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1.
Ecotoxicol Environ Saf ; 207: 111311, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32947212

RESUMO

Traditional Chinese medicine has become an important pillar of "Healthy China" and the national medical system in recent years. Due to the wide range of raw materials in traditional Chinese medicinal materials (TCMM), the issue of metals has attracted more and more attention. In this paper, a comprehensive review of public reports on metals in TCMM in recent decades was conducted. From a total of 1969 reported articles, a total of 296 research reports on metals in TCMM were screened. The 296 reports involved 255 species in 85 families, with a total of 274 medicinal materials. These TCMM were divided into taproot-type, leaf-type, flower and fruit-type, herba-type, stem-type and bark-type medicinal materials according to the medicinal parts. The content of five metals lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), chromium (Cr) in these TCMM was noted, and the distribution rules for metals were analyzed. The results showed that: (1) For the distribution of metals in different medicinal parts, Pb was mainly distributed in leaves; Cd was mainly distributed in flowers and fruits, stems and leaves; Hg was mainly distributed in barks; As was mainly distributed in stems; Cr was mainly distributed in stems, flowers and fruits. (2) The areas with the highest risk of metal residues were the Qinghai-Tibet Plateau, south China, and southwest China. (3) Among all types of TCMM, herba-type medicinal materials had the highest risk of metal content. (4) Combined with the pharmacopoeia metal limit standards implemented in 2019, the exceeding rate of Pb in TCMM was the highest, with a maximum value of 37.67%; among the six major types of TCMM, the medicinal materials with the highest exceeding rate were herba-type medicinal materials, among which Hg had the highest exceeding rate of 23.08%; in terms of medicinal parts, the highest exceeding rate of metals was in leaf-type medicinal materials, among which Pb had the highest exceeding rate of 37.67%. On the whole, the situation in regard to metal residues in TCMM was acceptable, but it cannot be ignored. It needed to be paid attention to in the industrialization and management of TCMM.


Assuntos
Medicamentos de Ervas Chinesas/análise , Monitoramento Ambiental/métodos , Poluentes Ambientais/análise , Metais Pesados/análise , Arsênico/análise , Grupo com Ancestrais do Continente Asiático , Cádmio/análise , China , Cromo/análise , Frutas/química , Humanos , Folhas de Planta/química , Tibet
2.
Sci Total Environ ; 756: 143816, 2021 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-33293091

RESUMO

Pine biomass (Pine), pine gasification biochar (PG) and pine biomass loaded with TiO2 (Pine/TiO2) were used as sorbent materials to remove Cr(III) or Cr(VI) ions from aqueous solutions. Our results showed that Pine/TiO2 had an improved adsorption capacity respect to Pine being the adsorption capacity for Cr(VI), 12.8 mg/g, much larger than for Cr(III), 1.23 mg/g. On the other hand, PG showed much higher adsorption for Cr(III), 12.4 mg/g, than Pine/TiO2, and negligible adsorption for Cr(VI). To understand this species-dependent adsorption behavior, the adsorption mechanisms, sorbents morphology and functional sites were characterized using a multi-technique approach. The chemical state and local coordination structure of the adsorbed Cr species was studied by X-ray absorption spectroscopy (XAS). Our results show that the adsorption of Cr(III) occurred mainly through cation exchange with mineral elements in PG biochar, whereas the Cr(III) adsorption by functional groups (carboxyl and hydroxyl groups) dominate in the biomass sorbent. The enhancement of Cr(VI) adsorption in Pine/TiO2 can be explained by the presence of TiOH2+groups present in the surface of the TiO2 microparticles. X-ray absorption spectroscopy (XAS) results reveal that Cr(VI) reduces to Cr(III) after being adsorbed by the sorbent materials.


