scholarly journals Cause analysis of PM2.5 pollution during the COVID-19 lockdown in Nanning, China

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Zhaoyu Mo ◽  
Jiongli Huang ◽  
Zhiming Chen ◽  
Bin Zhou ◽  
Kaixian Zhu ◽  
...  
Keyword(s):  
Motor Vehicle ◽  
Control Strategies ◽  
Feedback Mechanism ◽  
Vehicle Exhaust ◽  
Near Surface ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Particle Matter ◽  
Pollution Accumulation ◽  
Positive Feedback Mechanism

AbstractTo analyse the cause of the atmospheric PM2.5 pollution that occurred during the COVID-19 lockdown in Nanning, Guangxi, China, a single particulate aerosol mass spectrometer, aethalometer, and particulate Lidar coupled with monitoring near-surface gaseous pollutants, meteorological conditions, remote fire spot sensing by satellite and backward trajectory models were utilized during 18–24 February 2020. Three haze stages were identified: the pre-pollution period (PPP), pollution accumulation period (PAP) and pollution dissipation period (PDP). The dominant source of PM2.5 in the PPP was biomass burning (BB) (40.4%), followed by secondary inorganic sources (28.1%) and motor vehicle exhaust (11.7%). The PAP was characterized by a large abundance of secondary inorganic sources, which contributed 56.1% of the total PM2.5 concentration, followed by BB (17.4%). The absorption Ångström exponent (2.2) in the PPP was higher than that in the other two periods. Analysis of fire spots monitored by remote satellite sensing indicated that open BB in regions around Nanning City could be one of the main factors. A planetary boundary layer-relative humidity-secondary particle matter-particulate matter positive feedback mechanism was employed to elucidate the atmospheric processes in this study. This study highlights the importance of understanding the role of BB, secondary inorganic sources and meteorology in air pollution formation and calls for policies for emission control strategies.

scholarly journals Cause Analysis of PM2.5 pollution during the COVID-19 lockdown in Nanning, China

2021 ◽  
Author(s):  
Jiongli Huang ◽  
Zhiming Chen ◽  
Bin Zhou ◽  
Kaixian Zhu ◽  
Huilin Liu ◽  
...  
Keyword(s):  
Motor Vehicle ◽  
Control Strategies ◽  
Feedback Mechanism ◽  
Vehicle Exhaust ◽  
Near Surface ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Pollution Accumulation ◽  
Positive Feedback Mechanism

Abstract To analyze the cause of atmospheric PM2.5 pollution occurred during the COVID-19 lockdown in Nanning of Guangxi, China, Single Particulate Aerosol Mass Spectrometer, Aethalometer, Particulate Lidar, coupled with the monitoring of near-surface gaseous pollutants, meteorological conditions, remote fire spots sensing by satellite and Backward Trajectory Models were conducted during 18–24, Feb 2020. Three haze stages of pre-pollution period (PPP), pollution accumulation period (PAP) and pollution dissipation period (PDP) were identified. The dominant source of PM2.5 in PPP was biomass burning (BB) (40.4%), followed by secondary inorganics (28.1%) and motor vehicle exhaust (11.7%). The PAP was characterized by a large abundance of secondary inorganics, which contributed for 56.1% of the total PM2.5 concentration, followed by BB (17.4%). The absorption Ångström exponent (2.2) in PPP was higher than those of the other two periods. The analysis of fire spots monitored by remote satellite sensing indicated that open BB in regions around Nanning city could be one of the main facotrs matters. The planetary boundary layer-relative humidity-secondary particles matter-particulate matter positive feedback mechanism was employed to elucidate the atompheric process in this study. This study highlights the importance of understanding the role of BB and meteorology in air pollution formation to call for policy for emission control strategies.

scholarly journals Chemical characterization and source identification of PM<sub>2.5</sub> at multiple sites in the Beijing–Tianjin–Hebei region, China

