The temporal variation of Fukushima-derived ¹³⁷Cs deposition in Miyagi Prefecture and its relation to the air concentrations and other environmental factors

Deposition (rain and dry fallout) and surface air concentration of ¹³⁷Cs were observed in several sites in Sendai and other regions in Miyagi Pref, after the accident of Fukushima Dai-ichi Nuclear Power Plant (FDNPP) occurred in 2011. Those temporal variations and regional differences were compared among the sites considering the meteorological conditions and the surrounding environment. The monthly ¹³⁷Cs deposition at the site in Sendai (an urban area) was sometimes larger than that in Onagawa (a semi-urban area), and the ¹³⁷Cs concentration in the evaporated residues of deposition samples was also higher. Moreover, the air concentration of ¹³⁷Cs at the site in Sendai was higher than in Onagawa. It is considerd that higher amounts of ¹³⁷Cs in fallout and air samples in Sendai can be caused by resuspension of ¹³⁷Cs-rich particles due to the soil which is deposited on the building roofs or other ground surfaces such as pavements or roads. Further research is needed to clarify the resuspension mechanism, in the future. (author)