University of Huddersfield Repository Hyland, Robert Quentin Thomas. Spatial and temporal variations of radon and radon daughter concentrations within limestone caves Original Citation Hyland, Robert Quentin Thomas. (1995) Spatial and temporal variations of radon and radon daughter concentrations within limestone caves. Doctoral thesis, University of Huddersfield. This version is available at http://eprints.hud.ac.uk/4839/ The University Repository is a digital collection of the research output of the University, available on Open Access. Copyright and Moral Rights for the items on this site are retained by the individual author and/or other copyright owners. 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For more information, including our policy and submission procedure, please contact the Repository Team at: [email protected]. http://eprints.hud.ac.uk/ SPATIAL AND TEMPORAL VARIATIONS OF RADON AN]) RADON DAUGHTER CONCENTRATIONS WITHIN LIMESTONE CAVES BY ROBERT QIJENTIN THOMAS IIYLAND A thesis submitted to the University of Huddersfield in partial fhlflhlment of the requirements for the degree of Doctor of Philosophy January 1995 Volume One ABSTRACF This thesis outlines results from an investigation of radon and radon daughter concentrations in limestone caves, from a geographical and geological perspective Investigations were conducted at all geographical scales, ranging from a national investigation in the four major caving regions of England and Wales to a detailed survey within a single cave in the Peak District The measured radon concentrations in some limestone caves in England and Wales are amongst the highest ever recorded in the world Significant spatial and temporal variations were recorded m concentrations at all scales, within a single cave, between caves in the same region and between different regions Additionally, seasonal and diurnal variations in concentrations were highlighted. External climatic variables and the cave radon budget were demonstrated to account for variations in cave radon concentrations Within limestone caves seven primary sources of radon were identified and the relative importance of each to the overall radon budget was determined Sediments and the contaming limestone rock were the major sources although in certain cases water and the soil were demonstrated to be influential Models were developed to predict cave radon concentrations within a single cave However, these could not be transposed to predict radon concentrations in other caves in the same region or other regions The users of limestone caves were identified, their potential exposure times were examined and legislation concerning their exposure was discussed Four groups were identified as being at risk from radon while underground, and three groups were identified as bemg at little risk Methods by which the risk from radon exposure can be reduced were examined m ACKNOWLEDGMENTS Thanks go to Professor John (3unn and Dr Simon Bottrell for support and encouragement durmg the course of this research. Without the help of the 'Team' at home none of this would have been possible, especially Mm for all her support, Bar for his editorials and Mildred for always being willing to go for a walk when I needed to get away Thanks also go to all cavers who helped during the National project, and to Gill and all the employees at Peak Cavern for allowmg access and always bemg available with a cup of coffee at the end of a long day 'in the field' Thanks also to John and Cathy Gunn, John Beck, Dave Nixon and Steve Pratt for assistance with the production of figures and photos 'V TABLE OF CONTENTS SPATIAL AND TEMPORAL VARIATIONS OF RADON AND RADON DAUGHTER CONCENTRATIONS WITHIN LIMESTONE CAVES .......................I Frontispiece........................................................................................................ II ABSTRACT....................................................................................................... 111 ACKNOWLEDGMENTS ...................................................................................iv TABLEOF CONTENTS.....................................................................................v CHAPTERONE: INTRODUCTION ......................................................................... 1 1 .1 Background to the thesis................................................................................1 1.1.1 Project Definition...................................................................................1 1 .1.2 Impetus thesis.............................................................................1 1 .2AimsandObjectives.......................................................................................4 1 .3 Environmental radiation..................................................................................5 1 .3.1 Sources f radiation...............................................................................5 1.3.2 Radon isotopes 4 environmental significance fRadon-222 ..........5 1.3.3 Definition and characterisation of radon ?i4 radon daughters.................6 1 .4 Karst Environments: Definitions.....................................................................7 V 1.4.lKarst.7 1.4.2 Limestones .8 1.4.3 Caves.....................................................................................................8 1.4.4 Cave Microclimate.................................................................................9 1.5 Structure ofthethesis...................................................................................14 CHAPTER TWO: ENVIRONMENTAL IONISING RADIATIONS AND PROPERTIESOF RADON-222..............................................................................13 2.1 Introduction...................................................................................................13 2.2 Radiochemical principles...............................................................................14 2.2.1 Properties Qf atoms..............................................................................14 2.2.2 Radioactive decay...............................................................................15 2.2.3 Decay series.........................................................................................16 2.2.4 Radioactive equilibrium........................................................................17 2.2.5 Radioactive decay................................................................................19 2.2.6 Development discovery fradiochemistry. yj special reference radon-222.....................................................................................................20 2.3 Properties of radon and radon daughters.......................................................21 vi 2.3 Properties of radon and radon daughters .21 2.3.1 Properties Qf radon ....................................................................... 21 2.3.2 Properties short-lived radon daughters.......................................21 2.3.3. Attached 4 unattached fractions.......................................................23 2.3.4. Equilibrium f radon 4 radon daughters...........................................29 2.4. Units...........................................................................................................24 2.4.1 Introduction.........................................................................................24 2.4.2.Radonunits.........................................................................................25 2.4.3. Radon daughters.................................................................................26 2.4.4. Dose...................................................................................................28 2.5 Summary......................................................................................................29 CHAPTER THREE: RADON IN LIMESTONE CAVES: AN INTERNATIONAL LITERATUREREVIEW.........................................................................................31 3.1 Introduction .................................................................................................31 3.2 Historical summary of international radon literature......................................31 3.3 The general cave radon system.....................................................................33 3.4 Theories proposed to account for the cave radon system...............................33 vu 3.4.1 Cave moho10 .33 3.4.2 Temperature........................................................................................37 3.4.3 Pressure...............................................................................................38 3.4.4 Depth...................................................................................................39 3.4.5 Equilibrium between radon 4 radon daughters ..................................40 3.4.6 Radon-220 (Thoron)............................................................................40 3.4.7 Sources radon to limestone cave environments.................................40 3.4.8 Variations 21 radon j relation to height within passages..............41 3.4.9