Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 2.271
Filtrar
1.
Chemosphere ; 239: 124792, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526998

RESUMO

We systematically investigated the surface characteristics of polystyrene microplastic particles (PSMPs) prepared by ball milling to impart a porous surface structure and special surface characteristics, and studied the mechanism of adsorption of As(III) onto PSMPs. The sizes of the PSMPs prepared by ball milling for 2, 4, and 8 h were in the ranges of 0.1-1, 1-10, and 10-100 µm, respectively. That is, the longer the milling time is, the larger the specific surface area of the particles is. Moreover, the higher the point of zero charge is, the higher the adsorbed amount of As(III) is. The highest adsorption rate of As(III) onto PSMPs was found to be 1.12 mg g-1. After 1200 min, the adsorption reached equilibrium, and a pseudo-second-order model better fitted the As(III) adsorption kinetics. The Langmuir and Freundlich models could well describe the adsorption isotherms. Furthermore, hydrogen bonds between As(III) and PSMPs were broken at high temperatures, resulting in a decrease in As(III) adsorption onto PSMP, which indicated that the adsorption process was exothermic. Increases in the pH and concentrations of interfering nitrate and phosphate ions in the solution led to inhibited As(III) adsorption of PSMPs. The electrostatic potential of most areas of the PSMP surface was positive, and the H atom on the carboxyl group exhibited a very large positive potential (+56.6 kcal/mol), and thus attracted arsenic oxyanions. Thus, it was determined that As(III) adsorbed to the surface of PSMPs through hydrogen bonding with the carboxyl group. Electrostatic forces and non-covalent interactions are the key mechanisms affecting the adsorption of As(III) onto PSMPs. This work provides a clear theoretical basis for the behavior of the PSMP as an arsenic carrier and might aid to improve the environmental toxicity of arsenic.


Assuntos
Arsênico/química , Poliestirenos/química , Adsorção , Ligações de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Nitratos/química , Tamanho da Partícula , Fosfatos/química , Salinidade , Eletricidade Estática , Propriedades de Superfície , Temperatura Ambiente , Poluentes Químicos da Água/química
2.
Chemosphere ; 239: 124781, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514006

RESUMO

Variation in arsenolipid concentrations was assessed in 18 seafood samples including fish, shellfish, and crustaceans purchased in Japan. Analyses were performed by high performance liquid chromatography-inductively coupled plasma mass spectrometry/electrospray ionization tandem mass spectrometry. Stable isotope ratios for nitrogen and carbon were also measured in the samples for obtaining trophic level information of the species. Arsenic-containing hydrocarbons (AsHCs) and arsenic-containing fatty acids (AsFAs) were detected in the seafood samples; the toxic AsHCs were found in all of the seafood samples with large variation in the concentrations (83 ±â€¯73 ng As/g fw, coefficient of variation = 88%). Our previous point estimate of health risk of AsHCs intake via seafood consumption in Japan, based on average AsHC concentration in seafood, suggested insignificant risk, and the present study supports our previous estimate. AsHC concentrations significantly correlated with lipid content of the seafood samples (r = 0.67, p < 0.01), a result expected because of the fat solubility of the compounds. The AsHCs concentrations, however, were not significantly correlated with nitrogen stable isotope ratios suggesting that AsHCs do not biomagnify. The source of the observed large variation in AsHC concentrations will be the subject of further investigation.


Assuntos
Arsênico/análise , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Animais , Arsênico/química , Cromatografia Líquida de Alta Pressão/métodos , Ácidos Graxos/análise , Ácidos Graxos/química , Peixes , Japão , Lipídeos/análise , Lipídeos/química , Isótopos de Nitrogênio/análise , Alimentos Marinhos/análise , Frutos do Mar/análise , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem
3.
Chemosphere ; 240: 124871, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31546186

