The distribution of radon in tunnels with different geological characteristics in China

In China, as the economy is developing and the population is expanding, some underground buildings have been used as supermarkets, restaurants and entertainment places. Tunnels in mountains are one type of underground building, and the radon ((222)Rn) level in tunnels is an important issue. Radon levels in different type tunnels appear to differ, and relatively higher levels of (222)Rn are associated with particular types of bedrock. The (222)Rn levels in tunnels in five different geological characteristics were analyzed. Those built in granite had the highest (222)Rn levels with a geometric mean (GM) of 280Bqm(-3), while those built in limestone (GM: 100Bqm(-3)) and andesitic porphyry (GM: 96Bqm(-3)) were lower. The sequence of (222)Rn concentrations was: granite>tuff>quartz sandstone>limestone>andesitic porphyry, and the (222)Rn in granite was statistically significantly higher than in limestone and andesitic porphyry. Tunnels built in granite, tuff, quartz sandstone, limestone tended to have higher (222)Rn concentrations in summer than in winter, while the reverse tendency was true in andesitic porphyry tunnels. Only the difference in limestone was statistically significant.