A critical review of selenium biogeochemical behavior in soil-plant system with an inference to human health

Effect of inorganic arsenic in paddy soil on the migration and transformation of selenium species in rice plants

Selenium (Se) in paddy rice is one of the significant sources of human Se nutrition. However, the effect of arsenic (As) pollution in soil on the translocation of Se species in rice plants is unclear. In this research, a pot experiment was designed to examine the effect of the addition of 50 mg As/kg soil as arsenite or arsenate on the migration of Se species from soil to indica Minghui 63 and Luyoumingzhan. The results showed that the antagonism between inorganic As and Se was closely related to the rice cultivar and Se oxidation state in soil. Relative to the standalone selenate treatment, arsenite significantly (p < 0.05) decreased the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, sheaths, leaves, brans and kernels of both cultivars by 21.4%-100.0%, 40.0%-100.0%, 41.0%-100%, 5.4%-96.3%, 11.3%-100.0% and 26.2%-39.7% respectively, except for selenocystine in the kernels of indica Minghui 63 and selenomethionine in the leaves of indica Minghui 63 and the stems of indica Luyoumingzhan. Arsenate also decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, brans and kernels of both cultivars by 34.9%-100.0%, 30.2%-100.0%, 11.3%-100.0% and 5.6%-39.6% respectively, except for selenate in the stems of indica Minghui 63. However, relative to the standalone selenite treatment, arsenite and arsenate decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenite only in the roots of indica Minghui 63 by 45.5%-100.0%. Our results suggested that arsenite and arsenate had better antagonism toward Se species in selenate-added soil than that in selenite-added soil; moreover, arsenite had a higher inhibiting effect on the accumulation of Se species than arsenate.

Water-Soluble Se-Containing Proteins from Chicken Alleviate DSS-Induced Ulcerative Colitis in Mice via Inhibiting TLR4/MyD88 Pathway and Protecting the Goblet Cell Pathway

The influence of water-soluble selenium-containing proteins (WSSeP) in chicken on ulcerative colitis (UC) is not known. This work aims to investigate the effect of two WSSeP including h-Se with 1.78 μg Se/g and l-Se with 1.04 μg Se/g on mice UC induced by dextran sodium sulfate (DSS) versus 5-aminosalicylic acid (5-ASA). Seventy C57BL/6 mice were randomly divided into seven groups: groups 1 and 7 were given normal saline. Group 2 to group 4 were administrated orally 500, 1500, and 3000 mg/kg/day h-Se, respectively. Group 5 was given 1500 mg/kg/day l-Se as the control of group 3. From day 14 to day 21, groups 2 to 7 were fed with 3% DSS. Synchronously, group 6 was fed with 150 mg/kg/day 5-ASA. On day 21, the disease activity index, colon length, the histopathological changes, the expressions of claudin-1, occludin, ZO-1, TLR4, and MyD88 in colons, the levels of inflammatory cytokines (IFN-γ, IL-1β, IL-6, TNF-α), and antioxidant markers (LPS, GSH-Px, SOD, MDA) in serum were determined. WSSeP can effectively improve the damages of DSS to the colon, thymus, and spleen, which present protein and Se dose-dependent. 1.50 g h-Se dose can significantly promote the expression levels of claudin-1, occludin, and ZO-1, to surround crypt gland and goblet and epithelial cells and inhibit the attack of DSS, suppress TLR4/MyD88 pathway, decrease the levels of IL-1β, IL-6, TNF-α, IFN-γ, LPS, and MDA, and increase the activities of GSH-Px and SOD, which are better than those of 5-ASA. Therefore, WSSeP would be a natural and potential anti-inflammatory agent for UC.

Liposomes as selenium nanocarriers for foliar application to wheat plants: A biofortification strategy

In the present work, liposomes have been used as nanocarriers in the biofortification of wheat plants with selenium (Se) through foliar application. Liposomal formulations were prepared using 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and Phospholipon®90H (P90H) (average size <100 nm), loaded with different concentrations of inorganic Se (selenite and selenate) and applied twice to the plants in the stage of vegetative growth. Liposomes enhanced Se uptake by wheat plants compared to direct application. The highest Se enrichment was achieved using the phospholipid DPPC and a concentration of 1000 μmol·L-1 of Se without affecting the biomass, chlorophylls, carotenoids, and the concentration of mineral nutrients of the plants. The chemical speciation of Se in the plants was further investigated by X-ray absorption spectroscopy (XAS). The results from XAS spectra revealed that most of the inorganic Se was transformed to organic Se and that the use of liposomes influenced the proportion of C-Se-C over C-Se-Se-C species.

Response of selenium pools to drought stress by regulating physio‑biochemical attributes and anatomical changes in Gentiana macrophylla

Selenium (Se), as a vital stress ameliorant, possesses a beneficial effect on mediating detrimental effects of environmental threats. However, the mechanisms of Se in mitigating the deleterious effects of drought are still poorly understood. Gentiana macrophylla Pall. is a well-known Chinese medicinal herb, and its root, as the main medicinal site, has significant therapeutic effects. The purpose of this experiment was to investigate the functions of Se on the seedling growth and physiobiochemical characteristics in G. macrophylla subjected to drought stress. The changes in microstructure and chloroplast ultrastructure of G. macrophylla leaves under drought exposure were characterized by scanning electron microscopy (SEM), scanning electron microscopes and energy dispersive X-Ray spectroscope (SEM-EDX), and transmission electron microscopy (TEM), respectively. Results revealed that drought stress induced a notable increase in oxidative toxicity in G. macrophylla, as evidenced by elevated levels of hydrogen peroxide (H2O2), lipid peroxidation (MDA), enhanced antioxidative response, decreased plant photosynthetic function, and inhibited plant growth. Chloroplasts integrity with damaged membranes and excess osmiophilic granule were observed in the drought-stressed plants. Se supplementation notably recovered the stomatal morphology, anatomical structure damage, and chloroplast ultrastructure of G. macrophylla leaves caused by drought exposure. Exogenous Se application markedly enhanced SPAD, photosynthetic stomatal exchange parameters, and photosystem II activity. Se supplementation significantly promoted the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT), while reducing levels of MDA, superoxide anion (O2-.) and H2O2, and improving membrane integrity. Furthermore, the ameliorative effects of Se were also suggested by increased contents of osmotic substances (soluble sugar and proline), boosted content of gentiopicroside and loganinic acid in roots, and alleviated the inhibition in plant growth and biomass. Fourier transform infrared (FTIR) analysis of Se-treated G. macrophylla roots under drought stress demonstrated that Se-stimulated metabolites including O-H, C-H, N-H, C-N, and CO functional groups, were involved in resisting drought stress. Correlation analysis indicated an obvious negative correlation between growth parameters and MDA, O2-. and H2O2 content, while a positive correlation with photosynthetic gas exchange parameters. Principal component analysis (PCA) results explained the total variance into two principal components contributing the maximum (93.50 %) among the drought exposure with or without Se due to the various experiment indexes. In conclusion, Se exerts beneficial properties on drought-induced detrimental effects in G. macrophylla by relieving oxidative stress, improving photosynthesis indexes, PSII activity, regulating anatomical changes, altering levels of gentiopicroside and loganinic acid, and promoting growth of drought-stressed G. macrophylla.

A review on arsenic pollution, toxicity, health risks, and management strategies using nanoremediation approaches

OBJECTIVES

Over 50 countries are affected by arsenic contamination. The problem is becoming worse as the number of affected people increases and new sites are reported globally.

CONTENT

Various human activities have increased arsenic pollution, notably in both terrestrial and aquatic environments. Contamination of our water and soil by arsenic poses a threat to our environment and natural resources. Arsenic poisoning harms several physiological systems and may cause cancer and death. Excessive exposure may cause toxic build-up in human and animal tissues. Arsenic-exposed people had different skin lesion shapes and were vulnerable to extra arsenic-induced illness risks. So far, research shows that varying susceptibility plays a role in arsenic-induced diseases. Several studies have revealed that arsenic is a toxin that reduces metabolic activities. Diverse remediation approaches are being developed to control arsenic in surrounding environments.

SUMMARY AND OUTLOOK

A sustainable clean-up technique (nanoremediation) is required to restore natural equilibrium. More research is therefore required to better understand the biogeochemical processes involved in removing arsenic from soils and waters.

Geochemical characteristics, source analysis, influencing factors, and reserves of soil Selenium in Wuming, Guangxi, China

Although selenium (Se) reserves are crucial for the development and exploitation of Se-rich resources in karst soil areas, research on these reserves is still limited. A comprehensive study was conducted in a typical karst region known for its Se richness. A total of 12,547 surface soil samples, 134 deep soil samples, and 60 soil profiles from various locations were systematically collected. The findings showed that the Se content in the surface soil ranged from 0.073 to 9.04 mg/kg, with a baseline level of 0.84 mg/kg. This underscores the high background level and moderate variability in the region. Surface soil Se exhibited a notable positive correlation with deep soil Se, and an inverse correlation with pH (p < 0.01). One-way analysis of variance indicated that land formations and soil structure were the primary determinants affecting the concentration of Se in the topsoil (p = 0.000), with parent rock type and land-use type following closely (p = 0.003). In addition, the study included an investigation of soil Se variations with depth using 60 soil profiles. Through this analysis, it was revealed that Se content exhibited an exponential change with depth. Multiple integrations were employed to derive formulas for calculating Se reserves in the 0-200 cm depth range. Following these calculations, the estimations of Se stockpile across diverse types of source materials, varieties of soils, and land management methods were determined, highlighting the findings using a passive construction. This paper lays the groundwork for advancing the extraction and application of Se.

