Temporal dynamics of airborne lead-210 in Missouri (USA): implications forgeochronological methods

Lead-210 (Pb-210) deposited from the atmosphere is used in the dating of ce rtain geological materials such as glacial ice and lacustrine sediments, bu t its long-term atmospheric behavior has been little studied. The present i nvestigation reports measurements of airborne Pb-210 at 21 monitoring stati ons in Springfield, Missouri, during 1975-1995. Seasonal and diurnal patter ns of atmospheric concentrations are established, and the mean annual conce ntrations of Pb-210 in ground level air during the 20-year period are exami ned. Although airborne Pb-210 concentrations are found to vary diurnally an d seasonally, mean annual concentrations in southwest Missouri have remaine d relatively constant during this time period. This finding is important fo r geochronological methods that assume a constant Pb-210 flux from the atmo sphere.