Pollution with trace elements and rare-earth metals in the lower course of Syr Darya River and Small Aral Sea, Kazakhstan

Rare Earth Elements in Human Calcified Aortic Valves and Epicardial Adipose Tissue

Background/Objectives: Rare earth elements (REEs) are emerging environmental pollutants, with human exposure increasing due to recent industrial and technological activities. While most studies have focused on detecting REEs in human fluids, their presence in tissues remains understudied. Aortic valve degeneration is known to facilitate the adsorption of various chemical elements; however, the occurrence of REEs in human valves has not yet been investigated. This exploratory study aimed to determine the presence of REEs in the aortic valves of patients with aortic stenosis undergoing surgical valve replacement. It also analyzed potential correlations between REE levels in the valves, epicardial adipose tissue, serum, and selected disease markers. Methods: Samples of aortic valve, epicardial adipose tissue, and serum were collected from 20 adult patients undergoing elective aortic valve replacement. The concentrations of 14 REEs in these samples were measured using inductively coupled plasma mass spectrometry. Biochemical and clinical parameters of the patients were also considered to explore potential associations with the determined REE levels. Results: Total REEs, heavy REEs, and light REEs in aortic valves, epicardial fat, and serum were not intercorrelated. Moreover, for any sample type, they were not significantly related to the patient's demographics (age and sex), clinical characteristics (body mass index, heart failure severity, and systolic pressure gradients), kidney function (estimated glomerular filtration rate), and biochemical markers (creatinine, lipoprotein(a), total cholesterol, HDL, LDL, and fibrinogen). Smoking was the only factor influencing REE burden in studied patients, with active smokers revealing 61% higher serum REE concentrations and past smokers exhibiting 133% higher REE valvular deposition. Conclusions: The findings suggest that REE accumulation in aortic valve tissues occurs independently of systemic and clinical parameters but may be promoted by smoking, highlighting the need to investigate the underlying mechanisms of REE deposition. Given the small sample size and the cross-sectional, hypothesis-generating design, these observations should be interpreted with caution and treated as preliminary. Larger, longitudinal studies are needed to validate these results and explore potential causal relationships. Further research should also include the tissue originating from individuals without aortic stenosis for comparison. A deeper understanding of the pathways and health risks associated with REEs in cardiovascular tissues may offer valuable insights into their broader implications for human health.

Distribution characteristics and assessment of the content of heavy metals in small rivers of the Ulba riv. basin in the mining regions of East Kazakhstan

Water quality of small rivers in the Ulba basin has been assessed in the impact zone of the mining industry of the Ridder region in East Kazakhstan. Sixteen elements in the waters of small rivers and general chemical water indices were determined using mass spectrometry. The waters of the small rivers under investigation were primarily ultra-fresh and slightly alkaline. The chemical composition of the examined waters was characterised as a sodium-potassium sulphate type, a calcium-magnesium bicarbonate type, and a mixed chemical type, namely, sodium-calcium bicarbonate-sulphate. These waters do not conform to the Health Standards established by the Republic of Kazakhstan, as indicated by the hardness indices for the Filippovka and Bystrukha riv. The cadmium content exceeded the MPC set by the Health Standards of the Republic of Kazakhstan in the waters of the Ulba riv. (up to 21 MPC), Tikhaya (up to 5 MPC) and Filippovka riv. (up to 3 MPC) in 65%, 88% and 18% of water samples, respectively. Single samples were also found to contain elevated concentrations of manganese (Filippovka riv. and Breksa riv.) and ferrum (Breksa riv.). According to the standards set by the World Health Organization (WHO) and the US MPC, exceedances of manganese, aluminium, iron, and cadmium contents in the waters of the Ulba, Filippovka, Breksa, and Bystrukha rivers were observed, ranging from 1 to 7 times. The highest exceedances were recorded in the waters of the Ulba river, with manganese concentrations exceeding the WHO standards by 4 times and US EPA standards by 6.4 times and cadmium concentrations exceeding the WHO standards by 7 times and US EPA standards by 4.2 times. In most water samples from Tikhaya and Ulba riverbeds and in the upper reach of the Filippovka riv, high and average levels of water contamination were revealed (according to the pollution index of heavy metals (HPI)). Alternatively, low contamination levels (<15) with no elevated concentrations of heavy metals were observed in the waters of Zhuravlikha, Malaya Zhuravlikha, Gromotukha, Khariuzovka, Bystrukha and Breksa.

