1 Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel; Air Pollution Research Department, National Research Centre, 33 ElBohouth St., Dokki, Giza 12622, Egypt.
2 Environmental Geosciences, University of Basel, Bernoullistrasse 30, CH-4056 Basel;, Email: jen-how.huang@unibas.ch.