Wyniki wyszukiwania - BazTech

1

Dilatation of the method of the fixation of moveable sands

Muzaffarova Mauzhuda

Transport Problems

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2022

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T. 17, z. 4

79--89

EN

A new method of physicochemical blocking deflation of movable sands has been developed that represents their fixation in a wet state with binders. It is proposed to carry out sand-fixing works during rainy periods or after preliminary moistening of the sandy surface in order to intensify and reduce the cost of sand-fixing works. The substantiation is carried out on the example of some of the approved and recommended binders based on the express method of studying the possibility of their application to obtain a polymer sandy protective crust on wet sand. The emerging defensive hull is characterized by resistance to wind-sand stream and evaluated by plastic quality and thickness. The impregnation of damp sand with a smaller sum of cover than dry sand is related to an alteration within the nature of impregnation from gravity to capillary. With a decrease in the specific surface of the bulk material and an increase in the pore space, gravitational forces are predominant. The process of wet sand impregnation is associated with the acceleration of the adsorption of the dispersed phase and a reduction in the hole covered due to the partial occupation of the interpore space with water. As a result, in wet sand, the depth of sand impregnation with the binder increases at a lower consumption per unit volume of sand. The following has been established: the possibility of impregnation of approved and recommended binders into wet sand, the inverse dependence of the binder concentration in emulsion forms on the humidity of the sandy surface, the time of application of various binders after moistening the sand and the possible savings of binders.

2

Fizykochemiczne metody separacji zanieczyszczeń organicznych z gruntów i osadów

Wawrzacz B.

Przegląd Komunalny

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2001

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nr 9

93-94

PL

Technologie oczyszczania, polegające na oddzielaniu zanieczyszczenia organicznego od matrycy gruntu lub osadu, wykorzystują zjawiska fizykochemiczne zachodzące na granicach międzyfazowych wszystkich faz obecnych w układzie: faza organiczna olej-cząstki mineralne, olej-woda oraz woda-cząstki mineralne.

3

Mikrocystyny sinic w zbiornikach wodnych

Gajdek P.

Wiadomości Chemiczne

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2000

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[Z] 54, 7-8

637-650

EN

Many species of cyanobacteria forming blooms in eutrophic waters produce toxins. They are cytotoxins, neurotoxins, hepatotoxins and dermatotoxins. The hepatotoxins can be divided into microcystins and nodularins, cyclic hepta- and pentapeptides respectively. About 60 microcystins have been characterized and the most common is microcystin-LR, but their chemical structure may be also different. Since a long time cyanobacterial toxins have been the reason of lethal poisonings of wild and domestic animals and health problems of humans in different regions of the world. In 1996 in Brazil about 60 haemodialysis patients died after getting a lethal microcystin dose intravenously. The most frequent signs of poisoning are anorexia, general weakness, diarrhoea and vomiting. Microcystins repeatedly uptaken by organisms in trace amounts contribute to the development of cancer as a result of their inhibition of protein phosphatase 1 and 2A. There are epidemiological data indicating high rates of cancer in China due to long term exposure to cyanobacterial toxins in water. World Health Organization proposed 1 microgram per litre as a guideline value for maximum acceptable level of microcystin-LR or its equivalents in drinking water. Microcystins are chemically very stable and can not be decomposed by acid, alkaline or boiling. In field conditions their degradation is minimal. They are also difficult to decompose in water treatment processes. Conventional water treatment methods are not sufficient, while activated carbon filtration or ozonation makes them more effective, but still trace amounts of microcystins pass the full-scale treatment. Many methods of degradation or chemical modification of microcystins have been devised. Unfortunately, despite large body of research work cyanobacterial toxins are still dangerous, especially in drinking water reservoirs. In Poland, the cyanobacterial blooms in drinking water reservoirs constitute a serious problem, especially for large agglomerations. For instance in summer 1993 in Sulejowski reservoir being a drinking water source for the city of Łódź the microcystin content in a cyanobacterial bloom was in the range of 40 - 117 mg/g dry mass of phytoplankton, reaching in the following years the value of 427 mg/g dry mass of phytoplankton, which was in the years 1995 and 1996 on the average 5.7ug/L. In the samples gathered in 1996 in Jeziorsko and Zalew Włocławski the average microcystin content was around 300 mg/g dry mass of phytoplankton. The presence of cyanobacterial toxins in Polish lakes and water reservoirs establishes new problems for Polish waterworks and laboratories dealing with water quality analysis. This article contains many hints on construction of experimental set-ups for the determination of cyanobacterial toxins in water reservoirs, in particular sampling methods, choice of filters for separation of cyanobacterial cells, parameters in sample enrichment by means of solid-phase extraction and analysis with high performance liquid chromatography, detection methods, etc.