Peter J. Adams, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

A. Alastuey, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain.

C. Alves, Centre for Environmental & Marine Studies, Dep. of Environment, Univ. of Aveiro, 3810-193 Aveiro, Portugal.

F. Amato, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain. Email: fulvio.amato@idaea.csic.es

S. Becagli, Dep. of Chemistry, Università di Firenze, Sesto Fiorentino, 50019, Italy.

G. Calzolai, Dep. of Physics and Astronomy, Università di Firenze and INFN-Firenze, Sesto Fiorentino, 50019, Italy.

M. Cerqueira, Centre for Environmental & Marine Studies, Dep. of Environment, Univ. of Aveiro, 3810-193 Aveiro, Portugal.

L.-W. A. Chen, Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA. Graduate Faculty, University of Nevada, Reno, Nevada 89503, USA. Department of Environmental and Occupational Health, University of Nevada, Las Vegas 89154, USA.

J. C. Chow, Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA. Graduate Faculty, University of Nevada, Reno, Nevada 89503, USA. The State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, Shaanxi, 710075, China.

C. Colombi, Environmental Monitoring Sector, Arpa Lombardia, Via Rosellini 17, I-20124 Milano, Italy.

Rebecca Cordell, University of Leicester, Department of Chemistry, LE1 7RH Leicester, United Kingdom.

D. Custódio, Centre for Environmental & Marine Studies, Dep. of Environment, Univ. of Aveiro, 3810-193 Aveiro, Portugal.

Tiphaine Delaunay, atmo Nord-Pas-de-Calais, 55 Place Rihour, 59044 Lille Cedex, France.

E. Diapouli, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, N.C.S.R. Demokritos, 15341 Ag. Paraskevi, Attiki, Greece.

Marieke Dijkema, Public Health Service of Amsterdam, Department of Air Quality, Nieuwe Achtergracht 100, 1000 CE Amsterdam, the Netherlands.

Neil M. Donahue, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA. E-mail: nmd@andrew.cmu.edu

K. Eleftheriadis, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, N.C.S.R. Demokritos, 15341 Ag. Paraskevi, Attiki, Greece.

G. Engling, Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA. Graduate Faculty, University of Nevada, Reno, Nevada 89503, USA.

Julia C Fussell, MRC-PHE Centre for Environment and Health, Facility of Life Sciences and Medicine, King's College London, 150 Stamford Street, London, SE1 9NH, UK.

V. L. Gianelle, Environmental Monitoring Sector, Arpa Lombardia, Via Rosellini 17, I-20124 Milano, Italy.

Marc Guevara, Barcelona Supercomputing Center – Centro Nacional de Supercomputación (BSC-CNS), Earth Sciences Department, Jordi Girona 29, Edificio Nexus II, 08034 Barcelona, Spain. E-mail: marc.guevara@bsc.es

R. M. Harrison, School of Geography, Earth & Environmental Sci., University of Birmingham. Edgbaston, Birmingham B15 2TT, UK. Also at: Department of Environmental Sciences/Center of Excellence in Environmental Studies, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia.

Ronald Hoogerbrugge, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, the Netherlands.

Philip K. Hopke, Center for Air Resources Engineering and Science, Clarkson University, Potsdam, NY 13699, USA. Email: hopkepk@clarkson.edu

A. Karanasiou, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain.

Frank J Kelly, MRC-PHE Centre for Environment and Health, Facility of Life Sciences and Medicine, King's College London, 150 Stamford Street, London, SE1 9NH, UK. Email: frank.kelly@kcl.ac.uk

Isha Khanna, Indian Institute of Technology Delhi, Department of Civil Engineering, Room #220, Block IV, Hauz Khas, New Delhi – 110016, India.

Mukesh Khare, Indian Institute of Technology Delhi, Department of Civil Engineering, Room #220, Block IV, Hauz Khas, New Delhi – 110016, India. E-mail: kharemukesh@yahoo.co.in

Xiaoying Li, College of Environmental Sciences and Engineering, Peking University, 100871, Beijing, China.

Zhongju Li, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

F. Lucarelli, Dep. of Physics and Astronomy, Università di Firenze and INFN-Firenze, Sesto Fiorentino, 50019, Italy.

T. Maggos, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, N.C.S.R. Demokritos, 15341 Ag. Paraskevi, Attiki, Greece.

M. Manousakas, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, N.C.S.R. Demokritos, 15341 Ag. Paraskevi, Attiki, Greece.

M. C. Minguillón, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain.

Paul S. Monks, University of Leicester, Department of Chemistry, LE1 7RH Leicester, United Kingdom.

Dennis Mooibroek, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, the Netherlands.

S. Nava, Dep. of Physics and Astronomy, Università di Firenze and INFN-Firenze, Sesto Fiorentino, 50019, Italy.

T. Nunes, Centre for Environmental & Marine Studies, Dep. of Environment, Univ. of Aveiro, 3810-193 Aveiro, Portugal.

Spyros N. Pandis, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA. Department of Chemical Engineering, University of Patras, Patras, Greece.

Pavlos Panteliadis, Public Health Service of Amsterdam, Department of Air Quality, Nieuwe Achtergracht 100, 1000 CE Amsterdam, the Netherlands.

C. Pio, Centre for Environmental & Marine Studies, Dep. of Environment, Univ. of Aveiro, 3810-193 Aveiro, Portugal.

Laura N. Posner, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

Albert A. Presto, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

X. Querol, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain.

C. Reche, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, 08034, Spain.

Allen L. Robinson, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

Edward Roekens, Flanders Environment Agency (VMM), Department Air, Environment and Communication, Kronenburgstraat 45, 2000 Antwerp, Belgium.

M. Severi, Dep. of Chemistry, Università di Firenze, Sesto Fiorentino, 50019, Italy.

Manish Shrivastava, PNNL, USA.

Jeroen Staelens, Flanders Environment Agency (VMM), Department Air, Environment and Communication, Kronenburgstraat 45, 2000 Antwerp, Belgium. Email: j.staelens@vmm.be

Ryan C. Sullivan, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA.

Jordy Vercauteren, Flanders Environment Agency (VMM), Department Air, Environment and Communication, Kronenburgstraat 45, 2000 Antwerp, Belgium.

S. Vratolis, Institute of Nuclear and Radiological Science & Technology, Energy & Safety, N.C.S.R. Demokritos, 15341 Ag. Paraskevi, Attiki, Greece.

X. Wang, Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA. Graduate Faculty, University of Nevada, Reno, Nevada 89503, USA.

J. G. Watson, Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA. Graduate Faculty, University of Nevada, Reno, Nevada 89503, USA. The State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, Shaanxi, 710075, China. E-mail: john.watson@dri.edu

Ernie Weijers, Energy research Centre of the Netherlands, Department of Air Quality, Westerduinweg 3, 1755 LE Petten, the Netherlands.

Daniel M. Westervelt, Center for Atmospheric Particle Studies, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, USA. Present address: Lamont-Doherty Earth Observatory, Columbia University, Palisades USA.

Caiqing Yan, College of Environmental Sciences and Engineering, Peking University, 100871, Beijing, China.

Mei Zheng, College of Environmental Sciences and Engineering, Peking University, 100871, Beijing, China. E-mail: mzheng@pku.edu.cn