CONTROL OF ENVIRONMENTAL PARAMETERS FOR MANAGEMENT AND CONSERVATION OF NERJA CAVE (MALAGA, SPAIN)
Francisco Carrasco, Iñaki Vadillo , Cristina Liñán , Bartolomé Andreo , José Durán Juan - (31/1,2002)
The Nerja Cave receives on average more than 500,000 visitors per year. In order to know the possible impact in the underground environment by human visits, a monitoring network was installed since 1993, to control hourly several parameters. Also, since 1991 a hydrochemical control has been carried out in the drip water points of the cave and in the natural discharge points of the carbonate aquifer. This continuous record of physical-chemical parameters of drip water, its daily outflow, as well as temperature and relative humidity in the air, CO2 concentration and rock temperature shows the human influence. The main changes in environmental parameters are the following: 1. cave air temperature rises 0.2 °C by 1000 visitors/day, 2. a daily increase between 2 and 3 % in relative air humidity, reaching saturation on summer days, 3. CO2 concentration in air increases up to values between 500 and 700 ppm during low visitability periods and 10 times the background value during high visitability periods (2.800 ppm), 4. temperature of the rock rises between 0.02 °C and 0.15 °C/day, and (5) PCO2 of drip water also presents variations, increasing during the big influx of visits and decreasing the saturation index of carbonated minerals.