WP8 Assessment and Remediation of Mercury Contaminated Sites
202 Oregon Ballroom
1:20 PM - 4:40 PM, Wednesday
() Lack of Toxicity and Benthic Community Impacts in Hg Contaminated Sediments, Pinchi Mercury Mine, BC Canada.
Baker, R.F.1, Allard, P.J.1, Mann, G.S.1, 1 Azimuth Consulting Group, Vancouver, BC, Canada
ABSTRACT- Pinchi Lake Mine produced metallic Hg from 1940 to 1944 (wartime operation) and again from 1968 to 1975 (modern operation). Hg contaminated tailings (subsurface calcines) were deposited in the lake foreshore during wartime operation and later dispersed throughout the lake by wind-driven currents. In 2001 a modified sediment quality triad was conducted to examine ecological impacts of Hg contaminated subsurface calcines and bioaccumulation by chironomids. Fourteen stations were sampled for total metals, toxicity (Hyalella azteca and Chironomus tentans) and benthic community structure (abundance, richness) from subsurface calcines and lake sediments with inorganic Hg concentrations ranging from 0.86 ppm (reference) to 857 ppm dw. In addition, total and methyl Hg were analysed in chironomid tissue from each station. There was no relationship between Hg and MeHg and benthic community structure even in the most contaminated sediments and the benthic community appeared healthy. Toxicity was observed at some stations for either Hyalella or Chironomus, however, responses were not correlated with Hg concentration. Chironomid inorganic (THg) and MeHg tissue concentrations were elevated (up to 0.3 ppm dw) at the five stations with the highest THg and MeHg sediment concentrations, otherwise, tissue concentrations were low (0.03 ppm dw) and similar to tissue concentrations from uncontaminated environments. These findings suggest that Hg in the subsurface calcines is less bioavailable than would be expected based on the magnitude of contamination. Furthermore, subsurface calcine sediment and biota MeHg concentrations do not contribute significantly to overall Hg loading to fish in Pinchi Lake. This has important implications for risk assessment studies to support remedial actions at the former mine.
Key words: Toxicity, Mercury, Benthos, Risk Assessment