Determinación experimental del contenido en CO 2 del suelo sobre una cavidad kárstica en clima mediterráneo (Cueva de Nerja, Málaga) Experimental survey of soil CO 2 content over a karstic cave in mediterranean climate

The CO 2 content and the temperature of the air have been measured within the scarce soil (although with relatively high organic matter concentration) which partially covers the carbonate outcrops over the Nerja Cave (Malaga). General yearly average values of around 850 ppm and 25 oC have been identified, both using continuous recording devices and separated measures with portable equipment. Temperature evolution closely follows that of the outside atmosphere. Spatial variations in CO 2 contents are related with the vegetal cover and with the soil depth. Seasonal variations are important, with a maximum of more than 1000 ppm in May (main vegetation development) and minimum (around 350500) in December. Daily oscillations have also been identified, ranging up to more than 600 ppm in the period of maximum CO 2 production. These results agree with estimates based in hydrogeochemical modelling as well as in the TOC content of drip water to the cave.