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Closing Dichloramine Decomposition Nitrogen and Oxygen Mass Balances: Relative Importance of End-Products from the Reactive Nitrogen Species Pathway
Citation:
Pham, H., D. Wahman, AND J. Fairey. Closing Dichloramine Decomposition Nitrogen and Oxygen Mass Balances: Relative Importance of End-Products from the Reactive Nitrogen Species Pathway. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 58(4):2048-2057, (2024). https://doi.org/10.1021/acs.est.3c08088
Impact/Purpose:
The environmental or health problem addressed by the study: Evaluation of the end products associated with chloramine decomposition in drinking water. A general description of the work and results: NItrogen and oxygen mass balances were conducted to evaluate whether all the end products of inorganic chloramine decomposition are accounted for in existing kinetic models. The long-term importance or significance of the findings: Informs development of a comprehensive chloramine model that includes all important end products so that these models may be used to better understand disinfection byproduct formation in drinking water. Who would be interested in or could apply the results (e.g. program or regional partners, general public, local communities): Researchers and regulators trying to understand disinfectant byproduct formation from the use of chloramines in drinking water.
Description:
During dichloramine decomposition, the relative importance of nitrogen and oxygen containing end-products from the reactive nitrogen species pathway is unknown. At pH 9 with and without 10 μM total dimethylamine (TOTDMA) and 200, 400, or 800 μeq Cl2•L−1 initial dichloramine, nitrogen and oxygen mass balances were assessed under ambient (~500 μM-O) and low (≤ 40 μM-O) dissolved oxygen (DO) conditions. Without TOTDMA, the sum of free ammonia, monochloramine, dichloramine, nitrogen gas, nitrous oxide, nitrite, and nitrate indicated average N recoveries (± 95% confidence intervals) were not significantly different under ambient (90 ± 6%) and low (93 ± 7%) DO conditions. With TOTDMA, nitrogen recoveries were less under ambient (83 ± 5%) and greater under low (99 ± 8%) DO conditions. Oxygen recoveries under ambient DO conditions ranged from 90–98%, and the so-called unidentified product (UP) formed at about threefold greater concentration under ambient compared to low DO conditions, like N-nitrosodimethylamine, consistent with a DO limitation. UP formation stemmed from peroxynitrite and/or its decay products reacting with chloramine species, and based on a UP chemical formula 2:2:1 nitrogen:oxygen:chlorine atom ratio and its estimated molar absorptivity, UP inclusion in mass balances accounted for the remaining nitrogen and oxygen within error.
URLs/Downloads:
DOI: Closing Dichloramine Decomposition Nitrogen and Oxygen Mass Balances: Relative Importance of End-Products from the Reactive Nitrogen Species Pathway
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