Laboratory Studies on Secondary Organic Aerosol Formation from

Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States. § Chemical Sciences Div...
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Laboratory Studies on Secondary Organic Aerosol Formation from Crude Oil Vapors R. Li,*,†,‡,§ B. B. Palm,‡,∥ A. Borbon,⊥ M. Graus,‡,§ C. Warneke,‡,§ A. M. Ortega,†,‡ D. A. Day,‡,∥ W. H. Brune,# J. L. Jimenez,‡,∥ and J. A. de Gouw‡,§ †

Department of Atmospheric & Oceanic Sciences, University of Colorado, Boulder, Colorado 80309, United States Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Colorado 80309, United States § Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, Colorado 80305, United States ∥ Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309, United States ⊥ LISA, IPSL, CNRS UMR 7583, Université Paris Est and Paris Diderot, Créteil Cedex, France # Department of Meteorology, Pennsylvania State University, University Park, Pennsylvania, United States ‡

S Supporting Information *

ABSTRACT: Airborne measurements of aerosol composition and gas phase compounds over the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in June 2010 indicated the presence of high concentrations of secondary organic aerosol (SOA) formed from organic compounds of intermediate volatility. In this work, we investigated SOA formation from South Louisiana crude oil vapors reacting with OH in a Potential Aerosol Mass flow reactor. We use the dependence of evaporation time on the saturation concentration (C*) of the SOA precursors to separate the contribution of species of different C* to total SOA formation. This study shows consistent results with those at the DWH oil spill: (1) organic compounds of intermediate volatility with C* = 105−106 μg m−3 contribute the large majority of SOA mass formed, and have much larger SOA yields (0.37 for C* = 105 and 0.21 for C* = 106 μg m−3) than more volatile compounds with C*≥107 μg m−3, (2) the mass spectral signature of SOA formed from oxidation of the less volatile compounds in the reactor shows good agreement with that of SOA formed at DWH oil spill. These results also support the use of flow reactors simulating atmospheric SOA formation and aging.

1. INTRODUCTION A significant fraction of PM2.5 in the atmosphere consists of organic material, which is largely formed from oxidized gasphase compounds that condense onto existing particles or form new particles in a process referred to as secondary organic aerosol (SOA) formation.1−3 Although some volatile organic compounds (VOCs) can be efficient precursors of SOA,4−6 one class of compounds that is emerging as important for SOA formation is organic compounds of intermediate volatility (IVOCs), which are not frequently measured nor taken into account as precursors in all models.7−9 Because IVOCs are often coemitted with VOCs, it is difficult to separate their relative contributions to SOA formation. The Deepwater Horizon (DWH) oil spill in the Gulf of Mexico in April−August of 2010 provided an accidental case to study SOA formation from VOCs and IVOCs separately. The spill resulted in a significant release of crude oil to the sea surface. Different hydrocarbons in the oil were separated by their vapor pressure on the sea surface as the most volatile compounds evaporated promptly and were released to the atmosphere from an area of a few km2 near the spill site, while the less volatile © 2013 American Chemical Society

compounds spread out over a much larger area before evaporation.10,11 Airborne measurements indicated SOA was formed very efficiently downwind from the oil spill, and the width of the SOA plume indicated that IVOCs were much more important precursors than VOCs.12−14 As these same compounds are also expected to be present in vehicle exhaust and industrial processes such as petroleum refining, these findings have implications for urban atmospheres.8,15 In this work, we studied SOA formation from oil vapors in the laboratory. We obtained samples of South Louisiana (SL) crude oil that has a similar composition as the DWH oil,13,16 which comprises 80% alkanes, 12% aromatics, and 8% resins.17 Experiments were performed using a potential aerosol mass (PAM) flow reactor,18 which simulates SOA formation online. The evaporation of crude oil at a constant temperature provides a unique perspective to differentiate the contribution from Received: Revised: Accepted: Published: 12566

