Development and Implementation of a Highly Sensitive Method for Analyzing Chemical Forms of Iron Using XAFS Measurements

• Published in: Journal of Water and Environment Technology Vol. 23; no. 1; pp. 46 - 55
• Main Authors: Mishima, Iori, Kubota, Keiichi, Watanabe, Tomohide
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Society on Water Environment 2025; 公益社団法人 日本水環境学会; Japan Science and Technology Agency
• Subjects: anaerobic sediment; Environmental management; Fine structure; Goethite; Iron; iron form; Nutrient cycles; Nutrients; pattern fitting; Phosphates; Phosphorus; pretreatment; Quality management; Sediment samplers; Sediment samples; Ultrastructure; Water quality; Water quality management; X ray absorption; XAFS spectra
• ISSN: 1348-2165
• DOI: 10.2965/jwet.24-077

The chemical forms of iron significantly influence the dynamics of nutrients and biological productivity in the water environment. The most common oxidized form of iron, Fe(III), forms insoluble compounds such as goethite (α-FeOOH) in its oxidized state. Especially, Fe(III) compounds readily adsorb phosphate ions, effectively preventing phosphorus from dissolving into the water. Conversely, in a reductive environment, the reduction of Fe(III) to Fe(II) can release previously adsorbed phosphorus. These interactions are considered crucial for proper water quality management and environmental conservation, with a focus on the chemical forms of iron. In this study, highly sensitive methods for analyzing the chemical forms of iron using X-ray absorption fine structure (XAFS) measurements were developed. Four pretreatment methods were evaluated, and anaerobic drying was found to most effectively preserve the reduced iron state. Pattern fitting techniques were applied to sediment samples, and it was shown that the method could accurately describe the iron forms in these samples. These findings are considered to contribute to the understanding of iron’s role in nutrient cycling and its broader impact on water environments.