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1.
Biodegradation ; 2020 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-32112297

RESUMO

This study describes the effects of graphene oxide (GO) and reduced graphene oxide (rGO) on the acetoclastic, hydrogenotrophic and methylotrophic pathways of methanogenesis by an anaerobic consortium. The results showed that GO negatively affected the hydrogenotrophic and acetoclastic pathways at a concentration of 300 mg/L, causing a decrease of ~ 38% on the maximum specific methanogenic activity (MMA) with respect to the controls lacking GO. However, the presence of rGO (300 mg/L) promoted an improvement of the MMA (> 45%) achieved with all substrates, except for the hydrogenotrophic pathway, which was relatively insensitive to rGO. The presence of either rGO or GO enhanced the methylotrophic pathway and resulted in an increase of the MMA of up to 55%. X-ray photoelectron spectroscopy (XPS) analysis revealed that GO underwent microbial reduction during the incubation period. Electrons derived from substrates oxidation were deviated from methanogenesis towards the reduction of GO, which may explain the MMA decreased observed in the presence of GO. Furthermore, XPS evidence indicated that the extent of GO reduction depended on the metabolic pathway triggered by a given substrate.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31905046

RESUMO

A method for the analysis of different species of antimony (Sb) that couples liquid chromatography with an inductively coupled plasma-optical emission spectrometry (LC-ICP-OES) system is presented. The method is simple and reliable to separate and quantify directly and simultaneously Sb(III) and Sb(V) in aqueous samples. The calibration curves showed high linearity at the three wavelengths tested. The limits of detection ranged from 24.9 to 32.3 µg/L for Sb(III) and from 36.2 to 46.0 µg/L for Sb(V), at the three wavelengths evaluated. The limit of detection for this method varied depending on the wavelength used. The lowest limit of quantification for Sb(V) (49.9 µg/L) and Sb(III) (80.7 µg/L) was obtained at a wavelength of 217.582 nm. The method sensitivity for Sb(V) was higher compared to Sb(III) at all the wavelengths considered. Samples containing different concentrations of Sb(III) and Sb(V) in three different matrices, i.e., water, basal culture medium, and anaerobic sludge plus basal medium, were analyzed. The coefficients of variation were low and ranged from 0.1 to 5.0 depending on the sample matrix. Recoveries of Sb(III) and Sb(V) were higher than 90% independently of the matrix analyzed and the wavelength used in the analysis.

3.
Artigo em Inglês | MEDLINE | ID: mdl-31607225

RESUMO

III-V semiconductor materials such as gallium arsenide (GaAs) and indium arsenide (InAs) are increasingly used in the fabrication of electronic devices. There is a growing concern about the potential release of these materials into the environment leading to effects on public and environmental health. The waste effluents from the chemical mechanical planarization process could impact microorganisms in biological wastewater treatment systems. Currently, there is only limited information about the inhibition of gallium- and indium-based nanoparticles (NPs) on microorganisms. This study evaluated the acute toxicity of GaAs, InAs, gallium oxide (Ga2O3), and indium oxide (In2O3) particulates using two microbial inhibition assays targeting methanogenic archaea and the marine bacterium, Aliivibrio fischeri. GaAs and InAs NPs were acutely toxic towards these microorganisms; Ga2O3 and In2O3 NPs were not. The toxic effect was mainly due to the release of soluble arsenic species and it increased with decreasing particle size and with increasing time due to the progressive corrosion of the NPs in the aqueous bioassay medium. Collectively, the results indicate that the toxicity exerted by the arsenide NPs under environmental conditions will vary depending on intrinsic properties of the material such as particle size as well as on the dissolution time and aqueous chemistry.