Fertilizer application alters cadmium and selenium bioavailability in soil-rice system with high geological background levels

The co-occurrence of cadmium (Cd) pollution and selenium (Se) deficiency commonly exists in global soils, especially in China. As a result, there is great interest in developing practical agronomic strategies to simultaneously achieve Cd remediation and Se mobilization in paddy soils, thereby enhancing food quality/safety. To this end, we conducted a field-plot trial on soils having high geological background levels of Cd (0.67 mg kg-1) and Se (0.50 mg kg-1). We explored 12 contrasting fertilizers (urea, potassium sulfate (K2SO4), calcium-magnesium-phosphate (CMP)), amendments (manure and biochar) and their combinations on Cd/Se bioavailability. Soil pH, total organic carbon (TOC), soil available Cd/Se, Cd/Se fractions and Cd/Se accumulation in different rice components were determined. No significant differences existed in mean grain yield among treatments. Results showed that application of urea and K2SO4 decreased soil pH, whereas the CMP fertilizer and biochar treatments increased soil pH. There were no significant changes in TOC concentrations. Three treatments (CMP, manure, biochar) significantly decreased soil available Cd, whereas no treatment affected soil available Se at the maturity stage. Four treatments (CMP, manure, biochar and manure＋urea＋CMP＋K2SO4) achieved our dual goal of Cd reduction and Se enrichment in rice grain. Structural equation modeling (SEM) demonstrated that soil available Cd and root Cd were negatively affected by pH and organic matter (OM), whereas soil available Se was positively affected by pH. Moreover, redundancy analysis (RDA) showed strong positive correlations between soil available Cd, exchangeable Cd and reducible Cd with grain Cd concentration, as well as between pH and soil available Se with grain Se concentration. Further, there was a strong negative correlation between residual Cd/Se (non-available fraction) and grain Cd/Se concentrations. Overall, this study identified the primary factors affecting Cd/Se bioavailability, thereby providing new guidance for achieving safe production of Se-enriched rice through fertilizer/amendment management of Cd-enriched soils.

Soil respiration induces co-emission of greenhouse gases and methylated selenium from cold-region Mollisols: Significance for selenium deficiency

Mollisols rich in natural organic matter are a significant sink of carbon (C) and selenium (Se). Climate warming and agricultural expansion to the cold Mollisol regions may enhance soil respiration and biogeochemical cycles, posing a growing risk of soil C and Se loss. Through field-mimicking incubation experiments with uncultivated and cultivated soils from the Mollisol regions of northeastern China, this research shows that soil respiration remained significant even during cold seasons and caused co-emission of greenhouse gases (CO2 and CH4) and methylated Se. Such stimulus effects were generally stronger in the cultivated soils, with maximum emission rates of 7.45 g/m2/d C and 1.42 μg/m2/d Se. For all soil types, the greatest co-emission of CO2 and dimethyl selenide occurred at 25 % soil moisture, whereas measurable CH4 emission was observed at 40 % soil moisture with higher percentages of dimethyl diselenide volatilization. Molecular characterization with three-dimensional fluorescence and ultra-high resolution mass spectrometry suggests that CO2 emission is sensitive to the availability of microbial protein-like substances and free energy from organic carbon biodegradation under variable moisture conditions. Predominant Se binding to biodegradable organic matter resulted in high dependence of Se volatilization on rates of greenhouse gas emissions. These findings together highlight the importance of dynamic organic carbon quality for soil respiration and consequent Mollisol Se loss risk, with implications for science-based management of C and Se resources in agricultural lands to combat with Se deficiency.

Stratum affects the distribution of soil selenium bioavailability by modulating the soil physicochemical properties: A case study in a Se-enriched area, China

The soil selenium (Se) content and bioavailability are important for human health. In this regard, knowing the factors driving the concentration of total Se and bioavailable Se in soils is essential to map Se, enhance foodstuffs' Se content, and improve the Se nutritional status of humans. In this study, total Se and Se bioavailability (i.e., phosphate extracted Se) in surface soils (0-20 cm) developed on different strata were analyzed in a Se-enriched region of Southwest China. Furthermore, the interaction between the stratum and soil properties was assessed and how did the stratum effect on the concentration and spatial distribution of Se bioavailability in soils was investigated. Results showed that the median concentration of total Se in soils was 0.308 mg/kg, which is higher than China's soil background. The mean proportion of phosphate extracted Se in total Se was 12.2 %. The values of total Se, phosphate extracted Se, and soil organic matter (SOM) in soils increased with the increasing stratum age. In contrast, the coefficient of weathering and eluviation (BA) values decreased. The analysis of statistics and Geodetector revealed that the SOM, stratum, and BA were the dominant controlling factors for the contents and distributions of soil total Se and phosphate extracted Se. This study provided strong evidence that the soil properties that affected the total Se and Se bioavailability were modulated by the local geological background, and had important practical implications for addressing Se malnutrition and developing the Se-rich resource in the study region and similar geological settings in different parts of the globe.

Factors controlling accumulation and bioavailability of selenium in paddy soils: A case study in Luxi County, China

Selenium (Se) accumulation in rice (Oryza sativa L.) has become a major global concern. Se offers multiple health benefits in humans; however, its inadequate or excessive intake can be harmful. Therefore, determining the factors driving Se abundance and bioavailability in paddy soils is essential to ensure the safety of human Se intake. This study investigated the accumulation, bioavailability, and distribution of Se in 820 paddy soil and rice grain samples from Luxi County, China to assess how soil properties (soil organic matter [SOM], cation exchange capacity [CEC], and pH), geographical factors (parent materials, elevation, and mean annual precipitation [MAP] and temperature [MAT]), and essential micronutrients (copper [Cu], zinc [Zn], and manganese [Mn]) govern Se accumulation and bioavailability in paddy soils. Results showed that the average soil Se content was 0.36 mg kg-1, which was higher than that in China (0.29 mg kg-1). Alternatively, the average rice grain Se content was 0.032 mg kg-1, which was lower than the minimum allowable content in Se-rich rice grains (0.04 mg kg-1). Five studied parent materials all had a significant effect on soil Se content but had little effect on Se bioavailability (p < 0.05). CEC, elevation, and SOM, as well as the soil contents of Cu, Zn, and Mn were positively correlated with soil Se content, but pH, MAP, and MAT were negatively correlated. Correspondingly, Se bioavailability was negatively correlated with SOM and soil Zn content, but positively correlated with MAP and grain contents of Cu, Zn, and Mn. Furthermore, partial least squares path analysis revealed the interactive impacts of the influencing factors on Se accumulation and bioavailability in soils. On this basis, prediction models were established to predict Se accumulation and bioavailability in paddy soils, thereby providing theoretical support for developing efficient control measures to meet Se challenges in agriculture.

Associations Between Serum Selenium and Bone Mineral Density in 8-19-year-old children and adolescents: NHANES 2013-2018

The peak bone mass (PBM) in puberty has been proven to be a critical determinant of osteoporosis and brittle fractures in the elderly. Selenium is an essential trace element that could influence bone metabolism in our bodies. However, no study has investigated the impact of selenium status on bone mineral density (BMD) among children and adolescents. This was a cross-section study from National Health and Nutrition Examination Survey (NHANES) in the USA involving participants aged 8-19 years. We conducted multiple linear regression models to assess the relationship between selenium status and BMD among children and adolescents, and then stratified analyses were performed according to genders and races. Smooth curve fits and two-piecewise linear regression models were conducted to explore their nonlinear relationship. A total of 4570 participants (2338 boys and 2232 girls) were included in the present study, with a mean age of 13.57 ± 3.41 years. In the multivariable adjustment model, serum selenium was positively associated with lumbar spine BMD (β = 0.021 95% CI: 0.008, 0.034, P = 0.001). The dose-response analyses indicated a non-linear inverted U-shaped relationship between serum selenium and lumbar spine BMD. Lower and higher selenium concentrations were related to decreased BMD, and the inflection point of serum selenium was 2.60 umol/L. The inverted U-shaped association was also observed in females (inflection point: 2.49 umol/L), males (inflection point: 2.65 umol/L), Non-Hispanic White (inflection point: 2.50 umol/L), Non-Hispanic Black (inflection point: 2.50 umol/L), and other races (Including multi-racial) (inflection point: 2.81 umol/L). Our study first shows a non-linear inversed U-shaped association between selenium status and BMD among children and adolescents. The proper selenium status will benefit bone health in children and adolescents. More research is still required to verify our findings and their potential mechanisms.

