Integrating of airborne gamma-ray survey and geological data for environmental radioactivity map construction.

The airborne γ-ray spectrometry method (AGRS) is widely considered as an important tool for mapping environmental radioactivity both in geosciences studies and for purposes of emergency response. AGRS is a powerful tool with respect to in-situ gamma-ray measurements for monitoring large areas, especially if it is handled with informations brought by geological maps. Using a typical cluster of NaI crystals (16 L) mounted on microlight, we performed the first airborne gamma-ray survey on Elba Island (about 224 square km) with the purpose to measure the K-40, U and Th content in the top soil. The results provide comprehensive records of environmental radioactivity concentrations, by considering the geological setting of the area. In this study we advance a new multivariate approach by using Collocated CoKriging (CCoK) interpolator with geological constrains, in order to produce airborne gamma-ray maps. The very complex geological setting of Elba Island makes the indicator approach almost inapplicable, which would have been the more logical choice if the number of categories would have been relatively low. In fact, the most actual geological database is composed by a relatively large number of different geological formations (73 different geological formations mapped by a detailed field survey at scale 1:10,000), very high regarding to the usual application of indicator estimators