Dataset Direct Download Service (WFS): Mapping of soil radon potential areas in the department of Maine-et-Loire(49)

Radon is a naturally odourless, colourless and chemically inert radioactive gas. It is derived from the decay of uranium and radium present in soil and rocks. Radon is present everywhere: in air, soil, water with a very variable concentration from place to place, according to many factors: pressure, temperature, porosity, ventilation In outdoor air, radon dilutes rapidly and its average concentration generally remains very low. On the other hand, in enclosed spaces such as buildings, it can accumulate and sometimes reach high concentrations. The areas most affected by high levels of radon in buildings are those with naturally uranium-rich geological formations (granite and volcanic subsoils). Mapping of areas where radon is most likely to occur at high concentrations in buildings is based on the mapping of radon potential of geological formations by the Institute for Radioprotection and Nuclear Safety (IRSN). This mapping led to the classification of municipalities into 3 categories: *Category 1: Category 1 radon-potential municipalities are those located on geological formations with the lowest uranium content. On these formations, the vast majority of buildings have low radon concentrations. *Category 2: Category 2 radon-potential municipalities are those located on geological formations with low uranium content but where particular geological factors may facilitate the transfer of radon to buildings. These particular geological conditions can locally facilitate the transport of radon from the rock to the soil surface and thus increase the likelihood of high concentrations in buildings. *Category 3: Category 3 radon-potential municipalities are those with at least part of their area with geological formations with an estimated higher uranium content compared to other formations. Of these uranium-rich formations, the proportion of buildings with high radon concentrations is higher than in the rest of the territory.氡（Radon）是一种天然产生的无臭、无色且化学惰性的放射性气体，其来源于土壤与岩石中铀和镭的衰变过程。 氡广泛存在于空气、土壤及水体中，浓度因气压、温度、孔隙度、通风等诸多因素存在显著的地域差异。室外空气中的氡会快速稀释，平均浓度通常极低；而在建筑物等封闭空间内，氡易积聚，有时可达到较高浓度。 建筑物内氡浓度偏高的高发区域，多位于天然铀富集的地质构造（花岗岩与火山岩底土层）分布地带。放射防护与核安全研究所（Institute for Radioprotection and Nuclear Safety, IRSN）通过绘制地质构造氡潜势分布图，完成了建筑物高氡浓度高发区域的测绘工作。 基于该测绘结果，各自治市被划分为三类： * 一类氡潜势自治市：坐落于铀含量最低的地质构造之上，该类区域内绝大多数建筑物的氡浓度处于较低水平。 * 二类氡潜势自治市：位于铀含量较低的地质构造中，但存在特殊地质因素可促进氡向建筑物内迁移。这类特殊地质条件可在局部推动氡从岩层向土壤表层运移，进而提升建筑物内出现高氡浓度的概率。 * 三类氡潜势自治市：辖区至少有部分区域的地质构造铀含量高于其他区域。相较于辖区其他区域，该类铀富集地质构造范围内出现高氡浓度的建筑物占比更高。