pH of the Mohawk River By: Allie Shea, Liz Farley, and Maddie Karafonda Block 3
Definition & Acceptable Ranges • pH is a figure representing the measure of the acidity or alkalinity of an aqueous solution. It is based on a scale in which 7 is neutral and lower values are more acidic and higher values are more basic.(Anything less than 7 is an acid, anything greater than 7 is a base). There is no normal pH value in nature, but freshwater fish and organisms thrive in a range between 5.5 and 7.5 depending on the species. Neutral water is 7.0 and dissolved chemicals and minerals change the balance of the ions in the solution from the original state.
Sources from nature & pollution • Pure rainfall has a pH of about 5.6, which is some-what acidic, so that effects the pH of river water when it rains • If a watershed has pine or fir forests, streams within it may have a lower pH value • The decomposing needles of these trees add to the acidity of soils and also influence the acidity of nearby streams • acid rain (polluted precipitation), increases the acidity of surface water near many industrial or large urban areas (sulfuric acid and nitric acid) • Dumping industrial pollutants directly into waters can have intense and immediate effects on the pH of a stream. • Mining may expose rocks to rain water and produce acidic runoff • Chemical runoff from farms also have an effect on the pH
Problems due to excess/lack • The majority of aquatic animals and plants have adapted to life in water with a specific pH and may suffer from a little change • moderately acidic water (low pH) may reduce the hatching success of fish eggs, irritate fish and aquatic insect gills, &damage membranes. • Water with extremely high or low pH is deadly. A pH below 4 or above 10 will kill most fish • Amphibians are particularly vulnerable to low pH because their skin is so sensitive to pollutants. • A change in the pH can alter the behavior of other chemicals in the water. For example, ammonia becomes toxic to fish as the pH increases • Heavy metals like cadmium, lead, and chromium dissolve more easily in more acidic water. Many heavy metals also become much more toxic when dissolved in water.
Alleviating an Imbalance • Water can be kept in check by the buffer limestone. Most of the Earth's freshwater bodies surface are slightly acidic due to the abundance and absorption of carbon dioxide, so it can be solved by taking the co2 out of water.
pH scale & hydrogen ions • A low pH indicates a high concentration of hydronium ions, while a high pH indicates a low concentration. Pure (de-ionized) water is neutral, and can be considered either a very weak acid or a very weak base. The pH scale has no upper or lower limit and can be lower than 0 or higher than 14. 7 is neutral.
Works Cited • http://freshaquarium.about.com/cs/waterchemsitry/a/waterph.htm • http://en.wikipedia.org/wiki/PH • http://extension.usu.edu/files/publications/publication/nr_wq_2005-19.pdf • http://ga.water.usgs.gov/edu/phdiagram.html