AN A S'JRACTOF THE THESIS OF Paul Robert Crowley for the degree of Master of Science in Radiation Health Physics presented on January l42OOO. Title: Behavior of 59Fe in a Marine Estuarine Environment: Uptake and Retention by the Pacific Basket-Coclde Clinocardium nuttallii. Redacted for Privacy Abstract approved: Kathryn A. Higley Iron-59 and its speciation in a cold model estuary were chosen as the focus for this study on the effects and behavior of radionuclides in the marine environment. Iron-59 is a common constituent of the reactor effluent water found on U. S. Naval, nuclear powered warships. It could provide useful data in assessing the radiological impact of shipborne reactor accident resulting in the release of radionuclides to the marine estuarine environment. As sedimentary filter feeders, bivalves act as excellent bioindicators for marine contamination. Clinocardium nuttallhi, Pacific basket-cockles, were maintained in a recirculating chilled-seawater aquarium. Mi specimens, seawater and sediment were extracted from Yaquina Bay in Newport, Oregon. After allowing the organisms to acclimate to the laboratory conditions, 1.0 mCi of59Fe was added to the system in aqueous form as iron (Ill)chloride and allowed to homogeneously distribute. Over a twenty-onc day period, or one half of one half- life for 59Fe, frequent water, sediment, and cockle samples were drawn, weighed and counted for activity in a sodium iodide, NaII(Tl), solid scintillation detector. All specific activity measurements were corrected for radioactive decay and plotted vs. time after iron introduction to determine the ironspeciation pathways within the system. At the end of the data collection period, five cockles removed fromthe system at various times during the experiment were dissected for a tissue distribution study. The results show that 59Fe rapidly binds to suspended particulate in the water column, and within a few days, most of the iron added to the system was associated with the bottom sediment layer. During the first few days, while suspended particles filtered down through the water column, the cockles fed actively and assimilated 59Fe at a fairly high rate. These results confirm previous bivalve studies suggesting filter-feeding as the primary means for radionuclide uptake. Laboratory and time constraints as well as sampling inconsistencies limited the ability of this experiment to satisfactorily meet all objectives. No convincing evidence was found for: (1) sediment-to-seawater transfer of59Fe; (2) retention of 59Fe by clinocardium nuttaiii; (3) tissue distribution patterns for59Fe in Clinocardium nuttallii. Future research is needed in these areas to more accurately establish and predicate the behavior of 59Fe under varying marine conditions; however, this experiment successfully establishes sedimentation patterns and uptake mechanisms for 59Fe in the marine estuarineenvironment. ©Copyright by Paul Robert Crowley January 14, 2000 All Rights Reserved Behavior of 59Fe in a Marine Estuarine Environment: Uptake and Retention by the Pacific Basket-Cockle, Clinocardiumnuttallii by Paul Robert Crowley A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented January 14, 2000 Commencement June 2000 Master of Science thesis of Paul Robert Crowley presented on January 14, 2000 APPROVED: Redacted for Privacy Major Professor, representing RadiatIon Health Physics Redacted for Privacy Chair o partment of Nuclear Engineering Redacted for Privacy I understand that my thesis will become part of the permanent collectionof Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Redacted for Privacy Paulobert Crowley, Author ACKNOWLEDGEMENTS The completion of this work would not have been possible without the assistance of the followmg people Capt Marvm Rice, USN(Ret) and Capt Thomas Daniels, USN, who convinced me of the importance of thisundertakmg and provided me the latitude and encouragement to see it through to the end,Larry Tyler, who designed and built a superb cold water marme aquariumwith which to conduct my experiments and provided valuable assistance on its mamtenanceand upkeep, Oleg Povetko, who shared his laboratory space and his knowledgeof laboratory procedures and mstrument calibration, without which Iwould still be cursing all thmgs electromc, Mark Treen, mylaboratory assistant, whose patience and computer skills proved vital durmg the experimental stage of this project,Dr Robert Collier, professor of chemical oceanography and my minor professor,who provided me with a reality check m the world of marme biochemistry and estuarme processes. A special thank you is extended to Sherry West, aquarist forthe Hatfield Marine Science Center. Her assistance and guidance