RESUMO

In Paracatu, a city in Minas Gerais State (Brazil), the gold mineral extraction produces wastes that contribute to environmental contamination by arsenic. This work describes the evaluation of arsenic concentration from soil of a gold mining area in Paracatu and the selection of arsenic resistant bacteria. In the process of culturing enrichment, 38 bacterial strains were isolated and the minimum inhibitory concentration (MIC) was determined in solid medium for each strain. Three bacterial strains named P1C1Ib, P2Ic and P2IIB were resistant to 3000 mg L-1 of arsenite. Analysis of 16S rDNA gene sequences revealed that these bacteria belong to Bacillus cereus and Lysinibacillus boronitolerans species. After cultivation of the strains P1C1Ib, P2Ic and P2IIIb, 69.38%-71.88% of arsenite and 82.39%-85.72% of arsenate concentrations were reduced from the culture medium, suggesting the potential application of theses strains in bioremediation processes.


Assuntos
Arsênico/química , Bioacumulação/efeitos dos fármacos , Ouro/química , Mineração/métodos , Bactérias/genética , Brasil
4.
Chemosphere ; 239: 124823, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726520

RESUMO

Several studies have demonstrated that gypsum (CaSO4·2H2O) and calcite (CaCO3) can be important hosts of arsenic in contaminated hydrogeological systems. However, the extent to which microbial reducing processes contribute to the dissolution and transformation of carbonate and sulfate minerals and, thereby, to arsenic mobilization is poorly understood. These processes are likely to have a strong impact on arsenic mobility in iron-poor environments and in reducing aquifers where iron oxyhydroxides become unstable. Anoxic batch bioassays with arsenate (As(V)) coprecipitated with calcite, gypsum, or ferrihydrite (Fe(OH)3) were conducted in the presence of sulfate or molybdate to examine the impact of bioprocesses (i.e. As(V), sulfate, and Fe(III)-reduction) on arsenic dissolution, speciation, and eventual remineralization. Microbial reduction of As(V)-bearing calcite caused an important dissolution of arsenite, As(III), which remained in solution up to the end of the experiment (30 days). The reduction of As(V) from gypsum-As(V) also led to the release of As(III), which was subsequently remineralized, possibly as arsenic sulfides. The presence of sulfate triggered arsenic dissolution in the bioassays with ferrihydrite-As(V). This study showed that although gypsum and calcite have a lower capacity to bind arsenic, compared to iron oxides, they can play a critical role in the biogeochemical cycle of arsenic in natural calcareous and gypsiferous systems depleted of iron since they can be a source of electron acceptors for reducing bioprocesses.


Assuntos
Arsênico/química , Bactérias/metabolismo , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Compostos Férricos/química , Arseniatos/química , Arsenicais/química , Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Ferro/química , Molibdênio/química , Oxirredução , Solubilidade , Sulfatos/química , Sulfetos/química
5.
Sci Total Environ ; 701: 134363, 2020 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-31706211

RESUMO

Heavy metals (e.g., arsenic (As)) and tetracycline (TC) usually coexist in wastewater from livestock farm, whereas the co-adsorption behaviours and mechanisms of As(V) and TC were not well-known. This study investigated the adsorption and co-adsorption of As(V) and TC by a novel yttrium-immobilized-graphene oxide-alginate hydrogel (Y-GO-SA) to explore the adsorption behaviours and mechanisms. The adsorption of As(V) and TC was pH-dependent. The maximum adsorption capacities under the studied concentrations were 273.39 mg/g for As(V), and 477.9 mg/g for TC, respectively, which are much higher than many other reported adsorbents. Furthermore, As(V) adsorption was due to ion exchange between hydroxyl groups and H2AsO42- groups and H-bonds formed with O-containing groups on Y-GO-SA, and the adsorption of TC by Y-GO-SA was mainly ascribed to electrostatic interaction, H-bonds, π - π EDA interaction, n-π EDA interaction, and cation-bonding bridge effects. The co-adsorption of As(V) and TC in binary system indicated that the presence of TC obviously suppressed the adsorption of As(V) due to the competition for active sites, whereas the effect of presence of As(V) on adsorption of TC can be negligible due to the balance contributions from its contrary effects, i.e. enhancement (anion-π interaction) and reduction (competition for Y ions) in TC adsorption. Finally, the hydrogels performed well in the treatment of livestock farm waste water. It can be anticipated that the prepared 3D hydrogel can be used as a powerful adsorbent in the practical application of waste water treatment, owing to its easy separation, high adsorption and good reusability.


