Distribution Characteristics and Controlling Mechanisms of Radon and Primordial Radionuclides in a Certain Impact Crater in China

<title>Abstract</title> <p> To reveal the controlling mechanism of impact structure on the spatial distribution of radon and primordial natural radionuclides and provide basic data for planetary geological research, systematic field sampling and laboratory analyses were conducted at a certain impact crater in China. A high-purity germanium (HPGe) γ-ray spectrometer and scintillation-cell radon detector were adopted to measure the activity concentrations of ²³² Th, ⁴⁰ K and gaseous ²²² Rn in granite, surface sediment and ambient air across 11 sampling sites covering crater core, crater rim and outer rim zones. The results indicated obvious spatial differentiation of target radionuclides following the sequence: granite &gt; sediment and inner rim &gt; outer rim. The measured specific activities of ⁴⁰ K and ²³² Th fell within the global natural background range, jointly governed by parent rock lithology, impact-induced rock fragmentation, weathering leaching as well as coupled topography and hydrological conditions. Radon concentration exhibited a distinct spatial pattern with high values concentrated in crater core and decreasing towards peripheral areas, and sediment was identified as the dominant radon reservoir within the study area. Radon concentrations in surface water remained low, indicating limited radiological risk under the measured conditions.. This study clarifies the spatial distribution patterns and controlling mechanisms of natural radioactivity for granite-hosted impact craters in frigid-temperate regions, supplying fundamental datasets and technical support for radiation risk evaluation and element cycling research of planetary impact geology. </p>