Understanding pH Levels
Inside the Outdoors, November 13, 2009

In talking to my brother recently, he mentioned that he had seen a number of articles in the New York Times that may be of interest to me. One of subjects of which he made mention was pH levels in the water. I had to ‘fess up that I heard the term, but knew little about it. But that was all about to change. I hope the following provides clarity to you as it did for me.

The pH reflects how acidic or basic the water is. The measure of the acidity is on a scale of 0-14 with 7.0 being neutral. Acid waters are below 7.0, alkaline waters are above 7.0. All aquatic life tolerate and have adapted to a specific pH range. At high (9.6) or low (5.0) pH values, the water becomes unsuitable for most organisms.

Now, there are several factors that affect pH: carbon dioxide in the water, geology and soils of the watershed, drainage from mine sites and air pollution.

Carbon dioxide enters a water body from a variety of sources, including the atmosphere, runoff from land, release from bacteria in the water and respiration by aquatic organisms.

When calcite is present in the soil, it can increase the alkalinity of the water which raises the pH. When sulfide minerals, such as pyrite are present, water and oxygen interact with the minerals to form sulfuric acid. This significantly drops the pH.

Mining for metals often involves the removal of sulfide minerals buried in the ground. When water flows over or through sulfidic waste rock or tailings exposed at a mine site, this water can become acidic from the formation of sulfuric acid. In the absence of buffering material, such as calcareous rocks, streams that receive drainage from mine sites can have low pH levels. Finally, air pollution from car exhausts and power plant emissions increase the concentrations of nitrogen oxides and sulfur dioxide in the air. These pollutants can travel far from their place of origin, and react in the atmosphere to form nitric acid and sulfuric acid. These acids can affect the pH of streams by combining with moisture in the air and falling to the earth as acid rain or snow.

Understanding the relationship to acidity and alkalinity is next.

Keeping in mind that 7.0 is the neutral number, less than that is acidic, and a higher number, basic or alkaline, trout can live in acidic waters down to 4.5, perch and shad, 5.0 bass, musky, walleye, sunfish, bluegill, suckers, catfish and carp, 6.0, pike, 6.1 and crappie, 6.6. On the other side of the coin, musky will die if alkaline waters exceed 8.0, shad 8.5, pike, 8.6, trout and perch, 9.5, and the remaining fish listed, above 9.6.

I think it is extraordinary that the fish that one might think to have the greatest sensitivity concerning pH, trout, can adapt to conditions between 4.5 and 9.5. One may want to pay special attention to the following. According to the Pennsylvania Fish and Boat Commission, “A fish that could tolerate water with a pH less than 5 will die at a pH of 5.5 if the water contains as little as 1.0 parts per million (ppm) of iron. One ppm is equivalent to a drop of chocolate in 16 gallons of milk. Biologists call these relationships synergism – where two substances combine to have effects worse than just their sum. Water with low pH (less than 6.0) coming in contact with naturally occurring low concentrations of iron, lead, aluminum, magnesium or mercury creates a toxic cocktail. Therefore, pH is a critical factor in aquatic habitats.

Also, as pH approaches 5.0, non-desirable species of plankton and mosses may begin to invade, and population of fish, such as smallmouth bass, will disappear.

The most serious chronic effect of increased acidity in surface waters appears to be interference with the fish’s reproductive cycle. Calcium levels in the female fish may be lowered to the point where she cannot produce eggs or the eggs develop abnormally.

Over the last five to ten years, the Conemaugh River has improved its quality yielding a greater amount of fish population. That’s a good sign that the pH must be tolerable for quite a number of species. It goes without saying that Upper and Lower Twin, Donegal and especially Keystone Lakes have a favorable pH, for they contain numerous species.

Concerning the Loyalhanna Creek, the pH varies depending on where one tests for it. Surface Mine Conservation Inspector Glen Krallman for the Department of Environmental Protection told me that “Acid mine drainage has been flowing into the creek for many years from numerous different points.”

In addition, when discussing pH, he told me he has personally seen it in the 2.0’s at a discharge in the Slickville area. By touching the water, he pointed out, he felt a burning sensation on his hands.

I now have a much better understanding about the subject. I hope you do, too.

- Paul J. Volkmann
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