ACID RAIN: A Definition

 Acid deposition- commonly called acid rain- is caused by emissions of sulphur dioxide and nitrogen oxides. Although natural sources of sulphur oxides and nitrogen oxides do exist, more than 90% of the sulfur and 95% of the nitrogen emissions occuring in eastern North America are of human origin. These primary air pollutants arise from the use of coal in the production of electricitiy, from base-metal smelting, and from fuel combustion in vehicles. Once released into the atmosphere, they can be converted chemically into such secondary pollutants as nitric acid and sulfuric acid, both of which dissolve easily in water. The resulting acidic water droplets can be carried long distances by prevailing winds, returning to Earth as acid rain, snow, or fog.

 Acidity is measured by a scale of pH. Neutralilty is considered a pH of 7. Lower pH's are acidic, and higher pH's are basic. This scale is logarithmic, not linear. Acid rain's baseline of pH is considered 5.6, interestingly carbon dioxide is pH of 5.6 also. Acid rain is rainfall with an acidic level below pH of 5.6. Below is a scale for pH showing several chemicals pH.

pH Scale (pH Activity)


Click here to test your skills on pH.