radon in groundwater - Mark- och vattenteknik - KTH

Radon in groundwater - Influencing factors and prediction methodology for a Swedish environmentCONCLUSIONS• Radon concentration in groundwaterwas successfully analysed throughmultivariate statistical analyses. Therisk variable method was useful toidentify areas with increased radonconcentrations in the groundwater.• Factors of significance for the predictionof radon in groundwater were:type of bedrock, type of soil, altitude,distance to a fracture zone and the distributionof uranium in the bedrock.• Visual data mining revealed correlationpatterns in a preliminary stage ofdata analysis but were not useful as anindependent method to draw conclusionsregarding radon concentrationsin groundwater. The 3D visualisationsof the dataset did not show any newpattern but instead confirmed the correlationsgiven from statistical analyses.• A weak correlation existed between222 Rn and 226 Ra or 238 U in the groundwater,indicating that the main sourceof 222 Rn in groundwater was not originatingfrom its parent elements (asions) in solution.FUTURE WORKThe present research evaluated differentspatial data for the purpose of developing a222prediction methodology for Rn ingroundwater on a general scale. However,the dynamics of subsurface processes, whichprobably have a strong influence on theoccurrence and migration of radionuclides( 222 Rn, 226 Ra and 238 U), were not studied. Thegoals for future work would thus include thefollowing issues:1. Clarification of groundwater chemistryin connection with high natural radioactivityin groundwater. Geochemicalmodelling will be carried outin order to identify and quantify geochemicalprocesses governing uraniummobilisation and fixation and to developan understanding of the longtermeffects of oxidation-reduction onactinide (uranium) behaviour. Additionalchemical data are needed forthat purpose and a sampling programmeconsisting of water samplingand chemical analyses of groundwaterneeds to be carried out.2. The variation in radionuclides ingroundwater over time and season willalso be investigated. For that purpose,about five wells will be sampledmonthly over a period of one year.3. The transport mechanisms of 222 Rnand its parent elements ( 226 Ra and238 U) are highly relevant subsurfaceprocesses that need to be studied. Existingtransport models for these radionuclideshave previously been developedin connection with investigationsregarding repository sites fornuclear waste. These models are oftenvery detailed and their applications ona general scale have not been tested.The goal is to evaluate these modelsand formulate a simplified processbasedtransport model for radon ingroundwater.4. In a final stage, an operative methodfor vulnerability assessment of radoncontent in wells based on the outcomeof the modelling and previous generalisedstudies in GIS will be formulated.Such a tool will be helpful in decisionmakingprocesses concerning planningof new wells or effective remediationmeasures.19