decline of lead in tree rings of Carya spp. in urban Atlanta, GA, USA

Lead (Pb) concentrations in wood ring segments of Carya spp. in two urban forests in Atlanta, GA, have decreased approximately 20 percent in the last decade. This pattern is consistent with reduced atmospheric Pb over the same period. We have determined that changes in Pb concentrations in wood of urban hickory trees dramatically documents the historical periods of early urbanization, the addition of Pb to gasoline, and the recent period of restricted use of leaded gasoline.