PM08 Sediment Quality Assessment
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(PM107) Comparison of contaminant concentrations in sediments to toxicities shown in three Microtox bioassays.

Winger, P.1, Lasier, P.1, Bogenrieder, K.1, 1 USGS Patuxent Wildlife Research Center, Athens, GA, USA

ABSTRACT- Discrimination of sediment quality is enhanced when the toxicity elicited reflects the concentrations of contaminants in the sediments. The objective of this study was to evaluate the relationship between the toxicities measured using three bioassays with the photo-luminescent bacteria Vibrio fischeri (Microtox) and the concentrations of metal and organic contaminants in sediments collected from canals in Dade County, Florida. Toxicities of sediment pore water, solid-phase sediment and dichloromethane extracts from 92 sediment samples were evaluated using both 5- and 15-minute exposures to V. fischeri following the standard procedures given by the manufacturer for each matrix. Concentrations of copper, titanium and zinc were statistically (p < 0.05) correlated with toxicities from sediment pore-water exposures. Toxicities from exposures to solid-phase sediments and chemical extracts were statistically correlated with silver, cadmium, mercury, lead, zinc, PAHS, PCBs and OCLs in the sediments, but correlations were generally stronger with the extract toxicities. In addition to contaminants, physical and chemical characteristics of sediments and pore waters (percent moisture, percent organic matter, particle size, acid volatile sulfides and simultaneously extracted metals) were also correlated with the toxicities. The level of concordance between Mictotox toxicities and concentrations of metal and organic contaminants was lowest for tests with pore water, intermediate with solid-phase sediments and highest for extracts. Of the 20 sites with the highest extract toxicities, 14 corresponded with high concentrations of organic contaminants, compared to only 4 sites from tests with pore waters and 2 sites from solid-phase sediment tests. Extract toxicities from 13 sites corresponded to high metal concentrations, contrasted with 12 sites for solid-phase sediments and 10 sites for pore waters. This study suggests that Microtox toxicity assessments of sediment extractions may be more reflective of metal and organic contamination than tests with pore waters or solid-phase sediments.

Key words: toxicity, extracts, sediments, Microtox

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