Parameterization of Thermal Properties of Aging ... - ACS Publications

Article pubs.acs.org/est

Parameterization of Thermal Properties of Aging Secondary Organic Aerosol Produced by Photo-Oxidation of Selected Terpene Mixtures Eva U. Emanuelsson,†,# Thomas F. Mentel,‡ Ågot K. Watne,† Christian Spindler,‡ Birger Bohn,‡ Theo Brauers,‡ Hans-Peter Dorn,‡ Åsa M. Hallquist,§ Rolf Has̈ eler,‡ Astrid Kiendler-Scharr,‡ Klaus-Peter Müller,‡ Håkan Pleijel,⊥ Franz Rohrer,‡ Florian Rubach,‡ Eric Schlosser,‡,∥ Ralf Tillmann,‡ and Mattias Hallquist*,† †

Atmospheric Science, Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg S-405 30, Sweden Institut für Energie und Klimaforschung, IEK-8, Forschungszentrum Jülich, Jülich 52425, Germany § IVL Swedish Environmental Institute, Gothenburg, Sweden ⊥ Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg S-405 30, Sweden ‡

S Supporting Information *

ABSTRACT: Formation and evolution of secondary organic aerosols (SOA) from biogenic VOCs influences the Earth’s radiative balance. We have examined the photo-oxidation and aging of boreal terpene mixtures in the SAPHIR simulation chamber. Changes in thermal properties and chemical composition, deduced from mass spectrometric measurements, were providing information on the aging of biogenic SOA produced under ambient solar conditions. Effects of precursor mixture, concentration, and photochemical oxidation levels (OH exposure) were evaluated. OH exposure was found to be the major driver in the long term photochemical transformations, i.e., reaction times of several hours up to days, of SOA and its thermal properties, whereas the initial concentrations and terpenoid mixtures had only minor influence. The volatility distributions were parametrized using a sigmoidal function to determine TVFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. TVFR0.5 increased by 0.3 ± 0.1% (ca. 1 K), while the steepness increased by 0.9 ± 0.3% per hour of 1 × 106 cm−3 OH exposure. Thus, aging reduces volatility and increases homogeneity of the vapor pressure distribution, presumably because highly volatile fractions become increasingly susceptible to gas phase oxidation, while less volatile fractions are less reactive with gas phase OH.

■

INTRODUCTION Atmospheric aerosols significantly influence the Earth’s radiation balance, both directly by absorbing and scattering light, and indirectly by influencing the formation and properties of clouds.1 Secondary organic aerosol (SOA) is produced from atmospheric oxidation of organic trace gases, with subsequent gas-to-particle conversion.2 An important source of SOA is the gas phase oxidation of biogenic volatile organic compounds (BVOC), which include a vast range of compounds emitted from various ecosystems. Both the composition and concentration of SOA depend on numerous factors, such as temperature, humidity, nutrient supplies in source ecosystems, and solar radiation.3,4 Quantification of SOA and elucidation of its formation and transformation mechanisms is difficult due to its complexity, but essential in order to improve air quality and climate models. Thus, there has been substantial interest in biogenic SOA (BSOA) formation, with considerable focus on the emission, transformation, and SOA-forming potential of monoterpenes, such as α-pinene, β-pinene, Δ3-carene, and limonene.2,5 Sesquiterpenes have also attracted some attention, © 2014 American Chemical Society

and to a lesser extent, the monoterpene ocimene, arising from stress-induced emissions.2,6 During photo-oxidation of BVOC, volatile hydrocarbons are transformed to low volatility multioxygenated compounds, thereby initiating BSOA formation. Aerosol transformation processes have been addressed in several recent studies,7−13 and several processes (physical and chemical) have been identified that may transform an organic aerosol during its lifetime in the atmosphere.2,7,14 In addition to these processes, semivolatile compounds continuously partition between the gaseous and condensed phases, and as long as the source of low volatility gaseous compounds is present, SOA will continue to form. Another possibility is fragmentation of compounds generating smaller fragments with higher volatility. Thus, the size distribution of SOA particles and its composition Received: Revised: Accepted: Published: 6168

December 4, 2013 May 5, 2014 May 8, 2014 May 8, 2014 dx.doi.org/10.1021/es405412p | Environ. Sci. Technol. 2014, 48, 6168−6176

