scholarly journals Combined application of Online FIGAERO-CIMS and Offline LC-Orbitrap MS to Characterize the Chemical Composition of SOA in Smog Chamber Studies

2021 ◽  
Author(s):  
Mao Du ◽  
Aristeidis Voliotis ◽  
Yunqi Shao ◽  
Yu Wang ◽  
Thomas J. Bannan ◽  
...  
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Gas Phase ◽  
Carbon Number ◽  
Mode Analysis ◽  
Ionization Mass ◽  
Particle Phase ◽  
Negative Mode ◽  
Combined Application ◽  
Orbitrap Ms

Abstract. A combination of online and offline mass spectrometric techniques was used to characterize the chemical composition of secondary organic aerosol (SOA) generated from the photooxidation of α-pinene in an atmospheric simulation chamber. The filter inlet for gases and aerosols (FIGAERO) coupled with a high-resolution time-of-flight iodide chemical ionization mass spectrometer (I–ToF-CIMS) was employed to track the evolution of gaseous and particulate components. Extracts of aerosol particles sampled onto a filter at the end of each experiment were analyzed using ultra-performance liquid chromatography ultra-high-resolution tandem mass spectrometry (LC-Orbitrap MS). Each technique was used to investigate the major SOA elemental group contributions in each system. The online CIMS particle-phase measurements show that organic species containing exclusively carbon, hydrogen and oxygen (CHO group) dominate the contribution to the ion signals from the SOA products, broadly consistent with the LC-Orbitrap MS negative mode analysis which was better able to identify the sulphur-containing fraction. An increased abundance of high carbon number (nC ≥ 16) compounds additionally containing nitrogen (CHON group) was detected in the LC-Orbitrap MS positive ionisation mode, indicating a fraction missed by the negative mode and CIMS measurements. Time series of gas-phase and particle-phase oxidation products provided by online measurements allowed investigation of the gas-phase chemistry of those products by hierarchical clustering analysis to assess the phase partitioning of individual molecular compositions. The particle-phase clustering was used to inform the selection of components for targeted structural analysis of the offline samples. Saturation concentrations derived from near-simultaneous gaseous and particulate measurements of the same ions by FIGAERO-CIMS were compared with those estimated from the molecular structure based on the LC-Orbitrap MS measurements to interpret the component partitioning behaviour. This paper explores the insight brought to the interpretation of SOA chemical composition by the combined application of online FIGAERO-CIMS and offline LC-Orbitrap MS analytical techniques.

scholarly journals Direct contribution of ammonia to <i>α</i>-pinene secondary organic aerosol formation

2020 ◽  
Vol 20 (22) ◽  
pp. 14393-14405
Author(s):  
Liqing Hao ◽  
Eetu Kari ◽  
Ari Leskinen ◽  
Douglas R. Worsnop ◽  
Annele Virtanen
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Organic Acids ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Mass Concentration ◽  
Organic Aerosol ◽  
Particle Phase ◽  
Resolution Time ◽  
Aerosol Mass

Abstract. Ammonia (NH3), a gaseous compound ubiquitously present in the atmosphere, is involved in the formation of secondary organic aerosol (SOA), but the exact mechanism is still not well known. This study presents the results of SOA experiments from the photooxidation of α-pinene in the presence of NH3 in the reaction chamber. SOA was formed in in nucleation experiments and in seeded experiments with ammonium sulfate particles as seeds. The chemical composition and time series of compounds in the gas and particle phase were characterized by an online high-resolution time-of-flight proton-transfer-reaction mass spectrometer (HR-ToF-PTRMS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. Our results show that the mass concentration of ammonium (NH4+) was still rising even after the mass concentration of the organic component started to decrease due to aerosol wall deposition and evaporation, implying the continuous new formation of particle-phase ammonium in the process. Stoichiometric neutralization analysis of aerosol indicates that organic acids have a central role in the formation of particle-phase ammonium. Our measurements show a good correlation between the gas-phase organic mono- and dicarboxylic acids formed in the photooxidation of α-pinene and the ammonium in the particle phase, thus highlighting the contribution of gas-phase organic acids to the ammonium formation. The work shows that the gas-phase organic acids contribute to the SOA formation by forming organic ammonium salts through acid–base reaction. The changes in aerosol mass, particle size and chemical composition resulting from the NH3–SOA interaction can potentially alter the aerosol direct and indirect forcing and therefore alter its impact on climate change.

scholarly journals The importance of sesquiterpene oxidation products for secondary organic aerosol formation in a springtime hemiboreal forest

