Eelpout (Zoarces viviparus) in marine environmental monitoring     

Hedman JE  Rüdel H  Gercken J  Bergek S  Strand J  Quack M  Appelberg M  Förlin L  Tuvikene A  Bignert A 《Marine pollution bulletin》2011,62(10):2015-2029

The implementation of the EU Marine Strategy Framework Directive necessitates the development of common criteria and methodological standards for marine environmental monitoring and assessment across Europe. Eelpout (Zoarces viviparus) is proposed as a key indicator organism in the Baltic and North Sea regions. This benthic fish species is widely used in ecotoxicological studies and as a bioindicator of local pollution due to its stationary behavior. Eelpout is included in the environmental monitoring program of several Baltic States, covering both chemical and biological effects measurements, and samples have been archived in environmental specimen banks for >15 years. A method for evaluating the frequency of larval aberrations has been suggested as a standardized assessment tool. The large scientific knowledge-base and considerable experience of long-term chemical and biological effects monitoring and specimen banking, make eelpout a suitable species for the assessment of Good Environmental Status in the Baltic and North Seas.  相似文献   

Improving the representation of major landforms in analytical relief shading     

Brooke E. Marston  Bernhard Jenny 《International journal of geographical information science》2013,27(7):1144-1165

Relief shading is the most common type of cartographic relief representation for print and digital maps. Manual relief shading results in informative and visually pleasing representations of terrain, but it is time consuming and expensive to produce. Current analytical relief shading can be created quickly, but the resulting maps are not as aesthetically appealing and do not show landscape features in an explicit manner. This article introduces an automated digital method that produces shaded relief with locally adjusted illumination directions to simulate the techniques and cartographic principles of manual relief shading. Ridgelines and valley lines are derived from a digital terrain model, vectorized, and used in a diffusion curve algorithm. A graph analysis generalizes the lines before using them for diffusion curve shading. The direction of illumination is adjusted based on the spatial orientation of ridgelines and valley lines. The diffusion curve shading is combined with standard analytical relief shading to create a final diffusion relief shading image. Similar to manual relief shading, major landforms and the structure of the terrain are more clearly shown in the diffusion relief shading. The presented method best highlights major landforms in terrain characterized by sharp, clearly defined ridges and valleys.  相似文献   

Hässeldala – a key site for Last Termination climate events in northern Europe     

Barbara Wohlfarth  Francesco Muschitiello  Sarah L. Greenwood  August Andersson  Malin Kylander  Rienk H. Smittenberg  Margret Steinthorsdottir  Jenny Watson  Nicola J. Whitehouse 《Boreas: An International Journal of Quaternary Research》2017,46(2):143-161

The Last Termination (19 000–11 000 a BP) with its rapid and distinct climate shifts provides a perfect laboratory to study the nature and regional impact of climate variability. The sedimentary succession from the ancient lake at Hässeldala Port in southern Sweden with its distinct Lateglacial/early Holocene stratigraphy (>14.1–9.5 cal. ka BP) is one of the few chronologically well‐constrained, multi‐proxy sites in Europe that capture a variety of local and regional climatic and environmental signals. Here we present Hässeldala's multi‐proxy records (lithology, geochemistry, pollen, diatoms, chironomids, biomarkers, hydrogen isotopes) in a refined age model and place the observed changes in lake status, catchment vegetation, summer temperatures and hydroclimate in a wider regional context. Reconstructed mean July temperatures increased between c. 14.1 and c. 13.1 cal. ka BP and subsequently declined. This latter cooling coincided with drier hydroclimatic conditions that were probably associated with a freshening of the Nordic Seas and started a few hundred years before the onset of Greenland Stadial 1 (c. 12.9 cal. ka BP). Our proxies suggest a further shift towards colder and drier conditions as late as c. 12.7 cal. ka BP, which was followed by the establishment of a stadial climate regime (c. 12.5–11.8 cal. ka BP). The onset of warmer and wetter conditions preceded the Holocene warming over Greenland by c. 200 years. Hässeldala's proxies thus highlight the complexity of environmental and hydrological responses across abrupt climate transitions in northern Europe.  相似文献   

Goethite adsorption of Cu(II), Pb(II), Cd(II), and Zn(II) in the presence of sulfate: Properties of the ternary complex     

Peter J. Swedlund  Jenny G. Webster  Gordon M. Miskelly 《Geochimica et cosmochimica acta》2009,73(6):1548-43

