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Copenhagen, Denmark

Nielsen S.S.,Technical University of Denmark | Kjeldsen P.,Technical University of Denmark | Hansen H.C.B.,Copenhagen University | Jakobsen R.,GEUS
Applied Geochemistry | Year: 2014

Several soil remediation techniques for As, Cu and Cr contaminated soil utilize adsorption of contaminants to ferrihydrite as the removal mechanism, even though ferrihydrite will transform to secondary iron oxides and part of the sorption capacity will be lost. Transformation of ferrihydrite following 4. yr of in situ burial at a contaminated site was examined in samples of impure (Si-bearing) ferrihydrite in soil heavily polluted with As, Cr and Cu. The samples are so-called iron water treatment residues (Fe-WTR) precipitated from anoxic groundwater during aeration. The extent of transformation of ferrihydrites in the field was evaluated in the lab through experiments where the kinetics of iron and contaminant release was studied in a pH 3 ascorbic acid solution. Compared to fresh controls the aged samples had scavenged significant amounts of contaminants (up to 9.2. mmolAs/molFe and 1.5. mmolCu/molFe) and the reactivity had decreased by one order of magnitude, indicating partial transformation of ferrihydrite to more crystalline iron phases. Iron crystallinity increased during the 4. yr of aging with XRD suggesting goethite, α-FeO(OH), to be the most prominent transformation products. The study clarifies the fate of ferrihydrite and associated contaminants during burial enabling an improvement of the methods for amending contaminated soil with Fe-WTR. © 2014 Elsevier Ltd.

Anell I.,Copenhagen University | Thybo H.,Copenhagen University | Rasmussen E.,GEUS
Basin Research | Year: 2012

The North Sea Basin contains an almost complete record of Cenozoic sedimentation, separated by clear regional unconformities. The changes in sediment characteristics, rate and source, and expression of the unconformities reflect the tectonic, eustatic and climatic changes that the North Sea and its margins have undergone. While the North Sea has been mapped locally, we present the first regional mapping of the Cenozoic sedimentary strata. Our study provides a new regional sub-division of the main seismic units in the North Sea together with maps of depocentres, influx direction and source areas. Our study provides a regional synthesis of sedimentation based on a comprehensive interpretation of a regionally covering reflection seismic data set. We relate observations of sediment characteristics and unconformities to the geological evolution. The timing, regional expression and stratigraphic characteristics of many unconformities indicate that they were generated by eustatic sea-level fall, often in conjunction with other processes. Early Cenozoic unconformities, however, relate to tectonism associated with the opening of the North Atlantic. From observation on a regional scale, we infer that the sediment influx into the North Sea during the Cenozoic is more complex than previously suggested clockwise rotation from early northwestern to late southern sources. The Shetland Platform supplied sediment continuously, although at varying rates, until the latest Cenozoic. Sedimentation around Norway changed from early Cenozoic influx from the southwestern margin, to almost exclusively from the southern margin in the Oligocene and from all of southern Norway in the latest Cenozoic. Thick Eocene deposits in the Central Graben are sourced mainly from a western and a likely southern source, indicating that prominent influx from the south did not only occur from the mid-Miocene onwards. We infer a new age for the increased progradational sediment influx in the Pleistocene of 2.5 Ma, coeval with Fennoscandian glaciation. © 2011 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.

Frykman P.,GEUS
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

The filling of a reservoir with CO2 is a dynamic process influenced by heterogeneities at a range of different scales. If parts of the reservoir are by-passed during this process it will result in lowered filling efficiency and therefore smaller capacity than if assuming homogeneity. This study attempts to illustrate that even small-scale heterogeneity has implications for how the CO2 is distributed and trapped in sedimentary sequences, and outlines a workflow for the study of these effects. In certain reservoirs the distribution of the injected CO2 into partly or fully separated layers might mean efficient use of the pore space in the reservoir. However, the mobility may also cause CO2 to bypass some of the pore space, depending on the heterogeneity and anisotropy of the permeability. After injection has stopped, the heterogeneity will influence the imbibition process when brine displaces the CO2, which might cause additional trapping beyond that prescribed by the endpoints for the saturation functions.

Thibault N.,Copenhagen University | Anderskouv K.,Copenhagen University | Bjerager M.,GEUS | Boldreel L.O.,Copenhagen University | And 3 more authors.
Lethaia | Year: 2015

The lithostratigraphy, calcareous nannofossil biostratigraphy, carbon- and oxygen-isotope stratigraphy and gamma-ray profile are presented for the Skælskør-1 core, eastern Denmark. The correlation of carbon isotopes to Gubbio (Italy) and ODP Site 762C (Indian Ocean) provides the chronostratigrahical framework of the core through a tie to magnetostratigraphy. Two new carbon-isotope excursions are defined for the uppermost Maastrichtian of the core and prove useful for long-distance correlation. Twenty stratigraphic tie-points are used for correlation of the upper Campanian-Maastrichtian interval by combining carbon-isotope and gamma-ray variations. Significant dissimilarities in the gamma-ray profiles of the Danish Basin cores preclude the sole use of this tool for basin-scale correlations. Bulk oxygen-isotopes and semi-quantitative abundance changes in the warm-water calcareous nannofossil Watznaueria barnesiae and the cool-water Kamptnerius magnificus highlight the following past changes in sea-surface temperatures (SSTs): relatively warm late Campanian SSTs, cooling across the Campanian-Maastrichtian boundary and through the early Maastrichtian, warming across the early-late Maastrichtian transition, cooling in the late Maastrichtian, intense warming in the latest Maastrichtian chron C29r, followed by a very short episode of cooling immediately before the Cretaceous-Palaeogene boundary. The late Campanian-Maastrichtian evolution in sea water temperatures inferred from the Danish Basin is similar to that delineated at tropical latitude oceanic sites. © 2015 The Lethaia Foundation.

Rasmussen R.,GEUS
74th European Association of Geoscientists and Engineers Conference and Exhibition 2012 Incorporating SPE EUROPEC 2012: Responsibly Securing Natural Resources | Year: 2012

Different approaches in applying time lapse seismic monitoring for detecting CO2 propagation (and ultimately the frontal tip) have been investigated at a possible CO2 storage site characterised by an accumulation of individually thin layered reservoir subunits. Focus for the present case study is an investigation of accumulated frontal tip response from thin layered reservoir subunits compared to individual layer by layer response.

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