Metagenomic analysis of Fe(II)-oxidizing bacteria for Fe(III) mineral formation and carbon assimilation under microoxic conditions in paddy soil

Microbially mediated Fe(II) oxidation is prevalent and thought to be central to many biogeochemical processes in paddy soils. However, we have limited insights into the Fe(II) oxidation process in paddy fields, considered the world's largest engineered wetland, where microoxic conditions are ubiquitous. In this study, microaerophilic Fe(II) oxidizing bacteria (FeOB) from paddy soil were enriched in gradient tubes with FeS, FeCO₃, and Fe₃(PO₄)₂ as iron sources to investigate their capacity for Fe(II) oxidation and carbon assimilation. Results showed that the highest rate of Fe(II) oxidation (k = 0.836 mM d^-1) was obtained in the FeCO₃ tubes, and cells grown in the Fe₃(PO₄)₂ tubes yielded maximum assimilation amounts of ¹³C-NaHCO₃ of 1.74% on Day 15. Amorphous Fe(III) oxides were found in all the cell bands with iron substrates as a result of microbial Fe(II) oxidation. Metagenomics analysis of the enriched microbes targeted genes encoding iron oxidase Cyc2, oxygen-reducing terminal oxidase, and ribulose-bisphosphate carboxylase, with results indicated that the potential Fe(II) oxidizers include nitrate-reducing FeOB (Dechloromonas and Thiobacillus), Curvibacter, and Magnetospirillum. By combining cultivation-dependent and metagenomic approaches, our results found a number of FeOB from paddy soil under microoxic conditions, which provide insight into the complex biogeochemical interactions of iron and carbon within paddy fields. The contribution of the FeOB to the element cycling in rice-growing regions deserves further investigation.

Potentially toxic elements in iron mine tailings: Effects of reducing soil pH on available concentrations of toxic elements

Tailings from iron mining are characterized by high concentrations of iron and manganese oxides, as well as high pH values. With these characteristics, most of the potentially toxic elements (PTE) contained in the tailings are somewhat unavailable. The aim of the present study was to evaluate how a reduction in the pH of iron mine tailings may affect PTE availabilities. The tailings were collected on the banks of the Gualaxo do Norte River (Mariana, MG, Brazil), one of the main areas impacted by the rupture of the Fundão Dam (Barragem de Fundão). A completely randomized experimental design was used, including five pH values (6.4, 5.4, 4.3, 3.7, and 3.4) and five replications. The concentrations of the PTE (Ba, Cr, Cd, Co, Cu, Fe, Mn, Pb, Ni, and Zn) were determined after extraction following different methodologies: USEPA 3051A, DTPA, Mehlich-1, Mehlich-3, and distilled water. A comparison of the available concentrations of the elements in the tailings with those in a soil not impacted by tailings shows that Cr, Cd, Cu, Fe, Mn, Ni, Ba, and Co were higher in the soil impacted by the tailings. The different methods used for evaluating the availability of PTE in the tailings at various pH exhibited the following decreasing order in relation to the quantity extracted: Mehlich-3 > Mehlich-1 > DTPA > distilled water. However, regarding sensitivity to change in pH, the order was DTPA > water > Mehlich-1 > Mehlich-3. The increases in the concentrations of PTE due to the reduction in the pH of the tailings did not lead to concentrations that exceed the limits of Brazilian regulations. The DTPA extractant exhibited higher coefficients of correlation between the PTE concentrations and the pH of the tailings, proving to be suitable for use in areas affected by the deposition of iron mine tailings.

Smartphone-based spectrometry system as a prescreening assessment of copper and iron for real time control of water pollution

Due to anthropogenic actions, the presence of pollutants in water bodies, such as toxic metals, are increasingly negatively affecting water quality, biodiversity and sustainable goals worldwide. Therefore, decentralization of water pollution monitoring with low-cost devices, such as using smartphones, suggests an innovative green technology for in situ and real-time control. In this study, a Handheld Smartphone Spectrophotometry System (HSSS) was developed to estimate copper and iron concentration water samples. The system mainly comprises a portable commercial spectrometer (GoSpectro) that can measure the spectrum of light in the visible region. The HSSS LOD and LOQ for copper were equal to 0.589 and 1.784 mg/L, respectively, and 0.479 and 1.450 mg/L, respectively for iron. In addition, the results of copper and iron concentrations in samples with unknown concentrations using HSSS were close to the Benchtop Spectrophometer (BS). Finally, HSSS performance showed to be a new green technology for water quality management with potential applications for monitoring water resources and also providing further possibilities to measure other pollutants by the same technique, in addition to metals.

Phosphorus speciation and sedimentary phosphorus release in an urban bay (Dachan Bay, China) impacted by multiple anthropogenic perturbations

Sedimentary phosphorus (P) release and retention are important in controlling P dynamics in coastal waters. Here, two sediment cores were analysed to understand the P speciation and sedimentary P release characteristics in Dachan Bay, Shenzhen, where was highly influenced by human activity. Total phosphorus (TP) concentrations, 52.3 to 1119 μg g^-1, fluctuated greatly with depth. Four P binding forms were fractionated: iron-bound P (FeP), authigenic apatite (CaP), detrital P (De-P), and organic P (OP) with the following order of concentration: Fe-P > OP > De-P > Ca-P. The P pollution index (PPI) revealed the contamination of sediment with P in recent years. Additionally, the potentially mobile P pools and long-term P release in the sediments were estimated, and the results indicated that, sediment was an important potentially mobile P pools in the water column, especially in nearshore areas, which required the attention of management departments.

Geographical distribution of trace elements (selenium, zinc, iron, copper) and case fatality rate of COVID-19: a national analysis across conterminous USA

Severe outcome particularly death is the largest burden of COVID-19. Clinical observations showed preliminary data that deficiency in certain trace elements, essential for the normal activity of immune system, may be associated with worse COVID-19 outcome. Relevant study of environmental epidemiology has yet to be explored. We investigated the geographical association between concentrations of Se, Zn, Fe and Cu in surface soils and case fatality rate of COVID-19 in USA. Two sets of database, including epidemiological data of COVID-19 (including case fatality rate, from the University of John Hopkinson) and geochemical concentration data of Se, Zn, Fe and Cu in surface soils (from the National Geochemical Survey), were mapped according to geographical location at the county level across conterminous USA. Characteristics of population, socio-demographics and residential environment by county were also collected. Seven cross-sectional sampling dates, with a 4-week interval between adjacent dates, constructed an observational investigation over 24 weeks from October 8, 2020, to March 25, 2021. Multivariable fractional (logit) outcome regression analyses were used to assess the association with adjustment for potential confounding factors. In USA counties with the lowest concentration of Zn, the case fatality rate of COVID-19 was the highest, after adjustment for other influencing factors. Associations of Se, Fe and Cu with case fatality rate of COVID-19 were either inconsistent over time or disappeared after adjustment for Zn. Our large study provides epidemiological evidence suggesting an association of Zn with COVID-19 severity, suggesting Zn deficiency should be avoided.

Trial of Deferiprone in Parkinson's Disease

BACKGROUND

Iron content is increased in the substantia nigra of persons with Parkinson's disease and may contribute to the pathophysiology of the disorder. Early research suggests that the iron chelator deferiprone can reduce nigrostriatal iron content in persons with Parkinson's disease, but its effects on disease progression are unclear.

METHODS

We conducted a multicenter, phase 2, randomized, double-blind trial involving participants with newly diagnosed Parkinson's disease who had never received levodopa. Participants were assigned (in a 1:1 ratio) to receive oral deferiprone at a dose of 15 mg per kilogram of body weight twice daily or matched placebo for 36 weeks. Dopaminergic therapy was withheld unless deemed necessary for symptom control. The primary outcome was the change in the total score on the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS; range, 0 to 260, with higher scores indicating more severe impairment) at 36 weeks. Secondary and exploratory clinical outcomes at up to 40 weeks included measures of motor and nonmotor disability. Brain iron content measured with the use of magnetic resonance imaging was also an exploratory outcome.

RESULTS

A total of 372 participants were enrolled; 186 were assigned to receive deferiprone and 186 to receive placebo. Progression of symptoms led to the initiation of dopaminergic therapy in 22.0% of the participants in the deferiprone group and 2.7% of those in the placebo group. The mean MDS-UPDRS total score at baseline was 34.3 in the deferiprone group and 33.2 in the placebo group and increased (worsened) by 15.6 points and 6.3 points, respectively (difference, 9.3 points; 95% confidence interval, 6.3 to 12.2; P<0.001). Nigrostriatal iron content decreased more in the deferiprone group than in the placebo group. The main serious adverse events with deferiprone were agranulocytosis in 2 participants and neutropenia in 3 participants.

CONCLUSIONS

In participants with early Parkinson's disease who had never received levodopa and in whom treatment with dopaminergic medications was not planned, deferiprone was associated with worse scores in measures of parkinsonism than those with placebo over a period of 36 weeks. (Funded by the European Union Horizon 2020 program; FAIRPARK-II ClinicalTrials.gov number, NCT02655315.).

Long term exposure to air pollution and kidney parenchyma cancer - Effects of low-level air pollution: a Study in Europe (ELAPSE)

BACKGROUND

Particulate matter (PM) is classified as a group 1 human carcinogen. Previous experimental studies suggest that particles in diesel exhaust induce oxidative stress, inflammation and DNA damage in kidney cells, but the evidence from population studies linking air pollution to kidney cancer is limited.

METHODS

We pooled six European cohorts (N = 302,493) to assess the association of residential exposure to fine particles (PM2.5), nitrogen dioxide (NO2), black carbon (BC), warm season ozone (O3) and eight elemental components of PM2.5 (copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc) with cancer of the kidney parenchyma. The main exposure model was developed for year 2010. We defined kidney parenchyma cancer according to the International Classification of Diseases 9th and 10th Revision codes 189.0 and C64. We applied Cox proportional hazards models adjusting for potential confounders at the individual and area-level.

