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Accumulation of Cesium-137 and Strontium-90 in ponderosa pine and Monterey pine seedlings

Entry, J.A., Rygiewicz, P.T., Emmingham, W.H.
Journal of environmental quality 1993 v.22 no.4 pp. 742-746
land restoration, Pinus ponderosa, Pinus radiata, cesium, strontium, duration, polluted soils, afforestation, environmental exposure
Because ponderosa pine [pinus ponderosa (Dougl. ex Laws)] and Monterey pine (P. radiata D Don) have exceptionally fast growth rates and their abscised needles are not readily dispersed by wind, these species may be valuable for removing radioisotopes from contaminated soils. Ponderosa and Monterey pine seedlings were tested for their ability to accumulate 137Cs and 90Sr--characteristic radioisotopes of nuclear fallout--from contaminated soil. Seedlings were grown for 3 mo in 165 cm3 sphagnum peat moss/perlite (1:1 V/V) in a growth chamber. In Exp. 1, seedling accumulation of 137Cs and 90Sr after 1 mo of exposure was measured. In Exp. 2, seedling accumulation of the radioisotopes during different-length exposures was measured. Seedling accumulation of 137Cs and 90Sr at different concentrations of the radioisotopes in the growth medium was measured in Exp. 3. Ponderosa pine accumulated 6.3% of the 137Cs and 1.5% of the 90Sr present in the growth medium after 1 mo; Monterey pine accumulated 8.3% of the 137Cs and 4.5% of the 90Sr. Accumulation of 137Cs and 90Sr by both coniferous species was curvilinearly related to duration of exposure. Accumulation of 137Cs and 90Sr by both species increased with increasing concentration in the growth medium and correlated curvilinearly with radioisotope concentration in the growth medium. Large areas throughout the world are contaminated with 137Cs and 90Sr as a result of nuclear weapons testing or atomic reactor accidents. The ability of trees to sequester and store 137Cs and 90Sr introduces the possibility of using reforestation to remediate contaminated soils.