Many of us have heard about a danger to the environment called acid rain, but most of these people know little else. Acid rain affects places all around the world, including New Brunswick. It has been responsible for the destruction of entire forests, lakes and buildings. But what is acid rain? Where does it come from and how does it affect the world around us?
The most accurate term for acid rain is actually "acid precipitation. This term refers to acidic components in rain, snow, fog, dew, or dry particles. Distilled water has a neutral pH of seven and contains no carbon dioxide. Liquids with a pH under seven are acidic while liquids with a pH above seven are alkaline. Typically, unpolluted rain is slightly acidic with a pH of around five point six. This is because of carbon dioxide and water in the air which react to form a weak acid called carbonic acid. There are several pollutants which add the extra acidity in the rain. These are primarily nitrogen oxides and sulfur oxides generated by vehicles and industrial and power-generating plants. (John Watson, "What is Acid Rain? )
Specifically, sulfur dioxide emissions come from the burning of fossil fuels such as ore smelting, coal-fired power generators and natural gas processing. In nineteen-ninty-eight Canada's sulfur dioxide emissions were measured at two point seven million tonnes. That was six times less than the U.S.'s emissions which reached seventeen point seven million tonnes. One must keep in mind however that these emissions are coming from different places. (Figure 1.1) Seventy-four percent of Canada's emissions were directly from industrial sources however, sixty-seven percent of the U.S.'s emissions were actually from electric utilities. Today, Canada has reduced their sulfur dioxide emissions by thirty percent since nineteen-ninety-eight and fifty percent since nineteen-eighty. (Environment Canada, "Acid Rain and the Facts )
NOX emissions, unlike sulfu