4.
Chemosphere ; 241: 124993, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31600622

RESUMO

Azoles are emerging contaminants that are resistant to biodegradation during wastewater treatment. Their presence has been widely reported in wastewater effluents and receiving waters. In this work, the potential inhibition of nitrification process by six different azole compounds in wastewater treatment plants was investigated in batch bioassays. The azoles studied included three diazoles: pyrazole (Pz); 1-methylpyrazole (MePz); 3,5-dimethylpyrazole (DMePz); and three triazoles: 1,2,4-triazole (Tz); benzotriazole (BTz); and 5-methyl benzotriazole (MeBTz). The concentration of azoles causing 50% inhibition (IC50) increased (azoles became less inhibitory) in the following order (mg L-1): BTz (1.99) < MeBTz (2.18) < Pz (2.69) < Tz (3.53) < DMePz (17.3) < MePz (49.6). No clear structure-inhibitory relationships were found using Log P and pKa as structural properties. The toxicity of any given azole may be related to the role of substituent groups on disabling/enabling binding to the active sites of metallo-enzymes in nitrifying microorganisms. This is exemplified by the low toxicity of MePz, which has a cyclic N blocked by a methyl group. The observed inhibition caused to nitrifying bacteria is more severe than their cytotoxicity to other target organisms (e.g., methanogens and heterotrophic bacteria), suggesting a specific inhibition to the copper-containing enzyme, ammonium monooxygenase, in ammonia oxidizing nitrifying microorganisms.


Assuntos
Azóis/farmacologia , Biodegradação Ambiental , Nitrificação/efeitos dos fármacos , Esgotos/microbiologia , Compostos de Amônio/metabolismo , Azóis/química , Azóis/toxicidade , Bactérias/metabolismo , Processos Heterotróficos , Triazóis/farmacologia , Águas Residuárias/química
5.
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
6.
Environ Sci Technol ; 53(21): 12648-12656, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31553579

RESUMO

3-Nitro-1,2,4-triazol-5-one (NTO) is one of the main ingredients of many insensitive munitions, which are being used as replacements for conventional explosives. As its use becomes widespread, more research is needed to assess its environmental fate. Previous studies have shown that NTO is biologically reduced to 3-amino-1,2,4-triazol-5-one (ATO). However, the final degradation products of ATO are still unknown. We have studied the aerobic degradation of ATO by enrichment cultures derived from the soil. After multiple transfers, ATO degradation was monitored in closed bottles through measurements of inorganic carbon and nitrogen species. The results indicate that the members of the enrichment culture utilize ATO as the sole source of carbon and nitrogen. As ATO was mineralized to CO2, N2, and NH4+, microbial growth was observed in the culture. Co-substrates addition did not increase the ATO degradation rate. Quantitative polymerase chain reaction analysis revealed that the organisms that enriched using ATO as carbon and nitrogen source were Terrimonas spp., Ramlibacter-related spp., Mesorhizobium spp., Hydrogenophaga spp., Ralstonia spp., Pseudomonas spp., Ectothiorhodospiraceae, and Sphingopyxis. This is the first study to report the complete mineralization of ATO by soil microorganisms, expanding our understanding of natural attenuation and bioremediation of the explosive NTO.


Assuntos
Substâncias Explosivas , Nitrocompostos , Biodegradação Ambiental , Núcleo Familiar , Estresse Oxidativo , Triazóis
7.
Int. microbiol ; 22(3): 305-316, sept. 2019. ilus, graf, tab
Artigo em Inglês | IBECS | ID: ibc-184837

RESUMO

Effluents from petroleum refineries contain a toxic mixture of sulfide, nitrogen, and phenolic compounds that require adequate treatment for their removal. Biological denitrification processes are a cost-effective option for the treatment of these effluents, but the knowledge on the microbial interactions in simultaneous sulfide and phenol oxidation in denitrifying reactors is still very limited. In this work, microbial community structure and macrostructure of granular biomass were studied in three denitrifying reactors treating a mixture of inorganic (sulfide) and organic (p-cresol) electron donors for their simultaneous removal. The differences in the available substrates resulted in different community assemblies that supported high removal efficiencies, indicating the community adaptation capacity to the fluctuating compositions of industrial effluents. The three reactors were dominated by nitrate reducing and denitrifying bacteria where Thiobacillus spp. were the prevalent denitrifying organisms. The toxicity and lack of adequate substrates caused the endogenous decay of the biomass, leading to release of organic matter that maintained a diverse although not very abundant group of heterotrophs. The endogenous digestion of the granules caused the degradation of its macrostructure, which should be considered to further develop the denitrification process in sulfur-based granular reactors for treatment of industrial wastewater with toxic compounds


