16.12. Characteristics of soil-to-plant transfer of elements relevant to radioactive waste in boreal forest

 

Public examination of a doctoral dissertation in the field of environmental science

Doctoral candidate: M.Sc. Päivi Roivainen 

Date and venue: 16.12.2011, at 12, MET, Mediteknia, Kuopio campus 

ABSTRACT 

The use of nuclear energy generates large amounts of different types of radioactive wastes that can be accidentally released into the environment. Soil-to-plant transfer is a key process for the dispersion of radionuclides in the biosphere and is usually described by a concentration ratio (CR) between plant and soil concentrations in radioecological models. Our knowledge of the soil-to-plant transfer of many radionuclides is currently limited and concerns mainly agricultural species and temperate environments.The validity of radioecological modelling is affected by the accuracy of the assumptions and parameters used to describe soil-to-plant transfer. 

This study investigated the soil-to-plant transfer of six elements (cobalt (Co), molybdenum (Mo), nickel (Ni), lead (Pb), uranium (U) and zinc (Zn)) relevant to radioactive waste at two boreal forest sites and assessed the factors affecting the CR values. May lily (Maianthemum bifolium), narrow buckler fern (Dryopteris carthusiana) and blueberry (Vaccinium myrtillus) were selected as representatives of understory species, while rowan (Sorbus aucuparia) and Norway spruce (Picea abies) represented trees in this study. 

All the elements studied were found to accumulate in plant roots, indicating that separate CR values for root and above-ground plant parts are needed. The between-species variation in CR values was not clearly higher than the within-species variation, suggesting that the use of generic CR values for understory species and trees is justified. No linear relationship was found between soil and plant concentrations for the elements studied and a non-linear equation was found to be the best for describing the dependence of CR values on soil concentration. Thus, the commonly used assumption of a linear relationship between plant and soil concentrations may lead to underestimation of plant root uptake at low soil concentrations. Plant nutrients potassium, magnesium, manganese, phosphorus and sulphur were found to have major effects on the soil-to-plant transfer of Co, Mo, Ni, Pb, U and Zn.

The doctoral dissertation of M.Sc. Päivi Roivainen entitled Characteristics of soil-to-plant transfer of elements relevant to radioactive waste in boreal forest will be examined at the Faculty of Science and Forestry. The opponent in the public examination is Professor Jukka Lehto, the University of Helsinki and the custos is Professor Jukka Juutilainen of the University of Eastern Finland.

Photo available for download at http://www.uef.fi/vaitoskuvat

Contact: Päivi Roivainen, tel. + 358 40 355 3390, paivi.roivainen@uef.fi

Publishing year: 2011

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