Where does the pollutant that forms acid rain come from? How is acid rain formed?
Acid rain forms when molecules of oxidized sulfur and/or nitrogen in the atmosphere combine with water, forming acidic compounds that dissolve in the water that becomes rain. Typical sulfur compounds (SO2 ans SO3) get into the atmosphere from both natural (i.e. volcanoes, windblown dust containing gypsum-which has SO4 ions in it, etc..) and non-natural (i.e., burning of coal, refining of metal ores) sources. Nitrogen compounds also get into the atmosphere and form acids, although the natural sources are much more limited. The biggest non-natural source is buring fossil fuels, especially gasoline. How much acid rain falls yearly in Oregon? This is difficult to quantify, since it depends on how acidic the rain is (e.g., how low the pH is) and how much it rains. Both parameters vary widely over the state of Oregon. In general, Oregon rain is only mildly acidic. Rain there has typical pH values of 5.2 to 5.4. By contrast, parts of the North Eastern US and Southern California have rain with
