Importance of equilibration time in the partitioning and toxicity of zinc in spiked sediment bioassays

Environmental Toxicology and Chemistry
By: , and 

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Abstract

The influences of spiked Zn concentrations (1–40 μmol/g) and equilibration time (˜ 95 d) on the partitioning of Zn between pore water (PW) and sediment were evaluated with estuarine sediments containing two levels (5 and 15 μmol/g) of acid volatile sulfides (AVS). Their influence on Zn bioavailability was also evaluated by a parallel, 10‐d amphipod (Leptocheirus plumulosus) mortality test at 5, 20, and 85 d of equilibration. During the equilibration, AVS increased (up to twofold) with spiked Zn concentration ([Zn]), whereas Zn‐simultaneously extracted metals ([SEM]; Zn with AVS) remained relatively constant. Concentrations of Zn in PW decreased most rapidly during the initial 30 d and by 11‐ to 23‐fold during the whole 95‐d equilibration period. The apparent partitioning coefficient (Kpw, ratio of [Zn] in SEM to PW) increased by 10‐ to 20‐fold with time and decreased with spiked [Zn] in sediments. The decrease of PW [Zn] could be explained by a combination of changes in AVS and redistribution of Zn into more insoluble phases as the sediment aged. Amphipod mortality decreased significantly with the equilibration time, consistent with decrease in dissolved [Zn]. The median lethal concentration (LC50) value (33 μM) in the second bioassay, conducted after 20 d of equilibration, was twofold the LC50 in the initial bioassay at 5 d of equilibration, probably because of the change of dissolved Zn speciation. Sediment bioassay protocols employing a short equilibration time and high spiked metal concentrations could accentuate partitioning of metals to the dissolved phase and shift the pathway for metal exposure toward the dissolved phase.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Importance of equilibration time in the partitioning and toxicity of zinc in spiked sediment bioassays
Series title Environmental Toxicology and Chemistry
DOI 10.1897/03-176
Volume 23
Issue 1
Year Published 2004
Language English
Publisher SETAC
Contributing office(s) Toxic Substances Hydrology Program
Description 7 p.
First page 65
Last page 71