2017 ◽  
Vol 17 (21) ◽  
pp. 12941-12962 ◽  
Author(s):  
Xiaojuan Huang ◽  
Zirui Liu ◽  
Jingyun Liu ◽  
Bo Hu ◽  
Tianxue Wen ◽  
...  
Keyword(s):  
Coal Combustion ◽  
Vehicle Emissions ◽  
Motor Vehicle ◽  
Control Strategies ◽  
Vehicle Exhaust ◽  
Motor Vehicle Emissions ◽  
Haze Pollution ◽  
Inorganic Aerosol ◽  
Urban Sites ◽  
Bth Region

Abstract. The simultaneous observation and analysis of atmospheric fine particles (PM2.5) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing–Tianjin–Hebei (BTH) region from June 2014 to April 2015. The PM2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM2.5 source in this region, accounting for 29.2–40.5 % of the PM2.5 mass at the urban sites; the second-largest PM2.5 source was motor vehicle exhaust, particularly in Beijing (24.9 %), whereas coal combustion was also a large source in Tianjin (12.4 %) and Shijiazhuang (15.5 %), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OC ∕ EC mass ratio of PM2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).

scholarly journals Chamber simulation on the formation of secondary organic aerosols (SOA) from diesel vehicle exhaust in China

2016 ◽  
Author(s):  
Wei Deng ◽  
Qihou Hu ◽  
Tengyu Liu ◽  
Xinming Wang ◽  
Yanli Zhang ◽  
...  
Keyword(s):  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Vehicle Exhaust ◽  
Chemical Aging ◽  
Aerosol Mass Spectrometer ◽  
Particulate Matter Emission ◽  
Photo Oxidation ◽  
Diesel Vehicles ◽  
Aerosol Mass ◽  
Production Factors

Abstract. In China primary particulate matter emission from on-road vehicles is predominantly coming from diesels, yet secondary organic aerosols (SOA) formed from diesel emission may be also of greater significance due to more intermediate volatile organic compounds (IVOC) in the exhaust. Here we introduced exhaust from in-use diesel vehicles under warm idling condition directly into an indoor smog chamber with a 30 m3 Teflon reactor, and investigated the SOA formation as well as chemical aging of organic aerosols during photo-oxidation. The emission factors of primary organic aerosol (POA) and black carbon (BC) for the three typical Chinese diesel vehicles ranged 0.18–0.91 and 0.15–0.51 g kg-fuel−1, respectively; and the SOA production factors ranged 0.50–1.8 g kg-fuel−1 with an average SOA/POA ratio of 1.6. Aromatic hydrocarbons could only explain less than 3 % of SOA formed during aging, and IVOC and oxygenated VOC might contribute substantially to SOA formation. High resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) resolved that POA dominated by CH classes (alkanes, cycloalkanes and alkenes) with high abundances of the CnH2n+1 and CnH2n-1 fragments, and after photo-oxidation the fraction of CH classes and the H/C ratios decreased, while the fraction of CHO, as well as the ratios of O/C and of organic matter to organic carbon (OM/OC), all increased. The plot of f44 (ratio of m/z 44 to the total signal in a mass spectrum) versus f43 indicated that diesel SOA were semi-volatile oxygenated organic aerosols (SV-OOA). The slopes of O:C versus H:C element ratios in the Van Krevelen diagram ranged from −0.47 to −0.68, suggesting a combination of carboxylic acid and alcohols/peroxides formed during the aging of diesel exhaust.

scholarly journals Characterization of particulate matter emissions from on-road gasoline and diesel vehicles using a soot particle aerosol mass spectrometer

