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Formation and reactivity of the dichloride radical (Cl2-) in surface waters: A modelling approach

Brigante, Marcello, Minella, Marco, Mailhot, Gilles, Maurino, Valter, Minero, Claudio, Vione, Davide
Chemosphere 2014 v.95 pp. 464-469
brackish water, chlorides, dissolved organic matter, latitude, models, nitrites, nitrogen dioxide, nitrophenols, oxidants, phenol, pollutants, seawater, summer, surface water, France
The occurrence of Cl2- in natural waters would depend on the budget between triplet-sensitised photogeneration (which might have second-order rate constant of 107–109M−1s−1) and scavenging by dissolved organic matter (DOM, with possible rate constant of 10–103L (mg C)−1s−1). The steady-state [Cl2-] in brackish to saline waters might be in the range of 10−14–10−12M in mid-latitude summertime, coherently with data of phenol photochlorination in seawater. Steady-state [Cl2-] would be enhanced by chloride (up to a plateau above 0.1M Cl−) and inhibited by DOM. The radical Cl2- would also be a major oxidant of nitrite to the nitrating agent NO2 in brackish- and salt-water. This issue may explain the sustained formation of nitrophenols in phenol-spiked seawater and in natural brackish waters impacted by phenolic pollutants (Rhône delta, Southern France).