Accumulation of 242Pu by a macrophyte of the Yenisei River (Elodea canadensis) in laboratory experiments

The study addresses 242Pu accumulation by Elodea canadensis, one of the abundant species of submerged plants in the Yenisei River. 242Pu in water samples of the “Elodea – Yenisei River water” model system and in the biomass fractions was determined α-spectrometrically, following radiochemical recovery of 242Pu using 236Pu – a chemical yield tracer. The experiments on accumulation of 242Pu by Elodea biomass showed that the activity concentration of 242Pu can reach 21 ± 2 Bq/g dry wt, with the concentration factor for 242Pu 13100 ± 2100 L/kg dry wt. Results of chemical fractionation proved that during the first few hours of the experiment 242Pu contained in Elodea was mainly concentrated in the exchangeable and the adsorbed fractions of biomass (about 100%). As Elodea biomass accumulated 242Pu, the absolute amount of 242Pu in the exchangeable and the adsorbed fractions remained almost unchanged, although the portion of 242Pu tightly bound to biomass increased. At the end of the experiment, on day 7, 242Pu tightly bound to biomass (fractions of organics and mineral residue) constituted 43–63% (in different experiments) of the total 242Pu in the biomass.