The assessment of no adverse effect doses for plant populations chronically exposed to radionuclides of uranium and thorium decay series

Dose rates cause no adverse effects on natural populations of Pinus sylvestris L. and Vicia cracca L. inhabiting territories contaminated by uranium mill tailings and radium production wastes (Vodny settlement, Komi Republic) were determined. A significant increase in embryonic lethal mutation frequency in V. cracca legumes and decrease in seedlings survival rate as compared with control values were registered at dose rate equal to 1.67 mGy/day, that is 280 times higher than the one calculated for the reference site. The adverse effects in P. sylvestris expressed in increased frequency of chromosome aberrations in meristematic root tips and decreased reproductive capacity of seeds were determined at absorbed dose rate equal to 0.083 mGy/day. Data obtained show that the decrease in plant reproductive capacity in case of chronic exposure of radionuclides of uranium and thorium decay series can observe at lower weighted absorbed dose rates than in case of environmental contamination by artificial radionuclides.     

Genetic variance in Vicia cracca cenopopulation inhabiting site with enhanced level of natural radioactivity

The contribution of low dose rate ionizing radiation into genetic variance in Vicia cracca L. cenopopulation inhabiting high natural background territories more then 40 years quantity estimation was made. Incorporated in the aboveground parts of Vicia cracca 230Th determine both the level of intrapopulation genetic variance and the adaptive possibility. Significantly increased frequency of double fragments was revealed in root tips of plants inhabiting all experimental plots. This type of damages depends on 226Ra concentrations accumulated in the aboveground parts of Vicia cracca. External irradiation influences the embryonic lethals. It was found that the relative contribution on mutagenesis induced by ionizing radiation was significant and was about 3-5% of the total variance.     

The estimation of ionizing irradiation impact on Vicia cracca cenopopulations growing on the territory contaminated with the wastes of radium production

The radiation exposure on cenopopulations Vicea cracca L. growing on the territory contaminated with the wastes of radium production was estimated. The relationship between the chromosome aberration in seedlings root tip cells and irradiation dose was found to be linear. The significant cytogenetic effects in chronically irradiated Vicia cracca cenopopulation are observed at doses (equal to 0.006-0.7 Gy) 10 times upward the natural radiation background level. The reduced reproductive success (significantly increased embryonic lethal mutation level) is observed at weighted absorbed doses (equal to 0.2-0.7 Gy) up to 200-700 times higher than the natural radiation background level. It is showh, that the radiation hygienic standards of permissible exposure are noticeably stricter that the radioecological limits.     

Regularities of lateral distribution of uranium and thorium decay series radionuclides in the anthropogenically changed soils from the area of radium production waste storage

Cartographical investigations of the territory of radium production waste storage has shown some changes in lateral differentiation of radionuclides of uranium and thorium decay series to occur during 27 years (1981-2008). Those changes are caused mostly by flat denudation typical for fluvial terrace. At present radionuclides of uranium and thorium decay series are concentrated mostly in flood lands and relief depressions. At the same time, decrease in the radionuclide activity concentration in 0-20 cm soil layer is observed with changes in lateral distribution. Total stocks of 226Ra, 210Pb and 210Po within catena soils studied in the northern and southern parts of the waste storage decreased 3-6 times, 238U - 2 times, and did not significantly change in case of 232Th during 27 years. Nonetheless, most of the samples studied are referred to radioactive waste both according to Russian standards (SPORO-2002) and IAEA safety norms (IAEA, 2004).     

