Initial Se Research Articles

Effective selenate removal using pH modulated synthesis of biogenic jarosite: Comparative insight with non-biogenic jarosite and biogenic schwertmannite

Selenium, a crucial trace element for many organisms, including prokaryotes and humans, is toxic at high concentrations, necessitating its removal from wastewater. This study investigates the use of jarosite, a naturally occurring iron sulfate mineral with excellent heavy metal attenuation properties, for selenate (Se(VI)) removal for the first time. Biogenic jarosite was synthesized through Fe(II) oxidation by Acidithiobacillus ferrooxidans at an initial pH ranging from 1.5 to 4.0 (J-1.5 to J-4.0). This resulted in the formation of morphologically diverse particles of biogenic jarosite owing to varying Fe(II) oxidation and precipitation rates. For comparative analysis, non-biogenic jarosite (J-90C) and biogenic schwertmannite (S-2.5) were also synthesized. At 0.2 mM initial Se(VI) concentration, J-2.5 demonstrated superior Se(VI) removal compared to J-3.5 and J-90C. At 2.0 mM Se(VI), J-2.5 still outperformed J-3.5 and J-90C although its overall removal efficiency decreased. Notably, at 0.2 mM concentration, Se(VI) removal by J-2.5 was 63 %, which is comparable to 77 % removal by S-2.5. Furthermore, sulfate release from J-2.5 was significantly lower than that from S-2.5 in both Se-free and Se-containing solutions. This study provides critical insights into the synthesis and application of biogenic jarosite as a replacement for metastable schwertmannite, emphasizing its potential as an excellent Se sink for wastewater treatment.

A Retrospective Study of COVID-19 Based on A Dual-Stage Model

This study proposed initial stage SEI1I2I3RD and final stage SEQ I1I2I3RD models to deeply analyze the transmission dynamics of COVID-19 at different stages and propose scientific prevention and control strategies. The initial stage SE I1I2I3RD model divides infected individuals into mild, moderate, and severe cases during the early stage of the epidemic, effectively predicting the number of new infections and cumulative recoveries. The final stage SEQ I1I2I3RD model builds on the initial stage SE I1I2I3RD model by adding a quarantine compartment, which reflects the impact of nucleic acid testing and quarantine measures on epidemic control. By introducing dynamic parameters and nonlinear processing, the final stage SEQ I1I2I3RD model significantly improves prediction accuracy. The study demonstrates that increasing the isolation rate, reducing the daily contact rate of infected persons, and improving the recovery rate of mildly infected persons are effective control strategies. Based on the model's predictions, policy recommendations such as enhancing public health education, strictly implementing isolation measures, restricting population movement, and optimizing medical resource allocation are proposed to effectively control the spread of the epidemic, reduce the burden on the healthcare system, and create favorable conditions for economic recovery.

Migration of l-Selenomethionine in the Water-Soil Interface Dominated by Iron Oxides.

Organic selenium (Se) accounts for up to 10-80% of total Se in soils, and l-selenomethionine (SeMet) is a typical organic Se species. However, the migration of SeMet in soils remains elusive. This study investigated the solid-liquid distribution, adsorption, desorption by phosphate, and self-oxidization of SeMet in solution under the influence of ferrihydrite, goethite, and hematite through batch experiments. Iron oxides could adsorb a much larger amount of SeMet than inorganic Se. At the initial Se element concentrations of 0-200 mg/L, the solid/liquid partition coefficient of SeMet was constant, which was 0.41, 0.43, and 0.50 on ferrihydrite, goethite, and hematite, respectively. In addition, the adsorption process of SeMet on the three iron oxides could be well described by the linear driving force model. Accordingly, the intraparticle diffusion coefficient of SeMet in ferrihydrite, goethite, and hematite was 1.4 × 103, 7.9 × 104, and 1.2 × 105 nm2/min, respectively. The adsorption of SeMet on the three iron oxides was slightly influenced by the pH and the coexisting ions, such as Cl-, NO3-, SO42-, and H2PO4-. The desorption ratio of SeMet on the three iron oxides by phosphate was lower than 2.5%. SeMet would aggregate the nanoparticles of iron oxides, resulting in a synergistic effect on the adsorption of phosphate. The oxidization ratio of SeMet was 23.9% in the solution, while it decreased to 17.1-17.5% in iron oxide suspensions. For this oxidization process, the three iron oxides exhibited varying effects to decelerate SeMet oxidation, as represented by the equivalent reaction. The findings of this study reveal the migration of SeMet in the water-soil interface under the influence of iron oxides, which can improve the understanding of Se cycling in the environment as well as provide some guidance for the better utilization of Se in soils and environmental remediation of Se pollution.

