AbstractThe Arctic region is a seemingly pristine, remote environment, yet in the past few decades there has been increasing evidence that it is greatly impacted by anthropogenic metal contamination. The heavy metals are attributed to adverse effects on the health of biota and indigenous populations, due to their toxicity and bioaccumulative tendencies within the environment. There are three main metal contaminants of major concern, lead (Pb). mercury (Hg) and cadmium (Cd). They have all been reported as ubiquitous anthropogenic pollutants with elevated concentrations identified throughout the Arctic’s sedimentary environment. The aim of this research was to investigate further heavy metal contamination, specifically within the sediments of the Svalbard region, and the Barents Sea area, within the Arctic. Ten sediment cores were taken for analysis from three main fieldwork excursions. The cores were taken from three different environments; lacustrine, fjordic and marine. A comparison between these core sites allowed the identification of the major transport pathways within this region and the relative importance of atmospheric and oceanic transport. Three cores were taken from the inner Kongsfjorden area, four cores from the Barents Sea, with three further cores taken from the Vøring Plateau and the area south of Svalbard. Each core was analysed to ascertain metal concentrations and to reconstruct the temporal contaminant history of the area. The source of the contaminant can be determined through the use of stable isotope analysis. The isotopic ratio provides a ‘signature’: ultimately reflecting the source of the Pb, and this tool can also be used to verify the transport pathways of the anthropogenic Pb contamination. The 206Pb/207Pb isotopic ratio of western sources of anthropogenic Pb has a value of approximately 1.14, with Eastern Europe and Eurasian sources represented by a higher value of 1.18. Two cores taken from the Barents Sea (BASICC 1 and BASICC 40), along with cores taken from a freshwater lake (ICOS1), an anoxic lagoon (ICNL1), and the Vøring plateau (VP2a), show a clear increase in Pb concentration in modern sediments, corresponding with a decrease in the 206Pb/207Pb isotope ratio. This pattern signifies a change in the source of the Pb over time, associated with anthropogenic contamination: the results providing evidence of the long range distribution of contaminant Pb following the industrial revolution and the utilisation of alkyl Pb in petrol. Lake Ossian (ICOS1), a site situated close to Ny Ålesund provides unequivocal evidence for the atmospheric transport of Pb. The excess 206Pb/207Pb ratio was calculated as 1.165, indicative of an Eastern European emission source. The most compelling story, however, emerges from the contaminant archives contained in the marine sediment cores within the Barents Sea area, and from the Vøring Plateau. These sediment cores provide vital evidence that contaminant Pb is transported by oceanic currents to the Arctic environment. There is only one other study that has concentrated on the specific oceanic transport of Pb. This thesis further supports the hypothesis that the Atlantic water current is a prominent pathway for the transportation of Pb to the Eurasian Arctic Basin, with the Pb being scavenged to the underlying sediments en-route. From the area around Kongsfjorden, north-west Svalbard, four sediments cores were taken along a longitudinal transect, from freshwater to the marine environment, and analysed for Hg.
None of the four sediment cores displayed evidence of significant anthropogenic contamination. Sediment from Brandallaguna (ICNL1) showed a small increase in Hg concentration towards the surface of the core. Diagenetic processes, however, cannot be disregarded, with Hg forming HgS in anoxic conditions. It is evident in the literature and from this study that further research is required to improve the understanding of the complex Hg biogeochemical cycle.
For the contaminant Cd, there has been unequivocal evidence from snow and ice records, indicating an increase in Cd flux from the mid 18th century to the mid 19th century, associated with anthropogenic influence. None of the cores within this study show this temporal change in flux. Elevated concentrations of Cd, however, have been shown in the deep parts of two of the cores taken from the Barents Sea (BASICC 40 and BASICC 43), the Cd being precipitated as authigenic CdS in anoxic sediment. This research supports the hypothesis that the dissolution and remobilisation of Cd can make sediments a poor record of Cd temporal history.
|Date of Award||3 Jul 2008|
|Supervisor||Tracy Shimmield (Supervisor), Graham B Shimmield (Supervisor) & Kenny Black (Supervisor)|