Adsorption of Cu²⁺, Zn²⁺, Cd²⁺, and Pb²⁺ onto goethite is enhanced in the presence of sulfate. This effect, which has also been observed on ferrihydrite, is not predicted by the diffuse layer model (DLM) using adsorption constants derived from single sorbate systems. However, by including ternary surface complexes with the stoichiometry FeOHMSO₄, where FeOH is a surface adsorption site and M²⁺ is a cation, the effect of SO₄²⁻ on cation adsorption was accurately predicted for the range of cation, goethite and SO₄²⁻ concentrations studied. While the DLM does not provide direct molecular scale insights into adsorption reactions there are several properties of ternary complexes that are evident from examining trends in their formation constants. There is a linear relationship between ternary complex formation constants and cation adsorption constants, which is consistent with previous spectroscopic evidence indicating ternary complexes involve cation binding to the oxide surface. Comparing the data from this work to previous studies on ferrihydrite suggests that ternary complex formation on ferrihydrite involves complexes with the same or similar structure as those observed on goethite. In addition, it is evident that ternary complex formation constants are larger where there is a stronger metal-ligand interaction. This is also consistent with spectroscopic studies of goethite-M²⁺-SO₄²⁻ and phthalate systems showing surface species with metal-ligand bonding. Recommended values of ternary complex formation constants for use in SO₄-rich environments, such as acid mine drainage, are presented.  相似文献   

Amino acid and amino sugar yields and compositions as indicators of dissolved organic matter diagenesis     

Jenny Davis  Karl Kaiser  Ronald Benner 《Organic Geochemistry》2009,40(3):343-352

Microbial decomposition experiments were used to characterize changes in the amino acid and amino sugar yields and compositions of natural marine substrates during early diagenesis in seawater. On average, 63% of added carbon and 68% of added nitrogen were removed within the first 30 days of decomposition. In all cases, amino acid utilization accounted for a substantial fraction of the removed C and N. Carbon-normalized amino acid yields decreased to less than 50% of their starting values and most of this change occurred within the first 10 days of decomposition. Increases in the concentrations of amino sugars and decreases in the GlcN:GalN ratio in particulate organic matter (POM) illustrated the significance of microbial production during the decomposition of added substrates. Changes in the mol % composition of amino acids during early diagenesis were substantial but highly variable with substrate. Previous survey data collected from the same region were used in conjunction with the experimental data to investigate the utility of several established amino acid-based indices of organic matter diagenesis. This comparison showed that a combination of these degradation indexes is most effective for describing the diagenetic state of dissolved organic matter (DOM). Carbon-normalized amino acid yields were found to be the most effective indicator for early diagenesis. Relative abundances of amino acids were effective indicators of intermediate stages of diagenesis and the mol % composition of the non-protein amino acid γ-Aba (γ-aminobutyric acid) was an effective indicator of advanced DOM diagenesis.  相似文献   

Successive Holocene rock avalanches at Lake Coleridge, Canterbury, New Zealand     

Jenny Lee  Tim Davies  David Bell 《Landslides》2009,6(4):287-297

At Lake Coleridge, Canterbury, New Zealand, at least three rock avalanches have been released from a single source area during the Holocene. The first of these was of 10⁷ m³ volume and dates to about 9,750 BP, and two with volumes 5 × 10⁵ and 4 × 10⁴ m³ occurred about 700 BP. All three crossed the course of the Ryton River; the latter two were emplaced within the part of the first that had subsequently been eroded by the Ryton River. All three were most likely triggered by, or related to, seismicity. The first rock avalanche formed a long-lived landslide dam, and no evidence remains to indicate whether its eventual failure was catastrophic. The second formed a correspondingly smaller dam, but there is no evidence that its lake was long-lived; however, a set of anomalously steep outwash terraces downstream of the landslide deposits show that it failed catastrophically. A camping ground is sited about 1 km downstream of the landslide deposits, and proposals to develop it further risk potentially severe hazards from future rock avalanche activity at the site.  相似文献   

