1. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China.
2. College of Environmental Science and Engineering, Hunan University, Changsha 410082, China, Phone: +86 7318822754; Fax: +86 7318823701; E-mail: zgming@hnu.cn
3. Department of Soil Science, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran.
4. State Key Laboratory for Chemo/Biosensing and Chemometrics, Hunan University, Changsha 410082, China.