Unveiling mercury's hidden threat: An integrated methodology for soil mercury risk assessment in Syr Darya River Basin, Central Asia

Mercury (Hg) contamination of soil poses a significant threat to ecological and human health. Integrating risk assessment with a comprehensive analysis of the physical and chemical properties of soil enables macroscopic understanding of the potential risks associated with Hg. The integrated risk assessment framework was achieved by applying a projection pursuit clustering (PPC) model that considered ecological and human health risks, soil environmental factors derived from the SHapley Additive Explanation-eXtreme Gradient Boosting (SHAP-XGBoost) model, and exposure risk vulnerability. It was found that the concentrations of Hg in the soils of the Syr Darya River Basin ranged from 3.70 to 40.10 ng/g and Fe2O3, Al2O3, and soil organic carbon (SOC) were important factors in the variation in Hg concentrations. Regions with a high risk of soil Hg were identified using the proposed integrated risk assessment framework, with the geographical distribution concentrated near the cities of Kyzylorda and Kazalinsk. From the perspective of different land use types, shrub soil sampling sites had the largest percentage of high Hg risk values, followed by cropland, bare land, and grassland. These findings confirm that the combined risk values depend not only on Hg concentrations, but also on environmental variables and socioeconomic conditions. Integrated risk assessment of soil Hg is based on machine learning and projection pursuit clustering models, which can provide a novel perspective for potential toxic element pollution evaluation, prevention, and treatment.

Exploring the alteration of environmental radioactivity in terms of compositional elements of heavy minerals in an anthropogenically affected urban river: Radiological and ecological risks assessment

This study explored the alteration of naturally occurring radioactive materials (NORMs: 226Ra (≈238U), 232Th, 40K) in an anthropogenically disrupted urban river-basin (Turag, Bangladesh) in terms of constitutional substances (Sc, Ti, V, Fe, La, Ce, Sm, Eu, Tb, Dy, Ho, Yb, Lu, Hf, Ta, W, Th, U) of heavy-minerals. Average activity concentrations of 226Ra (≈238U), 232Th, and 40K were 41.5 ± 12.9, 72.1 ± 27.1, and 639 ± 100 Bqkg-1, respectively which were relatively higher compared to crustal origin. ∑REEs, Ta, W, Th, and U were ~2 times higher compared to crustal values with Ce and Eu-anomalies. APCS-MLR and PMF receptor models were used to determine the various anthropogenic and/or geogenic sources of NORMs and elements. Layer-wise variations of NORMs and elements were observed to trace the response of sedimentary processes towards the incoming pollution load. Presence of REEs indicates moderate degree of ecological risk to aquatic biota. However, carcinogenic risk (3.84 × 10-4 Sv-1) were significantly higher than threshold limit.

Geochemical behavior of rare earth elements in agricultural soils along the Syr Darya River within the Aral Sea Basin

The widespread use of rare earth elements (REEs) across various industries makes them a new type of pollutant. Additionally, REEs are powerful indicators of geochemical processes. As one of the two main rivers in the Aral Sea, identifying the geochemical behavior of REEs in agricultural soils of the Syr Darya River is of great significance for subsequent indicative studies. In this study, the geochemical characteristics, influencing factors, and potential application significance of REEs in agricultural soils from three sampling areas along the Syr Darya River were analyzed using soil geography and elemental geochemical analyses. The results showed that the highest total concentration of REEs in the agricultural soil was in Area I, with a mean value of 142.49 μg/g, followed by Area III with a mean value of 124.56 μg/g, and the lowest concentration was in Area II with a mean value of 122.48 μg/g. The agricultural soils in the three regions were enriched in light rare earth elements (LREEs), with mean L/H values of 10.54, 10.13, and 10.24, respectively. The differentiation between light and heavy rare earth elements (HREEs) was also high. The concentration of REEs in agricultural soil along the Syr Darya River was primarily influenced by minerals such as monazite and zircon, rather than human activities (the pollution index of all REEs was less than 1.5). The relationship between Sm and Gd can differentiate soils impacted by agricultural activities from natural background soils. The results of this study can serve as a basis for indicative studies of REEs in Central Asia.

Fish and Seafood Safety: Human Exposure to Toxic Metals from the Aquatic Environment and Fish in Central Asia

Toxic metals that are released into aquatic environments from natural and anthropogenic sources are absorbed by aquatic organisms and may threaten the health of both aquatic organisms and humans. Despite this, there have been limited studies on the metal concentrations in fish and humans in Central Asia. This study summarizes the presence of the toxic metals arsenic (As), mercury (Hg), cadmium (Cd), and lead (Pb) in aquatic bodies, fish, and seafood products and conducts a risk assessment. While certain areas show a notable increase in fish and seafood consumption, the overall intake in Central Asia remains below recommended levels. However, in regions with high fish consumption, there is a potential for elevated exposure to toxic metals, especially Hg. The risk of exposure to toxic metals in fish and seafood in Central Asia emerges as a significant concern. Comprehensive monitoring, regulation, and remediation efforts are imperative to ensure the safety of water sources and food consumption in the region. Public awareness campaigns and the establishment of dietary guidelines play a crucial role in minimizing the health risks associated with consumption.