No disponible


Assuntos
Águas Residuárias/microbiologia , Desnitrificação , Microbiota , Sulfetos/metabolismo , Cresóis/química , Bactérias/metabolismo , Indústria de Petróleo e Gás , Ciclo do Nitrogênio , Sulfetos/química , Nitratos/química , Thiobacillus/isolamento & purificação , Biomassa
8.
J Chem Technol Biotechnol ; 94(2): 468-474, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31105372

RESUMO

BACKGROUND: To help mitigate future problems in the supply of platinum group metals (PGM) due to their scarcity and high demand, new recovery processes must be developed. Microbial processes are a great alternative for the recovery of PGM from waste since they are clean and environmentally friendly techniques. This research studied the microbial reduction of Pt(II) using an anaerobic granular sludge under different physiological conditions. RESULTS: The anaerobic granular sludge was able to reduce Pt(II) to Pt(0) nanoparticles that were deposited intracellularly as well as extracellularly as confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Hydrogen (H2) and formate supported the chemical reduction of Pt(II) while ethanol supported the biologically catalyzed reduction of Pt(II). Increasing initial concentrations of Pt(II), ethanol or biomass were each shown to increase the Pt(II) reduction rates. CONCLUSIONS: This study reported for the first time the reduction of Pt(II) using anaerobic granular sludge and provided insights that could help develop biorecovery techniques to alleviate future problems in the supply of PGMs.

9.
Int Microbiol ; 22(3): 305-316, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30810994

RESUMO

Effluents from petroleum refineries contain a toxic mixture of sulfide, nitrogen, and phenolic compounds that require adequate treatment for their removal. Biological denitrification processes are a cost-effective option for the treatment of these effluents, but the knowledge on the microbial interactions in simultaneous sulfide and phenol oxidation in denitrifying reactors is still very limited. In this work, microbial community structure and macrostructure of granular biomass were studied in three denitrifying reactors treating a mixture of inorganic (sulfide) and organic (p-cresol) electron donors for their simultaneous removal. The differences in the available substrates resulted in different community assemblies that supported high removal efficiencies, indicating the community adaptation capacity to the fluctuating compositions of industrial effluents. The three reactors were dominated by nitrate reducing and denitrifying bacteria where Thiobacillus spp. were the prevalent denitrifying organisms. The toxicity and lack of adequate substrates caused the endogenous decay of the biomass, leading to release of organic matter that maintained a diverse although not very abundant group of heterotrophs. The endogenous digestion of the granules caused the degradation of its macrostructure, which should be considered to further develop the denitrification process in sulfur-based granular reactors for treatment of industrial wastewater with toxic compounds.


Assuntos
Cresóis/metabolismo , Microbiota , Nitratos/metabolismo , Esgotos/microbiologia , Sulfetos/metabolismo , Poluentes Químicos da Água/metabolismo , Reatores Biológicos/microbiologia , Biotransformação , Resíduos Industriais
10.
Chemosphere ; 222: 789-796, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30739063

