Measurement of technetium-99 in soil samples collected in Marshall Islands

Extraction techniques for recovery of technetium-99 (99Tc) for ICP-MS measurements were evaluated using soil samples collected from the Marshall Islands. The results of three different extraction techniques were compared: (M1) acid leaching of Tc from ashed soil; (M2) acid leaching of Tc from raw dry soil; and (M3) Tc volatilization from ashed soil using a combustion apparatus. Total Tc recoveries varied considerably between the extraction techniques but each method yielded similar analytical results for 99Tc. Applications of these extraction techniques to a series of environmental samples and ICP-MS measurements have yielded first data on the 99Tc content of Marshall Islands soil samples contaminated with close-in radioactive fallout from nuclear weapons testing. The 99Tc activity concentration in the soil samples ranged between 0.1 and 1.1 mBq/g-dw. The limit of detection for 99Tc by ICP-MS was 0.17 mBq per sample or 0.014 mBq/g-dw under standard operating conditions. (author)