The Effect of Environmental Disasters on Endocrine Status, Hematology Parameters, Body Composition, and Physical Performance in Young Soccer Players: A Case Study of the Aral Sea Region

The Aral Sea region (Uzbekistan) is infamous because of the ecological disaster characterized by the disappearance of the Aral Sea due to excessive uncontrolled water intake for agriculture needs. A new desert occurrence, soil and climate aridization led to pesticide and toxic metals environment pollution. The impact of environmental conditions in some areas of Uzbekistan on the health of soccer players is not as noticeable as, for example, the effectiveness of training, so it is not widely discussed in scientific papers. The aim of the present study was to study the features of endocrine status, hematology parameters (e.g., red blood cells (RBC) and hemoglobin (Hb)), and their influence on body composition and physical fitness performance in local young soccer players of the Aral Sea region as the territory of ecological disaster. The study involved 60 male soccer players aged from 18 to 22 years. Participants were divided into two groups: the experimental group (EG), which consisted of 30 soccer players living on the territory of the Aral ecological disaster region, and the control group (CG), which included 30 soccer players, natives of the ecologically favorable region of Uzbekistan. All volunteers had anthropometric measurements, concentrations of insulin-like growth factor-1 (IGF-1), total testosterone (TT), estradiol (E2), cortisol (C), RBC, and Hb count. Moreover, Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1) and professional skills tests such as dribbling shuttle test (DSt) and goal accuracy test (GAt) were assessed. When comparing the CG group to the EG group, it was observed that the EG group exhibited statistically significantly reduced levels of TT and E2 (p < 0.05). No significant statistical difference was observed between the two groups in terms of IGF-1 and C (p > 0.05). Regarding hematological parameters, Hb, Ht, and mean corpuscular volume (MCV) were found to be significantly lower in the EG compared with the CG (p < 0.05). Moreover, the distance covered in the YYIR1 test was found to be significantly lower in soccer players within the EG compared with the CG (p < 0.05). Additionally, it was determined that there was no significant difference between the groups in terms of DSt and GAt values (p > 0.05). Lastly, significant differences were observed between the EG and CG in terms of anthropometric characteristics (diameters, skinfold, and somatotype profile) (p < 0.05). The present study showed that the changes in evaluated characteristics might result from the complex influence of endocrine-disrupting chemicals, the content of which is high in the environment of the Aral Sea region. The results obtained may help monitor the health of athletes living in an environmentally unfriendly environment.

Oxic effects of Pb-Ce compound pollution on Chinese cabbage and programmed cell death in root tip cells

Heavy metal pollution is increasing, and rare earth elements (REE) play an important role in the environmental impact of heavy metals. Mixed heavy metal pollution is a major issue with complex effects. Despite substantial research on single heavy metal pollution, relatively few studies have focused on pollution from rare earth heavy metal composites. We studied the effects of different concentrations of Ce-Pb on the antioxidant activity in root tip cells and biomass of Chinese cabbage. We also used the integrated biomarker response (IBR) to evaluate the toxic effects of rare earth-heavy metal pollution on Chinese cabbage. We used programmed cell death (PCD) for the first time to reflect the toxicological effects of heavy metals and rare earths and studied the interaction between Ce and Pb in root tip cells in depth. Our results showed that Ce-Pb compound pollution can induce PCD in the root cells of Chinese cabbage, and the toxicity of compound pollutants is greater than that of single pollutants. Our analyses also provide the first evidence that Ce and Pb exert interaction effects in the cell. Ce induces Pb transfer in plant cells. The Pb content in the cell wall decreases from 58% to 45%. Additionally, Pb induced Ce valence changes. Ce (III) decreased from 50% to 43%, while Ce (IV) increased from 50% to 57%, directly resulting in PCD in the roots of Chinese cabbage. These findings improve our understanding of the harmful effects of compound pollution with rare earth metals and heavy metals on plants.

Comparative analysis and human health risk assessment of contamination with heavy metals of Central Asian rivers

The study focuses on heavy metals contamination, drinking water quality, and associated health risks for adults and children by consuming water from Central Asian Rivers (Syr-Darya, Nura, and Ili Rivers). Water samples were collected from three rivers within the 2014-2019 period by the RMS "Kazhydromet" and analyzed for various physicochemical parameters. The study revealed that the concentrations of Fe, Cd, Cr (VI), Hg, Mn, and As significantly exceeded local and international drinking water standards in at least one water body. The lowest total water quality index (55.1%) was observed in the Nura River ("marginal water category"). Coal, soil, non-ferrous metals, and iron ore industries were found to be the major sources of heavy metals in the regions. Deterministic risk assessment revealed serious cancer risks (>1E-5) in rivers due to As and Cr (VI) exposure by oral and dermal contact for adults and children. Stochastic risk assessment confirmed high cancer risks (>1E-4) due to Cr (VI) contamination of the Syr-Darya River. The study results indicate the serious lifetime cancer risk to the residents due to the use of river water for drinking and household activities. Therefore, the study area urgently and continuously requires heavy metal removal, effective monitoring, and good quality drinking water supply.

