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Schematic diagram of the IR-CRDS setup. HR = highly reflective mirror; LS = focusing lens; IS = iris; IRD = IR Detector; QMS = quadrupole mass spectrometer.
Source publication
Photolysis of alkene-terminated self assembled monolayers (SAM) deposited on Degussa SiO(2) nanoparticles is studied following oxidation of SAM with a gaseous ozone/oxygen mixture. Infrared cavity ring-down spectroscopy is used to observe gas-phase products generated during ozonolysis and subsequent photolysis of SAM in real time. Reactions taking...
Context in source publication
Context 1
... (C 6 = SAM on SiO 2 nanoparti- cles) was transferred onto the inner wall of a quartz tube and dried by flowing nitrogen gas over it. Only one side of the tube was coated to allow UV radiation to enter the tube through the uncoated side. After installing the quartz tube between two highly reflective mirrors of a cavity ring-down spectrometer ( Fig. 1), residual toluene was pumped out overnight before proceeding with the ozonolysis ...
Similar publications
The gas‐phase ozonolysis reaction of methylbutenol through the Criegee mechanism is investigated. The initial reaction leads to a primary ozonide (POZ) formation with barriers in the range of 10–28 kJ mol⁻¹. The formation of 2‐hydroxy‐2‐methyl‐propanal (HMP) and formaldehyde‐oxide is more favorable, by 10 kJ mol⁻¹, than the syn‐CI and formaldehyde....
Citations
... With the urban centre and the principle traffic artery located to the N/ NW of the sampling site, it appears fresh pollution titrates ozone (through high NO x ) and facilitate formic acid formation. This observation implies that formic acid is potentially a combination of production through ozonolysis of terminal alkenes from biomass burning (Neeb et al., 1997;Paulot et al., 2011), and involvement of multiphase chemistry processes (Franco et al., 2021;Lelieveld and Crutzen, 1991), or even organic aerosol aging (Malecha and Nizkorodov, 2016;Park et al., 2006;Vlasenko et al., 2008). ...
Biomass combustion releases a complex array of Volatile Organic Compounds (VOCs) that pose significant challenges to air quality and human health. Although biomass burning has been extensively studied at ecosystem levels, understanding the atmospheric transformation and impact on air quality of emissions in urban environments remains challenging due to complex sources and burning materials. In this study, we investigate the VOC emission rates and atmospheric chemical processing of predominantly wood burning emissions in a small urban centre in Greece. Ioannina is situated in a valley within the Dinaric Alps and experiences intense atmospheric pollution accumulation during winter due to its topography and high wood burning activity. During pollution event days, the ambient mixing ratios of key VOC species were found to be similar to those reported for major urban centres worldwide. Positive matrix factorisation (PMF) analysis revealed that biomass burning was the dominant emission source (>50 %), representing two thirds of OH reactivity, which indicates a highly reactive atmospheric mixture. Calculated OH reactivity ranges from 5 s-1 to an unprecedented 278 s-1, and averages at 93 ± 66 s-1 at 9 PM, indicating the presence of exceptionally reactive VOCs. The highly pronounced photochemical formation of organic acids coincided with the formation of ozone, highlighting the significance of secondary formation of pollutants in poorly ventilated urban areas. Our findings underscore the pressing need to transition from wood burning to environmentally friendly sources of energy in poorly ventilated urban areas, in order to improve air quality and safeguard public health.
... Other identified primary sources include agriculture (Ngwabie et al., 2008) and combustion of biomass (Chaliyakunnel et al., 2016;Goode et al., 2000) and fossil fuels (Kawamura et al., 1985;Talbot et al., 1988). Heterogeneous sources have also been proposed, including in-cloud formaldehyde oxidation (Jacob, 1986;Lelieveld & Crutzen, 1991), as well as aging of organic aerosol via OH (Vlasenko et al., 2008), O 3 (Eliason et al., 2003;Pan et al., 2009), and photolysis (Malecha & Nizkorodov, 2016;Park et al., 2006). Wet and dry deposition are the predominant HCOOH sinks; together with photochemical loss and a minor contribution from dust uptake, these yield an overall atmospheric lifetime of 2-4 days (Chebbi & Carlier, 1996;Paulot et al., 2011;Stavrakou et al., 2012). ...
