HR: 16:45h
AN: PP34A-04    [Abstracts]
TI: Zinc Isotopic Composition Along A Peat Bog Profile
AU: * Weiss, D J
EM: d.weiss@imperial.ac.uk
AF: Imperial College, Prince Consort Road, London, SW7 2AZ United Kingdom
AU: Mason, T
EM:
AF: Imperial College, Prince Consort Road, London, SW7 2AZ United Kingdom
AU: Rausch, N
EM:
AF: University of Heidelberg, Im Neuenheimer Feld 236, Heidelberg, 69120 Germany
AU: Shotyk, W
EM:
AF: University of Heidelberg, Im Neuenheimer Feld 236, Heidelberg, 69120 Germany
AU: Wilkinson, J
EM:
AF: University of Heidelberg, Im Neuenheimer Feld 236, Heidelberg, 69120 Germany
AU: Nieminen, T
EM:
AF: Finish Forest Research Institute, Box 18, Vantaa, 01301 Finland
AB: We measured Zn concentrations and isotope variations in three peat bog profiles in Finland. The cores were situated next to a smelter (Harjavalta), a mining site (Outokumpu), and in a remote location (Hietajarvi). The three peat cores were also measured for trace and major elements in solid peat and pore waters providing all essential data needed for a geochemical assessment. Close to the top of all three cores a peak in Zn concentration is observed. The Zn peaks correlate well with other metals at Outokumpu and Harjavalta, respectively. The increased Zn concentration in the remote site (Hietajarvi) is tentatively explained with Zn that accumulated in the roots of plants and/or deposited via long-range transport. There are significant isotope variations found in all three cores and the ratio vs. depth patterns are very similar. Lighter zinc is observed near the surface, where the concentrations are high (δ⁶⁶Zn ~ 0.4 relative to the Lyon JMC 3-0749L Zn standard), whereas isotopically heavy Zn (δ⁶⁶Zn > 0.8) is observed in the deeper parts of the profiles, where concentrations reach background values. To constrain possible sources, we measured the Zn isotopic composition of the host rocks (dolomite, schist) and ore minerals at the Outokumpu mine site. Isotopically light Zn was found in the dolomite (δ⁶⁶Zn ~ -0.3) and isotopically heavy Zn (δ⁶⁶Zn ~ 0.9) in the black schist. The measured Zn isotopic compositions of the ore at Outokumpu is consistent with those observed at the top of the peat profile, suggesting that this `pollutant ore Zn' is indeed the dominant Zn source in the Outokumpu peat. In all three profiles the isotopic composition of the background Zn (ranging between 0.8 and 1.5) is heavier than published Zn data on loess (serving as a proxy for atmospheric dust or average continental crust) suggesting that natural dust is influenced by the local geology (as previously suggested for Pb during other peat studies) and that biological fractionation contributes to the fractionation of Zn in the profile by taking up isotopically light Zn in the top layer and leaving heavy Zn back, which then gets concentrated in the deeper layer
DE: 1041 Stable isotope geochemistry (0454, 4870)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005