4-nitroso-sulfamethoxazole generation in soil under denitrifying conditions: Field observations versus laboratory results

Abstract : The formation of 4-nitroso-sulfamethoxazole and 4-nitro-SMX, two transformation products (TPs) of sulfamethoxazole (SMX) was investigated under batch soil slurry experiments and in a field study. Due to their low occurrence levels (ng/L) in environmental waters, a suitable analytical method based on liquid chromatography - high resolution - mass spectrometry was developed. Consequently, field observations revealed, for the first time, the occurrence of 4-nitroso-SMX in groundwater at concentrations as high as 18ng/L.Nitric oxide (NO) steady-state concentrations were determined in soil slurry experiments because this reactive specie accounted for the formation of 4-nitroso-SMX and 4-nitro-SMX. Measurements revealed that environmental SMX concentrations (0.2-2μg/L) at neutral pH induced the accumulation of nitric oxide. Under acidic conditions (pH<6), nitrous acid (HONO) was the major source of nitric oxide while under neutral/basic conditions nitric oxide release was related to the inhibition of denitrification processes. Under laboratory experiments, SMX nitration reaction appeared to be an irreversible transformation pathway, while 4-nitroso-SMX was slowly transformed over time. The occurrence of 4-nitroso-SMX conditions was therefore unexpected in the field study but could be due to its continuous input from soil and/or its relative persistence under anoxic conditions. A mechanism for 4-nitroso-SMX formation was proposed involving a nitrosative desamination pathway through a phenyl radical.
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Journal articles
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https://hal.archives-ouvertes.fr/hal-02068760
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Submitted on : Friday, March 15, 2019 - 11:28:22 AM
Last modification on : Monday, September 2, 2019 - 2:46:08 PM

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Monica Brienza, Celine Duwig, Sandra Perez, Serge Chiron. 4-nitroso-sulfamethoxazole generation in soil under denitrifying conditions: Field observations versus laboratory results. Journal of Hazardous Materials, Elsevier, 2017, 334, pp.185-192. ⟨10.1016/j.jhazmat.2017.04.015⟩. ⟨hal-02068760⟩

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