Environmental effects of ashfall in Argentina from the 2008 Chaitén volcanic eruption

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 PM ∼ 200 μg m, PM ∼ 300 μg m and PM ∼ 1000 μg m; 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.