Ion‐induced nucleation around radon daughters in remote Arctic maritime air

ABSTRACT Measurements made of radon daughters during the International Arctic Ocean Expedition of 1991 did not usually show the expected decrease in apparent concentration due to losses to the surface when aerosol concentrations were very low. The evidence suggests that except on some occasions after the equinox when the air had been near the North Pole for the previous 5 days, sufficient supersaturations of condensible vapours existed to allow nucleation of new particles on radioactively produced ions. This would drastically reduce the mobility of the ions and therefore surface losses. As a result, the measurement usually gave a satisfactory estimate of radon that was very useful in checking on air trajectory predictions and providing more detailed information on contact of the air with land. The exceptions suggest that the measurement might be quite unreliable in conditions where aerosol and oxidizable gas concentrations are very low such as in the Arctic or Antarctic winter.