The Legacy of Mercury Contamination from Colonial Nonferrous Mining in the Southern Hemisphere

The Mount Lyell copper (Cu) mine in Tasmania, Australia, underwent historical operational changes that influenced mercury (Hg) emissions from ore processing and smelting. This study presents the first record of Hg concentrations (HgC) and accumulation rates (HgAR) using sediment cores from four lakes around Mount Lyell. HgC and HgAR increased from the 1890s (onset of smelting), peaked from the 1920s (introduction of the flotation processing method), and declined after 1969 (smelter closure). Mercury isotopic signatures confirmed its anthropogenic source. Modeling of Hg deposition vs distance over the period 1922–1969 showed that it followed a power-law function. The Mount Lyell emissions may have affected an area up to ∼270,000 km2, beyond which deposition was indistinguishable from the natural background. Estimated total Hg loadings ranged from 23 to 43 t, compared to an estimated ∼150 t Hg contained in the ore floated. Isotopic data showed Δ199Hg trending toward zero near the smelter, indicating that the smelter was the main source of Hg. Our findings highlight that pyrometallurgical smelting methods contributed more significantly to Hg emissions than production volume. Studying legacy mines in the Southern Hemisphere, responsible for 29.1% of global Cu production during the preregulatory era (1880–1950), is critical to understanding historical Hg dispersion in this understudied region.