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 center dot OH. NCP has a polychromatic photolysis quantum yield Phi(NCP) = (1.27 +/- 0.22).10(-5), a rate constant with center dot OH k(NCP,center dot OH) = (1.09 +/- 0.09).10(10) M-1 s(-1), a rate constant with O-1(2) k(NCP,1O2) = (2.15 +/- 0.38).10(7) M-1 s(-1), a rate constant with the triplet state of anthraquinone-2-sulphonate k(NCP,3AQ2S*) = (5.90 +/- 0.43).10(8) M-1 s(-1), and is poorly reactive toward CO3-center dot The k(NCP,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 Rhone delta (Southern France). (C) 2012 Elsevier B.V. All rights reserved.