Mechanisms of Ni, Cu, Zn, Pb, Cd, As and Se retention in Finnish peat bogs, and the chronology of their accumulation from natural and anthropogenic sources

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We propose to construct high resolution records of atmospheric deposition of trace metals (Ni, Cu, Zn, Pb, Cd) and non-metals (As and Se) using peat cores collected from Finnish bogs: Outokumpu and Harjavalta have been impacted by atmospheric emissions from metal mining and refining, whereas the peat bog at Alkkia has received experimental addition of Ni, Cu, and Zn salts in 1962; for comparison, Hietajärvi is remote from industrial activity. The chronology of peat accumulation during the past 50 years will be determined using 14C (atmospheric bomb pulse curve measured using AMS). By comparing the chronology of metal accumulation preserved in the peat cores with the historical records of metal emissions, the mobilities of the elements within the peat profiles will be quantified. Deeper, pre-anthropogenic peat layers (several thousand years old), will provide the "natural background" fluxes for this region, for comparison with modern fluxes. Fractionation of the metals in both the solid and aqueous phases will be undertaken to determine the relative importance of various possible metal retention mechanisms: uptake by plants and incorporation into biomolecules, organic complexation, or metal sulphide formation.