Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.208
Filtrar
1.
Chemosphere ; 286(Pt 2): 131812, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34375829

RESUMO

This work deals with the use of layered double hydroxides for a double environmental remediation. The residue obtained in the use of these materials as a chromate sorbent in water, was subsequently studied as a photocatalyst for the removal of NOx gases. With this aim, MgAl-CO3 layered double hydroxides were synthesized by the coprecipitation method with a divalent/trivalent metal ratio of 3. After its calcination at 500 °C, the mixed oxide was obtained and MgAl-CrO4 were synthesized by the reconstruction method. A complete chemical, morphological and photochemical study of the samples was carried out with techniques such as XRD, FT-IR, TGA, XRF, PL, DRIFTS and UV-Vis spectroscopy. Results showed that LDH materials presented no significant changes in their structure after their use as a sorbent. Photocatalytic tests of the samples showed a very good NO removal efficiency, as well as a high selectivity (low NO2 emissions) through complete oxidation of these oxides to nitrate. The incorporation of chromate into the LDH structure improved the absorption of light in the visible region of the spectra, producing an improvement of 20% in the NO elimination compared with the LDH without chromate.


Assuntos
Cromatos , Hidróxidos , Adsorção , Óxidos , Espectroscopia de Infravermelho com Transformada de Fourier
2.
J Hazard Mater ; 424(Pt A): 127314, 2022 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-34600376

RESUMO

The recent work aims at the use of Pantoea conspicua (MT5) and Aspergillus niger (CRS3) to assess their bioremediation potential and growth restoration of Helianthus annuus L. under chromate (Cr+6) stress. The growth of the P. conspicua and A. niger was tested in Cr+6 supplemented media. The strains can withstand up to 1200 and 900 ppm respectively in the media and effectively bio-transform it to nontoxic form. Supplemented metal's levels significantly decreased the growth attribute of H. annuus (p< 0.05). On the other hand, P. conspicua and A. niger rescued the host plant by establishing higher colonization frequency with the host roots. Moreover, MT5 bio-transformed the toxic Cr+6 to non-toxic Cr+3 form in the rhizosphere. It also enhanced the host plant growth by producing phytohormones and ceasing Cr uptake and accumulation. Contrarily, CRS3 tends to accumulate and bio-transform metal in their hyphae. Nonetheless, both of the microbes tend to modulate phytohormones production and strengthening antioxidant system of the host. Improvement in the antioxidant system enabled the host plant to produce higher phenolics and flavonoids, and lower peroxidase. The associated plant species also exhibited higher ROS scavenging and lower ROS accumulation. Besides, the strains were able to produce higher amounts of phytohormones, including IAA, GA, and SA. Such activities rendered them as excellent phytostimulants, that can be used as biofertilizers in chromium polluted soils.


Assuntos
Cromatos , Poluentes do Solo , Aspergillus niger , Biodegradação Ambiental , Cromo/análise , Pantoea , Poluentes do Solo/análise
3.
Environ Res ; 204(Pt A): 111984, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34492275

RESUMO

Exposure to hexavalent chromium [Cr(VI)] may occur in several occupational activities, e.g., welding, Cr(VI) electroplating and other surface treatment processes. The aim of this study was to provide EU relevant data on occupational Cr(VI) exposure to support the regulatory risk assessment and decision-making. In addition, the capability and validity of different biomarkers for the assessment of Cr(VI) exposure were evaluated. The study involved nine European countries and involved 399 workers in different industry sectors with exposures to Cr(VI) such as welding, bath plating, applying or removing paint and other tasks. We also studied 203 controls to establish a background in workers with no direct exposure to Cr(VI). We applied a cross-sectional study design and used chromium in urine as the primary biomonitoring method for Cr(VI) exposure. Additionally, we studied the use of red blood cells (RBC) and exhaled breath condensate (EBC) for biomonitoring of exposure to Cr(VI). Personal measurements were used to study exposure to inhalable and respirable Cr(VI) by personal air sampling. Dermal exposure was studied by taking hand wipe samples. The highest internal exposures were observed in the use of Cr(VI) in electrolytic bath plating. In stainless steel welding the internal Cr exposure was clearly lower when compared to plating activities. We observed a high correlation between chromium urinary levels and air Cr(VI) or dermal total Cr exposure. Urinary chromium showed its value as a first approach for the assessment of total, internal exposure. Correlations between urinary chromium and Cr(VI) in EBC and Cr in RBC were low, probably due to differences in kinetics and indicating that these biomonitoring approaches may not be interchangeable but rather complementary. This study showed that occupational biomonitoring studies can be conducted successfully by multi-national collaboration and provide relevant information to support policy actions aiming to reduce occupational exposure to chemicals.


