Development of a new low-cost device to measure calcium carbonate content, reactive surface area in solid samples and dissolved inorganic carbon content in water samples

Abstract

Estimates of soil carbonate dynamics are still very scarce, despite their importance in the global carbon budget. Geochemical models used to estimate carbonate precipitation–dissolution rates require important inputs including carbonate content and calcite reactive surface area in soil as well as dissolved inorganic carbon (DIC) content in soil solution. However, most methods currently available to accurately measure these parameters can be time-consuming and/or often require expensive laboratory equipment. To tackle this problem, we aimed to develop a sensitive device to measure these variables at low cost and with little time investment. By taking advantage of the recent development of low-cost CO2 sensors and microcontrollers, a low-cost and easy-to-mount analyzer was developed based on direct measurements of CO2 evolved during an acidic reaction. The new instrument proved to be sensitive, accurate, precise and able to quickly perform the analyses. It was therefore used in a pilot experiment on the inorganic component of CO2 flows from crusted semi-arid soils, and to evaluate the variation in DIC content through a spring-cave-downstream river water continuum. The device could facilitate these analyses for scientists from different fields since it can potentially analyse any solid or aqueous sample.