RESULTS

The participants were followed from baseline (1985-2005) to 2011-2015. A total of 847 cases occurred during 5,497,514 person-years of follow-up (average 18.2 years). Median (5-95%) exposure levels of NO2, PM2.5, BC and O3 were 24.1 μg/m3 (12.8-39.2), 15.3 μg/m3 (8.6-19.2), 1.6 10-5 m-1 (0.7-2.1), and 87.0 μg/m3 (70.3-97.4), respectively. The results of the fully adjusted linear analyses showed a hazard ratio (HR) of 1.03 (95% confidence interval [CI]: 0.92, 1.15) per 10 μg/m³ NO2, 1.04 (95% CI: 0.88, 1.21) per 5 μg/m³ PM2.5, 0.99 (95% CI: 0.89, 1.11) per 0.5 10-5 m-1 BCE, and 0.88 (95% CI: 0.76, 1.02) per 10 μg/m³ O3. We did not find associations between any of the elemental components of PM2.5 and cancer of the kidney parenchyma.

CONCLUSION

We did not observe an association between long-term ambient air pollution exposure and incidence of kidney parenchyma cancer.

Effective R2 relaxation rate, derived from dual-contrast fast-spin-echo MRI, enables detection of hemisphere differences in iron level and dopamine function in Parkinson's disease and healthy individuals

BACKGROUND

Clinical estimates of brain iron concentration are achievable with quantitative transverse relaxation rate R₂, via time-consuming multiple spin-echo (SE) sequences. The objective of this study was to investigate whether quantitative iron-sensitive information may be derived from 3.0 T dual-contrast fast-spin-echo (FSE) sequences (typically employed in anatomical non-quantitative evaluations), as a routinely-collected alternative to evaluate iron levels in healthy (HC) and Parkinson's disease (PD) brains.

NEW METHOD

MRI 3.0 T FSE data from the Parkinson's Progression Markers Initiative (PPMI) (12 PD, 12 age- and gender-matched HC subjects) were cross-sectionally and longitudinally evaluated. A new measure, 'effective R₂', was calculated for bilateral subcortical grey matter (caudate nucleus, putamen, globus pallidus, red nucleus, substantia nigra). Linear regression analysis was performed to correlate 'effective R₂' with models of age-dependent brain iron concentration and striatal dopamine transporter (DaT) receptor binding ratio.

RESULTS

Effective R₂ was strongly correlated with estimated brain iron concentration. In PD, putaminal effective R₂ difference was observed between the hemispheres contra-/ipsi-lateral to the predominantly symptomatic side at onset. This hemispheric difference was correlated with the putaminal DaT binding ratios in PD.

COMPARISON WITH EXISTING METHOD(S)

Effective R₂, derived from rapid dual-contrast FSE sequences, showed viability as an alternative to R₂ from SE sequences. Linear correlation of effective R₂ with estimated iron concentration was comparable to documented iron-dependent R₂. The effective R₂ correlation coefficient was consistent with theoretical R₂ iron-dependence at 3.0 T.

CONCLUSIONS

Effective R₂ has clinical potential as a fast quantitative method, as an alternative to R₂, to aid evaluation of brain iron levels and DaT function.

Legacy of contamination with metal(loid)s and their potential mobilization in soils at a carbonate-hosted lead-zinc mine area

Chemical weathering of carbonate-hosted Pb-Zn mines via acid-promoted or oxidative dissolution generates metal-bearing colloids at neutral mine drainage sites. However, the mobility and bioavailability of the colloids associated with metals in nearby soils are unknown. Here, we monitored the mobility of metal(loid)s in soils affected by aeolian deposition and river transport in the vicinity of a carbonate-hosted Pb-Zn mine. Using chemical extraction, ultrafiltration, and microscopic and spectroscopic analysis of metals we find that contamination levels of the soil metals cadmium (Cd), lead (Pb) and zinc (Zn) were negatively correlated with metal extractability. However, nano-scale characterization indicates that colloid-metal(loid) interactions induced potential mobilization and increased risk from metal(loid)s. Dynamic light scattering (DLS) and HRTEM-EDX-SAED analysis further indicate that organic matter (OM)-rich nano-colloids associated with calcium (Ca), silicon (Si) and iron (Fe) precipitates accounted for the majority of the dissolved metal fractions in carbonate-hosted Pb-Zn mine soils. More stable nano-crystals (ZnS, ZnCO₃, Zn-bearing sulfates, hematite and Al-Si-Fe compounds) were present in the pore water of aeolian-impacted upland soils rather than in river water-impacted soils. Our results suggest that future work should consider the possibility that potential mobilization of metal(loid)s induced by the weathering and transformation of these metal-bearing nano-crystals to metal-bearing amorphous colloids, potentially elevating metal mobility and/or bioavailability in river water-impacted agricultural soils.

Co-incorporation of Chinese milk vetch (Astragalus sinicus L.), rice straw, and biochar strengthens the mitigation of Cd uptake by rice (Oryza sativa L.)

Soil cadmium (Cd) contamination is becoming a widespread concern because of its threat to global ecosystem health and food security. Co-incorporation of Chinese milk vetch (MV) and rice straw (RS) is a common agricultural practice in Southern China; however, the effects of combining these two materials with biochar on Cd bioavailability remain unclear. This study investigated the effects of MV, RS, rape straw biochar (RB), iron-modified biochar (FB), and their combinations on Cd uptake by rice through incubation and field experiments. The results showed that compared with the control without material input (CK), MV + RS (MR), MV + RS + RB (MRRB), and MV + RS + FB (MRFB) considerably reduced the Cd concentration in brown rice by 61.20 %, 65.38 %, and 62.65 %, respectively. Furthermore, the treatments increased the formation of iron‑manganese plaque (IMP) at different growth stages; MRRB and MRFB exhibited the highest increase rates among the treatments. Quantitatively, the Fe plaque and Mn plaque were increased by 20.61 %-47.23 % and 80.18 %-172.74 %, respectively. Compared with CK, the MRRB and MRFB treatments reduced the soil available Cd by 35.09 %-54.45 % and 38.20 %-50.20 %, respectively, at all stages. This decrease was substantially lower than that observed in the MV, RS, and MR treatments. Similar trends were observed in the incubation experiment. Additionally, the Community Bureau of Reference Sequential Extraction Analysis indicated that the MRRB and MRFB treatments converted the bioavailable Cd fractions into a stable form. Partial least squares path model and redundancy analysis revealed that pH was the major factor influencing Cd bioavailability. This study emphasized that the dual impact factors from the enhancement of Cd passivation capability and IMP formation jointly result in the reduction of Cd uptake by rice. Consequently, the co-incorporation of MV, RS, and biochar is promising for remediating Cd-contaminated paddy soils in Southern China.

Toxic metal and trace element status in the breast milk of Turkish new-born mothers

BACKGROUND AND AIM

This study aims to evaluate the toxic metal and trace element concentrations in breast milk obtained from new-born nursing mothers in rural Giresun province, located on the coast of the Black Sea.

METHODS

Milk samples were randomly collected once from early lactation of 50 nursing mothers. Inductively coupled plasma mass spectrometry was used to analyse the concentrations of iron (Fe), nickel (Ni), manganese (Mn), cobalt (Co), chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), molybdenum (Mo), cadmium (Cd) and lead (Pb) in the breast milk. Shapiro-Wilk test was used to evaluate the distribution of data. The Pearson-J correlation was used for normally distributed elements, and Spearman correlation analysis was used for others.

RESULTS

The mean amounts of elements were 3.36 µg kg^-1 of Cr, 9.26 µg kg^-1 of Mn, 797 µg kg^-1 of Fe, 1.99 µg kg^-1 of Ni, 5.92 µg kg^-1 of Cu, 379 µg kg^-1 of Zn and 2.23 µg kg^-1 of Pb. Co, As, Mo and Cd concentrations were below the detection limit. A highly significant correlation was found between iron and Nickel in breast milk.

CONCLUSION

Our findings were evaluated in comparison with the WHO data, and whether they were in accordance with the recommended Dietary Reference Intake (DRI) values for 0-6-months-old infants was calculated. Pb levels were similar to those of WHO, while As and Cd were below the measurable limit. Fe, Mn, and Cr concentrations were higher than WHO data, while Co, Ni, Cu and Zn were lower. This research is the first study conducted in this region.

Removal of oxytetracycline from water by liquid-phase plasma process with an iron precipitated TiO2 photocatalyst

This study developed a new water treatment method using liquid-phase plasma (LPP) process that can decompose oxytetracycline (OTC) remaining in the aquatic environment. Relatedly, the OTC causes damage to the human body and cannot be removed by traditional water treatment methods. The study also prepared Fe/TiO₂ photocatalyst responding to visible light using the LPP process. In particular, the OTC decomposition efficiency of the LPP process improved by more than 10% with the use of the Fe/TiO₂ photocatalyst as compared to that of the one with the use of bare TiO₂ photocatalyst. Further, the optimal LPP process parameters and Fe/TiO₂ photocatalyst amount in the LPP process for OTC decomposition were established in the study. Finally, the degradation pathway of the OTC in the LPP process was found based on the five intermediates of the LPP reaction that were detected by the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analysis. In particular, the decomposition pathway was estimated to be involving the mineralization of the OTC through demethylation, deamination, dehydration, and ring cleavage.

Wildlife hair as bioindicators of metal exposure

Animal hair is a useful biomonitoring tool for assessing the occurrence of trace elements in ecosystems. Essential (chromium, copper, iron, manganese, nickel, and zinc) and nonessential (aluminum, arsenic, cadmium, mercury, lead, palladium, platinum, rubidium, tin, and vanadium) elements were investigated in hair of badger (Meles meles), wild boar (Sus scrofa), marmot (Marmota marmota), wolf (Canis lupus), fox (Vulpes vulpes) and deer (Cervus elaphus) from Northwestern Italy. Badger was found to be the highest bioaccumulator of metals, while wolf, fox and deer recorded the lowest values. Essential elements contribute in higher degree to the sum of metals for all species except for wild boar. Results have shown that animals with omnivorous diet such as badger, marmot and wild boar have metal content (especially Al, As, Cr, Cu, Fe, Ni, V) higher than carnivores (wolf and fox) and herbivores (deer) and could represent an effective sentinel of environmental exposure to metals.

