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Advanced source apportionment of size-resolved trace elements at multiple sites in London during winter

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posted on 10.01.2017, 09:40 by S. Visser, J. G. Slowik, M. Furger, P. Zotter, N. Bukowiecki, F. Canonaco, U. Flechsig, K. Appel, D. C. Green, A. H. Tremper, D. E. Young, P. I. Williams, J. D. Allan, H. Coe, L. R. Williams, C. Mohr, L. Xu, N. L. Ng, E. Nemitz, J. F. Barlow, C. H. Halios, Z. L. Fleming, U. Baltensperger, A. S. H. Prévôt
Trace element measurements in PM10–2.5, PM2.5–1.0 and PM1.0–0.3 aerosol were performed with 2 h time resolution at kerbside, urban background and rural sites during the ClearfLo winter 2012 campaign in London. The environment-dependent variability of emissions was characterized using the Multilinear Engine implementation of the positive matrix factorization model, conducted on data sets comprising all three sites but segregated by size. Combining the sites enabled separation of sources with high temporal covariance but significant spatial variability. Separation of sizes improved source resolution by preventing sources occurring in only a single size fraction from having too small a contribution for the model to resolve. Anchor profiles were retrieved internally by analysing data subsets, and these pro- files were used in the analyses of the complete data sets of all sites for enhanced source apportionment. A total of nine different factors were resolved (notable elements in brackets): in PM10–2.5, brake wear (Cu, Zr, Sb, Ba), other traffic-related (Fe), resuspended dust (Si, Ca), sea/road salt (Cl), aged sea salt (Na, Mg) and industrial (Cr, Ni); in PM2.5–1.0, brake wear, other traffic-related, resuspended dust, sea/road salt, aged sea salt and S-rich (S); and in PM1.0–0.3, traffic-related (Fe, Cu, Zr, Sb, Ba), resuspended dust, sea/road salt, aged sea salt, reacted Cl (Cl), S-rich and solid fuel (K, Pb). Human activities enhance the kerb-to-rural concentration gradients of coarse aged sea salt, typically considered to have a natural source, by 1.7–2.2. These site-dependent concentration differences reflect the effect of local resuspension processes in London. The anthropogenically influenced factors traffic (brake wear and other traffic-related processes), dust and sea/road salt provide further kerb-to-rural concentration enhancements by direct source emissions by a factor of 3.5–12.7. The traffic and dust factors are mainly emitted in PM10–2.5 and show strong diurnal variations with concentrations up to 4 times higher during rush hour than during night-time. Regionally influenced Srich and solid fuel factors, occurring primarily in PM1.0–0.3, have negligible resuspension influences, and concentrations are similar throughout the day and across the regions.

Funding

We thank the Swiss National Science Foundation (SNSF grant 200021_132467/1), the UK Natural Environment Research Council (NERC) ClearfLo consortium (NERC grant NE/H00324X/1, NE/H0081368/1), and the European Community’s Seventh Framework Programme (FP/2007-2013, grant number 312284). J. G. Slowik was supported by the SNSF Ambizione programme (grant PX00P2_31673), and D. E. Young by a NERC PhD studentship (grant NE/I528142/1). The Detling site was supported by the US Department of Energy Atmospheric Systems Research Program (DOE award no. DE-SC0006002). We thank Empa for the RDI they loaned us during the ClearfLo project. Parts of the work were carried out at the Swiss Light Source, Paul Scherrer Institute, Villigen, Switzerland. We thank Andreas Jaggi and Christophe Frieh for technical support at the beamline X05DA. Parts of the study were also performed at the light source facility DORIS III at HASYLAB/DESY. DESY is a member of the Helmholtz Association (HGF).

History

Citation

Atmospheric Chemistry and Physics Discussions 15, 11291-11309, 2015

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Chemistry

Version

VoR (Version of Record)

Published in

Atmospheric Chemistry and Physics Discussions 15

Publisher

European Geosciences Union (EGU), Copernicus Publications

issn

1680-7367

eissn

1680-7375

Acceptance date

21/09/2015

Copyright date

2015

Available date

10/01/2017

Publisher version

http://www.atmos-chem-phys.net/15/11291/2015/

Notes

The Supplement related to this article is available online at doi:10.5194/acp-15-11291-2015-supplement.

Language

en

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