Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 34
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Environ Int ; 137: 105556, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-32059148

RESUMO

Air pollution events occurred frequently in China, and tremendous efforts were devoted to the reduction of air pollution in recent years. Here, analysis of ambient monitoring data of six criteria air pollutants from 367 Chinese cities during 2015-2018, showed that PM2.5, PM10, SO2 and CO were reduced significantly by 22.1%, 13.5%, 46.4% and 21.5%, respectively, NO2 reduction was less significant (6.3%) while O3 level instead increased over China (13.7%). Spatial distribution, seasonal, monthly and diurnal variations of the air pollutants during 2018, implicated of effective control measures, were discussed in details, especially for the five key densely populated regions of Jing-Jin-Ji (JJJ), Fen Wei Plains (FWP), Yangtze River Delta (YRD), Sichuan Basin (SCB) and Pearl River Delta (PRD). Moreover, excess health risks (ERs) of the six pollutants were estimated for 2018, and such risks was two times higher if the World Health Organization (WHO) air quality guideline rather than Chinese guideline was adopted. PM10 rather than PM2.5 was the dominant contributor to ERs, and the case with both PM2.5 and PM10 exceeding threshold values occupied ~1/3 of total days, yet contributed ~2/3 of total ERs. For 2018, the health-risk based air quality index (HAQI) was further calculated by combining health risks from multiple pollutants, and it was found that high HAQI mostly distributed in North China Plain (NCP). ~15%, ~85% and ~95% people in YRD, FWP and JJJ were exposed to polluted air (HAQI > 100), and population-normalized HAQI further added the inequality, JJJ and a small region of SCB had much higher HAQI (>280). Investigations on HAQI with socioeconomic factors show that total population, population density and built-up area presented an inverted U-shape, suggesting existence of Environmental Kuznets Curve (EKC), while a positive relationship was found between HAQI and share of secondary industry. Multiple regression analysis suggested that built-up area was the most prominent factor to HAQI, followed by the gross domestic product (GDP). The findings here demonstrate in great details the current characteristics of air pollution and its associated health risks in China, therefore providing important implications for effective air pollution control strategies in near future for different regions of China.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32041887

RESUMO

Although regional haze adversely affects human health and possibly counteracts global warming from increasing levels of greenhouse gases, the formation and radiative forcing of regional haze on climate remain uncertain. By combining field measurements, laboratory experiments, and model simulations, we show a remarkable role of black carbon (BC) particles in driving the formation and trend of regional haze. Our analysis of long-term measurements in China indicates declined frequency of heavy haze events along with significantly reduced SO2, but negligibly alleviated haze severity. Also, no improving trend exists for moderate haze events. Our complementary laboratory experiments demonstrate that SO2 oxidation is efficiently catalyzed on BC particles in the presence of NO2 and NH3, even at low SO2 and intermediate relative humidity levels. Inclusion of the BC reaction accounts for about 90-100% and 30-50% of the sulfate production during moderate and heavy haze events, respectively. Calculations using a radiative transfer model and accounting for the sulfate formation on BC yield an invariant radiative forcing of nearly zero W m-2 on the top of the atmosphere throughout haze development, indicating small net climatic cooling/warming but large surface cooling, atmospheric heating, and air stagnation. This BC catalytic chemistry facilitates haze development and explains the observed trends of regional haze in China. Our results imply that reduction of SO2 alone is insufficient in mitigating haze occurrence and highlight the necessity of accurate representation of the BC chemical and radiative properties in predicting the formation and assessing the impacts of regional haze.