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A test experiment was performed to evaluate O3 oxidation of oil vapors, in which the same amount of O3 (∼1.5 ppm) was present as the only oxidant. The result showed little SOA was formed in the O3-only oxidation process. This is because oil vapors comprise only saturates and aromatics, which have much smaller reaction rate coefficients with O3 than with OH.23,24 This result indicates the O3 oxidation of oil vapors during the OH oxidation experiment was of negligible importance for SOA formation. It should also be noted that ambient levels of NOx were present at the inlet of the reactor, although there were no quantitative measurements in this study due to the lack of NOx instruments. Nonetheless, the exact amount of NOx is unimportant in our experiments, because any NOx present will be very quickly destroyed in PAM based on very-wellknown and quantified reactions (reactions of NO + O3 and NO2 + OH) and converted to HNO3, and because the amount of radical recycling by NOx is inconsequential compared to the direct radical source from photolysis. In the highly oxidizing conditions, NOx is rapidly reacted with high O3 to form NO2 (given kO3‑NO = 1.9 × 10−14 cm3 molecules−1 s−1, NO lifetime τ = 1.7 s),25 with NO2 subsequently reacting with OH and forming HNO3 (given kOH‑NO2 = 2.8 × 10−11 cm3 molecules−1 s−1, NO2 lifetime τ = 24 s),25 whereas the photolysis of HNO3 at our settings of UV lights at 185 and 254 nm is slow (J = 10−5 s−1).26 Therefore, SOA formation in the reactor is estimated to be under very low NOx levels. Since most of the RO2 radicals are alkane-based with the radical located in a secondary carbon and these are known to react slowly with other RO2,27 the RO2 + RO2 channel should play a small role under our laboratory conditions, and the RO2 + HO2 channel should dominate the fate of the RO2 radicals. The conditions observed over the oil spill in Gulf of Mexico showed 58 ppbv O3, 30 pptv NO and 250 pptv NO2 at 48 km downwind of the DWH site.13,28 Under these conditions, the reaction of RO2 + HO2 is dominant but the reaction of RO2 + NO also plays a role. Therefore, the fate of RO2 under our experimental conditions was similar but not identical vs over the oil spill. 2.1.2. Proton Transfer Reaction Mass Spectrometer (PTRMS). Trace gases evaporated from the crude oil were measured by PTR-MS. The application of PTR-MS for atmospheric measurements has been reviewed by de Gouw et al,29 and only a brief description is given here. A large number (over 107 counts s−1) of primary ions, H3O+, are produced in the ion source of PTR-MS, where water vapor is ionized in a high voltage field. H3O+ ions enter the drift tube from the ion source and undergo proton transfer reactions with VOCs (R) of higher proton affinity (PA) than water to form RH+ and H2O. The protonated VOCs (RH+) are analyzed by a quadrupole mass spectrometer. It should be noted that PTR-MS is relatively insensitive and not selective for alkanes, which are the main constituents of crude oil, due to their PA being lower than water. The mixing ratio of different VOCs is calculated as a function of H3O+, RH+ ion counts, and calibration factors for each species. The instrument was calibrated for aromatics of C6−C9 before the crude oil experiments. The calibration factors for compounds that we did not calibrate for were estimated using the transmission efficiency of each compound in the quadrupole mass spectrometer and the rate coefficient for the proton transfer with H3O+ similar to Warneke et al.29 The calibration factors used here are shown in Supporting Information, SI, Figure S1(B).

different classes of volatility (volatility is expressed in the form of effective saturation concentration C*):7,12,19 oil vapors with high volatility evaporate earlier and faster, but less volatile compounds take much longer to evaporate, depending on the vapor pressure of each compound. Therefore, compounds of different volatilities are temporally separated, and SOA formed via rapid oxidation (faster than the time scales of evaporation) can be attributed to different classes of precursors. Here, we conducted laboratory studies on the SOA formation from crude oil vapors to better understand which classes of compounds in crude oil contribute the most to SOA formation, as well as to compare the mass spectral characteristics of laboratory SOA with the SOA formed downwind from DWH oil spill.

2. EXPERIMENTAL SECTION 2.1. Instrumentation. 2.1.1. Potential Aerosol Mass (PAM) Flow Reactor. The PAM reactor is a 13 L cylindrical aluminum vessel that provides highly oxidizing conditions to simulate atmospheric oxidation processes at an accelerated rate.18,20 High concentrations of hydroxyl radicals (OH) are produced in the reactor under continuous flow conditions. SOA can be formed by OH oxidation of gas-phase organic compounds in the reactor, leading to new particle formation and/or growth by condensation. Two mercury lamps producing 185 and 254 nm light are mounted inside the reactor. The major photochemistry associated with UV light at 185 and 254 nm for OH formation is as follows: 185nm