Contribution of sedimentary organic matter to arsenic mobilization along a potential natural reactive barrier (NRB) near a river: The Meghna river, Bangladesh

Elevated dissolved arsenic (As) concentrations in the shallow aquifers of Bangladesh are primarily caused by microbially-mediated reduction of As-bearing iron (Fe) (oxy)hydroxides in organic matter (OM) rich, reducing environments. Along the Meghna River in Bangladesh, interactions between the river and groundwater within the hyporheic zone cause fluctuating redox conditions responsible for the formation of a Fe-rich natural reactive barrier (NRB) capable of sequestering As. To understand the NRB's impact on As mobility, the geochemistry of riverbank sediment (<3 m depth) and the underlying aquifer sediment (up to 37 m depth) was analyzed. A 24-hr sediment-water extraction experiment was performed to simulate interactions of these sediments with oxic river water. The sediment and the sediment-water extracts were analyzed for inorganic and organic chemical parameters. Results revealed no differences between the elemental composition of riverbank and aquifer sediments, which contained 40 ± 12 g/kg of Fe and 7 ± 2 mg/kg of As, respectively. Yet the amounts of inorganic and organic constituents extracted were substantially different between riverbank and aquifer sediments. The water extracted 6.4 ± 16.1 mg/kg of Fe and 0.03 ± 0.02 mg/kg of As from riverbank sediments, compared to 154.0 ± 98.1 mg/kg of Fe and 0.55 ± 0.40 mg/kg of As from aquifer sediments. The riverbank and aquifer sands contained similar amounts of sedimentary organic matter (SOM) (17,705.2 ± 5157.6 mg/kg). However, the water-extractable fraction of SOM varied substantially, i.e., 67.4 ± 72.3 mg/kg in riverbank sands, and 1330.3 ± 226.6 mg/kg in aquifer sands. Detailed characterization showed that the riverbank SOM was protein-like, fresh, low molecular weight, and labile, whereas SOM in aquifer sands was humic-like, older, high molecular weight, and recalcitrant. During the dry season, oxic conditions in the riverbank may promote aerobic metabolisms, limiting As mobility within the NRB.

Mercury background values in soils and saprolites in the gold-rich greenstone belt of Suriname, Guiana Shield: The role of parent rock and residual enrichment

In order to develop criteria to distinguish polluted from unpolluted materials in areas subjected to artisanal small-scale gold mining, background mercury values were established in 62 natural soil and saprolite profiles on 16 different parent rock types in the greenstone belt of Suriname. Hg values in pristine topsoils often amount to up to 200 μg/kg, about 100 times higher than Hg in common parent rocks. Additional analyses of 40 major and trace elements in two pilot profiles show that Hg values are strongly correlated to Fe, Cr and V values, which suggests that just as those elements Hg is residually enriched in topsoils by laterisation processes. In the deeper pallid zones of the profiles, Hg has often been leached almost completely together with iron by reducing groundwater action. In this way the range of Hg values within a single profile can be greater than between profiles. Maximum and average Hg values of 196 samples from the 16 different parent rock types fall apart into two main groups. Felsic parent rocks with predominance of quartz and feldspar have maximum Hg values around 100 μg/kg and averages around 50 μg/kg, mafic ones with less silica and higher Fe, Mg and Ca have maximum values around 250-300 μg/kg and averages around 150 μg/kg. In general the natural soil and saprolite Hg values are in the same order of magnitude as many published mine tailings and stream sediments, and therefore cannot be used to separate polluted from unpolluted materials.

Nanoscale Iron trioxide catalyzes the synthesis of auxins analogs in artificial humic acids to enhance rice growth

Humic acids (HAs), kinds of valuable active carbon, are critical for improving soil fertility. However, the majority of soils are poor in HAs, arousing the development of artificial HAs. In this study, two iron-based catalysts (nanoscale iron trioxide (nFe₂O₃) and FeCl₃) were used to catalyze the hydrothermal humification of waste corn straw. With the help of ultra-performance liquid chromatography-mass spectrometry, we proposed the specific humification process with the action of catalysis for the first time, which is of great significance for the design, synthesis and application of artificial HAs in the future. Moreover, the growth-promoting effect and mechanisms of the artificial HAs were determined by rice planting in a greenhouse. Results showed that compared to no catalyst treatment, the FeCl₃ and nFe₂O₃ catalysts increased the decomposition rate of macromolecular biomass by 39 and 14 %, respectively, increasing the yield of artificial HAs. During the humification process, nFe₂O₃ catalysts benefit the formation of many aromatic structure monomers including furfural and hydroxycaproic acids. These monomers were condensed into growth hormone analogs such as vanillin and methionine sulfoxide and were further built in the artificial HAs. Therefore, the artificial HAs from nFe₂O₃ catalytic treatment promoted the rice growth the best, showing that the resultant germination rate, root activity, and photosynthetic rate of rice increased by 50, 167, and 72 %, respectively; moreover, the uptake and accumulation of water and nutrient by roots as well as the contents of soluble protein and sugar of rice are also significantly increased. This could be ascribed to the upregulated expression of functional genes including OsRHL1, OsZPT5-07, OsSHR2 and OsDCL. Considering both the economic and environmental benefits, we suggested that the artificial HAs, especially that produced with the action of nFe₂O₃ catalysis, are promising in alleviating environmental stress from waste biomass and sustainably improving agricultural production.

Increased hemoglobin concentration and related factors in maintenance hemodialysis patients in Anhui, China

To investigate the hemoglobin (Hb) concentration and related factors among maintenance hemodialysis (MHD) patients in Anhui province in 2020, so as to compare with the results in 2014. The cases of 3025 MHD patients were investigated in 27 hemodialysis centers of Anhui province from January 2020 to December 2020. The data of age, sex, primary disease, dialysis age, dialysis mode, drug use and laboratory tests were collected and analyzed. Compared with the survey in 2014, the average Hb level of MHD patients in Anhui province was increased (107.41 ± 20.40 g/L vs 100.2 ± 28.1 g/L), the anemia prevalence was decreased (65.9% vs 82.4%), and the percentage of patients with standard Hb level was increased significantly (47.1% vs 32.9%). Compared with low-Hb patients (Hb < 110 g/L), patients with Hb ≥ 110 g/L had lower age, higher proportion of males, longer dialysis age, higher levels of serum Alb, creatinine, total cholesterol, triglyceride, low density lipoprotein, calcium, phosphorus, magnesium, and lower high-density lipoprotein (P < .05). The multivariate logistic regression analysis results showed that male, longer duration of dialysis therapy, treatment with iron, higher triglyceride and albumin were protective factors of anemia, but older age was independent risk factors. The anemia treatment in MHD patients in Anhui province was significantly improved. Male, long dialysis age, use of iron, high serum albumin and triglyceride levels may be protective factors for Hb reaching standard level, and old age may be an independent risk factor.

Occurrence and characteristics of atmospheric microplastics in Mexico City

While atmospheric microplastics have attracted scientific attention as a significant source of microplastic contamination in the environment, studies in large population centers remain sparse. Here we present the first report on the occurrence and distribution of atmospheric microplastics in Mexico City (Latin America's second most densely populated city), collected using PM₁₀ and PM_2.5 active samplers at seven monitoring stations (urban, residential, and industrial) during the dry and wet seasons of 2020. The results showed that microplastics were detected in all of the samples examined, with mean microplastic concentrations (items m^-3) of 0.205 ± 0.061 and 0.110 ± 0.055 in PM₁₀ and PM_2.5, respectively. The spatial distribution of microplastics showed seasonal variation, with greater abundances in locations closer to industrial and urban centers. There was also a significant difference in microplastic concentrations in PM₁₀ and PM_2.5 between the dry and wet seasons. The mean PM_2.5/PM₁₀ ratio was 0.576, implying that microplastics were partitioned more towards PM_2.5 than PM₁₀ in Mexico City. Fibers were the most prominent shape (>75 %), and blue was the most common color (>60 %). The size characteristics indicated microplastics of varying lengths, ranging from 39 to 5000 μm, with 66 % being <500 μm. Metal contaminants such as aluminum, iron, and titanium were detected using SEM-EDX on randomly selected microplastics. The microplastics were identified as cellophane, polyethylene, polyethylene terephthalate, polyamide, and cellulose (rayon) using ATR-FTIR spectral analysis. Our findings unravel the extent and characteristics of atmospheric microplastics in the Mexico City metropolitan area, which will aid future research to better understand their fate, transport, and potential health risks, demanding more investigations and close monitoring.

A new insight into Cd reduction by flooding in paddy soil: The different dominant roles of Fe and S on Cd immobilization under fluctuant pe + pH conditions

The unsteady comprehensive system of pe + pH strongly affects the fate of Cd in paddy soils. However, the specific pe + pH threshold determining Cd bioavailability is largely unknown especially considering the roles of Fe and S reduction. The experiment set different water managements to obtain paddy soil samples with unstable pe + pH, and chemical analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization were applied to reveal the dynamic process and mechanism about how Fe and S controlled Cd mobilization. The results showed that low pe + pH was favorable to soil Cd immobilization. Compared with high and medium pe + pH, the exchangeable Cd content decreased by 67.57 % and 64.71 % at low pe + pH, respectively. The XPS results showed that the contents of Fe(II) and S(-II) increased to 65.1 % and 75.2 % at low pe + pH condition, which was higher than that in other treatments. In the process of flooding for reducing Cd mobility, first it was attributed to the formation of amorphous iron oxides that can provide amount of adsorption sites for Cd. After then, S^2- began to play a dominant role to combine with Cd²⁺ to form CdS with continuous decreased pe + pH. Therefore, Fe and S played the different dominant roles on Cd immobilization in paddy soil, and soil pe + pH value could work as a threshold.