Environmental Science & Technology

Article

system that can be fully opened or completely closed. Photochemistry within the chamber is trigged by natural solar radiation. The pressure inside the chamber is held at 40 Pa above ambient pressure to avoid contamination with outside air. Losses due to sampling and small leaks are compensated by a replenishment flow of about 15 m3 h−1 of clean air, which dilutes all constituents by about 5% h−1. A flow controller monitors the dilution rate. In addition to VTDMA, Q-AMS and T-AMS, the chamber is equipped with a suite of analytical instruments. These allowed determinations of: ozone (chemiluminescence), OH radicals (differential optical absorption spectroscopy, DOAS), NOx (chemiluminescence), hydrocarbons by gas chromatography, proton transfer reaction-mass spectrometry (GC- and PTR-MS), and physical properties of aerosols, such as particle number size distributions (scanning mobility particle sizer, SMPS). The standard VTDMA setup has three main parts.23,24 First, there is an initial differential mobility analyzer (DMA), where a nearly monodisperse fraction of the aerosol particles (typically 100 or 150 nm) is selected. Second, the aerosol flow (300 mL min −1 ) enters one of four parallel ovens (thermodenuders = TD) that includes a heating module (a 50 cm stainless steel tube mounted in an aluminum block with a heating element, 2.8 s residence time, assuming plug-flow conditions) and an adsorption section (activated charcoal diffusion scrubbers), where the volatile fraction is evaporated and adsorbed. Here, the temperature of the ovens was set between 298 and 573 K. Finally, the residual particle size distribution is measured with an SMPS. Precision of a typical tandem-DMA can be around 0.3%, corresponding to diameter changes of 0.03−0.6 nm. 25 The upper limit on the reproducibility of VTDMA measurements using the current system has been estimated to be 1.6% (in normalized modal particle diameter) using repeated SOA production in a smog chamber.23 For consistency, in the presented study, two replicates were measured at each temperature. It took 2 h to obtain a full temperature range characterization (298−573 K in 20 K intervals). From the initial SOA particle mode diameter (Dref), determined at a reference temperature of 298 K, and the final particle mode diameter (DT) after evaporation at an elevated temperature T, the Volume Fraction Remaining (VFR) at a specific temperature can be determined. Assuming spherical particles, the VFR at temperature T is given by VFR(T) = (DT/Dref)3. A sigmoidal curve was fitted to the VFR data acquired in each experiment over the entire temperature range, given by the following:26

continuously change. After formation, either from nucleation or partitioning/condensation on a pre-existing aerosol, evaporation of volatile compounds can occur due to dilution or temperature variations.15,16 Compounds with sufficient saturation vapor pressures to exist in the gas phase can be transformed by gas-phase oxidation (e.g., by OH) into compounds that mostly contribute to the condensed phase.8,11 This type of oxidation can be deduced from increases in the oxygen content of the aerosol particles. Other important processes in the aging of SOA include oligomerization of semivolatiles and other heterogeneous or condensed phase reactions resulting in macromolecules with high molar mass and low volatility.17,18 These processes do not necessarily increase the oxygen content of the SOA.14,19 However, increases in either the oxygen content of SOA or molar masses of its molecular components will lead to aerosol fractions with lower volatility. The volatility of aerosol particles thus reflects changes in the chemical composition of both the condensed and gaseous phases. To verify postulated atmospheric processes, assess their importance, and accurately incorporate them into air quality and climate models, field observations and laboratory experiments are essential.20 Large reaction chambers are valuable for these purposes, as they allow repeatable analysis of atmospheric processes under controlled conditions. For example, temperature, pressure, light, or gas composition settings can be maintained for days at a time. Thus, studies in reaction chambers, evaluated using experimentally derived reaction kinetics and mechanisms, provide most of the data currently used to elucidate and model SOA formation and transformation.2,7,19 Here, we present results of photochemical experiments conducted in the outdoor chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). This chamber enables long residence times (several days), the use of gas concentrations down to ambient conditions, and natural solar radiation. The main aim of the study was to acquire more insights into the formation of SOA from terpenoids emitted from the boreal forest. More specifically: to determine and parametrize the main driving processes of SOA aging as reflected in its thermal and chemical properties for mixtures containing the main VOC observed in the emissions from the boreal forest.21

■

EXPERIMENTAL SECTION As part of the EUCAARI-project (European integrated project on aerosol cloud climate and air quality interactions) the photochemical formation and aging of BSOA driven by oxidation of BVOC mixtures (mono- and sesquiterpenes) were investigated using the SAPHIR chamber at the Forschungszentrum Jülich, Germany. The thermal properties and composition of the generated SOA were monitored using a volatility tandem differential mobility analyzer (VTDMA), and two aerosol mass spectrometers (AMS): a Quadrupole-AMS (Q-AMS) and a time-of-flight AMS (T-AMS), both supplied by Aerodyne. The SOA was formed from the precursor compounds by reaction with ozone and OH radicals and then exposed to natural solar radiation and OH radicals for up to three days to initiate close-to-natural chemical aging. The SAPHIR chamber has been extensively described in previous publications.8,22 Briefly, it consists of a 270 m3 cylindrical, double-walled FEP-Teflon chamber. It is used for atmospheric photo-oxidation simulations with near ambient concentrations of reactants. The chamber has a louvre shading

VFRT = VFR min +

(VFR max − VFR min) 1+

(

Tposition S VFR T

)

(1)

