Mineral soil and fibric peat from acid-sensitive western boreal catchments in the Athabasca Oil Sands Region of Alberta, Canada were evaluated for their ability to adsorb and release SO4 2− Laboratory batch studies indicated that SO4 2− adsorption in mineral soil from both the A and B horizons exhibits a limited response to elevated SO4 2− concentrations, with the slope of initial mass isotherms <0.2 for all soils, likely due to low iron and aluminum oxide content. Although S retention is the dominant process in peat soils in the region, drought simulations in the lab using fibric peat collected from a poor fen exhibited as much as a five-fold increase in SO4 2− concentration after drying and rewetting. Given the limited SO4 2− adsorption capacity of mineral soils and the potential drought-induced S release from peatlands in this region where increased S deposition is expected, further investigation of acidification impacts is warranted.