EFFECT OF WATER TABLE FLUCTUATIONS ON RADON EMANATION FROM SOIL

Under laboratory conditions, simulations of water table fluctuations produce changes in radon emanation from soil. A falling water table, as might occur during a dry interval after a heavy rainfall interval, initially causes a decrease in soil radon concentration (probably because the increased depth having pore spaces not filled by water acts as a void into which soil radon diffuses, and/or the water table acts as a sinking source of radon enrichment to the overlying soil). When the lower water table stabilizes, radon emanation from the soil increases (probably because the increased volume of connected water-free pores). Conversely, a rising water table, as might occur during a heavy rainfall interval after a dry interval, initially causes an increase in soil radon concentration. When the higher water table stabilizes, soil radon emanation decreases. Field testing suggests that these changes in water table may affect indoor radon measurements.