Activities of ²³²Th, ²²⁶Ra, ⁴⁰K, and ¹³⁷Cs in surface soil and external dose assessment at two zones of Buenos Aires Province, Argentina

Abstract

In the frame of establishing the radiological baseline of the Buenos Aires Province, Argentina, this work assesses the total outdoor external dose and the activity values of ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs in superficial soils of La Plata and Lima cities. In the latter, the most important nuclear emplacement of the country is located. At La Plata, 49 sites were analyzed, which correspond to the green public spaces of the city while at Lima 6 sites around the nuclear power plants were studied. For La Plata, the external dose contribution and activity distribution maps of ⁴⁰K, ²²⁶Ra, ²³²Th and ¹³⁷Cs were obtained using the Kriging geo-statistical method. Activity values of ²²⁶Ra and ²³²Th resulted lower than their worldwide average ones, while the ⁴⁰K levels were higher than the corresponding one. The activity dataset was analyzed together with the activity values determined previously in unperturbed soils of the region. The Pearson correlation coefficient was re-calculated, obtaining correlations more significant when all activity data were considered. No correlation between activity superficial distributions and the height above sea level or the geomorphological units was found. The activity values obtained in Lima soils lie in the range of the values determined for La Plata soils. Like in La Plata, ¹³⁷Cs activity around the nuclear facility could be associated only with the nuclear power tests. The average total external annual dose for La Plata inhabitants are in the range of 0.19 to 0.25 mSv/year, similar to those determined for Lima residents. The present work complements previous reports contributing to the establishment of the radiological baseline for soils of Buenos Aires Province, Argentina, the province with the most important nuclear activities of the country.