中国北方广布野豌豆细胞地理学研究

对中国北方8个产地的广布野豌豆Vicia cracca L.种群的核型进行了对比研究,发现不同种群的染色体数分别是12、14和24。支持12条染色体类型由14条染色体类型通过罗伯逊易位所形成的观点。12条染色体类型和24条染色体类型在植株外部形态上没有可识别的差异,在分类学上应作同一单元处理。14条染色体类型的植株具有形态上可以识别的性状,可作为变种或亚种处理。     

Comparative evaluation of 238U and 226Ra absorption by herbaceous and woody species under conditions of technogenic pollution

The results of studies on uranium and radium distribution in soil and vegetation at the territory contaminated by wastes of radium plant in 1930-1950 are presented. Specific activities of 226Ra and 238U in soil varied as 0.01-200 and 0.004-7.58 Bq/g per ash respectively. The radionuclides are mainly concentrated in the upper layer of soil profile. In the vegetation concentrations of 226Ra and 238U varied as 0.64-132 0.001-0.02 Bq/g per ash respectively. Among the woody species studied, Betula pubescens and Sorbus aucuparia are characterized by the highest absorption of radionuclides. For all plants studied a negative linear dependence is shown between logarithm of TF (TF = [226Ra, 238U in plant, Bq/g per ash]/[226Ra, 238U in soil, Bq/g per ash]) and logarithm of 226Ra and 238U concentrations in soil. The findings obtained can be used in modeling of biological absorption in radioecological investigations.     

Restoration of pine plantations after effect of ionizing radiation in the region of the accident at the Chernobyl Atomic Energy Station

The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in the Pinus sylvestris L. forest plantations from the zone of the accident at the Chernobyl nuclear power plant presented. Acute ionizing irradiation at doses > 1 Gy was shown to induce the formation of morphoses and depressed growth; at doses > 2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear (or close to linear) dose-effect relationship. Acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of sprouts obtained from seeds annually (1986-1998) collected in zones of slight, moderate, and strong damage of Pinus sylvestris L. are presented.     

Radiation-population monitoring of Pinus sylvestris L. in the zone of the Chernobyl power plant

Cytogenetic and genetic effects in populations of Pinus sylvestris L. suffered wiak, average, strong and sublethal radiation damage after the Chernobyl accident in 1986 were studied. The absorbed dozes for trees in these plantings were from 0.1 up to 20 Gy. It was shown that the amount of cells with chromosome aberrations in sprouts of seeds of a crop of 1993, are comparable with effects marked at once after accident in 1986. In 1997 and in 1998 the amount of cells with chromosome aberrations in sprouts of seeds in majority inspected plantings decreased to control values. The effect of adaptation was detected, when seeds of Pinus sylvestris L., gathered in 1997 from inspected trees, were exposed to additional 4 Gy gamma-radiation.     

Quantification of cyanamide contents in herbaceous plants

Cyanamide (NH2CN) is found in nature, although it has long been recognized as an industrial product. Distribution of cyanamide in the plant kingdom was investigated using a direct quantitative determination method to detect and measure cyanamide by stable isotope dilution gas chromatography-mass spectrometry (the SID-GC-MS method). The SID-GC-MS method proved to be a robust way to quantify cyanamide contents in the extracts of 101 species of herbaceous plants. The average recovery of cyanamide from all plants tested was 55.6+/-20.3%. Vicia villosa and V. cracca contained cyanamide at 369-498 microg/gFW and 3,460-3,579 microg/gFW respectively, while the other 99 species contained no detectable cyanamide (<1 microg/gFW). This result suggests that distribution of cyanamide in the plant kingdom is limited and uneven.     

4-Chloroindole-3-acetic acid and plant growth

4-Chloroindole-3-acetic acid (4-Cl-IAA) is a potent auxin in various auxin bioassays. Researchers have used 4-Cl-IAA as well as other halogenated auxins in biological assays to understand the structural features of auxins required to induce auxin mediated growth in plants. 4-Cl-IAA is a naturally occurring auxin in plants from the Vicieae tribe of the Fabaceae family; and 4-Cl-IAA has also been identified in one species outside the Vicieae tribe, Pinus sylvestris. The apparent function of the unique auxin 4-Cl-IAA in normal plant growth and development will be discussed with a focus on Pisum sativum and Vicia faba     