Assuntos
Arsênico/química , Grafite/química , Tetraciclina/química , Poluentes Químicos da Água/química , Adsorção , Hidrogéis , Cinética , Eliminação de Resíduos Líquidos , Águas Residuárias/química
6.
Cell Physiol Biochem ; 53(6): 910-920, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31769258

RESUMO

BACKGROUND/AIMS: Exposure to heavy metals is today a threat to society. The understanding of the molecular processes related to diseases related to exposure to metals mixture involve changes in the expression of microRNAs. Changes on microRNAs expression may alter several cellular processes, among them, DNA repair inhibition has been described as an essential event leading to the initiation of metal-induced carcinogenesis. METHODS: We evaluate the miR-222 expression in the two-stage transformation Balb/c 3T3 cell assay treated with As-Cd-Pb mixture. RESULTS: We could appreciate that up-regulation of miR-222 reduces the expression both gene and as a protein expression of Rad51c by RT-PCR and immunoblot, respectively. CONCLUSION: Here, we demonstrate that the mixture of As-Cd-Pb at epidemiologically relevant concentrations induces miR-222 up-regulation, which directly negatively regulates Rad51c expression and impairs homologous recombination of DNA during the initiation stage of cell transformation. This inhibition triggers morphological transformation in a murine two-stage Balb/c 3T3 cell assay, suggesting that this small RNA acts as an initiator of the carcinogenesis process.


Assuntos
Transformação Celular Neoplásica/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Metais Pesados/farmacologia , MicroRNAs/metabolismo , Rad51 Recombinase/metabolismo , Animais , Antagomirs/metabolismo , Arsênico/química , Células 3T3 BALB , Cádmio/química , Sobrevivência Celular/efeitos dos fármacos , Quebras de DNA de Cadeia Dupla/efeitos dos fármacos , Chumbo/química , Camundongos , MicroRNAs/antagonistas & inibidores , MicroRNAs/genética , Rad51 Recombinase/genética
7.
Environ Monit Assess ; 191(10): 602, 2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31478102

RESUMO

Globally, millions of tons of coal fly ash (CFA) are generated per year, and the majority of this material is usually stored in stock piles or landfills, and in a long-term, it can be an environmental hazard if rainwater infiltrates the ashes. Long-term leaching studies of Brazilian ashes are scarce. The purpose of this study was to evaluate arsenic, cadmium, molybdenum, lead, and zinc leaching behavior from a Brazilian CFA by a column experiment designed to simulate field conditions: slightly acid rain considering seasonality of precipitation and temperature for a long-term leaching period (336 days). All elements were leached from CFA, except lead. Elements leaching behavior was influenced by leaching time, leaching volume, and temperature. Higher leachability of As and Cd from CFA during warm and wet season was observed. Results indicate a potential risk to soil and groundwater, since ashes are usually stored in uncovered fields on power plants vicinity.


Assuntos
Cinza de Carvão/química , Monitoramento Ambiental , Metais Pesados/análise , Arsênico/análise , Arsênico/química , Brasil , Cádmio/análise , Cádmio/química , Água Subterrânea , Chumbo/análise , Chumbo/química , Molibdênio/análise , Molibdênio/química , Centrais Elétricas , Solo/química , Instalações de Eliminação de Resíduos , Zinco/análise , Zinco/química
8.
J Environ Sci (China) ; 85: 168-176, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471023

RESUMO

Cadmium (Cd) and arsenic (As) are two of the most toxic elements. However, the chemical behaviors of these two elements are different, making it challenging to utilize a single adsorbent with high adsorption capacity for both Cd(II) and As(V) removal. To solve this problem, we synthesized HA/Fe-Mn oxides-loaded biochar (HFMB), a novel ternary material, to perform this task, wherein scanning electron microscopy (SEM) combined with EDS (SEM-EDS) was used to characterize its morphological and physicochemical properties. The maximum adsorption capacity of HFMB was 67.11 mg/g for Cd(II) and 35.59 mg/g for As(V), which is much higher compared to pristine biochar (11.06 mg/g, 0 mg/g for Cd(II) and As(V), respectively). The adsorption characteristics were investigated by adsorption kinetics and the effects of the ionic strength and pH of solutions. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) revealed that chelation and deposition were the adsorption mechanisms that bound Cd(II) to HFMB, while ligand exchange was the adsorption mechanism that bound As(V).