Assuntos
Poluentes Ocupacionais do Ar , Exposição Ocupacional , Poluentes Ocupacionais do Ar/análise , Monitoramento Biológico , Cromatos , Cromo/análise , Estudos Transversais , Monitoramento Ambiental , Humanos , Exposição Ocupacional/análise
4.
Environ Res ; 204(Pt A): 112005, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34499894

RESUMO

Efficient reduction of chromate is highly desirable for its detoxification and remediation of the contaminated environment. This study described a fusion of the concepts of precious metal biorecovery and fabrication of Pd/Fe@biomass derived from simulated wastewater. The effectiveness of Pd/Fe@biomass during reduction process of Cr(VI) was evaluated by comparing with pure nZVI, E. faecalis and Pd@biomass. Results showed that Pd(II) could be recovered by E. faecalis with Fe(II) as the electron donor, and precipitation could yield nZVI anchored onto Pd-loaded E. faecalis. The nano particles (NPs) on Pd/Fe@biomass were well-dispersed, which provided 2.70 folds specific surface area comparing with nZVI. Efficient Cr(VI) reduction could be achieved at a higher catalyst dosage, the most appropriated Pd/Fe molar ratio of 2% and a wide pH range. Typically, 0.5 mM Cr(VI) could be completely reduced in 5 min driven by Pd/Fe@biomass under the conditions of dosage of 1.0 g/L and pH 3. Moreover, the mechanisms of Cr(VI) reduction by Pd/Fe@biomass were proposed, which intimately related to nZVI electron donating capacities, Pd catalysis for hydrogenation and galvanic cell effects between Fe and Pd. Therefore, Pd/Fe@biomass could be an alternative for rapid and complete reduction of Cr(VI).


Assuntos
Cromo , Poluentes Químicos da Água , Biomassa , Cromatos , Cromo/análise , Enterococcus faecalis , Ferro , Poluentes Químicos da Água/análise
5.
J Drugs Dermatol ; 20(12): 1340-1342, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34898150

RESUMO

Chromate causes persistent, difficult to treat irritant and allergic contact dermatitis in cement-handling occupational workers. When therapeutics such as topical corticosteroids, topical calcineurin inhibitors, phototherapy and immune-modulating treatments like methotrexate fail, many patients are advised that avoidance may be the only remaining option – an option that may be particularly challenging if the patient’s occupation necessitates chromate exposure. We report a case of severe chromate-induced allergic contact dermatitis in a 55-year-old cement mason that presented to the outpatient dermatology clinic with multiple scaly, erythematous, >5 cm plaques scattered over the skin of his hands, head and neck. After a prior failed course of treatment with high potency topical corticosteroid, this patient was successfully treated with dupilumab. Given the success of dupilumab in our patient, we propose the consideration of dupilumab as an alternative treatment option for those suffering from chromate-induced allergic contact dermatitis that is refractory to ultra-high potency topical corticosteroids. J Drugs Dermatol. 2021;20(12):1340-1342. doi:10.36849/JDD.6246.


