Chemical composition and volatility distribution of SOA formed by ozonolysis of β-caryophyllene between 213-313 K

2020 ◽  
Author(s):  
Linyu Gao ◽  
Magdalena Vallon ◽  
Junwei Song ◽  
Wei Huang ◽  
Thomas Leisner ◽  
...  
Keyword(s):  
Significant Contribution ◽  
Basis Set ◽  
Emission Rates ◽  
Particle Phase ◽  
Reaction Products ◽  
Iodide Ions ◽  
Phase Partitioning ◽  
Aerosol Mass ◽  
Different Temperatures

<p>β-Caryophyllene is the most common and abundant of the sesquiterpenes emitted into the atmosphere (Duhl et al., 2008). Although sesquiterpene emission rates were estimated to be only 9–16% of the total terpene emissions (Duhl et al., 2008), they are more reactive and larger in size than monoterpenes. Consequently, their aerosol mass yields are large and result in a significant contribution to the SOA budget in the atmosphere (Tasoglou and Pandis, 2015). Therefore, we studied the composition of both gas and particle phases as well as phase partitioning of SOA from ozonolysis of β-caryophyllene in presence and absence of NOx at five temperatures (213 K, 243 K, 273 K, 298 and 313 K) in the AIDA aerosol simulation chamber. This work focusses on the characterization of the SOA by mass spectrometry employing a FIGAERO-HR-TOF-CIMS operated with iodide ions and a HR-TOF-AMS (both Aerodyne Inc.). Particle phase analysis shows three groups of compound masses with m/z 240-400, (C<sub>5-16</sub>),  (m/z 400-560, (C<sub>20-34</sub>), and m/z 560-680, (C<sub>35-40</sub>) classified as monomers, dimers, and trimers, respectively.  Trimeric compounds were observed preferentially in SOA formed at higher temperatures (273 K, 298 K, 313 K), while only monomeric and dimeric compounds were detected at lower temperatures (243 K and 213 K). Interestingly, dimeric compounds, including C<sub>x</sub>H<sub>y</sub>O<sub>z</sub> and C<sub>x</sub>H<sub>y</sub>O<sub>z</sub>N<sub>1</sub>, contribute more to SOA mass for the lower temperatures. Comparing volatility distributions for the five different temperatures using the Volatility Basis Set (VBS) and thermal desorption information from FIGAERO-CIMS (298-473 K) we find more compounds with lower volatility for lower SOA formation temperatures. This contribution will discuss the volatility distributions obtained with and without NOx as well as the abundance of specific reaction products.</p>

Characterization of Aerosol Release during Spraying of Isocyanate Products

2019 ◽  
Vol 63 (7) ◽  
pp. 773-783
Author(s):  
Colin Ehnes ◽  
Manfred Genz ◽  
Jörn Duwenhorst ◽  
Jurij Krasnow ◽  
Jan Bleeke ◽  
...  
Keyword(s):  
Size Fraction ◽  
Spray Coating ◽  
Reaction Products ◽  
Residual Monomer ◽  
Particle Size Fractions ◽  
Aerosol Mass ◽  
Two Component ◽  
Mass Release ◽  
Monomer Content

Abstract The aerosol release during the professional application of two different isocyanate based two component spray systems was identified and the physicochemical properties of the released airborne aerosols were characterized. For this purpose, aerosol release fractions were measured using a mass balance method described by Schwarz and Koch. Besides the release of total aerosol mass special emphasis was directed to the content of free monomeric MDI (4,4′- and 2,4′-diphenylmethane diisocyanate) in three particle size fractions relevant for inhalation uptake: inhalable, thoracic, and respirable size fraction. Two products were investigated: a two component PUR (polyurethane) spray foam (Elastopor) and a polyurea spray coating (Elastocoat). The mass fraction of the applied products released with the overspray as inhalable aerosol is 6.3 × 10−4 (Elastopor) and 4.0 × 10−4 (Elastocoat). Of the released total overspray aerosol 75 or 80% were in the thoracic size range, and 26 or 47% in the respirable regime for the PUR spray foam or the polyurea spray coating, respectively. At the time point of release the content of monomeric MDI in the aerosol corresponds to the composition of the bulk product. However, analysis of air samples indicates that <1% of the spray foam aerosol mass release fraction is attributed to free monomeric 4,4′- and 2,4′-MDI. For the Spray Coating the monomeric MDI fraction is <0.1%. Higher oligomers of MDI and prereacted oligomeric reaction products make up a few percent of the aerosol. This results in a total fraction of 0.0023% (spray foam) and 0.00015% (spray coating), respectively, of the sprayed monomeric MDI that is transferred into an inhalable aged aerosol. This data demonstrates, that during professional spraying only a small fraction of the total applied mass is released as airborne aerosol. The potential distribution of the theoretically inhalable aerosol in the respiratory tract and a low residual monomer content is described, significantly contributing to a refined safety assessment of the spray applications at the workplaces.

