Soil-to-crop transfer of natural radionuclides in farm soil of South Africa
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Soil-to-crop transfer of natural radionuclides in farm soil of South Africa Abiola Olawale Ilori
&
Naven Chetty
Received: 30 July 2020 / Accepted: 12 November 2020 # Springer Nature Switzerland AG 2020
Abstract The activity concentration of natural radionuclides in farm soil and most common indigenous food crops (maize, potato, cowpea) in oil-producing (Philippi, Uitenhage, and Hertenbos farms) and non-oilproducing (Ukulinga farm) areas of South Africa was measured using a Hyper Pure Germanium detector. Consequently, the transfer of these radionuclides from soil-to-crops was estimated. The mean activity concentration of 226Ra, 232Th, and 40K for farm soil samples are 30.71 ± 11.77, 31.97 ± 8.90, 345.97 ± 98.62 Bq.kg−1 for Philippi; 18.67 ± 6.70, 31.55 ± 11.48, 191.93 ± 33.39 Bq.kg−1 for Uitenhage; 38.03 ± 17.44, 41.18 ± 31.54, 381.89 ± 163.40 Bq.kg−1 for Hartenbos; and 8.47 ± 2.87, 8.65 ± 3.52, 94.22 ± 25.97 ± 25.97 Bq.kg−1 for Ukulinga. The mean activity concentration of 226Ra, 232 Th, and 40K for crop samples are 4.54 ± 1.47, 4.87 ± 1.69, 140.18 ± 35.38 Bq.kg−1 for Philippi; 9.17 ± 4.79, 3.85 ± 1.87, 136.75 ± 22.04 Bq.kg−1 for Uitenhage; 7.97 ± 2.91, 4.62 ± 2.40, 105.97 ± 48.65 Bq.kg−1 for Hartenbos; and 4.23 ± 1.63, 2.72 ± 1.19, 48.36 ± 15.55 Bq.kg−1 for Ukulinga. The activity concentration and soil-to-crop transfer factors for 40K were found to be much higher, possibly because this element is critical in crop growth. The results showed that the crop samples’ transfer factor is in the order cowpea>potato>maize. This study showed that activity concentrations of 226 Ra, 232Th, and 40K in crops and the corresponding A. O. Ilori : N. Chetty (*) School of Chemistry and Physics, University of KwaZulu–Natal, Scottsville, Pietermaritzburg, South Africa e-mail: [email protected]
transfer factors depend on activity concentrations of the same radionuclides in soil. Keywords Activity concentration . Crops . Farm soil . HPGe detector . NORMs . transfer factor
Introduction The environment contains different degrees of natural radioactive materials (NORMs), which vary by geographical location and are enhanced by human activities through industrialization (Karahan and Bayulken 2000; IAEA 2007). Natural radionuclides include the primordial radionuclides 235U, 238U, 232Th and their decay chains, 14C, and 3H cosmogenic radionuclides, and 40 K (Morcos et al. 1992; UNSCEAR 2000; Larivière and Guérin 2010; Ajanaku et al. 2018; Ilori and Alausa 2019). Naturally occurring radionuclides are available in various samples of the environment, including air, water, plant, and soil (Barišić 1996; Poschi and Nollet 2007). Oil exploration, extensive uses of fertilizers on farmlands, and mining activities have also been established as primary sources of radiation to the environment and a source of radiological risk to humans (IAEA 1994; NRC 1999; Carvalho 2017). South Africa’s oil and gas sector has been the leading importers and consumers of radioactive materials from 1913 principally for its oil exploration (SAES 2018). The oil and gas
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