Assuntos
Cromatos , Dermatite Alérgica de Contato , Anticorpos Monoclonais Humanizados , Dermatite Alérgica de Contato/diagnóstico , Dermatite Alérgica de Contato/tratamento farmacológico , Dermatite Alérgica de Contato/etiologia , Humanos , Pessoa de Meia-Idade , Pele
6.
J Hazard Mater ; 417: 126019, 2021 09 05.
Artigo em Inglês | MEDLINE | ID: mdl-34229378

RESUMO

Sulfidated microscale zero-valent iron (SmZVI) attracts much attention recently in remediation of contaminated groundwater, but whether polymer coating on SmZVI would impact on its reactivity and capacity is yet to be understood. In this work, SmZVI was prepared by milling mZVI with elemental sulfur, and its stability in agar solution was evaluated. The impact of polymer coating on SmZVI grains' capacity and reactivity for chromate reduction was then examined. Experimental results indicated that SmZVI having the best overall performance was attained by grinding mZVI with elemental sulfur at 0.05 S/Fe molar ratio for 10 h. SmZVI's stability can be substantially improved if dispersed in 2.0 g/L agar solution. Existence of agar films on the SmZVI grain (A-SmZVI) lowered the material's capacity for chromate reduction by 56%, and the associated reaction kinetics by 70.4%, as estimated by pseudo first-order reaction model using the early-stage experimental data. Analysis of XPS spectra of A-SmZVI post reaction with chromate indicated that multiple reductive species including Fe0, Fe(II), FeS, and S(-II) may have jointly participated in the redox reaction taking place on the A-SmZVI-water interface. Fitting of XPS data supported that S(-II) was oxidized to SO42-, S2O32-, and S0, in order of decreasing surface concentration.


Assuntos
Água Subterrânea , Poluentes Químicos da Água , Ágar , Cromatos , Ferro , Poluentes Químicos da Água/análise
7.
Chemosphere ; 284: 131379, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34225108

RESUMO

Sulfidated nanoscale valent iron in form of FeS/Fe (0) shell-core nanoparticle has the aptitude to be a promising remediation material toward reductive removal of metal oxyanions. However, disrupted contact between Fe (0) core and FeS shell by thick iron oxides limited its reactivity improvement, and its mechanism of electron transfer remains unveiled. In this study, a novel sulfidated nZVI core-shell particles (FeS/Fe (0)) was fabricated via a modified post sulfidation approach to achieve a more uniform coverage of FeS for aqueous Cr(VI) sequestration. SEM and STEM tests confirmed the formation of the core-shell FeS/Fe (0) structure with a more solid interaction between FeS layer and Fe (0) core. The highest Cr(VI) removal rate was offered at optimal S/Fe molar ratio of 1/25 that the most chelated Fe2+ was also observed. The improved performance was due to that FeS shell with greater electronegativity could significantly accelerate the corrosion of Fe (0), facilitate the electron transfer form Fe (0) core to FeS shell according to the electrochemical tests. Moreover, FeS shell provided a protective layer for Fe (0) core so as to alleviate its anoxic passivation in water that FeS/Fe (0) had a better longevity for Cr(VI) removal than nFe (0). Characterizations of STEM and XPS revealed that Cr(VI) was reduced to Cr(III) and evenly coprecipitated with surface Fe(II)/Fe(III).


Assuntos
Cromatos , Poluentes Químicos da Água , Cromo/análise , Elétrons , Compostos Férricos , Compostos Ferrosos , Poluentes Químicos da Água/análise
8.
Int J Biol Macromol ; 184: 188-199, 2021 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-34119544

RESUMO

Water-soluble luminescent lanthanide complexes that can be excited with visible light could enable rapid detection of toxic anions and cations in biological systems. Eu3+-induced hyaluronic acid-chitosan aggregates (EIHCA) can improve the stability, biocompatibility, efficiency, and light absorption of luminescent Eu3+ complexes. Visible-range excitation may avoid phototoxicity associated with overexposure to UV light in biological and ecological applications. In this work, we synthesized and characterized series of EIHCA complexes having three N-donor heterocyclic ligands: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Dphen), 2,2': 6',2″-terpyridine (Tpy) and 1,10-phenanthroline monohydrate (Phen). These complexes possessed bright red fluorescence with a visible range excitation maximum. The photophysical properties of one formulation (we denote as EDL6) include fast quenching response (20 s) of the fluorescence, multi-selectivity, low limit of detection, and high quenching (Ksv) values, enabling selective, rapid and sensitive recognition of Cr2O72- and Fe3+ in aqueous solution. Furthermore, EDL6 exhibits cytocompatibility with mammalian cells that make these complexes promising biocompatible candidate as a safe replacement of organic fluorophores for fluorescence sensing applications. Thus, these new EIHCA complexes were successfully employed for the selective detection of hazardous materials in biological and aqueous environment samples.