3.
J Chromatogr A ; : 460941, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32044124

RESUMO

Carbohydrates (such as levoglucosan) are a class of important water-soluble organic compounds in atmosphere. In this study, a high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was applied to characterize carbohydrates in aerosol particles. Since carbohydrate was a kind of compound with low response in mass spectrometry, the conventional HPLC-MS/MS method was not sensitive enough to determine it. When acetate acid was added into mobile phase as buffer, the transition of [M+CH3COO]-→[M-H]- could be selected as the quantification ions. In the range from 1.0 µg L-1 to 20 µg mL-1, the coefficients of regression (r2) were more than 0.990, and relative standard deviations (RSD) for replicated injections were lower than 2%. The limit of detection (LOD) and quantification (LOQ) were lower than 2.5 ng L-1 and 10 ng L-1, respectively. The precision and accuracy were examined by spiked samples at three different concentration levels (10 µg L-1, 100 µg L-1, and 500 µg L-1) in five replicates. Recovery ratios ranged from 85% to 115% with RSD lower than 16%. Matrix effects of different carbohydrates ranged from 62% to 120%. The most sensitive HPLC-MS/MS method was developed and validated to analyze 40 aerosol samples successfully. The carbohydrates including three sugar alcohols (threitol, arabitol and sorbitol), one monosaccharide sugar (inositol), two disaccharides (sucrose, trehalose), one anhydrosugar (levoglucosan) and one 2-methyltetrols (2-Methylbutane-1,2,3,4-tretraol) were successfully quantified.

5.
Chemosphere ; 238: 124620, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31472354

RESUMO

Particulate toxic species, such as polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), polycyclic aromatic hydrocarbons (PAHs) and heavy metals may have significant health risks. This study investigated characteristics, sources and health risks of all three classes of toxic species in PM2.5 (particles with aerodynamic diameter ≤2.5 µm) samples collected at an industrial area in Changzhou, a big city in the Yangtze Delta region of China. Fourteen heavy metals altogether constituted 2.87% of PM2.5 mass, with Fe, Al and Zn as the major elements. Principal component analysis (PCA) suggested that heavy metals came from four sources: vehicles, industry, crustal dust, mixed coal combustion and industrial process. The daily average concentration of 18 PAHs was 235.29 ng/m3, accounting for 0.21% of PM2.5 mass. The dominant PAHs were high molecular weight ones, contributing 73.5% to the total PAHs. Diagnostic analyses indicated that sources of PAHs included vehicle/coal combustion and petroleum emissions, wherein diesel emission played a more important role than gasoline emission. PCA showed that the largest contributor of PAHs was vehicle exhaust mixed with coal combustion, followed by three industry-related sources. Total concentration of 17 PCDD/Fs varied between 3.14 and 37.07 pg/m3, with an average of 14.58 pg/m3. The 10 PCDFs accounted for 70.5% of total concentration of 17 PCDD/Fs. Health risk assessments showed that the carcinogenic risk of heavy metals was acceptable, while risks from PAHs and PCDD/Fs cannot be ignored. Back trajectory analysis indicated that local/regional transported air masses from northern China was the major source areas of the toxic species.


Assuntos
Exposição por Inalação/efeitos adversos , Metais Pesados/análise , Neoplasias/induzido quimicamente , Material Particulado/efeitos adversos , Dibenzodioxinas Policloradas/análise , Hidrocarbonetos Policíclicos Aromáticos/análise , Medição de Risco/métodos , Adulto , Poluentes Atmosféricos/análise , Carcinógenos/análise , Criança , China , Monitoramento Ambiental , Feminino , Humanos , Indústrias , Exposição por Inalação/análise , Masculino , Material Particulado/administração & dosagem , Dibenzodioxinas Policloradas/efeitos adversos , Hidrocarbonetos Policíclicos Aromáticos/efeitos adversos , Estações do Ano , Emissões de Veículos/análise
6.
Environ Sci Technol ; 53(24): 14212-14221, 2019 Dec 17.
Artigo em Inglês | MEDLINE | ID: mdl-31722174