Patterns of divergence among conifer ESTs and polymorphism in Pinus sylvestris identify putative selective sweeps

Finding genes that are under positive selection is a difficult task, especially in non-model organisms. Here, we have analyzed expressed sequence tag (EST) data from 4 species (Pinus pinaster, Pinus taeda, Picea glauca, and Pseudotsuga menziesii) to investigate selection patterns during their evolution and to identify genes likely to be under positive selection. To confirm selection, population samples of these genes have been sequenced in Pinus sylvestris, a species that was not included in the EST data set. The estimates of branch-specific Ka/Ks (nonsynonymous/synonymous substitution rates) across all genes in the EST data set were similar or smaller than estimates from other higher plant species. There was no evidence for the traditional indication of positive selection, Ka/Ks above 1. However, several lines of evidence based on polymorphism patterns suggest that genes with high Ka/Ks (0.20-0.52) in the EST data set are in fact more affected by positive selection in P. sylvestris than genes with low Ka/Ks (0.01-0.04). The high Ka/Ks genes have a lower level of polymorphism and more negative Tajima's D than the low Ka/Ks genes. Further, in the high Ka/Ks group, the Hudson-Kreitman-Aguade test is significant. This suggests that the EST data set is a good starting point for finding genes under positive selection in conifers and that even moderate Ka/Ks values could be indicative of selection. A group of 5 genes with high Ka/Ks collectively show evidence for positive selection within P. sylvestris.     

The host plant range of the pea aphid subspecies Acyrthosiphon pisum ssp. destructor (Johnson) (Hom., Aphididae)

Abstract:  In order to establish the host range of the pea aphid subspecies, Acyrthosiphon pisum ssp. destructor , and hence from which plant species pea crops are likely to become infested, the performance of this aphid on different leguminous plants was assessed. The plant species used were: Lotus uliginosus , Medicago sativa , Melilotus officinalis , Ononis repens , Sarothamnus scoparius , Trifolium hybridum , Trifolium pratense , Trifolium repens , Vicia cracca and Vicia faba . Vicia faba and Trifolium hybridum were the plants on which aphids reached the greatest size, took the least time to reach maturity, and experienced the lowest mortality. The time taken for the aphids to develop to maturity was negatively correlated with adult size, whereas survival to maturity was positively correlated with adult size. The host preference of the aphids was also assessed. The plant species selected as hosts by alatae were those on which their offspring performed best.     

Using the RESRAD Code to Assess Human Exposure Risk to 226Ra, 232Th,and 40K in Soil

This article evaluates the health risk raised by exposure to naturally occurring radionuclides in soil around Khak-Sefid, Ramsar, Iran, which is an area of high natural background radiation. A high purity germanium detector was used to determine levels of radionuclides in soil samples and the cancer morbidity risk for a hypothetical resident farmer was evaluated using the RESidual RADioactivity (RESRAD) code. The average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were found to be 13,201 ± 391, 27.9 ± 2.4, and 415.5 ± 16 Bq/kg, respectively. The maximum assessed cancer morbidity risks were calculated from external and internal exposure pathways as 4.73 × 10^?2 and 3.40 × 10^?2 for ²²⁶Ra, 1.41 × 10^?4 and 7.88 × 10^?5 for ²³²Th, and 1.3 × 10^?4 and 4.233 × 10^?4 for ⁴⁰K. The RESRAD calculations also showed total cancer morbidity risks from external gamma and plant ingestion pathways were more important than from other exposure pathways. A sensitivity analysis was also performed to determine the input parameter values in the risk assessment process. In general, due to the high calculated risk of ²²⁶Ra compared with ²³²Th and ⁴⁰K it can be the major source of concern for human heath in the study area.     

