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Bai M, Li C, Zhao X, Wang Q, Pan Q. Controllable Synthesis of Sheet-Flower ZnO for Low Temperature NO 2 Sensor. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:1413. [PMID: 37110998 PMCID: PMC10141483 DOI: 10.3390/nano13081413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 04/13/2023] [Accepted: 04/16/2023] [Indexed: 06/19/2023]
Abstract
ZnO is a wide band gap semiconductor metal oxide that not only has excellent electrical properties but also shows excellent gas-sensitive properties and is a promising material for the development of NO2 sensors. However, the current ZnO-based gas sensors usually operate at high temperatures, which greatly increases the energy consumption of the sensors and is not conducive to practical applications. Therefore, there is a need to improve the gas sensitivity and practicality of ZnO-based gas sensors. In this study, three-dimensional sheet-flower ZnO was successfully synthesized at 60 °C by a simple water bath method and modulated by different malic acid concentrations. The phase formation, surface morphology, and elemental composition of the prepared samples were studied by various characterization techniques. The gas sensor based on sheet-flower ZnO has a high response value to NO2 without any modification. The optimal operating temperature is 125 °C, and the response value to 1 ppm NO2 is 125. At the same time, the sensor also has a lower detection limit (100 ppb), good selectivity, and good stability, showing excellent sensing performance. In the future, water bath-based methods are expected to prepare other metal oxide materials with unique structures.
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Chu B, Liu Y, Li H, Jia Y, Liu J, Cao Q, Chen T, Zhang P, Ma Q, Zeng XC, Francisco JS, He H. Photocatalytic Oxidation of NO2 on TiO2: Evidence of a New Source of N2O5. Angew Chem Int Ed Engl 2023:e202304017. [PMID: 37057643 DOI: 10.1002/anie.202304017] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 04/07/2023] [Accepted: 04/11/2023] [Indexed: 04/15/2023]
Abstract
N2O5 is an important intermediate in the atmospheric nitrogen cycle. Using a flow tube reactor, N2O5 was found to be released from the TiO2 surface during the photocatalytic oxidation of NO2, revealing a previously unreported source of N2O5. The rate of N2O5 release from TiO2 was dependent on the initial NO2 concentration, relative humidity, O2/N2 ratio, and irradiation intensity. Experimental evidences and quantum chemical calculations showed that NO2 can react with the surface hydroxyl groups and the generated electron holes on the TiO2, followed by combining with another NO2 molecule to form N2O5. The latter was physisorbed on TiO2 and had a low adsorption energy of -0.13 eV. Box model simulations indicated that the new source of N2O5 released from TiO2 can increase the daytime N2O5 concentration by up to 20% in urban areas if abundant TiO2-containing materials and high NOx concentrations were present. This joint experimental/theoretical study not only demonstrates a new chemical mechanism for N2O5 formation but also has important implications for air quality in urban areas.
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Taha RA, Shalabi AS, Assem MM, Soliman KA. DFT study of adsorbing SO 2, NO 2, and NH 3 gases based on pristine and carbon-doped Al 24N 24 nanocages. J Mol Model 2023; 29:140. [PMID: 37059860 PMCID: PMC10104930 DOI: 10.1007/s00894-023-05547-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Accepted: 04/03/2023] [Indexed: 04/16/2023]
Abstract
The adsorption of SO2, NO2, and NH3 toxic gases on Al24N24 and Al24N23C nanocages was investigated by using density functional theory (DFT) calculations. The adsorption energies, frontier orbitals, charge transfer using natural bonding orbital (NBO) analysis, dipole moment, the partial density of states (PDOS), thermodynamic relationships, non-covalent interaction (NCI), and quantum theory of atoms in molecules (QTAIM) were considered. The results reveal that carbon-doped Al24N24 nanocage increases the adsorption energies for SO2 and NO2 gases while decreasing the adsorption energy of NH3 gas. The ΔG for all configurations were negative except the configurations A1 and G2 confirming the weak adsorption of these two complexes. In conclusion, Al24N24 and Al24N23C nanocages are in general promising adsorbents for the removal of SO2, NO2, and NH3 toxic gases. The Al24N24 and Al24N23C nanocages are ideal electronic materials.
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Li S, Yu L, Zhang C, Wang S, Li R, Zhao F, Yin M, Du H, Jia Y, Fan X. Template Based Synthesis of Porous Graphdiyne Nanosheet for Reversible and Fast NO2 Detection by UV Irradiation. Chemphyschem 2023:e202300073. [PMID: 37026532 DOI: 10.1002/cphc.202300073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 03/27/2023] [Accepted: 04/06/2023] [Indexed: 04/08/2023]
Abstract
Graphdiyne (GDY) formed by sp and sp2 hybridized carbon has been proved to be potential novel 2D material for efficiency toxic gas sensing material by density functional theory (DFT). However, almost no relevant research in experimental concerning its gas sensing capability has been reported due to the complex preparation process and harsh experimental conditions. Herein, porous GDY nanosheets are successfully synthesized through a facile solvothermal synthesis technique by using CuO microspheres (MSs) as both template and source of catalyst. The porous GDY nanosheets exhibit a broadband optical absorption, which are suitable for the light-driven optoelectronic gas sensing applications. The GDY-based gas sensor demonstrates excellent reversible to NO2 behaviors at 25 ℃ for the first time. More importantly, higher response value and faster response-recovery times once exposed to NO2 gas molecules are achieved by the illumination of UV light. In this way, our work paves the way for the exploration of GDY-based gas detection experimentally.
