An efficient method for measuring CO2 concentration in gassy lakes: Application to Lakes Nyos and Monoun, Cameroon

Abstract

A simple and efficient method for measuring CO2 concentration of deep water of gassy lakes is proposed. This method is based on the gas self-lifting in a plastic hose that is deployed into deep water of the lake. Physical parameters such as the volumes of separated gas and water, and their temperature were used to obtain CO2 concentration of lake water on site. We can measure the CO2 concentration as long as the gas self-lifting continues. Sampling depth can be easily changed little by little by pulling up the hose with a calibrated stainless steel wire. Thus, we can obtain data from finely separated depths. Here we present the CO2 profiles obtained by using the present method in 2007 and 2009 at Lakes Nyos and Monoun, Cameroon, to demonstrate its applicability on gassy lakes. Sharp reduction of CO2 content at Lake Monoun, and gradual reduction at Lake Nyos as a result of degassing operation were clearly shown by the current method. This gas selflifting method can be efficiently used to monitor gassy lakes.