Plain Language Summary
Formic acid (HCOOH) is one of the most abundant acids in the atmosphere and affects the acidity of precipitation. A number of recent studies have shown that the atmospheric abundance of HCOOH is much higher than predicted, implying some unknown or underrepresented source. Here we present new measurements of HCOOH and related species above, within, and below a mixed forest canopy and use the results to investigate its sources and sinks in this ecosystem. We find that the forest is simultaneously a source and a sink of atmospheric HCOOH, and vertically resolved measurements identify the canopy layer as the major HCOOH source for this environment. Soils have been shown to be a source of HCOOH in some cases, but we show that their influence is unimportant for this ecosystem. The magnitude of the gross HCOOH source from this forest is 15 times higher than predicted in a current atmospheric model. A correlation analysis suggests that the main HCOOH source from this forest is oxidation of other compounds rather than direct emissions from vegetation.
... Multiphase photochemical aging of ambient organic aerosols can also be a source of gas-phase organic acids ( Eliason et al., 2003;Ervens et al., 2004;Molina et al., 2004;Lim et al., 2005;Park et al., 2006;Walser et al., 2007;Sorooshian et al., 2007Sorooshian et al., , 2010Vlasenko et al., 2008;Pan et al., 2009). Organic acids may be formed in the particle phase during organic aerosol photochemical aging, with sub- sequent volatilization into the gas phase. ...
The sources and atmospheric chemistry of gas-phase organic acids are currently poorly understood, due in part to the limited range of measurement techniques available. In this work, we evaluated the use of SF6⁻ as a sensitive and selective chemical ionization reagent ion for real-time measurements of gas-phase organic acids. Field measurements are made using chemical ionization mass spectrometry (CIMS) at a rural site in Yorkville, Georgia, from September to October 2016 to investigate the capability of this measurement technique. Our measurements demonstrate that SF6⁻ can be used to measure a range of organic acids in the atmosphere. One-hour averaged ambient concentrations of organic acids ranged from a few parts per trillion by volume (ppt) to several parts per billion by volume (ppb). All the organic acids displayed similar strong diurnal behaviors, reaching maximum concentrations between 17:00 and 19:00EDT. The organic acid concentrations are dependent on ambient temperature, with higher organic acid concentrations being measured during warmer periods.
... While it is well known that ozonolysis of alkenes produces hydroxyl radicals [26][27][28][29][30], work by Pryor and coworkers investigating the thermal decomposition of the secondary ozonide of allylbenzene found evidence for the formation of carbon-and oxygen-centered radicals [21]. UVphotolysis of secondary ozonides has also been reported with several studies observing spectroscopic signatures consistent with products of biradical decomposition [17,24,[31][32][33]. While prior studies have found evidence for radical formation following secondary ozonide activation, the identity of the radicals themselves is most often not determined. ...
Reaction products from the ozonolysis of unsaturated lipids at gas–liquid interfaces have the potential to significantly influence the chemical and physical properties of organic aerosols in the atmosphere. In this study, the gas-phase dissociation behavior of lipid secondary ozonides is investigated using ion-trap mass spectrometry. Secondary ozonides were formed by reaction between a thin film of unsaturated lipids (fatty acid methyl esters or phospholipids) with ozone before being transferred to the gas phase as [M + Na]⁺ ions by electrospray ionization. Activation of the ionized ozonides was performed by either energetic collisions with helium buffer-gas or laser photolysis, with both processes yielding similar product distributions. Products arising from the decomposition of the ozonides were characterized by their mass-to-charge ratio and subsequent ion-molecule reactions. Product assignments were rationalized as arising from initial homolysis of the ozonide oxygen–oxygen bond with subsequent decomposition of the nascent biradical intermediate. In addition to classic aldehyde and carbonyl oxide-type fragments, carbon-centered radicals were identified with a number of decomposition pathways that indicated facile unimolecular radical migration. These findings reveal that photoactivation of secondary ozonides formed by the reaction of aerosol-bound lipids with tropospheric ozone may initiate radical-mediated chemistry within the particle resulting in surface modification.
Graphical Abstractᅟ
Electronic supplementary material
The online version of this article (doi:10.1007/s13361-017-1649-4) contains supplementary material, which is available to authorized users.
... Previous studies have reported evidence of secondary chemistry occurring within the ozonolysis of OL particles (Katrib et al., 2004; Hearn et al., 2005; Ziemann, 2005; Reynolds et al., 2006; Zahardis et al., 2006; Zahardis and Petrucci, 2007; Lee et al., 2012; Hosny et al., 2013). The presence of the liquid condensed-phase substrate for the CIs minimizes their molecular rearrangement (Katrib et al., 2004) via a solvent cage effect (Park et al., 2006) and maximises their lifetimes. Therefore, reaction probability of CIs with their corresponding carbonyl compounds to form secondary ozonide (SOZ) or with the alkene functionality becomes more significant (Neeb et al., 1998; Moise and Rudich, 2002; Zahardis et al., 2005). ...