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Urso P, Cattaneo A, Pulvirenti S, Vercelli F, Cavallo DM, Carrer P. Early-phase pandemic in Italy: Covid-19 spread determinant factors. Heliyon 2023; 9:e15358. [PMID: 37041936 PMCID: PMC10079324 DOI: 10.1016/j.heliyon.2023.e15358] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 04/02/2023] [Accepted: 04/04/2023] [Indexed: 04/13/2023] Open
Abstract
Although the Covid-19 pandemic is still ongoing, the environmental factors beyond virus transmission are only partially known. This statistical study has the aim to identify the key factors that have affected the virus spread during the early phase of pandemic in Italy, among a wide set of potential determinants concerning demographics, environmental pollution and climate. Because of its heterogeneity in pollution levels and climate conditions, Italy provides an ideal scenario for an ecological study. Moreover, the selected period excludes important confounding factors, as different virus variants, restriction policies or vaccines. The short-term relationship between the infection maximum increase and demographic, pollution and meteo-climatic parameters was investigated, including both winter-spring and summer 2020 data, also focusing separately on the two seasonal periods and on North vs Centre-South. Among main results, the importance of population size confirmed social distancing as a key management option. The pollution hazardous role undoubtedly emerged, as NO2 affected infection increase in all the studied scenarios, PM2.5 manifested its impact in North of Italy, while O3 always showed a protective action. Whereas higher temperatures were beneficial, especially in the cold season with also wind and relative humidity, solar irradiance was always relevant, revealing several significant interactions with other co-factors. Presented findings address the importance of the environment in Sars-CoV-2 spread and indicated that special carefulness should be taken in crowded areas, especially if they are highly polluted and weakly exposed to sun. The results suggest that containment of future epidemics similar to Covid-19 could be supported by reducing environmental pollution, achieving safer social habits and promoting preventive health care for better immune system response, as an only comprehensive strategy.
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Hambir S, Jagtap S. Nitrogen dioxide gas-sensing properties of hydrothermally synthesized WO 3 · nH 2O nanostructures. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221135. [PMID: 37063990 PMCID: PMC10090876 DOI: 10.1098/rsos.221135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Accepted: 03/14/2023] [Indexed: 06/19/2023]
Abstract
Nitrogen dioxide (NO2) has been identified as a serious air pollutant that threats to our environment, human life and world ecosystems. Therefore, detection of this air pollutant is crucial. Metal oxide semiconductor is one of the best approaches frequently used to detect NO2 at relatively low temperatures. Hydrated tungsten trioxide (WO3 · H2O), an n-type semiconductor, is regarded to be a promising material for fabricating gas sensors, which are widely used in environmental and safety monitoring. In this work, WO3 · nH2O nanoparticles have been synthesized using a polyfunctional surfactant-mediated hydrothermal approach in the addition of H2C2O4 and K2SO4 at a molar ratio of 1 : 1. This paper has also reported the effect of reaction temperature (120°C to 200°C) on morphological changes and gas-sensing performance. The characterization of these synthesized nanostructures was carried out by UV-Vis absorption spectroscopy, X-ray diffraction and field-emission scanning electron microscopy (FESEM). The UV absorption peak was obtained around 300 nm. FESEM analysis showed sheet-like structures come together to form flower-type morphology. The synthesized WO3 · nH2O flower-like structures was then used for NO2 gas-sensing application. The prepared sensors showed considerably better sensor response (R g/R a = 17.48) at 185°C for 25 ppm NO2.
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Mollaamin F, Monajjemi M. Transition metal (X = Mn, Fe, Co, Ni, Cu, Zn)-doped graphene as gas sensor for CO 2 and NO 2 detection: a molecular modeling framework by DFT perspective. J Mol Model 2023; 29:119. [PMID: 36988725 DOI: 10.1007/s00894-023-05526-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/22/2023] [Indexed: 03/30/2023]
Abstract
CONTEXT In this research, CO2 and NO2 adsorption on doped nanographene (NG) sheets with transition metals (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, have been applied for scavenging of these toxic gases as the environmental pollutants. The values of changes of atomic charge density have illustrated a more significant charge transfer for Ni-doped C-NG through CO2 adsorption and a more remarkable charge transfer for Co-doped C-NG through NO2 adsorption. The data of NMR spectroscopy has depicted several fluctuations around the graph of Zn-doped on the nanographene surface. The thermodynamic results from IR spectroscopy have indicated that [Formula: see text] values are almost similar for doped metal transitions of Mn, Co, and Cu on the C-NG nanosheet, while [Formula: see text] has the largest gap of Gibbs free energy adsorption with dipole moment. METHODS The Langmuir adsorption model with a three-layered ONIOM using CAM-B3LYP functional accompanying LANL2DZ, EPR-III and 6-31 + G (d,p) basis sets due to Gaussian 16 revision C.01 program on the complexes of CO2 → (Fe, Ni, Zn) and NO2 → (Mn, Co, Cu) doped on the C-NG has been accomplished. Then, NMR and IR spectroscopy, nuclear quadrupole resonance, and natural bond orbital analysis have been accomplished for evaluating chemical shielding tensors, thermodynamic properties, electric potential, and occupancy fluctuation through bond orbitals, respectively. In addition, frontier orbitals of LUMO, HOMO, and also a series of chemical reactivity parameters have been calculated. Finally, time-dependent-DFT method due to UV-VIS spectrums has been accomplished to discern the low-lying excited states of CO2 and NO2 adsorption on the (Fe, Ni, Zn) and (Mn, Co, Cu), respectively, doped C-NG sheet.
