1. Key
Laboratory for Environmental Pollution Prediction and Control, Gansu
Province, College of Earth and Environmental Sciences, Lanzhou University, Lanzhou 730000, China
2. Air
Quality Research Division, Atmospheric Science
and Technology Directorate, Environment Canada, 4905 Dufferin
St., Toronto, Ontario, Canada M3H 5T4
3. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China