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Sediment toxicity

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Description of key information

No effects at the highest test concentration. The 28 -d NOEC is 10000 mg/kg sediment d.w. in sediment microorganisms based on both emergence- and development rate.

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The long-term toxicity to organisms in freshwater sediment was determined in a study according to OECD guideline No 218 and in compliance with GLP criteria ( Noack Laboratorien GmbH, 2016). In this limit test, groups of sediment-dwelling larvae of the harlequin fly (Chironomus riparius) were exposed to nominal test concentrations of 0 (control) and 10000 mg/kg sediment dry weight for 28 days under static conditions. Test concentrations were analytical verified at test days 0, 7 and 28 and remained well within ± 20% of nominal concentrations. Therefore effect concentrations are expressed as nominal. Artificial sediment was used which consisted of 4% peat, 20% kaolin, 76% quartz sand and 0.35% CaCO3. The test amount was 180 g dry weight per vessel and reached ca. 2.0 cm from the ground with a ratio sediment:water depth ratio of ca. 1:4. The organic carbon content of the final mixture was 2.0%. After thorough mixing of test item with pre-moistened sediment, dilution water was added and the sediment-water-system allowed to equilibriate for 48 hours. The development time and the total number of fully emerged male and female midges was recorded daily. The emergence of the midges in the control started 14 days after larvae insertion and was finished at day 18 day after larvae insertion. The midges of the treatment hatched between day 14 to 19 after larvae insertion. The mean emergence of the midges in the control and the limit test item concentration was 98 %. No egg masses were deposited in the test replicates throughout the study. No abnormal behaviour (e.g. leaving sediment, unusual swimming) was recorded. Based on these findings the 28 -d NOEC is determined at 10000 mg/kg d.w. for both emergence- and development rates. The validity criteria were met.