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41.
Jarmo J. Meriläinen Juhani Hynynen Arja Palomäki Heikki Veijola Allan Witick Kaijo Mäntykoski Kaj Granberg Kari Lehtinen 《Journal of Paleolimnology》2001,26(1):11-35
Sedimentary diatom frustules and chironomid remains, in addition to the chemical stratigraphy of 32 elements and resin acids, were studied from short-core samples taken from two basins and a sheltered bay of Lake Päijänne in southern Finland (about 61 °10–62 °15 N, 25 °30 E). The lake was formerly oligotrophic but has been subject to effluent loading from pulp and paper mills during the past century since the opening of the first pulp mill in the 1880s. Four developmental phases were distinguished and named mainly according to the effects found in the basin close to the pollution source: (1) the pre-industrial phase (from the 1800s to ca. 1920), including the early years of industrialization, with low impacts; (2) the phase of increasing pollution (ca. 1920–1969); (3) the phase of severe pollution (1970–1981); and (4) the water protection phase (1982 onwards).Distinct differences were observed between pelagic (diatoms) and benthic (chironomid) ecosystems in their response to pollution. Effluent loading from the pulp and paper mills had a pronounced impact on chironomid assemblages, but only a slight influence on diatoms in the basin close to the pollution source. In the southern basin, approximately 60 km downstream, an increase in acidophilous species was observed in the diatom assemblages during the early years of pollution, but changes in chironomids in this basin were negligible. The water protection work of the past 30 years, which has led to an improvement in water quality and a marked recovery of the profundal biota, has also resulted in a slight increase in primary production of the lake. The decrease in brown-coloured effluent water has led to an increase in thickness of the lake's photic productive layer, while the toxicity of the water has simultaneously diminished. Rapid changes in chironomid assemblages and sedimentation observed in the sheltered bay highlight the importance of local land-use activities as causes of environmental change in this area, and especially their effects on sedimentation and benthic life. 相似文献
42.
Peter?A.?StaehrEmail author Jeremy?M.?Testa W.?Michael?Kemp Jon?J.?Cole Kaj?Sand-Jensen Stephen?V.?Smith 《Aquatic Sciences - Research Across Boundaries》2012,74(1):15-29
Measurements of the production and consumption of organic material have been a focus of aquatic science for more than 80 years.
Over the last century, a variety of approaches have been developed and employed for measuring rates of gross primary production
(Pg), respiration (R), and net ecosystem production (Pn = Pg − R) within aquatic ecosystems. Here, we reconsider the range of approaches and applications for ecosystem metabolism measurements,
and suggest ways by which such studies can continue to contribute to aquatic ecology. This paper reviews past and contemporary
studies of aquatic ecosystem-level metabolism to identify their role in understanding and managing aquatic systems. We identify
four broad research objectives that have motivated ecosystem metabolism studies: (1) quantifying magnitude and variability
of metabolic rates for cross-system comparison, (2) estimating organic matter transfer between adjacent systems or subsystems,
(3) measuring ecosystem-scale responses to perturbation, both natural and anthropogenic, and (4) quantifying and calibrating
models of biogeochemical processes and trophic networks. The magnitudes of whole-system gross primary production, respiration
and net ecosystem production rates vary among aquatic environments and are partly constrained by the chosen methodology. We
argue that measurements of ecosystem metabolism should be a vital component of routine monitoring at larger scales in the
aquatic environment using existing flexible, precise, and durable sensor technologies. Current and future aquatic ecosystem
studies will benefit from application of new methods for metabolism measurements, which facilitate integration of process
measurements and calibration of models for addressing fundamental questions involving ecosystem-scale processes. 相似文献
43.
细粒酒精模型冰物理力学性质评价的新指标 总被引：1，自引：0，他引：1
依据酒精细粒模型冰制冰过程中的物理本质和控制细粒酒精模型冰物理力学性质的物理本质,建立了一项适合于喷雾技术细粒模型冰性质评价综合指标.阐明了这一评价指标的物理意义,并给出这一指标与细粒酒精模型冰物理力学性质参数的关系. 相似文献
44.
45.
