Heavy metals in lichens, southern district of keewatin, Northwest Territories, Canada

A suite of 12 saxicolous lichen species were collected from a remote site in the south-central District of Keewatin, and analyzed for As, Cd, Cr, Cu, Ni, Pb, Sb, V, and Zn. Concentrations of these metals are comparable to results from elsewhere in the NWT obtained up to 28 years ago, and from remote sites in northern Quebec, Alaska, Greenland and northern Finland. Heavy metal concentrations of the lichens were compared to that of 7 immediate substrates. Substrate is not a significant source of metals to the lichens because: 1) correlation between lichen and substrate chemistry is generally poor; and 2) metal concentrations in lichen species growing on a substrate lacking measurable concentrations of trace metals are analytically indistinguishable from the same species growing on enriched substrates. Interspecies calibration ratios, calculated with respect to C. stellaris, decrease from crustose to foliose to fruiticose varieties, indicating that the crustose types are the most efficient accumulators and/or retainers of heavy metals.