Reactive and Nonreactive Ozone Uptake during Aging of Oleic Acid

Article pubs.acs.org/JPCA

Reactive and Nonreactive Ozone Uptake during Aging of Oleic Acid Particles Maxence Mendez,† Nicolas Visez,*,† Sylvie Gosselin,† Vincent Crenn,‡ Veronique Riffault,‡ and Denis Petitprez† †

Physicochimie des Processus de Combustion et de l’Atmosphère PC2A, UMR 8522 CNRS/Lille 1, Villeneuve d’Ascq, F-59655, France ‡ Sciences de l’Atmosphère et Génie de l’Environnement, Ecole Nationale Supérieure des Mines de Douai, Douai, F-59508, France ABSTRACT: The ozonolysis of submicrometer (150 nm) oleic acid (OL) particles in an aerosol flow tube has been studied for a wide range of initial ozone concentrations from 25 ppb to 1100 ppb. Both reactants were monitored, as well as the four main reaction products (nonanal, azelaic acid, nonanoic acid, and 9-oxononanoic), by gas chromatography−mass spectrometer, high resolution-time of flight-aerosol mass spectrometer, proton transfer reaction-time of flight-mass spectrometer, and ozone analyzer. The values for the initial uptake coefficients derived from each reactant decay are in the same range: γO3−0 = (1.5 ± 0.1) × 10−3 and γOL‑0 = (1.0 ± 0.2) × 10−3. The ozone uptake coefficient is highly decreased when particles are in an advanced oxidized state (γO3‑∞ = 5 × 10−5). Concerning reaction products, nonanal was mainly observed in the gas-phase (∼80%) with a carbon yield of ∼29%. Nonanoic, azelaic, and 9oxonanonoic acids have been quantified in the condensed phase with carbon yields of respectively 6.6%, 5.3%, and 31.4%. The changes in chemical composition induce a slight rise in particle density, whereas the aerodynamic particle diameter increases by 10%. The initial molar quantities of ozone and OL were chosen to obtain different initial stoichiometries in order to explore conditions where either of them is the limiting reactant. Drastic changes in reactivity were observed as a function of the initial stoichiometry. In conditions where OL was the initial limiting reactant, up to a total of four molecules of O3 were lost from the gas phase, whereas only one OL molecule was consumed.

1. INTRODUCTION Particulate organic matter is ubiquitous in the troposphere.1−5 The organic aerosol aging investigation is important because of the uncertainties about the role of aerosol on climate change.6 The hygroscopic properties change indeed according to the oxidation state of organic aerosol and it may lead to modification in the cloud condensation nuclei (CCN) activity of particles.7 Among the large variety of organic compounds found in particles (alkanes, alkenes, alcohols, aromatics, etc.),1,8,9 fatty acids are one of the most abundant chemical families. They are commonly observed in marine10 and continental aerosols11 because they have both anthropogenic and biogenic sources. Fatty acids are emitted by biological activities, more specifically by plankton blooms, in the marine boundary layer12,13 and especially during springtime.10 Fatty acids may contribute up to 50% of the identified organic matter from emissions sources such as biomass burning,14−16 cooking,17,18 and road traffic.19 Oleic acid (cis-9-octadecenoic acid) is a molecular marker for biomass burning20 and other combustion processes.21−23 For example, oleic acid appears to be the most prevalent of unsaturated fatty acids for vehicular emissions.21 The ozonolysis of OL is a laboratory model system for the studies of heterogeneous aging of organic matter in the atmosphere.24−39 © 2014 American Chemical Society

Previous studies have reported uptake coefficients, products formation, and gas-particle partitioning for a large set of experimental conditions: different types of chemical reactors, various ranges of ozone concentrations, particle sizes and concentrations, and the presence of other components in the particle. However, and despite such a simple model system, the knowledge of the physical chemistry of the OL/O3 system is still not completely understood. The ozonolysis of oleic acid occurs via the addition of O3 on the double bond and leads to the formation of a primary ozonide (POZ). The POZ is then decomposed by two different ways. The first one forms nonanal and a Criegee intermediate compound (CI 1). The second ozonide decomposition forms 9-oxononanoic acid and the second Criegee intermediate (CI 2). CI 1 has been shown to recombine into azelaic acid whereas CI 2 recombines into nonanoic acid. CI 1 and CI 2 may also react with water to form peroxides, or with oleic acid which leads to C27 compounds.24 Coated-wall flow tube studies are generally performed in excess of OL and kinetic measurements are done by monitoring the loss of ozone.25,28 On the other hand, aerosol flow tube Received: April 11, 2014 Revised: September 2, 2014 Published: September 5, 2014 9471

dx.doi.org/10.1021/jp503572c | J. Phys. Chem. A 2014, 118, 9471−9481

The Journal of Physical Chemistry A

Article

Upon exiting the AFT, a part of the flow is sent to a scanning mobility particle sizer (SMPS) and a HR-ToF-AMS.44 The remaining fraction of the flow is filtered by PTFE filters to (1) determine the collected particle composition by off-line analysis with a GC−MS; (2) determine the gas-phase composition with an ozone analyzer and a PTR-ToF-MS. (cf. section 2.3, Analytical Procedure, for details). 2.2. Particle Generation and Chemicals. Chemicals purchased from Sigma-Aldrich are dichloromethane (99.8%), azelaic acid (≥98%), nonanal (≥95%). Chemicals from Fluka are tetradecane (≥98%), hexadecane (≥98%), oleic acid (≥99%). N,O-bis(trimethylsilyl)-trifluoroacetamide (BSTFA) and trimethylchlorosilane (TMCS) solution (BSTFA 99%/ TMCS 1%) is purchased from Supelco. Gases purchased from Praxair are synthetic air 3.0, nitrogen 4.6. All chemicals were used without further purification. Pure oleic acid (OL) particles were formed by homogeneous nucleation as described in a previous work.45 A flow of 1 L min−1 of synthetic air was sent through a heated and insulated glass vessel containing 5 g of OL. After passing through a condenser (T = 10 °C), the stream of freshly condensed particles was then diluted by adding 1 L min−1 of synthetic air and sent into a 1.5 L buffer volume at room temperature to reach equilibrium of the gas-particle partition. Size distributions were recorded every 90 s by a SMPS (TSI 3080L) between 40 and 400 nm. The temperature of the vessel containing OL can be adjusted and controlled (±1 °C) between 105 and 130 °C; a rise in temperature induces a higher density number of particles with roughly the same mean surface-weighted diameter of 150 nm and a geometric standard deviation of 1.3 (log-normal distribution). So aerosol surface density varies also as a function of the temperature (see Figure 2) and this was used

(AFT) kinetic studies are mostly performed by monitoring the OL loss and the particle-phase products formation. In those experimental conditions, the ozone concentration is generally much higher than the oleic acid one ranging from 1 to 8000 ppmV.7 Four products of the oleic acid ozonolysis were observed or quantified in several works: nonanal (NN), nonanoic acid (NA), azelaic acid (AA), and 9-oxononanoic acid (OA). Vesna et al.40 have quantified them both in condensed and gas phases by off-line GC−MS. Some discrepancies still exist between product yields and gas-phase partitioning. Furthermore, ozonolysis mechanisms have been shown to change according to the initial stoichiometry (molar ratio of ozone to alkene) of the reactants.36,41−43 More specifically, Sage et al.36 have shown a change in the decay rate of OL with increasing particle oxidation and stoichiometry but only for a molar ratio of 0.12 up to 0.8. In this work, we have explored the influence of initial stoichiometry (SI = [O3]0/[OL]0) on the decay of ozone and OL by measuring both reactants simultaneously over an extended range compared to Sage et al.36 We have performed experiments for SI ranging from where either OL or ozone were the limiting reactant (SI = 0.4 to 12.0). The uptake coefficient have been determined by two methods monitoring the decay of each reactant, γO3 and γOL stand for the uptake coefficient determined by the decay of ozone and oleic acid, respectively. Kinetics appeared to be changed as a function of stoichiometry indicating the influence of initial stoichiometry when “new” particles were exposed to ozone. The decrease of γO3 as a function of ozone exposure seems to indicate that a protective effect of organic compounds on the degradation of OL limit the aging of oleic acid particles. Gaseous and particulate phase products were also quantified during the same experiments, respectively, by proton transfer reaction-time of flight-mass spectrometer (PTR-ToF-MS) for the gas phase and by gas chromatography−mass spectrometer (GC−MS) analyses and high resolution-time of flight-aerosol mass spectrometer (HRToF-AMS) for the particulate phase.