scholarly journals A new chemistry option in WRF-Chem v. 3.4 for the simulation of direct and indirect aerosol effects using VBS: evaluation against IMPACT-EUCAARI data

2015 ◽  
Vol 8 (9) ◽  
pp. 2749-2776 ◽  
Author(s):  
P. Tuccella ◽  
G. Curci ◽  
G. A. Grell ◽  
G. Visconti ◽  
S. Crumeyrolle ◽  
...  
Keyword(s):  
Optical Thickness ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Basis Set ◽  
Condensation Nuclei ◽  
Water Path ◽  
Aerosol Cloud ◽  
Aerosol Mass ◽  
Mass Concentrations

Abstract. A parameterization for secondary organic aerosol (SOA) production based on the volatility basis set (VBS) approach has been coupled with microphysics and radiative schemes in the Weather Research and Forecasting model with Chemistry (WRF-Chem) model. The new chemistry option called "RACM-MADE-VBS-AQCHEM" was evaluated on a cloud resolving scale against ground-based and aircraft measurements collected during the IMPACT-EUCAARI (Intensive Cloud Aerosol Measurement Campaign – European Integrated project on Aerosol Cloud Climate and Air quality interaction) campaign, and complemented with satellite data from MODIS. The day-to-day variability and the diurnal cycle of ozone (O3) and nitrogen oxides (NOx) at the surface are captured by the model. Surface aerosol mass concentrations of sulfate (SO4), nitrate (NO3), ammonium (NH4), and organic matter (OM) are simulated with correlations larger than 0.55. WRF-Chem captures the vertical profile of the aerosol mass concentration in both the planetary boundary layer (PBL) and free troposphere (FT) as a function of the synoptic condition, but the model does not capture the full range of the measured concentrations. Predicted OM concentration is at the lower end of the observed mass concentrations. The bias may be attributable to the missing aqueous chemistry processes of organic compounds and to uncertainties in meteorological fields. A key role could be played by assumptions on the VBS approach such as the SOA formation pathways, oxidation rate, and dry deposition velocity of organic condensable vapours. Another source of error in simulating SOA is the uncertainties in the anthropogenic emissions of primary organic carbon. Aerosol particle number concentration (condensation nuclei, CN) is overestimated by a factor of 1.4 and 1.7 within the PBL and FT, respectively. Model bias is most likely attributable to the uncertainties of primary particle emissions (mostly in the PBL) and to the nucleation rate. Simulated cloud condensation nuclei (CCN) are also overestimated, but the bias is more contained with respect to that of CN. The CCN efficiency, which is a characterization of the ability of aerosol particles to nucleate cloud droplets, is underestimated by a factor of 1.5 and 3.8 in the PBL and FT, respectively. The comparison with MODIS data shows that the model overestimates the aerosol optical thickness (AOT). The domain averages (for 1 day) are 0.38 ± 0.12 and 0.42 ± 0.10 for MODIS and WRF-Chem data, respectively. The droplet effective radius (Re) in liquid-phase clouds is underestimated by a factor of 1.5; the cloud liquid water path (LWP) is overestimated by a factor of 1.1–1.6. The consequence is the overestimation of average liquid cloud optical thickness (COT) from a few percent up to 42 %. The predicted cloud water path (CWP) in all phases displays a bias in the range +41–80 %, whereas the bias of COT is about 15 %. In sensitivity tests where we excluded SOA, the skills of the model in reproducing the observed patterns and average values of the microphysical and optical properties of liquid and all phase clouds decreases. Moreover, the run without SOA (NOSOA) shows convective clouds with an enhanced content of liquid and frozen hydrometers, and stronger updrafts and downdrafts. Considering that the previous version of WRF-Chem coupled with a modal aerosol module predicted very low SOA content (secondary organic aerosol model (SORGAM) mechanism) the new proposed option may lead to a better characterization of aerosol–cloud feedbacks.

