Migration of 238U and 226Ra Radionuclides in Technogenic Permafrost Taiga Landscapes of Southern Yakutia, Russia

This article describes the features and migration patterns of natural long-lived heavy radionuclides 238U and 226Ra in the major components of the environment including rocks, river waters, soils, and vegetation of permafrost taiga landscapes of Southern Yakutia, which helped us to understand the scale and levels of their radioactive contamination. Different methods have been used in this study to determine the content of 238U and 226Ra in various samples, including gamma-ray spectrometry, X-ray spectroscopy, laser excited luminescence, and emanation method. It was determined that the main source of radioactive pollution of soil and vegetation cover, as well as surface waters in these technogenic landscapes, are the dumps of radioactive rock that were formed here as the result of geological exploration carried out in this area during the last third of the 20th century. The rocks studied were initially characterized by a coarse, mainly stony gravelly composition and contrasting radiation parameters, where the gamma radiation exposure rate varied between 1.71 and 16.7 µSv/h, and the contents of 238U and 226Ra were within the range 126–1620 mg/kg and 428–5508 × 10−7 mg/kg, respectively, and the 226Ra: 238U ratio was 1.0. This ratio shifted later on from the equilibrium state towards the excess of either 238U or 226Ra, due to the processes of air, water, and biogenic migration. Two types of 238U and 226Ra radionuclides migration were observed in studied soils, namely aerotechnogenic and hydrotechnogenic, each of which results in a different intraprofile radionuclide distribution and different levels of radioactive contamination. In this study, we also identified plants capable of selective accumulation of certain radionuclides, including Siberian mountain ash (Sorbus sibiricus), which selectively absorbs 226Ra, and terrestrial green and aquatic mosses, which accumulate significant amounts of 238U.

Effect of Current Velocity on Cd Accumulation in the Aquatic Moss Fontinalis antipyretica

With the aim of further standardizing biomonitoring techniques with aquatic mosses, the relationship between the velocity of water flow and cadmium (Cd) accumulation in transplants of the moss Fontinalis antipyretica was investigated. For this purpose, moss transplants were exposed in a controlled aquatic environment to different concentrations of Cd (0, 4, 16 and 36 ng g−1) and different water velocities (10, 30, 50, 70 and 90 cm s−1). The Cd concentrations in the moss transplants mainly depended on the Cd concentration in the water, but a small fraction of the variance was explained by water velocity. The Cd concentrations in moss were standardized to remove the effect of the concentration in the water so all the data could be analyzed together. The regression model for the standardized concentrations explained 23% of the variance in Cd accumulation in F. antipyretica and water velocity proved to be a significant predictor of Cd accumulation.

Can Biomarkers Respond Upon Freshwater Pollution?—A Moss-Bag Approach

Moss-bags were applied to study the effect of contamination in three standing water bodies in Bulgaria (Kardzhali, Studen Kladenets and Zhrebchevo Reservoirs), the first two with old industrial contamination and the last polluted with short-chain chlorinated paraffins (SCCPs). Fontinalis antipyretica Hedw. collected from background (unpolluted) site was placed in cages for a period of 30 days. The present study examined whether inorganic and organic pollution detected with moss-bags resulted in corresponding differences in molecular, chemical and micromorphological markers. Suppressed large subunit of ribulose-1,5-bisphosphate carboxylase (rbcL) expression was assessed in moss-bags from two of the reservoirs, contaminated with heavy metals. There was a decrease of the total phenolic content (TPC) in the moss-bags, which provides a basis for further studies of the chemical content of aquatic mosses. Fontinalis antipyretica also showed a response through leaf micromorphological characteristics. In the all three reservoirs, an increase of the twig leaf cell number was recorded (p ≤ 0.01 for Kardzhali and p ≤ 0.001 for Studen Kladenets and Zhrebchevo reservoirs), as well as of the stem leaf cell number in Zhrebchevo Reservoir (p ≤ 0.001). On the contrary, the width of the cells decreased in the studied anthropogenically impacted reservoirs. All three studied groups of biomarkers (molecular, chemical and micromorphological) appeared to be sensitive to freshwater pollution. The results achieved indicated that rbcL gene expression, TPC, cell number and size are promising biomonitoring tools.

Flora and Its Analysis. Hydrophilic Plants of Different Water Bodies of the Samarkand Region (Uzbekistan)

Aquatic and coastal aquatic plants are one of the most important components of aquatic ecosystems. Therefore, at present, much attention is paid to the issues of rational use and development of the country's inland water bodies. Together with phytoplankton, this group of plants participates in the trophic cycle of biocenosis, providing various stages of the links of the food chain with appropriate products. For example, the plants of reservoirs serve as food for representatives of different taxonomic groups of animals, mollusks, crustaceans, insects, fish, birds and mammals. With moderate overgrowing of water bodies, favorable conditions are formed for the development of the phytophilous fauna of invertebrates. The flora of higher aquatic and coastal plants of the Samarkand region has not yet been fully studied. The species composition was not studied, taxonomic and floristic analysis was not carried out. In addition, it is very rare to find detailed information about the use of aquatic plants in the national economy, information about useful species and rare species common in this territory. The article presents the results of research on the study of aquatic and coastal plants of reservoirs of the Samarkand region. It was revealed that 72 species of aquatic and coastal plants, which belong to 51 genera, 34 families and 5 classes, grow in reservoirs of various types on the territory of the Samarkand region. Representatives of the families Potamogetonaceae, Poaceae, Cyperaceae and Polygonaceae make up 43% of the total number of plants of this group growing in the studied region. In terms of life forms, about 12.5% (9 species) are annuals, and 77.8% (56 species) are perennials. It was found that 7 species of aquatic mosses grow in the studied water bodies.