Facilitating Se(VI) adsorption and electron transfer by introducing αFeOOH to sulfidated zero-valent iron

Sulfidation of zerovalent iron (SZVI) enhances electron transfer ability due to the formation of FeSx, which facilitates pollutant removal. However, for pollutants that are difficult to adsorb onto SZVI, the longer electron transfer distance results in inefficient removal. The presence of iron (hydr)oxides on ZVI and SZVI is inevitable, and it can adsorb highly mobile pollutants (such as Se(VI)). Here, we regulated the composition of iron (hydr)oxides on ZVI and SZVI surfaces by aging treatment, which improves their Se(VI) removal performance. Based on this, αFeOOH which has a strong affinity for Se(VI), is introduced onto SZVI to synthesize the high-quality composite SZVI-αFeOOH. The characterization results showed that Fe-OH from αFeOOH and FeSx successfully combined and uniformly distributed on SZVI-αFeOOH, creating active sites, and the Se(VI) removal rate (kobs = 0.2211 min−1) increased ∼ 7.4 times over SZVI (kobs = 0.0297 min−1). The adsorption and reduction of Se(VI) were optimized by regulating the mass ratio of αFeOOH to SZVI. In addition, different initial Se(VI) concentrations and solution pH were designed to explore the effects on Se(VI) removal and evaluate the best removal reaction condition. The mechanism of Se(VI) removal by SZVI-αFeOOH is as follows: Se(VI) is firstly adsorbed on αFeOOH, which shortens the electron transfer distance, and then the absorbed Se(VI) is reduced to readily immobilized states by SZVI. This work proposes a targeted strategy to modify SZVI to efficiently remove pollutants with strong mobile and difficult adsorption.

Temporal trend of anisometropia incidence in Chinese school-aged children before and during the COVID-19 pandemic.

To analyze and compare the temporal trends in the incidence of anisometropia among Chinese school-aged children both before and during the COVID-19 pandemic, and to investigate the impact of the pandemic on the incidence of anisometropia. We conducted a retrospective study comprising six distinct and independent longitudinal cohorts, each including children aged 6 to 13 years who visited the Joint Shantou International Eye Center between January 2010 and December 2021. Children were grouped into cohorts based on the year of their first eye clinic visit: 2010, 2012, 2014, 2016, 2018, or 2020. Only children without anisometropia at initial visits, followed for 18 ± 6 months, were included. The cumulative incidence and risk factors of anisometropia were analyzed using Kaplan-Meier estimation and Cox proportional hazards regression models. Subgroup analyses were performed based on sex, age groups, initial refractive error status, and initial interocular SE difference. Anisometropic children were further categorized into myopic and non-myopic, with subsequent subgroup analyses conducted. Of 11,235 children were recruited from six cohorts (2010: n = 1,366; 2012: n = 1,708; 2014: n = 1,896; 2016: n = 2,354; 2018: n = 2,514; 2020: n = 1,397), 869 children developed anisometropia during a mean follow-up of 17.5 ± 3.7 months. After adjustment of confounding factors, we found that the risk of anisometropia remained relatively stable before 2020 but significantly increased in the 2020 cohort (adjusted HR 2.93, 95% CI 2.23 to 3.86; p < 0.001). This trend persisted in studies of spherical anisometropia (adjusted HR 2.52, 95% CI 1.60 to 3.97; p < 0.001) and cylindrical anisometropia (adjusted HR 2.91, 95% CI 1.69 to 3.62; p < 0.001). Older age and a greater initial difference in SE between the two eyes were also significantly associated with a higher risk of developing anisometropia (p < 0.001). Subgroup analyses consistently showed increased risk in the 2020 cohort. This study reveals a concerning rise in anisometropia incidence among Chinese school-aged children during the period of the COVID-19 pandemic. These findings highlight the worrisome rise in anisometropia risk during the COVID-19 pandemic and emphasize the importance of early detection and management to safeguard children's visual health.

