Characterization of Highly Oxidized Molecules in Fresh and Aged Biogenic Secondary Organic Aerosol

Tu, Peijun; Hall, Wiley A.; Johnston, Murray V.

doi:10.1021/acs.analchem.6b00378

Cited by 60 publications

(87 citation statements)

References 45 publications

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“…Gas-phase oxidation of volatile organic compounds occurs through a complex set of reaction pathways involving both the gas and particle phases to yield particle-phase products that often number in the hundreds or thousands based on accurate mass measurements (Bateman et al, 2008;Mentel et al, 2015;Reinhardt et al, 2007;Tu et al, 2016). Absorptive partitioning (Barsanti et al, 2017;Pankow, 1994) of gasphase products to the particle phase forms secondary organic aerosol (SOA), which includes both non-volatile (NVOCs) and semi-volatile (SVOCs) organic compounds (Kroll and Seinfeld, 2008;Riipinen et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle growth by particle-phase chemistry

Apsokardu¹,

Johnston²

2018

Atmos. Chem. Phys.

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Abstract. The ability of particle-phase chemistry to alter the molecular composition and enhance the growth rate of nanoparticles in the 2-100 nm diameter range is investigated through the use of a kinetic growth model. The molecular components included are sulfuric acid, ammonia, water, a non-volatile organic compound, and a semi-volatile organic compound. Molecular composition and growth rate are compared for particles that grow by partitioning alone vs. those that grow by a combination of partitioning and an accretion reaction in the particle phase between two organic molecules. Particle-phase chemistry causes a change in molecular composition that is particle diameter dependent, and when the reaction involves semi-volatile molecules, the particles grow faster than by partitioning alone. These effects are most pronounced for particles larger than about 20 nm in diameter. The modeling results provide a fundamental basis for understanding recent experimental measurements of the molecular composition of secondary organic aerosol showing that accretion reaction product formation increases linearly with increasing aerosol volume-to-surface-area. They also allow initial estimates of the reaction rate constants for these systems. For secondary aerosol produced by either OH oxidation of the cyclic dimethylsiloxane (D 5 ) or ozonolysis of β-pinene, oligomerization rate constants on the order of 10 −3 to 10 −1 M −1 s −1 are needed to explain the experimental results. These values are consistent with previously measured rate constants for reactions of hydroperoxides and/or peroxyacids in the condensed phase.

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Section: Introductionmentioning

confidence: 99%

Nanoparticle growth by particle-phase chemistry

Apsokardu¹,

Johnston²

2018

Atmos. Chem. Phys.

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“…Accretion chemistry, which produces non-volatile molecules directly in the particle phase, and ELVOC condensation represent two separate sources for oligomers that are detected in the particle phase. It has been noted that relatively few ELVOC molecular formulas obtained from gas phase measurements match those of oligomers detected in particle phase measurements (Mentel et al, 2015;Tu et al, 2016). This dissimilarity could arise from subsequent reaction of ELVOCs after they enter the particle phase, or by the formation of completely new oligomers in the particle phase through accretion chemistry.…”

Section: Introductionmentioning

confidence: 99%

“…SOA was generated in a flow tube reactor (FTR) (Fig. 1a) described previously (Hall et al, 2013;Tu et al, 2016). In most experiments, the concentrations of β-pinene and ozone after mixing in the reactor were 1 and 10 ppmv, respectively, giving an SOA mass loading of about 2300 µg m −3 at the reactor exit.…”

Section: Introductionmentioning

confidence: 99%

Particle size dependence of biogenic secondary organic aerosol molecular composition

Johnston

2017

Atmos. Chem. Phys.

