Chemistry September 2005 Vol 54/3 []

CONTENTS & ABSTRACTS

InEnglish. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.

Chemistry



Volume 54 No. 3September 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 atthree sites in Tallinn (Estonia). The concentration of particles with diametersless than 2.5 μm (PM2.5), reaching human alveoli in lungs, was alsomeasured. The collected samples of particulate matter were extracted with theaccelerated solvent extraction method and analysed with high performance liquidchromatography. The chemical analysis indicated the occurrence of polycyclicaromatic hydrocarbons in the airborne particulate matter samples. The datareceived were grouped into four categories for annual, seasonal, diurnal, andday-of-the-week trends. Thewinter concentrations of NOx and CO in the urban area were twice ashigh as in the summer period. Annual and diurnal variations were studied tofind out the main sources of pollution. Increasing traffic intensity andindustrial activity were suggested to be associated with changes in airquality.

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

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

Margit Laja, Natalja Irha, Gary Urb, Janek Reinik, and UuveKirso

Abstract. Thisstudy focuses on the behaviour of oil shale combustion ash during waterextraction processes. The oil shale ash samples were collected from twodifferent combustion processes in Narva PP. The leaching tests of the ashsamples were carried out in compliance with a European standardprEN 12457-2 (1999). The results show that both first and secondwater extracts are characterized by high alkalinity and conductivity and theycontain polycyclic aromatic hydro­carbons.

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

Complexediron and a groundwater treatment technology; 142–153

Rein Munter, Heldi Ojaste, and Johannes Sutt

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

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

Comparativecalculations of complexation enthalpies between Lewis bases andborontrifluoride; 154–164

Peeter Burk and Martin Kutsar

Abstract. Complexation enthalpies were calculated for complexes of eightLewis bases – dimethyl ether, diethyl ether, ethyl acetate, trimethylamine,trimethylphosphine, tetrahydropyran, tetrahydro­furan, and tetrahydrotiophenewith 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 experi­mentallydetermined ones. The best results were obtained with the CBS-QB3 method.Application of the BSSE correction by the counterpoise method overcorrected theerror and gave systematically too low enthalpy values. B3LYP/6-311+G**calculations seem to be best suited for investigating trends in BF3affinities of different bases in the sense of compromise between speed andaccuracy, while CBS-QB3 can be recommended for the calculation of absolutecomplexation energies between BF3 and Lewis bases.

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

Rateand 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 reactionsof tetraethoxysilane with n-butylmagnesiumchloride solvated with dibutyl ether, diethyl ether, and THF in toluene. Alsoisopropylmagnesium chloride and isopropyltriethoxysilane were involved in asimilar investi­ga­tion. Rate and equilibrium constants were calculated for thereactions and the steric effects in the reactions are discussed.

Key words: Grignard reaction, kinetics, silanes.

Instructionsto authors; 172–174

CopyrightTransfer Agreement; 175