Accumulation of americium-241 in the biomass of aquatic plants of the Yenisei river: experimental study

Due to the operation of the Mining-and-Chemical Combine (Krasnoyarsk-26), which has been manufacturing weapons-grade plutonium for several decades, the Yenisei River is contaminated with transuranic elements (including 241Am). 241Am was found in the riverside soil, sediment and in the biomass of aquatic plants (Bolsunovsky et al., 1999, 2002). Aquatic plants are an important link in the migration of radionuclides in an aquatic ecosystem. In laboratory experiments, we investigated accumulation of 241Am by the submerged macrophyte from the Yenisei River: the pond weed (Elodea canadensis) and the aquatic moss (Fontinalis antipyretica), and release of 241Am from the biomass. The content of 241Am was measured on a Canberra (USA) gamma-spectrometer. The experiments showed that specific accumulation and concentration factors of 241Am in the plants were in inverse proportion to their biomass. We obtained new data on release of 241Am from the biomass of macrophyte. Americium-241 was more firmly fixed in the biomass of the aquatic moss. In 12 months, the biomass of the aquatic moss released about 30% of the initial americium activity into the water. To compare, the biomass of the pond weed released into the water medium up to 64% of the initial 241Am activity in 1.5 4 months. The release rate was dependent on the decomposition rate of the plant biomass. The experiments showed that submerged macrophyte of the Yenisei River can accumulate considerable activities of 241Am and retain americium for long periods of time in biomass. (author)