DISTRIBUTION AND SIGNIFICANCE OF CO2 PARTIAL PRESSURES IN THE MENENGAI GEOTHERMAL AREA

Partial pressure of CO2 (PCO2) was computed for available analysis of local groundwater within the Menengai geothermal area in order to prepare a unique map of distribution of PCO2. The findings show that variations exist in the distribution of PCO2 suggesting that CO2 is possibly produced by different processes based on the general knowledge of CO2 geochemistry. These variations in PCO2 are ascribable to processes such as decay of organic matter and root respiration occurring in soils, which are systems exchanging gases with the atmosphere. However, these inferences are taken as working hypotheses to be confirmed by use of stable C isotope data in future works. The geographical distribution of PCO2 further defines tectonic structures that are gas leakage zones within the Menengai area. Moreover, gas partial pressures can be instrumental in mapping zones of fluid inflows geothermal wells as well as identify the aquifer(s) contributing the highest proportion of the gas in the discharge in the case of multiple aquifers in the wellbore.

Key words: partial pressure, CO2, Menengai, groundwater, geochemistry