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1.
Artigo em Inglês | MEDLINE | ID: mdl-31319616

RESUMO

This study examined the use of high dosages of ultraviolet germicidal irradiation (UVGI) (253.7 nm) to deal with various concentrations of air pollutants, such as formaldehyde (HCHO), total volatile organic compounds (TVOC), under various conditions of humidity. A number of irradiation methods were applied for various durations in field studies to examine the efficiency of removing HCHO, TVOC, bacteria, and fungi. The removal efficiency of air pollutants (HCHO and bacteria) through long-term exposure to UVGI appears to increase with time. The effects on TVOC and fungi concentration were insignificant in the first week; however, improvements were observed in the second week. No differences were observed regarding the removal of HCHO and TVOC among the various irradiation methods in this study; however significant differences were observed in the removal of bacteria and fungi.


Assuntos
Microbiologia do Ar , Poluentes Atmosféricos/isolamento & purificação , Poluição do Ar em Ambientes Fechados/prevenção & controle , Formaldeído/isolamento & purificação , Compostos Orgânicos Voláteis/isolamento & purificação , Aerossóis , Poluentes Atmosféricos/efeitos da radiação , Formaldeído/efeitos da radiação , Umidade , Fotólise , Raios Ultravioleta , Compostos Orgânicos Voláteis/efeitos da radiação
2.
Environ Sci Process Impacts ; 21(8): 1229-1239, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31173015

RESUMO

The chemistry of oxidants and their precursors (oxidants*) plays a central role in outdoor environments but its importance in indoor air remains poorly understood. Ozone (O3) chemistry is important in some indoor environments and, until recently, ozone was thought to be the dominant oxidant indoors. There is now evidence that formation of the hydroxyl radical by photolysis of nitrous acid (HONO) and formaldehyde (HCHO) may be important indoors. In the past few years, high time-resolution measurements of oxidants* indoors have become more common and the importance of event-based release of oxidants* during activities such as cleaning has been proposed. Here we review the current understanding of oxidants* indoors, including drivers of the formation and loss of oxidants*, levels of oxidants* in indoor environments, and important directions for future research.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar em Ambientes Fechados/análise , Radical Hidroxila/análise , Iluminação , Oxidantes , Fotólise , Poluentes Atmosféricos/efeitos da radiação , Formaldeído/análise , Formaldeído/efeitos da radiação , Radical Hidroxila/efeitos da radiação , Ácido Nitroso/análise , Ácido Nitroso/efeitos da radiação , Ozônio/análise , Ozônio/efeitos da radiação
3.
Environ Sci Pollut Res Int ; 26(11): 11314-11325, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30798499

RESUMO

The photochemical removal of acetaldehyde was studied in N2 or air (O2 1-20%) at atmospheric pressure using side-on and head-on types of 172 nm Xe2 excimer lamps. When CH3CHO was decomposed in N2 using the head-on lamp (HL), CH4, CO, and CO2 were observed as products in FTIR spectra. The initial removal rate of CH3CHO in N2 was ascertained as 0.37 min-1. In air (1-20% O2), HCHO, HCOOH, CO, and CO2 were observed as products in FTIR spectra. The removal rate of CH3CHO in air using the side-on lamp (SL) increased from 3.2 to 18.6 min-1 with decreasing O2 concentration from 20 to 1%. It also increased from 2.5 to 3.7 min-1 with increasing CH3CHO concentration from 150 to 1000 ppm at 20% O2. The best energy efficiency of the CH3CHO removal using the SL in a flow system was 2.8 g/kWh at 1% O2. Results show that the contribution of O(1D) and O3 is insignificant in the initial decomposition of CH3CHO. It was inferred that CH3CHO is initially decomposed by the O(3P) + CH3CHO reaction at 5-20% O2, whereas the contribution of direct vacuum ultraviolet (VUV) photolysis increases concomitantly with decreasing O2 pressure at < 5% O2. After initial decomposition of CH3CHO, it was oxidized further by reactions of O(3P), OH, and O3 with various intermediates such as HCHO, HCOOH, and CO, leading to CO2 as a final product.