A chemical reaction chamber system has been developed for the processing of oleic acid aerosol particles with ozone under two relative humidity conditions: dry and humidified to 65g %. The apparatus consists of an aerosol flow tube, in which the ozonolysis occurs, coupled to a scanning mobility particle sizer (SMPS) and an aerosol time-of-flight mass spectrometer (ATOFMS) which measure the evolving particle size and composition. Under both relative humidity conditions, ozonolysis results in a significant decrease in particle size and mass which is consistent with the formation of volatile products that partition from the particle to the gas phase. Mass spectra derived from the ATOFMS reveal the presence of the typically observed reaction products: azelaic acid, nonanal, oxononanoic acid and nonanoic acid, as well as a range of higher molecular weight products deriving from the reactions of reaction intermediates with oleic acid and its oxidation products. These include octanoic acid and 9- and 10-oxooctadecanoic acid, as well as products of considerably higher molecular weight. Quantitative evaluation of product yields with the ATOFMS shows a marked dependence upon both particle size association (from 0.3 to 2.1g μm diameter) and relative humidity. Under both relative humidity conditions, the percentage residual of oleic acid increases with increasing particle size and the main lower molecular weight products are nonanal and oxononanoic acid. Under dry conditions, the percentage of higher molecular weight products increases with increasing particle size due to the poorer internal mixing of the larger particles. Under humidified conditions, the percentage of unreacted oleic acid is greater, except in the smallest particle fraction, with little formation of high molecular weight products relative to the dry particles. It is postulated that water reacts with reactive intermediates, competing with the processes which produce high molecular weight products. Whilst the oleic acid model aerosol system is of limited relevance to complex internally mixed atmospheric aerosol, the generic findings presented in this paper give useful insights into the nature of heterogeneous chemical processes.
... Previous studies have reported evidence of secondary chemistry occurring within the ozonolysis of 18 OL particles (Katrib et al., 2004; Hearn et al., 2005; Ziemann, 2005; Reynolds et al., 2006; Zahardis 19 et al., 2006; Zahardis and Petrucci, 2007; Lee et al., 2012; Hosny et al., 2013). The presence of the 20 liquid condensed phase substrate for the CIs minimizes their molecular rearrangement (Katrib et al., 21 2004) via a solvent cage effect (Park et al., 2006) and maximizes their lifetimes. Therefore, reaction 22 probability of CIs with their corresponding carbonyl compounds to form secondary ozonide (SOZ) 23 or with the alkene functionality becomes more significant (Neeb et al., 1998; Moise and Rudich, 24 2002; Zahardis et al., 2005). ...
A chemical reaction chamber system has been developed for the processing of oleic acid aerosol particles with ozone under two relative humidity conditions: dry and humidified to 65 % R.H. The apparatus consists of an aerosol flow tube, in which the ozonolysis occurs, coupled to a scanning mobility particle sizer (SMPS) and an aerosol time-of-flight mass spectrometer (ATOFMS) which measure the evolving particle size and composition. Under both relative humidity conditions, ozonolysis results in a significant decrease in particle size and mass which is consistent with the formation of volatile products that partition from the particle to the gas phase. Mass spectra derived from the ATOFMS reveal the presence of the typically observed reaction products: azaleic acid, nonanal, oxononanoic acid and nonanoic acid, as well as a range of higher molecular weight products deriving from the reactions of reaction intermediates with oleic acid and its oxidation products. These include octanoic acid, and 9- and 10-oxooctadecanoic acid, as well as products of considerably higher molecular weight. Quantitative evaluation of product yields with the ATOFMS shows a marked dependence upon both particle size association (from 0.3 to 2.1 µm diameter) and relative humidity. Under dry conditions, the percentage residual oleic acid increases with increasing particle size, as does the percentage of higher molecular weight products, due to the poorer internal mixing of the larger particles. The main lower molecular weight products are nonanal and oxonononic acid. Under humidified conditions, the percentage unreacted oleic acid is greater, except in the smallest particle fraction, and oxononanoic acid dominates the product distribution, with little formation of high molecular weight products relative to the dry particles. It is postulated that water reacts with reactive intermediates, competing with the processes which produce high molecular weight products. Whilst the oleic acid model aerosol system is of limited relevance to complex internally mixed atmospheric aerosol, the generic findings presented in this paper give useful insights into the nature of heterogeneous chemical processes.
