A laboratory‐formulated sediment incorporating synthetic acid‐volatile sulfide

Abstract

Abstract-The application of laboratory-formulated sediment (LFS) could be expanded if toxicologically significant characteristics of sediment other than particle-size distribution, organic carbon content, and pH could be manipulated. This report describes the preparation of a LFS containing synthetic acid-volatile sulfide (AVS) and shows its similarity to natural sediment AVS. Several formulations were evaluated with respect to toxicity to Hyalella azteca and chemical stability. Amphipod survival was highest (95%) in LFS formulations in which the molar iron(II)/sulfide ratio was near 1, although amphipod survival was Ͼ80% in six of seven formulations with Յ20% excess metal or sulfide. Synthetic AVS in the test system oxidized rapidly at the sediment surface, but AVS at depth was stable for Ͼ30 d when isolated from air or aerated water. Oxidation-reduction potential measurements and AVS analysis of core slices revealed a vertical oxidation profile, apparently established and limited by oxygen diffusion. A formulation consisting of a 1:1 molar ratio of iron and sulfide (FeS) was evaluated with respect to complexation of copper, zinc, and nickel and to the corresponding reduction in toxicity using 10-d H. azteca toxicity tests. Amphipod mortality in metal-spiked LFS with metal/AVS molar ratios Ͼ1 was high relative to controls. In contrast, amphipod survival in metal-spiked LFS with metal/AVS molar ratios Ͻ1 was generally similar to amphipod survival in nonspiked LFS containing synthetic AVS. A few exceptions, where toxicity was noted when metal/AVS ratios were Ͻ1, could be explained by high concentrations of dissolved iron, which was released by the metal ϩ AVS displacement reaction. The LFS containing synthetic AVS appears to mimic natural sediment AVS and thus can provide consistent and controlled substrates suitable for investigating metal/sediment chemistry and toxicity and for developing realistic sediment quality criteria for metals.

Field measurement of nickel sediment toxicity: Role of acid volatile sulfide

“…1), demonstrating the importance of AVS for Ni partitioning. Porewater Ni variability when (SEM À AVS) approached zero was similar to that reported in earlier studies [10,38,39]. This variability of pore-water Ni is consistent with the low affinity of Ni for the AVS in comparison with that of Cu, Pb, Cd, and Zn, which results in Ni appearing first in the pore water as concentrations of SEM increase relative to that of AVS [33,40].…”

Metal Bioavailability and Toxicity in Sediments

“…At the sediment-water interface, the redox gradient quickly changes, and metal sulfide complexes may become oxidized due to oxygen diffusion, bioturbation, advection, or resuspension processes (e.g., Gonzalez, 1996;Millero et al, 1987;Peterson et al, 1996;Zhuang et al, 1994). When AVS oxidation occurs, free metal ions are released that may cause toxicity (Di Toro et al, 1996a).…”

Assessing the ecological risk of metals in sediments

“…Hassan et al [25] generate representative minimum partition coefficients for the five criteria metals for a number of sandy sediments and explore the basis of using these values as a SQC tool for screening a set of samples from Lake Michigan. In the 14th paper of the series, Gonzalez [26] describes procedures for generating AVS in formulated sediment; this technology results in a controlled medium facilitating further laboratory studies focused upon metal-sulfide partitioning dynamics. The final manuscript of the metal bioavailability series presents an example of the application of the metal SQC process to a set of marine and freshwater sediments collected in conjunction with the Environmental Monitoring and Assessment Program of EPA [27].…”