Effect of industrial pollution on soil-to-plant transfer of plutonium in aBoreal forest

Plutonium in a forest ecosystem was studied at different distances from the copper and nickel smelter at Monchegorsk, Kola Peninsula, Russia. Soil and plant samples were collected 7 (site A), 16 (B), 21 (C) and 28 (D) km from the smelter and at a reference site situated in Finland, 152 km from Monch egorsk. The deposition of Cu in litter and in the organic layer decreased f rom 10700 mg/m(2) at site A to 33 mg/m(2) at the reference site, the deposi tion of Ni from 14300 to 29 mg/m(2). From the reference site to site A, the volume of the litter layer increased almost five-fold. Most of the Pu-239, Pu-240 in soil was found in the organic layer and in the litter layer. When industrial pollution increased, the content of Pu-239,Pu-240 in the litter layer increased (from approx. 0.5 at site D to 15 Bq/m(2) at site A) where as, that in the organic layer decreased (from approx. 20 at site D to 5 Bq/ m(2) at site A). Four different plant species typical for the subarctic env ironment were collected at each sampling site: Deschampsia flexuosa (forest hair grass); Empetrum nigrum (crowberry); Vaccinium myrtillits (blueberry) ; and Vaccinium vitis idaea (lingonberry). The concentration of Pu-239,Pu-2 40 increased with pollution in Deschampsia flexuosa (from approx. 2 at site D to 7 mBq/kg at site A), Empetrum nigrum (from approx. 3 at site D to 14 mBq/kg at site A) and Vaccinium myrtillus (from approx. 1 at site D to 8 mB q/kg at site A). In Vaccinium vitis idaea, the Pu concentration did not hav e any clear trend of association with pollution. With the exception of Vacc inium vitis idaea, the aggregated transfer factors of plutonium (m(2)/kg) f or the plants studied increased almost ten-fold from site D to site A, the range being 3 X 10(-5)-3 X 10(-4) m(2)/kg for Deschampsia flexuosa, 7 X 10( -5)-5 X 10(-4) m(2)/kg for Empetrum nigrum and 3 X 10(-5)-3 X 10(-4) m(2)/k g for Vaccinium myrtillus. The most likely explanation for the higher trans fer factors of plutonium near the smelter is contamination of the plants by litter rather than root uptake. (C) 2001 Elsevier Science B.V. All rights reserved.