Ratiocalc: Software for processing data from multicomponent volcanic gas analyzers

Portable gas analyzers have become a powerful tool for the real-time monitoring of volcanic gas composition over the last decade. Gas analyzers make it possible to retrieve in real-time the chemical composition of a fumarole system or a plume in an open-conduit volcano via periodic field-deployments or at permanent stations. The core of a multicomponent volcanic gas analyzer (MultiGAS) consists of spectroscopic and electrochemical sensors that are used to determine the concentrations of the most abundant volcanic gases (H<inf>2</inf>O, CO<inf>2</inf>, SO<inf>2</inf>, H<inf>2</inf>S, H<inf>2</inf>, CO and HCl) in a diluted plume and their mutual molar ratios. Processing such data is often difficult due to the high sensitivity of the sensors to environmental conditions such as humidity, gas concentrations, and pressure, with all involving occasional instrumental drift. Analyses require accurate and time-consuming processing by an operator. This paper presents a stand-alone program for the processing of chemical data obtained using the MultiGAS, called Ratiocalc. The Ratiocalc program has a user-friendly interface to enable volcanologists to process large datasets in a simple and rapid manner, thereby reducing the processing time associated with volcano monitoring and surveying.