Strontium in the environment: Review about reactions of plants towards stable and radioactive strontium isotopes

Distribution, risk evaluation, and source allocation of cesium and strontium in surface soil in a mining city

Radioactive nuclides cesium (Cs) and strontium (Sr) possess long half-lives, with 135Cs at approximately 2.3 million years and 87Sr at about 49 billion years. Their persistent accumulation can result in long-lasting radioactive contamination of soil ecosystems. This study employed geo-accumulation index (Igeo), pollution load index (PLI), potential ecological risk index (PEPI), health risk assessment model (HRA), and Monte Carlo simulation to evaluate the pollution and health risks of Cs and Sr in the surface soil of different functional areas in a typical mining city in China. Positive matrix factorization (PMF) model was used to elucidate the potential sources of Cs and Sr and the respective contribution rates of natural and anthropogenic sources. The findings indicate that soils in the mining area exhibited significantly higher levels of Cs and Sr pollution compared to smelting factory area, agricultural area, and urban residential area. Strontium did not pose a potential ecological risk in any studied functional area. The non-carcinogenic health risk of Sr to the human body in the study area was relatively low. Because of the lack of parameters for Cs, the potential ecological and human health risks of Cs was not calculated. The primary source of Cs in the soil was identified as the parent material from which the soil developed, while Sr mainly originated from associated contamination caused by mining activities. This research provides data for the control of Cs and Sr pollution in the surface soil of mining city.

Recent trends in the phytoremediation of radionuclide contamination of soil by cesium and strontium: Sources, mechanisms and methods: A comprehensive review

This comprehensive review examines recent trends in phytoremediation strategies to address soil radionuclide contamination by cesium (Cs) and strontium (Sr). Radionuclide contamination, resulting from natural processes and nuclear-related activities such as accidents and the operation of nuclear facilities, poses significant risks to the environment and human health. Cs and Sr, prominent radionuclides involved in nuclear accidents, exhibit chemical properties that contribute to their toxicity, including easy uptake, high solubility, and long half-lives. Phytoremediation is emerging as a promising and environmentally friendly approach to mitigate radionuclide contamination by exploiting the ability of plants to extract toxic elements from soil and water. This review focuses specifically on the removal of 90Sr and 137Cs, addressing their health risks and environmental implications. Understanding the mechanisms governing plant uptake of radionuclides is critical and is influenced by factors such as plant species, soil texture, and physicochemical properties. Phytoremediation not only addresses immediate contamination challenges but also provides long-term benefits for ecosystem restoration and sustainable development. By improving soil health, biodiversity, and ecosystem resilience, phytoremediation is in line with global sustainability goals and environmental protection initiatives. This review aims to provide insights into effective strategies for mitigating environmental hazards associated with radionuclide contamination and to highlight the importance of phytoremediation in environmental remediation efforts.

Strontium leaching from municipal waste subjected to incineration

The aim of the study was to determine the content and leachability of Sr in ashes obtained through combusting municipal waste in household furnaces. The waste had been collected as a mixed stream and as separate fractions (i.e. furniture, sponges, waste paper, PCV packaging, plastic-coated paper cartons, imitation leather, rubber, textiles and polystyrene). Using single-step chemical extractions, (HCl + HNO3, H2O, 0.01 M CaCl2, 0.1 M CH3COOH), we determined the total content of Sr (TC) and proportions of the following fractions: water-leachable, phytoavailable and easily soluble and bound to carbonates. We also analyzed the effect of reducing pH in the extraction solutions on St leachability from the study material. The study showed that Sr concentration in ash generated from the combustion of conventional fuels, alternative fuels and municipal waste ranged from 114 to 1006 mg/kg. The largest amounts of Sr were found in ash generated from the combustion of alternative fuels (coal pellets 488-1006 mg/kg), conventional fuels (hard coal 430-670 mg/kg) and mixed waste (237-825 mg/kg). The most mobile fraction of Sr (water-leachable) comprised from 1.3% to nearly 91% TC; the phytoavailable fraction and the ion-exchange and carbonate-bound fraction comprised 3-92% TC and 9-72% TC, respectively. We also found that the greatest pH reductions do not always entail the greatest amounts of extracted Sr. A much more significant factor in this respect is the mineral and chemical composition of primary materials, which can buffer changes in pH. The Risk Assessment Code (RAC) values pointed to a varied environmental risk and the highest RAC values (> 70) were found for coal pellets, wood pellets, straw, rubber and plastic containers for mixed oils.

Emerging activated tungsten dust: Source, environmental behaviors, and health effects

Fusion energy investigation has stepped to a new stage adopting deuterium and tritium as fuels from the previous stage concentrating hydrogen plasma physics. Special radiation safety issues would be introduced during this stage. In addition to industrial and military uses, tungsten is also regarded as the most promising plasma facing material for fusion reactors. During the operation of fusion reactors, tungsten-based plasma facing materials can be activated via neutron nuclear reaction. Meanwhile, activated tungsten dust can be produced when high-energy plasma interacts with the tungsten-based plasma facing materials, namely plasma wall interaction. Activated tungsten dust would be an emerging environmental pollutant with radiation toxicity containing various radionuclides in addition to the chemical toxicity of tungsten itself. Nonetheless, the historical underestimation of its environmental availability has led to limited research on tungsten compared to other environmental contaminants. This paper presents the first systematic review on the safety issue of emerging activated tungsten dust, encompassing source terms, environmental behaviors, and health effects. The key contents are as follows: 1) to detail the source terms of activated tungsten dust from aspects of tungsten basic properties, generation mechanism, physical morphology and chemical component, radioactivity, as well as potential release pathways, 2) to illustrate the environmental behaviors from aspects of atmospheric dispersion and deposition, transformation and migration in soil, as well as plant absorption and distribution, 3) to identify the toxicity and health effects from aspects of toxicity to plants, distribution in human body, as well as health effects by radiation and chemical toxicity, 4) based on the research progress, research and development issues needed are also pointed out to better knowledge of safety issue of activated tungsten dust, which would be beneficial to the area of fusion energy and ecological impact caused by the routine tungsten related industrial and military applications.

Risk assessment and strontium isotopic tracing of potentially toxic metals in creek sediments around a uranium mine, China

The contamination of creek sediments near industrially nuclear dominated site presents significant environmental challenges, particularly in identifying and quantifying potentially toxic metal (loid)s (PTMs). This study aims to measure the extent of contamination and apportion related sources for nine PTMs in alpine creek sediments near a typical uranium tailing dam from China, including strontium (Sr), rubidium (Rb), manganese (Mn), lithium (Li), nickel (Ni), copper (Cu), vanadium (V), cadmium (Cd), zinc (Zn), using multivariate statistical approach and Sr isotopic compositions. The results show varying degrees of contamination in the sediments for some PTMs, i.e., Sr (16.1-39.6 mg/kg), Rb (171-675 mg/kg), Mn (224-2520 mg/kg), Li (11.6-78.8 mg/kg), Cd (0.31-1.38 mg/kg), and Zn (37.1-176 mg/kg). Multivariate statistical analyses indicate that Sr, Rb, Li, and Mn originated from the uranium tailing dam, while Cd and Zn were associated with abandoned agricultural activities, and Ni, Cu, and V were primarily linked to natural bedrock weathering. The Sr isotope fingerprint technique further suggests that 48.22-73.84% of Sr and associated PTMs in the sediments potentially derived from the uranium tailing dam. The combined use of multivariate statistical analysis and Sr isotopic fingerprint technique in alpine creek sediments enables more reliable insights into PTMs-induced pollution scenarios. The findings also offer unique perspectives for understanding and managing aqueous environments impacted by nuclear activities.

