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1.
Food Chem ; 304: 125284, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31476546

RESUMO

The reactions of different lipid-derived reactive carbonyls with ammonia-producing compounds were studied to investigate the formation of pyridines in foods. 2-Alkyl, 3-alkyl-, and 2,5-dialkylpyiridines were produced by oligomerization of short-chain aldehydes in the presence of ammonia. Thus, acetaldehyde/crotonaldehyde mixtures and 2,4-alkadienals were the main responsible for the formation of 2-alkylpyridines; acrolein or 2,4-alkadienals were needed for the formation of 3-alkylpyridines; and 2-alkenals were responsible for the formation of 2,5-dialkylpyridines. On the contrary, 2,6-dialkylpyridines were produced by cyclization of unsaturated ketones. Reactions pathways for formation of these pyridines are proposed, and confirmed by isotopic labelling experiments. Aldehydes and ketones required for their formation are produced in the course of lipid oxidation. Therefore, pyridine formation seems to be an additional consequence of the lipid oxidation pathway. This new knowledge can employed for the optimization of reactions to achieve the desired targeted flavor generation during food processing.


Assuntos
Aldeídos/química , Amônia/química , Manipulação de Alimentos , Temperatura Alta , Peroxidação de Lipídeos , Piridinas/química , Acetaldeído/química , Oxirredução
2.
Nat Commun ; 10(1): 4413, 2019 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-31562325

RESUMO

The synthesis of nucleobases in natural environments, especially in interstellar molecular clouds, is the focus of a long-standing debate regarding prebiotic chemical evolution. Here we report the simultaneous detection of all three pyrimidine (cytosine, uracil and thymine) and three purine nucleobases (adenine, xanthine and hypoxanthine) in interstellar ice analogues composed of simple molecules including H2O, CO, NH3 and CH3OH after exposure to ultraviolet photons followed by thermal processes, that is, in conditions that simulate the chemical processes accompanying star formation from molecular clouds. Photolysis of primitive gas molecules at 10 K might be one of the key steps in the production of nucleobases. The present results strongly suggest that the evolution from molecular clouds to stars and planets provides a suitable environment for nucleobase synthesis in space.


Assuntos
Adenina/química , Citosina/química , Hipoxantina/química , Timina/química , Uracila/química , Xantina/química , Adenina/síntese química , Amônia/química , Monóxido de Carbono/química , Citosina/síntese química , Evolução Química , Meio Ambiente Extraterreno , Hipoxantina/síntese química , Gelo , Metanol/química , Estrutura Molecular , Processos Fotoquímicos/efeitos da radiação , Timina/síntese química , Raios Ultravioleta , Uracila/síntese química , Água/química , Xantina/síntese química
3.
Environ Sci Pollut Res Int ; 26(32): 33067-33075, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31512139

RESUMO

Fe/activated coke (AC) and Cr-Fe/AC catalysts with AC as a supporter and Cr and Fe as active components were prepared by an impregnation method for low-temperature selective catalytic reduction (SCR) of NO with NH3. The effects of Cr addition and its concentrations on the deNOx performance of Fe/AC catalysts were studied at low temperature. The Cr addition promotes the low-temperature SCR activity of the 8Fe/AC catalyst and the 8Fe6Cr/AC catalyst has the best low-temperature SCR deNOx performance, which the NOx conversions are greater than 90% at 160-240 °C. The 8Fe6Cr/AC catalyst has good water resistance. However, when 100 ppm SO2 was introduced into the reaction gas, its deNOx efficiency drops to 45% at 180 °C. To clarify the specific effects of Cr addition on the NOx conversions and sulfur poisoning, the Cr-Fe/AC catalysts were characterized by X-ray diffraction, BET, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy, and Fourier infrared spectroscopy. The addition of Cr into Fe/AC catalysts greatly increases the BET surface area and the number of weak and medium-strong acid sites on the catalyst surface and improves the ratio of Fe3+/Fe2+. These factors enhance the NOx conversion of 8Fe/AC catalyst. The formed sulfates and hydrogen sulfates cover the active sites on the catalyst surface, which lead to the sulfur poisoning of the 8Fe6Cr/AC catalyst. Graphical abstract.