Assuntos
Acetaldeído/análise , Poluentes Atmosféricos/análise , Nitrogênio/química , Fotólise , Raios Ultravioleta , Compostos Orgânicos Voláteis/análise , Acetaldeído/efeitos da radiação , Poluentes Atmosféricos/efeitos da radiação , Pressão Atmosférica , Oxirredução , Vácuo , Compostos Orgânicos Voláteis/efeitos da radiação
4.
Environ Sci Pollut Res Int ; 26(5): 4242-4252, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29736638

RESUMO

Heterogeneous photocatalytic oxidation (PCO) is a widely studied alternative for the elimination of volatile organic compounds (VOC) in air. In this context, research on novel photoreactor arrangements to enhance PCO rates is desired. Annular fluidized bed photoreactors (AFBPR) have yielded prominent results when compared to conventional thin film reactors. However, very few works aimed at optimizing AFBPR operation. In this study, TiO2 photocalytic agglomerates were synthesized and segregated in specific size distributions to behave as Geldart groups A, B, C, and D fluidization. The TiO2 agglomerates were characterized by XRD, FTIR spectra, and N2 adsorption. Photocatalyst performances were compared in a 10-mm gapped AFBPR for degrading the model pollutant methyl-ethyl-ketone (MEK), using a 254-nm radiation source. Geldart group C showed to be inadequate for AFBPR operation due to the short operation range between fluidization and elutriation. In all the cases, photocatalytic reaction rates were superior to sole UV photolysis. Group A and group B demonstrated the highest reaction rates. Considerations based on mass transfer suggested that the reasons were enhanced UV distribution within the bed at lower flow rates and superior catalyst surface area at higher flow rates. Results also revealed that groups A, B, and D perform equally per catalyst area within an AFBPR if the fluidization numbers (FN) are high enough.


Assuntos
Poluentes Atmosféricos/análise , Butanonas/análise , Fotólise , Titânio/química , Compostos Orgânicos Voláteis/análise , Adsorção , Poluentes Atmosféricos/efeitos da radiação , Butanonas/efeitos da radiação , Catálise , Modelos Teóricos , Oxirredução , Compostos Orgânicos Voláteis/efeitos da radiação
5.
J Hazard Mater ; 366: 10-15, 2019 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-30500693

RESUMO

The present experimental study describes the characteristics of polycyclic aromatic hydrocarbons (PAHs) emitted with PM2.5 particles during wood and rice straw burning as well as impacts of photochemical ageing on the half lives of particulate PAHs and their diagnostic ratio values. The photochemical degradation kinetics experiments were carried out by exposing the PM2.5 to light and synthetic air flow. Pseudo first order rate constants were calculated based on PAH loss as a function of exposure time. Relatively quick degradation of lighter PAHs (3-rings) [(0.2-0.5)h-1] than heavier PAHs (4-6 rings) [(0.0005-0.03)h-1] indicates substantial impact of PAH-substrate interaction through π-π stacking with the carbonaceous substrates. Moreover, our results showed distinct PAH diagnostic ratios (DR) for wood and rice straw burnings which, however, change with time due to photochemical degradation. The later may add uncertainties in the applications of DR values for source apportionment. Furthermore, considerably large half lives (100-3000 h) of the carcinogenic PAHs as estimated under ambient solar radiation may cause poor and adverse air quality in long range and therefore demands immediate regulations against uncontrolled biomass burning.


Assuntos
Agricultura/métodos , Poluentes Atmosféricos/efeitos da radiação , Luz , Oryza , Material Particulado/efeitos da radiação , Hidrocarbonetos Policíclicos Aromáticos/efeitos da radiação , Madeira , Adsorção , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/química , Biomassa , Fogo , Meia-Vida , Índia , Material Particulado/análise , Material Particulado/química , Processos Fotoquímicos , Hidrocarbonetos Policíclicos Aromáticos/análise , Hidrocarbonetos Policíclicos Aromáticos/química
6.
Sci Total Environ ; 655: 787-795, 2019 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-30481706

RESUMO

Airborne bacteria-containing bioaerosols have attracted increased research attention on account of their adverse effects on human health. Ultraviolet germicidal irradiation (UVGI) is an effective method to inactivate airborne microorganisms. The present study models and compares the inactivation performance of three UV sources in the UVGI for aerosolized Escherichia coli. Inactivation efficiency of 0.5, 2.2 and 3.1 logarithmic order was obtained at an exposure UV dose of 370 J/m3 under UVA (365 nm), UVC (254 nm) and UVD (185 nm) sources, respectively. A Beer-Lambert law-based model was developed and validated to compare the inactivation performances of the UV sources, and modeling enabled prediction of inactivation efficiency and analysis of the sensitivity of several parameters. Low influent E. coli concentrations and high UV doses resulted in high energy consumption (EC). The change in airborne endotoxin concentration during UV inactivation was analyzed, and UVC and UVA irradiation showed no marked effect on endotoxin degradation. By contrast, both free and bound endotoxins could be removed by UVD treatment, which is attributed to the ozone generated by the UVD source. The results of this study can provide a better understanding of the air disinfection and airborne endotoxin removal processes.