Sizeable net export of base cations from a Carpathian flysch catchment indicates their geogenic origin while the 26Mg/24Mg, 44Ca/40Ca and 87Sr/86Sr isotope ratios in runoff are indistinguishable from atmospheric input

Nutrient imbalances may negatively affect the health status of forests exposed to multiple stress factors, including drought and bark beetle calamities. We studied the origin of base cations in runoff from a small Carpathian catchment underlain by base-poor flysch turbidites using magnesium (Mg), calcium (Ca) and strontium (Sr) isotope composition of 10 ecosystem compartments. Our objective was to constrain conclusions drawn from long-term hydrochemical monitoring of inputs and outputs. Annual export of Mg, Ca and Sr exceeds 5-to-15 times their atmospheric input. Mass budgets per se thus indicate sizeable net leaching of Mg, Ca and Sr from bedrock sandstones and claystones. Surprisingly, δ26Mg, δ44Ca and 87Sr/86Sr isotope ratios of runoff were practically identical to those of atmospheric deposition and soil water but significantly different from bedrock isotope ratios. We did not find any carbonates in the studied area as a hypothetical, easily dissolvable source of base cations whose isotope composition might corroborate the predominance of geogenic base cations in the runoff. Marine carbonates typically have lower δ26 Mg and 87Sr/86Sr ratios, and silicate sediments often have higher δ26Mg and 87Sr/86Sr ratios than runoff at the study site. Mixing of these two sources, if confirmed, could reconcile the flux and isotope data.

Microelement strontium and human health: comprehensive analysis of the role in inflammation and non-communicable diseases (NCDs)

Strontium (Sr), a trace element with a long history and a significant presence in the Earth's crust, plays a critical yet often overlooked role in various biological processes affecting human health. This comprehensive review explores the multifaceted implications of Sr, especially in the context of non-communicable diseases (NCDs) such as cardiovascular diseases, osteoporosis, hypertension, and diabetes mellitus. Sr is predominantly acquired through diet and water and has shown promise as a clinical marker for calcium absorption studies. It contributes to the mitigation of several NCDs by inhibiting oxidative stress, showcasing antioxidant properties, and suppressing inflammatory cytokines. The review delves deep into the mechanisms through which Sr interacts with human physiology, emphasizing its uptake, metabolism, and potential to prevent chronic conditions. Despite its apparent benefits in managing bone fractures, hypertension, and diabetes, current research on Sr's role in human health is not exhaustive. The review underscores the need for more comprehensive studies to solidify Sr's beneficial associations and address the gaps in understanding Sr intake and its optimal levels for human health.

Highly efficient removal of Sr2+ from aqueous solutions using a polyacrylic acid/crown-ether/graphene oxide hydrogel composite

With the development of nuclear power, efficiently treating nuclear wastes generated during operation has attracted extensive attention. Hydrogels are common adsorbent materials in the treatment of wastewater due to their high swelling rate and easy post-treatment. In this work, a novel polyacrylic acid/crown-ether/graphene oxide (PAA/DB18C6/GO) hydrogel composite was synthesized by a radical cross-linking copolymerization method and characterized using various analytical tools such as SEM, FT-IR, TGA and XPS. The effects of time, pH, initial Sr2+ concentration, and temperature on Sr2+ adsorption onto the PAA/DB18C6/GO were studied. The PAA/DB18C6/GO shows a high adsorption capacity of 379.35 mg g-1 at an initial Sr2+ concentration of 772 mg L-1 due to the unique structure of dibenzo-18-crown-ether-6 and high swelling. The composite has a high selectivity for Sr2+ with a removal rate of 82.4% when concentrations of Na+ and K+ were 10 times higher than that of Sr2+. The pH and temperature have no apparent impact on adsorption performance of the PAA/DB18C6/GO under the experimental conditions. The composite shows excellent reusability with more than 92% removal rate for Sr2+ after five continuous cycles. In addition, the mechanism of Sr2+ adsorption by PAA/DB18C6/GO was analyzed by fitting the adsorption data to the theoretical models and XPS data.

Photosynthetic Responses of Racomitrium japonicum L. to Strontium Stress Evaluated through Chlorophyll a Fluorescence OJIP Transient Analysis

Nuclides pollution and its biological effects are of great concern, especially for bryophytes during their terrestrial adaptation. Understanding PSII activity and electron transport response is vital for comprehending moss abiotic stress reactions. However, little is known about the photosynthetic performance of moss under nuclide treatment. Therefore, this study aimed to evaluate the chlorophyll fluorescence of Racomitrium japonicum L. The moss was subjected to Sr2+ solutions at concentrations of 5, 50, and 500 mg/L to evaluate chlorophyll a fluorescence using the OJIP test. Moderate and high Sr2+ stress led to inner cell membrane dissolution and reduced chlorophyll content, indicating impaired light energy absorption. At 5 mg/L Sr2+, fluorescence kinetics showed increased light energy capture, energy dissipation, and total photosynthetic driving force, thus stimulating transient photosynthetic activity of PSII and improving PSI reduction. Linear electron transfer and PSII stability significantly decreased under moderate and high Sr2+ stress, indicating potential photosynthetic center damage. Cyclic electron transfer (CEF) alleviated photosynthetic stress at 5 mg/L Sr2+. Thus, low Sr2+ levels stimulated CEF, adjusting energy flux and partitioning to protect the photosynthetic apparatus. Nevertheless, significant damage occurred due to inefficient protection under high Sr2+ stress.

Arthrocnemum Moq.: Unlocking Opportunities for Biosaline Agriculture and Improved Human Nutrition

(1) Background: This study provides novel insights into the elemental content and biomineralization processes of two halophytic species of the genus Arthrocnemum Moq. (A. macrostachyum and A. meridionale). (2) Methods: Elemental content was analyzed using ICP-MS, while biominerals were detected through electron microscopy (SEM and TEM) and X-ray diffraction. (3) Results: The elemental content showed significant concentrations of macronutrients (sodium, potassium, magnesium, and calcium) and micronutrients, especially iron. Iron was consistently found as ferritin in A. macrostachyum chloroplasts. Notably, A. macrostachyum populations from the Center of the Iberian Peninsula exhibited exceptionally high magnesium content, with values that exceeded 40,000 mg/kg d.w. Succulent stems showed elemental content consistent with the minerals identified through X-ray diffraction analysis (halite, sylvite, natroxalate, and glushinskite). Seed analysis revealed elevated levels of macro- and micronutrients and the absence of heavy metals. Additionally, the presence of reduced sodium chloride crystals in the seed edges suggested a mechanism to mitigate potential sodium toxicity. (4) Conclusions: These findings highlight the potential of Arthrocnemum species as emerging edible halophytes with nutritional properties, particularly in Western European Mediterranean territories and North Africa. They offer promising prospects for biosaline agriculture and biotechnology applications.

Lithium and strontium accumulation in native and invasive plants of the Sava River: Implications for bioindication and phytoremediation

The objective of this study was to investigate the potential of native and invasive plant species for the uptake and accumulation of lithium (Li) and strontium (Sr) along the Sava River, focusing on their bioindication and phytoremediation capabilities. Sampling was carried out in riparian zones exposed to different pollution sources in Slovenia, Croatia, and Serbia. Plant samples of native (Salix alba, Populus alba, Populus nigra, Ulmus glabra, Juglans regia) and invasive (Amorpha fruticosa, Reynoutria japonica, Solidago canadensis, Impatiens glandulifera) species were collected. The content of Li and Sr was analyzed in the soils, roots, and leaves of the selected plants, as well as physical and chemical soil properties. Both Li and Sr content in the soils increased from the source to the mouth of the Sava River. The native species showed significant potential for Li and Sr accumulation based on the metal accumulation index. The highest Sr accumulation was measured in the leaves of Salix alba and the roots of Juglans regia, while the highest Li accumulation was measured in Ulmus glabra. Native species, especially Salix alba, proved to be better bioindicators of Li and Sr. Invasive species, especially Amorpha fruticosa and Impatiens glandulifera, showed a remarkable ability to translocate Sr and Li, respectively, to leaves. These results provide valuable insight into the suitability of plants for biomonitoring soil contamination and potential applications in phytoremediation strategies. In summary, the study shows the importance of native species in the context of the accumulation and bioindication of soil pollution.

