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

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 OH. NCP has a polychromatic photolysis quantum yield ΦNCP = (1.27 ± 0.22) · 10− 5, a rate constant with OH kNCP,OH = (1.09 ± 0.09) · 1010 M− 1 s− 1, a rate constant with 1O2kNCP,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−. 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).

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► Phototransformation kinetics of 2-nitro-4-chlorophenol, relevant to surface waters.
► Determination of photochemical reactivity data in the laboratory.
► Model approach to combine photochemical reactivity with environmental variables.
► Good agreement with field data in lagoon water (Rhône delta, Southern France).
► Direct photolysis and reaction with OH as main photoprocesses in the environment.