Radiological assessment and heavy metal variability in Red Sea coastal sediments using integrated geochemical and...

This study aims to conduct an integrated assessment of radionuclides (²³⁸U, ²³²Th, and ⁴⁰ K), potentially toxic elements (including Pb, Cd, Zn, Cu, Rb, Br, Co and Ni), and geochemical composition (metals) in coastal sediments of the Red Sea. In addition, geophysical datasets (including Bouguer gravity) were integrated with statistical approaches. PCA (Principal Component Analysis) is a multivariate statistical method applied to the measured geochemical and radiological datasets to explore potential sources of metals and radioactive isotopes, as well as to find correlations and patterns. The analysis and interpretation of Bouguer, regional (deep), and residual (shallow) anomalies highlight the NW-SE direction as the primary structural influence in the region. In contrast, the E-W and NE-SW directions played lesser roles in affecting the structural situation. This detailed examination of gravity anomalies provides crucial insights into the subsurface structures, aiding in the comprehensive understanding of the area's geology. Twenty-six coastal sediment samples were analyzed using high-resolution gamma-ray spectrometry and ICP-MS for radionuclides, major oxides, and metals. Basic geophysical data (density contrast) supported the interpretation of spatial variability. Radiological hazard indices were calculated to evaluate exposure risks. The specific activity concentration of ²³⁸U, ²³²Th and ⁴⁰ K in sediments from the coast were measured to range between 5 - 38 Bq kg^-1, 0-13 Bq kg^-1 and 22 - 501 Bq kg^-1 respectively; all of these values are lower than worldwide average values. The radiological hazard indices, including radium equivalent activity (Ra_eq) ranges from 31 - 82 Bq kg^-1, which is much lower than the safety limit of 370 Bq kg^-1. Both the external (Hex) and internal hazard indices (Hin) are <1, which indicates that there is a minimal radiological risk. The absorbed dose rate (15-40 nGy h^-1) and the annual effective dose (0.04-0.06 mSv y^-1) are both significantly lower than the worldwide values. Therefore, all hazard indices demonstrate that the sediments have no significant radiological hazard to the public. Heavy metal abundance followed the order Sr > Ba > Cr > Br > V > Zr > Zn > Ni > Rb > Cu > Co > Pb > U > Th. All radiological indices indicated safe levels, although localized variations warrant continued environmental monitoring, specify which parameters were elevated. The study confirms that natural radioactivity in the Red Sea is generally low, but exhibits some variation in relation to lithological and mineral compositions.