Nickel Partitioning and Toxicity in Sediment during Aging: Variation in Toxicity Related to Stability of Metal Partitioning

  • M. Costello David (Contributor)
  • R. Hammerschmidt Chad (Contributor)
  • Allen Burton G. (Contributor)



Metals in sediment
can be complexed by minerals, partition between
solid and aqueous phases, and cause toxicity at high concentrations.
We studied how the oxidation of surface sediment that occurs during
aging alters the partitioning and toxicity of Ni. Two sediments (Burntwood
and Raisin) were amended with Ni, equilibrated, incubated in a flow-through
flume, and examined for sediment physicochemistry and toxicity to <i>Hyalella azteca</i> (7 day growth). Through time, the sediment
surface (5 mm) was oxidized, acid-volatile sulfide concentrations
declined in Raisin sediment, and amorphous Fe oxides increased. Porewater
Ni concentrations declined through time but total Ni concentrations
in sediment were unchanged, suggesting changes in Ni partitioning
through time. Both sediments elicited a toxic dose–response
by <i>H. azteca</i> early in the aging process; but only
Burntwood, for which Ni was primarily partitioned to Fe oxide minerals,
exhibited a consistent dose–response during aging. Low total
Ni concentrations (20 mg kg<sup>–1</sup>) in Raisin sediment
reduced <i>H. azteca</i> growth at initiation, but all Ni
treatments (up to 3000 mg kg<sup>–1</sup>) exhibited similar
growth after 12 days of aging. The dynamic toxicity observed in Raisin
sediment was likely due to the instability of NiS in surface sediments
early in the aging process. These data suggest that short-term toxicity
assays with homogenized Ni-amended sediment (i.e., standard sediment
toxicity tests) may be accurate for sediments where Ni speciation
is dominated by oxidized ligands; however, under high-AVS and high-Fe
conditions, calculated toxicity thresholds may be overly conservative
(here by >100-fold) with respect to natural sediment conditions.
Date made available16 Sep 2016

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