Alkalinity

Alkalinity is the capacity of <a href="/facts/Water/0lkXnJPK">water</a> to resist <a href="/facts/Freshwater_acidification/kY4ndEr8">acidification</a>. It should not be confused with <a href="/facts/Base_(chemistry)/M9wA7qeM">basicity</a>, which is an absolute measurement on the <a href="/facts/PH/RnSv8D7y">pH</a> scale. Alkalinity is the strength of a <a href="/facts/Buffer_solution/zrLz9eaa">buffer solution</a> composed of <a href="/facts/Weak_acid/vJ4rj6Lu">weak acids</a> and their <a href="/facts/Conjugate_acid/hohgQ07M">conjugate bases</a>. It is measured by <a href="/facts/Titration/gGUfvQcW">titrating</a> the <a href="/facts/Solution_(chemistry)/MGchhMQV">solution</a> with an acid such as <a href="/facts/HCl/7Wzkhomd">HCl</a> until its pH changes abruptly, or it reaches a known endpoint where that happens. Alkalinity is expressed in units of concentration, such as meq/L (<a href="/facts/Milliequivalents/ksgd425g">milliequivalents</a> per <a href="/facts/Liter/QKwbQz8I">liter</a>), μeq/kg (microequivalents per kilogram), or mg/L CaCO3 (milligrams per liter of <a href="/facts/Calcium_carbonate/UQ1wLFna">calcium carbonate</a>). Each of these measurements corresponds to an amount of acid added as a <a href="/facts/Titrant/gGUfvQcW">titrant</a>.
In <a href="/facts/Fresh_water/xMP2TxwI">freshwater</a>, particularly those on non-<a href="/facts/Limestone/8ntvtFnR">limestone</a> terrains, alkalinities are low and involve a lot of ions. In the ocean, on the other hand, alkalinity is completely dominated by <a href="/facts/Carbonate/FES1QHkN">carbonate</a> and <a href="/facts/Bicarbonate/zzSVVAl1">bicarbonate</a> plus a small contribution from <a href="/facts/Borate/5XwkBTv1">borate</a>.
Although alkalinity is primarily a term used by <a href="/facts/Limnology/1nHcCAkn">limnologists</a> and <a href="/facts/Oceanography/LtrG6peD">oceanographers</a>, it is also used by <a href="/facts/Hydrologists/Xh727cnE">hydrologists</a> to describe <a href="/facts/Temporary_hardness/Ay4aksF4">temporary hardness</a>. Moreover, measuring alkalinity is important in determining a stream's ability to neutralize acidic pollution from <a href="/facts/Acid_rain/f769GyNz">rainfall</a> or <a href="/facts/Wastewater/g6Bn8xvT">wastewater</a>. 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 such as acid rain generated by SOx and NOx emissions.

Alkalinity open-in-new

Alkalinity