Carbonate radical is a powerful oxidant which presents in sunlit surface waters, and is quenched by dissolved organic matter (DOM). In the current study, the reactions of carbonate radical with DOM were investigated to explore their effects on the photo-bleaching of DOM. Our results demonstrated that the presence of bicarbonate ion enhanced the photo-bleaching reaction rates of DOM in the initial stage, especially on the long wavelength of absorbance. A positive correlation between the steady state concentrations of carbonate radical and the photo-bleaching rates of absorbance was observed. With further irradiation, the effects of bicarbonate on the photo-bleaching rates of DOM significantly reduced. Meanwhile the presence of bicarbonate ion has no impacts on the fluorescence bleaching rates. Therefore we speculated that carbonate radical selectively reacts with certain moieties of DOM, probably phenolic groups. The reaction rate constants of carbonate radical with varied DOM were measured and linearly correlated with the phenolic moieties. Furthermore the reactivity of carbonate radical toward phenolic compounds were compared with one of <sup>3</sup>DOM<sup>●</sup>, suggesting that they share similar electron transfer mechanism. This study indicated that carbonate radical plays an important roles on the photo-bleaching of DOM under simulated natural conditions.

Photochemical formation of carbonate radical and its effects on the photo-bleaching of dissolved organic matter

253rd National Meeting (2017)

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