Episodic acidification of 5 rivers in Canada's oil sands during snowmelt; a 25-year record

Highlights • Surface water acidification during snowmelt was assessed using 25 years of automated data from Canada’s oil sands region. • Surface water acidification occurred in 39% of snowmelt events. • Aluminum and 11 priority pollutants were greatest during snowmelt acidification episodes. • Aluminum and copper during these episodes may be high enough to pose a risk to rainbow trout. • Long-term monitoring in the oil sands region will ideally include the snowmelt period.