Surficial redistribution of fallout 131iodine in a small temperate catchment

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 109; no. 11; pp. 4064 - 4069
• Main Authors: Landis, Joshua D, Hamm, Nathan T, Renshaw, Carl E, Dade, W. Brian, Magilligan, Francis J, Gartner, John D
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 13.03.2012; National Acad Sciences
• Subjects: Atmosphere - chemistry; Biological Sciences; Ecosystem; estuaries; Fluvial transport; Forest soils; Geologic Sediments - chemistry; Iodine; Iodine Radioisotopes; isotopes; Japan; lakes; Motion; nuclear power; nutrients; organic matter; Physical Sciences; Radioactive Fallout - analysis; Radionuclides; Rain - chemistry; rivers; Sedimentary soils; Sediments; soil; Soil - chemistry; Soil air; Soil biology; Soil pollution; sorption; Surface Properties; terrestrial ecosystems; toxins; Watersheds
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1118665109

Isotopes of iodine play significant environmental roles, including a limiting micronutrient (127I), an acute radiotoxin (131I), and a geochemical tracer (129I). But the cycling of iodine through terrestrial ecosystems is poorly understood, due to its complex environmental chemistry and low natural abundance. To better understand iodine transport and fate in a terrestrial ecosystem, we traced fallout 131iodine throughout a small temperate catchment following contamination by the 11 March 2011 failure of the Fukushima Daiichi nuclear power facility. We find that radioiodine fallout is actively and efficiently scavenged by the soil system, where it is continuously focused to surface soils over a period of weeks following deposition. Mobilization of historic (pre-Fukushima) 137cesium observed concurrently in these soils suggests that the focusing of iodine to surface soils may be biologically mediated. Atmospherically deposited iodine is subsequently redistributed from the soil system via fluvial processes in a manner analogous to that of the particle-reactive tracer 7beryllium, a consequence of the radionuclides’ shared sorption affinity for fine, particulate organic matter. These processes of surficial redistribution create iodine hotspots in the terrestrial environment where fine, particulate organic matter accumulates, and in this manner regulate the delivery of iodine nutrients and toxins alike from small catchments to larger river systems, lakes and estuaries.