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

Continuous measurements of atmospheric Rn-222 were made for the past three years by the Environmental Measurements Laboratory (EML) at the Atmosphere/Ocean Chemistry Experiment site located at Tudor Hill, Bermuda and at the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Mauna Loa Observatory. The Rn-222 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 significantly elevated when local winds traverse the island. At MLO, monthly median Rn-222 concentrations range from similar to 100 mBq m(-3) during the fall months to 400 mBq m(-3) during the spring months. The springtime maximum values correspond to periods of rapid transport in the free troposphere from the Asian continent, corroborated by backward air mass trajectories. The Rn-222 data are also used to help decipher local daily upslope/downslope conditions present at MLO. This study illustrates the value of atmospheric Rn-222 monitoring, when screened through the filter of local meteorology, in studying the transport of continental air to the oceans, as well as the dynamics of local meteorological effects.