Study of the Chemical Composition of Ash Nanoparticles from the Volcanoes of Kamchatka

Abstract

Obtained data on the composition and properties of ash nanoparticles from Klyuchevskoy, Tolbachik, Kizimen, and Shiveluch volcanoes (Kamchatka, Russia) are generalized. It has been shown that the concentration of toxic and potentially toxic metals and metalloids (Ni, Cu, As, Se, Ag, Cd, Sn, Te, Hg, Tl, Pb, Bi) in volcanic ash nanoparticles can be 10–535 times higher than their concentration in bulk polydisperse samples. The most volatile elements such as As, Sn, Te, Hg, Tl, and Bi have the highest concentration factors in the range of 100–535. Based on the data on single particle inductively coupled plasma mass spectrometry, it is assumed that the listed metals and metalloids are accumulated in the fraction of volcanic ash nanoparticles mainly through the condensation of these elements or their compounds from the gaseous phase and the formation of individual (single) nanophases with an average size in the range of 12–74 nm. It should be noted that approximately an order of magnitude less nanoparticles have been isolated from the acidic volcanic ashes of the Kizimen and Shiveluch volcanoes as compared to those of basic ashes of the Tolbachik and Klyuchevskoy volcanoes. This fact is inconsistent with published data showing that the fraction of fine ash is usually larger for acidic explosive eruptions compared to basaltic eruptions. The Pearson correlation coefficients between the basicity index of volcanic ash and the concentration of more than 50 elements in the ash and ash nanoparticles have been calculated. Some elements have a correlation coefficient |R| 0.7, which, according to the Chaddock scale, indicates the high degree of correlation. It is noted that a number of elements have an opposite correlation between the basicity index of ash and the concentration of elements in ash and ash nanoparticles. For example, Hg and Tl content in ash have a negative correlation with basicity index, that is, their concentration decreases with increasing basicity index of the ash, whereas their concentrations in nanoparticles positively correlate with ash basicity index. The concentration of Ca, Ho, and Er in the ash increases with an increase in the ash basicity index, whereas ash nanoparticles show an opposite correlation. The revealed regularities are unexpected and confirm the unique features of nanostructures and raise new questions of nanogeochemistry.