Microbial Activity of Bottom Sediments in a Stabilization Pond

The Pond of Dvorec, used for a final treatment of waste waters and at the same time for fish breeding, has been observed working in an assimilation and later on in a stabilization mode (SVOBODA and KOUBEK) . The data on the chemical composition and microbiological properties of its sediments are given. A comparative analysis of the stabilization pond sediments and the sediments of the second stabilization pond have shown a high purification function. An influence of temperature, aeration and thickness of the layer upon a microbial activity and a release of the substance into the water environment were verified in laboratory experiments. A higher layer of sediments can, above all at increased temperatures, negatively influence the water quality for fish breeding. After composting the drawn pond sediments can be recommended for the fertilization of an agricultural land in near surroundings.     

Late Ordovician evolution of the intracratonic basins in north-west Gondwana

The Palaeozoic intracratonic basins in northwest Gondwana, i.e. the Amazonas, Parnaiba and Acera basins, probably opened during late Caradoc and Ashgill times. The fluviatile sedimentation later changed to littoral at the basinal margins. A transgression from the north-west region of Gondwana slowly overlapped the margins of the intracratonic basins. The transgression reached its maximum in the Rawtheyan (late Ashgill), as evidenced by fossiliferous shallow marine sediments in the Amazonas Basin. The Hirnantian glaciation in north Gondwana lowered the sea level, and in the Amazonas Basin a littoral sedimentation followed on shallow marine strata. From the opening of the basins onwards, a shallow sea probably existed close to the epicontinental basins in north-west Gondwana. The basins were connected via a narrow passage between the Guayana and Ivorian cratons.