Mercury and antimony in soils and non-vascular plants near two past-producing mercury mines, British Columbia, Canada

Abstract

Mercury and Sb in soils (humus, B horizon, C horizon) and environmental biomonitors (moss and epiphytic lichen) were examined near two past-producing Hg mines located in British Columbia, Canada: Pinchi Lake and Bralorne Takla mines. Sequential extraction analyses and scanning electron microscopy were used to determine the chemical associations of Hg and Sb and the mineralogical forms of Hg in soils. Mercury and Sb in the C horizon are derived mostly from natural sources because their concentrations are controlled by the bedrock geology, glacial transport, and sediment types. Distribution of Sb in the B horizon is similar to that of the C horizon suggesting a common geogenic source. Mercury in the B horizon at Pinchi Lake mine could be derived in part from anthropogenic sources, because (1) only at that site, and not at any other sites of cinnabar occurrences in bedrock, is there a labile Hg enrichment in the B compared to the C horizon, and (2) there is a weak correlation between non-labile Hg concentrations in the B horizon and distance from the mine which occurs independently of the natural concentrations of the C horizon. Mercury and Sb concentrations in humus near Pinchi Lake mine (<10 km) appear to be derived in part from anthropogenic sources because there are strong correlations between labile and non-labile Hg and Sb concentrations with distance from the mine which occurs independently of natural concentrations in the C horizon. Near Pinchi Lake mine, biogeochemical cycling and gaseous Hg derived from the substrate are thought to be minimal pathways and sources of Hg to the humus compared to anthropogenic sources, otherwise the strong Hg enrichment in the humus compared to the C horizon only observed near Pinchi Lake mine would also be present at several sites of cinnabar occurrences in bedrock along Pinchi Fault. Anthropogenic Hg and Sb enrichment in the soils near Bralorne Takla mine is indistinguishable from natural enrichment. Mercury and Sb levels in the sampled moss and lichen species reflect locally derived wind-borne soil and rock dust.