Assuntos
Cromo , Poluentes Químicos da Água , Adsorção , Biomassa , Carvão Vegetal , Cromo/análise , Concentração de Íons de Hidrogênio , Poluentes Químicos da Água/análise , Espectroscopia por Absorção de Raios X
3.
Sci Total Environ ; 757: 143803, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33293088

RESUMO

Guitarfishes and angelsharks are two of the most endangered elasmobranch groups. Despite this, limited knowledge exists regarding the effects of environmental contamination in these groups. For this reason, this study assessed the concentrations of metals in liver and muscle of three guitarfishes (Pseudobatos horkelii, P. percellens, and Zapteryx brevirostris) and one angelshark species (Squatina guggenheim) captured during the year of 2019 in one of the most impacted areas in South America: the São Paulo State coast, Brazil, Southwest Atlantic. Cadmium (Cd) Chromium (Cr) Cupper (Cu) Iron (Fe), Mercury (Hg), and Lead (Pb) were determined by atomic spectrometry, with samples being previously acid digested. Among the non-essential metals, Cd had the highest mean concentrations for all species, followed by Pb and Hg, whereas Fe had the highest mean levels among the essential metals analyzed, followed by Cu and Cr. Liver and muscle samples had different concentrations, with liver presenting the highest concentrations. Except for Cd, non-essential metals had relatively low concentrations when compared to other elasmobranch species reported in the literature, which could be explained by the efficiency in metabolizing these compounds or differential life history patterns among the species studied herein and other. Considering that all species analyzed herein are typically consumed, human health impacts must be considered, especially concerning Cd concentrations. Furthermore, Cd, Cr and Pb were above the safety limits, indicating potential hazard for human consumption. In conclusion, our results suggest that these species are exposed to metals and that concentrations above the safety limits observed for these species must be taken into consideration regarding human consumption.


Assuntos
Metais Pesados , Poluentes Químicos da Água , Animais , Brasil , Cádmio/análise , Cromo/análise , Monitoramento Ambiental , Humanos , Metais Pesados/análise , Poluentes Químicos da Água/análise
4.
Chemosphere ; 264(Pt 1): 128487, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33038755

RESUMO

EDTA and soluble Cr(III) are usually both present in wastewaters coming from treatment plants handling tannery effluents. A well-established method to determine EDTA is based on the conversion of free and complexed EDTA into its Fe(III) complex. This procedure gives inconsistent data when Cr(III)-EDTA is present. This fact was here demonstrated by studying the kinetics of the exchange reaction between Fe(III) and Cr(III)-EDTA at 90 °C and various pH values, from acidic to neutral. The reaction is very slow (several weeks); the slow kinetics of conversion of Cr(III)-EDTA to Fe(III)-EDTA is even more accentuated at room temperature and the low concentrations of reactants in wastewaters. The presence of EDTA complexes of Fe(III) and Cr(III) was demonstrated in industrial effluents and wastewaters by developing a selective method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS), which was able to detect free and complexed EDTA at concentration levels <1 µM. A systematic underestimation of the EDTA expressed as Fe(III) complex was demonstrated in samples containing Cr(III)-EDTA. Cr(III)-EDTA was identified for the first time as a component of wastewater samples at a concentration level of about 2 µM and turned out to be an inert species that significantly contributes to the final soluble Cr amount. This study gives new insights into the inertness of Cr(III) toward metal exchange equilibria of EDTA complexes, resolves a bias in the analysis of total EDTA in samples containing Cr(III)-EDTA, allowing the direct determination of free and complexed EDTA by LC-MS.


Assuntos
Cromo , Águas Residuárias , Cromatografia Líquida , Cromo/análise , Ácido Edético , Compostos Férricos , Ligantes , Espectrometria de Massas em Tandem
5.
Chemosphere ; 264(Pt 2): 128547, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33049514

RESUMO

Hexavalent chromium (Cr(VI)), the most toxic valence state of chromium, is widely present in industrial effluents and wastes. Although previous study has reported that Cr(VI) can cause cytomembrane structure impairment by aggravating lipid peroxidation in the heart, the detailed mechanism of Cr(VI)-induced heart dysfunction is still unclear. Sesn2, a novel antioxidant and stress-inducible molecule, is evidenced to protect against various cardiometabolic diseases such as atherosclerosis and cardiomyopathy. To define the potential mechanism of heart dysfunction induced by chronic Cr(VI) exposure, Wistar rats were intraperitoneal injected with potassium dichromate (K2Cr2O7) for 35 d in the present study. The data showed that chronic K2Cr2O7 exposure caused dose-dependently hematological variations, oxidative stress, dysfunction, and disorganized structure of heart, cardiomyocyte apoptosis, ATP depletion, and mitochondria impairment in rats. In addition, the expressions of Drp1 and Bax were increased by K2Cr2O7. However, the suppression of Mfn2, PGC-1α, Sesn2, nuclear Nrf2, HO-1, and NQO1 protein levels was observed in K2Cr2O7-treated rat hearts. In conclusion, these results demonstrate that chronic K2Cr2O7 exposure dose-dependently causes heart dysfunction, and the molecular mechanism of this event is associated with the loss of Sesn2 mediated mitochondrial function and energy supply impairment.