Ecotoxicity of non- and PEG-modified lanthanide-doped nanoparticles in aquatic organisms

Various types of nanoparticles (NPs) have been widely investigated recently and applied in areas such as industry, the energy sector, and medicine, presenting the risk of their release into the environment. The ecotoxicity of NPs depends on several factors such as their shape and surface chemistry. Polyethylene glycol (PEG) is one of the most often used compounds for functionalisation of NP surfaces, and its presence on the surfaces of NPs may affect their ecotoxicity. Therefore, the present study aimed to assess the influence of PEG modification on the toxicity of NPs. As biological model, we chose freshwater microalgae, a macrophyte and invertebrates, which to a considerable extent enable the assessment of the harmfulness of NPs to freshwater biota. SrF₂:Yb³⁺,Er³⁺ NPs were used to represent the broad group of up-converting NPs, which have been intensively investigated for medical applications. We quantified the effects of the NPs on five freshwater species representing three trophic levels: the green microalgae Raphidocelis subcapitata and Chlorella vulgaris, the macrophyte Lemna minor, the cladoceran Daphnia magna and the cnidarian Hydra viridissima. Overall, H. viridissima was the most sensitive species to NPs, which affected its survival and feeding rate. In this case, PEG-modified NPs were slightly more toxic than bare ones (non-significant results). No effects were observed on the other species exposed to the two NPs at the tested concentrations. The tested NPs were successfully imaged in the body of D. magna using confocal microscopy; both NPs were detected in the D. magna gut. The results obtained reveal that SrF₂:Yb³⁺,Er³⁺ NPs can be toxic to some aquatic species; however, the structures have low toxicity effects for most of the tested species.

Evaluation of dissolved and acid-leachable trace element concentrations in relation to practical water quality standards in the Syr Darya, Aral Sea Basin, South Kazakhstan

The Syr Darya is one of the major rivers supplying the Aral Sea with freshwater. Soviet programs aimed at maximizing agricultural productivity in the Syr Darya basin increased diversion of water drastically affecting its water quality with significant consequences to its suitability for irrigation, fisheries and other uses. While water quality standards for trace elements are typically measured in the dissolved phase, there is evidence that adsorbed phases may also be relevant. Here we report potentially available heavy metals and metalloid concentrations in the Syr Darya water through the treatment of unfiltered waters samples with dilute nitric acid. Significant differences were found for most studied elements (Mann-Whitney U Test, p < 0.05) between their dissolved and acid-leachable concentrations. For Sr and Se in both sampling campaigns, no significant differences were found between their dissolved and acid-leachable concentrations, indicating their low geochemical reactivity. Dissolved V concentrations and acid-leachable Ni and Zn were found to exceed Kazakhstan Maximum Permissible Concentrations (MPC) values for the protection of fishery water quality. Our study evaluates the importance of considering regulatory issues of measuring trace metal concentrations to assess the water suitability for fisheries and irrigation.

Function-Based Rhizosphere Assembly along a Gradient of Desiccation in the Former Aral Sea

The desiccation of the Aral Sea represents one of the largest human-made environmental regional disasters. The salt- and toxin-enriched dried-out basin provides a natural laboratory for studying ecosystem functioning and rhizosphere assembly under extreme anthropogenic conditions. Here, we investigated the prokaryotic rhizosphere communities of the native pioneer plant Suaeda acuminata (C.A.Mey.) Moq. in comparison to bulk soil across a gradient of desiccation (5, 10, and 40 years) by metagenome and amplicon sequencing combined with quantitative PCR (qPCR) analyses. The rhizosphere effect was evident due to significantly higher bacterial abundances but less diversity in the rhizosphere compared to bulk soil. Interestingly, in the highest salinity (5 years of desiccation), rhizosphere functions were mainly provided by archaeal communities. Along the desiccation gradient, we observed a significant change in the rhizosphere microbiota, which was reflected by (i) a decreasing archaeon-bacterium ratio, (ii) replacement of halophilic archaea by specific plant-associated bacteria, i.e., Alphaproteobacteria and Actinobacteria, and (iii) an adaptation of specific, potentially plant-beneficial biosynthetic pathways. In general, both bacteria and archaea were found to be involved in carbon cycling and fixation, as well as methane and nitrogen metabolism. Analysis of metagenome-assembled genomes (MAGs) showed specific signatures for production of osmoprotectants, assimilatory nitrate reduction, and transport system induction. Our results provide evidence that rhizosphere assembly by cofiltering specific taxa with distinct traits is a mechanism which allows plants to thrive under extreme conditions. Overall, our findings highlight a function-based rhizosphere assembly, the importance of plant-microbe interactions in salinated soils, and their exploitation potential for ecosystem restoration approaches. IMPORTANCE The desertification of the Aral Sea basin in Uzbekistan and Kazakhstan represents one of the most serious anthropogenic environmental disasters of the last century. Since the 1960s, the world's fourth-largest inland body of water has been constantly shrinking, which has resulted in an extreme increase of salinity accompanied by accumulation of many hazardous and carcinogenic substances, as well as heavy metals, in the dried-out basin. Here, we investigated bacterial and archaeal communities in the rhizosphere of pioneer plants by combining classic molecular methods with amplicon sequencing as well as metagenomics for functional insights. By implementing a desiccation gradient, we observed (i) remarkable differences in the archaeon-bacterium ratio of plant rhizosphere samples, (ii) replacement of archaeal indicator taxa during succession, and (iii) the presence of specific, potentially plant-beneficial biosynthetic pathways in archaea present during the early stages. In addition, our results provide hitherto-undescribed insights into the functional redundancy between plant-associated archaea and bacteria.