2014 ◽  
Vol 14 (3) ◽  
pp. 4007-4049 ◽  
Author(s):  
T. R. Dallmann ◽  
T. B. Onasch ◽  
T. W. Kirchstetter ◽  
D. R. Worton ◽  
E. C. Fortner ◽  
...  
Keyword(s):  
Trace Elements ◽  
Particulate Matter ◽  
Soot Particle ◽  
Organic Aerosol ◽  
Lubricating Oil ◽  
Vehicle Exhaust ◽  
Aerosol Mass Spectrometer ◽  
Diesel Vehicles ◽  
Aerosol Mass ◽  
Exhaust Plumes

Abstract. Particulate matter (PM) emissions were measured in July 2010 from on-road motor vehicles driving through a highway tunnel in the San Francisco Bay area. A soot particle aerosol mass spectrometer (SP-AMS) was used to measure the chemical composition of PM emitted by gasoline and diesel vehicles at high time resolution. Organic aerosol (OA) and black carbon (BC) concentrations were measured during various time periods that had different levels of diesel influence, as well as directly in the exhaust plumes of individual heavy-duty (HD) diesel trucks. BC emission factor distributions for HD trucks were more skewed than OA distributions, with the highest 10% of trucks accounting for 56 and 42% of total measured BC and OA emissions, respectively. A comparison of measured OA and BC mass spectra across various sampling periods revealed a high degree of similarity in BC and OA emitted by gasoline and diesel engines. Cycloalkanes predominate in exhaust OA emissions relative to saturated alkanes (i.e., normal and iso-paraffins), suggesting that lubricating oil rather than fuel is the dominant source of primary organic aerosol (POA) emissions in diesel vehicle exhaust. This finding is supported by the detection of trace elements such as zinc and phosphorus in the exhaust plumes of individual trucks. Trace elements were emitted relative to total OA at levels that are consistent with typical weight fractions of commonly used additives present in lubricating oil. The presence of trace elements in vehicle exhaust raises the concern that ash deposits may accumulate over time in diesel particle filter systems, and may eventually lead to performance problems that require servicing.

scholarly journals Laboratory investigation of photochemical oxidation of organic aerosol from wood fires 2: analysis of aerosol mass spectrometer data

2009 ◽  
Vol 9 (6) ◽  
pp. 2227-2240 ◽  
Author(s):  
A. P. Grieshop ◽  
N. M. Donahue ◽  
A. L. Robinson
Keyword(s):  
Source Apportionment ◽  
Mass Spectrometer ◽  
Mass Spectra ◽  
Motor Vehicle ◽  
Organic Aerosol ◽  
Photochemical Oxidation ◽  
Wood Smoke ◽  
Aerosol Mass Spectrometer ◽  
Aerosol Mass ◽  
Spectrometer Data

Abstract. Experiments were conducted to investigate the effects of photo-oxidation on organic aerosol (OA) in dilute wood smoke by exposing emissions from soft- and hard-wood fires to UV light in a smog chamber. This paper focuses on changes in OA composition measured using a unit-mass-resolution quadrupole Aerosol Mass Spectrometer (AMS). The results highlight how photochemical processing can lead to considerable evolution of the mass, volatility and level of oxygenation of biomass-burning OA. Photochemical oxidation produced substantial new OA, more than doubling the OA mass after a few hours of aging under typical summertime conditions. Aging also decreased the volatility of the OA and made it progressively more oxygenated. The results also illustrate strengths of, and challenges with, using AMS data for source apportionment analysis. For example, the mass spectra of fresh and aged BBOA are distinct from fresh motor-vehicle emissions. The mass spectra of the secondary OA produced from aging wood smoke are very similar to those of the oxygenated OA (OOA) that dominates ambient AMS datasets, further reinforcing the connection between OOA and OA formed from photo-chemistry. In addition, aged wood smoke spectra are similar to those from OA created by photo-oxidizing dilute diesel exhaust. This demonstrates that the OOA observed in the atmosphere can be produced by photochemical aging of dilute emissions from different types of combustion systems operating on fuels with modern or fossil carbon. Since OOA is frequently the dominant component of ambient OA, the similarity of spectra of aged emissions from different sources represents an important challenge for AMS-based source apportionment studies.

