Mercury accumulation in lake sediments on different time scales – the influence of algal primary production
The aim of this work is to test the proposed approach of algal scavenging as a driver of sediment mercury (Hg) on different time scales and to gain a better understanding of the mechanisms of Hg accumulation in lake sediments. A 3000-year sediment record from Nylandssjön in northern Sweden was analy...
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Umeå universitet, Institutionen för ekologi, miljö och geovetenskap
2023
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ftumeauniv:oai:DiVA.org:umu-203395 2023-10-09T21:54:38+02:00 Mercury accumulation in lake sediments on different time scales – the influence of algal primary production Kvicksilverackumulation i sjösediment över olika tidsskalor – effekten av primärproduktionen av alger Rebotzke, Anne 2023 application/pdf http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203395 eng eng Umeå universitet, Institutionen för ekologi, miljö och geovetenskap http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203395 info:eu-repo/semantics/openAccess mercury lake sediment primary productivity algal scavenging biogenic silica diatom proxy chlorophyll-a organic matter Geochemistry Geokemi Environmental Sciences Miljövetenskap Geosciences Multidisciplinary Multidisciplinär geovetenskap Student thesis info:eu-repo/semantics/bachelorThesis text 2023 ftumeauniv 2023-09-22T13:56:47Z The aim of this work is to test the proposed approach of algal scavenging as a driver of sediment mercury (Hg) on different time scales and to gain a better understanding of the mechanisms of Hg accumulation in lake sediments. A 3000-year sediment record from Nylandssjön in northern Sweden was analysed for this purpose, as well as a 20-year sediment record from the seasonal sediment traps of this lake. The diatom proxy biogenic silica (bSi) was determined by Fourier transform infrared spectroscopy (FTIRS) and chlorophyll-a (Chl-a) as a proxy for primary productivity by non-destructive visible near-infrared reflectance spectroscopy (VNIRS). Silica, normalised to minerogenic matter by aluminium (Si/Al) as an indirect diatom proxy and other geochemical parameters were analysed by the non-destructive method of X-ray fluorescence spectroscopy (XRF). The Hg content in the sediment was determined using the the thermal decomposition atomic absorption spectrophotometers (TD-AAS) method. Over the different time scales, organic matter (OM) is an important control factor for Hg, which in turn was strongly associated with primary productivity. Hg was normalised against OM by determining the Hg/LOI or Hg/C ratios. No positive correlation was found between the normalised Hg ratios and the proxies of primary productivity (bSi, Chl-a and Si/Al). Negative correlations between OM and minerogenic elements coinciding with human-induced erosion events and increasing Hg levels in the sediment were found. This is true, both for the long-term record in the sediment cores and the high-resolution data from the sediment traps. Furthermore, in the seasonal sediment record of the sediment traps, in-lake processes like lake turnover in spring and autumn could be linked to precipitation of iron oxyhydroxides (FeOOH) and increasing sedimentary Hg. This may be supported by the parallel sediment accumulation of other metals like nickel (Ni) and zinc (Zn) at the time of the lake turnover. Bachelor Thesis Northern Sweden Umeå University: Publications (DiVA) |
institution |
Open Polar |
collection |
Umeå University: Publications (DiVA) |
op_collection_id |
ftumeauniv |
language |
English |
topic |
mercury lake sediment primary productivity algal scavenging biogenic silica diatom proxy chlorophyll-a organic matter Geochemistry Geokemi Environmental Sciences Miljövetenskap Geosciences Multidisciplinary Multidisciplinär geovetenskap |
spellingShingle |
mercury lake sediment primary productivity algal scavenging biogenic silica diatom proxy chlorophyll-a organic matter Geochemistry Geokemi Environmental Sciences Miljövetenskap Geosciences Multidisciplinary Multidisciplinär geovetenskap Rebotzke, Anne Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
topic_facet |
mercury lake sediment primary productivity algal scavenging biogenic silica diatom proxy chlorophyll-a organic matter Geochemistry Geokemi Environmental Sciences Miljövetenskap Geosciences Multidisciplinary Multidisciplinär geovetenskap |
description |
The aim of this work is to test the proposed approach of algal scavenging as a driver of sediment mercury (Hg) on different time scales and to gain a better understanding of the mechanisms of Hg accumulation in lake sediments. A 3000-year sediment record from Nylandssjön in northern Sweden was analysed for this purpose, as well as a 20-year sediment record from the seasonal sediment traps of this lake. The diatom proxy biogenic silica (bSi) was determined by Fourier transform infrared spectroscopy (FTIRS) and chlorophyll-a (Chl-a) as a proxy for primary productivity by non-destructive visible near-infrared reflectance spectroscopy (VNIRS). Silica, normalised to minerogenic matter by aluminium (Si/Al) as an indirect diatom proxy and other geochemical parameters were analysed by the non-destructive method of X-ray fluorescence spectroscopy (XRF). The Hg content in the sediment was determined using the the thermal decomposition atomic absorption spectrophotometers (TD-AAS) method. Over the different time scales, organic matter (OM) is an important control factor for Hg, which in turn was strongly associated with primary productivity. Hg was normalised against OM by determining the Hg/LOI or Hg/C ratios. No positive correlation was found between the normalised Hg ratios and the proxies of primary productivity (bSi, Chl-a and Si/Al). Negative correlations between OM and minerogenic elements coinciding with human-induced erosion events and increasing Hg levels in the sediment were found. This is true, both for the long-term record in the sediment cores and the high-resolution data from the sediment traps. Furthermore, in the seasonal sediment record of the sediment traps, in-lake processes like lake turnover in spring and autumn could be linked to precipitation of iron oxyhydroxides (FeOOH) and increasing sedimentary Hg. This may be supported by the parallel sediment accumulation of other metals like nickel (Ni) and zinc (Zn) at the time of the lake turnover. |
format |
Bachelor Thesis |
author |
Rebotzke, Anne |
author_facet |
Rebotzke, Anne |
author_sort |
Rebotzke, Anne |
title |
Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
title_short |
Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
title_full |
Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
title_fullStr |
Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
title_full_unstemmed |
Mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
title_sort |
mercury accumulation in lake sediments on different time scales – the influence of algal primary production |
publisher |
Umeå universitet, Institutionen för ekologi, miljö och geovetenskap |
publishDate |
2023 |
url |
http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203395 |
genre |
Northern Sweden |
genre_facet |
Northern Sweden |
op_relation |
http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-203395 |
op_rights |
info:eu-repo/semantics/openAccess |
_version_ |
1779318313027895296 |