Spatial heterogeneity of chemistry of the Small Aral Sea and the Syr Darya River and its impact on plankton communities

The shrinking of the Aral Sea represents one of the greatest ecological disasters of modern time. The data on the surviving northern part (Small Aral) is scarce and requires an update. This study aimed to analyze the chemistry, phyto- and zooplankton composition, and their relation in the waters of the Small Aral and its tributary, Syr Darya River. The chemistry of both ecosystems was significantly different. Small Aral was characterized by higher ionic concentrations, salinity, and electric conductivity and more significant spatial variation of chemical properties. The area near the river mouth was more pristine, while the ions concentration and salinity in the distant bays were much higher (>10‰). The highest concentrations of nitrates and total phosphorus in the Syr Darya were observed near Kyzylorda, indicating urban pollution. Overall, 109 phytoplankton taxa were identified in both ecosystems, with diatoms, green algae, and cyanobacteria being most abundantly represented. Oligohalobes dominated, but no polyhalobes and euhalobes algal species were identified. In total, 27 taxa of zooplankton were identified in both studied ecosystems, with the domination of rotifers over microcrustaceans. An exceptionally high level of dominance (65-91%) of rotifer Keratella cochlearis in the Syr Darya was found. The phyto- and zooplankton species richness was higher in the Syr Darya. Plankton communities of the Small Aral reflected horizontal variability of chemical properties. The total phosphorus promoted the prevalence of diatoms, rotifers, and crustaceans. Increased nitrogen concentration promoted cyanobacteria, chlorophytes, cryptophytes and chrysophytes, and rotifers Keratella cochlearis and K. quadrata. The abundance of dinophytes, diatoms Navicula cryptotenella and Cocconeis placentula, green algae Mychonastes jurisii and rotifer Keratella tecta was driven by the higher alkalinity and conductivity/salinity levels. The results represent a reference point for future monitoring of the area and add to understanding the complexity of biological transformations in the Aral Sea and its tributary.

The Changing Dynamics of Kazakhstan’s Fisheries Sector: From the Early Soviet Era to the Twenty-First Century

Kazakhstan, a former Soviet republic that is now independent, lies near the center of arid Eurasia. Its sparse hydrographic network includes a small number of large rivers, lakes, and reservoirs, many ponds and smaller streams, as well as littoral zones bordering the Caspian Sea and the Aral Sea. A diverse fisheries sector, initially based on wild fish capture and later including aquaculture, developed in these waters during the Soviet era, when animal agriculture was unable to meet the protein needs of Soviet citizens. The sector, which was originally centered on the Volga–Caspian basin, was tightly managed by Moscow and benefitted from coordinated investments in research, infrastructure, and human resources, as well as policies to increase the consumption of fish products. Independence in 1991 administered a political and economic shock that disrupted these relationships. Kazakhstan’s wild fish harvests plummeted by more than two-thirds, and aquaculture collapsed to just 3% of its previous level. Per capita consumption of fish products also declined, as did processing capacity. Favorable recent policies to define fishing rights, incentivize investments, prevent illegal fishing, and make stocking more effective have helped to reverse these trends and stabilize the sector. Continued recovery will require additional steps to manage water resources sustainably, prioritize the use of water for fish habitats, and minimize the effects of climate change. This comprehensive assessment of Kazakhstan’s fisheries sector over the past century provides the basis to understand how long-term dynamic interactions of the environment with the political economy influence fisheries in Eurasia’s largest country.

Research on the Coordination between Agricultural Production and Environmental Protection in Kazakhstan Based on the Rationality of the Objective Weighting Method

In the context of sustainable development, agricultural production and environmental protection are inseparable, and environmental quality directly affects regional agricultural production safety. Kazakhstan is the largest food producer and exporter in Central Asia, and the quality of its agricultural environment is of great significance to international food security. This study focuses on the rationality of the entropy weight, factor weight, and CRITIC weight in the agricultural environmental evaluation within the common objective weight method, and comprehensively evaluates the coordination of environmental protection and agricultural production in Kazakhstan. The results show that (1) CRITIC weights are the most stable, followed by factor weights, while entropy weighting is the most unstable; objective weighting methods have their limitations and must be related to actual conditions and subjective experience. (2) The level of environmental protection and the degree of coordination are most problematic near the Aral Sea, followed by the remaining western region; the results reveal that these evaluation indexs are also insufficient at Kostany and Karagandy in the central region; this is caused by historical issues, climate change, natural conditions, and agricultural management patterns. Investment in environmental protection and agricultural production management should be coordinated in a targeted manner. (3) Except for the areas near the Aral Sea, the level of agricultural production in other states is very promising. This research serves as a reference for environmental assessment research, environmental governance investment, and agricultural production management in Kazakhstan.

