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Keywords:

  • atmospheric deposition;
  • Pb;
  • isotopes;
  • peat;
  • background

[1] 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 (206Pb and 207Pb) 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 m2 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 206Pb/207Pb ratios ≤1.20, which is significantly lower than unpolluted Swedish mineral soils (206Pb/207Pb > 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 206Pb/207Pb 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.