RESUMO

The hygroscopic properties of BC-containing particles (BCc) are important to determine their wet scavenging, atmospheric lifetime, and interactions with clouds. Such information is still lacking in the real world because of the challenges in isolating BCc from other aerosols to be directly characterized. In this study, the size-resolved chemical components of BCc including the refractory BC core and associated coatings were measured by a soot particle-aerosol mass spectrometer in suburban Nanjing. The size-resolved hygroscopicity parameter of BCc (κBCc) was obtained based on this full chemical characterization of BCc. We found increased inorganic fraction and more oxidized organic coatings with thicker coatings, which modified κBCc besides the determinant of particle size. The bulk κBCc was observed to range from 0.11 to 0.34. The size-resolved κBCc consistently showed minima at coated diameter (Dcoated) of 100 nm, parametrized as κ(x) = 0.28-0.35 × exp(-0.004 × x), x = Dcoated. Under critical supersaturations (SS) of 0.1% and 0.2%, the D50 values of BCc were 200 ± 20 and 135 ± 18 nm, respectively. On average 33 ± 16% and 59 ± 20% of BCc in number could be activated at SS = 0.1% and 0.2%, respectively. These results provide constraints on surface CCN sources for the light-absorbing BC-containing particles.

7.
Sci Total Environ ; 685: 976-985, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31390715

RESUMO

Secondary organic aerosol (SOA) species formed in atmospheric aqueous phases is recently recognized as an important contributor to fine aerosols, which is known to be a prominent human health risk factor internationally. This work, for the first time, systematically investigated aqueous-phase photochemical oxidation of 4-ethylphenol (4-EP) - a model compound from biomass burning and a surrogate of intermediate volatility organic compounds, under both ultraviolet (UV) (Hg lamp) and simulated sunlight (Xe lamp). We found that 4-EP could degrade upon hydroxal radical (OH) oxidation under UV light nearly 15 times faster than that under simulated sunlight, but large aqueous SOA (aqSOA) yields (108%-122%) were observed under both situations. AqSOA masses and oxidation states continuously increased under simulated sunlight, yet they increased first then decreased quickly under UV light. We proposed a reaction scheme based on identified products, showing that oligomerization, functionalization and fragmentation all can occur during 4-EP oxidation. Our results demonstrate that OH radical may suppress oligomerization and functionalization, but is favorable for fragmentation. Under UV light with H2O2 (high OH), fragmentation was dominant, producing more volatile and smaller molecules, and less aqSOA in later oxidation; Under simulated sunlight with H2O2 (moderate OH), functionalization that can form hydroxylated monomer was more important. Moreover, 4-EP oxidation by the organic triplet excited state (3C*) could form species with stronger visible light absorptivity than those from OH-mediated oxidation, and the absorptivity showed positive link with contents of humic-like substances.

8.
Sci Total Environ ; 678: 301-308, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31075597

RESUMO

Heavy metals are widely recognized as toxic components in urban air particulate matter (PM). However, the major toxic metals and their interactions are poorly understood. In this study, we attempted to explore the toxicity contribution and combined effects of PM-bounded metals in human lung epithelial cells (A549). Real-time cell analysis indicated that the critical toxic concentration (EC50) of PM detected in this study was 107.90 mg/L (r2 = 1.00, p < 0.01). The cell viability of A549 increased significantly (12.3%) after metal removal in PM, demonstrating an important contribution of metal components to PM toxicity. Among eleven elements examined (Zn, Cr, Mn, Fe, Ni, Cu, As, Se, Sr, Cd, and Pb), six heavy metals (Zn, Cr, Mn, Fe, Cu, and Pb) might account for PM toxicity in A549 cells, and their co-exposure led to a high mortality of A549 cells (36.5 ±â€¯7.3%). For combination treatments, cell mortality caused by single or multiple metal mixtures was usually alleviated by Fe addition, while it was often aggravated in the presence of Mn. The varying effects of other metals (Zn, Cu, Pb and Cr) on different metal mixtures might be explained by their interactions (e.g., similar or dissimilar membrane transporters and intracellular targets). Furthermore, the concentration addition model (CA), independent action model (IA), integrated addition model (IAM) and integrated addition and interaction model (IAI) were used to predict mixture toxicity, and the IAI model exhibited the least variation between observed and predicted toxic effects (r2 = 0.87, p < 0.01). Our results highlight the potential contribution from heavy metals and their interactions to PM toxicity, and promote the application of toxicity prediction models on metal components in PM.