The exponent SVFR and the parameter Tposition determine the steepness (“slope factor”), and midposition of the symmetric sigmoidal curve, respectively. VFRmax and VFRmin represent the highest and lowest VFRs, respectively. In order to obtain the best fit to the data, VFRmax and VFRmin were not restricted a priori. Generally, VFRmax was close to 1 and VFRmin was close to zero. From this equation, the temperature at which VFR is 0.5 (TVFR0.5) can be readily calculated. TVFR0.5 is a general measure of volatility, which is inversely correlated to the volatility of aerosol particles. The slope factor SVFR is a measure of the distribution of the constituent particles’ volatilities. A steep slope indicating a narrow saturation vapor 6169

dx.doi.org/10.1021/es405412p | Environ. Sci. Technol. 2014, 48, 6168−6176


Article

pressure distribution of the analyzed aerosol’s major constituents. Generally, measurements of the VFR over the full range of evaporation temperatures were taken at the end of each experiment day. In an AMS (here, either Q-AMS or T-AMS), the aerosol particles are focused via an aerodynamic lens, before entering the vacuum. The size of the particles is determined in the particle time-of-flight region (PToF). The particles are evaporated at a heated surface (∼900 K) and subjected to Electron Impact (EI) ionization at 70 eV before entering either the quadrupole (Q-AMS) or time-of-flight (T-AMS) mass spectrometer. The high temperature and energy used in the ionization step results in significant fragmentation of the organic aerosol (OA) fraction, which provides a standardized fragmentation pattern that can be related to changes in the particles’ chemical composition. The T-AMS has sufficient mass resolution to resolve different organic fragments (CxHy, CxHyOz) with the same nominal mass to charge ratio, thus allowing elemental analysis and calculation of O/C ratios. In this work, the T-AMS was used to monitor the chemical composition of the aerosol particles in the chamber and the acquired data were used as a reference for the Q-AMS measurements. The Q-AMS measures mass spectra and chemically resolved size distributions of aerosol particles with unit mass resolution and a time resolution of minutes. Both the Q-AMS and T-AMS measured f44 and f43, the signal fractions at m/z = 44 (CO2+) and m/z = 43 (C2H3O+ and C3H7+) in the total organic mass spectrum, respectively. The fractions f44 and f43 are proxies for carboxylic groups, indicating oxidized, more aged, less volatile SOA components and carbonylic groups, indicating fresh, less oxidized, semi volatile SOA components, respectively.27 The Q-AMS was operated behind the thermodenuder (TD) of the VTDMA system, enabling measurements of the particles’ chemical composition as a function of evaporation temperatures (TD-AMS setup). Due to the low aerosol masses, the first DMA was bypassed when Q-AMS was used. The mass spectra of the organic aerosol particles were measured at a reference temperature of 298 K and then at additional elevated temperatures, typically 348 and 398 K. The investigated SOA had rather narrow size distributions (GSD ≈ 1.3), still allowing detection of small changes in the aerosol peak diameter. In order to avoid differences in oven residence time relative to those in the VTDMA setup, an extra flow of clean air (80 mL min−1) was added downstream from the oven unit (before the split to SMPS and Q-AMS) to compensate for the sample flow of the Q-AMS. During these TD-AMS measurements, both the SMPS and Q-AMS were used as detectors and provided VFR and mass fraction remaining (MFR) estimates based on the aerosol volume and mass, respectively. In the SAPHIR chamber, the OH-concentration varies with the diurnal cycle of the actinic flux and by passing clouds (e.g., JHONO in Figure 1). To characterize the photochemical oxidation level, the OH exposure concept was utilized. The OH exposure is given by the integral of the OH concentration over time. This gives the cumulative OH concentrations that the gases, vapors and particles were exposed to at any given time during the experiments. For example, 1 h of exposure to a typical atmospheric OH concentration of 1 × 106 cm−3 results in an OH exposure of 3.6 × 109 cm−3 s. DOAS was used to measure the concentration of hydroxyl radicals (OH) in the chamber.28 The trueness of the OH-DOAS instrument is 6%, and its precision is 8 × 105 OH cm−3 (in 200 s, 1σ).29 In the

Figure 1. Changes in concentrations of indicated components and variables during photo-oxidation of the “BMT+SQT high” terpene mixture (see Table 1). The periods when the roof was open are indicated in beige. The colored lines indicate concentrations/values of ozone (purple), terpene (black), JHONO (red), particle mass (morg) (dark green), f43 (dark blue), f44 (pale blue), O/C ratio (pale green), and median particle diameter, Dp (pink).

SAPHIR chamber, OH radicals are predominantly formed by the photolysis of nitrous acid (HONO) from the walls, with minor contributions from ozone-mediated photolysis.22 The aerosol precursor compounds were selected to represent emissions from boreal forests with typical mixtures of monoand sesquiterpenes. Three sets of terpene mixtures were used: a reference set of five monoterpenes, with equal molar proportions of α-pinene, β-pinene, limonene, Δ3-carene, and ocimene (designated BMT); BMT with ocimene omitted (BMT−Oce); and BMT with the addition of equal molar amounts of two representative sesquiterpenes, β-caryophyllene and α-farnesene, to a BMT/SQT molar ratio of 9:1 (BMT +SQT). In all experiments reported here except one (in which the chamber roof was closed for the entire duration and ozone was used as an oxidant) the terpenes were added to the humidified chamber in the dark (i.e., with the roof closed). Their initial concentrations, measured over a period of 2 h, were allowed to stabilize. Ozone was then added, and the roof was immediately opened, thus initiating photo-oxidation. The roof was closed in the evening of the first day of the experiment, and opened again in the morning of the second day. In all experiments the NOx concentration was 90) contributed more to the aerosol at the high temperature.

