benzoquinone (DCBQ), the most ubiquitous HBQ, by solid-phase extraction followed by liquid chromatography-tandem mass spectrometry was investigated. DCBQ standard addition was found to be appropriate when it was applied before the evaporation of the solid-phase extraction solution. The limit of quantitation in this method was 8 ng·L^-1. The occurrence of DCBQ in drinking water from 12 water purification plants throughout Japan was investigated in the summer and winter of FY 2013. DCBQ was detected in 21 out of 24 samples and its concentration was in the range of 8-51 ng·L^-1. DCBQ was found in drinking water of all but one of the water purification plants. Thus, it was shown that DCBQ was widely present in drinking water in Japan. From Spearman's rank-order correlation coefficient, a significant relationship between DCBQ concentration and chloroform concentration in drinking water was observed.

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We conducted a high-resolution field survey at nine sampling stations from September 18 to 19, 2012, to evaluate the short-term dynamics of NH₄-N affected by the discharge of high-turbidity water into Isahaya Bay, Japan, from a reservoir of reclaimed land. In front of the north gate, the concentration of particulate nitrogen reached 100 μmol·L^-1 just after the discharge. In contrast, the NH₄-N concentration tended to vary with tidal height and reached 9.3 μmol·L^-1. The mean rate of increase of NH₄-N measured in front of the north gate was estimated to be 1.8 mmol N·m^-2·h^-1 on the basis of its time series variation. Thus, NH₄-N regenerated from the discharged organic matter would be one of the nutrient sources for the red tide in this bay.

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