The performance and mechanism of iron-modified aluminum sludge substrate tidal flow constructed wetlands for simultaneous nitrogen and phosphorus removal in the effluent of wastewater treatment plants

Aiming at the poor N and P removal performance in the effluent of wastewater treatment plants by constructed wetlands (CWs), aluminum sludge (AS) from water supply plants was used to prepare iron-modified aluminum sludge (IAS), and tidal flow constructed wetlands (TFCWs) using IAS as substrates were constructed. By means of high-throughput sequencing, X-ray diffractometer (XRD), etc., the removal mechanism of N and P in the system and fate analysis of key elements were also interpreted. Results showed that an interlayer structure beneficial to adsorbing pollutants was formed in the IAS, due to the iron scraps entering into the molecular layers of AS. The removal rates of TP and TN by IAS-TFCWs reached 95 % and 47 %, respectively, when the flooding/resting time (F/R) and C/N were 6 h/2 h and 6. During the three-year operation of the IAS-TFCWs, the effluent concentrations of COD_Cr, NH₄⁺-N, and TP could comply with Class IV Standard of "Environmental Quality Standards for Surface Water" (GB3838-2002). The mechanism analysis showed that the N removal was effectuated through Fe²⁺ as the electron donor of Fe(II)-driven the autotrophic denitrifying bacteria to reduce nitrate, while the P removal mainly depended on the adsorption reaction between FeOOH in IAS and phosphate. In conclusion, the stable Fe-N cycle in the IAS-TFCWs achieved simultaneous and efficient N and P removal.

Assessing the long-term evolution of mine water quality in abandoned underground mine workings using first-flush based models

Coal mining activities can leave an extensive network of abandoned underground workings that gradually flood after operations cease. This rising mine water can eventually lead to uncontrolled releases of harmful acid mine drainage (AMD) to the environment. Treatment plants are used to extract and treat the mine water to maintain its elevation below suspected discharge points. Accurate predictions of long-term water quality, and treatment plant operations, are highly challenging due to the complexity and volume of the underground workings. As numerical models require considerable effort to effectively implement, empirical models that are based on the 'first-flush' phenomenon, where mine water concentrations peak shortly after flooding and then exponentially decline, may provide suitable long-term predictions. The objective of this study was to assess the robustness of first-flush based models for describing mine water behavior at large, complex mine pools in the Sydney Coalfield (Nova Scotia, Canada). Numerous mine pools across the coalfield flooded at various times over 100+ years, with extensive mine water quality data available in various pools of different ages. The historical evolution of mine water quality demonstrated first-flush behavior across key AMD indicator parameters (acidity, sulfate, iron), concentration ranges, and mine pool depths. Two 'newer' mine pools, which only flooded in the past 10-15 years, rely on an active treatment plant to manage mine water levels below environmental discharge points. Influent water quality from each mine pool was sampled bi-weekly between 2011 and 2022, and first-flush models were then applied to predict the future quality of mine water entering the treatment plant over the long-term. Knowledge on long-term influent quality can help to optimize treatment plant requirements and related expenses.

[Distribution, Migration, and Transformation Mechanism of Labile Phosphorus in Sediments of Xixi River Estuary, Xiamen]

To explore the effect of manganese, iron, and sulfur geochemistry on the distribution of labile phosphorus in different estuarine areas, the diffusion gradient in thin-film (DGT) sampling technique was used for in-situ high-resolution monitoring of available phosphorus (DGT-P), manganese, iron, and sulfur in sediments from Xixi River estuary in Xiamen. The results showed that the distribution of DGT-P in the vertical profile was closely related to the redox transformation of iron and sulfur and the background value of active phosphorus in sediments. The passivation/activation of phosphorus was mainly controlled by the oxidative adsorption/reductive dissolution of phosphorus by iron oxides and the activation of phosphorus induced by sulfate reduction and sulfide accumulation. Along the sampling sites, the average concentration of DGT-P varied greatly (0.075-0.80 mg·L^-1), which was not related to salinity but closely related to redox conditions, that is, the deeper the oxidation zone, the lower the average concentration of DGT-P. The simulation results showed that the phosphorus resupply capacity from surface sediments to porewater was correlated with DGT-P concentration and redox conditions, that is, the oxidative environment was unconducive to the desorption and resupply of sediment phosphorus, whereas the coupling with iron and sulfur geochemistry in the reducing environment was conducive to the maintenance of high labile phosphorus concentration and the continuous release of phosphorus.

Carbon quantification in soils with different textures using laser-induced breakdown spectroscopy: spectral interference correction and use of a 3D plane model

Soil carbon (C) determinations have been widely studied due to soil C sequestration that contributes to the mitigation of greenhouse gas emissions and improves soil quality. However, traditional chemical processes for large-scale analysis generate waste, are time-consuming, and have a high cost per measurement. Laser-induced breakdown spectroscopy (LIBS) is a multi-element spectroanalytical technique that allows fast and low-cost analysis, almost no sample preparation is required, and does not generate hazardous chemical waste. Two emission lines are commonly used for LIBS C determination, 193.03 and 247.85 nm. However, Brazilian soils have a high concentration of aluminum (Al) and iron (Fe), directly interfering in those C emission lines. Furthermore, multiple soil textures increase the difficulty of building calibration models due to matrix effects. In the present work, a mathematical model is proposed to quantify the total C in soil samples having different textures bypassing spectral interferences. A LIBS-specific method for removing outliers has been developed with 6% spectrum removal. From the univariate analysis, it was noticed that some results were projections of a 3D surface in a 2D space, so a 3D plane model was obtained with good fits for the evaluated C emission lines, R² > 0.91, with limits of detection of 0.11% and 0.13% and limits of quantitation of 0.11% and 0.32% for lines 193.03 and 247.85 nm, respectively. Three repetitions were used to test the robustness of the methods and presented an R² of 0.95 and 0.93, a mean error of about 20.38% and 24.12% for lines 193.03 and 247.85 nm, respectively, and a root mean square error of prediction lower than 0.40% for both lines.

Arsenic extraction from seriously contaminated paddy soils with ferrihydrite-loaded sand columns

Reductive dissolution of iron oxides in flooded paddy soils is the most important cause of arsenic (As) release into soil aqueous solution and thus entry into rice. From the perspective of soil cleanup, however, As release under flooded condition could facilitate labile As removal. In this study, a porous column pre-loaded with ferrihydrite (Fh) was constructed, and its efficiency of soil As extraction was investigated using a purpose-designed mesocosm coupled with diffusive gradients in thin films (DGT) for in situ visualization. With Fh-column deployed in aqueous solution, >90% removal of As(III) was achieved within 5 days at initial As (100 mg L^-1) of two orders of magnitude higher than in most paddy soil solutions (1-1538 μg L^-1). By applying Fh-column in a seriously contaminated paddy soil (102 mg As kg^-1), porewater As showed stepwise decreases from 2727 μg L^-1 to 129-1455 μg L^-1 at a distance-dependent manner over four intermittent extractions during 91 days. Soil DGT-As exhibited similar spatiotemporal changes to porewater As. After four extractions, 17.8% of total soil As was removed by Fh-column in a 10 cm radius range on average and ∼1/3 of As bound to amorphous and crystalline Fe/Al oxides was depleted, which accounted for 88.7% of decline in total soil As. With the post-extracted soil, a 48% lower As accumulation in rice seedlings and a 65% decline in bulk soil DGT-As were attained. This study provides a conceptual foundation for rapid removal of high soluble As by Fh-columns from flooded soils, improving seriously As-contaminated paddies to sustainable resources for safe food production.

Increasing phosphorus inhibits the retention and prevention of cadmium by iron plaque and promotes cadmium accumulation in rice plants

Iron (Fe) plaque is an important component of rice roots because it influences the uptake and transport of cadmium (Cd) in rice. In this study, a hydroponic experiment was developed to investigate the influence of phosphorus (P) on the formation of iron plaque on the root surface as well as the influence on Cd uptake in rice plants. Three important results were obtained, as follows. (1) During the formation of iron plaque induced by exogenous Fe, P supply was beneficial for the iron plaque formation, but it restrained the Cd retention capability, resulting in a decrease in Cd in iron plaque by 35.48-61.93%, and leading to an increase in Cd in rice roots from 72.13 mg kg^-1 to 112.78 mg kg^-1 (2) After the iron plaque induction, the formation of iron plaque was inhibited by P supply, resulting in the amount of iron plaque decreasing by 18.46-54.57%, and the Cd in iron plaque decreased by 3.93-31.78%. Then, the Cd retention capability and the prevention effect simultaneously decreased, and as a result, the Cd in rice roots increased from 100.83 mg kg^-1 to 146.03 mg kg^-1 (3) Without exogenous Fe induction, P sufficiency continued to increase the amount of iron plaque and decrease the Cd in iron plaque, and increase the Cd in rice plants. These results suggested that P supply increases the amount of iron plaque, which is ineffective for Cd retention, such as non-reddish-brown iron plaque (NIP), and then decreases the capacity of iron plaque to retain Cd. Additionally, the P supply decreased the amount of formed iron plaque, causing the decreasing prevention effect. Therefore, excessive application of P fertilizer should be avoided in Cd-contaminated paddy fields.

Preparation of Mn/Ti-modified zeolite and its performance for removing iron and manganese

Excessive iron and manganese presented in groundwater sources may cause harm to human health that needs to be solved urgently. This research aims to develop high-performance Mn/Ti-modified zeolites using sol-gel method and hydrothermal synthesis method to remove Fe²⁺ and Mn²⁺ simultaneously. The preparation parameters were optimized by response surface methodology, and the results confirmed that the optimal preparation conditions were as follows: mass ratio of MnO₂-TiO₂/zeolite = 1, hydrothermal temperature = 200°C, and calcination temperature = 500°C. The results of batch adsorption experiments showed that the best removal rate of Fe²⁺ and Mn²⁺ by modified zeolite materials which was prepared under the optimum conditions reached 96.8% and 94.4%, respectively, at which the saturated adsorption capacity was 2.80 mg/g and 1.86 mg/g. Through the adsorption kinetics, thermodynamics, internal diffusion, and isothermal adsorption analyses, it is confirmed that the adsorption process of Fe²⁺ and Mn²⁺ by the modified zeolite is mainly chemical adsorption. The results of the Weber-Morris internal diffusion model prove that internal diffusion is not the only step that controls the adsorption process. In addition, combined with the characterization of the composite-modified zeolite and the adsorption experimental study, it shows that there is an autocatalytic reaction in the adsorption process.

