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

在这个合作项目中，将阐明氯化氧化剂(即氯和氯胺)与碘化X射线造影剂(ICM)或其生物转化产物(TPS)反应时形成碘化消毒副产物(IODO-DBPs)的机理并设计动力学模型。ICM和它们的TPS能够通过生物屏障，在某种程度上也能通过吸附屏障，如活性碳。在美国和欧洲的几个地表水中检测到的ICM含量高达几个μg/L，在饮用水中检测到的ICM TPS含量高达100 ng/L。在地下水和饮用水中检测到的ICM TPS含量高达500 ng/L。在初步实验中，只有异丙咪醇有显著的转化作用，而泛影葡胺、碘海醇、碘丙醇和碘普罗胺没有明显的氧化作用。对于这一美国-德国倡议，将阐明氧化剂与ICM反应的反应路径和动力学参数。此外，还将确定高相对分子质量和低相对分子质量ICM氧化产物的化学结构，并确定处理条件(即pH、天然有机物[NOM]和溴浓度)对形成碘-DBP的影响。此外，还将评估这些反应混合物的毒性，以确定氧化剂与ICM的反应是否会导致DBPs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.