Heavy metal levels in New Zealand molluscs     

Stephen A. Nielsen  Adrienne Nathan 《新西兰海洋与淡水研究杂志》2013,47(4):467-481

Cadmium, lead, copper, mercury, zinc and iron were analysed by atomic absorption spectrophotometry in 13 species of edible molluscs from 199 sites around New Zealand; these included all molluscs commonly eaten in New Zealand. From each sampling site, a minimum of 14 specimens were combined and analysed together, so that the result would be representative of the population in that area. Wide variations are shown to occur in heavy metals from one location to another, and explanations for some of these variations are given.  相似文献   

Exploring Geovisualization Symbology for Landscape Genetics     

Eoin Mac Aoidh  Jann Th. Martinsohn  Gregory E. Maes  Alessia Cariani  Einar E. Nielsen 《Transactions in GIS》2013,17(2):267-281

  相似文献   

Optimizing the Environmental Performance of In Situ Thermal Remediation Technologies Using Life Cycle Assessment   总被引：3，自引：0，他引：3  

Gitte Lemming  Steffen G. Nielsen  Klaus Weber  Gorm Heron  Ralph S. Baker  Jacqueline A. Falkenberg  Mads Terkelsen  Carsten B. Jensen  Poul L. Bjerg 《Ground Water Monitoring & Remediation》2013,33(3):38-51

In situ thermal remediation technologies provide efficient and reliable cleanup of contaminated soil and groundwater, but at a high cost of environmental impacts and resource depletion due to the large amounts of energy and materials consumed. This study provides a detailed investigation of four in situ thermal remediation technologies (steam enhanced extraction, thermal conduction heating, electrical resistance heating, and radio frequency heating) in order to (1) compare the life‐cycle environmental impacts and resource consumption associated with each thermal technology, and (2) identify options to reduce these adverse effects. The study identifies a number of options for environmental optimization of in situ thermal remediation. In general, environmental optimization can be achieved by increasing the percentage of heating supplied in off peak electricity demand periods as this reduces the pressure on coal‐based electricity and thereby reduces the environmental impacts due to electricity production by up to 10%. Furthermore, reducing the amount of concrete in the vapor cap by using a concrete sandwich construction can potentially reduce the environmental impacts due to the vapor cap by up to 75%. Moreover, a number of technology‐specific improvements were identified, for instance by the substitution of stainless steel types in wells, heaters, and liners used in thermal conduction heating, thus reducing the nickel consumption by 45%. The combined effect of introducing all the suggested improvements is a 10 to 21% decrease in environmental impacts and an 8 to 20% decrease in resource depletion depending on the thermal remediation technology considered. The energy consumption was found to be the main contributor to most types of environmental impacts; this will, however, depend on the electricity production mix in the studied region. The combined improvement potential is therefore to a large extent controlled by the reduction/improvement of energy consumption.  相似文献   

Meteorological observations 1998 at the arctic station,Qeqertarsuaq (69°15'N), Central West Greenland/Active layer monitoring in two Greenlandic permafrost areas: Zackenberg and Disko Island     

Ole Humlum  Birger Ulf Hansen  Niels Nielsen  Hanne H. Christiansen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):113-121

An automatic meteorological station has been operating at the Arctic Station (69°15'N, 53°31'W) in West Greenland since 1990. This paper summarises meteorological parameters during 1998, including snow cover, ground temperatures and active layer development, and presents comments on the local permafrost thickness.

Abstract

Active layer monitoring in Greenland was started in 1996 and 1997, and forms part of the Circumpolar Active Layer Monitoring (CALM) Network of the International Permafrost Association (IPA). The results of the first years of this monitoring of thaw progression and maximum active layer thickness in two Greenlandic permafrost areas are presented. Two sites are in the continuous permafrost zone at Zackenberg in NE Greenland (74 °N), and one at Disko Island in W Greenland (69 °N), at the border between discontinuous and continuous permafrost.

