Depth related analysis of sediment and pore-water in microcosms

Project duration: 2018–2021

Funding: Bayer AG

Principle investigator at the RWTH Aachen / Goethe University Frankfurt

• Prof. Dr. Henner Hollert

Supervisors at the Bayer AG, Department of Environmental Safety

• Philipp Dalkmann
Eduard Hellpointner Daniel Faber Klaus Hammel Eric Bruns Erika Seidel

Project process

• Alexander Dorn

Project description

Sediments are habitats for numerous organisms like bacteria, plant and invertebrates. Therefore, the anthropogenic contamination of aquatic systems is of great interest in the framework of the EU registration process for plant protection products (PPP). Within the aquatic compartment the environmental risk assessment therefore covers not only the water body but as well the sediment.
This implementation of the aquatic environmental risk assessment is addressed by three groups in the department of Environmental Safety at Bayer (Experimental Environmental Exposure, Aquatic Organism, Exposure Modelling).
The ecotoxicological potential of PPPs on sediment dwelling organisms is examined in sediment test systems according to OECD test guideline (TG) 218 (Sediment-Water Chironomid Toxicity Using Spiked Sediment) and OECD TG 219 (Sediment-Water Chironomid Toxicity Using Spiked Water). The environmental fate and behavior of PPPs in aquatic sediment systems is investigated in studies according to OECD TG 308 (Aerobic and Anaerobic Transformation in Aquatic Sediment Systems). Calculations of the redistribution and the transport of the test item in the mentioned water-sediment microcosms can be performed using the mechanistic TOXSWA model (toxic substances in surface waters). However, up to now there is a lack of experimental data to confirm the model predictions.
In this project, we generated experimental data by using a newly developed sampling methodology enabling the depth-related analysis of sediment and pore-water. In a previous study we tested this novel methodology and compared the experimental with the modelled data. The obtained results were promising.
The mechanistic model considers the diffusion of PPPs via pore water as relevant transport process. Since the diffusion via pore-water is depended on sorption properties of the model compounds, three model compounds with low, medium and high sorption affinity were selected. Further, we are using two natural sediments providing a low and high organic carbon (used in OECD TG 308 tests) and an artificial sediment (acc. to OECD TG 218/219) to follow the spatio-temporal dynamics of the three model compounds in the different experimental approaches.
The presented project will contribute to a more realistic sediment risk assessment, as it enables the examination of a depth integrated more realistic exposure concentration. These data allow a better estimation of the real exposure concentrations for benthic organisms living predominantly on and on the upper sediment layer.