Assuntos
Microbiologia do Ar , Poluentes Atmosféricos/análise , Desinfecção/métodos , Endotoxinas/análise , Escherichia coli/efeitos da radiação , Modelos Teóricos , Raios Ultravioleta , Poluentes Atmosféricos/efeitos da radiação , Desinfecção/economia , Desinfecção/instrumentação , Endotoxinas/efeitos da radiação , Exposição por Inalação/prevenção & controle , Ozônio/análise , Raios Ultravioleta/classificação
7.
Environ Sci Pollut Res Int ; 26(5): 4253-4259, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29998449

RESUMO

The plasma electrolytic oxidation (PEO) technique was used to prepare photocatalytic S-TiO2 coatings on Ti sheets; the incorporation of the S ions was possible from the electrolyte for modifying the structural and optics characteristics of the material. In this work, substrates of Ti (ASME SB-265 of 20 × 20 × 1 mm) were used in a PEO process in 10 min, using constant voltage pulses of 340 V with frequency of 1 kHz and duty cycles of 10% and of 30%. Solutions with H2SO4 (0.1 M) and CH4N2S (52 and 79 mM) were used as electrolytes. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy (EDS) were utilized to analyze the surface morphology, crystalline phase, and chemical composition of the samples. According to the results, the catalyst coatings had microporous structure and contained anatase-rutile TiO2 nanocrystalline mixture, until 73.2% rutile and 26.8% anatase in the samples grown with 30% duty cycle and the lowest concentration of CH4N2S. From the EDS measurements, the incorporation of sulfur ions to the coatings was 0.08 wt%. 99.5% reduction efficiency of Cr(VI)-EDTA with sunlight was observed after 2 h; it was determined by diphenyl carbazide spectrophotometric method. These coatings have potential for effective sunlight heterogeneous photoreduction of this toxic, cumulative, and non-biodegradable heavy metal that contaminates the soil and water and is a serious risk to sustainability, ecosystems, and human health.


Assuntos
Poluentes Atmosféricos/análise , Cromo/análise , Ácido Edético/química , Enxofre/química , Luz Solar , Titânio/química , Poluentes Atmosféricos/efeitos da radiação , Catálise , Cromo/efeitos da radiação , Eletrólitos/química , Oxirredução , Gases em Plasma/química , Porosidade , Propriedades de Superfície
8.
PLoS One ; 13(11): e0206506, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30383783

RESUMO

Atmospheric methane is rapidly lost when it enters humid subterranean critical and vadose zones (e.g., air in soils and caves). Because methane is a source of carbon and energy, it can be consumed by methanotrophic methane-oxidizing bacteria. As an additional subterranean sink, it has been hypothesized that methane is oxidized by natural radioactivity-induced radiolysis that produces energetic ions and radicals, which then trigger abiotic oxidation and consumption of methane within a few hours. Using controlled laboratory experiments, we tested whether radiolysis could rapidly oxidize methane in sealed air with different relative humidities while being exposed to elevated levels of radiation (more than 535 kBq m-3) from radon isotopes 222Rn and 220Rn (i.e., thoron). We found no evidence that radiolysis contributed to methane oxidation. In contrast, we observed the rapid loss of methane when moist soil was added to the same apparatus in the absence of elevated radon abundance. Together, our findings are consistent with the view that methane oxidizing bacteria are responsible for the widespread observations of methane depletion in subterranean environments. Further studies are needed on the ability of microbes to consume trace amounts of methane in poorly ventilated caves, even though the trophic and energetic benefits become marginal at very low partial pressures of methane.


