title: Simulation Studies to Explore Biodegradation in Water-Sediment Systems: From OECD 308 to OECD 309.
abstract: Studies according to OECD 308 and OECD 309 are performed to simulate the biodegradation of chemicals in water-sediment systems in support of persistence assessment and exposure modeling. However, several shortcomings of OECD 308 have been identified that hamper data evaluation and interpretation, and its relation to OECD 309 is still unclear. The present study systematically compares OECD 308 and OECD 309 and two variants thereof to derive recommendations on how to experimentally address any shortcomings and improve data for persistence and risk assessment. To this end, four (14)C-labeled compounds with different biodegradation and sorption behavior were tested across standard OECD 308 and 309 test systems and two modified versions thereof. The well-degradable compounds showed slow equilibration and the least mineralization in OECD 308, whereas the modified systems provided the highest degree of mineralization. Different lines of evidence suggest that this was due to increased oxygenation of the sediment in the modified systems. Particularly for rapidly degrading compounds, non-extractable residue formation was in line with degradation and did not follow the sediment-water ratio. For the two more slowly degrading compounds, sorption in OECD 309 (standard and modified) increased with time beyond levels proposed by equilibrium partitioning, which could be attributed to the grinding of the sediment through the stirring of the sediment suspension. Overall, the large differences in degradation observed across the four test systems suggest that refined specifications in test guidelines are required to reduce variability in test outcomes. At the same time, the amount of sediment and its degree of oxygenation emerged as drivers across all test systems. This suggests that a unified description of the systems was possible and would pave the way toward a more consistent consideration of degradation in the water-sediment systems across different exposure situations and regulatory frameworks.
authors.affiliation: Fraunhofer IME-AE , Auf dem Aberg 1, 57392 Schmallenberg, Germany.
authors.forename: Prasit
authors.initials: P
authors.lastname: Shrestha
authors.affiliation: ECT Oekotoxikologie GmbH , Böttgerstrasse 2-14, 65439 Flörsheim am Main, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Junker
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133, 8600 Dübendorf, Switzerland.
authors.forename: Kathrin
authors.initials: K
authors.lastname: Fenner
authors.affiliation: Fraunhofer ITEM , Nikolai-Fuchs-Strasse 1, 30625 Hannover, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hahn
authors.affiliation: MTA-BME Water Research Group, Hungarian Academy of Sciences , Mügyetem rkp. 3, 1111 Budapest, Hungary.
authors.forename: Mark
authors.initials: M
authors.lastname: Honti
authors.affiliation: Eawag, Swiss Federal Institute of Aquatic Science and Technology , Überlandstrasse 133, 8600 Dübendorf, Switzerland.
authors.forename: Rani
authors.initials: R
authors.lastname: Bakkour
authors.affiliation: Fraunhofer IME-AE , Auf dem Aberg 1, 57392 Schmallenberg, Germany.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Diaz
authors.affiliation: Fraunhofer IME-AE , Auf dem Aberg 1, 57392 Schmallenberg, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Hennecke
mesh_terms: D001673:Biodegradation, Environmental; D019015:Geologic Sediments / Q000737:chemistry*; D066150:Organisation for Economic Co-Operation and Development; D014867:Water / Q000737:chemistry*; D014874:Water Pollutants, Chemical
chemical_list: D014874:Water Pollutants, Chemical; D014867:Water