2021 ◽  
Vol 21 (15) ◽  
pp. 11781-11800
Author(s):  
Luis M. F. Barreira ◽  
Arttu Ylisirniö ◽  
Iida Pullinen ◽  
Angela Buchholz ◽  
Zijun Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Gas Phase ◽  
Organic Compounds ◽  
Field Experiments ◽  
Recovery Period ◽  
Particle Formation ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase ◽  
Aerosol Formation

Abstract. Secondary organic aerosols (SOAs) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to significantly affect the climate and air quality. Atmospheric SOA particulate mass yields and chemical composition result from a complex mixture of oxidation products originating from a diversity of BVOCs. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. However, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas-phase and particle-phase oxygenated compounds. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a springtime hemiboreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified for both situations. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase in some periods, while their gas-phase concentrations remained much lower than those of monoterpene products. This can be explained by favorable and effective partitioning of sesquiterpene products into the particle phase. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates that sesquiterpenes may have an important role in atmospheric SOA formation and oxidation chemistry, in particular during the spring recovery period.

scholarly journals Direct contribution of ammonia to CCN-size alpha-pinene secondary organic aerosol formation

2020 ◽  
Author(s):  
Liqing Hao ◽  
Eetu Kari ◽  
Ari Leskinen ◽  
Douglas R. Worsnop ◽  
Annele Virtanen
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Organic Acids ◽  
Gas Phase ◽  
Mass Spectrometer ◽  
Mass Concentration ◽  
Organic Aerosol ◽  
Particle Phase ◽  
Resolution Time ◽  
Aerosol Mass

Abstract. Ammonia (NH3), a gasous compound ubiquitiously present in the atmosphere, is involved in the formation of secondary organic aerosol (SOA), but the exact mechanisum is still not well known. This study presents the results of SOA experiments from the photooxidation of α-pinene in the presence of NH3 in the reaction chamber. SOA was formed in nucleation experiment and in seeded experiment with ammonium sulfate particles as seeds. The chemical composition and time-series of compounds in the gas- and particle- phase were characterized by an on-line high-resolution time-of-flight proton transfer reaction mass spectrometer (HR-ToF-PTRMS) and a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), respectively. Our results show that for the aerosol particles in cloud condensation nuclei (CCN) size, the mass concentration of ammonium (NH4+) was still rising even after the mass concentration of organic component started to decrease due to aerosol wall deposition and evaporation, implying the continuous new formation of particle phase ammonium in the process. Stoichiometric neutralization analysis of aerosol indicates that organic acids have a central role in the formation of particle phase ammonium. Our measurements show a good correlation between the gas phase organic mono- and di-carboxylic acids formed in the photooxidation of α-pinene and the ammonium in the particle phase, thus highlighting the contribution of gas-phase organic acids to the ammonium formation in the CCN-size SOA particles. The work shows that the gas-phase organic acids contribute to the SOA formation by forming ammonium salts through acid-base reaction. The changes in aerosol mass, particle size and chemical composition resulting from the NH3-SOA interaction can potentially alter the aerosol direct and indirect forcing and therefore alter its impact on climate change.

scholarly journals The importance of sesquiterpene oxidation products for secondary organic aerosol formation in a spring-time hemi-boreal forest

2021 ◽  
Author(s):  
Luis M. F. Barreira ◽  
Arttu Ylisirniö ◽  
Iida Pullinen ◽  
Angela Buchholz ◽  
Zijun Li ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Boreal Forest ◽  
Organic Compounds ◽  
Field Experiments ◽  
Complex Mixture ◽  
Particle Formation ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase ◽  
Aerosol Formation

Abstract. Secondary organic aerosols (SOA) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to affect significantly the climate and air quality. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. Most of them have focused on a few monoterpenes and isoprene. However, atmospheric SOA particulate mass yields and chemical composition result from a much more complex mixture of oxidation products originating from many BVOCs, including terpenes other than isoprene and monoterpenes. Thus, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas and particle phase atmospheric SOA. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a spring-time hemi-boreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase at some periods, while their gas phase concentrations remained much lower than those of monoterpene products. This can be explained by quick and effective partitioning of sesquiterpene products into the particle phase or their efficient removal by dry deposition. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates the important role of sesquiterpenes in atmospheric chemistry and suggests that the contribution of their products to SOA particles is being underestimated in comparison to the most studied terpenes.

scholarly journals Formation of Highly Oxygenated Low-Volatility Products from Cresol Oxidation

2016 ◽  
Author(s):  
Rebecca H. Schwantes ◽  
Katherine A. Schilling ◽  
Renee C. McVay ◽  
Hanna Lignell ◽  
Matthew M. Coggon ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Ring Opening ◽  
Chemical Ionization ◽  
First Generation ◽  
Direct Analysis ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Ionization Mass ◽  
Particle Phase