Assuntos
Ar/análise , Cavernas/química , Metano/efeitos da radiação , Radioatividade , Solo/química , Poluentes Atmosféricos/análise , Poluentes Atmosféricos/metabolismo , Poluentes Atmosféricos/efeitos da radiação , Monitoramento Ambiental , Metano/análise , Metano/metabolismo , Oxirredução/efeitos da radiação , Fatores de Tempo
9.
Environ Sci Pollut Res Int ; 25(15): 15216-15225, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29560594

RESUMO

The present study investigates the influence of calcination temperature on the properties and photoactivity of multi-element doped TiO2. The photocatalysts were prepared by incorporating silver (Ag), fluorine (F), nitrogen (N), and tungsten (W) into the TiO2 structure via the sol-gel method. Spectroscopic techniques were used to elucidate the correlation between the structural and optical properties of the doped photocatalyst and its photoactivity. XRD results showed that the mean crystallite size increased for undoped photocatalysts and decreased for the doped photocatalysts when calcination was done at higher temperatures. UV-Vis spectra showed that the absorption cut-off wavelength shifted towards the visible light region for the as-synthesized photocatalysts and band gap narrowing was attributed to multi-element doping and calcination. FTIR spectra results showed the shifting of OH-bending absorption bands towards increasing wave numbers. The activity of the photocatalysts was evaluated in terms of gaseous formaldehyde removal under visible light irradiation. The highest photocatalytic removal of gaseous formaldehyde was found at 88%. The study confirms the effectiveness of multi-element doped TiO2 to remove gaseous formaldehyde in air by visible light photocatalysis and the results have a lot of potential to extend the application to other organic air contaminants.


Assuntos
Poluentes Atmosféricos/análise , Formaldeído/análise , Luz , Titânio/química , Compostos Orgânicos Voláteis/análise , Poluentes Atmosféricos/efeitos da radiação , Poluição do Ar em Ambientes Fechados/análise , Poluição do Ar em Ambientes Fechados/prevenção & controle , Catálise , Formaldeído/efeitos da radiação , Temperatura Alta , Oxirredução , Propriedades de Superfície , Compostos Orgânicos Voláteis/efeitos da radiação
10.
Chemosphere ; 167: 462-468, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27750170

RESUMO

The photochemical reaction between biphenyl (Bp) and N(III) under irradiation at 365 nm UV light was investigated. The results showed that Bp conversion efficiency was strongly influenced by N (III) concentration, Bp initial concentration and pH. Species-specific rate constants determined by reaction of Bp with H2ONO+ (k1), HONO (k2) and NO2- (k3) were k1 = (0.058 ± 0.005 L mol-1 s-1), k2 = (0.12 ± 0.06 L mol-1 s-1) and k3 = (0.0019 ± 0.0003 L mol-1 s-1), respectively. Laser flash photolysis studies confirmed that OH radical deriving from the photolysis of N(III) attacked aromatic ring to form Bp-OH adduct with a rate constant of 9.4 × 109 L mol-1 s-1. The products analysis suggested that Bp-OH adduct could be nitrated by N (III) and NO2 to generate nitro-compounds.


Assuntos
Poluentes Atmosféricos/química , Compostos de Bifenilo/química , Ácido Nitroso/química , Raios Ultravioleta , Água/química , Aerossóis , Poluentes Atmosféricos/efeitos da radiação , Compostos de Bifenilo/efeitos da radiação , Radical Hidroxila/química , Lasers , Ácido Nitroso/efeitos da radiação , Oxirredução , Processos Fotoquímicos , Fotólise
11.
Chemosphere ; 150: 329-340, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26921586

RESUMO

Singlet and triplet potential energy surfaces for the atmospheric ozonation of trans-2-chlorovnyldichloroarsine (lewisite) are investigated theoretically. Optimizations of the reactants, products, intermediates and transition states are carried out at the BHandHLYP/6-311+G(d,p) level. Single point energy calculations are performed at the CCSD(T)/6-311+G(d,p) level based on the optimized structures. The detailed mechanism is presented and discussed. Various possible H (or Cl)-abstraction and C (or As)-addition/elimination pathways are considered. The results show that the As-addition/elimination is more energetically favorable than the other mechanisms. Rice-Ramsperger-Kassel-Marcus (RRKM) theory is used to compute the rate constants over the possible atmospheric temperature range of 200-3000 K and the pressure range of 10(-8)-10(9) Torr. The calculated rate constant is in good agreement with the available experimental data. The total rate coefficient shows positive temperature dependence and pressure independence. The modified three-parameter Arrhenius expressions for the total rate coefficient and individual rate coefficients are represented. Calculation results show that major product is CHClCHAs(OOO)Cl2 (s-IM3) at the temperature below 600 K and O2 + CHClCHAsOCl2 (s-P9) play an important role at the temperature between 600 and 3000 K. Time-dependent DFT (TD-DFT) calculations indicate that CHCl(OOO)CHAsCl2 (s-IM3) and CHOAsCl2 (s-P5) can take photolysis easily in the sunlight. Due to the absence of spectral information for arsenide, computational vibrational spectra of the important intermediates and products are also analyzed to provide valuable evidence for subsequent experimental identification.


