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

Abstract

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*.

Photochemical Fate of Carbamazepine in Surface Freshwaters: Laboratory Measures and Modeling

“…Indeed, nitrite and CDOM are usually more important than nitrate as • OH sources in surface waters, but they are less suitable for laboratory studies. 12,34,36 The fact that direct photolysis and • OH reaction are the main CBZ phototransformation pathways agrees well with previous studies. 18,19,24 It also allows exclusion of 3 CDOM* as important reactive species for CBZ phototransformation in humic waters.…”

“…Such considerations hold as well under conditions characterized by high DOM concentration, because organic matter is a source as well as a sink of • OH. 12 Note that the model takes into account competition for sunlight irradiance between the different light-absorbing species in solution, substrate (CBZ) included. 25,26,[34][35][36] Moreover, the laboratory use of nitrate as a reasonably "clean" • OH source to study the reaction kinetics of CBZ does not imply that it is the main • OH source in the environment.…”

“…shallow lagoons that collect water draining agricultural areas), where light-induced processes could be more important. 12 Table 2), for which commercial standards are available were monitored upon CBZ transformation via both reaction with • OH (produced by nitrate irradiation) and direct photolysis, which are the two main processes that CBZ is expected to undergo in surface waters. Intermediates I, II, IV and V were identified as acridine, CBZ-10,11-epoxide, 10,11-dihydro-10,11-cis-dihydroxy-CBZ and 10,11-dihydro-10,11-transdihydroxy-CBZ, respectively, by comparing their chromatographic and mass spectrometric behavior with that of authentic standards.…”

“…brackish waters) 12 should for instance include bromide as • OH scavenger. In brackish systems (e.g.…”

Phototransformation of the sunlight filter benzophenone-3 (2-hydroxy-4-methoxybenzophenone) under conditions relevant to surface waters

“…These species are generated by sunlight irradiation of photosensitisers such as nitrate, nitrite and CDOM (Boreen et al, 2003;Al Housari et al, 2010). In the case of CO 3 −• , the formation pathways include oxidation of bicarbonate and carbonate by • OH and of carbonate by 3 CDOM* (Canonica et al, 2005).…”