1. Ministry of Education Key Laboratory of West China’s Environmental System, Lanzhou Univ., Lanzhou 730000, China; and College of Resource and Environmental Science, Lanzhou Univ., Lanzhou 730000, China.
2. School of Architecture and Design, Beijing Jiaotong Univ., Beijing 100044, China (corresponding author).
3. College of Resource and Environmental Science, Lanzhou Univ., Lanzhou 730000, China.