Assuntos
Cardiomiopatias , Cromo , Animais , Cromo/toxicidade , Mitocôndrias , Estresse Oxidativo , Dicromato de Potássio , Ratos , Ratos Wistar
6.
Chemosphere ; 263: 127871, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297005

RESUMO

Biochars (BCs) derived from individual and blending lignocellulosic constituents were prepared to harbor zerovalent iron (ZVI/BC) in an effort to discriminate significance of each constituent or combination in ZVI/BC for Cr(VI) removal. BCs and ZVI/BC were characterized by TGA/GSC, XRD, Raman and BET analyses. Cellulose (BCC) and hemicellulose (BCH)-derived BCs has greater C content, H/C ratio, surface area and mass loss than BCs derived from lignin or lignin-containing biopolymer blends (BCLX). As per sorption and XPS analysis, ZVI/BC demonstrated greater Cr(VI) removal capacity than respective BCs, in which reduction accounted for over 77% Cr(VI) detoxification. Cr(VI) reduction by ZVI harbored by BCC and BCH was 19.72-16.54 g kg-1, compared to 5.97-4.26 g kg-1 for BCLX. ZVI/BC prepared by three-biopolymer blends with (12.63 g kg-1) or without (12.32 g kg-1) mineral approximated pinewood-BC (BCP) (13.02 g kg-1) for Cr(VI) reduction, suggesting minerals are not important constituent. Tafel analysis showed BCC and BCH, with lower ID/IG ratio owing to greater graphitization, were more conducible to transfer electron of ZVI in Cr(VI) reduction than BCLX. Thus, cellulose, hemicellulose and lignin can offer a good prediction of property of natural biomass, in which BCC and BCH favor electron transfer of ZVI but BCL is not electroactive.


Assuntos
Ferro , Poluentes Químicos da Água , Carvão Vegetal , Cromo/análise , Lignina , Poluentes Químicos da Água/análise
7.
Chemosphere ; 263: 127988, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297031

RESUMO

To the best of our knowledge, in few studies, biochar (BC)-based materials have been used as the photocatalyst for water purification, and their application is limited to a great extent due to catalyst agglomeration and inefficient electron migration. In this study, a novel Bi2WO6 loaded N, S co-doping corn straw biochar (Bi2WO6/NSBC) was successfully synthesized with a simple solvothermal method for the removal of ciprofloxacin (CIP) and Cr(VI) under visible light irradiation. The Bi2WO6/NSBC was featured with efficient and rapid catalytic removal toward CIP (5 mg/L) and Cr(VI) (10 mg/L), with efficiencies of ∼90.33% and ∼99.86% within 75 min, respectively. More attractively, this composite can be applied in a wide pH range (3.0-9.0) and with weak effects by coexisting ions (Cl-, CO32-, SO42-, and Ca2+). The facile synthesized porous graphitized structure demonstrates an outstanding performance of superior conductivity and promoted photoelectron transport. Meanwhile, it is found that N, S co-doping of the BC induces highly interconnected fibrous structures, high catalytic property, and favorable specific surface areas, which is considered to avoid agglomeration of Bi2WO6. The increased photocatalytic activity results from the synergistic effects of Bi2WO6 and NSBC by the optimized band gap and enhanced visible light response, due to higher migration and utilization efficiency of photoinduced carriers in photocatalytic reactions. In this approach, a cheap catalyst is provided, and at the same time, a synergistic effect of N, S co-doping is formed to rapidly remove contaminants in wastewater treatment.


