Characterizing long-term trends and spatiotemporal dynamics of ambient gamma radiation dose rates alongside...

Ambient gamma radiation constitutes an important component of environmental background radiation and is crucial for evaluating public exposure. In China, a nationwide survey conducted between 1983 and 1990 established the baseline for ambient gamma air-absorbed dose rates, with a nationwide range of 2.4-340.8 nGy/h. However, long-term spatiotemporal variations remain poorly documented due to limited publicly available monitoring data. Here, we analyzed ten years of national automatic radiation monitoring data to identify spatial and temporal patterns across China, including areas around operational nuclear power plants (NPPs), and to explore their potential links with climatic factors. Spatially, ambient dose rates followed a distinct west-to-east declining gradient, with both national and nuclear power plant (NPP)-proximal datasets fluctuating within historical natural background ranges. National dose rates declined gradually from 2016 to 2023 at 0.7 ± 0.1 nGy/h per year, with the most pronounced reductions occurred in the third and fourth quarters, aligned with seasonal precipitation patterns. Conversely, while initial analyses indicated a modest upward trend near NPPs, further spatial decomposition revealed that this pattern was driven entirely by the Taishan station; upon its exclusion, NPP-proximal dose rates remained temporally stable with no significant long-term drift. Overall, monthly mean variations exhibited no uniform seasonal pattern, indicating that individual meteorological factors exerted limited driving influence on the observed multi-year fluctuations. This study confirms that ambient gamma radiation nationwide remains within established natural background thresholds, providing a robust dataset to support regulatory radiation monitoring, public outreach, and environmental risk communication.