Influence of physical factors on radionuclides contents in soils from Biscay (Spain)

Abstract

The content of radioactive constituents in Biscay soils has been investigated in 15 cm cores, at three depth levels, for fourteen sampling positions. At the same time, each soil was characterized by physical parameters (depth level, geographical position, apparent density, and particle size distribution in clay+silt, fine sand and coarse sand fractions). Radionuclides analyses were performed in Marinelli flasks with a gamma spectrometer (Ge‐HP detector and 8000 channels analyser). Seven natural radioisotopes (⁴⁰K, ²²⁸Ac, ²¹²Bi, ²⁰⁸Tl, ²²⁶Ra, ²¹⁴Pb and ²¹⁴Bi) and the artificial radiocaesium were identified and measured. Relations among natural radionuclides and physical soil parameters are mainly obtained by two statistical multivariate methods (linear multiple regression analysis and numerical taxonomy). Dependences of all radionuclides with apparent density and size fractions were found. Some specific relations with depth level (¹³⁷Cs, ²¹⁴Bi and ²⁰⁸Tl) and geographical position (⁴⁰K, because of the proximity to the sea) were also detected. High relations were found among all natural radiosotopes, but a different behaviour is patent for the artificial radiocaesium. Specific activities of size fractions of soils were determined for samples from two points, suggesting an accumulation of activity in the clay+silt fraction.

Key words:

• Radionuclides
• soil radioanalysis