Determination of free CO2 in emergent groundwaters using a commercial beverage carbonation meter

0022-1694/$ see front matter 2012 Elsevier B.V. A http://dx.doi.org/10.1016/j.jhydrol.2012.03.015 ⇑ Corresponding author at: Department of Geology a University, 98 Beechurst Ave., Morgantown, WV 26506 fax: +1 304 293 6522. E-mail addresses: [email protected] [email protected] (H.M. Edenborn). Dissolved CO2 in groundwater is frequently supersaturated relative to its equilibrium with atmospheric partial pressure and will degas when it is conveyed to the surface. Estimates of dissolved CO2 concentrations can vary widely between different hydrochemical facies because they have different sources of error (e.g., rapid degassing, low alkalinity, non-carbonate alkalinity). We sampled 60 natural spring and mine waters using a beverage industry carbonation meter, which measures dissolved CO2 based on temperature and pressure changes as the sample volume is expanded. Using a modified field protocol, the meter was found to be highly accurate in the range 0.2–35 mM CO2. The meter provided rapid, accurate and precise measurements of dissolved CO2 in natural waters for a range of hydrochemical facies. Dissolved CO2 concentrations measured in the field with the carbonation meter were similar to CO2 determined using the pH-alkalinity approach, but provided immediate results and avoided errors from alkalinity and pH determination. The portability and ease of use of the carbonation meter in the field made it well-suited to sampling in difficult terrain. The carbonation meter has proven useful in the study of aquatic systems where CO2 degassing drives geochemical changes that result in surficial mineral precipitation and deposition, such as tufa, travertine and mine drainage deposits. 2012 Elsevier B.V. All rights reserved.