RESUMO

Explosives, pesticides, and pharmaceuticals contain toxic nitroaromatic compounds that may form even more toxic azo compounds if they encounter reducing conditions in the environment. We investigated the mechanism by which 4,4'-dimethoxyazobenzene forms in anaerobic sludge incubations of 4-nitroanisole, an analog for the insensitive munitions compound 2,4-dinitroanisole (DNAN). Because studies have reported the mechanism to involve the coupling of reduced nitroaromatic intermediates, specifically aromatic amines and nitrosoaromatics, by nucleophilic processes, we abiotically paired 10 mM 4-aminoanisole with 2 mM 4-nitrosoanisole in nitrogen-flushed microcosms. However, only 7 µM of 4,4'-dimethoxyazobenzene had formed after 24 h. We identified the major product to be 4-methoxy-4'-nitrosodiphenylamine. Repeating this experiment in phosphate buffer at pH 5.1, 7.1, and 8.6 demonstrated that the formation of this unexpected product is acid catalyzed. We found that 4-methoxy-4'-nitrosodiphenylamine is more toxic than 4,4'-dimethoxyazobenzene to the bioluminescent bacterium Aliivibrio fischeri, with IC50 values of 0.1 µM and 0.5 µM, respectively. Both products are several orders of magnitude more toxic than reduced 4-nitroanisole intermediates 4-aminoanisole and 4-nitrosoanisole, as well as DNAN and its aromatic amine metabolites. Six-fold more 4,4'-dimethoxyazobenzene formed when we incubated 4-nitrosoanisole with ascorbic acid, a reducing agent, than when we incubated 4-nitrosoanisole with 4-aminoanisole in the absence of ascorbic acid. We therefore suspect that 4-hydroxylaminoanisole, the first reduction product of 4-nitrosoanisole, is a better nucleophile than 4-aminoanisole and couples more readily with 4-nitrosoanisole. Slightly basic and reducing conditions can prevent the formation and persistence of toxic coupling products on sites contaminated with nitroaromatics, i.e. DNAN-contaminated firing ranges.


Assuntos
Anisóis/química , Aliivibrio fischeri/efeitos dos fármacos , Aminas/química , Anisóis/toxicidade , Compostos Azo/química , Substâncias Explosivas/química , Substâncias Explosivas/toxicidade , Oxirredução , Esgotos/química
11.
J Chem Technol Biotechnol ; 93(6): 1611-1617, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30140114

RESUMO

Background: The future supply of platinum group metals (PGM) is at risk because of their scarcity combined with a high demand. Thus recovery of platinum (Pt) from waste is an option worthy of study to help alleviate future shortages. This research explored the microbial reduction of platinum (Pt). The ability of anaerobic granular sludge to reduce Pt(IV) ions under different physiological conditions was studied. Results: X-Ray diffraction (XRD) and transmission electron microscope (TEM) analyses demonstrated the capacity of the microbial mixed culture to reduce Pt(IV) to Pt(0) nanoparticles, which were deposited on the cell-surface and in the periplasmic space. Ethanol supported the biologically catalyzed Pt(IV) reduction, meanwhile other electron donors; hydrogen (H2) and formate, promoted the chemical reduction of Pt(IV) with some additional biological stimulation in the case of H2. A hypothesis is proposed in which H2 formed from the acetogenesis of ethanol is implicated in subsequent abiotic reduction of Pt(IV) indicating an integrated bio-chemical process. Endogenous controls also resulted in slow Pt(IV) removal from aqueous solution. Selected redox mediators, exemplified by riboflavin, enhanced the Pt(IV) reduction rate. Conclusion: This study reported for the first time the ability of an anaerobic granular sludge to reduce Pt(IV) to elemental Pt(0) nanoparticles.

