Editing Alkalinity (section)

== Simplified summary ==
Alkalinity roughly refers to the molar amount of bases in a solution that can be converted to uncharged species by a strong acid. For example, 1&nbsp;mole of {{chem|HCO|3|−}} in solution represents 1 molar equivalent, while 1&nbsp;mole of {{chem|CO|3|2−}} is 2 molar equivalents because twice as many H<sup>+</sup> ions would be necessary to balance the charge. The total charge of a solution always equals zero.<ref name=":0">{{cite book|last=Drever|first=James I.|title=The Geochemistry of Natural Waters, Second Edition|year=1988|publisher=Prentice Hall|location=Englewood Cliffs, NJ|isbn=0-13-351396-3|url=https://archive.org/details/geochemistryofna0000drev|url-access=registration}}</ref> This leads to a parallel definition of alkalinity that is based upon the charge balance of ions in a solution.

:<math>\sum(\text{cations})=\sum(\text{anions})</math>

Certain ions, including Na<sup>+</sup>, K<sup>+</sup>, Ca<sup>2+</sup>, Mg<sup>2+</sup>, Cl<sup>−</sup>, {{chem|SO|4|2−}}, and {{chem|NO|3|−}} are "''conservative''" such that they are unaffected by changes in temperature, pressure or pH.<ref name=":0" />  Others such as {{chem|HCO|3|−}} are affected by changes in pH, temperature, and pressure.  By isolating the conservative ions on one side of this charge balance equation, the nonconservative ions which accept or donate protons and thus define alkalinity are clustered on the other side of the equation.

:<math>\begin{align}
&\sum(\text{conservative cations})-\sum(\text{conservative anions}) = \\
&\quad [\mathrm{HCO_3^-}]+2[\mathrm{CO_3^{2-}}]+[\mathrm{B(OH)_4^-}]+
[\mathrm{OH^-}]+[\mathrm{HPO_4^{2-}}]+2[\mathrm{PO_4^{3-}}]+[\mathrm{H_3SiO_4^-}]+[\mathrm{NH_3}]+[\mathrm{HS^-}]-[\mathrm{H^+}]-[\mathrm{HSO_4^-}]-[\mathrm{HF}]-[\mathrm{H_3PO_4}]-[\mathrm{HNO_2}]
\end{align}</math>

This combined charge balance and proton balance is called '''total alkalinity'''.<ref>{{Cite journal|last1=Wolf-Gladrow|first1=Dieter A.|last2=Zeebe|first2=Richard E.|last3=Klaas|first3=Christine|last4=Körtzinger|first4=Arne|last5=Dickson|first5=Andrew G.|date=July 2007|title=Total alkalinity: The explicit conservative expression and its application to biogeochemical processes|url=https://linkinghub.elsevier.com/retrieve/pii/S0304420307000047|journal=Marine Chemistry|language=en|volume=106|issue=1–2|pages=287–300|doi=10.1016/j.marchem.2007.01.006|bibcode=2007MarCh.106..287W }}</ref> Total alkalinity is not (much) affected by temperature, pressure, or pH, and is thus itself a conservative measurement, which increases its usefulness in aquatic systems.  All anions except {{chem|HCO|3|−}} and {{chem|CO|3|2−}} have low concentrations in Earth's surface water (streams, rivers, and lakes).  Thus '''carbonate alkalinity''', which is equal to {{nowrap|[{{chem|HCO|3|-}}] + 2[{{chem|CO|3|2-}}]}} is also approximately equal to the total alkalinity in surface water.<ref name=":0" />