Peter?A.?StaehrEmail author Lars?Baastrup-Spohr Kaj?Sand-Jensen Colin?Stedmon 《Aquatic Sciences - Research Across Boundaries》2012,74(1):155-169
We used a comparative data set for 25 lakes in Denmark sampled during summer to explore the influence of lake morphometry,
catchment conditions, light availability and nutrient input on lake metabolism. We found that (1) gross primary production
(GPP) and community respiration (R) decline with lake area, water depth and drainage ratio, and increase with algal biomass
(Chl), dissolved organic carbon (DOC) and total phosphorus (TP); (2) all lakes, especially small with less incident light,
and forest lakes with high DOC, have negative net ecosystem production (NEP < 0); (3) daily variability of GPP decreases with
lake area and water depth as a consequence of lower input of nutrients and organic matter per unit water volume; (4) the influence
of benthic processes on free water metabolic measures declines with increasing lake size; and (5) with increasing lake size,
lake metabolism decreases significantly per unit water volume, while depth integrated areal rates remain more constant due
to a combination of increased light and nutrient limitation. Overall, these meta-parameters have as many significant but usually
weaker relationships to whole-lake and benthic metabolism as have TP, Chl and DOC that are directly linked to photosynthesis
and respiration. Combining water depth and Chl to predict GPP, and water depth and DOC to predict R, lead to stronger multiple
regression models accounting for 57–63% of the variability of metabolism among the 25 lakes. It is therefore important to
consider differences in lake morphometry and catchment conditions when comparing metabolic responses of lakes to human impacts. 相似文献
46.
Cristina?PulidoEmail author Kaj?Sand-Jensen Esther?C.?H.?E.?T.?Lucassen Jan?G.?M.?Roelofs Klaus?P.?Brodersen Ole?Pedersen 《Aquatic Sciences - Research Across Boundaries》2012,74(2):351-360
Isoetids, as indicators of near-pristine softwater lakes, have a high priority in national and international (European Water
Directive Framework) assessments of ecological lake quality. Our main goal was to identify the most important environmental
factors that influence the composition of plant communities and specifically determine the presence and abundance of the isoetid
Lobelia dortmanna in NW European softwater lakes. Geographical position and composition of surface water, porewater, sediment and plant communities
were examined in 39 lakes in four regions (The Netherlands, Denmark, West Norway and East Norway) distributed over a 1,200-km
long distance. We confirmed that lake location was accompanied by significant changes in environmental variables between NW
European lakes. Lake location was the single most important determinant of vegetation composition and it had significant individual
contributions independent of the coupling to environmental variables. This influence of location was supported by a significant
decline of community similarity with geographical distance between pairs of lakes at regional, inter-regional and international
scales. Combining the geographical position with environmental variables for surface water, porewater and sediment significantly
improved prediction of vegetation composition. Specifically, the combination of latitude, surface water alkalinity, porewater
phosphate and redox potential offered the highest correlation (BIO ENV correlation 0.66) to vegetation composition. This complex
analysis can also account for high sediment variability in the littoral zone of individual lakes, by using site-specific physico-chemical
sediment factors, and offer better predictions of vegetation composition when lake water chemistry is relatively homogeneous
among lakes within regions. 相似文献
47.
Andreas Klügel Stefanie Schwarz Paul van den Bogaard Kaj A. Hoernle Cora C. Wohlgemuth-Ueberwasser Jana J. Köster 《Bulletin of Volcanology》2009,71(6):671-685
Ponta de São Lourenço is the deeply eroded eastern end of Madeira’s east–west trending rift zone, located near the geometric intersection of the Madeira rift axis with that of the Desertas Islands to the southeast. It dominantly consists of basaltic pyroclastic deposits from Strombolian and phreatomagmatic eruptions, lava flows, and a dike swarm. Main differences compared to highly productive rift zones such as in Hawai’i are a lower dike intensity (50–60 dikes/km) and the lack of a shallow magma reservoir or summit caldera. 40Ar/39Ar age determinations show that volcanic activity at Ponta de São Lourenço lasted from >5.2 to 4 Ma (early Madeira rift phase) and from 2.4 to 0.9 Ma (late Madeira rift phase), with a hiatus dividing the stratigraphy into lower and upper units. Toward the east, the distribution of eruptive centers becomes diffuse, and the rift axis bends to parallel the Desertas ridge. The bending may have resulted from mutual gravitational influence of the Madeira and Desertas volcanic edifices. We propose that Ponta de São Lourenço represents a type example for the interior of a fading rift arm on oceanic volcanoes, with modern analogues being the terminations of the rift zones at La Palma and El Hierro (Canary Islands). There is no evidence for Ponta de São Lourenço representing a former central volcano that interconnected and fed the Madeira and Desertas rifts. Our results suggest a subdivision of volcanic rift zones into (1) a highly productive endmember characterized by a central volcano with a shallow magma chamber feeding one or more rift arms, and (2) a less productive endmember characterized by rifts fed from deep-seated magma reservoirs rather than from a central volcano, as is the case for Ponta de São Lourenço. 相似文献
48.