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Abstract. Formation of secondary organic aerosol (SOA) is initiated by the oxidation of volatile organic compounds (VOCs) in the gas phase whose products subsequently partition to the particle phase. Non-volatile molecules have a negligible evaporation rate and grow particles at their condensation rate. Semi-volatile molecules have a significant evaporation rate and grow particles at a much slower rate than their condensation rate. Particle phase chemistry may enhance particle growth if it transforms partitioned semi-volatile molecules into non-volatile products. In principle, changes in molecular composition as a function of particle size allow non-volatile molecules that have condensed from the gas phase (a surface-limited process) to be distinguished from those produced by particle phase reaction (a volume-limited process). In this work, SOA was produced by β-pinene ozonolysis in a flow tube reactor. Aerosol exiting the reactor was size-selected with a differential mobility analyzer, and individual particle sizes between 35 and 110 nm in diameter were characterized by on-and offline mass spectrometry. Both the average oxygen-to-carbon (O / C) ratio and carbon oxidation state (OSc) were found to decrease with increasing particle size, while the relative signal intensity of oligomers increased with increasing particle size. These results are consistent with oligomer formation primarily in the particle phase (accretion reactions, which become more favored as the volume-to-surface-area ratio of the particle increases). Analysis of a series of polydisperse SOA samples showed similar dependencies: as the mass loading increased (and average volume-to-surface-area ratio increased), the average O / C ratio and OSc decreased, while the relative intensity of oligomer ions increased. The results illustrate the potential impact that particle phase chemistry can have on biogenic SOA formation and the particle size range where this chemistry becomes important.

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“…As such, certain reagent ions such as metal cations (e.g., Li + , Na + , and K + ) and NH + 4 , which are commonly used for detection of atmospheric organic compounds in offline techniques like electrospray ionization (ESI)-MS (Nizkorodov et al, 2011;Laskin et al, 2012;Witkowski and Gierczak, 2013), have remained largely unavailable for CIMS (Fujii et al, 2001). Compared to I − , NO − 3 , and acetate, which are generally more sensitive to more oxygenated organic compounds than to less oxygenated ones (Aljawhary et al, 2013;Lee et al, 2014;Hyttinen et al, 2015;Iyer et al, 2016;Berndt et al, 2016), these metal cations are expected to be able to sensitively detect both less oxygenated (e.g., compounds containing only carbonyl groups) and highly oxygenated multi-functional organic species (Gao et al, 2010;Nguyen et al, 2010;Nizkorodov et al, 2011;Laskin et al, 2012;Witkowski and Gierczak, 2013;Zhao et al, 2015Zhao et al, , 2016Tu et al, 2016;Zhang et al, 2017), and to form more strongly bound ion adducts. In addition, at present most CIMS techniques use a radioactive ion source such as 210 Po to produce the reagent ions, although more recently some utilize X-ray radiation, electrical discharge (Hirokawa et al, 2009;Yuan et al, 2016), or electron impact (Inomata and Hirokawa, 2017).…”

Section: Introductionmentioning

confidence: 99%

An electrospray chemical ionization source for real-time measurement of atmospheric organic and inorganic vapors

et al. 2017

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Abstract. We present an electrospray ion source coupled to an orthogonal continuous-flow atmospheric pressure chemical ionization region. The source can generate intense and stable currents of several specific reagent ions using a range of salt solutions prepared in methanol, thereby providing both an alternative to more common radioactive ion sources and allowing for the generation of reagent ions that are not available in current chemical ionization mass spectrometry (CIMS) techniques, such as alkaline cations. We couple the orthogonal electrospray chemical ionization (ESCI) source to a high-resolution time-of-flight mass spectrometer (HRToF-MS), and assess instrument performance through calibrations using nitric acid (HNO 3 ), formic acid (HCOOH), and isoprene epoxydiol (trans-β-IEPOX) gas standards, and through measurements of oxidized organic compounds formed from ozonolysis of α-pinene in a continuous-flow reaction chamber. When using iodide as the reagent ion, the HR-ToF-ESCIMS prototype has a sensitivity of 11, 2.4, and 10 cps pptv −1 per million counts per second (cps) of reagent ions and a detection limit (3σ , 5 s averaging) of 4.9, 12.5, and 1.4 pptv to HNO 3 , HCOOH, and IEPOX, respectively. These values are comparable to those obtained using an iodide-adduct HR-ToF-CIMS with a radioactive ion source and low-pressure ion-molecule reaction region. Applications to the α-pinene ozonolysis system demonstrates that HRToF-ESCIMS can generate multiple reagent ions (e.g., I − , NO − 3 , acetate, Li + , Na + , K + , and NH + 4 ) having different selectivity to provide a comprehensive molecular description of a complex organic system.

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Characterization of Highly Oxidized Molecules in Fresh and Aged Biogenic Secondary Organic Aerosol

Cited by 60 publications

References 45 publications

Nanoparticle growth by particle-phase chemistry

Nanoparticle growth by particle-phase chemistry

Particle size dependence of biogenic secondary organic aerosol molecular composition

An electrospray chemical ionization source for real-time measurement of atmospheric organic and inorganic vapors

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