Bedeutung des Makroporenflusses für den Austrag von Pflanzenschutzmitteln auf drainierten Flächen

Im Rahmen eines vom BMU/UBA geförderten Vorhabens wurden eine Reihe von Untersuchungen tum Austrag von Pflanzenschutzmitteln über die Drainage durchgeführt. Variiert wurden dabei sowohl die eingesetzten Pflanzenschutzmittel, die Applikationszeitpunkte, die Kulturen und die Flächen. Hauptuntersuchungsgebiet war die Soester Börde. Desweiteren wurde ein Feld in Brandenburg ausgewählt. Die vorgestellten Ergebnisse beziehen sich auf den Vergleich zweier Standorte (Soester Börde und Brandenburg). Desweiteren werden Befunde aus Plotversuchen zur Demonstration des Makroporenflusses in der Soester Börde dargestellt. Die Ergebnisse zeigen, daß neben dem Oberflächenabfluß von mit Pflanzenschutzmitteln behandelten Böden auch der Austrag über die Drainage zu einer Belastung von Oberflächengewässern mit Pflanzenschutzmitteln führen kann. Spitzenkonzentrationen in dem ersten Drainagefluß nach Applikation können in einer Konzentration bis 300 Mikrogramm/l auftreten. Bei Herbstanwendungen wurden Monats mittelwerte von 15 Mikrogramm/l gemessen. Demgegenüber treten nur geringe Konzentrationen bei sandigen Flächen auf. Signifikante Unterschiede können somit zwischen Löß- und Sandböden beobachtet werden. Die Abschätzung des Grundwassergefährdungspotentials von Pflanzenschutzmitteln basiert bisher sowohl beim Einsatz von Rechenmodellen als auch bei Lysimeterstudien auf Sandböden. Aufgrund der erhaltenen Ergebnisse stellt sich jedoch die Frage, ob bei der Konzentrierung auf Sandböden als "worst case" Scenarium nicht eine mögliche Grundwassergefährdung durch Makroporenfluß auf schweren Böden unterschätzt wird

Comparison of the fate of isoproturon in small- and large-scale water/sediment systems: Dedicated to Prof. Werner Klein on the occasion of his 60th birthday

A comparative study of the fate of the herbicide isoproturon using two different water/sediment systems, a small-scale laboratory system and a large-scale system (microcosm), was carried out in order to obtain information about possibilities for investigation and the applicability of the test results. Both of the test systems studied showed clear differences in the fate of the test substance as conditioned by the fundamental differences in size, complexity and incubation of the systems. The laboratory system prescribed by the BBA guideline IV, 5-1 showed significantly lower degradation of isoproturon than the microcosms. At the same time, however, it also produced relatively reproducible results that reflected the course of exposure and the metabolism of the test substance in essentially the same terms as the microcosms. Therefore, despite the limitations, small laboratory systems are useful instruments for examining the fate of pesticides in water and sediment. Microcosms are an impor tant supplement to existing small-scale systems

Environmental risk assessment of ivermectin A case study

The veterinary parasiticide ivermectin was selected as a case study compound within the project ERAPharm (Environmental Risk Assessment of Pharmaceuticals). Based on experimental data generated within ERAPharm and additional literature data, an environmental risk assessment (ERA) was performed mainly according to international and European guidelines. For the environmental compartments surface water, sediment, and dung, a risk was indicated at all levels of the tiered assessment approach. Only for soil was no risk indicated after the lower tier assessment. However, the use of effects data from additional 2-species and multispecies studies resulted in a risk indication for collembolans. Although previously performed ERAs for ivermectin revealed no concern for the aquatic compartment, and transient effects on dung-insect populations were not considered as relevant, the present ERA clearly demonstrates unacceptable risks for all investigated environmental compartments and hence suggests the necessity of reassessing ivermectin-containing products. Based on this case study, several gaps in the existing guidelines for ERA of pharmaceuticals were shown and improvements have been suggested. The action limit at the start of the ERA, for example, is not protective for substances such as ivermectin when used on intensively reared animals. Furthermore, initial predicted environmental concentrations (PECs) of ivermectin in soil were estimated to be lower than refined PECs, indicating that the currently used tiered approach for exposure assessment is not appropriate for substances with potential for accumulation in soil. In addition, guidance is lacking for the assessment of effects at higher tiers of the ERA, e.g.;for field studies or a tiered effects assessment in the dung compartment. Integr Environ Assess Manag 2010;6567587. © 2010 SETAC

Mixture toxicity of three photosystem II inhibitors (atrazine, isoproturon, and diuron) toward photosynthesis of freshwater phytoplankton studied in outdoor mesocosms

Mixture toxicity of three herbicides with the same mode of action was studied in a long-term outdoor mesocosm study. Photosynthetic activity of phytoplankton as the direct target site of the herbicides was chosen as physiological response parameter. The three photosystem II (PSII) inhibitors atrazine, isoproturon, and diuron were applied as 30% hazardous concentrations (HC30), which we derived from species sensitivity distributions calculated on the basis of EC50 growth inhibition data. The respective herbicide mixture comprised 1/3 of the HC30 of each herbicide. Short-term laboratory experiments revealed that the HC30 values corresponded to EC40 values when regarding photosynthetic activity as the response parameter. In the outdoor mesocosm experiment, effects of atrazine, isoproturon, diuron and their mixture on the photosynthetic activity of phytoplankton were investigated during a five-week period with constant exposure and a subsequent five-month postexposure period when the herbicides dissipated. The results demonstrated that mixture effects determined at the beginning of constant exposure can be described by concentration addition since the mixture elicited a phytotoxic effect comparable to the single herbicides. Declining effects on photosynthetic activity during the experiment might be explained by both a decrease in water herbicide concentrations and by the induction of community tolerance