A comparison of the natural survival of beagle dogs injected intravenously with low levels of 239Pu, 226Ra, 228Ra, 228Th, or 90Sr

The natural survival, relative to properly chosen controls, of 26 beagle dogs injected once intravenously with an average of 0.58 +/- 0.04 kBq 239Pu/kg, 23 dogs injected with 2.31 +/- 0.43 kBq 226Ra/kg, 13 dogs injected with 1.84 +/- 0.26 kBq 228Ra/kg, 12 dogs injected with 0.56 +/- 0.030 kBq 228Th/kg, and 12 dogs injected with 21.13 +/- 1.74 kBq 90Sr/kg was evaluated statistically. The amounts of these radionuclides are related directly to the estimated maximum permissible body burdens for humans suggested in ICRP II (1959). They constitute a level of exposure that initially was assumed to cause no deleterious effects in dogs. This study had two objectives: (1) identification of homogeneous control groups against which to evaluate the survival of the irradiated groups and (2) comparison of the survival characteristics and estimation of mortality or hazard rate ratios for control dogs vs dogs injected with the baseline dosages given above. It was shown, by goodness-of-fit plots, that the Cox proportional hazards model was an appropriate method of analysis. Therefore, covariates that possibly could influence survival were tested for significance. Only the effects of grand mal seizure, which is caused in epileptic dogs by an external stimulus and can be fatal if untreated, were significant (P less than 0.0001). Consequently, in the final model, death from grand mal seizure was considered as accidental. After censoring the dogs dying from grand mal seizure, it was established that the data for the control groups from previous and contemporary experiments could be pooled. The change in hazard rates relative to controls resulting from exposure to the baseline radionuclide level was modest, 1.6 times for 239Pu (P = 0.033), 1.0(4) for 226Ra (P = 0.86), 1.9 for 228Ra (P = 0.035), 2.5 for 228Th (P less than 0.001), and 0.52 for 90Sr (P = 0.041). Bone tumor induction was clearly elevated in dogs injected with 239Pu and 228Th. When the effect of these bone tumors on survival was removed by censoring, the dogs injected with 239Pu were indistinguishable from the controls. In contrast, the effects of bone tumor on group survival of the 228Ra and 228Th dogs were not significant. Thus, no additional life-shortening effects beyond those attributable to bone tumor were suggested by these data for 239Pu, but other, as yet unspecified, confounders are suggested for 228Ra and 228Th.     

The dose rate dependence of the relative biological effectiveness of 241Am versus 226Ra gamma rays

The survival of Chinese hamster cells exposed to 59.5 keV 241Am gamma rays was compared with that obtained after exposure to 226Ra gamma rays. The Fricke dosimeter in conjunction with the calculational techniques of transition-zone dosimetry was employed to determine the dose rates to the cells at the petri dish/growth medium interface. The dose rates to the cells ranged from 11 to 133 cGy/h. In all cases, cell survival versus dose was best described by a simple exponential function of dose. For both radiations, graphs of D0 versus dose rate show complex but similar patterns of peaks and valleys. As the curve for 241Am is displaced toward lower dose rates compared with that for 226Ra, the relative biological effectiveness of 241Am vs 226Ra varies considerably with dose rate, ranging from 1.7 at 20 cGy/h to 1.1 at 40 cGy/h to 1.6 at 50 cGy/h. This phenomenon may be due to the LET-dependent accumulation of cells at the G2 + M interface in the cell cycle. The mean unrestricted track-average LET of 241Am (3.7 keV/microns) is 12 times higher than that for 226Ra (0.31 keV/microns) but only one-fifth that of carbon ions (18 keV/microns) for which G2 + M pile-up is observed. Application of the in vitro data derived from this study to the clinical situation, where the dose rate decreases rapidly with distance from the source, suggests that, dose for dose, 241Am will produce results little different from those obtained with 226Ra.     

Comparison of Methods for Assessment of Radionuclide Speciation in Soils

Biology Bulletin - A comparison of sequential extraction methods proposed by F.I. Pavlotskaya [1, 2] and A. Tessier [3] for fractionation of technogenic (137Cs and 90Sr) and natural (226Ra, 232Th,...     