Abstract. Hydroxyl radical (OH) oxidation of toluene produces the ring-retaining products cresol and benzaldehyde, and the ring-opening products bicyclic intermediate compounds and epoxides. Here, first- and later-generation OH oxidation products from cresol and benzaldehyde are identified in laboratory chamber experiments. For benzaldehyde, first-generation ring-retaining products are identified, but later-generation products are not detected. For cresol, low-volatility (saturation mass concentration, C* ~ 3.5 × 104–7.7 × 10−3 μg m−3) first- and later-generation ring-retaining products are identified. Subsequent OH addition to the aromatic ring of o-cresol leads to compounds such as hydroxy, dihydroxy, and trihydroxy methyl benzoquinones and dihydroxy, trihydroxy, tetrahydroxy, and pentahydroxy toluenes. These products are detected in the gas phase by chemical ionization mass spectrometry (CIMS) and in the particle phase using offline direct analysis in real time mass spectrometry (DART-MS). Our data suggest that the yield of trihydroxy toluene from dihydroxy toluene is substantial. While an exact yield cannot be reported as authentic standards are unavailable, we find that a yield for trihydroxy toluene from dihydroxy toluene of ~ 0.7 (equal to the yield of dihydroxy toluene from o-cresol) is consistent with experimental results for o-cresol oxidation under low-NO conditions. These results suggest that even though the cresol pathway accounts for only ~ 20 % of the oxidation products of toluene, it is the source of a significant fraction (~ 20–40 %) of toluene secondary organic aerosol (SOA) due to the formation of low-volatility products.

scholarly journals Relating the hygroscopic properties of submicron aerosol to both gas- and particle-phase chemical composition in a boreal forest environment

2015 ◽  
Vol 15 (11) ◽  
pp. 15511-15541
Author(s):  
J. Hong ◽  
J. Kim ◽  
T. Nieminen ◽  
J. Duplissy ◽  
M. Ehn ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Growth Factor ◽  
Boreal Forest ◽  
Gas Phase ◽  
Mixing Rule ◽  
Particle Phase ◽  
Hygroscopic Growth ◽  
Forest Environment ◽  
Composition Data

Abstract. Measurements of the hygroscopicity of 15–145 nm particles in a boreal forest environment were conducted using two Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) systems during the Pan-European Gas-AeroSOIs-climate interaction Study (PEGASOS) campaign in spring 2013. Measurements of the chemical composition of non-size segregated particles were also performed using a High-Resolution Aerosol Mass Spectrometer (HR-AMS) in parallel with hygroscopicity measurements. On average, the hygroscopic growth factor (HGF) of particles was observed to increase from the morning until afternoon. In case of accumulation mode particles, the main reasons for this behavior were increases in the ratio of sulfate to organic matter and oxidation level (O : C ratio) of the organic matter in the particle phase. Using an O : C dependent hygroscopic growth factor of organic matter (HGForg), fitted using the inverse Zdanovskii–Stokes–Robinson (ZSR) mixing rule, clearly improved the agreement between measured HGF and that predicted based on HR-AMS composition data. Besides organic oxidation level, the influence of inorganic species was tested when using the ZSR mixing rule to estimate the hygroscopic growth factor of organics in the aerosols. While accumulation and Aitken mode particles were predicted fairly well by the bulk aerosol composition data, the hygroscopicity of nucleation mode particles showed little correlation. However, we observed them to be more sensitive to the gas phase concentration of condensable vapors: the more there was sulfuric acid in the gas phase, the more hygroscopic the nucleation mode particles were. No clear dependence was found between the extremely low-volatility organics (ELVOCs) concentration and the HGF of particles of any size.

scholarly journals Seasonal characteristics of organic aerosol chemical composition and volatility in Stuttgart, Germany

2019 ◽  
Vol 19 (18) ◽  
pp. 11687-11700 ◽  
Author(s):  
Wei Huang ◽  
Harald Saathoff ◽  
Xiaoli Shen ◽  
Ramakrishna Ramisetty ◽  
Thomas Leisner ◽  
...  
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Organic Compounds ◽  
Mass Spectrometer ◽  
Time Of Flight ◽  
Organic Aerosol ◽  
Molecular Composition ◽  
Winter Period ◽  
Ionization Mass ◽  
Resolution Time

