Qualitative Analysis and Plasma Characteristics of Soil from a Desert Area using LIBS Technique

Qualitative Analysis and Plasma Characteristics of Soil from a Desert Area using LIBS Technique

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collectedfrom different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parametersare studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. Theelectron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, aredetermined for all the collected samples. It is found that both Te and Ne vary from one desert area toother. This variation is due to the change of the elemental concentration in different desert areas that affectsthe sample’s matrices. Time dependent measurements have also been performed on the soil samples. Whilethe signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne andTe reach values of 4×1017cm-3and 9235 K, respectively, at 2.5 microsecond. The later indicate that theplasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS inthe remote on-line environmental monitoring application, by following up only the values of Ne and Tefor one element of the soil desert sample using an optical fiber probe.

In this work, laser induced breakdown spectroscopy (LIBS) is used to investigate soil samples collectedfrom different desert areas of Riyadh city in Saudi Arabia. Both qualitative analysis and plasma parametersare studied via the observed LIBS spectra. These experiments have been done using a Spectrolaser-7000system with 50 mJ fundamental wavelength of Nd:YAG laser and detection delay time of 1 microsecond. Many spectral lines are highly resolved for many elements like Al, Fe, Mg, Si, Mn, Na, Ca and K. Theelectron temperatures Te and electron densities Ne, for the constituent of generated LIBS plasma, aredetermined for all the collected samples. It is found that both Te and Ne vary from one desert area toother. This variation is due to the change of the elemental concentration in different desert areas that affectsthe sample’s matrices. Time dependent measurements have also been performed on the soil samples. Whilethe signal-to-base ratio (SBR) reached its optimal value at 1 microsecond, the plasma parameters Ne andTe reach values of 4×1017cm-3and 9235 K, respectively, at 2.5 microsecond. The later indicate that theplasma cooling processes are slow in comparison to the previously observed results for metallic samples. The observed results show also that in the future it is possible to enhance the exploitation of LIBS inthe remote on-line environmental monitoring application, by following up only the values of Ne and Tefor one element of the soil desert sample using an optical fiber probe.