Vertical distribution of dissolved CO 2 in lakes Nyos and Monoun (Cameroon) as estimated by sound speed in water

Abstract

AbstractVertical profiles of sound speed (SS) in lake water were measured at lakes Nyos and Monoun (Cameroon) in 2012 and 2014. A significant linear correlation with Pearson's r of 0.987 to 0.995 between total CO2 concentration ([CO2]=[CO2(aq)]+[HCO3−]) and SS excess (Δv) in water was found. Based on this correlation, we propose the SS method as a new simple tool to monitor CO2 concentration in lakes Nyos and Monoun. We applied this method to multipoint measurements of CO2 in lakes Nyos and Monoun, and found horizontal differences between CO2 distributions in the two lakes. The results indicated that Lake Nyos water was stably stratified, and the total CO2 decreased from 2012 to 2014. At Lake Monoun, which consists of three basins (the western basin, the central basin, and the main basin), waters in the western and central basins exhibited a higher dissolved CO2 content than those in the main basin at the same depth. An increase in CO2 was also detected in the main basin from 2012 to 2014.