Assuntos
Ciprofloxacino , Elétrons , Carvão Vegetal , Cromo , Zea mays
8.
Chemosphere ; 263: 128042, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297057

RESUMO

Solid wastes from chromium-processing facilities, when used as fill material, have generated chromium point source contamination of soils and groundwaters, that remains after decades in many urban and peri urban areas all over the world, causing environmental impacts that need to be addressed in a sustainable economic, social and environmental way. Representative surface soil samples, from a polluted area affected by chromite wastes burials, were used to carry on a feasibility study on Phytoextraction applicability, and chelating agents' selection to reduce environmental risks, considering chromium bioaccessible forms reduction as an objective. Tests for natural (only vegetation), and induced phytoextraction (plants + chelating agents) applicability were performed at greenhouse facilities under controlled conditions at two rounds. Natural phytoextraction tests, using first wheat and then corn plants, allowed to observe a low but significant 4,8% reduction in soil chromium. At induced phytoextraction trials, when comparing the action of the different chelating agents versus a blank on final soil chromium concentration, the results were not so conclusive globally (0,5% less soil chromium in trials in which the first crop was wheat followed by corn, and 2% in trials in which the first and the second crop was corn). In each group, the most "effective" chelating agent differed: EDDS for the first set, MGDA for the second one.The addition of chelating compounds in the soil could result in an increasing of the Cr oxidizable fraction mainly composed by Cr species associated to the organ mineral complexes.


Assuntos
Poluentes do Solo , Solo , Biodegradação Ambiental , Quelantes , Cromo/análise , Plantas , Poluentes do Solo/análise
9.
Chemosphere ; 263: 128109, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297102

RESUMO

Herein, the novel polyaniline@nano hollow carbon sphere (PANI@NHCS) adsorbents with different mass of NHCS were prepared by in-situ polymerization method. The microstructure of obtained PANI@NHCS-10, PANI@NHCS-20, PANI@NHCS-30 and PANI@NHCS-40 samples were observed through both scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which showed that the PANI@NHCS-30 possessed hollow structure like lappaceum shell. Then, the performance of obtained PANI@NHCS-30 was studied for removing hexavalent chromium (Cr(VI)) from waste water. With the help of unique hollow structure and reduction ability of PANI@NHCS-30, the Cr(VI) was fleetly adsorbed and then reduced to less toxic Cr(III). The maximum adsorption capacity was 250.0 mg/g for PANI@NHCS-30 under the optimal condition. Moreover, the effects of initial Cr(VI) concentration, solution pH and different ions on the adsorption performance were investigated in detail. Importantly, the PANI@NHCS-30 still shows superb adsorption ability after five cycles, which suggests its satisfactory reusability ability. The accumulated data revealed the crucial role of PANI and hollow structure co-promoting effect on Cr(VI) reduction reactions over PANI@NHCS-30, which could be applied to the practical use.


Assuntos
Carbono , Poluentes Químicos da Água , Adsorção , Cromo/análise , Concentração de Íons de Hidrogênio , Poluentes Químicos da Água/análise
10.
Chemosphere ; 263: 128138, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297126

RESUMO

Suzhou (SZ), Wuxi (WX) and Changzhou (CZ) (collectively called the SXC area) in southern Jiangsu Province surround Tai Lake on three sides and have an important impact on its ecology. The emission and circulation of Cr in the three cities were quantified according to the six categories (including industry production, agricultural livestock, vehicle exhaust, solid waste, atmospheric subsidence and runoff) to analyze its regional characteristics and source category characteristics and to build a Cr cycle diagram to evaluate the pollution situation. The results showed that the Cr emissions from solid waste were the highest and mostly came from industrial sludge, accounting for 76.4% of the total circulation. The Cr emissions from SZ and WX were significantly higher than those of CZ, accounting for 47.0% and 42.9% of the regional total. The Cr in the excrement of pigs and poultry, dry sedimentation and surface runoff exceeded 100 tons every year, which needed to be valued. The Cr concentration in the surface water, soil and atmosphere in SXC area all met with the highest national standards. Studies have shown that the sediments and benthic organisms in the west and north of Tai Lake were already in a low-pollution state, but which was overall acceptable. Through this study, Cr circulation was clarified in typical areas, which was convenient for the monitoring and management of heavy metal pollution in the areas surrounding Tai Lake.