Figure 2. VFR, measured at indicated evaporation temperatures, of aerosols generated in experiments with (a) the BMT high concentration mixture with three OH exposures (3.5 × 1010, 1.3 × 1010, and 0 cm−3 s in the sunny, cloudy, and dark experiments, respectively) and (b) the BMT−Oce mixture at high (1000−1100 ppbC) and medium concentrations (500−600 ppbC) with similar OH exposures: 1.79 × 1010 and 2.08 × 1010 cm−3 s, respectively. The lines are sigmoidal fittings to the data.

■

DISCUSSION The volatility of SOA produced in the SAPHIR chamber has been described in two previous studies.8,30 Salo et al. investigated the photo-oxidation of α-pinene and general evolution of the VFR of resulting SOA with time during a three day experiment.8 The general features observed for α-pinene are comparable to the boreal mixtures investigated in the present study. For a direct comparison of the thermal properties, the sigmoidal fitting was applied to the α-pinene experiment and is presented in Figure 3b. The derived TVFR0.5 is lower (4−5 K) than for the complex mixtures. The effect on OH exposure is comparable to the mixed cases, during the first two days (the data points up to 4 × 1010 cm−3 s), while the response to OH exposure is lower for day three. The lower initial TVFR0.5 is attributed to the fact that the α-pinene ozonolysis generally produces more volatile SOA compared to, e.g., limonene.14 In the mixtures, compounds with high SOA potential will contribute more to the initial SOA and dominate their thermal properties. The attenuation of the OH exposure effect on the third day for the α-pinene case is an effect of the reduced amount of organic material left in the chamber (1.6 μg m−3). It should be noted that in the data matrix for the complex mixtures presented in Table 1, there is no general sign of an attenuation of the OH exposure effect as a function of aerosol loading. A priori, one expects significant effects of composition and precursor concentration related to the partitioning of semivolatile compounds at higher precursor

(383 K). Figure 3b further illustrates the relationship between OH exposure and thermal properties, using the parameters TVFR0.5 and the slope factor (SVFR) derived from fitting eq 1 to the VFR data. TVFR0.5 clearly increased with the OH exposure, in accordance with expectations since OH radical-induced aging reduces aerosols’ volatility. In contrast, the slope factor decreased with OH exposure, resulting in a steeper slope. Thus, the saturation vapor pressures of the aerosols’ major constituents became more homogeneous. This trend is also reflected in the increasing slope of the linear relationship between the VFR and OH exposure with decreasing evaporation temperature, cf. Table 2 and Figure 3a. A plausible explanation for these observations is that vapors with a significant portion in the gas phase at a given time are oxidized more efficiently with OH radicals than low volatility compounds. This acts to increase VFRs at lower evaporation temperatures more rapidly compared to those at higher temperatures, resulting in a more compressed shape of the curves, e.g., those shown in Figure 2, providing a higher TVFR0.5 and a more negative SVFR, i.e., lower and narrower distribution of vapor pressures of the SOA constituents. Analogously to the thermal properties, the chemical composition, as measured by the T-AMS, was primarily 6172



Article

Figure 3. Effects of OH exposure. The lines represent the linear relationships described in Table 2. (a) VFR at selected absolute temperatures; (b) the parameters TVFR0.5 and SVFR derived from sigmoidal fits to VTDMA data; (c) the aerosol chemical properties (O/C, f44 and f43) derived from T-AMS measurements; and (d) the mass fraction remaining (MFR) at m/z = 44 and 43 after evaporation in the TD, versus the OH exposure. Dotted lines are for 43MFR, whereas solid lines are for 44MFR.

Table 2. Linear Relationships between Thermal Properties and OH Exposurea parameter VFR(343 K) VFR(363 K) VFR(383 K) VFR(423 K) VFR(463 K) TVFR0.5 SVFR 43MFR(348 K) 44MFR(348 K) 43MFR(398 K) 44MFR(398 K)

slope 2.58 2.42 2.13 1.80 0.96 3.20 −2.76 6.27 8.46 6.82 8.00

± ± ± ± ± ± ± ± ± ± ±

0.34 0.28 0.26 0.29 0.10 0.56 0.88 1.08 1.28 0.80 1.03

× × × × × × × × × × ×

−12

10 10−12 10−12 10−12 10−12 10−10 10−11 10−12 10−12 10−12 10−12

3

(cm (cm3 (cm3 (cm3 (cm3 (cm3 (cm3 (cm3 (cm3 (cm3 (cm3

−1

s ) s−1) s−1) s−1) s−1) s−1 K) s−1) s−1) s−1) s−1) s−1)

intercept

R2

± ± ± ± ± ± ± ± ± ± ±

0.72 0.70 0.72 0.64 0.74 0.73 0.45 0.49 0.55 0.74 0.70

0.774 0.607 0.460 0.214 0.083 378.4 −11.06 0.669 0.654 0.210 0.230

0.012 0.010 0.010 0.010 0.005 2.0 (K) 0.31 0.024 0.029 0.016 0.021

relative change per hour (%) 1.2 1.4 1.7 3.0 4.2 0.3 0.9 3.4 4.7 11.7 12.5

± ± ± ± ± ± ± ± ± ± ±

0.2 0.2 0.2 0.5 0.5 0.1 0.3 0.6 0.7 1.6 2.0

a

The MFR is the mass fraction at m/z = 44 and 43 remaining after evaporation. Also shown are the relative changes in each parameter assuming exposure to OH radicals at a concentration of 1 × 106 cm−3 for one hour.

