PM09 Sediment Quality Assessment Cases
Exhibit Hall
8:00 AM - Monday
(PM139) Toxicity of chromium(III)-spiked freshwater sediments to Hyalella azteca.
Besser, J1, Brumbaugh, W1, Kunz, J1, Kemble, N1, Ingersoll, C1, 1 U.S. Geological Survey, Columbia, MO, USA
ABSTRACT- The two predominant redox states of chromium (Cr) in aquatic ecosystems differ in their toxicity, solubility, and affinity for sorption to sediments. Although Cr(VI) is more toxic and more soluble in water, Cr(III) is the predominant form in sediments, especially in the presence of organic matter or reduced inorganic species such as acid-volatile sulfide (AVS). Previous studies in our laboratory documented severe toxic effects of small amounts of Cr(VI) spiked into freshwater sediments without AVS, but little or no toxicity of larger amounts of Cr(VI), spiked into sediments with high levels of AVS. These results suggest that chemical reduction of Cr(VI) to Cr(III) effectively eliminates Cr toxicity. However, toxicity studies with the amphipod, Hyalella azteca, conducted at aqueous Cr(III) concentrations near solubility limits (up to 76 
g/L at pH 6.0) suggest that Cr(III) may be toxic to benthic invertebrates. We evaluated the toxicity of Cr(III) in freshwater sediments by conducting chronic toxicity tests with H. azteca exposed to Cr(III)-spiked freshwater sediments. Survival, growth, and reproduction of amphipods were compared between Cr(III)-spiked sediments and controls for each of three sediment types. No significant reductions in amphipod survival were observed after 28-d exposure to Cr(III)-spiked sediments containing up to 350 moles/g total Cr (1.8% total Cr on a dry weight basis). However, small but significant reductions in amphipod total length (8-12% less than controls) were observed in all three Cr(III)-spiked sediments, and a substantial reduction in reproduction (67% less than controls) was observed in one of the three Cr(III)-spiked sediments. Sublethal effects of Cr(III)-spiked sediments did not correspond closely to measured Cr concentrations in sediments or pore waters, and may be attributable to physical effects of large quantities of Cr(III) salts in the spiked sediments. These results are consistent with the hypothesis that risks of Cr toxicity are greatly reduced in sediments where Cr(VI) is chemically reduced to Cr(III) by AVS or other sediment components.
Key words: sediment toxicity, chromium, amphipods, sediment chemistry