pH

Water (H2O) contains both H+ (hydrogen) ions and OH- (hydroxyl) ions. The pH test measures the H+ ion concentration of liquids and substances. Each measured liquid or substance is given a pH value on a scale that ranges from 0 to 14.

Pure deionized water contains equal numbers of H+ and OH- ions, and has a pH of 7. This is considered neutral, neither acidic or basic. If a water sample has more H+ than OH- ions, it is considered acidic and has a pH less than 7. If a sample contains more OH- ions than H+ ions, it is considered basic with a pH greater than 7.

It is important to remember that for every one unit change on the pH scale, there is approximately a ten-fold change in how acidic or basic the sample is. For example, lakes with a pH of 4 (acidic) are roughly 100 times more acidic than lakes with a pH of 6.

So why are pH values so important? Changes in the pH value of water are important to many organisms. Most organisms have adapted to life in water of a specific pH and may die if it changes even slightly. At extremely high or low pH values, the water becomes unsuitable for most organisms. Immature stages of aquatic insects and young fish are extremely sensitive to pH values below 5. Waters with high acidic values can also cause heavy metals, such as copper and aluminum, to be released into the water. Heavy metals can accumulate on the gills of fish or cause deformities in young fish, reducing their chance of survival.

In the United States, the pH of natural water is usually between 6.5 and 8.5, although wide variations can occur. Increased amounts of nitrogen oxides (NOx) and sulfur dioxides (SOx), primarily from automobile and coal-fired power plant emissions, are converted to nitric acid and sulfuric acid in the atmosphere. These acids combine with moisture in the atmosphere and fall to the earth as acid rain or acid snow.

Acid rain is responsible for thousands of lakes in eastern Canada, northeastern United States, Sweden and Finland becoming acidic. In many areas of the United States, the type of rocks and minerals that are present determine the acidity of the local water. If limestone is present, the alkaline (basic) limestone neutralizes the effect the acids might have on lakes and streams. The areas hardest hit by acid rain and snow are downwind of urban/industrial areas and do not have any limestone to reduce the acidity of the water.

Why is the pH level of the water acidic or basic?

Check out the local geology of the watershed - what types of rocks and minerals do you find?

What is the quality of air in your area and up wind of your sampling location? Are you downwind of urban and industrial areas?

Where did you conduct your sampling in the United States? Why would this be important?

When collecting your water sample, did you test the pH level immediately? How can the change in temperature of your water sample affect the pH level?

What is the cause(s) of your problem? What did you find that led you to this conclusion?

Now is the time to take ACTION!