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The exhalation characteristic of Rn and CO <inf>2</inf> at the Xidatan segment of east Kunlun active fault zone

Abstract:

It's the first time to observe the exhalation flux of soil Rn and CO 2 in Xidatan segment of East Kunlun active fault in September, 2006 and first-hand data of the Rn and CO 2 in this fault were obtained. A significant Rn flux, reaching up to 433 mBq·m -2·s -1 and the concentration of Rn ranging from 505 up to 2380 Bq·m -3 was observed in the excavated trench with 2~3 meters deep across the fault. On the surface, the Rn flux ranges from 7 to 28.19 mBq·m -2·s -1, with the mean value of 14.7 mBq·m -2·s -1, similar to the world average. The CO 2 flux on the surface with an average value of 18.9 g·m -2·s -1 also remains similar to regular background values. It shows no systematic spatial variation up to a distance of 1.2 km from the fault and no clear change in the trench. But a high CO 2 flux of 421 g·m -2·s -1 is observed at phyllite outcrops on a hill 3 km north of the fault. A large Rn flux, 503 mBq·m -2·s -1, is observed at the point where the maximal CO 2 flux is observed. These results indicate the advective pore gas transport from the subsurface to the atmosphere in the vicinity of the East Kunlun active fault zone.