Inhaltszusammenfassung

Freshwater ecosystems deliver various goods and services for human societies such as provisioning of water and fish resources. Modern agriculture is associated with the release of a large amount of agrochemicals that may enter into streams and result in deterioration of freshwater ecosystems. The present thesis contributes to the assessment of exposure and effects resulting from pesticide input into stream ecosystems and presents one of the largest field studies on the i...Freshwater ecosystems deliver various goods and services for human societies such as provisioning of water and fish resources. Modern agriculture is associated with the release of a large amount of agrochemicals that may enter into streams and result in deterioration of freshwater ecosystems. The present thesis contributes to the assessment of exposure and effects resulting from pesticide input into stream ecosystems and presents one of the largest field studies on the impacts of pesticide contamination in agricultural streams. The field study was conducted in 29 streams of two regions in France and Finland and comprised monitoring of invertebrate community composition and of an important ecosystem process, the leaf-litter breakdown. Furthermore, pesticide monitoring was performed for selected compounds that were previously found at ecotoxicologically relevant concentrations in streams of the study area according to information from local authorities. After the general introduction (Chapter 1), Chapters 2-4 introduce and evaluate sampling and determination methods for pesticide exposure. The results concerning the effects of pesticides in the field studies are presented in Chapter 5. In Chapter 2, a new method for the determination of 10 particle-bound pesticides using accelerated solvent extraction (ASE) is presented. The method developed here showed good results in terms of accuracy and precision in the extraction of polar and semi-polar pesticides belonging to different chemical classes. When applied to the extraction of field samples from streams, the detected concentrations reached levels that may have toxic effects on invertebrate species. In addition, the use of 6 deuterated analogues of the target compounds as internal standards during extraction, cleanup and analysis was examined. The study demonstrates that dissimilarities may occur in the behaviour of target compounds and deuterated analogues for analogues with less than 10 deuterium atoms. The following chapter describes a calibration approach to derive sampling rates for the ChemcatcherOR passive sampler equipped with a receiving phase for polar and semi-polar pesticides. Sampling rates are needed to estimate time- weighted average water concentrations from field deployments of non-equilibrium passive samplers. The sampling rates obtained in the experiment were in the range of 0.1 to 0.5 L/day for the study compounds. In general, the experiment demonstrated that the ChemcatcherOR passive sampler is suitable for field deployments up to 14 days in the configuration without a diffusion-limiting membrane. In Chapter 4 the provided sampling rates are used to compute time-weighted average water concentrations for the field deployment of the ChemcatcherOR in the French streams. Furthermore, this chapter compares the performance of the ChemcatcherOR to the performance of two other sampling systems when used to detect pesticide exposure in streams. The study suggests that sampling waterborne exposure with the ChemcatcherOR or an event- driven water sampler gives a more appropriate picture of the contamination with polar and semi-polar pesticides than sampling suspended particles. Chapter 5 is devoted to the effect side, where the risk assessment of the pesticide input in the French and Finnish streams for invertebrate communities is presented. In addition, the impact of pesticides on leaf-litter breakdown was investigated and the applicability of the trait-based Species At Risk (SPEAR) index to detect pesticide stress in large-scale biomonitoring was evaluated. The results of this chapter show that pesticides may alter invertebrate community composition and lead to an impairment of the leaf-litter breakdown at levels that were considered to be protective previously. Moreover, the study demonstrates the suitability of the SPEAR index to detect effects of pesticides when used on biomonitoring data including different biogeographical regions. In conclusion, the thesis adds to the growing evidence that pesticides present an important stressor for aquatic ecosystems and provides tools that can be applied in future studies on the exposure and the effects of pesticides in aquatic systems.» weiterlesen» einklappen

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