2. EXPERIMENTAL SECTION 2.1. Aerosol Flow Tube. Aerosol and ozone flows were isokinetically injected on the top of an aerosol flow tube mainly consisting of a 1 m long and 10 cm inner diameter quartz tube (see Figure 1). Total flows of 1.8, 2.4, 3.2, or 4.0 L min−1 were used in laminar conditions (synthetic air as carrier gas). The corresponding mean contact times were calculated by the ratio/ reactor volume/total flow. All experiments were done at roomtemperature of 22(±2) °C.

Figure 2. Aerosol surface density as a function of the temperature of the oleic acid tank.

as a kinetic variable for the determination of the uptake coefficient. Using the value of the density of pure oleic acid, dOL = 0.895 g cm−3, the corresponding mass loading of OL in the particulate phase was in the range of several hundreds of micrograms per cubic meter, which is much higher than the OL vapor pressure (2.4 μg m−3 at 298 K46). Ozone was generated from O2 photolysis using pen-ray UV lamps (UVP stable ozone generators SOG-1 and SOG-2, λ = 185 nm). Ozone concentrations from 25 to 1100 ppb were used in this study and monitored with a Thermo Scientific ozone analyzer 49i. This UV absorption technique allows the

Figure 1. Schematic of the experimental setup. 9472



Article

Table 1. Uptake Coefficient Definition uptake

definition

monitored reactant

involved processes

γO3

number of ozone molecules lost in the gas phase normalized by the number of ozone surfacecollisions number of oleic acid molecules lost normalized by the number of ozone surface-collisions

gas-phase ozone loss (O3 analyzer)

includes all processes leading to the loss of ozone from the gas phase: reaction with OL, nonreactive uptake, secondary ozonolysis

particulate-phase oleic acid loss (GC−MS)

includes the reactive processes leading to the loss of OL from the particulatephase: reaction with O3, reaction with the products or the Criegee intermediates

γOL

ozone concentration measurement every 10 s in a 1.45 L min−1 flow. 2.3. Analytical Procedure. 2.3.1. Gas Chromatography. The chemical composition of the particulate phase was analyzed by a GC−MS. At the reactor outlet, the particles were sampled on a PTFE filter (Millipore FALP, 1.0 μm, diameter 47 mm) during 10 min at a constant sampling flow of 2.1 L min−1. The filtration efficiency for 150 nm diameter oleic acid particles was measured downstream of the filter holder with the SMPS and was higher than 99.9%. An ozone scrubber was inserted between the AFT and the sampling filter. It consists in a two meter long copper tube treated with a saturated solution of KI.47 The aerosol loss in the ozone scrubber was evaluated and was negligible. Analysis of carboxylic acids by gas chromatography requires derivatization of the −COOH function.40 In this work, silylation by BSTFA was performed as previously described for the identification of mono- and dicarboxylic acids in atmospheric particles collected on filters.40,48−51 Once particles were collected, the filter was introduced in a 1.5 mL vial and 10 μL of a solution containing two internal standards (tetradecane and hexadecane) were added. Then 25 μL of a commercial mixture containing 99% BSTFA and 1% TMCS (trimethylchlorosilane) were deposited directly on the membrane. TMCS acts as a catalyst of the silylation reaction by increasing the silyl donor strength of the BSTFA. After finally adding 1 mL of dichloromethane, the filter was subjected to 10 min of sonication to extract the oleic acid and particle-phase products from the filter to the solvent. After the extraction and silylation steps, 1 μL of the solution was injected in a GC (PerkinElmer Clarus 680). Chromatographic conditions were as follow: inlet, 250 °C; split mode, 5 mL min−1; constant column flow, 1 mL min−1; and oven temperature of 50 °C for 0.5 min followed by a ramp of +20 °C min−1 to reach the final temperature of 310 °C. Separation was provided by an Elite-5MS 30 m long column (diameter 250 μm and film thickness 0.5 μm). Identification and quantification were performed on a Clarus 600C mass spectrometer in 70 eV electron impact mode with a source temperature of 180 °C. Quantification of OL was performed by injecting standard solutions of known concentrations. The ion fragment corresponding to the silyl group Si(CH3)3 (m/z = 73 amu) is the most intense peak in TMS-fatty acids spectra, so it was chosen for the quantification of silylated oleic acid. All samples were injected in triplicate in selected ion monitoring (SIM) mode for quantification and once in scan mode for identification. Nonanal, azelaic acid, and nonanoic acid have been calibrated with standards solutions. 2.3.2. PTR-ToF-MS. The gas phase was also analyzed with a PTR-ToF-MS (Kore Technology) with a mass resolution m/ Δm of 1200 and a drift tube operated at E/N 144 Td (where E is the electric field and N is the gas number density). The filtered outlet flow was sampled at 300 mL min−1; mass spectra were collected during 1 min (average of 35 μs scans; mass

range, 0 to 330 amu). The PTR-ToF-MS was calibrated by a gas mixture containing known concentrations of nonanal (PV = 0.29 Torr at 295 K).25 2.3.3. HR-ToF-AMS. For additional measurements, an Aerodyne HR-ToF-AMS was connected downstream of the AFT to investigate the size-resolved evolution of the particulate organic phase.44,52 Briefly, particles are sampled through a 100 μm critical orifice at a flow rate of ∼80 mL min−1 and focused into a narrow beam by aerodynamic lenses. Particles are then accelerated in the vacuum chamber, and a chopper synchronized with the detector allows for the determination of their size distributions according to their aerodynamic diameter. Particle nonrefractory constituents are flash-vaporized at 600 °C after impaction on a heated conical surface and the resultant molecules are ionized by electron impact at 70 eV. Ions are separated in the time-of-flight mass spectrometer according to their mass-to-charge ratio. Calibrations (particle velocity, ionization efficiency) were performed using dried ammonium nitrate particles generated by atomizing a 0.01 M ammonium nitrate solution. Mass spectra recorded every 10 s were averaged over 2 min in low resolution mode (V mode; 1 min in MS mode, 1 min in PToF mode) and 2 min in high resolution mode (W mode). AMS data were analyzed using Pika 1.11L and Squirrel 1.52L software packages. Because the experiments were carried out in CO2-free synthetic air and as confirmed by filter blanks, the gasphase contribution of CO2+ at m/z 44 was set to 0. In the pure OL particles spectrum, the parent peak of OL at m/z 282 appeared less intense than the dehydrated ion at m/z 264 (0.042% of the total signal), which was thus chosen to monitor oleic acid signals and to calculate OL mass concentrations in the AFT, assuming that the detection efficiency of m/z 264 does not vary with particle oxidation. Two other products could be calibrated using the same approach, azelaic acid and nonanoic acid, whose peaks at m/z = 152 (C9H12O2+) and 129 (C7H13O2+) contributed respectively to 0.571% and 0.673% of the total organic mass. Oxononanoic acid (OA) was identified in the HR spectra at its parent peak (m/z 172; C9H16O3+). However, owing to the lack of commercially available standards, the m/z 155 fragment (C9H15O2+), which showed good correlation with m/z 172 whatever the ozone exposure (implying there was no significant interferences from other products at this m/z), was used to quantify OA using the mass contribution determined by Katrib et al. (0.2% of the total mass).29 The collection efficiency (CE) for oleic acid particles exposed to ozone, mostly due to particle bouncing at the vaporizer,53 was determined by comparing the total organic mass concentrations measured by the AMS to those derived from SMPS measurements, considering a variable particle density as calculated in this work (see section 3.2) and assuming spherical particles. CE appeared constant over the interval of ozone exposure and was equal to 34.3%. The relative ionization efficiency (RIE) was kept at 1.4 for organics 9473



