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

测定和测量饮用水中的所有物质是不可能的。生物测定结果作为综合水质指标，有望用于水质管理。当使用消毒副产物作为饮用水水质指标时，应在水处理工艺和配水中进行合理选择。在配水系统中，MX被认为是一个合适的指标。在本研究中，发现MX在水中由于水解和氯化分解而不稳定。同时发现，水溶液中MX的衰变速率与ph有很强的关系，在碱区MX的衰变速率要快得多。此外，当氯含量较高时，MX衰变速度更快。诱导染色体畸变和MX转化的活性表现出相似的趋势。琵琶湖非两阶段法测定的诱导染色体畸变活性和诱导转化活性在加氯后迅速上升，然后开始逐渐下降。从定性和定量上看，MX是评价配水系统氯化水毒性的适宜指标。但是，有必要考虑残氯。

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.