Sulfates and nitrates work together to increase the acidity of rain, while ammonium works to lower the acid level. Look at various parts of the United States and consider how these three factors work together to determine the pH levels for different parts of the country. Neutral pH is 7, and precipitation with a pH level below 5 is considered acid rain.

  !   Use the buttons on the map to switch between the sulfate, nitrate, ammonium, and pH views of the United States.

10. Explain how sulfate, nitrate, and ammonium levels work together to produce the observed pH level in central Pennsylvania.

11. Explain how sulfate, nitrate, and ammonium levels work together to produce the pH level in the Panhandle region of western Oklahoma.