Colonialism and the environment: The pollution legacy of the Southern Hemisphere’s largest copper mine in the 20th century

Mining has been a major contributor to economic development in Australia since British arrival in the late 1700s, with little to no thought regarding the long-term environmental consequences. This study assesses the metal pollution legacy caused by different smelting methods and mining activities during the British colonialism in western Tasmania. This region was the largest copper producer in the Southern Hemisphere during the 20th century. Lake sediments from Basin Lake and Owen Tarn, 12 and 5 km from Queenstown’s mines, respectively, were used to reconstruct historical metal contamination. Temporal changes in metal concentrations (iron, copper, arsenic, selenium and lead) were assessed in relation to the scale of mining activities and the technologies used. Sedimentation rates and metal influxes increased from 1900, reflecting the beginning of copper mining in Mount Lyell. Observed metal concentrations peaked after 1930, coinciding with the introduction of large-scale open-cut operations and an expansion of the mining machinery used. All elements underwent at least minor enrichment (EF 1-3) during the lifespan of the mine, with lead and copper undergoing extremely severe enrichment (EF > 50). Although smelters contributed to metal increases in the lakes, large open-cut large operations in the 1930s contributed most to metal contamination. Local metal deposition from mining-related activities decreased significantly once operations decreased, with selenium and arsenic decreasing nearly to background levels within 50 years. Lead and copper, the elements which underwent major enrichment, have not yet reached background values. The ecological consequences include the current degraded local landscape, poor water quality and disrupted local biota. Knowledge about the environmental impacts of mining in western Tasmania is less known compared to other sites around the world with a similar history. Our results demonstrate the urgent need to develop better policies and remediation programs that can mitigate the consequences of metal pollution from abandoned mines in Australia.