Assuntos
Arsênico/química , Cádmio/química , Poluentes Ambientais/química , Carvão Vegetal , Óxidos/química
9.
J Environ Sci (China) ; 85: 66-73, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31471032

RESUMO

Arsenic (As) mobilization in soils is a fundamental step controlling its transport and fate, especially in the presence of the co-existing components. In this study, the effect of two commonly used herbicides, glyphosate (PMG) and dicamba, and two competing ions including phosphate and humic acid, on As desorption and release was investigated using batch and column experiments. The batch kinetics results showed that As desorption in the presence of competing factors conformed to the pseudo-second order kinetics at pH range of 5-9. The impact of phosphate on desorption was greatest, followed by PMG. The competitive effect of dicamba and humic acid was at the same level with electrolyte solution. In situ flow cell ATR-FTIR analysis was performed to explore the mechanism of phosphate and PMG impact on As mobilization. The results showed that PMG promoted As(III) desorption by competiting for available adsorption sites with no change in As(III) complexing structure. On the other hand, phophate changed As(III) surface complexes from bidentate to monodentate structures, exhibiting the most siginficant effect on As(III) desorption. As(V) surface complexes remained unchanged in the presence of PMG and phosphate, implying that the competitive effect for As(V) desorption was primarily determined by the available adsorption sites. Long-term (10 days) soil column experiments suggested that the effect of humic acid on As mobilization became pronounced from 3 days (18 PVs). The insights of this study help us understand the transport and fate of As due to herbicides application.


Assuntos
Arsênico/química , Herbicidas/química , Poluentes do Solo/química , Adsorção , Substâncias Húmicas , Cinética , Solo/química
10.
Artigo em Inglês | MEDLINE | ID: mdl-31397623

RESUMO

The kinetic, isotherm and thermodynamic modeling of the adsorption of arsenite by layered double hydroxide have been performed to analyze the feasibility, efficacy and mechanism of the system. The fast uptake was observed during the initial phase of the process, which reached equilibrium at 240 min following Elovich model. The diffusion kinetic model exhibited that the rate-limiting step of adsorption was controlled by film diffusion as well as intraparticle diffusion. The isotherm modeling revealed the applicability of the Freundlich equation with the Kf values as 8.19-13.99 (mg g-1)(L mg-1)1/n at 283-323 K showing the increasing trend of adsorption capacity, which was further confirmed by the positive value of ΔH0 (9.49 kJ mol-1) demonstrating the endothermic nature of the adsorption process. The spontaneous nature of the adsorption reaction was established by the negative values of ΔG0. Application of the calcined Mg-Fe-LDH adsorbent for the removal of arsenic from real arsenic contaminated groundwater was also successfully performed. The effect of process parameters of the adsorption system was modeled by an artificial neural network (ANN) for adsorption capacity and removal efficiency. The optimized model exhibited high R2, F-value and low values of error functions, establishing the significant applicability of the ANN model.


Assuntos
Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Hidróxidos/química , Ferro/química , Magnésio/química , Adsorção , Arsênico/química , Difusão , Concentração de Íons de Hidrogênio , Cinética , Modelos Químicos , Termodinâmica , Poluentes Químicos da Água/química , Purificação da Água
11.
Chemosphere ; 237: 124503, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31398610

