Airborne uranium data in support of radon potential mapping in Derbyshire, Central England

Abstract

In order to assess if uranium (eU) data gathered by airborne survey could support the radon potential mapping process in areas with few indoor radon measurements, the relationship between airborne eU values, ground-based eU measured by in situ gamma spectrometry, indoor radon and soil gas radon was investigated for Derbyshire, Central Britain. Significant correlations between the airborne eU geometric mean and the geometric mean of indoor radon for a single geological unit can be demonstrated in some urban areas (e.g. Buxton, Derbyshire, England) where there are many indoor radon measurements. Significant correlation was also shown in the Buxton area between airborne eU data, soil gas radon measurements and the percentage of houses estimated to exceed the UK Action Level of 200 Bq m-3. At the regional scale, airborne eU data correlates significantly (p=0.0005) with geometric mean indoor radon for data grouped by generalised geology and 1-km grid square when data for all geologies are considered together. Significant correlations for individual geological units are found only when these include a wide range of eU and indoor radon values (e.g. Visean Limestone). Permeability of the parent material (soil, superficial deposits and/or bedrock) is an important controlling factor in the relationship between eU and indoor radon as the same level of uranium generally gives rise to higher indoor radon when the bedrock is permeable and lower indoor radon when the bedrock is impermeable. Linear regression modelled estimates of indoor radon with K, eTh, eU and permeability as independent predictor variables correlate better with measured indoor radon than when eU is the sole predictor variable