Mercury in a geothermal and volcanic area in Patagonia, southern South America

Mercury and heavy metal contents are monitored using lichens as a tool for evaluation of air pollution. Lichens allow the identification of zones with anthropic impact, pollution hotspots and natural sources of contamination like volcanic emissions. The concentration of mercury (Hg) semivolatiles and rare-earth elements (REEs) were measured in our case in fruticose lichen thalli and soils collected in an active volcanic area: the Copahue-Caviahue Volcanic Complex, in northern Patagonia, South America. The present research focus on Hg-release patterns and its association to elements such as sulphur (S) and bromine (Br). In order to discriminate the particulate from the gaseous forms the concentration ratios of elements to magnesium (Mg) were computed. The Hg vs. Br concentration linear regression, together with the Hg normalised concentration vs. volcano distance, suggest that Hg from volcanic origin may be oxidised changing to reactive forms in the ash plume. Total mercury concentration in fruticose lichens (0.207–0.331 μg g−1) in Copahue-Caviahue volcanic area were higher than those from several other volcanic areas in South America, USA and Italy (0.010–0.290 μg g-1). Nevertheless, the consequent deposition has not generated a net contamination in soils.