Final report: Mercury concentration in Thule period ringed seal mandibles from Cape Espenberg, Alaska (KTZ-087, KTZ-088, and KTZ-101)

Halffman, Carrin

Research Summary: A total of 23 ringed seal mandibles from three prehistoric Cape Espenberg sites (KTZ-087, KTZ-088, and KTZ-101) were analyzed for total mercury content as part of my PhD dissertation research, which examined the potential for using archaeological bone to reconstruct preindustrial mercury levels in subsistence animals and in humans. To use bone as an indicator of mercury exposure level, a relationship must be established between bone mercury levels and dietary mercury intake, the main route of exposure for humans and other mammals. In free-ranging animals and archaeofauna, actual mercury exposure is unknown, so an indicator or proxy measure of exposure must be used to evaluate correspondence between tissue levels of mercury and exposure level. To this end, bone mercury level was compared to the stable nitrogen isotope ratio (δ15N), a proxy measure of mercury exposure, in the Cape Espenberg seal remains. Results of the statistical analysis show that bone mercury level is significantly and positively related to δ15N, supporting the idea that bone mercury level reflects exposure level. In addition, bone mercury level is significantly and positively related to the content of nitrogen, carbon, and sulfur in bone. Because these elements occur mostly in the bone protein, these findings suggest that mercury may be physically associated with the protein phase of bone, rather than the mineral phase.

Final report: Mercury concentration in Thule period ringed seal mandibles from Cape Espenberg, Alaska (KTZ-087, KTZ-088, and KTZ-101)

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