Gradual fall of s-triazine herbicides in drinking and wastewater samples as influenced by light and temperature

The effect of light and temperature on the dissipation of four s-triazine herbicides ( terbuthylazine, simazine, atrazine and prometryn) was studied in drinking and wastewaters during long-term laboratory incubation ( 4 months), and by comparing the results with those obtained in purified water (Milli-Q). Residues were analyzed by GC-NPD and confirmed by GC-MSD. A micro on-line method for isolating the herbicide residues was used. The results showed that temperature and light had a certain influence on the behaviour of the s-triazine herbicides. In drinking water, prometryn dissipated more rapidly than the other compounds under all laboratory conditions ( t(1/2) = 75 - 128 days), while atrazine showed the highest degree of persistence (t(1/2) = 132 - 227 days). In general, atrazine was the least (t(1/2) = 90 - 142 days) and simazine the most (t(1/2) = 118 - 278 days) persistent compound in Milli-Q and wastewater. Only in the case of atrazine in drinking water was the remaining percentage at the end of the experiment higher than 50% ( 53 - 69%). Dissolved organic substances in wastewater (DOC, 53.3 mg l(-1)) appear to be particularly important in the photosensitization process. The time required to reach the maximum admissible concentration ( MAC) according to European legislation (0.1mug l(-1)) ranged from 3 to 10 years for prometryn and atrazine, respectively, in drinking water depending on the used conditions.