Laser induced breakdown spectroscopy for elemental analysis in environmental, cultural heritage and space applications: a review of methods and results

Abstract

Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, so as fast multi-elemental response, micro-destructiveness, instrumentation portability, have rendered it particularly suitable for analytical applications in the field of environmental science, space exploration and cultural heritage. This review reports and discusses LIBS achievements in these areas and results obtained for soils and aqueous samples, meteorites and terrestrial samples simulating extraterrestrial planets, and cultural heritage samples, including buildings and objects of various kinds.

Keywords: Laser Induced Breakdown Spectroscopy (LIBS); cultural heritage; elemental analysis; meteorites; optical emission; soils; space exploration.

Figure 1.

Block diagram of a typical experimental set-up for Single Pulse LIBS experiments. The acronym PG stands for Pulse Generator.

Figure 2.

Sn and Pb weight percentages (w%) in a fragment of a bronze basin as a function of the number of laser shots focused on the sample. Each spectrum resulted from 100 accumulations, with laser energy 1.5 mJ and focused laser spot of diameter 200 μm. The sample was drilled through from side to side, displaying a significant depletion of Sn in the external layers.

Figure 3.

(a) Bar charts of Sn and Pb weight percentages at increasing sampling depth in the four nailed parts constituting the bronze belt samples A; (b) spectra of the zone repaired from the external layers 2(a,b,c) to the internal ones (2(d,e,f), used for the bar chart in Figure 3 (a)). The spectra from the external layers show typical features from the soil elements (Si, Mg) and were not used for the quantitative analysis, while increasing the sampling depth peaks of bronze components (Cu, Pb, Sn) appear. It is interesting to note that the spectrum 2(c) lacks the Sn peaks, which indicates some inhomogeneity in the alloy composition, and was therefore not used for the analysis.

Figure 4.

Calibration lines of Cr, Cu, Pb, V, Zn in samples of polluted soils and sewage sludge collected in various Italian regions.

Figure 5.

Anthropogenic index calculated with Cr emission intensities (line at 520.45 nm) for samples of polluted soils (S1, S2, S3, S4) and sewage sludge (SS). S1 and S2 are two loam soils from Apulia, Southern Italy; S3 a clay loam from Lombardy, Northern Italy; S4 a sandy clay loam from Marche, Central Italy.

Figure 6.

(a) Slab of Toluca iron meteorite (medium octahedrite, class IAB) displaying on its surface the peculiar Widmanstätten pattern; (b) weight percentage profile of Ni, Fe and Co across one lamella of the Widmanstätten structure of Toluca.