CSA Materials Research Database with METADEX

Preliminary analysis of the data of ultraviolet (UV) radiation and ground-level ozone concentration measurements from Rugšteliškės Monitoring Station over the years 2002-2003 is presented. Observations showed that an average UV radiation value in January and July of 2002 differed about 10 times. Maximum intensity of UVA radiation was observed in July (about 2,4 W/m2), and minimum one - in December (0,1 W/m2), the highest UVB radiation intensity was in May (0,09 W/m2), while a minimal UVB radiation value as well as that of UVA was registered in December (0,07 W/m2). Relationship between the highest ozone concentration and UVB radiation values during the summer of the investigation period was found to be linear.

Fern accumulates radionuclides in abundance, including 137Cs. Transfer of 137Cs and 40K in plants which have different root systems (fern or grass), or have no roots at all (moss) was compared. Samplings were performed in regions contaminated with 137Cs after Chernobyl Nuclear Power Plant (ChNPP) accident in 1994 and 1997-2000. The male fern (Dryopteris filix-mas) most prevailing in Lithuania was studied. Fern accumulates 137Cs more effectively than grass or moss. The average 137Cs activity concentration in fern is 180[...]60 Bqxkg-1, and the transfer factor is 0,074 m2xkg-1. The fern stipe accumulates 137Cs most of all (200[...]90 Bqxkg-1), the transfer factor is 0,087 m2xkg-1. Accumulation of 137Cs is influenced by the content of K in the soil. 137Cs and 40K activity concentrations in fern are higher than those in the soil what shows that fern accumulates 137Cs better than 40K. Fern can clean the soil because this plant accumulates radionuclides in its stipe rather than roots.

The state of two-phase flow ‘liquid-gas’ has been modeled numerically by the three-dimensional method of complex research of heat and mass transfer. This allows examining the interaction of some transfer processes in a natural cooling basin (the Drūkšiai lake): the wind power and direction, variable water density, the coefficient of heat conduction and heat transfer of the water-air interface. Combined effect of these natural actions determines the heat amount that the basin is able to dissipate to the surrounding atmospheric media in thermal equilibrium (without changes in the mean water temperature). This paper presents a number of the most widely used expressions for the coefficients of vertical and horizontal heat transfer. On the basis of stream velocity and mean temperature profiles measured in the cooling pond as well as on that of their time variations suggestions are made that the mixing rate at the water surface is caused by natural space – time variation of the wind, and can be described by the value of eddy viscosity coefficient – 1 m2/s (numerical modeling with 0,9–1,3 m2/s). The wind influences the surface of the lake according to the experimental data, i e 1–3 % of the mean wind velocity. The model applies to the weakly wind, approximately 1–5 m/s of the mean wind velocity. Comparison of experimental and numerical results showed a qualitative agreement. For a better quantitative approximation, it is necessary to have more boundary conditions variable with time and to solve unsteady set equations for transfer processes.

Physical modeling of sediment transport and morphology in rivers as well as wastewater dilution processes are closely related to the modeling of macro turbulent fluctuations. The physical modeling of hydraulic macro turbulent fluctuations is complicated and underestimated. The study of turbulent flow structure and verification as well as model calibration is required in this case. Some methods of model verification by means of kinematics and turbulent coefficients scaling aKa, ax and aK are presented in the paper. Experience in hydraulic modeling of bed processes in the Neris and Nemunas rivers contributed to the viable results. As laboratory tests showed, after the scales of the Nemunas bed had been distorted 12 times, the turbulence of modeled flow increased causing 3 times more intensive wastewater dilution processes in a physical model of the Nemunas bed. When modeling the bed processes of the Neris in Vilnius in a hydraulic model with the scale distorted 6,7 times, it was determined that a more intensive turbulence caused a 25 % thinner bed soil layer and nearly 3 times higher velocity of vertical turbulent flow. This was considered when calculating the results obtained in a model into natural ones and when choosing proper means for designing riverbed hydraulic structures.

The paper presents the results of thermodynamic calculations while performing the pyrolysis and oxidation of ammonia at different ratios of ammonia and oxygen and while ammonia is oxidated when methane is present in the process. It is demonstrated that during the most reliable process of ammonia oxidation hydrogen and oxygen are bonded into the molecules of water and nitrogen oxides. While performing a partial ammonia oxidation, hydrazine and hydrocyanic acid, may be educed, if methane is present. The most reliable equations of ammonia oxidation reactions are presented.

Investigation of toxicity of oil hydrocarbons, especially of water soluble and emulsifying hydrocarbons, is very important, since oil hydrocarbons comprise significant part of pollutants in the inner waters and sea. Oil terminals, oil-refinery plants, railroads and railway stations are the potential objects of risk. Serious accidents and oil spills have to be investigated in terms of their impact on water invertebrates. This work is aimed at establishing an impact of oil products – dieseline and fuel oil – on the planktonic Crustacean – Daphnia magna. This small filter-feeding Crustacean is an ideal object in toxicological research. D. magna is very sensitive to the pollution by contaminants of a different nature. This was the reason for its use in establishing the toxicity of dieseline and fuel oil by acute tests. Using regression analysis in the calculation of test results regressive equations were obtained and the concentrations of LC50 and LC100 were estimated. The dangerous concentrations of toxins for the water invertebrate D. magna were established. On the basis of experimental data and reference material it is possible to assert that D. magna is the most sensitive test-object in the research of such a type. The aim of investigation is to establish lethal concentrations of different forms of hydrocarbons to water invertebrates – D. magna.