RESUMO

The coprecipitation of arsenic with Fe(III) by lime neutralization is widely used in industrial practices to treat arsenic-containing waste waters generated from mineral processing operations. In this work, coprecipitation was conducted directly at pH 8 to simulate the operations in hydrometallurgical practices, which differed from the conventional laboratory operations. Moreover, although ferric is the major species of iron in arsenic-containing waste waters, the coexistence of ferrous ions cannot be ignored. Therefore, the effect of different neutralization modes, as well as the effect of ferrous ions on the removal of arsenic and the stability of the generated arsenic-bearing wastes, was systematically investigated. The result showed that arsenic was still released back into the liquid phase under alkaline conditions even for the samples formed directly at alkaline pH. It was found that the extra addition of Fe(II) may exert negative effect on the stability of the as-formed Fe(II)-Fe(III)-As(V) coprecipitates at pH 7 - 10. The concentration of ferrous ions in the liquid/solid phase decreased with increasing pH for each sample formed at different Fe(II)/Fe(tot). The results indicated that complete oxidation of the ferrous ions before coprecipitation with arsenic should be conducted to achieve optimal stability of the arsenic-bearing wastes for hydrometallurgical practice and waste disposal.


Assuntos
Arsênico/química , Ferro/química , Compostos de Cálcio , Compostos Férricos , Compostos Ferrosos , Concentração de Íons de Hidrogênio , Minerais , Oxirredução , Óxidos
12.
Environ Pollut ; 254(Pt A): 112950, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31394339

RESUMO

Microplastics exhibit active environmental behavior and unique surface characteristics, and act as carriers for the migration of trivalent arsenic (As(III)) in the environment. Herein, the mechanism by which polytetrafluoroethylene (PTFE) microplastic particles adsorb As(III) is systematically determined. The larger the size of PTFE particles, the smaller the specific surface area, the higher the point of zero charge (PZC), and the more unfavorable adsorption of As(III); the highest adsorption amount can reach 1.05 mg g-1. The adsorption process can be divided into three stages by the intraparticle diffusion model: external mass transfer, intraparticle diffusion, and dynamic equilibrium, of which the external mass transfer stage is the adsorption rate-limiting stage. The Langmuir isotherm model better represented the equilibrium adsorption results. The adsorption of As(III) by PTFE was an exothermic process, and because the increase in temperature broke the hydrogen bond, the amount of adsorption was decreased, which was not conducive to spontaneous adsorption. In the pH range of 3-7, as the pH value increased, the amount of As(III) adsorbed by PTFE gradually decreased, which may be related to the change in PZC for PTFE and the protonation of As(III). The H on the surface hydroxyl group of the PTFE exhibited a very large positive potential (+82.37 kcal mol-1). Thus, it can attract the arsenic oxyanion, and As(III) was subsequently adsorbed on the surface of the PTFE through the hydrogen bond on the hydroxyl group. Electrostatic force and non-covalent interaction were the key mechanisms affecting the PTFE adsorption.


Assuntos
Arsênico/química , Politetrafluoretileno/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Plásticos , Temperatura Ambiente
13.
Mar Pollut Bull ; 146: 377-386, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31426170

RESUMO

The effects of nutrient distribution and structure on the behavior and speciation of dissolved inorganic arsenic (DIAs) in coastal waters were analyzed based on the data of 48 surface water samples collected in the southwestern coast of Laizhou Bay and its adjacent rivers (SWLZB). The concentration of DIAs in the SWLZB ranged from 0.016 to 0.099 µmol l-1 and generally decreased from west to south. The inshore waters exhibited higher DIAs level than the open ocean. The As5+/As3+ ratio was significantly positively correlated with the concentration of TDN, NO3-N, PO4-P, DSi, Chl-a and DO. The concentration of DIAs was strongly correlated with the concentration of PO4-P and DSi, suggesting that adsorption/desorption was an important process for regulating the total DIAs concentration. The results indicated that the distribution of nutrients might well be an important environmental factor affecting the speciation and behavior of DIAs in surface water of the SWLZB.