Assuntos
Amônia/química , Modelos Químicos , Óxido Nítrico/química , Catálise , Coque , Temperatura Baixa , Oxirredução , Temperatura Ambiente , Água/química , Difração de Raios X
4.
J Chem Theory Comput ; 15(11): 6085-6096, 2019 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-31545600

RESUMO

We present a strategy to generate "concentrically local orbitals" for the purpose of decreasing the computational cost of wave function-in-density functional theory (WF-in-DFT) embedding. The concentric localization is performed for the virtual orbitals by first projecting the virtual space onto atomic orbitals centered on the embedded atoms. Using a one-particle operator, these projected orbitals are then taken as a starting point to iteratively span the virtual space, recursively creating virtual orbital "shells" with consecutively decreasing correlation energy recovery at each iteration. This process can be repeated to convergence, allowing for tunable accuracy. Assessment of the proposed scheme is performed by application to the potential energy diagram of the Menshutkin reaction of chloromethane and ammonia inside a segment of a carbon nanotube and the torsional potential of a simplified version of the retinal chromophore.


Assuntos
Teoria da Densidade Funcional , Amônia/química , Cloreto de Metila/química , Modelos Moleculares , Nanotubos de Carbono/química
5.
Chemosphere ; 237: 124532, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31551202

RESUMO

Biochar (BC) potentially accelerates ammonia (NH3) volatilization from rice paddy soils. In this regard, however, application the floating duckweed (FDW) to biochar-amended soil to control the NH3 volatilization is not studied up-to-date. Therefore, the impacts of BC application with and without FDW on the NH3 and nitrous oxide (N2O) emissions, NUE and rice grain yield were evaluated in a soil columns experiment. We repacked soil columns with Hydragric Anthrosol and Haplic Acrisol treated in triplicates with Urea, Urea + BC and Urea + BC + FDW. Total NH3 losses from Hydragric Anthrosol and Haplic Acrisol were 15.2-33.2 kg N ha-1 and 19.6-39.7 kg N ha-1, respectively. Urea + BC treatment recorded 25.6-43.7% higher (p < 0.05) NH3 losses than Urea treatment, attributing to higher pH value of floodwater. Floating duckweed decreased soil pH and therefore significantly reduced (p < 0.05) the NH3 volatilizations from the two soils by 50.6-54.2% over Urea + BC and by 34.2-38.0% over Urea treatment. Total N2O emissions from Hydragric Anthrosol and Haplic Acrisol were 1.19-3.42 kg N ha-1 and 0.67-2.08 kg N ha-1, respectively. Urea + BC treatment increased N2O emissions by 58.8-68.7% and Urea + BC + FDW treatment further increased N2O emission by 187.4-210.4% over Urea treatment. Higher ammonium content of the topsoil, explained the N2O increases in the Urea + BC and Urea + BC + FDW treatments. Urea + BC slightly reduced the rice grain yield and NUE, while the Urea + BC + FDW promoted both rice yield and NUE. Our data indicate that co-application of FDW along with BC in paddy soil could mitigate the NH3 volatilization and enhance the rice grain yield and NUE.


Assuntos
Amônia/metabolismo , Biodegradação Ambiental , Carvão Vegetal/química , Nitrogênio/metabolismo , Solo/química , Amônia/química , Grão Comestível/química , Fertilizantes/análise , Nitrogênio/química , Óxido Nitroso/análise , Oryza/química , Ureia/química , Volatilização
6.
Mater Sci Eng C Mater Biol Appl ; 104: 109943, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31500025