Assuntos
Quitosana/química , Európio/química , Ácido Hialurônico/química , Íons/análise , Células A549 , Técnicas Biossensoriais , Cromatos/análise , Humanos , Ferro/análise , Ligantes , Luz , Limite de Detecção , Teste de Materiais
9.
J Occup Environ Med ; 63(7): 600-608, 2021 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-34184653

RESUMO

OBJECTIVES: To evaluate the alteration of protein of programmed cell death 5 (PDCD5) in peripheral blood mononuclear cells (PBMC) and DNA methylation caused by hexavalent chromium exposure. METHODS: There were 112 workers and 56 controls in this study. The chromium in RBC and urine, PBMC with PDCD5+, DNA methylation, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and score of DNA damage were measured. RESULTS: In chromate exposed workers, the percent of PBMC with PDCD5+, urine 8-OHdG, and score of DNA damage were significantly higher, whereas global DNA methylation was significantly lower. The binary logistic regression and generalized linear mixed model analysis showed that the percent of PBMC with PDCD5+ was significantly associated with global DNA hypomethylation. CONCLUSIONS: The aberrant DNA hypomethylation plays an important role in PBMC apoptosis of occupational hexavalent chromium exposure.


Assuntos
Cromatos , Exposição Ocupacional , 8-Hidroxi-2'-Desoxiguanosina , Proteínas Reguladoras de Apoptose/genética , Cromo , Dano ao DNA , Metilação de DNA , Humanos , Leucócitos Mononucleares , Proteínas de Neoplasias , Exposição Ocupacional/efeitos adversos , Exposição Ocupacional/análise
10.
J Environ Manage ; 288: 112463, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33823443

RESUMO

Chromate and phosphate are contaminant frequently present in industrial effluents such as tanneries. The objective of this work is to evaluate the efficiency of different operational combinations with dolomite and banana peel for the adsorption of phosphate and chromate in binary solutions. Both adsorbents are residuals from construction and food industries, respectively. Therefore, its use propitiates the reduction of treatment costs and it is an approach to the premises of the circular economy. In this work, the dolomite and banana peel adsorption efficiencies in simple and binary systems were studied. Equilibrium and kinetics tests were carried out in batch and in a fixed bed reactor. Dolomite was found to be selective for the adsorption of phosphate and banana peel for that of chromate. The mixture of adsorbents produced similar phosphate and chromate removal than each adsorbent individually. Therefore, the removals of both contaminants from binary solutions were tested using a fixed bed reactor filled with the mix of adsorbents and the breakthrough curves were analyzed. The obtained removals were 99% of phosphate and 70% of chromate. Finally, a brief discussion was held on the reuse and disposal of saturated adsorbents.


Assuntos
Musa , Poluentes Químicos da Água , Adsorção , Carbonato de Cálcio , Cromatos , Cinética , Magnésio , Fosfatos
11.
Plant Cell ; 33(4): 1268-1285, 2021 05 31.
Artigo em Inglês | MEDLINE | ID: mdl-33793849

RESUMO

A deficiency of the essential macronutrient sulfur leads to stunted plant growth and yield loss; however, an association with a symbiotic fungus can greatly improve nutrient uptake by the host plant. Here, we identified and functionally characterized a high-affinity sulfate transporter from the endophytic fungus Serendipita indica. SiSulT fulfills all the criteria expected of a functional sulfate transporter responding to sulfur limitation: SiSulT expression was induced when S. indica was grown under low-sulfate conditions, and heterologous expression of SiSulT complemented a yeast mutant lacking sulfate transport. We generated a knockdown strain of SiSulT by RNA interference to investigate the consequences of the partial loss of this transporter for the fungus and the host plant (maize, Zea mays) during colonization. Wild-type (WT) S. indica, but not the knockdown strain (kd-SiSulT), largely compensated for low-sulfate availability and supported plant growth. Colonization by WT S. indica also allowed maize roots to allocate precious resources away from sulfate assimilation under low-sulfur conditions, as evidenced by the reduction in expression of most sulfate assimilation genes. Our study illustrates the utility of the endophyte S. indica in sulfur nutrition research and offers potential avenues for agronomically sound amelioration of plant growth in low-sulfate environments.


