Fe(III) oxyhydroxides play critical roles in arsenic immobilization due to their strong surface affinity for arsenic. However, the role of bacteria in Fe(II) oxidation and the subsequent ...immobilization of arsenic has not been thoroughly investigated to date, especially under the micro-oxic conditions present in soils and sediments where these microorganisms thrive. In the present study, we used gel-stabilized gradient systems to investigate arsenic immobilization during microaerophilic microbial Fe(II) oxidation and Fe(III) oxyhydroxide formation. The removal and immobilization of dissolved As(III) and As(V) proceeded via the formation of biogenic Fe(III) oxyhydroxides through microbial Fe(II) oxidation. After 30 days of incubation, the concentration of dissolved arsenic decreased from 600 to 4.8 μg L−1. When an Fe(III) oxyhydroxide formed in the presence of As(III), most of the arsenic ultimately was found as As(V), indicating that As(III) oxidation accompanied arsenic immobilization. The structure of the microbial community in As(III) incubations was highly differentiated with respect to the As(V)-bearing ending incubations. The As(III)-containing incubations contained the arsenite oxidase gene, suggesting the potential for microbially mediated As(III) oxidation. The findings of the present study suggest that As(III) immobilization can occur in micro-oxic environments after microbial Fe(II) oxidation and biogenic Fe(III) oxyhydroxide formation via the direct microbial oxidation of As(III) to As(V). This study demonstrates that microbial Fe(II) and As(III) oxidation are important geochemical processes for arsenic immobilization in micro-oxic soils and sediments.
The heavy metal pollution, mainly caused by mining-related activities over extended period of time, is imposing a severe threat to environments and human health. Environmental systems, including ...rivers and paddy soils, have been widely established as one of the key sinks of potentially harmful metals. Aiming to understand contamination sources and pathways of Zn in karst area, we studied the Zn concentration and isotope composition of river waters, sediments, mine tailings, paddy soils, dust and three soil profiles with different levels of Zn-pollution around a Zn-mine, southwestern China. The distinct Zn isotope compositions among tailing (−0.42 ± 0.02‰), dust (−0.24 ± 0.02‰), and geogenic soil (−0.16 ± 0.03‰) allowed for separation of anthropogenic-Zn from native Zn. In the plot of δ66Zn value and 1/Zn, all samples can be explained by the mixing of three components: mining-input, agricultural input, and background. Evolution of these three components helps produce direct sources: dust and geogenic soil. Under this framework, the Zn pollution in paddy soil and sediment can be explained by mixing of mine-tailing, dust, and geogenic soil. Our study shows that the contamination of mine drainage is limited in the area due to the relatively high pH buffered by carbonate in karst area. While the dust contributes most of the anthropogenic Zn with an average value of 19.5%. The dominant pathway of anthropogenic Zn from dust to paddy soil or sediment is through the long-term wind dispersion of fine-grained material from the tailing and the physical transmission. Under the special hydrogeological conditions of karst, mining activities will increase the migration of heavy metals. The Fe-Al oxides control the migration of Zn in soil profile, but probably do not lead to significantly Zn isotopes fractionation. This further enhances the reliability of Zn isotopes as a “fingerprint” in karst area.
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•Tailings, rivers, sediments, dusts and soils were analyzed for Zn isotope ratios.•Anthropogenic Zn in karst area was mainly from dust through physical transmission.•Zn in paddy soil was imported by long-term wind dispersion of fine-grained material.•Pollution sources and pathways of heavy metals can be traced using Zn isotopes in karst area.
Paddy soils around mining areas suffer from the great threat of heavy metal pollution. The traditional source-tracing methods based on metal concentrations limit our ability to quantify the sources ...of heavy metals and trace their transport processes to paddy soils. In this study, Zn isotope compositions of paddy soils in Dabaoshan mine area, a typical sulfide deposit in southern China, have been systematically studied. According to a plot between 1/Zn (i.e. inverse concentration) and δ66Zn value, all the polluted paddy soils fall on the mixing line between acid mine drainage precipitate (AMD-precipitate) and fertilizer while the unpolluted paddy soil falls on the mixing line between fertilizer and bedrock. This indicates the mixing of Zn sources at least three end-members: the mining end-member (i.e. AMD-precipitate), the agricultural end-member (i.e. fertilizer), and bedrock whose geochemical signature is often overprinted by the former two sources around the mining area. The quantitative calculations to apportion the end-member’s contributions show that the mining activity contributes most Zn in the paddy soils with an average of ∼66.2%. The contribution of mining activities has significant spatial variations. Specifically, the mining activities have relatively low impacts on the lower reach and the deep soil. Additionally, the apparent Zn isotope fractionation between AMD and AMD-precipitate (Δ66ZnAMD-precipitate − AMD of −0.35 to −0.08‰) in the tailings dam suggests that Zn cations in AMD coprecipitated with the secondary Fe-bearing minerals (e.g. jarosite and goethite). After being discharged from the tailings dam, Zn is mainly carried by the Fe-oxide minerals and migrated during surface runoff. Our study highlights the contribution of human activities to the Zn pollution in the paddy soils and the key role of Fe-bearing minerals in the migration of Zn. These findings provide a scientific base for the development of policy for pollution control in mining-affected region.