Assuntos
Poluentes Atmosféricos/toxicidade , Pulmão/efeitos dos fármacos , Metais Pesados/toxicidade , Material Particulado/toxicidade , Células A549 , Humanos , Testes de Toxicidade
9.
Chemosphere ; 221: 452-463, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30654259

RESUMO

The North China Plain and the Yangtze River Delta are the two of the most heavily polluted regions in China. Observational studies revealed that 'explosive' PM2.5 mass concentration growths frequently occurred in the two regions. This study analyzed all the PM2.5 mass concentration growth processes from clean condition (i.e., <35 µg m-3) to heavy pollution condition (i.e., >150 µg m-3) in Beijing (BJ) and Shanghai (SH), two representative cities of the two regions, using hourly monitored PM2.5 concentrations during 2013-2016. 173 and 76 growth processes were identified in BJ and SH, respectively. PM2.5 rising rates (PMRR) and dynamic growth durations were calculated to illustrate the characteristics of the growth processes. Hourly particulate chemical composition data and meteorological data in BJ and SH were further analyzed. The 4-year averaged PMRR of PM2.5 total mass were similarly of 7.11 ±â€¯9.82 µg m-3 h-1 in BJ and 6.71 ±â€¯6.89 µg m-3 h-1 in SH. A decreasing trend was found for the PM2.5 growth processes in two cities from 2013 to 2016, reflecting the effectiveness of emission controls implemented in the past years. The contributions of particulate components to the PM2.5 total mass growth were different in BJ and SH. Average PMRR value of PM1 organic aerosols (OA), SO42-, NO3-, and NH4+ in BJ was 1.90, 0.95, 0.82, and 0.53 µg m-3 h-1, respectively. Average PMRR of PM2.5 OA, SO42-, NO3-, and NH4+ in SH was 1.70, 1.18, 1.99 and 1.14 µg m-3 h-1, respectively. Based on the contributions of different components, the PM2.5 mass concentration growth processes in BJ and SH were proposed to be classified into 'other components-dominant growth processes', 'all components-contributing growth processes', 'one or more explosive secondary components-dominant growth processes', and 'mixed-factor growth processes'. Potential source contribution function analysis and the meteorological condition analysis showed that source origins and prevailing wind for the two cities during different categories of growth processes had substantial difference. The important source areas included Hebei and Shandong for BJ, and Jiangsu and Anhui for SH. The dominant wind directions during growth processes were northeast, south and southwest in BJ, and were west to north in SH. The results suggested the contributing components, the prevailing wind conditions, and the formation processes were substantially different in the two cities, despite the similar PMRR of PM2.5 total mass during the growth processes between BJ and SH. Future research is needed to study the detailed formation mechanisms of the different PM2.5 mass concentration growth processes in the two cities.


Assuntos
Poluentes Atmosféricos/análise , Monitoramento Ambiental , Material Particulado/análise , Aerossóis/análise , Poluição do Ar/análise , Poluição do Ar/prevenção & controle , Pequim , China , Cidades , Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Vento
10.
Sci Total Environ ; 646: 1567-1577, 2019 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-30235641

RESUMO

The activated bio-chars (AB) were successfully synthesized from rice husk by one- and two-step KOH-catalyzed pyrolysis. The two-step pyrolysis can produce the high yields of AB compared to the one-step pyrolysis. Moreover, the yield of AB decreased with the increase of the mass ratio of KOH and char, which had a significant effect on the development of the surface area and porosity of carbon. In particular, the AB derived from the two-step pyrolysis at 750°C (mass ratio of KOH and char was 3) had the highest specific surface area (SBET=2138m2/g) with many micro-porous structures, which was favored for the phenol adsorption. The maximum adsorption capacity of AB2-3-750 reached 201mg/g because of its excellent surface porosity property. The phenol can be efficiently removed from water by only several minutes. The Langmuir model defined well the adsorption isotherm with a high correlation coefficient value, indicating a monolayer adsorption behavior. And the adsorption process defined well with the pseudo-second-order model. The phenol molecules passed into the internal surface via the liquid-film controlled diffusion, so the behavior of phenol adsorption onto the AB was predominantly controlled via the chemisorption. Furthermore, the functional groups on the outer surfaces of AB can attract the phenol molecules onto the internal surfaces via "π-π dispersion interaction" and "donor-acceptor effect".


