Use of a multi-proxy method to support the restoration of estuaries receiving inputs from industry

In New South Wales (NSW), Australia, the availability of water from estuarine lakes combined with the use of coal as an energy source has resulted in coal-fired power stations on the margins of coastal lakes. The purpose of this study was to use a multi-proxy method to evaluate the extent and trends of historical metal inputs from a coal-fired power station to sediments in Lake Budgewoi. Metal concentrations in 15-cm sediment cores showed a uniform depth profile. The highest concentrations of zinc and copper were found close to the Munmorah Power Station outlet, while arsenic and lead were found in the deposition basin of sediments. Background values for metal concentrations of Zn < 80 mg/kg, As < 15 mg/kg, Se < 1 mg/kg, Cu < 16 mg/kg, Cd < 0.8 mg/kg and Pb < 20 mg/kg were used as the baseline for future studies in this lake. The history of sediment metal concentrations is consistent with power station activities in the lake. Maximum metal concentrations found in sediments of Lake Budgewoi were Zn 122 mg/kg, Cu 45 mg/kg, As 10 mg/kg, Se 1.8 mg/kg, Cd 0.2 mg/kg and Pb 41 mg/kg. The ratio of these values to the national interim sediment quality guidelines are Pb 0.8, Cu 0.7, Zn 0.6, As 0.5 and Cd 0.1. Although concentrations were below guideline values, the multi-proxy method applied in this study was sensitive enough to detect metal concentration changes over the 45 years of power station operation. The results of this study provide environmental regulators with a baseline of the past and current situation of power station metal contamination, and in the future will provide insights into how long it takes the environment to revert to background metal concentrations.