Accumulation and distribution of radionuclides in higher aquatic plants during the vegetation period

Phytotoxicity of radionuclides: A review of sources, impacts and remediation strategies

Various anthropogenic activities and natural sources contribute to the presence of radioactive materials in the environment, posing a serious threat to phytotoxicity. Contamination of soil and water by radioactive isotopes degrades the environmental quality and biodiversity. They persist in soils for a considerable amount of time and disturb the fauna and flora of any affected area. Hence, their removal from the contaminated medium is inevitable to prevent their entry into the food chain and the organisms at higher levels of the food chain. Physicochemical methods for radioactive element remediation are effective; however, they are not eco-friendly, can be expensive and impractical for large-scale remediation. Contrastingly, different bioremediation approaches, such as phytoremediation using appropriate plant species for removing the radionuclides from the polluted sites, and microbe-based remediation, represent promising alternatives for cleanup. In this review, sources of radionuclides in soil as well as their hazardous impacts on plants are discussed. Moreover, various conventional physicochemical approaches used for remediation discussed in detail. Similarly, the effectiveness and superiority of various bioremediation approaches, such as phytoremediation and microbe-based remediation, over traditional approaches have been explained in detail. In the end, future perspectives related to enhancing the efficiency of the phytoremediation process have been elaborated.

Radiation dose reconstruction for higher aquatic plants and fish in Glyboke Lake during the early phase of the Chernobyl accident

This study deals with an assessment of radiation dose dynamics to fish and higher aquatic plants (helophytes) in Glyboke Lake (10-km exclusion zone) during the early phase of the Chernobyl accident. Models of radioactive contamination of water and sediment and models of radioactive contamination and radiation dose to fish and aquatic plants were developed. It was found that, in 1986, the total dose rate to fish reached 0.25 Gy d^-1. Within 6 months after the accident, the dose rate due to ⁹⁰Sr, ¹³⁴Cs and ¹³⁷Cs had increased. The absorbed dose to prey fish of Glyboke Lake for this period was estimated as being 27-81 Gy of which 4-40 Gy was formed by ¹³¹I exposure. The radiation dose rate due to ⁹⁰Sr, ¹⁰⁶Ru, ^134+137Cs and ¹⁴⁴Ce to aquatic plants reached its quasi-equilibrium values approximately 50 days after the accident and remained virtually unchanged until the end of the 1986 growing season. The highest levels of ⁸⁹Sr, ⁹¹Y, ⁹⁵Zr, ¹⁰³Ru, ¹⁴¹Ce exposure were observed between 30 and 50 days with a decrease by 2-3 times at the end of the growing season. Radiation exposure of the short-lived ¹³¹I, ¹⁴⁰Ba, ¹⁴⁰La, ²³⁹Np reached its maximum within 5-15 days after the accident. The absorbed dose rate to aquatic plants reached 0.69 Gy d^-1, while the contribution of cerium radionuclides to the total dose rate formed 50% in the initial period and reached 90% at the end of the growing season. The magnitude of the radiation dose rate to plant roots was 2.4 times higher than aboveground organs, and that of rhizomes was 1.6 times higher. During the growing season of 1986 the total dose of exposure of plants in Glyboke Lake was about 78 Gy. The results of this study emphasise the necessity to consider the history of exposure of past generation of living organisms as part of the assessment of current radiation effects.

Cytogenetic effects of β-particles in Allium cepa cells used as a biological indicator for radiation damages

Analysis of cytogenetics effects of ionizing radiation for flora and fauna is essential to determine the impact on these communities and may produce an efficient warning system to avoid harm to human health. Onion (Allium cepa) is a well-established in vivo standard model, and it is widely used in cytogenetics studies for different environmental pollutants. In this work, onion roots were exposed to 0.04-1.44 Gy of β-particles from a ⁹⁰Sr/⁹⁰Y source. We investigated the capacity of brief external exposures to β-particles on inducing cytogenetic damages in root meristematic cells of onion aiming to verify if onion can be used as a radiation-sensitive cytogenetic bioindicator. A nonlinear increase in the frequencies of chromosomal aberrations and cells with micronuclei was observed. Onion roots exposed to doses 0.13 Gy or higher of β-particles showed a significant difference (p<0.05) in these frequencies when compared to the unirradiated group. The frequencies of these endpoints showed to be suitable to assess the difference in the dose of beta radiation received from 0.36 Gy. Our research shows the potential of using cytogenetic effects in Allium cepa cells as a biological indicator for a first screening of genotoxic damages induced by brief external exposures to β-particles.

Diversity and dynamics of hydrophilic flora of Lowland Polissya (on the example of the Sluch River basin)

Study and analysis of hydrophilic flora diversity are important parts of environmental research due to various functions of vascular macrophytes in freshwater ecosystems, which deteriorate under the influence of anthropogenic activity and climate change. The aim of this study is to analyze the hydrophilic flora diversity (taxa, biology, ecology, and conservation status of species) and current population trends in the Sluch River basin, the largest tributary of the Horyn River (the Pripyat River basin), within the Polissya Lowland in the northern-west region of Ukraine. The list of hydrophilic flora is based on materials of the authors’ field researches in 2014–2020 within the upper and middle parts of the river basin, herbarium materials, and archive data. The study shows that the natural flora consists at least of 105 species of vascular plants belonging to 66 genera, 36 families, and 22 orders. Structural analysis shows the predominance of a few families in the systematic structure of the flora (Cyperaceae, Potamogetonaceae, Poaceae, Ranunculaceae, Plantaginaceae, and Typhaceae) and genera (Potamogeton, Carex); the dominant categories are hemicryptophytes and geophytes, entomophiles and anemophiles, heliophytes and hygrohelophytes. C- and S-strategists are dominant. This is the generally typical taxonomic and ecological structure of the hydrophilic flora of water bodies in the Pripyat River basin. The list of rare species includes 20 species from 15 genera and 12 families, for instance, species listed as vulnerable in The Red Book of Ukraine (Juncus bulbosus, Utricularia intermedia, Nymphoides peltata). Even rare and vulnerable species can form numerous populations in some localities, for example, Nymphoides peltata and Calla palustris. Five alien species were identified (Acorus calamus, Elodea canadensis, Zizania latifolia, Bidens frondosa, and Echinocystis lobata), some of which tend to expand and displace aboriginal species. In the future, it will be important to further study the structure and changes in the hydrophilic flora of the region under conditions of anthropogenic impact, to monitor the dynamics of populations of alien species, and to develop conservation measures for rare species and communities.