Alana Mackay

Mining and urban impacts on semi-arid freshwater aquatic systems: the example of Mount Isa, Queensland

This paper examines the environmental risk and impact of trace metals affecting river water and sediment in and around Mount Isa, Queensland, Australia. Bacterial indicator densities are also analysed throughout the catchment to assess the impacts and the potential hazards arising from agricultural activities, sewage treatment plant releases and urban runoff. The area is drained by the ephemeral Leichhardt River, which bisects Mount Isa City and the major Pb, Zn, Cu and Ag Mount Isa Mine. Runoff is captured downstream in Lake Moondarra, with the water being used following natural filtration via a lagoon-reed bed system for potable purposes by the residents of Mount Isa City. During the dry season, the channel is characterised by numerous pools that act as storage zones for sediment and water-soluble metals as well as urban and agriculturally derived nutrients and pathogens. Our results show that sediment and water quality within the Leichhardt River adjacent to and downstream of the mine frequently exceed Australian government sediment guidelines with average values of Cu, Pb and Zn found adjacent to the footprint of the mine being 1550, 510 and 470 mg kg(-1), respectively. Dry season analysis of water-soluble Cu, Pb and Zn concentrations within pools showed that Australian government low trigger guidelines are exceeded in 100, 46 and 100% cases, respectively. The densities of bacterial indicators in remnant pools throughout the Leichhardt River also exceeded acceptable guidelines. Maximum dry season faecal coliform densities of 2000 colony forming units (CFU) per 100 mL and Enterococcus counts of 900 organisms per 100 mL were recorded in dry season remnant pools compared to wet season maximum faecal coliform and Enterococcus densities of 119 000 CFU per 100 mL and 95 000 organisms per 100 mL, respectively. The impacts on biota were also examined by assessing the metal content of the tissue of seven fish from Lake Moondarra for their Cd, Cu, Hg, Pb and Zn concentrations. Tissue metal values were generally low with only a few samples having Cu and Zn values in excess of the recommended Australian retail guideline values for fish suitable for human consumption. The effectiveness of the Citys natural reed bed potable water processing facility for removing metals held within the water body (soluble and particulate) was also assessed. The results show that the treated water generally meets Australian drinking water guidelines. Overall it is clear that sediment and water quality in the area upstream of the potable water storage zone is seriously impaired. The combined effects of industrial, agricultural and urban activities present a considerable risk to the consistency and reliability of water quality, especially during highly turbid wet season flows, which transfer highly elevated concentrations of water-soluble metal and microbial contaminants.

Floodwater Metal Contaminants in an Australian Dryland River: A Baseline for Assessing Change Downstream of a Major Lead-Zinc-Silver and Copper Mine

The variations in the quality of floodwaters from the upper Leichhardt River catchment (1113 km), Mount Isa, in northwest Queensland, Australia, were examined to better understand the impact of urban, mining, and industrial activity on receiving waters. Water sampling was conducted during the 2006-2007 wet season and captured during rainfall and runoff events. Samples were analyzed for total and dissolved (0.45-μm filter) metals (Cd, Cu, Pb, and Zn) and water quality indicators (pH, electrical conductivity, and total suspended solids). The results show that tributaries draining the large Cu and Pb-Zn-Ag mines and smelters complex located at Mount Isa contained the highest concentrations of dissolved (780 μg L Cu, 61 μg L Pb, and 1500 μg L Zn) and total (3600 μg L Cu, 3600 μg L Pb, and 4900 μg L Zn) metals. The results indicate that total and dissolved Cu, Pb, and Zn are well correlated (Pearson correlation ≥ 0.343; < 0.05) and that floodwater metals are primarily particulate bound. Water management and remediation strategies should target the mine-side tributaries and should include improvements to stormwater retention infrastructure, bank stabilization works, and installation of appropriate signage along the upper Leichhardt River indicating the potential environmental and human health hazards of floodwaters.

Comments on manuscript—Zheng, J., Huynh, T., Gasparon, M., Ng, J. and Noller, B., 2013. Human health risk assessment of lead from mining activities at semi-arid locations in the context of total lead exposure. Environmental Science and Pollution Research, 20, 8404–8416

[Extract] Zheng et al. (2013) examined the total concentration and in vitro bioaccessibility of Pb in air (PM10), soil and carpet dust samples from an unnamed Australian mining community. The Integrated Exposure Uptake Biokinetic (IEUBK) model was used to estimate the potential Pb exposure in young children (0–7 years) residing in the community from five measured Pb pathways (air, diet, water, soil and dust). The results showed that the ingestion of soils and settled dusts is the driving factor in terms of Pb exposure by children. We reviewed Zheng et al. (2013) and identified significant issues with respect to transparency, disclosure of funding, disclosure of the study location and lack of citation of relevant research. Consequently, we request that the manuscript be withdrawn from Environmental Science and Pollution Research, pending further independent blind peer review to address our concerns, which are detailed below.