DISSOLVED GAS CONCENTRATION (CH4, CO2) ACCORDING TO DEPTH.

Using the experimental column allowed sample collection of water and gas at levels where priming of the auto-siphon mechanisn was possible, that is to say below a depth of 270 metres.

Prelimiary analysis of the CO2 and CH4 content was done in situ, at the exit of the small separator. The figures obtained by means of the Ga2000 infra-red analyser are exact and reproducible.

We have added the respective contents in CO2 and CH4 in the gas taken from different depths between 270 and 400 m to the figure. One can note a small but absolutely crucial diminution in methane content as depth increases. The difference in methane content between the layer at 270 m (27% CH4, 73% CO2) and the layer at 400 m (20.5% CH4, 79.5% CO2) is of 7%.

In the rate of content of gas concentration one can again remark the existence of those homogenous layers mentioned previously (notably the 280 - 300 m layer and the 330 - 355 m layer).