In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 54 No. 3 September 2005


Atmospheric pollution in Tallinn: levels of priority pollutants; 123–133

Gary Urb, Erik Teinemaa, Antonius Kettrup, Istvan Gebefügi, Margit Laja, Janek Reinik, Eduard Tamm, and Uuve Kirso

Abstract. The levels of priority air pollutants (NOx, CO, SO2, O3, particulate matter) were investigated at three sites in Tallinn (Estonia). The concentration of particles with diameters less than 2.5 μm (PM2.5), reaching human alveoli in lungs, was also measured. The collected samples of particulate matter were extracted with the accelerated solvent extraction method and analysed with high performance liquid chromatography. The chemical analysis indicated the occurrence of polycyclic aromatic hydrocarbons in the airborne particulate matter samples. The data received were grouped into four categories for annual, seasonal, diurnal, and day-of-the-week trends. The winter concentrations of NOx and CO in the urban area were twice as high as in the summer period. Annual and diurnal variations were studied to find out the main sources of pollution. Increasing traffic intensity and industrial activity were suggested to be associated with changes in air quality.

Key words: ambient air, gaseous pollutants, particulate matter, air quality, PAH.

Characterization of water extracts of solid waste generated by oil shale combustion; 134–141

Margit Laja, Natalja Irha, Gary Urb, Janek Reinik, and Uuve Kirso

Abstract. This study focuses on the behaviour of oil shale combustion ash during water extraction processes. The oil shale ash samples were collected from two different combustion processes in Narva PP. The leaching tests of the ash samples were carried out in compliance with a European standard prEN 12457-2 (1999). The results show that both first and second water extracts are characterized by high alkalinity and conductivity and they contain polycyclic aromatic hydro­carbons.

Key words: oil shale fly ash, bottom ash, leaching.

Complexed iron and a groundwater treatment technology; 142–153

Rein Munter, Heldi Ojaste, and Johannes Sutt

Abstract. The quality parameters and a possible treatment technology of the groundwater in Kogalym (Russian Federation) are discussed. The key problem is stable complexes of di- and trivalent iron and organics in groundwater, which after aeration tend to pass through the hydroanthracite–sand gravity filters. The total organic carbon concentration in raw groundwater is in the range 3.2–6.4 mg/L, total iron concentration is 2.7–6.0 mg/L, and divalent iron concentration 2.4–4.0 mg/L. The humic matter fraction separated from Kogalym groundwater by XAD-16 adsorbent was homogeneous, with only one peak on the chromatogram with maximum Rt = 10.75 min and the corresponding molecular mass of about 2000. The final treatment technology elaborated consists of intensive aeration of raw water in the Gas–Degas Treatment unit followed by sequent filtration through hydroanthracite and special anthracite Everzit.

Key words: groundwater, iron, organics, iron and organic complexes, aeration, filtration.

Comparative calculations of complexation enthalpies between Lewis bases and borontrifluoride; 154–164

Peeter Burk and Martin Kutsar

Abstract. Complexation enthalpies were calculated for complexes of eight Lewis bases – dimethyl ether, diethyl ether, ethyl acetate, trimethylamine, trimethylphosphine, tetrahydropyran, tetrahydro­furan, and tetrahydrotiophene with BF3 using HF/6-311+G**, B3LYP/6-311+G**, MP2/6-311+G**, MP2/6-311+G(2df,2pd), G2(MP2), and CBS-QB3 methods and compared to experi­mentally determined ones. The best results were obtained with the CBS-QB3 method. Application of the BSSE correction by the counterpoise method overcorrected the error and gave systematically too low enthalpy values. B3LYP/6-311+G** calculations seem to be best suited for investigating trends in BF3 affinities of different bases in the sense of compromise between speed and accuracy, while CBS-QB3 can be recommended for the calculation of absolute complexation energies between BF3 and Lewis bases.

Key words: Lewis basicity, BF3, DFT calculations, ab initio calculations.

Rate and equilibrium constants for the Grignard reaction with alkoxysilanes; 165–171

Anu Ploom, Dmitri Panov, and Ants Tuulmets

Abstract. Pseudo-first-order rate constants were determined for the reactions of tetraethoxysilane with n-butylmagnesium chloride solvated with dibutyl ether, diethyl ether, and THF in toluene. Also isopropylmagnesium chloride and isopropyltriethoxysilane were involved in a similar investi­ga­tion. Rate and equilibrium constants were calculated for the reactions and the steric effects in the reactions are discussed.

Key words: Grignard reaction, kinetics, silanes.

Instructions to authors; 172–174

Copyright Transfer Agreement; 175