Radiological, geochemical, and environmental assessment in Xuancheng, China: The airborne gamma-ray spectrometric view

Radionuclides in the environment have been considered a health risk for many years owing to their contribution to the radiation dose to the human body. A great deal of field survey research has been conducted in this area. However, few researchers have studied the key sources of geological and geochemical substances that pose radioactive environmental problems from the perspective of airborne gamma-ray spectrometry. This study aims to determine the radiation variations in geological units caused by rocks containing radionuclides, evaluate the level of radiation, and analyze as well as identify the key radio-elements. The content of 40K, 238U, 232Th, and the total count (TC) in 15 different geological units were studied based on the concentration data. The gamma absorbed dose rate (D) of the whole region was calculated to identify and evaluate the main areas of high radiation. The quantitative statistical methods, the Pearson correlation analysis, principal component analysis (PCA), hierarchical cluster analysis (HCA), and geochemical mapping were used to analyze the selected high radiation areas and reveal potential key lithological factors. The results indicate that the Cretaceous intrusive rock, in the northeast of the study area, is a major source of natural radionuclides and continuous radiation. The high radiation in this area is strongly associated with the Yaocun rock mass containing K-feldspar granite, and the correlation coefficient of the 232Th with effective dose was the highest (0.91), whereas that of 238U was the lowest (0.49). The study has determined that 232Th is the key radio-element, causing high radiation by comparing the results of HCA of field gamma-ray measurement data. The findings from this study are valuable for determining the key factors causing high radiation levels in similar exposure conditions.