12.
Waste Manag ; 77: 1-9, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30008399

RESUMO

Gallium arsenide (GaAs) is a material widely used in electronic devices. Disposal of electronic waste containing GaAs in municipal solid waste landfills raises concerns about the public health and ecological risks associated with the potential release of toxic arsenic (As) species. In this study, different tests were performed to investigate the leaching behavior of particulate GaAs in aqueous solutions. In the U.S. Toxicity Characteristic Leaching Procedure (TCLP) and California Waste Extraction Test (WET), the concentrations of As released from the GaAs particles were about 2.6-2.8-fold higher than the regulatory limit (5 mg/L). A much higher As concentration (72 mg/L), accounting for as much as 15.4% of the initial As in GaAs, was solubilized in a pH-7.6 synthetic landfill leachate under ambient atmosphere after 120 days. Additional tests performed to evaluate the dissolution of GaAs under a range of redox conditions, pH levels, ionic strength, and presence of organic constituents commonly found in landfills revealed that oxic environments and mildly alkaline conditions (pH 8.1-8.5) promote release of As (chiefly arsenite) and gallium species to the surrounding aqueous environment. The rate of As release in long-term exposure experiments was initially constant but later progressively diminished, likely due to the formation of a passivating layer on the surface of GaAs consisting of corrosion products rich in poorly soluble gallium oxides (Ga2O3 and Ga(OH)3). This hypothesis was confirmed by surface analysis of GaAs particles subjected to leaching using X-ray photoelectron spectroscopy (XPS). These findings suggest that further research is needed to assess the potential release of toxic As from electronic waste in municipal landfills.


Assuntos
Arsenicais/química , Gálio/química , Instalações de Eliminação de Resíduos , Arsênico , California , Poluentes Químicos da Água
13.
Environ Pollut ; 240: 200-208, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29738948

RESUMO

The emerging insensitive munitions compound (IMC) 3-nitro-1,2,4-triazole-5-one (NTO) is currently being used to replace conventional explosives such as 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), but the environmental fate of this increasingly widespread IMC remains poorly understood. Upon release from unexploded solid phase ordinances, NTO exhibits high aqueous solubility and, hence, potential mobilization to groundwater. Adsorption and abiotic transformation at metal oxide surfaces are possible mechanisms for natural attenuation. Here, the reactions at ferrihydrite and birnessite surfaces of NTO and its biotransformation product, 3-amino-1, 2, 4-triazol-5-one (ATO), were studied in stirred batch reactor systems at controlled pH (7.0). The study was carried out at metal oxide solid to solution ratios (SSR) of 0.15, 1.5 and 15 g kg-1. The samples were collected at various time intervals up to 3 h after reaction initiation, and analyzed using HPLC with photodiode array and mass spectrometric detection. We found no detectable adsorption or transformation of NTO upon reaction with birnessite, whereas ATO was highly susceptible to oxidation by the same mineral, showing nearly complete transformation within 5 min at 15 g kg-1 SSR to urea, CO2(g) and N2(g). The mean surface-area-normalized pseudo-first order rate constant (k) for ATO oxidation by birnessite across all SSRs was 0.05 ±â€¯0.022 h-1 m-2, and oxidation kinetics were independent of dissolved O2 concentration. Both NTO and ATO were resistant to oxidation by ferrihydrite. However, NTO showed partial removal from solution upon reaction with ferrihydrite at 0.15 and 1.5 g kg-1 SSR and complete loss at 15 g kg-1 SSR due to strong adsorption. Conversely, ATO adsorption to ferrihydrite was much weaker than that measured for NTO.


Assuntos
Substâncias Explosivas/química , Modelos Químicos , Nitrocompostos/química , Triazóis/química , Adsorção , Amitrol (Herbicida) , Biotransformação , Compostos Férricos/química , Água Subterrânea , Cinética , Nitrocompostos/análise , Oxirredução , Óxidos/química , Triazóis/análise , Ureia
14.
Ultrason Sonochem ; 45: 213-222, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29705315

