Acid rain, therefore, is any precipitation with a pH value lower than 5.6. Currently, rainfall in New England has an average pH value in the range of 4.6-4.0, although individual storms can be higher or lower than this range. The two principle causes of acid rain are sulfur oxides and nitrogen oxides. A major source of sulfur oxides in the atmosphere is the burning of coal and oil. Nitrogen oxides are formed by the burning of fossil fuels, primarily gasoline in car and truck engines.
Acidity is measured on the pH scale.
Low numbers represent acidic substances, high numbers represent alkaline substances. 7.0 is in the middle of the scale and represents a neutral substance. Because the scale is based on logarithms, a substance like lemon juice with a pH of 2.2 is ten times more acidic than vinegar with a pH of 3.2, and 100 times more acidic than acid rain with a pH of 4.2. The purpose of this project is to get students involved in measuring the pH of precipitation and to use this as a means of researching, discussing, and analyzing the complex issues of acidified precipitation and atmospheric pollution, especially in New England. The acid rain issue is a complex and interesting topic.