concentrations.31 This is probably also the case here for the first hours of oxidation during fast formation of semivolatile compounds; however, during the long-term photo-oxidation, it was clearly demonstrated that the OH exposure is the main driver in processing organic compounds into low volatile material. Recently, Emanuelsson et al.30 presented SOA volatility data obtained from experiments where aromatic SOA precursors, typically emitted from anthropogenic sources, were mixed with limonene and α-pinene. Again, the OH exposure was very important for the aging, but here the aromatics had an additional effect on the long-term thermal properties. Apparently, after a few hours of photo-oxidation, the

thermal properties of SOA from investigated BVOC mixtures are more homogeneous compared to aromatic compounds that are known to produce small reactive entities that might be susceptible for heterogeneous chemistry.32 The effects of OH exposure on both TVFR0.5 and SVFR were pronounced and for the data shown in Figure 3b gave R2 = 0.73 and 0.45, respectively, assuming a linear relationship. For TVFR0.5 this assumption is further strengthen by intraexperimental relationship, where the increases between first and second day are scaled by OH exposure with a similar trend to the overall linear relationship (Table 1, and illustrated by SI Figure S1). Regarding SVFR the scatter is larger but consistent 6173



Article

NOx < 2 ppb as prevailing in forest areas. Furthermore, using the changes in parameters for TVFR0.5 and SVFR, we estimate that this correspond to a lowering of effective saturation vapor pressure by 15% per hour of 1 × 106 OH exposure. Here the so-called effective saturation vapor pressures were calculated using several assumptions but in general following the procedure for determination of saturation vapor pressures from pure compounds using the VTDMA technique and using the input data for pinonic acid, as representative of a BSOA constituent.24 Utilizing this or similar procedures the derived relationships between changes in thermal properties and OH exposure, can now be used either integrated or in comparison to current aging algorithms in air quality models,36,37 e.g., as an extension to Volatility Basis Sets derived from smog chamber studies.38

Figure 4. Difference between normalized mass spectra at 398 and 298 K obtained from analysis of the SOA in the first day of the experiment denoted “BMT high sunny” (Table 1) as an illustration of the general behavior. High temperature exposure of SOA affects all m/z fractions, but the most pronounced effect is a general increase in heavy fragments (m/z > 90).

■

(see SI Figure S2). Aerosol loading is from a partitioning perspective expected to influence thermal properties. However, with similar analysis as for OH exposure, rather poor correlations were obtained (R2 = 0.29 (TVFR0.5) and 0.16 (SVFR)) between aerosol loading and thermal properties. This again is illustrating that the OH exposure is the most important driver for the long-term changes in thermal properties during photo-oxidation. After evaporation, the Q-AMS mass spectra of the residual particles showed all features indicative of a less volatile material remaining. But the overall change was not as clear as would be expected if specific groups of compounds would determine volatility.33 This may be due to the experimental limitations of the Q-AMS with high degree of fragmentation at low mass resolution, however other mechanisms may also play a role. The trend seems to be consistent with the previous findings by Cappa and Wilson34 that temperature has little effect on the mass spectra of SOA generated from α-pinene. This may be because aerosols produced by oxidation of terpenes have high viscosity, and thus mass transfer restricts specific compound preferences in the evaporation. The effect of viscosity could change depending on how the aerosol is produced and may explain the difference from the study of Kostenidou et al.,33 where a variation in mass spectra with evaporation temperature was observed. Furthermore, Cappa and Wilson 34 also evaporated lubrication oil and did observe a mass spectral difference. Here the lower m/z peaks, corresponding to compounds with higher saturation vapor pressures, disappear more rapidly than the high m/z peaks upon heating. A key question is how the observed changes are related to aging in the real atmosphere. Recently, Ng et al.27 presented an overview of AMS measurements taken in different environments capturing the transformation from a fresh to an aged aerosol. Our data are within ranges of measured variables for a typical atmospheric oxidized organic aerosol (OOA), although the changes due to aging are relatively small. The f44 values we obtained (0.048 to 0.108, for an OH exposure of 6 × 1010 cm−3 s; Figure 3c) are well within the range of the previously reported f44 values for BSOA from plant emissions (0.097 ± 0.034) and roughly consistent with ambient observations (0.088).35 The corresponding values for f43 range from 0.108 to 0.125. Nevertheless, the trends are consistent with a transition toward an atmospheric aged aerosol and there is a clear trend in 44/43 versus TVFR0.5 (SI Figure S3). Table 2 reports the relative changes in critical variables, including 44MFR and 43MFR, per hour at an OH radical concentration of 1 × 106 cm−3. This allows predictions of the evolution (calculated from OH exposure) of BSOA thermal properties, i.e., provides a measure of aging, applicable for conditions of

