MX as an Index of Tocicity of Drinking Water in Distribution Systems

不可能测定和测量饮用水中的所有物质。生物测定结果作为综合水质指标，可望用于水质管理。消毒副产物作为饮用水水质指标时，在水处理工艺和配水过程中应合理选择。在配水系统中，MX被认为是一个合适的指标。在这项研究中，MX被发现是不稳定的，在水中由于水解和分解氯化。MX在水相中的衰减速率对pH值有很强的依赖性，在碱性区MX的衰减速率更快。此外，当存在较高的氯时，MX衰减得更快。MX诱发染色体畸变和转化的活性表现出相似的趋势。经非二阶段法测定，在投加氯后，染色体畸变活性和转化活性迅速增加，然后逐渐下降。MX可作为给水管网氯化水毒性的定性和定量指标。但是，必须考虑到余氯。

It is impossible to determine and measure all substances in drinking water. The bioassay results used as comprehensive water quality indicators are expected to be utilized for water quality management. When disinfection by-products are used as indicators of drinking water quality, they should be chosen properly in water treatment process and water distribution. In the water distribution systems, MX was supposed to be a suitable indicator. In this study, MX was found to be unstable in water due to the hydrolysis and the decomposition by chlorination. Also, it was found that the decay rate of MX in aqueous phase strongly depends on pH. The decay rate of MX is much faster in alkali region. Furthermore, MX decayed faster when higher chlorine was present. The activities inducing chromosomal aberrations and transformations of MX showed similar tendency. The activity inducing chromosomal aberrations and the activity inducing transformations measured by non-two-stage assay in Lake Biwa increased rapidly after the addition of chlorine, and then began to decrease gradually. MX seemed to be an appropriate indicator qualitatively and quantitatively for the toxicity of chlorinated water in distribution system. However, it was necessary to take the residual chlorine into consideration.