BEDROCK RADON CONCENTRATION IN THE QINGDAO URBAN PLANNING AREA AND ITS BEARING ON LITHOLOGY

The bedrock of the Qingdao area is dominated by granite. This paper is devoted to the radon concentrations in various bedrocks with different characteristics and influence factors. The results show that the radon concentrations the bedrocks of Qingdao change in a range from 0.05 to 19.51 KBq/m³, with an average of 2.56 KBq/m³ (n=210), and the average is only 1.54 KBq/m³for granite, which is much lower than that of other rocks. The average of radon in other samples reads as follows: silty clay＞mudstone＞sandy mudstone＞argillaceous sandstone＞diorite＞silt / filled soil＞sandstone＞syenogranite＞coarse sand＞granite＞monzonitic granitic gneiss. Highest radon concentration is found in consolidated soil, followed by sedimentary rock and magmatic rock, and the lowest remains with metamorphic rocks. It is observed that the radon concentrations in bedrocks is positively related to uranium content or porosity. The highest radon concentration observed in sedimentary rocks is not only related to its high porosity, but also the water-rich sandy interlayers in the sedimentary sequence. The unconsolidated soil is loose and porous, there is large space to keep radon-bearing water in the soil.