scholarly journals Role of glyoxal in SOA formation from aromatic hydrocarbons: gas-phase reaction trumps reactive uptake

2011 ◽  
Vol 11 (11) ◽  
pp. 30599-30625 ◽  
Author(s):  
S. Nakao ◽  
Y. Liu ◽  
P. Tang ◽  
C.-L. Chen ◽  
J. Zhang ◽  
...  
Keyword(s):  
Aromatic Hydrocarbon ◽  
Gas Phase ◽  
Phase Reaction ◽  
Oh Radical ◽  
Near Surface ◽  
Aerosol Mass Spectrometer ◽  
Seed Particles ◽  
Aerosol Mass ◽  
Experimental Approaches

Abstract. This study evaluates the significance of glyoxal acting as an intermediate species leading to SOA formation from aromatic hydrocarbon photooxidation under humid conditions. Rapid SOA formation from glyoxal uptake onto aqueous (NH4)2SO4 seed particles is observed; however, glyoxal did not partition to SOA or SOA coated aqueous seed during all aromatic hydrocarbon experiments (RH up to 80%). Glyoxal is found to only influence SOA formation by raising hydroxyl (OH) radical concentrations. Four experimental approaches supporting this conclusion are presented in this paper: (1) increased SOA formation and decreased SOA volatility in the toluene + NOx photooxidation system with additional glyoxal was reproduced by matching OH radical concentrations through H2O2 addition; (2) glyoxal addition to SOA seed formed from toluene + NOx photooxidation did not increase observed SOA volume; (3) SOA formation from toluene + NOx photooxidation with and without deliquesced (NH4)2SO4 seed resulted in similar SOA growth, consistent with a coating of SOA preventing glyoxal uptake onto deliquesced (NH4)2SO4 seed; and (4) the fraction of a C4H9+ fragment (observed by Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer, HR-ToF-AMS) from SOA formed by 2-tert-butylphenol (BP) oxidation was unchanged in the presence of additional glyoxal despite enhanced SOA formation. This study suggests that glyoxal uptake onto aerosol is minor when the surface (and near-surface) of aerosols are primarily composed of secondary organic compounds.

Analysis of Cigarette Smoke Aerosol by Single Particle Aerosol Mass Spectrometer

2013 ◽  
Vol 40 (6) ◽  
pp. 936-939
Author(s):  
Mei LI ◽  
Jun-Guo DONG ◽  
Zheng-Xu HUANG ◽  
Lei LI ◽  
Wei GAO ◽  
...  
Keyword(s):  
Cigarette Smoke ◽  
Mass Spectrometer ◽  
Single Particle ◽  
Aerosol Mass Spectrometer ◽  
Smoke Aerosol ◽  
Aerosol Mass

scholarly journals HOPF BIFURCATION FROM NEW-KEYNESIAN TAYLOR RULE TO RAMSEY OPTIMAL POLICY

2020 ◽  
pp. 1-33
Author(s):  
Jean-Bernard Chatelain ◽  
Kirsten Ralf
Keyword(s):  
Hopf Bifurcation ◽  
Optimal Policy ◽  
Ad Hoc ◽  
Taylor Rule ◽  
Dynamic Properties ◽  
Feedback Mechanism ◽  
New Keynesian ◽  
Negative Feedback Mechanism ◽  
Positive Feedback Mechanism ◽  
Forward Looking

This paper compares different implementations of monetary policy in a new-Keynesian setting. We can show that a shift from Ramsey optimal policy under short-term commitment (based on a negative feedback mechanism) to a Taylor rule (based on a positive feedback mechanism) corresponds to a Hopf bifurcation with opposite policy advice and a change of the dynamic properties. This bifurcation occurs because of the ad hoc assumption that interest rate is a forward-looking variable when policy targets (inflation and output gap) are forward-looking variables in the new-Keynesian theory.

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