H 2O + hν ⎯⎯⎯⎯⎯⎯→ OH + H H + O2 → HO2 185nm

O2 + hν ⎯⎯⎯⎯⎯⎯→ 2O(3P) O(3P) + O2 + M → O3 254nm

O3 + hν ⎯⎯⎯⎯⎯⎯→ O(1D) + O2 O(1D) + H 2O → 2OH

(1)

Total OH exposure in the reactor, defined as the product of OH concentration integrated over residence time, is estimated indirectly from the water vapor concentration, flow rate (i.e., residence time), and the amount of O3 formed in the reactor. This calibration relationship was determined before and after oil experiments by measuring the decay of SO2 due to reaction with OH. In the calibration experiments, OH exposure was varied over a large range (1010−1012 molecules cm−3 s) by controlling the UV light intensity and relative humidity (RH).21 Unlike in other studies where the OH exposure is varied in steps,20,22 in this study, a constant OH exposure of (3.57 ± 0.36) × 1011 molecules cm−3 s was used for simulating SOA formation with a similar oxidation level as the SOA observed in the Gulf of Mexico by the NOAA aircraft. Bahreini et al.13 estimated an average OH concentration of (8.0 ± 3.5) × 106 molecules cm−3 over the oil spill in the region where the SOA was formed. The estimated SOA formation and aging time at 48 km downwind of the DWH site was less than 5 h, which results in an estimated OH exposure of (1.44 ± 0.63) × 1011 molecules cm−3 s. Therefore, the OH exposure in the laboratory and field measurements are comparable (within a factor of 2). 12567

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2.1.3. Instruments for Particle Measurements. The SOA formed in the reactor is analyzed by two instruments: (1) a high resolution time-of-flight Aerosol Mass Spectrometer (HRToF-AMS)30,31 for measuring the chemical speciation of nonrefractory submicrometer aerosol particles; (2) a TSI Scanning Mobility Particle Sizer (SMPS) for measuring aerosol size distribution, number concentration, and volume concentration.32 The SOA mass concentration is estimated from the SMPS data assuming an average particle density of 1.25 (g m−3), which is calculated from the parametrization of Kuwata et al.32,33 2.2. Experimental Setup. A schematic diagram of the experimental setup is shown in Figure 1. Clean air at 13% RH

to every experiment. To start the experiment, a drop of oil was inserted in a cleaned sealed glass jar. The amount of oil was 2.5 μL, which was chosen as a trade-off between better VOC signalto-noise ratio in the later phase of the oil evaporation and less OH suppression in the beginning. A bypass of the sample jar was used when clean air was passed through the system or when a crude oil sample was being put in the jar. Once the oil sample was inserted in the jar, two three-way valves were immediately switched to the jar, and the sample was introduced to the reactors. Ambient laboratory temperature was constant at 22 ± 1 °C during these experiments. As the vapor pressure of volatile organic compounds (VOCs) is a function of temperature, maintaining a constant temperature for the entire system is important to eliminate spurious changes in VOC evaporation and SOA formation.

3. RESULTS AND DISCUSSION 3.1. Crude Oil Evaporation Experiments. The results of an experiment with SL crude oil are shown in Figure 2. Four

Figure 1. Schematic diagram of the experimental setup.

