Radon 222 and tropospheric vertical transport

Radon 222 is an inert gas whose loss is due only to radioactive decay with a half life of 3.83 days (5.51-day ''exponential'' lifetime). It is a very useful tracer of continental air because only ground level continental sources are significant. Thus it is similar in several ways to many air pollutants (e.g., NO/sub x/) (NO+NO2), SO2, and certain hydrocarbons. Previously published measured 222Rn profiles are analyzed here by averaging for the summer, winter, and spring-fall seasons. The analysis shows that in summer, about 55% of the 222Rn is transported above the planetary boundary layer, considerably more than during the other seasons. Similarly, in summer, about 20% rises to over 5.5 km (500 mbar). The average profiles have been used to derive vertical eddy diffusion coefficients with maximum values of 5-7 x 105 cm2 s-1 in the midtroposphere and 8 x 103 to 5 x 104 cm2 s-1 near the surface