Butterfly Puddling: an Alternative Cs-137 Pathway to the Pale Grass Blue Butterfly Following the Fukushima Nuclear Accident
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AN ABSTRACT OF THE THESIS OF David A. Hermann for the degree of Master of Science in Radiation Health Physics presented on April 24, 2020. Title: Butterfly Puddling: An Alternative Cs-137 Pathway to the Pale Grass Blue Butterfly Following the Fukushima Nuclear Accident Abstract approved: ______________________________________________________ Kathryn A. Higley Environmental modeling as a result of the Fukushima accident has been at the forefront for present day health physics. The accident released radionuclides in the environment and the fate and transport of these radionuclides are of interest when considering doses to non-human biota. The Pale Grass Blue Butterfly was studied following the accident due to previous research and its abundance in rural and urban areas. The most studied pathways of exposure for the Pale Grass Blue Butterfly were the traditional ingestion and external pathways, but another potential exposure pathway is through the behavior of butterfly puddling. Butterfly puddling is a behavior of adult male butterflies to congregate around puddles to drink large amounts of water in order to concentrate the puddles dissolved nutrients, primarily sodium. The fluid passes through the males to adjust for low diet concentrations of sodium from plants. The concentrated sodium is then transferred to females as gifts during copulation and distributed to their eggs. As cesium and potassium have similar chemical properties because both are alkali metals, radiocesium may permeate biological sodium channels due to the same properties. This paper will entail a literature review of this concept, with a proposed butterfly egg dose to determine if it may have caused the researchers unconventional results. ©Copyright by David A. Hermann April 24, 2020 All Rights Reserved Butterfly Puddling: An Alternative Cs-137 Pathway to the Pale Grass Blue Butterfly Following the Fukushima Nuclear Accident by David A. Hermann A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented April 24, 2020 Commencement June 2020 Master of Science thesis of David A. Hermann presented on April 24, 2020 APPROVED: Major Professor, representing Radiation Health Physics School of Nuclear Science and Engineering Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. David A. Hermann, Author ACKNOWLEDGEMENTS The author expresses sincere appreciation to the United States Army for the opportunity to attend Oregon State University as part of the Army Medical Department’s Long-Term Health Education and Training program. My sincere appreciation to Dr Kathryn A. Higley for providing exceptional academic advisement, and the Radioecology research group for providing additional guidance and research input. CONTRIBUTION OF AUTHORS Contributions include the OSU NSE Radioecology Research group, with Dr. Higley serving as academic advisor and group leader. TABLE OF CONTENTS Page 1 Introduction...……………………………………………………………………………………1 2 Literature Review.……………….………………………………………………………………3 2.1 Fukushima Nuclear Accident & Cs-137 Deposition……………………..……………….…3 2.2 Cesium-137………..………………………………………..…………………..……………5 2.2.1 Cesium-137 Radioactive Transformation and Decay…………...….…..…………..….5 2.2.2 Cs-137 Dose………………………….……………….……………..………..………11 2.2.3 Cs-137 Uptake………………………………………...……......….……….…………20 2.3 Pale Grass Blue Butterfly………...………………........................………………...………25 2.3.1 Species…………….……………….…….…………………………………………...25 2.3.2 Anatomy and Lifecycle…………………….…………………………………………25 2.3.3 Lepidoptera Anatomy and Lifecycle to Irradiation…………………………………...29 2.3.4 Reproduction…………...…………………….……………………………………….30 2.3.5 Habitat ………………………………………………………….…………………….31 2.3.6 Butterfly Puddling Behavior………………………………………………………….32 2.3.7 Environmental Studies…………...……………………...……….………..………….37 2.3.7.1 Environmental Indicator Species.…………………………………….………37 2.3.7.2 Environmental Study Complexities……………………………………….….39 3 Materials & Methods.……….…………………..…...…………………………………………47 3.1 Internal Absorbed Dose……………………………………………………………………..47 3.2 External Absorbed Dose…………………………...………………………………………..48 TABLE OF CONTENTS (Continued) Page 4 Results …………………………………………………………………………………………51 4.1 Internal Absorbed Dose Due to Puddling Behavior………………………………………..51 4.2 External Absorbed Dose due to Cs-137 Dispersion………………………………………..53 4.3 Internal + External Absorbed Dose………………………………………………………...56 5 Discussion ……………………………………………………………………………………..57 6 Conclusion.……………………………...….…………………………………………………..65 References.………………………………………………………………………...……………..66 Appendices.………………………………………………………………………………………78 LIST OF FIGURES Figure Page 2.1 Cs-137 Decay ……………...