Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 31

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
Changes in the chemical composition of the water in three dam reservoirs are presented against the background of the chemical composition of their affluents, and the effect of these changes on the phytoplankton in terms of the chlorophyll a content, are discussed. Changes in the chemical properties of the water, an increase in trophy, and the existing differences in the fertility of the water between the reservoirs are associated with the ways of utilization of the catchment basins and with their population density. On the basis of the whole collected material a scheme of the eutrophication of the examined reservoirs is presented.
Acta Hydrobiologica
|
1993
|
tom 35
|
nr 2
97-107
The loads of nitrogen and phosphorus compounds flowing into the Goczałkowice Reservoir and out of it in the annual cycle were determined. The main source of biogenic substances was the River Vistula (78% N tot. and 69 P tot.). The intermediate pumping stations supplied altogether 12% N tot. and 18% P tot. The high loading of the Reservoir with phosphorus, amounting to 0.65 g P m-2 year-1 (including in the calculations the frequency of water exchange), exceeded about 4 times the admissible values.
On the basis of data from many years an increase was found in the degree of mineralization and fertility of the water of the River Vistula. Quantitative and qualitative changes in the bottom macrofauna against the background of changing physico-chemical conditions of the River Vistula were shown by a constant increase in the share of larvae of Chironomidae and Oligochaeta and a decrease in that of Ephemeroptera and Plecoptera.
The present work gives the characteristics of the bottom macrofauna against the background of the changing chemical composition and pollution of the water of the Vistula in a section of about 45 km of its upper course. A fairly rich and differentiated bottom macrofauna was found. The variability in bottom macrofauna throughout the area was the result of changes in the environmental conditions, while the increase in water fertility and pollution corresponded to the rising numbers of Chironomidae and the appearance and increasing numbers of Oligochaeta.
The main disturbancies in hydrological and chemical features of the Upper Vistula River were discussed as well as geological structure and soils of its drainage basin. Examined section of the river is 337 km long. Catchment area of 28 000 km² inhabited by 50 to 800 residents km⁻². Three main problems concerning the river were considered: salinity, pollution and water management. Between 89 and 95 km the river obtaines salty water from coal mines and down the 95 km of the river - huge load of pollution by the Przemsza River. The inflow supplying 91% of Vistulian flow at this point. This unusual proportion is caused by far transfer of drinking water from submontainous part of the Vistula or its tributaries. Polluted water comes back to the river by Przemsza River. Vistula had here too much of suspension, phosphorus, nitrite and ammonia, and sometimes zinc. Water quality between 90 and 170 km was useless for cyprinid fishes according to EC directive. Vistula River and its affluents flow through holocenic river terraces - covered with alluvial and fluvioglacial deposits. In the region of Cracow there are small areas of upper Jurassic origin (marls and lime) and from the Cretaceous period. Holocenic terrace of the river is covered by alluvial soils. On the left bank, between the Przemsza and Nida rivers, there are large areas of loesses. Investigations were carried out in the period between 3rd March 1997 and March 4th 1998. Also the present state of investigations of the Vistula River is discussed. In 1997 in the period from 7th to 15th of July extreme and disastrous flood in the Vistula occurred. Flows, which usually in Cracow (on 165 km) provide 50 to 100 m³ s⁻¹, grew up to 1430 m³ s⁻¹ and during the culmination of wave up to 2400 m³ s⁻¹.
The following paper is one part of the complex studies and intends to provide the background for explaining the spatial differentiation of plant and animal communities settled in the Upper Vistula River. The study has been conducted from 10.9 to 336.7 km of the river course. Concentrations of the following heavy metals in the river water have been studied: copper, zinc, cadmium, lead, manganese and iron. These investigations indicated that lowest concentrations of heavy metals in the Vistula River corresponded to those found in clean waters while maximal ones in same cases, to their concentrations in heavily polluted water. Comparing the present content of heavy metals in the water of the Upper Vistula River with data gathered 25 years ago, a decrease in concentrations of these elements was found.
A tendency to an increase in electrolytes and nutrients (mineral nitrogen and total phosphorus) was found. The bottom macrofauna was not affected by human activity in the period from 1955 to 1982, when the degree of eutrophication was small. From 1983 the effect of human activity was revealed in both qualitative and quantitative changes in the composition of the macrofauna.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 2 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.