Assuntos
Basidiomycota/fisiologia , Transportadores de Sulfato/metabolismo , Enxofre/metabolismo , Zea mays/crescimento & desenvolvimento , Zea mays/microbiologia , Cultura Axênica , Basidiomycota/metabolismo , Transporte Biológico , Cromatos/metabolismo , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Regulação da Expressão Gênica de Plantas , Mutação , Micologia/métodos , Filogenia , Interferência de RNA , Transportadores de Sulfato/genética , Sulfatos/metabolismo , Leveduras/genética , Zea mays/metabolismo
12.
ACS Appl Mater Interfaces ; 13(15): 17586-17598, 2021 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-33847119

RESUMO

Exploring active and ecological materials for the restoration of complex pollution system is highly desired. This study presents a facile defect-tailoring strategy for combined pollutants purification with BiVO4 photocatalysis in which the jointed synchronous reaction of oxidation and reduction is integrated instead of the sequential reaction in two individual systems. XPS and EPR reveal that BiVO4 with a suitable oxygen vacancies (OVs) concentration and distribution exhibits superior photocatalytic activity under the coexistence of TC-HCl and Cr(VI) with Cr(VI) reduction efficiency increased by 71 times compared with the individual Cr(VI) system along with TC-HCl removal efficiency comparable to a single TC-HCl system. The mechanism of synchronous redox reactions mediated by surface OVs is revealed by comprehensive characterization together with reaction kinetic analysis, and the electronic band structure adjustment induced by the OVs variation is confirmed. Active species identification tests and intermediate product analysis confirm that singlet oxygen (1O2) accounts for the selective oxidation of TC-HCl, while electrons dominate the reduction of Cr(VI), under a coexistent environment. The influence of water quality parameters (e.g., pH, cations, anions, and organic substances) on the photocatalytic activity is investigated considering the complexity of the real aquatic environment. Importantly, toxicity assessment with Gram-negative strain E. coli as a model bacterium validates that the toxicity of the intermediates can be reduced to low or even ultralow levels. This work is dedicated to the mechanistic study of defect photocatalysis over BiVO4 and provides a jointed synchronous reaction system for combined pollutant purification.


Assuntos
Bismuto/química , Bismuto/toxicidade , Cromatos/química , Processos Fotoquímicos , Vanadatos/química , Vanadatos/toxicidade , Relação Dose-Resposta a Droga , Escherichia coli/efeitos dos fármacos , Concentração de Íons de Hidrogênio , Oxirredução
13.
Environ Sci Technol ; 55(9): 5857-5867, 2021 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-33825446

RESUMO

Schwertmannite effectively sorbs chromate (Cr(VI)), yet the sorption mechanisms remain elusive. We determined the Cr(VI) sorption mechanisms on schwertmannite at pH 3.2 and 5 using combined macroscopic sorption experiments with molecular-scale characterization and by comparing them to arsenate (As(V)) sorption. Cr(VI) adsorbs as bidentate-binuclear (BB) inner-sphere complexes through exchanging more sulfate and less >Fe-OH/OH2, with 0.59-0.71 sulfate released per Cr(VI) sorbed. While As(V) also forms BB complexes, it exchanges sulfate and >Fe-OH/OH2 equally with 0.49-0.52 sulfate released per As(V) sorbed. At high As(V) loadings, As(V) precipitates as amorphous FeAsO4, particularly at low pH. The abovementioned differences between Cr(VI) and As(V) can be related to their different ionic radii and binding strength. Moreover, Cr(VI) and As(V) preferentially exchange sulfate inner-sphere complexes, increasing the proportion of sulfate outer-sphere complexes in schwertmannite. In turn, the concentration of sulfate outer-sphere complexes increases and then decreases with increasing Cr(VI) loading. Results suggest that an oxyanion, which would form inner-sphere complexes on a mineral surface, preferentially exchanges inner-spherically bound oxyanions than outer-spherically bound ones on the surface, even though both are exchanged. This study improves our understanding of the sorption of oxyanions on schwertmannite and their capabilities to template schwertmannite formation and stabilize its structure.


