KYT 14C - Fate of radionuclide 14C in soil-plant-atmosphere continuum

Principal investigator:  Assoc. Prof. Christina Biasi

Funding period: 2010-2011 (Public Nuclear Waste Management Program in Finland (KYT 2010))

Radiocarbon (14C) has been identified as one of the key radionuclides relevant to deep geological disposal of spent nuclear fuel. Though a basic understanding exists on the dynamics of carbon in terrestrial ecosystems, there are still major data gaps. Specifically, the amount of 14C possibly taken up by the plants is largely unknown, and differences between assumptions lead to large differences in model results on the behaviour of 14C.  It is difficult to follow the fate of soil-derived carbon with traditional methods, since they carry no information on the origin of CO2. Our innovation in this project is to use  a recently planted cut-away peatland where the plants have a modern 14C signature and the left-over peat is old, being thus naturally depleted in 14C. This difference in 14C content between plants and soil, the largest  found in terrestrial ecosystems, will be used to trace carbon  from underground sources in plants, CO2 and soil biota. This innovation has not yet been used before in 14C-studies. The relative roles of  roots  and sub-canopy assimilation in uptake of soil carbon  will be further determined  in laboratory experiments. Through these unique experimental set-ups a better understanding of migration of 14C into biosphere/atmosphere and better basis for environmental risk assessment of radioactive waste will be provided.