Article

compared to nitrate.54 No significant contribution from species other than organics was observed as expected. 2.4. Uptake Coefficient Determination Methods. The uptake coefficient is determined with two approaches according to the species monitored (Table 1). In the first case, we measure the gas phase reactant loss (ozone) as a function of the particle concentration and the contact time, the corresponding uptake coefficient is named γO3. In the second one, the uptake coefficient, γOL, is derived by measuring the OL particle phase loss as a function of the ozone exposure (atm s) which is defined as the product of the contact time with the initial ozone concentration. By monitoring both concentrations, nonreactive uptake of ozone can be highlighted. 2.4.1. γO3 Uptake Coefficient. The uptake coefficient, γO3, is given by γO = 3

as defined in Table 1 is to measure the loss of oleic acid as a function of the ozone exposure. The uptake coefficient can then be expressed with the following expression:45 γOL =

where [OL]0 is the initial concentration (molecules cm ) of the particle-phase oleic acid and kOL is the second-order rate constant of the reaction of OL with ozone (cm3 molecule−1 s−1). The loss of particle-phase OL as a function of the reaction time is expressed as d[OL] = −k OL[O3][OL] dt

where ϕeff is the flux of the ozone loss and ϕcoll is the flux of ozone colliding over the particle surface. Assuming a first order surface process, the ozone loss can be expressed as

[OL]t = e−kOL−0([O3]0 t ) [OL]0

(2)

V d[O3] V = k[O3] S P dt SP

(3)

[OL]0 =

where SP/V is the particle surface density (cm2 cm−3). ϕcoll is expressed as ϕcoll =

(4) −1

where ωO3 is the mean thermal velocity of ozone (cm s ). Finally, γO3 is expressed as γO = 3

ϕeff ϕcoll

=4×

Vk SPωO3

γOL ‐ 0 =

(11)

4k OL ‐ 0DmeandOLNA ωO36MOL

(12)

where Dmean is the mean surface-weighted diameter of the particle distribution and is derived from VP/SP = Dmean/6.56 The mean particle diameter is determined by SMPS measurements. 2.4.3. Diffusion Correction. Uptake can be limited by gasphase diffusion of ozone toward oleic acid particles. Then the uptake measurements should be corrected and according to the resistor model:57

(5)

Rather than determining k by performing a kinetic experiment as a function of the reaction time while keeping the OL surface density (V/Sp) constant, we measured the decay of ozone during a temperature ramp and consequently for various (V/ Sp) ratios at a fixed reaction time. The integration of eq 2 leads to [O ] ln 3 0 = kt [O3]t

VPdOLNA VMOL

where VP/V is the particle volume density, MOL is the molar mass of oleic acid (MOL = 282 g mol−1), dOL is the oleic acid density (dOL = 0.895 g cm−3) and NA is the Avogadro’s number. Finally, the uptake coefficient can be expressed as

[O3]ωO3 4

(10)

[OL]0 and [OL]t are the initial and final concentrations (molecules cm−3) of particle-phase oleic acid, respectively, measured by both GC−MS and AMS. Moreover, [OL]0 can be replaced in the uptake coefficient expression by the equation:

where [O3] is the time-dependent ozone concentration (molecules cm−3), k is the first-order rate constant (s−1). So, ϕeff is calculated as the following: ϕeff = −

(9)

where [O3] and [OL] are the reactant concentrations (molecules cm−3). The rate constant for oleic acid is expressed as a function of the loss of OL and the initial ozone exposure as shown in eq 9. Therefore, we identified the uptake coefficient to the initial uptake coefficient (γOL‑0) by measuring the initial rate constant, kOL‑0.

(1)

d[O3] = −k[O3] dt

(8) −3

ϕeff ϕcoll

4Vk OL[OL]0 SPωO3

1 1 1 = + γmeas Γdiff γ

(6)

(13)

The diffusion correction was estimated using

where [O3]0 and [O3]t are, respectively, the initial ozone concentration and the remaining ozone concentration after a reaction time t. Combining eqs 5 and 6 leads to γO tωO3 ⎛ S ⎞ [O ] P⎟ ⎜ ln 3 0 = 3 [O3]t 4 ⎝ V ⎠t (7)

0.75 + 0.28KnO3 1 = Γdiff KnO3(1 + KnO3)

(14)

KnO3 is the Knudsen number and is defined as the following:58

KnO3 =

As the reaction times are known for a given flow in the AFT, we can evaluate the uptake coefficient γO3 by measuring the ozone loss as a function of the surface density.55 2.4.2. γOL Uptake Coefficient. In aerosol flow tube studies, the most common way to determine the uptake coefficient γOL

λO3 2λ = O3 rp dp

(15)

where λO3 is the mean free path of ozone and is defined as a function of Dg,O3, the gas-phase diffusion coefficient of ozone in air, as follows: 9474



λO3 =

Article

3λ Dg,O3 ωO3

(16)

Finally, the Knudsen number of ozone is KnO3 =

6Dg,O3 ωO3Dmean

(17)

In our case, Dg,O3 = 0.14 cm2 s−1, ωO3 = 36 260 cm s−1, and Dmean = 1.5 × 10−5 cm lead to KnO3 = 1.54. When injecting this value in eqs 13 and 14, corrections due to gas-phase diffusion limitation appear to be less than 1%, which is negligible compared to the estimated experimental errors for gamma measurements. So no further corrections were applied to the measured uptake coefficients. Figure 4. Normalized ozone decay (log scale) as a function of Sp/V and linear fit of the data according to eq 7

3. RESULTS AND DISCUSSION 3.1. Kinetic Measurements. 3.1.1. Ozone Uptake Coefficient (γO3). In this section, we evaluate the uptake coefficient γO3 by recording the decay of ozone concentration as a function of oleic acid particle surface density (see eq 7). An uptake experiment was started by a slow increase of the temperature in the oleic acid tank from 50 °C to 115 °C. When the temperature reached 115 °C, the heating was stopped and the temperature decreased back to its initial value. The controlled temperature variation allows us to produce a reproducible pattern for the density number of OL particles as shown in Figure 3. The ozone concentration logically followed an opposite behavior: the higher the particle surface density is, the higher the ozone losses.

