Results

We detected the distribution of decay tracks from several radioactive isotopes of small sizes on surface of soil and plants collected in a 30-km radius of Chernobyl (Fig. 18.1) and distribution 241Am by tissues of the plant Arabidopsis thaliana which grown at contaminated 241Am soil with specific radioactivity 105 Bq/kg in laboratory conditions (Fig. 18.2). The number of radiation tracks appearing on upper leaves (Figs. 18.1a and 18.2a) of phase rosette differed from leaves of the top apex (1b and 2b) of the plants white blow (Erophila verna (L.) Bess.) from Yaniv (1) and Chistogalovka (2), respectively. As shown in Fig. 18.2, the experiments under laboratory conditions reveal alpha-tracks from 241Am decay in apical meristem of the Arabidopsis thaliana.

The transfer coefficient (TC) is a ratio of specific plant activities (kBq/kg) to specific activity of soil (kBq/kg). It characterizes movement of a radionuclide from the plant root to its vegetative parts. The TC calculated for radionuclide 137Cs and 90Sr revealed that fallout of these isotopes in the environment introduces additional contamination for top plants and those grown under laboratory conditions (Table 18.2). These experiments with soybean seedlings indicate that the TC for a vegetative plant path (0.008) was less than for top soybeans (0.019) under Chernobyl conditions. But for plants grown at Chistogalovka, the TC for radionuclide 137Cs was 9.2 times greater than the Chernobyl samples. This is possible by foliar uptake of plant radioactivity micro- or nano-particles on leaves which move freely in the environment. There may be some dissipation of "hot" particles following the Chernobyl accident under influence of biotic and abiotic factors in soybean seedling resulting in uptake of radionu-clide by foliar pathway in plants grown at Chistogalovka [8]. Our experimental data confirms that radioactivity fallout in the environment influenced the TC. As a result, the tracks reserve amount on the apex of a shoot and flower were observed.

After rainfall, isotopes accumulate on the surface of plants, soil, and water. In time, the dead plants and contaminated soil may be transported by erosion and settle with fallout to the bottom of the reservoirs. We conducted a risk assessment a b

Fig. 18.1 Detection of radionuclide nano- and micro- sizes particles from soil Yaniv (1), from Chistogalovka (2), on surface of leaves (a) and top shoot apical meristem (b) of the plant white blow Erophila verna L.

based on genotoxicity effects of contamination with radionuclide 137Cs and 90Sr water and soil on transgenic lines Arabidopsis thaliana L. and compared this data with Allium-assay and Tradescantia-stamen-hair- assay (Table 18.3). Three plant assays (Arabidopsis GUS-gene, Allium chromosome aberrations and Tradescantia stamen hair mutations) are used to evaluate the genotoxicity of water reservoirs and soil sites from Chernobyl and Kyiv regions [5, 9].

Soybean Apical Meristem
Fig. 18.2 Alpha-track distribution in low level layer of the leave tissues (a) top shoot apical meristem, (b) of the plant Arabidopsis thaliana grown in contaminated soil with radionuclide 241Am in laboratory conditions where fallout of radionuclide contaminated dust was absent

Table 18.2 Measurement of radionuclide 137Cs (Bq/kg) and 90Sr (Bq/kg) for soil and soybean plants grown at the Chistogalovka village field experimental area, Chernobyl site, and under laboratory conditions. TC is the transfer coefficient for isotopes 137Cs and 90Sr

Content of radionuclide, Bq/kg

Site grow soybean plant

137Cs

90Sr

TC for 137Cs TC for 90Sr

Top soybean (Chernobyl) Chernobyl soil activity Top soybean (Chistogalovka) Chistogalovka soil activity Top soybean (laboratory experiments) Soil activity in laboratoryCondition

27 ± 2 1,414 ± 71 3,600 ± 144 20,650 ± 1,050 13 ± 5

1,720 ± 170 550 ± 55 54,000 ± 2,800 5,180 ± 550 12 ± 2

0.019

0.174

0.008

Table 18.3 Comparison of radioactivity in lakes, river, and soil using three test-systems (1) Arabidopsis GUS-gene-assay, (2) Allium-chromosome aberration-assay, and (3) Tradescantia-stamen-hair- assay

Samples

Radioactivity 137Cs, Bq/l (Bq/kg)

Yield mutation, %

Level of reliability, P

GUS-gene activity in transgenic line BAR/BinAR/RPD3-9/5 of Arabidopsis thaliana L.

Glyboke Lake 6.27

Pripyat River 0.07

Dnipro River (control) 0.02

Control (soil from Kyiv region) 110

Soil from Chernobyl 1,528

Soil from Kopachi 30,727

Soil content only 241Am 105 Bq/kg

1.97 ± 0.10 0.25 ± 0.05 0.21 ± 0.05 0.21 ± 0.05 0.25 ± 0.05 2.05 ± 0.15 0.53 ± 0.08

<0.01 <0.05 <0.05 <0.05 <0.05 <0.01 <0.05

Level of chromosome instability Allium cepa L. cells induced by waters from reservoirs

Control 0.01

Telbin Lake 0.06

Verbne Lake 0.02

Berizka Lake 0.02

Pushcha-Vodycja Lake 0.02

Dnipro River 0.02 Mutations induced in Tradescantia-SH assay

Control 1 0.02

Telbin Lake 0.06

Verbne Lake 0.02

Berizka Lake 0.02

Dnipro River 0.02

Dnipro River 1 0.02

1.93 + 0.45 3.52 + 0.57 5.85 + 0.75 2.35 + 0.56 3.65 + 0.65 2.54 + 0.71

0.025 ± 0.024 0.296 ± 0.082 0.018 ± 0.018 0.249 ± 0.051 0.109 ± 0.045 0.104 ± 0.035

<0.05 <0.01 <0.05 <0.01 < 0.01 < 0.05

All samples taken from lakes revealed mutagenicity in Arabidopsis GUS-gene, Allium or Tradescantia assays. At the same time, only two of six probes of river soils were mutagenic. We supposed that local chemical pollution or relief features determined these effects. Studying the Arabidopsis GUS-gene-assay we found genotoxicity in water samples from lakes Glyboke and Telbin. By contrast, the samples taken from the Dnipro river did not show any mutagenic effects. Our experiments demonstrate that the lakes are more polluted by mutagens than river sites.

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