Isotopic trends and background fluxes of atmospheric lead in northern Europe: Analyses of three ombrotrophic bogs from south Sweden

Knowledge about the natural atmospheric background deposition rate of lead (Pb) prior to anthropogenic pollution is critical in the understanding of present‐day pollution and for establishing realistic goals for the reduction of atmospheric Pb. We utilize stable Pb isotopes ( 206 Pb and 207 Pb) in radiocarbon‐dated peat cores from three ombrotrophic bogs from south Sweden, to calculate fluxes and to survey atmospheric Pb trends prior 3500 BP (the so far known onset of large‐scale anthropogenic pollution). The estimated atmospheric Pb deposition rate was between 1 and 10 μg Pb m 2 yr −1 between 5900 and 3700 calendar years BP, which is 100 to 1000 times lower than present‐day deposition rates. The majority of the samples older than 3500 calendar years BP had 206 Pb/ 207 Pb ratios ≤1.20, which is significantly lower than unpolluted Swedish mineral soils ( 206 Pb/ 207 Pb > 1.30), suggesting that even the natural atmospheric deposition of Pb was dominated by long‐range transport, rather than local inputs from soil dust. Low 206 Pb/ 207 Pb ratios (1.16–1.18) of several samples indicate that this distant transport originated at least partly from early pollution sources. A possible climatic connection with the observed Pb deposition trends is suggested.