I am using Spatial Analyst to interpolate surfaces for several groundwater parameters based on point observations at monitoring bores, including groundwater level and pH.
It suddenly occurred to me however, that pH itself is a logarithmic measure of concentration of hydrogen ions. I can't seem to clarify in my head if this requires special attention.
In the most basic conceptual example, if point A is pH=4.0 and point B is pH=6.0, it could be assumed that a point C directly in the middle of the two (equidistant to both) might be ph=5.0 (left-hand mark on graphic attached). If we were looking at actual hydrogen ion concentration as the parameter, the value at point C might be closer to 5.7-5.8 (right-hand mark on the graphic attached).
Could someone please help clarify the assumptions I might be missing here and the correct way to handle this when interpolating?