Abstract
Studied water bodies of left-bank flood-lands of Prypyat’ river are located in the 10-km zone of Chornobyl NPP. They are among the most heavily contaminated aquatic objects in the exclusion zone. Higher aquatic plants represent the majority of hydrobionts in those water bodies and are characterized by high productivity and ability to actively absorb radionuclides . Occupying the dominating place among other components of freshwater biocenosis according to their biomass, higher aquatic plants play an essential role in processes of radionuclides distribution in water ecosystems. They serve as a natural “biofilter” that accumulates radionuclides and by that way removes them temporarily from the water ecosystem’s matter turnover. Diversity of aquatic plants species results in a wide range of radonuclides uptake. Maximal values of radionuclides content in highest aquatic plants were observed for Glyboke Lake. Apparently, those phenomena occurred due to high concentrations of radionuclides in water and bottom deposits. The lake is covered with macrophytes. They grow intensively and occupy almost half of the lake’s water table. About 25% of water plants consist of air-water species and about 75% include water species. A major part of highest water plants grow in the dam area and on the lake’s perimeter with reed mace (Typha angustifolia) and glyceria (Glyceria maxima) as dominants. Quite frequently the sedge (Carex sp.) was also identified on the lake’s perimeter. The main stretch of the lake was covered with yellow pond lily (Nuphar lutea L. Smith) and Stratiotes aloides L. in a ratio of 1:2 [1]. Groups of Stratiotes aloides L. were quite powerful and as a rule with hornwort (Ceratophyllum demersum L.) in lower tier. All radionuclides concentrations are given in Bq/kg of air-dry weight. In 1998 concentrations of Sr in plants varied from 7.2 to 58.2 kBq/kg, and Cs from 2.3 to 411 kBq/kg. Values of the upper limit of Sr content in plants from other water bodies that are located in flood-lands, varied from 21.6 to 43.2 kBq/kg. Concentrations of Cs in water plants from water objects were found to be within following limits: Daleke Lake – 2.2 – 96.4 kBq/kg; Krasnyans’ky Branch before the dam and in cold section of Chornobyl NPP cooling pond – 0.68 – 53.8 kBq/kg; warm section of Chornobyl NPP cooling pond and Krasnyans’ky Branch behind the dam – 1.2 – 27.4 kBq/kg. Minimal values of concentrations were observed in aquatic plants from Prypyat’ river (Chornobyl town). Concentrations of Sr varied from 0.03 to 2.9 and Cs from 0.06 to 1.36 kBq/kg. In Fig. 1-9 the dynamics of Sr and Cs content in specific aquatic plant species that were available for systematic sampling for the period of 1989-2000 is presented. Gradual decreasing of Sr and Cs concentrations in aquatic plants of both sections of Chornobyl NPP cooling pond is clearly seen (fig. 1 and 2).
Published Version
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