Assuntos
Cromo , Metais Pesados , Animais , China , Cidades , Monitoramento Ambiental , Metais Pesados/análise , Medição de Risco , Suínos
11.
Chemosphere ; 263: 128221, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297177

RESUMO

The present paper reports the efficiency of bog peat-derived humic acid (HA) in the reductive removal of hexavalent chromium (CrVI) from aqueous solution as affected by solution pH, the dose of FeIII and reaction time (numeric variables) and light irradiation (categorical variable). A three-level Box-Behnken design (BBD) applied to design experimental matrix, model the effects and interactions of variables on four determined responses (residual concentration of dissolved CrVI, dissolved CrIII, dissolved FeII and total CrVI) and optimize the experimental conditions for highest CrVI removal efficiency (CrVI RE). Reaction mechanisms are also well discussed. Regression models were developed and analyzed by the ANOVA test and models determination coefficient R2. Obtained models were significant (F values > 13) and an excellent relationship between experimental and predicted responses (R2: 98.1-99.6%) was observed. The optimum conditions were established corresponding to the residual concentration of dissolved CrVI as an index for CrVI removal efficiency (RE). In the dark system, the highest CrVI RE (98.1%) was obtained under the following conditions: pH = 1, reaction time = 7 d and FeIII dosage = 0.110 mM. In the light-irradiated system, the optimal CrVI RE of 98.3% was observed in pH = 1, reaction time = 5 d and FeIII dosage = 0.075 mM. Almost all reduced CrIII remained in the solution even at high pH value. No adsorption or precipitation of CrIII on the HA surface at pH 5 was confirmed by surface analyses of HA using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM).


Assuntos
Substâncias Húmicas , Poluentes Químicos da Água , Adsorção , Cromo/análise , Compostos Férricos , Substâncias Húmicas/análise , Concentração de Íons de Hidrogênio , Solo , Áreas Alagadas
12.
Chemosphere ; 263: 128250, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297195

RESUMO

Copper(II) phthalocyanine (CuPc) and non-peripheral octamethyl-substituted copper(II) phthalocyanine (N-CuMe2Pc) were combined with reduced graphene oxide (rGO) via a precipitation method to form CuPc/rGO and N-CuMe2Pc/rGO nanocomposites, respectively. CuPc nanorods are distributed on rGO, and N-CuMe2Pc exists as nanorods and nanoparticles on rGO. The Cr(VI) removal ratio of N-CuMe2Pc/rGO exposed in simulated sunlight is 99.0% with a fast photocatalytic reaction rate of 0.0320 min-1, which is approximately 1.5 times faster than that of CuPc/rGO (0.0215 min-1) and far surpasses that of pristine phthalocyanine and rGO. As an electron acceptor, rGO can suppress the recombination of photo-induced electron-hole pairs and also can provide a large surface area for Cr(VI) removal, both of which are beneficial to the reducing capacity of the nanocomposites. The higher removal efficiency of N-CuMe2Pc/rGO compared with that of CuPc/rGO is attributed to the higher specific surface area, higher light harvesting, higher conductivity and more negative lowest unoccupied molecular orbital level of N-CuMe2Pc/rGO. The N-CuMe2Pc/rGO nanocomposite shows excellent photochemical recyclability which is essential for application in wastewater treatment.


Assuntos
Grafite , Nanocompostos , Poluentes Químicos da Água , Catálise , Cromo , Indóis , Compostos Organometálicos
13.
Chemosphere ; 263: 128281, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297225

RESUMO

Hexavalent chromium (Cr(VI)) is a carcinogenic compound that can be removed from contaminated sites by the activity of metal-reducing bacteria. The model bacterium Geobacter sulfurreducens reduces Cr(VI) to less toxic Cr(III) and accumulates Cr ions intracellularly. However, this process is usually slow with small concentrations of Cr(VI) removed in a matter of days. Here, high-density G. sulfurreducens cultures were tested for the capacity to remove Cr(VI) readily. With an initial G. sulfurreducens density of 5.8 × 108 cells ml-1, 99.0 ± 0.8% of 100 mg l-1 Cr(VI) was removed after 20 min. With a higher starting Cr(VI) concentration of 200 mg l-1, G. sulfurreducens with a density of 11.4 × 108 cells ml-1 removed 99.0 ± 0.4% Cr(VI) after 2 h. Experiments performed with cell-free spent medium indicate that extracellular proteins are major contributors for the reduction of Cr(VI) to Cr(III). Furthermore, results show that most Cr(III) ions ultimately end up inside the bacterial cells where they are less susceptible to re-oxidation. The fast Cr(VI) removal rates observed with high-density G. sulfurreducens demonstrate the potential of this bacterium for bioremediation applications such as the cleaning of industrial wastewaters.


