Formation Mechanisms of Iodinated Disinfection By-Products from X-Ray Contrast Media

在本合作项目中，将阐明氯化氧化剂（即氯和氯胺）与碘x射线造影剂（ICM）或其生物转化产物（TPs）反应时形成碘消毒副产物（iodo-DBPs）的机理，并设计动力学模型。ICM及其tp能够通过生物屏障，并在一定程度上通过吸附屏障，如活性炭。在美国和欧洲的一些地表水中检测到的ICM高达几微克/升，在饮用水中检测到的ICM高达100纳克/升。在500ng /L的地下水和饮用水中检测到ICM TPs。用氯化氧化剂消毒导致只将选定的ICM转化为高毒性、低分子量dbp，如碘酸和碘三卤甲烷（碘thms）。在初步实验中，HOCl对异丙酸酯、碘己醇、异丙醇和碘丙啶的氧化作用不明显，只有iopamidol被显著转化。对于这个美国-德国的倡议，反应途径和动力学参数将阐明与ICM氧化反应。此外，还将鉴定高分子量和低分子量ICM氧化产物的化学结构，并确定处理条件（即pH、天然有机质[NOM]和溴化物浓度）对碘- dbp形成的影响。此外，将评估这些反应混合物的毒性，以确定与ICM的氧化反应是否会导致dbp引起的毒性增加。

In this cooperative project, the mechanisms will be elucidated and a kinetic model will be designed for the formation of iodinated disinfection by-products (iodo-DBPs) when chlorinated oxidants (i.e., chlorine and chloramines) react with iodinated X-ray contrast media (ICM) or their biological transformation products (TPs). ICM and their TPs are capable of passing biological barriers, as well as to some extent, sorptive barriers, such as activated carbon. ICM have been detected in several U.S. and European surface waters up to several μg/L, as well as in drinking water up to several 100 ng/L. ICM TPs were detected in ground water and drinking water up to 500 ng/L. Disinfection with chlorinated oxidants leads to the transformation only of selected ICM to form highly toxic, low molecular weight DBPs, such iodo-acids and iodo-trihalomethanes (iodo-THMs). In preliminary experiments, only iopamidol was significantly transformed, while diatrizoate, iohexol, iomeprol and iopromide were not significantly oxidized by HOCl. For this U.S.-German initiative, reaction pathways and the kinetic parameters will be elucidated for the oxidant reactions with ICM. Furthermore, the chemical structures of higher molecular weight and lower molecular weight ICM oxidation products will be identified, and the influence of treatment conditions (i.e., pH, natural organic matter [NOM], and bromide concentrations) on iodo-DBP formation will be determined. Additionally, the toxicity of these reaction mixtures will be assessed to determine whether oxidant reactions with ICM result in increased toxicity caused by DBPs.