Gradual Fall of s-Triazine Herbicides in Drinking and Wastewater Samples as Influenced by Light and Temperature

Abstract

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 (t1/2= 75–128 days), while atrazine showed the highest degree of persistence (t1/2= 132–227 days). In general, atrazine was the least (t1/2= 90–142 days) and simazine the most (t1/2= 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 (0.1 μg l−1) ranged from 3 to 10 years for prometryn and atrazine, respectively, in drinking water depending on the used conditions.