Genetic effects of acute and chronic ionizing irradiation on Pinus sylvestris L., inhabiting the Chernobyl' meltdown area]

The main results of the 12-year radiation-genetic monitoring of radiobiological, cytogenetic, and genetic parameters in Pinus sylvestris forest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses > 1 Gy was shown to induce formation of morphoses and depressed growth; at doses > 2 Gy, the reproductive ability of the trees declined. The radiobiological parameters showed a linear or close to linear dose-dependence relationship. The acute irradiation at a dose of 0.5 Gy induced cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of the mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, moderate, and strong damage of Pinus sylvestris L. are presented.     

Transfer of radionuclides to ants, mosses and lichens in semi-natural ecosystems

There is a scarcity of data on transfer of both natural and anthropogenic radionuclides to detritivorous invertebrates for use in the assessment of radiation exposure. Although mosses and lichens have been extensively used in biomonitoring programs, the data on transfer of radionuclides to these species are limited, particularly for natural radionuclides. To enhance the available data, activity concentrations of ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra were measured in ants, mosses and lichens and corresponding undisturbed soil collected from semi-natural ecosystems in Serbia and Montenegro and biota/soil concentration ratios (CR) calculated. Since the majority of internal dose to biota is expected to come from ⁴⁰K, the activity concentrations of this radionuclide were also determined. The mean CR values for ¹³⁷Cs, ²²⁶Ra and ²²⁸Ra in ants analyzed in this study were found to be 0.02, 0.06 and 0.02, respectively. The mean CR values of radionuclides in mosses were found to be 2.84 for ¹³⁷Cs, 0.19 for ²²⁶Ra and 0.16 for ²²⁸Ra, while those in lichens were found to be 1.08 for ¹³⁷Cs, 0.15 for ²²⁶Ra and 0.13 for ²²⁸Ra. The CR values obtained in this study were compared with default CR values used in the ERICA Tool database and also with those reported in other studies.     

Effects of heavy metal pollution on genetic variation and cytological disturbances in thePinus sylvestris L. population

This isoenzymatic and cytogenetic study has shown significant differences in genetic composition between two groups of Pinus sylvestris trees: tolerant and sensitive to heavy metal pollution. Total and mean numbers of alleles and genotypes per locus were higher in the pollution-sensitive group of trees, but heterozygosity (Ho) was lower in this group. Fixation index (F) indicates that trees tolerant for pollution were in the Hardy-Weinberg equilibrium, while the sensitive group had a significant excess of homozygosity. Cytological analyses demonstrated numerous aberrations of chromosomes in meristematic root tissue of seedlings developed from seeds collected from trees in the polluted area. The aberrations included chromosome bridges and stickiness, laggards, retarded and forward chromosomes, and their fragments. The mitotic index was markedly lower in this group of seedlings, as compared to the control. Both isoenzymatic and cytological analyses showed a significant influence of heavy metal ions on the genetic structure of the Pinus sylvestris population.     

Radiation and genetic consequences of ionizing irradiation on population of Pinus sylvestris L. within the zone of the Chernobyl NPP

Main results of the nineteen year radiation-genetic monitoring of radiobiological, of cytogenetic, and of genetic parameters of Pinus sylvestris L. of forest plantation from the Chernobyl meltdown area are presented. The acute ionizing irradiation at doses >1 Gy induces the formation of morphoses and of depressed growth; at doses >2 Gy, the reproductive ability of the trees declined. The radiobiological parameters shown linear or close to it dose-dependence relationship. The acute irradiation at dose of 0.5 Gy induces cytogenetic and genetic effects that were significantly higher than the corresponding control values. The relationship between the cytogenetic effects and the absorbed dose was exponential. The dependence of mutation frequency at specific loci on the absorbed dose was described by a nonlinear curve. The results of the cytogenetic analysis of seedlings obtained from seeds annually collected in zones of slight, of moderate, and of strong damage of Pinus sylvestris L. are presented.