Assuntos
Poluentes Atmosféricos/análise , Arsenicais/análise , Substâncias para a Guerra Química/análise , Modelos Teóricos , Ozônio/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Arsenicais/química , Arsenicais/efeitos da radiação , Substâncias para a Guerra Química/química , Substâncias para a Guerra Química/efeitos da radiação , Cinética , Fotólise , Pressão , Temperatura Ambiente
12.
Environ Sci Pollut Res Int ; 23(8): 7482-93, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26711293

RESUMO

Portable photocatalytic air cleaners were investigated in 24 and 48 m(3) emission test chambers with regard to efficiency and by-product generation. For this purpose, formaldehyde, decane, 1,2-dichlorobenzene, toluene, α-pinene and heptanal were doped at sub-ppm concentration levels into the chambers individually and in mixtures. By way of specified test protocols, efficiencies could be distinguished but were strongly dependant on the choice of test compounds, especially on whether single or multi compound dosing was used, and on long-term effects. Initial clean air delivery rates (CADRs) up to 137 m(3)/h were measured. Typical by-products were found in significant concentrations. The main ones were formaldehyde up to 50 ppb (62 µg/m(3)) and acetone up to 80 ppb (190 µg/m(3)). Other aldehydes were also found, but at smaller levels. The detection of chloroacetone, a strong irritating compound, at concentrations up to 15 ppb (57 µg/m(3)) strengthens the importance of such investigations especially in cases were chloro-organic compounds are involved.


Assuntos
Acetona/análogos & derivados , Ar Condicionado/métodos , Poluentes Atmosféricos/análise , Poluição do Ar em Ambientes Fechados/análise , Formaldeído/análise , Raios Ultravioleta , Acetona/análise , Acetona/efeitos da radiação , Ar Condicionado/instrumentação , Poluentes Atmosféricos/efeitos da radiação , Aldeídos/análise , Aldeídos/efeitos da radiação , Catálise , Clorobenzenos/análise , Clorobenzenos/efeitos da radiação , Formaldeído/efeitos da radiação , Monoterpenos/análise , Monoterpenos/efeitos da radiação
13.
Toxicol In Vitro ; 32: 220-31, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26689327

RESUMO

We tested the toxicity of thirdhand smoke (THS) using two controlled laboratory exposure scenarios and low levels of THS. One exposure modeled THS in a car parked outdoors, while the second modeled THS in a room without sunlight. The fabrics were exposed to cigarette smoke and then extracted in culture medium. Concentrations of nicotine, nicotine related alkaloids, and tobacco specific nitrosamines (TSNAs) were determined in fresh and aged extracts. The concentration of TSNAs increased with aging in the indoor experiment. THS extracts were used for cytotoxicity testing using mouse neural stem cells (mNSC), human dermal fibroblasts (hDF) and human palatal mesenchyme cells (hPM). Extracts from the car experiment inhibited mNSC proliferation in a live cell imaging assay and induced single strand DNA breaks in mNSC and hDF. In the indoor experiment, THS extracts made with medium containing serum proteins were significantly more toxic than extracts made with basal medium, and mNSC and hPM were more sensitive than hDF. These data indicate that: (1) aging of THS chemical differs on different fabrics and differs with and without sunlight; (2) very few cigarettes are sufficient to produce a toxic THS residue; and (3) protein enhances the efficiency of extraction of cytotoxic chemicals.