Different efficacy in myopia control: Comparison between orthokeratology and defocus-incorporated multiple segment lenses

PurposeTo compare the efficiency of orthokeratology (OK) and defocus-incorporated multiple segment (DIMS) lenses in myopia control in children. MethodsThis prospective study involved 540 subjects (7–14 years) categorized into three groups: DIMS lenses (180 cases), OK lenses (180 cases), or single-vision spectacles (SVS) (180 cases). After a one-year follow-up, changes in axial length (AL) and differences among the groups were analyzed. The subjects were further divided into a low myopia degree subgroup (LM, −1.50 D ≤ SE ≤ −0.50 D), a moderate myopia degree subgroup (MM, −3.00 D ≤ SE ＜ −1.50 D), and a high myopia degree subgroup (HM, −5.00 D ≤ SE ＜ −3.00 D). A one-way ANOVA and multiple linear regression analysis were used to compare AL elongation and the factors influencing the different groups. ResultsA total of 496 (92 %) subjects completed the study. The mean AL change in the OK lenses, DIMS lenses, and SVS were 0.20±0.18 mm, 0.30±0.22 mm, and 0.38±0.19 mm, respectively (P < 0.001). In the LM subgroup, the OK and DIMS groups showed similar AL changes, but both exhibited slower changes than the SVS group (P = 0.001). In the MM and HM subgroups, the OK lens performed the shortest AL elongation compared with the DIMS lenses and SVS (P < 0.001). Multiple regression analysis showed that the AL change was associated with age (β = −0.038 and P = 0.005), initial AL (β = −0.010 and P = 0.011), initial SE (β = 0.028 and P = 0.007), and interventions using OK lenses (β = −0.172 and P = 0.020) and DIMS lenses (β = −0.089 and P = 0.020). ConclusionOver a one-year treatment period, OK and DIMS lenses can significantly retard AL elongation compared with SVS. In addition, the OK lenses were more effective than the DIMS lenses in controlling AL in patients with higher degrees of myopia.

Environmental selenium volatilization is possibly conferred by promiscuous reactions of the sulfur metabolism

Selenium deficiency affects many million people worldwide and volatilization of biogenically methylated selenium species to the atmosphere may limit Se entering the food chain. However, there is very little systematic data on volatilization at nanomolar concentrations prevalent in pristine natural environments. Pseudomonas tolaasii cultures efficiently methylated Se at these concentrations. Nearly perfect linear correlations between the spiked Se concentrations and Dimethylselenide, Dimethyldiselenide, Dimethylselenylsulfide and 2-hydroxy-3-(methylselanyl)propanoic acid were observed up to 80 nM. The efficiency of methylation increased linearly with increasing initial Se concentration, arguing that the enzymes involved are not constitutive, but methylation proceeds promiscuously via pathways of S methylation. From the ratio of all methylated Se and S species, one can conclude that between 0.30% and 3.48% of atoms were Se promiscuously methylated at such low concentrations. At concentrations higher than 640 nM (∼50 μg/L) a steep increase in methylation and volatilization was observed, which suggested the induction of specific enzymes. Promiscuous methylation at low environmental concentrations calls into question that view that methylated Se in the atmosphere is a result of a purposeful Se metabolism serving detoxification. Rather, the concentrations of methylated Se in the atmosphere may be “coincidental” i.e., determined by the activity of S cycling microorganisms. Further, a steep increase in methylation efficiency when surpassing a certain threshold concentration (here ∼50 μg/L) calls into question that natural methylation can be estimated from high Se spikes in laboratory systems, yet highlights the possibility of using bacterial methylation as an effective remediation strategy for media higher concentrated in Se.

