EA-IRMS: Tracing geographical origin of timber using oxygen and hydrogen isotope fingerprints

Importance of the topic

The illegal trade in high‐value timber threatens both economic stability and environmental health, driving deforestation and endangering biodiversity. Reliable methods to verify the geographic origin of wood are essential to enforce regulations, support sustainable forestry, and combat illicit trafficking. Combining oxygen (δ18O) and hydrogen (δ2H) isotope fingerprints offers a scientifically robust tool to trace provenance and validate labeling of timber products.

Objectives and overview of the study

This application brief demonstrates how isotope ratio mass spectrometry (IRMS) can establish distinctive O and H isotope signatures in tree bark. Key objectives include:

• Assessing the precision and accuracy of combined δ18O and δ2H analysis on certified reference materials.
• Comparing isotope fingerprints of 25 diverse bark samples from multiple geographic regions.
• Illustrating how combined isotope data enable classification of wood origin.

Methodology and used instrumentation

Approximately 0.3 mg of finely ground tree bark was placed in silver capsules, dried at 80 °C to remove moisture, and loaded into the MAS Plus autosampler. Samples entered the EA IsoLink pyrolysis reactor to produce CO and H₂ gases, which were measured by the DELTA V IRMS. All isotope ratios were calibrated against VSMOW and GISP standards, and repeatability was assessed with four replicates (1σ).

Instrumentation used

• Thermo Scientific™ EA IsoLink™ IRMS System
• Thermo Scientific™ MAS Plus Autosampler
• Thermo Scientific™ DELTA V™ Isotope Ratio Mass Spectrometer

Key results and discussion

Analysis of USGS reference materials 54–56 showed close agreement with certified values:

• USGS 54: δ2H measured −151.64 ‰ (certified −150 ‰), δ18O measured −18.23 ‰ (certified −17.8 ‰)
• USGS 55: δ2H measured −27.20 ‰ (certified −28 ‰), δ18O measured −18.95 ‰ (certified −19.1 ‰)
• USGS 56: δ2H measured −44.11 ‰ (certified −44 ‰), δ18O measured −26.97 ‰ (certified −27.2 ‰)

Combined isotope fingerprints of 25 bark samples revealed distinct clusters corresponding to known geographic regions. Coastal species exhibited heavier isotopic values compared to inland or high‐altitude species, reflecting regional rainfall patterns and local environmental factors.

Benefits and practical applications

Oxygen and hydrogen isotope fingerprinting offers laboratories:

• High confidence in wood origin verification to enforce legal regulations.
• Rapid, low‐cost analysis with full automation capability.
• Flexibility to handle diverse sample matrices and evolving analytical requirements.
• Support for sustainability certification and anti‐fraud measures in timber supply chains.

Future trends and applications

Advancements likely to enhance isotope‐based provenance studies include:

• Development of comprehensive global isotope databases covering diverse tree species and regions.
• Integration with multivariate statistical models and machine learning for automated classification.
• Expansion to additional stable isotopes (e.g., carbon, nitrogen) for multi‐element fingerprinting.
• Miniaturized and field‐deployable IRMS platforms for on‐site screening.

Conclusion

Combined δ18O and δ2H analysis via EA‐IRMS provides a powerful framework to trace geographic origin of timber. The demonstrated precision, accuracy, and sample throughput support enforcement of forestry regulations, promote legal trade, and contribute to environmental conservation efforts.

References

1. INTERPOL. Forestry crime. International Criminal Police Organization.
2. Gori Y., Wehrens R., La Porta N., Camin F. (2015). PLoS ONE, 10, e0118941.
3. Dansgaard W. (1964). Tellus, 16, 436–468.
4. Dawson T.E., Siegwolf R. (2007). Stable Isotopes as Indicators of Ecological Change. Academic Press.