The data collected at Zackenberg demonstrate interannual variation in the timing of thaw progression in the monitoring grid holding a seasonal snowpatch, while there is less variation in the horizontal grid without a snowpatch. The maximum active layer thickness for the two Zackenberg grids is more or less consistent for the first three years with averages from 58 to 66 cm in mid and late August. At Disko the active layer reached 71 cm in mid August 1998. Spatially the distribution of the maximum, annual active layer thickness within the grids is concordant.  相似文献   

Varves in a Proglacial Lake,Sermilik, South East Greenland/Meterological Observations at Arctic Station,Qeqertarsuaq (Godhavn), Central West Greenland/Den Danske Nationalkomité for Geografi 1994–95     

Bent Hasholt  N. Nielsen  B. U. Hansen  O. Humlum  M. Rasch  Christian Wichmann Matthiessen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):92-106

Danish Journal of Geography 95: 92–96, 1995.

Three cores collected from a proglacial lake with an Axelsson corer are x-rayed. The stratification is interpreted as varves. The cores cover periods of sedimentation with a duration from 5—23 years. The average thickness of the varves vary from 1.9—20.0 mm indicating a tenfold variation in the sedimentation rate.

Geografisk Tidsskrift 96: 97–104, 1995.

In October 1990 a new automatic meteorological station was established at the Arctic Station, Qeqertarsuaq (Godhavn), managed by the University of Copenhagen. It is the purpose of this note to draw the attention to the existence of this meteorological station, the character of climate parameter monitored and to the environment in which the station is functioning.

Examples of climate data measured during 1994 are presented, and general trends in the fluctuation of the selected parameters are annotated. Furthermore, it is mentioned how users may obtain the climate data. In the years to come we plan to publish a similar status of the climatic development at the Arctic Station in this periodical.  相似文献   

Total sediment budget of a transgressive barrier-spit,Skallingen, SW Denmark: A review     

Christian Christiansen  Troels Aagaard  Jesper Bartholdy  Merete Christiansen  Jørgen Nielsen  Niels Nielsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):107-126

Average sea-level rise in the northern part of the Danish Wadden Sea has been 1.3 mm a^?1 during the last 100 years but during the last 25 years a rise of 4.2 mm a^?1 was observed. Concurrent with the recent sea-level rise the Skallingen barrier spit has migrated landward by 3–5 m a^?1. Long term sediment budgets for each of the morphological units involved in the migration are reviewed (e.g. onshore in the shore face +90.000 m³ a^?1, longshore -641.000 m³ a^?1, foredunes +65,000 m³ a^?1, overwash fan including shorenormal dunes +11,000 m³ a^?1, spit terminus -96,000 m³ a^?1, tidal flat + 10,000 m³ a^?1 and backbarrier salt marsh +33,000 m³ a^?1) and used to establish the relative importance of sediment transport processes involved in barrier migration. Strong interannual variations exist in the long term budget making evaluation of barrier behaviour based on short term measurements doubtful. In a cross shore sense the barrier spit is accreting in spite of the sea level rise. This is specially pronounced at an active overwash fan. However, due to substantial sediment losses to longshore transport the barrier, gets narrower and shorter during its transgressive behaviour. This may indicate that preservation of barriers in the geological record during rapid sea level rise is promoted when sediment loss to longshore transport is insignificant.  相似文献   

Role of landscape parameters in riverine run-off,and sediment and organic matter yield on Disko Island,West Greenland     

Morten Rasch  Niels Nielsen  Christian Christiansen  Thomas Balstrøm  Robert Gilbert  Joseph Desloges 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):1-11

Measurements of discharge and suspended sediment and organic matter yield from nine different drainage basins on the island Disko in central West Greenland were carried out in the period 19–30 July 1997. A series of landscape properties (glacier cover, altitude, slope, aspect and vegetation cover) were measured for each drainage basin from a digital elevation model and a satellite image. Principal Component Analysis and regression statistics have been used to examine which landscape parameters dominate the measured discharges and yields. It is concluded that differences in suspended sediment and organic matter yield between the drainage basins can be explained by the measured morphometric properties while differences in water run-off can not. Glacier cover percentage and percent area above 800 m a.s.l. were the most important parameters influencing suspended sediment and organic matter yield in the drainage basins on Disko during the study period.  相似文献   