AI-assisted systematic review on remediation of contaminated soils with PAHs and heavy metals

This systematic review addresses soil contamination by crude oil, a pressing global environmental issue, by exploring effective treatment strategies for sites co-contaminated with heavy metals and polycyclic aromatic hydrocarbons (PAHs). Our study aims to answer pivotal research questions: (1) What are the interaction mechanisms between heavy metals and PAHs in contaminated soils, and how do these affect the efficacy of different remediation methods? (2) What are the challenges and limitations of combined remediation techniques for co-contaminated soils compared to single-treatment methods in terms of efficiency, stability, and specificity? (3) How do various factors influence the effectiveness of biological, chemical, and physical remediation methods, both individually and combined, in co-contaminated soils, and what role do specific agents play in the degradation, immobilization, or removal of heavy metals and PAHs under diverse environmental conditions? (4) Do AI-powered search tools offer a superior alternative to conventional search methodologies for executing an exhaustive systematic review? Utilizing big-data analytics and AI tools such as Litmaps.co, ResearchRabbit, and MAXQDA, this study conducts a thorough analysis of remediation techniques for soils co-contaminated with heavy metals and PAHs. It emphasizes the significance of cation-π interactions and soil composition in dictating the solubility and behavior of these pollutants. The study pays particular attention to the interplay between heavy metals and PAH solubility, as well as the impact of soil properties like clay type and organic matter on heavy metal adsorption, which results in nonlinear sorption patterns. The research identifies a growing trend towards employing combined remediation techniques, especially biological strategies like biostimulation-bioaugmentation, noting their effectiveness in laboratory settings, albeit with potentially higher costs in field applications. Plants such as Medicago sativa L. and Solanum nigrum L. are highlighted for their effectiveness in phytoremediation, working synergistically with beneficial microbes to decompose contaminants. Furthermore, the study illustrates that the incorporation of biochar and surfactants, along with chelating agents like EDTA, can significantly enhance treatment efficiency. However, the research acknowledges that varying environmental conditions necessitate site-specific adaptations in remediation strategies. Life Cycle Assessment (LCA) findings indicate that while high-energy methods like Steam Enhanced Extraction and Thermal Resistivity - ERH are effective, they also entail substantial environmental and financial costs. Conversely, Natural Attenuation, despite being a low-impact and cost-effective option, may require prolonged monitoring. The study advocates for an integrative approach to soil remediation, one that harmoniously balances environmental sustainability, cost-effectiveness, and the specific requirements of contaminated sites. It underscores the necessity of a holistic strategy that combines various remediation methods, tailored to meet both regulatory compliance and the long-term sustainability of decontamination efforts.

Straw with different fermentation degrees mediate Se/Cd bioavailability by governing the putative iron reducing bacteria

Straw returning is a crucial agronomic practice in fields due to its various benefits. However, effects and mechanisms of straw with different fermentation degrees on Se and Cd bioavailability have not been sufficiently investigated. In this study, straw with different fermentation degrees were applied to a Cd-contaminated seleniferous soil to investigate their effects on Se and Cd bioavailability. Results revealed that the effects of straw application on Se/Cd bioavailability in soil depended on the fermentation degrees of straw. Both original and slightly fermented straw had pronounced impacts on microbial iron reduction compared to fully fermented straw, and thus led to a significant increase in Se and Cd bioavailability. The linear discriminant analysis effect size (LEfSe) showed that norank_f_Symbiobacteraceae, Micromonospora, WCHB1-32, Ruminiclostrdium, and Cellulomonas were the major biomarkers at genus level in straw application soils, additional network analysis and random forest analysis suggested that Ruminiclostrdium and Cellulomonas might be implicated in microbial iron reduction. Furthermore, the microbial iron reduction had negative effects on mineral-associated Se with coefficient of -0.81 and positive effects on mineral-associated Cd with coefficient of 0.72, while Mn fractions exhibited positive effects on mineral-associated Se with a coefficient of 0.53 and negative effects on mineral-associated Cd. In conclusion, straw with different fermentation degrees governed Se and Cd mobility by regulating abundance of Ruminiclostrdium and Cellulomonas, subsequently affecting Fe and Mn fractions and consequently influencing Se and Cd bioavailability.

Selenium Improves the Control Efficacy of Phytophthora nicotianae by Damaging the Cell Membrane System and Promoting Plant Energy Metabolism

Tobacco black shank (TBS), caused by Phytophthora nicotianae, poses a significant threat to tobacco plants. Selenium (Se), recognized as a beneficial trace element for plant growth, exhibited inhibitory effects on P. nicotianae proliferation, disrupting the cell membrane integrity. This action reduced the energy supply and hindered hyphal transport through membrane proteins, ultimately inducing hyphal apoptosis. Application of 8 mg/L Se through leaf spraying resulted in a notable decrease in TBS incidence. Moreover, Se treatment preserved chloroplast structure, elevated chitinase activities, β-1,3-GA, polyphenol oxidase, phenylalanine ammonia-lyase, and increased hormonal content. Furthermore, Se enhanced flavonoid and sugar alcohol metabolite levels while diminishing amino acid and organic acid content. This shift promoted amino acid degradation and flavonoid synthesis. These findings underscore the potential efficacy of Se in safeguarding tobacco and potentially other plants against P. nicotianae.

Mechanisms of adsorption and functionalization of biochar for pesticides: A review

Agricultural production relies heavily on pesticides. However, factors like inefficient application, pesticide resistance, and environmental conditions reduce their effective utilization in agriculture. Subsequently, pesticides transfer into the soil, adversely affecting its physicochemical properties, microbial populations, and enzyme activities. Different pesticides interacting can lead to combined toxicity, posing risks to non-target organisms, biodiversity, and organism-environment interactions. Pesticide exposure may cause both acute and chronic effects on human health. Biochar, with its high specific surface area and porosity, offers numerous adsorption sites. Its stability, eco-friendliness, and superior adsorption capabilities render it an excellent choice. As a versatile material, biochar finds use in agriculture, environmental management, industry, energy, and medicine. Added to soil, biochar helps absorb or degrade pesticides in contaminated areas, enhancing soil microbial activity. Current research primarily focuses on biochar produced via direct pyrolysis for pesticide adsorption. Studies on functionalized biochar for this purpose are relatively scarce. This review examines biochar's pesticide absorption properties, its characteristics, formation mechanisms, environmental impact, and delves into adsorption mechanisms, functionalization methods, and their prospects and limitations.

Epigallocatechin gallate (EGCG) nanoselenium application improves tea quality (Camellia sinensis L.) and soil quality index without losing microbial diversity: A pot experiment under field condition

Applying selenium (Se) fertilizer is the only way to alleviate soil Se deficiency. Although effects of nanoselenium foliar application on plant growth and stress resistance have been extensively investigated, soil application of nanoselenium on soil microorganisms and their relationship with crop quality and soil health remains unclear. In this study, a steady-state homogeneous nanoparticle of epigallocatechin gallate Se (ESe) was synthesized, and a pot experiment was conducted applying ESe at five concentrations (0, 1, 10, 50, and 100 mg kg-1) to the tea planattion soil. The study revealed a significant increase in Se concentration in soil and tea with ESe application and identified 2.43-7.8 mg kg-1 as the safe and optimal range for soil application. Specifically, the moderate dose of ESe improved the tea quality [reduced tea polyphenols (TP), increased free amino acids (AA), and reduced TP/AA] and soil quality index (SQI). Besides, in marure tea leaves, antioxidant enzyme activities [promote catalase (CAT) superoxide dismutase (SOD), and peroxidase (POD)] increased, while level of oxidative stress [malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide anion (O2-)] decreased with ESe application. The 16S rRNA of the soil bacteria showed that ESe application significantly changed the community structure of soil bacteria but did not alter the diversity of the bacteria and the abundance of dominant taxa (phylum and genus levels). Statistical analysis of the taxonomic and functional profiles (STAMP) detected 21 differential taxa (genus level), mainly low-abundance ones, under the ESe application. Linear regression and random forest (RF) modeling revealed that the low-abundance bacterial taxa were significantly correlated with SQI (R2 = 0.28, p < 0.01) and tea quality (R2 = 0.23-0.37, p < 0.01). Thus, the study's findings suggest that ESe application affects soil and tea quality by modulating the low-abundance taxa in soil. The study also highlights the crucial role of low-abundance bacterial taxa of the rhizosphere in regulating soil functions under the ESe application.

Polyurethane with β-Selenocarbonyl Structure Enabling the Combination of Plastic Degradation and Waste Upcycling

Degradable polymers offer a promising solution to mitigate global plastic pollution, but the degraded products often suffer from diminished value. Upcycling is a more sustainable approach to upgrade polymer waste into value-added products. Herein, we report a β-selenocarbonyl-containing polyurethane (SePU), which can be directly degraded under mild conditions into valuable selenium fertilizers for selenium-rich vegetable cultivation globally, enabling both plastic degradation and waste upcycling. Under oxidation condition, this polymer can be easily and selectively degraded via selenoxide elimination reaction from mixed plastic waste. The degraded product can serve as effective selenium fertilizers to increase selenium content in radish and pak choi. The SePU exhibits excellent mechanical properties. Additionally, we observed the formation of spherulites-like selenium particles within the materials during degradation for the first time. Our research offers a successful application of selenoxide elimination reaction in the field of plastic degradation for the first time, endowing plastics with both degradability and high reusable value. This strategy provides a promising solution to reduce pollution and improve economy and sustainability of plastics.

