| 1. |
- Kulmala, M., et al.
(author)
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General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales
- 2011
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 13061-13143
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Journal article (peer-reviewed)abstract
- In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.
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| 2. |
- Crippa, M., et al.
(author)
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Organic aerosol components derived from 25 AMS data sets across Europe using a consistent ME-2 based source apportionment approach
- 2014
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 14:12, s. 6159-6176
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Journal article (peer-reviewed)abstract
- Organic aerosols (OA) represent one of the major constituents of submicron particulate matter (PM1) and comprise a huge variety of compounds emitted by different sources. Three intensive measurement field campaigns to investigate the aerosol chemical composition all over Europe were carried out within the framework of the European Integrated Project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) and the intensive campaigns of European Monitoring and Evaluation Programme (EMEP) during 2008 (May-June and September-October) and 2009 (February-March). In this paper we focus on the identification of the main organic aerosol sources and we define a standardized methodology to perform source apportionment using positive matrix factorization (PMF) with the multilinear engine (ME-2) on Aerodyne aerosol mass spectrometer (AMS) data. Our source apportionment procedure is tested and applied on 25 data sets accounting for two urban, several rural and remote and two high altitude sites; therefore it is likely suitable for the treatment of AMS-related ambient data sets. For most of the sites, four organic components are retrieved, improving significantly previous source apportionment results where only a separation in primary and secondary OA sources was possible. Generally, our solutions include two primary OA sources, i.e. hydrocarbon-like OA (HOA) and biomass burning OA (BBOA) and two secondary OA components, i.e. semi-volatile oxygenated OA (SV-OOA) and low-volatility oxygenated OA (LV-OOA). For specific sites cooking-related (COA) and marine-related sources (MSA) are also separated. Finally, our work provides a large overview of organic aerosol sources in Europe and an interesting set of highly time resolved data for modeling purposes.
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| 3. |
- Donahue, N. M., et al.
(author)
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Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions
- 2012
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In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 109:34, s. 13503-13508
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Journal article (peer-reviewed)abstract
- The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.
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| 4. |
- Fountoukis, C., et al.
(author)
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Organic aerosol concentration and composition over Europe: insights from comparison of regional model predictions with aerosol mass spectrometer factor analysis
- 2014
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In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 14:17, s. 9061-9076
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Journal article (peer-reviewed)abstract
- A detailed three-dimensional regional chemical transport model (Particulate Matter Comprehensive Air Quality Model with Extensions, PMCAMx) was applied over Europe, focusing on the formation and chemical transformation of organic matter. Three periods representative of different seasons were simulated, corresponding to intensive field campaigns. An extensive set of AMS measurements was used to evaluate the model and, using factor-analysis results, gain more insight into the sources and transformations of organic aerosol (OA). Overall, the agreement be-tween predictions and measurements for OA concentration is encouraging, with the model reproducing two-thirds of the data (daily average mass concentrations) within a factor of 2. Oxygenated OA (OOA) is predicted to contribute 93% to total OA during May, 87% during winter and 96% during autumn, with the rest consisting of fresh primary OA (POA). Predicted OOA concentrations compare well with the observed OOA values for all periods, with an average fractional error of 0.53 and a bias equal to -0.07 (mean error = 0.9 mu g m(-3), mean bias =-0.2 mu g m(-3)). The model systematically underpredicts fresh POA at most sites during late spring and autumn (mean bias up to -0.8 mu g m(-3)). Based on results from a source apportionment algorithm running in parallel with PMCAMx, most of the POA originates from biomass burning (fires and residential wood combustion), and therefore biomass burning OA is most likely underestimated in the emission inventory. The sensitivity of POA predictions to the corresponding emissions' volatility distribution is discussed. The model performs well at all sites when the Positive Matrix Factorization (PMF)-estimated low-volatility OOA is compared against the OA with saturation concentrations of the OA surrogate species C* <= 0.1 mu g m(-3) and semivolatile OOA against the OA with C* > 0.1 mu g m(-3).
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| 5. |
- Knote, C., et al.
