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 km²), 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 fi lter) 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^-1 Cu, 61 μg L^-1 Pb, and 1500 μg L^-1 Zn) and total (3600 μg L^-1 Cu, 3600 μg L^-1 Pb, and 4900 μg L^-1 Zn) metals. Th e results indicate that total and dissolved Cu, Pb, and Zn are well correlated (Pearson correlation ≥ 0.343; p < 0.05) and that fl oodwater metals are primarily particulate bound. Water management and remediation strategies should target the mineside 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.