Why, oh, why do people like the government’s chief scientific adviser Sir Mark Walport, who really don’t understand the basic science, go on about ‘acid’ oceans? Such a condition is well nigh impossible in the real world.
The oceans are PERMANENTLY buffered to maintain pH fluctuating between around 7.6 and 8.2 (this means they are always slightly alkaline; pH7 is neutral)
- The oceans are always saturated with CO2. There is liquid CO2 in the deep ocean trenches (that is the chemical definition of a saturated solution by the way). Surface layers tend to fluctuate a bit more due to their ‘restless’ condition. The warmer the oceans become the LESS CO2 they can hold.
- The oceans could only ever become acidic, that is have a pH of less than 7, IF the earth were to run out of rocks.
- The buffer chemistry is not that difficult to understand.
The oceans contain what is effectively an unlimited supply of CaCO3 (calcium carbonate) an insoluble substance which makes up most of the rocks, sea sediments and suspended particles: limestones, chalks and I would add dolomites too which are made of MgCO3.
Carbonic acid (CO2 dissolved in water or H2CO3) is a weak acid which reacts with CaCO3 to form Calcium bicarbonate Ca(HCO3)2.
H2CO3 + CaCO3 = Ca(HCO3)2
This salt is both soluble and alkaline and prevents the oceans ever becoming acidic. The more CO2 dissolves the more bicarbonate forms.
You may remember your school chemistry lessons where the test for CO2 gas was to bubble it through ‘lime water’ (a dilute solution of Ca(OH)2 calcium hydroxide). It went ‘milky’; this was a precipitate of insoluble CaCO3. However, if you went on bubbling CO2 into this solution it would go clear again as the extra CO2 reacted with the suspended CaCO3 to form soluble Calcium bicarbonate.
- Living things are not particularly phased by changing external pH anyway. Their cells have membranes which have active ‘pumps’ that keep the internal chemistry of the cell at the optimum pH. So for example fresh water shellfish can indeed live quite happily in acidic lakes or rivers.
Public figures such as Sir Mark Walport, a scientific adviser to government, should check their sources of information before making statements which are at odds with well known scientific fact.