(author)
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Towards an online-coupled chemistry-climate model: evaluation of trace gases and aerosols in COSMO-ART
- 2011
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In: Geoscientific Model Development. - : Copernicus GmbH. - 1991-959X .- 1991-9603. ; 4:4, s. 1077-1102
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Journal article (peer-reviewed)abstract
- The online-coupled, regional chemistry transport model COSMO-ART is evaluated for periods in all seasons against several measurement datasets to assess its ability to represent gaseous pollutants and ambient aerosol characteristics over the European domain. Measurements used in the comparison include long-term station observations, satellite and ground-based remote sensing products, and complex datasets of aerosol chemical composition and number size distribution from recent field campaigns. This is the first time these comprehensive measurements of aerosol characteristics in Europe are used to evaluate a regional chemistry transport model. We show a detailed analysis of the simulated size-resolved chemical composition under different meteorological conditions. Mean, variability and spatial distribution of the concentrations of O-3 and NOx are well reproduced. SO2 is found to be overestimated, simulated PM2.5 and PM10 levels are on average underestimated, as is AOD. We find indications of an overestimation of shipping emissions. Time evolution of aerosol chemical composition is captured, although some biases are found in relative composition. Nitrate aerosol components are on average overestimated, and sulfates underestimated. The accuracy of simulated organics depends strongly on season and location. While strongly underestimated during summer, organic mass is comparable in spring and autumn. We see indications for an overestimated fractional contribution of primary organic matter in urban areas and an underestimation of SOA at many locations. Aerosol number concentrations compare well with measurements for larger size ranges, but overestimations of particle number concentration with factors of 2-5 are found for particles smaller than 50 nm. Size distribution characteristics are often close to measurements, but show discrepancies at polluted sites. Suggestions for further improvement of the modeling system consist of the inclusion of a revised secondary organic aerosols scheme, aqueous-phase chemistry and improved aerosol boundary conditions. Our work sets the basis for subsequent studies of aerosol characteristics and climate impacts with COSMO-ART, and highlights areas where improvements are necessary for current regional modeling systems in general.
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| 6. |
- Morgan, W. T., et al.
(author)
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Enhancement of the aerosol direct radiative effect by semi-volatile aerosol components : airborne measurements in North-Western Europe
- 2010
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In: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 10:17, s. 8151-8171
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Journal article (peer-reviewed)abstract
- A case study of atmospheric aerosol measurements exploring the impact of the vertical distribution of aerosol chemical composition upon the radiative budget in North-Western Europe is presented. Sub-micron aerosol chemical composition was measured by an Aerodyne Aerosol Mass Spectrometer (AMS) on both an airborne platform and a ground-based site at Cabauw in the Netherlands. The examined period in May 2008 was characterised by enhanced pollution loadings in North-Western Europe and was dominated by ammonium nitrate and Organic Matter (OM). Both ammonium nitrate and OM were observed to increase with altitude in the atmospheric boundary layer. This is primarily attributed to partitioning of semi-volatile gas phase species to the particle phase at reduced temperature and enhanced relative humidity. Increased ammonium nitrate concentrations in particular were found to strongly increase the ambient scattering potential of the aerosol burden, which was a consequence of the large amount of associated water as well as the enhanced mass. During particularly polluted conditions, increases in aerosol optical depth of 50-100% were estimated to occur due to the observed increase in secondary aerosol mass and associated water uptake. Furthermore, the single scattering albedo was also shown to increase with height in the boundary layer. These enhancements combined to increase the negative direct aerosol radiative forcing by close to a factor of two at the median percentile level. Such increases have major ramifications for regional climate predictions as semi-volatile components are often not included in aerosol models. The results presented here provide an ideal opportunity to test regional and global representations of both the aerosol vertical distribution and subsequent impacts in North-Western Europe. North-Western Europe can be viewed as an analogue for the possible future air quality over other polluted regions of the Northern Hemisphere, where substantial reductions in sulphur dioxide emissions have yet to occur. Anticipated reductions in sulphur dioxide in polluted regions will result in an increase in the availability of ammonia to form ammonium nitrate as opposed to ammonium sulphate. This will be most important where intensive agricultural practises occur. Our observations over North-Western Europe, a region where sulphur dioxide emissions have already been reduced, indicate that failure to include the semi-volatile behaviour of ammonium nitrate will result in significant errors in predicted aerosol direct radiative forcing. Such errors will be particularly significant on regional scales.