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•Zn isotope compositions in paddy soils and other environmental media were examined.•Mining activities contributed 66.2% of Zn to paddy soils.•Zn was mainly carried by the Fe-bearing minerals during migration in mining area.•Zn isotope is a powerful source tracer in a complex mining-affected area.
Mining activities are the main Zn source in the paddy soils around mining area and Zn was mainly carried by the Fe-bearing minerals during migration.
Recrystallization of iron (hydr)oxides by ferrous iron Fe(II) is an important part of the biogeochemical cycling of iron in earth surface environments. Ferromanganese nodules are complex assemblages ...of natural Fe and Mn minerals, which are widely found in soils and marine environments, and critically impact the geochemical behavior of trace metals and nutrients. However, little is known regarding the Fe(II)-induced recrystallization of ferromanganese nodules, in comparison to pure iron (hydr)oxides. Accordingly, the objective of this study was to elucidate the reaction processes of aqueous Fe(II) with ferromanganese nodules, and to use complementary spectroscopic techniques to characterize the products. Goethite in the nodule that underwent phase transformation to magnetite or Fe(II) oxidation to form magnetite has not been reported in previous studies with respect to pure goethite. 57Fe-enriched isotope tracer experiments confirmed Fe atom exchange between aqueous Fe(II) and structural Fe(III) of the nodule and was enhanced at higher pH conditions. The coexistence of Mn oxides and other minerals possibly make the goethite in the nodule more reactive for phase transformation to magnetite than pure synthetic goethite. In addition, Fe(III) precipitates were formed due to Fe(II) oxidation by Mn(III) of the nodule, and magnetite was likely consequently produced through further Fe(II)-induced reaction. Considering the enrichment of trace metals and nutrients in ferromanganese nodules, the observed Fe(II)-induced recrystallization of nodules in the study is expected to exert important effects on the geochemical behavior of the elements, especially in nodule-enriched soils.
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•Fe atom exchange between aqueous Fe(II) and ferromanganese soil nodules occurred and the rate increased at higher pH.•The goethite component in the nodule was transformed to magnetite induced by aqueous Fe(II).•Mn(III)/Mn(IV) oxides in the ferromanganese soil nodules oxidized Fe(II) to form Fe(III) precipitates.•Fe(III) precipitates formed from Fe(II) oxidation can be also transformed to magnetite induced by aqueous Fe(II).
•Combined Cd and Pb isotope analysis was used to trace the fate of Cd.•The variation of pH influences Cd isotope ratios in sediments.•Distinct Cd migration processes were found in siliceous and ...calcareous watersheds.
Cd-rich wastes from open-pit mining can be transported into rivers, which are often followed by deposition in river sediments and/or further transfer into agricultural soils. The lithology of bedrock exerts a huge effect on physicochemical properties (e.g., buffering capacities, metal species, mineral phases, etc.) of the river system, thereby potentially impacting the Cd mobility in watersheds. However, to date, little is known about the microscopic processes (e.g., dissolution, adsorption, and precipitation) controlling the migration of Cd from mines to varied watersheds. This study, therefore, aims to determine the controlling factors on Cd mobilization in two mining-impacted watersheds with contrasting bedrock lithology using both Cd and Pb isotopes. The Pb isotope ratios of sediments and soils in both watersheds fall into a binary mixing model with two isotopically distinct sources, i.e., mining wastes and bedrock. These results indicate that mining activities are the main sources of Cd in sediments and soils. However, the Cd isotope ratios reveal different Cd migration processes between the two watersheds. In the siliceous watershed, the δ114/110Cd values of sediments decrease from -0.116‰ in the upper reach to -0.712‰ in the lower reach, with a concomitant increase in Cd concentration, which may result from Cd adsorption by goethite due to the increased pH. In contrast, in the calcareous watershed, the Cd isotope compositions of sediments (-0.345 to -0.276‰) and the pH of river water are nearly invariable, suggesting that the adsorption and release of Cd in sediments are limited. This may result from the strong pH buffering effect due to the presence of carbonate rocks. This study highlights the different fates of Cd in siliceous and calcareous watersheds and suggests that the development of Cd pollution control policies must consider regional lithology.
