ABSTRACT
Natural waters may be contaminated with pesticides and other chemicals. Many pesticides absorb light in the ultraviolet (UV) spectral range and therefore may be degraded photochemically. This chapter aims to determine photoreaction rate constants and quantum yields for the degradation of the s-triazine pesticides atrazine, desethylatrazine, simazine, and terbutylazine and the anilide pesticides metazachlor and metolachlor under UV irradiation in distilled water. It attempts to determine the influence of the hydrogen sulfide (HS) of a natural water on the photolysis; and to compare the results to get an insight on the effect of HS on the photo degradation of the six pesticides investigated. The photochemical degradation of the six investigated pesticides is strongly inhibited in natural water containing HS. The decrease in photolysis rate must be due to the optical filter effect of HS, which shows a strong absorption at the irradiation wavelength.
