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 self-lifting method can be efficiently used to monitor gassy lakes.