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Liu S, Cheng S, Ma J, Xu X, Lv J, Jin J, Guo J, Yu D, Dai X. MAX-DOAS Measurements of Tropospheric NO 2 and HCHO Vertical Profiles at the Longfengshan Regional Background Station in Northeastern China. SENSORS (BASEL, SWITZERLAND) 2023; 23:3269. [PMID: 36991980 PMCID: PMC10099724 DOI: 10.3390/s23063269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/12/2023] [Accepted: 03/15/2023] [Indexed: 06/19/2023]
Abstract
The vertical profiles of nitrogen dioxide (NO2) and formaldehyde (HCHO) in the troposphere at the Longfengshan (LFS) regional atmospheric background station (127°36' E, 44°44' N, 330.5 m above sea level) from 24 October 2020 to 13 October 2021 were retrieved from solar scattering spectra by multi-axis differential optical absorption spectroscopy (MAX-DOAS). We analyzed the temporal variations of NO2 and HCHO as well as the sensitivity of ozone (O3) production to the concentration ratio of HCHO to NO2. The largest NO2 volume mixing ratios (VMRs) occur in the near-surface layer for each month, with high values concentrated in the morning and evening. HCHO has an elevated layer around the altitude of 1.4 km consistently. The means ± standard deviations of vertical column densities (VCDs) and near-surface VMRs were 4.69 ± 3.72 ×1015 molecule·cm-2 and 1.22 ± 1.09 ppb for NO2, and they were 1.19 ± 8.35 × 1016 molecule·cm-2 and 2.41 ± 3.26 ppb for HCHO. The VCDs and near-surface VMRs for NO2 were high in the cold months and low in the warm months, while HCHO presented the opposite. The larger near-surface NO2 VMRs appeared in the condition associated with lower temperature and higher humidity, but this relationship was not found between HCHO and temperature. We also found the O3 production at the Longfengshan station was mainly in the NOx-limited regime. This is the first study presenting the vertical distributions of NO2 and HCHO in the regional background atmosphere of northeastern China, which are significant to enhancing the understanding of background atmospheric chemistry and regional ozone pollution processes.
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Vaičiulis V, Venclovienė J, Miškinytė A, Ustinavičienė R, Dėdelė A, Kalinienė G, Lukšienė D, Tamošiūnas A, Seiduanova L, Radišauskas R. Association between Outdoor Air Pollution and Fatal Acute Myocardial Infarction in Lithuania between 2006 and 2015: A Time Series Design. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2023; 20:4549. [PMID: 36901560 PMCID: PMC10002310 DOI: 10.3390/ijerph20054549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 02/26/2023] [Accepted: 03/02/2023] [Indexed: 06/18/2023]
Abstract
BACKGROUND Air pollution has a significant effect on human health and there is a broad body of evidence showing that exposure to air pollution is associated with an increased risk of adverse health effects. The main objective of this study was to assess the association of traffic-related air pollutants with fatal AMI during the ten-year period. METHODS The study was conducted in Kaunas city, where the WHO MONICA register included a total of 2273 adult cases of fatal AMI cases during the 10-year study period. We focused on the period between 2006 and 2015. The associations between exposure to traffic-related air pollution and the risk of fatal AMI were evaluated by using a multivariate Poisson regression model, RR presented per an increase in IQR. RESULTS It was found that the risk of fatal AMI was significantly higher in all subjects (RR 1.06; 95% CI 1.00-1.12) and women (RR 1.12; 95% CI 1.02-1.22) when the concentration of PM10 in the ambient air was increased 5-11 days before the onset of AMI, adjusting for NO2 concentration. The effect was stronger during spring in all subjects (RR 1.12; 95% CI 1.03-1.22), in men (RR 1.13; 95% CI 1.01-1.26), in younger-aged (RR 1.15; 95% CI 1.03-1.28), and in winter in women (RR 1.24; 95% CI 1.03-1.50). CONCLUSIONS Our findings show that ambient air pollution increases the risk of fatal AMI, and this pertains to PM10 specifically.
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Volke MI, Abarca-Del-Rio R, Ulloa-Tesser C. Impact of mobility restrictions on NO 2 concentrations in key Latin American cities during the first wave of the COVID-19 pandemic. URBAN CLIMATE 2023; 48:101412. [PMID: 36627949 PMCID: PMC9816081 DOI: 10.1016/j.uclim.2023.101412] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 12/13/2022] [Accepted: 01/03/2023] [Indexed: 06/17/2023]
Abstract
Between March and June 2020, activity in the major cities of Latin America declined due to containment efforts implemented by local governments to avoid the rapid spread of COVID-19. Our study compared 2020 with the previous year and demonstrated a considerable drop in tropospheric NO2 levels obtained by the SENTINEL 5P satellite in major Latin American cities. Lima (47.5%), Santiago (36.1%), São Paulo (27%), Rio de Janeiro (23%), Quito (18.6%), Bogota (17.5%), Buenos Aires (16.6%), Guayaquil (15.3%), Medellin (14.2%), La Paz (9.5%), Belo Horizonte (7.8%), Mexico (7.6%) and Brasilia (5.9%) registered statistically significant decreases in NO2 concentrations during the study period. In addition, we analyzed mobility data from Google and Apple reports as well as meteorological information from atmospheric reanalysis data along with satellite fields between 2011 and 2020, and performed a refined multivariate analysis (non-negative matrix approximation) to show that this decrease was associated with a reduction in population mobility rather than meteorological factors. Our findings corroborate the argument that confinement scenarios may indicate how air pollutant concentrations can be effectively reduced and managed.
