Quality Assessment: Chemical: Alkalinity
Alkalinity values of 20-200 ppm are common in freshwater ecosystems. Alkalinity levels below 10 ppm indicate poorly buffered streams. These streams are the least capable of resisting changes in pH, therefore they are most susceptible to problems which occur as a result of acidic pollutants.
The Chemistry of
As depicted in the above set of reactions, carbonate (CO32- ) and bicarbonate (HCO3-) ions act as hydrogen ion absorbers. This causes the reactions of the bicarbonate buffering system to shift left or right while maintaining a relatively constant pH. If hydrogen ions are added to the solution, they combine with available bicarbonate or carbonate ions, causing the reactions to shift to the left and eventually liberate carbon dioxide and water molecules. The addition of carbonate to the solution causes the hydrogen ions to be occupied and shifts the reactions to the right. In this way, an alkaline stream with a large buffering capacity is able to "hold" more acidic pollutant without displaying a significant decrease in pH.
/ Alkalinity / Hardness / Nitrates.
Nitrites, and Ammonia / Ortho- and Total
Phosphate / Dissolved Oxygen and Biochemical
Oxygen Demand / Fecal Coliform / Conductivity
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