Yingying Yao, Xi'an Jiaotong University, Department of Earth & Environmental Sciences, Xian, China, Chunmiao Zheng, Southern University of Science and Technology, School of Environmental Science and Engineering, Shenzhen, China, Charles Andrews, S.S. Papadopulos and Associates, Inc., Bethesda, United States and Yiping Wu, Xi'an Jiaotong University, Department of Earth & Environmental Sciences, Xi'an, China