John Wiley & Sons, Ltd.

Development of a bioavailability‐based risk assessment approach for nickel in freshwater sediments

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To assess nickel (Ni) toxicity and behavior in freshwater sediments, a large‐scale laboratory and field sediment testing program was conducted. The program used an integrative testing strategy to generate scientifically based threshold values for Ni in sediments and to develop integrated equilibrium‐partitioning based bioavailability models for assessing risks of Ni to benthic ecosystems. The sediment testing program was a multi‐institutional collaboration that involved extensive laboratory testing, field validation of laboratory findings, characterization of Ni behavior in natural and laboratory conditions, and examination of solid phase Ni speciation in sediments. The laboratory testing initiative was conducted in three phases to satisfy the following objectives: 1) evaluate various methods for spiking sediments with Ni to optimize the relevance of sediment Ni exposures; 2) generate reliable ecotoxicity data by conducting standardized chronic ecotoxicity tests using nine benthic species in sediments with low and high Ni binding capacity; and, 3) examine sediment bioavailability relationships by conducting chronic ecotoxicity testing in sediments that showed broad ranges of acid volatile sulphides, organic carbon, and iron. A subset of six Ni‐spiked sediments was deployed in the field to examine benthic colonization and community effects. The sediment testing program yielded a broad, high quality dataset which was used to develop a Species Sensitivity Distribution for benthic organisms in various sediment types, a reasonable worst case Predicted No‐Effect Concentration for Ni in sediment (PNECsediment), and predictive models for bioavailability and toxicity of Ni in freshwater sediments. A bioavailability‐based approach was developed using the ecotoxicity data and bioavailability models generated through the research program. The tiered approach can be used to fulfil the outstanding obligations under the EU Existing substances RA, EU REACH, and other global regulatory initiatives. This article is protected by copyright. All rights reserved

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