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NO 2 Sensing Capability of Pt-Au-SnO 2 Composite Nanoceramics at Room Temperature. Molecules 2023; 28:molecules28041759. [PMID: 36838747 PMCID: PMC9967472 DOI: 10.3390/molecules28041759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 02/09/2023] [Accepted: 02/10/2023] [Indexed: 02/17/2023] Open
Abstract
Composite ceramics of metal oxides and noble metals have received much attention for sensing reducing gases at room temperature. Presently, composite ceramics of SnO2 and noble metals have been prepared and investigated for sensing oxidizing NO2 at room temperature. While dramatic increases in resistance were observed for both 1 wt% Pt-SnO2 and 5 wt% Au-SnO2 composite nanoceramics after being exposed to NO2 at room temperature, the largest increase in resistance was observed for 1 wt% Pt-5 wt% -Au-SnO2 composite nanoceramics among the three composites. The response to 0.5 ppm NO2--20% O2-N2 was as high as 875 at room temperature, with a response time of 2566 s and a recovery time of 450 s in the air of 50% relative humidity (RH). Further investigation revealed that water molecules in the air are essential for recovering the resistance of Pt-Au-SnO2 composite nanoceramics. A room temperature NO2-sensing mechanism has been established, in which NO2 molecules are catalyzed by Pt-Au to be chemisorbed on SnO2 at room temperature, and desorbed from SnO2 by the attraction of water molecules in the air. These results suggest that composite ceramics of metal oxides and noble metals should be promising for room temperature sensing, not only reducing gases, but also oxidizing gases.
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Parasin N, Amnuaylojaroen T, Saokaew S. Exposure to PM 10, PM 2.5, and NO 2 and gross motor function in children: a systematic review and meta-analysis. Eur J Pediatr 2023; 182:1495-1504. [PMID: 36754867 DOI: 10.1007/s00431-023-04834-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 02/10/2023]
Abstract
Air pollution exposure has been related to negative gross motor development in children. However, there is currently a lack of conclusive evidence for such a relationship. We carried out a systematic review and meta-analysis using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria to examine whether exposure to air pollution has an impact on children's gross motor development. Of the 9746 papers found, 7 studies examined the impact of air pollutant characteristics, such as PM2.5, PM10, and NO2, on children's gross motor development. The results of the study reveal a significant association between air pollutants and an increased likelihood of negative gross motor development. PM10 was discovered to be considerably riskier for children's gross motor development (effect: - 1.83, 95% CI: - 3.04, - 0.62, p value = 0.002). Additionally, NO2 exhibited indications of a tendency to be connected to a detrimental impact on children's gross motor development (effect - 0.18, 95% CI: - 0.42, 0.07, p value = 0.097). Conclusion: Our study indicates that exposure to PM10, PM2.5, and NO2, especially PM2.5 and PM10, is negatively associated with children's gross motor development. However, further research is required to determine how exposure to prenatal air pollution affects children's gross motor development. What is Known - What is New: • In this study, we provide an overview of emerging data related to PM10, PM2.5, and NO2 exposure in child development, especially on the gross motor function that continues to emerge, and key findings are highlighted. • Additionally, we summarize the evidence on the underlying effect of air pollution on gross motor function from human studies.. • Overall, we emphasize that evidence from human studies is critical in suggesting detrimental child health outcomes of an action to promote preventive strategies that will effectively protect children's health..
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Al Yammahi A, Aung Z. Forecasting the concentration of NO2 using statistical and machine learning methods: A case study in the UAE. Heliyon 2023; 9:e12584. [PMID: 36793966 PMCID: PMC9922785 DOI: 10.1016/j.heliyon.2022.e12584] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 10/06/2022] [Accepted: 12/15/2022] [Indexed: 12/26/2022] Open
Abstract
Nitrogen dioxide (NO2) is the most active pollutant gas emitted in the industrial era and is highly correlated with human activities. Tracking NO2 emissions and predicting their concentrations represent important steps toward controlling pollution and setting rules to protect people's health indoors, such as in factories, and in outdoor environments. The concentration of NO2 was affected by the COVID-19 lockdown period and decreased because of restrictions on outdoor activities. In this study, the concentration of NO2 was predicted at 14 ground stations in the United Arab Emirates (UAE) during December 2020 based on training over a full time period of two years (2019-2020). Statistical and machine learning models, such as autoregressive integrated moving average (ARIMA), seasonal autoregressive integrated moving average (SARIMA), long short-term memory (LSTM), and nonlinear autoregressive neural network (NAR-NN), are used with both open- and closed-loop architectures. The mean absolute percentage error (MAPE) was used to evaluate the performance of the models, and the results ranged from "very good" (MAPE of 8.64% at the Liwa station with the closed loop) to "acceptable" (MAPE of 42.45% at the Khadejah School station with the open loop). The results show that the predictions based on the open loop are generally better than those based on the closed loop because they yield statistically significantly lower MAPE values. For both loop types, we selected stations exhibiting the lowest, medium, and highest MAPE values as representative cases. In addition, we demonstrated that the MAPE value is highly correlated with the relative standard deviation of NO2 concentration values.