Assuntos
Cromo , Geobacter , Biodegradação Ambiental , Cromo/toxicidade , Oxirredução
14.
Chemosphere ; 263: 128308, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297245

RESUMO

Soil particle size significantly affects the distribution and migration of chromium (Cr) in soil. Limited studies have investigated the impact of soil particle size on Cr partitioning at chromate contaminated sites. In this study, the physicochemical properties of coarse sand, medium sand, fine sand, and silt-clay were analyzed. And the particle size effects on partitioning, leachability, and bioaccessibility of total Cr and Cr(VI) were determined. The results showed the distribution factor (DF) of Cr(VI) in the coarse sand, medium sand, fine sand, and silt-clay fractions were 0.70, 0.79, 1.35, and 1.60, respectively. The total Cr DF values also had the similar result. The leached concentrations of total Cr and Cr(VI) in silt-clay (562.89 mg/L and 551.71 mg/L) was higher than in coarse sand (238.55 mg/L and 228.68 mg/L) fraction. The bioaccessibility of total Cr and Cr(VI) in silt-clay (77.72% and 88.58%) was higher than in fine sand (60.72% and 79.55%) fraction. The total Cr proportion of the exchangeable fraction (45.92%-73.67%) was relatively high in the four soil particle size fractions and gradually increased as soil particle size decreased. These implied that finer soil particles are more capable of enriching, mobilizing, and bioaccessibility of Cr and Cr(VI) than the coarse particles, which was related to the higher organic matter, cation exchange capacity, specific surface area, and clay components in smaller particles. The results suggested that higher environmental risk occurred in the finer fraction than in the coarser fraction for the chromate production contaminated soil.


Assuntos
Poluentes do Solo , Solo , Cromatos , Cromo/análise , Argila , Tamanho da Partícula , Poluentes do Solo/análise
15.
J Environ Sci (China) ; 101: 304-312, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33334525

RESUMO

Chromium (Cr) is used in many manufacturing processes, and its release into natural waters is a major environmental problem today. Low concentrations of Cr(VI) are toxic to human health and living organisms due to the carcinogenic and mutagenic nature of this mineral. This work examined the conversion of Cr(VI) to Cr(III) via electrochemical reduction using gold electrode in an acidic sodium alginate (SA) solution and subsequent removal of the produced Cr(III)-SA by the polymer-enhanced ultrafiltration (PEUF) technique. A solution of SA in nitric acid was used both as an electrolytic medium during the voltammetric measurements and bulk electrolysis and as an extracting agent during the PEUF technique. The electroanalysis of Cr(VI) was performed by linear sweep voltammetry in the presence of acidic SA solution to study its voltammetric behavior as a function of the Cr(VI) concentration, pH, presence of Cr(III), SA concentration and scan rate. In addition, the quantitative reduction of Cr(VI) to Cr(III) was studied through the bulk electrolysis technique. The results showed efficient reduction with well-defined peaks at approximately 0.3 V vs. Ag/AgCl, using a gold working electrode. As the pH increased, the reduction signal strongly decreased until its disappearance. The optimum SA concentration was 10 mmol/L, and it was observed that the presence of Cr(III) did not interfere in the Cr(VI) electroanalysis. Through the quantitative reduction by bulk electrolysis in the presence of acidic SA solution, it was possible to reduce all Cr(VI) to Cr(III) followed by its removal via PEUF.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Adsorção , Alginatos , Cromo , Humanos , Concentração de Íons de Hidrogênio , Oxirredução
16.
J Environ Sci (China) ; 101: 351-360, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33334529

RESUMO

Pyrite is the most abundant sulfide semiconductor mineral with excellent optical properties. However, few reports have investigated its photocatalytic activity because of the low photogenerated carrier separation efficiency. In this work, a Z-scheme FeS2/Fe2O3 composite photocatalyst was fabricated in situ via structural transformation of pyrite through heat treatment. A remarkably enhanced photocatalytic performance was observed over the FeS2/Fe2O3 composite photocatalyst. Compared with the pristine pyrite, the degradation efficiency of carbamazepine (CBZ) reached 65% at the added hexavalent chromium (Cr(Ⅵ)) concentration of 20 mg/L and the Cr(Ⅵ) was nearly completely reduced in the mixed system using FeS2/Fe2O3 within 30 min under simulated solar light irradiation. The enhanced photocatalytic activity can be attributed to the efficient separation and transfer of photogenerated carriers in the FeS2/Fe2O3 composite photocatalyst. This facilitated the generation of •OH, hole (h+) and •O2- species, which participated in the photocatalytic reaction with CBZ. Based on the measurement of the active species and electric properties, a Z-scheme electron transfer pathway was proposed for the FeS2/Fe2O3 composite photocatalyst. This work broadens the application potential of pyrite in environmental remediation.


