Simple download service (Atom) of the dataset: 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）是一种天然存在的无臭、无色且化学性质惰性的放射性气体，其源自土壤与岩石中铀与镭的衰变过程。

氡广泛分布于空气、土壤与水体中，浓度因气压、温度、孔隙度、通风条件等诸多因素在不同地域存在显著差异。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，氡易发生积聚，有时可达到较高浓度。

建筑物内氡浓度偏高的区域，多分布于天然铀富集的地质构造区（如花岗岩与火山岩层）。法国放射防护与核安全研究所（Institut de Radioprotection et de Sûreté Nucléaire, IRSN）通过绘制地质构造氡潜势分布图，以此划定建筑物内高氡浓度的高发区域。基于该分布图，所有市镇被划分为三类：
* 第一类氡潜势市镇：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均处于较低水平。
* 第二类氡潜势市镇：所在地质构造的铀含量较低，但存在特殊地质因素会促进氡向建筑物内迁移。这类特殊地质条件可局部增强氡从岩层向土壤表层的运移，进而提升建筑物内出现高浓度氡的概率。
* 第三类氡潜势市镇：辖区至少有部分区域的地质构造铀含量高于其他区域。相较于其他地区，这类铀富集构造区内，建筑物出现高氡浓度的比例更高。