1. The Key Laboratory of Water and Sediment Sciences, Ministry of Education, State Environmental Protection Key Laboratory of All Material Fluxes in River Ecosystems, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, P. R. China
2. Southwest United Graduate School, Kunming 650092, P. R. China
3. X-ray Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
4. Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States