Highly oxygenated molecules and their chemistry in polluted urban environments

2020 ◽  
Author(s):  
Qi Chen ◽  
Xi Cheng ◽  
Yongjie Li ◽  
Yan Zheng ◽  
Keren Liao ◽  
...  
Keyword(s):  
Mass Spectra ◽  
Flow Reactor ◽  
Particle Growth ◽  
Urban Environments ◽  
Oxidation Products ◽  
Initial Particle ◽  
Positive Matrix ◽  
Ionization Time ◽  
Flight Mass Spectrometry ◽  
Aerosol Mass

<p>Highly oxygenated molecules (HOMs) are important atmospheric oxidation products that may contribute to new particle formation and initial particle growth. Thousands of such compounds were quantified in both winter and summer of 2016 in Beijing by using online nitrate ion chemical ionization time-of-flight mass spectrometry. Positive-matrix factorization of the time series of the high-resolution mass spectra identified at least 10 major groups of gaseous HOMs in Beijing. We compared these PMF factors with the HOMs produced in a Potential Aerosol Mass (PAM) flow reactor in the laboratory from the oxidation of typical biogenic and aromatic precursors under various oxidation conditions. Our results show that four of the ten PMF factors perhaps correspond to biogenic precursors, and another four factors are likely related to aromatic precursors. The chemistry of these aromatic HOMs are discussed based on the results from the PAM experiments.</p>

scholarly journals Development of a versatile source apportionment analysis based on positive matrix factorization: a case study of the seasonal variation of organic aerosol sources in Estonia

2019 ◽  
Vol 19 (11) ◽  
pp. 7279-7295 ◽  
Author(s):  
Athanasia Vlachou ◽  
Anna Tobler ◽  
Houssni Lamkaddam ◽  
Francesco Canonaco ◽  
Kaspar R. Daellenbach ◽  
...  
Keyword(s):  
Matrix Factorization ◽  
Organic Aerosol ◽  
Positive Matrix Factorization ◽  
Water Soluble ◽  
Oxidation Products ◽  
Positive Matrix ◽  
Bootstrap Analysis ◽  
Seasonal Behavior ◽  
Yearly Cycle ◽  
Aerosol Mass

Abstract. Bootstrap analysis is commonly used to capture the uncertainties of a bilinear receptor model such as the positive matrix factorization (PMF) model. This approach can estimate the factor-related uncertainties and partially assess the rotational ambiguity of the model. The selection of the environmentally plausible solutions, though, can be challenging, and a systematic approach to identify and sort the factors is needed. For this, comparison of the factors between each bootstrap run and the initial PMF output, as well as with externally determined markers, is crucial. As a result, certain solutions that exhibit suboptimal factor separation should be discarded. The retained solutions would then be used to test the robustness of the PMF output. Meanwhile, analysis of filter samples with the Aerodyne aerosol mass spectrometer and the application of PMF and bootstrap analysis on the bulk water-soluble organic aerosol mass spectra have provided insight into the source identification and their uncertainties. Here, we investigated a full yearly cycle of the sources of organic aerosol (OA) at three sites in Estonia: Tallinn (urban), Tartu (suburban) and Kohtla-Järve (KJ; industrial). We identified six OA sources and an inorganic dust factor. The primary OA types included biomass burning, dominant in winter in Tartu and accounting for 73 % ± 21 % of the total OA, primary biological OA which was abundant in Tartu and Tallinn in spring (21 % ± 8 % and 11 % ± 5 %, respectively), and two other primary OA types lower in mass. A sulfur-containing OA was related to road dust and tire abrasion which exhibited a rather stable yearly cycle, and an oil OA was connected to the oil shale industries in KJ prevailing at this site that comprises 36 % ± 14 % of the total OA in spring. The secondary OA sources were separated based on their seasonal behavior: a winter oxygenated OA dominated in winter (36 % ± 14 % for KJ, 25 % ± 9 % for Tallinn and 13 % ± 5 % for Tartu) and was correlated with benzoic and phthalic acid, implying an anthropogenic origin. A summer oxygenated OA was the main source of OA in summer at all sites (26 % ± 5 % in KJ, 41 % ± 7 % in Tallinn and 35 % ± 7 % in Tartu) and exhibited high correlations with oxidation products of a-pinene-like pinic acid and 3-methyl-1, 2, 3-butanetricarboxylic acid (MBTCA), suggesting a biogenic origin.

