Re: [APD] CO2 Absorption

[Chuck Gadd <cgadd at cfxc_com>]

Bill D wrote:

> I have read that the equilibrium level of CO2 in an aquarium under normal
> conditions is about .5 ppm.  To me that means that in an open aquarium with
> no flora, fauna, lighting, or substrate, the CO2 level would be that.
> Right?
>  
A simple experiement suggests otherwise:

Take a sample of tap water in a cup, aerate the water sample with a 
clean airstone for 30 minutes.  Measure the pH/KH and calculate the CO2 
level.   I end up with about 3ppm.  

I think the equilibrium level of CO2 in water is about .5ppm, but some 
CO2 will dissolve into the water from the air.    CO2 levels in the air 
will typically be somewhere around 400ppm.   But indoors it can be much 
higher, depending on the ventilation.   CO2 levels indoors of 1200ppm 
are not uncommon.  OSHA sets a maximum indoor level of 5000ppm for an 8 
hour exposure.  

So, with a higher CO2 level in the air, more of that CO2 will dissolve 
into the water.    It might be interesting to do the tap water aeration 
experiment once indoors, then repeat experiement outdoors.  I would 
guess the outdoor aeration sample would show less dissolved CO2.






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