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RE: Carbon Dioxide Concentrations in Water

The recent discussion on CO2 concentrations in water remind me of a question 
I had when I read Diana Walstad's book recently.

On page 93, she says, "The low productivity of submerged plants is not 
because there is less CO2 in water than in air. (On average, most natural 
waters have about three times more mg/l CO2 than air [8,9]). It is because 
CO2 diffuses so slowly in water (i.e., 10,000 times slower than air)."

I included the last sentence of her quote just to complete her thought. What 
baffles me is the statement that "most natural waters have about three times 
more mg/l CO2 than air". I thought, and the recent APD discussion appears to 
confirm, that the concentration of CO2 in air was about 350 ppm while the 
concentration in sterile water is about 0.5 ppm. Even if the concentration 
in natural water is significantly higher due to decomposition of organic 
wastes, etc., I thought it got no higher than 3-5 ppm. Walstad's statement 
of "three times more mg/l CO2 than air" implies a CO2 concentration in 
natural water of over 1,000 ppm.

Am I not understanding something or is Walstad wrong?


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