Phosphorus can effectively reduce selenium adsorption in selenium-rich lateritic red soil

Phosphorus (P) application can improve the availability of selenium (Se) in soil, which benefits the output of Se-rich agricultural products. However, the mechanism by which P affects the adsorption of Se in Se-rich soil is still unclear. Therefore, this study took Se-rich lateritic red soil as the research object and studied the adsorption behavior of P and Se in the soil through batch adsorption tests and soil characterization technology. The results showed that the adsorption of P or Se in lateritic red soil increased with an increase in equilibrium concentration. The P or Se adsorption process was explained using the Langmuir and Freundlich isotherm models. After adding P, the adsorption of Se decreased from 276–423 mg/kg to 52–201 mg/kg at different initial Se concentrations. The scanning electron microscope and energy dispersive spectrometry (SEM-EDS) results showed that the lateritic red soil was rich in C, O, Fe, Al, and other elements, and the free oxidation states of these elements could efficiently facilitate the adsorption of P and Se. Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses indicated that both Se and P could react with ferrite groups in the soil to form iron-containing complexes, and there was a competitive adsorption phenomenon, which was the main reason for the decrease in Se adsorption. This study provides theoretical support for further exploring the effect of P on Se behavior in the geochemical cycle. Furthermore, it promotes the efficient use of Se-rich soil resources.

Direct immobilization of Se(IV) from acidic Se(IV)-rich wastewater via ferric selenite Co-precipitation

The attenuation of acidic Se(IV)-rich wastewater, including those associated with acid mine drainage (AMD) and nonferrous metallurgical wastewater (NMW), presents a serious environmental challenge. This study investigates the effects of diverse factors from pH values to Se(IV)/Fe(III) molar ratios, initial Se(IV) concentrations, and alkali neutralization agents on the direct co-precipitation of ferric selenites in AMD and NMW systems involving different orders of Fe(III) and alkali addition. Our results show that amorphous sulfate-substituted ferric (hydrogen) selenite and Se(IV)-bearing ferrihydrite-schwertmannite are the major Se(IV)-attenuation solids except that gypsum is an additional phase in the NMW system with Ca(OH)2 neutralization. Produced ferric selenites achieve 98–99.8% of Se(IV) immobilization under optimal conditions of pH 4.5, Se(IV)/Fe(III) molar ratios of 0.0625–0.5, and initial Se(IV) concentrations of 0.15–1.3 mmol·L-1. Moreover, completing FeSO4+ and FeHSeO32+/FeSeO3+ complexes as well as different ferric selenite co-precipitates are shown to collectively control aqueous Se(IV) remaining. Specifically, three distinct trends of aqueous Se(IV) concentrations separately correspond to changes in the four factors. The co-precipitation in the NMW system via pH adjustment followed by Fe(III) addition is more efficient for Se(IV) fixation than that in the AMD system because of minimal complexation, concurrent Fe(III) hydrolysis, and enhanced ferric selenite co-precipitation in the former.

Factors affecting selenium-enrichment efficiency, metabolic mechanisms and physiological functions of selenium-enriched lactic acid bacteria

• Summarize the factors affecting the Se enrichment capacity of Se-enriched LABs. • Discuss the metabolic mechanisms and physiological functions of Se-enriched LABs. • Conclude the applications of selenium-enriched LABs in food production. Selenium (Se)-enriched lactic acid bacteria (LAB) are live bacteria preparations that accumulate and bio-transform inorganic Se into organic Se forms including Se-nanoparticles (SeNPs), Se-amino acids and selenoproteins. Se-enriched LAB can play the dual role of organic Se supplement and probiotic effects, and have great applications in the food and biomedical fields. Therefore, more and more attentions have been paid on the Se-enriched LAB. This paper firstly summarized the factors affecting the Se-enrichment efficiency of Se-enriched LAB, then discussed the metabolic mechanisms and physiological functions of Se-enriched LAB, and finally reviewed their applications in food production, in order to provide a guidance for the theoretical and practical implementation of Se-enriched LAB. We concluded that 1) both biomass and the amount of Se enrichment should be used as dual indicators to screen Se-enriched LAB and comprehensively optimize the influencing factors including initial Se concentration, pH, inoculation amount, species of LAB to ensure the Se enrichment efficiency. 2) The metabolic mechanism underlining Se-enriched LAB needs to be further revealed, which will facilitate the production of higher value Se compounds by LAB. 3) The proven physiological functions of Se-enriched LAB include 5 categories: antioxidant activity, antibacterial activity, improving the physical function of animals, detoxification and disease prevention. However, the application of Se-enriched LAB in medical field currently still lacks clinical research, and convincing clinical evidence of effectiveness for Se-enriched LAB on human being must be established. 4) The application in the food field will benefit from the stable existence in the food system of Se-enriched LAB and public acceptance, which come before the various health benefits. In any case, the great potential value of Se-enriched LAB formulations deserves further comprehensive exploration and development.

