Analysis of geochemical and mineral compositions of volcanic soil affected by Merapi eruption in Central Java Indonesia using laser-induced breakdown spectroscopy with calibration-free

Abstract

Volcanic materials are crucial for the rejuvenation process as they positively influence agricultural factors by progressively enhancing soil fertility. In this study, the quantification of geochemical and mineral constituents of Merapi volcanic soil was carried out to assess its substantial influence on enhancing soil fertility using laser-induced breakdown spectroscopy (LIBS) technique via a calibration-free approach. The volcanic soil samples were obtained from 24 locations in the Merapi volcano in Central Java Indonesia. In the experiment, a pulse Nd:YAG laser (1064 nm, 83 mJ, 10 ns) was experimentally directed and focussed on the samples to generate a luminous plasma containing the elemental makeup of the samples. The volcanic soil in all directions contained the same elements with different concentrations for each sampling location. The volcanic soil contains major elements of Si, Ca, Fe, Al, and K and minor elements of P, Ti, Mn, Cu, and Zn. The soil of Merapi volcano contains a total of 13 oxides, including three elemental oxides from the silicate mineral framework (SiO₂, Al₂O₃, Fe₂O₃), five essential macronutrients for plant growth (CaO, MgO, K₂O, SO₃, P₂O₅), five micronutrients for plant growth (MnO, CuO, ZnO, Cl, Br), and two total oxide elements from rare earth elements (Y₂O₃ and Eu₂O₃). The results of the LIBS method demonstrate a substantial concordance with the findings obtained from the conventional X-ray fluorescence (XRF) technique.

Keywords: Elemental analysis; LIBS; Laser-induced breakdown spectroscopy; Merapi volcanic soil; Nd:YAG laser.