Assuntos
Carbamazepina , Sulfetos , Catálise , Cromo , Ferro
17.
Environ Sci Pollut Res Int ; 28(3): 3533-3543, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32918689

RESUMO

Considering one health concept, human health is thought to be affected by many factors. Heavy metal toxicity is now gaining its place as one of the major factors contributing to detrimental outcomes for human health. The study encompassed to target sites close to the industrial area of Lahore where heavy metal levels are believed to be higher, as industrial waste is drained into the two main drains. Sheep and goats (n = 5 from each species) reared in the locality were included in the study, and effects of heavy metal toxicity were evaluated in the selected organs (intestine, kidneys, liver, and muscles) via histopathological examination along with residual concentration of these heavy metals in the aforementioned organs. Heavy metals chromium, copper, zinc, lead, iron, magnesium, manganese, and nickel were detected in sample of selected organs by atomic absorption spectrometry (AAS) along with digestion method. The findings of the study indicated a statistically significant difference of residual concentrations of almost all the selected elements in almost all the tissue samples between the two sites where the values of site 1 (close to the drain) were higher compared with site 2 (away from the drain). Similar trend was depicted in histopathological examination where a higher degree of tissue degeneration, necrosis, and hence organ damage was observed in tissue samples collected from site 1 compared with site 2.


Assuntos
Metais Pesados , Águas Residuárias , Animais , Cromo/análise , Cobre/análise , Monitoramento Ambiental , Metais Pesados/análise , Ruminantes , Ovinos
18.
Ecotoxicol Environ Saf ; 208: 111391, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33039869

RESUMO

Hexavalent chromium [Cr(VI)] is a pervasive environmental pollutant that can enter the body through a variety of routes and cause organ toxicity, genetic damage, and cancer. Cr(VI)-induced apoptosis is a toxicant mechanism of Cr(VI). Studies have shown that Cr(VI) can induce p53-independent apoptosis, but the mechanisms are not fully understood. The intracellular calcium concentration affects cellular life. Apoptosis-inducing factor (AIF), a caspase-independent apoptotic effector, can induce DNA degradation. Using p53-null Hep3B cells, we investigated the effects of cytoplasmic calcium homeostasis and AIF on Cr(VI)-induced apoptosis. We found that 20 µM of Cr(VI) induced DNA damage and mitochondrial permeability transition pore (MPTP) openings, causing calcium overload that was accompanied by decreased Ca2+-Mg2+-ATPase and Na+-K+-ATP activities, downregulation of calmodulin (CaM) and Ca2+/CaM-dependent protein kinase II (CAMKII) mRNA, and increased expression of p-CaMKII/CaMKII protein. After treatment with calcium chelating agent BAPTA-AM, Cr(VI)-induced DNA damage, calcium overload, and apoptosis were reduced. AIF was released from the mitochondria and translocated into the nuclei. As the Cr(VI) treatment time progressed, the mRNA and protein expression of B cell lymphoma 2 (Bcl-2) and heat-shock protein 70 (HSP70) decreased, whereas the mRNA and protein expression of Bcl-2-associated X (Bax), cyclophilin A (CypA), and endonuclease G (EndoG) were upregulated. These results indicated that Cr(VI)-induced apoptosis of Hep3B cells (p53-null) was closely associated with calcium overload, and was accompanied by the activation of Ca2+/CaM/CaMKII signaling pathway. Besides, Cr(VI) triggered AIF nuclear translocation in Hep3B cells, accompanied by the changes in the levels of apoptosis-associated factors. These results provide additional experimental evidence of the molecular mechanisms involved in Cr(VI)-induced p53-independent apoptosis.


