Publication Summary

To support ongoing efforts to develop freshwater sediment quality criteria, sediments from Lake Washington, which are contaminated with high concentrations of polycyclic aromatic hydrocarbons (PAHs), were tested against several bioassays.

To support ongoing efforts to develop freshwater sediment quality criteria, sediments from Lake Washington, which are contaminated with high concentrations of polycyclic aromatic hydrocarbons (PAHs), were tested against several bioassays.

Eleven sediment samples were collected at eight sites adjacent to Quendall Terminals and the J.H. Baxter site in Lake Washington for chemical analyses, bioassays, and benthic macroinvertebrate identification and enumeration. Laboratory bioassays performed on the sediments included Daphnia magna, Ceriodaphnia dubia, Hyalella azteca, Chironomus tentans, Hexagenia limbata, ostracods, and Microtox. Benthic invertebrate samples were identified to the genus and species level where possible.

Total PAH concentrations ranged from 3.6 to 33,000 mg/kg, dry weight. Hyalella azteca showed statistically significant reduction in survival at the four most contaminated sites. One Microtox series showed impairment correlated with increasing PAH concentrations. However, a second series run at a different lab and using a different procedure, showed no such correlation. No other bioassay showed a significant reduction in survival that corresponded to contaminant levels. With one exception, diversity or abundance of benthic macroinvertebrate communities showed no clear relationship to concentrations of contaminants.

PAH concentrations were normalized to total organic carbon (TOC) and compared to the Provincial Sediment Quality Guidelines established by the Ontario Ministry of the Environment (OMOE). Significantly reduced survival of Hyalella azteca occurred at all four sites which exceeded the severe effect level of 11,000 mg PAH/kg TOC. Microtox was used at three of these sites and indicated toxicity at all of them. Benthic diversity was examined at two of these sites and was shown to be reduced at one of them.