Wyniki wyszukiwania - Biblioteka Nauki

1

The history of the sedimentation processes and heavy metal pollution in the Central Danube Delta (Romania)

100%

Begy R. C. , Kelemen S. , Simon H. , Tănăselia C.

Geochronometria

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2018

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tom Vol. 45, no. 1

97--106

EN

The aim of this study was to investigate the effects of the Iron Gates (IG) hydroelectric power station on the Danube Delta sediment dynamics, and to assess the heavy metal concentrations and pollution in a typical Central Danube Deltaic lake. Eight sediment cores were analysed. The total 210Pb content was measured with 210Po using alpha spectrometry, and the supported 210Pb (226Ra) and 137Cs were measured by gamma spectrometry. The age depth model was derived by applying the 210Pb dating method, and for the calculation of the ages and the sedimentation rates the CRS model was used. The sedimentation rates can be divided into four periods:1940–1972, 1972–1980, 1972–1989 and 1989–2013. In the case of Lake Iacob in the first period, the average sedimentation rate was 0.418 g/cm2y, while in the second it slowly decreased to 0.376 g/cm2y. In the third period, the sedimentation fell to 0.209 g/cm2y, which means the retention of 27.3% of the sediment by the IG dam. In the case of Lake Isac the changes were more visible: in the first period the average sedimentation rate was 0.446 g/cm2y, while in the second it decreased to 0.197 g/cm2y, which means a 42.35% retention of sediment. In the last period, in both cases, a high increase in the sedimentation rate is shown: 0.677 g/cm2y for Lake Iacob and 0.715 g/cm2y for Lake Isac. The heavy-metal concentrations for As, Co, Cr and Ni show decreasing and Hg increasing tendencies, while Cd and Pb show constant values of 310 ± 12 ppb and 9 ± 1 ppm respectively.

2

Natural radioactivity of coastal sediments as tracer in dynamic sedimentology

88%

Thereska J.

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2009

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tom Vol. 54, No. 1

45-50

EN

Natural radioactivity of coastal sediments could provide interesting information on sediment dynamics. Natural radioactivity measurements were performed in two areas of the Adriatic Sea littoral of Albanian cost, in the gulfs of Durres and Vlora, where complex studies were carried out in the framework of the maintenance of existing Durres harbour and the design of a new harbour in Vlora. Dynamic mapping of the gamma total radioactivity at the sea bottom sediment was carried out using a 2" × 2" NaI probe. Radiometric data were converted to lithological map, and the sand and silt distribution configuration was interpreted in terms of sediment transport. The obtained results have shown that the natural radioactivity of sediments provides qualitative data about the sediment dynamics. This cost-effective method is recommended to be used as complementary to other tracer techniques for sediment transport in coastal engineering investigations.

3

Spectral structure of surface waves and its influence on sediment dynamics

75%

Divinsky B. V. , Kosyan R. D.

Oceanologia

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2019

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tom 61

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nr 1

4

Temporal changes of sediment dynamics within the Nairobi River sub-basins between 1998-2006 time scale, Kenya

63%

Kithiia S. M. , Wambua B. N.

Annals of Warsaw University of Life Sciences - SGGW. Land Reclamation

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2010

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tom 42

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nr 1

17-22

EN

The city of Nairobi is the heart of both industrial production and the economic hub in Kenya and the Eastern Africa region. The city of Nairobi and its environs are drained by three streams, namely: Nairobi, Mathare and Ngong rivers. These streams drain areas of diverse land use activities. The land use changes in a spatial manner from the rich agricultural system through residential cum urban to industrial. The signifi cance of these various land use systems to pollutants generation, pollution, sediment generation and hence water pollution and quality degradation is quite enormous and worth investigation. The land use changes in a spatial manner making the basin ideal for a temporal variation of sediments yields along the river profi le and their impacts on the water quality status. This paper examines the results of study carried out within the basins in the years 1998–2006. The method of study involved water sampling and laboratory analysis to reveal the trends in sediment load increases downstream the investigated streams. Soil samples were also investigated to determine their relationship to soil erosion rates and sediment fl uxes. The study attempts further to fi nd the best sediment management strategies in reversing their increasing trends and restoring water quality within the basin.

