In-situ measurement of free trace metal concentrations in a flooded paddy soil using the Donnan Membrane Technique

Y. Pan, G.F. Koopmans, L.T.C. Bonten, J. Song, Y. Luo, E.J.M. Temminghoff, R.N.J. Comans

Research output: Contribution to journalArticleAcademicpeer-review

10 Citations (Scopus)


The field Donnan Membrane Technique (DMT) has been used successfully to measure in-situ free trace metal concentrations in surface waters. However, it has not been applied previously in submerged soil systems including flooded paddy rice fields.Wetested this technique in a columnexperimentwith a flooded paddy soil contaminated with trace metals and compared the DMT measurements with predictions from a geochemical speciation model. Flooding led to a strong gradient in the redox potential (Eh) along the soil column, and the pH and concentrations ofMn, Fe, and dissolved organic carbon increased with decreasing Eh. Total dissolved tracemetal concentrations decreased from the overlying water layer to the soil layers, which might be ascribed to the elevated pH outweighing the effect of the increased DOC concentrations under anaerobic conditions. Also, free trace metal concentrations were lower in the soil solution of the upper and bottom soil layers than in the overlying water layer, largely due to the increased pH under anaerobic conditions. The DMT measurements and model predictions were similar in the aerobic water layer, except for Pb. In both anaerobic soil layers, however, Cu and Pb were poorly predicted. The applied geochemical modeling approach, which is frequently being used and performswell under aerobic conditions, does not fully capture all the chemical processes occurring under anaerobic conditions. Overall, the field DMT proved to be a useful tool for the in-situ measurement of free trace metal concentrations in flooded paddy soils.
Original languageEnglish
Pages (from-to)59-67
Number of pages8
Publication statusPublished - 2015


  • dissolved organic-matter
  • ray-absorption spectroscopy
  • copper redox transformation
  • reduced sulfur groups
  • ion activity model
  • sandy soil
  • humic substances
  • natural-waters
  • higher-plants
  • heavy-metals

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