Assuntos
Arsênico/análise , Água do Mar/química , Poluentes Químicos da Água/análise , Arsênico/química , Baías , China , Clorofila A/análise , Monitoramento Ambiental , Concentração de Íons de Hidrogênio , Nitratos/análise , Nitrogênio/análise , Nutrientes/análise , Fosfatos/análise , Fósforo/análise , Rios/química , Água do Mar/análise , Poluentes Químicos da Água/química
14.
Sci Total Environ ; 689: 1037-1043, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31466144

RESUMO

Dissolved organic matter (DOM) elucidated from biochars enhances the dissolution of iron oxides and reduction of iron. However, given that reduction mechanism of iron (Fe(III)) in the practical biochar applications for soil amendment and environmental remediation have not been fully elucidated, this study laid great emphasis on the photo-induced Fe(II) liberated from DOM-Fe(III) complexes. Thus, pyrolysis of biomass was carried out at 300 °C to maximize DOM release from biochars. Moreover, three different biomass samples (rice straw (R), granular sludge (G) from an anaerobic digester, and spent coffee grounds (C)) were chosen as carbon substrates for biochars preparation. To demonstrate the transformation of Fe(III), 1 and 5 wt% biochar was applied to the clean (S1) and arsenic-contaminated (S2) soil with/without the light. The results indicate that the light condition produces more Fe(II). The amount of Fe(II) accounts for 25.3, 28.6, and 30.7% of total iron under the light with 5 wt% GB, RB, and CB in S1, and 10.6, 13.1, and 13.8% in S2. This study demonstrates that Fe(II) is generated more under ultraviolet irradiation than visible light and dark condition. In addition, a control experiment without biochar showed that DOM plays an important role in the reduction of Fe(III). The mobility of arsenic increased under the light condition since the intermediates of DOM photo-degradation accelerates the dissolution of iron oxides and arsenic competes with DOM for the adsorption. Therefore, there was no significant correlation between the elution of arsenic and the formation of Fe(II) during the reductive dissolution of iron oxide under the light condition.


Assuntos
Arsênico/análise , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/análise , Adsorção , Arsênico/química , Biomassa , Carbono , Carvão Vegetal/química , Compostos Férricos , Ferro/química , Oryza , Oxirredução , Solo/química , Poluentes do Solo/química
15.
Environ Sci Pollut Res Int ; 26(28): 29234-29245, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31396866

RESUMO

To conduct a comprehensive ecological analysis on the solid residues derived from the thermal disposal of hyperaccumulator Pteris vittata, this study focused on the behaviors of As and Pb and the characteristics of environmentally persistent free radicals (EPFRs) in the solid residues under different thermal treatment conditions. The analysis results revealed that the concentrations of As in the biochars and bio-slag were approximately 350 and 1100 mg/kg, respectively. Moreover, the concentrations of Pb in the solid residues varied from 34 to 1050 mg/kg. According to the results of the modified BCR sequential extractions, As is more stable in the biochar while Pb is more stable in the combustion slags. In addition, As showed a higher volatilization temperature compared with Pb. The ecological risk assessment indicated that the correlation index between the contamination factor (Cf) of As and the risk index (R2 = 0.995) is considerably larger than the correlation index between the contamination factor of Pb and the risk index (R2 = 0.117), which implies that the pyrolysis method should be selected at priority. Moreover, the EPFR concentrations of the biochar declined by approximately 75 times when the pyrolysis temperature increased from 500 to 600 °C. This behavior indicated that high-temperature pyrolysis (> 600 °C) could simultaneously control both the heavy metal behavior and EPFR concentrations.


Assuntos
Carvão Vegetal/química , Radicais Livres/química , Metais Pesados/análise , Pteris/química , Gerenciamento de Resíduos/métodos , Arsênico/análise , Arsênico/química , Biodegradação Ambiental , Radicais Livres/análise , Chumbo/análise , Chumbo/química , Metais Pesados/química , Pirólise , Fatores de Risco , Poluentes do Solo/análise , Temperatura Ambiente , Termogravimetria , Volatilização
16.
Chemosphere ; 237: 124465, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31374397