PL

Miasto Nairobi jest centrum produkcji przemysłowej i centrum ekonomicznym Kenii oraz wschodniego regionu Afryki. Miasto Nairobi i jego otoczenie jest odwadniane przez trzy następujące strumienie: Nairobi, Mathare i Ngong. Te strumienie odwadniają obszary o różnym użytkowaniu i działalności. Użytkowanie terenu zmienia się w sposób przestrzenny od bogatego systemu rolnego poprzez miejski mieszkaniowy do przemysłowego. Znaczenie tych różnych systemów użytkowania terenu było bardzo istotne i warte badań z punktu widzenia tworzenia zanieczyszczeń, zanieczyszczenia i generacji rumowiska a tym samym zanieczyszczenia wody oraz degradacji jakości. Zmiany przestrzenne użytkowania terenu czynią zlewnie idealnymi dla czasowych zmian przyrostu ilości rumowiska wzdłuż profilu rzeki i ich wpływu na stan jakości. W referacie przedstawiono wyniki badań przeprowadzonych w zlewniach w latach 1998–2006. Metoda badań obejmowała pobór próbek wody i analizę laboratoryjną w celu określenia trendów zwiększenia ilości rumowiska w badanych strumieniach w ich odcinkach dolnych. Próbki rumowiska były także badane w celu określenia ich zależności od wielkości erozji i strumieni rumowiska. Badania mają na celu znalezienie najlepszych strategii gospodarowania rumowiskiem w celu odwrócenia ich trendów wzrostowych i przywrócenia jakości wody w zlewni.

5

Extended models of sedimentation in coastal zone

63%

Selezov I.

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2014

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tom Vol. 26

243--250

EN

Construction of a generalized hyperbolic model of sediment dynamics predicting a sediment evolution on the bottom surface with a finite velocity is presented. The transport equation is extended with introducing a generalized operator of flux change and a generalized operator of gradient. Passing to the convenient model is a singular degeneration of extended model. In this case the results are obtained in the class of generalization solutions. Some expressive examples of constructions of hyperbolic models predicting a finite velocity of disturbance propagation are presented. This problem is developed starting from Maxwell (1861). His approach in the theory of electromagnetism and the kinetic theory of gases is commented. A brief review on propagation of heat and diffusive waves is presented. The similar problems in the theory of probability and diffusion waves are considered. In particular, it was shown on the microscopic level for metals that the conservation law can be violated.

6

A deeper understanding of river habitat-scale ecohydraulics: interpreting the relationship between habitat type, depth and velocity using knowledge of sediment dynamics and macrophyte growth

51%

Kemp J. L. , Harper D. M. , Crosa G. A.

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tom 02

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nr 1-4

EN

Late spring/summer depth and velocity conditions of 16 ‘functional habitats’ were investigated in lowland rivers. The habitats significantly associated with shallower, faster areas were 'submerged, fine-leaved macrophytes' (20-40 cm deep, >0.45 ms-1) and 'macroalgae' (10-30 cm, >0.60 ms-1). 'Cobbles' were associated with slightly slower, shallower conditions (0-20 cm, 0.45 ms-1), 'gravels' with slower conditions again (around 0.15 ms-1, depths from 0-30 cm). The slowest velocity class (0-0.05 ms-1) was associated with 'silt' (depths 20-70 cm), ‘marginal plants' (0-20 cm deep), 'emergent macrophytes' (10-80 cm deep), 'submerged, broad-leaved macrophytes' (40-110 cm deep), 'floating leaved macrophytes' (40-150 cm deep) and a second mode of ‘macroalgae’ (145-180 cm deep). The factors thought to be behind these findings are discussed.