Influence of soil cap depth and vegetation on reclamation of phosphogypsum stacks in Fort Saskatchewan, Alberta

This study quantified environmental parameters to develop reclamation strategies for phosphogypsum stacks. Research was conducted on phosphogypsum stack experimental plots established in 2006 (6 soil cap depths, 5 vegetation treatments), and soil capped slopes seeded in 1998. Significant root mass accumulations occurred at soil-phosphogypsum interfaces with 8, 15, 30 and 46 cm caps in 50% of cores. Peak water content occurred at this interface with all cap depths in fall 2010; trends differed in 2011. Maximum rooting depth increased with increased cap depth, root biomass did not. Vegetation performed better in capped than uncapped plots; cap depths . 15 cm supported healthy vigorous plants. Vegetation on stacks had elevated fluorine, cobalt and nickel; plants from cap depths . 8 cm had tissue concentrations safe for animal consumption. Snow metal concentrations increased with proximity to a neighbouring metal refinery. Nineteen years after capping and seeding stack slopes had 35 plant species.