Chemical and biological approaches to contaminated site assessment: case studies using legacy mines

Contamination from legacy mines can be a significant human and environmental health problem where contamination travels beyond the source. Particularly important in this regard is contamination by metals. The United States Environmental Protection Agency (USEPA) identifies chromium, nickel, copper, zinc, arsenic, cadmium, mercury and lead as priority contaminants for remediation because of their known health effects. In order to remediate contaminated sites, first the extent and severity of any impacts of the contamination must be assessed, so that the limited resources available for remediation can be optimised. I have investigated new methods for the assessment of contaminated sites, using base metal legacy mines as an example. The outcomes of this thesis provide tangible benefits for the environment and communities near and downstream of contaminated areas who will benefit from thorough knowledge and assessment of the impacts of those former land uses. The history of contamination at one legacy mine was first studied to illustrate the ongoing nature of contamination from a former land use. The result indicated that Meta-analysis can be a promising tool to evaluate the background of contamination at impacted sites. Environmental DNA (eDNA) metabarcoding was then used to investigate two contaminated environments; one with simple and one with complex geographical settings. eDNA revealed that sediment and water chemistry data alone could over- or underestimate the importance of pollution in aquatic environments. eDNA provided information on the whole biological communities living with different concentrations of metals and metalloids. eDNA could detect impacts from long-term contamination where chemistry analyses were unable to detect contamination. Responses of biological communities to contaminants can reflect discrete or cumulative impacts from multiple sources of contamination. eDNA can provide more sensitive results for determining the pollution status at different locations. Assessment of terrestrial contamination was also investigated using ants as indicators of metal contamination. The genera of the ants can play an important role in accumulation of metals and as a result, genera should be taken into account before using ants for assessment of contaminated sites. Biogeographic distribution patterns of biota reconstructed from eDNA analyses can provide vital insights into the status of contaminants in soil, sediments and water at and downstream of contaminated sites. eDNA is a promising tool for reconstruction of the contamination of terrestrial environments, and plumes of contaminants in aqueous environments downstream of both active and legacy land uses. eDNA analyses in terrestrial contaminated environments can provide large-scale information for water, sediment, soil and ecosystem health and help determine where ecosystems are under stress as a result of contamination. Finally, this research provides insights for future use of eDNA as a new tool for assessment of contaminated environments. These outcomes could help managers of natural resource management agencies to have broader understanding of impacted sites and have better management plans for restoration of contaminated sites.