Slow Accumulation and Transfer and Radiostrontium by Young Loblolly Pines (pinus Taeda L.)

Stems of seven young loblolly pines on the Savannah River Plant Reservation, South Carolina, were each inoculated with 3.28 x 10 3 μCi of radiostrontium. Accumulation of radiostrontium in foliage continued for 13 months after inoculation, when a maximum of 1.27 x 10 3 μCi/tree was attained. Radiostrontium concentration was consistently higher in lower crown foliage than in upper crown foliage, and higher in second—year needles than new needles. There was little evidence of basipetal translocation of radiostontium to roots. About 2% of the maximum foliage burden of radiostrontium was released by leaching during the 16 months following inoculation. Radioactivity of rainwater falling through crowns was best correlated with needle radioactivity, but was also inversely correlated with intensity of precipitation. Transfer of leached radiostrontium to the ground by rainwater flowing down stems was only 23% of that transferred by rainwater falling through tree crowns. Twenty per cent of the maximum foliar uptake was released by needles falling from the trees. The inoculated pines accumulated three times more radiostrontium in foliage than they released by needle fall and leaching. After 16 months 94% of the radiostrontium released from the inoculated trees was in litter and only 4.6% in mineral soil. Radiostrontium transferred to soil was generally confined to the top 2.5 cm where feeder roots are most abundant, but less than 10% of the radionuclide accumulated in soil was in roots. Accumulation in soil and roots closely approximated input from needle fall and foliar leaching, indicating that there was negligible input of basipetally translocated radiostrontium and negligible output due to leaching to subsoil, runoff, blowing away of litter, or recycling. The radiostrontium burden of a pine forest might be reduced considerably by removal of litter after contaminated needles have fallen.