RESUMO

Aqueous film-forming foams (AFFFs) contain a mixture of organic chemicals, including per- and poly-fluorinated, alkyl sulfonate substances (PFAS) (1-5%, w/w). Some longer-chain PFAS can be toxic, moderately bioaccumulative and persistent in the environment. In the present work, decomposition of PFAS present in two commercially available AFFFs (ANSUL- and 3M-) was investigated using a sono-chemical reactor of volume 91 L. The reactor consists of 12 transducers with operating frequencies of 1 MHz or 500 kHz and total input power of 12 kW. Degradation of PFASs performed using various dilutions of AFFF revealed that release of F- and SO4-2 ions was inversely proportional to initial pH of up to 4. Defluorination of ANSUL-AFFF resulted in an increase in the concentration of F- released from 55.6 ±â€¯0.3 µM (500× dilution) to 58.6 ±â€¯0.6 (25× dilution), while for 3M AFFF it increased from 19.9 ±â€¯0.7 µM (500× dilution) to 217.1 ±â€¯2.4 µM (25× dilution). Though amounts of F- released were less for ANSUL-AFFF than for 3M-AFFF, there was a considerable increase in removal of TOC and release of SO4-2 present in ANSUL-AFFF. Approximately 90.5% and 26.6% reduction of perfluoroalkyl sulfonates (PFSA) and perfluoroalkyl carboxylates (PFCA) in 3M, respectively, and 38.4% reduction of fluorotelomer sulfonates in ANSUL-AFFF were achieved in 13 h. Estimated costs of energy for the treatment of ANSUL-AFFF and 3M-AFFF at a 500× dilution were $0.015 ±â€¯0.0001/L and $0.019 ±â€¯0.0002/L, respectively.

15.
Chemosphere ; 201: 790-798, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29550573

RESUMO

Abiotic transformation of anthropogenic compounds by redox-active metal oxides affects contaminant fate in soil. The capacity of birnessite and ferrihydrite to oxidize the insensitive munitions compound, 2,4-dinitroanisol (DNAN), and its amine-containing daughter products, 2-methoxy-5-nitro aniline (MENA) and 2,4-diaminoanisole (DAAN), was studied in stirred reactors at controlled pH (7.0). Aqueous suspensions were reacted at metal oxide solid to solution mass ratios (SSR) of 0.15, 1.5 and 15 g kg-1 and solutions were analyzed after 0-3 h by high performance liquid chromatography coupled with photodiode array or mass spectrometry detection. Results indicate that DNAN was resistant to oxidation by birnessite and ferrihydrite. Ferrihydrite did not oxidize MENA, but MENA was susceptible to rapid oxidation by birnessite, with nitrogen largely mineralized to nitrite. This is the first report on mineralization of nonphenolic aromatics and the release of mineralized N from aromatic amines following reaction with birnessite. DAAN was oxidized by both solids, but ca. ten times higher rate was observed with birnessite as compared to ferrihydrite at an SSR of 1.5 g kg-1. At 15 g kg-1 SSR, DAAN was removed from solution within 5 min of reaction with birnessite. CO2(g) evolution experiments indicate mineralization of 15 and 12% of the carbon associated with MENA and DAAN, respectively, under oxic conditions with birnessite at SSR of 15 g kg-1. The results taken as a whole indicate that initial reductive (bio)transformation products of DNAN are readily oxidized by birnessite. The oxidizability of the reduced DNAN products was increased with progressive (bio)reduction as reflected by impacts on the oxidation rate.


Assuntos
Anisóis/química , Substâncias Explosivas/química , Compostos Férricos/química , Óxidos/química , Poluentes do Solo/química , Compostos de Anilina/química , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas , Oxirredução , Fenilenodiaminas/química , Solo/química
16.
Environ Res ; 164: 452-458, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29574255

