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x1t simulate weathering in soil profiles

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Just finished the 2020 workshop, and I’m practicing the users’ guide example “weathering.x1t.” I’m trying to simulate the weathering in a soil profile under various precipitation (rainfall) conditions.

Here is my conceptual model:
(1) The soil profile is 1cm * 1cm * 300cm.
(2) The porosity of the soil profile is 45% and the water content is 25%.
(3) The water infiltration rate is 0.3m/yr.
(4) The annual rainfall is 600 mm/year.
(5) The simulation time is 20000 years.
(6) temperature is 13℃

So far, the software settings are like the attached file.
I am not sure whether the software settings match my conceptual model mentioned above.
Also, what does it mean if the “reactant times” was set to be “1” in this software settings?

Thanks for any response or suggestions. Appreciated.

loess weathering 10-interglacial.x1t

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Hello Hou-Chun,

The reactant times command allows you to scale the amount of reactant you are adding to the system from your Reactants pane.

Here are a couple of suggestions regarding your model setup.. 

The flow rate on the Flow pane is the specific discharge which is a volumetric flux rather than the average linear velocity of flow. To obtain the average linear velocity of your fluid flow, you would need to divide the specific discharge by the porosity of your domain. If your measured flow rate is the average linear velocity, then you would need to multiply by the porosity to calculate the specific discharge.  Please refer to section 3.2 Setting the flow rate in the Reactive Transport Modeling User Guide for more details. You can choose to set the discharge rate for each individual reaction interval or all intervals.  

Please note that in the example Weather.x1t, the saturated fraction is entered as the "porosity" rather than true porosity of the soil. Further explanation of how to setup unsaturated media can be found in section 2.12 Porosity evolution in the Reactive Transport Modeling User Guide. 

If your simulation is taking a while to run, you can always try shortening the simulation to see if you are seeing the correct rate constants, flow rate, mineral volume, and etc before continuing on to run the length of time. 

Hope this helps,
Jia Wang

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