scholarly journals A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra

2012 ◽  
Vol 12 (4) ◽  
pp. 2189-2203 ◽  
Author(s):  
M. F. Heringa ◽  
P. F. DeCarlo ◽  
R. Chirico ◽  
T. Tritscher ◽  
M. Clairotte ◽  
...  
Keyword(s):  
High Resolution ◽  
Mass Spectra ◽  
Principal Component ◽  
Particle Growth ◽  
Organic Aerosol ◽  
Diesel Emissions ◽  
Anthropogenic Sources ◽  
Inlet System ◽  
Alpha Pinene ◽  
Aerosol Mass

Abstract. Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 μm) mass. Secondary organic aerosol (SOA) is an important contributor to the OA and can be formed from biogenic and anthropogenic precursors. Here we present results from the characterization of SOA produced from the emissions of three different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from α-pinene. The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra showing Pearson's r values >0.94 for the correlations between the four different SOA types after five hours of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+ and CO2+, respectively, similarly to the relatively fresh semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The atomic O:C ratios were found to be in the range of 0.25–0.55 with no major increase during the first five hours of aging. On average, the diesel SOA showed the lowest O:C ratio followed by SOA from wood burning, α-pinene and the scooter emissions. Grouping the fragment ions revealed that the SOA source with the highest O:C ratio had the largest fraction of small ions. The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended.

scholarly journals Analysis of secondary organic aerosol formation and aging using positive matrix factorization of high-resolution aerosol mass spectra: application to the dodecane low-NO<sub>x</sub> system

2012 ◽  
Vol 12 (24) ◽  
pp. 11795-11817 ◽  
Author(s):  
J. S. Craven ◽  
L. D. Yee ◽  
N. L. Ng ◽  
M. R. Canagaratna ◽  
C. L. Loza ◽  
...  
Keyword(s):  
High Resolution ◽  
Matrix Factorization ◽  
Mass Spectra ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Positive Matrix Factorization ◽  
Aerosol Formation ◽  
Positive Matrix ◽  
Aerosol Mass ◽  
Van Krevelen Diagram

Abstract. Positive matrix factorization (PMF) of high-resolution laboratory chamber aerosol mass spectra is applied for the first time, the results of which are consistent with molecular level MOVI-HRToF-CIMS aerosol-phase and CIMS gas-phase measurements. Secondary organic aerosol was generated by photooxidation of dodecane under low-NOx conditions in the Caltech environmental chamber. The PMF results exhibit three factors representing a combination of gas-particle partitioning, chemical conversion in the aerosol, and wall deposition. The slope of the measured high-resolution aerosol mass spectrometer (HR-ToF-AMS) composition data on a Van Krevelen diagram is consistent with that of other low-NOx alkane systems in the same O : C range. Elemental analysis of the PMF factor mass spectral profiles elucidates the combinations of functionality that contribute to the slope on the Van Krevelen diagram.

scholarly journals Secondary organic aerosol formation and primary organic aerosol oxidation from biomass-burning smoke in a flow reactor during FLAME-3

2013 ◽  
Vol 13 (22) ◽  
pp. 11551-11571 ◽  
Author(s):  
A. M. Ortega ◽  
D. A. Day ◽  
M. J. Cubison ◽  
W. H. Brune ◽  
D. Bon ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Biomass Burning ◽  
Flow Reactor ◽  
Organic Aerosol ◽  
Proton Transfer Reaction ◽  
Oxidation Products ◽  
Chemical Transformations ◽  
Aerosol Formation ◽  
Aerosol Mass ◽  
Smog Chambers

