Using mosses as biomonitors to study trace element emissions and their distribution in six different volcanic areas

Abstract

Volcanoes emit SO2, CO2, andH2S, but also trace elements gases and particles such as As, Cd, Cr, Cu, Hg, Ni, Pb, and Sb. Active moss bag biomonitoring, an easy to apply and low budget method, was used to determine trace element release from volcanic areas of different geological context and climates. Exposure height variations (0.7–1.6 m above ground) due to different availability of natural tie points did not affect the results. Accumulation was linear for exposure durations from three days to nine weeks, so values were comparable by normalization to moss exposure time. Uncovered moss bags showed higher accumulation than co-exposed covered ones because of additional dust and wet deposition while washout by rain was negligible. The selection of a specific moss significantly affected element accumulation with moss of lower shoot compactness accumulating more. For all volcanic areas, highest accumulation was found for S (1–1000 μmol·(g·d)−1), followed by Fe and Mg (0.1–10 μmol·(g·d)−1), Sr, Ba, Pb, Cr, Li (10−4–10−1 μmol·(g·d)−1), then Co, Mo and the volatile elements As, Sb, Se, Tl, Bi (10−6–10−2 μmol·(g·d)−1). Formost elements, open conduit volcanoes (Etna, Stromboli, Nyiragongo) showed highermoss accumulation rates than more quiescent hydrothermal areas (Vulcano > Nisyros > Yellowstone National Park) and a correlation of S, Fe, and Pb fromeruptive ash and lava emissions. For some volatile elements (S, As, Se), higher accumulation was observed within fumarolic fields compared to crater rims of open conduit volcanoes which is a relevant information for risk assessment of tourist exposure to volcanic gases.