A SIMPLE, DIRECT METHOD TO MEASURE DISSOLVED CO2 USING SODA LIME

Abstract

A method for the direct assessment of the dissolved CO 2 concentration in supersaturated water is presented that is based on changes to the physical chemistry of soda lime due to uptake of CO 2. The approach is an adaptation of a standard method used for the quantification of soil respiration, and was found to agree with pCO 2 measurements made using infrared gas analysis. In this method, the soda lime is deployed in a CO 2 bucket chamber, and a water sample is allowed to outgas for 48 hours. The initial dissolved CO 2 concentration is then determined from changes in the dry mass of soda lime, which is blank-corrected and adjusted based on differences in molecular weights of soda lime before and after the chemical adsorption of CO 2. The method is applicable to highly-supersaturated surface water and emergent groundwater.