1. College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, China
2. School of Geography and Environment Science, Northwest Normal University, Lanzhou 730070, China
3. Qinghai Provincial Key Laboratory of Nanomaterials and Nanotechnology, Qinghai Minzu University, Qinghai 810007, China
4. School of Environment Science and Engineering, Chang'an University, Xi'an 710060, China