RESUMO

Arsenic (As) is a toxic element can experience phase and speciation changes during the early diagenesis of sediments across the sediment-water interface, affecting its mobility and toxicity. Maharlu Lake is a hypersaline lake in Southern Iran that today receives significant inflow from urban, industrial and agricultural wastewater. A 1-m core was sampled from the lake sediment in an area far away from the major inflows. We performed a semi-quantitative analysis of the elemental composition, and a quantitative analysis of the total As concentration, pH, loss on ignition, water content, salt content, and grain size distribution to characterize changes in sediment composition with depth and their influence on the variability of As partitioning and speciation. Nine characterized lithologies were selected for a sequential As extraction analysis to study the vertical variations in phase and speciation of As in the heterogenic lithologies. Total As concentrations range from 1.0 µg g-1 to 13.6 µg g-1. As is present mostly in HNO3 and HCl extractable fractions with As5+ being the predominant species. As3+ was mostly found in phosphate and NH2OH·HCl extractable fractions. The concentration of mobile As fractions generally decrease with depth. It seems that the As stored in volatile sulfides and very poorly crystalline Fe and Al hydr-oxides in the shallow sediment transforms to sulfides phases during burring. Our findings show that the mobility and toxicity of As decreases during early diagenetic processes in Maharlu lake. However, the As can be remobilized either via changes in the redox conditions in the lake.


Assuntos
Arsênico/química , Sedimentos Geológicos/química , Lagos/química , Poluentes Químicos da Água/química , Arsênico/análise , Monitoramento Ambiental , Sedimentos Geológicos/análise , Concentração de Íons de Hidrogênio , Irã (Geográfico) , Ferro/química , Lagos/análise , Óxidos/química , Fosfatos/química , Sulfetos/química , Poluentes Químicos da Água/análise
17.
Environ Monit Assess ; 191(8): 528, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31367959

RESUMO

The distribution and bioavailability of arsenic (As) in indoor/outdoor total suspended particulates (TSP), inhalable particulate matters (PM10), and fine particulate matters (PM2.5) in Baoding, China were investigated. The average I/O ratios for TSP, PM10, and PM2.5 were 0.52, 0.66, and 0.96, respectively. There was no significant correlation between indoor/outdoor TSP, PM10, and PM2.5. The indoor/outdoor concentrations of As surpassed the limited value of As. I/O ratios of arsenic in TSP, PM10, and PM2.5 were 0.52, 0.58, and 0.55, respectively. The contents of arsenic in different fractions were mainly affected by the total concentrations of arsenic in particulate matters (PM) rather than the particle sizes for TSP and PM10. Arsenic was mainly in non-specifically sorbed fraction (F1) in both indoor and outdoor PM2.5. The evaluated carcinogenic risk (CR) was within the safe level. The bioavailability of As increased with particle size decreasing for both indoor and outdoor PM. The potential bioavailability of As in outdoor particles was higher than that of indoor particles with the same size, especially PM2.5.


Assuntos
Poluentes Atmosféricos/análise , Arsênico/análise , Material Particulado/química , Poluentes Atmosféricos/química , Poluição do Ar em Ambientes Fechados/análise , Arsênico/química , China , Monitoramento Ambiental , Humanos , Tamanho da Partícula , Material Particulado/análise
18.
Chemosphere ; 233: 946-953, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31340422

RESUMO

Scorodite is an important mineral not only for arsenic (As) removal from industrial wastewaters but also in the mobility and final fate of As in waste rocks, contaminated soils and sediments, and mine tailings. Because of the mineral's high As-loading capacity and stability, numerous studies have been done to understand its formation. Unfortunately, most of these studies were limited to elevated temperatures (>70 °C), so the processes involved in scorodite formation under ambient conditions remain unclear. This study provides evidence of the catalytic effects of hematite on the formation of scorodite at 25 °C in a pyrite-rich natural geologic material. Scorodite peaks were detected in the XRD patterns of the leaching residues with and without hematite, but those in the former were stronger and more pronounced than the latter. These results suggest that the formation of scorodite was catalysed by hematite, a generalisation that is further supported by strong characteristic IR absorption bands of scorodite at 819 cm-1 (As-O bending vibration), 785 and 725 cm-1 (As-O stretching vibrations), and 2990 cm-1 (OH-vibration) as well as the distinct XPS binding energies of Fe(III)-As (709.7 eV), As(V)-O (44.8, 44.31 and 43.7 eV), O2- (530.5 eV) and coordinated water (531.3 eV) in scorodite. This phenomenon could be attributed to three possible mechanisms: (1) more rapid precipitation promoted by the "seeding" effect of hematite particles, (2) additional supply of Fe3+ from hematite dissolution under acidic conditions, and (3) enhanced oxidations of Fe2+ to Fe3+ and As(III) to As(V) on the surface of hematite.


