Discovery of radioactive silver (110mAg) in spiders and other fauna in the terrestrial environment after the meltdown of Fukushima Dai-ichi nuclear power plant

Six months after the explosion of TEPCO’s Fukushima Dai-ichi nuclear power plant, radioactivesilver (^110mAg), was detected in concentrations of 3754 Bq/kg in Nephilaclavata (the orb-web spider; Joro-gumo in Japanese) collected atNimaibashi, Iitate village in Fukushima Prefecture, whereas ^110mAg in the soil was43.1 Bq/kg. A survey of 35 faunal species in the terrestrial environment during the 3.5 yearsafter the accident showed that most of Anthropoda had two orders higher ^110mAg intheir tissues than soils, although silver is not an essential element for their life. However,tracing of the activity of ^110mAg detected in spider Atypus karschicollected regularly at a fixed location showed that it declined much faster than the physicalhalf-life. These results suggest that ^110mAg was at once biologically concentratedby faunal species, especially Arthropoda, through food chain. The factors affecting thesubsequent rapid decline of ^110mAg concentration in faunal species arediscussed.