Effects of environmental factors on selenite volatilization by freshwater microalgae

The accumulation and volatilization of Se by algae in surface water are important parts of the biogeochemical cycle of selenium but are also variable and complex. Experiments with 5–8 day of exposure under various temperatures, solution pH values, lighting regimes, and different initial Se concentrations were carried out to study the change in Se accumulation and volatilization behavior of algae. The study showed that algae accumulated and volatilized more Se under harsher environments, such as a lower pH, a shorter lighting time, and a higher Se load. The maximum average daily volatilization rate of Se was 234 ± 23 μg Se (g algae·d)−1, much greater than the values of previous studies. Therefore, in some Se-polluted water environments, when the pH of lakes is acidic, Se emissions to the atmosphere are much higher than currently estimated. Both the accumulation rate (Raccu) and volatilization rate (Rvol) of Se by algae were significantly negatively correlated with final pH, final OD, and residual Se in solution (Cres). Moreover, multiple linear regression equations were used to estimate the rates of Se accumulation and volatilization. This study provides theoretical basis data to quantify the contribution of selenium metabolism by algae to selenium biogeochemistry and a technical reference for the treatment of Se-containing wastewater.

Longitudinal Changes in Refractive Error Among Preschool Children Aged 1–6 Years: The Changsha Children Eye Study

PurposeTo investigate the longitudinal changes in refractive error of preschool children and explore the factors related to these changes and the timing of intervention.MethodsThe refractive data of preschool children aged 1–6 years were collected from 16 community Health Service Centers in Changsha during April 2016 to July 2019 for the retrospective cohort study. The refractive data of each participant was measured with a hand-held vision screener without cycloplegia. A follow-up for all the included participants was performed. The spherical equivalent change was calculated, subsequently, an analysis of risk factors related to the change was performed.ResultsFour thousand nine hundred twenty-one cases were included in the study with the follow-up for 1–2 years. The refractive status was found smoothly changed in 67.8% of children. The overall initial SE was 0.62 ± 1.13 D, and the average SE change was −0.20 ± 1.23 D per year. However, profound myopic shift was observed in 32.2% of children. The change of SE in 3-year-old group is most overt. The proportions of 1–6 years old who showed moderate and severe myopic shift (SE change ≥–1.00 D) were 21.6, 18.9, 28.2, 25.5, 13.4, and 10%, respectively. At the first visit, the younger children with greater hyperopic state exhibited more noticeable myopic shift, no significant difference was found in gender.ConclusionThe shift from hyperopia to myopia in preschool children is smooth, with −0.20D change on average per year. We suggest that an optometry screening should start at 3-year-old to track children's refractive status. We recommend that preschool children whose SE changes more than −1.00 D per year go to the ophthalmology department for further examination. Our study also found that at the first visit, the younger the child is and the more positive initial SE is, the degree of shift of myopia is greater.