scholarly journals Chemical characterization of oxygenated organic compounds in the gas phase and particle phase using iodide CIMS with FIGAERO in urban air

2021 ◽  
Vol 21 (11) ◽  
pp. 8455-8478
Author(s):  
Chenshuo Ye ◽  
Bin Yuan ◽  
Yi Lin ◽  
Zelong Wang ◽  
Weiwei Hu ◽  
...  
Keyword(s):  
Organic Acids ◽  
Gas Phase ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Organic Aerosol ◽  
Urban Site ◽  
Organic Nitrates ◽  
Particle Phase ◽  
Aerosol Mass

Abstract. The atmospheric processes under polluted environments involving interactions of anthropogenic pollutants and natural emissions lead to the formation of various and complex secondary products. Therefore, the characterization of oxygenated organic compounds in urban areas remains a pivotal issue in our understanding of the evolution of organic carbon. Here, we describe measurements of an iodide chemical ionization time-of-flight mass spectrometer installed with a Filter Inlet for Gases and AEROsols (FIGAERO-I-CIMS) in both the gas phase and the particle phase at an urban site in Guangzhou, a typical megacity in southern China, during the autumn of 2018. Abundant oxygenated organic compounds containing two to five oxygen atoms were observed, including organic acids, multi-functional organic compounds typically emitted from biomass burning, oxidation products of biogenic hydrocarbons and aromatics. Photochemistry played dominant roles in the formation of gaseous organic acids and isoprene-derived organic nitrates, while nighttime chemistry contributed significantly to the formation of monoterpene-derived organic nitrates and inorganics. Nitrogen-containing organic compounds occupied a significant fraction of the total signal in both the gas and particle phases, with elevated fractions at higher molecular weights. Measurements of organic compounds in the particle phase by FIGAERO-I-CIMS explained 24 ± 0.8 % of the total organic aerosol mass measured by aerosol mass spectrometer (AMS), and the fraction increased for more aged organic aerosol. The systematical interpretation of mass spectra of the FIGAERO-I-CIMS in the urban area of Guangzhou provides a holistic view of numerous oxygenated organic compounds in the urban atmosphere, which can serve as a reference for the future field measurements by FIGAERO-I-CIMS in polluted urban regions.

scholarly journals Constraining a hybrid volatility basis set model for aging of wood burning emissions using smog chamber experiments

2016 ◽  
Author(s):  
Giancarlo Ciarelli ◽  
Imad El Haddad ◽  
Emily Bruns ◽  
Sebnem Aksoyoglu ◽  
Ottmar Möhler ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Organic Aerosol ◽  
Reaction Rates ◽  
Box Model ◽  
Basis Set ◽  
Smog Chamber ◽  
Aerosol Mass ◽  
Volatile Organic ◽  
Different Temperatures