RESUMO

The main objective of this work was to reduce the inhibitory effects of high contents of organics, ammonia, and heavy metals in an anaerobic buffled reactor (ABR), and to prevent the sludge wash-out using zeolites as media. In this work, a pilot scale of ABR with 8 compartments and a working volume of 14.4 L was used, and the last four ABR compartments were filled with a zeolite. The bioreactor was operated at HRTs of 3, 4, and 5 days, zeolite filling ratios of 10, 20, and 30%, and influent chemical oxygen demand (COD) concentrations of 10,000, 20,000, and 30,000 mg/L. The results obtained showed that the maximum removal efficiencies of COD and BOD5 reached 78 and 68%, respectively. The maximum removal was observed at a HRT of 5 days, a 30% medium filling ratio, and a COD of 10,000 mg/L. Increasing the filling ratio in the reactor increased the removal efficiencies of COD and BOD5 but increasing the concentration of the influent COD and decreasing HRT reduced the removal efficiency of the reactor. The initial BOD5/COD ratio was equal to 0.36, which increased by 46% when the medium filling ratio was elevated to 30%. The maximum biogas yield was 0.23 L/g of CODRemoved, and the specific methanogenic activity test verified the toxicity effect of the leachate on the gas-producer organisms. The results of scanning electronic microscopy and EDS showed that the zeolite medium immobilized the microorganisms and a biofilm was formed. Also the zeolite, as a well-known ion exchanger, decreased the concentrations of the major inhibitors (ammonia and heavy metals) and improved the reactor efficiency.


Assuntos
Anaerobiose/efeitos dos fármacos , Biodegradação Ambiental/efeitos dos fármacos , Zeolitas/química , Amônia/química , Biofilmes/efeitos dos fármacos , Biocombustíveis , Análise da Demanda Biológica de Oxigênio/métodos , Reatores Biológicos , Metais Pesados/química , Oxigênio/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química
7.
Toxicol Lett ; 316: 94-108, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31499141

RESUMO

The toxic effects resulting from inhalation exposure depend on both the concentration (C) of the inhaled substance and the exposure duration (t), including the assumptions that the exposure-limiting toxic effect is linearly linked with the accumulated C × t (inhaled dose), and detoxification or compensatory responses diminishing this dose are negligible. This interrelationship applies for both constant and fluctuating concentrations and is usually expressed by the toxic load equation Cn × t = constant effect (k). The toxic load exponent 'n' is derived from both C- and t-dependent exponents with Cb2×tb3 = k with n = b2/b3. This model is taken as a fundamental basis for assessing the acute hazard posed by atmospheric releases of noxious substances, whether deliberate or accidental. Despite its universal use, especially for inhaled irritants, the toxicological significance of this mathematical construct is still discussed controversially. With n = 1 this equation is called Haber's rule. The underlying assumption is that the exposure-based calculated and the actually inhaled Cb2×tb3 are identical. Unlike the calculated dose, the latter is dependent on the test species and its t-dependent change in respiratory minute volume (MV). The retention patterns of inhaled irritant vapors may differ in obligate nasal breathing rodents and oronasally breathing humans as well. Thus, due to the interdependence of n on both C, t and k, this mathematical construct generates a bioassay-specific 'n' which can hardly be considered as human-equivalent, especially following exposure to sensory irritants known to elicit reflex-related changes in MV. The C- and t-dependent impact on Cn × t = k was analyzed with the sensory irritant n-butyl monoisocyanate and compared with t-dependent changes elicited by highly, moderately, and poorly water-soluble sensory irritants ammonia, toluene diisocyanate, and phosgene, respectively. This comparison reveals that n depends on several factors: In cases where MV is instantly and plateau-like depressed with onset of exposure, n appears to be most dependent on Cb2 × MV whereas for a similar slower time-dependent response n becomes more dependent on MV × tb3. For any ensuing risk characterization that focuses on acute non-lethal threshold Cb2 × tb3's, the sensory irritation-related depression in MV must be known to arrive at meaningful conclusions. In summary, both Cn- and t-dependent dosimetry-related pitfalls may occur in acute bioassays on rodents following inhalation exposure to irritants. These must be identified and dealt with judiciously prior to translation to apparently similar human exposures. By default, extrapolations from one duration to another should start with that Cn × t eliciting the least depression in MV with n = 1.


