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Description
Hard mineralized tissues such as ivory represent valuable archives of environmental and biological information and are frequently the only available material in archaeological, environmental, and forensic investigations. In addition to age determination, which is essential for assessing the legality of ivory artefacts, information on geographic origin and dietary history is crucial for conservation research and anti-poaching efforts. These parameters can be reconstructed through a combination of elemental and isotopic analyses.
This study presents a complementary analytical approach combining spatially resolved Laser-Induced Breakdown Spectroscopy (LIBS) with Accelerator Mass Spectrometry (AMS) for the investigation of strontium distribution and isotopic composition in ivory samples.
LIBS was employed to determine spatially resolved Ca/Sr ratios across ivory cross-sections. In the LIBS technique, a short, high-energy laser pulse is focused onto the sample surface, leading to rapid local heating, micro-ablation, and vaporization of nanogram to microgram quantities of material. The ablated material forms a transient high-temperature plasma plume. During plasma cooling, excited atoms and ions emit characteristic optical emission lines that are spectrally resolved for qualitative and quantitative elemental analysis. This approach enables micrometer-scale mapping of elemental distributions with minimal sample preparation and quasi-nondestructive character. The obtained LIBS maps revealed a periodic structure in strontium distribution, reflecting biological growth increments. Variations in Ca/Sr ratios between samples indicate differences in environmental strontium availability and dietary intake. The Sr/Ca ratio was evaluated from the ratio of Gaussian-fitted integrated intensities of the Sr I 460.7 nm and Ca I 452.7 nm emission lines. For radiochemical characterization, isotopic ratios $^{88}\mathrm{Sr}/^{90}\mathrm{Sr}$ were determined by AMS. The presence of $^{90}\mathrm{Sr}$, a long-lived anthropogenic fission product, provides information related to nuclear fallout and environmental contamination history, while the stable isotope $^{88}\mathrm{Sr}$ serves as a reference for total strontium normalization. A correlation between the AMS-derived isotopic ratios and the LIBS-determined Ca/Sr values enabled estimation of total strontium concentrations and cross-validation of elemental quantification. Additionally, $^{14}\mathrm{C}$ analysis was performed to determine the age of the ivory samples, providing chronological context necessary for forensic and legal assessment.
The integration of spatially resolved elemental mapping (LIBS) with highly sensitive isotopic analysis (AMS) represents a powerful radiochemical–analytical strategy for the investigation of ivory. This combined methodology allows simultaneous evaluation of growth-related elemental patterns, environmental isotopic signatures, and chronological information. The approach expands the application of radiochemical techniques in cultural heritage studies and contributes to improved provenance determination and monitoring of illegal ivory trade.