in the collectionand maintenance of marine organisms was impressive. Braving the windsand wet winter cold to dig up cockles and worms went far beyond the call of duty. Iwill remain forever in your debt. A special note of appreciation must go to my major professorDr Kathryn Higley, who patiently saw me through the entire research and degree process.Her practical advice and encouragement helped steady me on the oft-wandering path I wove to completion of this project. She showed patiencein accommodating my undergraduate shortcomings and full-time employment and inspired me to think for myself instead of choosing the "easier" path. Special recognition, of course, must go to my wife Salome and to my family. Without their help, which ranged from accompanying me on clamdigging trips and water collection to proofreading rough drafts, I would havesuffered mightily in completing my work (thanks even to Moose and 011ie for keepingthose pesky seagulls from stealing our catch). Their support, patience, and encouragement, especially down the homestretch, were integralcontributions to the successful completion of this degree. TABLE OF CONTENTS Page INTRODUCTION I Iron 2 Sources of Radioactive Iron m the Marme Environment 3 Behavior of 59Fe m the Marme Environment 4 Bivalves as Biomdicators 5 The Pacific Basket - Cockle 6 Taxonomy 6 Filter Feedmg Mechamsms 10 Objectives of this Study 14 MATERIALS AND METHODS 17 Radioisotope 17 Countmg System 18 Marme Ecosystem 23 Sample Collection and Mamtenance 26 Laboratory Experiment 30 RESULTS 34 Sediment 34 Water 37 Bivalves 42 Tissue Distribution Study 48 TABLE OF CONTENTS (Continued) Page DISCUSSION 51 Iron Speciation Uptake and Retention by Clinocardium nuttallii 55 CONCLUSIONS 57 Summary 57 Recommendation for Future Research 58 BIBLIOGRAPHY 60 APPENDIX 64 LIST OF FIGURES Figure Page A cockle, Cardium sp., in its normal feeding position ..8 Lateral view and cross section view through the shell of a bivalve 8 Burrowing sequence of a cockle 9 Internal anatomy of a bivalve ...13 The digestive system of a suspension-feeding lamellibranch bivalve .15 A lamellibranch bivalve gill 15 Detector calibration PLOT - total counts vs. LLD setpoint .20 Optimum LLD Setting vs. gamma energy plot 21 Yaquina Bay, Oregon 24 Chilled-seawater aquarium schematic drawing 25 Photograph of Yaquina Bay tidal flats ...27 Sediment - specific count rate plot (activity decay corrected) .... 35 Sediment mean specific count rate plot (activity decay corrected) .... 36 Water specific count rate plot (activity decay corrected) .... 38 Water mean specific count rate plot (activity decay corrected) 39 Sump tank water specific count rate plot (activity decay corrected) 41 Cockle specific count rate plot 1 (activity decay corrected) 43 Cockle specific count rate plot 2 (activity decay corrected) ....44 Cockle specific count rate plot 3 (activity decay corrected) ...45 LIST OF FIGURES (Continued) Figure Page Cockle mean specific count rate plot (activity decay corrected) .....46 Tissue distribution sample count rate plot (activity decay corrected)49 LIST OF APPENDIX TABLES Table Page Sediment sample count rate data ...65 Surface water sample count rate data ..68 Deep water sample count rate data 70 Bottom (interstitial) water sample count rate data 72 Sump tank water sample count rate data ..74 Cockle (Clinocardium nuttallii) sample count rate data 75 Retention experiment sample data 79 Bent-nose clam (Macoma nasuta) sample count rate data ..80 Tissue distribution sample count rate data 81 Behavior of 59Fe in a Marine Estuarine Environment: Uptake and Retention by the Pacific Basket-Cockle, Clinocardium nuttallii INTRODUCTION Knowledge of the behavior of radionuclides in the marine environment is of considerable importance when attempting to assess the potential radiological impact of radionuclide releases The environmental presence of radioactive iron isotopes as a result of nuclear weapons testmg and the nuclear fuel cycle has been known for quite some time [NAS, 1971, Burton, 1975], despite this, surprismgly limited research has been undertaken to mvestigate its environmental and radiobiological impact Iron is of mterest m the study of marme ecosystems because it is such an important metabolic element and is not found m great quantities in the ocean. One specific isotope of iron, 59Fe, is of particular interest, due to its relative abundance m reactor effluent water and its rapid sorption on sediment and suspended particulate matter This study then, has been undertaken m order to add to the body of knowledge concermng the behavior of radioactive ironin the marine environment, specifically in the seawater-sediment interface of an estuarine ecosystem. 2