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Wu M, Hu X, Wang Z, Zeng X. Lockdown effects of the COVID-19 on the spatio-temporal distribution of air pollution in Beijing, China. ECOLOGICAL INDICATORS 2023; 146:109862. [PMID: 36624881 PMCID: PMC9812845 DOI: 10.1016/j.ecolind.2023.109862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 12/30/2022] [Accepted: 01/02/2023] [Indexed: 06/17/2023]
Abstract
To prevent the spread of COVID-19, China enacted a series of strict policies, which reduced anthropogenic activities to a near standstill. This provided a precious window to explore its effects on the spatio-temporal distribution of air pollution in Beijing, China. In this study, continuous wavelet transforms and spatial interpolation methods were used to explore the spatiotemporal variations in air pollutants and their lockdown effects. The results indicate that except O3, the annual average concentration of NO2, PM2.5 and SO2 showed a decreasing trend during 2016 and 2019; NO2, PM2.5 and SO2 show a trend of "low in summer and high in winter"; the diurnal variation of NO2 concentration was mainly related to the rush hours of traffic volume, with the first peak at the morning peak (7:00), and then accumulating gradually to second peak (22:00). The continuous wavelet analysis shows that PM2.5, SO2 and NO2 had four primary periods, while O3 only had two primary periods. The high NO2 concentration areas were mainly in Dongcheng, Xicheng, Chaoyang and Fengtai, while the low concentration areas were located in the northern areas, such as Miyun and Huairou; the PM2.5 concentration decreased from south to north; this characteristic presented more obviously in winter. Compared to the pre-lockdown, NO2 and SO2 decreased considerably during lockdown, whereas PM2.5 and O3 increased dramatically. The contribution rates of transportation activities to the NO2, O3, PM2.5 and SO2 were estimated be 9.4 % ∼ 17.2 %, -76.4 % ∼ -42.9 %, -39.5 % ∼ -22.8 % and 5.7 % ∼ 43.7 %, respectively; the contribution rates of industrial activities were 19.9 % ∼ 26.7 %, 7.8 % ∼ 30.9 %, 1.6 % ∼ 36.2 % and -10.5 % ∼ 15.9 %, respectively. Considering meteorological factors, we inferred that pauses in anthropogenic activities indeed help improving air pollution, but it is difficult to offset the impact of extreme weather. These findings can enhance our understanding on the sources of air pollution, and can therefore provide insights on urban air pollution mitigation.
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Misawa N, Yasui K, Sakai K, Kobayashi T, Nagahama H, Haraguchi T, Sasaki S, Torrung V, Luangtongkum T, Taniguchi T, Yamada K, Minamimagari M, Usami T, Kinoshita H. Fine Particle Adsorption Capacity of Volcanic Soil from Southern Kyushu, Japan. NANOMATERIALS (BASEL, SWITZERLAND) 2023; 13:568. [PMID: 36770529 PMCID: PMC9921741 DOI: 10.3390/nano13030568] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 01/24/2023] [Accepted: 01/27/2023] [Indexed: 06/18/2023]
Abstract
"Akahoya" is a volcanic soil classified as a special soil deposited in Kyushu, Japan. Many of its properties are not yet clearly understood. We found that Akahoya had the potential to adsorb bacteria in cattle feces, which prompted us to investigate its material properties and perform experiments to comprehensively evaluate its adsorption performance for various fine particles such as acidic and basic dyes, NOx/SOx gas, and phosphoric acid ions, in addition to bacteria. Akahoya had a very high specific surface area owing to the large number of nanometer-sized pores in its structure; it exhibited a high adsorption capacity for both NO2 and SO2. Regarding the zeta potential of Akahoya, the point of zero charge was approximately pH 7.0. The surface potential had a significant effect on the adsorption of acidic and basic dyes. Akahoya had a very high cation exchange capacity when the sample surface was negatively charged and a high anion exchange capacity when the sample surface was positively charged. Akahoya also exhibited a relatively high adsorption capacity for phosphoric acid because of its high level of Al2O3, and the immersion liquid had a very high Al ion concentration. Finally, filtration tests were performed on Escherichia coli suspension using a column filled with Akahoya or another volcanic soil sample. The results confirmed that the Escherichia coli adhered on the Akahoya sample. The results of the Escherichia coli release test, after the filtration test, suggested that this adhesion to Akahoya could be phosphorus-mediated.
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Saggu IS, Singh S, Chen K, Xuan Z, Swihart MT, Sharma S. Ultrasensitive Room-Temperature NO 2 Detection Using SnS 2/MWCNT Composites and Accelerated Recovery Kinetics by UV Activation. ACS Sens 2023; 8:243-253. [PMID: 36647806 DOI: 10.1021/acssensors.2c02104] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
High performance with lower power consumption is one among the essential features of a sensing device. Minute traces of hazardous gases such as NO2 are difficult to detect. Tin disulfide (SnS2) nanosheets have emerged as a promising NO2 sensor. However, their poor room-temperature conductivity gives rise to inferior sensitivity and sluggish recovery rates, thereby hindering their applications. To mitigate this problem, we present a low-cost ultrasensitive NO2 gas sensor with tin disulfide/multiwalled carbon nanotube (SnS2/MWCNT) nanocomposites, prepared using a single-step hydrothermal method, as sensing elements. Relative to pure SnS2, the conductivity of nanocomposites improved significantly. The sensor displayed a decrease in resistance when exposed to NO2, an oxidizing gas, and exhibited p-type conduction, also confirmed in separate Mott-Schottky measurements. At a temperature of 20 °C, the sensor device has a relative response of about ≈5% (3%) for 25 ppb (1 ppb) of NO2 with complete recovery in air (10 min) and excellent recovery rates with UV activation (0.3 min). A theoretical lower limit of detection (LOD) of 7 ppt implies greater sensitivity than all previously reported SnS2-based gas sensors, to the best of our knowledge. The improved sensing characteristics were attributed to the formation of nano p-n heterojunctions, which enhances the charge transport and gives rise to faster response. The composite sensor also demonstrated good NO2 selectivity against a variety of oxidizing and reducing gases, as well as excellent stability and long-term durability. This work will provide a fresh perspective on SnS2-based composite materials for practical gas sensors.
