Alkalinity

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 does not measure the same property as the pH (namely basicity).

Simplified summary

Alkalinity roughly refers to the amount of bases in a solution that can be converted to uncharged species by a strong acid. The cited author, James Drever, provides an equation expressed in terms of molar equivalents, which means the number of moles of each ion type multiplied by (the absolute value of) the charge of the ion. For example, 1 mole of HCO₃¹⁻ in solution represents 1 molar equivalent, while 1 mole of CO₃²⁻ is 2 molar equivalents because twice as many H⁺ ions would be necessary to balance the charge. The total charge of a solution always equals zero.