Estimating soil radon concentration by kriging in the Biggin area of Derbyshire (UK)

A survey of radon concentration in the soil gas was carried out on a single geological formation: the Monsal Dale Limestone, to the South of the village of Biggin, in Derbyshire (England): a 'radon affected area'. An irregular sampling scheme was used with the interval between sampling points varying from 50 m to 250 m. Ninety-three dosimeters were placed at a depth of 50 cm in the soil over an area of 4 km(2) to measure the soil radon concentration. The values were found to range between 3 kBq m(-3) and 35 kBq m(-3), with a mean value of 13.03 +/- 7.60 kBq m(-3). The 'variogram' of Regionalized Variable Theory showed that there is spatial autocorrelation in the variation of radon over the surveyed area within the lithological unit, and also that a considerable proportion of the variation is occurring over distances less than the smallest sampling interval of 50 m. The 'kriged' map of radon shows that there is a distinctive pattern in its variation with an apparent inverse relation between radon concentration and elevation.