Assuntos
Poluentes Atmosféricos/toxicidade , Poluição do Ar em Ambientes Fechados/efeitos adversos , Têxteis , Poluição por Fumaça de Tabaco/efeitos adversos , Poluentes Atmosféricos/efeitos da radiação , Alcaloides/análise , Animais , Automóveis , Células Cultivadas , Dano ao DNA , Feminino , Fibroblastos/efeitos dos fármacos , Humanos , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Pessoa de Meia-Idade , Células-Tronco Neurais/efeitos dos fármacos , Nitrosaminas/análise , Luz Solar , Têxteis/análise
14.
J Environ Sci (China) ; 32: 189-95, 2015 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-26040745

RESUMO

It is important to develop efficient and economic techniques for removing volatile organic compounds (VOCs) in indoor air. Heterogeneous TiO2-based semiconductors are a promising technology for achieving this goal. Anatase/brookite/rutile tricrystalline TiO2 with mesoporous structure was synthesized by a low-temperature hydrothermal route in the presence of HNO3. The obtained samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherm. The photocatalytic activity was evaluated by photocatalytic decomposition of toluene in air under UV light illumination. The results show that tricrystalline TiO2 exhibited higher photocatalytic activity and durability toward gaseous toluene than bicrystalline TiO2, due to the synergistic effects of high surface area, uniform mesoporous structure and junctions among mixed phases. The tricrystalline TiO2 prepared at RHNO3=0.8, containing 80.7% anatase, 15.6% brookite and 3.7% rutile, exhibited the highest photocatalytic activity, about 3.85-fold higher than that of P25. The high activity did not significantly degrade even after five reuse cycles. In conclusion, it is expected that our study regarding gas-phase degradation of toluene over tricrystalline TiO2 will enrich the chemistry of the TiO2-based materials as photocatalysts for environmental remediation and stimulate further research interest on this intriguing topic.


Assuntos
Poluentes Atmosféricos/isolamento & purificação , Poluição do Ar em Ambientes Fechados/análise , Titânio/química , Compostos Orgânicos Voláteis/isolamento & purificação , Poluentes Atmosféricos/efeitos da radiação , Catálise , Cristalização , Recuperação e Remediação Ambiental , Oxirredução , Processos Fotoquímicos , Tolueno/isolamento & purificação , Raios Ultravioleta , Compostos Orgânicos Voláteis/efeitos da radiação
15.
J Hazard Mater ; 294: 41-6, 2015 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-25841085

RESUMO

Abatement of fluorinated compounds (FCs) used in semiconductor and display industries has received an attention due to the increasingly stricter regulation on their emission. We have developed a 2.45GHz microwave plasma torch with reverse vortex reactor (RVR). In order to design a reverse vortex plasma reactor, we calculated a volume fraction and temperature distribution of discharge gas and waste gas in RVR by ANSYS CFX of computational fluid dynamics (CFD) simulation code. Abatement experiments have been performed with respect to SF6, NF3 by varying plasma power and N2 flow rates, and FCs concentration. Detailed experiments were conducted on the abatement of NF3 and SF6 in terms of destruction and removal efficiency (DRE) using Fourier transform infrared (FTIR). The DRE of 99.9% for NF3 was achieved without an additive gas at the N2 flow rate of 150 liter per minute (L/min) by applying a microwave power of 6kW with RVR. Also, a DRE of SF6 was 99.99% at the N2 flow rate of 60 L/min using an applied microwave power of 6kW. The performance of reverse vortex reactor increased about 43% of NF3 and 29% of SF6 abatements results definition by decomposition energy per liter more than conventional vortex reactor.


Assuntos
Poluentes Atmosféricos , Fluoretos , Micro-Ondas , Compostos de Nitrogênio , Hexafluoreto de Enxofre , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Pressão Atmosférica , Fluoretos/química , Fluoretos/efeitos da radiação , Hidrodinâmica , Compostos de Nitrogênio/química , Compostos de Nitrogênio/efeitos da radiação , Gases em Plasma , Semicondutores , Espectroscopia de Infravermelho com Transformada de Fourier , Hexafluoreto de Enxofre/química , Hexafluoreto de Enxofre/efeitos da radiação , Resíduos
16.
J Hazard Mater ; 271: 89-97, 2014 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-24632363