Assuntos
Arseniatos , Compostos de Ferro , Adsorção , Cromatos , Concentração de Íons de Hidrogênio , Sulfatos
14.
Res Microbiol ; 172(3): 103833, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33901608

RESUMO

The oxidative stress response represents a sum of antioxidative mechanisms that are essential for determining the adaptation and abundance of microorganisms in the environment. Leptospirillum ferriphilum and Acidithiobacillus ferrooxidans are chemolithotrophic bacteria that obtain their energy from the oxidation of ferrous ion. Both microorganisms are important for bioleaching of sulfidic ores and both are tolerant to high levels of heavy metals and other factors that can induce oxidative stress. In this work, we compared the tolerance and response of L. ferriphilum and At. ferrooxidans to Fe3+, H2O2, K2CrO4, and UV-C radiation. We evaluated growth, generation of reactive oxygen species (ROS), oxidative damage to lipid membranes and DNA, and the activity of antioxidative proteins in cells exposed to these stressors. L. ferriphilum had higher cell density, lower ROS content and less lipid and DNA damage than At. ferrooxidans. Consistent with this, the activity levels of thioredoxin and superoxide dismutase in L. ferriphilum were upregulated and higher than in At. ferrooxidans. This indicated that L. ferriphilum has a higher capacity to respond to oxidative stress and to manage redox homeostasis. This capacity could largely contribute to the high abundance of this species in natural and anthropogenic sites.


Assuntos
Acidithiobacillus/efeitos da radiação , Bactérias/efeitos da radiação , Ferro/metabolismo , Estresse Oxidativo , Acidithiobacillus/efeitos dos fármacos , Acidithiobacillus/crescimento & desenvolvimento , Acidithiobacillus/metabolismo , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Bactérias/metabolismo , Cromatos/farmacologia , Peróxido de Hidrogênio/metabolismo , Peróxido de Hidrogênio/farmacologia , Ferro/farmacologia , Oxirredução , Compostos de Potássio/farmacologia
15.
Ecotoxicol Environ Saf ; 217: 112233, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33862430

RESUMO

A microwave (MA) irradiation-persulfate-formate system was constructed to detoxify Cr contamination and solidify the geopolymerization of the alkali-activated composite material. Three series of experiments were correspondingly conducted to evaluate the treatment for the chromate-contaminated soil. The changes in the molar ratios of formate to persulfate and the mass rates of fortifier to soil led to a significantly greater reduction of CrVI in the detoxification experiments. The increase of blast furnace slag from 50% to 80% in the composite cementitious materials (CCM) intensified the immobilization efficiencies of chromate and the compressive strengths of geopolymer blocks. MA irradiation potentially enhanced the binding of Ca cations to the aluminosilicate compounds. The degree of reaction in the phenomenological kinetics model mathematically verified the geopolymerization process. Ettringite was formed within the structure of the geopolymer in the coupling system. Sulfate radicals released from persulfate not only contributed to the detoxification process but also strengthened the immobilization process.


Assuntos
Cromatos/análise , Recuperação e Remediação Ambiental/métodos , Micro-Ondas , Poluentes do Solo/análise , Álcalis , Silicatos de Alumínio , Poluição Ambiental , Formiatos , Solo/química , Sulfatos
16.
Int J Hyg Environ Health ; 234: 113725, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33714856

RESUMO

The EU human biomonitoring initiative, HBM4EU, aims to co-ordinate and advance human biomonitoring (HBM) across Europe. As part of HBM4EU, we presented a protocol for a multicentre study to characterize occupational exposure to hexavalent chromium (Cr(VI)) in nine European countries (HBM4EU chromates study). This study intended to collect data on current occupational exposure and to test new indicators for chromium (Cr) biomonitoring (Cr(VI) in exhaled breath condensate and Cr in red blood cells), in addition to traditional urinary total Cr analyses. Also, data from occupational hygiene samples and biomarkers of early biological effects, including genetic and epigenetic effects, was obtained, complementing the biomonitoring information. Data collection and analysis was completed, with the project findings being made separately available. As HBM4EU prepares to embark on further European wide biomonitoring studies, we considered it important to reflect on the experiences gained through our harmonised approach. Several practical aspects are highlighted for improvement in future studies, e.g., more thorough/earlier training on the implementation of standard operating procedures for field researchers, training on the use of the data entry template, as well as improved company communications. The HBM4EU chromates study team considered that the study had successfully demonstrated the feasibility of conducting a harmonised multicentre investigation able to achieve the research aims and objectives. This was largely attributable to the engaged multidisciplinary network, committed to deliver clearly understood goals. Such networks take time and investment to develop, but are priceless in terms of their ability to deliver and facilitate knowledge sharing and collaboration.


