Alkaline Water, What is it?
Alkalinity is the name given to the quantitative capacity of an aqueous solution to neutralize an acid.
Measuring alkalinity is important in determining a stream’s ability to neutralize acidic pollution from rainfall or wastewater. It is one of the best measures of the sensitivity of the stream to acid inputs. There can be long-term changes in the alkalinity of streams and rivers in response to human disturbances.
Alkalinity is related to the pH of a solution (its basicity), but measures a different property. Roughly, the pH of a solution is a measure of how “strong” the bases are in a solution, whereas the alkalinity measures the “amount” of chemical bases. A good example is a buffer solution, which can have many available bases (high alkalinity) despite having only a moderate pH level.
Alkalinity roughly refers to the amount of bases in a solution that can be converted to uncharged species by a strong acid.
The lower the pH, the higher the concentration of bicarbonate will be. This shows how a lower pH can lead to higher alkalinity if the amount of bicarbonate produced is greater than the amount of H+ remaining after the reaction.
There are many methods of alkalinity generation in the ocean. Perhaps the most well known is the dissolution of CaCO3 (calcium carbonate, which is a component of coral reefs) to form Ca2+ and CO32− (carbonate). The carbonate ion has the potential to absorb two hydrogen ions. Therefore, it causes a net increase in ocean alkalinity. Calcium carbonate dissolution is an indirect result of ocean pH lowering. It can cause great damage to coral reef ecosystems, but has a relatively low effect on the total alkalinity (AT) in the ocean. Lowering of pH due to absorption of CO2 actually raises the alkalinity by causing dissolution of carbonates.
Anaerobic degradation processes, such as denitrification and sulfate reduction, have a much greater impact on oceanic alkalinity. Denitrification and sulfate reduction occur in the deep ocean, where there is an absence of oxygen. Both of these processes consume hydrogen ions and releases quasi-inert gases (N2 or H2S), which eventually escape into the atmosphere. This consumption of H+ increases the alkalinity. It has been estimated that anaerobic degradation could be as much as 60% of the total oceanic alkalinity.