Delineating Nitroxyl Formation Pathways from Chloramines and Free Chlorine and Cascades of Reactive Nitrogen Species to N-Nitrosamines and N-Nitramines

描述从氯胺和游离氯以及活性氮级联到 N-亚硝胺和 N-硝胺的硝酰基形成途径

基本信息

批准号：
2034481
负责人：
Julian Fairey
金额：
$ 32.95万
依托单位：
University of Arkansas
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-09-01 至 2024-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2034481&HistoricalAwards=false
关键词：
Delineating Nitroxyl Formation Pathways Chloramines

项目摘要

Disinfection is a critical unit operation used in water treatment to protect the public from waterborne diseases. Chloroamines are utilized to disinfect about one-half of the drinking water produced in the United States. The use of chloramines in water disinfection provides several advantages. Because they are less reactive and more stable than chlorine, chloroamines have much less tendency to form disinfection by-products by reacting with dissolved organic matter (DOM). In addition, chloramines provide longer-lasting disinfection and better protection against microorganism regrowth and contamination as treated water is delivered through the distribution pipe networks. However, recent research has linked the presence of the cancer-causing compound N-nitrosodimethylamine (NDMA)in drinking water to reactive nitrogen species (RNS) that are formed in chloramine systems used in water disinfection. The goal of this research is to investigate the role of RNS in the formation of NDMA in chloroamine water disinfection systems. The successful completion of this project will benefit society through the development of new knowledge and insight to control and mitigate the formation of NDMA in chloramine water disinfection systems. Further benefits to society will be achieved through student education and training including the mentoring of a doctoral student and an undergraduate student.Reactive nitrogen species (RNS) have long been postulated to form in chloramine systems used in water disinfection. However, the identification of these RNS and delineation of their roles in the formation of toxic disinfection by-products (DBPs) such as N-nitrosodimethylamine (NDMA) has remained elusive. Thus, there is a critical need to identify RNS formed from chloramines and free chlorine and delineate the subsequent RNS cascades that initiate NDMA formation in drinking water. The goal of this project is to address these knowledge gaps. To achieve this goal, the PI propose to test the hypothesis that that nitroxyl is the “missing link” in understanding NDMA formation via (1) dichloramine hydrolysis and (2) the reactions of monochloramine or hypochlorous acid with hydroxylamine. The project will integrate batch kinetic experiments and modeling to (1) evaluate the formation and role of peroxynitrite as a parent nitrosating agent, (2) delineate nitroxyl formation pathways from chloramines and free chlorine, and (3) determine the proportion of N-nitrosamines (e.g. NDMA) and N-nitramines formed through the nitroxyl pathway under typical chloramination conditions used during water disinfection. The kinetic experiments will measure and quantify the concentrations of the relevant reactive species including reactants (free chlorine, chloramine species, precursors, and dissolved oxygen), RNS intermediates, stable products (nitrous oxide, nitrogen gas, nitrite, and nitrate), and N-nitrosamines and N-nitramines. Thus, the successful completion of this project has the potential for transformative impact through the development of new fundamental knowledge that could enable the control and mitigation of the formation of toxic DBPs such as NDMA in chloramine water disinfection systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

消毒是水处理中用于保护公众免受水传播疾病的关键单元操作，美国生产的约一半的饮用水都使用氯胺进行消毒。在水消毒中使用氯胺具有多种优点。与氯相比，氯胺的反应性更小且更稳定，因此与溶解的有机物 (DOM) 反应形成消毒副产物的可能性要小得多。此外，氯胺提供更持久的消毒和更好的保护。然而，最近的研究发现，饮用水中存在的致癌化合物 N-亚硝基二甲胺 (NDMA) 与水中形成的活性氮 (RNS) 存在关联。本研究的目的是研究 RNS 在氯胺水消毒系统中 NDMA 形成中的作用，该项目的成功完成将通过开发新知识和见解造福社会。控制和减少氯胺水消毒系统中 NDMA 的形成将通过学生教育和培训（包括指导一名博士生和一名本科生）实现。长期以来，人们一直认为活性氮 (RNS) 会在氯胺水消毒系统中形成。然而，对这些 RNS 的识别以及它们在 N-亚硝基二甲胺 (NDMA) 等有毒消毒副产物 (DBP) 形成中的作用仍然存在。因此，迫切需要确定由氯胺和游离氯形成的 RNS，并描述随后在饮用水中引发 NDMA 形成的 RNS 级联。 PI 提议检验以下假设：硝酰基是通过 (1) 二氯胺水解和 (2) 一氯胺或次氯酸与 NDMA 的反应来理解 NDMA 形成的“缺失环节”。该项目将整合批量动力学实验和建模，以（1）评估过氧亚硝酸盐作为母体亚硝化剂的形成和作用，（2）描绘氯胺和游离氯的硝酰基形成途径，以及（3）确定氮的比例。动力学实验将测量在水消毒过程中使用的典型氯胺化条件下通过硝酰基途径形成的亚硝胺（例如 NDMA）和 N-硝胺。并量化相关活性物质的浓度，包括反应物（游离氯、氯胺物质、前体和溶解氧）、RNS中间体、稳定产物（一氧化二氮、氮气、亚硝酸盐和硝酸盐）以及N-亚硝胺和N-因此，该项目的成功完成有可能通过开发新的基础知识来产生变革性影响，从而能够控制和减轻氯胺水中 NDMA 等有毒 DBP 的形成。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。