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

Radon-222 is a good natural tracer of groundwater flow into the coastal oce an. Unfortunately, its usefulness is limited by the time consuming nature o f collecting individual samples and traditional analysis schemes. We demons trate here an automated system which can determine, on a "continuous" basis , the radon activity in coastal ocean waters. The system analyses Rn-222 fr om a constant stream of water passing through an air-water exchanger that d istributes radon from the running flow of water to a closed air loop. The a ir stream is feed to a commercial radon-in-air monitor which determines the concentration of Rn-222 by collection and measurement of the alpha -emitti ng daughters, Po-214 and Po-218, via a charged semiconductor detector. Sinc e the distribution of radon at equilibrium between the air and water phases is governed by a well-known temperature dependence, the radon concentratio n in the water is easily calculated.