Heavy metal pollution in the Derwent estuary: history, science and management

In this review we provide an overview of the Derwent estuary, Tasmania, Australia. The Derwent flows through the centre of Hobart, a city with a population of approximately 200,000 people. It provides a mechanism for trade and transport, and plays a key role in community recreation. There is significant metal contamination throughout the estuary as a result of historic industry practices, to the extent that the Derwent has an unenvied reputation as one of the most highly metal polluted estuaries in the world. The most recent sediment survey (2012) showed zinc, copper, lead, cadmium, arsenic and mercury levels as still particularly high; with levels in the mid-estuary exceeding 14000, 550, 1800, 120, 420 and 45 ug/g respectively. Zinc is the most abundant metal contaminant in the Derwent, with water column levels in the mid-estuary ranging between 30–60 ug/L. Considerable management and research efforts over the last 50 years have been focused on addressing these legacy issues. As a result, the Derwent Estuary Program was instigated and has proven to be a highly successful body for co-ordination of both remediation and research efforts in the estuary. Whilst the legacy issues have been a key focus for management to date, like other waterbodies worldwide, the estuary is also facing contemporary issues associated with increased urbanisation, changes in catchment usage and climate change. This review provides a comprehensive summary of management initiatives and research to date, and outlines those emerging issues.