Analysis of n-Alkanes and n-Alkenes in Chukchi Sea Sediments

• Main Author: Sasu, Salomey Asantewaa
• Other Authors: Winkelmann, Kurt
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2019
• Subjects: Arctic; Arctic Ocean; Chukchi Sea; Chukchi; Climate change
• Online Access: http://hdl.handle.net/11141/2925

Thesis (Ph.D.) - Florida Institute of Technology, 2019. This study determined the concentrations, distribution and sources of n-alkanes in core sediments from four locations: Stations H24, H30, H32 and BarC5 in the Chukchi Sea, which is in the Arctic Ocean. n-Alkanes are valuable tracers of aquatic, terrigenous and petroleum inputs and may give evidence to the extent of climate change. The study of climate change in the Arctic is important since the Arctic is warming faster than any other part of Earth. The increase in temperature is causing enhanced evaporation leading to a higher precipitation rate and hence enhanced erosion. The n-alkanes C12-C35 were analysed and characterized using GC-MS in all four core sediments. The core sediment concentrations varied from 6.3 µg/g dry weight at depth 12-14 cm in Station H24 to 136 µg/g at depth 10-12 cm in Station BarC5. In most cases, vertical profiles of n-alkane concentrations did not exhibit systematic trends. A predominance of odd and high molecular weight n-alkanes is observed which is indicative of terrestrial input in the sediments. Thus, the most abundant n-alkanes determined were C27, C29 and C31 which originate from higher plant waxes. n-Alkane source apportionment was quantified using carbon preference index (CPI), odd-even predominance (OEP), terrigenous aquatic ratio (TAR) and low molecular weight (LMW)/high molecular weight (HMW) ratio. Most of the CPI, OEP, TAR and LMW/HMW values suggest terrestrial over aquatic input of n-alkanes. Contribution of aquatic sources was minimal given the low concentrations of low molecular n-alkanes at all four stations. Predominance of even numbered short chain n-alkanes is unusual and is being reported for the first time in Chukchi Sea sediments. This predominance is attributed to various sources including bacteria, fungi and yeast. Unresolved complex mixtures (UCM), which is a sign of petroleum input, was observed in some core sediments at Station H24; however, odd-even predominance was observed which is indicative of ...