Why this particular ion? My O-level chemistry is pretty rusty these days, but I think in the general case there should be quite a few ions that can contribute to total alkalinity. Is the HCO3 anion just the only one that is likely to occur in signifcant amounts in the water supply? Or is there some sort of equivalence relationship between the other ions and HCO3- such that one might actually say the water alkalinity is equivalent to some given concentration of HCO3-?Alkalinity is determined by the concentration of the bicarbonate (more properly hydrogen-carbonate, HCO3-) ion
I'm interested in particular because I assume our water must contain some level of Cl- ions and I believe these would also contribute to alkalinity, but I'm not sure how that fits in with the above.
James