Figure 5. Ozone uptake coefficient measured as a function of ozone exposure: squares, experimental values; solid line, exponential fit to guide the eye.

initial ozone uptake γO3‑0 is defined as the ozone uptake coefficient when ozone exposure tends to zero and is equal to (1.5 ± 0.1) × 10−3. At high ozone exposure levels, the uptake coefficient γO3 decreases down to γO3‑∞ = (5.0 ± 1.0) × 10−5. To verify that only heterogeneous reactions took place within the AFT, experiments were performed with particle filters at the reactor inlet (>99.9% efficiency). No noticeable decrease in ozone concentration occurred in these conditions showing that the gas-phase reactivity of OL could therefore be neglected in our experimental conditions. 3.1.2. γOL Determination. For γOL uptake coefficient determination, a constant OL aerosol concentration was generated and exposed to ozone concentrations from 25 to 780 ppb with a total flow of 2.4 L min−1 (reaction time of 240 s and exposure ranging from 0 to 2.0 × 10−4 atm s). The unreacted OL mass concentrations, normalized by initial OL mass concentration ([OL]t/[OL]0) were determined by GC− MS analyses and are reported as a function of ozone exposure in Figure 6. An exponential function was used to fit the experimental values of the remaining oleic acid fraction as a function of ozone exposure according to eq 10 in order to determine the second order rate constant: kOL‑0 = 2.17 × 10 −15 cm3 molecule−1 s−1 (1.31 × 106 M−1 s−1). The resulting calculation (eq 12) for the experimental uptake coefficient is γOL‑0 = (1.0 ±

Figure 3. Simultaneous evolution at the outlet of the AFT of the surface density of oleic acid particles measured by SMPS (black squares, left axis) and the ozone concentration (gray squares, right axis). Experimental conditions: [O3]0 = 585 ppb, Qtot = 2.4 L min−1, tc = 240 s, temperature increases between t = 5 and t = 20 min and decreases from t = 20 to t = 35 min.

The data ([O3], Sp/V) are extracted from Figure 3 in order to plot ln([O3]0/[O3]t) versus (Sp/V)t (Figure 4). The data fit to a linear function (eq 7) and γO3 is calculated from the determination of the slope (γO3 = 1.55 × 10−4 for data reported in Figure 4). This methodology has been applied to different ozone initial concentrations ranging from 60 ppb to 1100 ppb and reaction times from 180 s to 490 s. The ozone uptake coefficient decreases with the increase in ozone exposure (Figure 5). The 9475



Article

In our case the mode of the distribution of the particles is centered at 150 nm, and the derived second-order rate constant is kOL‑0 = 1.31 × 106 M−1 s−1. Using these values, we determine an ozone diffuso-reactive length, l = (DO3/(K2[OL]))1/2 = 17 nm, where DO3 = ozone diffusion coefficient in oleic acid (DO3 = 1 × 10−5 cm2 s−1),60 k2 = second-order rate constant (k2 = 1.31 × 106 M−1 s−1) and [OL] = 3.16 M. So the mean radius of the particles is around five times greater than the ozone diffusoreactive length. This situation represents an intermediate case between rapid diffusion of ozone throughout the particle and reaction limited by ozone diffusion or a near surface reaction as described in details in the work of Smith.60 Similarly to what can be inferred from the work of Smith et al., the model involves too many parameters which continuously change as the reaction goes on. These parameters cannot be individually fitted using experimental data coming from one heterogeneous reaction with a unique size of particles. To discriminate between all these processes, uptake of ozone by nonreactive species should be considered. If possible, such studies must be conducted with liquid droplets for different sizes and different viscosities. 3.2. Organic Density and Oxidation State of Particles. The HR-ToF-AMS data were used to investigate the state of oxidation of the particulate organic phase for the following conditions: [OL]0 = 750 μg m−3; [O3] = (0−770 ppb). O/C and H/C elemental ratios were calculated for increasing ozone exposures and the particulate organic density was derived (Figure 7) according to the expression of Kuwata et al.,61 valid for 0.750 < dorg < 1.9 g cm−3:

Figure 6. Remaining oleic acid fraction ([OL]t/[OL]0) as a function of the ozone exposure measured by GC−MS (squares) and the exponential fit (solid line) according to eq 10. Error bars correspond to the [min−max] values of three GC−MS analyses repeated for two different filters.

0.2) × 10−3. This uptake coefficient value is in good agreement with the accepted literature value of 0.8 × 10−3.24 3.1.3. Discussion on Uptake Coefficients. The values for uptake coefficients from ozone and oleic acid losses are summarized in Table 2. γO3‑0 is the ozone monitored uptake Table 2. Uptake Coefficient Values Determined in This Work Uptake Coefficient γO3‑0 γO3‑∞ γOL‑0

(1.5 ± 0.1) × 10−3 (0.05 ± 0.01) × 10−3 (1.0 ± 0.2) × 10−3

dorg =

12 + 1(H/C) + 16(O/C) 7 + 5(H/C) + 4.15(O/C)

(18)

The organic density increased over increasing ozone exposures up to 0.967 g cm−3 (Figure 7) and the exponential fit at very low exposure leads to an initial value of 0.898 g cm−3, very close to that of pure OL (dOL = 0.895 g cm−3). It is clear

coefficient for low ozone exposure (fresh particle surface). Contrariwise γO3‑∞ is the uptake coefficient measured through the decay of ozone for the highest exposure. Both kinetic methods (ozone or OL loss) are in good agreement, giving comparable values for γO3‑0 and γOL‑0. A fraction of oleic acid (between 10 and 20%) remains nonoxidized in the particles even for the higher exposure (Figure 6), and the O3 uptake coefficient decreases as a function of ozone exposure up to a factor of 30 and reaches a plateau for exposures greater than 6 × 10−5 atm s (Figure 5). Uptake experiments do not give access to the elementary steps involved in the whole heterogeneous process but some hypothesis can be proposed to explain the observed trends for the OL incomplete consumption and the O3 uptake decrease: (a) Oxygenated products are rapidly formed in the outer layer of the particle. Assuming that the reactivity of these products is low, the surface layer can be rapidly saturated with ozone limiting its further uptake from the gas phase. (b) As new products are formed, one can imagine that the phase of the outer layer is modified as the reaction goes forward. This trend (a more viscous liquid) was already suspected by previous works59 and is also confirmed by the change of the particle density observed in this study (see later). This phase change will limit the ozone diffusion toward the center of the particle but also the transport by diffusion of the products, which prevents the renewal of the surface with fresh oleic acid.

Figure 7. (top) Evolution of the density of the organic particulate phase, dorg; (bottom) elemental ratios H/C (black open squares) and O/C (gray full circles), as a function of ozone exposure. The density is calculated from the elemental ratios using Kuwata et al. expression61 (see text) and is fitted by an unweighted exponential curve. The dashed line is also an unweighted exponential fit through O/C data. The uncertainties on each ratio represent one standard deviation. 9476



Article

distribution fitted for each ozone exposure is equal to 1.10 which is close to the corresponding ratio of the density, 1.08. 3.3. Products Study and Chemical Mechanism. Nonanoic acid, 9-oxononanoic acid, and azelaic acid were identified and quantified in the particulate phase by GC−MS and HRToF-AMS analyses. Nonanal has been identified and quantified in the gas-phase by PTR-ToF-MS and in the particulate phase by GC−MS analyses as well. For each product P, the relative carbon yields (Yp) have been calculated as

that the increase of the O/C elemental ratio follows the same behavior as the particulate density, while the H/C remains almost constant. An increase of density with ozone exposure has also been reported by Morris et al.35 With a similar exposure range (1−3 × 10−4 atm s), Katrib et al.29 showed that the particle density increased up to 1.12 g cm−3. The latter was determined for coated PSL particles with a thin layer of OL and almost all OL reacting. In our case the remaining OL is in the order of 10−20% leading thereby to less dense aged particles. On the other hand, no evolution of the electric mobility mean diameter measured by SMPS was noticed. For spherical particles, the electrical mobility diameter is proportional to the geometrical diameter62 so the geometrical diameter of oleic acid is unchanged upon ozone exposure. Figure 8 shows the mass-size distribution of all organic fragments measured by the AMS for low and high ozone

YP = 100

[P]C P [OL]lost COL

(19)