Environmental health risk assessment and source apportion of heavy metals using chemometrics and pollution indices in the upper Yamuna river basin, India

River Yamuna is the largest tributary of the Ganges with great economic importance, and provides water for about 57 million people and accounts for more than 70% of Delhi's water supply. Various pollution indices and chemometric methods were used to investigate heavy metal pollution, associated risks, and probable sources in the upper Yamuna river water. A total of 56 river water samples, 28 each in pre and post-monsoon season were collected and analysed for 15 heavy metals. The findings reveal that Al (38.66 ± 21.14 μg/L), As (16.52 ± 15.81 μg/L), and Mn (41.06 ± 89.25 μg/L) in pre-monsoon and Al (45.77 ± 29.46 μg/L), As (10.30 ± 12.15 μg/L), Fe (48.03 ± 81.11 μg/L), and Mn (31.02 ± 70.13 μg/L) in post-monsoon exceeded the Bureau of Indian Standards (BIS) acceptable limits. The pollution indices (HPI, NPI, HEI, and Cd) indicate that most locations are low to moderately polluted, except for the lower catchment. Health indices, i.e., hazard Index (HI) and incremental lifetime cancer risk (ILCR), suggest that the prolonged consumption of river water may cause potential human health hazards. In contrast, the water is suitable for domestic and other uses as the dermal risk is less prominent. The ecological risk index (ERI) of pre (0.22-58.75) and post-monsoon (0.12-44.21) were in the low-risk category (<110), indicating no ecological risk associated with heavy metals. In pre and post-monsoon, four principal components (PCs) described 73.97% and 76.18% of the total variance respectively, suggesting the mixed impact of numerous geogenic and anthropogenic sources in the region's water chemistry. Cluster analysis demonstrates that the lower catchment samples (National Capital Region, Delhi) significantly vary from each other due to wastewater discharge, industrialisation, and rapid urbanization, while the upper and mid-catchment samples are less distinct. Hence, more than 90% of the Yamuna water is extracted from the upper region; present findings may aid in developing an effective catchment scale management strategy.

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.

Chronic drought alters extractable concentrations of mineral elements in Mediterranean forest soils

Soil mineral elements play a crucial role in ecosystem productivity and pollution dynamics. Climate models project an increase in drought severity in the Mediterranean Basin in the coming decades, which could lead to changes in the composition and concentrations of mineral elements in soils. These changes can have significant impacts on the fundamental processes of plant-soil cycles. While previous studies have predominantly focused on carbon, nitrogen, and phosphorus, there is a notable lack of research on the biogeochemical responses of other mineral elements to increasing drought. In this study, we investigated the effects of chronic drought (15 years of experimental rainfall exclusion) and seasonal drought (summer period) on the extractable soil concentrations of 17 mineral elements (arsenic (As), calcium (Ca), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), potassium (K), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), lead (Pb), sulphur (S), strontium (Sr), vanadium (V) and zinc (Zn)) in a Mediterranean holm oak forest. We also explored the potential biotic and abiotic mechanisms underlying the changes in extractable elemental concentrations under chronic drought conditions. Our findings reveal that soil elemental concentrations varied significantly due to seasonal changes and chronic drought, with soil microclimate, biological activity, and organic matter being the main drivers of this variability. Levels of soil water content primarily explained the observed variations in soil elemental concentrations. Most of the mineral elements (13 out of 17) exhibited higher concentrations during winter-spring (wet seasons) compared to summer-autumn (dry seasons). The chronic drought treatment resulted in K limitation, increasing vegetation vulnerability to drought stress. Conversely, the accumulation of S in soils due to drought may intensify the risk of S losses from the plant-soil system. Under drought conditions, certain trace elements (particularly Mn, V, and Cd) exhibited increased extractability, posing potential risks to plant health and the exportation of these elements into continental waters. Overall, our results suggest that alterations in mineral element concentrations under future drier conditions could promote ecosystem degradation and pollution dispersion in the Mediterranean Basin. Understanding and predicting these changes are essential for effective ecosystem management and mitigating the potential negative impacts on plant health and water quality.

Climate and soil properties regulate the vertical heterogeneity of minor and trace elements in the alpine topsoil of the Hengduan Mountains

Soil minor and trace elements are vital regulators of ecological processes that sustain alpine ecosystem functions. In this study, the vertical pattern and driving factors of element concentrations in alpine soils of the Tibetan Plateau were investigated. Three snow mountains (Meili, Baima, and Haba) part of the Hengduan Mountain range, were selected as the study area to determine the vertical distribution of 12 typical elements (Cr, Ni, Cu, Fe, Mn, Zn, Cd, Pb, Ca, Sr, As, and Se) in topsoil with increasing and decreasing elevation, as well as the dominant driving factors of their spatial heterogeneity. Results showed that all elements, except Se, showed strong vertical heterogeneity, among which Cr, Ni, Cu, and Fe showed peak concentrations at 2700-3000 m; the highest concentrations of Mn and Zn were at 3200 m and 2700 m, with Cd and Pb at 2500 m. Ca and Sr levels gradually decreased with increasing elevation. According to the structural equation model and random forest analysis, the vertical heterogeneity of soil elements is directly regulated by the variability of climate and soil properties due to changes in elevation. A three-way PERMANOVA further quantized the contributions of climate and soil properties on vertical heterogeneity of all soil elements, which were 35.2 % and 50.5 %, respectively. This study used various statistical tools to reveal the dominant factors affecting the vertical heterogeneity of soil elements. These findings provided a scientific overview of element distribution on the Tibetan Plateau and significant references for the vertical distribution of elements in the topsoil of other snow mountains worldwide.

Aggregated transfer factors of fresh Cs and Sr pollution to various vegetables from six common European soils - mesocosm experiment

Aggregated transfer factors (Tag) were identified for three common vegetables grown in six common European soils freshly contaminated by 134Cs and 85Sr. The experiment was carried out as a mesocosm experiment in pots with an average soil weight of 15.8 kg per pot. The vegetables were grown one after the other during one vegetation season, in the order lettuce, onion, and radish (the order usually applied in private gardens and small farms). Despite the fact that lettuce was grown in the most contaminated soil, it had the lowest Tag (in m2/kg) of both radionuclides (3.6E-4 for Cs, 2.0E-2 for Sr), while onion had 6.4E-3 for Cs and 3.2E-2 for Sr and radish had 1.9E-3 for Cs and 8.1E-2 for Sr. Potassium supply did not show any statistically significant effect on Cs Tag; there was a significant impact of K on the decrease in Sr Tag. The experiments indicated that Tag is more affected by plant species than by soil type; therefore, selection of plants with a lower capacity to uptake radionuclides may be an important measure to reduce food contamination and thus minimize the committed effective dose.

Identification of strontium substitution mechanism in hematite via calcium solution

Nonradioactive strontium (Sr) are produced as a result of radioactive decay of heavier elements such as uranium and thorium. Nonradioactive Sr shares physicochemical similarities with Ca and can replace it during bone formation, which may cause bone cancer in humans. Hence, concerning the potential hazards associated with strontium, it is imperative to eliminate it. The present study aimed to investigate the removal mechanisms of hematite-adsorbed strontium by calcium solution. Strontium was adsorbed to hematite at pH 8 and 10 and washed with calcium solution. X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), scanning electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (after Ca washing) were performed on the samples before and after washing. Analyses and fitting by XANES and EXAFS confirmed the formation of an inner-sphere complex of strontium at pH 10. The XRD spectra showed that SrCO3 and SrFe2O4 formed at pH 8 and 10, respectively. After washing with the calcium solution, strontium was directly substituted to form CaCO3 and CaFe2O4. The X-ray photoelectron spectroscopy results provided a systematic analysis of the proportions of hematite and strontium, confirming the substitution of strontium with calcium. This substitution could be attributed to the physicochemical similarities between calcium and strontium. This study confirms the substitution of Sr with Ca, highlighting the physicochemical similarity of the Sr and Ca that facilitates substitution reactions.

