The pH Scale

• The pH scale measures the acidity or alkalinity of a liquid, from 0 to 14---7 is neutral, anything below 7 is acidic and anything higher is alkaline.
  
  

Natural Water

• Rain and groundwater tend to be naturally slightly acidic, usually no lower than 6 on the pH scale. Most plants and animals tolerate this level of acidity without any problems.
  
  

Pollution

• Byproducts of air and water pollution are acidic. While natural alkaline substances in the soil can reduce their impact, the result of such pollution is often a much more acidic environment than normal.
  
  

Acid Rain

• When low-pH water spreads via precipitation, it is called acid rain. As it soaks into the ground and collects in streams, it can drastically change the ecosystem.
  
  

Consequences

• As pH drops, more fragile plants and animals may become sick and die. In addition, a pH change in a body of water can affect the microorganisms living within, with domino effects that can destroy the entire aquatic food chain.