Learning to do geography? University students posing questions in GIS laboratory exercises     

Lene Møller Madsen  Thomas Theis Nielsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2013,67(3):157-161

In many higher education curricula, pre-structured step-by-step laboratory exercises in introductory courses in geographical information systems (GIS) are an important part of the training of future geographers. The reasons for this approach to teaching GIS are manifold, such as large numbers of students, off-the-shelf desktop software that is often complex, technical challenges, and scarce faculty resources. Often the reasons are well agreed upon by members of a university faculty and among the students. Research in other fields has shown that the use of a controlled manual for laboratory work often provides low learning potentials. However, not much empirical research has dealt with this issue within a GIS learning environment. Inspired by research on the value of student-generated questions within science education, the authors take a closer look at the type of student-generated questions and their relation to students' self-image of their learning approach in two pre-structured GIS laboratory settings at two Danish universities. They conclude that the vast majority of student-generated questions are of a basic information type and independent of the students' self-image of their learning approach. Further, it is found that wonderment questions, i.e. questions that are reflective in nature and show students the process towards acquiring extended geographical knowledge and software proficiency, are rarely asked.  相似文献   

Habitat selection in birds feeding on ocean shores: landscape effects are important in the choice of foraging sites by oystercatchers     

Thomas A. Schlacher  Justin J. Meager  Tara Nielsen 《Marine Ecology》2014,35(1):67-76

Food availability is a fundamental determinant of habitat selection in animals, including shorebirds foraging on benthic invertebrates. However, the combination of dynamic habitats, patchy distributions at multiple spatial scales, and highly variable densities over time can make prey less predictable on ocean‐exposed sandy shores. This can, hypothetically, cause a mismatch between prey and consumer distributions in these high‐energy environments. Here we test this prediction by examining the occurrence of actively foraging pied oystercatchers (Haematopus longirostris) in relation to physical habitat attributes and macrobenthic prey assemblages on a 34 km long, high‐energy beach in Eastern Australia. We incorporate two spatial dimensions: (i) adjacent feeding and non‐feeding patches separated by 200 m and (ii) landscape regions with and without foraging birds separated by 2–17 km. There was no support for prey‐based or habitat‐based habitat choice at the smaller dimension, with birds being essentially randomly distributed at the local scale. Conversely, at the broader landscape dimension, the distribution of oystercatchers was driven by the density of their prey, but not by attributes of the physical beach environment. This scale‐dependence suggests that, on open‐coast beaches, landscape effects modulate how mobile predators respond to variations in prey availability.  相似文献   

Staying with the system: theoretical consistency and change in Danish geographical work on the Sahel     

Laura Vang Rasmussen  Jonas Ø. Nielsen 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):3-16

Scholars have studied the Sahel intensely since major droughts hit the region in the early 1970s. One of the most persistent of these in terms of both volume and time span is Anette Reenberg. In this paper we explore her studies of the Sahel published in peer-reviewed journals and their impact over the last three decades. Reenberg has had a remarkably stable theoretical agenda concerned with the importance of understanding the social and biophysical systems as one coupled human-environmental system. This agenda has influenced contemporary as well as subsequent Danish scholars publishing on the Sahel. Taking papers published in Geografisk Tidsskrift-Danish Journal of Geography as an example we show how scholars have moved from treating aspects of the Sahelian droughts according to the traditional natural-social science divide towards a much more coupled manner. This rise of the coupled human-environmental system framework in the journal may be attributed to Reenberg’s theoretical agenda as well as a new international stream of research joining the human and environmental sciences in an interdisciplinary effort. Hence, it is also shown how Reenberg’s theoretical agenda have influenced scholars trying to grasp contemporary global change. This is especially evident in the land science community.  相似文献