Structure characterization and antioxidant activity of abalone visceral peptides-selenium in vitro

Peptide-selenium chelate is widely regarded as one of the best selenium supplements for relieving selenium deficiency. In this study, abalone visceral peptides (AVP) was used to prepare a new type of peptides-selenium chelate to develop an organic selenium supplement with antioxidant activity. AVP prepared by alcalase exhibited the highest selenium-chelating ability. UV-visible spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy and other structural analysis showed that selenium was mainly bound to the functional groups of -NH, -OH, -CH, CC, CO, and CN bonds on AVP. The formation of AVP-selenium chelate enhanced thermal stability and generated a new crystal structure. The ABTS•+ and •OH scavenging activities of AVP-selenium chelate were increased after in vitro digestion than that of AVP. Conclusively, this study analyzed the chelating mechanism of AVP and selenium from a structural perspective, which would provide a theoretical basis for the development of new selenium supplements.

Exogenous application of silicon and selenium improves the tolerance of tomato plants to calcium nitrate stress

Silicon (Si) and selenium (Se) can improve the tolerance of plants to NaCl-induced salt stress. However, few studies are available on their regulatory effects on plants' tolerance to calcium nitrate stress, which often occurs in protected facilities, causing secondary soil salinization. In this study, we report the effects of Si (6 mM) and Se (20 μM) applied separately or in combination on the growth, photosynthesis, oxidative damage, and nitrogen metabolism of tomato plants, as well as fruit quality under calcium nitrate stress. The results showed that applications of Si or Se alone or in combination improved the plant growth and photosynthetic performance and reduced oxidative damage of the stressed plants. Applications of Si and Se did not decrease the calcium accumulation in leaves of the stressed plants. Under calcium nitrate stress, the concentrations of NO3-, NO2- and NH4+ in leaves were significantly increased, while the activities of nitrogen assimilation-related enzymes (including nitrate reductase, nitrite reductase, glutamine synthase, glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase) were decreased. Applications of Si and Se, especially their combined treatment, decreased the NO3-, NO2-, and NH4+ concentrations and enhanced the activities of nitrogen assimilation-related enzymes in the stressed plants. Applied Si and Se also decreased the nitrate and titratable acid concentrations and increased vitamin levels in tomato fruits under calcium nitrate stress. It is suggested that Si and Se improved the tomato plant growth and fruit quality under calcium nitrate stress by alleviating oxidative damage and promoting both photosynthesis and nitrogen assimilation.

Tuning active sites on biochars for remediation of mercury-contaminated soil: A comprehensive review

Mercury (Hg) contamination is acknowledged as a global issue and has generated concerns globally due to its toxicity and persistence. Tunable surface-active sites (SASs) are one of the key features of efficient BCs for Hg remediation, and detailed documentation of their interactions with metal ions in soil medium is essential to support the applications of functionalized BC for Hg remediation. Although a specific active site exhibits identical behavior during the adsorption process, a systematic documentation of their syntheses and interactions with various metal ions in soil medium is crucial to promote the applications of functionalized biochars in Hg remediation. Hence, we summarized the BC's impact on Hg mobility in soils and discussed the potential mechanisms and role of various SASs of BC for Hg remediation, including oxygen-, nitrogen-, sulfur-, and X (chlorine, bromine, iodine)- functional groups (FGs), surface area, pores and pH. The review also categorized synthesis routes to introduce oxygen, nitrogen, and sulfur to BC surfaces to enhance their Hg adsorptive properties. Last but not the least, the direct mechanisms (e.g., Hg- BC binding) and indirect mechanisms (i.e., BC has a significant impact on the cycling of sulfur and thus the Hg-soil binding) that can be used to explain the adverse effects of BC on plants and microorganisms, as well as other related consequences and risk reduction strategies were highlighted. The future perspective will focus on functional BC for multiple heavy metal remediation and other potential applications; hence, future work should focus on designing intelligent/artificial BC for multiple purposes.

Synthesis of novel liquid phase exfoliation of chitosan/Bi2Se3 hybrid nanocomposites for in-vitro wound healing

Numerous studies have recently established the potential of chitosan (Chi) to enhance wound healing. Chi is a carbohydrate biopolymer that is biocompatible, low-cost, toxic-free, and has excellent antibacterial properties. In this study, we synthesized Chi/Bi2Se3 hybrid nanocomposites (NCs) using a liquid exfoliation approach. The physicochemical characterization of the hybrid NCs was investigated using X-ray diffraction, Fourier transforms infrared, Thermogravimetric, Scanning electron microscope, and Transmission electron microscope. The antibacterial ability has been investigated versus two pathogens, S. aureus and E. coli. In comparison to bare materials, the hybrid NCs demonstrated better antibacterial activity against both bacterial strains. As a result, the electrostatic attraction of positively charged Chi can easily attract the negatively charged surface of the bacteria cell membrane and NCs generate reactive oxygen species (ROS). This ROS can attack bacteria's intracellular components and eventually kill bacteria. The biocompatibility of the Chi/Bi2Se3 NCs was evaluated against L929 mice fibroblast cells, and there was no evident cytotoxicity. Furthermore, an in-vitro wound scratch test was carried out on L929 mouse fibroblast cells and the Chi/Bi2Se3 hybrid NCs promote wound healing and cell proliferation. These findings suggest that the Chi/Bi2Se3 hybrid NCs as a promising future material for bacteria-infected in-vivo wound healing.

Environmental selenium and human longevity: An ecogeochemical perspective

Selenium (Se) has been called the "longevity element" by the scientific community because it has anti-cancer, anti-inflammatory, and anti-oxidant activity in humans. The geochemical properties and biological functions of Se have been widely studied in various fields, including geology, agriculture, and medicine. Bama Yao Autonomous County (Bama), a typical township in China with high longevity among the population, was selected as the research area. The present study organically combines the geological background, dietary structure, absorption and metabolism, and other biogeochemical aspects to comprehensively analyze the anti-aging properties of Se under high-Se conditions and a fiber-rich polysaccharide diet. Biogeochemical samples of surface soil, food, human hair, and urine were systematically collected from the environment and the residents, and the content and speciation of Se were analyzed. Concentrations of Se in the soil were moderate to high for Bama, with high-Se soil in 77.21% of the samples. Water-soluble Se concentrations were also high, 90% of the samples with moderate to high Se, and had a significant positive correlation with Se concentrations in crops. With both high total and high available Se, dietary samples from the study area showed Se-enriched characteristics. Accordingly, Se intake was also high (82.54 μg/d) in the population, strongly maintaining the normal bodily functions of the elderly. Accumulation and metabolism of Se in the population were assessed based on concentrations of Se in the hair and urine of residents over 60 years old. Continuous accumulation of Se was found to occur from 71 to 80 years of age. Concentrations of Se in residents under 71 years old and over 80 years old were in a state of loss. Overall, Se absorption and metabolism are maintained at the optimal physiological state, which is one of the primary factors maintaining the health and longevity of the elderly people in the study area.

Influencing factors of selenium transformation in a soil-rice system and prediction of selenium content in rice seeds: a case study in Ninghua County, Fujian Province

Selenium (Se) is an essential element for human and animal health and has antioxidant, anticancer, and antiviral effects. However, more than 100 million people in China do not have enough Se in their diets, resulting in a state of low Se in the human body. Since the absorption of Se by crop seeds depends not only on the Se content in soil, there are many omissions and misjudgments in the division of Se-rich producing areas. Soil pH, total iron oxide content (TFe2O3), soil organic matter (SOM), and P and S contents were the main factors affecting Se migration and transformation in the soil-rice system. In this study, we compared the performance of the back propagation neural network (BP network) and multiple linear regression (MLR) using 177 pairs of soil-rice samples. Our results showed that the BP network had higher accuracy than MLR. The accuracy and precision of the prediction data met the requirements, and the prediction data were reliable. Based on the Se data of surface paddy fields, 26,900 ha of Se-rich rice planting area was planned using this model, accounting for 77% of the paddy field area. In the planned Se-rich area for rice, the proportion of soil Se content greater than 0.4 mg·kg-1 was only 5.29%. Our research is of great significance for the development of Se-rich lands.

Preparation of polysaccharide-conjugated selenium nanoparticles from spent mushroom substrates and their growth-promoting effect on rice seedlings

Selenium nanoparticles (SeNPs) have gained significant attention in the agricultural field due to their favorable bioavailability and low toxicity, making them a highly researched subject. In this study, crude polysaccharides from spent mushroom substrate of Agrocybe aegerita (AaPs) were extracted for preparing the polysaccharide‑selenium-nanoparticles (AaPs-SeNPs) by ascorbic acid reduction method. The structure of AaPs-SeNPs was analyzed and their growth-promoting effects on rice seedlings were studied by adopting different application methods. The results revealed that AaPs-SeNPs exhibited improved free radical scavenging ability, with a lower half-maximal inhibitory concentrations compared to AaPs. Rice seedlings treated with AaPs-SeNPs showed significant enhancements in growth characteristics when compared to AaPs treatment, and foliar application exhibited a better growth-promoting effect compared to root application. Moreover, the growth performance and antioxidant enzyme activities of rice seedlings were enhanced by the addition of AaPs-SeNPs, and the absorption efficiency of essential nutrients such as N/P/K and Fe/Zn/Mn was also improved at appropriate concentrations, which could be one of the key factors contributing to the improved growth performance of plants. This study provides new aspects for the utilization of SMS, and also offers new insights from the perspective of nutrient absorption on how polysaccharide-conjugated selenium nanoparticles enhance crop growth.

