Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties

  • 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 acidsAbstract. 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.show moreshow less

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Author:E. U. EmanuelssonORCiD, M. Hallquist, K. Kristensen, M. GlasiusORCiD, Birger BohnORCiD, H. FuchsORCiD, B. Kammer, A. Kiendler-ScharrORCiD, Sascha NehrORCiDGND, F. Rubach, R. TillmannORCiD, A. WahnerORCiD, H.-C. Wu, Th. F. MentelORCiD
Qualitätssicherung:peer reviewed
open access:Gold - Erstveröffentlichung mit Lizenzhinweis
Fachbereich/Einrichtung:Hochschule Düsseldorf / Fachbereich - Maschinenbau und Verfahrenstechnik
Document Type:Article
Year of Completion:2013
Language of Publication:English
Publisher:Copernicus
Parent Title (English):Atmospheric Chemistry and Physics
Volume:13
Issue:5
Page Number:19
First Page:2837
Last Page:2855
DOI:https://doi.org/10.5194/acp-13-2837-2013
ISSN:1680-7324
Tag:Luftreinhaltung
Dewey Decimal Classification:6 Technik, Medizin, angewandte Wissenschaften / 62 Ingenieurwissenschaften / 620 Ingenieurwissenschaften und zugeordnete Tätigkeiten
Licence (German):Creative Commons - CC BY - Namensnennung 3.0
Release Date:2024/12/04
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