gas mass balance

[T.C. Onstott]

Dear Brian,

 

I have been trying to simulate the gas lost from a sediment column using X1t as part of an experimental program where we monitor greenhouse gas production or consumption in the 1L head space of a 1 meter column. I have attached a simplified code. In this case I am just permitting diffusive flux of methane from pore water into overlying water with a 600 mL headspace. Initially there is insignificant methane in the headspace and top water layer. I have taken advantage of the X1t code to define the headspace by specifying a porosity that is 0.4 and in the sediment quartz which is 0.6. so the sediment has no headspace. what I found was that the code simulate diffusion of dissolved methane from the pore space into the water. it then calculates the fugacity of methane in the headspace as a function of the dissolved methane in the water. but X1t does not seem to account for this methane in the total budget. I do not know if there is a special command that permits this to occur (kind of like an include command for sorption) or whether I need to specify a kinetic gas transfer reaction from cell#5 into cell#4 based upon a diffusion constant. I am thinking that it must be the latter.

 

cheers, tco

Permafrost3.x1t

[Brian Farrell]

Hi,

 

I'm taking a look at your script but I don't see the amount of Quartz mentioned in the Initial system. It also looks like you're using a custom thermo dataset. Would you mind posting that or sending it to support@gwb.com?

 

You might be interested in this earlier forum discussion about gas fugacities.

 

Thanks,

 

Brian Farrell

Aqueous Solutions LLC

Edited May 30, 2012 by Brian Farrell
added link to older forum post