Québec, October 15, 1998 – Environment Minister Christine Stewart today released a study showing an improvement in the St. Lawrence River quality and detailing the challenges ahead.

The study titled St. Lawrence River Mass Balance Study shows that PCB concentrations in the St. Lawrence are between 5 and 10 times lower than those recorded in Lake Ontario during the 1980s, indicating a clear improvement.

"This study provides a portrait of the chemicals in the St. Lawrence River" said Minister Stewart, "and will assist in further reducing the pollution levels which in some cases are some of the lowest levels in the world when compared with other major river systems."

The eighty-five chemical contaminants targeted in this study by the St. Lawrence Centre (SLC) were grouped into the following six categories: metals, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), organochlorine and organophosphorous pesticides and triazines.

"Although this study answers important questions related to the chemical contamination in the St. Lawrence River and shows an improvement in water quality, we are still faced with major challenges in restoring one of the world’s greatest river systems back to health," said Minister Stewart.

One of the key tools to clean up the river is the St. Lawrence Vision 2000 (SLV2000) agreement signed in April 1994 (phase III of the St.Lawrence Action Plan -SLV2000- agreement signed in June 1998). This agreement involves the participation of over ten Canadian and Quebec government departments, who agreed to work together to protect, preserve and restore the St. Lawrence River and its tributaries in order to return their use to the public with a view of sustainable development.

This study is part of Phase II of the St.Lawrence Action Plan and quantifies the amounts of chemicals reaching the St. Lawrence from the Great Lakes and its main tributary, the Ottawa River. It also estimates the quantities of contaminants carried into the Estuary of the St. Lawrence.

The study was conducted between May 1995 and September 1996.

For further information, please contact:

Michael Barluk
Office of the Minister
(819) 997-1441

Backgrounder

Mass Balance of Contaminants in the St. Lawrence

Environment Canada’s St. Lawrence Centre (SLC) today October 15, 1998 published the "St. Lawrence River Mass Balance Study". This study is part of Phase II of the St. Lawrence Action Plan Vision 2000 and quantifies the amounts of chemicals reaching the St. Lawrence from the Great Lakes and its main tributary, the Ottawa River. It also estimates the quantities of contaminants carried into the Estuary of the St. Lawrence.

Between May 1995 and September 1996, scientists at the SLC estimated the amounts of contaminants entering the St. Lawrence at the two main gateways, Cornwall for water coming from Lake Ontario and Carillon for water coming from the Ottawa River, as well as at the exit from the Cornwall-Québec segment, the mouth of the River off Québec city. The Eighty-five chemical contaminants included in this study by SLC were grouped into the following six categories: metals, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) , organochlorine and organophosphorous pesticides and triazines.

Concentrations of contaminants found in the St. Lawrence River were so low that scientists had to use sampling techniques normally adapted to the analysis of trace levels of chemicals. These levels corresponded to less than one billionth of one gram (and often to one thousandth of one billionth of one gram) of a contaminant contained in one litre of water. This is equal to one-half teaspoon in 2000 Olympic-size swimming pools!

The study shows that concentrations of toxic metals measured at the three stations involved in this study are of the same order of magnitude as those recorded in aquatic environments which are felt to be not very contaminated, if at all. Depending on the metals in question, concentrations are between 10 and 100 times lower than those recorded in Europe’s most polluted rivers. The scientists estimate that most metals come from natural sources and are linked with tributaries and erosion of the river bed and banks.

When compared with those for other water courses in the world, readings of PCB contamination taken during this study indicate that the St. Lawrence is one of the least contaminated rivers in the world. The mass balance of contaminants shows that the load of PCBs and PAHs is five times higher at Quebec City than the combined loads at the two entry stations, Cornwall and Carillon. In addition, the load increase recorded indicates that the sources are located in the Cornwall-Quebec City segment of the River.

The mass balance also shows that PCB concentrations in the St. Lawrence are between 5 and 10 times lower than those recorded in Lake Ontario during the 1980s, indicating a clear improvement. PAH concentrations, on the other hand, do not show any decline over the figures for previous years. This may be accounted for by the constant presence of PAHs in the environment.

As for the herbicides, the concentrations of the four herbicides detected (atrazine, simazine, metolachlorine and cyanazine) are the same at Quebec City as at Cornwall. This would indicate that, on an annual basis, the Great Lakes Basin is by far the major source of this type of contamination in the St. Lawrence. On the contrary, the measured loads are up to one hundred times lower than those measured in rivers with high agricultural potential.

The study shows that, although waters from the Great Lakes and the Ottawa River account for 61% and 16% respectively of the water flowing past Quebec City, the combined burden of suspended matter at Quebec City was only 11% of the figure recorded there in 1995-1996. The scientists believe that this matter was primarily the result of erosion of the banks and bed of the St. Lawrence.

Although this mass balance of contaminants answers important questions relating to chemical contamination in the St. Lawrence, it does not permit the evaluation of the impact of a particular discharge on the level of contamination of the river, nor does it let us know the effects of chemical contamination on the aquatic life. However, it raises new issues concerning, among other things, the importance of internal and natural sources of contamination, the need to characterize existing sources of PCBs and PAHs within the segment of the River that was studied and the importance of suspended matter added to the River. The potential of contaminated sediments as a source of contamination along the River corridor also needs to be determined.

The team of scientists at the St. Lawrence Centre recommends that a similar study be carried out every ten years, since this would make it possible to monitor developments in concentration levels and flows of contaminants from the Great Lakes and the Ottawa River.

For further information, please call:

Thanh-Thao Pham
St. Lawrence Centre
Environment Canada
(514) 283-3668