  We present an experimental technique for determining the pH and the total
carbon concentration when \ch{CO2} diffuses and flows in water. The technique
employs three different pH indicators, which, when combined with an image
analysis technique, provides a dynamic range in pH from 4.0 to 9.5. In contrast
to usual techniques in which a single pH indicator is used, the methodology
presented allows not only to produce a binary classification (pH larger or
smaller than a given threshold) but to access a much more complete continuous
spatial distribution of pH and concentration levels in the system. We calibrate
the method against benchmark solutions and further demonstrate its potential by
measuring the pH and total carbon concentration in a density driven convection
(DDC) of carbon-enriched water. The motivation for testing the method in this
particular experiment comes from the fact that DDC plays a pivotal role in the
efficiency of engineered carbon storage processes. The application of the
technique presented here provided a direct window for the analysis of the
spatial distribution of captured carbon in the DDC flow.