In-situ elemental quantitative imaging in plant leaves by LA-ICP-MS with matrix-matching external calibration

Due to the enormous interest in plants related to bioscience, environmental and toxicological research, analytical methods are expected with the ability of getting information on elemental transfer, distribution and contents in plants. In this work, a mixture of gelatin (GA) and hydroxypropyl methyl cellulose (HPMC) was prepared to simulate plant matrix, a method based on laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) with matrix-matching external calibration was proposed for direct quantification of multiple elements in plants. The composition of GA&HPMC substrate was optimized, such as the concentration of spiked nitric acid, the mass fraction of both GA and HPMC in the substrate and the mass ratio of GA: HPMC. After spiking elemental solution, coating the mixture onto a glass slide and drying overnight at room temperature, GA&HPMC substrate was obtained. The substrate obtained with GA: HPMC of 8: 2 was used to fabricate the standard series, which exhibited good elemental homogeneity and similar elemental signal intensities in LA-ICP-MS detection to that obtained for plant Certified Reference Material (CRM). CRMs of different plants including Citrus leaf (GBW10019), Tea (GBW07605), Beans (GBW10021) and Scallions (GBW10049) were further pressed into pellets and subjected to the proposed method, and the quantification accuracy was demonstrated. The limits of detections of this method were found to be 0.003 (Ce)-104 (Ca) μg g-1, with a wide linear range (0.01-10000 μg g-1) for 17 target elements. The application potential of the method was further demonstrated by performing elemental imaging in Trigonotis peduncularis leaves. Rapid in-situ quantitative imaging of Zn, Cu, Sr and Mn was achieved, and the elemental quantitative distributions were discussed. The constructed substrate helped direct elemental quantification in plants. It provided a powerful and efficient tool for the investigation of the distribution and transfer of elements in plants, favoring further exploration of elemental bioavailability, transport and toxicity mechanisms.

Leaching of metals from red mud and toxicity in human cells in vitro

Toxicity of red mud, a waste from alumina production, was studied using human breast cancer MCF-7 cells. Culture medium was prepared by mixing water for 3 days with the red mud and removing solid particles afterwards (red mud water). Culture for 48 h of the cells in this medium in neutral pH decreased the cell viability, as analyzed by the MTT-test, and increased the formation of reactive oxygen species. Thus, neutralization does not eliminate the toxicity of red mud. In preliminary experiments, a combined effect of five metals (Cr, Li, V, Al, As) increased the formation of ROS (reactive oxygen species) statistically significantly. Each element separately did not have a similar effect. In environmental applications, red mud is likely to be used after activation. In this work, the red mud was activated using hydrochloric acid to study the physical and chemical properties before and after the treatment. Activation increased the specific surface area of red mud from 16 m2 g-1 to 148 m2 g-1, which is beneficial in many environmental applications such as in the adsorptive removal of pollutants. After activation, leaching of some elements from the red mud decreased (e.g. Al from 38.0 to 0.56 mg L-1, As from 21.0 to 2.1 μg L-1, V from 172.0 to 29.8 μg L-1) while some increased (e.g. Li from 0.04 to 2.81 mg L-1, Cr from 0.35 to 3.23 mg L-1).

Foliar Calcium Absorption by Tomato Plants: Comparing the Effects of Calcium Sources and Adjuvant Usage

The deficiency of calcium (Ca) reduces the quality and shelf life of fruits. In this scenario, although foliar spraying of Ca²⁺ has been used, altogether with soil fertilization, as an alternative to prevent deficiencies, little is known regarding its absorption dynamics by plant leaves. Herein, in vivo microprobe X-ray fluorescence was employed aiming to monitor the foliar absorption of CaCl₂, Ca-citrate complex, and Ca₃(PO₄)₂ nanoparticles with and without using adjuvant. We also investigated whether Sr²⁺ can be employed as Ca²⁺ proxy in foliar absorption studies. Moreover, the impact of treatments on the cuticle structure was evaluated by scanning electron microscopy. For this study, 45-day-old tomato (Solanum lycopersicum L., cv. Micro-Tom) plants were used as a model species. After 100 h, the leaves absorbed 90, 18, and 4% of aqueous CaCl₂, Ca-citrate, and Ca₃(PO₄)₂ nanoparticles, respectively. The addition of adjuvant increased the absorption of Ca-citrate to 28%, decreased that of CaCl₂ to 77%, and did not affect Ca₃(PO₄)₂. CaCl₂ displayed an exponential decay absorption profile with half-lives of 15 h and 5 h without and with adjuvant, respectively. Ca-citrate and Ca₃(PO₄)₂ exhibited absorption profiles that were closer to a linear behavior. Sr²⁺ was a suitable Ca²⁺ tracer because of its similar absorption profiles. Furthermore, the use of adjuvant affected the epicuticular crystal structure. Our findings reveal that CaCl₂ was the most efficient Ca²⁺ source. The effects caused by adjuvant suggest that CaCl₂ and Ca-citrate were absorbed mostly through hydrophilic and lipophilic pathways.

Efficient Co-Adsorption and Highly Selective Separation of Cs+ and Sr2+ with a K+ -Activated Niobium Germanate by the pH Control

¹³⁷ Cs and ⁹⁰ Sr are hazardous to ecological environment and human health due to their strong radioactivity, long half-life, and high mobility. However, effective adsorption and separation of Cs⁺ and Sr²⁺ from acidic radioactive wastewater is challenging due to stability issues of material and the strong competition of protons. Herein, a K⁺ -activated niobium germanate (K-NGH-1) presents efficient Cs⁺ /Sr²⁺ coadsorption and highly selective Cs⁺ /Sr²⁺ separation, respectively, under different acidity conditions. In neutral solution, K-NGH-1 exhibits ultrafast adsorption kinetics and high adsorption capacity for both Cs⁺ and Sr²⁺ (q_m ^Cs  = 182.91 mg g^-1 ; q_m ^Sr  = 41.62 mg g^-1 ). In 1 M HNO₃ solution, K-NGH-1 still possesses q_m ^Cs of 91.40 mg g^-1 for Cs⁺ but almost no adsorption for Sr²⁺ . Moreover, K-NGH-1 can effectively separate Cs⁺ from 1 M HNO₃ solutions with excess competing Sr²⁺ and M^{n +} (M^{n +}  = Na⁺ , Ca²⁺ , Mg²⁺ ) ions. Thus, efficient separation of Cs⁺ and Sr²⁺ is realized under acidic conditions. Besides, K-NGH-1 shows excellent acid and radiation resistance and recyclability. All the merits above endow K-NGH-1 with the first example of niobium germanates for radionuclides remediation. This work highlights the facile pH control approach towards bifunctional ion exchangers for efficient Cs⁺ /Sr²⁺ coadsorption and selective separation.

White clover from the exclusion zone of the Chernobyl NPP: Morphological, biochemical, and genetic characteristics

A comprehensive study of the biological effects of chronic radiation exposure (8 μGy/h) in populations of white clover (Trifolium repens L.) from the Chernobyl exclusion zone was carried out. White clover is one of the most important pasture legumes, having many agricultural applications. Studies at two reference and three radioactively contaminated plots showed no stable morphological effects in white clover at this level of radiation exposure. Increased activities of catalase and peroxidases were found in some impacted plots. Auxin concentration was enhanced in the radioactively contaminated plots. Genes involved in the maintenance of water homeostasis and photosynthetic processes (TIP1 and CAB1) were upregulated at radioactively contaminated plots.

