scholarly journals Supplementary material to "Characterization of submicron particles by Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) during wintertime: aerosol composition, sources and chemical processes in Guangzhou, China"

2020 ◽  
Author(s):  
Junchen Guo ◽  
Shengzhen Zhou ◽  
Minfu Cai ◽  
Jun Zhao ◽  
Wei Song ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Chemical Processes ◽  
Submicron Particles ◽  
Aerosol Composition ◽  
Supplementary Material

scholarly journals Characterization of submicron particles by Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) during wintertime: aerosol composition, sources and chemical processes in Guangzhou, China

2020 ◽  
Author(s):  
Junchen Guo ◽  
Shengzhen Zhou ◽  
Minfu Cai ◽  
Jun Zhao ◽  
Wei Song ◽  
...  
Keyword(s):  
Gas Phase ◽  
Mass Concentration ◽  
Chemical Speciation ◽  
Time Of Flight ◽  
Chemical Processes ◽  
Traffic Emissions ◽  
Multiphase Reactions ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Linear Regressions

Abstract. Particulate matter (PM) pollution in China is an emerging environmental issue which policy makers and public have increasingly paid attention to. In order to investigate the characteristics, sources, and chemical processes of PM pollution in Guangzhou, a field measurement was conducted from 20 November 2017 to 5 January 2018, with a Time-of-Flight Aerosol Chemical Speciation Monitor (ToF-ACSM) and other collocated instruments. Mass concentrations of non-refractory submicron particulate matters (NR-PM1) measured by the ToF-ACSM were correlated well with those of PM2.5 or PM1.1 measured by filter-based methods. The organic mass fraction increased from 45 % to 53 % when the air switched from non-pollution periods to pollution episodes, indicating significant roles of organic aerosols (OA) during the whole study. Based on the mass spectra measured by the TOF-ACSM, Positive Matrix Factorization (PMF) with multilinear engine (ME-2) algorithm was performed to deconvolve OA into four factors, including hydrocarbon-like OA (HOA, 12 %), cooking OA (COA, 18 %), semi-volatile oxygenated OA (SVOOA, 30 %), and low-volatility oxygenated OA (LVOOA, 40 %). Furthermore, we found that SVOOA and nitrate were significantly contributed from local traffic emissions while sulfate and LVOOA were mostly attributed to regional pollutants. Comparisons between this work and other previous studies in China show that SOA fraction in total OA increases spatially across China from the North to the South. Two distinctly opposite trends for NR-PM1 formation were observed during non-pollution period and pollution EPs. The ratio of secondary PM (SPM = SVOOA + LVOOA + sulfate + nitrate + ammonium) to primary PM (PPM = HOA + COA + chloride), together with peroxy radicals RO2* and ozone, increased with increasing NR-PM1 concentration during non-pollution period, while an opposite trend of these three quantities was observed during pollution EPs. Furthermore, oxidation degrees of both OA and SOA were investigated using the f44/f43 space and the results show that at least two OOA factors are needed to cover a large range of f44 and f43 in Guangzhou. Comparisons between our results and other laboratory studies imply that volatile organic compounds (VOCs) from traffic emissions in particular from diesel combustion and aromatic compounds are most possible SOA precursors in Guangzhou. Peroxy radical RO2* was used as a tracer for SOA formed through gas phase oxidation. For non-pollution period, SOA concentration was reasonably correlated with RO2* concentration during both daytime and nighttime, suggesting that gas phase oxidation was primarily responsible for SOA formation. For pollution EPs, when NR-PM1 mass concentration was divided into six segments, in each segment except for the lowest one, SOA concentration was correlated moderately with RO2* concentration, suggesting that gas phase oxidation still plays important roles in SOA formation. In addition, the slopes of linear regressions for the above correlations increased with increasing NR-PM1 mass concentration, probably representing enhanced gas-to-particle partitioning under high NR-PM1 concentration. The intercepts of the above linear regressions, which correspond to the extent of other mechanisms (i.e., heterogeneous and multiphase reactions), increased with increasing NR-PM1 mass concentration. Our results suggest that while gas phase oxidation contributes predominantly to SOA formation during non-pollution periods, other mechanisms such as heterogeneous and multiphase reactions play more important roles in SOA formation during pollution EPs than gas phase oxidation.

scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (11) ◽  
pp. 3225-3241 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the time-of-flight aerosol chemical speciation monitor (ToF-ACSM), combining precision state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of < 30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~ 8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation and calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (> 10 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps, agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

scholarly journals The ToF-ACSM: a portable aerosol chemical speciation monitor with TOFMS detection

2013 ◽  
Vol 6 (4) ◽  
pp. 6767-6814 ◽  
Author(s):  
R. Fröhlich ◽  
M. J. Cubison ◽  
J. G. Slowik ◽  
N. Bukowiecki ◽  
A. S. H. Prévôt ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Time Of Flight ◽  
Mass Resolution ◽  
Remote Access ◽  
Swiss Alps ◽  
Scanning Mobility Particle Sizer ◽  
Aerosol Composition ◽  
Flight Mass Spectrometry ◽  
New Instrument