The removal of selenite and cadmium by immobilized biospheres: Efficiency, mechanisms and bacterial community

In this study, a complex bacterial consortium was enriched from a typical Pb–Zn mine area and immobilized by sodium alginate to form biospheres, which were used for treatment of selenite (Se(IV))- and cadmium (Cd(II))-containing wastewater without external carbon source. Batch experiments showed that the maximum Se(IV) removal efficiency was 92.36% under the optimal conditions of an initial pH of 5, dosage of 5 g/L, initial Se(IV) concentration of 7.9 mg/L and reaction time of 168 h. Subsequently, more than 99% of 11.2 mg/L Cd(II) was removed by the biospheres within 10 h. Physicochemical characterization showed that reduction and adsorption were the main mechanisms for Se(IV) and Cd(II) removal, respectively. During the removal process, selenium and CdSe nanoparticles were formed. Bacterial community analysis showed the dominant bacterial genera changed after treatment of Se(IV)- and Cd(II)-containing wastewater. Additionally, 16S rRNA gene function prediction results showed that amino acid transport, carbohydrate transport, ion transport and metabolism were the dominant gene functions. The present study provides a potential way for the biological treatment of Se(IV)- and Cd(II)-containing wastewater using immobilized biospheres without external carbon source in short-term.

Differential Impact of Severity and Duration of Status Epilepticus, Medical Countermeasures, and a Disease-Modifier, Saracatinib, on Brain Regions in the Rat Diisopropylfluorophosphate Model.

Acute organophosphate (OP) toxicity poses a significant threat to both military and civilian personnel as it can lead to a variety of cholinergic symptoms including the development of status epilepticus (SE). Depending on its severity, SE can lead to a spectrum of neurological changes including neuroinflammation and neurodegeneration. In this study, we determined the impact of SE severity and duration on disease promoting parameters such as gliosis and neurodegeneration and the efficacy of a disease modifier, saracatinib (AZD0530), a Src/Fyn tyrosine kinase inhibitor. Animals were exposed to 4 mg/kg diisopropylfluorophosphate (DFP, s.c.) followed by medical countermeasures. We had five experimental groups: controls (no DFP), animals with no continuous convulsive seizures (CS), animals with ∼20-min continuous CS, 31-60-min continuous CS, and > 60-min continuous CS. These groups were then assessed for astrogliosis, microgliosis, and neurodegeneration 8 days after DFP exposure. The 31-60-min and > 60-min groups, but not ∼20-min group, had significantly upregulated gliosis and neurodegeneration in the hippocampus compared to controls. In the piriform cortex and amygdala, however, all three continuous CS groups had significant upregulation in both gliosis and neurodegeneration. In a separate cohort of animals that had ∼20 and > 60-min of continuous CS, we administered saracatinib for 7 days beginning three hours after DFP. There was bodyweight loss and mortality irrespective of the initial SE severity and duration. However, in survived animals, saracatinib prevented spontaneous recurrent seizures (SRS) during the first week in both severity groups. In the ∼20-min CS group, compared to the vehicle, saracatinib significantly reduced neurodegeneration in the piriform cortex and amygdala. There were no significant differences in the measured parameters between the naïve control and saracatinib on its own (without DFP) groups. Overall, this study demonstrates the differential effects of the initial SE severity and duration on the localization of gliosis and neurodegeneration. We have also demonstrated the disease-modifying potential of saracatinib. However, its’ dosing regimen should be optimized based on initial severity and duration of CS during SE to maximize therapeutic effects and minimize toxicity in the DFP model as well as in other OP models such as soman.

THE EFFECT OF TWO DIFFERENT DOSES OF SELENIUM YEAST AND SODIUM SELENITE ON SELENIUM LEVEL IN BLOOD, COLOSTRUM, MILK AND METABOLIC PROFILE IN DAIRY COWS