Assuntos
Carvão Vegetal/química , Hidróxidos/química , Fenol/metabolismo , Compostos de Potássio/química , Adsorção , Modelos Químicos , Oryza , Fenóis
11.
Dalton Trans ; 47(43): 15382-15390, 2018 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-30303508

RESUMO

Graphitic carbon nitride (g-C3N4) is a low cost photocatalyst for the visible light-driven degradation of aqueous organic pollutants. Nevertheless, the fast recombination of electron-hole pairs significantly inhibits its photocatalytic activity. Consequently, we report a novel strategy in which the low cost α-Fe2O3 photocatalyst is in situ introduced to accelerate the photogenerated charge separation of g-C3N4 based on a Z-scheme mechanism. Under the irradiation of visible light, the photocatalytic activity significantly improved on coupling g-C3N4 and α-Fe2O3, and a peak Rhodamine B (RhB) degradation efficiency of over 99% were observed. This value is significantly higher than that over pure g-C3N4 (ca. 67%) and α-Fe2O3 (ca. 6%). Additionally, the as-prepared g-C3N4/Fe2O3 exhibits highly stable photocatalytic activity. The loading of α-Fe2O3 on the g-C3N4 surface results in the formation of a direct solid-state Z-scheme structure. The improved separation of electron-hole pairs and strong redox ability of the charge carriers are responsible for the improved photocatalytic activity of g-C3N4/Fe2O3. Finally, the h+ and ˙O2- radicals are confirmed as the major oxidation species and a possible photocatalytic mechanism is proposed in the g-C3N4/Fe2O3 reaction system. This work is of significance to promote the large-scale application of g-C3N4-based photocatalysts in water purification.

12.
Bioresour Technol ; 269: 67-73, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30149256

RESUMO

This paper studied the KOH-catalyzed pyrolysis of rice husk (RH) and its pellet (RHP) at a high temperature (750 °C) for activated bio-carbons production. The mass ratio of KOH and biomass greatly impacted the pyrolysis kinetic and biochar property. The KOH catalysis (mass ratio: 1) reduced significantly the activation energy to 41 kJ/mol. During carbonization with KOH, the in-situ generated K2CO3 tailored the morphology and size of the self-template (SiO2 nanoparticles), giving rise to the chars with the open foam-like porous architectures enrich in micro- and meso-pores. Thus, the KOH activation via one-step pyrolysis could produce the micro-mesoporous carbons (e.g., RH-char 1 and RHP-char 1) with high specific surface areas and high content of oxygen-functionalities. Furthermore, the hierarchical porous carbons have high potential applications in adsorption process and electrochemical energy storage (e.g., supercapacitor) because of their unique physicochemical properties.


Assuntos
Carbono/química , Oryza , Adsorção , Catálise , Dióxido de Silício
13.
J Environ Manage ; 214: 94-103, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29518601

RESUMO

This work studied the disposal of the non-metallic fraction from waste printed circuit board (NMF-WPCB) via the chemical pretreatments followed by pyrolysis. As a main heavy metal, the metallic Cu could be significantly removed by 92.4% using the HCl leaching process. Subsequently, the organic-Br in the brominated flame retardants (BFRs) plastics could be converted into HBr by pyrolysis. The alkali pretreatment was benefit for the Br fixation in the solid char. The Br fixation efficiency could reach up to 53.6% by the NaOH pretreatment followed by the pyrolysis process. The formed HBr could react with NaOH/KOH to generate the stabilized NaBr/KBr. Therefore, the integrated chemical pretreatment could be used for the eco-friendly disposal of the NMF-WPCB via pyrolysis.


