Major and trace element distributions around active volcanic vents determined by analyses of grasses: implications for element cycling and bio-monitoring

Abstract

Samples of grass were collected at Masaya Volcano (Nicaragua; Rhynchelytrum repens and Andropogon angustatus) and the Piton de La Fournaise (around the April 2007 eruptive vent, La Réunion; Vetiveria zizanioides) to investigate the controls on major and trace element concentrations in plants around active volcanic vents. Samples were analysed using inductively coupled plasma mass spectrometry for a wide range of elements, and atomic absorption spectroscopy for Hg. At Masaya, As, Cu, Mo, Tl and K concentrations in both grass species showed a simple pattern of variability consistent with exposure to the volcanic plume. Similar variability was found in A. angustatus for Al, Co, Cs, Hg and Mg. At the Piton de La Fournaise, the patterns of variability in V. zizanioides were more complex and related to variable exposures to emissions from both the active vent and lava flow. These results suggest that exposure to volcanic emissions is, for many elements, the main control on compositional variability in vegetation growing on active volcanoes. Thus, vegetation may be an important environmental reservoir for elements emitted by volcanoes and should be considered as part of the global biogeochemical cycles.

High‐resolution size distributions and emission fluxes of trace elements from Masaya volcano, Nicaragua

“…Masaya lavas contain 23.2 ng mg −1 Ce and 4.31 ng mg −1 Dy [ Moune et al , 2010] so we calculate the silicate mass on each filter as 0.05 mg (using Ce as a basis) or 0.04 mg (using Dy as a basis). Inspection of the filters with SEM (Figure 7) reveals large amounts of spherical silicate particles (identified as silicate due to their smooth glassy appearance) with diameters in the 1–10 μ m range as observed previously at Masaya [ Martin et al , 2009a, 2010a, 2010b] and elsewhere [e.g., Lefèvre et al , 1986; Meeker and Hinkley , 1993; Martin et al , 2008; Sawyer et al , 2011]. The size distribution of the spherical silicate particles (Figure 7) is consistent with that of the F1 elements (Figure 3).…”

“…However, the high concentrations of particles measured ∼2 km below the plume of Etna [ Allen et al , 2006] suggests that the actual rate of dry deposition may be enhanced further by complex wind fields around volcanoes. While few direct measurements of trace element deposition fluxes are available [ Calabrese et al , 2011], spatial and temporal variability in trace element deposition can be usefully assessed, at least qualitatively, using lichens, tree leaves and grasses as bio‐indicators [ Varrica et al , 2000; Bellomo et al , 2007; Watt et al , 2007; Martin et al , 2009b, 2010a, 2012]. …”

Halogens and trace metal emissions from the ongoing 2008 summit eruption of Kīlauea volcano, Hawai`i

“…However, it is worthy of note that the sample collected close to the Halemaumau vent (V13) had markedly lower concentrations of lithophile elements. While clear conclusions cannot be drawn from a single sample, this result may indicate very localised leaching of lithophiles from soils in the summit area due to deposition of acidic species (e.g., Delfosse et al, 2005;Martin et al, 2010b). Although there is a suggestion of a general trend in terms of enhanced volatiles in the samples downwind of the Halemaumau vent, these trends are not as pronounced as in previous studies of vegetation associated with active volcanism (e.g., Martin et al, 2009a,b).…”

Selenium mobilization in soils due to volcanic derived acid rain: An example from Mt Etna volcano, Sicily

“…2) that could be related to Se deposition (Calabrese, 2009). Furthermore, there is no correlation in the leachates between Se and other elements strongly enriched in the plume (Calabrese, 2009) and in plant leaves (Martin et al, 2009(Martin et al, , 2010, such as Thallium (TI) and Cadmium (Cd) (Table A1, R 2 = 0.11 and 0.02 respectively). The influence of the volcanic Se emissions has been clearly demonstrated in the rainwater Se concentrations (Calabrese, 2009).…”

“…On the other hand, the plume dispersion characteristics are different for both volcanoes. Wind directions are more variable around Etna than at Masaya (Allen et al, 2000;Martin et al, 2009Martin et al, , 2010. Additionally, the sites at Masaya are at approximately the same altitude of the plume vent, so direct plume fumigation occurs regularly increasing the deposition of acidic compounds (Delmelle et al, 2001).…”