... However, formate itself is also rapidly oxidized by OH (aq) , and as a result evasion of HCOOH to the gas phase would only be expected for moderately acidic clouds (pH < 5) (Jacob, 1986). In addition, HCOOH production has been observed during organic aerosol aging in the laboratory (Eliason et al., 2003;Molina et al., 2004;Pan et al., 2009;Park et al., 2006;Vlasenko et al., 2008;Walser et al., 2007), raising the question of whether this is also important in the ambient atmosphere . With a continental organic aerosol source of approximately 150 TgC yr −1 globally , a large HCOOH yield from aerosol oxidation would be needed to have a major impact on its overall budget (given a recent topdown HCOOH source estimate of ∼ 30 TgC yr −1 ; Stavrakou et al., 2012). ...
Formic acid (HCOOH) is one of the most abundant acids in the atmosphere,
with an important influence on precipitation chemistry and acidity. Here we
employ a chemical transport model (GEOS-Chem CTM) to interpret recent airborne
and ground-based measurements over the US Southeast in terms of the
constraints they provide on HCOOH sources and sinks. Summertime boundary
layer concentrations average several parts-per-billion, 2–3× larger
than can be explained based on known production and loss pathways. This
indicates one or more large missing HCOOH sources, and suggests either a key
gap in current understanding of hydrocarbon oxidation or a large,
unidentified, direct flux of HCOOH. Model-measurement comparisons implicate
biogenic sources (e.g., isoprene oxidation) as the predominant HCOOH source.
Resolving the unexplained boundary layer concentrations based (i) solely on
isoprene oxidation would require a 3× increase in the model HCOOH
yield, or (ii) solely on direct HCOOH emissions would require approximately a
25× increase in its biogenic flux. However, neither of these can
explain the high HCOOH amounts seen in anthropogenic air masses and in the
free troposphere. The overall indication is of a large biogenic source
combined with ubiquitous chemical production of HCOOH across a range of
precursors. Laboratory work is needed to better quantify the rates and
mechanisms of carboxylic acid production from isoprene and other prevalent
organics. Stabilized Criegee intermediates (SCIs) provide a large model
source of HCOOH, while acetaldehyde tautomerization accounts for
~ 15% of the simulated global burden. Because carboxylic
acids also react with SCIs and catalyze the reverse tautomerization
reaction, HCOOH buffers against its own production by both of these
pathways. Based on recent laboratory results, reaction between
CH3O2 and OH could provide a major source of atmospheric HCOOH;
however, including this chemistry degrades the model simulation of
CH3OOH and NOx : CH3OOH. Developing better constraints on SCI
and RO2 + OH chemistry is a high priority for future work. The model
neither captures the large diurnal amplitude in HCOOH seen in surface air,
nor its inverted vertical gradient at night. This implies a substantial bias
in our current representation of deposition as modulated by boundary layer
dynamics, and may indicate an HCOOH sink underestimate and thus an even
larger missing source. A more robust treatment of surface deposition is a
key need for improving simulations of HCOOH and related trace gases, and our
understanding of their budgets.
... However, formate itself is also rapidly oxidized by OH (aq) , and as a result evasion of HCOOH to the gas phase would only be expected for moderately acidic clouds (pH < 5) (Jacob, 1986 ). In addition , HCOOH production has been observed during organic aerosol aging in the laboratory (Eliason et al., 2003; Molina et al., 2004; Pan et al., 2009; Park et al., 2006; Vlasenko et al., 2008; Walser et al., 2007), raising the question of whether this is also important in the ambient atmosphere (Paulot et al., 2011 ). With a continental organic aerosol source of approximately 150 TgC yr −1 globally (Heald et al., 2010), a large HCOOH yield from aerosol oxidation would be needed to have a major impact on its overall budget (given a recent topdown HCOOH source estimate of ∼ 30 TgC yr −1 ; Stavrakou et al., 2012). ...