Assuntos
Monitoramento Biológico , Exposição Ocupacional , Cromatos , Cromo/análise , Monitoramento Ambiental , Humanos
17.
Environ Sci Pollut Res Int ; 28(31): 41760-41771, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33788088

RESUMO

Chromite ore processing residues (COPR) are real environmental threats, leading to CrO42-, i.e., Cr (VI) leaching into groundwater. It is of serious concern as Cr (VI) is proven to be carcinogenic. Here we emphasize the application of novel and eco-friendly chitin functionalized iron-enriched hydroxyapatite nanocomposite (HAP-Fe0-Ct) in the remediation of Cr (VI)-contaminated groundwater samples collected from Khan Chandpur, India, where the level of Cr (VI) is found to be 11.7 mg/L in a complex aqueous matrix having 793 mg/L of total dissolved solids. Chitin functionality in the composite has resulted in positive zeta potential at circum-neutral pH, favoring electrostatic attraction of chromate ions and resulting in its bulk surface transport. The HAP-Fe0-Ct showed faster kinetics of removal with efficiency (qm = 13.9 ± 0.46 mg/g) for Cr (VI). The composite has shown sorption equilibrium and 100% removal of Cr (VI) within 3 h of interaction time in groundwater samples. No Cr (VI) leaching in the acid wash process at pH 3.5 also suggests chromium's strong chemisorption onto nanocomposite. During the interaction in aqueous solutions, the reduced iron (Fe0) on the nanocomposite becomes oxidized, suggesting the probable simultaneous reduction of Cr (VI) and its co-precipitation. Continuous column extraction of chromate ions was also efficient in both spiked solutions (39.7 ± 0.04 mg/g) and COPR contaminated water (13.2 ± 0.09 mg/g). Reusability up to three cycles with almost complete Cr (VI) removal may be attributed to surface protonation, new binding sites generation, and electron transfer from Fe0 core through defects. The study concludes that HAP-Fe0-Ct could be utilized for continuous Cr (VI) removal from COPR contaminated complex groundwater matrices.


Assuntos
Água Subterrânea , Nanocompostos , Poluentes Químicos da Água , Quitina , Cromatos , Cromo/análise , Durapatita , Íons , Ferro , Poluentes Químicos da Água/análise
18.
Environ Res ; 197: 111059, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33766568

RESUMO

The concentration of chromium (Cr) in natural water and soil environments has gradually increased in recent decades, owing to intensive use of Cr in industry and its subsequent disposal. In this study, we performed a comparison study on chromate (Cr6+) reduction by tea waste (green tea, black tea, red tea, and chamomile) in water (25 °C) and ice (-20 °C) to develop a new strategy for environmental-friendly stabilization of hazardous Cr6+ by freezing. This study shows that the freezing process can enhance the reduction of Cr6+ by tea waste. The residual Cr6+ concentration ratios (C/C0, where C is the concentration of Cr6+ after the reaction (5 h) and C0 is the initial concentration of Cr6+ (20 µM) in the system) by tea wastes in water were in the range of 0.71 (green tea) to 0.92 (chamomile); however, the ratios dramatically decreased under the freezing process (i.e., 0.06 by green tea, 0.13 by black tea, 0.18 by red tea, and 0.08 by chamomile). According to the results obtained from the fluorescent, chromatographic, and spectroscopic analyses, under the freezing process, the enhanced reduction of Cr6+ could be explained by the freeze concentration of Cr6+, phenolic components in tea extracts, and protons in small liquid pockets in liquid-like layers (LLLs). In addition, the proposed system can efficiently purify the real Cr6+-containing wastewater (i.e., electroplating wastewater), indicating that the system will be economically feasible in cold regions (i.e., polar regions).