Abstract. Semi-volatile and intermediate volatility organic compounds (SVOCs, IVOCs) are not included in the current non-methane volatile organic compounds (NMVOCs) emission inventories but may be important for the formation of secondary organic aerosol (SOA). In this study, novel wood combustion aging experiments performed at different temperatures (263 K and 288 K) in a ~7 m3 smog chamber were modelled using a hybrid volatility basis set (VBS) box model, representing the emission partitioning and their oxidation against OH. We combine aerosol-chemistry box model simulations with unprecedented measurements of nontraditional volatile organic compounds (NTVOCs) from a high-resolution proton transfer reaction mass spectrometer (PTR-MS) and with organic aerosol measurements from an aerosol mass spectrometer (AMS). In so-doing, we are able to observationally-constrain the amounts of different NTVOCs aerosol precursors (in the model) relative to low-volatility and semi-volatile primary organic material (OMsv) which is partitioned based on current published volatility distribution data. By comparing the NTVOCs/OMsv ratios at different temperatures, we determine the enthalpies of vaporization of primary biomass burning organic aerosols. Further, the developed model allows for evaluating the evolution of oxidation products of the semi-volatile and volatile precursors with aging. More than 30,000 box model simulations were performed to retrieve the combination of parameters that fit best the observed organic aerosol mass and O:C ratios. The parameters investigated include the NTVOC reaction rates and yields as well as enthalpies of vaporization and the O:C of secondary organic aerosol surrogates. Our results suggest an average ratio of NTVOCs to the sum of non-volatile and semi-volatile organic compounds of ~4.75. The mass yields of these compounds determined for a wide range of atmospherically relevant temperatures and organic aerosol (OA) concentrations were predicted to vary between 8 and 30 % after 5 hours of continuous aging. Based on the reaction scheme used, reaction rates of the NTVOC mixture range from 3.0 × 10–11 cm3 molec−1 s−1 to 4.0 × 10–11 cm3 molec−1 s−1. The average enthalpy of vaporization of SOA surrogates was determined to be between 55,000 J mol−1 and 35,000 J mol−1 which implies a yield increase of 0.03–0.06 % K−1 with decreasing temperature. The improved VBS scheme is suitable for implementation into chemical transport models to predict the burden and oxidation state of primary and secondary biomass burning aerosols.

scholarly journals Constraining a hybrid volatility basis-set model for aging of wood-burning emissions using smog chamber experiments: a box-model study based on the VBS scheme of the CAMx model (v5.40)

2017 ◽  
Vol 10 (6) ◽  
pp. 2303-2320 ◽  
Author(s):  
Giancarlo Ciarelli ◽  
Imad El Haddad ◽  
Emily Bruns ◽  
Sebnem Aksoyoglu ◽  
Ottmar Möhler ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Organic Aerosol ◽  
Reaction Rates ◽  
Box Model ◽  
Basis Set ◽  
Smog Chamber ◽  
Model Simulations ◽  
Aerosol Mass ◽  
Volatile Organic ◽  
Different Temperatures

Abstract. In this study, novel wood combustion aging experiments performed at different temperatures (263 and 288 K) in a ∼ 7 m3 smog chamber were modelled using a hybrid volatility basis set (VBS) box model, representing the emission partitioning and their oxidation against OH. We combine aerosol–chemistry box-model simulations with unprecedented measurements of non-traditional volatile organic compounds (NTVOCs) from a high-resolution proton transfer reaction mass spectrometer (PTR-MS) and with organic aerosol measurements from an aerosol mass spectrometer (AMS). Due to this, we are able to observationally constrain the amounts of different NTVOC aerosol precursors (in the model) relative to low volatility and semi-volatile primary organic material (OMsv), which is partitioned based on current published volatility distribution data. By comparing the NTVOC ∕ OMsv ratios at different temperatures, we determine the enthalpies of vaporization of primary biomass-burning organic aerosols. Further, the developed model allows for evaluating the evolution of oxidation products of the semi-volatile and volatile precursors with aging. More than 30 000 box-model simulations were performed to retrieve the combination of parameters that best fit the observed organic aerosol mass and O : C ratios. The parameters investigated include the NTVOC reaction rates and yields as well as enthalpies of vaporization and the O : C of secondary organic aerosol surrogates. Our results suggest an average ratio of NTVOCs to the sum of non-volatile and semi-volatile organic compounds of ∼ 4.75. The mass yields of these compounds determined for a wide range of atmospherically relevant temperatures and organic aerosol (OA) concentrations were predicted to vary between 8 and 30 % after 5 h of continuous aging. Based on the reaction scheme used, reaction rates of the NTVOC mixture range from 3.0 × 10−11 to 4. 0 × 10−11 cm3 molec−1 s−1. The average enthalpy of vaporization of secondary organic aerosol (SOA) surrogates was determined to be between 55 000 and 35 000 J mol−1, which implies a yield increase of 0.03–0.06 % K−1 with decreasing temperature. The improved VBS scheme is suitable for implementation into chemical transport models to predict the burden and oxidation state of primary and secondary biomass-burning aerosols.

scholarly journals Chemical characterization of oxygenated organic compounds in gas-phase and particle-phase using iodide-CIMS with FIGAERO in urban air

