[Stoves] more on ocean acidification

Thu Aug 8 06:41:37 CDT 2013

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 <crispinpigott at gmail.com> 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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  Dalat
  Vietnam

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