The fallout rate of PB-210 on the western coast of the United States

The deposition rate of atmospheric Pb-210 has been measured during a one year period using plastic funnels as collectors. Observed rates were 0.15 dpm cm⁻² yr⁻¹ at a site in Palo Alto, California and 0.21 dpm cm⁻² yr⁻¹ at a site in Los Angeles. The Palo Alto value agrees well with a long-term average of 0.14 dpm cm⁻² yr⁻¹, obtained from a nearby salt marsh core. These rates are only one-third of those previously estimated using global models for Pb-210 fallout and indicate the need to consider both longitude and precipitation as factors controlling fallout rates. More than 75% of the Pb-210 fallout occurs as wet deposition at the Los Angles site.