Re: [Stoves] more on ocean acidification

Kevin Thu, 08 Aug 2013 04:43:34 -0700

Dear Paul

Crispin indicates that the mass of the ocean is about 1.33 billion billion 
tons, i.e., 1.33 x 10^12 tons. That is a lot of water.

The oceans are now alkaline. Some CO2 additions will lower the pH of the ocean,
but the oceans will still be alkaline.

How much CO2 would be required to actually make the oceans acidic?

At current rates of anthropogenic CO2 production, how long would it take for
the Oceans to actually become acidic?

Thanks!

Kevin
----- Original Message -----
From: Paul Olivier
To: Discussion of biomass cooking stoves
Sent: Thursday, August 08, 2013 7:08 AM
Subject: Re: [Stoves] more on ocean acidification

Crispin,

The term that the scientific community uses is "ocean acidification," and
this is a very real environmental problem that most people in the scientific
community do not deny.

Many thanks.

Paul Olivier

On Thu, Aug 8, 2013 at 12:27 PM, Crispin Pemberton-Pigott
<[email protected]> wrote:

Dear Friends

I have been catching up on less important correspondence after being in
Asia for a while. There is one thing that still needs to be put down like a
broken-legged horse and that of course is the idea that CO2 ‘acidifies’ the
ocean.

Because this is a high school chemistry level topic and I know some of us
took other things – or as the drummer in my brothers class said, “I don’t
remember Chemistry, I was stoned that year.”

So for those of you who were also stoned that year or can’t remember back
that far, here is a simple review of pH with special reference to the oceans,
CO2 and the false, badly mis-named idea that CO2 ‘increases the acidity of the
oceans’.

The term pH refers to one of three distinct chemical conditions which bear
no relationship to each other. One is called acidity, another is called
alkalinity and third is ‘neutral’. Acidity and alkalinity are so different that
if equal in ‘strength’ they cancel each other completely leaving a neutral
condition. Different pH numbers refer to different conditions.

Acid solutions (it has to be a solution with water in it) have a chemistry
that has Hydrogen atoms stripped of their single electron. They are thus
positively changed and seeking an electron. This they will happily strip out of
anything passing by if they can find it, tearing the molecules to bits in the
process which is why acids ‘eat’ things.

Alkaline solutions (again, involving water) have molecules that have an
extra electron available (but not Hydrogen) and are thus negatively charged.
They will give away an electron happily, often wrecking the object that
receives it which is why they eat things too but by a completely different
process.

Both acidic and alkaline solutions can corrode things like metals and
rocks. One takes electrons and one gives them. Quote opposite. The two
conditions are so incompatible they cannot be present at the same time in a
mixed solution. It is one, the other or ‘neutral’ if neither condition is
present.

If you have an alkaline solution like the ocean (pH 7.8 - 8.4 depending on
where you are, the time of day and a host of other things) and you want to
neutralise it so that all its spare electrons are taken up by various things,
you would have to add something acidic. Adding CO2 by bubbling it through the
seawater will convert some of the CO2 (about 1%) to carbonic acid which has a
deficiency of electrons and that acid will merge with whichever passing
opportunity presents itself. The corresponding alkaline molecule will be
neutralised as its spare electron will be passed to the carbonic acid molecule
(which has an H- in it) and afterwards neither will have any charge. Both will
be neutralised if the charges are balanced.

Because this happens very quickly, you cannot actually find any carbonic
acid in the ocean. Nor any other acid. The oceans are not acidic at all. Any
ocean has quite a store of available electrons. Anything acidic you dump into
the sea is quickly neutralised and the pH drops slightly because it is closer
to a neutral condition. The oceanic capacity to hand over electrons to any
passing electron gap is very, very large. There are several processes that
would begin to offer electrons but do not because the ocean is too alkaline to
allow them to get started. The ability to do this is called the ‘buffering’
capacity. You may remember ‘Bufferin’ the pill that neutralises stomach acid.
The pill is alkaline and has a large buffering capacity so it can hand a lot of
electrons over to the acid in the stomach, thus neutralising it. If you took a
whole bottle of Bufferin pills, your stomach would not become less and less and
less acidic. It would be neutralised and then become alkaline and remains so
until the spare electrons were taken up in a neutralising process. People are,
in general, alkaline and should eat alkaline foods to remain healthy. Excess
acid is a problem.

