Acknowledgements
The authors wish to thank Dr S.L. Ranamukharachchi, Dr. W. Gallardo and late Dr. Yang Yi, for their valuable comments and constructive criticism during this research. Special thanks are due to Laboratory and field staff of the School of Environment Resources and Development, Asian Institute of Technology, Thailand for their assistance in water and plant tissue analysis. Authors greatly acknowledge the Icelandic International Development Agency (ICEIDA) for funding this study.