Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 15, 6351-6366, 2015
https://doi.org/10.5194/acp-15-6351-2015
© Author(s) 2015. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
11 Jun 2015
Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London
D. E. Young1,*, J. D. Allan1,2, P. I. Williams1,2, D. C. Green3, M. J. Flynn1, R. M. Harrison4,5, J. Yin4, M. W. Gallagher1, and H. Coe1 1School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
2National Centre for Atmospheric Science, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
3School of Biomedical and Health Sciences, King's College London, London, UK
4School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
5Department of Environmental Sciences/Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
*now at: Department of Environmental Toxicology, University of California, Davis, CA, 95616, USA
Abstract. For the first time, the behaviour of non-refractory inorganic and organic submicron particulate through an entire annual cycle is investigated using measurements from an Aerodyne compact time-of-flight aerosol mass spectrometer (cToF-AMS) located at a UK urban background site in North Kensington, London. We show that secondary aerosols account for a significant fraction of the submicron aerosol burden and that high concentration events are governed by different factors depending on season. Furthermore, we demonstrate that on an annual basis there is no variability in the extent of secondary organic aerosol (SOA) oxidation, as defined by the oxygen content, irrespective of amount. This result is surprising given the changes in precursor emissions and contributions as well as photochemical activity throughout the year; however it may make the characterisation of SOA in urban environments more straightforward than previously supposed.

Organic species, nitrate, sulphate, ammonium, and chloride were measured during 2012 with average concentrations (±1 standard deviation) of 4.32 (±4.42), 2.74 (±5.00), 1.39 (±1.34), 1.30 (±1.52), and 0.15 (±0.24) μg m−3, contributing 44, 28, 14, 13, and 2 % to the total non-refractory submicron mass (NR-PM1) respectively. Components of the organic aerosol fraction are determined using positive matrix factorisation (PMF), in which five factors are identified and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2). OOA1 and OOA2 represent more and less oxygenated OA with average concentrations of 1.27 (±1.49) and 0.14 (±0.29) μg m−3 respectively, where OOA1 dominates the SOA fraction (90%).

Diurnal, monthly, and seasonal trends are observed in all organic and inorganic species due to meteorological conditions, specific nature of the aerosols, and availability of precursors. Regional and transboundary pollution as well as other individual pollution events influence London's total submicron aerosol burden. High concentrations of non-refractory submicron aerosols in London are governed by particulate emissions in winter, especially nitrate and SFOA, whereas SOA formation drives the high concentrations during the summer. The findings from this work could have significant implications for modelling of urban air pollution as well as for the effects of atmospheric aerosols on health and climate.


Citation: Young, D. E., Allan, J. D., Williams, P. I., Green, D. C., Flynn, M. J., Harrison, R. M., Yin, J., Gallagher, M. W., and Coe, H.: Investigating the annual behaviour of submicron secondary inorganic and organic aerosols in London, Atmos. Chem. Phys., 15, 6351-6366, https://doi.org/10.5194/acp-15-6351-2015, 2015.
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Short summary
For the first time, the behaviour of non-refractory inorganic and organic submicron particulates through an entire annual cycle is investigated at a UK urban background site. We show secondary aerosols account for a significant fraction of the submicron aerosol burden, high concentration events are governed by different factors depending on season, and on an annual basis there is no variability in the extent of secondary organic aerosol oxidation.
For the first time, the behaviour of non-refractory inorganic and organic submicron particulates...
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