John Wiley & Sons, Ltd.

Chronic toxicity of nickel‐spiked freshwater sediments: Variation in toxicity among eight invertebrate taxa and eight sediments

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We evaluated the chronic toxicity of nickel‐spiked freshwater sediments to benthic invertebrates. A two‐step spiking procedure (spiking + sediment dilution) and a two‐stage equilibration period (10 weeks anaerobic + 1 week aerobic) was used to spike 8 freshwater sediments with wide ranges of acid‐volatile sulfide (AVS; 0.94–38 µmol/g) and total organic carbon (TOC; 0.42–10%). Chronic sediment toxicity tests were conducted with 8 invertebrates (Hyalella azteca, Gammarus pseudolimnaeus, Chironomus riparius, Chironomus dilutus, Hexagenia sp., Lumbriculus variegatus, Tubifex tubifex, and Lampsilis siliquoidea) in 2 spiked sediments. Nickel toxicity thresholds estimated from species‐sensitivity distributions were 97 µg/g and 752 µg/g (total‐recoverable nickel; dry wt. basis) for sediments with low and high concentrations of AVS and TOC, respectively. Sensitive species were tested with 6 additional sediments. Twenty‐percent effect concentrations (EC20s) for Hyalella and Gammarus, but not Hexagenia, were consistent with US Environmental Protection Agency benchmarks based on nickel in pore water and in simultaneously extracted metals (SEM) normalized to AVS and TOC. For Hexagenia, sediment EC20s increased at less than an equimolar basis with increased AVS, and toxicity occurred in several sediments with SEM > AVS. We hypothesize that circulation of oxygenated water by Hexagenia led to oxidation of AVS in burrows, creating microenvironments with high nickel exposure. Despite these unexpected results, a strong relationship between Hexagenia EC20s and AVS could provide a basis for conservative site‐specific sediment quality guidelines for nickel. Environ Toxicol Chem © 2013 SETAC

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