Assuntos
Cromo/toxicidade , Substâncias Perigosas/toxicidade , Apoptose/efeitos dos fármacos , Fator de Indução de Apoptose/metabolismo , Fator de Indução de Apoptose/farmacologia , Cálcio/metabolismo , Morte Celular , Ácido Egtázico/análogos & derivados , Humanos , Mitocôndrias/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais
19.
Ecotoxicol Environ Saf ; 208: 111484, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33120265

RESUMO

Industrial wastes, for instance, tannery wastes are rich soups of resistant and bioremediation-potent bacteria. In the present work, Chromium (Cr) and tannic acid (TA) resistance bacterial strains were isolated from tannery effluent and identified as Bacillus subtilis (MCC 3275) and Bacillus safensis (MCC 3283) based on its 16S Ribosomal RNA homology. Hexavalent Cr is highly toxic and mutagenic due to its high mobility and reactivity. Whereas, TA is known to inhibit enzyme activity, substrate deprivation, and interaction with membranes and matrix-metal ions. The developed In vitro co-cultured microcosm of B. subtilis and B. safensis was able to remove Cr(VI) up to 95% and TA up to 23%. The bacteria cultures separately were able to degrade Cr(VI) to 88% by B. subtilis and 91% by B. safensis and TA up to 27%. Plackett Burman design (PBD) followed by Response surface methodology (RSM) was applied for the optimization of physio-chemical parameters. The optimized conditions for co-culture development were recorded as K2HPO4 = 0.2 g/L, MgSO4 = 0.2 g/L, NH4Cl = 0.5 g/L, glucose - 0.2 g/L, TA - 5%, Cr = 200 ppm, incubation period of 96 h, agitation speed of 110 rpm, pH = 5.0, temperature= 30 °C and inoculum size = 3%. Scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) revealed the thorough mechanism of cellular uptake followed by degradation of Cr(VI) and TA. The efficiency of co-culture for other heavy metals was observed as follows: Zn 65%, Pb 63%, Cd 65%, and Ni 65%. Bioremediation using bacteria is an economical and environmentally better alternative to conventional remediation methods. The isolated bacteria are useful in the effluent treatment of tannery or related industries and in metal recovery in mining processes.


Assuntos
Bacillus subtilis/metabolismo , Bacillus/metabolismo , Cromo/metabolismo , Taninos/metabolismo , Poluentes Químicos da Água/metabolismo , Poluição Química da Água/prevenção & controle , Biodegradação Ambiental , Resíduos Industriais/análise
20.
Ecotoxicol Environ Saf ; 208: 111506, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33120269

RESUMO

Chromium (Cr) pollution in soil is a global problem owing to its wide industrial use. The mobility, toxicity, and crop uptake of Cr depends on its valence state. Cr(VI) is highly mobile and toxic whereas Cr(III) is generally considered immobile and less toxic. We performed a pot experiment to investigate the combined effects of rice straw-derived biochar and water management on transformation of Cr and its uptake by rice in contaminated soils. The main plots had water management treatments of alternating wetting and drying (AWD) and continuous flooding (CF), and the subplots had three levels of straw biochar (0, 5, and 10 g kg-1). The results showed that water management and the addition of biochar had a significant effect on the dynamics of soil redox potential (Eh), pH, dissolved organic carbon (DOC), and Fe(II) concentration. As these parameters are important factors affecting Cr transformation in paddy soils, the dynamics of the Cr(III) and Cr(VI) concentrations were clearly different under different treatments. The highest reduction of Cr(VI) was observed in the treatment with CF water management in combination with 10 g kg-1 of biochar amendment, which resulted in a 62% reduction of Cr(VI) to Cr(III) in soil. The alterations in the oxidation state of Cr greatly affected its accumulation in the rice grains. The CF combined with 10 g kg-1 of biochar treatment, caused the Cr concentration in rice grains to be 66.2% lower compared with that of the unamended control under AWD water management. Possibly owing to the reduction in phytotoxic effects of Cr(VI), the combined treatment showed an improvement in rice grain weight. In conclusion, the combination of 10 g kg-1 of biochar amendment and CF water management may potentially be used in Cr-contaminated soil to mitigate the impacts of Cr contamination on rice production.


Assuntos
Irrigação Agrícola/métodos , Carvão Vegetal/metabolismo , Cromo/metabolismo , Oryza/metabolismo , Poluentes do Solo/metabolismo , Biotransformação , Cromo/análise , Cromo/química , Grão Comestível/química , Grão Comestível/metabolismo , Inundações , Oryza/química , Oxirredução , Solo/química , Poluentes do Solo/análise , Poluentes do Solo/química
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