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 ((1)O(2)) and chromophoric dissolved organic matter triplet state ((3)CDOM*) 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 (lambda > 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 (1)O(2). HO* and (1)O(2) 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) x 10(-16) M and (9.41 +/- 0.12) x 10(-17) M for Vaccarès and Canal waters samples, respectively, and the respective concentrations of (1)O(2) was (2.06 +/- 0.22) x 10(-13) M and (5.44 +/- 0.04) x 10(-14) M. The interference of (3)CDOM* or other species in the determination of (1)O(2) with furfuryl alcohol, and of (1)O(2) in the quantification of (3)CDOM* 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*, (1)O(2) and (3)CDOM*.