Assuntos
Resíduo Eletrônico , Plásticos , Retardadores de Chama , Metais Pesados
14.
Artigo em Inglês | MEDLINE | ID: mdl-29584626

RESUMO

Particulate matter (PM) air pollution has become a serious environmental problem in Nanjing and poses great health risks to local residents. In this study, characteristics of particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) over Nanjing were analyzed using hourly and daily averaged PM2.5 concentrations and meteorological parameters collected from nine national monitoring sites during the period of March 2014 to February 2017. Then, the integrated exposure-response (IER) model was applied to assess premature mortality, years of life lost (YLL) attributable to PM2.5, and mortality benefits due to PM2.5 reductions. The concentrations of PM2.5 varied among hours, seasons and years, which can be explained by differences in emission sources, secondary formations and meteorological conditions. The decreased ratio of PM2.5 to CO suggested that secondary contributions decreased while the relative contributions of vehicle exhaust increased from increased CO data. According to the values of attributable fractions (AF), stroke was the major cause of death, followed by ischemic heart disease (IHD), lung cancer (LC) and chronic obstructive pulmonary disease (COPD). The estimated total deaths in Nanjing due to PM2.5 were 12,055 and 10,771, leading to 98,802 and 87,647 years of life lost in 2014 and 2015, respectively. The elderly and males had higher health risks than youngsters and females. When the PM2.5 concentrations meet the World Health Organization (WHO) Air Quality Guidelines (AQG) of 10 µg/m³, 84% of the premature deaths would be avoided, indicating that the Nanjing government needs to adopt more stringent measure to reduce PM pollution and enhance the health benefits.


Assuntos
Poluentes Atmosféricos/análise , Neoplasias Pulmonares/mortalidade , Mortalidade Prematura , Isquemia Miocárdica/mortalidade , Material Particulado/análise , Doença Pulmonar Obstrutiva Crônica/mortalidade , Acidente Vascular Cerebral/mortalidade , Adulto , Idoso , Monóxido de Carbono/análise , China/epidemiologia , Monitoramento Ambiental , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tamanho da Partícula , Emissões de Veículos
15.
Sci Total Environ ; 621: 1074-1083, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29056388

RESUMO

Stabilized iron sulfide (FeS) nanoparticles have been proven effective in the adsorption of Hg from the water environment. However, previous work with these nanoparticles determined that the separation from the treated water was difficult and time-consuming. In this study, nanoscale FeS-Fe3O4 nanocomposites were firstly synthesized with chitosan as the stabilizer (CTO-MFeS). Then, the Hg adsorption capacity and mechanism were studied. Results showed that the size of the prepared nanoparticles was about 20nm and the specific surface area was 21.3m2/g. Hg removal by the CTO-MFeS nanoparticles involved both adsorption and precipitation. Further investigation with XPS showed that Hg2+ was adsorbed on the surface of the CTO-MFeS nanoparticles and reacted with CTO-MFeS to form HgS and [Fe(1-x)Hgx]S. It was also found as pH decreased below 4, the adsorption capacity of CTO-MFeS was significantly reduced that might be due to the dissolving of Fe. Additionally, the presence of Cl- resulted in the transformation of Hg2+ to HgClx2-x (x=1, 2, 3, 4) that competed with OH in solution for Hg2+ and therefore inhibited the adsorption of Hg. Our findings provide additional information that may be useful for a theoretical basis for Hg treatment in water environment.

16.
Environ Sci Technol ; 51(24): 14072-14082, 2017 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-29131606

RESUMO

Refractory black carbon (rBC) aerosol is an important climate forcer, and its impacts are greatly influenced by the species associated with rBC cores. However, relevant knowledge is particularly lacking at the Tibetan Plateau (TP). Here we report, for the first time, highly time-resolved measurement results of rBC and its coating species in central TP (4730 m a.s.l), using an Aerodyne soot particle aerosol mass spectrometer (SP-AMS), which selectively measured rBC-containing particles. We found that the rBC was overall thickly coated with an average mass ratio of coating to rBC (RBC) of ∼7.7, and the coating species were predominantly secondarily formed by photochemical reactions. Interestingly, the thickly coated rBC was less oxygenated than the thinly coated rBC, mainly due to influence of the transported biomass burning organic aerosol (BBOA). This BBOA was relatively fresh but formed very thick coating on rBC. We further estimated the "lensing effect" of coating semiquantitatively by comparing the measurement data from a multiangle absorption photometer and SP-AMS, and found it could lead to up to 40% light absorption enhancement at RBC > 10. Our findings highlight that BBOA can significantly affect the "lensing effect", in addition to its relatively well-known role as light-absorbing "brown carbon."