Distribution of dissolved and suspended forms of heavy metals in the water of the Syr Darya, South Kazakhstan

The water of the Syr Darya is the main source of fresh water in South Kazakhstan and heavily used for agriculture. The use water from the Syr Darya for irrigation of agricultural fields affects its chemical composition and is reflected in the water quality class provided in the bulletins of the Ministry of Ecology, Geology and Natural Resources of the Republic of Kazakhstan. In the present work, the distribution of suspended and dissolved forms of heavy metals in the water of the Syr Darya has been studied in two areas – the upper reaches of the river from the Shardara reservoir to the «Koksaray» bridge and the lower reaches of the river from Turkestan to Terenozek. Concentrations of heavy metals and metalloids were determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500A, United States) and compared to these recommended levels. Total concentrations of several metals (V, Cu, Mn, Fe, Sr) exceed the Maximum Permissible Concentrations established for waters of fishery reservoirs. The role of the suspended form in the geochemical migration of a number of metals in the water of the Syr Darya River is estimated and it was shown that this form is a significant fraction of the total metal concentration. The distribution of suspended forms of metals correlates to the turbidity of the water of the Syr Darya.

Agricultural impacts drive longitudinal variations of riverine water quality of the Aral Sea basin (Amu Darya and Syr Darya Rivers), Central Asia

River ecosystems are under increasing stress in the background of global change and ever-growing anthropogenic impacts in Central Asia. However, available water quality data in this region are insufficient for a reliable assessment of the current status, which come as no surprise that the limited knowledge of regulating processes for further prediction of solute variations hinders the development of sustainable management strategies. Here, we analyzed a dataset of various water quality variables from two sampling campaigns in 2019 in the catchments of two major rivers in Central Asia-the Amu Darya and Syr Darya Rivers. Our results suggested high spatial heterogeneity of salinity and major ion components along the longitudinal directions in both river catchments, pointing to an increasing influence of human activities toward downstream areas. We linked the modeling outputs from the global nutrient model (IMAGE-GNM) to riverine nutrients to elucidate the effect of different natural and anthropogenic sources in dictating the longitudinal variations of the riverine nutrient concentrations (N and P). Diffuse nutrient loadings dominated the export flux into the rivers, whereas leaching and surface runoff constituted the major fractions for N and P, respectively. Discharge of agricultural irrigation water into the rivers was the major cause of the increases in nutrients and salinity. Given that the conditions in Central Asia are highly susceptible to climate change, our findings call for more efforts to establish holistic management of water quality.

What do we know about the ecotoxicological implications of the rare earth element gadolinium in aquatic ecosystems?

Gadolinium (Gd) is one of the most commercially exploited rare earth elements, commonly employed in magnetic resonance imaging as a contrast agent. The present review was performed aiming to identify the Gd concentrations in marine and freshwater environments. In addition, information on Gd speciation in the environment is discussed, in order to understand how each chemical form affects its fate in the environment. Biological responses caused by Gd exposure and its bioaccumulation in different aquatic invertebrates are also discussed. This review was devoted to aquatic invertebrates, since this group of organisms includes species widely used as bioindicators of pollution and they represent important resources for human socio-economic development, as edible seafood, fishing baits and providing food resources for other species. From the literature, most of the published data are focused on freshwater environments, revealing concentrations from 0.347 to 80 μg/L, with the highest Gd anomalies found close to highly industrialized areas. In marine environments, the published studies identified a range of concentrations between 0.36 and 26.9 ng/L (2.3 and 171.4 pmol/kg), reaching 409.4 ng/L (2605 pmol/kg) at a submarine outfall. Concerning the bioaccumulation and effects of Gd in aquatic species, most of the literature regards to freshwater species, revealing concentration ranging from 0.006 to 0.223 μg/g, with high variability in the bioaccumulation extent according to Gd complexes chemical speciation. Conversely, no field data concerning Gd bioaccumulation in tissues of marine species have been published. Finally, impacts of Gd in invertebrate aquatic species were identified at different biological levels, including alterations on gene expression, cellular homeostasis, shell formation, metabolic capacity and antioxidant mechanisms. The information here presented highlights that Gd may represent an environmental threat and a risk to human health, demonstrating the need for further research on Gd toxicity towards aquatic wildlife and the necessity for new water remediation strategies.

Evaluation of environmental contamination by toxic trace elements in Kazakhstan based on reviews of available scientific data

The environmental situation concerning pollution by (eco)toxic and persistent trace elements in Kazakhstan has been investigated by analytical reviews of scientific studies published over the past 20 years reporting concentrations of 10 toxic trace elements (TTE) observed in soil, sediments, or surface water. A database of 62 articles published in Kazakh, Russian, or English covered the majority of the territory of the country for soil and water samples but to a lesser extent for sediments. Reported concentrations were summarized using statistical parameters, then spatialized and finally classified in contamination classes according to local legislation. This analysis revealed some hotspots of TTE in surface waters (Cd and Pb), soil (As), and sediments (Cd and As). Hotspots of less toxic Cu, Zn, and Mn were also detected. Spatialization of results allowed localization of these hotspots close to industrial sites, such as smelters or mining and metallurgic combines. Others have been shown to be close to disused mining sites or landfills with municipal waste. Methodological improvements for further studies have been suggested, such as to integrate more West Kazakhstan or remote areas in sampling campaigns, but also to describe more exhaustively the used analytical methods and to be more attentive to the speciation of the analyzed form of the element. Finally, a management strategy to strengthen a sustainable food policy has been proposed: to reduce emissions by modernization of industrial facilities and better waste management, to organize land use depending on the contamination levels, and to reduce the bioavailability of the toxic elements.