[P] is the product concentration, [OL]lost is the oleic acid concentration that reacted, CP and COL are, respectively, the number of carbon atoms in the molecular structure of the product P and the oleic acid. Although 10 min of particle filter collection can modify the measured carbon yields of the more volatile products like nonanal, sensitivity tests were performed and showed that the particle phase concentration of nonanal was not significantly modified as a function of the time collection. Carbon yields for the four main products were calculated with eq 19 for the highest exposure and were reported together with literature values in Table 3. Despite the number of product studies of the oleic acid ozonolysis, discrepancies remain in the relative product carbon yields. Moreover, the product speciation may vary as a function of the exposure.40 The theoretical nonanal carbon yield has been estimated to be 25% given the chemical mechanism proposed in the literature24 and experimental observations.25,28 In the current study, nonanal has been observed with a 29% carbon yield which is in good agreement with the accepted value. 90% of the nonanal was observed in the gas-phase while only 10% remained in the condensed-phase. Katrib et al.30 did not observe nonanal in the condensed-phase assuming that nonanal is volatile and completely transferred in the gas-phase which was not analyzed. Those different behaviors are not contradictory considering that the gas-particle partitioning of nonanal has to be related to the available organic particulate matter. In the Katrib et al. study, ozonolyses were performed on a 2 to 30 nm thickness coating of oleic acid while, in this study, 150 nm diameter particles were generated. Contrariwise, the Thornberry et al. and Moise et al. studies reported coated-wall flow tube experiments in which the condensed phase was not

Figure 8. Mass-weighted size distribution of all organic fragments measured by AMS for [O3]0·t = 6.5 × 10−6 atm s (■) and 185 × 10−6 atm s (▲). Data are fitted by a log-normal model (mode1 = 153 nm and mode2 = 168 nm).

exposures, respectively, 6.5 × 10−6 atm s and 185 × 10−6 atm s for which the density derived from Figure 7 is 0.898 and 0.967. Each distribution has been fitted by a log-normal law in order to determine the mode. A small shift of the mode toward higher diameter is observed meaning that the vacuum aerodynamic diameter (Dva) is increasing as ozone exposure increases. As Dva is proportional to the density of the particle,62 this observation tends to confirm the change of particle density as the reaction proceeds. Indeed the ratio of the mode of the log-normal

Table 3. Carbon Yields (in %) of Observed Products from the Ozonolysis of OL in Aerosol Flow Tube and Coated-Wall Flow Tube Studiesa this study YNN, gas phase YNN, particle phase total YNN YNA YAA YOA other

24.1 5.2B

Hearn and Smith63

A

29.3 6.6B−C 5.3B−C 31.4C 27.4

42 42 9 6 42b 1

Vesna et al.40

Hung et al.33

Katrib et al.30

Shilling et al.7

51.7 3.3

9 21

0

0

55 2−3 3−8 7−14 20−33b peroxide

30 7 6 14 43

0 2 1−3 20−35 60−77

0 3−5b 3−5b 30 60−64

Thornberry and Abbatt25 25

Moise and Rudich28

Ziemann38

25 0

25

75

27 identified identified 0 73

0 0 6 46 48 peroxide

a

Superscripted A, B, and C denote values that have been reported using PTR-ToF-MS, GC−MS, and HR-ToF-AMS measurement techniques, respectively. bValues suggested by the authors but not quantified. 9477



Article

analyzed. In the Hearn et al. study,63 a higher particle phase nonanal carbon yield is reported and could be due to the secondary chemistry involving the Criegee intermediates recombination into nonanal. Nonanoic acid and azelaic acid are formed by the rearrangement of Criegee intermediates. Their carbon yields determined in this study by two very different methods are in good agreement with most of the published values using different online as well as offline detection techniques.7,30,33,40,64 In the HR mass spectra, 36 product fragments increasing as a function of ozone exposure were identified and are presented in Table 4. Five of them (CH2O2+, m/z 46; C4H8+, m/z 56;

then assumed to be equal to the ozone uptake coefficient with the oleic acid particle. Therefore, secondary processes like the nonreactive ozone uptake or secondary chemistry involving ozone or oleic acid cannot be highlighted. In this study, ozone and oleic acid consumptions were monitored simultaneously during kinetic experiments for γOL determination. Both reactants consumption are shown in Figure 9 as a function of exposure. It allows us to give

Table 4. Product Fragments Increasing with Increasing Ozone Exposure and Identified in HR Mass Spectra m/z (amu)

identified product fragment(s) (from HR data)

269 221 213 171 157 155 144 126 125 101 99 90 88 87 86 85 75 74 73 72 62 61 60 59 58 57 56 48 47 46

C16H9O3+ C12H34O4+ C13H25O2+ C9H15O3+ C11H9O+ C9H15O2+ C8H16O2+ C7H10O2+, C8H14O+ C8H13O+ C4H5O3+, C5H9O2+, C6H13O+ C5H7O2+ C7H6+ C4H8O2+ C4H7O2+, C5H11O+ C4H6O2+ C4H5O2+, C6H13+ C3H7O2+ C3H6O2+ C3H5O2+ C3H4O2+, C4H8O+ C2H6O2+, C5H2+ C2H5O2+, C5H+ C2H4O2+ C3H7O+ C3H6O+ C3H5O+ C3H4O+, C4H8+ CH4O2+ CH3O2+ CH2O2+

Figure 9. Reactant loss of ozone (solid squares) and OL (open squares) as a function of the ozone exposure on the left axis. Decay stoichiometry (SD = [O3]lost/[OL]lost) is represented on the right axis (cross).

information on the decay stoichiometry (SD = [O3]lost/[OL]lost) by calculating the molar ratio of reactant losses. The consumption of reactants was summed for a time period of 10 min corresponding to a typical particle filter collection duration. The Sage et al. study reports a minimum in decay stoichiometry of 0.27 in an atmospheric simulation chamber.36 In their work, oleic acid aerosol was introduced with low ozone initial concentrations ([O3]0 = 12 ppb) during 4 h of reaction time with an initial stoichiometry (SI = [O3]0/[OL]0) equal to 0.125, the decay stoichiometry increasing for each additional ozone introduction in the simulation chamber. In those conditions, ozone was the limiting reactant. Our stoichiometry data together with those from the study of Sage et al. are reported as a function of initial stoichiometry (SI = [O3]0/ [OL]0) in Figure 10. In the work of Sage et al., O3 is the limiting reactant in all experimental conditions (SI < 1). In the current study, the minimal initial stoichiometry is equal to 0.42 and varies up to 12 and thus the limiting reactant is either ozone or OL (SI > 1). So the decay stoichiometry has been studied over a large range of initial stoichiometries. For the lowest initial ozone-to-OL ratio (SI = 0.125) used by Sage et al.,36 up to four molecules of OL were consumed for one ozone molecule lost. In this case, the secondary chemistry is leading the consumption of OL. For the highest ozone-to-OL ratio (SI = 12, this work), up to a maximum of four molecules of ozone were lost for one OL, although there is no evidence of secondary ozonolysis given the detected products. This upper limit in SD shows that, at least, 65−75% of ozone molecules lost from the gas phase do not directly react with OL. Two hypotheses reported in the literature can explain this ozone overconsumption.31,33 First, ozone can be consumed through the ozonolysis of n-alkanoic acids but their reaction rates are 1000 times lower than those with alkenes. Second, the

C3H5O+, m/z 57; C2H4O2+, m/z 60; C3H5O2+, m/z 73) accounted for ∼75% of all the increasing fragments but could not be associated with specific molecules. The chemical mass balance between the total organic mass measured by the AMS and the mass concentrations for the three acids identified in the particulate phase showed that they represented 67.5% of the particulate products, leaving 32.5% of the aerosol mass unexplained. Therefore, at least part of the missing carbons (and associated species) estimated in Table 3 necessarily belong to the particulate phase. 3.4. Decay Stoichiometry. In previous AFT studies, the ozonolysis of oleic acid was generally monitored through the decay of oleic acid as a function of reaction time or ozone exposure.28,35,63,65 The measured uptake coefficient γOL was 9478



Article

observed by SMPS or AMS. A slight increase of density from 0.895 to 0.967 has been derived from HR-ToF-AMS data. Two main processes intervene in particle size: uptake of ozone and volatilization of products (more than 80% of NN was found in the gas phase). Lee et al.67 have shown that these two processes could offset each other. Phase and morphology changes may also occur for the oxidized particles and interfere with aerodynamic particle sizing, but no observations were made in this work to explore the formation of a solid or viscous phase in the particles. A wide range of initial ozone-to-OL initial stoichiometries was covered so that either ozone or OL were the limiting reactant. The decay stoichiometry varies from 0.25 (Sage et al.) up to 4 (this study) depending on the initial stoichiometry. Higher consumption of ozone when OL was the limiting reactant shows that part of ozone was probably trapped into the particle without reactivity. This nonreactive uptake may have important atmospheric significance as oxidative processes into the particle may continue after gas-phase ozone exposure.

