I have modeled a contaminant transport from a spill in feflow and got some results. My first setup was implementing no sorption. In second simulation, I applied k=0.2 as Henry (linear) sorption coefficient and surprisingly the concentrations were higher than initial case with no sorption, which is opposite to the expectation.
I tried k=-0.2 and the results make sense, but I could not find a reference to this. Anyone know if we actually should put the sorption coefficient in negative?