Retaliation of Alstonia scholaris (L.) R.Br. to caesium and strontium in hydroponics: effect on morpho-physiology and induction of enzymatic defence

The habitation and environment are affected by the stable isotopes of caesium (Cs) and strontium (Sr), as well as by their radioactive isotopes. The current work gives insight on Alstonia scholaris' capacity to phytoextract stable caesium (Cs) and strontium (Sr), as well as the plant's ability to protect against the toxicity of both elements. Experiments with Cs [0-5 mM (CsCl)] and Sr [0-3 mM (SrCl₂. 6H₂O)] dosing in controlled light, temperature, and humidity condition in greenhouse for 21 days were undertaken. Cs and Sr accumulation in different plant parts was quantified with atomic absorption spectroscopy (AAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) respectively. Hyper-accumulation capacity for Cs and Sr was estimated with indices like transfer factor (TF) and translocation factors (TrF). The uptake pattern of caesium in Alstonia scholaris is 5452.8-24,771.4 mg/kg DW (TF = 85.2-57.6) and in the case of Sr is 1307.4-8705.7 mg/kg DW (TF = 85.3-1.46). The findings demonstrated the plant's ability to transfer Cs and Sr to aboveground biomass on the basis of dry weight, with the majority of the metals being deposited in the shoot rather than the root portion of the plant. For Cs and Sr, with increasing concentration, the plants exhibited the enzymatic expression for defence against metal toxicity by free radicals compared to control. Field emission electron microscopy with energy-dispersive spectroscopy (FESEM with EDS) was employed to assess the spatial distribution of Cs and Sr in plant leaf, indicating the accumulation of Cs, Sr, and their homologous components.

Multi-isotope fingerprints of recent environmental samples from the Baltic coast and their implications for bioarchaeological studies

Stable isotopes in coastal regions are influenced by the so-called sea spray effect which masks the actual terrestrial isotope fingerprint with a marine isotope signal. The sea spray impact on plants was investigated by analyzing different stable isotope systems (δ¹³C_cellulose, δ¹⁸O_cellulose, δ¹⁸O_sulfate, δ³⁴S_sulfate, δ³⁴S_{total S}, δ³⁴S_{organic S}, ⁸⁷Sr/⁸⁶Sr) in recent environmental samples (plants, soil, water) collected close to the Baltic Sea. All these isotopic systems are influenced by the sea spray, either by the uptake of ions (HCO₃^-, SO₄^2-, Sr²⁺) of marine origin, thus exhibiting a marine isotopic signature, or by biochemical reactions associated with, e.g., salinity stress. A shift towards seawater values is observed for δ¹⁸O_sulfate, δ³⁴S, and ⁸⁷Sr/⁸⁶Sr. Cellulose becomes enriched in ¹³C and ¹⁸O due to sea spray, further enhanced (δ¹³C_cellulose) or mitigated (δ¹⁸O_cellulose) by salinity stress. The effect differs both regionally and seasonally, probably as a result of, e.g., differences in wind strength or prevailing wind direction, as well as between plants collected only few meters apart, in either the open field or at more wind-protected sites, reflecting samples more or less influenced by sea spray. The stable isotope data of recent environmental samples are compared to previously analyzed archaeological bone samples of animals from the Viking Haithabu and Early Medieval Schleswig sites located close to the Baltic Sea. Potential regions of origin can be predicted based on the magnitude of the (recent) local sea spray effect. This enables the identification of probably non-local individuals. The insights into sea spray mechanisms, biochemical reactions in plants, as well as seasonal, regional, and small-scale differences in stable isotope data will help to interpret multi-isotope fingerprints at coastal sites. Our study demonstrates the usefulness of environmental samples for bioarchaeological studies. Moreover, the detected seasonal and small-scale differences require adjusted sampling strategies for, e.g., isotopic baselines in coastal areas.

Radionuclide contents in sediment and seafood from Makoko Lagoon, Lagos State, Nigeria

Sediment and seafood samples were collected from Makoko Lagoon, Lagos state, Nigeria. Gamma-ray spectrometry was used to determine the activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in the samples. The average activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th in the sediment were 41.04 ± 6.41, 10.15 ± 3.19 and 4.39 ± 2.10 Bq kg^-1, respectively, while the annual effective dose was 0.01 mSv/year. In seafood, the average activity concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th were 15.66 ± 8.07, 1.72 ± 1.51 and 1.93 ± 0.30 Bq kg^-1, respectively. The cumulative effective ingestion dose obtained ranged from 0.016 μSv/year (giant prawn) to 1.08 μSv/year (Parrotgrunt). The mean activity concentrations and absorbed dose rate in sediment were below the worldwide average values. The cumulative dose from the ingestion of seafood was also significantly low. Sediment and seafood from the lagoon in Makoko pose no health risk from a radiological point of view to the population.

Do transient hydrological processes explain the variability of strontium-90 activity in groundwater downstream of a radioactive trench near Chernobyl?

The Chernobyl Pilot Site (CPS) was created in 2000 in order to study radionuclide migration processes to the geosphere from radioactive material of the Red forest buried in a trench. In this article, the data collected in the CPS up to 2015 are analyzed to identify the links between hydrological conditions and release of strontium-90 (⁹⁰Sr) from the trench. Then, a flow-and-transport model is used for simulating distribution of ⁹⁰Sr both in the unsaturated and saturated zones downstream of the trench. The results show that the ⁹⁰Sr activity in groundwater is strongly transient in time, due to the high inter-annual variability of both the recharge rate and the groundwater level (some particularly wet winters resulted in saturation of the bottom part of the trench). In addition, the parameters that govern the sorption of ⁹⁰Sr in trench material appear to vary significantly in space (the retardation factor ranges from 10 to 50 depending on the location). This spatiotemporal variability could hide some critical processes, e.g., related to a long-term trend, and needs to be characterized through an appropriate sampling frequency.

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.

Phytoremediation Potential of Native Plant Species in Mine Soils Polluted by Metal(loid)s and Rare Earth Elements

Mining activity has an adverse impact on the surrounding ecosystem, especially via the release of potentially toxic elements (PTEs); therefore, there is an urgent need to develop efficient technologies to remediate these ecosystems, especially soils. Phytoremediation can be potentially used to remediate contaminated areas by potentially toxic elements. However, in soils affected by polymetallic contamination, including metals, metalloids, and rare earth elements (REEs), it is necessary to evaluate the behavior of these toxic elements in the soil-plant system, which will allow the selection of the most appropriate native plants with phytoremediation potential to be used in phytoremediation programs. This study was conducted to evaluate the level of contamination of 29 metal(loid)s and REEs in two natural soils and four native plant species (Salsola oppositifolia, Stipa tenacissima, Piptatherum miliaceum, and Artemisia herba-alba) growing in the vicinity of a Pb-(Ag)-Zn mine and asses their phytoextraction and phytostabilization potential. The results indicated that very high soil contamination was found for Zn, Fe, Al, Pb, Cd, As, Se, and Th, considerable to moderate contamination for Cu, Sb, Cs, Ge Ni, Cr, and Co, and low contamination for Rb, V, Sr, Zr, Sn, Y, Bi and U in the study area, dependent of sampling place. Available fraction of PTEs and REEs in comparison to total concentration showed a wide range from 0% for Sn to more than 10% for Pb, Cd, and Mn. Soil properties such as pH, electrical conductivity, and clay content affect the total, available, and water-soluble concentrations of different PTEs and REEs. The results obtained from plant analysis showed that the concentration of PTEs in shoots could be at a toxicity level (Zn, Pb, and Cr), lower than toxic but more than sufficient or natural concentration accepted in plants (Cd, Ni, and Cu) or at an acceptable level (e.g., V, As, Co, and Mn). Accumulation of PTEs and REEs in plants and the translocation from root to shoot varied between plant species and sampling soils. A. herba-alba is the least efficient plant in the phytoremediation process; P. miliaceum was a good candidate for phytostabilization of Pb, Cd, Cu, V, and As, and S. oppositifolia for phytoextraction of Zn, Cd, Mn, and Mo. All plant species except A. herba-alba could be potential candidates for phytostabilization of REEs, while none of the plant species has the potential to be used in the phytoextraction of REEs.