Abstract. We report the physical and chemical effects of photochemically aging dilute biomass-burning smoke. A "potential aerosol mass" (PAM) flow reactor was used with analysis by a high-resolution aerosol mass spectrometer and a proton-transfer-reaction ion-trap mass spectrometer during the FLAME-3 campaign. Hydroxyl (OH) radical concentrations in the reactor reached up to ~1000 times average tropospheric levels, producing effective OH exposures equivalent to up to 5 days of aging in the atmosphere, and allowing for us to extend the investigation of smoke aging beyond the oxidation levels achieved in traditional smog chambers. Volatile organic compound (VOC) observations show aromatics and terpenes decrease with aging, while formic acid and other unidentified oxidation products increase. Unidentified gas-phase oxidation products, previously observed in atmospheric and laboratory measurements, were observed here, including evidence of multiple generations of photochemistry. Substantial new organic aerosol (OA) mass ("net SOA"; secondary OA) was observed from aging biomass-burning smoke, resulting in total OA average of 1.42 ± 0.36 times the initial primary OA (POA) after oxidation. This study confirms that the net-SOA-to-POA ratio of biomass-burning smoke is far lower on average than that observed for urban emissions. Although most fuels were very reproducible, significant differences were observed among the biomasses, with some fuels resulting in a doubling of the OA mass, while for others a very small increase or even a decrease was observed. Net SOA formation in the photochemical reactor increased with OH exposure (OHexp), typically peaking around three days of equivalent atmospheric photochemical age (OHexp~3.9 × 1011 molecules cm−3 s), then leveling off at higher exposures. The amount of additional OA mass added from aging is positively correlated with initial POA concentration, but not with the total VOC concentration or the concentration of known SOA precursors. The mass of SOA formed often exceeded the mass of the known VOC precursors, indicating the likely importance of primary semivolatile/intermediate volatility species, and possibly of unidentified VOCs as SOA precursors in biomass burning smoke. Chemical transformations continued even after mass concentration stabilized. Changes in the biomass-burning tracer f60 ranged from substantially decreasing to remaining constant with increased aging. With increased OHexp, oxidation was always detected (as indicated by f44 and O/C). POA O/C ranged from 0.15 to 0.5, while aged OA O/C reached up to 0.87. The rate of oxidation and maximum O/C achieved differs for each biomass, and appears to increase with the initial O/C of the POA.

scholarly journals The driving factors of new particle formation and growth in the polluted boundary layer

2021 ◽  
Author(s):  
Mao Xiao ◽  
Christopher R. Hoyle ◽  
Lubna Dada ◽  
Dominik Stolzenburg ◽  
Andreas Kürten ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sulfuric Acid ◽  
Particle Growth ◽  
Quantitative Information ◽  
Particle Formation ◽  
Urban Environments ◽  
Mitigation Strategies ◽  
Oxidation Products ◽  
Minor Role ◽  
New Particle Formation

Abstract. New-particle formation (NPF) is a significant source of atmospheric particles, affecting climate and air quality. Understanding the mechanisms involved in urban aerosols is important to develop effective mitigation strategies. However, NPF rates reported in the polluted boundary layer span more than four orders of magnitude and the reasons behind this variability subject of intense scientific debate. Multiple atmospheric vapours have been postulated to participate in NPF, including sulfuric acid, ammonia, amines and organics, but their relative roles remain unclear. We investigated NPF in the CLOUD chamber using mixtures of anthropogenic vapours that simulate polluted boundary layer conditions. We demonstrate that NPF in polluted environments are largely driven by the formation of sulfuric acid-base clusters, stabilized by the presence of amines, high ammonia concentrations and lower temperatures. Aromatic oxidation products, despite their extremely low volatility, play a minor role in NPF in the chosen urban environment but can be important for particle growth and hence for the survival of newly formed particles. Our measurements quantitatively account for NPF in highly diverse urban environments and explain its large observed variability. Such quantitative information obtained under controlled laboratory conditions will help the interpretation of future ambient observations of NPF rates in polluted atmospheres.

scholarly journals Size and composition measurements of background aerosol and new particle growth in a Finnish forest during QUEST 2 using an Aerodyne Aerosol Mass Spectrometer

2005 ◽  
Vol 5 (5) ◽  
pp. 8755-8789 ◽  
Author(s):  
J. D. Allan ◽  
M. R. Alfarra ◽  
K. N. Bower ◽  
H. Coe ◽  
J. T. Jayne ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Cloud Condensation Nuclei ◽  
Particle Diameter ◽  
Particle Growth ◽  
Small Mass ◽  
Oxidation Products ◽  
Particle Nucleation ◽  
Aerosol Mass Spectrometer ◽  
Mass Spectral ◽  
Aerosol Mass

