title: Chemical speciation of silver (Ag) in soils under aerobic and anaerobic conditions: Ag nanoparticles vs. ionic Ag.
abstract: This study investigated how silver nanoparticles (AgNP) and ionic silver (AgNO3) 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 AgNO3was completely transformed into Ag associated with humus and clay minerals. In the anaerobic soil, 83% of the spiked AgNP was transformed into Ag2S, accompanied by significant decrease in water- and acid-extractable Ag fractions. About 50% of AgNO3spiked to the anaerobic soil underwent transformations into metallic Ag and associations with clay minerals. Oxide (Ag2O) and carbonate (Ag2CO3) 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.
authors.affiliation: Department of Bioapplications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology, 2-24-16 Koganai, Tokyo 184-8588, Japan. Electronic address: yhashim@cc.tuat.ac.jp.
authors.forename: Yohey
authors.initials: Y
authors.lastname: Hashimoto
authors.affiliation: Department of Bioapplications and Systems Engineering (BASE), Tokyo University of Agriculture and Technology, 2-24-16 Koganai, Tokyo 184-8588, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takeuchi
authors.affiliation: Institute for Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mitsunobu
authors.affiliation: Korea Biochar Research Center & Department of Biological Environment, Kangwon National University, Chuncheon 200-701, South Korea.
authors.forename: Yong-Sik
authors.initials: YS
authors.lastname: Ok
keywords: Chemical speciation; Nanomaterials; Redox; XAFS