Reactive photoinduced species in estuarine waters. Characterization of hydroxyl radical, singlet oxygen and dissolved organic matter triplet state in natural oxidation processes

This paper describes the reactive photo-induced species (RPS) hydroxyl radical (HO˙), singlet oxygen (1O2) and chromophoric dissolved organic matter triplet state (3CDOM*) in fresh water (Canal Fumemorte) and estuarine water (Vaccarès), sampled in the Camargue region, southern France. Experiments were conducted with a medium-pressure Hg lamp in a glass photoreactor (λ > 290 nm, 220 W m−2 irradiance between 290 and 400 nm). Steady-state concentration and initial production rate of RPS were determined for HO˙ and for 1O2. HO˙ and 1O2 were indirectly identified in the presence of benzene and furfuryl alcohol, respectively, as specific probes. The steady-state measured concentration of HO˙was (1.72 ± 0.01) × 10−16 M and (9.41 ± 0.12)×10−17 M for Vaccarès and Canal waters samples, respectively, and the respective concentrations of 1O2 was (2.06 ± 0.22) × 10−13 M and (5.44 ± 0.04) × 10−14 M. The interference of 3CDOM* or other species in the determination of 1O2 with furfuryl alcohol, and of 1O2 in the quantification of 3CDOM* with 2,4,6-trimethylphenol was also quantitatively assessed. We developed a kinetic model describing the solar photo-transformation of xenobiotic organic compounds induced by the three different photooxidants HO˙, 1O2 and 3CDOM*.