with added oil vapors (from the generation system discussed below) is split evenly into two reactors, one with high levels of OH with the UV lights on (“OH flowtube”) and one with the UV lights off and thus without OH (“dark flowtube”). A constant RH was chosen for this study because changing the amount of water vapor would affect both radical production and SOA chemistry, which would increase the complexity of the results. In addition, a previous study on SOA from the oil spill suggests minor water dependence on SOA formation.13 The AMS and SMPS instruments measured SOA from the outflow of the OH flowtube. The PTR-MS measured trace gases from both flowtubes, alternating every 105 s to capture rapid evaporation changes in the beginning of the experiment, while also allowing for sticky compounds to reach stable values. The dark flowtube is used to introduce a buffer volume of identical shape as the OH flowtube, such that the outflows from the OH and dark flowtubes only differ by the chemistry in the OH flowtube. SI Figure S2 confirms that this is the case by showing a comparison of the output of both flowtubes when OH was absent. This approach has two benefits. First, the OH flowtube does not remove hydrocarbons completely and the difference with and without chemistry needs to be measured to determine yields quantitatively. Second, for the no-photochemistry case, we use an identical flowtube rather than the inlet of the OH flowtube. The VOC composition changes during the evaporation due to the different volatility of the VOCs, and therefore, VOCs are transferred through the flowtube at different times.34 The buffer volume from the dark flowtube allows for optimal time alignment of the unreacted vs reacted VOCs in the two flowtubes. In between experiments, the system was flushed with clean humidified air (with UV lights on in the OH flowtube) until particle mass concentrations were 2 h evaporation). This trend is consistent with previous chamber studies20,37,45,46 that showed a similar SOA concentration dependence of f44 from the oxidation of α-pinene and pentacosane. Similar results were also observed over DWH oil spill13: less SOA was formed with higher f44 away from DWH site (many smaller markers of Gulf SOA on the left and upper area of large markers in Figure 5A), indicating SOA is more oxidized with lower SOA concentration. This could be due to increased oxidation due to less OH reduction at lower gas-phase concentrations, or dilution leading to preferential evaporation of more volatile species producing f43, resulting in higher f44. The lab SOA is able to reach similar oxidation level as the Gulf SOA, for similar OH exposures and OA concentrations in the reactor. A previous study20 has shown that the amount of aerosol mass affects the O/C ratio for the same amount of OH exposure. Our results in this study confirm that less volatile compounds (e.g., IVOCs) are the primary precursors of SOA formed from crude oil vapors. These were oxidized by OH radicals, in similar processes of SOA formation as in the atmosphere over the DWH oil spill. The compounds from the SL crude oil vapors are expected to be present in vehicle exhaust and petroleum industry emissions and therefore, the result has implications for urban atmospheres as well. The oxidation of these species under simulated ambient conditions in the OH flow reactor provided a unique perspective for comparing SOA yields from precursors with different volatility and characteristics of laboratory-generated SOA with those formed in ambient conditions. These results will improve quantitative understanding of IVOC chemistry for SOA formation in other polluted atmospheres.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected] . Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We thank Roya Bahreini (University of Denver) and Ann Middlebrook (NOAA) for sharing the AMS data from oil spill measurements. We thank Abby Koss for providing useful results from her oil evaporation experiments. We thank David Valentine (University of California at Santa Barbara) and Andrew Lambe (Boston College) for sharing photos of oil spill and OH flowtube for the TOC art in the abstract. This project was supported by a CIRES Innovative Research Program Seed Grant. B.B.P., D.A.D., A.M.O., and J.L.J. were also supported by DOE (BER, ASR Program) DE-SC0006035. A.M.O. is grateful for a graduate fellowship from the DOE SCGP Fellowship Program (ORAU, ORISE). R.L. and B.B.P. acknowledge a CIRES Graduate Student Fellowship

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REFERENCES

(1) Kanakidou, M.; Seinfeld, J. H.; Pandis, S. N.; Barnes, I.; Dentener, F. J.; Facchini, M. C.; Van Dingenen, R.; Ervens, B.; Nenes, A.; Nielsen, C. J.; Swietlicki, E.; Putaud, J. P.; Balkanski, Y.; Fuzzi, S.; Horth, J.; Moortgat, G. K.; Winterhalter, R.; Myhre, C. E. L.; Tsigaridis, K.; Vignati, E.; Stephanou, E. G.; Wilson, J. Organic aerosol and global climate modelling: A review. Atmos. Chem. Phys. 2005, 5 (4), 1053−1123. (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.; Pré vô t, 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) Jimenez, J. L.; Canagaratna, M. R.; Donahue, N. M.; Prevot, A. S. H.; Zhang, Q.; Kroll, J. H.; DeCarlo, P. F.; Allan, J. D.; Coe, H.; Ng, N. L.; Aiken, A. C.; Docherty, K. S.; Ulbrich, I. M.; Grieshop, A. P.; Robinson, A. L.; Duplissy, J.; Smith, J. D.; Wilson, K. R.; Lanz, V. A.; Hueglin, C.; Sun, Y. L.; Tian, J.; Laaksonen, A.; Raatikainen, T.; Rautiainen, J.; Vaattovaara, P.; Ehn, M.; Kulmala, M.; Tomlinson, J. M.; Collins, D. R.; Cubison, M. J.; E.; Dunlea, J.; Huffman, J. A.; Onasch, T. B.; Alfarra, M. R.; Williams, P. I.; Bower, K.; Kondo, Y.; Schneider, J.; Drewnick, F.; Borrmann, S.; Weimer, S.; Demerjian, K.; Salcedo, D.; Cottrell, L.; Griffin, R.; Takami, A.; Miyoshi, T.; Hatakeyama, S.; Shimono, A.; Sun, J. Y.; Zhang, Y. M.; Dzepina, K.; Kimmel, J. R.; Sueper, D.; Jayne, J. T.; Herndon, S. C.; Trimborn, A. M.; Williams, L. R.; Wood, E. C.; Middlebrook, A. M.; Kolb, C. E.; Baltensperger, U.; Worsnop, D. R. Evolution of organic aerosols in the atmosphere. Science 2009, 326 (5959), 1525−1529. (4) Ng, N. L.; Kroll, J. H.; Chan, A. W. H.; Chhabra, P. S.; Flagan, R. C.; Seinfeld, J. H. Secondary organic aerosol formation from m-xylene, toluene, and benzene. Atmos. Chem. Phys. 2007, 7 (14), 3909−3922. (5) Ng, N. L.; Chhabra, P. S.; Chan, A. W. H.; Surratt, J. D.; Kroll, J. H.; Kwan, A. J.; McCabe, D. C.; Wennberg, P. O.; Sorooshian, A.; Murphy, S. M.; Dalleska, N. F.; Flagan, R. C.; Seinfeld, J. H. Effect of NOx level on secondary organic aerosol (SOA) formation from the photooxidation of terpenes. Atmos. Chem. Phys. 2007, 7 (19), 5159− 5174. (6) Kroll, J. H.; Ng, N. L.; Murphy, S. M.; Flagan, R. C.; Seinfeld, J. H. Secondary organic aerosol formation from isoprene photooxidation under high-NOx conditions. Geophys. Res. Lett. 2005, 32 (18), n/a−n/ a.

ASSOCIATED CONTENT

S Supporting Information *

Calculation of OH suppression, the estimates of high masses calibration factors, setup test results, time series of OH exposure and the correction factor due to OH suppression, relative mass fraction of oil vapors change during evaporation, the estimate of alkanes removal, and tables of aromatics and alkanes removal fraction. This material is available free of charge via the Internet at http://pubs.acs.org. 12572

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(7) Robinson, A. L.; Donahue, N. M.; Shrivastava, M. K.; Weitkamp, E. A.; Sage, A. M.; Grieshop, A. P.; Lane, T. E.; Pierce, J. R.; Pandis, S. N. Rethinking organic aerosols: Semivolatile emissions and photochemical aging. Science 2007, 315 (5816), 1259−1262. (8) Gentner, D. R.; Isaacman, G.; Worton, D. R.; Chan, A. W. H.; Dallmann, T. R.; Davis, L.; Liu, S.; Day, D. A.; Russell, L. M.; Wilson, K. R.; Weber, R.; Guha, A.; Harley, R. A.; Goldstein, A. H. Elucidating secondary organic aerosol from diesel and gasoline vehicles through detailed characterization of organic carbon emissions. Proc. Natl. Acad. Sci. 2012, 109 (45), 18318−18323. (9) Jordan, C. E.; Ziemann, P. J.; Griffin, R. J.; Lim, Y. B.; Atkinson, R.; Arey, J. Modeling SOA formation from OH reactions with C8−17 n-alkanes. Atmos. Environ. 2008, 42 (34), 8015−8026. (10) Ryerson, T. B.; Aikin, K. C.; Angevine, W. M.; Atlas, E. L.; Blake, D. R.; Brock, C. A.; Fehsenfeld, F. C.; Gao, R. S.; de Gouw, J. A.; Fahey, D. W.; Holloway, J. S.; Lack, D. A.; Lueb, R. A.; Meinardi, S.; Middlebrook, A. M.; Murphy, D. M.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Roberts, J. M.; Schwarz, J. P.; Spackman, J. R.; Stark, H.; Warneke, C.; Watts, L. A. Atmospheric emissions from the Deepwater Horizon spill constrain air−water partitioning, hydrocarbon fate, and leak rate. Geophys. Res. Lett. 2011, 38 (7), n/a−n/a. (11) Ryerson, T. B.; Camilli, R.; Kessler, J. D.; Kujawinski, E. B.; Reddy, C. M.; Valentine, D. L.; Atlas, E.; Blake, D. R.; de Gouw, J.; Meinardi, S.; Parrish, D. D.; Peischl, J.; Seewald, J. S.; Warneke, C. Chemical data quantify Deepwater Horizon hydrocarbon flow rate and environmental distribution. Proc. Natl. Acad. Sci. 2012, 109 (50), 20246−20253. (12) de Gouw, J. A.; Middlebrook, A. M.; Warneke, C.; Ahmadov, R.; Atlas, E. L.; Bahreini, R.; Blake, D. R.; Brock, C. A.; Brioude, J.; Fahey, D. W.; Fehsenfeld, F. C.; Holloway, J. S.; Le Henaff, M.; Lueb, R. A.; McKeen, S. A.; Meagher, J. F.; Murphy, D. M.; Paris, C.; Parrish, D. D.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Robinson, A. L.; Ryerson, T. B.; Schwarz, J. P.; Spackman, J. R.; Srinivasan, A.; Watts, L. A. Organic aerosol formation downwind from the Deepwater Horizon oil spill. Science 2011, 331 (6022), 1295−1299. (13) Bahreini, R.; Middlebrook, A. M.; Brock, C. A.; de Gouw, J. A.; McKeen, S. A.; Williams, L. R.; Daumit, K. E.; Lambe, A. T.; Massoli, P.; Canagaratna, M. R.; Ahmadov, R.; Carrasquillo, A. J.; Cross, E. S.; Ervens, B.; Holloway, J. S.; Hunter, J. F.; Onasch, T. B.; Pollack, I. B.; Roberts, J. M.; Ryerson, T. B.; Warneke, C.; Davidovits, P.; Worsnop, D. R.; Kroll, J. H. Mass spectral analysis of organic aerosol formed downwind of the Deepwater Horizon oil spill: Field studies and laboratory confirmations. Environ. Sci. Technol. 2012, 46 (15), 8025− 8034. (14) Middlebrook, A. M.; Murphy, D. M.; Ahmadov, R.; Atlas, E. L.; Bahreini, R.; Blake, D. R.; Brioude, J.; de Gouw, J. A.; Fehsenfeld, F. C.; Frost, G. J.; Holloway, J. S.; Lack, D. A.; Langridge, J. M.; Lueb, R. A.; McKeen, S. A.; Meagher, J. F.; Meinardi, S.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Roberts, J. M.; Ryerson, T. B.; Schwarz, J. P.; Spackman, J. R.; Warneke, C.; Ravishankara, A. R. Air quality implications of the Deepwater Horizon oil spill. Proc. Natl. Acad. Sci. 2011, 109 (50), 20222−20228. (15) Leppard, W. R.; Rapp, L. A.; Burns, V. R.; Gorse, R. A.; Knepper, J. C.; Koehl, W. J. Effects of gasoline composition on vehicle engine-out and tailpipe hydrocarbon emissionsThe auto/oil air quality improvement research program. SAE Tech. Papers 1992, (920329). (16) Lehr, B. B.; Possolo, A.Oil Budget Calculator: Deepwater Horizon; 2012. (17) Wang, Z.; Hollebone, B. P.; Fingas, M.; Fieldhouse, B. ; Sigouin, L.; Landriault, M.; Smith, P.; Noonan, J.; , and Thouin, G. ., Characteristics of Spilled Oils, Fuels, and Petroleum Products: 1. Composition and Properties of Selected Oils; Environmental Technology Centre: Ottawa, Ontario, 2003. (18) Kang, E.; Root, M. J.; Toohey, D. W.; Brune, W. H. Introducing the concept of potential aerosol mass (PAM). Atmos. Chem. Phys. 2007, 7 (22), 5727−5744.

