New version 6.2.3

A major update of the methane submodel is the most important change but besides that many minor issues are also updated and bugs have been removed.

The methane submodel which is part of the GasModule has some new features and there are a lot of uncertainties if it can reproduce exactly old versions. Most important is that a number of parameters have got new units and partly new meaning which can create confusion.

Units are modified to be for concentration in the water to be in mg/l or g/m3. For concentrations in the air concentrations are PPM or g/m3. Previous concentrations was mostly as fractions.

The Ebulition function has been modied so the threshold is specied in mg/l for the concentration in water. This threshold parameter was in the old versions fixed without any temperature dependence. The new version has built in a temperature dependence that decrase the threshold when the temperature increase.

The methane production function was before following a general common temperature dependence according to the choice of the user. The new model is using a function that force the production to be zero when the soil is below zero degree, for low temperatures up to 5 C a simple linear function is currently used and above this Q10 is applied with a reference temperature at 20 C.

The previous version estimated also an possible aerobic fraction beneath the ground water level. This could result in oxidation especially in frozen soils. The model is considering a small residual air porosity (1 vol %) also in a saturated soil horizons for possible gas transport. However, those will not be considered for potential oxidation of methane in the new version. However, redistribution of methane will take place both in the liquid and air pore space as estimated by the Henry law.

Bugs have been removed in the oxidation functions. Please check carefully current and new oxidations rates. If you want to see more details on the methane model development please ask for the source code.

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