RESUMO

A simple and efficient method for simultaneous desulfurization and denitrification via vacuum ultraviolet (VUV) irradiation and with no additional chemicals is presented. The simultaneous removal of 90% SO2 and 96% NOx (NO+NO2) was achieved from the simulated flue gas under the irradiation from a low-pressure mercury lamp with main wavelengths of 185 and 254 nm, respectively. The composition, flow rate, and temperature of the simulated flue gas, as well as the VUV light intensity, were evaluated as the factors impacting on the efficiency of SO2 and NOx removal. The OH, HO2, O, and O3 produced from the photolysis of H2O and O2 were concluded as the major reactive oxygen species that oxidized SO2 and NOx. The additional OH and HO2 generated through the reactions of NO+HO2 and SO2+OH/HO2 improved treatment efficiency, while the oxidation products of NOx, e.g., NO2, HNO2, HNO3, and HNO4, consumed massive reactive oxygen species (such as O, OH, and HO2) and thereby reducing the removal efficiencies. The main reaction products were characterized as H2SO4 and HNO3 by ion chromatography, which could be used as chemical or fertilizer raw materials.


Assuntos
Poluentes Atmosféricos/efeitos da radiação , Poluição do Ar/prevenção & controle , Óxidos de Nitrogênio/efeitos da radiação , Dióxido de Enxofre/efeitos da radiação , Raios Ultravioleta , Poluentes Atmosféricos/química , Ácido Nítrico/química , Óxidos de Nitrogênio/química , Oxirredução , Espécies Reativas de Oxigênio/química , Dióxido de Enxofre/química , Ácidos Sulfúricos/química , Vácuo
17.
Environ Sci Technol ; 48(3): 1557-65, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24280000

RESUMO

In this work, the photolysis rate coefficient of CH3SCH2Cl (MClDMS) in the lower atmosphere has been determined and has been used in a marine boundary layer (MBL) box model to determine the enhancement of SO2 production arising from the reaction DMS + Cl2. Absorption cross sections measured in the 28000-34000 cm(-1) region have been used to determine photolysis rate coefficients of MClDMS in the troposphere at 10 solar zenith angles (SZAs). These have been used to determine the lifetimes of MClDMS in the troposphere. At 0° SZA, a photolysis lifetime of 3-4 h has been obtained. The results show that the photolysis lifetime of MClDMS is significantly smaller than the lifetimes with respect to reaction with OH (≈ 4.6 days) and with Cl atoms (≈ 1.2 days). It has also been shown, using experimentally derived dissociation energies with supporting quantum-chemical calculations, that the dominant photodissocation route of MClDMS is dissociation of the C-S bond to give CH3S and CH2Cl. MBL box modeling calculations show that buildup of MClDMS at night from the Cl2 + DMS reaction leads to enhanced SO2 production during the day. The extra SO2 arises from photolysis of MClDMS to give CH3S and CH2Cl, followed by subsequent oxidation of CH3S.


Assuntos
Poluentes Atmosféricos/análise , Cloro/química , Modelos Químicos , Fotólise , Sulfetos/análise , Dióxido de Enxofre/análise , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Atmosfera/química , Cinética , Oxirredução , Água do Mar/química , Sulfetos/química , Sulfetos/efeitos da radiação , Dióxido de Enxofre/química , Dióxido de Enxofre/efeitos da radiação , Luz Solar
18.
Environ Health Perspect ; 121(11-12): 1344-8, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24148996

RESUMO

BACKGROUND: The cardiopulmonary effects of the individual criteria air pollutants have been well investigated, but little is known about the cardiopulmonary effects of inhaled multipollutant mixtures that more realistically represent environmental exposures. OBJECTIVES: We assessed the cardiopulmonary effects of exposure to photochemically altered particle-free multipollutant mixtures. METHODS: We exposed mice to filtered air (FA), multipollutant mixtures, or ozone (O3) for 4 hr in a photochemical reaction chamber. Eight hours after exposure, we assessed cardiac responses using a Langendorff preparation in a protocol consisting of 20 min of global ischemia followed by 2 hr of reperfusion. Cardiac function was assessed by measuring the index of left-ventricular developed pressure (LVDP) and contractility (dP/dt) before ischemia. On reperfusion after ischemia, recovery of postischemic LVDP and size of infarct were examined. We used bronchoalveolar lavage (BAL) cell counts to assess lung inflammation. RESULTS: Exposure to the multipollutant mixtures decreased LVDP, baseline rate of left ventricular contraction (dP/dtmaximum), and baseline rate of left ventricular relaxation (dP/dtminimum) compared with exposure to FA. Exposure to O3 also decreased heart rate and dP/dtminimum. Time to ischemic contracture was prolonged in the multipollutant-mixture group relative to that in the FA group. Mice in the multipollutant-mixture group had better recovery of postischemic LVDP and smaller infarct size. Exposure to multipollutant mixtures and to O3 exposure increased numbers of macrophages in the BAL fluid. CONCLUSIONS: Exposure to photochemically altered urban air pollution appears to affect cardiac mechanics in isolated perfused hearts. Inhalation of acute multipollutant mixtures decreases LVDP and cardiac contractility in isolated non-ischemic murine hearts, prolongs ischemic contracture, increases postischemic recovery of LVDP, and reduces infarct size.