Platyhypnidium aquaticum as Bioindicator of Metal and Metalloid Contamination of River Water in a Neotropical Mountain City

Water contamination is a major environmental problem in many cities of the world. Most water contamination results from industry and human activities that generate toxic substances (e.g., metals). Rheophilic and aquatic mosses are found in lotic ecosystems, and their morphological and physiological traits are responsive to ecological and pollution gradients. Here we hypothesized that the native rheophilic moss Platyhypnidium aquaticum (A. Jaeger) M. Fleisch exposed to polluted waters can bioaccumulate greater amounts of metals, and a metalloid, than P. aquaticum exposed to pollution-free water. To this aim, we tested the bioindicator capacity of the aquatic P. aquaticum for 15 metals (Cd, Pb, Zn, Fe, K, Ca, Na, Mn, V, Co, Ba, Cr, Al, Sr, and Mg) and one metalloid (As), in twelve river samples coming from three urban and one control zone along the Zamora river in the city of Loja. When compared to the control, our results showed that P. aquaticum in the Southern, Central, and Northern zones of the city bioaccumulated higher concentrations of Ba, Cd, Co, Fe, Mg, Mn, Na, Sr, Zn, and the metalloid As. On the other hand, concentrations of Al, Ca, Cr, Pb, and V in P. aquaticum tended to be lower in the control zone, but these differences were not significant. We suggest that the presence of these contaminants may be related to water pollution (e.g., residual discharges and a lack of treatment systems) along urban zones of the river. We report for the first time the utility of P. aquaticum as a model species for development of long-term biomonitoring programs of water contamination in South America. Passive biomonitoring with P. aquaticum can be a simple and low-cost method to obtain reliable data of the current state of water contamination with metals and metalloids in tropical regions.

Aquatic Mosses as Adaptable Bio-Filters for Heavy Metal Removal from Contaminated Water

Heavy metals (HMs) are released into the environment by many human activities and persist in water even after remediation. The efficient filtration of solubilized HMs is extremely difficult. Phytoremediation appears a convenient tool to remove HMs from polluted water, but it is limited by the choice of plants able to adapt to filtration of polluted water in terms of space and physiological needs. Biomasses are often preferred. Aquatic moss biomasses, thanks to gametophyte characteristics, can act as live filtering material. The potential for phytoremediation of Hypnales aquatic mosses has been poorly investigated compared to aquatic macrophytes. Their potential is usually indicated as a tool for bioindication and environmental monitoring more than for pollutant removal. When phytoremediation has been considered, insufficient attention has been paid to the adaptability of biomasses to different needs. In this study the heavy metal uptake of moss Taxiphyllum barbieri grown in two different light conditions, was tested with high concentrations of elements such as Pb, Cd, Zn, Cu, As, and Cr. This moss produces dense mats with few culture needs. The experimental design confirmed the capacity of the moss to accumulate HMs accordingly to their physiology and then demonstrated that a significant proportion of HMs was accumulated within a few hours. In addition to the biosorption effect, an evident contribution of the active simplistic mass can be evidenced. These reports of HM accumulation within short time intervals, show how this moss is particularly suitable as an adaptable bio-filter, representing a new opportunity for water eco-sustainable remediation.

A novel leaf-rolling chironomid, Eukiefferiella endobryonia sp. nov. (Diptera, Chironomidae, Orthocladiinae), highlights the diversity of underwater chironomid tube structures

The non-biting midges, Chironomidae (Diptera), are dominant components of most freshwater ecosystems. Many chironomids construct tubes or cases as larvae out of various materials bound together with silk. The structures of tubes show a wide range of variation, and some are morphologically comparable to those of caddisflies. Herein a new species is described, Eukiefferiella endobryoniasp. nov., which exhibits a very unusual behavior in which it constructs tubes from aquatic mosses. This species’ fourth-instar larvae construct their cases exclusively from the leaves of Fontinalis mosses (Hypnales: Fontinalaceae) and exhibit a stereotyped behavior in which they remain attached to the apical shoot of the moss stem. The larvae then pupate within the case. The case of E. endobryoniasp. nov. represents one of only a few examples of chironomid tubes made exclusively out of plants. Based on the species delimitation analyses using the partial COI sequences, together with some morphological and behavioral characteristics, this species is hypothesized to be a member of devonica group, and especially may have a close affinity to E. dittmari (Lehman). A provisional typology for the diversity of chironomid tube structures is provided, with a summary of different tube structures, which can be used for future research.