ASSOCIATED CONTENT

S Supporting Information *

The effect of OH exposure on thermal property TVFR0.5 for all experimental conditions (Figure S1); the effect of OH exposure on thermal property SVFR for all experimental conditions (Figure S2); and the relation between m/z 44/43 and the thermal property TVFR0.5 (Figure S3). This material is available free of charge via the Internet at http://pubs.acs.org/

■

AUTHOR INFORMATION

Corresponding Author

*Phone: +46 31 7869019; e-mail: [email protected]. Present Addresses ∥

Institute for Meteorology and Climate Research, Atmospheric Aerosol Research, Karlsruhe Institute of Technology, Karlsruhe, Germany. # Department of Chemistry, Aarhus University, Aarhus, Denmark. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the SAPHIR team at FZJ for their support during the measurement campaign. This work was financially supported by FP6 project EUCAARI (Contract No. 34684), the Swedish research council Formas (Grant No. 214-2010-1756), ACCENT (Contract No. 505337), and Tellus: The Centre of Earth Systems Science at the University of Gothenburg. E.U.E. acknowledges support from The Royal Swedish Academy of Agriculture and Forestry and from the Royal and Hvitfeldtska foundation.

■

REFERENCES

(1) Lohmann, U.; Rotstayn, L.; Storelvmo, T.; Jones, A.; Menon, S.; Quaas, J.; Ekman, A. M. L.; Koch, D.; Ruedy, R. Total aerosol effect: radiative forcing or radiative flux perturbation? Atmos. Chem. Phys. 2010, 10 (7), 3235−3246. (2) Hallquist, M.; Wenger, J. C.; Baltensperger, U.; Rudich, Y.; Simpson, D.; Claeys, M.; Dommen, J.; Donahue, N. M.; George, C.; Goldstein, A. H.; Hamilton, J. F.; Herrmann, H.; Hoffmann, T.; Iinuma, Y.; Jang, M.; Jenkin, M. E.; Jimenez, J. L.; Kiendler-Scharr, A.; Maenhaut, W.; McFiggans, G.; Mentel, T. F.; Monod, A.; Prevot, A. S. H.; Seinfeld, J. H.; Surratt, J. D.; Szmigielski, R.; Wildt, J. The formation, properties and impact of secondary organic aerosol: current and emerging issues. Atmos. Chem. Phys. 2009, 9 (14), 5155−5236. (3) Schurgers, G.; Arneth, A.; Holzinger, R.; Goldstein, A. H. Process-based modelling of biogenic monoterpene emissions combin-

