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

摘要

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 Φ_(NCP) = ( 1.27 ± 0.22 )· 10 ~(-5), a rate constant with ·OH k_(NCp).·0_(OH) = (1.09 ± 0.09) • 10~(10)M~(-1) s~(-1), a rate constant with ~1O_2 k_(NCP.102) = (2.15±038) • 10~7M~(-1) s~(-1) a rate constant with the triplet state of anthraquinone-2-sulphonate k_(NCP,3AQ25*)-= (5.90 ± 0.43) •10~8M~(-1)s~(-1) and is poorly reactive toward CO~3~-• 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).