Investigation of the effect of pH of spraying water on the degradation of some pesticides

Despite the use of various methods to protect agricultural products from diseases, weeds and harmful pests, these methods are unfortunately inadequate. As a result, the easiest method of control, chemical control, is preferred, leading to intensive use of pesticides. Errors in pesticide application can cause the pesticide to break down before it is applied, reducing its concentration in the spray tank. To avoid this, it is essential to determine the appropriate pH of the water in the spray tank for different pesticides. The aim of this study is to determine the pH range in which selected pesticides remain stable in spray water and to calculate their half-life (DT50). The pesticides used in this study include active ingredients such as deltamethrin, chlorantraniliprole, gammacyhalothrin, lambda-cyhalothrin, isoxaflutole, thiencarbazone-methyl, cyprosulfamide, dicamba, tritosulfuron, s-metolachlor, nicosulfuron, terbuthylazine, mesotrione, foramsulfuron, iodosulfuron-methyl-sodium, isoxadifen-ethyl, azoxystrobin and cyproconazole. Experiments were conducted with spray water at pH 5, 6, 7, 8 and 9. Samples were taken at 0, 1, 2, 3, 24, 48, 72, 168 and 336 hours. After extraction by the QuEChERS method, the samples were analysed by LC/MS/MS. No statistically significant differences were observed in the percentage loss of insecticide at different pH levels. Although pH 8 was found to be the most appropriate pH for deltamethrin, no significant statistical differences were found between pH levels. The fastest hydrolysis and the lowest half-life for deltamethrin were observed at pH 7. For fungicides, no statistically significant differences were found in the effect of different pH levels on pesticide degradation in tank mixes. For herbicides, pH 5 was calculated as the spray water condition that caused the least degradation for isoxaflutole. For foramsulfuron, pH 8 and pH 6 were identified as the recommended values. Each active ingredient has a unique chemical structure that interacts differently with water molecules and is influenced by different environmental factors. This study highlights the need to increase similar research efforts to calculate pesticide losses in spray tanks for each active ingredient. Keywords: pH, Spray water, Pesticide, Hydrolysis