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Copenhagen, Denmark

Frei R.,Copenhagen University | Poire D.,National University of La Plata | Frei K.M.,National Museum of Denmark | Frei K.M.,Copenhagen University
Chemical Geology | Year: 2014

We have investigated the pathway of chromium from its mobilization on land and along its riverine transport in a subtropical region of South America (Misiones Province, Argentina), in an attempt to link Cr stable isotope compositions recently measured in seawater with signals prevailing in rivers and, ultimately, with Cr isotope effects observed during oxidative surface weathering in subtropical red soils. Cr concentrations and stable Cr isotopic compositions (expressed as δ53Cr ‰ values) in two typical and representative surface profiles of weathered basalt show significant depletion of Cr in the soils of up to 50%, together with pronounced negatively fractionated δ53Cr values which are indicative of oxidative mobilization of heavy Cr(VI) into the run-off. The behavior of Cr in the studied weathering profiles is not correlated with that of other redox sensitive elements, such as Ce and U; this is essentially due to the affinity of REE and U, but not Cr with secondary phosphates which form during weathering processes.Smaller tributaries in NW Argentina to the Paraná River (second largest river in South America) carry dissolved Cr in the order of 0.7-1.4ppb (13-27nM) with δ53Cr values of +0.2 to +0.4‰, balancing the negatively fractionated weathering products. The isotope composition and concentration of dissolved Cr in the ca. 1200km long Paraná River from Misiones to its estuary and discharge area into the South Atlantic Ocean remains relatively constant with an average Cr concentration around 2.4ppb (46nM) and an average δ53Cr value of +0.32‰. The Cr concentration in the estuary itself drops by ca. 50% but with only minor change in its Cr isotope composition. Results from the Paraná estuary are identical with recently analyzed surface seawater from the Argentine Basin with Cr contents of ~0.3ppb (~6nM) and δ53Cr values ~+0.4‰ (Bonnand et al., 2013), and indicate that there is only a minimal Cr isotopic variability during riverine transport, even during long transport distances as shown in our example of the Paraná River. Simple Cr input flux calculations reveal that the Paraná River accounts for ~5% of the total yearly Cr flux to the world's oceans today and that its isotopic signature seems to be, at least locally, imparted to the surface seawater of the Argentine Basin. Whether or not this Cr isotope signature is generally exhibited by the world's oceans needs further investigations, particularly the characterization of seawater around the globe. © 2014 Elsevier B.V.

Jorkov M.L.S.,Museum of Copenhagen | Jorkov M.L.S.,Copenhagen University | Jorgensen L.,National Museum of Denmark | Lynnerup N.,Copenhagen University
American Journal of Physical Anthropology | Year: 2010

A systematic dietary investigation during Danish Roman Iron Age (1-375AD) is conducted by analyzing stable isotope ratios of carbon (δ 13C) and nitrogen (δ 15N) in the collagen of human and animal bone. The human sample comprises 77 individuals from 10 burial sites. In addition 31 samples of mammals and fish were analyzed from same geographical area. The investigation characterizes the human diet among different social groupings and analyses dietary differences present between sex, age, and site phase groups. Diachronically, the study investigates the Roman influences that had an effect on social structure and subsistence economy in both the Early and Late Period. Geographically the locations are both inland and coastal. The isotopic data indicate extremely uniform diet both between and within population groups from Early and Late Roman periods and the data are consistent throughout the Roman Iron Age. Protein consumption was dominated by terrestrial animals with no differences among social status, age, sex, or time period, while terrestrial plant protein only seems to have contributed little in the diet. Furthermore, the consumption of marine or aquatic resources does not seem to have been important, even among the individuals living next to the coast. © 2010 Wiley-Liss, Inc.

Andresen S.T.,Museet for Varde By og Omegn | Karg S.,National Museum of Denmark
Vegetation History and Archaeobotany | Year: 2011

During the last decade, a new type of structure has been found at several archaeological sites in Denmark. These structures can be interpreted as having been used for retting the stems of textile plants such as Linum usitatissimum L. (flax), Cannabis sativa L. (hemp) and Urticadioica L. (nettle). In order to obtain fine threads for textile production, these plants need to pass through several biological and technical processes. The first process is the retting of the plant stems to dissolve the pectin which fixes the fibres to the stalk. This can either be done by water retting, where the plant stems are soaked in lakes, rivers or waterlogged pits, or by field retting, where the stems are laid out in a field in order to absorb dew. The first method is shorter in time and the process is easier to control. In this article, details of archaeological structures are presented from eight sites in southern Scandinavia that can be interpreted as textile plant retting pits. The constructions of the pits are described, as well as the archaeological contexts and the relevant associated archaeobotanical records. Some of the presented sites, of which the oldest are dated to the late Bronze Age and early pre-Roman Iron Age (800-250 b. c.) and the youngest to the Viking Age (a. d. 750-1050), indicate a large-scale production of flax that had been underestimated up to now. © 2011 Springer-Verlag.

Khan F.R.,Roskilde University | Syberg K.,Roskilde University | Shashoua Y.,National Museum of Denmark | Bury N.R.,Kings College London
Environmental Pollution | Year: 2015

This study aimed to determine whether the uptake and localization of Ag in zebrafish was affected by the presence of polyethylene microplastic beads (PE MPBs). Zebrafish were exposed to 1 μg Ag L-1 (radiolabelled with 110mAg) for 4 and 24 h in the presence or absence of PE MPBs (10, 100 or 1000 MPBs mL-1), and one treatment in which MPBs (1000 MPBs mL-1) were incubated with Ag to promote adsorption. The presence of MPBs, at any of the tested doses, had no effect on the uptake or localization of Ag. However, exposure to the Ag-incubated MPBs (∼75% of the Ag bound to MPBs) significantly reduced Ag uptake at both time points and also significantly increased the proportion of intestinal Ag. This study demonstrates that microplastics can alter the bioavailability and uptake route of a metal contaminant in a model fish species. © 2015 Elsevier Ltd. All rights reserved.

Matthiesen H.,National Museum of Denmark | Wonsyld K.,Topsoe Fuel Cell
Corrosion Engineering Science and Technology | Year: 2010

This paper presents a novel non-destructive method to measure the actual corrosion rate of precorroded metal objects, such as historical and archaeological artefacts. The corrosion rate is estimated from the oxygen consumption of the objects, which is measured in a small volume of air encapsulated directly on the surface of the object. An optical method is used for the oxygen measurements, making it possible to measure through transparent materials such as glass. The method is tested on iron and copper samples in different environments using both new uncorroded metal and historical artefacts, which have thick corrosion scales from more than 50 years outdoors. The results show the following: the method has a good reproducibility; there is a good correspondence between oxygen consumption and weight loss; the corrosion rates of precorroded cast iron are significantly lower than the rates found for new steel samples, whereas corrosion rates for precorroded copper are equal to or higher than rates for new copper samples; and corrosion rates as low as 0.1 μm/year can be measured by the method. © 2010 Maney Publishing.

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