Soil-Solution Distribution Coefficients, K_d s, of I^- and IO^- ₃ for 68 Japanese Soils

Abstract

Soil-solution distribution coefficients, K d s, of I and IO s were measured by a batch method using 125 I for 68 wet (fresh) and autoclaved soils collected from upland fields, paddies, forests and open areas throughout Japan. Nine soil properties, such as soil-pH, cation exchange capacity (CEC), anion exchange capacity (AEC), active-Al (extractable Al by oxalic acid + ammonium oxalate) and total organic carbon (TOC), were also measured. The K d s for wet soils ranged widely from 1.1 to 10,200 1 kg"' for I" and from 2.1 to 8210 1 kg ' for 10,. The medians for I~ and IOi were 525 and 437 1 kg -1 , respectively. These values were almost two orders of magnitude higher than previously reported K d s for air-dried Japanese soils. The medians of K d s for I and IO, were the highest for Andosols, followed by Gley soils and Brown Forest soils. The K d s for sandy samples were low. Relatively good correlations (r > 0.65) were found between K d s for wet soils and TOC and total-N, indicating the contribution of organic materials on the sorption of I. The K d s were markedly reduced by autoclaving. The medians of K d s for autoclaved soils for I" and IO3 were 2.4 and 12.41 kg -1 , respectively. The effects of autoclaving on the sorption of I~ were more remarkable than those for It was estimated that 86% of I sorption and 50% of IOj sorption were attributable to the microbial activities and/or soil fractions which are sensitive to autoclaving.

Biogeochemical Considerations Related To The Remediation Of I-129 Plumes

“…In lysimeter studies of four soils with organic contents ranging from 0.2-6.8 wt %, Sheppard and Thibault (1991) measured K d values that were 1-2 orders of magnitude higher in the organic-rich soils relative to the organic-poor soils. Similar results were shown in comparative studies by Yoshida et al (1992), Bird and Schwartz (1996), Sheppard et al (1996), and Yoshida et al (1998). Kaplan (2003) compared iodide uptake by two sediments that had similar grainsize, mineralogy, and pH values, but had very different organic carbon contents, <0.02 versus 0.14 wt %.…”

“…Many researchers have tested this hypothesis by comparing iodine sorption onto sterilized and unsterilized soils (Behrens, 1982;Bird and Schwartz, 1997;Sheppard, 1995;Yoshida et al, 1998). These studies have confirmed that microbial activity is involved, but the nature of that involvement is unresolved.…”

Comportement de radionucléides (Cs, I, Sr, Se, Tc) dans le sol : proposition de valeurs de Kd par défaut

“…Une partie de ces dernières valeurs, sources des données par défaut, doit être négligée, en raison de conditions de détermination trop particulières. Par exemple, certains Kd ont été acquis sur du charbon de bois, considéré ensuite comme sol de catégorie « organic » ou bien sur des substrats du sous-sol ; de même, les valeurs très élevées obtenues par Yoshida et al (1998) sur des andosols sont écartées en raison du caractère spécifique de ces sols que l'on n'observe que rarement (Puy de Dôme) en France. Si l'on excepte ces valeurs très élevées, le pool de données de l'intervalle 0-100 L kg -1 présente une moyenne géométrique de 3 pour un intervalle de valeurs variant de 0,04 à 120.…”

Environmental Geochemistry of Radioactive Contamination

“…Organic iodo compounds are not soluble and form readily through reaction with I 2 and, to a lesser extent, I - (Lieser and Peschke, 1982;Couture and Seitz, 1985); retention of iodine in soils is mostly associated with the organic matter (Wildung et al, 1974;Muramatsu, et al, 1990;Gu and Schultz, 1991;Yoshida et al, 1998;Kaplan et al, 2000). Several studies have suggested that fixation of iodine by organic soil compounds appears to be dependent upon microbiological activity, because sterilization by heating or radiation commonly results in much lower iodine retention (Bunzl and Schimmack, 1988;Koch et al, 1989;Muramatsu et al, 1990;Bors et al, 1991;Rädlinger and Heumann, 2000).…”