Air CO2 in Comblain-au-Pont Cave (Belgium). Relationships with soil CO2 and open air meteorology ; Le CO2 de l'air dans la grotte de Comblain-au-Pont (Belgique). Relations avec le CO2 du sol et la météorologie

peer reviewed ; Carbon dioxide (thought to come in the main from plant root and biomass respiration) displays seasonal variations related to outside temperature, but some oscillations of the CO content of cave air are related to surface barometric variations (i.e., when the barometric pressure falls, a certain amount of air trapped in the remote parts of the system leaks outside and vice versa). A sudden drop of temperature, inducing a chimney effect may cause a drop of the air-CO2 content of a deep pit from 4000 to 1300 ppm.