Geochemistry of Cu, Zn and Fe in the Tambo River, Australia II. Field investigation under low-flow conditions
Barry T. Hart A B , Tina Hines A and Bruce A.W. Coller AA Water Studies Centre and School of Chemistry, Monash University, Victoria 3800, Australia.
B Corresponding author. Email: barry.hart@waterscience.com.au
Marine and Freshwater Research 59(1) 80-88 https://doi.org/10.1071/MF07057
Submitted: 15 March 2007 Accepted: 7 September 2007 Published: 25 January 2008
Abstract
The behaviour of Fe, Cu and Zn, added to the upper Tambo River (Victoria, Australia) via a metal-enriched groundwater input, was studied during a period of very low river flow. Water samples were collected over a 1.3-km section of the river located immediately downstream of the spring input. Heavy metals were separated into three fractions (dissolved, colloidal and particulate) using tangential flow filtration. Within the ‘input region’, the pH was low (5.1–5.8) and sulphate (306–359 mg L–1), total Fe (2.81 mg L–1), total Cu (19.7 mg L–1) and total Zn (24.1 mg L–1) concentrations all increased significantly. Subsequently, the total metal concentrations reduced with distance downstream of the input, and approached values similar to those recorded upstream of the input region at the end of the study region. Most of the Fe was oxidised before it entered the river as a thick hydrous iron oxide floc that travelled downstream close to the riverbed. The remaining dissolved Fe (mainly Fe(II)) that entered the river largely controlled the behaviour of Cu and Zn in the ‘active region’ (75–400 m). This Fe(II) was rapidly oxidised to Fe(III), which then removed large amounts of the dissolved Cu (65%) and Zn (55%) into the colloidal fraction. Processes such as settling of particles, dilution by groundwater inputs and sorption of dissolved Cu and Zn onto sediments removed the remainder of the Cu and Zn.
Additional keywords: acid mine drainage, contamination, hydrous iron oxide, oxidation, surface precipitation, transport.
Acknowledgements
Macquarie Resources Ltd. funded the present study and also provided a scholarship for T.H. We are grateful to Jovo Basic, Paul Dowd, Craig Jeffs and Hugh Stein of Macquarie Resources Ltd. for their support and assistance, and to Steven Hines for his assistance with the field work. B.T.H. thanks the University of Western Australia for awarding him a Senior Gledden Fellowship and to the Centre for Water Research at UWA for providing him facilities during which time this paper was completed.
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