09:30 〜 11:30
▲ [20a-PB2-5] Semi quantitative Elemental Analysis of Volcanic Ashes from Populations Surrounding the Tungurahua Volcano of the Eruptive Period 2008-2010, Using the LIBS Spectroscopy (Laser-Induced Breakdown Spectroscopy)
キーワード：LIBS, Calibration-free, spectroscopy
The geochemical characterization of volcanic ash is of a great scientific interest since it allows to determine the physical conditions of volcanic eruptions. This work applied the LIBS technique in 18 ash samples from the Tungurahua volcano from the 2008-2010 eruptive period. LIBS is based on the spectral analysis of plasma produced by an intense laser focused on a sample, this plasma evolves over time, producing a de-excitation of ions and atoms, giving rise to emission lines that contain information about the elements in the sample. The technique requires a minimum preparation of the sample, its measurement time is very short and can be applied to arbitrary samples. This work proposes suitable preparation methods for volcanic ash to guarantee the homogeneity of the sample and the data obtained. The analysis was carried out in two different environments, common air and atmosphere saturated with argon. For the quantitative analysis Calibration-free LIBS (CF-LIBS) is used, a technique used to determine the elemental composition of an arbitrary sample by statistical distributions of Saha-Boltzmann and Boltzmann without calibration curves. The instrumental response function of the LIBS equipment of the EPN was determined. A comparison was made of the data obtained by CF-LIBS with EDS and with ICP-AES. The concentrations determined with these techniques coincide within the experimental range, and this allowed to define correction factors for the concentrations obtained with CF-LIBS. A list of the chemical elements in ashes of andesitic volcanoes was defined for future analyzes with CF-LIBS.