The Embryotoxic Potential and Photocatalytic Degradation of Thiophanate-Methyl

Abstract

Pesticides are substances designed to protect plants from various types of diseases and pests [1]under UV irradiation is studied using synthesized Zinc oxide (ZnO. Synthetic organic pesticides, in addition to the high efficiency, have led to frequent adverse environmental impact, as a consequence of their high accumulation and toxicity. Due to the increased pollution of water with mixture pesticides, it is necessary to use different processes for their removal and degradation. Therefore, oxidative processes have been developed, commonly named as Advanced Oxidation Processes (AOPs). Among them, special attention was attributed to photocatalysis, as a process that enables the degradation of difficult-to-decompose organic molecules under the action of UV radiation in the presence of catalysts [2]. In this study the photocatalytic degradation of thiophanate- methyl (TM) in the presence of the TiO2 Degussa P-25 catalyst was investigated. Different experimental conditions were varied, such as the concentration of the pesticide solution, the mass of the catalyst and the influence of the anions (chloride, sulphate, nitrate, etc.). The pesticide concentration in the reaction system was monitored based on the decrease in system absorbance using a Shimadzu 1800 UV spectrophotometer. For optimized conditions of complete photodegradation, the environmental acceptability of the defined degradation process was examined. The toxic effect of the TM solution before and after degradation was examined using the embryotoxicity test with Danio rerio, in order to prove the reduction of toxicity and the success of the degradation process [3]which raises the issue of potential influence of different formulation types on herbicide toxicity. The present study evaluated the toxicity and teratogenic effects of the active ingredient clomazone and its two formulations (Rampa® EC and GAT Cenit 36 CS, both containing 360 g a.i./l of clomazone. Comparing the obtained results of the influence of ions on the processes of photocatalysis, it was noticed that all ions have catalytic effects on the kinetics of the degradation process of TM. The presence of sulphates and carbonates had the greatest catalytic effect, while hydrogen phosphates and bicarbonates showed the lowest catalytic capacity. The optimal experimental conditions were obtained using 0,2 g/L of TiO2 and 5 mg/L of TM solution. In addition, the embryotoxicity test followed the analytical examination. Comparison of results obtained in embryotoxicity assay testing of the initial solution, partly and completely degraded samples confirmed suitability of applied degradation method. Increase in toxicity, compared to the initial solution, was registered in partly degraded sample. This observation can be attributed to increase in concentration of carbendazim (TM metabolite) more toxic than parent substance. Finally, completely degraded sample caused no mortality or adverse effects in D. rerio embryos after 120 h exposure. Toxicity of samples, in decreasing order is half degraded > initial >completely degraded sample. Based on the obtained results it can be concluded that used photocatalytic degradation process can be successfully applied in pesticide contaminated water management.