Activity concentrations of radionuclides in lichens following the Fukushima nuclear accident

Abstract

The activity concentration of 131I, 134Cs and 137Cs radionuclides in lichens was traced one and a half months after the Fukushima nuclear accident. The samples were collected in Tsukuba City, which is located c. 170 km south of the Fukushima Daiichi nuclear power plant (NPP). The activity concentrations differed depending on species and habitat. For example, the maximum activity concentration of 137Cs was 22596 Bq kg–1 dry weight in Physcia orientalis (collected from the trunk of Zelkova serrata on 30 June 2011), and 1928 Bq kg–1 in Hyperphyscia crocata (from the trunk of Quercus myrsinaefolia collected on 8 March 2012). The activity concentration of 137Cs in Dirinaria applanata and Phaeophyscia spinellosa growing on vertical habitats decreased by c. 50% within a year, indicating radionuclides might have been washed off by rain. The radionuclides were apparently derived from the Fukushima NPP accident because: 1) one specimen collected at the same place one year before the accident did not contain radionuclides, 2) high activity concentrations of radionuclides were detected after the accident, 3) 131I, which has a short half-life of 8 days, was detected one and a half months after the accident, and 4) the ratio of 134Cs/137Cs in lichens was 0·90–0·98 on 26 April 2011, which is consistent with the values reported for radiocesium from the Fukushima NPP accident.

Temporal variations of 7Be, 40K, 134Cs and 137Cs in epiphytic lichens (genus Usnea) at the Sakhalin and Kunashir islands after the Fukushima accident

“…(5)] is calculated as 1.15 y and 1.08 y for Kunashir and Sakhalin, respectively. These estimates of T eff for the Fukushima-borne 137 Cs in our epiphytic lichens are in agreement with data by Ohmura et al [12] who report that the activity concentration of 137 Cs in Dirinaria applanata growing on tree trunks in Tsukuba City (Honshu Island, Japan) decreased by ca. 50% within a year (2011-2012).…”

“…from Northern Finland after the Fukushima accident. At the same time, the levels of 134 Cs in our lichens appeared to be significantly lower that the levels reported for some epiphytic lichens from Japan in 2011-2013 [10,12]: 19843±273 Bq kg -1 [Physcia orientalis from Tsukuba City (170 km south of the FDNPP)] and 1000000±20000 Bq kg -1 [Parmotrema clavuliferum from Okuma Town (4 km south-west of the FDNPP)]. The strong differences between the 134 Cs levels in lichens from Eastern Russia, Northern Finland and Honshu Island in Japan (Table 6) can be mostly attributed to the global spatial variations in amount of Fukushima fallout.…”

“…The maximum activity concentration of 137 Cs was reported for the foliose lichen Parmotrema clavuliferum from the Fukushima prefecture, and the maximum 137 Cs deposition density on soil for the study area was estimated as 2920 kBq m -2 [10]. Almost all 137 Cs in the epiphytic lichens in Russia and Japan was apparently derived from the FDNPP [12,24], while in the samples in Finland, the radionuclide origin could be mostly attributed to the Chernobyl accident and the atmospheric nuclear weapons tests conducted in the 1950-1960s. It was estimated that the Fukushima accident increased the 137 Cs concentrations in the epiphytic beard lichens (Bryoria sp.…”

“…from Northern Finland in 2011-2013. Within the same time period (2011-2013), elevated activity concentrations of 137 Cs, ranging from 1096±27 Bq kg -1 to 1740000±20000 Bq kg -1 , were found in several species of epiphytic lichens at Honshu Island in Japan (Table 6) [10,12,13]. The maximum activity concentration of 137 Cs was reported for the foliose lichen Parmotrema clavuliferum from the Fukushima prefecture, and the maximum 137 Cs deposition density on soil for the study area was estimated as 2920 kBq m -2 [10].…”

“…The nuclear reactor accident at the Fukushima-Dai-ichi Nuclear Power Plant (FDNPP) in Japan in 2011 (for review see e.g., [9]) has triggered a new wave of research on the lichens ability to intercept and retain the fallout 137 Cs and 134 Cs [10,11,12,13]. Specifically, Dohi et al [10] demonstrated that activity concentrations of 137 Cs in some epiphytic lichens (Parmeliaceae, Ascomycota) were positively correlated with the 137 Cs deposition density on soil.…”