RN-222 AT BERMUDA AND MAUNA-LOA - LOCAL AND DISTANT SOURCES

Continuous measurements of atmospheric Rn-222 were made for the past t hree years by the Environmental Measurements Laboratory (EML) at the A tmosphere/Ocean Chemistry Experiment site located at Tudor Hill, Bermu da and at the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Mauna Loa Observatory. The Rn-22 2 analyzer is based on the two-filler tube method. At the Bermuda site , monthly median Rn-222 concentrations range from similar to 50 to 700 mBq m(-3), and the concentrations vary seasonally, with a maximum in the winter and a minimum in the summer. The concentrations are signifi cantly elevated when local winds traverse the island. At MLO, monthly median Rn-222 concentrations range from similar to 100 mBq m(-3) durin g the fall months to 400 mBq m(-3) during the spring months. The sprin gtime maximum values correspond to periods of rapid transport in the f ree troposphere from the Asian continent, corroborated by backward air mass trajectories. The Rn-222 data are also used to help decipher loc al daily upslope/downslope conditions present at MLO. This study illus trates the value of atmospheric Rn-222 monitoring, when screened throu gh the filter of local meteorology, in studying the transport of conti nental air to the oceans, as well as the dynamics of local meteorologi cal effects.