Particulate matter from water moss of a large Siberian river: Morphometric, mineral, elemental and radionuclide composition

Particulate matter trapped by tufts of water moss Fontinalis antipyretica inhabiting fast flowing waters of the Yenisei River (Siberia, Russia) contaminated with artificial radionuclides has been studied as a potential monitor of radioactive releases to the river. Particulate matter, which was removed from wet tufts of water moss of the Yenisei by rinsing them in water, constituted at least 38% of bulk dry weight of the moss biomass sample and was similar in the contents of chemical elements, minerals, organic matter, and artificial radionuclides to bottom sediments of the Yenisei. Considerable bulk percentages of artificial radionuclides in the sample of water moss, 77% of 137Cs, 44% of 60Co, 41% of 152Eu, 55% of 154Eu, 66% of 241Am, and 34-36% of plutonium were associated with extracellular particles. The comparative study and correlation analysis suggested that 137Cs was mainly associated with mineral particles trapped by moss and that organic matter was responsible for binding plutonium in samples of water moss. Consequently, analysis of extracellular particles of water moss can provide data on contents and speciation of radionuclides transported by water current. Although a considerably high proportion of particulate matter had been washed out from tufts of water moss, some extracellular mineral particulate material and a large number of epiphytic diatoms remained attached to leaves of water moss. Our study proves that particulate matter trapped by water moss can be used as an informative monitor to trace radioactive pollutants transported by water current in running waters deficient in bottom sediments and potential biomonitors.

A comparative study of biota and sediments as monitors of plutonium in the Yenisei River (Siberia, Russia)

MOX-fuel production and spent nuclear fuel reprocessing started recently at the Mining-and-Chemical Combine (MCC, Zheleznogorsk, Russia) have caused an increase in controlled releases of plutonium to the Yenisei River. In this study, we analyzed time-dependent trends of plutonium (^239,240Pu and ²³⁸Pu) in biota and bottom sediments of the Yenisei during 2008-2019, to estimate comparatively the potential of abundant representatives of biota as bio-monitors of contamination of the Yenisei by plutonium. Gamma-emitting radionuclides (⁴⁰ K; ⁶⁰Co; ¹³⁷Cs; ¹⁵²Eu; ²⁴¹Am) were measured in environmental samples of the Yenisei as well. Samples of bottom sediments, water moss (Fontinalis antipyretica), shining pondweed (Potamogeton lucens), caddisfly larvae with casings (Apatania crymophila), and amphipods (Eulimnogammarus viridis and Palaseopsis cancelloides) were collected downstream and upstream of the radioactive discharge site. Environmental samples of the Yenisei collected downstream of the radioactive discharge site differed considerably in activity concentrations of plutonium but were similar in time-dependent trends of plutonium, reflecting the trends of annual discharges of plutonium. In 2018, the year of a sharp increase in controlled discharge of plutonium, the concentration of ^239,240Pu in water moss (26 Bq kg^-1 d.w.) was higher than in sediments (14 Bq kg^-1 d.w.). In other years, the highest activity concentration of ^2391,240Pu was observed in bottom sediments. In view of the higher magnitude of increase in plutonium concentration, water moss and shining pondweed can be considered as more sensitive indicators of increased fresh releases of plutonium than bottom sediments. Taking into account the food-related mechanism of plutonium uptake by amphipods, this representative of biota can be regarded as a sensitive monitor of bioavailable plutonium in the Yenisei.