Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 1139-1160, 2016
http://www.atmos-chem-phys.net/16/1139/2016/
doi:10.5194/acp-16-1139-2016
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
02 Feb 2016
Wintertime aerosol chemical composition, volatility, and spatial variability in the greater London area
L. Xu1, L. R. Williams2, D. E. Young3,a, J. D. Allan3,4, H. Coe3, P. Massoli2, E. Fortner2, P. Chhabra2,b, S. Herndon2, W. A. Brooks2, J. T. Jayne2, D. R. Worsnop2, A. C. Aiken5, S. Liu5,c, K. Gorkowski5,d, M. K. Dubey5, Z. L. Fleming6,7, S. Visser8, A. S. H. Prévôt8, and N. L. Ng1,9 1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
2Aerodyne Research Inc., Billerica, MA, USA
3School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
4National Centre for Atmospheric Science, University of Manchester, Manchester, UK
5Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM, USA
6Department of Chemistry, University of Leicester, Leicester, UK
7National Centre for Atmospheric Science, University of Leicester, Leicester, UK
8Laboratory of Atmospheric Chemistry, Paul Scherrer Institute, Villigen, Switzerland
9School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
anow at: Department of Environmental Toxicology, University of California, Davis, CA, USA
bnow at: PerkinElmer Inc., Hopkinton, MA, USA
cnow at: Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, CO, USA
dnow at: Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, PA, USA
Abstract. The composition of PM1 (particulate matter with diameter less than 1 µm) in the greater London area was characterized during the Clean Air for London (ClearfLo) project in winter 2012. Two high-resolution time-of-flight aerosol mass spectrometers (HR-ToF-AMS) were deployed at a rural site (Detling, Kent) and an urban site (North Kensington, London). The simultaneous and high-temporal resolution measurements at the two sites provide a unique opportunity to investigate the spatial distribution of PM1. We find that the organic aerosol (OA) concentration is comparable between the rural and urban sites, but the contribution from different sources is distinctly different between the two sites. The concentration of solid fuel OA at the urban site is about twice as high as at the rural site, due to elevated domestic heating in the urban area. While the concentrations of oxygenated OA (OOA) are well-correlated between the two sites, the OOA concentration at the rural site is almost twice that of the urban site. At the rural site, more than 70 % of the carbon in OOA is estimated to be non-fossil, which suggests that OOA is likely related to aged biomass burning considering the small amount of biogenic SOA in winter. Thus, it is possible that the biomass burning OA contributes a larger fraction of ambient OA in wintertime than what previous field studies have suggested.

A suite of instruments was deployed downstream of a thermal denuder (TD) to investigate the volatility of PM1 species at the rural Detling site. After heating at 250 °C in the TD, 40 % of the residual mass is OA, indicating the presence of non-volatile organics in the aerosol. Although the OA associated with refractory black carbon (rBC; measured by a soot-particle aerosol mass spectrometer) only accounts for < 10 % of the total OA (measured by a HR-ToF-AMS) at 250 °C, the two measurements are well-correlated, suggesting that the non-volatile organics have similar sources or have undergone similar chemical processing as rBC in the atmosphere. Although the atomic O : C ratio of OOA is substantially larger than that of solid fuel OA and hydrocarbon-like OA, these three factors have similar volatility, which is inferred from the change in mass concentration after heating at 120 °C. Finally, we discuss the relationship between the mass fraction remaining (MFR) of OA after heating in the TD and atomic O : C of OA and find that particles with a wide range of O : C could have similar MFR after heating. This analysis emphasizes the importance of understanding the distribution of volatility and O : C in bulk OA.


Citation: Xu, L., Williams, L. R., Young, D. E., Allan, J. D., Coe, H., Massoli, P., Fortner, E., Chhabra, P., Herndon, S., Brooks, W. A., Jayne, J. T., Worsnop, D. R., Aiken, A. C., Liu, S., Gorkowski, K., Dubey, M. K., Fleming, Z. L., Visser, S., Prévôt, A. S. H., and Ng, N. L.: Wintertime aerosol chemical composition, volatility, and spatial variability in the greater London area, Atmos. Chem. Phys., 16, 1139-1160, doi:10.5194/acp-16-1139-2016, 2016.
Publications Copernicus
Download
Short summary
We investigate the spatial distribution of submicron aerosol in the greater London area as part of the Clean Air for London (ClearfLo) project in winter 2012. Although the concentrations of organic aerosol (OA) are similar between a rural and an urban site, the OA sources are different. We also examine the volatility of submicron aerosol at the rural site and find that the non-volatile organics have similar sources or have undergone similar chemical processing as refractory black carbon.
We investigate the spatial distribution of submicron aerosol in the greater London area as part...
Share