Assessment of natural radioactivity levels and their relationship with soil characteristics in undisturbed soils of the northeast of Buenos Aires province, Argentina

• Published in: Journal of environmental radioactivity 2012-02, Vol.105, p.30-39
• Main Authors: Montes, M.L., Mercader, R.C., Taylor, M.A., Runco, J., Desimoni, J.
• Format: Article
• Language: English
• Subjects: Adult; Applied sciences; Argentina; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Fe phases; Ferric Compounds - analysis; Ferric Compounds - chemistry; Humans; Mössbauer spectroscopy; Natural radioactivity; Pollution; Pollution sources. Measurement results; Pollution, environment geology; Potassium Radioisotopes - analysis; Radiation Dosage; Radiation Monitoring - methods; Radioactivity; Radium - analysis; Soil; Soil and sediments pollution; Soil properties; Spectroscopy, Mossbauer; Thorium - analysis
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2011.09.014

Surface and depth profile concentrations (down to 50 cm) of 232Th chain, 226Ra, and 40K radionuclides were determined in undisturbed coastal and inland soils of La Plata city region, Argentina, through their gamma-ray activity using a high-purity Ge detector spectrometer. These results were compared with superficial activities determined in soils from the surroundings of the Centro Atómico Ezeiza (Ezeiza Atomic Center) located in Ezeiza, Buenos Aires Province, Argentina. The hyperfine and magnetic Fe phase’s properties of soil profiles were characterized by Mössbauer spectroscopy, magnetic hysteresis loops and AC magnetic susceptibility. No dependence of the activity of the 232Th natural chain on depth was found, whereas variations for 226Ra and 40K activities were observed. Positive correlations, determined by the Pearson correlation coefficients, were established between 40K, 226Ra and 232Th activity concentrations for the whole set of soil samples. The annual external equivalent dose for adults was similar for La Plata and Ezeiza regions, with average values of 0.08 ± 0.01 mSv and 0.06 ± 0.02 mSv, respectively. The thermal dependence of the AC magnetic susceptibility revealed the existence of magnetite and hematite. The Mössbauer spectra of all soils were made up of signals associated with α-Fe 2O 3, a paramagnetic relaxation component, and Fe 3+ and Fe 2+ doublets. In addition, the spectra of inland soils revealed the presence of Fe 3O 4. A negative correlation was found between the activity concentrations and the α-Fe 2O 3 and Fe 3O 4 relative fractions, whereas a positive correlation was found between the Fe 3+ relative fraction and the 40K activity. ► 40 K, 226Ra and 232Th activity profiles of soil of northeast of Buenos Aires Province. ► The study has been complemented with magnetic and Mössbauer spectroscopy measurements. ► Correlations between natural activities and activities - Mössbauer relative areas. ► Determined annual committed effective doses slightly higher than UNSCEAR data.