Environmental dose rate values for the quartz and K-feldspar fractions measured in this study.

a Long-term water content, expressed as % of dry mass of sample and assigned a relative uncertainty of ±20%. Long-term water contents are calculated as 60% of saturated values following assessments made in deeper parts of the endokarst system [47].b Radionuclide concentrations and specific activities have been converted to dose rates using the conversion factors given in [68], [105], making allowance for beta-dose attenuation [106], [107].c Gamma dose rates were calculated from in situ measurements made at each sample position with a NaI:Tl or LaBr3:Ce detector using the ‘energy windows’ method [67].d Beta dose rates were calculated using a Risø GM-25-5 low-level beta counter [108], after making allowance for beta dose attenuation due to grain-size effects and HF etching [107].e Cosmic-ray dose rates were calculated following published procedures [69] and assigned a relative uncertainty of ±10%.f Assumed internal (alpha plus beta) dose rate for the quartz fractions are based on published 238U and 232Th measurements for etched quartz grains from a range of locations [109]–[112] and an alpha efficiency factor (a-value) of 0.04±0.01 [113], [114]. For K-feldspar grains, the internal alpha and beta dose rate contributions from 238U and 232Th were calculated using assumed concentrations of 0.15±0.03 ppm and 0.35±0.07 ppm, respectively, based on modal values [112] and similar published values [115]–[117]. An a-value of 0.09±0.03 was used to estimate the internal alpha dose rate contributions from these 238U and 232Th concentrations based on published estimates obtained for a wide range of K-feldspar samples [14], [113], [118]–[121].g Internal dose rate of feldspar grains arising from 40K and 87Rb concentrations were calculated using assumed values of 12.5±0.5% [122] and 400±100 ppm [123], respectively.h Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties.iTT-OSL measurements have not been made on sample ATZ10-3 and pIR-IR measurements have not been made on sample ATG10-4. Hence, only the relevant quartz or K-feldspar dose rates are shown for these two samples.Environmental dose rate values for the quartz and K-feldspar fractions measured in this study.