Torres Silvana Beltrán, Petrik Attila, Szabó Katalin Zsuzsanna, Jordan Gyozo, Yao Jun, Szabó Csaba
Lithosphere Fluid Research Laboratory, Department of Petrology and Geochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, 1117, Budapest, Hungary.
Department of Earth, Environment and Resources Sciences, University of Naples Federico II, Via Cintia snc, 80126, Naples, Italy.
J Environ Radioact. 2018 Dec;192:267-278. doi: 10.1016/j.jenvrad.2018.07.001. Epub 2018 Jul 7.
In order to estimate the annual dose that the public receive from natural radioactivity, the identification of the potential risk areas is required which, in turn, necessitates understanding the relationship between the spatial distribution of natural radioactivity and the geogenic risk factors (e.g., rock types, presence of dikes, faults, physical conditions of soil, etc.). A detailed spatial analysis of outdoor ambient gamma dose equivalent rate was performed in the western side of Velence Hills, the largest outcropped granitic area in Hungary. In order to assess the role of local geology in the spatial distribution of gamma dose rates, field measurements were carried out at ground level at 300 sites along a 250 m x 250 m regular grid in a total surface of 19.8 km. Digital image processing methods were applied to identify anomalies, heterogeneities and spatial patterns in the measured gamma dose rates, including local maxima and minima determination, digital cross sections, gradient magnitude and gradient direction, second derivative profile curvature, local variability, lineament density, 2D autocorrelation and directional variogram analyses. Statistical inference shows that different gamma dose rate levels are associated with the geological formations, with the highest level on the Carboniferous granite including outlying values. Moreover, digital image processing reveales that linear gamma dose rate spatial features are parallel to the SW-NE dike system and to the NW-SE main fractures. The results of this study underline the importance of understanding the role of geogenic risk factors influencing the ambient gamma dose equivalent rate received by public. The study also demonstrates the power of the image processing techniques for the identification of spatial pattern in field-measured geogenic radiation.
为了估算公众从天然放射性中接受的年剂量，需要识别潜在风险区域，而这又需要了解天然放射性的空间分布与地质风险因素（如岩石类型、岩脉、断层的存在、土壤的物理条件等）之间的关系。在匈牙利最大的花岗岩露头区韦伦采山的西侧，对室外环境伽马剂量当量率进行了详细的空间分析。为了评估当地地质在伽马剂量率空间分布中的作用，沿着一个250米×250米的规则网格在地面上300个地点进行了实地测量，总面积为19.8平方千米。应用数字图像处理方法来识别测量的伽马剂量率中的异常、不均匀性和空间模式，包括局部最大值和最小值的确定、数字横截面、梯度大小和梯度方向、二阶导数剖面曲率、局部变异性、线性密度、二维自相关和方向变异函数分析。统计推断表明，不同的伽马剂量率水平与地质构造相关，石炭纪花岗岩上的水平最高，包括外围值。此外，数字图像处理显示，线性伽马剂量率空间特征与西南-东北向岩脉系统和西北-东南向主要裂缝平行。这项研究的结果强调了了解地质风险因素对公众接受的环境伽马剂量当量率影响作用的重要性。该研究还展示了图像处理技术在识别实地测量的地质辐射空间模式方面的能力。
