Abstract View
Secondary Organic Aerosol Volatility on Mixed Anthropogenic and Biogenic Precursor Systems
ARISTEIDIS VOLIOTIS, Yu Wang, Yunqi Shao, Mao Du, Thomas Bannan, Rami Alfarra, Gordon McFiggans, University of Manchester
Abstract Number: 375
Working Group: Aerosol Chemistry
Abstract
Secondary organic aerosols (SOA) are ubiquitous in the atmosphere and contribute a large fraction of the total aerosol mass with substantial impacts on climate (Jimenez et al., 2009; Kanakidou et al., 2005). Aerosol volatility is linked with the partitioning of their components between the gas and the particle phase, defining their transformation pathways into the atmosphere and eventually, their physical and chemical properties (Ehn et al., 2014). Over the last decades, smog chamber studies have proposed several mechanisms through which gas to particle partitioning is governed (Hallquist et al., 2009). Nevertheless, the vast majority of these studies are focused on single-component precursors.
Recent evidence has showed that upon mixtures of atmospheric vapours, the potential of aerosol formation is governed by the mechanistic interactions between the products of the oxidised precursors (McFiggans et al., 2019). These results demonstrate the deficit in our knowledge regarding the aerosol behaviour in such conditions.
This study is exploring the volatility of SOA formed from the photo-oxidation of mixtures of characteristic biogenic and anthropogenic volatile organic precursors, in an atmospheric simulation chamber. Furthermore, our analysis is framed by detailed gas and particle phase chemical composition measurements and the effect of the various chemical processes on the volatility is investigated.
The experiments were representative of “daytime” photo-oxidation and conducted at the University of Manchester Aerosol Chamber (MAC) facilities. Two types of experiments conducted: (a) single precursor and (b) mixture experiments. All the experiments conducted under low NOx conditions (VOC/NOx ~6±2), moderate RH and temperature conditions (~50±5% and 25±2 oC, respectively), under the presence of ammonium sulfate seed (~53±12 μg m-3).
A scanning mobility particle sizer and a high-resolution time of flight aerosol mass spectrometer were sampling downstream of a thermal denuder (TD), operating at temperatures ranging from 25 to 90 oC. To obtain SOA volatility distributions, the resulted mass fraction remaining (MFR) in each step was used under the approach of Karnezi et al (2014). Furthermore, near-real time gas and particle molecular composition was measured by employing the Filter Inlet for Gas and Aerosols coupled to an Iodine high-resolution time of flight chemical ionisation mass spectrometer (FIGAERO-CIMS).
The results that will be presented provide new and additional information on SOA volatility, clearly illustrating the effect of mixing on SOA volatility. The combination of TD and FIGAERO techniques has the potential to substantially contribute to an improved understanding of the processes influencing the phase partitioning of the organic components.
References
[1] Ehn, M., et al., (2014). Nature, 506, 476.
[2] Hallquist, M., et al., (2009). Atmos. Chem. Phys., 9(14), 5155-5236.
[3] Jimenez, J. L., et al., (2009). Science, 326(5959), 1525-1529.
[4] Kanakidou, M., et al., (2005). Atmos. Chem. Phys., 5(4), 1053-1123.
[5] Karnezi, E., Riipinen, I., & Pandis, S. N. (2014). Atmospheric Measurement Techniques, 7(9), 2953-2965.
[6] McFiggans, G., et al., (2019). Nature, 565(7741), 587-593.