By the same measure, reducing the availability of spare electrons in the
ocean water does not at all make the water acidic because it still has many
more available electrons. It is less alkaline, but it is not acidic at all –
zero in the ‘acidic scale’ (there isn’t one).

In order to make a convenient metric for describing these two conditions
(which can cancel each other out very predictably) the pH scale is used. Above
7.0 the solution has available electrons and is termed alkaline. Below 7.0 is
has a deficiency of electrons and is called ‘acidic’. The reason for the use of
two different terms is they are chemically dissimilar and cannot coexist.

Acidity of a solution is often represented by the Hydrogen equivalent [H+]T
which is the total number of Hydrogen electrons that would be needed to
neutralise it.

Alkalinity is often expressed in terms of its equivalence to Calcium
Carbonate CACO3 in mg/Litre.

Q. Can CO2 ‘acidify’ water?

A. Yes, if the water is neutral to begin with, or already
acidic, like rain water. Because rain water is acidic, when it falls into the
ocean it neutralises the drops of seawater where it touches, before becoming
diluted again by the surrounding ocean. Rainwater does not impart to the ocean
any microscopic ability to withdraw electrons. It is quickly neutralised by
some seawater. When it is finished a few seconds later, the acid has been
destroyed.

Q. If one bubbled CO2 through sea water, would it eventually
become acidic?

A. Yes. If you were to first neutralise all the available
electrons by mopping them up, after that it would start to become acidic. It
would not considered be acidic at all until the whole body of the sample had
first been neutralised. These two conditions cannot co-exist.

Q. What about ‘acid rain’.

A. All rain is acidic. It is acidic because fresh water absorbs
CO2 rapidly from the atmosphere, converting about 1% into carbonic acid. This
falls into the oceans and reacts with the available alkaline molecules. It is
easy to acidify rain. It is very difficult to neutralise the oceans because of
the rocks upon which they sit which have a huge, massive buffering capacity.
There are numerous life cycles of creatures that withdraw CO2, CO3-2 and HCO3-
when it is available. Obviously CACO3 is high on the list for uptake by
creatures that make shells.

Q. Which has a larger impact on ocean alkalinity: atmospheric CO2
or rain containing CO2?

A. Not clear. Rain has a big effect because oceans actually have
difficulty picking up enough CO2 to drive the level much above 600 ppm because
of the limited surface area compared with the volume and the huge buffering
capacity. Rain is much higher - about 1120 ppm CO2. Global rainfall totals
about half a million cubic kilometers per year and contains about 600 billion
tons of CO2 which is about 20 times human output.

Q. What is the mass of the oceans?

A. 1.332 billion billion tons.

Q. Do reputable scientific organisations refer to ‘acidifying’
the oceans even though that is not, chemically, what it happening?

A. Yes. NASA does. “As we burn fossil fuels and atmospheric
carbon dioxide levels go up, the ocean absorbs more carbon dioxide to stay in
balance. But this absorption has a price: these reactions lower the water’s pH,
meaning it’s more acidic.”

Q. But it is less alkaline, not more acidic. Why do they write
that when it is untrue, in fact it is unscientific?

A. I don’t think anyone knows. Perhaps they too missed
Chemistry in high school.

+++++++

Regards
Crispin

Sent: Friday, July 26, 2013 3:25 PM
Subject: [Stoves] more on ocean acidification

http://www.scientificamerican.com/article.cfm?id=noaa-scientists-embark-voyage-asses-ocean-acidification

--
Paul A. Olivier PhD
26/5 Phu Dong Thien Vuong
Dalat
Vietnam

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