Analytical solution of CO2 mass flux measurement with Non-Dispersive Infrared sensors for soil in diffusive and advective-diffusive regime: Tool for the continuous and telemetric measurement of volcanic gases in an open chamber

Abstract

Measuring the carbon dioxide (CO2) mass flux in a volcanic environment is necessary for volcanic monitoring. CO2 mass flux must be measured continuously and telemetrically to get, almost in real-time, a better understanding of the dynamics of the volcanic degassing processes, contributing to the building, together with other monitoring technics, of a volcano behavior model. This study presents two analytical solutions, 1) a simple diffuse solution and 2) an advective-diffusive solution, which both implement NDIR (Non-Dispersive Infrared Emitter) sensor arrays in an open chamber (diffusion chimney) and an exchange chamber (gas interchanger). The first system, for which the gas speed is negligible, despite being basic (with values reflected in the slope of an equation line), introduces mass flux calculations with a single sensor NDIR. For the second system, where the gas speed is part of the equation, another mathematical solution and three measuring points are required, which demands the system to include a se­cond NDIR sensor for the correct mathematical solution of the equations system. In addition, an embedded system can automate the method by calibrating, controlling an agitation fan, and recording temperature, pressure, and mass flux in volcanic soils at the surface. Since this theoretically proposed method needs to be tested, experimental data are expected to validate the measurement of CO2 mass flux, which will be used as a helpful tool for volcanic monitoring.