Abstract. The study of the growth of nucleation-mode particles is important, as this prevents their loss through diffusion and allows them to reach sizes where they may become effective cloud condensation nuclei. Hyytiälä, a forested site in southern Finland, frequently experiences particle nucleation events during the spring and autumn, where particles first appear during the morning and continue to grow for several hours afterwards. As part of the QUEST 2 intensive field campaign during March and April 2003, an Aerodyne Aerosol Mass Spectrometer (AMS) was deployed alongside other aerosol instrumentation to study the particulate composition and dynamics of growth events and characterise the background aerosol. Despite the small mass concentrations, the AMS was able to distinguish the grown particles in the <100 nm regime several hours after an event and confirm that the particles were principally organic in composition. The AMS was also able to derive a mass spectral fingerprint for the organic species present, and found that it was consistent between events and independent of the mean particle diameter during non-polluted cases, implying the same species were also condensing onto the accumulation mode. The results were compared with those from offline analyses such as GC-MS and were consistent with the hypothesis that the main components were alkanes from plant waxes and the oxidation products of terpenes.

scholarly journals Corynebacterium phoceense – a rare Corynebacterium species isolated from a urine sample

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Claudia M. Barberis ◽  
Germán M. Traglia ◽  
Marisa N. Almuzara ◽  
Danilo J. P. G. Rocha ◽  
Carolina S. Santos ◽  
...  
Keyword(s):  
Urinary Tract ◽  
Urine Sample ◽  
Dna Hybridization ◽  
Mass Spectra ◽  
Ionization Time ◽  
Content Type ◽  
Flight Mass Spectrometry ◽  
Corynebacterium Species ◽  
Tract Infections ◽  
Clinical Conditions

Corynebacterium spp. are Gram-positive rods that are recognized to cause opportunistic diseases under certain predisposing clinical conditions. Some species have been described in urinary tract infections. In this report we document a new episode of urinary tract infection caused by Corynebacterium phoceense and describe the whole-genome sequencing, phenotypic characteristics and mass spectra obtained by matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Based on genome identification and DNA-to-DNA hybridization, we can assume that our strain is the second isolate of C. phoceense to be described in a urine sample. No other infectious diseases have been reported to be associated with this species.

scholarly journals Chemical evolution of secondary organic aerosol from OH-initiated heterogeneous oxidation

2010 ◽  
Vol 10 (2) ◽  
pp. 3265-3300 ◽  
Author(s):  
I. J. George ◽  
J. P. D. Abbatt
Keyword(s):  
Mass Spectra ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Heterogeneous Oxidation ◽  
Atmospheric Aging ◽  
Aerosol Mass ◽  
Degree Of Oxidation ◽  
Aerosol Aging

Abstract. The heterogeneous oxidation of laboratory Secondary Organic Aerosol (SOA) particles by OH radicals was investigated. SOA particles, produced by reaction of α-pinene and O3, were exposed to OH radicals in a flow tube, and particle chemical composition, size, and hygroscopicity were measured to assess modifications due to oxidative aging. Aerosol Mass Spectrometer (AMS) mass spectra indicated that the degree of oxidation of SOA particles was significantly enhanced due to OH-initiated oxidation. Particle O/C ratios calculated from m/z 44 fraction from organic mass spectra rose by a maximum of ~0.04 units under equivalent atmospheric aging timescales of 2 weeks assuming a 24-h average OH concentration of 106 cm−3. Particle densities also increased with heterogeneous oxidation, consistent with the observed increase in the degree of oxidation. Minor reductions in particle size, with volume losses of up to 10%, were observed due to volatilization of oxidation products. The SOA particles became slightly more CCN active with an increase in the κ hygroscopicity parameter of up to a factor of two for the equivalent of 2 weeks of OH atmospheric exposure. These results indicate that OH heterogeneous oxidation of typical SOA proceeds sufficiently rapidly to be an atmospherically important organic aerosol aging mechanism.

scholarly journals Development of a versatile source apportionment analysis based on positive matrix factorization: a case study of the seasonal variation of organic aerosol sources in Estonia

2018 ◽  
Author(s):  
Athanasia Vlachou ◽  
Anna Tobler ◽  
Houssni Lamkaddam ◽  
Francesco Canonaco ◽  
Kaspar R. Daellenbach ◽  
...  
Keyword(s):  
Road Dust ◽  
Organic Aerosol ◽  
Bulk Water ◽  
Water Soluble ◽  
Oxidation Products ◽  
Positive Matrix ◽  
Bootstrap Analysis ◽  
Yearly Cycle ◽  
Pmf Model ◽  
Aerosol Mass

