Annual tritium exposures were reconstructed using tree cores from Pinus jeffreyi and Eucalyptus globulus near a tritiated water vapor release stack. Both tritium (H-3) and carbon-14 (C-14) from the wood were measured from milligram samples using accelerator mass spectrometry. Because the annual nature of the eucalyptus tree rings was in doubt, C-14 measurements provided growth rates used to estimate the age for H-3 determinations. A 30-yr comparison of organically bound tritium (OBT) levels to reported H-3 release data is achieved using OBT measurements from three trees near the stack. The annual average H-3,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 H-3 discharge patterns. References: 18
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