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Feng YT, Lang CF, Chen C, Harry Asena M, Fang Y, Zhang RD, Jiang LQ, Fang X, Chen Y, He YS, Wang P, Pan HF. Association between air pollution exposure and coronary heart disease hospitalization in a humid sub-tropical region of China: A time-series study. Front Public Health 2023; 10:1090443. [PMID: 36711381 PMCID: PMC9874291 DOI: 10.3389/fpubh.2022.1090443] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Accepted: 12/16/2022] [Indexed: 01/12/2023] Open
Abstract
Objective Emerging evidence has highlighted the possible links of environmental pollution with several cardiovascular diseases (CVDs). The current study aimed to explore the impact of short-term air pollution exposure on CHD hospitalization in Hefei. Methods Data about the daily number of CHD admissions (from 2014 to 2021) were retrieved from the First Affiliated Hospital of Anhui Medical University. Air pollutants and meteorological data were obtained from the China Environmental Monitoring Station and the China Meteorological Data Service Center, respectively. The correlation between air pollution and CHD hospitalization was assessed using distributed lag non-linear model (DLNM) and Poisson generalized linear regression. Results In the single-pollutant model, NO2, O3, and CO strongly correlated with CHD hospitalization rate. Specifically, exposure to NO2 (lag0, relative risk [RR]: 1.013, 95%CI: 1.002-1.024, per 10 μg/m3 increase) and CO (lag13, RR: 1.035, 95%CI: 1.001-1.071, per 1 μg/m3 increase) revealed a positive correlation with an increased rate of CHD hospitalization. Interestingly, O3 had a protective association with hospitalization of CHD (lag0, RR: 0.993, 95%CI: 0.988-0.999, per 10 μg/m3 increase). Similar results, to those of the single-pollutant model, were revealed following verification using two-pollutant models. Subgroup analyses indicated that young people, women, and people in hot seasons were more susceptible to NO2 exposure, while the elderly, women, and people in cold seasons were more susceptible to O3. Furthermore, the elderly were more susceptible to CO exposure. Conclusion Overall, exposure to NO2 and CO increases the rate of CHD hospitalization, but exposure to O3 shows a protective association with the rate of CHD hospitalization. Therefore, early preventive measures against air pollutants should be applied to protect vulnerable patients with CHD.
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Wi CI, Gent JF, Bublitz JT, King KS, Ryu E, Sorrentino K, Plano J, McKay L, Porcher J, Wheeler PH, Chiarella SE, DeWan AT, Godri Pollitt KJ, Sheares BJ, Leaderer B, Juhn YJ. Paired Indoor and Outdoor Nitrogen Dioxide Associated With Childhood Asthma Outcomes in a Mixed Rural-Urban Setting: A Feasibility Study. J Prim Care Community Health 2023; 14:21501319231173813. [PMID: 37243352 PMCID: PMC10226331 DOI: 10.1177/21501319231173813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2023] [Revised: 04/17/2023] [Accepted: 04/18/2023] [Indexed: 05/28/2023] Open
Abstract
INTRODUCTION Nitrogen dioxide (NO2) is known to be a trigger for asthma exacerbation. However, little is known about the role of seasonal variation in indoor and outdoor NO2 levels in childhood asthma in a mixed rural-urban setting of North America. METHODS This prospective cohort study, as a feasibility study, included 62 families with children (5-17 years) that had diagnosed persistent asthma residing in Olmsted County, Minnesota. Indoor and outdoor NO2 concentrations were measured using passive air samples over 2 weeks in winter and 2 weeks in summer. We assessed seasonal variation in NO2 levels in urban and rural residential areas and the association with asthma control status collected from participants' asthma diaries during the study period. RESULTS Outdoor NO2 levels were lower (median: 2.4 parts per billion (ppb) in summer, 3.9 ppb in winter) than the Environmental Protection Agency (EPA) annual standard (53 ppb). In winter, a higher level of outdoor NO2 was significantly associated with urban residential living area (P = .014) and lower socioeconomic status (SES) (P = .027). For both seasons, indoor NO2 was significantly higher (P < .05) in rural versus urban areas and in homes with gas versus electric stoves (P < .05). Asthma control status was not associated with level of indoor or outdoor NO2 in this cohort. CONCLUSIONS NO2 levels were low in this mixed rural-urban community and not associated with asthma control status in this small feasibility study. Further research with a larger sample size is warranted for defining a lower threshold of NO2 concentration with health effect on asthma in mixed rural-urban settings.