Spatially varying relationships of soil Se concentration and rice Se concentration in Guangxi, China: A geographically weighted regression approach

In recent years, the biogeochemical behavior and environmental impact of Selenium (Se) on soil-plant systems have received widespread attention, and traditional statistical methods reveal generally positive correlations between rice Se and soil Se. However, that initial positive relationship may have been obscured by local external factors. Using local scale data from the geochemical evaluation of land quality project, this work employed geographically weighted regression (GWR) to examine the spatial variation of rice Se (as the dependent variable) and soil Se (as the independent variable) in Guangxi. Strong and weak correlation coefficients occur between rice Se and soil Se, thereby indicating that their relationships are spatially varying. Guangxi is characterized by significantly positive correlations in most areas, with weak correlations mostly found in the south-western and central-eastern regions. Areas with weak correlation can be divided into two patterns: high soil Se with low rice Se and high rice Se with low soil Se. The unique patterns are correlated with distinct natural factors, particularly the abundance of Fe-rich soils in the carbonate area; by contrast, sandstone areas in central Guangxi may have been affected by anthropogenic activities. To reveal the spatially varying relationships at the local scale, we employed GWR, an effective tool that allowed us to identify the association between environmental variables and influencing factors and explore spatially varying relationships between them. This study breaks through the existing understanding that soil Se is completely positively correlated with rice Se for the first time, and concludes that their correlation is spatially variable, providing an effective approach for the study of complex relationships.

Mechanism of selenite tolerance during barley germination: A combination of tissue selenium metabolism alterations and ascorbate-glutathione cycle modulation

Selenite is widely used to increase Selenium (Se) content in cereals, however excessive selenite may be toxic to plant growth. In this study, barley was malted to elucidate the action mechanism of selenite in the generation and detoxification of oxidative toxicity. The results showed that high doses (600 μM) of selenite radically increased oxidative stress by the elevated accumulation of superoxide and malondialdehyde, leading to phenotypic symptoms of selenite-induced toxicity like stunted growth. Barley tolerates selenite through a combination of mechanisms, including altering Se distribution in barley, accelerating Se efflux, and increasing the activity of some essential antioxidant enzymes. Low doses (150 μM) of selenite improved barley biomass, respiratory rate, root vigor, and maintained the steady-state equilibrium between reactive oxygen species (ROS) and antioxidant enzyme. Selenite-induced proline may act as a biosignal to mediate the response of barley to Se stress. Furthermore, low doses of selenite increased the glutathione (GSH) and ascorbate (AsA) concentrations by mediating the ascorbate-glutathione cycle (AsA-GSH cycle). GSH intervention and dimethyl selenide volatilization appear to be the primary mechanisms of selenite tolerance in barley. Thus, results from this study will provide a better understanding of the mechanisms of selenite tolerance in crops.

A review on sources of soil antimony pollution and recent progress on remediation of antimony polluted soils

Antimony (Sb) is a serious toxic and non-essential metalloid for animals, humans, and plants. The rapid increase in anthropogenic inputs from mining and industrial activities, vehicle emissions, and shoot activity increased the Sb concentration in the environment, which has become a serious concern across the globe. Hence, remediation of Sb-contaminated soils needs serious attention to provide safe and healthy foods to humans. Different techniques, including biochar (BC), compost, manures, plant additives, phyto-hormones, nano-particles (NPs), organic acids (OA), silicon (Si), microbial remediation techniques, and phytoremediation are being used globally to remediate the Sb polluted soils. In the present review, we described sources of soil Sb pollution, the environmental impact of antimony pollution, the multi-faceted nature of antimony pollution, recent progress in remediation techniques, and recommendations for the remediation of soil Sb-pollution. We also discussed the success stories and potential of different practices to remediate Sb-polluted soils. In particular, we discussed the various mechanisms, including bio-sorption, bio-accumulation, complexation, and electrostatic attraction, that can reduce the toxicity of Sb by converting Sb-V into Sb-III. Additionally, we also identified the research gaps that need to be filled in future studies. Therefore, the current review will help to develop appropriate and innovative strategies to limit Sb bioavailability and toxicity and sustainably manage Sb polluted soils hence reducing the toxic effects of Sb on the environment and human health.

28-Homobrassinolide Primed Seed Improved Lead Stress Tolerance in Brassica rapa L. through Modulation of Physio-Biochemical Attributes and Nutrient Uptake

Brassinosteroids (BRs) influence a variety of physiological reactions and alleviate different biotic and abiotic stressors. Turnip seedlings were grown with the goal of further exploring and expanding their function in plants under abiotic stress, particularly under heavy metal toxicity (lead stress). This study's objective was to ascertain the role of applied 28-homobrassinolide (HBL) in reducing lead (Pb) stress in turnip plants. Turnip seeds treated with 1, 5, and 10 µM HBL and were grown-up in Pb-contaminated soil (300 mg kg-1). Lead accumulation reduces biomass, growth attributes, and various biochemical parameters, as well as increasing proline content. Seed germination, root and shoot growth, and gas exchange characteristics were enhanced via HBL treatment. Furthermore, Pb-stressed seedlings had decreased total soluble protein concentrations, photosynthetic pigments, nutrition, and phenol content. Nonetheless, HBL increased chlorophyll a and chlorophyll b levels in plant, resulting in increased photosynthesis. As a result, seeds treated with HBL2 (5 µM L-1) had higher nutritional contents (Mg+2, Zn+2, Na+2, and K+1). HBL2-treated seedlings had higher DPPH and metal tolerance indexes. This led to the conclusion that HBL2 effectively reduced Pb toxicity and improved resistance in lead-contaminated soil.

Research Progress of Selenium-Enriched Foods

Selenium is an essential micronutrient that plays a crucial role in maintaining human health. Selenium deficiency is seriously associated with various diseases such as Keshan disease, Kashin-Beck disease, cataracts, and others. Conversely, selenium supplementation has been found to have multiple effects, including antioxidant, anti-inflammatory, and anticancer functions. Compared with inorganic selenium, organic selenium exhibits higher bioactivities and a wider range of safe concentrations. Consequently, there has been a significant development of selenium-enriched foods which contain large amounts of organic selenium in order to improve human health. This review summarizes the physiological role and metabolism of selenium, the development of selenium-enriched foods, the physiological functions of selenium-enriched foods, and provides an analysis of total selenium and its species in selenium-enriched foods, with a view to laying the foundation for selenium-enriched food development.

Arbuscular mycorrhizal fungi improve selenium uptake by modulating root transcriptome of rice (Oryza sativa L.)

Although selenium (Se) is an essential trace element in humans, the intake of Se from food is still generally inadequate throughout the world. Inoculation with arbuscular mycorrhizal fungi (AMF) improves the uptake of Se in rice (Oryza sativa L.). However, the mechanism by which AMF improves the uptake of Se in rice at the transcriptome level is unknown. Only a few studies have evaluated the effects of uptake of other elements in rice under the combined effects of Se and AMF. In this study, Se combined with the AMF Funneliformis mosseae (Fm) increased the biomass and Se concentration of rice plants, altered the pattern of ionomics of the rice roots and shoots, and reduced the antagonistic uptake of Se with nickel, molybdenum, phosphorus, and copper compared with the treatment of Se alone, indicating that Fm can enhance the effect of fertilizers rich in Se. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the hub genes in modules significantly associated with the genes that contained Se and were related to protein phosphorylation, protein serine/threonine kinase activity, membrane translocation, and metal ion binding, suggesting that the uptake of Se by the rice roots may be associated with these genes when Fm and Se act in concert. This study provides a reference for the further exploration of genes related to Se uptake in rice under Fm treatment.

Selenate triggers diverse oxidative responses in Astragalus species with diverse selenium tolerance and hyperaccumulation capacity

Selenium (Se) hyperaccumulators are capable of uptake and tolerate high Se dosages. Excess Se-induced oxidative responses were compared in Astragalus bisulcatus and Astragalus cicer. Plants were grown on media supplemented with 0, 25 or 75 μM selenate for 14 days. Both A. bisulcatus and A. cicer accumulated >2000 μg/g dry weight Se to the shoot but the translocation factors of A. cicer were below 1 suggesting its non hyperaccumulator nature. A. cicer showed Se sensitivity indicated by reduced seedling fresh weight, root growth and root apical meristem viability, altered element homeostasis in the presence of Se. In Se-exposed A. bisulcatus, less toxic organic Se forms (mainly MetSeCys, γ-Glu-MetSeCys, and a selenosugar) dominated, while these were absent from A. cicer suggesting that the majority of the accumulated Se may be present as inorganic forms. The glutathione-dependent processes were more affected, while ascorbate levels were not notably influenced by Se in either species. Exogenous Se triggered more intense accumulation of malondialdehyde in the sensitive A. cicer compared with the tolerant A. bisulcatus. The extent of protein carbonylation in the roots of the 75 μM Se-exposed A. cicer exceeded that of A. bisulcatus indicating a correlation between selenate sensitivity and the degree of protein carbonylation. Overall, our results reveal connection between oxidative processes and Se sensitivity/tolerance/hyperaccumulation and contribute to the understanding of the molecular responses to excess Se.