Figure 10. Decay stoichiometry SD ([O3]lost/[OL]lost) as a function of the initial stoichiometry SI ([O3]0/[OL]0): ▲, this study; and gray ■, Sage et al.

■

mass accommodation coefficient is certainly larger, under high exposure conditions, than the reactive uptake coefficient, thus ozone molecules can be incorporated in the particle without chemical reaction.

AUTHOR INFORMATION

Corresponding Author

■

*E-mail: [email protected]. Tel.: +33.(0)3.20.43.65.62.

CONCLUSIONS Our experimental approach for the study of the ozone−oleic acid system was to monitor both reactant losses in the same experimental setup. Oxidant uptake was found to dramatically decrease from ∼1.5 × 10−3 to 5 × 10−5 when OL particles were more oxidized. The limitation of uptake of ozone can be explain by simultaneous elementary processes: (a) limitation of the reactivity by slow diffusion of the ozone throughout the particles or slow diffusion of oleic acid from the center to the out layers of the particle, (b) formation of less reactive products at the surface followed by a phase change limiting the diffusion of O3 and OL. Unfortunately these processes are driven by the change of several chemical or physical parameters: Henry’s constant, liquid diffusion coefficient of ozone and oleic acid, density of the particle. These parameters cannot be separately determined from our experimental data as already mentioned in the previous study of Smith.60 The reaction products may be seen as acting as a protective shell against oxidative processes. The products may be responsible in part for the prolonged lifetime of OL in the atmosphere compared to short lifetimes usually assessed in laboratory conditions. Without the limiting case of reactive uptake, oleic acid should be oxidized within minutes in a polluted atmosphere with an ozone concentration of 100 ppb.24,63,66 Laboratory oxidized particles have complex chemical compositions and we suggest that those particles probably reproduce more accurately the composition of real atmospheric particles. The lowest value for ozone uptake may be more atmospherically relevant than the commonly accepted value of 8 × 10−4 which is specific to laboratory conditions. The four main products of oxidation were quantified by GC−MS, HR-ToF-AMS and PTR-ToF-MS showing good agreements with other laboratory works. HR-ToF-AMS gave quantitative analysis of NA and AA very close to GC−MS analysis without the use of time-consuming sampling/ derivatization/extraction procedures, whereas up to 80% of OL was oxidized, no changes in particle diameter have been

Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS

■

REFERENCES

The laboratory is part of the IRENI Institute (Institut de Recherche en ENvironnement Industriel) which is financed by the Nord-Pas de Calais regional council and the European Regional Development Fund (FEDER). The CaPPA project (Chemical and Physical Properties of the Atmosphere) is funded by the French National Research Agency (ANR) through the PIA (Programme d’Investissement d’Avenir) under Contract ANR-11-LABX-005-01. We would like to thank Coralie Schoemaecker for providing her expertise on PTRToF-MS measurements. V. Crenn acknowledges support from Armines and the Nord-Pas de Calais Regional Council for his Ph.D. grant.

(1) Schauer, J. J.; Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.; Simoneit, B. R. T. Source apportionment of airborne particulate matter using organic compounds as tracers. Atmos. Environ. 1996, 30, 3837−3855. (2) Fuzzi, S.; Andreae, M. O.; Huebert, B. J.; Kulmala, M.; Bond, T. C.; Boy, M.; Doherty, S. J.; Guenther, A.; Kanakidou, M.; Kawamura, K.; et al. Critical Assessment of the Current State of Scientific Knowledge, Terminology, and Research Needs Concerning the Role of Organic Aerosols in the Atmosphere, Climate, and Global Change. Atmos. Chem. Phys. 2006, 6, 2017−2038. (3) Kawamura, K.; Yasui, O. Diurnal Changes in the Distribution of Dicarboxylic Acids, Ketocarboxylic Acids and Dicarbonyls in the Urban Tokyo Atmosphere. Atmos. Environ. 2005, 39, 1945−1960. (4) Wang, G.; Kawamura, K.; Lee, S.; Ho, K.; Cao, J. Molecular, Seasonal, and Spatial Distributions of Organic Aerosols from Fourteen Chinese Cities. Environ. Sci. Technol. 2006, 40, 4619−4625. (5) Aiken, A. C.; Salcedo, D.; Cubison, M. J.; Huffman, J. A.; DeCarlo, P. F.; Ulbrich, I. M.; Docherty, K. S.; Sueper, D.; Kimmel, J. R.; Worsnop, D. R.; et al. Mexico City Aerosol Analysis during MILAGRO using High Resolution Aerosol Mass Spectrometry at the Urban Supersite (T0)−Part 1: Fine Particle Composition and Organic Source Apportionment. Atmos. Chem. Phys. 2009, 9, 6633−6653.