Visualization and quantification of carbon "rusty sink" by rice root iron plaque: Mechanisms, functions, and global implications

Paddies contain 78% higher organic carbon (C) stocks than adjacent upland soils, and iron (Fe) plaque formation on rice roots is one of the mechanisms that traps C. The process sequence, extent and global relevance of this C stabilization mechanism under oxic/anoxic conditions remains unclear. We quantified and localized the contribution of Fe plaque to organic matter stabilization in a microoxic area (rice rhizosphere) and evaluated roles of this C trap for global C sequestration in paddy soils. Visualization and localization of pH by imaging with planar optodes, enzyme activities by zymography, and root exudation by ¹⁴ C imaging, as well as upscale modeling enabled linkage of three groups of rhizosphere processes that are responsible for C stabilization from the micro- (root) to the macro- (ecosystem) levels. The ¹⁴ C activity in soil (reflecting stabilization of rhizodeposits) with Fe²⁺ addition was 1.4-1.5 times higher than that in the control and phosphate addition soils. Perfect co-localization of the hotspots of β-glucosidase activity (by zymography) with root exudation (¹⁴ C) showed that labile C and high enzyme activities were localized within Fe plaques. Fe²⁺ addition to soil and its microbial oxidation to Fe³⁺ by radial oxygen release from rice roots increased Fe plaque (Fe³⁺ ) formation by 1.7-2.5 times. The C amounts trapped by Fe plaque increased by 1.1 times after Fe²⁺ addition. Therefore, Fe plaque formed from amorphous and complex Fe (oxyhydr)oxides on the root surface act as a "rusty sink" for organic matter. Considering the area of coverage of paddy soils globally, upscaling by model revealed the radial oxygen loss from roots and bacterial Fe oxidation may trap up to 130 Mg C in Fe plaques per rice season. This represents an important annual surplus of new and stable C to the existing C pool under long-term rice cropping.

Susceptibility networks reveal independent patterns of brain iron abnormalities in multiple sclerosis

Brain iron homeostasis is necessary for healthy brain function. MRI and histological studies have shown altered brain iron levels in the brains of patients with multiple sclerosis (MS), particularly in the deep gray matter (DGM). Previous studies were able to only partially separate iron-modifying effects because of incomplete knowledge of iron-modifying processes and influencing factors. It is therefore unclear to what extent and at which stages of the disease different processes contribute to brain iron changes. We postulate that spatially covarying magnetic susceptibility networks determined with Independent Component Analysis (ICA) reflect, and allow for the study of, independent processes regulating iron levels. We applied ICA to quantitative susceptibility maps for 170 individuals aged 9-81 years without neurological disease ("Healthy Aging" (HA) cohort), and for a cohort of 120 patients with MS and 120 age- and sex-matched healthy controls (HC; together the "MS/HC" cohort). Two DGM-associated "susceptibility networks" identified in the HA cohort (the Dorsal Striatum and Globus Pallidus Interna Networks) were highly internally reproducible (i.e. "robust") across multiple ICA repetitions on cohort subsets. DGM areas overlapping both robust networks had higher susceptibility levels than DGM areas overlapping only a single robust network, suggesting that these networks were caused by independent processes of increasing iron concentration. Because MS is thought to accelerate brain aging, we hypothesized that associations between age and the two robust DGM-associated networks would be enhanced in patients with MS. However, only one of these networks was altered in patients with MS, and it had a null age association in patients with MS rather than a stronger association. Further analysis of the MS/HC cohort revealed three additional disease-related networks (the Pulvinar, Mesencephalon, and Caudate Networks) that were differentially altered between patients with MS and HCs and between MS subtypes. Exploratory regression analyses of the disease-related networks revealed differential associations with disease duration and T2 lesion volume. Finally, analysis of ROI-based disease effects in the MS/HC cohort revealed an effect of disease status only in the putamen ROI and exploratory regression analysis did not show associations between the caudate and pulvinar ROIs and disease duration or T2 lesion volume, showing the ICA-based approach was more sensitive to disease effects. These results suggest that the ICA network framework increases sensitivity for studying patterns of brain iron change, opening a new avenue for understanding brain iron physiology under normal and disease conditions.

Diazotrophic bacteria improve Hymenaea courbaril seedlings growth and survival in iron mine tailings

One of the largest accidents with mine tailings happened in Brazil in 2015, with the rupture of the Fundão dam, and the physical characteristics of these tailings make it difficult to recover degraded areas. Hymenaea courbaril is a tree species native to Brazil that has low nutritional and water requirements, besides its capacity for survival in contaminated environments. In this study we hypothesized that inoculation with diazotrophs would improve the growth and physiology of H. courbaril in tailings, favoring the reforestation process aiming the recovery of the accident site. Every 20 days for 60 days, we investigated the morphophysiology of H. courbaril grown in iron mine tailings or soil, with the addition of nitrate (N-positive control), non-inoculation (negative control) or inoculation with native diazotrophic bacteria previously isolated from the tailings (UNIFENAS100-569; UNIFENAS100-654 and UNIFENAS100-638). We found that H. courbaril has survival capacity under mine tailings, with no growth alteration in the tailings, although there were signs of reduced ability for photoprotective responses. Inoculation with diazotrophic bacteria improved physiological aspects of H. courbaril and strain UNIFENAS100-638 was the most effective in favoring total growth of plants, net photosynthetic rate and root morphology under mine tailings. The survival capacity and growth of H. courbaril indicates the possibility of its use for reforestation in areas degraded by mine tailings. Further studies are necessary in field conditions and with a larger experimental period to more thoroughly understand H. courbaril tolerance.

Probabilistic health risk assessment of occupational exposure to crystalline silica in an iron foundry in Urmia, Iran

This study aimed to quantify the exposure of foundry workers to crystalline silica and associated cancer and non-cancer health risks using a probabilistic approach. Breathing zone air samples were collected according to the NIOSH 7602 method and analyzed using Fourier transform infrared spectroscopy. The health risks posed by crystalline silica were then assessed using the EPA-developed inhalation risk assessment model and Monte Carlo simulation. The sensitivity analysis was also conducted to determine the contribution of input parameters to the health risks. The mean concentration of crystalline silica in six foundry stations ranged from 0.029 to 0.064 mg m-3, exceeding the occupational exposure limits. The average values of cancer risks were greater than the USEPA level, i.e., 1E - 6 in all workstations of the foundry. Workers in sand preparation and molding stations suffered the greatest cancer risks, with the mean value of 2.35E - 5 and 2.10E - 5, respectively. Non-cancer hazard quotient exceeded 1 in all foundry stations ranging from 1.56 (in melting and pouring) to 3.37 (in sand preparation). The 95% upper-bound values of the health risks decreased by 77.52% and 56.77%, assuming the use of engineering controls and wearing respirators by workers, respectively. Sensitivity analyses indicate that concentration was the most sensitive factor contributing to the carcinogenic (46.13%) and non-carcinogenic (67.08%) risks. These findings can aid managers in gaining a better understanding of the silica risks faced by foundry workers and the role of engineering controls and respirators in protecting workers' health.

Degradation of tetracycline by UV/Fe3+/persulfate process: Kinetics, mechanism, DBPs yield, toxicity evaluation and bacterial community analysis

As a widely produced and used antibiotic, tetracycline (TC) has been frequently found in rivers, soil and drinking water. In this study, the degradation of TC was investigated by UV/Fe³⁺/persulfate (PS) coupled process. The degradation behavior was well fitted with pseudo-first-order model. Hydroxyl radicals (·OH), sulfate radicals (SO₄^-·) and superoxide radical (O₂^-·) were identified as the primary reactive oxygen species (ROS) in UV/Fe³⁺/PS process, the contribution to TC degradation were found to be 41.94%, 33.94% and 17.44% at pH 3.0, respectively. Fe(IV) generated from the system also played a crucial role in TC removal. The effects of process parameters (PS/Fe³⁺ dosages, pH, humic acid, Cl^-, HCO₃^-, NO₃^- and CO₃^2-) on degradation were investigated. It was found that the degradation of TC was highly pH-dependent, and the optimal performance was obtained at pH 3.0. Except for Cl^-, the presence of HA, HCO₃^-, NO₃^- and CO₃^2- inhibited TC degradation. The possible transformation pathway involving the hydroxylation, N-demethylation, hydrogenation and dehydroxylation was proposed. Furthermore, the toxicity and mutagenicity of TC and transformation products (TPs) were estimated using ECOSAR and TEST softwares, demonstrating that the toxicity level of most TPs was lower/equal to their precursors. The evaluation of DBPs showed that UV/Fe³⁺/PS process could reduce the potential of DBPs formation, especially for TCAA and TCM. Microbial community composition was analyzed by 16 S rDNA sequencing, and the relative abundance of ARG-carrying opportunistic pathogens was significantly declined after UV/Fe³⁺/PS treatment. In general, this study provides an economical, efficient and safe strategy for TC removal.

Metals in Wild and Cultured Dicentrarchus labrax (Linnaeus, 1758) from Fish Markets in Sinop: Consumer's Health Risk Assessment

Concentrations of Cd, Hg, Pb, As, Al, Cu, Fe, and Zn were determined in the muscles of wild and farmed European seabass in Sinop markets between September and December in 2020, using inductively coupled plasma mass spectrometry after microwave digestion. In the study, iron (Fe), zinc (Zn), aluminum (Al), and copper (Cu) were found higher than the other metals both in wild and cultured Dicentrarchus labrax. These are essential elements, but excess amounts act as a poison. Arsenic (As) concentration was higher than cadmium (Cd), mercury (Hg), and lead (Pb) both in wild and cultured D. labrax. The estimated maximum total dietary intakes of these eight metals from both wild and farmed European seabass were below the maximum acceptable daily intake values set by the Turkish Food Codex and European Union Regulation. Results showed that according to metal amounts, consumption of D. labrax had no threat to consumers' health. The target hazard quotient (THQ) revealed that harmful health impacts may not occur. Furthermore, risk index (RI) indicated that there may have a lower risk of developing cancer in the future who have been exposed to Pb and As through fish intake. Although the fish are not overly contaminated, the metal level is rising. Increased amounts of heavy metals in fish in different areas could be due to an increase in farm inflow water, domestic sewage, and a number of other anthropogenic sources, all of which should be looked into further. Precautions should be made to safeguard this fish from metal contamination and to reduce the risk to human health.