Analysis of the Water Quality of the Ishim River within the Akmola Region (Kazakhstan) Using Hydrochemical Indicators

For the first time in scientific literature, this work addresses the current situation of the Ishim River water quality in the Akmola Region (Northern Kazakhstan). This work uses environmental monitoring techniques to analyze the current state of surface waters in the river. The content of main ions, biogenic and inorganic ions, heavy metals, organic impurities in seasonal and annual dynamics have been studied. Results show that, despite the tightening of requirements for wastewater discharge into the Ishim River basin, a number of water quality indicators did not fulfill the regulatory requirements for surface water bodies during 2013–2019. It has been identified that the greatest pollution in the Ishim River is brought by enterprises of the Karaganda-Temirtau technogenic region, located in the upper reaches of the river. Future water quality monitoring is needed and should include increasing the number of sampling locations and the sampling frequency in order to characterize the spatial and temporal variability of hydrochemical parameters and allow a comprehensive monitoring of legally fixed water quality parameters/indicators.

Distributions, Relationship and Assessment of Major Ions and Potentially Toxic Elements in Waters of Bosten Lake, the Former Largest Inland and Freshwater Lake of China

As one of the important water sources of the desert ecosystem in the Tarim Basin, the largest fishery base in Xinjiang, and the former largest inland and freshwater lake of China, the water quality of Bosten Lake is worthy of government and public attention. To determine the water’s hydrochemical composition and the water quality of Bosten Lake, analyses of the spatial distribution, water pollution status and irrigation suitability were conducted with statistical methods, including redundancy and factor analyses, inverse distance weighted interpolation, and water quality assessment and saturation index simulation of minerals in the water from a survey done in 2018. The results suggested that the average total dissolved solids (TDS) of Bosten Lake in 2018 was 1.32 g/L, and the lake is alkaline with a pH of 8.47. The strength of the water exchange capacity affected the spatial distribution of TDS. The spatial distribution of TDS and its value can be significantly changed by restoring the water supply of seasonal rivers in the northwest. The water of Bosten Lake contains sulfate and sodium groups, which are mainly affected by lake evaporation. As the pH increases, the content of carbonate ions increases, while the content of bicarbonate ions decreases. The spatial distributions of other major ions are consistent with that of the TDS. The spatial distribution of potentially toxic elements is more complicated than that of major ions. In general, the spatial distribution of Cu and As is more consistent with the spatial distribution of electrical conductivity or TDS. The spatial distributions of the Zn, Se and pH values are more consistent with respect to other variables. Although the water of Bosten Lake is still at a permissible level for water irrigation, the lake is moderately polluted, and the local site almost has a highly polluted status. The research results are of great significance for lake environmental protection and management as well as watershed ecological restoration.

Multiannual monitoring (1974-2019) of rare earth elements in wild growing edible mushroom species in Polish forests

There is a growing demand for rare earth elements (REEs) due to their use in modern technologies, and this may result in their emission to the environment. This is the first long-term study to monitor the content of REEs in four edible mushroom species. Over 21,900 samples of fruit bodies (sporocarps) of Boletus edulis, Imleria badia, Leccinum scabrum and Macrolepiota procera and their underlying soils, collected between 1974 and 2019 from 42 forest sites in Poland were examined in an attempt to understand the time evolution of the presence of REEs in the environment. In general, I. badia and B. edulis displayed a greater total content of REEs on mg per kg basis than L. scabrum and M. procera. A gradual increase in REEs in the studied mushrooms as well as associated forest soil samples was observed over the monitored period. Both levels were also highly correlated. Regardless of the considered period, human consumption of these mushrooms would not contribute significantly to dietary exposure to REEs. Wild growing mushroom species studied over a long time period may be a good bioindicator of REE migration to the environment.

Historical Change and Ecological Risk of Potentially Toxic Elements in the Lake Sediments from North Aral Sea, Central Asia

The Aral Sea has received worldwide attention for the deterioration of its biological and chemical status. The accumulation of potentially toxic elements (PTEs) in the lake sediments reflects changes in the surrounding watershed and represents a potential hazard for the lake ecosystem. In conjunction with existing environmental records from the Aral Sea basin, sedimentary records of PTEs in North Aral Sea covering a short time scale, anno Domini (AD) 1950–2018, were used to reveal historical changes in PTE concentrations and potential risks to lake functioning. The results suggested that the levels of PTEs in lake sediments from North Aral Sea changed abruptly around 1970 AD, which is concurrent with the intensification of human activities within the basin. After 1970 AD, with the exception of As, which remained at unpolluted-to-moderately polluted levels, the geo-accumulation indices of the remaining PTEs studied (V, Cr, Zn, Co, Pb, Ni, Cu and Cd) inferred a moderately polluted status. Before 1970 AD, the total ecological risk was low, but since 1970, the total ecological risk index has exceeded 150, indicating moderate risk. Historical changes in PTE levels of lake sediments from North Aral Sea and their potential ecological risks are reported for the first time. The conclusions provide an important reference for the protection of lake ecosystems and will provide data for regional/global comparisons of environmental change during the Anthropocene.