9479



Article

(6) Rudich, Y.; Donahue, N. M.; Mentel, T. F. Aging of Organic Aerosol: Bridging the Gap Between Laboratory and Field Studies. Annu. Rev. Phys. Chem. 2007, 58, 321−352. (7) Shilling, J. E.; King, S. M.; Mochida, M.; Worsnop, D. R.; Martin, S. T. Mass Spectral Evidence That Small Changes in Composition Caused by Oxidative Aging Processes Alter Aerosol CCN Properties. J. Phys. Chem. A 2007, 111, 3358−3368. (8) Sciare, J.; d’Argouges, O.; Sarda-Estève, R.; Gaimoz, C.; Gros, V.; Zhang, Q. J.; Beekmann, M.; Sanchez, O. Comparison Between Simulated and Observed Chemical Composition of Fine Aerosols in Paris (France) during Springtime: Contribution of Regional versus Continental Emissions. Atmos. Chem. Phys. 2010, 10, 11987−12004. (9) Pisoni, E.; Carnevale, C.; Volta, M. Sensitivity to Spatial Resolution of Modeling Systems Designing Air Quality Control Policies. Environ. Modell. Softw. 2010, 25, 66−73. (10) Mochida, M.; Kitamori, Y.; Kawamura, K.; Nojiri, Y.; Suzuki, K. Fatty Acids in the Marine Atmosphere: Factors Governing Their Concentrations and Evaluation of Organic Films on Sea-Salt Particles. J. Geophys. Res. 2002, 107, 4325. (11) Oliveira, C.; Pio, C.; Alves, C.; Evtyugina, M.; Santos, P.; Gonçalves, V.; Nunes, T.; Silvestre, A. J. D.; Palmgren, F.; Wåhlin, P.; Harrad, S. Seasonal Distribution of Polar Organic Compounds in the Urban Atmosphere of Two Large Cities From the North and South of Europe. Atmos. Environ. 2007, 41, 5555−5570. (12) Tervahattu, H.; Hartonen, K.; Kerminen, V.-M.; Kupiainen, K.; Aarnio, P.; Koskentalo, T.; Tuck, A. F.; Vaida, V. New Evidence of an Organic Layer on Marine Aerosols. J. Geophys. Res. 2002, 107, 4053. (13) Tervahattu, H.; Juhanoja, J.; Kupiainen, K. Identification of an Organic Coating on Marine Aerosol Particles by TOF-SIMS. J. Geophys. Res. 2002, 107, 4319. (14) Nolte, C. G.; Schauer, J. J.; Cass, G. R.; Simoneit, B. R. Highly Polar Organic Compounds Present in Wood Smoke and in the Ambient Atmosphere. Environ. Sci. Technol. 2001, 35, 1912−1919. (15) Schauer, J. J.; Kleeman, M. J.; Cass, G. R.; Simoneit, B. R. T. Measurement of Emissions from Air Pollution Sources. 3. C1−C29 Organic Compounds from Fireplace Combustion of Wood. Environ. Sci. Technol. 2001, 35, 1716−1728. (16) Fine, P. M.; Cass, G. R.; Simoneit, B. R. Chemical Characterization of Fine Particle Emissions from Fireplace Combustion of Woods Grown in the Northeastern United States. Environ. Sci. Technol. 2001, 35, 2665−2675. (17) He, L.-Y.; Hu, M.; Huang, X.-F.; Yu, B.-D.; Zhang, Y.-H.; Liu, D.-Q. Measurement of Emissions of Fine Particulate Organic Matter from Chinese Cooking. Atmos. Environ. 2004, 38, 6557−6564. (18) Schauer, J. J.; Kleeman, M. J.; Cass, G. R.; Simoneit, B. R. Measurement of Emissions from Air Pollution Sources. 4. C1-C27 Organic Compounds from Cooking with Seed Oils. Environ. Sci. Technol. 2002, 36, 567−575. (19) He, L.-Y.; Hu, M.; Huang, X.-F.; Zhang, Y.-H.; Tang, X.-Y. Seasonal Pollution Characteristics of Organic Compounds in Atmospheric Fine Particles in Beijing. Sci. Total Environ. 2006, 359, 167. (20) Tervahattu, H.; Juhanoja, J.; Vaida, V.; Tuck, A. F.; Niemi, J. V.; Kupiainen, K.; Kulmala, M.; Vehkamäki, H. Fatty Acids on Continental Sulfate Aerosol Particles. J. Geophys. Res. 2005, 110, D06207. (21) Rogge, W. F.; Hildemann, L. M.; Mazurek, M. A.; Cass, G. R.; Simoneit, B. R. T. Sources of Fine Organic Aerosol. 2. Non-catalyst and Catalyst-Equipped Automobiles and Heavy-Duty Diesel Trucks. Environ. Sci. Technol. 1993, 27, 636−651. (22) Robinson, A. L.; Donahue, N. M.; Rogge, W. F. Photochemical Oxidation and Changes in Molecular Composition of Organic Aerosol in the Regional Context. J. Geophys. Res-Atmos. 2006, 111, D03302. (23) Robinson, A. L.; Subramanian, R.; Donahue, N. M.; BernardoBricker, A.; Rogge, W. F. Source Apportionment of Molecular Markers and Organic Aerosol. 3. Food Cooking Emissions. Environ. Sci. Technol. 2006, 40, 7820−7827. (24) Zahardis, J.; Petrucci, G. A. The Oleic Acid-Ozone Heterogeneous Reaction System: Products, Kinetics, Secondary

Chemistry, and Atmospheric Implications of a Model System: A Review. Atmos. Chem. Phys. 2007, 7, 1237−1274. (25) Thornberry, T.; Abbatt, J. P. D. Heterogeneous Reaction of Ozone with Liquid Unsaturated Fatty Acids: Detailed Kinetics and Gas-Phase Product Studies. Phys. Chem. Chem. Phys. 2004, 6, 84−93. (26) Nash, D. G.; Tolocka, M. P.; Baer, T. The Uptake of O3 by Myristic Acid−Oleic Acid Mixed Particles: Evidence for Solid Surface Layers. Phys. Chem. Chem. Phys. 2006, 8, 4468−4475. (27) Knopf, D. A.; Anthony, L. M.; Bertram, A. K. Reactive Uptake of O3 by Multicomponent and Multiphase Mixtures Containing Oleic Acid. J. Phys. Chem. A 2005, 109, 5579−5589. (28) Moise, T.; Rudich, Y. Reactive Uptake of Ozone by AerosolAssociated Unsaturated Fatty Acids: Kinetics, Mechanism, and Products. J. Phys. Chem. A 2002, 106, 6469−6476. (29) Katrib, Y.; Biskos, G.; Buseck, P. R.; Davidovits, P.; Jayne, J. T.; Mochida, M.; Wise, M. E.; Worsnop, D. R.; Martin, S. T. Ozonolysis of Mixed Oleic-Acid/Stearic-Acid Particles: Reaction Kinetics and Chemical Morphology. J. Phys. Chem. A 2005, 109, 10910−10919. (30) Katrib, Y.; Martin, S. T.; Hung, H.-M.; Rudich, Y.; Zhang, H.; Slowik, J. G.; Davidovits, P.; Jayne, J. T.; Worsnop, D. R. Products and Mechanisms of Ozone Reactions with Oleic Acid for Aerosol Particles Having Core−Shell Morphologies. J. Phys. Chem. A 2004, 108, 6686− 6695. (31) Gonzalez-Labrada, E.; Schmidt, R.; DeWolf, C. E. Kinetic Analysis of the Ozone Processing of an Unsaturated Organic Monolayer as a Model of an Aerosol Surface. Phys. Chem. Chem. Phys. 2007, 9, 5814−5821. (32) Hung, H.-M.; Ariya, P. Oxidation of Oleic Acid and Oleic Acid/ Sodium Chloride(aq) Mixture Droplets with Ozone: Changes of Hygroscopicity and Role of Secondary Reactions. J. Phys. Chem. A 2007, 111, 620−632. (33) Hung, H.-M.; Katrib, Y.; Martin, S. T. Products and Mechanisms of the Reaction of Oleic Acid with Ozone and Nitrate Radical. J. Phys. Chem. A 2005, 109, 4517−4530. (34) Hung, H.-M.; Tang, C.-W. Effects of Temperature and Physical State on Heterogeneous Oxidation of Oleic Acid Droplets with Ozone. J. Phys. Chem. A 2010, 114, 13104−13112. (35) Morris, J. W.; Davidovits, P.; Jayne, J. T.; Jimenez, J. L.; Shi, Q.; Kolb, C. E.; Worsnop, D. R.; Barney, W. S.; Cass, G. Kinetics of Submicron Oleic Acid Aerosols with Ozone: A Novel Aerosol Mass Spectrometric Technique. Geophys. Res. Lett. 2002, 29, 1357. (36) Sage, A. M.; Weitkamp, E. A.; Robinson, A. L.; Donahue, N. M. Reactivity of Oleic Acid in Organic Particles: Changes in Oxidant Uptake and Reaction Stoichiometry with Particle Oxidation. Phys. Chem. Chem. Phys. 2009, 11, 7951−7962. (37) Shiraiwa, M.; Pfrang, C.; Pöschl, U. Kinetic Multi-layer Model of Aerosol Surface and Bulk Chemistry (KM-SUB): the Influence of Interfacial Transport and Bulk Diffusion on the Oxidation of Oleic Acid by Ozone. Atmos. Chem. Phys. 2010, 10, 3673−3691. (38) Ziemann, P. J. Aerosol Products, Mechanisms, and Kinetics of Heterogeneous Reactions of Ozone with Oleic Acid in Pure and Mixed Particles. Faraday Discuss. 2005, 130, 469−490. (39) Dennis-Smither, B. J.; Hanford, K. L.; Kwamena, N.-O. A.; Miles, R. E. H.; Reid, J. P. Phase, Morphology, and Hygroscopicity of Mixed Oleic Acid/Sodium Chloride/Water Aerosol Particles before and after Ozonolysis. J. Phys. Chem. A 2012, 116, 6159−6168. (40) Vesna, O.; Sax, M.; Kalberer, M.; Gaschen, A.; Ammann, M. Product Study of Oleic Acid Ozonolysis as Function of Humidity. Atmos. Environ. 2009, 43, 3662−3669. (41) Horie, O.; Neeb, P.; Moortgat, G. K. Ozonolysis of Trans- and Cis-2-Butenes in Low Parts-per-Million Concentration Ranges. Int. J. Chem. Kinet. 1994, 26, 1075−1094. (42) Japar, S.; Wu, C.; Niki, H. Effect of Molecular Oxygen on the Gas Phase Kinetics of the Ozonolysis of Olefins. J. Phys. Chem. 1976, 80, 2057−2062. (43) Horie, O.; Moortgat, G. K. Gas-Phase Ozonolysis of Alkenes. Recent Advances in Mechanistic Investigations. Acc. Chem. Res. 1998, 31, 387−396. 9480



