Study of the Effect of UV Radiation on the Decomposition of 4-Chloro-2-Methylphenoxyacetic Acid

The influence of UV radiation wavelength on the disappearance kinetics of 4-chloro-2-methylphenoxyacetic acid (MCPA) in the presence of activated sludge and humic acids has been examined. Variations in the kinetic curves of MCPA removal in the presence of humic acids were determined from results on accumulation of carbon dioxide gas. Spectral-luminescence and chromato-mass-spectrometry data reveal the presence in the medium of the biotransformation product 2-methyl-4-chlorophenol, which is utilized after 14 days. Addition of humic acids, on the one hand, reduced the rates of subsequent biodecomposition of MCPA. On the other hand, in the process of transformation of the herbicide in the presence of humic acids a photobioproduct was detected which does not contain chlorine: 2-methylphenoxyacetic acid.