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Abstract: Biomagnetic monitoring, using tree leaves as passive surfaces for particle collection, has been shown to be a promising technique for assessing the dispersion and deposition of particles in the context of anthropogenic pollution. By comparing leaves'' magnetic properties with trace metal levels measured in the leaves, we here assess the utility of the biomagnetic technique as a sensitive, fast and inexpensive method for assessment of volcanic plume deposition. Samples of sweet chestnut leaves (Castanea sativa) were collected from the area surrounding Mt. Etna volcano in Sicily during the 2008 growing season when the volcano was displaying mild eruptive activity. Previous work has shown that the trace metal concentrations of these leaves show promise as a bio-indicator of volcanic gas, aerosol and ash deposition on the flanks of Mt. Etna. For 2008, ICP-MS analysis of the elemental abundances within the leaves showed that As, Cd, Cu, Mo, Tl, K, B, Al and Co displayed elevated concentrations downwind of the volcanic source, to the E–ESE, but with overall reduced concentrations relative to 2007. Less explosive activity than 2007 and a broader, more easterly wind field may have distributed the volcanic plume over a wider area, both of which would account for reduced trace element concentrations in 2008. Correspondence of elevated concentrations in both years (2007 and 2008) with their respective wind fields suggests that plume deposition is the controlling factor rather than variability in the soils and that these leaves do indeed have potential as bio-indicators of the plume''s dispersion. Magnetic analysis of the leaves shows that the spatial distribution of saturation isothermal remanent magnetisation (SIRM) and magnetic susceptibility (χ lf) values display a strong correlation with the wind-influenced plume transport direction for 2008, with elevated concentrations of magnetic minerals on the eastern flanks, in broad agreement with the ICP-MS data. This spatial distribution provides further evidence of plume variability as the main control on the concentrations of magnetic particles on the leaf surfaces and on elemental uptake by the tree and suggests that biomagnetic monitoring may also hold promise as a method of assessing the dispersion and impacts of volcanic plumes. The dominant magnetic mineral on the leaf surfaces is a magnetite-like mineral (contributing >90% of the SIRM), of coarse, multi-domain (MD) grain size (∼5 to 15μm). A volcanogenic source is most likely, as magnetites from anthropogenic sources are typically an order of magnitude smaller in grain size (∼0.1–1μm). These new results from the use of environmental magnetism on leaves, in a volcanically-affected region, suggest that biomagnetic monitoring offers a new, sensitive and rapid means for the assessment of volcanic plume deposition over wide areas. [Copyright &y& Elsevier]

Abstract: Analyses of air, water and vegetation samples collected in June 2008 offer new insights into the environmental effects of the May 2008 Chaitén eruption on Argentina, which was subject to significant ashfall between 42°S and 46°S. Results from air filtration in the ash-affected town of Esquel (with samples analysed by gravimetry and scanning electron microscopy) show the total mass of resuspended ash in the air is well-correlated with traffic activity. However, this variation is primarily related to varying amounts of the largest particles, with little variation in the amounts of fine ash particles (i.e., d <4 μm). This result suggests that the hazard associated with resuspended ash remains high even when traffic activity is low and the air is not visibly dusty. We estimate PM2.5 ∼200 μg m−3, PM4 ∼300 μg m−3 and PM10 ∼ 1000 μg m−3; these concentrations far exceed WHO air quality guidelines and likely persisted for several months. Results from water and vegetation sampling (with samples analysed by inductively coupled plasma mass spectrometry and ion chromatography) indicate that ashfall resulted in significant compositional changes in ephemeral lakes and coirón grass (Festuca pallescens). For B, Cd, Zn, Tl, Cu and Ni, there are strong linear correlations between concentrations and ash thickness (where >2 mm) in both datasets. These results suggest that the eruption of Chaitén led to significant changes in the concentrations of trace volatile elements within the environment. Analysis of vegetation samples collected in January 2009 indicates that the elevated element concentrations in coirón grass persisted for <8 months. These results offer insights into the environmental fate of volatile trace elements emitted during volcanic eruptions. [Copyright &y& Elsevier]