Introduce lichen Lepraria incana as biomonitor of Cesium-137 from Ramsar, northern Iran

Abstract

Lichens have been used as biomonitors of airborne radionuclides released in conjunction with nuclear bomb testing as well as nuclear power plant accidents. The potential of lichens for monitoringof radionuclides has been well documented. However, there are no studies that determine natural and artificial radionuclide monitoring by lichens, in Iran. Thus, as a first step, we have conducted a comparison of 137Csactivity concentration capacity of three epiphytic lichen species including Lepraria incana, Xanthoria parietina and Ramalina farinacea from Ramsar Northern Iran. In this work, accumulation capacity of 137Cs was determined in 36 lichen samples using a gamma spectrometer equipped with a high purity germanium (HPGe) detector. The results showed that highest accumulation capacity of 137Cs in the lichen species was found in Lepraria incana and Xanthoria parietina, 30.2, 9.8 Bq/kg respectively, and lowest average accumulation capacity were found in Ramalina farinacea 2.7 Bq/kg (dry weight). This study showed that activity concentration 137Cs is in crustose > foliose > fruticose lichens in the same biotope. Thus, crustose lichens are capable to accumulate higher 137Cs than foliose and fruticose species because of different factors such as special morphological characteristics in these species and large surface/volume ratio or longer biological half-life of 137Cs in lichen Lepraria incana. Therefore, Lepraria incana due to high concentration capability of 137Cs (approximately 3 and 11 time higher than Xanthoria parietina and Ramalina farinacea, respectively), is introduced as biomonitor of Cesium-137 from Ramsar, North of Iran.