Assuntos
Cromatos , Poluentes Químicos da Água , Cromatos/análise , Cromo/análise , Gelo , Oxirredução , Chá , Águas Residuárias , Água , Poluentes Químicos da Água/análise
19.
Chemosphere ; 271: 129446, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33454661

RESUMO

Agricultural, industrial and household chemicals are emitted in large rivers along populated areas, transported by water and deposited in sediments, posing (eco)toxicological risks. Sediments have received less attention than surface waters, likely because of the intrinsic complexity of interactions between sediment constituents complicating correct framing of exposures. Sadly, thorough assessment of the in situ behavior of sediment constituents in bioassays is often not practical. Alternatively, we related physicochemical properties of sediments from field testing to results from bioassays. The case study covers Flemish sediment (incl. Scheldt and Meuse) and mortality of Hyalella azteca, a sensitive bio-indicator. Though variable across Flanders' main water bodies, heavy metals and ammoniacal nitrogen dominate the observed toxicity according to toxic unit (TU) assessments. Depending on the water body we explain between 50 and 90% of the variance in the observed H. azteca mortality, substantially more than previous ecotoxicity studies. We attribute the remaining variance to potential incoherently documented biophysicochemical sediment properties and concentrations of non-target biocides, testing conditions/set-ups and/or species variabilities. We discuss the relative influence of heavy metals/metaloxides, nitrogen (e.g. fertilizer), polycyclic aromatics and organochlorides. We highlight both direct and indirect mortality mechanisms. We note potential synergetic mixture effects between ammoniacal nitrogen and chromium. Such synergy may be phenomenological of 'standard' aerobic bioassays, and prove a complementary method alongside the 'acid-volatile sulfide test' to more effectively link concentration to toxicity. Future study ought to include variation in biophysicochemical properties between sampling locations and batch bioassays. Our approach enables water managers to interpret their monitoring data by converting sediment concentrations to H. azteca mortality and prioritize substances that contribute most.


Assuntos
Anfípodes , Poluentes Químicos da Água , Amônia , Animais , Bioensaio , Cromatos , Sedimentos Geológicos , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidade
20.
Anat Histol Embryol ; 50(1): 84-92, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32794251

RESUMO

Sheep are recognized as useful species for translational neurodegeneration research, in particular for the study of Huntington disease. There is a lack of information regarding the detailed anatomy and connections of the basal ganglia of sheep, in normal myeloarchitectonics and in tract-tracing studies. In this work, the organization of the corticostriatal projections at the level of the putamen and globus pallidus (GP) are explored. For the first time, the myeloarchitectonic pattern of connections between the internal (IC) and the external (EC) capsules with the GP have been investigated in the sheep. Formaldehyde-fixed blocks of the striatum were treated with a metallic stain containing potassium dichromate and visualized using micro-CT (µ-CT). The trivalent chromium (Cr3+), attached to myelin phospholipids, imparts a differential contrast to the grey and white matter compartments, which allows the visualization of myelinated fascicles in µ-CT images. The fascicles were classified according to their topographical location in dorsal supreme fascicles (X, Y, apex) arising from the IC and EC; pre-commissurally, basal fascicles connecting the ventral part of the EC with the lateral zone of the ventral pallidum (VP) and, post-commissurally, superior (Z1 ), middle (Z2 ) and lower (Z3 ) fascicles, connecting at different levels the EC with the GP. The results suggest that the presumptive cortical efferent and afferent fibres to the pallidum could be organized according to a dorsal to ventrolateral topography in the sheep, similar to that seen in other mammals. The proposed methodology has the potential to delineate the myeloarchitectonic patterns of nervous systems and tracts.


Assuntos
Cromatos/química , Globo Pálido/anatomia & histologia , Globo Pálido/diagnóstico por imagem , Ovinos/anatomia & histologia , Microtomografia por Raio-X/veterinária , Animais , Masculino , Coloração e Rotulagem/veterinária
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...