Geochemistry and Toxicity of a Large Slag Pile and its Drainage Complex in Sudbury, Ontario

Description

This study was designed to determine the geochemistry and potential toxicity of water draining a large slag pile in Sudbury, Ontario, which runs through a pond complex prior to entering Alice Lake. Slag leaching experiments confirmed slag is a source of sulphate, heavy metals (including Fe, Al, Ni, Co, Cu, Zn, Pb, Cr, Mn) and base cations (Ca, K, Mg, Na). Concentrations of most metals draining through slag in column experiments were similar to metal concentrations measured at the base of the slag pile, although base cations, S and pH were much higher, possibly because of water inputs interacting with the surrounding basic glaciolacustrine landscape. The increase in pH rapidly precipitates metals leading to high accumulation in the surface sediments. Away from the base of the pile, an increase in vegetation cover leads to an increase in DOC and nutrients and transport of metals with strong binding affinities (Cu). Total metal concentration in water and sediment exceed provincial water quality guidelines, particularly near the slag pile, however WHAM7 modeling indicated that the free metal ion concentration in water is very low. Nevertheless, toxicity experiments showed that water with greater concentrations of solutes collected close to the slag pile negatively impacts D. magna suggesting that water draining the slag pile can adversely impact biota in nearby drainage areas.
Author Keywords: geochemistry, heavy metals, leaching, non-ferrous slag, precipitation, toxicity