MICROCLIMATIC CHARACTERIZATION OF A KARSTIC CAVE - HUMAN IMPACT ON MICROENVIRONMENTAL PARAMETERS OF A PREHISTORIC ROCK ART CAVE (CANDAMO CAVE, NORTHERN SPAIN)

The Candamo Cave contains an important group of paleolithic paintings which have been seriously deteriorated due to mass tourism. In this wo rk, an analysis was carried out of different climatic parameters (CO2, temperature, humidity, Rn-222) during annual cycles with the cave clo sed to the public and during an experimental period of controlled visi ts. The effect of visits on the geochemical characteristics of karstic water was also analyzed together with the cave ventilation. The natur al variations in the cave air CO2 were above 3000 ppm, the increase pr oduced through visits was only 100-110 ppm and since the humidity is a lmost permanently at saturation point, the critical parameter which li mits the visitor capacity becomes air temperature. The temperature cha nges during the annual cycle are of the order of 1 degrees C in the ex ternal part and less than 0.5 degrees C in the internal part of the ca ve and a maximum increase of 0.13 degrees C was observed during the pe riod of the visits. The Rn-222 and CO2 concentration minimums in the s ummer period (July-October) show that this is the most propitious time for visits, since the greatest ventilation is produced in the cave at this time and, therefore, the greatest capacity for recovery. The geo chemistry of the water, on the other hand, indicated that this is the period of the year in which processes of wall corrosion can be most ea sily introduced, although this would be of limited magnitude. The visi tor capacity calculated was 29 visitors/day.