Iron-doped hydroxyapatite for the simultaneous remediation of lead-, cadmium- and arsenic-co-contaminated soil

Since lead, cadmium and arsenic have completely opposite chemical behaviors, it is very difficult to stabilize all these three heavy metals simultaneously. Herein, a novel iron-doped hydroxyapatite composite (Fe-HAP) was developed via an ultrasonic-assisted microwave hydrothermal method for the simultaneous remediation of lead-, cadmium-, and arsenic-co-contaminated soil in Hunan Province, South China. Using DTPA/sodium bicarbonate extractant to extract bioavailable Pb, Cd and As in soil after Fe-HAP remediation for 60 days, the immobilization efficiencies were 79.77%, 51.3% and 37.5% for Pb, Cd and As, respectively. The soil extractable and exchangeable fractions of Pb, Cd and As decreased significantly. In batch experiments, the adsorption kinetics of Pb, Cd and As on Fe-HAP were well described by pseudo-second-order models, indicating that the adsorption is controlled by chemisorption. In the Langmuir adsorption isotherm, the maximum adsorption capacities of Cd²⁺ and As(V) were 476.2 mg g^-1 and 195.69 mg g^-1, respectively, while Pb²⁺ fit the Freundlich model better. The XRD, SEM and XPS analyses indicated that Fe-HAP formed stable minerals of Pb₅(PO₄)₃OH, Cd₃(PO₄)₂·4H₂O, Cd(OH)₂ and Fe₃(AsO₄)₂·6H₂O with Pb, Cd and As. Overall, its facile and efficient immobilization performance indicate that Fe-HAP has potential for practical applications in integrative remediation of Pb-, Cd-, and As- co-contaminated soil.

Aerosol mass and size-resolved metal content in urban Bangkok, Thailand

Inhalable particulate matter (PM) is a health concern, and people living in large cities such as Bangkok are exposed to high concentrations. This exposure has been linked to respiratory and cardiac diseases and cancers of the lung and brain. Throughout 2018, PM was measured in northern Bangkok near a toll road (13.87°N, 100.58°E) covering all three seasons (cool, hot and rainy). PM₁₀ was measured in 24- and 72-h samples. On selected dates aerodynamic size and mass distribution were measured as 3-day samples from a fixed 5th floor inlet. Particle number concentration was measured from the 5th floor inlet and in roadside survey measurements. There was a large fraction of particle number concentration in the sub-micron range, which showed the greatest variability compared with larger fractions. Metals associated with combustion sources were most found on the smaller size fraction of particles, which may have implications for associated adverse health outcomes because of the likely location of aerosol deposition in the distal airways of the lung. PM₁₀ samples varied between 30 and 100 μg m^-3, with highest concentrations in the cool season. The largest metal fractions present in the PM₁₀ measurements were calcium, iron and magnesium during the hot season with average airborne concentrations of 13.2, 3.6 and 2.0 μg m^-3, respectively. Copper, zinc, arsenic, selenium, molybdenum, cadmium, antimony and lead had large non-crustal sources. Principal component analysis (PCA) identified likely sources of the metals as crustal minerals, tailpipe exhaust and non-combustion traffic. A health risk analysis showed a higher risk of both carcinogenic and non-carcinogenic health effects in the drier seasons than the wet season due to ingestion of nickel, arsenic, cadmium and lead.

The effects of redox conditions on arsenic re-release from excavated marine sedimentary rock with naturally suppressed arsenic release

Massive quantities of marine sedimentary rock are excavated from urban coastal areas. The excavated rock often releases arsenic with concurrent oxidation of framboidal pyrite, but the arsenic release is naturally suppressed with subsequent atmospheric exposure. The present study evaluated the re-release of arsenic from excavated rock in which arsenic release has been naturally suppressed by the atmospheric exposure in the presence of sulfate ions under various redox conditions using the biological reduction method. The atmospheric exposure and subsequent batch leaching test revealed that the amount of arsenic release that was naturally suppressed corresponded to 1.2% of the total arsenic content. The sequential extraction analysis also showed that the arsenic in the exposed rock was altered to insoluble phases. We observed a re-release of 6.0-18.2% of the total arsenic content under reductive conditions (< + 70 mV of Eh), exceeding the amount of arsenic that was naturally suppressed, even in the presence of sulfate ions. The correlation in the amount of arsenic and iron re-released demonstrates that arsenic re-release under reductive conditions is mainly regulated by the iron dissolution up to 10 mg kg^-1 even in the presence of sulfate ion. Further reduction and dissolution of iron did not cause further increase in the arsenic re-release. Therefore, excavated marine sedimentary rock should be reused under redox conditions in which iron is not reduced. Otherwise, treatments such as chemical immobilization should be performed.

Dynamic multivariate analysis for pollution assessment and river habitat conservation in the Vietnamese La Buong watershed

Analysis of temporal patterns of high-dimensional time-series water quality data is essential for pollution management worldwide. This study has applied dynamic factor analysis (DFA) and cluster analysis (CA) to analyze time-series water quality data monitored at the five stations installed along the La Buong river in Southern Vietnam. Application of the DFA identified two types of temporal patterns, one of the run-off driven parameters (total suspended solid (TSS), turbidity, and iron) and the other of diffuse source pollution. The association of the variables like BOD₅ and COD at most stations to the run-off-driven parameters revealed their sharing of drivers. On the contrary, separating variables like phosphate (PO₄³) at the three upstream stations from the run-off patterns suggested their local point-source origin. The DFA-derived factors were later used in the time-point CA to explore the seasonality of water quality parameters and their pollution intensities compared to regulatory levels. The result suggested intensification in wet season of Fe, TSS, BOD₅, and COD concentrations at most sites, which are unobservable in run-off detached parameters like reactive nitrogen, phosphate (PO₄^3-), and E. coli. These findings generated robust insights to support water quality management for river habitat conservation.

Peelu (Salvadora oleoides Decne.): An Unexplored Medicinal Fruit with Minerals, Antioxidants, and Phytochemicals

The Peelu (Salvadora oleoides Decne.) fruit is well known for its nutritional and medicinal values. The current study analyzed the chemical composition of Salvadora oleoides fruit. Fresh Peelu fruits were harvested, and physicochemical properties, proximate composition, macro- and micronutrients, and phytochemical properties were determined. Moreover, ethanol and methanol fruit extract was analyzed for physicochemical properties. The Peelu fruit seemed to be a potential source of essential macro- ((nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg)) and micronutrients (zinc (Zn), manganese (Mn), iron (Fe), and copper (Cu)). The fruit had significant biochemical properties (total soluble solids (TSS), total acidity (TA), and TSS : TA ratio) with appreciable moisture, crude fiber, and ash contents. The fruit extracts demonstrated significantly higher antioxidants and phenolics, ascorbic acid contents, and carotenoids. Phytochemical screening of fruit revealed the presence of coumarins, flavonoids, phlobatannins, tannins, and terpenoids. Physicochemical and sensory evaluation of extracts indicated its potential for further in vivo study trials. The Peelu fruit was found to be a good source of mineral nutrients, proximate contents, vitamins (ascorbic acid and carotenoid), phytochemicals (total phenolic sand antioxidant contents), and pharmaceutically important metabolites that can be used as functional drink.

In Situ Simultaneous Analysis of Nitrogen and Phosphorus Migration in Urban Black Odorous Runoff

The extremely serious urban runoff eutrophication and black odorous phenomenon pose a significant threat to the lake aquatic ecosystem, resulting in a significantly increased frequency, magnitude, and duration of algal blooms in lakes. However, few investigations focus on small tributaries of the lakes, despite the ubiquity and potential local importance of these runoffs. Thus, the labile sediments NH₄⁺-N, NO₃^--N, PO₄^3-, Fe²⁺, and S^2- in black odorous runoff at Wuxi were overall analyzed at high resolution using diffusive gradients in thin films (DGT). The variations in labile N, P, Fe, and S distribution profiles at different sampling sites indicated high heterogeneity in sediments. The concentrations of labile P, Fe, and S showed synchronous variation from the sediment-water interface (SWI) up to -20 mm along sediment profiles. Moreover, there existed a significant positive correlation among labile P, Fe, and S concentrations (p < 0.05), which might represent typical odor compounds' FeS and H₂S synchronous release process in urban runoff. Furthermore, the apparent diffusion fluxes of labile P, Fe, and S across the SWI were all released upward, while fluxes of NH₄⁺-N and NO₃^--N release downward, indicating the sediments act as source and sink of P and N, respectively. Sediments' potential for endogenous P and N fractions release results in the black-odorous water, and sediment finally abouchement the Taihu, which intensifies further lake eutrophication phenomenon.

Rate of Change of Liver Iron Content by MR Imaging Methods: A Comparison Study

Objective: Magnetic resonance imaging (MRI) can accurately quantify liver iron concentration (LIC), eliminating the need for an invasive liver biopsy. Currently, the most widely used relaxometry methods for iron quantification are R2 and R2*, which are based on T2 and T2* acquisition sequences, respectively. We compared the rate of change of LIC as measured by the R2-based, FDA-approved commercially available third-party software with the rate of change of LIC measured by in-house analysis using R2*-relaxometry-based MR imaging in patients undergoing follow-up MRI scans for liver iron estimation. Methods: We retrospectively included patients who had undergone serial MRIs for liver iron estimation. The MR studies were performed on a 1.5T scanner; standard multi-slice, multi-echo T2- and T2*-based sequences were acquired, and LIC was estimated. The comparison between the rate of change of LIC by R2 and R2* values was performed via correlation coefficients and Bland−Altman difference plots. Results: One hundred and eighty-nine MR abdomen studies for liver iron evaluation from 81 patients (male: 38; female: 43) were included in the study. Fifty-nine patients had two serial scans, eighteen patients had three serial scans, three patients had four serial scans, and one patient had five serial scans. The average time interval between the first and last scans for each patient was 13.3 months. The average rates of change of LIC via R2 and R2* methods were −0.0043 ± 0.0214 and −0.0047 ± 0.012 mg/g per month, respectively. There was no significant difference in the rate of change of LIC observed between the two methods. Linearity between the rate of change of LIC measured by R2 (LIC R2) and R2* (LIC R2*) was strong, showing a correlation coefficient of r = 0.72, p < 0.01. A Bland−Altman plot between the rate of change of the two methods showed that the majority of the plotted variables were between two standard deviations. Conclusion: There was no significant difference in the rate of change of LIC detected between the R2 method and the R2* method that uses a gradient echo (GRE) sequence acquired with breath-hold. Since R2* is relatively faster and less prone to motion artifacts, R2*-derived LIC is recommended for iron homeostasis follow-up in patients with liver iron overload.