Assuntos
Aerossóis , Poluentes Atmosféricos , Fuligem , Biomassa , Carbono , Tibet
17.
Environ Pollut ; 231(Pt 1): 752-760, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28865380

RESUMO

The present study aimed to investigate biodegradation mechanisms of black carbon (BC)-bound contaminants in BC-amended sediment when BC was applied to control organic pollution. The single-point Tenax desorption technique was applied to track the species changes of nonylphenol (NP) during biodegradation process in the rice straw carbon (RC)-amended sediment. And the correlation between the biodegradation and desorption of NP was analyzed. Results showed that microorganisms firstly degraded the rapid-desorbing NP (6 h Tenax desorption) in RC-amended sediment. The biodegradation facilitated the desorption of slow-desorbing NP, which was subsequently degraded as well (192 h Tenax desorption). Notably, the final amount of NP degradation was greater than that of NP desorption, indicating that absorbed NP by RC amendment can be degraded by microorganisms. Finally, the residual NP amount in RC-amended sediment was decided by RC content and its physicochemical property. Moreover, the presence of the biofilm was observed by the confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM) so that microorganisms were able to overcome the mass transfer resistance and directly utilized the absorbed NP. Therefore, single-point Tenax desorption alone may not be an adequate basis for the prediction of the bioaccessibility of contaminants to microorganisms or bioremediation potential in BC-amended sediment.


Assuntos
Biodegradação Ambiental , Sedimentos Geológicos/química , Fenóis/análise , Poluentes do Solo/análise , Carbono/química , Fuligem/química
18.
Environ Sci Pollut Res Int ; 24(31): 24473-24484, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-28895018

RESUMO

A composite catalyst for the selective catalytic reduction (SCR) of NOx with NH3 is investigated, in which the rare earth (RE, including La, Ce, Pr, and Nd) is doped into manganese oxides supported on activated semi-coke (MnOx/ASC) via hydrothermal method at the molar ratio of Mn:RE = 1:5. It is evidenced that the addition of RE at a rather low molar ratio can enhance the catalytic activity of MnOx/ASC. The catalyst with a Mn:Ce molar ratio of 10:1 yields an over 90% NOx removal efficiency in the temperature range of 150-250 °C. An approximate 100% NO conversion and 95% N2 selectivity are achieved at about 200 °C. The catalysts are characterized by N2 physisorption, X-ray powder diffraction (XRD), scanning electron microscope (SEM), hydrogen temperature-programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS). The results indicated that the Ce additive is conducive to the NOx adsorption and then accelerates the SCR reaction due to the formation of more chemisorbed oxygen (Oß), which is favored during the oxidation of NH3 and NO. Moreover, the in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) results confirm that the Ce additive on MnOx/ASC catalyst could provide more active Brønsted acid sites, which eventually contributes to the SCR reaction. The generation of ad-NH4+ and nitrite species is proved to play the crucial role in the promotional effect of RE addition.


