Wang Yanwei, Luo Weijun, Zeng Guangneng, Wang Yang, Yang Hanling, Wang Meifang, Zhang Lin, Cai Xianli, Chen Jia, Cheng Anyun, Wang Shijie
University of Chinese Academy of Sciences, Beijing, 100049, China; State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang, 550081, China.
State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, CAS, Guiyang, 550081, China; Puding Karst Ecosystem Research Station, CAS, Puding, 562100, China.
J Environ Radioact. 2019 Apr;199-200:16-24. doi: 10.1016/j.jenvrad.2018.12.029. Epub 2019 Jan 12.
Cave Rn has been a major health issue and subject of scientific debate for decades. While the basics of natural ventilation physics are well understood, it is difficult to make blind predictions of Rn concentrations in a given cave due to the complexity of cave systems. In-situ continuous observation is necessary to improve our ability to quantify radiation dose exposure and reduce radiation hazard to cave users, and trace the air exchange patterns occurring in caves. In this study, continuous monitoring using a RAD7 radon detector revealed high Rn concentrations and large fluctuations in Rn concentration in a small karst cave in southwest China, Shawan Cave. From August 2016 to July 2017, the average annual concentration was 47,419 Bqm and ranged between 3720 and 123,000 Bqm, with lower values during summer than other seasons. Taking Shawan Cave as a case study, we suggest a framework to evaluate the potential dose exposure, allowing cave users to minimize risk of exposure to hazardous levels of Rn. Furthermore, we comparing results from this study with other studies in 35 caves worldwide, and conclude that there are three patterns of seasonal Rn variation. They were classified into five types of ventilation mode based on diversity of cave locations, geometry and connectivity of bed rock fracture networks, together with temperature differences between outside atmosphere and cave air.
几十年来，洞穴氡一直是一个主要的健康问题和科学辩论的主题。虽然自然通风物理的基本原理已被充分理解，但由于洞穴系统的复杂性，很难对给定洞穴中的氡浓度进行盲目预测。进行现场连续观测对于提高我们量化辐射剂量暴露的能力、降低洞穴使用者的辐射危害以及追踪洞穴中发生的空气交换模式是必要的。在本研究中，使用RAD7氡探测器进行的连续监测显示，中国西南部的一个小喀斯特洞穴——沙湾洞穴中氡浓度很高且浓度波动很大。从2016年8月到2017年7月，年平均浓度为47419贝克勒尔每立方米，范围在3720至123000贝克勒尔每立方米之间，夏季的值低于其他季节。以沙湾洞穴为例，我们提出了一个评估潜在剂量暴露的框架，以使洞穴使用者将暴露于危险水平氡的风险降至最低。此外，我们将本研究的结果与全球35个洞穴的其他研究结果进行了比较，并得出氡季节性变化有三种模式的结论。根据洞穴位置的多样性、基岩裂隙网络的几何形状和连通性以及外部大气与洞穴空气之间的温差，将它们分为五种通风模式类型。
