Introduction European colonies were first established in Australia in 1788. The discovery of gold and subsequent gold rushes in the 1850s brought migrants to the country and developed mining into a full-fledged industry (Blainey, 1993; Davies and Oliver, 2018). The prosperity of this industry formed an economic backbone of early European Australia, and the country enjoys the legacy of that prosperity to this day. Much of this mining industry, however, has also left a legacy of contamination. Given the lack of metal contamination control in these historical mines, a comprehensive environmental assessment is needed to comprehend the extent and nature of mining legacy impacts on ecosystems and communities across Australia. It is estimated that more than 50,000 legacy mines in the country require environmental assessments to avoid ongoing and future environmental issues (Pepper et al., 2014). Captains Flat, in New South Wales, is home to the Lake George Mine, a legacy mine site that predates the implementation of any environmental protection legislation in New South Wales (Zillig et al., 2015). The earliest relevant legislation in the state, the Mining Act 1992, was introduced 30 years after the mine closed (Zillig et al., 2015). Mining in Captains Flat originally sought gold, but later targeted galena, sphalerite, chalcopyrite and pyrite deposits in the orebody, seeking lead, zinc, copper and iron (Pryke, 1995). Hg amalgamation techniques in Captains Flat were used to extract gold, but the sulfide ores targeted in later mining were also known to contain Hg by-products (Pryke, 1995; Rytuba, 2003). These mining operations contaminated the Molonglo River, which feeds Lake Burley Griffin, an artificial lake in Canberra, the Australian capital. The lake was completed in 1963 after the Molonglo River was dammed (Caitcheon et al., 1988). The lake is located in the approximate geographic centre of the capital and is a popular location for many recreational uses; including swimming, rowing, fishing, and sailing. While Lake Burley Griffin has social and heritage importance, it is a focus of study here because it acts as a sink for sediment transported by the Molonglo River (Caitcheon et al., 1988). Previous studies have shown significant contamination of metals in both the Molonglo