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| 7. |
- Snider, J. R., et al.
(author)
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Intercomparison of cloud condensation nuclei and hygroscopic fraction measurements: Coated soot particles investigated during the LACIS Experiment in November (LExNo)
- 2010
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In: Journal of Geophysical Research. - 2156-2202. ; 115, s. 11205-11205
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Journal article (peer-reviewed)abstract
- Four cloud condensation nuclei (CCN) instruments were used to sample size-selected particles prepared at the Leipzig Aerosol Cloud Interaction Simulator facility. Included were two Wyoming static diffusion CCN instruments, the continuous flow instrument built by Droplet Measurement Technologies, and the continuous flow Leipzig instrument. The aerosols were composed of ammonium sulfate, levoglucosan, levoglucosan and soot, and ammonium hydrogen sulfate and soot. Comparisons are made among critical supersaturation values from the CCN instruments and derived from measurements made with a humidified tandem differential mobility system. The comparison is quite encouraging: with few exceptions the reported critical supersaturations agree within known experimental uncertainty limits. Also reported are CCN- and hygroscopicity-based estimates of the soot particles' solute fraction. Relative differences between these are as large as 40%, but an error analysis demonstrates that agreement within experimental uncertainty is achieved. We also analyze data from the Droplet Measurement Technologies and the two Wyoming static diffusion instruments for evidence of size distribution broadening and investigate levoglucosan particle growth kinetics in the Wyoming CCN instrument.
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| 8. |
- Emanuelsson, Eva U., et al.
(author)
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Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties
- 2012
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In: Atmospheric Chemistry and Physics Discussions. - : Copernicus Publications. - 1680-7367 .- 1680-7375. ; 12:8, s. 20311-20350
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Journal article (peer-reviewed)abstract
- Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. Several experiments with exclusively anthro- 5 pogenic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μgm−3. The yields (0.5–9 %) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The 10 reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Further 15 more, the OH measurements in combination with the derived yields for anthropogenic SOA enabled application of a simplified model to calculate the chemical turnover of the anthropogenic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (8 %) up to significant fraction (>50 %) providing a suitable range to study the effect of aerosol 20 composition on the aerosol volatility (volume fraction remaining at 343 K: 0.86–0.94). The anthropogenic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of anthropogenic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. A strong positive correlation was found between 25 changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. This change in volatility under dark conditions is likely due to chemical or morphological changes not affecting O/C.
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| 9. |
- Emanuelsson, Eva U., et al.
(author)
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Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties
- 2013
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In: Atmos. Chem. Phys.. - : Copernicus Publications. - 1680-7324. ; 13:5, s. 2837-2855
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Journal article (peer-reviewed)abstract
- Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. In this study aromatic compounds served as examples of anthropogenic volatile organic compound (VOC) and a mixture of α-pinene and limonene as an example for biogenic VOC. Several experiments with exclusively aromatic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m−3. The yields (0.5 to 9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for aromatic SOA enabled application of a simplified model to calculate the chemical turnover of the aromatic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining (VFR) at 343 K: 0.86–0.94). The aromatic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of aromatic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. The SOA yields, O/C, and f44 (the mass fraction of CO2+ ions in the mass spectra which can be considered as a measure of carboxylic groups) in the mixed photo-chemical experiments could be described as linear combinations of the corresponding properties of the pure systems. For VFR there was in addition an enhancement effect, making the mixed aerosol significantly less volatile than what could be predicted from the pure systems. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. Thus, this change in volatility under dark conditions as well as the anthropogenic enhancement is due to chemical or morphological changes not affecting O/C.
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| 10. |
- Emanuelsson, Eva U., et al.
(author)
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Parameterization of Thermal Properties of Aging Secondary Organic Aerosol Produced by Photo-Oxidation of Selected Terpene Mixtures
- 2014
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In: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 48:11, s. 6168-6176
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Journal article (peer-reviewed)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 T-VFR0.5 (the temperature yielding a 50% particle volume fraction remaining) and the steepness of the volatility distribution. T-VFR0.5 increased by 0.3 +/- 0.1% (ca. 1 K), while the steepness increased by 0.9 +/- 0.3% per hour of 1 x 10(6) 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.
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