LICHENS AS BIOINDICATORS OF GEOTHERMAL AIR-POLLUTION IN CENTRAL ITALY

The suitability of lichens as bioindicators of geothermal air pollutio n was evaluated in central Italy. Fifty-one sites were sampled in the Travale-Radicondoli geothermal field, an area of about 15 km(2). Liche ns on 1-5 trees per station were sampled, using 30 x 50 cm grids on tr ee boles, where lichens were most dense. Index of Atmospheric Purity ( IAP) was calculated as the sum of the frequencies of all lichen specie s present at the station. Using automatic mapping programs, the area w as divided into four air quality zones and the lowest IAP values were found within about 500 m of geothermal power plants. No direct measure ments of air pollution are available for the whole study area, however , other studies show that air pollution levels (mercury, boron) fall w ith distance from a geothermal source. Also no substrate parameter (he ight, circumference, bark pH, and buffer capacity of the trees) discri minates between IAP zones. This suggests that air pollution arising fr om geothermal emissions is responsible for the zonation shown, with va lues for species richness and IAP rising with distance from geothermal installations. It is concluded that lichens are reliable bioindicator s of geothermal air pollution.