Abstract. The chemical composition and volatility of organic aerosol (OA) particles were investigated during July–August 2017 and February–March 2018 in the city of Stuttgart, one of the most polluted cities in Germany. Total non-refractory particle mass was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS; hereafter AMS). Aerosol particles were collected on filters and analyzed in the laboratory with a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS; hereafter CIMS), yielding the molecular composition of oxygenated OA (OOA) compounds. While the average organic mass loadings are lower in the summer period (5.1±3.2 µg m−3) than in the winter period (8.4±5.6 µg m−3), we find relatively larger mass contributions of organics measured by AMS in summer (68.8±13.4 %) compared to winter (34.8±9.5 %). CIMS mass spectra show OOA compounds in summer have O : C of 0.82±0.02 and are more influenced by biogenic emissions, while OOA compounds in winter have O : C of 0.89±0.06 and are more influenced by biomass burning emissions. Volatility parametrization analysis shows that OOA in winter is less volatile with higher contributions of low-volatility organic compounds (LVOCs) and extremely low-volatility organic compounds (ELVOCs). We partially explain this by the higher contributions of compounds with shorter carbon chain lengths and a higher number of oxygen atoms, i.e., higher O : C in winter. Organic compounds desorbing from the particles deposited on the filter samples also exhibit a shift of signal to higher desorption temperatures (i.e., lower apparent volatility) in winter. This is consistent with the relatively higher O : C in winter but may also be related to higher particle viscosity due to the higher contributions of larger-molecular-weight LVOCs and ELVOCs, interactions between different species and/or particles (particle matrix), and/or thermal decomposition of larger molecules. The results suggest that whereas lower temperature in winter may lead to increased partitioning of semi-volatile organic compounds (SVOCs) into the particle phase, this does not result in a higher overall volatility of OOA in winter and that the difference in sources and/or chemistry between the seasons plays a more important role. Our study provides insights into the seasonal variation of the molecular composition and volatility of ambient OA particles and into their potential sources.

scholarly journals Semicontinuous measurements of gas–particle partitioning of organic acids in a ponderosa pine forest using a MOVI-HRToF-CIMS

2014 ◽  
Vol 14 (3) ◽  
pp. 1527-1546 ◽  
Author(s):  
R. L. N. Yatavelli ◽  
H. Stark ◽  
S. L. Thompson ◽  
J. R. Kimmel ◽  
M. J. Cubison ◽  
...  
Keyword(s):  
Organic Acids ◽  
Ponderosa Pine ◽  
Model Comparison ◽  
Carbon Number ◽  
Measurement Model ◽  
Pine Forest ◽  
Ionization Mass ◽  
Particle Phase ◽  
Absolute Agreement ◽  
Ponderosa Pine Forest

Abstract. Hundreds of gas- and particle-phase organic acids were measured in a rural ponderosa pine forest in Colorado, USA, during BEACHON-RoMBAS (Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics &amp; Nitrogen – Rocky Mountain Biogenic Aerosol Study). A recently developed micro-orifice volatilization impactor high-resolution time-of-flight chemical ionization mass spectrometer (MOVI-HRToF-CIMS) using acetate (CH3C(O)O−) as the reagent ion was used to selectively ionize and detect acids semicontinuously from 20 to 30 August 2011, with a measurement time resolution of ~1.5 h. At this site 98% of the organic acid mass is estimated to be in the gas phase, with only ~2% in the particle phase. We investigated gas–particle partitioning, quantified as the fraction in the particle phase (Fp), of C1–C18 alkanoic acids, six known terpenoic acids, and bulk organic acids vs. carbon number. Data were compared to the absorptive partitioning model and suggest that bulk organic acids at this site follow absorptive partitioning to the organic aerosol mass. The rapid response (<1–2 h) of partitioning to temperature changes for bulk acids suggests that kinetic limitations to equilibrium are minor, which is in contrast to conclusions of some recent laboratory and field studies, possibly due to lack of very low ambient relative humidities at this site. Time trends for partitioning of individual and groups of acids were mostly captured by the model, with varying degrees of absolute agreement. Species with predicted substantial fractions in both the gas and particle phases show better absolute agreement, while species with very low predicted fractions in one phase often show poor agreement, potentially due to thermal decomposition, inlet adsorption, or other issues. Partitioning to the aqueous phase is predicted to be smaller than to the organic phase for alkanoic and bulk acids, and has different trends with time and carbon number than observed experimentally. This is due to the limited additional functionalization observed for the bulk acids. Partitioning to water appears to only play a role for the most oxidized acids during periods of high aerosol liquid water. Based on measurement–model comparison we conclude that species carbon number and oxygen content, together with ambient temperature, control the volatility of organic acids and are good predictors for partitioning at this site. Partitioning of bulk acids is more consistent with model predictions for hydroxy acids, hydroperoxyacids, or polyacids, and less so for keto acids.

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