Assuntos
Exposição por Inalação/efeitos adversos , Irritantes/toxicidade , Pneumopatias/induzido quimicamente , Pulmão/efeitos dos fármacos , Modelos Teóricos , Respiração/efeitos dos fármacos , Limiar Sensorial/efeitos dos fármacos , Amônia/química , Amônia/toxicidade , Animais , Relação Dose-Resposta a Droga , Irritantes/química , Isocianatos/química , Isocianatos/toxicidade , Dose Letal Mediana , Pulmão/fisiopatologia , Pneumopatias/fisiopatologia , Masculino , Camundongos , Fosgênio/química , Fosgênio/toxicidade , Ratos Wistar , Medição de Risco , Solubilidade , Fatores de Tempo , Tolueno 2,4-Di-Isocianato/química , Tolueno 2,4-Di-Isocianato/toxicidade
8.
Sci Total Environ ; 697: 134114, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31487592

RESUMO

Ammonia (NH3) volatilization is considered as one of the major mechanisms responsible for the loss of nitrogen (N) from soil-plant systems worldwide. This study investigated the effect of biochar amendment to a calcareous soil (pH 7.8) on NH3 volatilization and plant N uptake. In particular, the effect of biochar's feedstock and application rate on both NH3 volatilization and plant growth were quantified using a specially designed closed chamber system. Two well-characterized biochars prepared from poultry manure (PM-BC) and green waste compost (GW-BC) were applied to the soil (0, 0.5, 1, 1.5 and 2% w/w equivalent to 0, 7.5, 15, 22 and 30 t ha-1) and wheat (Triticum aestivum, variety: Calingiri) was grown for 30 days. Both PM-BC and GW-BC decreased NH3 volatilization to a similar degree (by 47 and 38%, respectively), in the soil-plant system compared to the unamended control. Higher plant biomass production of up to 70% was obtained in the closed chamber systems with the addition of biochar. The increase in plant biomass was due to the reduction in N loss as NH3 gas, thereby increasing the N supply to the plants. Plant N uptake was improved by as much as 58% with biochar addition when additional NPK nutrients were supplied to the soil. This study demonstrates that the application of biochars can mitigate NH3 emission from calcareous agricultural cropping soil and that the retained N is plant-available and can improve wheat biomass yield.


Assuntos
Amônia/química , Carvão Vegetal/química , Fertilizantes/análise , Desenvolvimento Vegetal , Concentração de Íons de Hidrogênio , Solo/química
9.
J Agric Food Chem ; 67(38): 10756-10763, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31483626

RESUMO

AFEX treatment of crop residues can greatly increase their nutrient availability for ruminants. This study investigated the concentration of acetamide, an ammoniation byproduct, in AFEX-treated crop residues and in milk and meat from ruminants fed these residues. Acetamide concentrations in four AFEX-treated cereal crop residues were comparable and reproducible (4-7 mg/g dry matter). A transient acetamide peak in milk was detected following introduction of AFEX-treated residues to the diet, but an alternative regimen showed the peak can be effectively mitigated. Milk acetamide concentration following this transition was 6 and 10 ppm for cattle and buffalo, respectively, but also decreased over time for cattle while tending to decrease (p = 0.08) for buffalo. There was no difference in acetamide concentration in the meat of cattle consuming AFEX-treated residues for 160 days compared to controls. Further investigation is necessary to determine the metabolism of acetamide in ruminants and a maximum acceptable daily intake for humans.


Assuntos
Acetamidas/análise , Ração Animal/análise , Bovinos/metabolismo , Produtos Agrícolas/química , Resíduos de Drogas/análise , Contaminação de Alimentos/análise , Carne/análise , Leite/química , Acetamidas/metabolismo , Amônia/química , Animais , Búfalos , Dieta/veterinária , Digestão , Leite/metabolismo
10.
Nat Commun ; 10(1): 3944, 2019 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-31477724

RESUMO

Microscale interactions in soil may give rise to highly localised conditions that disproportionally affect soil nitrogen transformations. We report mechanistic modelling of coupled biotic and abiotic processes during drying of soil surfaces and biocrusts. The model links localised microbial activity with pH variations within thin aqueous films that jointly enhance emissions of nitrous acid (HONO) and ammonia (NH3) during soil drying well above what would be predicted from mean hydration conditions and bulk soil pH. We compared model predictions with case studies in which reactive nitrogen gaseous fluxes from drying biocrusts were measured. Soil and biocrust drying rates affect HONO and NH3 emission dynamics. Additionally, we predict strong effects of atmospheric NH3 levels on reactive nitrogen gas losses. Laboratory measurements confirm the onset of microscale pH localisation and highlight the critical role of micro-environments in the resulting biogeochemical fluxes from terrestrial ecosystems.


