Environmental impact of trace element emissions from geothermal power plants.

Concentrations of several trace elements were determined in mosses, higher plants and organs of small mammals from a geothermal area in Tuscany (central Italy). Increased deposition of Hg, As, B, and Sb was detected in biological samples collected within a few hundred meters of geothermal power plants. Among the species considered, the moss Hypnum cupressiforme was the most efficient accumulator of trace elements. Contamination levels in a fodder-plant (Hedysarum coronarium) and vegetables grown in the geothermal field did not seem to pose health risks for consumers. However, a statistically significant increase in Hg, B, and As concentrations was found in the kidney and muscle of small mammals living close to geothermal installations. Biological effects of B pollution were detected in two sensitive plant species. In view of plans to increase the exploitation of geothermal resources in the area, adequate measures to monitor the environment should be taken. Mosses are the most suitable accumulative biomonitors for a surveillance network, and studies on small mammal populations should be intensified. Available technologies should be used to diminish atmospheric emissions from geothermal power plants.