Abstract. We present a new instrument for monitoring aerosol composition, the economy time-of-flight-aerosol chemical speciation monitor (ToF-ACSM), combining precision of state-of-the-art time-of-flight mass spectrometry with stability, reliability, and easy handling, which are necessities for long-term monitoring operations on the scale of months to years. Based on Aerodyne aerosol mass spectrometer (AMS) technology, the ToF-ACSM provides continuous online measurements of chemical composition and mass of non-refractory submicron aerosol particles. In contrast to the larger AMS, the compact-sized and lower-priced ToF-ACSM does not feature particle sizing, similar to the widely-used quadrupole-ACSM (Q-ACSM). Compared to the Q-ACSM, the ToF-ACSM features a better mass resolution of M/ΔM = 600 and better detection limits on the order of <30 ng m−3 for a time resolution of 30 min. With simple upgrades these limits can be brought down by another factor of ~8. This allows for operation at higher time resolutions and in low concentration environments. The associated software packages (single packages for integrated operation &amp; calibration and analysis) provide a high degree of automation and remote access, minimising the need for trained personnel on site. Intercomparisons with Q-ACSM, C-ToF-AMS, nephelometer and scanning mobility particle sizer (SMPS) measurements, performed during a first long-term deployment (>6 months) on the Jungfraujoch mountain ridge (3580 m a.s.l.) in the Swiss Alps agree quantitatively. Additionally, the mass resolution of the ToF-ACSM is sufficient for basic mass defect resolved peak fitting of the recorded spectra, providing a data stream not accessible to the Q-ACSM. This allows for quantification of certain hydrocarbon and oxygenated fragments (e.g. C3H7+ and C2H3O+, both occurring at m/Q = 43 Th), as well as improving inorganic/organic separation.

scholarly journals Characterization of submicron particles by time-of-flight aerosol chemical speciation monitor (ToF-ACSM) during wintertime: aerosol composition, sources, and chemical processes in Guangzhou, China

2020 ◽  
Vol 20 (12) ◽  
pp. 7595-7615 ◽  
Author(s):  
Junchen Guo ◽  
Shengzhen Zhou ◽  
Mingfu Cai ◽  
Jun Zhao ◽  
Wei Song ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Gas Phase ◽  
Mass Concentration ◽  
Chemical Speciation ◽  
Time Of Flight ◽  
Chemical Processes ◽  
Traffic Emissions ◽  
Multiphase Reactions ◽  
Phase Oxidation ◽  
Gas Phase Oxidation

Abstract. Particulate matter (PM) pollution in China is an emerging environmental issue which policy makers and the public have increasingly paid attention to. In order to investigate the characteristics, sources, and chemical processes of PM pollution in Guangzhou, field measurements were conducted from 20 November 2017 to 5 January 2018, with a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and other collocated instruments. Mass concentrations of non-refractory submicron particulate matter (NR-PM1) measured by the ToF-ACSM correlated well with those of PM2.5 or PM1.1 measured by filter-based methods. The organic mass fraction increased from 45 % to 53 % when the air switched from non-pollution periods to pollution episodes (EPs), indicating significant roles of organic aerosols (OAs) during the whole study. Based on the mass spectra measured by the ToF-ACSM, positive matrix factorization (PMF) with the multilinear engine (ME-2) algorithm was performed to deconvolve OA into four factors, including hydrocarbon-like OA (HOA, 12 %), cooking OA (COA, 18 %), semi-volatile oxygenated OA (SVOOA, 30 %), and low-volatility oxygenated OA (LVOOA, 40 %). Furthermore, we found that SVOOA and nitrate were significantly contributed from local traffic emissions while sulfate and LVOOA were mostly attributed to regional pollutants. Comparisons between this work and other previous studies in China show that secondary organic aerosol (SOA) fraction in total OA increases spatially across China from the north to the south. Two distinctly opposite trends for NR-PM1 formation were observed during non-pollution periods and pollution EPs. The ratio of secondary PM (SPM = SVOOA + LVOOA + sulfate + nitrate + ammonium) to primary PM (PPM = HOA + COA + chloride), together with peroxy radicals RO2∗ and ozone, increased with increasing NR-PM1 concentration during non-pollution periods, while an opposite trend of these three quantities was observed during pollution EPs. Furthermore, oxidation degrees of both OA and SOA were investigated using the f44∕f43 space and the results show that at least two OOA factors are needed to cover a large range of f44 and f43 in Guangzhou. Comparisons between our results and other laboratory studies imply that volatile organic compounds (VOCs) from traffic emissions, in particular from diesel combustion and aromatic compounds, are the most likely SOA precursors in Guangzhou. Peroxy radical RO2∗ was used as a tracer for SOA formed through gas-phase oxidation. For non-pollution periods, SOA concentration was reasonably correlated with RO2∗ concentration during both daytime and nighttime, suggesting that gas-phase oxidation was primarily responsible for SOA formation. However, there was no correlation between SOA and RO2∗ in pollution EPs, suggesting a dramatically changed mechanism for SOA formation. This conclusion can also be supported by different features of SOA in a van Krevelen diagram between non-pollution periods and pollution EPs. Furthermore, for pollution EPs, when NR-PM1 mass concentration was divided into six segments, in each segment except for the lowest one SOA concentration was correlated moderately with RO2∗ concentration, suggesting that gas-phase oxidation still plays important roles in SOA formation. The intercepts of the above linear regressions, which likely correspond to the extent of other mechanisms (i.e., heterogeneous and multiphase reactions), increase with increasing NR-PM1 mass concentration. Our results suggest that while gas-phase oxidation contributes predominantly to SOA formation during non-pollution periods, other mechanisms such as heterogeneous and multiphase reactions play more important roles in SOA formation during pollution EPs than gas-phase oxidation.

Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

2019 ◽  
Author(s):  
Oriol Planas ◽  
Feng Wang ◽  
Markus Leutzsch ◽  
Josep Cornella
Keyword(s):  
Transition Metal ◽  
Main Group ◽  
Group Element ◽  
Oxidation States ◽  
Boron Compounds ◽  
Main Text ◽  
Main Group Element ◽  
Rational Ligand Design ◽  
Supplementary Material

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts.<br>A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.<br>

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