A continuous monitor for assessment of 222Rn in the coastal ocean

Radon-222 is a good natural tracer of groundwater flow into the coastal ocean. Unfortunately, its usefulness is limited by the time consuming nature of collecting individual samples and traditional analysis schemes. We demonstrate here an automated system which can determine, on a “continuous” basis, the radon activity in coastal ocean waters. The system analyses 222Rn from a constant stream of water passing through an airwater exchanger that distributes radon from the running flow of water to a closed air loop. The air stream is feed to a commercial radon-in-air monitor which determines the concentration of 222Rn by collection and measurement of the α-emitting daughters, 214Po and 218Po, via a charged semiconductor detector. Since the distribution of radon at equilibrium between the air and water phases is governed by a well-known temperature dependence, the radon concentration in the water is easily calculated.