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dc.contributor.authorGelena, Samuel Kebede
dc.date.accessioned2015-09-28T22:00:25Z
dc.date.issued2015
dc.identifier.citationGelena, Samuel Kebede. Capping of Contaminated Sediments in a Formerly Anoxic Basin in Inner Oslofjord, Norway: Temporal Processes and Ecological Effects. Master thesis, University of Oslo, 2015
dc.identifier.urihttp://hdl.handle.net/10852/46127
dc.description.abstractCapping, the placement of uncontaminated (clean) sediments over contaminated sediments, has been practiced in the last three decades as ecologically friendly and cost efficient remediation technique. The polluted, formerly anoxic Bekkelag basin (study area), inner Oslofjord, was re-aerated in 2001 and contaminated sediments were partly capped with post glacial clean clay in 2007. On 18th of June 2014, the sediment and water samples were collected at RC5 (capped) and RC9 (uncapped) site and then macrofauna, benthic foraminifera, water content and geochemical parameters (organic and inorganic contaminants, TOC, and bottom water dissolved oxygen concentration) were analysed. The temporal development of ecological status and bioturbation depth at the two sites and comparison of the present-day supply of contaminants to the basin with supply it received during maximum pollution load were investigated. Even though the two sites were being exposed to the same external environmental forcing, the biogeochemical properties of the sediments are the main reason for the variation in temporal development of the benthic fauna. The two sites have the same, 6 cm, bioturbation depth and bioturbation was the main factor for distributing the contaminants further down into the sediment at the capped site. Throughout the core thickness the concentration of contaminants, both inorganic and organic, in the sediment at the capped RC5 site was lower than at the uncapped RC9 site. Almost all contaminant results show a convergence pattern, i.e. an increasing trend upwards to the sediment-water interface at the capped and the opposite trend (upward decreasing trend) at the uncapped site. While the opportunistic foraminiferal species Stainforthia fusiformis dominated the uncapped site since 2008, its relative abundance at the capped site increased from 10 % in 2008 to 60 % in 2014. The dominant Bulimina marginata species in the 2008-2010 data was insignificant in 2014 and instead Hippocrepina spp had a relative abundances >10 % at both sites. Hence, the temporal development in the benthic foraminiferal assemblage composition strongly supported the converging tendency.eng
dc.language.isoeng
dc.subjectBekkelag
dc.subjectbasin
dc.subjectinner
dc.subjectOslofjord
dc.subjectcapped
dc.subjectuncapped
dc.subjectbioturbation
dc.subjectmacrofauna
dc.subjectbenthic
dc.subjectforaminifera
dc.subjectecological
dc.subjectquality
dc.subjectstatus
dc.titleCapping of Contaminated Sediments in a Formerly Anoxic Basin in Inner Oslofjord, Norway: Temporal Processes and Ecological Effectseng
dc.typeMaster thesis
dc.date.updated2015-09-28T22:00:25Z
dc.creator.authorGelena, Samuel Kebede
dc.date.embargoenddate3015-06-22
dc.rights.termsDette dokumentet er ikke elektronisk tilgjengelig etter ønske fra forfatter. Tilgangskode/Access code A
dc.identifier.urnURN:NBN:no-50315
dc.type.documentMasteroppgave
dc.rights.accessrightsclosedaccess
dc.identifier.fulltextFulltext https://www.duo.uio.no/bitstream/handle/10852/46127/1/Samuel_kebede_Thesis_2015.pdf


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