[Characteristics and Causes of High-manganese Groundwater in Pearl River Delta During Urbanization]

The high concentration of iron and manganese in groundwater is harmful to human health, and the sources of manganese in rapidly urbanization areas are complex. Based on more than 2500 sets of hydrochemical data in different historical periods, the spatial distribution characteristics, sources, and genesis of groundwater manganese in different aquifers and areas with different urbanization levels in the Pearl River Delta were studied by using mathematical statistics and principal component analysis. The results showed that the concentration of manganese in groundwater in the pore aquifer was obviously higher than that in the fissure and karst aquifer. The proportion of high-manganese groundwater in the pore aquifer was twice that in the fissure and karst aquifer. The proportion of high-manganese groundwater in urbanized and suburban areas was significantly higher than that in non-urbanized areas. On a regional scale, the decomposition of organic matter and the reductive dissolution of Fe-Mn (oxygen) hydroxide in sedimentary strata under reductive conditions may have been the main factors controlling the increase in manganese concentration in pore aquifers. High-manganese groundwater in fissured aquifers may have been affected by low-oxygen domestic sewage leakage accompanying urbanization and industrial wastewater leakage and infiltration accompanying industrialization. The pore high-manganese groundwater was controlled by reduction conditions, and the weakly acidic environment of fissure and karst high-manganese groundwater was the important influencing factor. In the past 10 years, the groundwater environment in the study area has been improving, and the increase in groundwater redox potential and pH was not conducive to the formation of high-manganese groundwater, which was also the main cause of the overall decrease in Mn²⁺ concentration in groundwater of different types of aquifers in the process of urbanization.

On the Geochemistry of the Danube River Sediments (Serbian Sector)

To determine the nature and origin of the unconsolidated bottom sediments, as well as to demonstrate and quantify the presence of Presumably Contaminating Elements (PCE) in the Serbian Danube River, as a novelty, the mass fractions on nine major elements as oxides-SiO₂, TiO₂, Al₂O₃, FeO, MnO, MgO, CaO, Na₂O, and K₂O, as well as Sc, V, Cr, Co, Ni, Cu, Zn, As, Rb, Sr, Zr, Sb, Cs, Ba, La, Hf, Ta, W, Th, and U were determined by Instrumental Neutron Activation Analysis (INAA) in 13 sediment samples collected between Belgrade and Iron Gate 2 dam. INAA was chosen for its ability to perform elemental analysis without any preliminary sample treatment that could introduce systematic errors. The distribution of major elements was relatively uniform, with the sampling locations having less influence. Concerning the trace elements, excepting the PCE Cr, Ni, Cu, Zn, As, and Sb, their distributions presented the same remarkable similarity to the Upper Continental Crust (UCC), North American Shale Composite (NASC), Average Bottom Load (ABL), and Average Dobrogea Loess (AVL), and were in good concordance with the location of the Serbian Danube River in the Pannonian Plain. In the case of considered PCE, both Enrichment Factor and Pollution Load Index showed values higher than the pollution threshold, which pointed towards a significant anthropogenic contamination, and rising concern to what extent the water quality and biota could be affected.

Insights into site-specific influences of emission sources on accumulation of heavy metal(loid)s in soils by wheat grains

Excessive accumulation of heavy metal(loid)s in agricultural environment usually originates from anthropogenic activities. Both large diversities of emission sources and complexity of plant accumulation challenge the understanding of the site-specific effects of emission sources on heavy metal(loid)s in wheat grains. Herein, both soil samples and wheat grain samples (n = 80) were collected from the farmland of Jiyuan City, China. Soil and grain burdens of heavy metal(loid)s were determined by inductively coupled plasma mass spectrometry (ICP-MS) and/or X-ray fluorescence spectrometry (XRF). The quotients (Q) were developed to indicate relative impacts of industrial plants and traffic to soil sites. Principal component analysis-absolute principal component scores-multivariate linear regression (PCA-APCS-MLR) analysis was conducted to reveal the source contributions to heavy metal(loid)s in grains, considering Q values, soil, and wheat grain data. Results showed that contributions of main sources and factors drastically varied with soil sites, and usually overlapped to different extents. For grain Cd and grain Pb, natural soil silicate (0.066/0.104 mg/kg) and iron-bearing minerals (- 0.044/ - 0.174 mg/kg) contributed to high extents, while metal smelting activities (0.018/0.019 mg/kg) and agronomic activities (- 0.017/ - 0.019 mg/kg) unexpectedly posed low or moderate contributions. The pH-mediated availability of soil Cd (0.035 mg/kg) and the sand-dust weather (0.028 mg/kg) also made considerable contributions to grain Cd. For grain As, both natural soil iron-bearing (- 0.048 mg/kg) and silicate minerals (- 0.013 mg/kg) made negative contributions. The results benefit to the decision-making of pollution remediation of farmland soils in the regional scales.

Determining groundwater quality using indices and multivariate statistical techniques: a study of Tosham block, Haryana, India

Water is the most important component for human survival and often the most misused one. The present study deals with the assessment of groundwater quality of Tosham block, Bhiwani District, Haryana, India, and its nearby villages. A total of 23 samples were collected from different groundwater sources and were analysed for 16 different physico-chemical parameters. Correlation coefficients were calculated to identify highly correlated and interrelated water quality parameters. It provides an excellent tool for the prediction of parameter values within the reasonable rank of exactness. A strong correlation was observed between total hardness, magnesium and total dissolved solids, especially between total dissolved solids and electrical conductivity. The obtained results were compared with Indian Standard Drinking water specifications IS: 10500-2012. Concentration of total hardness, iron and chloride was found above the permissible limit in all the samples. Multivariate statistical techniques, namely cluster analysis and principal component analysis, were used to find the relationship between studied parameters. Water quality index (WQI) was also calculated. The WQI of groundwater samples ranged from 125 to 556. The water quality index revealed that out of 23 samples, 13 were found to have poor water quality and 6 samples were of very poor water quality. High value of WQI was found mainly from total dissolved solids, electrical conductivity, total hardness, Mg, Cl and Fe. Groundwater analysis of the studied water samples indicated that there is a need to treat the water before its use for drinking and other domestic activities. Necessary precautions should be taken to prevent the groundwater from being contaminated.

Determination of trace element and fatty acid levels in tissues of mirror and scaly carp (Cyprinus carpio L., 1758) living in Keban Dam Reservoir (Elazig)

This study investigated the concentrations of some accumulated trace metals (iron, manganese, zinc and copper) and fatty acids in liver and muscle tissues of mirror and scaly carp varieties (Cyprinus carpio L., 1758) living in Keban Dam Reservoir (Elazig), which is the second-largest artificial lake in Turkey that hosts commercially valuable and preferred fish varieties for human consumption. The inductively coupled plasma mass spectrometry (ICP-MS) method was used to analyse the concentrations of trace elements. Fatty acid levels were measured in a gas chromatography mass spectrometry (GC-MS) device, using a flame ionization detector (FID). Considering the two fish varieties and tissues that were studied, the mean metal concentrations (μg g^-1 ) were found in the following ranges: Fe 12.32-49.97, Mn 0.12-0.62, Zn 10.45-86.59 and Cu 2.74-11.86. Although the lowest levels were detected in the muscle tissue for all the metals examined, the levels in the liver tissue were significantly higher. According to the results of the analyses on fatty acid concentrations, the mean total saturated fatty acid levels in the muscle tissue of the scaly carp and mirror carp varieties were found to be 31.07 and 31.43 (%), respectively, whereas these values for the liver tissue were consecutively 22.36 and 22.08 (%). Successively, the mean total levels of unsaturated fatty acids were determined as 68.93 and 68.40 (%) in the muscle tissue and 77.64 and 77.92 in the liver tissue. This study, with the finding that the trace (metallic) element accumulation rates were below the upper limits of the tolerable range, and the examined fish varieties were rich in fatty acids, shows that mirror carp and scaly carp living in Keban Dam Reservoir are highly nutritious for human diets.

Influence of magnetite incorporation into chitosan on the adsorption of the methotrexate and in vitro cytotoxicity

Emerging pollutants are a group of substances involved in environmental contamination resulting mostly from incomplete drug metabolism, associated with inadequate disposal and ineffective effluent treatment techniques. Methotrexate (MTX), for instance, is excreted at high concentrations in unchanged form through the urine. Although the MTX is still effective in cancer and autoimmune disease treatment, this drug shows the ability of bioaccumulation and toxicity to the organism. Thus, the present work aimed to evaluate the adsorption of the MTX drug onto magnetic nanocomposites containing different amounts of incorporated magnetite (1:1, 1:5, and 1:10 wt%), combining the theoretical-experimental study as well as the in vitro cytotoxicity. Moreover, equilibrium studies (Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Hill, Redlich-Peterson, and Sips), kinetic (PFO, PSO, and IPD), and thermodynamic (ΔG°, ΔH°, and ΔS°) were used to describe the experimental data, and ab initio simulations were employed in the theoretical study. Magnetic nanocomposites were synthesized by the co-precipitation method using only FeCl₂ as the iron precursor. Adsorbents were characterized by FTIR, XRD, Raman, SEM-EDS, BET, and VSM analysis. Meanwhile, cytotoxic effects on L929 and A375 cell lines were evaluated through MTT, NR, and LDH assays. The adsorption of the MTX was carried out in a typical batch system, exploring the different experimental conditions. The theoretical study suggests the occurrence of chemisorption between CS·Fe₃O₄-MTX. The maximum adsorption capacity of MTX was 285.92 mg g^-1, using 0.125 g L^-1 of CS·Fe₃O₄ 1:1, with an initial concentration of the MTX (50 mg L^-1), pH 4.0 at 293 ± 1.00 K. The best adjustment of equilibrium and kinetic data were the Sips (low values for statistical errors) and PSO (q_e = 96.73 mg g^-1) models, respectively. Thermodynamic study shows that the adsorption occurred spontaneously (ΔG° < 0), with exothermic (ΔH° =  - 4698.89 kJ mol^-1) and random at the solid-solution interface (ΔS° = 1,476,022.00 kJ mol^-1 k^-1) behavior. Finally, the in vitro study shows that magnetic nanomaterials exhibit higher cytotoxicity in melanoma cells. Therefore, the magnetic nanocomposite reveals to be not only an excellent tool for water remediation studies but also a promising platform for drug delivery.

