Charlotte Sparrenbom

Holocene relative sea-level changes in the Qaqortoq area, southern Greenland

We present results from an investigation of relative sea-level changes in the Qaqortoq area in south Greenland from c. 11 000 cal. yr BP to the present. Isolation and transgression sequences from six lakes and two tidal basins have been identified using stratigraphical analyses, magnetic susceptibility, XRF and macrofossil analyses. Macrofossils and bulk sediments have been dated by AMS radiocarbon dating. Maximum and minimum altitudes for relative sea level are provided from two deglaciation and marine lagoon sequences. Initially, relative sea level fell rapidly and reached present-day level at similar to 9000 cal. yr BP and continued falling until at least 8800 cal. yr BP. Between 8000 and 6000 cal. yr BP, sea level reached its lowest level of around 6-8 m below highest astronomical tide (h.a.t.). At around 3750 cal. yr BP, sea level has reached above 2.7 m below h.a.t. and continued to rise slowly, reaching the present-day level between similar to 2000 cal. yr BP and the present. As in the Nanortalik area further south, initial isostatic rebound caused rapid isolation of low elevation basins in the Qaqortoq area. Distinct isolation contacts in the sediments are observed. The late Holocene transgression is less well defined and occurred over a longer time interval. The late Holocene sea-level rise implies reloading by advancing glaciers superimposed on the isostatic signal from the North American Ice Sheet. One consequence of this transgression is that settlements of Palaeo-Eskimo cultures from similar to 4000 cal. yr BP may have been transgressed by the sea. (Less)

Dating of the Narssarssuaq stade in southern Greenland

Following the Holocene thermal maximum, the Greenland ice sheet began to expand, and many local glaciers formed. The maximum extent of most outlet glaciers from the Inland Ice was reached around 100 to 200 years ago. However, some exceptions have been recorded. In southern Greenland, the Neoglacial Narssarssuaq stade marks an older re-advance that exceeded the historical advance. The dating of the Narssarssuaq stade has been much debated. Here we present new radiocarbon dates from a sediment core collected from a small lake within the moraines formed during this stade. A minimum age for the Narssarssuaq stade of around 1200 yr BP is suggested from the dates.

Glacial and palaeoenvironmental history of the Cape Chelyuskin area, Arctic Russia

Quaternary glacial stratigraphy and relative sea-level changes reveal at least two glacial expansions over the Chelyuskin Peninsula, bordering the Kara Sea at about 77°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raisedbeach sequences mapped to altitudes of at least up to ca. 80 m a.s.l. Chronological control is provided by accelerator mass spectrometry 14C dating, electron-spin resonance and optically stimulated luminescence geochronology. Major glaciations, followed by deglaciation and marine inundation, occurred during marine oxygen isotope stages 6–5e (MIS 6–5e) and stages MIS 5d–5c. These glacial sediments overlie marine sediments of Pliocene age, which are draped by fluvial sediment of a pre-Saalian age, thereby forming palaeovalley/ basin fills in the post-Cretaceous topography. Till fabrics and glacial tectonics record expansions of local ice caps exclusively, suggesting wet-based ice cap advance, followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains and the Severnaya Zemlya archipelago, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with the exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice neither impacted the Chelyuskin Peninsula nor Severnaya Zemlya, and barely touched the northern coastal areas of the Taymyr Peninsula.

A review of contamination of surface-, ground-, and drinking water in Sweden by perfluoroalkyl and polyfluoroalkyl substances (PFASs)

Abstract Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are found in aquatic systems, flora, and fauna worldwide. These potentially harmful compounds are also frequently detected in Sweden and have already resulted in severe problems for public drinking water supply, i.e., some wells had to be closed due to high PFAS concentrations both in raw water and produced drinking water. Knowledge on PFAS occurrence in Sweden is still quite low, although monitoring is currently ongoing. This work describes potential sources for PFASs to enter the drinking water supply in Sweden and compares different occurrences of PFASs in raw and drinking water in the country. Moreover, the monitoring history, the legal situation, and remediation actions taken are presented. Finally, future challenges and the way forward in Sweden are discussed.

On the scope and management of pesticide pollution of Swedish groundwater resources: The Scanian example

Twenty-three south-Swedish public supply wells were studied to assess pesticide pollution of regional groundwater resources. Relations between pesticide occurrence, hydrogeology, and land use were analyzed using Kohonen’s Self-Organizing Maps approach. Pesticides are demonstrated to be substantially present in regional groundwater, with detections in 18 wells. Concentrations above the drinking water threshold are confirmed for nine wells. Observations indicate considerable urban influence, and lagged effects of past, less restricted use. Modern, oxic waters from shallow, unconfined, unconsolidated or fracture-type bedrock aquifers appear particularly vulnerable. Least affected waters appear primarily associated with deeper wells, anoxic conditions, and more confined sediment aquifers lacking urban influence. Comprehensive, standardized monitoring of pesticides in groundwater need to be implemented nationwide to enable sound assessments of pollution status and trends, and to develop sound groundwater management plans in accordance with the Water Framework Directive. Further, existing water protection areas and associated regulations need to be reassessed.

Investigation of chlorinated solvent pollution with resistivity and induced polarization.

Globally, an enormous number of polluted areas are in need of remediation to prevent adverse effects on health and environment. In situ remediation and especially the monitoring thereof needs further development to avoid costly and hazardous shipments associated with excavation. The monitoring of in situ remediation actions needs easier and cheaper nondestructive methods for evaluation and verification of remediation degree and degradation status of the contaminants. We investigate the Direct Current resistivity and time-domain Induced Polarization tomography (DCIP) method and its use within the context of a DNAPL (Dense Non-Aqueous Phase Liquids) contaminated site in Varberg, Sweden, where an in situ remediation pilot test has been performed by stimulated reductive dechlorination by push injection. Our results show that the DCIP technique is an emerging and promising technique for mapping of underground structures and possibly biogeochemical spatial and temporal changes. The methodology could in combination with drilling, sampling and other complementary methods give an almost continuous image of the underground structures and delineation of the pollutant situation. It can be expected to have a future in monitoring approaches measuring time lapse induced polarization (IP), if more research is performed on the parameters and processes affecting the IP-signals verifying the interpretations. The IP technique can possibly be used for verification of the effectiveness of in situ remediation actions, as the current sampling methodology is inadequate.

Identification of Possible Weakness Zones in Limestone Bedrock by Resistivity and Induced Polarization

In connection to an environmental investigation of a former industrial site, the cretaceous sandy limestone bedrock in the surrounding area were mapped with resistivity and time domain induced polarization (DCIP). The aim of the DCIP survey was to delineate geological units and possible preferential pathways of DNAPL contaminated groundwater. Although IP anomalies corresponding to fractured crystalline bedrock have been observed previously and are commonly interpreted as results of clay weathering, there are not many studies of the IP behavior of limestone in previous research. In contrast to silicates, the weathering of calcite minerals in pure limestone results only in dissolution, without any weathering products in form of minerals. In this study, varying resistivity values and large IP anomalies were found in the sandy limestone bedrock, which are probable indications of weakness zones. The observed strong IP anomalies may be caused by calcite dissolution and precipitation processes or by clay mineral precipitation from chemical weathering of the silica grains contained in the sandy limestone. Another possibility may be sporadic presence of glauconitic sand in the limestone. More research is needed to confirm the sources of the observed anomalies.