title: Vertical distribution and characteristics of soil humic substances affecting radionuclide distribution.
abstract: The humic substances extracted from different soil depths are separated into humic (HA) and fulvic (FA) acids, and characterized for their chemical composition, proton exchange capacity, spectroscopic characteristics and binding properties to the europium ion. The chemical and spectroscopic results show that FA compared to HA has a relatively high O/C ratio, high acidic functional group contents and low aromatic contents. The synchronous fluorescence spectroscopic results show that the stability constant (K) of the soil humic substances with Eu(III) ion tends to increase as the soil depth becomes deeper, and HA has a slightly stronger binding ability than FA. The measured total site concentrations (C(L)) reveal that Eu(III) ion is loaded onto HA by 62-77% of the total acid sites, but FA is only approximately 50% covered by Eu(III) ion. Information could be useful in understanding the migration of radionuclides in soil layer.
authors.affiliation: Nuclear Environment Research Division, Korea Atomic Energy Research Institute, P.O. Box 105, Yuseong, Daejeon 305-600, South Korea.
authors.forename: Kun Ho
authors.initials: KH
authors.lastname: Chung
authors.forename: Geun Sik
authors.initials: GS
authors.lastname: Choi
authors.forename: Hyun Sang
authors.initials: HS
authors.lastname: Shin
authors.forename: Chang Woo
authors.initials: CW
authors.lastname: Lee
mesh_terms: D001578:Benzopyrans; D004784:Environmental Monitoring; D005063:Europium / Q000032:analysis*; D006812:Humic Substances; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D013050:Spectrometry, Fluorescence
chemical_list: D001578:Benzopyrans; D006812:Humic Substances; D012990:Soil Pollutants, Radioactive; D005063:Europium; C005023:fulvic acid