Sedimentary geochemical record of recent environmental changes around Lake Middle Marviken,Sweden |
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| Authors: | Joyanto Routh Philip A Meyers Tomas Hjorth Mark Baskaran Rolf Hallberg |
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| Institution: | (1) Department of Geology and Geochemistry, Stockholm University, 10691 Stockholm, Sweden;(2) Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA;(3) Department of Geology, Wayne State University, Detroit, MI 48202, USA |
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| Abstract: | Geochemical properties of sediments deposited in Lake Middle Marviken over the last 185 years record the impacts of a succession
of environmental changes that have occurred in the watershed. Clear-cutting of forests for wood and charcoal and extensive
water harnessing to support the local iron mills from 1897 to 1957 is recorded by low C/N ratios, high black carbon, and low
TOC and Ntotal accumulation rates. Larger δ13C and δ15N values in sediments deposited during this period imply higher productivity. Fluctuations in Ntotal and Ptotal accumulation rates show that the lake chemistry has varied between P or N-depleted systems that affected the δ15N values. Organic matter in the sediments is predominantly immature terrestrial material. Furthermore, hydrocarbon CPI, TAR,
and Paq values conform with the observed geochemical trends, variations in organic matter sources, and changes in the watershed.
Accumulation rates of Cd, Pb, Zn, and S remained mostly unchanged throughout the period of mining, but an increase from 1957
to 1980 is most likely associated with air-borne industrial and fossil fuel emissions from regional urbanization. In situ
microbial processes, such as iron and manganese reduction, also appear to be important in carbon cycling and in affecting
the sediment and water chemistry of this lake. |
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| Keywords: | Hydrocarbon biomarkers Accumulation rates Carbon and nitrogen isotopes Trace elements |
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