Assuntos
Amônia/análise , Dessecação/métodos , Gases/análise , Ácido Nitroso/análise , Solo/química , Algoritmos , Amônia/química , Atmosfera/química , Clima Desértico , Ecossistema , Microbiologia Ambiental , Concentração de Íons de Hidrogênio , Modelos Teóricos , Nitrogênio/análise , Nitrogênio/química , Ácido Nitroso/química , Água/metabolismo
11.
Sci Total Environ ; 694: 133658, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31398644

RESUMO

Biochar has been demonstrated to reduce nitrous oxide (N2O) emissions from soils, but its effect is highly soil-dependent. In particular, in soils with strong nitrification potential, biochar addition may increase N2O emissions. Thus, in soils with strong nitrification potential, the combination of biochar with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) may be more effective in reducing N2O emissions than biochar alone. However, the combined use of biochar and DMPP on soil N2O emissions is relatively unexplored, and underlying microbial mechanisms of how biochar and/or DMPP amendment affect N2O emissions is still largely unknown. Here, a 30-day incubation experiment was established with four treatments: CK (control), BC (biochar), DMPP, and BD (biochar and DMPP), all at agronomically recommended rates, and N cycling assessed following addition of urea. Treatment of soil with BC, DMPP and BD reduced N2O emissions (compared with urea alone) by 59.1%, 95.5% and 74.1%, respectively. Quantification of N cycling genes (amoA, nirS, nirK, and nosZ) indicated that biochar stimulated growth of ammonia oxidizing archaea (AOA) and bacteria (AOB), while DMPP alone inhibited the activity and growth of AOB. In the BD treatment, DMPP was absorbed onto biochar reducing its efficacy in inhibiting AOB growth. The response patterns of nirS/nirK nitrite-reducing denitrifiers to biochar and/or DMPP addition varied among clades. Notably, biochar and/or DMPP increased the abundance of nosZI and nosZII-N2O reducers, but nosZI-clade taxa were more closely associated with reducing N2O emission than nosZII taxa. Overall, our findings proved that the dynamics of AOB and nosZI-N2O reducers resulting from the addition of biochar and/or DMPP played a key role in governing soil N2O emissions.


Assuntos
Amônia/química , Carvão Vegetal/química , Dióxido de Nitrogênio/análise , Pirazóis/química , Microbiologia do Solo , Biodegradação Ambiental , Solo/química
12.
Int J Mol Sci ; 20(15)2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31370230

RESUMO

Effect of H2O and NH3 on the synergistic oxidation reaction of SO2 and NO2 is investigated by theoretical calculation using the molecule system SO2-2NO2-nH2O (n = 0, 1, 2, 3) and SO2-2NO2-nH2O-mNH3 (n = 0, 1, 2; m = 1, 2). Calculated results show that SO2 is oxidized to SO3 by N2O4 intermediate. The additional H2O in the systems can reduce the energy barrier of oxidation step. The increasing number of H2O molecules in the systems enhances the effect and promotes the production of HONO. When the proportion of H2O to NH3 is 1:1, with NH3 included in the system, the energy barrier is lower than two pure H2O molecules in the oxidation step. The present study indicates that the H2O and NH3 have thermodynamic effects on promoting the oxidation reaction of SO2 and NO2, and NH3 has a more significant role in stabilizing product complexes. In these hydrolysis reactions, nethermost barrier energy (0.29 kcal/mol) can be found in the system SO2-2NO2-H2O. It is obvious that the production of HONO is energetically favorable. A new reaction mechanism about SO2 oxidation in the atmosphere is proposed, which can provide guidance for the further study of aerosol surface reactions.


