Chemical speciation of silver (Ag) in soils under aerobic and anaerobic conditions: Ag nanoparticles vs. ionic Ag

Yohey Hashimoto, Satoshi Takeuchi, Satoshi Mitsunobu, Yong Sik Ok

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


This study investigated how silver nanoparticles (AgNP) and ionic silver (AgNO 3 ) undergo phase-transformations in soils under aerobic and anaerobic conditions using extended X-ray absorption fine structure (EXAFS) spectroscopy. After 30 days of aerobic incubation, 88% of AgNP added to the soil remained persistent, whereas AgNO 3 was completely transformed into Ag associated with humus and clay minerals. In the anaerobic soil, 83% of the spiked AgNP was transformed into Ag 2 S, accompanied by significant decrease in water- and acid-extractable Ag fractions. About 50% of AgNO 3 spiked to the anaerobic soil underwent transformations into metallic Ag and associations with clay minerals. Oxide (Ag 2 O) and carbonate (Ag 2 CO 3 ) forms of Ag were not predominant in aerobic and anaerobic soils. The redox potential of soil had a profound effect on determination of the phase-transformation pathways for AgNP and ionic Ag.

Original languageEnglish
Pages (from-to)318-324
Number of pages7
JournalJournal of hazardous materials
Publication statusPublished - 2017 Jan 15
Externally publishedYes

Bibliographical note

Funding Information:
The authors are grateful to Noriko Yamaguchi (National Institute for Agro-Environmental Sciences) for supporting the XAFS experiment. The XAFS spectroscopy experiment was conducted using a Beamline BL01B1 at SPring-8, Hyogo, Japan, supported by the Japan Synchrotron Radiation Research Institute (proposal numbers: 2012B1327, 2013B1068, and 2014B1245). This study was funded in part by Challenging Exploratory Research, MEXT KAKENHI Grant Number 24658062 for Y.H., provided by The Ministry of Education, Culture, Sports, Science, and Technology, Japan. The following data are included in Supporting Information: time-series Eh data in the soil during the incubation period, SPOIL scores for LCF-EXAFS investigation, chemical equilibrium reactions and stability constants of Ag compounds used for constructing an Eh-pH diagram, Fourier transformed EXAFS shell fitting, and the best and second-best results of LCF on Ag K-edge EXAFS spectra.

Publisher Copyright:
© 2015 Elsevier B.V.


  • Chemical speciation
  • Nanomaterials
  • Redox
  • XAFS

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis


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