Discrimination of moist oil shale and limestone using laser induced breakdown spectroscopy

Laser-induced plasma emission spectra of Estonian oil shale and associated limestone with varying moisture content were studied. Time gated spectra excited by 1064 nm laser radiation were recorded. Spectral lines for determination of plasma parameters were selected. Moisture causes the reduction of the intensity of the total emission, and increases the intensity of the H_α line. It was found that the effect of the moisture content on the plasma temperature and electron concentration was inconsiderable. Using the ratio of intensities of H_α and Mg spectral lines, it was possible to distinguish reliably between limestone and oil shale independently of their moisture content. - Highlights: • Laser induced plasma emission spectra of both; Estonian oil shale and limestone with varying moisture content were studied. • The temporal change of the laser induced plasma plume temperature T_e and electron density n_e were evaluated. • Plasma temperature and electron concentration changed with the moisture content inconsiderably. • Limestone and oil shale are distinguished independently of their moisture content by the intensity ratio of H_α and Mg lines