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Tamehri Zadeh SS, Khajavi A, Ramezankhani A, Azizi F, Hadaegh F. The impact of long-term exposure to PM10, SO2, O3, NO2, and CO on incident dysglycemia: a population-based cohort study. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:3213-3221. [PMID: 35943653 DOI: 10.1007/s11356-022-22330-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 07/28/2022] [Indexed: 06/15/2023]
Abstract
To examine the associations between long-term exposure to five major air pollutants including SO2, PM10, O3, NO2, and CO, and incident dysglycemia, impaired fasting glucose (IFG), and diabetes, separately. A total of 4254 (1720 men) normoglycemic individuals aged 20-69 years at baseline were followed from 2001 to 2018 every 3 years. To measure the long-term hazards of air pollutants for incident dysglycemia, the Weibull proportional hazards models for every 10-unit increment adjusted for diabetes risk factors were fitted. The air pollutants were put in the models in the form of averages of 1-, 2-, and 3-year periods. During a median follow-up of 12.2 years, we observed 1780 dysglycemia events. In contrast to NO2, the increase in SO2, O3, and PM10 levels were significantly associated with a higher risk of dysglycemia and IFG in all time spans excluding PM10 at 2 years. The largest hazard ratios for incident dysglycemia and IFG were attributable to PM10 in 3 years (2.20 (95% CI 1.67, 2.89) and 2.08 (1.55, 2.80), respectively). Moreover, exposure to all the pollutants except NO2 in 1 year (0.89 (0.80, 0.98)) had no significant associations with incident diabetes. There was a signal that younger (< 45 years) and never-smoker individuals were more predispose to dysglycemic effects of air pollution (all P for interactions > 0.03). Our findings suggested that long-term exposure to air pollution increased incident dysglycemia risk, the effect which was mainly attributable to IFG status.
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Hung TH, Chen PH, Tung TH, Hsu J, Hsu TY, Wan GH. Risks of preterm birth and low birth weight and maternal exposure to NO 2/PM 2.5 acquired by dichotomous evaluation: a systematic review and meta-analysis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2023; 30:9331-9349. [PMID: 36474040 DOI: 10.1007/s11356-022-24520-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
No consistent results from past studies have been found on the relationship between the effects of air pollutant exposure, preterm birth (PTB) and low birth weight (LBW) in fetuses. This study aimed to analyze the impact of high concentrations of air pollutants on the health outcomes of fetuses, especially regarding PTB and LBW. This study used keywords related to air pollutants, pregnancy, and birth outcomes, to search the literature within the databases of the Cochrane Library, PubMed, and Embase, which were published as of July 26, 2022. A total of 24 studies were included in this meta-analysis. This meta-analysis revealed that nitrogen dioxide (NO2) exposure throughout pregnancy was associated with an increased risk of PTB. Maternal exposure to PM2.5 (particulate matter sized less than 2.5 μm) during gestation was associated with the risk of LBW. The findings of this meta-analysis provide an important foundation for evaluating the relationship between exposure of air pollutants and fetal birth outcomes in countries with severe air pollution in the future.
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Gharibvand LK, Jamali AA, Amiri F. Changes in NO2 and O3 levels due to the pandemic lockdown in the industrial cities of Tehran and Arak, Iran using Sentinel 5P images, Google Earth Engine (GEE) and statistical analysis. STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT : RESEARCH JOURNAL 2023; 37:2023-2034. [PMID: 37091315 PMCID: PMC10073783 DOI: 10.1007/s00477-022-02362-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Revised: 11/23/2022] [Accepted: 12/07/2022] [Indexed: 05/03/2023]
Abstract
Air pollution has very damaging effects on human health. In recent years the Coronavirus disease (COVID-19) pandemic has created a worldwide economic disaster. Although the consequences of the COVID-19 lockdowns have had severe effects on economic and social conditions, these lockdowns also have also left beneficial effects on improving air quality and the environment. This research investigated the impact of the COVID-19 lockdown on NO2 and O3 pollutants changes in the industrial and polluted cities of Arak and Tehran in Iran. Based on this, the changes in NO2 and O3 levels during the 2020 lockdown and the same period in 2019 were investigated in these two cities. For this purpose, the Sentinel-5P data of these two pollutants were used during the lockdown period from November 19 to December 05, 2020, and at the same time before the pandemic from November 19 to December 05, 2019. For better results, the effect of climatic factors such as rain and wind in reducing pollution was removed. The obtained results indicate a decrease in NO2 and O3 levels by 3.5% and 6.8% respectively in Tehran and 20.97% and 5.67% in Arak during the lockdown of 2020 compared to the same time in 2019. This decrease can be caused by the reduction in transportation and socio-economic and industrial activities following the lockdown measures. This issue can be a solid point to take a step toward controlling and reducing pollution in non-epidemic conditions by implementing similar standards and policies in the future.
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Jagiełło P, Struzewska J, Jeleniewicz G, Kamiński JW. Evaluation of the Effectiveness of the National Clean Air Programme in Terms of Health Impacts from Exposure to PM2.5 and NO 2 Concentrations in Poland. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2022; 20:530. [PMID: 36612853 PMCID: PMC9819996 DOI: 10.3390/ijerph20010530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 12/19/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
The health impact of air quality has recently become an emerging issue. Many regions, especially densely populated regions, have deteriorating air quality. The primary source of pollution in Poland is the municipal sector. Air pollutants have a negative impact on human health, contribute to premature deaths, and are the cause of various diseases. Over recent years, Europe's air quality has largely improved due to several measures to reduce pollutant emissions. The following paper presents the impact of annual average PM2.5 and NO2 concentrations on premature deaths in Poland in 2019. Exposure to PM2.5 caused more than 19 000 premature deaths, and exposure to NO2 contributed to around 6000 premature deaths in 2019. Taking 2019 as a baseline, the impact of the envisaged implementation of the national Clean Air Programme on the number of premature deaths is analysed. Implementing the mitigation measures focused on replacing inefficient stoves and boilers in individual households would significantly improve air quality, mainly particulate matter. Reducing PM2.5 concentrations would reduce premature deaths by around 3000 cases, while for NO2, the number of premature deaths would not change much.
