Heavy metal pollution and coastal environmental change in South Australia: Evidence from carbonate sediments in the lower Coorong

This reconnaissance ICP-MS based study of the heavy metal composition of a core in proto-dolomites in a hyper-saline small lagoon in the lower Coorong reveals a distinctive record of eochemical change. A provisional interpretation of the core, estimated to cover a period of ∼2-2.5 thousand years, has been made by inferences to the known chronology of industrial developments on the basis of metal signatures. The heavy metal signatures of nineteenth and twentieth century developments appear clear - for example - in distinctive peaks in the abundance of vanadium, chromium, copper, arsenic, and especially lead and uranium in the top 24 cm of the core, in particular fluctuations in the sources of emissions of lead that have existed - distant industrial sources, local vehicles and domestic sources, off-road recreational vehicles in the vicinity, perhaps power stations, as well as natural sources, may be apparent. A 'lead-focussed' approach may also suggest an earlier but less clear episode in the 19th century associated with the release of copper and arsenic that would reflect the known industrial history of the State. Changes in surface hydrology, re-working, chemical mobilisation and bioturbation are likely to have affected the concentrations of heavy metals deposited at the sediment surface. Distinctive longer term patterns of change are also indicated, on occasion with relatively sharp boundaries. These patterns and the changes between them were perhaps ultimately climatically-driven and modified in their record through complexes of biological, hydrological, geochemical and geomorphic processes. This study is unusual in that it has recovered a history of metal-cycling from an arid, coastal, calc-alkaline sedimentary and environment. It broadens the range of environments from which to infer natural environmental and historical pollution histories.