Assuntos
Amônia/química , Dióxido de Nitrogênio/química , Dióxido de Enxofre/química , Água/química , Aerossóis , Cinética , Oxirredução , Termodinâmica
13.
Artigo em Inglês | MEDLINE | ID: mdl-31423891

RESUMO

Hydrogen sulfide (H2S) and ammonia (NH3), common impurities in biogas, need to be removed before utilizing it. In this study, a combined system, which consisted of an absorption column and an electrochemical oxidation reactor, was tested to simultaneously remove these impurities. The effects of the current density and the chemical loading rate on the system performance were investigated. Firstly, the mass transfer coefficients for the absorption column were determined at various gas flow rates. More mass of NH3 was transferred, compared with that of H2S, because of its higher solubility. In the electro-oxidation reactor, reactive chlorine species (RCSs) were generated and oxidized both H2S and NH3; however, NH3 started to degrade only after H2S was completely eliminated. At a current density of 400 A/m2, the current efficiencies of H2S and NH3 were 23.1% and 5.9%, respectively. In the combined system, the removal efficiency of H2S was closely related to the mass ratio of the H2S transferred and the RCSs generated. The removal efficiency of H2S was greater than 99% when the ratio was less than 1. The mass transfer potential and the oxidation kinetics should be balanced to improve the system performance for the simultaneous removal of H2S and NH3.


Assuntos
Amônia/isolamento & purificação , Sulfeto de Hidrogênio/isolamento & purificação , Amônia/química , Biocombustíveis/análise , Reatores Biológicos , Depuradores de Radicais Livres , Sulfeto de Hidrogênio/química , Cinética , Oxirredução
14.
Molecules ; 24(16)2019 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-31426488

RESUMO

Food waste (FW) collected from a university canteen was treated in acidogenic fermenters to produce volatile fatty acids (VFA) under biological pretreatment with mature compost. Batch assays working at pH 6 revealed an increment of 9.0%, 7.9%, and 4.1% (on COD basis) of VFA concentration when adding 2.5%, 3.5%, and 4.5% w/w of mature compost, respectively, even though the volatile solids (VS) concentration of food waste was lower in the tests with increasing doses of mature compost. For batch tests at pH 7, this VFA generation improvement was lower, even though enhanced COD solubilization was recorded. Operating in semi-continuous conditions at 35 °C, pH of 6, and hydraulic retention time (HRT) of 3.5 days, the addition of 2.5% w/w of mature compost led to a VFA concentration up to 51.2 ± 12.3% more (on VS basis) when compared to a reference reactor without compost addition. Moreover, the percentage of butyric acid on VS basis in the fermentation broth working at a pH of 6 increased from up to 12.2 ± 1.9% (0% compost addition) to up to 23.5 ± 2.7% (2.5% compost addition). The VFA production was not improved when a higher percentage of mature compost was used (3.5% instead of 2.5% w/w), and it slightly decreased when mature compost addition was lowered to 1.5% w/w. When working at a pH of 7 in the semi-continuous fermenters with the addition of 2.5% w/w mature compost at an HRT of 3.5 days, an improvement of 79% and 104% of the VFA concentration (on VS basis) were recorded as compared to fermenters working at a pH of 6 with 2.5% and 0% w/w of mature compost addition, respectively. At a pH of 7, higher production of propionic and valeric acids was found with respect to the reactor working at a pH of 6. The effect of pH on VFA generation was estimated to have greater contribution than that of only biological pretreatment using mature compost. At a pH of 7, the VFA yield was higher for the fermenter working with 2.5% w/w mature compost but at a pH of 7 and HRT of 5 days, the effect of mature compost on VFA production improvement was lower than that obtained at a pH of 6. Moreover, higher solubilization in terms of soluble chemical oxygen demand and total ammonium was detected when biological pretreatment using mature compost was applied at both a pH of 6 and a pH of 7, which indicates enhanced hydrolysis in both conditions.


Assuntos
Ácido Butírico/química , Compostagem/métodos , Ácidos Graxos Voláteis/síntese química , Propionatos/química , Amônia/química , Análise da Demanda Biológica de Oxigênio , Reatores Biológicos , Fermentação , Alimentos , Humanos , Concentração de Íons de Hidrogênio , Ácidos Pentanoicos/química
15.
Sensors (Basel) ; 19(17)2019 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-31450646