………………………………………..…….…...……………...9 2.2 Oxalis corniculata Plant………………………………………………………………………32 2.3 Scanning Electron Microscope of Probiscus………………………………………….……...33 5.1 ICRP 30 GI Model vs Proposed Lepidoptera Cs/Na Ratio Biokinetic Uptake Model……….58 LIST OF TABLES Table Page 2.1 Biological and Environmental Half-Life of 137Cs………………………..…………………..7 2.2 Cs-137 Average and Maximum Energy……………………………………………………….8 2.3 Absorbed Fractions for Uniform Distribution of Activity in Small Spheres and Thick Ellipsoids………………………………………………………………………….14 2.4 Absorbed Fractions for Energies and Sphere Sizes for Electrons……………………………15 2.5 Decay Data for for 137Cs…………………...…………………………………………...…....17 2.6 Decay Data for 137mBa…………………………………………………….………………….17 2.7 MIRD vs ICRP Methods for Dose…………………………………..……………………….19 2.8 Atomic and Ionic Radii of Alkali Metals and Monovalent Cations…………………………22 2.9 Permeability Ratios for Metal Cations in Sodium Channels…………………………….…...23 2.10 Radiotolerances of different stages of Lepidoptera………………………………………....29 2.11 Biological impacts of radiation conducted since the Fukushima accident……..…………...41 2.12 Typical attributes of male lepidopteran insects (and their progeny) receiving substerilizing doses of radiation………………………………………………………………….42 4.1 Egg Mass Calculation………………………..………………………….…………………....51 4.2 Lycaena hippothoe Egg Density Calculation………..……………………………………......51 4.3 Sodium (Na), Cs-137 and Nuclear Transformation per Egg…………………………………51 4.4 Internal MeV/g (x, γ, beta, ce, and auger)……..…..………………………..………..……...51 4.5 Sum of Cs-137Decay Yield, Energy and Absorbed Fraction…………………………………52 4.6 Absorbed Fraction Interpolation Calculations………………………………………………..52 4.7 Internal Absorbed Dose per Egg per Day…………………………………………………….53 4.8 Internal Absorbed Dose per Egg for 4 Days…………………………………………………53 LIST OF TABLES (Continued) Table Page 4.9 Egg Volume, height and Cs-137 Dispersion Activity (Bq/cm2)………………….………….53 4.10 Ground External Flux (Photons and Betas)……..…………………………………………..54 4.11 Ground Contamination Absorbed Dose (Photons and Betas)……………………………....54 4.12 Leaf Top Contamination External Flux (Photons and Beta)………………………………..55 4.13 Leaf Top Contamination Shielding and Half-life Reduction………………………………..55 4.14 Leaf Top Contamination Absorbed Dose (Photons and Betas)……………………………..55 4.15 Internal + External Absorbed Dose Per Day……………..………………………….………56 4.16 Internal + External Absorbed Dose 4 Days…..………………………………….…………..56 LIST OF APPENDICES Appendix Page A. Abbreviations………. …………………………………………………………….…...….....78 DEDICATION This thesis is dedicated to my family, for all their dedication and support. 1 1. INTRODUCTION The Fukushima Daiichi nuclear power plant (FDNPP) nuclear accident (described in Section 2.1) brought much research and discussion to the nuclear field. The World was watching as agencies came together to describe what was happening and to minimize effects. A major factor that contributed to the accident was the widespread assumption in Japan that its nuclear power plants were so safe that an accident of this magnitude was simply unthinkable (Amano & IAEA, 2015). The questions which evolved placed researchers in the spotlight with environmental radiation modeling and effects. Because of the large-scale nature of the accident, many research questions have been developed for studies on the biological consequences of the accident at the ecological, organismal, and molecular levels (Otaki, 2018). The Pale Grass Blue Butterfly, with its relatively short life cycle of 30 days and dependence on a single plant, allowed researchers the opportunity to reduce confounding factors and evaluate it in the laboratory. However, Hyama et al. and Nohara et. al. concluded low-dose radiation effects seen in the butterfly are not compatible with the conventional understanding of Lepidoptera’s high radioresistence, with their studies focused on external exposure and laboratory studies on radioactive cesium consumption. This paper will provide another mechanism of radioactive cesium uptake through puddling behavior to determine if this may have caused their unconventional results. Butterfly puddling (described in Section 2.4), is the behavior which male butterflies suck water from puddles to concentrate sodium. As the Malpighian tubules secrete urine (much like kidneys), water and ions are taken up by the hindgut. Sodium is then transferred to the female during copulation, and subsequently to the egg. Cesium-137 is known to be an analog to potassium; could there be similar properties due to 2 cesium and sodium being alkali metals (described in Section 2.2.3)? The next question is then, is the egg the most radiosensitive life-stage of the butterfly? The literature review