Reconstructing Tritium Exposure Using Tree Rings at Lawrence Berkeley National Laboratory California

摘要

Annual tritium exposures were reconstructed using tree cores from Pinus jeffreyi and Eucalyptus globulus near a tritiated water vapor release stack. Both tritium (³H) and carbon-14 (¹⁴C) from the wood were measured from milligram samples using accelerator mass spectrometry. Because the annual nature of the eucalyptus tree rings was in doubt, ¹⁴C measurements provided growth rates used to estimate the age for ³H determinations. A 30-yr comparison of organically bound tritium (OBT) levels to reported ³H release data is achieved using OBT measurements from three trees near the stack. The annual average ³H, determined from atmospheric water vapor monitoring stations, is comparable to the OBT in proximal trees. For situations without adequate historical monitoring data, this measurement-based historical assessment provides the only independent means of assessing exposure as compared to fate and transport models that require prior knowledge of environmental conditions and ³H discharge patterns.