High strontium adsorption performance of layered zirconium phosphate intercalated with a crown ether

Effective removal of strontium isotopes in radioactive waste streams has important implications for the environment and the sustainable development of nuclear energy. In this work, a zirconium phosphate/18-crown-ether-6 (ZrP/18C6) composite was prepared using the intercalation method by loading crown ether into zirconium phosphate. The composite was structurally and morphologically characterized by XRD, FT-IR, XPS, and SEM. The adsorption experiments of Sr²⁺ onto the ZrP/18C6 composite were conducted as a function of temperature, pH, Sr²⁺ concentration and competing ions. The results indicate ZrP/18C6 can adsorb 98.6% of Sr²⁺ within 30 minutes at an Sr²⁺ concentration of 100 mg L^-1 and maintain a high removal rate with a distribution coefficient of 7 × 10⁵ mL g^-1 when Sr²⁺ is at a low level of 4.28 mg L^-1. The ZrP/18C6 composite reached a maximum adsorption capacity of 195.74 mg g^-1 at an Sr²⁺ concentration of 380 mg L^-1, which is significantly higher than the 43.03 mg g^-1 of α-ZrP. The adsorption performance of Sr²⁺ onto ZrP/18C6 is not significantly affected by temperature, pH and competing ions. Furthermore, the adsorption kinetics and thermodynamics were analyzed based on the adsorption data obtained in the present work. It is shown that the adsorption of Sr²⁺ onto ZrP/18C6 follows the pseudo-second-order model and the Langmuir monolayer model, respectively. Additionally, the adsorption mechanism of Sr²⁺ by ZrP/18C6 is discussed.

A strategy for bioremediation of nuclear contaminants in the environment

Radionuclides released from nuclear contamination harm the environment and human health. Nuclear pollution spread over large areas and the costs associated with decontamination is high. Traditional remediation methods include both chemical and physical, however, these are expensive and unsuitable for large-scale restoration. Bioremediation is the use of plants or microorganisms to remove pollutants from the environment having a lower cost and can be upscaled to eliminate contamination from soil, water and air. It is a cheap, efficient, ecologically, and friendly restoration technology. Here we review the sources of radionuclides, bioremediation methods, mechanisms of plant resistance to radionuclides and the effects on the efficiency of biological adsorption. Uptake of radionuclides by plants can be facilitated by the addition of appropriate chemical accelerators and agronomic management, such as citric acid and intercropping. Future research should accelerate the use of genetic engineering and breeding techniques to screen high-enrichment plants. In addition, field experiments should be carried out to ensure that this technology can be applied to the remediation of nuclear contaminated sites as soon as possible.

Phosphonation of Alginate-Polyethyleneimine Beads for the Enhanced Removal of Cs(I) and Sr(II) from Aqueous Solutions

Although Cs(I) and Sr(II) are not strategic and hazardous metal ions, their recovery from aqueous solutions is of great concern for the nuclear industry. The objective of this work consists of designing a new sorbent for the simultaneous recovery of these metals with selectivity against other metals. The strategy is based on the functionalization of algal/polyethyleneimine hydrogel beads by phosphonation. The materials are characterized by textural, thermo-degradation, FTIR, elemental, titration, and SEM-EDX analyses to confirm the chemical modification. To evaluate the validity of this modification, the sorption of Cs(I) and Sr(II) is compared with pristine support under different operating conditions: the pH effect, kinetics, and isotherms are investigated in mono-component and binary solutions, before investigating the selectivity (against competitor metals) and the possibility to reuse the sorbent. The functionalized sorbent shows a preference for Sr(II), enhanced sorption capacities, a higher stability at recycling, and greater selectivity against alkali, alkaline-earth, and heavy metal ions. Finally, the sorption properties are compared for Cs(I) and Sr(II) removal in a complex solution (seawater sample). The combination of these results confirms the superiority of phosphonated sorbent over pristine support with promising performances to be further evaluated with effluents containing radionuclides.

Uptake and Translocation of Cesium in Lettuce (Lactuca sativa L.) under Hydroponic Conditions

The uptake of radiocesium (RCs) by plants is key to the assessment of its environmental risk. However, the transfer process of RCs in the water-vegetable system still remains unclear. In this work, the uptake and accumulation processes of Cs+ (0-10 mM) in lettuce were explored under different conditions by using hydroponics. The results showed that the higher exposure concentration of Cs+ could lead to a faster uptake rate and would be beneficial to the uptake and accumulation of Cs+. The uptake of K+ by roots and leaves was inhibited significantly when Cs+ concentration increased, but unapparent for Ca2+ and Mg2+. It was found that the higher K+ and Ca2+ concentration was, the higher inhibition was found for the uptake of Cs+ in root. The uptake of Cs+ leads the decrease of chlorophyll content and brought a negative effect on plant photosynthesis, consequently, a negative effect on lettuce morphology and obvious decrease of biomass and root length. The contents of glutathione (GSH), malondialdehyde (MDA), and root vitality were increasing during the growth following stress of high concentrations of Cs+, which caused stresses on the antioxidant system of lettuce. The enrichment coefficient for Cs+ in leaves was in the range of 8-217. Moreover, the transfer factor was in the range of 0.114-0.828, which suggested that the high Cs+ concentration could enhance the transfer of Cs+ from lettuce root to leaf. This study provides more information on the transfer of RCs from water to food chain, promoting the understanding of the potential risk of RCs.

The elements of life: A biocentric tour of the periodic table

Living systems are built from a small subset of the atomic elements, including the bulk macronutrients (C,H,N,O,P,S) and ions (Mg,K,Na,Ca) together with a small but variable set of trace elements (micronutrients). Here, we provide a global survey of how chemical elements contribute to life. We define five classes of elements: those that are (i) essential for all life, (ii) essential for many organisms in all three domains of life, (iii) essential or beneficial for many organisms in at least one domain, (iv) beneficial to at least some species, and (v) of no known beneficial use. The ability of cells to sustain life when individual elements are absent or limiting relies on complex physiological and evolutionary mechanisms (elemental economy). This survey of elemental use across the tree of life is encapsulated in a web-based, interactive periodic table that summarizes the roles chemical elements in biology and highlights corresponding mechanisms of elemental economy.

Identification and quantification of the sea spray effect on isotopic systems in α-cellulose (δ13C, δ18O), total sulfur (δ34S), and 87Sr/86Sr of European beach grass (Ammophila arenaria, L.) in a greenhouse experiment

The sea spray effect can severely influence the isotopic signature of terrestrial individuals in coastal regions. To further specify this effect, beach grass was grown in a greenhouse under controlled environmental conditions and sprayed with mineral salt solution containing different mineral salts but only traces of NaCl (group 1). Another group of plants was sprayed with salty water from the Schlei inlet and the Baltic Sea, respectively (group 2). Control plants were only sprayed with tap water. Isotope analyses were conducted on the unwashed and washed plants (δ¹³C_cellulose, δ¹⁸O_cellulose, δ³⁴S_{total S}, ⁸⁷Sr/⁸⁶Sr), soil (δ¹⁸O_sulfate, δ³⁴S_sulfate, ⁸⁷Sr/⁸⁶Sr), and spray as well as irrigation water (δ¹⁸O_sulfate, δ³⁴S_sulfate, ⁸⁷Sr/⁸⁶Sr). Moreover, elemental analyses were performed on the water samples. The sea spray effect was visible in all isotopic systems under study. The uptake of SO₄^2-, HCO₃^-, and Sr²⁺ directly affected plants of group 1, while plants of group 2, sprayed with salty water, additionally showed salinity stress in the case of α-cellulose and total sulfur due to biochemical reactions of the plants. Very high concentrations in HCO₃^- or SO₄^2- also affected the plants' isotopic signatures. The impact of the sea spray and additional stress reactions were quantified. Our study is the first experiment creating an artificial sea spray effect in a greenhouse. This experiment for the first time enables the identification and quantification of the sea spray effect in environmental samples. The marine signature taken up by the plants and recorded by the investigated isotopic systems is apparently high and should have an impact on the isotopic fingerprints of animal consumers at the coast, as evidenced for archaeological animals from the Viking Haithabu and the early medieval Schleswig sites located close to the Baltic Sea. This result demonstrates the potential of greenhouse experiments as an isotopic predictor of the past local sea spray effect.

