Effect of industrial pollution on behaviour of radionuclides in forest ecosystems

To investigate how and to what extent industrial pollution affects the behaviour of radionuclides in forest ecosystems, studies were conducted in the vicinity of two Cu-Ni smelters: one in a pine forest at Harjavalta, Finland, and the other in a spruce forest at Monchegorsk, Russia. Industrial pollution had significant effects on the distribution of radionuclides in soil horizons. With the increase in pollution towards the smelter, radionuclides were accumulated more in the litter layer because the conversion of litter into organic material was diminished due to inhibited microbial activity. As a result, the organic layer contained less radionuclides towards the smelter. The effect of industrial pollution on soil-to-plant transfer was complex. The effect varied with radionuclide, plant species and also on forest type. For 137Cs, soil-to-plant transfer decreased significantly as industrial pollution increased in pine forest, whereas the decrease was less pronounced in spruce forest. Root uptake of 239,240Pu by plants is extremely small, and plant contamination by resuspended soil is an important factor in considering the soil-to-plant transfer of this radionuclide. In spruce forest, more plutonium was transferred into plants when pollution load increased due to resuspension of litter particles, which contained higher concentrations of plutonium in the vicinity of the smelter. Soil-to-plant transfer of plutonium was much less affected in pine forests contaminated with industrial pollution. This research clearly indicates the sensitivity of the northern forest ecosystem to inorganic pollutants. Prediction of the soil-to-plant transfer of radionuclides in industrially polluted forest ecosystems requires detailed information on the total deposition, vertical distribution of radionuclides in soil, soil microbiological factors, other soil parameters as well as the rooting depths of the plants. (LN)