Assessment of geogenic radon potential based on granulometric analysis of soil in Vojvodina region

A method based on soil permeability estimates and radon in soil concentration measurements was used to assess radon potential for the first time in our region. The methodology for soil permeability evaluation proposed in the literature is based on determining the weight percentage of fine fraction (particles smaller than 65 μm) in soil samples and classifying of soil permeability index for the radon according to it. Soils with the weight percentage of the fine fraction below 15% were classified as high permeable, in the range 15-65% as medium permeable, and in the case of the fine fraction above 65% as low permeable. A soil grain size distribution analysis was performed by laser diffraction dry method using a particle size analyzer Mastersizer 2000, Malvern Instruments. Radon concentrations in soil gas were measured in situ by an active RAD7 radon monitor with stainless soil gas probe inserted down to a depth of 80 cm using grab protocol which considers sniff mode of pumping and four five-minute cycles of counting. Combining the obtained results for soil permeability indexes and soil radon concentrations, the radon potential in the Vojvodina region was estimated at 14 locations, indicating that the radon risk is in the low and medium class. Parent material for all analyzed types of soil is loess – a typical example of soil with a high amount of the fine fraction which corresponds to low permeability, but in great dependence on soil humidity. Two additional locations in the Southern part of Serbia were included also in this study with a different geological substrate. (author)