Salt concentration, the greater the conductivity of the Leftover ions from acid-generating and acid-neutralizing reactions canĮffectively increase the salt concentration, or salinity, of the water. Ferrous iron (Fe 2+ ) fromĪcid generating reactions and calcium (Ca 2+ ) fromĪcid-neutralizing reactions may contribute to higher than average levels of water Water hardness may be higher in watersheds
Water hardness and conductivity are useful indicators of upstream The carbonic acid is relatively harmless because it is a weak acid and can beĭissociated as water and carbon dioxide, as described in the bicarbonate buffering system The resulting hydroxide (OH - ) andĬombine with hydrogen (H+) ions, taking them out of solution. Because they are strong bases, they ionizeĪnd dissolve in water. Neutralizing the acidity of the mine effluent. The bases used in the treatment of acid mine drainage work by Of the presence of sulfate (SO 4 2- ), sodium (Na + ), and calcium (Ca 2+ ) ions remaining from acid neutralization reactions. Pond, indicated by the area where the red water turns green. The iron precipitate eventually settles to the bottom of the Mechanical aeration speeds the process by making oxygen more available in The red color indicates that iron hydroxide is precipitating out of the waterĬolumn. The water is red where mine effluent enters the Treatment commonly consists ofĪdding strong bases, such as caustic soda (NaOH, sodium hydroxide), soda ash (Na 2 CO 3, sodium carbonate), or lime (CaO, calcium oxide, or Ca(OH) 2, calcium dihydroxide). Metals before being discharged into a receiving stream. Acid mine drainage must be treated to increase pH and remove heavy The upper reaches of Wheeling Creek follow state and federal regulations for dischargingĮffluent from a mine. Stream bed, smothering the bottom-dwellers and their food resources. Futhermore, when the precipitate settles, it blankets the Reduce the amount of light that can penetrate the water, affecting photosynthesis and The precipitates can be harmful to aquatic life. When the pH rises, the iron oxidizes and precipitates out.ĭepending on the conditions, the orange-colored precipitates may form inside the mine or Precipitate forms as the acid mine drainage becomes neutralized. The orange color is caused by ferric hydroxide ( Fe(OH) 3 ) precipitating out of the water. Table comparing waters receiving acid mineīright orange-colored water and stained rocks are usually tell-tale The carbonic acid readily breaks down into water and carbon dioxide. The buffering system is completelyĭestroyed below a pH of 4.2, where all carbonate and bicarbonate ions are converted toĬarbonic acid. System is not able to control changes in pH as well. Once exposed to acid mine drainage, the affected carbonate buffering Neutralizing carbonate and bicarbonate ions to form carbonic acid (H 2 CO 3 ). Ions,"total acidity," is a better measurement of acid mine drainage.Īcid mine drainage depletes the buffering ability of water by Assessing the excess of hydrogen ions over basic Measurements may not detect heavy acid mine drainage in a stream because of highĪlkalinity due to dissolved carbonates. Solution after the natural buffering of the stream is completed. Of acid mine drainage, it is important to know the amount of hydrogen ions remaining in pH, however, is not always a good indicator of acid mine drainageīecause it only indicates the concentration of hydrogen ions. Acidity is commonly measured by pH values, which are easy "Yellow-Boy," or ferrous hydroxide (Fe(OH) 3 ) formed during Reaction 3 above.Įquation 4 shows that by introducing hydrogen ions, acid mine drainageĪffects the acidity of a stream. Seen in streams receiving acid mine drainage is actually a stain on the rocks called Production of acid mine drainage can occur long after mines have beenĪbandoned if piles of waste rock are in contact with air and water. The following oxidation and reduction reactions express the breakdown ofĤ. When exposed to water and oxygen, it can react to form sulfuric acid (H 2 SO 4 ). Pyrite is one of the most important sulfides found in the waste rock of Known as "fool's gold," is iron disulfide (FeS 2 ). This includes the mining ofĬoal, copper, gold, silver, zinc, lead, and uranium. When mineral deposits that contain sulfides are mined, they have the potential Acid mine drainage impacts stream and river ecosystems through acidity, ferric ion (Fe 3+ ) precipitation, oxygen depletion, and release of heavy metals associated withĬoal and metal mining, such as aluminum (Al 3+ ), zinc (Zn 2+ ), and manganese (Mn 2+ ).
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