Article

(63) Hearn, J. D.; Smith, G. D. Kinetics and Product Studies for Ozonolysis Reactions of Organic Particles Using Aerosol CIMS. J. Phys. Chem. A 2004, 108, 10019−10029. (64) Broekhuizen, K. E.; Thornberry, T.; Kumar, P. P.; Abbatt, J. P. Formation of Cloud Condensation Nuclei by Oxidative Processing: Unsaturated Fatty Acids. J. Geophys. Res., Atmos. 2004, 109, D24206. (65) Smith, I. W. M.; Ravishankara, A. R. Role of Hydrogen-Bonded Intermediates in the Bimolecular Reactions of the Hydroxyl Radical. J. Phys. Chem. A 2002, 106, 4798−4807. (66) Hearn, J. D.; Lovett, A. J.; Smith, G. D. Ozonolysis of Oleic Acid Particles: Evidence for a Surface Reaction and Secondary Reactions Involving Criegee Intermediates. Phys. Chem. Chem. Phys. 2005, 7, 501−511. (67) Lee, A. K.; Chan, C. K. Single Particle Raman Spectroscopy for Investigating Atmospheric Heterogeneous Reactions of Organic Aerosols. Atmos. Environ. 2007, 41, 4611−4621.

(44) DeCarlo, P. F.; Kimmel, J. R.; Trimborn, A.; Northway, M. J.; Jayne, J. T.; Aiken, A. C.; Gonin, M.; Fuhrer, K.; Horvath, T.; Docherty, K. S.; et al. Field-Deployable, High-Resolution, Time-ofFlight Aerosol Mass Spectrometer. Anal. Chem. 2006, 78, 8281−8289. (45) Mendez, M.; Ciuraru, R.; Gosselin, S.; Batut, S.; Visez, N.; Petitprez, D. Reactivity of Chlorine Radical with Submicron Palmitic Acid Particles: Kinetic Measurements and Products Identification. Atmos. Chem. Phys. 2013, 13, 11661−11673. (46) Rader, D.; McMurry, P. Application of the Tandem Differential Mobility Analyzer to Studies of Droplet Growth or Evaporation. J. Aerosol Sci. 1986, 17, 771−787. (47) Helmig, D. Ozone Removal Techniques in the Sampling of Atmospheric Volatile Organic Trace Gases. Atmos. Environ. 1997, 31, 3635−3651. (48) Docherty, K. S.; Ziemann, P. J. On-Line, Inlet-Based Trimethylsilyl Derivatization for Gas Chromatography of Mono- and Dicarboxylic Acids. J. Chromatogr. A 2001, 921, 265−275. (49) Wang, X.; Luo, L.; Ouyang, G.; Lin, L.; Tam, N. F. Y.; Lan, C.; Luan, T. One-Step Extraction and Derivatization Liquid-Phase Microextraction for the Determination of Chlorophenols by Gas Chromatography−Mass Spectrometry. J. Chromatogr. A 2009, 1216, 6267−6273. (50) Zuo, Y.; Zhang, K.; Lin, Y. Microwave-Accelerated Derivatization for the Simultaneous Gas Chromatographic−Mass Spectrometric Analysis of Natural and Synthetic Estrogenic Steroids. J. Chromatogr. A 2007, 1148, 211−218. (51) Yu, J.; Flagan, R. C.; Seinfeld, J. H. Identification of Products Containing −COOH, −OH, and −CO in Atmospheric Oxidation of Hydrocarbons. Environ. Sci. Technol. 1998, 32, 2357−2370. (52) Aiken, A. C.; DeCarlo, P. F.; Jimenez, J. L. Elemental Analysis of Organic Species with Electron Ionization High-Resolution Mass Spectrometry. Anal. Chem. 2007, 79, 8350−8358. (53) Middlebrook, A. M.; Bahreini, R.; Jimenez, J. L.; Canagaratna, M. R. Evaluation of Composition-Dependent Collection Efficiencies for the Aerodyne Aerosol Mass Spectrometer Using Field Data. Aerosol Sci. Technol. 2012, 46, 258−271. (54) Jayne, J. T.; Leard, D. C.; Zhang, X.; Davidovits, P.; Smith, K. A.; Kolb, C. E.; Worsnop, D. R. Development of an Aerosol Mass Spectrometer for Size and Composition Analysis of Submicron Particles. Aerosol Sci. Technol. 2000, 33, 49−70. (55) Worsnop, D. R.; Zahniser, M. S.; Kolb, C. E.; Gardner, J. A.; Watson, L. R.; Van Doren, J. M.; Jayne, J. T.; Davidovits, P. The Temperature Dependence of Mass Accommodation of Sulfur Dioxide and Hydrogen Peroxide on Aqueous Surfaces. J. Phys. Chem. 1989, 93, 1159−1172. (56) Smith, J. D.; Kroll, J. H.; Cappa, C. D.; Che, D. L.; Liu, C. L.; Ahmed, M.; Leone, S. R.; Worsnop, D. R.; Wilson, K. R. The Heterogeneous Reaction of Hydroxyl Radicals with Sub-Micron Squalane Particles: A Model System for Understanding the Oxidative Aging of Ambient Aerosols. Atmos. Chem. Phys. 2009, 9, 3209−3222. (57) Hanson, D. R. Surface-Specific Reactions on Liquids. J. Phys. Chem. B 1997, 101, 4998−5001. (58) Seinfeld, J. H.; Pandis, S. N. Atmospheric Chemistry and Physics: From Air Pollution to Climate Change; John Wiley & Sons: New York, 2012. (59) Pfrang, C.; Shiraiwa, M.; Pöschl, U. Chemical Ageing and Transformation of Diffusivity in Semi-solid Multi-component Organic Aerosol Particles. Atmos. Chem. Phys. 2011, 11, 7343−7354. (60) Smith, G. D.; Woods, E.; DeForest, C. L.; Baer, T.; Miller, R. E. Reactive Uptake of Ozone by Oleic Acid Aerosol Particles: Application of Single-Particle Mass Spectrometry to Heterogeneous Reaction Kinetics. J. Phys. Chem. A 2002, 106, 8085−8095. (61) Kuwata, M.; Zorn, S. R.; Martin, S. T. Using Elemental Ratios to Predict the Density of Organic Material Composed of Carbon, Hydrogen, and Oxygen. Environ. Sci. Technol. 2012, 46, 787−794. (62) DeCarlo, P. F.; Slowik, J. G.; Worsnop, D. R.; Davidovits, P.; Jimenez, J. L. Particle Morphology and Density Characterization by Combined Mobility and Aerodynamic Diameter Measurements. Part 1: Theory. Aerosol Sci. Technol. 2004, 38, 1185−1205. 9481


Reactive and Nonreactive Ozone Uptake during Aging of Oleic Acid

Recommend Documents