Biofortification of baby leafy vegetables using nutrient solution containing selenium

BACKGROUND

Biofortification of vegetables is an important innovation technique in the horticultural sector. Vegetables can be a vector of different minor elements that have beneficial effects on human health. Selenium (Se) is an important element for human nutrition and plays a significant role in defence mechanisms. The aim of this work was to investigate the effect of Se in the nutrient solutions on the crop biofortification ability, yield, and quality parameters of four baby leafy vegetables destined to the minimally processed industry. Experiments were performed on lamb's lettuce, lettuce, wild rocket, and spinach. These crops were cultivated in the floating systems with nutrient solution enriched with 0, 2.6, 3.9, and 5.2 μmol L-1 Se provided as sodium selenate.

RESULTS

At harvest, Se concentrations, yield, nitrate concentration, sugars, and some mineral elements were measured. Data collected and analyses showed that yield, nitrate, sucrose, and reducing sugars were not affected by Se treatments, even if varied among species. Se concentrations linearly increased in leaves of different species by increasing the Se concentration in the nutrient solution. Rocket was the species with the highest accumulation ability and reached a concentration of 11 μg g-1 fresh weight Se in plants grown with 5.2 μmol L-1 Se.

CONCLUSION

A floating system with Se-enriched nutrient solution is an optimal controlled growing biofortification system for leafy vegetables. The accumulation ability decreased in different species in the order wild rocket, spinach, lettuce, and lamb's lettuce, highlighting a crop-dependent behaviour and their attitude to biofortification. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Spectroscopic Analyses Highlight Plant Biostimulant Effects of Baker's Yeast Vinasse and Selenium on Cabbage through Foliar Fertilization

The main aim of this study is to find relevant analytic fingerprints for plants' structural characterization using spectroscopic techniques and thermogravimetric analyses (TGAs) as alternative methods, particularized on cabbage treated with selenium-baker's yeast vinasse formulation (Se-VF) included in a foliar fertilizer formula. The hypothesis investigated is that Se-VF will induce significant structural changes compared with the control, analytically confirming the biofortification of selenium-enriched cabbage as a nutritive vegetable, and particularly the plant biostimulant effects of the applied Se-VF formulation on cabbage grown in the field. The TGA evidenced a structural transformation of the molecular building blocks in the treated cabbage leaves. The ash residues increased after treatment, suggesting increased mineral accumulation in leaves. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) evidenced a pectin-Iα-cellulose structure of cabbage that correlated with each other in terms of leaf crystallinity. FTIR analysis suggested the accumulation of unesterified pectin and possibly (seleno) glucosinolates and an increased network of hydrogen bonds. The treatment with Se-VF formulation induced a significant increase in the soluble fibers of the inner leaves, accompanied by a decrease in the insoluble fibers. The ratio of soluble/insoluble fibers correlated with the crystallinity determined by XRD and with the FTIR data. The employed analytic techniques can find practical applications as fast methods in studies of the effects of new agrotechnical practices, while in our particular case study, they revealed effects specific to plant biostimulants of the Se-VF formulation treatment: enhanced mineral utilization and improved quality traits.

Glutathione: Lights and Shadows in Cancer Patients

In cases of cellular injury, there is an observed increase in the production of reactive oxygen species (ROS). When this production becomes excessive, it can result in various conditions, including cancerogenesis. Glutathione (GSH), the most abundant thiol-containing antioxidant, is fundamental to re-establishing redox homeostasis. In order to evaluate the role of GSH and its antioxi-dant effects in patients affected by cancer, we performed a thorough search on Medline and EMBASE databases for relevant clinical and/or preclinical studies, with particular regard to diet, toxicities, and pharmacological processes. The conjugation of GSH with xenobiotics, including anti-cancer drugs, can result in either of two effects: xenobiotics may lose their harmful effects, or GSH conjugation may enhance their toxicity by inducing bioactivation. While being an interesting weapon against chemotherapy-induced toxicities, GSH may also have a potential protective role for cancer cells. New studies are necessary to better explain the relationship between GSH and cancer. Although self-prescribed glutathione (GSH) implementation is prevalent among cancer patients with the intention of reducing the toxic effects of anticancer treatments and potentially preventing damage to normal tissues, this belief lacks substantial scientific evidence for its efficacy in reducing toxicity, except in the case of cisplatin-related neurotoxicity. Therefore, the use of GSH should only be considered under medical supervision, taking into account the appropriate timing and setting.

A critical analysis of wastewater use in agriculture and associated health risks in Pakistan

Freshwater shortage and its contamination with various types of pollutants are becoming the most alarming issues worldwide due to impacts on socioeconomic values. Considering an increasing freshwater scarcity, it is imperative for the growers, particularly in semiarid and arid areas, to use wastewater for crop production. Wastewaters generally contain numerous essential inorganic and organic nutrients which are considered necessary for plant metabolism. Besides, this practice provokes various hygienic, ecological and health concerns due to the occurrence of toxic substances such as heavy metals. Pakistan nowadays faces a severe freshwater scarcity. Consequently, untreated wastewater is used routinely in the agriculture sector. In this review, we have highlighted the negative and positive affectivity of wastewater on the chemical characteristics of the soil. This review critically delineates toxic metal accumulation in soil and their possible soil-plant-human transfer. We have also estimated and deliberated possible health hazards linked with the utilization of untreated city waste effluents for the cultivation of food/vegetable crops. Moreover, we carried out a multivariate analysis of data (144 studies of wastewater crop irrigation in Pakistan) to trace out common trends in published data. We have also compared the limit values of toxic metals in irrigation water, soil and plants. Furthermore, some viable solutions and future viewpoints are anticipated taking into account the on-ground situation in Pakistan-such as planning and sanitary matters, remedial/management technologies, awareness among local habitants (especially farmers) and the role of the government, NGOs and pertinent stakeholders. The data are supported by 13 tables and 7 figures.

Foraging for selenium: a comparison between hyperaccumulator and non-accumulator plant species

Selenium (Se) hyperaccumulators are a unique group of plants that can accumulate this element in their aerial parts at concentrations exceeding 100 mg kgDW-1. These plants actively search for Se in the soil, a phenomenon known as root foraging, reported to date only by few studies. In this study, the effect of localized Se enrichment, in the form of selenite and selenate, was investigated on the root architecture of two Se-hyperaccumulators (Stanleya pinnata and Astragalus bisulcatus) and two non-accumulators (Brassica juncea and Medicago sativa). Rhizoboxes were divided into two halves: one half was filled with control soil while the other with selenate or selenite (30 mg kgDW-1) spiked soil. Seedling were transferred into the interface of the two soils and allowed to grow for three weeks under controlled light and temperature conditions. Staneya pinnata exhibited equal root density in both halves of the rhizobox when grown in control/control and selenite/control soil treatments. However, in the presence of selenate, S. pinnata developed 76% of the roots towards the selenate-enriched half, indicating an active root foraging. In contrast, A. bisulcatus and the non-accumulators B. juncea and M. sativa did not show any preferential distribution of roots. This study revealed that only S. pinnata showed the ability to detect and forage for Se when provided as selenate. Non-accumulators did not show any morphological or Se-accumulation difference associated with the presence of Se in soil in either form.

Selenium in soil-plant system: Transport, detoxification and bioremediation

Selenium (Se) is an essential micronutrient for humans and a beneficial element for plants. However, high Se doses always exhibit hazardous effects. Recently, Se toxicity in plant-soil system has received increasing attention. This review will summarize (1) Se concentration in soils and its sources, (2) Se bioavailability in soils and influencing factors, (3) mechanisms on Se uptake and translocation in plants, (4) toxicity and detoxification of Se in plants and (5) strategies to remediate Se pollution. High Se concentration mainly results from wastewater discharge and industrial waste dumping. Selenate (Se [VI]) and selenite (Se [IV]) are the two primary forms absorbed by plants. Soil conditions such as pH, redox potential, organic matter and microorganisms will influence Se bioavailability. In plants, excessive Se will interfere with element uptake, depress photosynthetic pigment biosynthesis, generate oxidative damages and cause genotoxicity. Plants employ a series of strategies to detoxify Se, such as activating antioxidant defense systems and sequestrating excessive Se in the vacuole. In order to alleviate Se toxicity to plants, some strategies can be applied, including phytoremediation, OM remediation, microbial remediation, adsorption technique, chemical reduction technology and exogenous substances (such as Methyl jasmonate, Nitric oxide and Melatonin). This review is expected to expand the knowledge of Se toxicity/detoxicity in soil-plant system and offer valuable insights into soils Se pollution remediation strategies.

