Chemical fertilizers as a source of 238U, 40K, 226Ra, 222Rn, and trace metal pollutant of the environment in Saudi Arabia
2015
Alshahri, Fatimh | Alqahtani, Muna
The specific activities of ²³⁸U, ²²⁶Ra, ⁴⁰K, and ²²²Rn in chemical fertilizers were measured using gamma ray spectrometer and Cr-39 detector. In this study, 21 chemical fertilizers were collected from Eastern Saudi Arabian markets. The specific activities of ²³⁸U ranged from 23 ± 0.5 to 3900 ± 195 Bq kg⁻¹; ²²⁶Ra ranged from 5.60 ± 2.80 to 392 ± 18 Bq kg⁻¹; and ⁴⁰K ranged from 18.4 ± 3 to 16,476 ± 820 Bq kg⁻¹. The radon concentrations and the radon exhalation rates were found to vary from 3.20 ± 1.20 to 1532 ± 160 Bq m⁻³ and from 1.60 to 774 mBq m⁻² h⁻¹, respectively. Radium equivalent activities (Raₑq) were calculated for the analyzed samples to assess the radiation hazards arising due to the use of these chemical fertilizers in the agriculture soil. The Raₑq for six local samples (nitrogen, phosphorous, and potassium (NPK) and single superphosphate (SSP)) and one imported sample (Sulfate of Potash (SOP)) were greater than the acceptable value 370 Bq kg⁻¹. The total air absorbed doses rates in air 1 m above the ground (D) were calculated for all samples. All samples, except one imported granule sample diammonium phosphate (DAP), were higher than the estimated average global terrestrial radiation of 55 nGy h⁻¹. The highest annual effective dose was in triple super phosphate (TSP) fertilizers (2.1 mSv y⁻¹). The results show that the local TSP, imported SOP, and local NPK (sample 13) fertilizers were unacceptable for use as fertilizers in agricultural soil. Furthermore, the toxic elements and trace metals (Pb, Cd, Cr, Co, Ni, Hg, and As) were determined using atomic absorption spectrometer. The concentrations of chromium in chemical fertilizers were higher than the global values.
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