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•57Fe Mössbauer is analyzed to study Fe isotope fractionation in tropical laterite.•Atomic distribution of Fe in Fe phases controls isotope fractionation in laterite.•The apparent fractionation ...factor between hematite and goethite is 0.99 ± 0.18‰.
Laterites are important iron (Fe) reservoirs impacting the biogeochemical cycle of Fe at Earth’s surface, and Fe oxides are critical Fe-host minerals in laterites that affect the geochemical behavior of Fe. Whether and how the differentiation of Fe minerals controls Fe isotope fractionation during laterization, however, remains unclear. In this study, the mineralogy, element concentrations, and Fe isotope compositions are reported for a basalt-derived lateritic profile on Hainan Island, China, to investigate the role of Fe solid-phase differentiation in controlling Fe isotope fractionation during lateritic weathering. 57Fe Mössbauer spectroscopy at 13 K is conducted to quantitatively identify the solid-phase Fe, including FeIII-(oxy)hydroxides, FeIII-oxides, and organic/silicate-bound FeIII. The results from soil samples in the lower section show that RMZr,Fe values are positive and that δ56Fe values (−0.01‰ to 0.07‰; 0.05 ± 0.05‰ on average) are identical to those in parent basalt (0.03 ± 0.04‰). The limited variation in δ56Fe values is likely caused by the compaction effect and/or the downward transport of Fe from the upper soils. In contrast, RMZr,Fe values in soils from the upper section are generally negative, and their δ56Fe values (0.01‰ to 0.29‰) display zigzag variations and are linearly correlated with the amount of Fe present in hematite and goethite. The variation in δ56Fe value is likely caused by the atomic distribution of Fe in hematite and goethite, with heavy Fe preferentially incorporated into hematite rather than goethite. Based on the linear regression analysis, we calculated the apparent Fe isotope fractionation factor between hematite and goethite as 0.99 ± 0.18‰ (SD). A comparison of published Fe isotope data shows that the variation in δ56Fe value of silicate-derived soils and rivers may have a potential link with climatic factor (mostly temperature). Our study highlights the importance of Fe-mineral differentiation in controlling Fe isotope fractionation in laterite systems.
Fe(II)-oxidizing bacteria (FeOB) are important catalysts for iron cycling in iron-rich marine, groundwater, and freshwater environments. However, few studies have reported the distribution and ...diversity of these bacteria in flooded paddy soils. This study investigates the microbial structure and diversity of microaerophilic Fe(II)-oxidizing bacteria (mFeOB) and their possible role in Fe(II) oxidation in iron-rich paddy soils. Using enrichment experiments that employed serial transfers, the changes in microaerophilic microbial community were examined via 16S rRNA gene high-throughput sequencing. During enrichments, the Fe(II) oxidation rate decreased as transfers increased, and the maximum rate of Fe(II) oxidation was observed in the first transfer (0.197 mM day
−1
). Results from X-ray diffraction of minerals and scanning electron microscopy of the cell-mineral aggregates revealed that cell surfaces in all transfers were partly covered with amorphous iron oxide formed by FeOB. After four transfers, the phyla of
Proteobacteria
had a dominant presence that reached up to 95%. Compared with the original soil, the relative abundances of
Cupriavidus
,
Massilia
,
Pseudomonas
,
Ralstonia
,
Sphingomonas
, and
Variovorax
increased in FeS gradient tubes and became dominant genera after transfers.
Cupriavidus
,
Pseudomonas
, and
Ralstonia
have been identified as FeOB previously. Furthermore, the structure of the microbial community tended to be stable as transfers increased, indicating that other bacterial species might perform important roles in Fe(II) oxidation. These results suggest the potential involvement of mFeOB and these other microorganisms in the Fe(II)-oxidizing process of soils. It will be helpful for future studies to consider their role in related biogeochemical processes, such as transformation of organic matters and heavy metals.