Spatial and seasonal variation and sources of deposition fluxes of polycyclic aromatic hydrocarbons (PAHs) in Shanghai

Spatial and temporal variations of polycyclic aromatic hydrocarbons (PAHs) deposition fluxes and sources may significantly facilitate risk evaluation and pollution control of super megacity in China. A study on PAHs of wet and dry deposition in Shanghai was conducted from January to December of 2019. Seventeen sampling sites located in four functional areas were set, including the Baoshan iron and steel industry area (BS), Jinshan petrochemical industry area (JS), city center (CC), and Chongming agricultural area (CM). A total of 15 PAHs were determined by gas chromatography-mass spectrometry (GC-MS, Agilent 7890A/5975C). PAHs atmospheric deposition flux in winter was highest (3.12 ± 1.98 μg/(m²·day), mostly attributed to local emissions accumulation under adverse meteorological diffusion conditions, as well as pollutants transport from northern China during heating season. PAHs deposition fluxes in industrial area (BS and JS) were 3.75 ± 4.08 μg/(m²·day) and 3.18 ± 3.62 μg/(m²·day) respectively, which were greater than those in CC and CM, accounting for 1.91 ± 1.06 μg/(m²·day) and 1.41 ± 0.61 μg/(m²·day) respectively. Proportional composition and isomer ratios of PAHs indicated that the PAHs deposition in winter and spring samples were more homogeneous, whereas those of summer and autumn seemed to be more variable and dispersed. Positive matrix factorization model were employed to identify the potential sources of PAHs in specific functional areas. A dominance of contribution was attributed to coal combustion (46%) at BS, petroleum volatilization (48%) at JS, biomass burning (55%) at CM, and vehicle emission (49%) at CC. This study highlighted that local urbanization and industrialization have a significant contribution to PAHs deposition to specific functional regions in Shanghai.

Abnormal Level of Manganese, Iron, Iodine, and Selenium in the Hair of Children Living in Kashin-Beck Disease Endemic Areas

Biological geochemistry is a main suggested cause of Kashin-Beck disease (KBD), due to the absence or excess of elements in the environment. Initially, Se deficiency is regarded as the most key role in the etiology of KBD, and selenium supplementation effectively helps to prevent and control KBD. However, several elements are reported to be relevant to KBD or selenium in succession, which indicated selenium deficiency is not the original etiology of KBD. The study comprehensively analyzed the characteristics of the bio-element profile of KBD and further re-examined the unique role of selenium in etiology. The study measured 14 elements, including sodium, potassium, calcium, phosphorus, magnesium, copper, iron, zinc, selenium, iodine, manganese, lead, arsenic, and mercury, which were detected from hair samples collected from 150 boys. Research participants were separated based on whether they had received any preventative treatment (with and without selenium supplementation). From endemic areas, 30 KBD and 30 healthy children without any preventative treatment were selected alongside 30 KBD and 30 healthy children with selenium supplementation. The participants from endemic areas were then compared to 30 healthy children living in non-endemic areas. Compared to the non-endemic group, the levels of iron and manganese were all significantly higher in the endemic groups and were further elevated in KBD participants (p < 0.05). In contrast, selenium and iodine levels in endemic areas were much lower than those of the control group (p < 0.05). The proportions of selenium excess (p < 0.05) and iodine deficiency (p < 0.05) in endemic groups were significantly lower than participants from non-endemic areas. Meanwhile, excess levels of iron (p < 0.05) and manganese (p < 0.05) were higher in the endemic groups. Moreover, the proportions of Zn/Fe and Se/Mn were found to be significantly lower in endemic area participants than those in the control group (p < 0.05). Three pairs of elements had a correlation coefficient value of more than 0.6: 0.7423 for manganese and calcium, 0.6446 for potassium and sodium, and 0.6272 for manganese and iron. The ratios of Se/Mn and Zn/Fe were associated with a correlation coefficient value of 0.8055. Magnesium, sodium, copper, and iodine levels were meticulously examined using binary regression analysis. This was also used to determine the ratios of Ca/Mg, Ca/P, Zn/Fe, Se/Mn, and Se/I. Thus, the study largely revealed the vital role of manganese, iron, and iodine (in conjunction with selenium) in KBD etiology and pathogenesis. High manganese and iron levels with low selenium and iodine levels were identified as characteristic features of the bio-element profile of KBD. The different element ratios reflect the interaction between several elements. The most significant of these were the proportions of Se/Mn and Zn/Fe, which may be significant in the occurrence and development of KBD.

Biogeochemical properties and potential risk of shallow arsenic-rich sediment layers to groundwater quality in Western Bangladesh

The arsenic-contaminated groundwater has attracted attention in much south and southeast Asian deltas, however, mainly on the deep aquifers. Here, arsenic (As) concentration and its fractionation of the sediment cores in a shallow aquifer in Bangladesh were investigated using ICP-MS, FE-EPMA, XRD and ¹⁴C-AMS chronology techniques. The results of the present study indicated that the peak concentrations of As (54.7-79.1 µg/g) were in peat layers (at a depth of 7.5-8.0 m). Several types of iron (oxyhidr)oxides and framboidal pyrite, which contain As also, were found in the peat samples. The high concentrations of As were in an exchangeable form, As-bearing iron crystalline and As-bearing organic materials. We revealed that the As-rich peat layers were formed from 3170 to 3901 cal yrs before, due to the sea level decrease in this area. The 16S rRNA gene-based phylogenetic analysis revealed that the bacterial strains in the As-rich peats were mainly affiliated with genera Acinetobacter, Enterobacter, Escherichia, Bacillus, Clostridiaceae and Acinetobacter. The geo-accumulation index (I_geo) and ecological risk index assessment were calculated for the sediments, which shows that As-rich sediment layers were in range of moderately to heavily contaminated and considerable classes, respectively. Under the permanent saturated condition, the As-rich peat layers should be considered as an important potential driver of the groundwater As in this area.

Microbial diversity response to geochemical gradient characteristics on AMD from abandoned Dashu pyrite mine in Southwest China

The formation and release of acid mine drainage (AMD) have caused extremely serious pollution in the environment around many mining areas. The biological oxidation of metal sulfide minerals causes the production and release of AMD. To understand the interaction mechanism between microbial and AMD, the study uses Southwest Dashu pyrite as an example to investigate the geochemical gradient characteristics and microbial diversity response on AMD from abandoned mine. Through collecting and testing the water samples, the geochemical parameters such as physical and chemical indexes, main ion composition and microbial community composition of seven mine drainage points were obtained. The results showed that the geochemical and microbial community structure the decrease of AMD pollution in the study area with the decrease of altitude has obvious gradient characteristics. Although AMD has the distribution of acid-resistant iron and sulfur bacteria oxidizing bacteria, the microbial community diversity has obvious gradient characteristics. The categories with a relative abundance of > 5% include Proteobacteria, Actinobacteriota, Firmicutes, WPS-2, Chloroflexi, Bacteroidota, and Acidobacteriota. Actinobacteriota, which was common in the AMD, was distributed throughout the samples. The correlation analysis between water quality parameters and microbial community showed that the microbial community structure was affected by environmental factors. With the increase of acidity and metal ion content, the diversity of microbial community decreased, and the content of acid-resistant iron and sulfur oxidizing bacteria increased. The results showed that pH, dissolved oxygen (Do), the total iron (Fe) content (TFe), SO₄^2-, and Al³⁺ were the five parameters that most affected microbiological diversity and interaction. Hydrogeochemistry and major ions analysis revealed that AMD in the study area mainly comes from the biological oxidation of metal sulfides and the dissolution and cation exchange of other minerals around the deposit. The degree of AMD pollution is related to the hydrogeochemical conditions in the mine. The higher the mine's water level, the lower the pollutants, and the less AMD is produced and released. The findings confirmed that geochemical gradients significantly changed the biota of the mine water and enriched the related microbial diversity adapted to different environmental factors. Therefore, the findings provide strong support for mine containment to inhibit oxidation and lay the foundation for prevention and control strategies of AMD pollution sources.

Evaluating configuration of dual unit ceramic filter for arsenic removal from highly contaminated groundwater

Iron (Fe) amended dual unit ceramic filters (DUCF) can be a viable treatment option for arsenic (As) removal from highly contaminated groundwater. The present field study investigated the effect of filter configurations, the separate-unit dual filter (SUDF) and connect-unit dual filter (CUDF), on As removal from groundwater having As concentration of 475 μg/L. SUDF was configured by placing 1st and 2nd filter units side-by-side, whereas the 1st filter unit was placed on the top of the 2nd filter unit in CUDF configuration. Comparing the two filter configurations, SUDF achieving As concentration in the effluent below 50 μg/L (standard value) was found more effective due to sufficient Fe²⁺ in the 2nd filter. Average As concentrations in the final product (effluent of 2nd filter) were 43 μg/L from SUDF and 111 μg/L from CUDF. The short hydraulic residence time (3.3 min) in the 2nd filter of CUDF, along with limited contact between water and the iron net, lead to inadequate soluble Fe²⁺ resulting in poor As removal. Both filter configurations effectively removed Fe, P, and Mn with more than 90% reduction of these parameters by the 1st filter. Analysis of insoluble hydrous ferric oxides flocs through XAFS L3-edge spectra confirmed the oxidation of As(III) to As(V) in both the SUDF and CUDF systems resulting in enhanced As removal efficiency. The study results found SUDF as an appropriate configuration for filter design to treat highly contaminated groundwater in rural areas of developing countries.