水中ピレンの塩素化反応によるモノクロロピレン及びジクロロピレンの生成

抄録

In order to investigate the possible formation of chlorinated pyrene in the chlorination process for tap water, we carried out a model experiment on the chlorination reaction of pyrene (Py), and studied the chlorinated products and their stability by the light. The mutagenicities of the products were also investigated. The results obtained were as follows : 1) The main product was monochloropyrene (PyCl), when the chlorination reactions of Py were performed at pH 4.3, 20°C for 0.5-24 h in the dark with a hypochlorite solution containing 0.6 mg/l free chlorine (F-Cl₂). PyCl was hardly formed at pH 6.0 and above, and the formative amount of PyCl increased with the rise of reaction temperature. 2) Dichloropyrene (PyCl₂) was also formed, when the chlorination reactions of Py were performed at pH 3 with F-Cl₂ 0.6 mg/l and at pH 3-4.3 with F-Cl₂ 9 mg/l. 3) The concentrations of Py and PyCl decreased quickly in the presence of bromide ion under the acidic condition partly because monobromopyrene was produced. They decreased by the light irradiation. 4) PyCl and PyCl₂ were found to be mutagenic to both TA 98 and TA 100 strains in the presence of S-9 mix. From these results, and from pH value and residential time of treated water in a filter plant, the formation of the chlorinated products, such as PyCl and PyCl₂, seemed to be not likely to occur in the chlorination process for tap water.