The aim of the study was to compare effects of two levels of selenium yeast (SY) and sodium selenite (SS) supplementation on blood, colostrum and milk Se levels, blood chemistry parameters in dairy cows under field conditions. The study included 36 Holstein cows from 5 weeks prepartum to 12 weeks postpartum. The cows were divided into 4 treatments (n = 9): 1. Negative Control (NC) – no Se supplement ; 2. Positive Control (PC) – 0.3 ppm Se (from sodium selenite) ; 3. S1 – 0.3 ppm Se (from selenium yeast – SELSAF ® , Lesaffre Feed Additives, France ) ; 4 . S2 – 5 ppm Se ( SELSAF ® , Lesaffre Feed Additives, France ). At 5 and 1 weeks prepartum, on the calving day, and 4, 8, 12 weeks postpartum, blood samples were taken . Colostrum and milk were collected on the calving day and 4, 8 and 12 weeks postpartum and analysed for Se content. Initial Se status in all the cows was marginal. Negative Control cows showed suboptimal blood Se levels for the whole period under study. S1 and S2 showed significantly (P &lt; 0.01) higher values than NC and PC cows. Colostrum Se levels were significantly higher in S1 (128.17 ug/L) and S2 (155.58 ug/L) than in NC (94.68 ug/L) and PC (99.3 ug/L) cows. Overall mean milk Se levels in S1 (20.4 ug/L) and S2 (50.0 ug/L) were higher than in NC (10.9 ug/L) and PC (16.6 ug/L). Biochemical indicators of blood did not significantly differ between the treatments and were within the physiological ranges. Se levels in whole blood, colostrum and milk, and GSH-Px activity were significantly increased by selenium yeast supplementation. The response was dose dependent and consistent. Selenium from organic source was more bioavailable than selenium from sodium selenite. Dietary Se at a tolerance dose (5 ppm) had no detrimental effect on the blood chemistry parameters analysed.

Comparison of Longitudinal Changes in Refractive Error of Hyperopic Children with or without Refractive Accommodative Esotropia.

We investigated longitudinal changes in the spherical equivalent refractive error (SE) in hyperopic children with or without refractive accommodative esotropia (AccET). A total of 456 patients met the inclusion criteria: 190 (41.7%) in the hyperopic control group and 266 (58.3%) in the AccET group. All patients received at least 3 years of follow-up after spectacle prescription. Subgroups were divided according to age when spectacles were prescribed, presence of amblyopia, or initial SE. Longitudinal changes in SE in children with hyperopia showed a gradual decrease, although SE of younger children with AccET increased over the first 4 years and then decreased thereafter. SE in eye with higher SE was tended to decrease significantly in patient with Acc ET than hyperopic control group (group × time p = 0.015). Amblyopic eyes showed a greater decreased in SE compared with non-amblyopic eyes, but it was not statistically significant (p = 0.07). SE was significantly decreased in children with more hyperopia (≥ 3 D) compared with children with less hyperopia (<3 D) (p = 0.008). Emmetropization of hyperopia was faster in hyperopic patients without AccET and could be affected by the age of the initial spectacles prescription, initial amount of SE, or presence of amblyopia.

Comparative performance of activated sludge and aerobic granular sludge sequencing batch reactors for removing metalloid SeIV/VI oxyanions

Biotransformation of soluble selenite (SeIV) and selenate (SeVI) to biomass-associated Se0 (Bio-Se) provides a solution for mitigating Se pollution coupled to securing scarce element. Here, we demonstrated an efficient Se oxyanion removal process by converting to Bio-Se using aerobic granular sludge (AGS). SeIV and SeVI removal was dependent on lactate availability, and proportional to initial Se and biomass concentrations. Laboratory-scale sequencing batch reactors (SBR) were operated for 100 days by feeding an influent containing 100 μM SeIV, 100 μM SeVI, or 100 μM each of SeIV and SeVI to evaluate Se and nutrient removal performance. At 34 h hydraulic retention time, complete and sustained removal of influent SeIV, SeVI or SeIV-SeVI was achieved in 24 h cycles containing anaerobic (8 h) and aeration (15 h) phases. Removal of NH4+-N was sustained in AGS reactor through nitritation-denitritation under Se-loading conditions. AGS process demonstrated SeIV/VI, COD, ammonia, and total nitrogen removal efficiencies of 99 %, 99 %, 99 % and 98 %, respectively. Both batch and SBR experiments revealed that AGS is superior to activated sludge in achieving simultaneous SeIV/VI oxyanion and nutrient removal. This study shows that AGS process could be applied for treating acid mine and agricultural drainage that contain Se oxyanions and ammoniacal-nitrogen.

