Characterisation of the Etna tephra to explore its suitability as growing media

Mount Etna (Sicily, Italy) is the highest and most active volcano in Europe. From 2011 its activity has been considerably increasing compared with previous years. Ashes ejected from the Etna volcano cause much nuisance to inhabitants in the surrounding area, and to farmers burying agricultural lands and destroying crops. Volcanic eruptions, in fact, produce great amount of volcanic ash, which needs to be separated and disposed as a different waste in Italy. This material, on the other hand, can represent a resource for farmers to improve land fertility and to obtain growing media for pot cultivation. Ash granulometry plays a key role: tephra refers to ashes that are less than 2 mm of diameter. This material has great properties such as low density, high porosity, presence of organic carbon and nutrient elements, useful for growing ornamental plants. Therefore, it could be used in plant nurseries and in green infrastructure (green roofs, green walls). A complete characterisation is necessary to fully understand its potential. Some properties necessary for the definition of the suitability as growing media have been investigated in tephra coming from Etna eruptions of spring 2021. Electrical conductivity (EC), cation exchange capacity, pH, macro, micro and trace elements (Cd, Cr, Cu, Ni, Pb, Zn, As, Hg, Ca, Fe, K, Mg, Mn, V, Na, P, Al, Ti) total and H2O soluble quantities were determined. EC was under the salinity limit, pH was neutral. All the potentially toxic elements were low especially as water soluble values. The investigation carried out represents a preliminary study for the feasibility of the use of Etna tephra as a component of growing media.