Modeling of shear failure in fractured reservoirs with a porous matrix     

Rajdeep Deb  Patrick Jenny 《Computational Geosciences》2017,21(5-6):1119-1134

A finite volume-based numerical modeling framework using a hierarchical fracture representation (HFR) has been developed to compute flow-induced shear failure. To accurately capture the mechanics near fracture manifolds, discontinuous basis functions are employed which ensure continuity of the displacement gradient across fractures. With these special basis functions, traction and compressive forces on the fracture segment can be calculated without any additional constraints, which is extremely useful for estimating the irreversible displacement along the fracture (slip) based on a constitutive friction law. The method is further extended to include slip-dependent hydraulic aperture change and grid convergent results are obtained. Further, the change in hydraulic aperture is modeled using an asymptotic representation which respects the experimentally observed behavior of pore volume dilation due to shear slip. The model allows the initial rapid increase in hydraulic aperture due to shear slip and asymptotically approaches a finite value after repeated shearing of a fracture segment. This aperture increase is the only feedback for mechanics into the fluid flow for a linear elastic mechanics problem. The same model is also extended to include poroelastic relations between flow and mechanics solver. The grid convergence result in the case of poroelastic flow-mechanics coupling for flow-induced shear failure is also obtained. This proves the robustness of the numerical and analytical modeling of fracture and friction in the extended finite volume method (XFVM) set-up. Finally, a grid convergent result for seismic moment magnitude for single fracture and fracture network with random initial hydraulic and friction properties is also obtained. The b-value, which represents the slope of seismic moment occurrence frequency decay vs seismic moment magnitude, which is approximately constant in a semi-logarithmic plot, is estimated. The numerical method leads to converged b-values for both single fracture and fracture network simulations, as grid and time resolutions are increased. For the resulting linear system, a sequential approach is used, that is, first, the flow and then the mechanics problems are solved. The new modeling framework is very useful to predict seismicity, permeability, and flow evolution in geological reservoirs. This is demonstrated with numerical simulations of enhancing a geothermal system.  相似文献   

Postcolonialising Geography: Tactics and Pitfalls   总被引：4，自引：3，他引：4  

Jenny Robinson 《Singapore journal of tropical geography》2003,24(3):273-289

The moves within postcolonial theory to "provincialise Europe" encourage an acknowledgement of the parochial nature of much of what still passes for universal theory in the western academy. Within geography, postcolonialism has generated a strong interest in colonial histories and contemporary postcolonial politics, but this has not displaced the dominant parochial forms of theorising in the discipline. The paper argues for a more cosmopolitan theoretical project within geography, one whose routes through a range of intellectual traditions and contexts might encourage a broader scope to conversations about space and nature, and produce more lively and creative insights into some of the urgent political issues facing the world today. A geography whose intellectual vision is limited to the concerns and perspectives of the richest countries in the world has little hope of effectively participating in the debates that will matter in the twenty-first century. Within the frame of this long-term intellectual project, this paper will suggest some initial practical steps which researchers, writers, teachers and students in geography might take to start to decentre the predominant Euro-Americanism of the discipline. The specific sources of inspiration for this argument are drawn from comparative urbanism and Southern African geography.  相似文献   

Climate Variability and Land-use Change in Danangou Watershed, China—Examples of Small-Scale Farmers' Adaptation   总被引：2，自引：0，他引：2  

Johanna Hageback  Jenny Sundberg  Madelene Ostwald  Deliang Chen  Xie Yun  Per Knutsson 《Climatic change》2005,72(1-2):189-212

With global concern on climate change impacts, developing countries are given special attention due their susceptibility. In this paper, change and variability in climate, land use and farmers' perception, adaptation and response to change are examined in Danangou watershed in the Chinese Loess Plateau. The first focus is to look at how climate data recorded at meteorological stations recently have evolved, and how farmers perceived these changes. Further, we want to see how the farmers respond and adapt to climate variability and what the resulting impact on land use is. Finally, other factors causing change in land use are considered. Local precipitation and temperature instrumental data and interview data from farmers were used. The instrumental data shows that the climate is getting warmer and drier, the latter despite large interannual variability. The trend is seen on the local and regional level. Farmers' perception of climatic variability corresponds well with the data record. During the last 20 years, the farmers have become less dependent on agriculture by adopting a more diversified livelihood. This adaptation makes them less vulnerable to climate variability. It was found that government policies and reforms had a stronger influence on land use than climate variability. Small-scale farmers should therefore be considered as adaptive to changing situations, planned and non-consciously planned.  相似文献   

Participatory action research in a poststructuralist vein   总被引：1，自引：0，他引：1  

Jenny Cameron  Katherine Gibson 《Geoforum》2005,36(3):315-331

This paper introduces a participatory action research process that has been shaped by poststructuralist thought. We report on the stages and outcomes of a project conducted in the Latrobe Valley, Victoria, Australia, a resource region that has experienced downsizing and privatising of its major employer, the state-owned power industry. Through a participatory action research process involving community members, local Council and academic researchers the singular economic identity of the region was challenged and a more enabling representation developed. Drawing on a discourse of the diverse economy and the asset-based approach to community development the project shed light on the wide range of economic activities residents were already engaged in and the multitude of abilities and ideas they possessed. This exercise produced a new representation of the economy of the Latrobe Valley that helped to shift the vision of what was possible in the region. In the final stage of the project this alternative vision was acted on as groups turned shared ideas into projects and those who were most used to being defined as economically dependent and victims of economic circumstances increasingly came to identify as active and contributing economic subjects in the diverse economy. The paper considers the role of subjectivity, representation and micropolitics in participatory action research and concludes with a reflection on the project’s strengths and weaknesses.  相似文献