Humic Substance Photosensitized Degradation of Phthalate Esters Characterized by ~2H and ~(13)C Isotope Fractionation

摘要

The photosensitized transformation of organic chemicals is an important degradation mechanism in natural surface waters,aerosols,and water films on surfaces.Dissolved organic matter including humic-like substances(HS),acting as photosensitizers that participate in electron transfer reactions,can generate a variety of reactive species,such as OH radicals and excited triplet-state HS(~3HS*),which promote the degradation of organic compounds.We use phthalate esters,which are important contaminants found in wastewaters,landfills,soils,rivers,lakes,groundwaters,and mine tailings.We use phthalate esters as probes to study the reactivity of HS irradiated with artificial sunlight.Phthalate esters with different side-chain lengths were used as probes for elucidation of reaction mechanisms using 2H and ~(13)C isotope fractionation.Reference experiments with the artificial photosensitizers 4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein(Rose Bengal),3-methoxy-acetophenone(3-MAP),and 4-methoxybenzaldehyde(4-MBA)yielded characteristic fractionation factors(-4 ± 1,-4 ± 2,and-4 ± 1‰ for ~2H; 0.7 ± 0.2,1.0 ± 0.4,and 0.8 ± 0.2‰ for ~(13)C),allowing interpretation of reaction mechanisms of humic substances with phthalate esters.The correlation of ~2H and ~(13)C fractions can be used diagnostically to determine photosensitized reactions in the environment and to differentiate among biodegradation,hydrolysis,and photosensitized HS reaction.