This is like asking 'how long is a piece of string?'     The concentration of the ions must be known to estimate their effect on the matric potential.

Dear Professor Campbell,

Thank you for your response.

The thing I am going to know is the influence of increasing the concentration of alkali earth ions (for example), on the matric potential.

Is there any reference take into account this issue?

Kind regards,

Dear Ebrahim,

as you know, the total water potential is assumed to be the sum of several partial potentials: One of them is the osmotic (or solute) potential and one of them the matric potential, which is due to adhesion of water molecules to nondissolved structures of the system (for example capillary forces in soil pores). So any factor influencing the surface energy of soil particles would influence the matric potential. Am I correct to assume that you want to know the influence of cation adsorption/exchange on surface energies?

Best regards

Thomas

Dear Thomas,

You are right. I want to know the effect of Cation Exchange on the surface energy and the effect of surface energy on the matric potential. At the end, the effect of these parameters on the strength of a compacted soil.

Is there any reference regarding this issue, especially the ones connect the chemical aspect of the interaction of solid and liquid phase of a soil to the gaining or losing strength in the bulk soil?

Thank you for your response.

Kind regards,

Ebrahim

Dear Ebrahim,

B JANCZUK (1990): THE SURFACE FREE-ENERGY COMPONENTS OF HOMIONIC BENTONITE FROM CONTACT-ANGLE MEASUREMENTS. MATER CHEM PHYS 26 , volume 3-4, pp. 375-394

might be a good starting point.

Anyway, practical soil hydrology and hydrogeochemistry use a more empirical approach. I guess you are familiar with the HYDRUS group of models and with phreeqc, and with their combination HP1. So all those ionic strength and soil compaction issues are taken into account by empirical soil water retention curve, hydraulic conductivity, adsorption isotherm, and by soil solution, CEC and cation load measurements for HYDRUS and phreeqc, respectively. Moreover, surface complexation (for example phosphates on hydroferrous oxides) and phase equilibria (dissolution or precipitation of soil minerals) can be modelled.

Like any other simulation model, these models are not perfect, of course. But I guess if you consult again the manuals of these models, in particular the theoretical chapters and the references listed there, some of your questions might be answered.

Kind regards

Thomas