K. Vermonden R. S. E. W. Leuven G. van der Velde A. J. Hendriks M. M. van Katwijk J. G. M. Roelofs E. C. H. E. T. Lucassen O. Pedersen K. Sand-Jensen 《Aquatic Sciences - Research Across Boundaries》2010,72(3):379-389
Biodiversity in urban areas is affected by a multitude of stressors. In addition to physico-chemical stress factors, the native
regional species pool can be greatly reduced in highly urbanized landscapes due to area loss and fragmentation. In this study,
we investigated how macrophyte composition and diversity in urban water systems are limited by the regional species pool and
local environmental conditions. Canonical correspondence analysis of the macrophyte species composition revealed that urban
and semi-natural water systems differed and differences could be related to local abiotic variables such as pH and iron concentrations.
Macrophytes in the semi-natural area were typical for slightly acid and oligotrophic conditions. In urban water systems, exotic
species characteristic of eutrophic conditions were present. In the semi-natural areas, the number of macrophyte species exceeded
the number of species expected from species–area relationships of artificial water bodies in rural areas. In urban areas,
the number of macrophyte species was similar to artificial water systems in rural areas. Macrophyte species present in the
study areas also were generally found within 20–30 km distance to the study area. Macrophyte species composition in urban
water systems and semi-natural water systems appeared to be influenced by the regional species pool within approximately 30 km
of the locations. Nevertheless, site limitation ultimately determined the local macrophyte species composition and diversity
in urban water systems and in semi-natural water systems. 相似文献
49.
采用基于扩展UNIQUAC模型的AQSOL027软件针对水盐体系Li-Na-K-Mg-Cl-SO_4-H_2O的六个五元子体系进行相平衡理论计算,首次报道了多个五元子体系在多个温度条件下的相图,将计算相图与已有实验相图以及基于其它热力学模型的计算相图进行了比较。结果表明:AQSOL027在相图计算中具有较好的准确性和可靠性。AQSOL027是一款基于Excel、用于计算复杂多温水—盐体系Li-Na-K-Mg-Ca-H-Cl-(HSO_4/SO_4)-(CO_2/HCO_3/CO_3)-(H_3BO_3/B_4O_7/BO_2)-OH-H_2O的计算机软件,集成了扩展UNIQUAC模型和相平衡算法,该软件可结合SysCAD和Aspen过程模拟器,实现盐田工艺过程的计算机辅助设计。 相似文献
50.
Arvid M. Johnson Kaj M. Johnson Joe Durdella Mete Sözen Türel Gür 《Journal of Seismology》2002,6(3):329-346
The fault trace of the 12 November 1999 earthquake in theDüzce-Bolu region in Anatolia crossed the alignment of a 2.4 kmviaduct in Kaynali that had been carefully surveyed. The builders of theviaduct, the ASTALDI-BAYINDIR Co., resurveyed the viaduct after theearthquake. We repeated the survey for approximately one kilometre of theeastern end of the viaduct and obtained essentially identical results. Thoughit was unfortunate that the earthquake damaged the new structure, the piersdid produce a very rare record of ground deformation of an earthquake.In effect, the viaduct was a giant strain gage that yielded reliable data aboutground movement and distortion near a fault. This paper describes thesurvey data and their evaluation leading to convincing evidence that (a) thefault trace must be considered, not as a fault line or plane, but as a faultzone with a finite width and that (b) the structural damage within the zonewas caused, not primarily by ground acceleration, but by ground distortion.Along the right-lateral fault at Kaynali, the fault zone consists ofright-lateral movement at the main trace, a zone of right-lateral distortionnear the trace, bounded by left-lateral distortion. The 12 November 1999event in Turkey, like the ground deformation and fracturing at Landers,California (Johnson et al., 1994, 1996), thus affirmed a forgottenconclusion from the studies by Lawson (1908), Gilbert and Reid (1910)of the 1906 San Francisco earthquake that earthquake ruptures typicallyoccur throughout zones or belts, rather than along linear traces or planes. 相似文献