1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710075, China, Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819, Japan, School of the Environment, State Key Laboratory of Pollution Control and Resources Reuse, Nanjing University, Nanjing 210093, China, and Division of Atmospheric Sciences, Desert Research Institute, Reno, Nevada 89512-1095