RESUMO

The qualitative and quantitative analysis to trace gas in exhaled human breath has become a promising technique in biomedical applications such as disease diagnosis and health status monitoring. This paper describes an application of a high spectral resolution optical feedback cavity enhanced absorption spectroscopy (OF-CEAS) for ammonia detection in exhaled human breath, and the main interference of gases such as CO2 and H2O are approximately eliminated at the same time. With appropriate optical feedback, a fibered distributed feedback (DFB) diode laser emitting at 1531.6 nm is locked to the resonance of a V-shaped cavity with a free spectral range (FSR) of 300 MHz and a finesse of 14,610. A minimum detectable absorption coefficient of αmin = 2.3 × 10-9 cm-1 is achieved in a single scan within 5 s, yielding a detection limit of 17 ppb for NH3 in breath gas at low pressure, and this stable system allows the detection limit down to 4.5 ppb when the spectra to be averaged over 16 laser scans. Different from typical CEAS with a static cavity, which is limited by the FSR in frequency space, the attainable spectral resolution of our experimental setup can be up to 0.002 cm-1 owing to the simultaneous laser frequency tuning and cavity dither. Hence, the absorption line profile is more accurate, which is most suitable for low-pressure trace gas detection. This work has great potential for accurate selectivity and high sensitivity applications in human breath analysis and atmosphere sciences.


Assuntos
Amônia/isolamento & purificação , Técnicas Biossensoriais , Gases/isolamento & purificação , Amônia/química , Testes Respiratórios/métodos , Expiração , Gases/química , Humanos , Limite de Detecção , Espectroscopia de Luz Próxima ao Infravermelho
16.
Sensors (Basel) ; 19(17)2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31450808

RESUMO

Ammonia (NH3) emission is one of the major environmental issues in livestock farming. Gas measurements are required to study the emission process, to establish emission factors, and to assess the efficiency of emission reduction techniques. However, the current methods for acquiring reference measurements of NH3 are either high in cost or labor intensive. In this study, a cost-effective ammonia monitoring system (AMS) was constructed from a commercially-available gas analyzing module based on tunable diode laser absorption (TDLA) spectroscopy. To cope with the negative measurement biases caused by differing inlet pressures, a set of correction equations was formulated. Field validation of the AMS on NH3 measurement was conducted in a fattening pig barn, where the system was compared to a Fourier-transform infrared (FTIR) spectroscopy analyzer. Under two test conditions in a fattening pig barn, the absolute error of the AMS measurements with respect to the average obtained values between the AMS and the FTIR was respectively 0.66 and 0.08 ppmv, corresponding to 5.9% and 0.5% relative error. Potential sources of the measurement uncertainties in both the AMS and FTIR were discussed. The test results demonstrated that the AMS was capable of performing high-quality measurement with sub-ppm accuracy, making it a promising cost-effective tool for establishing NH3 emission factors and studying NH3 emission processes in pig houses.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Amônia/isolamento & purificação , Monitoramento Ambiental , Agricultura , Poluentes Atmosféricos/química , Amônia/química , Animais , Gado , Análise Espectral , Suínos
17.
Artigo em Inglês | MEDLINE | ID: mdl-31443230

RESUMO

To mitigate the potential environmental risks caused by nitrogen compounds from industrial wastewater, residual ammonia after conventional wastewater treatment should be further eliminated. In this work, an electrochemical oxidation process for converting ammonia to nitrogen in actual dyeing wastewater was investigated. The effects of the main operating parameters, including initial pH value, applied current density, NaCl concentration, and flow, were investigated on ammonia removal and products distribution. Experimental results indicated that, under optimal conditions of an initial pH value of 8.3, applied current density of 20 mA cm-2, NaCl concentration of 1.0 g L-1, and flow of 300 mL min-1, the ammonia could be completely removed with N2 selectivity of 88.3% in 60 min electrolysis. A kinetics investigation using a pseudo-first-order model provided a precise description of ammonia removal during the electro-oxidation process. Experimental functions for describing the relationships between kinetic constants of ammonia removal and main operating parameters were also discussed. Additionally, the mechanisms and economic evaluation of ammonia oxidation were conducted. All these results clearly proved that this electro-oxidation process could efficiently remove ammonia and achieve high N2 selectivity.