Assuntos
Poluentes Atmosféricos/química , Poluição do Ar/prevenção & controle , Amônia/química , Coque/análise , Compostos de Manganês/análise , Metais Terras Raras/análise , Óxido Nítrico/química , Óxidos/análise , Catálise , Oxirredução
19.
Environ Sci Pollut Res Int ; 24(26): 21386-21397, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28744677

RESUMO

Brown carbon (BrC) has recently received much attention because of its light absorption features. The chemical compositions, optical properties, and sources of fine aerosol at a high-elevation mountain observatory (4730 m a.s.l.) in the central Tibetan Plateau were measured between 31 May and 1 July 2015. A low flow-rate sampler was used to collect 24-h average fine particulate matter (PM2.5) filter samples. Water-soluble ions, organic carbon (OC), elemental carbon, water-soluble organic carbon (WSOC), and light absorption by water-soluble BrC were determined for 26 filter samples. The mean (± 1σ) OC and WSOC concentrations were 0.76 ± 0.43 and 0.39 ± 0.15 µgC/m3, respectively, and the mean WSOC/OC mass ratio was 0.59 ± 0.22. The OC and WSOC concentrations were relatively higher (0.59-1.80 and 0.33-0.83 µgC/m3, respectively) during the pre-monsoon period (2-13 June) and were relatively lower (0.27-0.77 and 0.12-0.50 µgC/m3, respectively) during the monsoon period (14 June to 1 July), probably because of wet scavenging of aerosols during long-range transport and the presence of cleaner marine air masses during the monsoon period. The absorption spectra of PM2.5 water extracts smoothly increase from visible range to ultraviolet range. The absorption Ångström exponent, which describes the wavelength dependence of water-soluble BrC, was 2.74-10.61 (mean 6.19 ± 1.70), and its value was similar in the pre-monsoon period (6.57 ± 0.56) to that in the monsoon period (5.91 ± 2.14). The water-soluble BrC mass absorption efficiency, 0.38 ± 0.16 m2/(g C), was much lower than those observed in most urban areas but similar to those in other remote sites. Absorption coefficient at 365 nm, typically used as a proxy for water-soluble BrC, correlated well with the WSOC concentration (R 2  = 0.57), K+ concentration (R 2  = 0.75), and organic aerosol biomass burning markers characterized by an Aerodyne aerosol mass spectrometer (C2H4O2+ + C3H5O2+, R 2  = 0.60). It can be inferred that biomass burning was an important source of water-soluble BrC in the study area combined with air mass back trajectory analysis using the NOAA HYSPLIT as well as MODIS data of fire dots and aerosol optical depths. The water-soluble BrC to BC light absorption (at 365 nm) coefficient ratios were 9-27%.


Assuntos
Poluentes Atmosféricos/análise , Carbono/análise , Monitoramento Ambiental/métodos , Luz , Material Particulado/análise , Água/química , Aerossóis , Movimentos do Ar , Altitude , Solubilidade , Tibet
20.
Sci Rep ; 7(1): 4726, 2017 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-28680053

RESUMO

The observed strong sorption of hydrophobic organic contaminants (HOCs) to biochar presents potential implications for HOCs bioavailability and bioaccessibility in sediments, while biochar could impact sediment microbial ecology. However, the comprehensive study on the effects of biochar on HOC biodegradation coupled with bioavailability and microbial ecology are rarely documented. In this paper, the effects of biochar on the biodegradation of nonylphenol (NP) were investigated using 3 different NP concentrations (20, 50 and 500 mg/Kg) in sediments amended with different percentage of rice straw biochar (RC). Results showed that the influence of RC on NP biodegradation varied with different NP concentrations. At low NP concentrations, RC suppressed NP biodegradation by reducing NP bioavailability, while at high NP concentrations, moderate RC addition promoted biodegradation by reducing toxicity of NP to microbes. The effects of NP on microbial community structures were significant (P < 0.01), but those of RC were not significant (P > 0.05). The RC affected microorganisms through altering NP toxicity, microbial quantity and activity, but not microbial community structures. This study indicated that there could be an optimal biochar percentage in biochar-sediment systems at different HOC concentrations, which strengthened HOC biodegradation process and accelerated biodegradation rate, forming adsorption-biodegradation coupled bioremediation.


Assuntos
Carvão Vegetal/química , Sedimentos Geológicos/microbiologia , Fenóis/química , Bactérias/efeitos dos fármacos , Biodegradação Ambiental , Disponibilidade Biológica , Sedimentos Geológicos/química , Oryza/química , Fenóis/toxicidade , Poluentes do Solo/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA