Top PDF Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry

Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry

Organic aerosol components observed in Northern Hemispheric datasets from Aerosol Mass Spectrometry

While Fig. 5 is a mathematically equivalent way of view- ing the information in Fig. 4, it can potentially provide a more useful way of connecting the AMS observations with other measurements. In particular, measurements of O:C can be obtained with other instruments such as thermal tech- niques and nanoaerosol mass spectrometry (Pang et al., 2006; Wang et al., 2006). As discussed before, m/z 44 in OOA spectra is thought to be due mostly to acidic groups (-COOH) and the m/z 43 in OOA spectra can potentially be linked to non-acid oxygenates. Thus, the ratio between these two ions may provide a measure of how the chemical functionality of the OOA evolves with oxidation. Recently, a study by Rus- sell et al. (2009) showed that ratios of AMS fragments (rather than the ratio of individual fragments to total OA) showed some correspondence with the relative abundances of various OA functional groups determined with FTIR. For instance, in regions where m/z 44 and m/z 57 are both well above the respective detection limits, it was shown that the 44/57 ratio correlates with the ratio of carboxylic acid to alkane functional groups from FTIR (Russell et al., 2009). Com- parisons of the FTIR measurements with 44/43 ratios were not reported by Russell et al. (2009). However, future stud- ies involving simultaneous measurements of laboratory stan- dards, or laboratory SOA (from “simple” systems in which both the gas-phase and product-phase chemistry and prod- ucts are better characterized) with HR-ToF-AMS and FTIR, NMR, or other techniques may provide more detailed insight into how the 44/43 ratio is related to the chemical functional- ity of OOA. For instance, a HR-ToF-AMS flow reactor study by Kroll et al. (2009) has suggested that C 2 H 3 O + (nominal
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Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data

Interpretation of organic components from Positive Matrix Factorization of aerosol mass spectrometric data

The splitting and mixing behavior seen in the synthetic datasets when too many factors were requested presents a clear warning that when evaluating a real dataset, the re- searcher must be careful about overinterpreting solutions with multiple factors, even though it may be tempting to “identify” additional sources and give them physical- sounding names. The characterized splitting behavior in which each split factor has comparable fractions of the mass of the original factor may be specific to the PMF2 algorithm, as other algorithms such as MCA (Zhang et al., 2007a) tend to split a factor into a dominant factor (in terms of mass) and a small factor. In particular, care must be taken because the spurious factors obtained due to “splitting” or “mixing” behavior have realistic-looking mass spectra and time series and could easily be interpreted by the unsuspecting user as a real factor, though we know that in the synthetic cases these factors must be mathematical artifacts. In cases where mix- ing behavior occurs, non-existent factors could be retained. Thus, it is critical to use external tracers to confirm the in- terpretation. In the absence of these tracers, the lower or- der solution may be the best choice. In our ambient case, for example, factors 3–6 are mathematically good solutions. The fourth factor in the 4-factor solution of the real Pitts- burgh dataset exhibits some of the behavior characterized by the splitting observed in the synthetic cases. The TS of this factor is very similar to the TS of the OOA-1 fac- tor (Fig. S3b, see http://www.atmos-chem-phys.net/9/2891/ 2009/acp-9-2891-2009-supplement.pdf) and these two fac- tors share approximately equal portions of the mass (Fig. 4a). The MS correlates well with many types of OA measured by the AMS (Fig. 6b). While this factor may reflect true vari- ability in OOA-1, we do not have an independent tracer to support this interpretation and prefer the 3-factor solution as the safest choice to avoid overinterpretation.
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Elemental ratio measurements of organic compounds  using aerosol mass spectrometry: characterization,  improved calibration, and implications

Elemental ratio measurements of organic compounds using aerosol mass spectrometry: characterization, improved calibration, and implications

Laboratory chamber studies provide the ideal means of simulating ambient aerosol formation and aging processes under controlled and reproducible experimental conditions (i.e., selected reactants, photochemical conditions, and aging times). However, previous work has shown that laboratory chamber studies are unable to generate SOA or photochem- ically aged OA with the same chemical composition as the LV-OOA species observed in the atmosphere (Chhabra et al., 2010; Ng et al., 2010). The elemental ratios obtained with I-A method reconfirm this difference. Figure 7 shows, for example, that the I-A elemental ratios observed for the SOA from terpene and sesquiterpene precursors are significantly less oxidized than the average ambient LV-OOA component. In fact, the terpene and sesquiterpene chamber SOA gener- ally only reach the O : C and OSc values observed for the less oxidized SV-OOA components. As shown in Table 2, the I-A elemental ratios of isoprene and toluene SOA expe- rience large changes compared to their corresponding A-A values. These changes are large enough to bring the O : C and OSc values of these SOA in good agreement with LV- OOA values. However, as shown in Fig. 4a, the oxygen con- taining functional groups in these SOA still do not reproduce the mass spectral signatures obtained from ambient LV-OOA. Thus, the gap in the AMS chemical compositions measured for chamber and ambient SOA remains even when the I-A method is used.
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Constraining condensed-phase formation kinetics of secondary organic aerosol  components from isoprene epoxydiols

Constraining condensed-phase formation kinetics of secondary organic aerosol components from isoprene epoxydiols

The gas-phase photooxidation of isoprene (2-methyl-1,3- butadiene), the largest biogenic volatile organic compound (VOC) emitted worldwide (Guenther et al., 2012), yields iso- meric isoprene epoxydiols (IEPOX) (Paulot et al., 2009). Subsequent acid-catalyzed multiphase chemistry of IEPOX is a significant source of secondary organic aerosol (SOA) mass (Lin et al., 2012; Surratt et al., 2010). In recent field studies, up to 50 % of summertime aerosol mass loadings in the southeastern United States have been attributed to SOA resulting from IEPOX heterogeneous reactions (Budisulis- tiorini et al., 2013, 2015; Lin et al., 2013b). Similar IEPOX- derived SOA influences are expected in areas with large isoprene emissions, such as forests primarily composed of broadleaf vegetation. As a significant SOA precursor, IEPOX has implications regarding potential climate forcing due to the scattering of incoming radiation and also impacts human health due to its large contribution to PM 2.5 (particulate mat-
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Loading-dependent elemental composition of α-pinene SOA particles

Loading-dependent elemental composition of α-pinene SOA particles

particle mass by consideration of the reversible absorption of semivolatile species. A molecule found both in the gas and particle phases of an aerosol increasingly partitions into the latter for higher mass loadings of organic particles. Moreover, species having lower vapor pressures in pure form partition to a greater extent to the particle phase, at least for most cases in which activity-based corrections are minor (Bowman and

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The aerosol-climate model ECHAM5-HAM

The aerosol-climate model ECHAM5-HAM

PROVE, EMEP, and GAW datasets. F. Dentener (JRC, Ispra) is to be thanked for his support with the emission data and many helpful discussions. Our thanks extends to our colleagues L. Kornblueh, S. Rast, A. Rhodin, E. Roeckner, and U. Schulzweida for their constant support with the ECHAM5-HAM model development and to M. Schultz for providing the MOZART chemistry data (Max Planck Institute for Meteorology, Hamburg). We would also like to acknowledge the

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Characterization of a real-time tracer for Isoprene   Epoxydiols-derived Secondary Organic Aerosol (IEPOX-SOA) from   aerosol mass spectrometer measurements

Characterization of a real-time tracer for Isoprene Epoxydiols-derived Secondary Organic Aerosol (IEPOX-SOA) from aerosol mass spectrometer measurements

H., Gilman, J. B., de Gouw, J., Park, C., Schade, G., Beaver, M., Clair, J. M. S., Crounse, J., Wennberg, P., Wolfe, G. M., Harrold, S., Thornton, J. A., Farmer, D. K., Docherty, K. S., Cubison, M. J., Jimenez, J.-L., Frossard, A. A., Russell, L. M., Kristensen, K., Glasius, M., Mao, J., Ren, X., Brune, W., Browne, E. C., Pusede, S. E., Cohen, R. C., Seinfeld, J. H., and Goldstein, A. H.: Observational insights into aerosol formation from isoprene, Environ. Sci.

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Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state

(CDNC) burden between runs ossa-ref and ctrl (Fig. 14a). This suggests two likely reasons for the positive indirect effect in our simulations. First, large sea salt particles take up so much water that they decrease the maximum supersaturation and thus pre- vent smaller particles from activating (Ghan et al., 1998; O’Dowd et al., 1999a, b; Gong and Barrie, 2003; Korhonen et al., 2010). Second, sea salt particles also act as a con-

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Identification of humic-like substances (HULIS) in oxygenated organic aerosols using NMR and AMS factor analyses and liquid chromatographic techniques

Identification of humic-like substances (HULIS) in oxygenated organic aerosols using NMR and AMS factor analyses and liquid chromatographic techniques

values of O/C ratio compared to LV-OOA and HOA, respectively. Therefore, SV-OOA might show only a partial solubility in water, which could explain why NMR analysis did not find any factors within WSOC showing the nocturnal enrichment characteristic of semivolatile compounds such as F2 AMS (SV-OOA) and ammonium nitrate. Another explanation for a missing semivolatile fraction from NMR analysis could be evaporation

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Atmospheric nutrient inputs to the northern levantine basin from a long-term observation: sources and comparison with riverine inputs

Atmospheric nutrient inputs to the northern levantine basin from a long-term observation: sources and comparison with riverine inputs

Table 5 demonstrates dry, wet and total atmospheric de- positions of nutrients obtained from different sites located at the Eastern Mediterranean. Estimated dry deposition for phosphate at Erdemli was comparable to value reported for Eilat, Israel, Israel (Chen et al., 2007) whereas (as expected) phosphate dry deposition at Erdemli was approximately two times lower than those calculated for Tel Shikmona and Is- raeli coast. Estimated NO − 3 dry depositions at Erdemli, Tel Shikmona, Israeli coast and Eilat were found to be similar, whilst the highest dry deposition for ammonium was esti- mated at Tel Shikmona (Herut et al., 2002) and Israeli coast (Carbo et al., 2005) on account of applied settling veloc- ity (0.6 cm s −1 ). Calculated wet depositions for phosphate and nitrate at Erdemli and Tel Shikmona were two to four times higher than those of observed at Crete, respectively. Whereas, wet deposition of ammonium at Erdemli was two times higher that those estimated for Tel Shikmona. Tak- ing into account the total atmospheric depositions, phosphate demonstrated decreasing fluxes in the order of Tel Shikmona > Erdemli > Crete while DIN showed declining fluxes in the order of Tel Shikmona ∼Erdemli > Crete.
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Mass yields of secondary organic aerosols from the oxidation of α-pinene and real plant emissions

Mass yields of secondary organic aerosols from the oxidation of α-pinene and real plant emissions

BVOC precursors in this study came from emissions of 1- yr-old Scots pine and Norway spruce seedlings. Cultivation and pretreatments of these seedlings have been described in Hao et al. (2009). In order to enhance total BVOCs emis- sions and simulate herbivore attack on tree bark, 3 cm long and 2 mm deep cuts were made on the base of main stem by a knife. Abiotic or biotic damage on the plant can change the BVOC emission profiles (e.g. Blande et al., 2009). How- ever the BVOC emission spectrum in this study (major com- pounds in the emission profile) is comparable to ambient ob- servations. Molar chemical composition of emissions from these two types of forest trees are shown in Fig. 3. Emit- ted monoterpenes from Scots pine mainly included α-pinene and 1 3 -carene, matching the field observations in the boreal Scots pine dominated forest (e.g. R¨ais¨anen et al., 2009; Man- ninen et al., 1998). No fractional contribution of 1 3 -carene in P1025 and P1026 were observed which depends on the 1 3 -carene genotype Scots pine (Manninen et al., 1998). The most abundant contributions from Norway spruce emission are α-pinene and β-pinene, making up 64.8%, 60.2% and 57.3% of total emitted monoterpenes for S1019, S1017 and S1015, respectively. These results are comparable to 70% of flux contribution of α-pinene and β-pinene to total emis- sions during measurements made in a spruce dominated for- est (Christensen et al., 2000). Other major contributions to emissions from these two types of trees came from myrcene, β-phellandrene and limonene. In all experiments, sesquiter- penes in the emitted compounds were lower than 0.05 ppb as
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High formation of secondary organic aerosol from the photo-oxidation of toluene

High formation of secondary organic aerosol from the photo-oxidation of toluene

from SMPS data rely on computing the small difference between two number size dis- tribution measurements. Furthermore, the mass yields calculated from the SMPS are strongly dependent on the measured particle wall deposition constant k w (t), which introduces additional uncertainty and potential for error. Consider, for example, exper- iments 11 and 12, which were run at very similar conditions and are hence expected

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J. Braz. Chem. Soc.  vol.16 número5

J. Braz. Chem. Soc. vol.16 número5

Taking into account their atmospheric characteristics, generally under photochemical conditions, forested areas of Mediterranean countries constitute an appropriate environment to investigate the secondary organic aerosols. The objective of this study was to study in situ the aerosol composition, particularly in the photo-oxidation products of biogenic volatile organic compounds, taking into consideration anthropogenic inputs, and to explain how these compounds appear in the aerosols. Atmospheric particulate matter was collected at two sites: an Abies boressi forest in central Greece and at Giesta, a coastal-rural site in the centre of Portugal. The collected aerosol was extracted with solvents and characterised by gas chromatography and mass spectrometry. The detected secondary organics include alkene derivatives, oxo-, di- and monocarboxylic acids, oxy-aromatics, aza and thia arenes, and many terpene photo-oxidation products. This in situ experiment allowed confirming the presence of secondary constituents, which have been studied almost exclusively under simulated laboratory conditions. Some reaction pathways leading to the formation of compounds in the particulate phase from precursors are presented.
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Multiday production of condensing organic aerosol mass in urban and forest outflow

Multiday production of condensing organic aerosol mass in urban and forest outflow

Abstract. Secondary organic aerosol (SOA) production in air masses containing either anthropogenic or biogenic (terpene- dominated) emissions is investigated using the explicit gas- phase chemical mechanism generator GECKO-A. Simula- tions show several-fold increases in SOA mass continuing for multiple days in the urban outflow, even as the initial air parcel is diluted into the regional atmosphere. The SOA mass increase in the forest outflow is more modest ( ∼50 %) and of shorter duration (1–2 days). The multiday production in the urban outflow stems from continuing oxidation of gas- phase precursors which persist in equilibrium with the par- ticle phase, and can be attributed to multigenerational reac- tion products of both aromatics and alkanes, especially those with relatively low carbon numbers (C4–15). In particular we find large contributions from substituted maleic anhydrides and multi-substituted peroxide-bicyclic alkenes. The results show that the predicted production is a robust feature of our model even under changing atmospheric conditions and dif- ferent vapor pressure schemes, and contradict the notion that SOA undergoes little mass production beyond a short ini- tial formation period. The results imply that anthropogenic aerosol precursors could influence the chemical and radia- tive characteristics of the atmosphere over an extremely wide region, and that SOA measurements near precursor sources may routinely underestimate this influence.
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Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC

Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC

Correlations between aerosol mass concentrations m GM obtained from the low-pressure impactor and aerosol volume obtained from the DMA and OPC in (a) the sub- µ m and (b) the super- µ m [r]

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Formation of hydroxyl radicals from photolysis of secondary organic aerosol material

Formation of hydroxyl radicals from photolysis of secondary organic aerosol material

droperoxides (ROOH). The presence of ROOH in SOA, especially ozonolysis SOA formed from terpenes, is likely (Ehn et al., 2014). They may form via Criegee biradicals, generated when ozone reacts with a carbon-carbon double bond, and also through H- abstractions that are part of chain oxidation mechanisms (Crounse et al., 2013; Ehn et al., 2014). Indeed, it is likely that the molecular structures of extremely low volatility

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Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

Assessing regional scale predictions of aerosols, marine stratocumulus, and their interactions during VOCALS-REx using WRF-Chem

Abstract. This study assesses the ability of the recent chem- istry version (v3.3) of the Weather Research and Forecast- ing (WRF-Chem) model to simulate boundary layer struc- ture, aerosols, stratocumulus clouds, and energy fluxes over the Southeast Pacific Ocean. Measurements from the VA- MOS Ocean-Cloud-Atmosphere-Land Study Regional Ex- periment (VOCALS-REx) and satellite retrievals (i.e., prod- ucts from the MODerate resolution Imaging Spectrora- diometer (MODIS), Clouds and Earth’s Radiant Energy Sys- tem (CERES), and GOES-10) are used for this assessment. The Morrison double-moment microphysics scheme is newly coupled with interactive aerosols in the model. The 31- day (15 October–16 November 2008) WRF-Chem simula- tion with aerosol-cloud interactions (AERO hereafter) is also compared to a simulation (MET hereafter) with fixed cloud droplet number concentrations in the microphysics scheme and simplified cloud and aerosol treatments in the radiation scheme. The well-simulated aerosol quantities (aerosol num- ber, mass composition and optical properties), and the inclu- sion of full aerosol-cloud couplings lead to significant im- provements in many features of the simulated stratocumulus clouds: cloud optical properties and microphysical proper- ties such as cloud top effective radius, cloud water path, and cloud optical thickness. In addition to accounting for the aerosol direct and semi-direct effects, these improvements feed back to the simulation of boundary-layer characteris- tics and energy budgets. Particularly, inclusion of interac-
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Organic aerosol concentration and composition over Europe: insights from comparison of regional model predictions with aerosol mass spectrometer factor analysis