Assuntos
Amônia/química , Corantes/química , Eletrólise/métodos , Nitrogênio/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/química , Oxirredução
18.
Food Chem ; 299: 125172, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31325716

RESUMO

The composition of inorganic elements is a key factor in determining the quality of fruit wines. However, the use of direct sample injection is challenging for multi-elemental analysis of fruit wine samples. In this paper, an analytical method using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was established for determining multiple elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in fruit wine. The fruit wine was diluted using ultrapure water and acidified with nitric acid before injecting into the ICP-MS/MS. Spectral interferences in the complex matrix composition of different fruit wine samples, in the MS/MS mode, were eliminated using mixed reaction gases of O2/H2 and NH3/He/H2 through the mass shift and on-mass methods. The limits of detection ranged from 0.41 to 58.1 ng L-1. This study demonstrates a new approach for multi-elemental analysis in fruit wine with great convenience and high accuracy.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas em Tandem/métodos , Oligoelementos/análise , Vinho/análise , Amônia/química , Frutas , Gases/química , Hidrogênio/química , Ácido Nítrico/química , Oxigênio/química
19.
Artigo em Inglês | MEDLINE | ID: mdl-31328626

RESUMO

Four low-cost materials, oyster shells, pumice stone, sand and zeolite were employed as adsorbents in an adsorption batch assays investigating the removal of ammonia, phosphate and nitrate from an aqueous solution. These compounds were chosen as they represent typical compounds found in landfill leachate (LFL). Assay performance was evaluated by the Langmuir and Freundlich adsorption isotherms. The top two materials, oyster shells and pumice stone, were employed as adsorbents in a fixed-bed column trial examining the effect of bed height and flow rate on the treatment of a synthetic LFL. The trial concluded that the highest rates of adsorption were achieved using bed heights of 20 cm with a flow rate of 5 mL min-1. After optimization, the system was employed for the treatment of LFL from Powerstown landfill, Carlow, Ireland. Ammonia and nitrate were effectively removed by both adsorption materials resulting in a reduction of influent ammonia and nitrate concentrations to below the national discharge limits set for these compounds of ≤4 mg L-1 and ≤50 mg L-1, respectively. In contrast, although similar high removal efficiencies were observed for phosphate, these rates were not maintained during the test period with overall results indicating reduced phosphate adsorption in comparison to the other compounds tested.


Assuntos
Amônia/isolamento & purificação , Nitratos/isolamento & purificação , Fosfatos/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Amônia/química , Exoesqueleto/química , Animais , Irlanda , Nitratos/química , Fosfatos/química , Silicatos/química , Eliminação de Resíduos Líquidos/economia , Poluentes Químicos da Água/química , Poluentes Químicos da Água/economia
20.
Molecules ; 24(13)2019 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-31324049

RESUMO

Odor emissions represent one of the important issues of aerobic composting. The addition of microbial agents to compost is an important method for solving this problem, but this process is often unstable when a single microbial agent is added to the compost. Therefore, in this study, five treatments comprising different proportions of Bacillus stearothermophilus, Candida utilis, and Bacillus subtilis were tested to determine the best combination of the three microbial agents for ammonia reduction, as follows: control group (CK), 2:1:1 (A), 1:1:2 (B), 1:2:1 (C), and 1:1:1 (D). Compared with the CK group, the A, B, C, and D groups reduced ammonia emissions by 17.02, 9.68, 53.11, and 46.23%, respectively. The total ammonia emissions were significantly lower in C and D than in CK (p < 0.05). These two treatment groups had significantly increased nitrate nitrogen concentrations and decreased pH values and ammonium nitrogen concentrations (p < 0.05). Throughout the composting process, the total bacterial number was significantly higher in C and D than in CK (p < 0.05). Therefore, it is likely that B. stearothermophilus, C. utilis, and B. subtilis compounded from 1:2:1 (C) to 1:1:1 (D) reduced the ammonia emissions due to (1) a reduction in the pH and (2) the promotion of the growth of ammonia-oxidizing bacteria and the conversion of ammonium nitrogen to nitrate nitrogen. This study provides a theoretical basis and technical support for the odor problem of layer manure compost and promotes the development of composting technology.


Assuntos
Amônia/química , Biodegradação Ambiental , Compostagem , Microbiologia Ambiental , Esterco , Amônia/análise , Candida/metabolismo , Geobacillus stearothermophilus/metabolismo , Concentração de Íons de Hidrogênio , Nitrogênio/metabolismo , Oxirredução , Temperatura Ambiente
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