Passive degassing at Nyiragongo (D.R. Congo) and Etna (Italy) volcanoes

Abstract

<p>Volcanoes are well known as an impressive large natural source of trace elements into the troposphere. Etna (Italy) and Nyiragongo (D.R. Congo) are two stratovolcanoes located in different geological settings, both characterized by persistent passive degassing from their summit craters. Here, we present some results on trace element composition in volcanic plume emissions, atmospheric bulk deposition (rainwater) and their uptake by the surrounding vegetation, with the aim to compare and identify differences and similarities between these two volcanoes. Volcanic emissions were sampled by using active filter-pack for acid gases (sulfur and halogens) and specific teflon filters for particulates (major and trace elements). The impact of the volcanogenic deposition in the surrounding of the crater rims was investigated by using different sampling techniques: bulk rain collectors gauges were used to collect atmospheric bulk deposition, and biomonitoring technique was carried out to collect gases and particulates by using endemic plant species. The estimates of the trace element fluxes confirm that Etna and Nyiragongo are large sources of metals into the atmosphere, especially considering their persistent state of passive degassing. The large amount of emitted trace elements has a strong impact on the close surrounding of both volcanoes. This is clearly reflected by in the chemical composition of rainwater collected at the summit areas both for Etna and Nyiragongo. Moreover, the biomonitoring results highlight that bioaccumulation of trace elements is extremely high in the proximity of the crater rim and decreases with the distance from the active craters.</p>

Volatile trace metals deposited in ice as soluble volcanic aerosols during the 17.7.ka eruptions of Mt Takahe, West Antarctic Rift

“…Compared to subalkalic basaltic volcanic gas plumes, only a small number of alkaline volcanic gas plumes have been sampled directly for their source metal emissions: at Mt. Erebus, Antarctica (Wardell et al, 2008), and Nyiragongo, Democratic Republic of the Congo (Calabrese et al, 2014). Alkaline intraplate magmas are typically chlorine-rich, which may produce higher concentrations of gaseous volatile metals than subalkalic basaltic intraplate volcanoes due to the higher availability of chloride ligands in the exsolved fluids (Mandon et al, 2019), although this has not yet been demonstrated.…”