1. Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, P. R. China
2. School of Resources and Environmental Science, Anhui Agricultural University, Hefei 230036, P. R. China
3. Water Quality Centre, Trent University, 1600 West Bank Drive, Peterborough, Ontario K9J 0G2, Canada