Nutrients, such as phosphorus and nitrogen, are crucial for growth of aquatic plants and the health of aquatic ecosystems but at high levels can cause noxious algal blooms and other problems such as increased density of rooted aquatic plants.
Nitrogen and phosphorus are naturally occurring, but concentrations in aquatic environments can be affected by human actions. Algal blooms may produce toxins that can affect the liver, the nervous system, or the skin and have a negative affect upon fisheries, tourism and recreation.
As well, blooms of cyanobacteria (also called blue-green algae) can present health risks to the liver and brains of anyone attempting to use the affected water.
Similar problems in the 1970s motivated Canadian regulations limiting phosphate in laundry detergents and discharge from sewage treatment plants.
Data only includes water releases from large industrial and municipal facilities; however, nutrients also enter the water system from the agricultural sector. Excessive use of fertilizers by, for example, applying more than crops require, leads to nutrients leaching into surface water.
It is unclear how great a source of increased nutrients this is, compared with industrial sources; however, evidence suggests that it is a significant source in many areas (Environment Canada, 2011b).
Nitrogen levels in rivers and lakes are also affected by atmospheric deposition. This refers to nitrogen in the air being deposited into the water system. Nitrogen oxides (NOx) are produced when burning fossil fuels, so emissions from motor vehicles and power plants can affect nitrogen levels in aquatic environments.
Natural sources, such as forest fires and biological processes, were responsible for around eight percent of Canada’s total NOx emissions (Environment Canada, 2010).
Regulations at the federal and provincial levels target a multitude of sources of nitrogen and phosphorus emissions. Concentrations of phosphorus in laundry detergents and household cleaning products have been regulated at the federal level since the 1970s.
There are also regulations on effluent released by industrial facilities and sewage treatment plants at both the federal and provincial levels. At the provincial level in most provinces, a large facility must obtain a permit for any effluent release.
The federal government has recently implemented the country’s first national standards for wastewater treatment, the Wastewater Systems Effluent Regulations.
There is also legislation at the federal level, such as the Fisheries Act, that allows for fines and criminal penalties for the release of a deleterious substance that will affect fish habitat. Air emissions of nitrogen oxides from motor vehicles are regulated at the federal level, and from industrial facilities at the provincial level.
A report by Environment Canada (2011b) examines nutrient levels and trends in Canadian water bodies. The amount of phosphorus in an aquatic environment is affected by natural and human factors, so looking at concentrations over a short period is not very informative about the impact of human activity.
For example, many prairie rivers have high phosphorus levels mainly due to geology, not human pollution.
However, the report also looks at phosphorus trends at 75 sites across Canada from 1990 to 2006. They find that phosphorus levels increased at 21 percent of sites, decreased at 31 percent of sites, and experienced no change at 48 percent of sites
These results suggest that, for the most part, water quality with respect to phosphorus is not getting worse in Canada. Monitoring stations in Ontario, British Columbia, Alberta, and New Brunswick generally show downward trends for phosphorus. Nova Scotian rivers generally have increasing levels of phosphorus.
An interesting result from the Environment Canada report is that only four out of 75 sites experienced upward trends for both phosphorus and nitrogen.
The locations experiencing increasing levels of phosphorus are generally not the same as those experiencing increasing levels of nitrogen.