Photochemical transformation of anionic 2-nitro-4-chlorophenol in surface waters: Laboratory and model assessment of the degradation kinetics, and comparison with field data Original Research Article

Anionic 2-nitro-4-chlorophenol (NCP) may occur in surface waters as a nitroderivative of 4-chlorophenol, which is a transformation intermediate of the herbicide dichlorprop. Here we show that NCP would undergo efficient photochemical transformation in environmental waters, mainly by direct photolysis and reaction with radical dotOH. NCP has a polychromatic photolysis quantum yield ΦNCP = (1.27 ± 0.22) · 10− 5, a rate constant with radical dotOH kNCP,radical dotOH = (1.09 ± 0.09) · 1010 M− 1 s− 1, a rate constant with 1O2 kNCP,1O2 = (2.15 ± 0.38) · 107 M− 1 s− 1, a rate constant with the triplet state of anthraquinone-2-sulphonate kNCP,3AQ2S* = (5.90 ± 0.43) · 108 M− 1 s− 1, and is poorly reactive toward CO3−radical dot. The kNCP,3AQ2S* value is representative of reaction with the triplet states of chromophoric dissolved organic matter. The inclusion of photochemical reactivity data into a model of surface–water photochemistry allowed the NCP transformation kinetics to be predicted as a function of water chemical composition and column depth. Very good agreement between model predictions and field data was obtained for the shallow lagoons of the Rhône delta (Southern France).