Phototransformation processes of 2,4-dinitrophenol, relevant to atmospheric water droplets

This paper shows that the polychromatic quantum yield for the photolysis of 2,4-dinitrophenol (24DNP) in the wavelength interval of 300–500 nm is (8.1 ± 0.4) × 10−5 for the undissociated phenol, and (3.4 ± 0.2) × 10−5 for the phenolate. The second-order rate constants for reaction with OH were determined here as (1.76 ± 0.05) × 109 M−1 s−1 and (2.33 ± 0.11) × 109 M−1 s−1 for the phenol and the phenolate, respectively. By combining laboratory results and a simple modelling approach of the atmospheric aqueous phase, this work shows that the direct photolysis and the reaction with OH would play a comparable role in the degradation of 24DNP at pH > 4. The OH reaction would prevail for pH < 4. Both pathways would be more important than the night-time reaction with NO3 as removal processes for 24DNP in the atmospheric waters.