(19) Donahue, N. M.; Robinson, A. L.; Stanier, C. O.; Pandis, S. N. Coupled partitioning, dilution, and chemical aging of semivolatile organics. Environ. Sci. Technol. 2006, 40 (8), 2635−2643. (20) Kang, E.; Toohey, D. W.; Brune, W. H. Dependence of SOA oxidation on organic aerosol mass concentration and OH exposure: Experimental PAM chamber studies. Atmos. Chem. Phys. 2011, 11 (4), 1837−1852. (21) Lambe, A. T.; Onasch, T. B.; Croasdale, D. R.; Wright, J. P.; Martin, A. T.; Franklin, J. P.; Massoli, P.; Kroll, J. H.; Canagaratna, M. R.; Brune, W. H.; Worsnop, D. R.; Davidovits, P. Transitions from functionalization to fragmentation reactions of laboratory secondary organic aerosol (SOA) generated from the OH oxidation of alkane precursors. Environ. Sci. Technol. 2012, 46 (10), 5430−5437. (22) Ortega, A. M.; Day, D. A.; Cubison, M. J.; Brune, W. H.; Bon, D.; de Gouw, J.; Jimenez, J. L. Secondary organic aerosol formation and primary organic aerosol oxidation from biomass burning smoke in a flow reactor during FLAME-3. Atmos. Chem. Phys. 2013, in press. (23) Atkinson, R.; Carter, W. P. L. Kinetics and mechanisms of the gas-phase reactions of ozone with organic compounds under atmospheric conditions. Chem. Rev. 1984, 84 (5), 437−470. (24) Atkinson, R. Gas-phase tropospheric chemistry of organic compounds: A review. Atmos. Environ. 2007, 41, Supplement, (0), 200−240. (25) Sander, S. P.;Friedl, R. R.Chemical kinetics and photochemical data for use in atmospheric studies, Evaluation Number 17. In Jet Propulsion Laboratory Publication; California Institute of Technology: Pasadena, CA,2011 (26) Johnston, H. S.; Chang, S.-G.; Whitten, G. Photolysis of nitric acid vapor. J. Phys. Chem. 1974, 78 (1), 1−7. (27) Ziemann, P. J.; Atkinson, R. Kinetics, products, and mechanisms of secondary organic aerosol formation. Chem. Soc. Rev. 2012, 41 (19), 6582−6605. (28) Middlebrook, A. M.; Murphy, D. M.; Ahmadov, R.; Atlas, E. L.; Bahreini, R.; Blake, D. R.; Brioude, J.; de Gouw, J. A.; Fehsenfeld, F. C.; Frost, G. J.; Holloway, J. S.; Lack, D. A.; Langridge, J. M.; Lueb, R. A.; McKeen, S. A.; Meagher, J. F.; Meinardi, S.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Roberts, J. M.; Ryerson, T. B.; Schwarz, J. P.; Spackman, J. R.; Warneke, C.; Ravishankara, A. R. Air quality implications of the Deepwater Horizon oil spill. Proc. Natl. Acad. Sci. 2012, 109 (50), 20280−20285. (29) de Gouw, J.; Warneke, C. Measurements of volatile organic compounds in the earth’s atmosphere using proton-transfer-reaction mass spectrometry. Mass Spectrom. Rev. 2007, 26 (2), 223−257. (30) 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.; Worsnop, D. R.; Jimenez, J. L. Field-deployable, highresolution, time-of-flight aerosol mass spectrometer. Anal. Chem. 2006, 78 (24), 8281−8289. (31) Canagaratna, M. R.; Jayne, J. T.; Jimenez, J. L.; Allan, J. D.; Alfarra, M. R.; Zhang, Q.; Onasch, T. B.; Drewnick, F.; Coe, H.; Middlebrook, A.; Delia, A.; Williams, L. R.; Trimborn, A. M.; Northway, M. J.; DeCarlo, P. F.; Kolb, C. E.; Davidovits, P.; Worsnop, D. R. Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer. Mass Spectrom. Rev. 2007, 26 (2), 185−222. (32) Knutson, E. O.; Whitby, K. T. Aerosol classification by electric mobility: apparatus, theory, and applications. J. Aerosol Sci. 1975, 6 (6), 443−451. (33) 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. 2011, 46 (2), 787−794. (34) Lambe, A. T.; Ahern, A. T.; Williams, L. R.; Slowik, J. G.; Wong, J. P. S.; Abbatt, J. P. D.; Brune, W. H.; Ng, N. L.; Wright, J. P.; Croasdale, D. R.; Worsnop, D. R.; Davidovits, P.; Onasch, T. B. Characterization of aerosol photooxidation flow reactors: Heterogeneous oxidation, secondary organic aerosol formation and cloud condensation nuclei activity measurements. Atmos. Meas. Tech. 2011, 4 (3), 445−461. 12573

