Determination of the sources and distribution of sewage and pulp-fibre-derived pollution in the Derwent Estuary, Tasmania, using sterol biomarkers

Abstract

A geographical survey of sediments in the Derwent Estuary, near Hobart (Tasmania), for sterol biomarkers of faecal pollution has established the extent, distribution and severity of sewage pollution in the estuary. Analysis of biomarkers for terrestrial plants has also determined the distribution of pulp fibre discharged from a paper mill at Boyer in the upper estuary. Contributions from other sources of extractable organics, such as hydrocarbons and terrestrial plant and animal faecal matter from stormwater and creeks were qualitatively evaluated. On the basis of the distribution of the faecal biomarker coprostanol, the mid estuary and parts of the upper estuary (from Newtown Bay to Taroona) are severely contaminated by sewage. Pollution from pulp fibre is worst in the upper estuary and concentrations of pulp-fibre biomarkers decrease downstream. Sediments of the lower estuary (south of Taroona) have biomarker distributions more typical of open marine systems with little evidence of pulp fibre. There is, however, evidence of low concentrations of faecal pollution in the lower estuary.