Determination of Arsenic and Arsenic Species in Ombrotrophic Peat Bogs from Finland

The main goal of this study was to evaluate how faithful arsenic (As) has been preserved in ombrotrophic peat bogs from Finland. The changing rates of atmospheric As deposition have been reconstructed using peat cores from three Finnish bogs: Harjavalta (Har), nearby a Copper (Cu) - Nickel (Ni) smelter, Outokumpu (Out), near a famous Cu-Ni mine, and a peat bog at Hietajärvi (Hie) which is remote from industrial activity. To study the preservation of As within these cores, firstly several new accurate and sensitive analytical procedures for the reliable and direct determination of As in nitric acid digests of ombrotrophic peat samples at low ng l-1 concentrations, namely hydride generation – atomic absorption spectrometry (HG-AAS), hydride generation – atomic fluorescence spectrometry (HG-AFS) and inductively coupled plasma – sector field – mass spectrometry (ICP-SF-MS) were developed. The analytical procedures were critically evaluated by analysing several certified plant and peat reference materials. Results for the determination of As in selected peat samples highly correlated underpinning the accuracy of all adopted analytical protocols (HG-AAS, HG-AFS, ICP-SF-MS). Secondly, chronologies of atmospheric As accumulation in these cores were compared with historical records of industrialisation. Comparison of anthropogenic and natural As and Pb concentrations showed that anthropogenic As and Pb decreased from ~1000 AD onwards (coal burning) and that additionally the As concentration profiles reflected the atmospheric deposition history of the mining and smelting sites (Out, Har). As an independent check of the retention of As by the peat cores, As was also determined in the pore waters using ICP-SF-MS. Only 0.02% to 0.05% of the total As concentrations were present in the pore waters, further suggesting that As is well retained in ombrotrophic peat bogs. As a further check on the preservation of As by the peat cores and to mimic the leaching ability of the natural pore fluids of the peat which are derived exclusively from rainwater, As was extracted from fresh Finnish peat samples using water and the predominant As species were determined using anion-exchange HPLC-ICP-SF-MS. Extraction yields (0.7% to 12% of the total As concentrations) were low. All water extracts from the Finnish peat samples contained arsenic acid, and arsenous acid was present in all but two Finnish peat samples. Dimethylarsinic acid was the dominant organic arsenic species. The low extraction yields together with the low As concentrations in the pore waters indicate, that the arsenic species may react with their functional groups (onium centers, hydroxyl groups, doubly bonded oxygen atoms) and thus become preserved in peat bogs.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Heidelberg

Year

2005

Author dc:creator

• Frank, Jutta

Contributors dc:contributor

• Schöler, Heinz Friedrich

Repository record source_url

http://www.ub.uni-heidelberg.de/archiv/5966

OAI identifier oai:identifier

oai:archiv.ub.uni-heidelberg.de:5966