Abstract. Bootstrap analysis is commonly used to capture the uncertainties of a bilinear receptor model such as the positive matrix factorisation (PMF) model. This approach can estimate the factor related uncertainties and partially assess the rotational ambiguity of the model. The selection of the environmentally plausible solutions though can be challenging and a systematic approach to identify and sort the factors is needed. For this, comparison of the factors between each bootstrap run and the initial PMF output, as well as with externally determined markers, is crucial. As a result, certain solutions that exhibit sub-optimal factor separation should be discarded. The retained solutions would then be used to test the robustness of the PMF output. Meanwhile, analysis of filter sample with the Aerodyne aerosol mass spectrometer and the application of PMF and bootstrap analysis on the bulk water soluble organic aerosol mass spectra has provided insight into the source identification and their uncertainties. Here, we investigated a full yearly cycle of the sources of organic aerosol (OA) at three sites in Estonia, Tallinn (urban), Tartu (suburban) and Kohtla–Järve (KJ, industrial). We identified six OA sources and an inorganic dust factor. The primary OA types included biomass burning, dominant in winter in Tartu accounting for 73 % ± 21 % of the total OA, primary biological OA which was abundant in Tartu and Tallinn in spring (21 % ± 8 % and 11 % ± 5 %, respectively) and two other primary OA types lower in mass. A sulphur containing OA was related to road dust and tire abrasion which exhibited a rather stable yearly cycle and an oil OA was connected to the oil shale industries in KJ prevailing at this site comprising 36 % ± 14 % of the total OA in spring. The secondary OA sources were separated based on their seasonal behaviour: a winter oxygenated OA dominated in winter (36 % ± 14 % for KJ, 25 % ± 9 % for Tallinn and 13 % ± 5 % for Tartu) and was correlated with benzoic and phthalic acid implying an anthropogenic origin. A summer oxygenated OA was the main source of OA in summer at all sites (26 % ± 5 % in KJ, 41 % ± 7 % in Tallinn and 35 % ± 7 % in Tartu) and exhibited high correlations with oxidation products of α-pinene like pinic acid and 3-methyl-1, 2, 3-butanetricarboxylic acid (MBTCA) suggesting a biogenic origin.

scholarly journals Application of positive matrix factor analysis in heterogeneous kinetics studies: an improvement to the mixed-phase relative rates technique

2014 ◽  
Vol 14 (6) ◽  
pp. 8695-8722 ◽  
Author(s):  
Y. Liu ◽  
S.-M. Li ◽  
J. Liggio
Keyword(s):  
Citric Acid ◽  
Heterogeneous Reaction ◽  
Organic Aerosol ◽  
Mixed Phase ◽  
Oxidation Products ◽  
Oh Radicals ◽  
Positive Matrix ◽  
Heterogeneous Kinetics ◽  
Aerosol Mass ◽  
Uptake Coefficients

Abstract. The mixed-phase relative rate approach for determining aerosol particle organic component heterogeneous reaction kinetics and OH uptake coefficients to particles is often performed utilizing mass spectral tracers as a proxy for particle phase reactant concentration. However, this approach may be influenced by signal contaminations from oxidation products during the experiment. In the current study, the mixed-phase relative rates technique has been improved by combining a Positive Matrix Factor (PMF) analysis with electron ionization Aerosol Mass Spectrometry, thereby removing the influence of m / z fragments from reaction products on the reactant signals. To demonstrate the advantages of this approach, the heterogeneous reaction between OH radicals and citric acid (CA) was investigated using a photochemical flow tube coupled to a compact time-of-flight aerosol mass spectrometer (C-ToF-AMS). The measured heterogeneous rate constant (k2) of citric acid toward OH was (3.31 ± 0.29) × 10−12 cm3 molecule−1 s−1 at 298 K and (30 ± 3)% RH and was ∼7.7 times greater than previously reported results utilizing individual m / z fragments. This phenomenon was further confirmed for particulate-phase organophosphates (TPhP, TDCPP, and TEHP), leading to k2 values significantly larger than previously reported. The results suggest that heterogeneous kinetics can be significantly underestimated when a non-molecular ion peak is used as the tracer. Finally, the results suggest that the heterogeneous lifetime of organic aerosol in models can be overestimated due to underestimated OH uptake coefficients, and that it may be necessary to revisit the heterogeneous kinetic data of organic aerosol components which were derived in the context of the relative rates technique.

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