A critical analysis of sources, pollution, and remediation of selenium, an emerging contaminant

Selenium (Se) is an essential metalloid and is categorized as emerging anthropogenic contaminant released to the environment. The rise of Se release into the environment has raised concern about its bioaccumulation, toxicity, and potential to cause serious damages to aquatic and terrestrial ecosystem. Therefore, it is extremely important to monitor Se level in environment on a regular basis. Understanding Se release, anthropogenic sources, and environmental behavior is critical for developing an effective Se containment strategy. The ongoing efforts of Se remediation have mostly emphasized monitoring and remediation as an independent topics of research. However, our paper has integrated both by explaining the attributes of monitoring on effective scale followed by a candid review of widespread technological options available with specific focus on Se removal from environmental media. Another novel approach demonstrated in the article is the presentation of an overwhelming evidence of limitations that various researchers are confronted with to overcome achieving effective remediation. Furthermore, we followed a holistic approach to discuss ways to remediate Se for cleaner environment especially related to introducing weak magnetic field for ZVI reactivity enhancement. We linked this phenomenal process to electrokinetics and presented convincing facts in support of Se remediation, which has led to emerge 'membrane technology', as another viable option for remediation. Hence, an interesting, innovative and future oriented review is presented, which will undoubtedly seek attention from global researchers.

Loss of Selenium from Mollisol Paddy Wetlands of Cold Regions: Insights from Flow-through Reactor Experiments and Process-Based Modeling

Mollisols are critical agricultural resources for securing global food supply. Due to its health importance, selenium (Se) fate in the Mollisols attracts growing concerns. Land use change from conventional drylands to paddy wetlands impacts Se bioavailability in the vulnerable Mollisol agroecosystems. The underlying processes and mechanisms however remain elusive. Here, results of flow-through reactor experiments with paddy Mollisols from northern cold-region sites indicate that continuous flooding with surface water for 48 d induced redox zonation that facilitated the loss of Mollisol Se by up to 51%. Further process-based biogeochemical modeling suggests largest degradation rates of dissolved organic matter (DOM) in 30 cm deep Mollisols that contained the highest-level labile DOM and organic-bound Se. Electron shunting from degradation of Se-bearing DOM coupled to reductive dissolution of Se-adsorbed Fe oxides accounts mainly for Se(IV) release into the pore water. Consequent changes in DOM molecular composition make the reservoir of organic-bound Se vulnerable to flooding-induced redox zonation and likely enhance Se loss through destruction of thiolated Se and emission of gaseous Se from the Mollisol layer. This study highlights a neglected scenario where the speciation-driven loss of bioavailable Se from the paddy wetlands can be a significant consequence in the cold-region Mollisol agroecosystems.

Fate of selenium in a Se-enriched region of North China: Translocation, bioaccumulation, source, and health benefits

There are limited studies on the translocation and bioaccumulation of selenium (Se) in weak alkaline cultivated Se-enriched soil, and the sources and speciation of Se in wheat grains remain unclear. In this study, we measured the Se levels in soils, roots, stems, and wheat grains from Se-enriched cultivated land in Ci County, China, which has a high incidence of esophageal cancer. The Se levels in the roots were higher than those in the soils, indicating that wheat plants bioaccumulated high concentrations of Se from the soil (enrichment coefficient [EC] range from the soil to the root: 0.94-3.29). Redundancy analysis indicated that the bioaccumulated factor, translocation coefficient, and EC were mainly controlled by phosphorus, pH, and Fe₂O₃ (contribution rates: 37.5%, 19.5%, and 15.9%, respectively). Linear regression analysis revealed that the sources of Se in grains were mainly from the water-soluble fraction (R² = 0.55, at p < 0.05), the weakly acidic fraction (R² = 0.84, at p < 0.05), the reducible fraction (R² = 0.84, at p < 0.05), and the oxidizable fraction (R² = 0.70, at p < 0.05), as well as from atmospheric deposition (R² = 0.37, at p < 0.01). There is a significant correlation between the Se from atmospheric deposition and the oxidizable fraction (R² = 0.62, at p < 0.01) and the residual fraction (R² = 0.33, at p < 0.01). The contribution of Se input flux from atmospheric deposition was 5.50 g/hm² for one year. Furthermore, the average content of organic Se in wheat grains was 58.93%. The Se concentrations found in wheat grains were considered beneficial for human health based on a comparison with the Chinese Society of Nutrition standard and worldwide levels. The results of this study will increase the overall knowledge on the theme, which could help prevent and control the harmful effects of undesirable concentrations of Se on human health.

The relationship between urinary selenium levels and risk of gestational diabetes mellitus: A nested case–control study

Background

Selenium (Se) is an essential trace element for the human body. Serum Se and urinary Se are also biomarkers to assess Se exposure status. However, studies focusing on the association between urinary Se and the risk of gestational diabetes mellitus (GDM) are rare.

Objective

To investigate the association between urinary Se and the risk of GDM.

Methods

A nested case–control study based on a prospective birth cohort in Wuhan, China, which focuses on the effects of prenatal environmental factors exposure on pregnant women and children’s health was conducted. Two hundred and twenty-six cases and 452 controls were included. Maternal urine samples were collected before GDM diagnosis, and the urinary Se levels were determined. We assessed the association of urinary Se with GDM by conditional logistic regression with maternal urinary Se level as a categorical variable, and estimated the association between Se and glucose levels by multiple linear regression. The potential modifier roles of maternal age and fetal sex have also been assessed.

Results

Lower urinary level of Se was significantly associated with a higher risk of GDM (OR = 2.35 for the tertile 1, 95% CI:1.36-4.06; adjusted OR = 1.79 for the tertile 2, 95%CI:1.09-2.95; p for trend = 0.01). Fetal sex had an interaction with Se in the association with GDM. The association was more pronounced among pregnant women with female fetuses than with male fetuses.

Discussion

Our study suggested a significant negative association between urinary Se and the risk of GDM, and this association may vary depending on the fetal sex.

Bioconversion of inorganic selenium to less toxic selenium forms by microbes: A review

In recent years, microbial conversion of inorganic selenium into an efficient and low-toxic form of selenium has attracted much attention. With the improvement of scientific awareness and the continuous progress of nanotechnology, selenium nanoparticles can not only play the unique functions of organic selenium and inorganic selenium but also have higher safety, absorption and biological activity than other selenium forms. Therefore, the focus of attention has gradually shifted beyond the level of selenium enrichment in yeast to the combination of biosynthetic selenium nanoparticles (BioSeNPs). This paper primarily reviews inorganic selenium and its conversion to less toxic organic selenium and BioSeNPs by microbes. The synthesis method and potential mechanism of organic selenium and BioSeNPs are also introduced, which provide a basis for the production of specific forms of selenium. The methods to characterize selenium in different forms are discussed to understand the morphology, size and other characteristics of selenium. In general, to obtain safer and higher selenium content products, it is necessary to develop yeast resources with higher selenium conversion and accumulation.

Selenium Speciation in Se-Enriched Soybean Grains from Biofortified Plants Grown under Different Methods of Selenium Application

Since soybean is widely cultivated around the world and has a high protein content, it is a great nutritional vehicle for increasing the dietary uptake of selenium (Se). Several studies have evaluated biofortification with Se through fertilizer application in several crops. However, it is not clear how each method and source affect the total Se content or Se species in soybean grains. This work aimed to assess the total Se content and Se speciation in Se-enriched soybean grains produced under different Se application methods in the field. The treatments consisted of Se application (soil or foliar), using organic or inorganic Se sources at 10 g ha−1 or 80 g ha−1, in two genotypes. The results showed that all treatments with inorganic Se (soil and foliar) increased the Se content in grains compared with the control. More than 80% of the total Se in grains was present as selenomethionine (SeMet), and the speciation was affected by the Se source and the method of application. The treatments using inorganic Se, applied via soil or foliar, produced the highest content of Se as SeMet in soybean grains. Finally, we propose that the preservation of the Se species in products derived from soybean grains be evaluated as the following step.

Se(IV)/Se(VI) adsorption mechanisms on natural and on Ca-modified zeolite for Mediterranean soils amended with the modified zeolite: prospects for agronomic applications

In the present study, the ability of a modified CaCl₂ zeolite (Ca-Z) to both increase Se(IV) availability and restrict Se(VI) mobility in soils is examined. As it was resulted from batch experiments and verified by X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectroscopies, higher amounts of both Se species adsorbed on Ca-Z compared to natural zeolite (Z-N) forming outer-sphere complexes while the oxidation state did not alter during agitation of samples. Thereafter, Ca-Z was incorporated in six Greek soils, divided into acid and alkaline, at a 20% (w/w) rate and a series of equilibrium batch experiments were performed with soils alone and soils-Ca-Z mixtures to investigate sorption and desorption processes and mechanisms. The acid soils, either treated with Ca-Z or not, adsorbed higher amounts of Se(IV) than alkaline ones, whereas soils alone did not adsorb Se(VI) but impressively high adsorption of Se(VI) occurred in the Ca-Z-treated soils. Desorption of Se(IV) was higher from the Ca-Z-treated soils and especially from the acid soils. Higher distribution coefficients of desorption than the distribution coefficients of sorption were observed, clearly pointing to a hysteresis mechanism. The experimental data fitted with Langmuir and Freundlich isotherms. In the presence of Ca-Z, the Langmuir q_m values increased indicating higher Se(IV) retention while Langmuir b_L values decreased suggesting lower bonding strength and higher Se(IV) mobility. Overall, treating the soils with Ca-Z increased Se(IV) adsorption and mobility whereas it provided sites for Se(VI) adsorption that did not exist in the studied soils.

