Surface Complexation Model and Diffuse Layer Thickness

[JRen]

Does the program take into the account the impact of ionic strength on diffuse double layer thickness?

Does a higher ionic strength decrease the thickness of the diffuse layer or does it stay the same thickness despite the ionic strenght and present of divalent ions?

[dlparkhurst]

If you use -diffuse_layer, you can only specify a fixed thickness.

However, -donnan is a more robust calculation, and with -donnan, you have the option of specifying a fixed thickness, or a number of Debye lengths. The Debye length is dependent on ionic strength. So you can specify 1.5 Debye lengths, and the thickness will be 1.5 x Debye length, and the Debye length will vary with ionic strength.