Determination of 241Am in sediments by direct counting of low-energy photons

A method is described for the non-destructive measurement of 241Am in sediments. The procedure involves direct counting of the 59.6-keV γ-ray emission of 241Am. The dependence of self-absorption of this low-energy γ-ray on sample density is accounted for by a simple technique utilizing direct γ-ray transmission measurements on the sample and efficiency calibration standard. Measurements on five sediment and soil reference materials show that the technique provides a detection limit of about 1 mBq/g for a 2.5 x 105s count. The utility of the technique in environmental studies is illustrated through results of 241Am measurements on a 210Pb-dated Lake Ontario sediment core. (author)