Environmentalists want Ottawa to set caps on emissions from Alberta's oil sands that are likely responsible for acid rain falling over northern Saskatchewan's pristine rivers and lakes.
"It's not just regulation on every individual plant that's needed. There also needs to be a regional cap that's established for the industry," said Peter Prebble of the Saskatchewan Environmental Society. "The federal government has the authority to do so."
Alberta's oil sands are located just west of the boundary between the two provinces. The massive industrial plants emit more than 150,000 tonnes of acid-rain-causing gases every year and previous studies have suggested that about 70 per cent of those gases blow into Saskatchewan.
The province has been monitoring rainfall in the La Loche area just across from Fort McMurray. Results from nine samples over 18 months that ended last March showed an average pH level of 4.93. That level is about three times as acidic as unpolluted rainfall and about the same acidity as a cup of black coffee.
"We do have concerns and have been putting significant resources in to determine what the baseline situation is up there," said Murray Hilderman, air policy analyst for Saskatchewan Environment.
He cautions that the data so far is limited.
"We wouldn't be able to get a trend with just a couple of years data," Mr. Hilderman said.
The province is sampling hundreds of lakes in northwestern Saskatchewan to find out what's happening in the area. However, previous studies already suggest the region is growing more acidic.
A 2008 review conducted for the Canadian Council of Ministers of the Environment found that up to 12 per cent of Alberta's forest soils had probably reached the limit of how much acid they could hold, probably because of the oil sands. In 2006, the same researchers concluded that about 2 per cent of forest soils in Saskatchewan downwind from Alberta were over their limit.
Alberta Environment - which has been monitoring the area for 40 years - says acid in both the rain and the soil is within acceptable limits.
"We haven't seen anything moving toward those [limits]" spokeswoman Lisa Grotkowski said.
The province's field measurements suggest soil pH in the oil sands region has hovered around 4 since 2004, Ms. Grotkowski said. The level at which vegetation begin to be affected is between 3.7 and 4.
Acid rain forms when chemicals such as sulphur dioxide and various nitrogen oxides are expelled from smokestacks and mix with atmospheric moisture. Too much soil acid damages trees roots and leaches nutrients too deep for plants to use.
Mr. Prebble said it's important to start thinking beyond boundaries.
"There needs to be pressure from the Saskatchewan government to say to Alberta, 'Listen, your pollution is putting our lakes at risk and we need a new set of regulations.' "
"If an end result can't be produced through that process, then the government of Canada needs to step in."
Alberta and Saskatchewan signed an agreement in 2002 to co-operate on air quality issues.
Saskatchewan isn't the only one of Alberta's neighbours to express environmental concerns about the oil sands.
Last May, all 33 communities in the Northwest Territories - most of which are downstream of the oil sands - approved a motion asking the Alberta government to shut down further activity in the region until the province worked out an environmental deal with the territory.
Virtually all the effects were predicted more than a decade ago in a 1997 Environment Canada report written at the start of the oil sands boom. That report warned Alberta that it should consider the cumulative efforts of oil sands development.