Assessment of radon gas level in underground stations of Tehran-Karaj plain in Iran

Abstract

The gas radon is one of the most significant elements released when natural uranium and radium decay. Hence, the gas concentration may be higher in enclosed locations, especially in underground spaces, and it is vital to measure the amount of radon gas radiation in dense underground stations. Here, in this experiment, a domestically manufactured environmental radon gas measuring device – electret ionization chamber detector – was utilized to degree the concentration in various underground of Tehran-Karaj plain. During the spring season, all 42 underground stations of Tehran and Karaj cities were measured at continuous time intervals. The trace of radon gas was observed in all undergrounds, but unfortunately, high radon concentrations were recorded in some locations, such as Ghaem and Tajrish undergrounds in the northern plain by virtue of fault type, water resources, and discrete geological constructions. Based on the US Environmental Protection Agency (EPA) standard, the maximum allowable concentration of radon gas in the air is 148 Bq/m3, while the average quantity at Tajrish station was 156 Bq/m3. This amount is above the permissible limit and therefore can be considered a health hazard. Accordingly, measures to improve ventilation and facilitate air movement are required in such undergrounds.