Lanzhou University of Technology, Chinese Academy of Sciences (CAS), Lanzhou University of Technology, Lanzhou University of Technology, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, Lanzhou University of Technology, Lanzhou University of Technology, affiliation not provided to SSRN, affiliation not provided to SSRN, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences (CAS), Lanzhou University of Technology, Chinese Academy of Sciences (CAS) - Northwest Institute of Eco-Environment and Resources, Lanzhou University of Technology and Lanzhou University of Technology