In:
Environmental Science: Processes & Impacts, Royal Society of Chemistry (RSC), Vol. 23, No. 11 ( 2021), p. 1791-1802
Abstract:
Knowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters. Here, we investigated carbon (C) and nitrogen (N) isotope fractionation during direct and indirect photodegradation of the herbicides atrazine and S -metolachlor in synthetic agriculturally impacted surface waters containing nitrates (20 mg L −1 ) and dissolved organic matter (DOM, 5.4 mg C L −1 ). Atrazine and S -metolachlor were quickly photodegraded by both direct and indirect processes (half-lives 〈 5 and 〈 7 days, respectively). DOM slowed down photodegradation while nitrates increased degradation rates. The analysis of transformation products showed that oxidation mediated by hydroxyl radicals (HO˙) predominated during indirect photodegradation. UV light (254 nm) led to significant C and N isotope fractionation, yielding isotopic fractionation values ε C = 2.7 ± 0.3 and 0.8 ± 0.1‰, and ε N = 2.4 ± 0.3 and −2.6 ± 0.7‰ for atrazine and S -metolachlor, respectively. In contrast, photodegradation under simulated sunlight led to negligible C and slight N isotope fractionation, emphasizing the effect of the radiation wavelengths on the isotope fractionation induced by direct photodegradation. Altogether, these results highlight the importance of using simulated sunlight to obtain environmentally-relevant isotopic fractionation values and to distinguish photodegradation and other dissipation pathways in surface waters.
Type of Medium:
Online Resource
ISSN:
2050-7887
,
2050-7895
Language:
English
Publisher:
Royal Society of Chemistry (RSC)
Publication Date:
2021
detail.hit.zdb_id:
2703791-5
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