6174



Article

ing production and release from storage. Atmos. Chem. Phys. 2009, 9 (10), 3409−3423. (4) Penuelas, J.; Staudt, M. BVOCs and global change. Trends Plant Sci. 2010, 15 (3), 133−144. (5) Jonsson, A. M.; Hallquist, M.; Ljungstrom, E. Impact of humidity on the ozone initiated oxidation of limonene, Δ3-carene, and α-pinene. Environ. Sci. Technol. 2006, 40 (1), 188−194. (6) Griffin, R. J.; Cocker, D. R.; Flagan, R. C.; Seinfeld, J. H. Organic aerosol formation from the oxidation of biogenic hydrocarbons. J. Geophys. Res. Atmos. 1999, 104 (D3), 3555−3567. (7) Donahue, N. M.; Henry, K. M.; Mentel, T. F.; Kiendler-Scharr, A.; Spindler, C.; Bohn, B.; Brauers, T.; Dorn, H. P.; Fuchs, H.; Tillmann, R.; Wahner, A.; Saathoff, H.; Naumann, K. H.; Mohler, O.; Leisner, T.; Muller, L.; Reinnig, M. C.; Hoffmann, T.; Salo, K.; Hallquist, M.; Frosch, M.; Bilde, M.; Tritscher, T.; Barmet, P.; Praplan, A. P.; DeCarlo, P. F.; Dommen, J.; Prevot, A. S. H.; Baltensperger, U. Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions. Proc. Natl. Acad. Sci. U.S.A 2012, 109 (34), 13503−13508. (8) Salo, K.; Jonsson, A. M.; Hallquist, M.; Saathoff, H.; Naumann, K.-H.; Spindler, C.; Tillmann, R.; Fuchs, H.; Bohn, B.; Rubach, F.; Mentel, T. F.; Müller, L.; Reinnig, M.; Hoffmann, T.; Donahue, N. M. Volatility of secondary organic aerosol during OH radical induced aging. Atmos. Chem. Phys. 2011, 8 (11), 11055−11067. (9) Alfarra, M. R.; Hamilton, J. F.; Wyche, K. P.; Good, N.; Ward, M. W.; Carr, T.; Barley, M. H.; Monks, P. S.; Jenkin, M. E.; Lewis, A. C.; McFiggans, G. B. The effect of photochemical aging and initial precursor concentration on the composition and hygroscopic properties of β-caryophyllene secondary organic aerosol. Atmos. Chem. Phys. 2012, 12 (14), 6417−6436. (10) Henry, K. M.; Donahue, N. M. Photochemical aging of α-pinene secondary organic aerosol: Effects of OH radical sources and photolysis. J. Phys. Chem. A 2012, 116 (24), 5932−5940. (11) Muller, L.; Reinnig, M. C.; Naumann, K. H.; Saathoff, H.; Mentel, T. F.; Donahue, N. M.; Hoffmann, T. Formation of 3-methyl1,2,3-butanetricarboxylic acid via gas phase oxidation of pinonic acid a mass spectrometric study of SOA aging. Atmos. Chem. Phys. 2012, 12 (3), 1483−1496. (12) Sato, K.; Takami, A.; Kato, Y.; Seta, T.; Fujitani, Y.; Hikida, T.; Shimono, A.; Imamura, T. AMS and LC/MS analyses of SOA from the photooxidation of benzene and 1,3,5-trimethylbenzene in the presence of NOx: Effects of chemical structure on SOA aging. Atmos. Chem. Phys. 2012, 12 (10), 4667−4682. (13) Yasmeen, F.; Vermeylen, R.; Maurin, N.; Perraudin, E.; Doussin, J. F.; Claeys, M. Characterisation of tracers for aging of α-pinene secondary organic aerosol using liquid chromatography/negative ion electrospray ionisation mass spectrometry. Environ. Chem. 2012, 9 (3), 236−246. (14) Kroll, J. H.; Donahue, N. M.; Jimenez, J. L.; Kessler, S. H.; Canagaratna, M. R.; Wilson, K. R.; Altieri, K. E.; Mazzoleni, L. R.; Wozniak, A. S.; Bluhm, H.; Mysak, E. R.; Smith, J. D.; Kolb, C. E.; Worsnop, D. R. Carbon oxidation state as a metric for describing the chemistry of atmospheric organic aerosol. Nat. Chem. 2011, 3 (2), 133−139. (15) Saathoff, H.; Naumann, K. H.; Mohler, O.; Jonsson, Å. M.; Hallquist, M.; Kiendler-Scharr, A.; Mentel, T. F.; Tillmann, R.; Schurath, U. Temperature dependence of yields of secondary organic aerosols from the ozonolysis of α-pinene and limonene. Atmos. Chem. Phys. 2009, 9 (5), 1551−1577. (16) Pathak, R. K.; Stanier, C. O.; Donahue, N. M.; Pandis, S. N. Ozonolysis of α-pinene at atmospherically relevant concentrations: Temperature dependence of aerosol mass fractions (yields). J. Geophys. Res. Atmos. 2007, 112, D3. (17) Gao, S.; Keywood, M.; Ng, N. L.; Surratt, J.; Varutbangkul, V.; Bahreini, R.; Flagan, R. C.; Seinfeld, J. H. Low-molecular-weight and oligomeric components in secondary organic aerosol from the ozonolysis of cycloalkenes and α-pinene. J. Phys. Chem. A 2004, 108 (46), 10147−10164. (18) Kalberer, M.; Paulsen, D.; Sax, M.; Steinbacher, M.; Dommen, J.; Prevot, A. S. H.; Fisseha, R.; Weingartner, E.; Frankevich, V.;

