Extensive study of the fate of triazole fungicides using model systems
- In order to provide nutrition for a growing world population pesticides are a necessary tool. Crop protection agents may be considered safe, if handled correctly. Nevertheless, they are subject to transformation processes and metabolisation in the environment and technical installations. Transformation products (TP) and metabolites may exhibit properties other than those of the mother substance. They can be more harmful and thereby pose a threat to environmental and human health. With 19 % market share in 2014, triazole pesticides are the class of organic fungicides which are most commonly used in Germany.1 However, only little data is available concerning their TP and metabolites. During this study the fate of the triazole fungicides propiconazole and difenoconazole in soil and water using model reaction systems mimicking their pathway in the environment and the industrial water treatment is investigated. During application the substances may directly contaminate soil as well asIn order to provide nutrition for a growing world population pesticides are a necessary tool. Crop protection agents may be considered safe, if handled correctly. Nevertheless, they are subject to transformation processes and metabolisation in the environment and technical installations. Transformation products (TP) and metabolites may exhibit properties other than those of the mother substance. They can be more harmful and thereby pose a threat to environmental and human health. With 19 % market share in 2014, triazole pesticides are the class of organic fungicides which are most commonly used in Germany.1 However, only little data is available concerning their TP and metabolites. During this study the fate of the triazole fungicides propiconazole and difenoconazole in soil and water using model reaction systems mimicking their pathway in the environment and the industrial water treatment is investigated. During application the substances may directly contaminate soil as well as surface waters. Both pesticides are considered persistent in soil and very stable towards aqueous photolysis.2 In this case however, the role of natural organic matter has not yet been examined. Since both pesticides also show moderate mobility in soils they may end up in ground water from which drinking water is produced. During this process, waters are treated with chlorine agents, ozone, and energy-rich UV radiation. Owing to the vigorous conditions the formation of a variety of technical TP can be expected. Additionally, for all environmental compartments the degradation of the fungicides by bacteria is a factor which needs to be taken into account. For this survey, iron-oxidising bacteria of the leptothrix variety were chosen as model organisms. Their potential for the metabolisation of the analytes is investigated. In this work degradation and transformation of the fungicides is monitored using quantitative target analysis. Major components in the reaction mixtures are identified by non-target analysis. GC-EI-MS-spectra, HR-MS-measurements, or the comparison with native standards are utilised for structural elucidation. For identification, products will be isolated and characterised by NMR. Toxicity assessment of these TP is essential to define threshold values in the environment. The model reaction system considering the interaction with organic matter will be presented and possible TP will be shown.…