Huangqi Guizhi Wuwu Decoction (HGWD), as a classic Chinese herbal decoction, has been widely used in treating various diseases for hundreds of years. However, systematically elucidating its ...mechanisms of action remains a great challenge to the field. In this study, taking advantage of the network pharmacology approach, we discovered a potential new use of HGWD for patients with colon cancer (CC). Our
in vivo
result showed that orally administered HGWD markedly inhibited the growth of CC xenografts in mice. The subsequent enrichment analyses for the core therapeutic targets revealed that HGWD could affect multiple biological processes involving CC growth, such as metabolic reprogramming, apoptosis and immune regulation, through inhibiting multiple cell survival-related signalings, including MAPK and PI3K-AKT pathways. Notably, these
in silico
analysis results were most experimentally verified by a series of
in vitro
assays. Furthermore, our results based on serum metabolomics showed that the lipid metabolic pathways, including fatty acid biosynthesis and cholesterol metabolism, play key roles in delivery of the anti-CC effect of HGWD on tumor-bearing mice, and that cytochrome P450 family 2 subfamily E member 1 (CYP2E1) is a potential therapeutic target. Together, our integrated approach reveals a therapeutic effect of HGWD on CC, providing a valuable insight into developing strategies to predict and interpret the mechanisms of action for Chinese herbal decoctions.
We previously established a hepatocellular carcinoma (HCC) targeting system of conditionally replicative adenovirus (CRAd) delivered by human umbilical cord-derived mesenchymal stem cells (HUMSCs). ...However, this system needed to be developed further to enhance the antitumor effect and overcome the limitations caused by the alpha-fetoprotein (AFP) heterogeneity of HCC. In this study, a bispecific T cell engager (BiTE) targeting programmed death ligand 1 controlled by the human telomerase reverse transcriptase promoter was armed on the CRAd of the old system. It was demonstrated on orthotopic transplantation model mice that the new system had a better anti-tumor effect with no more damage to extrahepatic organs and less liver injury, and the infiltration and activation of T cells were significantly enhanced in the tumor tissues of the model mice treated with the new system. Importantly, we confirmed that the new system eliminated the AFP-negative cells on AFP heterogeneous tumor models efficiently. Conclusion: Compared with the old system, the new system provided a more effective and safer strategy against HCC.
This study sought to explore the immunogenicity of a booster dose of an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine in people living with human immunodeficiency ...virus (HIV) and identify the factors affecting the magnitude of anti-SARS-CoV-2 antibody levels.
A total of 34 people living with HIV (PLWH) and 34 healthy donors (HD) were administered a booster dose of the same SARS-CoV-2 vaccine. Anti-SARS-CoV-2 antibody and immunoglobulin G (IgG) levels were measured using the SARS-CoV-2 S protein neutralizing antibody Enzyme-Linked Immunosorbent Assay (ELISA) and 2019-nCov IgG Chemiluminescent Immunoassay Microparticles, respectively. Spearman correlation analysis was used to measure the correlation between laboratory markers and neutralizing antibody and IgG levels. Peripheral blood mononuclear cells (PBMCs) were extracted from each subject using density gradient centrifugation and the numbers of memory T and T follicular helper (Tfh) cells were determined using flow cytometry.
PLWH had a marked reduction in CD4 and B cell levels that was accompanied by a lower CD4/CD8 T cell ratio. However, those who received a supplementary dose of inactivated SARS-CoV-2 vaccines exhibited antibody positivity rates that were analogous to levels previously observed. The booster vaccine led to a reduction in IgG and neutralizing antibody levels and the amplitude of this decline was substantially higher in the PLWH than HD group. Correlation analyses revealed a strong correlation between neutralizing antibody levels and the count and proportion of CD4 cells. Anti-SARS-CoV-2 IgG antibody levels followed a similar trend. The expression of memory T and Tfh cells was considerably lower in the PLWH than in the HD group.
PLWH had an attenuated immune response to a third (booster) administration of an inactivated SARS-CoV-2 vaccine, as shown by lower neutralizing antibody and IgG levels. This could be attributed to the reduced responsiveness of CD4 cells, particularly memory T and cTfh subsets. CD4 and cTfh cells may serve as pivotal markers of enduring and protective antibody levels. Vaccination dose recalibration may be critical for HIV-positive individuals, particularly those with a lower proportion of CD4 and Tfh cells.
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