Effects of strontium on the morphological and photosynthetic physiological characteristics of Vicia faba seedlings

The adaptation of plants to strontium (Sr) stress requires a more systematic understanding. In the present study, the morphological and photosynthetic physiological characteristics of Vicia faba seedlings under Sr stress (⁸⁸Sr, 0-1,000 mg·L^-1) were analyzed in solution culture. The results showed that Sr treatment decreased the biomass and root activity of V. faba seedlings significantly, but fortunately, there was almost no root necrosis. In plant morphology, the taproot length, lateral root number, plant height, branching number and internodes number of V. faba were significantly inhibited, thus the apical dominance of taproot and terminal bud was more obvious. The accumulation of Sr resulted in the decrease of leaf area, dry weight, stomatal density and stomatal aperture, while the guard cell length increased, and the specific leaf weight (SLW) increased first and then decreased. These changes in stomatal morphology may be a positive regulation to reduce water loss. In addition, V. faba increased the non-photochemical quenching (NPQ) and the activities of peroxidase (POD) and ascorbate peroxidase (APX) to protect the photosynthetic structure. Low concentration of Sr (250 mg·L^-1) promoted the photochemical efficiency and electron transfer of PSII (e.g., increased F_v/F_m, Φ_PSII, qP and ETR). However, Sr (250-1,000 mg·L^-1) inhibited the net photosynthetic rate (P_n), transpiration rate (T_r) and stomatal conductance (G_s) in leaves. In general, the P_n was affected by both stomatal and non-stomatal factors. Since Sr did not cause significant damage to the PSII function, the non-stomatal factor may be the dark reaction in photosynthesis affected, but this needs to be proved by further studies.

Pilot study on provenance tracing of cocoons via strontium isotopes

Isotopic analysis has seen significant use in archaeological sciences to date objects, determine their origin, and depict ancient human dietary habits. However, the potential of this technique for provenance studies of ancient silks remains underdeveloped. In this study, we applied Sr isotopic ratios to the provenance tracing of silkworm cocoons. We investigated the ⁸⁷Sr/⁸⁶Sr ratios of cocoons from seven Chinese provinces to determine their regional differences. The ⁸⁷Sr/⁸⁶Sr ratios of mulberry leaves and cocoons in Shandong and Sichuan were analyzed and silkworms were cultured at four sampling locations in Hangzhou, Zhejiang, to determine isotopic signature relationships between mulberry leaves and cocoons. Those results showed that the ⁸⁷Sr/⁸⁶Sr signature of cocoons not only reflected regional differences, but also was related to the type of soil in each sampling location from which the samples were collected. It is suggested that the Sr isotope ratios was able to be an effective tool for the provenance tracing of cocoons. The Mann-Whitney test result indicated no significant differences in isotopic ratios between mulberry leaves and cocoons. In other words, mulberry leaves may predict mean isotopic values in the cocoons. No clear evidence of Sr isotopic fractionation was found in our control experiments. However, mulberry leaves and cocoons from Sichuan did not show significant correlation between them, overall reducing the predictive power of the ⁸⁷Sr/⁸⁶Sr ratios of mulberry leaf for provenance studies of cocoons. Finally, in order to improve the accuracy of Sr isotope ratios for the provenance tracing of cocoons, more ⁸⁷Sr/⁸⁶Sr data should be complemented and the relationship needs to be established between Sr isotope information in more kinds of proxies and cocoons.

One-Pot Environmentally Friendly Synthesis of Nanomaterials Based on Phytate-Coated Fe3O4 Nanoparticles for Efficient Removal of the Radioactive Metal Ions 90Sr, 90Y and (UO2)2+ from Water

We report the fast (three minutes) synthesis of green nanoparticles based on nanoparticles coated with the natural organic receptor phytate for the recognition and capture of ⁹⁰Sr, ⁹⁰Y, and (UO₂₎²⁺. The new material shows excellent retention for (UO₂)²⁺, 97%; these values were 73% and 100% for ⁹⁰Sr and ⁹⁰Y, respectively. Recovery of the three radioactive metal ions occurs through a non-competitive process. The new hybrid material is harmless, easy to prepare, and immobilizes these radioactive contaminants in water with great efficiency.

Multielement Determination in Turmeric (Curcuma longa L.) Using Different Digestion Methods

The antioxidant, anti-inflammatory and antiseptic properties of turmeric (Curcuma longa L.) derive from its rich nutritional composition making it interesting for medicinal uses, besides being used as spice in cooking. To complete the picture on the composition of turmeric, not only the organic compounds need to be known, but also the elemental composition covering essential and potentially toxic elements. The samples were digested in a microwave assisted digestion system using different reagent mixtures. The best digestion mixture was semi-concentrated nitric acid combined with hydrogen peroxide. After optimization of the sample preparation method, the contents of Ag, Al, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Rb, Se, Sr, Te, Tl, V and Zn in curcuma were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES), as well as by inductively coupled plasma mass spectrometry (ICP-MS). Even if the general composition found is in line with the scarce data in literature, clear differences can be seen between the analyzed samples, considering provenience, production procedures, and harvesting year as potential influencing factors. Whereas all samples contained less As and Pb than regulated by WHO, one limit exceeding was found for Cd.

Photosynthesis and growth of Amaranthus tricolor under strontium stress

Amaranthaceae are effective plants for cleaning soil contaminated by heavy metals and radionuclides. In this paper, Amaranthus tricolor was used to investigate the response of the plant photosynthesis to various concentration of strontium ions (0.2, 0.6, 3 and 6 mM), in order to determine the possibility of A. tricolor to remediate strontium contamination. The results showed that strontium ions (0.2-6 mM) had effect on light energy conversion and utilization in A. tricolor. Low level of strontium (0.2 mM) promoted the energy utilization in A. tricolor, while higher Sr concentration (3 mM or higher) increased the excess light energy in the plants. Under strontium stress of 6 mM, the acceptor side of PSII in A. tricolor leaves was more vulnerable to strontium stress than the donor side. Furthermore, strontium stress led to accumulation of Q_A^- and block in Q_B downstream of the electron transfer chain in PSII of A. tricolor leaves. The tolerance ability of A. tricolor to strontium and remediation is also reflected in its biomass and strontium content in plants. Strontium at 3 mM or below promoted the growth of A. tricolor, while higher concentration inhibited the plant growth, but without obvious wilting or curling of leaves. The maximal dry weight increased by 36.29% in shoots, and 60.14% in roots when the spiked-strontium concentration reached 0.2 mM. The maximal strontium content achieved 8.75 mg/g dry wt in shoots, and 1.71 mg/g dry wt in roots respectively, when strontium concentration was 6 mM. Transfer factors (TFs: ratio of Sr content in shoots to that in roots) of strontium in A. tricolor ranged from 2.85 to 5.93, while bio-concentration factors (BCFs: ratio of Sr content in shoots to that in solutions) ranged from 22.57 to 49.66. In summary, A. tricolor showed the excellent potential to remediate strontium contamination.