Microbial selenate detoxification linked to elemental sulfur oxidation: Independent and synergic pathways

Elevated selenium levels in the environment, with soluble selenate [Se(VI)] as the common chemical species, pose a severe threat to human health. Anaerobic Se(VI) bioreduction is a promising approach for selenium detoxification, and various organic/inorganic electron donors have proved effective in supporting this bioprocess. Nevertheless, autotrophic Se(VI) bioreduction driven by solid inorganic electron donors is still not fully understood. This work is the first to employ elemental sulfur [S(0)] as electron donor to support Se(VI) bioreduction. A batch trial with mixed culture demonstrated the feasibility of this bioprocess, with Se(VI) removal efficiency of 92.4 ± 0.7% at an initial Se(VI) concentration of 10 mg/L within 36 h. Continuous column tests showed that increased initial concentration, flow rate, and introduction of NO3--N depressed Se(VI) removal. Se(VI) was mainly bioreduced to solid elemental Se with trace selenite in the effluent, while S(0) was oxidized to SO42-. Enrichment of Thiobacillus, Desulfurivibrio, and Sulfuricurvum combined with upregulation of genes serA, tatC, and soxB indicated Se(VI) bioreduction was coupled to S(0) oxidation. Thiobacillus performed S(0) oxidation and Se(VI) reduction independently. Intermediate metabolites as volatile fatty acids, hydrogen and methane from S(0) oxidation were utilized by heterotrophic Se(VI) reducers for Se(VI) detoxification, indicative of microbial synergy.

Competing Sorption of Se(IV) and Se(VI) on Schwertmannite

Schwertmannite (SHM) is a naturally occurring mineral that has been shown to effectively scavenge oxyanions from contaminated water. In this study, Fourier-transform infrared spectroscopy and X-ray absorption spectroscopy techniques in combination with wet-chemical techniques were used to study the competitive sorption of Se(IV) and Se(VI) at pH 3. The experiments were conducted with three types of schwertmannite obtained from oxidative synthesis, biogenic synthesis and high-pressure compaction at different initial Se concentrations and mixing ratios for 48 h and 56 days, respectively. A threshold value for the uptake mechanisms was identified, which reflects the amount of easily exchangeable sulphate (~0.5 mmol/g). At adsorbate concentrations below this threshold, an inner-sphere corner-sharing bidentate binuclear complex forms upon exchange with sulphate. At higher concentrations, both oxyanions become bound to SHM through co-occurrence of mainly inner-sphere and partly outer-sphere corner-sharing bidentate binuclear complexes with Fe(III) containing surface sites. Single species experiments clearly indicate a higher affinity of SHM for Se(IV). However, in mixed species experiments, competitive sorption occurs with equal or even preferential uptake of Se(VI) at concentrations much lower than the threshold value, presumably due to geometrical similarity between selenate and sulphate, and increasing preference for Se(IV) at high Se concentrations.

Hydrodynamics- and hydrochemistry-affected microbial selenate reduction in aquifer: Performance and mechanisms

Selenate [Se(VI)] with higher content in groundwater will be harmful for human beings. Hence, effective treatment for Se(VI) in aquifer should be conducted reasonably. Microbial reduction of Se(VI) to elemental selenium with weak movability and toxicity has attracted significant attention due to its high efficiency and no secondary contamination. However, hydrodynamic and hydrochemical influences with corresponding mechanisms during Se(VI) bioreduction are still not clear. In this study, influences of flow rate, initial Se(VI) and organic concentrations, coexisting nitrate were evaluated. Se(VI) removal efficiency and capacity reached 96.42 ± 6.82% and 41.28 ± 3.41 (g/m3·d) with flow rate of 0.56 mL/min, initial Se(VI) and chemical organic demand concentrations of 10 mg/L and 400 mg/L. Dechloromonas and Pseudomonas were presumably contributed to Se(VI) reduction, with upregulated serA and tatC genes. Solid Se0 was identified as the final product from Se(VI) reduction. These results will be beneficial for the further comprehending of Se(VI) remediation in aquifer.