Organic aerosol concentration and composition over Europe: insights from comparison of regional model predictions with aerosol mass spectrometer factor analysis

Other possible sources of uncertainty that are not explored here but have been investigated in past applications of PM- CAMx include uncertainties in the aging scheme, the mag- nitude of IVOC emissions and others. For example Murphy et al. (2011) explored a two-bin reduction in volatility upon one oxidation step with a simultaneous decrease (by a fac- tor of 2) in the aging rate constants. They found a slight un- derprediction of the OA mass observed at Finokalia during May 2008 compared to the base-case one-bin shift. Hodzic et al. (2010) and Grieshop et al. (2009) investigated a two- bin reduction (in addition to the one-bin base-case satura- tion concentration reduction) with a reduced OH reaction rate constant and found both to perform adequately. Mur- phy et al. (2012) added a detailed functionalization scheme to approximate the effect on volatility of adding relevant func- tional groups to the carbon backbone (Donahue et al., 2011). This approach alone resulted in a significant increase of the OA mass. Adding fragmentation to the detailed functional- ization scenario decreased OA mass concentrations to the approximate magnitude predicted by the base case (which employs a simplified scheme that is currently used in PM- CAMx) and brought the model into reasonable agreement with the OA mass concentration measurements. In our base- case aging scheme we use this simplified scenario that tries to describe the net effect of the chemical aging reactions (both functionalization and fragmentation) without treating any of the two types explicitly. The sensitivity of the model’s predic- tions to the uncertain IVOC emissions was stressed by Tsim- pidi et al. (2010). An additional SOA formation pathway that is not simulated here is the in-cloud SOA formation from gly- oxal and methylglyoxal. Murphy et al. (2012) explored the contribution of this pathway to OOA concentrations at sev- eral European sites that are also studied in our work (Mace Head, Cabauw, Finokalia) during both May 2008 and Febru- ary/March 2009. They reported small enhancements to both average OA mass loadings (< 3 %) and O : C (< 10 %) at the surface. Their estimated OA production from this pathway was found lower (in absolute magnitude) than that seen by Carlton et al. (2008) or measured during the CalNEX cam- paign, but the contribution to total SOA formed was similar (0–4 %). Aqueous-phase SOA formation from glyoxal and methylglyoxal was also investigated by Myriokefalitakis et al. (2011) using the global 3-D chemistry/transport model TM4-ECPL. They reported significant contributions of ox- alate to SOA mass mainly over oceans, possibly due to long- range transport of oxidation products of terrestrial biogenic VOC and subsequent cloud processing, as well as to the mul- tiphase processing of the marine VOC emissions.
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Volatility of secondary organic aerosol during OH radical induced ageing

Volatility of secondary organic aerosol during OH radical induced ageing

Schlosser, E., Brauers, T., Dorn, H.-P., Fuchs, H., H ¨aseler, R., Hofzumahaus, A., Holland, F., Wahner, A., Kanaya, Y., Kajii, Y., Miyamoto, K., Nishida, S., Watanabe, K., Yoshino, A., Ku- bistin, D., Martinez, M., Rudolf, M., Harder, H., Berresheim, H., Elste, T., Plass-D ¨ulmer, C., Stange, G., and Schurath, U.: Technical Note: Formal blind intercomparison of OH measure- ments: results from the international campaign HOxComp, Atmos. Chem. Phys., 9, 7923–

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Modeling of secondary organic aerosol yields from laboratory chamber data

Modeling of secondary organic aerosol yields from laboratory chamber data

Claeys, M., Iinuma, Y., Szmigielski, R., Surratt, J. D., Blockhuys, F., Van Alsenoy, C., B ¨oge, O., Sierau, B., G ´omez-Gonz ´alez, Y., Vermeylen, R., Van der Veken, P., Shahgholi, M., Chan, A. W. H., Herrmann, H., Seinfeld, J. H., and Maenhaut, W.: Terpenylic acid and related com- pounds from the oxidation of α-pinene: Implications for new particle formation and growth above forests, submitted, 2009. 9467, 9481

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