2020 ◽  
Author(s):  
Chenshuo Ye ◽  
Bin Yuan ◽  
Yi Lin ◽  
Zelong Wang ◽  
Weiwei Hu ◽  
...  
Keyword(s):  
Organic Acids ◽  
Gas Phase ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Organic Aerosol ◽  
Urban Site ◽  
Organic Nitrates ◽  
Particle Phase ◽  
Aerosol Mass

Abstract. The characterization of oxygenated organic compounds in urban areas remains a pivotal gap in our understanding of the evolution of organic carbon under polluted environments, as the atmospheric processes involving interactions between organics and inorganics, anthropogenic pollutants and natural emissions lead to formation of various and complex secondary products. Here, we describe measurements of an iodide chemical ionization time-of-flight mass spectrometer installed with a Filter Inlet for Gases and AEROsols (FIGAERO-I-CIMS) in both gas-phase and particle-phase at an urban site in Guangzhou, a typical mega-city in southern China, during the autumn of 2018. Abundant oxygenated organic compounds containing 2~5 oxygen atoms were observed, including organic acids, multi-functional organics typically emitted form biomass burning, oxidation products of biogenic hydrocarbons and aromatics. Photochemistry played dominant roles in the formation of gaseous organic acids and isoprene-derived organic nitrates, while nighttime chemistry contributed significantly to the formation monoterpene-derived organic nitrates and inorganics. Nitrogen-containing organic compounds occupied a significant fraction of the total signal in both gas and particle phases, with elevated fractions at higher molecular weights. Measurements of organic compounds in particle phase by FIGAERO-I-CIMS explained 24 % of the total organic aerosol mass measured by aerosol mass spectrometer (AMS), and the fraction increased for more aged organic aerosol. The systematically interpretation of mass spectra of the FIGAERO-I-CIMS in urban of Guangzhou provides a holistic view of numerous oxygenated organic compounds in the urban atmosphere, which can serve as a reference for the future field measurements by FIGAERO-I-CIMS in polluted urban regions.

scholarly journals Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets

2016 ◽  
Vol 113 (6) ◽  
pp. 1516-1521 ◽  
Author(s):  
Ben H. Lee ◽  
Claudia Mohr ◽  
Felipe D. Lopez-Hilfiker ◽  
Anna Lutz ◽  
Mattias Hallquist ◽  
...  
Keyword(s):  
Large Fraction ◽  
Carbon Number ◽  
Organic Aerosol ◽  
Reactive Nitrogen ◽  
Organic Nitrates ◽  
Particle Phase ◽  
Alkyl Nitrates ◽  
Nitrogen Budgets ◽  
Phase Partitioning ◽  
Aerosol Mass

Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas–particle equilibrium and (ii) have a short particle-phase lifetime (∼2–4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.

TEM characterization of reaction zone in a SiC fiber-reinforced titanium alloy

1988 ◽  
Vol 46 ◽  
pp. 738-739
Author(s):  
G. Das ◽  
R. E. Omlor
Keyword(s):  
Titanium Alloys ◽  
Reaction Zone ◽  
Carbon Layer ◽  
Fiber Reinforced ◽  
Reaction Products ◽  
Sic Fibers ◽  
Sic Fiber ◽  
The Matrix ◽  
Immense Potential

Fiber reinforced titanium alloys hold immense potential for applications in the aerospace industry. However, chemical reaction between the fibers and the titanium alloys at fabrication temperatures leads to the formation of brittle reaction products which limits their development. In the present study, coated SiC fibers have been used to evaluate the effects of surface coating on the reaction zone in the SiC/IMI829 system.IMI829 (Ti-5.5A1-3.5Sn-3.0Zr-0.3Mo-1Nb-0.3Si), a near alpha alloy, in the form of PREP powder (-35 mesh), was used a茸 the matrix. CVD grown AVCO SCS-6 SiC fibers were used as discontinuous reinforcements. These fibers of 142μm diameter contained an overlayer with high Si/C ratio on top of an amorphous carbon layer, the thickness of the coating being ∽ 1μm. SCS-6 fibers, broken into ∽ 2mm lengths, were mixed with IMI829 powder (representing < 0.1vol%) and the mixture was consolidated by HIP'ing at 871°C/0. 28GPa/4h.

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