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The amount of dissolved CO2(CO2aq) in Lake Nyos, Cameroon, has been measured annually since January 2011. First, [Formula] concentration was estimated by a chemical analysis with the assumption of equilibria between CO2aq, [Formula] and [Formula]. The estimated [Formula] was correlated with the observed electrical conductivity of lake water. The profile of [CO2aq] was generated from the electrical conductivity, pH and temperature profiles. The [CO2aq] profile was integrated over the water column to obtain the total amount of CO2aq. The amounts were 8.4, 6.8, 5.5, 4.4 and 3.9 Gmol (=109mol) in 2011, 2012, 2013, 2014 and 2015, respectively. The fast reduction between 2011 and 2013 was attributed to the installation of two additional degassing pipes in April 2011. However, the rate of reduction decreased between 2014 and 2015 due to the reduced [CO2aq] at the inlet of the degassing pipes.

The effect of stoichiometry ratio and ash deposits on the corrosion of mild steel and 0.5Cr-0.5Mo steel has been investigated at 450 °C in the simulated combustion gases burning three kinds of coals. Under the assumption that the gas reacts with the metal at the same temperature as the surface and gas has not changed in composition, the corrosion behavior could be estimated from the Fe-S-O phase stability diagram at 450 °C and pseudo equilibrium Ps2, and Po2, based on H20 : H2at 1200 °C for simulated combustion gases. Ash deposits accelerated the corrosion rates of steels. It is considered that ash deposits act as catalyst and shift the gas composition to the low temperature equilibrium state