dx.doi.org/10.1021/es402265y | Environ. Sci. Technol. 2013, 47, 12566−12574

Environmental Science & Technology

Article

(35) Tsimpidi, A. P.; Karydis, V. A.; Zavala, M.; Lei, W.; Molina, L.; Ulbrich, I. M.; Jimenez, J. L.; Pandis, S. N. Evaluation of the volatility basis-set approach for the simulation of organic aerosol formation in the Mexico City metropolitan area. Atmos. Chem. Phys. 2010, 10 (2), 525−546. (36) Ryerson, T. B.; Aikin, K. C.; Angevine, W. M.; Atlas, E. L.; Blake, D. R.; Brock, C. A.; Fehsenfeld, F. C.; Gao, R. S.; de Gouw, J. A.; Fahey, D. W.; Holloway, J. S.; Lack, D. A.; Lueb, R. A.; Meinardi, S.; Middlebrook, A. M.; Murphy, D. M.; Neuman, J. A.; Nowak, J. B.; Parrish, D. D.; Peischl, J.; Perring, A. E.; Pollack, I. B.; Ravishankara, A. R.; Roberts, J. M.; Schwarz, J. P.; Spackman, J. R.; Stark, H.; Warneke, C.; Watts, L. A. Atmospheric emissions from the Deepwater Horizon spill constrain air−water partitioning, hydrocarbon fate, and leak rate. Geophys. Res. Lett. 2011, 38 (7), L07803. (37) 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.; Prévôt, 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. (38) Ng, N. L.; Canagaratna, M. R.; Jimenez, J. L.; Zhang, Q.; Ulbrich, I. M.; Worsnop, D. R. Real-time methods for estimating organic component mass concentrations from aerosol mass spectrometer data. Environ. Sci. Technol. 2010, 45 (3), 910−916. (39) McFiggans, G.; Alfarra, M. R.; Allan, J.; Bower, K.; Coe, H.; Cubison, M.; Topping, D.; Williams, P.; Decesari, S.; Facchini, C.; Fuzzi, S. Simplification of the representation of the organic component of atmospheric particulates. Faraday Discuss. 2005, 130 (0), 341−362. (40) Aiken, A. C.; DeCarlo, P. F.; Kroll, J. H.; Worsnop, D. R.; Huffman, J. A.; Docherty, K. S.; Ulbrich, I. M.; Mohr, C.; Kimmel, J. R.; Sueper, D.; Sun, Y.; Zhang, Q.; Trimborn, A.; Northway, M.; Ziemann, P. J.; Canagaratna, M. R.; Onasch, T. B.; Alfarra, M. R.; Prevot, A. S. H.; Dommen, J.; Duplissy, J.; Metzger, A.; Baltensperger, U.; Jimenez, J. L. O/C and OM/OC ratios of primary, secondary, and ambient organic aerosols with high-resolution time-of-flight aerosol mass spectrometry. Environ. Sci. Technol. 2008, 42 (12), 4478−4485. (41) 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. (42) Duplissy, J.; Gysel, M.; Alfarra, M. R.; Dommen, J.; Metzger, A.; Prevot, A. S. H.; Weingartner, E.; Laaksonen, A.; Raatikainen, T.; Good, N.; Turner, S. F.; McFiggans, G.; Baltensperger, U. Cloud forming potential of secondary organic aerosol under near atmospheric conditions. Geophys. Res. Lett. 2008, 35 (3), L03818. (43) Bahreini, R.; Keywood, M. D.; Ng, N. L.; Varutbangkul, V.; Gao, S.; Flagan, R. C.; Seinfeld, J. H.; Worsnop, D. R.; Jimenez, J. L. Measurements of secondary organic aerosol from oxidation of cycloalkenes, terpenes, and m-xylene using an aerodyne aerosol mass spectrometer. Environ. Sci. Technol. 2005, 39 (15), 5674−5688. (44) Ng, N. L.; Canagaratna, M. R.; Jimenez, J. L.; Chhabra, P. S.; Seinfeld, J. H.; Worsnop, D. R. Changes in organic aerosol composition with aging inferred from aerosol mass spectra. Atmos. Chem. Phys. 2011, 11 (13), 6465−6474. (45) Shilling, J. E.; Chen, Q.; King, S. M.; Rosenoern, T.; Kroll, J. H.; Worsnop, D. R.; DeCarlo, P. F.; Aiken, A. C.; Sueper, D.; Jimenez, J. L.; Martin, S. T. Loading-dependent elemental composition of αpinene SOA particles. Atmos. Chem. Phys. 2009, 9 (3), 771−782. (46) Atkinson, R. Gas-phase tropospheric chemistry of organic compounds: A review. Atmos. Environ. A. Gen. Topics 1990, 24 (1), 1− 41.

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