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The Effects of High Acidity on Creeks

Acidity is measured on the pH scale, which represents the concentration of free hydrogen ions, or charged atoms, that are responsible for the acidic nature of water. Normally, freshwater streams, creeks and lakes maintain a pH between six and eight, which is ideal for most freshwater fish and amphibians. This pH is also optimal for the hatching of insect eggs that are a food source for most animals inhabiting these waterways.

  1. pH Levels and Acidity

    • A decrease in pH equals an increase in acidity. When the pH of a freshwater system reaches five, most animals can no longer survive or reproduce. According to a survey published by the U.S. Environmental Protection Agency, bodies of fresh water become acidic when the systems are unable to buffer, or filter, acid rain and other materials that lead to decreases in pH. The authors also state that more than 1,000 U.S. lakes larger than 10 acres and their associated thousands of miles of streams and creeks are believed to be affected by acidity. The report asserts that acidic conditions are responsible for a cascade of events that lead to massive fish kills and, in some cases, can lead to the elimination of entire species.

    Lethal pH Levels

    • Young fish, referred to as juveniles, are especially sensitive to changes in pH. When the pH of water reaches about five, most juvenile fish are unable to correctly process oxygen and other essential nutrients. Additionally, at this pH, eggs are not able to hatch, which leads to further declines in fish populations. However, some species of animals can better tolerate lower pH levels. For example, according to the EPA, clams and snails will die off as pH levels approach six, whereas mayflies and crayfish can survive in waters with a pH approaching five. Perch cannot survive when the acidity reaches four, but frogs will hold out until the acidity reaches a pH of slightly less than four.

    Heavy Metals and Acidity

    • Deposits of heavy metals in the shorelines of creeks can add to the acidity of a creek by leeching the material into the water during rainfalls. An article in the November 2007 issue of "Science of the Total Environment" investigated the effects of soil pH, or acidity, as well as organic matter and the heavy metal copper. Researchers analyzed soil samples taken from a dumping site in Zimbabwe, known for deposits of copper that leech into the water. Random soil samples showed that a compound, called copper oxy chloride, increased the amount of copper in the water by 500-fold. The authors noted that high concentrations of this transitional metal were directly associated with an increase in acidity.

    Impact of the Clean Water Act of 1972

    • Since the federal government enacted the Clean Water Act of 1972, massive efforts have been undertaken to restore creeks and other bodies of fresh water. A study published in the June 2004 issue of "Science of the Total Environment" documented the condition of Decker's Creek in West Virginia for a 25-year period, beginning in 1974. The authors analyzed pH levels of water samples from 29 locations along the creek that had been polluted by mining metals from the mountains. The study found that pH levels improved by 1999-2000 due to enforcement of water quality laws.

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