Development and application of sedimentary pigments for assessing effects of climatic and environmental changes on subarctic lakes in northern Sweden     

Nina Reuss  Peter R. Leavitt  Roland I. Hall  Christian Bigler  Dan Hammarlund 《Journal of Paleolimnology》2010,43(1):149-169

A surface-sediment survey of pigments in 100 lakes in the Scandes Mountains, northern Sweden, was combined with a reconstruction of Holocene sedimentary pigments from Lake Seukokjaure to assess the major factors regulating phototrophic communities, and how these controls may have changed during the period from the deglaciation (~9700 cal. years BP) to the present. The study area covers a pronounced gradient of temperature and precipitation, and encompasses the subarctic tree line, an important ecotonal boundary in this region. Lake Seukokjaure is located in a presently treeless basin close to the modern tree line. The spatial survey of sedimentary pigments was analyzed using principle components analysis (PCA) and redundancy analysis (RDA). PCA explained 73–83% of variance in pigment abundance and composition, whereas RDA explained 22–32% of variation in fossil assemblages. Dissolved organic carbon (DOC) content of lake water, sediment δ¹³C, maximum lake depth, elevation and lake-water conductivity were all identified as environmental variables with significant association with pigment abundances in the spatial survey, although phototrophic communities of lakes situated in different vegetation zones (alpine, birch, conifer/birch) were incompletely distinguished by the ordinations. In the RDAs, the primary pigment variability occurred along a production gradient that was correlated negatively to water-column DOC content and δ¹³C signature of sediments. This pattern suggested that the important controls of primary production were light regime and terrestrial supplies of ¹³C-depleted carbon. In contrast, depth, elevation and conductivity were found to be more important for the differentiation of the phototrophic community composition. Application of these spatial survey results to the Holocene sediment record of Lake Seukokjaure demonstrated the importance of DOC for the temporal development of the lake, from an early state of high production to a period of slight oligotrophication. In general, the algal changes were regulated by the interaction of DOC and conductivity, although transitions in the phototrophic community during the late Holocene were less easily interpreted. Terrestrial vegetation development thus appears to be of utmost importance for the regulation of primary production in oligotrophic alpine and subarctic lakes and climate impacts on lakes, whereas other basin-specific factors may control the ontogeny of algal community composition.  相似文献   

Interdisciplinary and participatory approaches: the key to effective groundwater management     

Roland Barthel  Stephen Foster  Karen G. Villholth 《Hydrogeology Journal》2017,25(7):1923-1926

The challenges of a changing world, which are progressively threatening sustainable use of groundwater resources, can only be rationally and effectively addressed through close collaboration between experts and practitioners from different disciplines. Furthermore, science and management need to build on stakeholder opinions and processes in order to generate useful knowledge and positive outcomes in terms of sustainable and equitable groundwater management. This essay provides a discussion of the status of and vision for participatory and inter-disciplinary approaches to groundwater evaluation and management as well as a conceptual framework and relevant research questions that will facilitate such approaches.  相似文献   

Borehole deviation limits and injection permeability     

Abdulhakim G.H.Al-Khulaidi  SUN Youhong  SUN Zhifeng  G.Roland Nguimbi 《世界地质(英文版)》2013,16(2):106-112

Monitoring drilling deviation is important for drilling of boreholes and measuring injection rock permeability by Lugeon value for safe and efficient drilling and grouting. This paper is aiming at the study drilling deviation and relationship between drilling and injection permeability at the depth of 100 m in dam of Pushi River. The results show that at different depths the deviation of grouting borehole is within the allowable range according to specifications. LU value decreases with the depth increased in general, but at the depths between 40-41 m the permeability is 1.5 LU, and at 24 m the LU value is the largest (2 LU) in this site by this study. The study thus concludes that even though the rocks are hard and their injection permeability decreases with depth increased, good drilling practices including carefully considering technical and geological specifications can get good drilling boreholes.  相似文献   

Rapid physicochemical changes in the high Arctic Lake Kongressvatn caused by recent climate change     

Trine Marianne Holm  Karin A. Koinig  Tom Andersen  Espen Donali  Anne Hormes  Dag Klaveness  Roland Psenner 《Aquatic Sciences - Research Across Boundaries》2012,74(3):385-395

High Arctic lakes are among the most sensitive ecosystems and climate change strongly affects their physical properties, especially water temperature, and mixing processes. To study the effect of recent climate change on such a lake in the Arctic environment, we measured water chemistry and temperature from 2005 to 2010 in Kongressvatn, a crenogenic meromictic lake in Spitsbergen (Svalbard). In addition, we monitored water column temperatures during two consecutive years and compared them to regional air temperature data and physicochemical lake data from 1962 and 1968, two relatively cold years. Summer surface water temperature was highly correlated to air temperature, and both have increased by approximately 2°C since 1962. Temperature monitoring during 2?years showed that the warm summer of 2007 resulted in increased water temperatures even in the stratified, denser hypolimnion. Our water chemistry measurements showed that the chemocline position in 2005?C2010 was ca 12?m deeper than in 1962?C1968, and a second, weaker, chemocline appeared at metalimnetic depths of 7?C15?m. During the study period, the water level decreased by 4?m, and this change accelerated between 2008 and 2010. Our data support the hypothesis that water temperatures and stratification patterns are changing rapidly with air temperature, but changes in the catchment, such as glacial retreat and permafrost melting, may have an even stronger impact on lake properties.  相似文献   

Simulating compound flooding events in a hurricane     

Zhang  Yinglong J.  Ye  Fei  Yu  Haocheng  Sun  Weiling  Moghimi  Saeed  Myers  Edward  Nunez  Karinna  Zhang  Ruoyin  Wang  Harry  Roland  Aron  Du  Jiabi  Liu  Zhuo 《Ocean Dynamics》2020,70(5):621-640

Ocean Dynamics - Compound flooding is usually induced by the concurrence of coastal storm surge and heavy precipitation induced river flooding, with the former involving oceanic processes and the...  相似文献   

Density function evaluation from borehole gravity meter data – regularized spectral domain deconvolution approach          下载免费PDF全文

Roland Karcol  Roman Pašteka 《Geophysical Prospecting》2017,65(1):365-378

We present a new method of transforming borehole gravity meter data into vertical density logs. This new method is based on the regularized spectral domain deconvolution of density functions. It is a novel alternative to the “classical” approach, which is very sensitive to noise, especially for high‐definition surveys with relatively small sampling steps. The proposed approach responds well to vertical changes of density described by linear and polynomial functions. The model used is a vertical cylinder with large outer radius (flat circular plate) crossed by a synthetic vertical borehole profile. The task is formulated as a minimization problem, and the result is a low‐pass filter (controlled by a regularization parameter) in the spectral domain. This regularized approach is tested on synthetic datasets with noise and gives much more stable solutions than the classical approach based on the infinite Bouguer slab approximation. Next, the tests on real‐world datasets are presented. The properties and presented results make our proposed approach a viable alternative to the other processing methods of borehole gravity meter data based on horizontally layered formations.  相似文献