RESUMO

The production and application of engineered nanoparticles (NPs) are increasing in demand with the rapid development of nanotechnology. However, there are concerns that some of these novel materials could lead to emerging environmental and health problems. Some NPs are able to facilitate the transport of contaminants into cells/organisms via a "Trojan Horse" effect which enhances the toxicity of the adsorbed materials. In this work, we evaluated the toxicity of arsenite (As(III)) adsorbed onto cerium dioxide (CeO2) NPs to human bronchial epithelial cells (16HBE14o-) using the xCELLigence real time cell analyzing system (RTCA). Application of 0.5 mg/L As(III) resulted in 81.3% reduction of cell index (CI, an RTCA measure of cell toxicity) over 48 h when compared to control cells exposed to medium lacking As(III). However, when the cells were exposed to 0.5 mg/L As(III) in the presence of CeO2 NPs (250 mg/L), the CI was only reduced by 12.9% compared to the control. The CeO2 NPs had a high capacity for As(III) adsorption (20.2 mg/g CeO2) in the bioassay medium, effectively reducing dissolved As(III) in the aqueous solution and resulting in reduced toxicity. Transmission electron microscopy was used to study the transport of CeO2 NPs into 16HBE14o- cells. NP uptake via engulfment was observed and the internalized NPs accumulated in vesicles. The results demonstrate that dissolved As(III) in the aqueous solution was the decisive factor controlling As(III) toxicity of 16HBE14o- cells, and that CeO2 NPs effectively reduced available As(III) through adsorption. These data emphasize the evaluation of mixtures when assaying toxicity.


Assuntos
Arsenitos , Cério/química , Células Epiteliais/citologia , Nanopartículas Metálicas , Nanopartículas , Arsenitos/toxicidade , Humanos , Nanopartículas Metálicas/química
17.
J Hazard Mater ; 343: 340-346, 2018 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-28992572

RESUMO

The insensitive munitions compound 3-nitro-1,2,4-triazol-5-one (NTO) was recently approved by the U.S. Army to replace cyclotrimethylene trinitramine (RDX) in conventional explosives. As its use becomes widespread, concern about the potential toxicity of NTO increases. NTO can undergo microbial reduction to 3-amino-1,2,4-triazol-5-one (ATO), which is recalcitrant in waterlogged soils. In this study, the acute toxicity of NTO and ATO towards various organisms, including microorganisms (i.e., methanogenic archaea, aerobic heterotrophs, and Aliivibrio fischeri (Microtox assay)), the microcrustacean Daphnia magna (ATO only), and zebrafish embryos (Danio rerio), was assessed. NTO was notably more inhibitory to methanogens than ATO (IC50=1.2mM,>62.8mM, respectively). NTO and ATO did not cause noteworthy inhibition on aerobic heterotrophs even at the highest concentrations tested (32.0mM). High concentrations of both NTO and ATO were required to inhibit A. fischeri (IC20=19.2, 22.4mM, respectively). D. magna was sensitive to ATO (LC50=0.27mM). Exposure of zebrafish embryos to NTO or ATO (750µM) did not cause lethal or developmental effects (22 endpoints tested). However, both compounds led to swimming behavior abnormalities at low concentrations (7.5µM). The results indicate that the reductive biotransformation of NTO could enhance or lower its toxicity according to the target organism.

18.
Chemosphere ; 195: 372-380, 2018 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-29274576

RESUMO

Nitroaromatic compounds are widely used in agricultural pesticides, pharmaceuticals, military explosives, and other applications. They enter the environment via manufacturing and municipal wastewater discharges and releases from agricultural and military operations. Because of their ubiquity and toxicity, they are considered an important class of environmental contaminants. Nitroaromatics are known to undergo reductive transformation to aromatic amines, and under aerobic conditions they are susceptible to coupling reactions which may lead to their irreversible incorporation into soil organic matter. However, there is also evidence of coupling reactions in the absence of oxygen between reduced intermediates of the insensitive munitions compound 2,4-dinitroanisole, leading to the formation of azo dimers. The formation of such products is a concern since they may be more toxic than the original nitroaromatic compounds. The objective of this research is to provide evidence of the anaerobic formation of azo coupling products. 4-Nitroanisole was used as a model compound and was spiked into incubations containing anaerobic granular sludge with H2 as the electron donor. Using liquid chromatography, UV-Vis spectroscopy, and mass spectrometry, the formation of the azo dimer 4,4'-dimethoxyazobenzene was confirmed. However, due to the instability of the azo bond under the reducing conditions of our incubations, the azo dimer did not accumulate. Consequently, 4-aminoanisole was the major product formed in our experiment. Other minor suspected coupling products were also detected in our incubations. The results provide clear evidence for the temporal formation of at least one azo dimer in the anaerobic reduction of a model nitroaromatic compound.


