Alkalinity

Definition

Alkalinity is the name given to the quantitative capacity of water to neutralize an acid to the equivalence point of carbonate or bicarbonate (Water Quality Association, 2000). The total alkalinity of sea water was defined by Dickson (1981) as “. . . the number of moles of hydrogen ion equivalent to the excess of proton acceptors (bases formed from weak acids with a dissociation constant K ≤ 10^−4.5 at 25 °C and zero ionic strength) over proton donors (acids with K > 10^−4.5) in 1 kg of sample.” For the compounds found in water, the total alkalinity (A_T) is expressed as:

$$ \begin{array}{c}{\mathrm{A}}_{\mathrm{T}} = \left[{{\mathrm{H}\mathrm{CO}}_3}^{-}\right]+2\left[{{\mathrm{CO}}_3}^{-2}\right]+\left[\mathrm{B}{{\left(\mathrm{O}\mathrm{H}\right)}_4}^{-}\right]+\left[{\mathrm{OH}}^{-}\right]\\ {}+\left[{{\mathrm{H}\mathrm{PO}}_4}^{-2}\right]+2\left[{{\mathrm{PO}}_4}^{-3}\right]+\left[{\mathrm{H}}_3{{\mathrm{SiO}}_4}^{-}\right]+\left[{\mathrm{NH}}_3\right]\\...