Assuntos
Poluentes Atmosféricos/efeitos da radiação , Poluentes Atmosféricos/toxicidade , Exposição Ambiental/análise , Luz , Contração Miocárdica/efeitos dos fármacos , Traumatismo por Reperfusão Miocárdica/fisiopatologia , Poluentes Atmosféricos/análise , Animais , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Lavagem Broncoalveolar , Camundongos , Ozônio , Estatísticas não Paramétricas , Função Ventricular Esquerda/efeitos dos fármacos , Função Ventricular Esquerda/fisiologia
19.
Environ Sci Process Impacts ; 15(10): 1883-8, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23955120

RESUMO

A laboratory reactor system was developed to examine the role of light and aerosol composition in the reduction of oxidized mercury (Hg(ii)) in laboratory-generated aerosols. Aerosolized sodium chloride, doped with mercury chloride, was exposed to light in a fixed-bed flow-through reactor. Three spectral ranges (UV, visible and a simulated solar spectrum) were examined, along with dark experiments, to investigate the role of light conditions in mercury reduction. In addition, the role of iron in the aerosol matrix was examined. The effluent from the reactor was analyzed for Hg(0) as evidence of reduction of Hg(ii) in the reactor. Significant reduction of Hg(ii) (1.5-9.9%) was observed for all three light sources and the rate of mercury reduction was proportional to the light irradiance. The presence of iron in the aerosol matrix inhibited the reduction rate and the degree of inhibition was dependent on the chemical form of the iron in the aerosol. The observed reduction reactions may be important chemical processes in the atmosphere and could be incorporated in atmospheric transport models that are used to understand the fate of atmospheric mercury.


Assuntos
Poluentes Atmosféricos , Luz , Compostos de Mercúrio , Fotólise , Aerossóis , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Compostos de Mercúrio/química , Compostos de Mercúrio/efeitos da radiação , Modelos Teóricos , Oxirredução
20.
Berl Munch Tierarztl Wochenschr ; 126(3-4): 143-8, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23540197

RESUMO

There is a need for technical solutions to reduce the concentrations of bioaerosols in the air and in the exhaust air of livestock buildings. A prototype of an air washer combined with a UV-irradiation system was positioned in a commercial pig fattening unit to test its efficiency of reducing culturable airborne microorganisms. No significant reduction in airborne bacteria and fungi was observed when untreated air passed through the device. However, when the air washer or the UV-irradiation system was activated, the concentrations of mesophilic aerobic bacteria, methicillin resistant Staphylococcus aureus and mesophilic aerotolerant cocci were reduced significantly (p < 0.01). Washing the air reduced bacteria by 84 to 96% and the relative reduction due to UV-irradiation ranged between 55 and 90%. The highest relative reduction in airborne bacteria (90 to 99%) was detected when the air washer and the UV-irradiation systems were in simultaneous operation. The concentration of total airborne fungi was reduced significantly (p < 0.05) only when the air was washed and UV-irradiated. Although these preliminary results provided significant and comprehensible findings, long-term studies are required to assess the efficiency of the device in more detail.The combination of air washing and UV-irradiation seem to be a useful technique for abating airborne microorganisms within or emitting from piggery buildings. However, some technical problems remain, such as the deposition of particulate matter on the surface of UV-irradiators and the consumption of fresh water by the air washer. These issues must be resolved before the system may be implemented for general practice.


Assuntos
Microbiologia do Ar , Poluentes Atmosféricos/isolamento & purificação , Filtração/métodos , Abrigo para Animais , Sus scrofa , Doenças dos Suínos/prevenção & controle , Poluentes Atmosféricos/efeitos da radiação , Animais , Contagem de Colônia Microbiana , Suínos , Doenças dos Suínos/microbiologia , Raios Ultravioleta
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