Formic acid (HCOOH) is one of the most abundant acids in the atmosphere, with an important influence on precipitation chemistry and acidity. Here we employ a chemical transport model (GEOS-Chem) to interpret recent airborne and ground-based measurements over the US Southeast in terms of the constraints they provide on HCOOH sources and sinks. Summertime boundary layer concentrations average several parts-per-billion, 2–3× larger than can be explained based on known production and loss pathways. This indicates one or more large missing HCOOH sources, and suggests either a key gap in current understanding of hydrocarbon oxidation or a large, unidentified, direct flux of HCOOH. Model-measurement comparisons implicate biogenic sources (e.g., isoprene oxidation) as the predominant HCOOH source. Resolving the unexplained boundary layer concentrations based: (i) solely on isoprene oxidation would require a 3× increase in the model HCOOH yield, or (ii) solely on direct HCOOH emissions would require approximately a 25× increase in its biogenic flux. However, neither of these can explain the high HCOOH amounts seen in anthropogenic air masses and in the free troposphere. The overall indication is of a large biogenic source combined with ubiquitous chemical production of HCOOH across a range of precursors. Laboratory work is needed to better quantify the rates and mechanisms of carboxylic acid production from isoprene and other prevalent organics. Stabilized Criegee intermediates (SCIs) provide a large model source of HCOOH, while acetaldehyde tautomerization accounts for ~ 15% of the simulated global burden. Because carboxylic acids also react with SCIs and catalyze the reverse tautomerization reaction, HCOOH buffers against its own production by both of these pathways. Based on recent laboratory results, reaction between CH3O2 and OH could provide a major source of atmospheric HCOOH; however, including this chemistry degrades the model simulation of CH3OOH and NOx:CH3OOH. Developing better constraints on SCI and RO2 + OH chemistry is a high priority for future work. The model does not capture the large diurnal amplitude in HCOOH seen in surface air, nor its inverted vertical gradient at night. This implies a substantial bias in our current representation of deposition as modulated by boundary layer dynamics, and may indicate an HCOOH sink underestimate and thus an even larger missing source. A more robust treatment of surface deposition is a key need for improving simulations of HCOOH and related trace gases, and our understanding of their budgets.
... Here, the UV photolysis and ozonolysis are the key processes to remove the organic molecules attached to the nanoparticle surface. 16,17 The UV/ozone treatment of a self-assembled nanoparticle monolayer results in a discontinuous layer with many defects and voids. 18 Such a submonolayer is not suitable for gas-sensing applications. ...
We report on an in situ observation of reassembly and oxidation of a self-assembled silver nanoparticle bilayer due to an UV/ozone treatment and removal of the nanoparticle surfactant molecules. Such arrays of metal oxide nanoparticles are designated for sensor applications. To follow simultaneously the temporal evolution of particular processes taking place at different length scales, we employed the small- and wide-angle X-ray scattering in situ. In this way, all relevant transformation stages were identified: removal of the nanoparticle surfactant shell accompanied by a loss of the nanoparticle position correlations, oxidation of the nanoparticle crystalline core, and final reassembly of the silver oxide nanoparticles into agglomerates. Study of these processes on a common timeline provides a detailed insight into the kinetics of the UV/ozone treatment which represents a simple and effective method for preparation of metal oxide nanoparticle arrays for sensors.
... SOA formed under low-NO x conditions is sensitive to UVlight photolysis (Presto et al., 2005b;Lee et al., 2006;Park et al., 2006;Henry et al., 2012). Previous experiments in our laboratory have shown that low-NO x SOA formation from α-pinene ozonolysis is cut in half in the presence of UV illumination vs dark conditions when SOA loadings are below 10 µg m −3 (Presto et al., 2005b), and also that SOA growth for the same system under further aging by OH radicals can be halted or even reversed by UV illumination (Henry and Donahue, 2012b). ...
Pinonaldehyde oxidation by OH radicals under low-NOx
conditions produces significant secondary organic aerosol (SOA) mass
yields. Under concurrent UV illumination, mass yields are lower than
high-NOx yields published earlier by our group. However, when
OH radicals are produced via dark ozonolysis the SOA mass yields are
comparable at high and low NOx. Because pinonaldehyde is a
major first-generation gas-phase product of α-pinene oxidation by
either ozone or OH radicals, its potential to form SOA serves as a
molecular counterpoint to bulk SOA aging experiments involving SOA
formed from α-pinene. Both the general tendency for aging
reactions to produce more SOA and the sensitivity of the
low-NOx products to UV photolysis observed in the bulk
clearly occur for this single species as well. Photochemical oxidation
of pinonaldehye and analogous first-generation terpene oxidation
products are potentially a significant source of additional SOA in
biogenically influenced air masses.