Association of Urinary Strontium with Cardiovascular Disease Among the US Adults: A Cross-Sectional Analysis of the National Health and Nutrition Examination Survey

Previous studies have demonstrated the effects of environmental metals on the cardiovascular system. However, the relationship of strontium (Sr) to cardiovascular disease (CVD) in the general population has not been established. This cross-sectional study aimed to investigate the association between urinary Sr (U-Sr) and CVD in the US adults using data of 5255 participants from the National Health and Nutrition Examination Survey (NHANES) 2011-2016. Multivariable logistic regression and restricted cubic spline (RCS) regression were performed to assess the association between U-Sr and CVD. After multivariable adjustments, compared to the lowest quartile, the adjusted odds ratios (ORs) of CVD with 95% confidence intervals (CIs) across the quartiles were 0.65 (0.46, 0.92), 0.87 (0.61, 1.25), and 0.78 (0.55, 1.10). RCS plot revealed a nonlinear relationship between U-Sr levels and CVD (P for nonlinearity = 0.004). Threshold effect analysis identified the inflection point of U-Sr for the curve was 90.18 μg/g urinary creatinine (μg/g UCr). Each 1-unit increase in U-Sr was associated with a 1.1% decrease in CVD (OR 0.989; 95% CI 0.980-0.998) on the left side of the inflection point, but no significant association was observed on the right side of the inflection point. This study suggests a nonlinear association of U-Sr with CVD prevalence in the US general adults. These findings may have positive implications for the determination of appropriate Sr levels for public cardiovascular health. Given the cross-sectional study design, further prospective studies are warranted.

Effect of strontium on nutrient uptake, physiological parameters, and strontium localization in lettuce

Human activities increase the risk of stable and radioactive strontium (Sr) isotopes entering the environment and food chain. In this study, the effects of Sr on the nutrient uptake and physiological responses of lettuce under different "Sr treatment" concentrations (0, control, 1, 2, 3, 4, and 5 mM) and "times" (7, 14, and 21 day) were studied in a hydroponic system. In addition, the distribution of Sr on the surfaces and cross-sections of lettuce leaves was revealed by scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) analysis. A two-way analysis of variance (ANOVA) method was used to analyze the significance of "Sr treatment," "time," and their "interaction." The results showed that an increase in Sr uptake in lettuce could significantly reduce the uptake of calcium (Ca). The contents of sulfur (S), potassium (K), and iron (Fe) in lettuce leaves showed significant differences with the sampling day. Similarly, the fresh weight of lettuce leaves and roots as well as the photosynthetic pigment contents of lettuce leaves was also significantly different with the sampling day. The activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) showed significant differences with the sampling day. The activities of SOD and CAT decreased significantly with the sampling day, while POD increased significantly. The MDA content increased significantly with increasing hydroponic Sr concentration on the 21st day. SEM-EDX analysis showed that the weight percentage of Sr in the vascular bundle sheath in the cross-section of lettuce leaves was relatively higher than that in the mesophyll. This study aids our understanding of the distribution of Sr in lettuce leaf tissues and the effect of Sr on lettuce physiology.

Establishing historical 90Sr activity in seawater of the China seas from 1963 to 2018

Historical ⁹⁰Sr activity in seawater was established in the China seas from 1963 to 2018. Based on the exponential decrease in ⁹⁰Sr activity in seawater, the effective half-life (EHL) of ⁹⁰Sr was quantified to be 11.5 ± 1.6 a, 16.5 ± 2.4 a, 27.2 ± 6.2 a, and 26.7 ± 4.3 a in the Bohai Sea, Yellow Sea, East China Sea, and South China Sea, respectively. We found contrasting patterns in the EHL of ⁹⁰Sr and ¹³⁷Cs in the marginal seas and open oceans that were closely related to the subtly different pathways of ⁹⁰Sr and ¹³⁷Cs in marine environment. Additionally, we demonstrated that Fukushima-derived ⁹⁰Sr (<0.01 Bq/m³) would be difficult to identify in the China seas. Our study not only provided the key parameter of the EHL in marine models for predicting the ⁹⁰Sr activity in the China seas in the post-Fukushima era but also enhanced our understanding of ⁹⁰Sr behavior and its fate in marine environments.

A review on the use of lichens as a biomonitoring tool for environmental radioactivity

Lichens have been widely used as a biomonitoring tool to record the distribution and concentration of airborne radioactivity and pollutants such as metals. There are limitations, however: although pollutants can be preserved in lichen tissues for long periods of time, not all radioactive and inert elements behave similarly. The chemical species of elements at the source, once captured, and the mode of storage within lichens play a role in this biomonitoring tool. Lichens are a symbiotic association of an algal or cyanobacterial partner (photobiont) with a fungal host (mycobiont). Lichens grow independently of the host substrates, including rocks, soils, trees and human-made structures. Lacking a root system, lichen nutrient or contaminant uptake is mostly through direct atmospheric inputs, mainly as wet and dry deposition. As lichens grow in a large variety of environments and are resilient in harsh climates, they are adapted to capture and retain nutrients from airborne sources. The context of this review partially relates to future deployment of small modular reactors (SMRs) and mining in remote areas of Canada. SMRs have been identified as a future source of energy (electricity and heat) for remote off-grid mines, potentially replacing diesel fuel generation facilities. For licensing purposes, SMR deployment and mine development requires capabilities to monitor background contaminants (natural radioactivity and metals) before, during and after deployment, including for decommissioning and removal. Key aspects reviewed herein include: (1) how lichens have been used in the past to monitor radioactivity; (2) radiocontaminants capture and storage in lichens; (3) longevity of radiocontaminant storage in lichen tissues; and (4) limitations of lichens use for monitoring radiocontaminants and selected metals.

Impacts of environmental pollution on mangrove phenology: Combining remotely sensed data and generalized additive models

Mangrove ecosystems worldwide have been affected by anthropogenic activities that modify natural conditions and supply trace elements that affect mangrove health and development. In order to gain a better understanding of these ecosystems, and assess the influence of physicochemical (granulometry, pH, salinity and ORP) and geochemical variables (concentrations of V, Cr, Co, Ni, Cu, Zn, Pb, Rb, Sr and Zr) on mangrove phenology, we combined field and satellite derived remotely sensed data. Phenology metrics in combination with Generalized Additive Models showed that start of the season was strongly influenced by Pb and Cu pollution as well as salinity and pH, with a large percentage of deviance explained (92.10%) by the model. Start of season exhibited non-linear delays as a response to pollution. Other phenology parameters such as the length of season, timing of the peak of season, and growth peak also indicated responses to both trace elements and physicochemical and geochemical variables, with percentages of deviance explained by the models ranging between 33.90% and 97.70%. While the peak of season showed delays as a response to increased pH and decreased salinity, growth peak exhibited a non-linear decrease as a response to increased Sr concentrations. These results suggest that trace element pollution is likely to lead to altered phenological patterns in mangroves.

The concentration and health risk assessment of radionuclides in the muscle of tuna fish: A worldwide systematic review and meta-analysis

Exposure to radionuclides, especially in food, can endanger the health of consumers. In this study, a systematic review and meta-analysis were performed regarding the concentration of radionuclides in tuna fish muscle. International databases including PubMed, Scopus, and Embase were searched to find articles regarding the concentration of radionuclides in tuna fish muscle from 1 January 2000 to 20 February 2021. The lowest and highest concentration of radionuclides was related to Caesium-137 (¹³⁷Cs) and Potassium-40 (⁴ K), respectively. The rank order of radionuclides based on their pooled concentration was ⁴ K (370.157 Bq/kg) > ²¹⁰Po Polonium-210 (26.312 Bq/kg) > ²¹⁰Pb (5.339 Bq/kg) > ²²⁶Ra (4.005 Bq/kg) > ¹³⁷Cs (0.415 Bq/kg). The health risk assessment based on annual effective dose indicates that consumers are at the safe range of health risk (H < 1 mSv/y). The continuous monitoring concentration of radionuclides in seafood and health risk assessment should be recommended.