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Altenburger R.,Helmholtz Center for Environmental Research | Kruger J.,Helmholtz Center for Environmental Research | Eisentrager A.,UBA Federal Environmental Agency
Chemosphere | Year: 2010

Ecotoxicological assessment of chemicals and contaminated sites relies on bioassays using apical endpoints such as detection of growth inhibition using suspension cultures of green algae. For valid effect assessment observable responses should be causally linked to chemical exposure and thus confounding factors should be minimised. In this study we report that concentration response relationships for substances in current standardised protocols for unicellular algal growth assays are prone to variation from ill-defined assay conditions. The currently used growth media are not optimised to provide a stable pH regime for an exposure period of 72 h, resulting in undefined speciation for charged or ionising molecules. We therefore propose a modified pH-stabilised growth medium for algal bioassays and demonstrate that this can substantially reduce variation in effect determination for reference compounds. © 2009. Source

Emeis S.,Karlsruhe Institute of Technology | Forkel R.,Karlsruhe Institute of Technology | Junkermann W.,Karlsruhe Institute of Technology | Schafer K.,Karlsruhe Institute of Technology | And 12 more authors.
Atmospheric Chemistry and Physics | Year: 2011

The spatial structure and the progression speed of the first ash layer from the Icelandic Eyjafjallajökull volcano which reached Germany on 16/17 April is investigated from remote sensing data and numerical simulations. The ceilometer network of the German Meteorological Service was able to follow the progression of the ash layer over the whole of Germany. This first ash layer turned out to be a rather shallow layer of only several hundreds of metres thickness which was oriented slantwise in the middle troposphere and which was brought downward by large-scale sinking motion over Southern Germany and the Alps. Special Raman lidar measurements, trajectory analyses and in-situ observations from mountain observatories helped to confirm the volcanic origin of the detected aerosol layer. Ultralight aircraft measurements permitted the detection of the arrival of a second major flush of volcanic material in Southern Germany. Numerical simulations with the Eulerian meso-scale model MCCM were able to reproduce the temporal and spatial structure of the ash layer. Comparisons of the model results with the ceilometer network data on 17 April and with the ultralight aircraft data on 19 April were satisfying. This is the first example of a model validation study from this ceilometer network data. © 2011 Author(s). Source

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