Dp. Hessler et al., DEGRADATION OF AQUEOUS ATRAZINE AND METAZACHLOR SOLUTIONS BY UV AND UV H2O2 - INFLUENCE OF PH AND HERBICIDE CONCENTRATION/, Acta hydrochimica et hydrobiologica, 21(4), 1993, pp. 209-214
The degradation of two pesticides: atrazine and metazachlor was invest
igated in aqueous solution under UV-irradiation with and without H2O2.
Rate constants of the photochemical degradation were determined apply
ing a first order kinetics and quantum yields of the processes were ca
lculated. This approach leads to an apparent decrease of the quantum y
ield with increasing initial pesticide concentration. At low H2O2 init
ial concentrations, the pesticide degradation was shown to be much mor
e efficient than the degradation under UV-irradiation only. However, a
t high H2O2 concentrations (>2 mmol L-1), the efficiency of the UV/H2O
2 system dropped down and the quantum yields of degradation were lower
than for the direct photolysis. In the absence of H2O2, no influence
of the pH value on the photodegradation of the pesticides could be not
iced in a range between pH 3 and pH 11. At low H2O2 initial concentrat
ions, the photochemical degradation of the pesticides was much faster
at pH 3 and pH 7 compared with the degradation at pH 11. The results e
mphasize the potential of optimized reaction conditions in advanced ox
idation.