Geochemistry of smelter slag and stream sediment-pore water in Lower Area One

Abstract

This talk will summarize the results of two NRDP-funded student projects to help understand metal cycling in Lower Area One. Despite great progress, the lower Blacktail Creek-upper Silver Bow Creek corridor in Butte still experiences loading of heavy metals, including zinc and copper. Part one of the talk will address the slagwalls that border Silver Bow Creek below Montana Street. The mineralogy and leaching behavior of the slag is reviewed. Although freshly broken slag is relatively inert, secondary salts formed by chemical weathering that are stored in cracks in the walls have the potential to release metals during rain events. Part two of the talk will summarize the results of sediment pore-water (“peeper”) sampling in the creeks to better understand cycling of metals between surface water and fine-grained stream sediment. Metals such as Cu, Pb, and Zn are stable in the mucky sediment, but may be remobilized and redissolved during storm events