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Fernández-González M, Ribeiro H, Rodríguez-Rajo FJ, Cruz A, Abreu I. Short-Term Exposure of Dactylis glomerata Pollen to Atmospheric Gaseous Pollutants Is Related to an Increase in IgE Binding in Patients with Grass Pollen Allergies. PLANTS (BASEL, SWITZERLAND) 2022; 12:76. [PMID: 36616204 PMCID: PMC9823458 DOI: 10.3390/plants12010076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 12/07/2022] [Accepted: 12/20/2022] [Indexed: 06/17/2023]
Abstract
The concentrations of nitrogen dioxide (NO2) and tropospheric ozone (O3) in urban and industrial site atmospheres are considered key factors associated with pollen-related respiratory allergies. This work studies the effects of NO2 and O3 on the protein expression profile and IgE binding in patients with grass allergies to Dactylis glomerata pollen extracts. Pollens were collected during the flowering season and were exposed to NO2 and O3 in a controlled environmental chamber. The amount of soluble protein was examined using the Bradford method, and the protein expression profile and antigenic properties were analysed using the immunoblotting and enzyme-linked immunosorbent assay (ELISA), respectively. Our results showed apparent inter-sera differences concerning the number and intensity of IgE reactivity, with the most prominent at bands of 55 kDa, 35, 33, and 13 kDa. In the 13 kDa band, both gases tend to induce an increase in IgE binding, the band at 33 kDa showed a tendency towards a reduction, particularly pollen exposed to O3. Reactive bands at 55 and 35 kDa presented an increase in the IgE binding pattern for all the patient sera samples exposed to NO2, but the samples exposed to O3 showed an increase in some sera and in others a decrease. Regarding the ELISA results, out of the 21 tested samples, only 9 showed a statistically significant increase in total IgE reactivity after pollen exposure to the pollutants. Our study revealed that although airborne pollen allergens might be affected by air pollution, the possible impacts on allergy symptoms might vary depending on the type of pollutant and the patient's sensitisation profile.
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Wang J, Cao Q, Cheng XF, Ye W, He JH, Lu JM. Moisture-Insensitive and Highly Selective Detection of NO 2 by Ion-in-Conjugation Covalent Organic Frameworks. ACS Sens 2022; 7:3782-3789. [PMID: 36384296 DOI: 10.1021/acssensors.2c01631] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
As a common toxic gas, nitrogen dioxide (NO2) seriously threatens the environment and human respiratory system even at part per billion (ppb) level. Covalent organic frameworks (COFs) have gained widespread attention in sensing applications because of the benefits of designability, environmental stability, and a large number of active sites. However, the competitive adsorption of water molecules and the target gas molecules at room temperature as well as the weak interaction between COFs and gas molecules hinder their practical applications. Here, we introduce ion-in-conjugation (IIC) into a covalent organic framework (COF) by preparing a condensate of squaraine (SA) with 1,3,5-tris(4-aminophenyl)benzene (TAPB) to form a mesoporous macrocyclic material (SA-TAPB). Layers of SA-TAPB, drop cast onto interdigitated Ag-Pd alloy electrodes, show a statistically significant conductivity response to NO2 at concentrations as low as 30 ppb and a theoretical detection limit of 10.9 ppb. The sensor displays a lower sensitivity to variations in humidity when operated at 80 °C compared to room temperature. The density functional theory (DFT) calculations indicated that the main adsorption site of NO2 is dual hydrogen bonds formed between two amide hydrogen atoms of SA-TAPB and the NO2 molecule. Gas adsorption experiments revealed that SA-TAPB has the largest adsorption capacity of NO2 versus other interference gases, which were responsible for the excellent selectivity toward NO2.
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Sun Y, Fu Y, Shan Y, Du J, Liu Z, Gao M, Shi X, He G, Xue S, Han X, Yu Y, He H. Si/Al Ratio Determines the SCR Performance of Cu-SSZ-13 Catalysts in the Presence of NO 2. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:17946-17954. [PMID: 36322164 DOI: 10.1021/acs.est.2c03813] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
A comparative study was performed to investigate the NH3-selective catalytic reduction (SCR) reaction activity of Cu-SSZ-13 zeolites having Si/Al ratios (SARs) of 5, 18, and 30. Remarkably, the Cu-SSZ-13 zeolite catalysts exhibited completely opposite behaviors as a function of SAR under standard SCR (SSCR) and fast SCR (FSCR) reaction atmospheres. Under SSCR conditions, the NOx conversion increased as expected with the decreasing SAR. Under FSCR conditions, however, the NOx conversion decreased as the SAR decreased, contrary to expectations. In this study, based on characterization of the catalysts by X-ray diffraction, transmission electron microscopy, electron paramagnetic resonance, H2-temperature-programmed reduction, temperature-programmed desorption, and diffuse reflectance infrared Fourier transform spectroscopy, together with theoretical calculations, the authors found that the amount of Brønsted acid sites goes up while the SAR goes down, leading to an increase in the accumulation of NH4NO3 under FSCR reaction conditions. Moreover, the accumulated NH4NO3 is of greater stability for those low SAR Cu-SSZ-13 catalysts. These two reasons cause the FSCR performance of Cu-SSZ-13 to decrease with a decrease in SAR. As a result, the NO2 effect on SCR activity changes from promotion to inhibition as the SAR decreases.
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