Influence of toxic elements on the simultaneous uptake of rare earth elements from contaminated waters by estuarine macroalgae

The present study tested whether the presence of potentially toxic elements (PTEs) (Cd, Cr, Cu, Pb, Hg and Ni), commonly found in wastewaters, interferes with the ability of macroalgae (Ulva intestinalis, Ulva lactuca, Fucus spiralis, Fucus vesiculosus, Gracilaria sp. and Osmundea pinnatifida) to remove rare earth elements (REEs) (La, Ce, Pr, Nd, Eu, Gd, Tb, Dy and Y), which are key elements for most high technologies (e.g. electronics, aerospace, renewable energy). Results proved the high capacity of living macroalgae to remove REEs from multielement solutions, with the following sequence of bioconcentration factors being observed: U. intestinalis (2790) > Gracilaria sp. (2119) > O. pinnatifida (1742) > U. lactuca (1548) > F. vesiculosus (944) > F. spiralis (841). Competition among REEs to sorption sites on the six macroalgae was minor due to the chemical similarities between the elements. However, Ce and Y were the less removed while Gd, La and Eu the most removed among REEs. Ionic strength was an important factor in the sorption process, with salinity affecting differently the six macroalgae. Surprisingly, the presence of potential toxic elements in solution enhanced the removal of REEs. The most plausible explanation is the preferentially complexation of those elements by carbonates over REEs, which facilitates the binding of REEs cations onto the surface of macroalgae.

Rare earth elements in poplar leaves as indicators of geological environment and technogenesis

Background and anomalous rare earth element (RЕЕ) concentrations in poplar (Populus spp.) leaves in urban areas of Siberia, Russian Far East, and Kazakhstan were determined. Regions with the highest RЕЕ levels were identified. Ratios of light to middle RЕЕs are geochemical indicators of the impacts of oil refining and mining. Airborne dust transport by prevailing winds from ash and slag dumps of power plants and industrial sites, and alluvial terraces control the REE distribution in cities.

Human-Induced Enrichment of Potentially Toxic Elements in a Sediment Core of Lake Balkhash, the Largest Lake in Central Asia

Over the past century, the impacts of human activities on the natural environment have continued to increase. Historic evolution of the environment under anthropogenic influences is an important reference for sustainable social development. Based on the geochemical analyses of a short sediment core of 49 cm from Lake Balkhash, the largest lake in Central Asia, potential factors historically influencing geochemical variation were revealed, and influences of human activity on regional environmental change were reconstructed over the past 150 years. The results showed that the dominant factor inducing changes in potentially toxic elements (V, Cr, Co, Ni, Zn, Cu, Cd, and Pb) is the physical weathering of the terrestrial materials. The variation in Ca content was influenced by the formation of authigenic carbonate. Since 1930, potentially toxic elements (Cr, Co, Ni, Zn, Cu, Cd, and Pb) in the lake sediments have obviously been affected by human activities, but the impact of human activities has not exceeded that of natural terrestrial weathering. In particular, the enrichment factors (EFs) for Cd and Pb reached 1.5. The average ecological risks of Cd were higher than the criterion of 30, suggesting a moderate risk to the local ecosystem in recent years. Total risk indices indicated moderate potential ecological risk for the lake ecology. The results will provide support for the environmental protection and better management practices of the Lake Balkhash watershed.

Potential Hazard of Lanthanides and Lanthanide-Based Nanoparticles to Aquatic Ecosystems: Data Gaps, Challenges and Future Research Needs Derived from Bibliometric Analysis

Lanthanides (Ln), applied mostly in the form of nanoparticles (NPs), are critical to emerging high-tech and green energy industries due to their distinct physicochemical properties. The resulting anthropogenic input of Ln and Ln-based NPs into aquatic environment might create a problem of emerging contaminants. Thus, information on the biological effects of Ln and Ln-based NPs is urgently needed for relevant environmental risk assessment. In this mini-review, we made a bibliometric survey on existing scientific literature with the main aim of identifying the most important data gaps on Ln and Ln-based nanoparticles' toxicity to aquatic biota. We report that the most studied Ln for ecotoxicity are Ce and Ln, whereas practically no information was found for Nd, Tb, Tm, and Yb. We also discuss the challenges of the research on Ln ecotoxicity, such as relevance of nominal versus bioavailable concentrations of Ln, and point out future research needs (long-term toxicity to aquatic biota and toxic effects of Ln to bottom-dwelling species).