Seasonal characteristics of organic aerosol chemical composition and volatility in Stuttgart, Germany
<p><strong>Abstract.</strong> The chemical composition and volatility of organic aerosol (OA) particles were investigated during July-August 2017 and February-March 2018 in the city of Stuttgart, one of the most polluted cities in Germany. Total non-refractory particle mass was mea...
Saved in:
| Main Authors: | , |
|---|---|
| Format: | Article (Journal) |
| Language: | English |
| Published: |
19 September 2019
|
| In: |
Atmospheric chemistry and physics
Year: 2019, Volume: 19, Issue: 18, Pages: 11687-11700 |
| ISSN: | 1680-7324 |
| DOI: | https://doi.org/10.5194/acp-19-11687-2019 |
| Online Access: | Verlag, Volltext: https://doi.org/https://doi.org/10.5194/acp-19-11687-2019 Verlag: https://www.atmos-chem-phys.net/19/11687/2019/ 
|
| Author Notes: | Wei Huang, Harald Saathoff, Xiaoli Shen, Ramakrishna Ramisetty, Thomas Leisner, and Claudia Mohr |
| Summary: | <p><strong>Abstract.</strong> The chemical composition and volatility of organic aerosol (OA) particles were investigated during July-August 2017 and February-March 2018 in the city of Stuttgart, one of the most polluted cities in Germany. Total non-refractory particle mass was measured with a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS; hereafter AMS). Aerosol particles were collected on filters and analyzed in the laboratory with a filter inlet for gases and aerosols coupled to a high-resolution time-of-flight chemical ionization mass spectrometer (FIGAERO-HR-ToF-CIMS; hereafter CIMS), yielding the molecular composition of oxygenated OA (OOA) compounds. While the average organic mass loadings are lower in the summer period (<span class="inline-formula">5.1±3.2</span> <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>) than in the winter period (<span class="inline-formula">8.4±5.6</span> <span class="inline-formula">µ</span>g m<span class="inline-formula"><sup>−3</sup></span>), we find relatively larger mass contributions of organics measured by AMS in summer (<span class="inline-formula">68.8±13.4</span> %) compared to winter (<span class="inline-formula">34.8±9.5</span> %). CIMS mass spectra show OOA compounds in summer have O : C of <span class="inline-formula">0.82±0.02</span> and are more influenced by biogenic emissions, while OOA compounds in winter have O : C of <span class="inline-formula">0.89±0.06</span> and are more influenced by biomass burning emissions. Volatility parametrization analysis shows that OOA in winter is less volatile with higher contributions of low-volatility organic compounds (LVOCs) and extremely low-volatility organic compounds (ELVOCs). We partially explain this by the higher contributions of compounds with shorter carbon chain lengths and a higher number of oxygen atoms, i.e., higher O : C in winter. Organic compounds desorbing from the particles deposited on the filter samples also exhibit a shift of signal to higher desorption temperatures (i.e., lower apparent volatility) in winter. This is consistent with the relatively higher O : C in winter but may also be related to higher particle viscosity due to the higher contributions of larger-molecular-weight LVOCs and ELVOCs, interactions between different species and/or particles (particle matrix), and/or thermal decomposition of larger molecules. The results suggest that whereas lower temperature in winter may lead to increased partitioning of semi-volatile organic compounds (SVOCs) into the particle phase, this does not result in a higher overall volatility of OOA in winter and that the difference in sources and/or chemistry between the seasons plays a more important role. Our study provides insights into the seasonal variation of the molecular composition and volatility of ambient OA particles and into their potential sources.</p> |
|---|---|
| Item Description: | Gesehen am 25.10.2019 |
| Physical Description: | Online Resource |
| ISSN: | 1680-7324 |
| DOI: | https://doi.org/10.5194/acp-19-11687-2019 |