[JOEMTN82]

Hello,

I am a graduate student studying stream biogeochemistry and I wish to do an experiment involving a stream reach where I deoxygenate the system for 12 hours.  I have been doing a little research into potential chemical reactions which would aid this process and came across a method involving 7.9g/m^3 of sodium sulphite and 3.3g/m^3 of cobalt II chloride (as catalyst) for each 1g/m^3 of oxygen desired to be removed.  Besides the removal of oxygen I do not wish to pollute or alter the stream environment in any way.  I am curious if anyone is familiar with this reaction and may know what the products are so I may have an idea as to whether this would be an acceptable method for deoxygenation. 

If there are any other friendly ways of oxygen stripping that you are aware of I would greatly appreciate your input.  Thanks for your time and consideration.

Best,
Joe

[Borek]

Could you explain what the experiment is in layman terms (taking into account fact that for some of us English is a second language )?

Sulfite will get oxidized to sulfate - that's the non-harmfull part of the story. Cobalt is completely different.

[JOEMTN82]

The goal of the experiment is to remove dissolved oxygen from a stream reach (<150 meters) to create anoxic conditions so that biogeochemical dynamics associated with aneorobic respiration of the stream microbial community may be observed.  If a chemical solution were used for the oxygen stripping, then the solute would be added to the stream water at one location and at constant discharge.  If mixing is sufficient I would hope that the plume of sodium sulphite and cobalt II chloride could reduce dissolved oxygen from anywhere between 50 and 200m downstream of the solute addition.  Water samples would be taken before and after the solute addition for comparison.

[JOEMTN82]

Just came across a good fact sheet on Cobalt...  It is toxic to aquatic life both short term and long term - it bioaccumulates in fish tissues...  It seems sodium sulphite and cobalt II chloride will not be how I deoxygenate.  Any other ideas?
Best
Joe 

[Borek]

Cobalt...  It is toxic to aquatic life both short term and long term - it bioaccumulates in fish tissues...

That's what I was suggesting

But to say the truth I have no idea what you can do. In lab environement it will be "enough" to use boiled water in closed vessel. No idea what to do in the field - and I suppose it will be dangerous for the stream - aren't you afraid of suffocating every animal other than anaerobic bacteria?