Salinity/sodicity vs. CEC

I'm curious about the differences in CEC between the soils on question 3. I would have expected the CEC to correlate with pH, given that mineral particles can have a pH dependent charge. However, there's no correlation. Nor can I see any correlation between CEC and any other given variable.

Among commonly present soil mineral particles, only Fe & Al oxides/hydroxides have pH-dependent charge,while phyllosilicate minerals have very limited pH-dependent charges (ie their charge is permanent or constant).
You are also forgetting that CEC is also driven by soil organic matter (besides clay particles) and you were not given organic matter contents in question #3. Different soil organic matter contents in those 4 soils are most likely reason for the different CEC values reported in this question.

Spencer, consider that both SOM and % clay contribute to CEC. You have no information about %OM in each of the soils. All four mineral soils have a clay loam texture; but there is some range in %clay within each texture class (28-40% in the case of clay loam soil - see lab 3 and the texture triangle). Remember that soil are complex, so when interpreting data you need to consider more than one parameter.