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Developments in analytical techniques and their applications to datable environmental archives (e.g. ice, sediment and peat cores) over the past half-century have enabled the extent of metal (e.g. Pb) contamination of the natural environment as a consequence of human activities over the past 250 years to be placed in longer-term historical perspective. The main initial emphasis and motivation of such studies was indirect historical monitoring allied to concomitant direct monitoring of the release and environmental dispersion of metals at a time of maximum emissions associated with industrial, energy-related and transportation activities in the mid- to late 20th century. While the principal outcome at that time was clearly the provision of underpinning evidence to confirm the need to reduce and, if possible, eliminate emissions of potentially harmful metals, much of fundamental scientific importance was also discovered with respect to potential perturbatory processes (e.g. diagenetic remobilisation) capable of distorting the historical record. At the same time, opportunistic advantage was taken of specific time-related releases of radionuclides (e.g. Cs-137) to the environment from nuclear weapons testing as well as nuclear industry facilities and of source-related changes in the stable isotopic composition of, for example, Pb emissions to assist quantification of rates of accumulation and of relative contributions from different anthropogenic activities. With the effectiveness of legislative measures to restrict emissions (e.g. of Pb) now manifest, much greater emphasis is being placed on improving fundamental understanding of geochemical and hydrological processes responsible for the retention, remobilisation and release of previously emitted and deposited metals, for example from catchments to receiving water bodies, in contaminated areas as diverse as urban, rural and remote locations. That this will become the main focus of research in environmental metal contamination over the coming decades seems assured, especially in view of the potential impact of seemingly inevitable climate change (e.g. thawing of frozen regions, sea-level rise, greater frequency and intensity of storms, drought) arising from human-induced global warming. The scientific challenges that lie ahead call for a vision encompassing scales ranging from atomic to global and strategies involving much greater integration of analytical, modelling and disciplinary effort, as will be argued in this presentation.
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