radon in groundwater - Mark- och vattenteknik - KTH

Radon in groundwater - Influencing factors and prediction methodology for a Swedish environmentDetailed Study on LjusteröFor analyses on a detailed scale (Paper III),groundwater samples from 38 private wellswere collected during summer 2004 on theisland of Ljusterö, Stockholm archipelago(Fig. 1). Several areas on the island exhibitwide variations in radon concentrations(very low concentrations and very highconcentrations in the same neighbourhood)and these areas were delineated in a priorstep using GIS. Whereas it was easily decidedwhich areas would be sampled, it wasdifficult to determine which specific wellswould be the subject of investigation becausethe consent of the private well ownerswas needed prior to any sampling. It wasensured that sampling was carried out only ifwater had been in circulation for a satisfactoryperiod of time, hence the water wasdirectly extracted from the bedrock. Sampleswere sent to an accredited laboratory for themeasurement of 222 Rn, 226 Ra and 238 U insolution. 222 Rn was measured using a Lucascell (ZnS scintillation cell). It should, however,be mentioned that only preliminaryresults of chemical analyses are presented inthis thesis. Geochemical modelling to understandthe influence of chemical processes isto be conducted in future work. In thisdetailed study, in addition to analysis ofairborne uranium measurements collectedfrom the Geological Survey of Sweden (witha scale of 1:50 000), measurements ofequivalent uranium (via gamma radiationmeasurements) were performed on outcrops(Emell and Moen, 2005). The instrumentsused were a scintillation counter, a gammaspectrometer counter and a gamma spectrometerwith a Bismuth Germanate crystal,GR-130BGO.9