Metal and solute transportation through a wetland at a Lead Zinc Mine, Northern Territory, Australia

B.N. Noller1*, G.K. Parker2 and G.H. Gao2

1 National Research Centre for Environmental Toxicology (EnTox), University of Queensland, 39 Kessels Road Coopers Plains Qld 4108 Australia
2 Mines Division, Department of Business, Industry and Resource Development, Northern Territory Government, GPO Box 3000, Darwin, NT 0801, Australia

Received 30 June 2002; accepted 3 January 2003


This paper presents an evaluation of historical data for metal and solute transport from underground dewatering through a wetland at the Woodcutters lead-zinc mine in the Northern Territory, Australia. Groundwater aquifers drain into the underground workings that were then pumped into an ephemeral stream, which was developed as an extended wetland system, dominated by Typha sp. The tropical monsoonal climate comprising an extended wet season from December to April gave flow to the creek system. Only dewatering contributed flow during the dry season. The significant metal contaminants were antimony, cadmium, copper, lead and zinc and the major components of solutes magnesium and calcium sulfates. Retardation ratios for each metal relative to sulfate showed attenuation of all metals by the wetland system except for some copper under high creek flow conditions. Measurement of electrical conductivity by continuous logger at the inlet and the outlet of the wetland showed that solutes were higher at the outlet compared to the wetland inlet. This anomaly was attributed to the addition of solutes from tailings seepage to the wetland system. Comparison of the loads of solutes revealed a higher load at the inlet indicating that some loss of salts occurred within the wetland. The characteristics of carbon in water were investigated and revealed that inorganic carbon was derived essentially from dewatering and seepage whereas organic carbon was added to the water column from the wetland vegetation. Generally there was a reduction in metal load for wetland inlet compared to that downstream. The efficiency of the wetland system was considered to be high and presents a model system for treating mine wastewater containing such metal impurities.

Keywords: Wetlands; mine wastewater; heavy metals; tropical; organic carbon

* Corresponding author
   E-mail : b.noller@mailbox.uq.edu.au