Preliminary Study on Mosses and Lichens as Bioindicators for Radioactive Fallout Monitoring

Background:The objective of this study is to investigate the suitability of moss and lichen as bioindicators that can substitute for existing bioindicators, such as mugwort and pine needles. Materials and Methods:Fifteen moss (Hypnaceae) and lichen (Parmeliaceae) samples were collected from three differing ecological environments in Korea: a high-altitude mountainous region; a high-humidity coastal area; and an urban community park.The samples were collected from tree trunks, rocks, and soil substrates and were dried, ground, sieved, ashed, and enclosed in polyethylene containers for activity concentration measurements via gamma spectrometry.The reference date for decay correction was based on sampling dates and measured activity. Results and Discussion:The activity concentrations of 137 Cs, 40 K, and 7 Be in mosses by dry weight were 1.89-47.8,156-506, and 60.6-1,227 Bq • kg -1 , respectively.The concentration values varied depending on the substrate and ecological environment.The moss accumulated greater amounts of 137 Cs than the lichen, which was attributed to the greater surface-to-volume ratio of moss.The 137 Cs activity concentrations in moss adhered to tree trunks were substantially lower than those in moss covering rock or soil.This was attributed to differences in 137 Cs resuspension effect, which may occur through the spattering of raindrops and the effects of wind.The transfer factors of radionuclides from soil to moss were 0.61, 0.65, and 0.46 for 137 Cs, 40 K, and 7 Be, respectively. Conclusion:This preliminary study showed that moss accumulates a considerably higher amount of 137 Cs than mugwort.Therefore, mosses seem to be more suitable bioindicators than mugwort for the routine monitoring of radioactive fallout in Korea.However, further research using various moss species from ecological environments and sampling sites with different topography and other geographical properties is needed to reduce the uncertainties in the values estimated in the present study.