Zenobi, R.; Baltensperger, U. Identification of polymers as major components of atmospheric organic aerosols. Science 2004, 303 (5664), 1659−1662. (19) Kroll, J. H.; Seinfeld, J. H. Chemistry of secondary organic aerosol: Formation and evolution of low-volatility organics in the atmosphere. Atmos. Environ. 2008, 42 (16), 3593−3624. (20) Fiore, A. M.; Naik, V.; Spracklen, D. V.; Steiner, A.; Unger, N.; Prather, M.; Bergmann, D.; Cameron-Smith, P. J.; Cionni, I.; Collins, W. J.; Dalsoren, S.; Eyring, V.; Folberth, G. A.; Ginoux, P.; Horowitz, L. W.; Josse, B.; Lamarque, J. F.; MacKenzie, I. A.; Nagashima, T.; O’Connor, F. M.; Righi, M.; Rumbold, S. T.; Shindell, D. T.; Skeie, R. B.; Sudo, K.; Szopa, S.; Takemura, T.; Zeng, G. Global air quality and climate. Chem. Soc. Rev. 2012, 41 (19), 6663−6683. (21) Tarvainen, V.; Hakola, H.; Rinne, J.; Hellén, H.; Haapanala, S. Towards a comprehensive emission inventory of terpenoids from boreal ecosystems. Tellus B-Chem. Phys. Meteor. 2011, 59 (3), 526− 534. (22) Rohrer, F.; Bohn, B.; Brauers, T.; Bruning, D.; Johnen, F. J.; Wahner, A.; Kleffmann, J. Characterisation of the photolytic HONOsource in the atmosphere simulation chamber SAPHIR. Atmos. Chem. Phys. 2005, 5, 2189−2201. (23) Jonsson, A. M.; Hallquist, M.; Saathoff, H. Volatility of secondary organic aerosols from the ozone initiated oxidation of α-pinene and limonene. J. Aerosol Sci. 2007, 38 (8), 843−852. (24) Salo, K.; Jonsson, A. M.; Andersson, P. U.; Hallquist, M. Aerosol volatility and enthalpy of sublimation of carboxylic acids. J. Phys. Chem. A 2010, 114 (13), 4586−4594. (25) Rader, D. J.; McMurry, P. H. Application of the tandem differential mobility analyzer to studies of droplet growth or evaporation. J. Aerosol Sci. 1986, 17 (5), 771−787. (26) Emanuelsson, E. U.; Watne, Å. K.; Lutz, A.; Ljungström, E.; Hallquist, M. Influence of humidity, temperature, and radicals on the formation and thermal properties of secondary organic aerosol (SOA) from ozonolysis of β-pinene. J. Phys. Chem. A 2013, 117 (40), 10346− 10358. (27) Ng, N. L.; Canagaratna, M. R.; Zhang, Q.; Jimenez, J. L.; Tian, J.; Ulbrich, I. M.; Kroll, J. H.; Docherty, K. S.; Chhabra, P. S.; Bahreini, R.; Murphy, S. M.; Seinfeld, J. H.; Hildebrandt, L.; Donahue, N. M.; DeCarlo, P. F.; Lanz, V. A.; Prevot, A. S. H.; Dinar, E.; Rudich, Y.; Worsnop, D. R. Organic aerosol components observed in Northern Hemispheric datasets from aerosol mass spectrometry. Atmos. Chem. Phys. 2010, 10 (10), 4625−4641. (28) Fuchs, H.; Dorn, H. P.; Bachner, M.; Bohn, B.; Brauers, T.; Gomm, S.; Hofzumahaus, A.; Holland, F.; Nehr, S.; Rohrer, F.; Tillmann, R.; Wahner, A. Comparison of OH concentration measurements by DOAS and LIF during SAPHIR chamber experiments at high OH reactivity and low NO concentration. Atmos. Meas. Technol. Discuss. 2012, 5 (2), 2077−2110. (29) Hausmann, M.; Brandenburger, U.; Brauers, T.; Dorn, H.-P. Detection of tropospheric OH radicals by long-path differentialoptical-absorption spectroscopy: Experimental setup, accuracy, and precision. J. Geophys. Res. Atmos. 1997, 102 (D13), 16011−16022. (30) Emanuelsson, E. U.; Hallquist, M.; Kristensen, K.; Glasius, M.; Bohn, B.; Fuchs, H.; Kammer, B.; Kiendler-Scharr, A.; Nehr, S.; Rubach, F.; Tillmann, R.; Wahner, A.; Wu, H. C.; Mentel, T. F. Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties. Atmos. Chem. Phys. 2013, 13 (5), 2837−2855. (31) Shilling, J. E.; Chen, Q.; King, S. M.; Rosenoern, T.; Kroll, J. H.; Worsnop, D. R.; McKinney, K. A.; Martin, S. T. Particle mass yield in secondary organic aerosol formed by the dark ozonolysis of α-pinene. Atmos. Chem. Phys. 2008, 8 (7), 2073−2088. (32) Volkamer, R.; Jimenez, J. L.; San Martini, F.; Dzepina, K.; Zhang, Q.; Salcedo, D.; Molina, L. T.; Worsnop, D. R.; Molina, M. J. Secondary organic aerosol formation from anthropogenic air pollution: Rapid and higher than expected. Geophys. Res. Lett. 2006, 33, L17811. (33) Kostenidou, E.; Lee, B. H.; Engelhart, G. J.; Pierce, J. R.; Pandis, S. N. Mass spectra deconvolution of low, medium, and high volatility 6175



Article

biogenic secondary organic aerosol. Environ. Sci. Technol. 2009, 43 (13), 4884−4889. (34) Cappa, C. D.; Wilson, K. R. Evolution of organic aerosol mass spectra upon heating: Implications for OA phase and partitioning behavior. Atmos. Chem. Phys. 2011, 11 (5), 1895−1911. (35) Kiendler-Scharr, A.; Zhang, Q.; Hohaus, T.; Kleist, E.; Mensah, A.; Mentel, T. F.; Spindler, C.; Uerlings, R.; Tillmann, R.; Wildt, J. R. Aerosol mass spectrometric features of biogenic SOA: Observations from a plant chamber and in rural atmospheric environments. Environ. Sci. Technol. 2009, 43 (21), 8166−8172. (36) Bergström, R.; Denier van der Gon, H. A. C.; Prévôt, A. S. H.; Yttri, K. E.; Simpson, D. Modelling of organic aerosols over Europe (2002−2007) using a volatility basis set (VBS) framework: Application of different assumptions regarding the formation of secondary organic aerosol. Atmos. Chem. Phys. 2012, 12 (18), 8499−8527. (37) Shrivastava, M.; Zelenyuk, A.; Imre, D.; Easter, R.; Beranek, J.; Zaveri, R. A.; Fast, J. Implications of low volatility SOA and gas-phase fragmentation reactions on SOA loadings and their spatial and temporal evolution in the atmosphere. J. Geophys. Res. Atmos. 2013, 118 (8), 3328−3342. (38) Donahue, N. M.; Kroll, J. H.; Pandis, S. N.; Robinson, A. L. A two-dimensional volatility basis setPart 2: Diagnostics of organicaerosol evolution. Atmos. Chem. Phys. 2012, 12 (2), 615−634.

6176


Parameterization of Thermal Properties of Aging ... - ACS Publications

Recommend Documents