Assuntos
Anisóis/química , Poluentes Ambientais/química , Aminas/química , Anaerobiose , Compostos Azo/química , Cromatografia Líquida , Substâncias Explosivas/química , Espectrometria de Massas , Esgotos
19.
Environ Sci Technol ; 51(22): 13327-13334, 2017 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-29072907

RESUMO

2,4-Dinitrosanisole (DNAN) is an insensitive munitions component replacing conventional explosives. While DNAN is known to biotransform in soils to aromatic amines and azo-dimers, it is seldom mineralized by indigenous soil bacteria. Incorporation of DNAN biotransformation products into soil as humus-bound material could serve as a plausible remediation strategy. The present work studied biotransformation of DNAN in soil and sludge microcosms supplemented with uniformly ring-labeled 14C-DNAN to quantify the distribution of label in soil, aqueous, and gaseous phases. Electron donor amendments, different redox conditions (anaerobic, aerobic, sequential anaerobic-aerobic), and the extracellular oxidoreductase enzyme horseradish peroxidase (HRP) were evaluated to maximize incorporation of DNAN biotransformation products into the nonextractable soil humus fraction, humin. Irreversible humin incorporation of 14C-DNAN occurred at higher rates in anaerobic conditions, with a moderate increase when pyruvate was added. Additionally, a single dose of HRP resulted in an instantaneous increased incorporation of 14C-DNAN into the humin fraction. 14C-DNAN incorporation to the humin fraction was strongly correlated (R2 = 0.93) by the soil organic carbon (OC) amount present (either intrinsic or amended). Globally, our results suggest that DNAN biotransformation products can be irreversibly bound to humin in soils as a remediation strategy, which can be enhanced by adding soil OC.


Assuntos
Anisóis , Solo , Radioisótopos de Carbono , Poluentes do Solo
20.
Chemosphere ; 184: 730-737, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28641224

RESUMO

Soluble ions released by elemental copper nanoparticles (Cu0 NP) are toxic to key microorganisms of wastewater treatment processes. However, their toxicity to anaerobic ammonium oxidation (anammox) has not yet been studied. Chelating agents occurring in wastewater may decrease copper ions (Cu2+) concentration and consequently, decrease copper toxicity. This study evaluated Cu0 NP and CuCl2 toxicity to anammox and the influence of ethylene diamine-tetra acetic acid (EDTA) on copper toxicity. Bioassays were supplemented with Cu0 NP or CuCl2 with and without EDTA. Anammox activities were used to calculate inhibition constants (Ki). Results showed that Cu0 NP are toxic to anammox. Ki constants with respect to added copper were 1.8- and 2.81-fold larger (less toxic) in EDTA-containing assays for Cu0 NP and CuCl2, respectively, compared to EDTA-free assays. Additionally, Ki constants calculated in EDTA-free assays with respect the measured dissolved copper concentration were 0.023 mM Cu0 NP and 0.014 mM CuCl2. The similarity of these Ki constants indicates that Cu0 NP toxicity to anammox is caused by the release of Cu2+. Finally, severe toxicity caused by 0.315 mM and Cu0 NP 0.118 mM CuCl2 was attenuated by 88-100% when 0.14 mM EDTA was supplied. Toxicity attenuation likely occurred because EDTA complexed Cu2+ ions, thus, decreasing their bioavailability. Overall, this study indicates that Cu0 NP and CuCl2 are toxic to anammox, and furthermore, that EDTA attenuates Cu0 NP and CuCl2 toxicity to anammox by complexing Cu2+ ions.


Assuntos
Cobre/toxicidade , Nanopartículas Metálicas/toxicidade , Ácido Acético , Compostos de Amônio/química , Quelantes , Ácido Edético/química , Etilenos , Águas Residuárias
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