GPX4 utilization by selenium is required to alleviate cadmium-induced ferroptosis and pyroptosis in sheep kidney

Cadmium (Cd), a persistent and harmful heavy metal in the environment, can accumulate in the kidneys and cause nephrotoxicity. Selenium (Se) is a beneficial natural element that alleviates the toxicity of Cd. To ascertain the relationship between the protective mechanism of Se against Cd nephrotoxicity and ferroptosis and pyroptosis, we randomly divided 48 sheep into four groups and treated them with Cd chloride and/or sodium selenite for 50 days. The data confirmed that Cd apparently resulted in impaired kidney histology and function, depletion of GSH and nicotinamide adenine dinucleotide phosphate contents and CAT and SOD activities, elevation of MDA level, as well as the reduction in selenoprotein mRNA (GPX1, GPX4, TXNRD1, SELP) levels and GPX4 protein level and immunofluorescence intensity. Meanwhile, Cd induced ferroptosis by causing iron overload, up-regulating PTGS2, NCOA4, TFR1, and LC3B mRNA levels and PTGS2 and LC3B-II/LC3B-I protein levels, reducing SLC7A11 and FTH1 mRNA and protein levels, and enhancing the immunofluorescence co-localization of FTH1/LC3B. Moreover, it was also found that Cd triggered pyroptosis, which was evidenced by the increase of NLRP3 immunohistochemical positive signal, GSDMD-N immunofluorescence intensity, IL-1β and IL-18 release and the levels of pyroptosis-related mRNA (NLRP3, ASC, Caspase-1, GSDMD, IL-1β and IL-18) and proteins (NLRP3, Caspase-1p20, GSDMD-N, IL-1β and IL-18). Notably, Se increased the expression level of GPX4 and the transcription factors TFAP2c and SP1, and ameliorated Cd-induced changes in aforementioned factors. In conclusion, GPX4 utilization by Se might be required to alleviate Cd-induced ferroptosis and pyroptosis in sheep kidney.

Identification of the spatial patterns and controlling factors of Se in soil and rice in Guangxi through hot spot analysis

Selenium (Se) is essential to human health, anti-cancer, possessing antioxidant, and antiviral properties. In this study, the spatial patterns of rice Se and their varying relationship with soil Se on a regional scale were studied using hot spot analysis for the agricultural soils in Guangxi. According to the hot and cold spot maps, rice Se correlates positively with soil Se in Guangxi agricultural soils. High rice Se accompanies high soil Se in the central part of Guangxi (e.g., Liuzhou, Laibin), and low rice Se is in line with low soil Se in the western part (e.g., Baise). However, the hot spot analysis maps indicate that southwestern Guangxi exhibits a special characteristic of low rice Se with high soil Se (e.g., Chongzuo). This special pattern is strongly associated with the high concentrations of Fe₂O₃ (ferromanganese nodules) in the carbonate rock area. The hot spot analysis proves useful in revealing the spatial patterns of rice Se in Guangxi and identifying the hidden patterns.

Topographic constraints on the distribution of selenium in the supergene environment: A case study at Yutangba, China

The local topography and leaching conditions significantly affect the spatial distribution of selenium (Se) in the local environment. However, the driving factors controlling Se distribution have not been well addressed. In this paper, taking Yutangba, a village known for human selenosis in China, as an example, we demonstrate how topographic factors influence the spatial distribution of Se in soils and plants. In the scenarios of slope ≤25°, the correlations among slope and soil/extractable/plant Se are significantly negative (P < 0.05), whereas they become weak or unclear when the slope is > 25°, suggesting that 25° of slope is a critical transition boundary. Similar observations were further verified by the soil erosion modulus (SEM) and the surface runoff intensity index (SRI), indicating that Se transport via soil erosion is limited and accounts for 11.2-17% of the soil Se, while surface runoff plays a dominant role in the Se distribution, accounting for 83-88.1%. Soil extractable Se is negatively correlated with SRI (Pearson r = -0.87 at slope < 25°), showing that the migration capacity of Se is higher at steep terrain and controlled by topography through soil erosion and surface runoff. The positive relationship between plant Se and soil/extractable Se demonstrates that topography indirectly influences plant Se through soil Se bioavailability. Abnormally local Se enrichment observed at the elevated steep hillside (>25°) in northwestern Yutangba primarily was resulted from the weathering of Se-rich rocks. These observations confirm that the topographic slope gradient influences the transport and spatial distribution of soil Se, implying that topography should be considered when studying the spatial distribution of soil Se at a regional scale, especially for the Se-poor belt in China.

Spatial Metallomics Reveals Preferable Accumulation of Methylated Selenium in a Single Seed of the Hyperaccumulator Cardamine violifolia†

Cardamine violifolia is a Se hyperaccumulator found in Enshi, China. In this study, spatial metallomics was applied to visualize the distribution and speciation of Se in a single seed of C. violifolia. It was found that Se reached 1729.89 ± 28.14 mg/kg and the main Se species were SeCys and SeMet in bulk seeds. Further in situ study on a single seed found that the methylated Se species located mostly in the episperm. This is the first visualized evidence of the in situ distribution of methylated Se species in the seeds of C. violifolia. In all, spatial metallomics finds a preferable accumulation of methylated Se species in the seed coat, which deepens the understanding of the tolerance of Se by C. violifolia. The protocol applied in this study may also be used for the understanding of the tolerance of heavy metals/metalloids in other hyperaccumulators.

Evaluation of Selenium Nanoparticles in Inducing Disease Resistance against Spot Blotch Disease and Promoting Growth in Wheat under Biotic Stress

In the present study, SeNPs were synthesized using Melia azedarach leaf extracts and investigated for growth promotion in wheat under the biotic stress of spot blotch disease. The phytosynthesized SeNPs were characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and Fourier-transformed infrared spectroscopy (FTIR). The in vitro efficacy of different concentrations of phytosynthesized SeNPs (i.e., 100 μg/mL, 150 μg/mL, 200 μg/mL, 250 μg/mL, and 300 μg/mL) was evaluated using the well diffusion method, which reported that 300 μg/mL showed maximum fungus growth inhibition. For in vivo study, different concentrations (10, 20, 30, and 40 mg/L) of SeNPs were applied exogenously to evaluate the morphological, physiological, and biochemical parameters under control conditions and determine when infection was induced. Among all treatments, 30 mg/L of SeNPs performed well and increased the plant height by 2.34% compared to the control and 30.7% more than fungus-inoculated wheat. Similarly, fresh plant weight and dry weight increased by 17.35% and 13.43% over the control and 20.34% and 52.48% over the fungus-treated wheat, respectively. In leaf surface area and root length, our findings were 50.11% and 10.37% higher than the control and 40% and 71% higher than diseased wheat, respectively. Plant physiological parameters i.e., chlorophyll a, chlorophyll b, and total chlorophyll content, were increased 14, 133, and 16.1 times over the control and 157, 253, and 42 times over the pathogen-inoculated wheat, respectively. Our findings regarding carotenoid content, relative water content, and the membrane stability index were 29-, 49-, and 81-fold higher than the control and 187-, 63-, and 48-fold higher than the negative control, respectively. In the case of plant biochemical parameters, proline, sugar, flavonoids, and phenolic contents were recorded at 6, 287, 11, and 34 times higher than the control and 32, 107, 33, and 4 times more than fungus-inoculated wheat, respectively. This study is considered the first biocompatible approach to evaluate the potential of green-synthesized SeNPs as growth-promoting substances in wheat under the spot blotch stress and effective management strategy to inhibit fungal growth.

Antifungal activity of green synthesized selenium nanoparticles and their effect on physiological, biochemical, and antioxidant defense system of mango under mango malformation disease

Plant extract-based green synthesis of nanoparticles is an emerging class of nanotechnology that has revolutionized the entire field of biological sciences. Green synthesized nanoparticles are used as super-growth promoters and antifungal agents. In this study, selenium nanoparticles (SeNPs) were synthesized using Melia azedarach leaves extract as the main reducing and stabilizing agent and characterized by UV-visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and fourier transform infrared spectrometer (FTIR). The green synthesized SeNPs were exogenously applied on Mangifera indica infected with mango malformation disease. The SeNPs at a concentration of 30 μg/mL were found to be the best concentration which enhanced the physiological (chlorophyll and membrane stability index), and biochemical (proline and soluble sugar) parameters. The antioxidant defense system was also explored, and it was reported that green synthesized SeNPs significantly reduced the biotic stress by enhancing enzymatic and non-enzymatic activities. In vitro antifungal activity of SeNPs reported that 300 μg/mL concentration inhibited the Fusarium mangiferae the most. This study is considered the first biocompatible approach to evaluate the potential of green synthesized SeNPs to improve the health of mango malformation-infected plants and effective management strategy to inhibit the growth of F. mangifera.