Assuntos
Arsênico/química , Arsenicais/síntese química , Compostos Férricos/química , Águas Residuárias/química , Purificação da Água/métodos , Catálise , Ferro/química , Oxirredução , Poluentes do Solo/análise , Sulfetos/química , Poluentes Químicos da Água/análise
19.
Chemosphere ; 236: 124325, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31326754

RESUMO

Despite the knowledge of AS-induced reprotoxicity, the literature concerning arsenic trioxide (As2O3)-induced oxidative stress and consequent intracellular events, like autophagy process, in the hypothalamic-pituitary- gonadal (HPG) axis of F1- pubertal male mice is sparse to date. Hence, we made an attempt to study the reproductive toxicities and the underlying mechanisms induced by As2O3 in the HPG axis of pubertal F1- male mice in correlation with oxidative stress-induced autophagy. Parental mice were challenged with As2O3 (0, 0.2, 2, and 20 ppm) from five weeks before mating, and continued till puberty age for the male pups. It was recorded that higher As2O3 doses (2 and 20 ppm) were a potent inducer of oxidative stress and autophagy in the HPG axis. Concomitant with a decrease on mean body weight, total antioxidant capacity, and stereology indices, an increase in the number of MDC-labeled autophagic vacuoles, and MDA/GSH ratio in HPG axis of pubertal F1- male mice which were exposed to higher As2O3 doses was observed. Meanwhile, concomitant with a dose-dependent increment in the gene expression of ATG3, ATG5, Beclin, as well as protein expression of P62, ATG12, and Beclin in HPG axis tissues; a dose-dependent decrease in PI3K and mTOR gene expression was recorded in the HPG tissues of pubertal F1-males. Altogether, our observations suggest that higher doses of As2O3 have detrimental effects on the functionality of HPG axis in pubertal male mice offspring by increasing MDA/GSH ratio and autophagic cell death-related genes and proteins, as well as by reducing total antioxidant capacity.


Assuntos
Arsênico/toxicidade , Autofagia/efeitos dos fármacos , Filho de Pais Incapacitados/estatística & dados numéricos , Estresse Oxidativo/efeitos dos fármacos , Exposição Paterna/efeitos adversos , Animais , Arsênico/química , Masculino , Camundongos
20.
Int J Mol Sci ; 20(14)2019 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-31330881

RESUMO

As concerns about public health and environmental problems regarding contamination by toxic substances increase worldwide, the development of a highly effective and specific treatment method is imperative. Although physicochemical arsenic treatment methods have been developed, microbial in vivo remediation processes using live cell fabricated nanoparticles have not yet been reported. Herein, we report the development of magnetic iron nanoparticles immobilized an extremophilic microorganism, Deinococcus radiodurans R1, capable of removing toxic arsenic species. First, in vivo synthesis of magnetic iron nanoparticles was successfully achieved with the D. radiodurans R1 strain and characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), dynamic light scattering (DLS), zeta-potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Second, the maximum removal capacity of the magnetic iron nanoparticle-immobilized D. radiodurans R1 strain (DR-FeNPs) for arsenic [As(V)] was evaluated under the optimized conditions. Finally, the removal capacity of DR-FeNPs in the presence of various competitive anions was also investigated to simulate the practical application. More than 98% of As(V) was efficiently removed by DR-FeNPs within 1 h, and the removal efficiency was stably maintained for up to 32 h (98.97%). Furthermore, the possibility of recovery of DR-FeNPs after use was also suggested using magnets as a proof-of-concept.


Assuntos
Arsênico/química , Arsênico/metabolismo , Deinococcus/metabolismo , Nanopartículas de Magnetita/química , Adsorção , Ânions/química , Biodegradação Ambiental , Humanos , Nanopartículas de Magnetita/ultraestrutura , Análise Espectral
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA