Authors
Tarek Manasfi, Christoph Dieziger, Simon A Rath, Daisuke Minakata, Urs von Gunten
Published in
Environmental science & technology. Jun 18, 2026. Epub Jun 18, 2026.
Abstract
The formation of toxicologically relevant nitro compounds has been observed during ozonation of nitrite-containing secondary wastewater effluents, but their formation mechanism remains unknown. To identify key nitrating species, three reaction systems were investigated: ozonation of nitrite (O3/NO2-), peroxynitrite (ONOOH/ONOO-), and hydroxyl radical oxidation of nitrite with γ-radiolysis (γ/NO2-). Nitrite ozonation (O3/NO2-) yielded significant amounts of the nitrating agent nitrogen dioxide •NO2 (9.4% at pH 7 to 22% at pH 12) besides the main product nitrate. No peroxynitrite formation was detected during ozonation of nitrite-containing waters, suggesting that •NO2 is the key nitrating species. A comparison of nitro compound formation from 20 aromatic compounds in the three reaction systems showed a consistent formation of nitro compounds with minor differences. Furthermore, the pH-dependence patterns of nitration for two micropollutants (diuron and carbendazim) revealed similarities between the O3/NO2- and γ-radiolysis (γ/NO2-) systems, unlike peroxynitrite. These trends, combined with the lack of detection of peroxynitrite during ozonation, a fast reaction of peroxynitrite with ozone (kpH=9 = (4.96 ± 0.40) × 106 M-1s-1), suggest that a significant contribution of peroxynitrite is highly unlikely. Overall, nitration during ozonation involves nitrite oxidation to •NO2, mostly by hydroxyl radical and to a minor extent by ozone.
PMID:
42314008
Bibliographic data and abstract were imported from PubMed on 19 Jun 2026.
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