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gas mass balance

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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


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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.




Brian Farrell

Aqueous Solutions LLC

Edited by Brian Farrell
added link to older forum post
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