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Updated Reaction Pathway for Dichloramine Decomposition: Formation of Reactive Nitrogen Species and N-Nitrosodimethylamine
Citation:
Pham, H., D. Wahman, AND J. Fairey. Updated Reaction Pathway for Dichloramine Decomposition: Formation of Reactive Nitrogen Species and N-Nitrosodimethylamine. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 55(3):1740-1749, (2021). https://doi.org/10.1021/acs.est.0c06456
Impact/Purpose:
The environmental or health problem addressed by the study: Proposed new mechanism for NDMA formation from chloramines A general description of the work and results: Experiments have been conducted to evaluate a proposed scheme for NDMA formation in drinking water The long term importance or significance of the findings: Provides a new mechanism for NDMA formation in chloraminated water Who would be interested in or could apply the results (e.g. program or regional partners, general public, local communities): Researchers and drinking water utilities trying to understand NDMA formation
Description:
Nitrous oxide (N2O) and dissolved oxygen (DO) were quantified during 800 μeq Cl2 L–1 dichloramine (NHCl2) decomposition (pH 7–10) with or without 10 μM total dimethylamine (TOTDMA) addition. Chemical kinetics and yields supported nitroxyl (HNO) formed from NHCl2 hydrolysis and dimerized to N2O or reacted with DO to form peroxynitrite (ONOOH/ONOO–). N2O formation and DO consumption paralleled NHCl2 decomposition and were maximal at pH 9 (13 μM N2O formation and 64 μM DO consumption). With TOTDMA addition, N–nitrosodimethylamine (NDMA) paralleled N2O formation and DO consumption (maximal NDMA yield at pH 9; 3.8 μM or 38%), and N–nitrodimethylamine (DMNO) yields were 0.8–1.1% of NDMA. These results implicated ONOOH/ONOO– formation because its decomposition results in nitric oxide and nitrous oxide radicals which may react with DMA to form NDMA and DMNO, respectively. An ONOOH/ONOO– assay proved subject to interferences, likely from total nitroxyl (HNO/NO–) as measured profiles tracked with simulations of the unknown intermediate (I) formed from NHCl2 hydrolysis in the unified model of chloramine chemistry. Weight–of–evidence supports I is HNO, providing motivation to include reactions with DO and reactive nitrogen species (RNS) and assess RNS–scavengers to curb N–nitrosamines and N–nitramines.
URLs/Downloads:
DOI: Updated Reaction Pathway for Dichloramine Decomposition: Formation of Reactive Nitrogen Species and N-Nitrosodimethylamine
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