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Heavy metal composition of turbid river waters associated with coal mine-affected water releases in the Fitzroy River Basin (Central Queensland)
conference contributionposted on 06.12.2017, 00:00 by Catherine Jones, Victoria Vicente-Beckett, James Chapman
Over 40 coal mines have mine-affected water release points into the sub-tropical Fitzroy River Basin (Central Queensland). The Fitzroy Basin is ≈140000 km2 and comprises 11 sub-basins. Turbidity is an important environmental health parameter of coal mine-affected water releases and is regulated by environmental authorities. Turbidity indicates the presence of suspended particulates. The potential metal contaminants transported and/or released by suspended particulates in coal mine-affected receiving and release waters are not well-known. Additionally, there is a knowledge gap surrounding background metal concentrations within the Fitzroy Basin. Secondary Fitzroy Basin water quality datasets from 2008-2013 were analysed particularly to examine turbidity and metal concentration ranges at the sub-basin level. Preliminary results indicate that:• Turbidity is highly variable within the Fitzroy River system (e.g. in 2008-2011, the average turbidity in the Mackenzie River sub-basin was 556± 655 NTU, n = 853).• >90% of these observations were above the 2011 Fitzroy River Water Quality Objective (<50 NTU).• Dissolved copper, zinc, aluminum and nickel, often exceeded the ANZECC/ARMCANZ (2000) toxicant trigger levels; for example ≈70% of the dissolved aluminum data, from both upstream and downstream of coal mine-affected water release points, exceeded the trigger value (55 μg/L, pH >6.5).• Since bioavailability depends on metal speciation, the existing data were modeled using Visual MINTEQ to identify possible metal chemical forms. For example, the predicted copper species at a site directly downstream of an Upper Isaac Sub-basin mine-affected release point were CuCO3(aq) (86%), CuOH+ (5.9%), Cu(CO3)2-2(3.8%) and Cu2+ (1.4%).The current research project further investigates temporal and spatial changes in turbidity levels, heavy metal concentrations and metal speciation, and seeks to deduce interactions (based on laboratory experiments) of coal mine-affected waters and the Mackenzie River receiving waters. This research will hopefully inform water managers and help validate/establish regionally relevant guidelines and objectives.