Aliphatic and olefinic hydrocarbons in recent sediments of Greifensee, Switzerland
1980; Elsevier BV; Volume: 44; Issue: 1 Linguagem: Inglês
10.1016/0016-7037(80)90182-9
ISSN1872-9533
AutoresWalter Giger, Christian Schaffner, Stuart G. Wakeham,
Tópico(s)Isotope Analysis in Ecology
ResumoQualitative and quantitative determinations of aliphatic and olefinic hydrocarbons in Recent sediment cores of Greifensee, Switzerland show that n-heptadecane is most abundant in the surface sediments (8–24 μg/g dry sediment). This compound is due to the extensive phytoplankton production in the highly-eutrophic lake. The levels of n-heptadecane decrease rapidly in the uppermost 10 cm of the core (to less than 2 μg/g), probably by microbial degradation processes. An 80-week incubation experiment provided evidence of anaerobic degradation of sedimentary-heptadecane. The predominance of n-heptadecane in the older section of lacustrine chalk (back to approximately 11,000 yr B.P.) can still be considered as a qualitative historic record of primary productivity in the lake. In postglacial mud (> 11,000 yr B.P.), n-heptadecane is accompanied by equally abundant n-alkanes and an unresolved complex mixture of branched and cyclic hydrocarbons. These latter were present in sedimentary rocks outcropping in the catchment basin of the lake and were eroded, transported by glaciers and rivers, and finally redeposited in the postglacial Greifensee. This group of hydrocarbons is absent in the lacustrine chalk section (~ 11,000-100 yr B.P.) but appears again in the youngest sediments (100 yr B.P. to present). Thus changes in erosion rate in the past and acceleration of erosion through human activities are recorded in the hydrocarbon content of the sediment cores.
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