Nuclear track autoradiography for radon-related radiobiological hazards in Abu-Sannan Petroleum Area, Egypt

Abstract

Abu-Sannan Petroleum Area (ASPA) is situated in Egyptian Western Desert and presents a suitable site for oil exploration. This study aimed to evaluate the radiological hazards linked to technologically enhanced naturally occurring radioactive materials (TENORM), particularly Radium (²²⁶Ra) and Radon (²²²Rn), in the General Petroleum Y-Field (GPY) situated in the northeastern area of ASPA. The study was examined significant deficiencies in radiological monitoring by evaluating ²²²Rn dynamics, geological correlations, and related radiation hazards. CR-39 nuclear track detector was used to examine 23 sedimentary samples for ²²²Rn and ²²⁶Ra radioactivity concentration. The samples under study were taken from depths 100 to 2600 m ASPA. A radioecological assessment of shale, limestone, and sandstone formations was also conducted. Results showed that the radioactivity concentrations of ²²²Rn and ²²⁶Ra increased with depth, reaching a maximum of 1906.85 ± 194.52 Bq.m^-3 and 89.99 ± 1.69 Bq.m^-3 at 2600 m, respectively. The value of ²²²Rn and ²²⁶Ra were higher than the limits set by the IAEA and UNSCEAR. The annual effective doses (AED) varied from 7.41 ± 4.82 to 48.11 ± 12.27 m.Sv.y^{- 1}, exceeding the international safety threshold of 1-10 m.Sv.y^{- 1}. Increased hazards were observed in deeper layers, notably the Bahariya Sandstone, due to the presence of uranium-rich rocks and highly porous matrices. Radiometric and geological analyses indicated that shale strata contain ²²⁶Ra but cracked limestone and sandstone formations permit the migration of ²²²Rn. Principal component analysis (PCA) revealed significant correlations among ²²²Rn concentration, exhalation rates, and AED, underscoring the lithological influence on radiation hazards. The results highlight considerable occupational health hazards in ASPA, necessitating improved radiation protection measures and ongoing surveillance to reduce lung cancer risks associated with prolonged ²²²Rn exposure, in accordance with WHO guidelines. This study offers essential data to inform regulatory strategies in petroleum-producing areas with similar geological characteristics and radiation protection protocols.

Keywords: Nuclear detector; Petroleum; Radiation dose; Radioactivity; Radiobiological impacts.

Fig. 1

Set-up of nuclear autoradiographic system used to determine ²²²Rn radioactivity concentrations.

Fig. 2

Overall comparsion of ²²²Rn concentration and other radiation paramter: ²²²Rn concentration generally increases with depth, except for minor dips at 200 m (293 Bq.m⁻³) and 700 m (717 Bq.m⁻³). Irregularities: A temporary plateau occurs between 1400–1600 m (concentration stabilizes around ~ 1350 Bq.m⁻³). Sharp increases are seen from 2300 m to 2600 m (244 Bq.m⁻³ over 300 m). Geological annotations: (i) Khoman Formation (1495 m): Chalk and limestone correlate with a stabilization in ²²²Rn levels; (ii) Bahariya Formation (2360 m): Sandstone/shale layers align with the steepest ²²²Rn increase.

Fig. 3

Petroleum stratigraphic column represents formation names, geologic ages, depths, lithologies, and lithologic descriptions of General Petroleum Y-filed (GPY), northeast of ASPA.

Fig. 4

Pearson correlation heatmap with dendrogram for calculated radiological parameters.

Fig. 5

Scatter plot matrix with regression lines; ²²⁶Ra Concentration shows the most extreme fluctuations (e.g., sudden spikes); Working Level and Indoor Annual Effective Dose follow similar upward trajectories; Surface Exhalation Rate ↔ Indoor Annual Effective Dose: Near-perfect correlation (r² = 0.99); Mass Exhalation Rate ↔ ²²⁶Ra Concentration: Strong correlation (r² = 0.98).

Fig. 6

Histograms show actual distribution frequency of the following: (1)²²²Rn: Shows right-skewed distribution with increasing frequency at higher radioactivity concentrations. (2) E_A: Bimodal distribution suggesting multiple populations. (3) E_M: Left-skewed distribution with most values < 0.07 Bq.kg^-1. (4) ²²⁶Ra: Normal-like distribution with central peak around 50 Bq.kg^-1. (5) WL: Uniform distribution between 0.03 and 0.20. (6) AED: Right-skewed distribution reflecting radiation exposure risks.

Fig. 7

Q-Q plot demonstrated how the data compares to normal distribution.

Fig. 8

Principal components (PC1 and PC2) explain > 95% of the total variance (PC1 ≈ 90%, PC2 ≈ 5–6%), (PC) means that ²²²Rn, E_A, E_M, ²²⁶Ra, WL, and AED can be effectively visualized in 2D without significant loss of information.