Direct photodegradation of aromatic carbamate pesticides: Kinetics and mechanisms in aqueous vs. non-aqueous media

作者：Yufan Yuan, Danping Li, Huajun Huang, Jinbao He, Chenglong Yu, Yanpeng Gao, Davide Vione, Hansun Fang · 发表于：Journal of Hazardous Materials · 年份：2025 · DOI：10.1016/j.jhazmat.2025.137648 · 被引用次数：12 · 研究领域：Toxic Organic Pollutants Impact、Water Quality Monitoring and Analysis、Pharmaceutical and Antibiotic Environmental Impacts

The direct photodegradation quantum yields ( Φ ) of five representative aromatic carbamate pesticides - carbaryl, carbofuran, propoxur, isoprocarb, and metolcarb - were examined in both aqueous and non-aqueous solutions, the latter mimicking hydrophobic environments such as leaf surfaces. For carbaryl, carbofuran, isoprocarb, and metolcarb, the Φ values generally followed the order Φ water < Φ MeOH < Φ n - hexane , while propoxur showed a different trend, Φ MeOH < Φ n-hexane < Φ water . Scavenging and laser flash photolysis experiments, combined with quantum chemical calculations, were used to clarify the photodegradation mechanisms. Photodegradation is primarily initiated by the singlet excited state (S*), with the triplet state (T * ) also contributing in compounds with conjugated structures, such as carbaryl. Upon excitation, methylcarbamate aromatic esters (MCAEs) generated both radical cations (S •+ ) and phenoxyl radicals (S-O • ), and S •+ would convert to S-O • subsequently. S-O • is predominantly generated through the cleavage of C-O bonds in ester groups, subsequently abstracting hydrogen from solvent molecules. The reactivity of hydrogen donors in these solvents follows the order: -CH 2 - > -CH 3 > -OH. For propoxur, the ether group also contributes to the formation of S-O • , which further reacts with H 2 O and enhances degradation in aqueous environments. Solvent polarity had a minimal effect on photodegradation. This comparative study of degradation in aqueous a...