Acid-free continuous alkalinity measurement by equilibration with CO2 gas across a silicone membrane
log(AT+[H+]) = log( (K0)i(pCO2)/KI) + E + log((R(25)-e1)/(e2-R(25)e3))
where the pCO2 is partial pressure of CO2 gas. E is a system calibration constant. R is ratio of absorbances at wavelengths 589 and 432. K0 and KI are dissociation constant of CO2 and BCP.
This measurenent system combined with a channel for pH measurements, constitutes a robust system for characterizing CO2 system chemistry, providing either in situ, underway, or discrete measurements. It is especially useful for applications in which sample volumes are limited such as pore waters extracted from sediments.