Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms

[摘要] Leaching experiments were carried out on fresh ash samples fromPopocatépetl 2012, Etna 2011, and Etna 2012 eruptions, in order to investigatethe release of compounds in both double-deionized and lake (Lake Ohrid, FYRof Macedonia) waters. The experiments were carried out using different grainsizes and variable stirring times (from 30 min to 7 days). Resultswere discussed in the light of changing pH and release of compounds for thedifferent leachates. In particular, Etna samples induced alkalinization, andPopocatépetl samples induced acidification of the correspondingleachates. The release of different elements does not show correlation withthe stirring time, with the measured maximum concentrations reached in thefirst hours of washing. General inverse correlation with grain size wasobserved only for Na⁺, K⁺, Cl⁻, Ca²⁺, Mg²⁺,SO₄²⁻, and Mn²⁺, while the other analysed elements show a complex,scattering relationship with grain size.

Geochemical modelling highlights leachates' saturation only for F and Si,with Popocatépetl samples sometimes showing saturation in Fe.

The analysed leachates are classified as undrinkable for humans on the basisof European laws, due to excess in F⁻, Mn²⁺, Fe, andSO₄²⁻ (the latter only for Popocatépetl samples).

Finally, the Etna 2012 and Popocatépetl leachates were used for toxicityexperiments on living biota (Xenopus laevis). They are mildly toxic, and no significantdifferences exist between the toxic profiles of the two leachates. Inparticular, no significant embryo mortality was observed; while even at highdilutions, the leachates produced more than 20 % of malformed larvae.

[学科分类] 地球化学与岩石