VOLCANIC INFLUENCES ON HEAVY METAL CONCENTRATIONS IN VEGETATION

Volcanoes are prodigious sources of heavy metals (e.g., As, Cd, Cu, Hg, Tl) into the environment and likely a key element of global biogeochemical cycles (particularly for Hg). However, the environmental processing of volcanogenic heavy metals remains largely unconstrained. Here, we summarise a series of our recent works on heavy metals in vegetation exposed to different volcanic influences (ranging from volcanic ashfall to fumigation by dilute volcanic gas and aerosol). The case studies described are Mt Etna, Sicily; Masaya, Nicaragua; Piton de La Fournaise, La Reunion; and Chaiten, Chile. We show that the level of exposure to volcanic emissions is often the primary control on heavy metal concentrations in vegetation growing around active volcanoes. Furthermore, where levels of exposure are variable through time (e.g., due to changes in volcanic activity), the heavy metal concentrations in vegetation respond rapidly (i.e., < 1 week).

These results, and their presumed ubiquity, indicate that vegetation may be an important environmental reservoir for volcanogenic heavy metals and should be considered as part of global biogeochemical cycles. In addition, vegetation species growing in areas where exposure to the volcanic emissions is persistent should be regarded as candidates for both bioindication and bioremediation of heavy metal contamination.