The Canadian Soil Guidelines are derived similarly from Canadian based investigations (CCME, 2007). McLaughlin et al. (2000)

outline the disadvantages associated with adoption of international standards formed on studies undertaken in the northern hemisphere. Variations in climate and soil for example, strongly influence the mobility of metal contamination (Alloway, 1995). In light of these considerations, the National Environmental Protection Council (NEPC) recently implemented changes to the NEPM with new and altered methods for deriving Health Investigation Levels (HIL) and Ecological Investigation Levels GSK3 inhibitor (EIL) for the assessment of site contamination (COAG, 2014). Although it is important to note these limitations, the selection of particular field and laboratory approaches are likely to be considered more robust in an applied and legal context where they respond to current practice and associated benchmarks for definitions of environmental impact and risk. Previous studies of rivers contaminated by mining operations show that in most cases, trace metal concentrations systematically decrease downstream of mining activity in both channel and floodplain deposits. The observed decrease has been attributed to factors including (i) hydraulic sorting, (ii) sediment storage, (ii) dilution associated

with the mixing of contaminated sediment with uncontaminated materials, and through the spreading of the contaminated material, (iv) biological uptake, and (v) geochemical remobilisation Palbociclib and abstraction processes (Macklin, 1996 and Miller and Orbock Miller, 2007). The spatial patterns for sediment concentrations of As, Cr, and Cu produced during

the Lady Annie spill differ from those observed typically in mine-contaminated rivers impacted over long periods of time. Arsenic channel sediment values were predominantly above tributary control sample concentrations and also floodplain depth values (Table 4) to around 18 km (Fig. 3), at which point concentrations decrease by about half. The decline these is coincident with Wire Yard Dam and the influx of sediment from Bustard Creek (main tributary 1, Fig. 2). The abrupt decrease suggests that As concentrations were diluted by tributary sediments as well as by the storage of sediment behind the dam. Interestingly, As concentrations increase to values observed upstream near the mine immediately downstream of the confluence with the main tributary 2, Dingo Creek (Fig. 2). By contrast, Cr displayed no clear trend with distance, although Cr concentrations also increase immediate downstream of the tributary (Fig. 2 and Fig. 3). The increase in both As and Cr downstream of main tributary 2 suggests that the trends may reflect localised mineralisation in the catchment. Channel sediment Cu values were highest near the mine and show a rapid decrease in concentrations within the first 10 km of the sampled area.