Historical mine sites as modern-day sources of contamination : Measurement and characterisation of arsenic in historical gold mine wastes to identify the potential for mobility and human exposure

Centuries of metalliferous mining activities have resulted in a legacy of contamination throughout the world. Unremediated mine wastes and tailings, as well as contaminated soils, water and sediments, represent ongoing sources of environmental degradation and human exposure, long after mine closure and abandonment. Despite global concern over these contaminant sources, there remain uncertainties surrounding the nature of human exposure to mine wastes and their toxicologically relevant characteristics. As urbanisation expands into areas proximal to abandoned mine sites, an understanding of the human-contaminant interface at this boundary is critical for assessing the potential health risks. This thesis addresses this knowledge gap by investigating the importance of particle size as a factor governing the distribution of metals and metalloids in historical gold mine wastes in regional Victoria, Australia, with an emphasis on arsenic as a contaminant of potential concern. By characterising those particle size fractions that are relevant to dust mobilisation and human exposure, this thesis examines the human-contaminant interface using a multi-pathway approach. In particular, this thesis focuses on the potential for exposure via inhalation of mine waste particulates. The outcomes of the studies presented in this body of work demonstrate that historical gold mine wastes in regional Victoria represent a source of readily ingestible and inhalable particulates characterised by extremely elevated levels of arsenic (and other contaminants) well above their bulk (in situ) concentrations. Although lung bioaccessibility testing and mineralogical analyses revealed that most of the arsenic in inhalable dust has been naturally immobilised, the lung-soluble fraction should be considered when undertaking risk assessments for chronic exposure. This thesis provides a framework for the development of targeted management strategies for unremediated historical gold mining wastes in regional Victoria. The findings suggest there is a need for environmental regulations to shift from generic guideline values to exposure-specific guidelines that more accurately reflect the human health risks posed by historical mine sites. This thesis has emphasised the notion that in order for remedial action to accurately match the level of risk, the sourcepathway- receptor linkage must be evaluated using a systematic size-resolved approach.Doctor of Philosoph